# SwiftE



## PatricioIN (Jun 13, 2008)

that looks very interesting. One questions about the heaters: It was my understanding that Lithium batts weren't as affected by cold as LA; do you think the battery heaters will make much difference?


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## tomofreno (Mar 3, 2009)

> It was my understanding that Lithium batts weren't as affected by cold as LA; do you think the battery heaters will make much difference?


 Yes. According to the SkyEnergy spec charging is above 0 C or 32 F. Dave at evcomponents told me it is difficult to charge the cells at low temperatures, and they only take about a 60% charge at around 30 F. Night temperatures where I live are many times in the twenties (F) and sometimes around 5 F. The heaters are powered by 120VAC. The plan on cold nights is to plug them in prior to charging with the thermostat set to around 60 F and turn on the charger when the sensor gets to about 45 F - hopefully in an hour or so. They will be off the rest of the time. The temperature sensor is bolted to the battery clamp on one of the set of four cells in the front box. Each heater, which heats about 4 cells is only 35W, so will provide only gentle warming. I'm hoping that the insulation, small amount of heat generated by the cells during vehicle operation, and daytime temperatures typically above 35 F will keep them above 50 F or higher the rest of the day. One problem will be equalizing temperature of the front box with they other two since it is exposed to more air flow when the car is moving. I'll see how this setup works, and modify if necessary. I can add insulation to the outside of the front box. During summer I'll remove the front box top for cooling, and I have a 145 cfm bilge blower to put a bit of air through the other two boxes. Have to see if it requires more. Have to start somewhere and gather data.


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## 80N541 (Jan 11, 2009)

great work!


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## vpoppv (Jul 27, 2009)

To see that engine bay with those lithium cells.....I'm so jealous!!


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## JRP3 (Mar 7, 2008)

What are you using for a pot box, PB6? I'm looking for other solutions, probably make my own or modify something.


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## dtbaker (Jan 5, 2008)

I can't wait to see how this compares in price, performance, and (eventually) battery life to my 'lead' version of almost the same car.....


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## tomofreno (Mar 3, 2009)

Yes, PB6. HPGC said they use the PBF6, F for foot pedal. I've seem some postings of complaints, particularly non-linearity, but they seem to work well with Curtis controllers as they are designed for them. There are a lot of them out there, so you might expect some bad ones to show up. Hope mine is not one of them.
Tom


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## tomofreno (Mar 3, 2009)

Hey Dan,

I think the main difference will be in acceleration at highway speeds, due to lighter weight (lithium cells) and higher current controller, 550A versus 400A. If you put a Curtis 500A controller in yours performance would be quite close I think, but a bit different due to the weight difference. I wouldn't expect to notice much if any difference driving on secondary roads and in town - unless you want to lay rubber. There is also of course the range difference due to pack energy/weight. Cell life is the big one to me as I am hoping for cost/mile similar to sealed lead acid cells. That is why I designed for max 70% DoD and 1C or less current at 60 mph.

Tom


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## madderscience (Jun 28, 2008)

looks like good engineering and a great build. bravo. I hope a BMS will be involved to protect your battery investment.

If you get the rolling resistance and aerodynamics dialed in on that sucker you will probably be looking at somewhere around 180 to 200 wh/mile at 55mph easy. This will mean with 15KwH usable battery capacity you will probably be looking at more like 70 miles of range.

I usually say good luck here, but you don't need any. You engineered it.


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## JRP3 (Mar 7, 2008)

My main problem with the PB6 is the price for what you get. A $10 pot, spring, housing, and switch shouldn't go for $100 or more, especially considering the number of problems reported.


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## tomofreno (Mar 3, 2009)

> I hope a BMS will be involved to protect your battery investment.


 I am using the Voltblocher shunt regulators with HCV and LCV signals made by Brian Blocher and purchased through evcomponents. I plan to use the HCV signal with a circuit being made by evcomponents to throttle back the PFC30 to about 1A output (been waiting for this for a couple months now though, with no response to my last email sent a couple weeks ago ). I also am epoxying a thermal fuse (open at 200 F) to the backside of each shunt regulator board, and daisy chaining these with 12V to the "coil" side of a solid state relay to shut down the PFC30 if a board exceeds 200 F. If I can't get a circuit from evcomponents, I'll have to determine the input signal to the PFC30 Regbus that is used to throttle back the output based on thermal input and make my own. Anyone familiar with this?



> If you get the rolling resistance and aerodynamics dialed in...


 I used the equation from Bob Brant's book that gives rolling resistance as a function of vehicle speed, but of course that is some rough average. It may overestimate it, as I seem to get conservative numbers for range compared to what Brian Blocher and Dave Kois have posted for their vehicles under "ev performance" on this forum. I also don't know the actual Peukert exponent for these cells, and just used 1.02 as an estimate. However, to match their numbers for range I have to set the Peukert exponent to 1.0, and unrealistically reduce the drag coefficient and vehicle weight for their vehicles. I don't understand this. Range numbers are very difficult to interpret as many times the average speed and DoD are not reported, and average grade and whether the path was a closed loop is rarely reported. The drag coeff for the Swift was given as 0.32 and I just roughly estimated cross sectional area from a few measurements.

Engineering is good, but good luck is better. 

Tom


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## tomofreno (Mar 3, 2009)

I think they have a healthy margin on it, but consider that it is made of $tainless $teel, and the number of cycles the spring and pot must undergo. I figured the time and materials I spent trying to make something reliable (don't want it to fail as I pull out into traffic) would have a much higher cost. I question whether there are a "lot" of problems as a proportion of the total population of these controllers in use. There are likely tens of thousands of Curtis potboxes out there on industrial vehicles and golf cars around the world. A few people complaining about bad potboxes on a formum like this can give the impression of "a lot of problems", when in reality it might be 0.01% of the population of controllers. It is of course a concern. I think the complaint about non-linearity is irrelevant if you are using a Curtis controller designed to use that signal.

Tom


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## JRP3 (Mar 7, 2008)

I don't know, people have been complaining about the noisy pots in the PB6 for years on the EVDL as well as here. A noisy pot probably doesn't cause much problem in low speed forklifts. The stamped stainless steel sheet metal parts can't cost more than a few dollars, and the spring need be no more durable than any automotive throttle spring. Since they are probably made in China I'd be surprised if they cost more than $20 in volume. Even if they functioned perfectly I still feel they are way overpriced and can't bring myself to purchase one, but that's my personal hangup


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## JRP3 (Mar 7, 2008)

tomofreno said:


> I plan to use the HCV signal with a circuit being made by evcomponents to throttle back the PFC30 to about 1A output (been waiting for this for a couple months now though, with no response to my last email sent a couple weeks ago ).


 Have you tried emailing James directly? He's usually good about responding.


> If I can't get a circuit from evcomponents, I'll have to determine the input signal to the PFC30 Regbus that is used to throttle back the output based on thermal input and make my own. Anyone familiar with this?


Have you tried contacting Manzanita and seeing what is required?


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## tomofreno (Mar 3, 2009)

> Have you tried emailing James directly? He's usually good about responding.


 Turns out Dave didn't receive, or didn't see my email. He said he will check on progress on the circuit and also have someone there send me info on pin outs for the regbus (some techs there also work at Manzanita).


> Have you tried contacting Manzanita and seeing what is required?


 Yes. Rich told me to short pins 1 & 3 to shut down the charger - I think. Been a while. I was just fishing for info from someone with experience. I expect I'll get the info I need from evcomponents. If not I'll contact Rich again.

Tom


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## tomofreno (Mar 3, 2009)

> A noisy pot probably doesn't cause much problem in low speed forklifts.


 I would think it could be a real problem if you are inching up to a pallet or near a coworker, but dunno. I see a lower priced potbox is a bit of a quest on your part (posts on the soliton thread)  We all have our pet issues, this was just a something I didn't think was worth spending much time on. I likely will if the PB6 starts acting up.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> I see a lower priced potbox is a bit of a quest on your part (posts on the soliton thread)  We all have our pet issues...


Yeah you got me  I've struggled with the potbox issue for a while, going back to my AMPhibian build. I ended up with this one and have had no issues with it, very fine control http://www.cloudelectric.com/product_p/th-bz31686.htm
I've even toyed with adapting one of them for my car build. I realize it's an important piece but it should also be a simple and relatively inexpensive piece, at least in my mind. I should let it go, I'm obsessed


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## vpoppv (Jul 27, 2009)

JRP3 said:


> Yeah you got me  I've struggled with the potbox issue for a while, going back to my AMPhibian build. I ended up with this one and have had no issues with it, very fine control http://www.cloudelectric.com/product_p/th-bz31686.htm
> I've even toyed with adapting one of them for my car build. I realize it's an important piece but it should also be a simple and relatively inexpensive piece, at least in my mind. I should let it go, I'm obsessed


If price is an issue, then using the stock one on the Swift would seem to be a cheap solution....


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## JRP3 (Mar 7, 2008)

Indeed, but this isn't my thread and I'm not building a Swift  My '88 Fiero doesn't have one.


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## vpoppv (Jul 27, 2009)

JRP3 said:


> Indeed, but this isn't my thread and I'm not building a Swift  My '88 Fiero doesn't have one.


 Then take your talk off this thread!! Yes, I am totally kidding. No TPS in a Fiero? Bummer. Wasn't there a TPS at some point in ANY Fiero? I would think that it would make it easy on 2 fronts: no need to fuss with adapting your accelerator cable and you (theoretically) would already know where Fiero parts are available. Also, isn't there a mega cheap pot at Radio Shack?


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## JRP3 (Mar 7, 2008)

You know I might be mistaken, I thought it was too old to have a TPS, I'll have to look. I was hoping to sell the motor as a running unit but I haven't had any takers so maybe I'll grab it.


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## tomofreno (Mar 3, 2009)

Completed the electrical box a couple days ago. LHS is the high current components, just the main relay (contactor) and shunt. RHS has the potbox, relays for passenger heater, 12V (off when charging), controller, DC/DC converter (off when ignition is off), and fuses.









Today was the day I dreaded for weeks, removing the dash to replace the heater core. The $140 shop manual I bought from a dealer was very helpful in determining what wiring connections (12 or so) had to be broken, it said "Disconnect wires."  But it was not too bad. I got the dash and core removed, and new electric core in a "custom" aluminum frame installed, and heater re-installed in the car. I made the frame from 1/16" sheet by bending it in a vise. This is the new heater in its frame, slid into one side of the heater:


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## dtbaker (Jan 5, 2008)

how bad a job (hours?) was it to pull the dash for access? I am looking at it, and thinking I want to put the heater element in the duct jest outside the fan rather than pull apart the dash.....


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## tomofreno (Mar 3, 2009)

> how bad a job (hours?) was it to pull the dash for access? I am looking at it, and thinking I want to put the heater element in the duct jest outside the fan rather than pull apart the dash.....


 It took me about 7 hours to pull the steering column, dash, and heater, make the aluminum frame and bolt the heater onto it, stick some foam to the sides of the frame, insert it into the heater box/re-assemble the box, and bolt the heater box back into the car. That was yesterday. This morning I wiped the dust off the back of the dash with a damp cloth, bolted it back in, and connected the heater wires to the leads from the relay located up in the electrical box under the hood (about 2 hrs), but have to reconnect the other wires. Also have to re-install the steering column. 

It would be a good idea to have a manual if you pull the dash. It didn't say what wires to disconnect, but it did show the location of the bolts that hold it on, explained to pull the entire steering column and leave the steering wheel in place, and other required steps such as to remove the speedometer cable. These instructions are under the section on removing the heater box.

I think Canev uses a sheet metal box mounted between the heater box and blower, similar to what you are thinking. That might be less work, if you can make an airtight box easy, and figure out a way to make an airtight connection between it and the ducting. You don't risk messing up wiring that way, but you loose air conductance - two heater cores in the path. I was way disappointed when I saw I had to remove the dash - but I took inspiration from Atkill's complete disassembly of his Aspire.

Tom


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## paker (Jun 20, 2008)

Wouldn't it have been easier to use a block heater and water pump with the existing overflow tank for heating the car?


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## tomofreno (Mar 3, 2009)

> Wouldn't it have been easier to use a block heater and water pump with the existing overflow tank for heating the car?


 I looked at those block heaters a bit and only saw ones that were about 800W. I'll need more than that to defrost the windshield and heat the car much at 15 - 20 F or so. Seems like a nice solution if they had more power, or if you live where it doesn't get that cold.

Tom


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## JRP3 (Mar 7, 2008)

Katz 1500 watt heater $40
http://www.amazon.com/gp/product/B000BQUUR6
Water pump $40
http://www.adventurerv.net/shurflo-nautilus-single-station-water-pump-gpm-p-1713.html
Hook a relay to the heater thermostat to power the heater as the thermostat won't handle the DC voltage.
Cost will be higher than a ceramic but probably a lot less work, some heater cores are worse than others.


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## tomofreno (Mar 3, 2009)

Re-installed the dash and steering column yesterday. Altogether it took maybe 12-13 hrs or so to remove, install new core, and re-install everything. The electric heater is good in that there are no moving parts, no possible water leaks, no antifreeze required, and nothing to mount under the hood which is a bit crowded in this small car. It's bad in that for this car it is quite a bit of work to install the core. I may well have gone the block heater route, but I planned to install the TBS and Curtis gauges where the ICE temperature and and fuel gauges are and figured that would be easier with the dash off. Turns out there isn't enough depth to mount them there. 

I don't have a thermostat, just a multi-position on/off switch with a few speeds for the heater blower, and a lever/cable that opens/closes the air flow path from the blower to the core change from ambient air to heated air. I obviously don't want the heater to come on when the blower is turned on during summer. I also don't want the heater on very long with the blower off. I guess I will pull 12V from the blower switch and add a heater on/off switch in series to provide current to the coil of the heater relay.

Tom


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## dtbaker (Jan 5, 2008)

wow, this confirms my plan NOT to pull the dash! I do need to finish up though as it is starting to get cold in the AMs.... For your gauging, take a look at the pillar mount I put in mine, it came out really nicely I think! It took some fooling around cutting and bending the 'universal' ABS piece to fit well. I did a fair amount of trimming, and a little bending with a heat gun.

http://www.envirokarma.org/ev/13.Instruments.shtml


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## tomofreno (Mar 3, 2009)

> wow, this confirms my plan NOT to pull the dash!


 Yeah, I hate to think that if I have to service it I will have to go through the dash removal again.  Think I could do it in half the time now though. Where did you purchase the gauge holder? My gauges are little LCD ones about 2 1/4" diameter, not sure they will fit, but well worth looking into.

Tom


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## dtbaker (Jan 5, 2008)

tomofreno said:


> Where did you purchase the gauge holder?


It was off the shelf at either Auto-Zone or Checker.... probably available at JCWhitney or any auto supply store. It was like $15-20, something like that I think.


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## tomofreno (Mar 3, 2009)

I had the ev grin today for about 30 minutes. I finished the conversion of the Swift except for a few odds and ends, and drove it around the driveway after testing out relays, gauges, etc.  But I noticed it seemed I had used quite a bit of energy for the little testing I had done, so I started looking around and noticed the green LED on a Voltblocher in the front box seemed very dim. I measured the cell voltage at 1.80V.  I then measured all cells and most were very close to their value when I received them about 2 1/2 months ago. They were 3.28 to 3.29 when received and 3.26 to 3.27 now. But 3 cells were considerably lower at 1.80, 2.98, and 3.06, and one was dead at 0.67V.  

I had installed the Voltblochers and connected the cells about 2 1/2 weeks ago. I called Dave at evcomponents and he said "Get those Voltblochers off your cells." They are in the process of recalling them after 10 or so reports of problems like mine, and finding no quick answer for it. I have 36 cells and Voltblochers total, and only 4 of the VB's seem to have failed. 

On top of that, I started up my Manzanita PFC30 last Friday and it blew the output fuse. I had the AC supply lines through an EKM meter to it, and it never drew more than 1A and 18W, even when I turned up the current adjust a bit. I then noticed the "limits" LED was on, so adjusted the volts trim pot per the manual, but couldn't get it to go out. I kept turning, then the red "warning" LED came on and I quickly shut off the charger. I shipped it back to Manzanita today.

I thought I would be driving the ev this week, but looks like it may be a month or more now since I don't know what I'll do for a bms. 

The issue with the VB's is very unfortunate for all involved. Dave said Brian had never seen such problems before. I'm wondering if some components were faulty since I only had 4 out of 36 fail. I hope some resolution can be found as they were a relatively inexpensive solution.

Tom


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## pdhsolar (Aug 31, 2009)

Fantastic! I am also converting a swift and really enjoyed seeing the pics. Mine is here but not as far on as yours. Do you have a website or a link to see more? Cheers, 
http://www.evalbum.com/2951


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## tomofreno (Mar 3, 2009)

It was a bit odd driving the ev since I had to push the accelerator pedal quite a bit to get the car to move. I thought something was wrong. Then I set the Curtis meter to show motor rpm and the TBS to show battery current and watched as I pushed the accelerator. I had to push quite a bit to get around 8-10 amps and a few hundred rpm and the car moving. Pushed more to get 50A and the car started moving more as I expected. I stopped, pushed the accelerator harder to get over 50A and the car accelerated more like I expected. It seems the potbox is quite non-linear. I was excited, and ready to take a real test drive tomorrow until I discovered the VB problem. 

I used the gauge mount Dan recommended. Very nice having both gauges right there where I can easily glance at them (drivers side post, at eye level as in Dan's car). Between the two I have SOC, battery I, V ( V on both meters), motor rpm, motor temp, controller current, and controller temp. The Curtis also has an LED array that gives 3 green for regen (can see the regen current on the TBS), 2 green for good efficiency, 1 green for ok efficiency, yellow for inefficient, red for very inefficient - based on motor slip.

When I took my foot off the accelerator to stop I glanced a negative current reading on the TBS, wondered what the...then thought regen! Disappointing, to put it mildly, that the car will be out of commission a while. I likely will just manually charge it with no bms for a while when I get cells to replace the two worst ones and get the charger back. The other two should be ok I think.

Tom


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## dtbaker (Jan 5, 2008)

bummer on the VB problems.... sounds like an unacceptable failure rate when it could have zapped your cells!

The 'cheap' BMS at kta-ev.com is about the same price for the whole pack at $1000.... so I am debating for my next project going LiFePO4..... The FLA have been fine, but I sure would love a 120v Li pack instead!


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## dtbaker (Jan 5, 2008)

pdhsolar said:


> Fantastic! I am also converting a swift and really enjoyed seeing the pics. Mine is here but not as far on as yours. Do you have a website or a link to see more? Cheers,
> http://www.evalbum.com/2951


Did you check mine out!? I LOVE that little Swift.... 96v of FLA is about all you can fit without using cargo/rear seat area. 120v of Li would be FUN.


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## JRP3 (Mar 7, 2008)

Sorry to hear about the VB problem, but it reinforces my plan to not use a balancing system. It introduces another potential failure point, or actually 36 failure points. Have you tried to recover the low cells? They may not necessarily all be damaged.


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## dtbaker (Jan 5, 2008)

JRP3 said:


> Sorry to hear about the VB problem, but it reinforces my plan to not use a balancing system. It introduces another potential failure point, or actually 36 failure points. Have you tried to recover the low cells? They may not necessarily all be damaged.



yeah.... I am really riding the fence on a BMS. Jack Ricard is a case that seems to be having good luck with a careful charge cycle; including 3x 'balance' phases with a rest between and no BMS. But then you've got $3000 in a fancy charger like the Brusa or Manzanita rather than a $1000 charger and $1000 BMS. I am trying to learn more.....


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## tomofreno (Mar 3, 2009)

> Do you have a website or a link to see more?


 No. but Dan has one on his Swift conversion that has lots of photos and details at envirokarma.org


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## dtbaker (Jan 5, 2008)

tomofreno said:


> No. but Dan has one on his Swift conversion that has lots of photos and details at envirokarma.org


thx, and by the way I have added my heater install to the Gallery, but not a separate summary page yet. Turns out I had all the wiring correct, but it seems to be drawing a little too much for 20a fuses at the start before the coils are hot.... I have temp 'custom' fuses with 22ga wire, but will try to borrow a clamp ammeter to see what it is actually pulling. I think that as my FLA voltage sags under load, the pull may go up over 20a if I happen to have the heater on full blast too....

ANd, not that you guys with Li care, but I added a 'watering system' for the FLA which really takes all the pain out of that process!


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## JRP3 (Mar 7, 2008)

dtbaker said:


> yeah.... I am really riding the fence on a BMS. Jack Ricard is a case that seems to be having good luck with a careful charge cycle; including 3x 'balance' phases with a rest between and no BMS. But then you've got $3000 in a fancy charger like the Brusa or Manzanita rather than a $1000 charger and $1000 BMS. I am trying to learn more.....


If you don't need 30 amps you can get a Manzanita PFC20 for about $2k. The Manzanita doesn't do the 3 balance phase with resting that the Brusa does, but if you aren't pushing the voltage too high I'm not sure it's necessary.


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## dtbaker (Jan 5, 2008)

JRP3 said:


> If you don't need 30 amps you can get a Manzanita PFC20 for about $2k. The Manzanita doesn't do the 3 balance phase with resting that the Brusa does, but if you aren't pushing the voltage too high I'm not sure it's necessary.


what would the Manzanita for $2k get me that the Elcon for $1100 wouldn't?
http://store.kta-ev.com/Battery_Chargers/PFC-3000_Charger.aspx

...I really wanna know! I am trying to firm up the shopping list for my next project...


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## tomofreno (Mar 3, 2009)

> Have you tried to recover the low cells?


 I just noticed it today, and I have no charger, so no. I plan to replace the two lowest ones, but the two at 2.98 and 3.06V should be fine I think. Brian confirmed that he has not had this problem on his units, and said the few problems he has seen from others have been due to sloppy soldering of components on the board. He tests his completed units for current draw using a power supply. I'm leaning toward getting a small lab supply for this, and just replacing the bad units. The other 32 cells are fine. They have only gone from 3.27 - 3.28 to 3.26 - 3.27 in the 2 1/2 months I've had them, and 2 1/2 weeks with VBs connected. I could pretty quickly replace the bad units and be "on the road again" if the charger comes back soon. Jack's method is too labor intensive to be practical for most. I plan to charge at night. 'Course those first few nights I'll be sleeping pretty lightly. I'll likely charge in the early evening so I can keep an eye on things until I become more confident. With the PFC30 and 240VAC outlet I can charge 12kWh in about 3 1/2 hours. And you can bet I'll be keeping an eye on pack voltage, and checking cell voltages regularly. It is easy to get at them in my boxes. I made them so it is easy because I knew I wouldn't bother to open them often if it was too much trouble.

Tom


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## tomofreno (Mar 3, 2009)

> what would the Manzanita for $2k get me that the Elcon for $1100 wouldn't?


 A regbus input for one thing, which can be used with simple circuitry to cut back charger output or shut it down. How is your bms going to control the Elcon? I asked KTA this, and they responded a couple days later that there is no bms input. It appears the Chinoz simply shuts off with an external signal. If that is all it does, there is no balancing of cell voltages. From what I've heard from others, it sounds like the cells don't get much out of balance anyway, but eventually you would need to balance them. 

Make sure you think all these details through and know exactly how it is going to work before you purchase something. There is nothing out there that I know of that is simple plug and play, and I've spent a lot of time studying. Make sure you know exactly what the "bms" can do, what signals it puts out at what levels, what, if any, additional circuitry you will have to make, and how it will all work with the charger you plan to use. I have found it difficult to get all such details from suppliers/manufacturers. That is one of the reasons I went with VB's, Brian is very helpful, the circuits are simple with operation I understand, and the source is fairly local. Get this all worked out before you start a conversion as you will need to plan space for boards and run wires for them.

I don't know what is best. I almost went with Agnimotors/Stybrook's shunt regulators (also because I understand how they work), but preferred a local source. They seem to have a very good reputation in the Battery Vehicle Society website in the UK. Dave at evcomponents seems to like the much more pricey Elithion, but I've lately seen someone with ev conversion experience complaining they can't figure out how to install the one they bought and are having trouble getting info. It does have a lot of nice features though, like readout of all individual cell voltages and temperatures and is likely worth the cost, just not to me. 

Tom


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## tomofreno (Mar 3, 2009)

> ...but it reinforces my plan to not use a balancing system


 How do you plan to balance? My understanding is that Jack uses the simple shunt circuits he described on the yahoo thundersky site, he just keeps them off board and stands by checking things as he charges. Has that changed? I expect the cells will get enough out of balance eventually that you will have to balance or significantly limit the energy you get from the pack in order to avoid overcharging the highest cell and overdischarging the lowest. 

Tom


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## JRP3 (Mar 7, 2008)

I know Jack talked about having off board shunt circuits that only get plugged in when charging but I don't know if he actually implemented that. My initial plan is to monitor each half of the pack as Jack does, which will show any imbalance, (and would have shown up your problem immediately), and if imbalance occurs I will manually bring up the low cells with a power supply. If this becomes cumbersome then I will probably do an off board charge balancer.


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## JRP3 (Mar 7, 2008)

You could try this to recover the cells. It would take a while but it's cheaper than a new cell if it works:
http://www.all-battery.com/TenergyLiFePO4BatteryCharger01300.aspx


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## tomofreno (Mar 3, 2009)

> You could try this to recover the cells. It would take a while but it's cheaper than a new cell if it works:


 I guess that's your prospective balancing system.  From what Dimitri says, you can likely go a long time without balancing. 

It's still not clear to me that I can automatically balance with the PFC30. You can cut back current to a low value if you use a voltage divider between pins 1, 2 & 4 adjusted to the proper value with a relay to close this connection (or zero current with the divider adjusted for close to 5V to pin2). I think with switchpack switch3 on this will also start the timer. So I am hoping I can adjust the divider so an HVC will cut back current to around 3/4A, and charge for the timer set minutes at this low current, then the charger will stop charging when it times out. I am not clear on Rich's responses to me on the regbus. I outlined the above scenario to him and asked if it was correct but he didn't respond. It sounds like with regbus boards the charger just runs full current, shuts off when a regbus board gets hot, then runs full current again when the board is cool, and keeps cycling like this until enough of the boards are shunting and hot that the combined signal results in high enough voltage to pin2 to shut down the current output of the charger. But I may be completely wrong.

I have the divider with 25 turn 5k trimmer pot and relay installed on the car and ready to test but no charger. I also have two relays installed connected to the thermal fuse chain and verified one cuts AC power to the charger and the other connects pins 1&2 on the regbus when the thermal fuse chain is broken. I like this, as it is "active" - there has to be current through this fuse chain for the charger to run, ie it has to be "right" in order to run, rather than it runs unless some signal says something is wrong. The relays are connected to the 12V battery through a N.O. relay with AC coil. Plugging in AC to the charger activates this relay supplying 12V through the fuse chain to open the relay connecting pins1&2, and close the relay supplying AC to the charger. If the current path through this fuse chain is broken, charging is stopped. The fuses open at 200 C.

I would like a bms that has some "heartbeat" signal that continuously checks functionality of the boards. If anything is wrong it would prevent the charger from coming on, or turn it off - like the fuse chain, only a check of functionality of the entire system.

Tom


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## JRP3 (Mar 7, 2008)

tomofreno said:


> I guess that's your prospective balancing system.


The cheapest I've found so far.  I'd like a higher amperage unit but I may start out with this one.


> From what Dimitri says, you can likely go a long time without balancing.


That's my hope. Also, I think Dimitri unbalances his pack by having Paktrackers hooked up which draw from a few cells, so without that I can probably go even longer.


> It sounds like with regbus boards the charger just runs full current, shuts off when a regbus board gets hot, then runs full current again when the board is cool, and keeps cycling like this until enough of the boards are shunting and hot that the combined signal results in high enough voltage to pin2 to shut down the current output of the charger. But I may be completely wrong.


That's the way I understand it as well.


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## tomofreno (Mar 3, 2009)

I ordered a power supply yesterday to use to test Voltblochers, thinking I would place the defective ones and continue using them. I found out today that the problem is worse than I thought. Randy at Canev tested 200 of them to find 50 good ones to use in a conversion. Then some of those failed. I thought If they tested good they would remain so, but at least in some cases apparently not. So I'll be joining JRP3 in charging without a bms - for a while at least. 

I'll be getting two cells from evcomponents on the next shipment that is enroute now. Dave said they have found the cells discharged by the VB's don't recover if discharged below around 2V. The other two that were discharged are at 2.98V and 3.06V so should recover. I'll use my new voltage supply to charge them up to match the others in the pack.

I plan to just set the voltage limit on the PFC30 to 125V or about 3.47V/cell. and check cells frequently with a dvm to see if they are staying balanced - when I get my charger back that is. Disappointing, as I had my HVC and LVC relays all ready to test when I got the charger back. Plus there were 8 wires to each VB and 2 to the thermal fuse I adhered to each board, so 360 wires to cut to length, strip ends... Now I just sit and wait for cells and charger.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> So I'll be joining JRP3 in charging without a bms - for a while at least.


Welcome to the dark side


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## dimitri (May 16, 2008)

Just stumbled on this thread... Tom, real bummer about your VB issues. I cannot understand how a simple circuit can fail if it was QC'd and tested prior to install. I test every one of mine with variable DC bench supply to ensure there is no current draw before HVC and proper current flow after HVC. I strongly suspect that assembly and QC weren't that good since reseller's were assembling them and not Brian himself. It takes a lot of patience and attention to details to assemble dozens of PCBs, especially when 3 ICs have same look and its so easy to mix them up. I assemble one day, then QC each one next day with fresh eyes, quality is critical. Funny how Brian had no complains from DIY people, who work for themselves and pay utmost attention.

As for balancing, its not as important as overharge protection IMHO. Even if your charger max voltage is moderate, you still have no idea if one cells gets a little ahead of others, due to differences in internal resistance. 

JRP, comparing half pack voltages ( which is BTW an idea originated from Metric Mind's E-meter, not Jack Rickard ) is not going to help when charging is finishing up and you are sound asleep in your bed. Overcharging would occur within few minutes interval right before end of charge and depending on how dumb your charger is, couple of times would be enough to swell a cell or two.

BMS market is so messed up because everyone has ideas, but no one can produce high quality product at reasonable price. Why is that Elithion BMS is being marketed and has a great Web site, but no one has come forward with a decent review? Not even EV Components who sells them?


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## dimitri (May 16, 2008)

Also, if you had VBs on cells for 480 hours ( 2.5 weeks ) and cell is 100Ah ( not sure what you have, just making an example ) and its fully charged, then it would take approx 0.2 Amps to kill a cell. At 3 Volts this would take 15 Ohms resistance and would produce 0.6 Watt of heat. I'm assuming red LED never came on, since that would have been a red flag sign, but even a little warm up should be a warning sign. Working module drains about 0.005 Amps or less. 

I would also advise against assembling a pack with BMS unless you are ready to charge it shortly, why have it sitting for 2 weeks with live circuits on each cell?

Again, really sorry for your troubles, I wish there was a bulletproof way to manage battery packs. I check all green LEDs on my VBs every day, and every couple weeks I turn on the charger during the day after nightly full charge just to observe red LEDs come up properly.

Also, reducing charger current to less than 2 amps at the end is critical, if you can't do that, then you should just shut off the charger on first cell HVC and forget the balancing, otherwise you will cook off either VBs or cells or both.


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## tomofreno (Mar 3, 2009)

> Also, if you had VBs on cells for 480 hours


 As you know, the off state resistance of such a shunt circuit should be orders of magnitude greater than 15 Ohm unless you are near the knee of the curve in the subthreshold region of the transistor. There is some problem with some of the circuits, as evidenced by the fact that the other 32 cells have lost hardly any voltage as you would expect. I was too complacent because Brian had been using the circuits for many months with no issues. It first made me nervous to leave the VB's on, but I was working on the car most days, and regularly did spot checks on cell voltages and checked LEDs on the VBs. I also touched the 1.5 Ohm resistors fairly regularly to see if any were warm. I just didn't check the right ones. I noticed the pack voltage dropping a bit, but didn't pay enough attention. Ah, only a volt or two across 36 cells, too focused on other things. I thought I was just using up energy doing testing, DC/DC running during testing, etc. Then I finally did the mental calculation and saw it was too much energy to explain this way. That is when I grabbed my dvm, measured all cells and caught the problem. 

It is interesting to realize that if I had been driving and recharging the car each day I likely would not have noticed the problem. I would just have had a bit lower range, but I would have had no way to know that because I would have had the VB's in from day one. It is questionable I would have caught it in this case even monitoring half pack voltages since the failed circuits were distributed through the pack. I would have to have been logging individual cell voltages and checking for steady differences. Even then I may have just attributed the small daily voltage differences to differences in internal resistance or capacity.

I think checking half pack voltages is of limited value and requires paying very close attention and keeping a log. I plan to monitor two blocks of 8 and two of 10 since I have two boxes of 8 cells each and one with 20. I'll keep a log on the total V/#cells in each block. I will also measure all cells once every 4 -5 days. It is not difficult, I just have to flip the box lid up and take dvm measurements before I hook up the charger. I have a printed map of the cells and just write the voltage on each cell in the drawing and date it. Of course now I say that. I have learned my lesson!

Monitoring this way should permit catching any imbalancing issue, so I think I am safe doing this and just setting the charger to max voltage of 125V or 3.47V/cell. Of course I will be standing there watching closely the first several times to ensure it shuts off! And I will not leave it to charge at night. I will charge in the evening, check it periodically, and ensure it is off prior to going to bed. At 240V/30A it should typically take me less than 3 hours to charge except for occasional days when I use more of the pack energy. 

I'll be keeping my eye out for a suitable replacement bms. I don't think the lack of a review on the Elithion from evcomponents should be taken as evidence against it. My impression is that those guys have taken on more than they can handle and are just scrambling from one task to the next with many things falling to the side. Writing a review is likely way, way, down on their list of priorities. I don't have any evidence for the Elithion either. I first planned to go with it, but didn't feel I understood its operation or how to install it well enough to buy one. Since I have an HPGC AC50 I am watching their bms development closely. It uses the motor controller as the bms controller and controls regen. The prototype is in a car now. Don't know any details of how it works.

Tom


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## tomofreno (Mar 3, 2009)

Oh, and thanks for the condolences Dimitri. Much appreciated. I also feel sorry for Brian. He was just trying to help fellow ev'ers. As you've pointed out there is little money in it for all the headaches. I think the circuit could be made to work fine once the problem is found. But why should he bother to deal with it?

Tom


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## dimitri (May 16, 2008)

tomofreno said:


> Oh, and thanks for the condolences Dimitri. Much appreciated. I also feel sorry for Brian. He was just trying to help fellow ev'ers. As you've pointed out there is little money in it for all the headaches. I think the circuit could be made to work fine once the problem is found. But why should he bother to deal with it?
> 
> Tom


Tom,

I assure you there is no issue with the circuit design, it was pretty much taken from popular open source TPPacks project by Fechter/Goodrum. The only thing was changed is power transistor and resistor to increase shunting ability. Its most simple design and its rock solid if properly assembled. Brian and I collaborated on circuit and PCB design at first, then he designed his own PCB version and I did my own PCB, but its the same exact circuit.

I assembled over a hundred of them so far, some for myself and some for others, the devil is in assembly, QC and testing. If done right it works great. I can't say for sure and its not my battle, but I strongly suspect the culprit is poor assembly and QC. It is impossible for 150 out of 200 units to be faulty, they would have to be assembled by a blind man with shaking hands on Monday after a huge hangover 

In fact any BMS, I don't care who designs it, will have basic voltage reading and shunting components, and by virtue all will have similar risks of draining a cell. They might have a better way of alerting you, but IMHO a system with complex digital communication will have even more points of failure than simple analog one.

Can you take very high resolution pics of faulty unit and working unit, both top and bottom side? I could look it over if you want to, although I am sure you could compare them yourself and see if there are any shorts, sloppy work or wrong polarity on semiconductors.


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## JRP3 (Mar 7, 2008)

dimitri said:


> As for balancing, its not as important as overharge protection IMHO. Even if your charger max voltage is moderate, you still have no idea if one cells gets a little ahead of others, due to differences in internal resistance.


That should only happen pretty near the end of the charge cycle from the charge curves I've seen, and I don't really need to get near that part of the curve. A non shunting cell monitor with HVC would take care of that, and I may eventually go that way. You could use a HVC signal to shut off the charger.


> JRP, comparing half pack voltages ( which is BTW an idea originated from Metric Mind's E-meter, not Jack Rickard ) is not going to help when charging is finishing up and you are sound asleep in your bed. Overcharging would occur within few minutes interval right before end of charge and depending on how dumb your charger is, couple of times would be enough to swell a cell or two.


I won't be charging when I'm asleep. One advantage of a 30 amp 240 volt charger.


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## dimitri (May 16, 2008)

JRP3 said:


> A non shunting cell monitor with HVC would take care of that, and I may eventually go that way. You could use a HVC signal to shut off the charger.


Which is basically VB minus power transistor and resistor... so if whoever you buy it from has poor QC quality then you end up draining a cell, just like Tom. Like I said, any BMS has a risk, assembly quality and final QC is the key.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> It is questionable I would have caught it in this case even monitoring half pack voltages since the failed circuits were distributed through the pack.


Unless you had the same voltage drops in an equal number of cells in each half of the pack,(unlikely), I think it would have shown up, especially under load. It's going to be a lot harder to monitor a number of different sized groups of cells on the go and compare them looking for problems than two halves of a pack. Plus, in their "natural" state I doubt you'd have something pulling down a bunch of cells at once.


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## JRP3 (Mar 7, 2008)

dimitri said:


> Which is basically VB minus power transistor and resistor... so if whoever you buy it from has poor QC quality then you end up draining a cell, just like Tom. Like I said, any BMS has a risk, assembly quality and final QC is the key.


I agree, but wouldn't a shunt-less BMS have less potential for current drain, especially if fused properly?


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## tomofreno (Mar 3, 2009)

> I assure you there is no issue with the circuit design


 When I listed "design" as a possible cause I was thinking more board layout - like a trace too close to a solder point, so if not assembled carefully there might be a problem. It is obvious that the circuit design itself is not the problem as most work fine. I did find one such issue. There is a resistor with a solder point/lead under the heat sink for the power transistor, TIP122. If the heat sink is installed tilted, it can contact the resistor lead. The heat sink on the board that drained a cell to 0.67V is installed this way. However, I think I measure 993 Ohm between this resistor lead and the collector where it is bolted to the heat sink, same as I measure on a spare board (unknown good or bad) where the heat sink is not touching. I say think, because sometimes I measure tens of Ohms, but I think my probe is touching the heat sink in that case. It is very close. The other end of this resistor appears to connect to an LM431 transistor by the pot (hard to see the traces under components). I also measured 993 Ohm when I removed the heat sink. Otherwise I see no obvious issue like bridging solder joints, or component installed differently.


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## Coulomb (Apr 22, 2009)

I'd be interested in the quality of the trimpots. I assume that sets the bypass voltage; if so, if the wiper didn't make contact with the rest of the resistor, the bypass voltage could float and change (depending on the circuit). It's the one moving part in the whole circuit.

I'd be tempted to replace the trimpot with a pair of high stability, low tolerance resistors. If the voltage needs adjusting, wire an appropriate value resistor in parallel with one or other half.


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## tomofreno (Mar 3, 2009)

> I'd be interested in the quality of the trimpots. I assume that sets the bypass voltage; if so, if the wiper didn't make contact with the rest of the resistor, the bypass voltage could float and change


 Yeah, my guess is it is something like this because only a minority of boards failed (in my case) and they failed with great variability (one cell at 0.67V a couple others only down to 3.06V and 2.98V.). I used this pot to set the HVC (red LED just coming on) at 3.50 to 3.51V on all boards. It was very touchy but I don't know if it was unstable. I rechecked this voltage a second time maybe 10 - 15 seconds after setting each and it was stable, but of course that doesn't mean it couldn't change later, especially if jostled a bit. It sure would be nice to know the cause, as they should have very high resistance between cell terminals as designed - and most do. I'll recheck the HVC on the board that was on the 0.67V cell - with and without the heat sink tilted. I'll also measure current on it at 3.2V when I received my voltage supply. I'll also check the other problem boards at that time.

Tom


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## tomofreno (Mar 3, 2009)

> I agree, but wouldn't a shunt-less BMS have less potential for current drain, especially if fused properly?


 I would certainly think so. I see Elcon is advertising a "regulator" that puts out a signal that notifies the charger the pack is ready to charge. It didn't say if this is a signal from each cell. I kind of like this "active" operation - a signal has to be actively given to charge, no signal it doesn't charge. Of course there is some probability any circuit reading cell voltage may fail in a way that lowers resistance between the cell terminals. Seems that probability can be made quite small though with say only a fixed resistive divider between cell terminals giving input to an op amp. 

Tom


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## JRP3 (Mar 7, 2008)

Question, did you get the VB's from evcomponents, and if so are they replacing the damaged cells for free?


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## dimitri (May 16, 2008)

Its silly to blame trimpots, these are used in thousands of electronic devices, no one would be using them if they had such poor quality. Not sure what trimpots Tom got on his units, but I use 25 turn precision trimpots, those do not loose contact easily, they are sealed and have internal worm gear for precise value setting. Trimpots are most expensive components in these modules, that is why I prefer to build modules with static resistors set for predefined HLVC levels, its cheaper and no need for calibration. Even basic resistor with 2% variation is good enough, you don't need THAT much precision in this circuit. 

Unfortunately due to compact size and need for heatsink, the issue you describe is valid. In my PCB design I pay utmost attention to heat sink install, to ensure there are no shorts. Careful handling during shipping and install is also important, as with any exposed electronic circuits.

Shuntless design would certainly have less risks, but sloppy soldering can ruin any product. I think surface mounted components are much better, but those require significant investment in production equipment, so we'd have to wait for some established business to make those. VBs were meant to fill a DIY market void and it worked for most people, until poor attempts to mass produce them messed it all up.


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## dimitri (May 16, 2008)

Also, any failure associated with voltage sensing or trimpot will cause red LED to light up when its not expected to. I assume none of yours did since that would be a dead giveaway. Current leaking outside of normal opening of power FET means a short somewhere or wrong polarity on semiconductors, including wrong polarity of red LED, which would have been spotted by even a simple QC procedure.

Tom, I can't see from pics you posted, but do you have positive clearance between VBs and your battery box covers? Any chance of pressure applied to VBs by box covers?


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## tomofreno (Mar 3, 2009)

> Question, did you get the VB's from evcomponents, and if so are they replacing the damaged cells for free?


 Yes and yes, I bought the boards from them assembled. They are replacing the two they think could not be recovered. I didn't asked to replace the two others at 2.98 and 3.06 as they should not be any problem to just recharge.


> Careful handling during shipping and install is also important, as with any exposed electronic circuits.


 Mine came in static bags with about 10 per bag tossed in and tangled together. A heat sink in this ball of boards could have easily been moved during transit. I don't see any sloppy soldering.


> VBs were meant to fill a DIY market void and it worked for most people, until poor attempts to mass produce them messed it all up.


 That's what I meant when I said this was unfortunate for all involved. Although we don't know what caused the problem yet. 

Tom


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## tomofreno (Mar 3, 2009)

I received my voltage supply today and measured current versus voltage for a bad VB (I bad) and a good VB (I good). Here are the results:

View attachment VB1.txt


I also measured V versus I for the bad cell with the heat sink pushed against the resistor lead located under it. I held my finger on it to ensure it was pushed hard against it. Made no difference at all. Same readings of current as with it not touching. HVC was set at 3.50V for both. The knee of the curve for the good one is quite sharp, 0.01 at 3.5V and 1.10A at 3.6V, in contrast to the bad one. The bad VB was on the cell that was at 0.67V. Of course I pulled it lower by driving around the driveway pulling 20 - 50A for 2-3 minutes, plus testing relays, DC/DC etc. But 50A for 3 minutes is only about 2.5Ah. Any guesses for the cause of the slope below the knee of the curve for the bad VB?

Tom


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## JRP3 (Mar 7, 2008)

What did you get for a voltage supply?


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## Coulomb (Apr 22, 2009)

tomofreno said:


> Any guesses for the cause of the slope below the knee of the curve for the bad VB?


Edit: oops, there is no op-amp.

_It's like the op-amp has very little gain. Is there feedback from the output to negative input of the op-amp? You'll have to do some circuit tracing and looking up of op-amp pinouts to determine this. If the feedback resistor is too small (say 1/10 or 1/100 of its proper value, those blue 1% resistors can be very hard to read), that could explain the extreme roundness. You could just check the resistors near the op-amp, to make sure they have the same colour bands as the good board. The other possibility is some sort of leakage from negative to positive inputs on the op-amp. Or a short from one of the inputs to somewhere else.

It would be good to do an ohms test from the op-amp inputs to nearby connections, comparing good and bad boards. If/when you find a significant difference, investigate closer._


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## tomofreno (Mar 3, 2009)

> What did you get for a voltage supply?


 The one Brian uses and gave me this link to:
http://www.circuitspecialists.com/prod.itml/icOid/8770

Good price for the power output. Only 3 place display, but is ok for me. Sure wish I had ordered it earlier and tested the VBs before installing them.


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## tomofreno (Mar 3, 2009)

There is no op amp, just a power transistor, TIP122, and it turns on with similar gain to the good circuit if you look at the data around the knee of the curve. The difference is it is conducting below the knee where the good one is not. Seems to have two regions with different slope below the knee, with a break at about 2.2V.

Tom


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## tomofreno (Mar 3, 2009)

Sorry, the TIP122 is a darlington pair. I checked resistors yesterday. They are the same on both boards, color bands and R measured with a dvm.

Tom


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## Coulomb (Apr 22, 2009)

tomofreno said:


> There is no op amp


Oops! That's a dual opto-isolator. Sorry, my bad.

One of the two TO92 devices must be the reference for the bypass voltage. Do they measure the same on both boards? Just check all 3 pins with respect to the cell -.


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## Coulomb (Apr 22, 2009)

Also, there is a capacitor near the trimpot. Is it in backwards?


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## tomofreno (Mar 3, 2009)

> One of the two TO92 devices must be the reference for the bypass voltage. Do they measure the same on both boards? Just check all 3 pins with respect to the cell -.


 TO92? I don't see anything with this on it. There are 3 other transistors on the board. I don't think any are labeled TO92, but they are difficult to read. Seems to me the biasing must be the same though, since they both turn on at 3.50V and have the same gain from there on. It is just that there is conduction below this threshold on the bad board, and not on the good one. Almost like there is a parallel conducting path to the TIP122. When graphed, it is clear the gain is the same from 3.5V on, but there is an offset in current due to the bad board conducting before the TIP122 turns on (or so it seems). The capacitors are in the same on both boards. I wish I had a schematic for this circuit.


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## JRP3 (Mar 7, 2008)

The assembly instructions say there are 3 TO-92's.
http://www.voltblocher.com/uploads/Volt_Blocher_Li_v2.01__Assembly_.pdf


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## Travdude (May 11, 2009)

To-92 is a transistor case size i believe.

I just assembled 45 Voltblochers and they all work fine. One thing that would be very easy to do while assembling them would be to switch the transistors because they look identical and the labels are very small and hard to read.


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## tomofreno (Mar 3, 2009)

> The assembly instructions say there are 3 TO-92's.


 Oh, I see. TO-92 is a package designation. Yes there are three components in this packaging. One is an LM431, a precision zener shunt regulator, the same voltage reference the Fletcher-Goodrum board uses. Another is a MCP131, a voltage supervisor, and the third is a 2N3906, a PNP transistor. These are all in the same places on the two boards. I recall Brian saying something in his write up about changing out the voltage supervisor if you need a different range for setting the HVC. It is looking to me like a faulty component, as I have found no assembly error or bad soldering yet. I guess Coulomb was referring to the LM131 since that should be providing the bias for the TIP122. I'm pretty confident that the bias is the same on the two boards as I said, because both TIPs turn on at 3.50V. Current is leaking through a fairly constant resistance on the bad board at voltage levels below 3.50V.

Tom


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## Coulomb (Apr 22, 2009)

tomofreno said:


> I guess Coulomb was referring to the LM431 since that should be providing the bias for the TIP122.


Actually, I ws thinking that the voltage reference would have a constant voltage across it that you could check, but this is not the case. It would be useful to know whether the reference inputs (across the ends, ignoring the middle pin) are the same on both boards at the same input voltage of say 3.2 V.



> I'm pretty confident that the bias is the same on the two boards as I said, because both TIPs turn on at 3.50V. Current is leaking through a fairly constant resistance on the bad board at voltage levels below 3.50V.


Well, not really. Yes, there is a constant drain at very low input levels; that sounds like a resistor across the cell or a very leaky darlington. But the current starts increasing too early; on the bad board, the current starts increasing non-linearly at about 2.2 V, and by 3.4 V is equivalent to a resistance of about 8.3 ohms.

So I'm back to predicting a leaky darlington, and it's starting to amplify the leakage at 2.2 V or so.

I'm guessing that the ~0.01 A (~10 mA) current from the good boards at about 3 V input is the low voltage OK opto LED turning on. That seems a little high for the low voltage LED circuit to come on, but that may be the resolution of your meter, presumably set to the 10A range.


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## Coulomb (Apr 22, 2009)

A quick check to see if it's the darlington would be to lift the base lead of the bypass transistor, and short it to the emitter. If the vast majority of the current goes away, then the transistor is OK. If most of it stays, the transistor is bad.


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## Coulomb (Apr 22, 2009)

Oh, internal resistors on the TIP122. No need to short base to emitter, just lift the base lead.


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## tomofreno (Mar 3, 2009)

> So I'm back to predicting a leaky darlington, and it's starting to amplify the leakage at 2.2 V or so.


 I would expect current to increase exponentially with voltage when the darlington turns on, as it does at 3.5V, not linearly as it does at 2.2V. Something definitely changes at 2.2 volt, but there appears to be a constant resistance of about 26 Ohm below this, and about 8 Ohm above it all the way to 3.5V. I could believe there is some problem with the darlington. The leads are cut off very short, making it very difficult to lift one. Easier to remove it. I'll see how quickly I can get some more TIP122's and replace it. I might de-solder one from a good board to replace it, but then I add the unknown of whether I overheated it de-soldering it. Any other guesses? How about leakage through the LM431? The curve kind of looks like a superposition of current through a resistance (except for that change in slope at 2.2) and current as expected through the darlington.

Tom


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## dimitri (May 16, 2008)

> How about leakage through the LM431?


That would make red LED come on, which does not, does it? If red LED is installed correctly and does not come on, then culprit is most likely a leaky TIP122.


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## tomofreno (Mar 3, 2009)

> That would make red LED come on...


 Oh, that's good to know. No, the red LED comes on at 3.5V as on the good boards.


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## dimitri (May 16, 2008)

That bench DC supply is awesome to bring individual or small groups of cells up to full charge. Have you tried to charge up those 2 cells which are supposed to recover? Just set dials on DC supply to whatever HVC you want the cell at and let her rip  , watch the current drop as it gets closer to final voltage. If they suck current for hours and don't heat up, they are OK. I would do one cell at a time since they are at different SoC levels now.

You should probably charge these 2 to same voltage as other cells have, to avoid significant imbalance. It would be more difficult to balance the pack later if some cells have large difference in SoC.

I used my bench supply to bring couple of cells up to par with the rest of the pack, it works great. As you watch current display and time, you can see how many AH you put in.


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## tomofreno (Mar 3, 2009)

> That bench DC supply is awesome to bring individual or small groups of cells up to full charge. Have you tried to charge up those 2 cells which are supposed to recover? Just set dials on DC supply to whatever HVC you want the cell at and let her rip
> 
> 
> 
> ...


 Yep, that's what I plan to do today. I'll set it at 3.27V in constant voltage mode, and after charging check that they remain at 3.26V or above (most cells are 3.26-3.27V), if not charge a bit more. That's how I partially justified purchasing the ps. 

I also plan to check the boards on the other lower cells today and see if they display the same I-V characteristic. If it turns out to be a leaky darlington on all (not at all sure this is the case of course), I may well replace them on the bad boards , replace the pot with a fixed resistor, and hook them back up. These are evidently 3 layer boards as I cannot see traces on the front or back from many component leads. Could be an issue with a trace on that inner layer.

Tom


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## JRP3 (Mar 7, 2008)

So EVC isn't taking the VB's back and refunding the money? If you put them back on and have more problems will they still warranty the cells?


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## tomofreno (Mar 3, 2009)

> So EVC isn't taking the VB's back and refunding the money? If you put them back on and have more problems will they still warranty the cells?


 They will. I seriously doubt it, as they don't trust the VB's. I expect it would be my liability from then on. 

Tom


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## tomofreno (Mar 3, 2009)

Some more data from VBs. The graph is current versus voltage. The label in the legend refers to the final discharge voltage of the cell that VB was mounted on. There is a fairly good correlation with resistance below 3.5V and final voltage to which the cells discharged. The VB from the cell that discharged to 2.98V is a bit squirrely. The current drifted over about 15 seconds from around 0.10 to 0.18A at the 3.0V setting. This drift is repeatable. All other readings for this and other VBs were stable. At 3.6V all are very touchy. Turning the V dial just slightly so the digital readout remains at 3.6V results in a large change in current as the TIP turns on. Typically about 0.8A to 1.5A, but I, 2.98 went up to 1.7A. The ps is charging up the low cells nicely. 

View attachment VB I versus V.pdf


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## Coulomb (Apr 22, 2009)

tomofreno said:


> These are evidently 3 layer boards as I cannot see traces on the front or back from many component leads. Could be an issue with a trace on that inner layer.


I'd be very surprised if such a simple board needed to go to three layers. A lot of the tracks seem to be on the top of the board, which is obviously hard to get to. Did you say you had some spares? It might be worth (at least part) depopulating one so you can do comfortable tracing, and then you have some parts spare. If you test the board first, and find it's a known good, then you have some known good parts for substitution.

On the new (pdf) data, it seems to me that the worst board (0.67) is rather different to the other bad boards. None of the others has significant current under 2 volts. Though it's possible that the bad one is the same as the others, just magnified.

I'm starting to think that this could be a design issue. Maybe the combination of an LM431 with higher than typical leakage (but still within spec), combined with higher than typical gain on the TIP122, might cause this excess current. In that case, replacing either component with a new one might fix the problem, or (in rare cases) make it worse.

It would help me to see the actual circuit diagram; the assembly instructions seem to indicate that the schematic comes with the blochers, but it's not (as far as I can find) on the http://www.voltblocher.com/ site. I've recently co-designed the BMS for a conversion, and it went through a lot of iterations, so I may be able to help here. It would be nice to get to the core of the problem, for you and for any others that may have these boards.


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## dimitri (May 16, 2008)

> I'm starting to think that this could be a design issue. Maybe the combination of an LM431 with higher than typical leakage (but still within spec), combined with higher than typical gain on the TIP122, might cause this excess current.


LM431 does not drive TIP122 directly, there is another transistor in between, 2N3906. Like I said, if LM431 was opening too soon, then red LED would come on as its driven by 2N3906 along with TIP122. Since LED is off, this points the issue to TIP122 leaking, perhaps they are installed too close in the PCB with leads cut off too close to the case and overheated during soldering. I don't know how else to explain it, I assembled over a hundred of these kits and every single one worked fine. In my case, however, TIP122 is mounted horisontally with long leads between the case and PCB.


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## Coulomb (Apr 22, 2009)

dimitri said:


> LM431 does not drive TIP122 directly, there is another transistor in between, 2N3906.


Right, a 1-transistor (PNP) inverter and amplifier.



> Like I said, if LM431 was opening too soon, then red LED would come on as its driven by 2N3906 along with TIP122.


I'm not so sure. A darlington can start conducting at 0.8 V (0.4 V per junction), and I'm pretty sure you won't see even a red LED lighting at 0.8 V.



> I don't know how else to explain it, I assembled over a hundred of these kits and every single one worked fine.


You might have been lucky with batches of components that didn't have the bad combination (e.g. leakage and gain near the top end of specifications for the LM431 and the two transistors respectively).



> In my case, however, TIP122 is mounted horizontally with long leads between the case and PCB.


Ok, so that's a possible difference with Tom's boards, but really with a TO-220 package, I find it hard to believe that soldering heat would be an issue.


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## tomofreno (Mar 3, 2009)

> ...perhaps they are installed too close in the PCB with leads cut off too close to the case and overheated during soldering...


 The leads are very short, about 1/10", so the device junctions could have been overheated.

If I just remove the TIP122 from a board will this affect functioning of HVC and LVC? Would you be willing to post a schematic of the board?


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## tomofreno (Mar 3, 2009)

I removed the 1.5 Ohm shunt resistor from the bad VB board and verified both HVC and LVC work as before. It did not affect the current draw below 3.5V though. Current versus voltage below 3.5V is the same as it was with the resistor in place.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> I removed the 1.5 Ohm shunt resistor from the bad VB ... It did not affect the current draw below 3.5V though. Current versus voltage below 3.5V is the same as it was with the resistor in place.


Interesting. So it's not leaking through the collector. So you're saying there is still ~400 mA at 3.2-3.4 V? Or are you counting that as the 3.5 V bypassing coming on?

400 mA is difficult to explain without the large transistor. I guess the 2N3904 could pass that much current, for a short period, just. It would get burning hot, though; surely you would have noticed that.

Oh, I'm assuming that the collector of the transistor is now open circuit. There is still the possibility that it is shorting to somewhere it shouldn't. I guess taking out the transistor altogether (all 3 leads) is the next logical step, just to make sure.


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## dimitri (May 16, 2008)

Tom,

this makes no sense, there isn't any other stage in the circuit capable of 200 mA except TIP122 and power resistor. With resistor removed I don't know what else can be passing so much current. All other stages go thru 1K or 0.5K resistance, so can't pass more than 5-10 mA.

Of course I am going by my schematics, which used to be same as VBs in older version, not sure if Brian changed something. Have you Emailed Brian for help? I'm sure he could supply schematics for you.

BTW, just assembled 45 more modules today for a forum member, each one is working perfectly, 5 mA current until HVC, then 2 A.


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## Coulomb (Apr 22, 2009)

dimitri said:


> This makes no sense, there isn't any other stage in the circuit capable of 200 mA except TIP122 and power resistor.


The current might be going into the base-emitter of the TIP122. If the resistors on a good board should be such that no such current is possible, then a resistor must be too low in value, or there is a short. But as you point out, there isn't anything legitimate that the base could short to that could cause that sort of current and not get stinking hot. 

If the capacitor was in backwards, it might conduct that sort of current, and might have enough bulk to not heat up noticeably over a short period of time, like the time of the test. Without the circuit, I don't know if that would cause the problem.


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## tomofreno (Mar 3, 2009)

> So you're sayhing there is still ~400 mA at 3.2-3.4 V? Or are you counting that as the 3.5 V bypassing coming on?


 Yes, as I said, the current versus voltage data below the point the TIP turns on at a bit above 3.5V is the same as when the 1.5 Ohm resistor was in. I'm controlling voltage and reading current off the ps display. I was very surprised the readings were pretty much identical below 3.5V. I expected to see the current remain low for all voltage settings.


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## tomofreno (Mar 3, 2009)

> Oh, I'm assuming that the collector of the transistor is now open circuit.


 the collector (center pin) is tied to the positive terminal. Looks to me like the emitter is tied to the 1.5 Ohm resistor, base to the output of the pnp. Appears this same pnp output drives the red LED through a resistor and the pot to ground. With the 1.5 Ohm resistor removed I measure 760 Ohm non-rectifying between the emitter and base of the TIP122. Resistance to other components on the board appears to be > 20kOhm (didn't check the LTV826 pins).


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## tomofreno (Mar 3, 2009)

> Have you Emailed Brian for help?


 Yes. I emailed him some questions and he was helpful, but he hasn't responded to the last email I sent several days ago. 

What does the voltage supervisor do? It appears two of its legs are tied between the positive and negative terminals of the board. It is determining the resistance between them with no power to the board, which is only 31 Ohm.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> the collector (center pin) is tied to the positive terminal.


Oh, voltage follower. Not the way I'd do it. Ok.



> Looks to me like the emitter is tied to the 1.5 Ohm resistor


And nothing else, right?



> With the 1.5 Ohm resistor removed I measure 760 Ohm non-rectifying between the emitter and base of the TIP122.


Sure it's not 7.6 K, i.e. 7600 ohms? According to the Fairchild datasheet, it should be 8K in series with 120 ohms. If it really is 760 ohms, then either this TIP122 is very different to the Fairchild ones, or is faulty.

I was going to say that the resistance should be less in the forward direction (positive lead on the base), but multimeters usually don't put much current into their resistance measurement, so the 8K (or certainly 760 ohms) would swamp that.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> What does the voltage supervisor do?


It is a circuit designed (as I understand it) to keep the reset input of a microprocessor low while a board is being powered up. This avoids unwanted behaviour (like firing a missile without authorisation ) because the circuits aren't within spec until the voltage comes up.

In this case, it is emitting a logic signal that depends on whether the voltage across the chip has reached a certain threshold, often about 2.1 V. So this will be determining the low voltage cutoff. It's possible it is driving the opto it's connected to too early, which could possibly explain the 0.01 A at 0.2 and 0.4 V, except that the opto wouldn't turn on at all at those voltages. Also, the current keeps increasing too fast, so at this stage, I'd say the whole low voltage part of the circuit is off the hook.



> It is determining the resistance between them with no power to the board, which is only 31 Ohm.


If you mean a multimeter across the cell terminals (with no cell connected) reads 31 ohms, then that certainly explains the low voltage behaviour, up to about 2.2 volts. I bet a good board doesn't measure 31 ohms. That 0.1 A will drain a 100 Ah cell (from full to dangerously low) in about 1000 hours, or about 40 days. They probably come from the factory about half full, so ~ 20 days or less.

You could do worse than taking components off (especially transistors and the capacitor) until it reads much higher than 31 ohms.

Edit: would explain -> could possibly explain


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## tomofreno (Mar 3, 2009)

> Sure it's not 7.6 K, i.e. 7600 ohms?


 You are correct. I thought I had the dvm on 2k range but guess I had it on 20k.


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## tomofreno (Mar 3, 2009)

> Also, the current keeps increasing too fast, so at this stage, I'd say the whole low voltage part of the circuit is off the hook.


 From what I can surmise of the circuit design, it appears there are 5 current paths between the positive and negative terminal leads: through the voltage supervisor, through the pnp/red LED/resistor/pot, through the TIP122/1.5 Ohm R, through two resistors in series with the LM431, and through the green LED/resistor/pot. Maybe I'll pull a resistor from these paths one at a time and see how the circuit behaves.


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## tomofreno (Mar 3, 2009)

> In this case, it is emitting a logic signal that depends on whether the voltage across the chip has reached a certain threshold, often about 2.1 V.


 It seems the current below 3.5V might be due to leakage through this device, with the two slopes due to something changing internally in the device at some threshold voltage. The graph show that even after the TIP turns on the current on the bad boards is offset higher than the good board by the magnitude of the current just before the TIP turned on.


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## dimitri (May 16, 2008)

Sounds like LVC supervisor ( Microchip TC54 unless Brian changed it recently ) could be faulty and conducting without any resistor limiting it.

My schematics is a bit different on LVC, I have additional voltage divider, which is why TC54 cannot conduct more than resistors allow. I think Brian went a different way, choosing specific TC54 model for specific LVC value and connected it directly across cell terminals, which is fine unless TC54 fails and opens wide.

You can just remove TC54 and see if current disappears...


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## tomofreno (Mar 3, 2009)

I clipped off the voltage supervisor. Zero current below 3.5V.


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## tomofreno (Mar 3, 2009)

> Zero current below 3.5V.


Well, zero at the about 5mA resolution of the ps display.


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## dimitri (May 16, 2008)

tomofreno said:


> I clipped off the voltage supervisor. Zero current below 3.5V.


Wow, so I guess we have the answer, faulty or burned during assembly LVC detectors. 

Although I regret to hear about your troubles, I'm a little glad that I went a different way on my modules, in my case a failed TC54 will not drain a cell anymore than green LED does.

Again, simple QC procedure with checking current leak would immediately reveal this problem before shipping to a customer.

Several lessons learned here, thanks Tom for sharing.


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## tomofreno (Mar 3, 2009)

I clipped the leads because I couldn't melt the solder well, even with my larger iron which I use for 18 awg and larger wires. It is much higher temperature solder than what I use. I mainly pulled the 1.5 Ohm resistor off yesterday, with slight melting. My guess is the voltage supervisor was overheated too much on the "bad" boards. I'm pretty busy today, but maybe I can check some other bad ones to confirm.


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## tomofreno (Mar 3, 2009)

> You can just remove TC54 and see if current disappears...


 Heh, heh, I was out clipping it off and measuring current when you wrote this. It seemed that had to be it as no other path could offer 31 Ohm resistance.

So as you say it is a combination of design issue and assembly issue. The design is very susceptible to failure of this device as it can short the terminals.

Thanks for your help Dimitri, Coulomb.


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## tomofreno (Mar 3, 2009)

Well, I couldn't stand the suspense so I clipped the voltage supervisor off another bad board and measured current versus voltage (with 1.5 Ohm resistor on the board). It worked as it is supposed to, zero current on the ps display up through 3.2V, then 0.01 at 3.4 and 3.5V, then the TIP122 turned on at just above 3.5V giving about 1.09A at 3.6V and 1.42A at 3.7V. So the cause of failure is confirmed. Better get to work on other things now.


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## dtbaker (Jan 5, 2008)

so.... for those of us just barely able to follow along, can you summarize whether you would use the VB units again? Or something specific to inspect or check for prior to installation?

In your opinion.... if you were doing it again, would you go with the VB units, or a central BMS like the ElCon (as a minimal BMS protecting over/under voltage and monitoring temp) for about the same price...


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## dimitri (May 16, 2008)

dtbaker said:


> so.... for those of us just barely able to follow along, can you summarize whether you would use the VB units again? Or something specific to inspect or check for prior to installation?
> 
> In your opinion.... if you were doing it again, would you go with the VB units, or a central BMS like the ElCon (as a minimal BMS protecting over/under voltage and monitoring temp) for about the same price...


Dan, do you have a link to this ElCon BMS? Is it available for purchase? Where and what cost?

Thanks


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## dtbaker (Jan 5, 2008)

dimitri said:


> Dan, do you have a link to this ElCon BMS? Is it available for purchase? Where and what cost?
> 
> Thanks



oops, I got the name wrong... I remembered the name of the CHARGER I was looking at because it was the most reasonable price I could find on something with truely programmable curves. The ElCon PFC 3000 retailing for $1099 at KTA: http://store.kta-ev.com/Battery_Chargers/PFC-3000_Charger.aspx

The BMS I was looking at (also from KTA) as a minimal active over/under voltage plus thermal and optional datalogging is something called the Hardy EV BMS-48.... for $998 that handles up to 48 cells. I am probably going with 120v (40 cell) build.... so this might do it?
http://store.kta-ev.com/Battery_Management_Systems/BMS_48_cells.aspx

I like the idea of it being centralized, and off-the-shelf.... But I sure would like to hear/see somebody else who has used one! Especially since it looks like the Volt-Blochers will be DIY at the very best unless somebody else starts building them.


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## JRP3 (Mar 7, 2008)

Good detective work Tom, with support from Dimitri and Coulomb of course.


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## Coulomb (Apr 22, 2009)

Coulomb said:


> so at this stage, I'd say the whole low voltage part of the circuit is off the hook.





Tom said:


> I clipped off the voltage supervisor. Zero current below 3.5V.


Huh!  Looks like I was utterly and completely wrong there. Somehow I was dismissing faulty components.

I don't suppose you checked if it was installed the right way?

Is it a different brand to the equivalents on the good boards? Perhaps a slightly different part number from the good ones?


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## Coulomb (Apr 22, 2009)

tomofreno said:


> It seems the current below 3.5V might be due to leakage through this device, with the two slopes due to something changing internally in the device at some threshold voltage.


Yes, of course! The LVC turns on at around 2.1 V.



> The graph show that even after the TIP turns on the current on the bad boards is offset higher than the good board by the magnitude of the current just before the TIP turned on.


Another clue!

With the enormous benefit of hindsight,  there were a lot of clues pointing to this device. I totally missed all of them.


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## Coulomb (Apr 22, 2009)

In my defence though, surely the LVC would get burning hot at about 3.4 V?

Well, the one from the first board should have. The others, which would seem to have less leakage, may not get anywhere near as hot.

Perhaps when you're testing the next one, you could see if that thing gets warm at least when you're at about 3.4 V?

I wonder if this was a victim of the leadless solder that is used these days? I know it has different temperature characteristics, but not exactly what those differences are.


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## tomofreno (Mar 3, 2009)

> In my defence though, surely the LVC would get burning hot at about 3.4 V?


 I don't know. Didn't check it. I should have checked for something getting hot. I was concentrating on the rest of the circuit assuming the optos and this supervisor weren't in a current path between the two terminals - until I finally measured the resistance between its leads and the terminals and found it was directly connected to them. I of course don't know whether the devices were faulty before soldering or overheated during soldering. The solder is quite high temperature though, and the leads are short. The supervisors look the same on good and bad boards. I compared every component on the good board with a magnifying glass - part number, color, position...


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## tomofreno (Mar 3, 2009)

> so.... for those of us just barely able to follow along, can you summarize whether you would use the VB units again? Or something specific to inspect or check for prior to installation?


 I don’t like the VBs susceptibility to this failure mode. If assembled properly and QC’ed, the probability of this failure is very low as Dimitri has said. But I am just wary now because I was burned by it. Of course in normal use, charging everyday or two, you would have to keep careful track to even notice the effect of this failure. My cells with the bad boards discharged because I left them sitting for 2 1/2 weeks without charging. As far as checking them, Dimitri and Brian have already pointed it out - run current versus voltage curves like I posted on each board after assembly. They should all look like the good board, less than 10mA current up until the TIP122 turns on to bypass current.  A resistive divider like Dimitri uses would reduce the effect of this failure mode to loss of LVC, but of course that might result in over-discharge of cells if you are expecting an LVC warning and don’t get it. [edit: this is incorrect. The LVC function worked on the defective boards, the supervisor chips just leaked.]

 After the discussion on balancing on the other thread, I’ve thought about it some more. I used to think that internal cell resistance could lead to imbalancing but then I realized that it can only affect energy required to move the charge, not how much charge moves into or out of the cell. That leaves only differences in capacity to lead to unbalance. That seems to be pretty small on new cells purchased together as evidenced by Jack’s and Dimitri’s cells. It will likely worsen as they age due to changes in the cathode material affecting the number of sites, and access to sites for lithium ions. But who knows how much, and how long that will take? Maybe you only need to balance once every 4 -6 months . In this case it might not be too inconvenient to just use a 5A ps or charger on individual cells. You mainly care about balancing to avoid over charging or discharging a cell. If you charge to about 95% of pack capacity (capacity of lowest capacity cell) like I intend to do, and discharge to 30% soc or 20% worst case as I also plan, then the “ragged edge” of soc as Jack aptly called it doesn’t affect you unless it gets quite ragged – whether at the top or bottom. Checking cell voltages every month or so would keep track of this and see when you should balance. Of course JRP3 was way ahead of the curve on this, but only because he is so parsimonious.

So right now I am thinking of a board that just does HVC and LVC signals. The HVC signal would simply turn off the charger, and LCV would sound a buzzer and/or turn on a light as Dimitri does ( I installed a buzzer so it turns on the “check engine” light and sounds the buzzer). Jack has said cell voltage frequently drops to 2V or so when drawing large amps during acceleration or going up a hill. If it does this even when the cells are above 30% soc, the LVC warning will be annoying and possibly ignored for too long. If this is only the case at 30% soc or less, I think that is exactly what you want. It would give you an early warning during acceleration that you are getting low, but you still have sufficient charge to drive at moderate speed to home or a charging station. Dimitri, when does your LVC come on?

For an off the shelf solution, you might check the Chinoz chargers. They make a bms that shuts off the charger based on cell voltage. Don’t know if they offer LVC. Maybe that is what kta-ev is selling. I’m keeping tabs on HPGC’s bms development, as it manages regen also, and uses the Curtis controller as the bms controller using their VCL code.

For the interim, I’ll likely just go without a bms, charge to 95% soc or so, and discharge to 30%. Watch the TBS gauge for soc, set the voltage limit on the charger for 124V or 3.44V/cell out of 3.6 for SkyEnergy full charge, and lift the box lids and measure cell voltages a couple times per week with a dvm – maybe near bottom before I hook up the charger, and at top when it is done so I see how much capacities differ, and whether balance is changing. It’s pretty easy. I have printed maps of the cells in their boxes on a clipboard. I just probe a cell and write the voltage on its image on the map.

There is lots going on. Davide is working on a new, lower cost bms, Otmar is supposedly working on one, HPGC...I'll bide my time and check them out I think. 'Course all that could change in a few weeks if I find that cells aren't staying well enough balanced. Either way, I'd prefer not go without LVC and HVC for too long, just for more peace of mind. Have to wait and see how much of an issue balancing is.

Tom


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Of course JRP3 was way ahead of the curve on this, but only because he is so parsimonious.


You can say it, I'm cheap!  If I can find a good reason to keep a dollar in my pocket I'll do it. As I pointed out, for the price of a set of VB's I can kill 5 cells and still be out less money. Some of these balancing solutions cost one quarter or more of the total pack.


> So right now I am thinking of a board that just does HVC and LVC signals. The HVC signal would simply turn off the charger, and LCV would sound a buzzer and/or turn on a light as Dimitri does ( I installed a buzzer so it turns on the “check engine” light and sounds the buzzer). Jack has said cell voltage frequently drops to 2V or so when drawing large amps during acceleration or going up a hill. If it does this even when the cells are above 30% soc, the LVC warning will be annoying and possibly ignored for too long.


 Some sort of time delay might be useful in this case, so that momentary drops to 2V do nothing but sustained 2.8V or so would trigger the alarm. Of course I have no idea how to implement that.


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## tomofreno (Mar 3, 2009)

I've been recharging the cells (180Ah SkyEnergy) that were partially discharged by the bad VB's and thought I'd share some data. I'm charging at 5A using a small power supply. The cell that was at 1.8V charged to 3.0V in about 1 3/4 hrs. That's around 8.75Ah. So as Jack has pointed out, there isn't much charge available from the cell below 3.0V. 

It took another hour to charge it from there to 3.2V. Then another hour to go from 3.2 to 3.25V. A bit over an hour from 3.25 to 3.26, and around 75 minutes from 3.26 to 3.27. You can see they pretty much follow the SkyEnergy discharge curves, with quick change in voltage with charge/discharge when they are low, and slow change above about 3.2V. The 3 cells I've charged so far gain around 0.007 to 0.01V/hr at 5A charging over the part of the SkyEnergy discharge curve from 3.2 to 3.3V. So at 100A discharge I would expect roughly about 0.14 to 0.2V per hour drop neglecting sag. The cells may well behave a bit differently at higher discharge current, but this gives some rough estimate.

Tom


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## tomofreno (Mar 3, 2009)

> A resistive divider like Dimitri uses would reduce the effect of this failure mode to loss of LVC, but of course that might result in over-discharge of cells if you are expecting an LVC warning and don’t get it.


 Not sure what I was thinking here. This is incorrect. The LVC function still worked on the boards with defective supervisor. It just leaked.


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## tomofreno (Mar 3, 2009)

> You can say it, I'm cheap!  If I can find a good reason to keep a dollar in my pocket I'll do it.


 Thrift and efficient use of resources is an admirable trait.



> As I pointed out, for the price of a set of VB's I can kill 5 cells and still be out less money. Some of these balancing solutions cost one quarter or more of the total pack.


 Good point. But then that is not efficient use of resources. I want the cells to last a long time. Long enough that there is a well-established recycling industry developed by the time they go bad.


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## tomofreno (Mar 3, 2009)

Kudos to Dimitri for looking into design of a low cost HLVC board! See his thread under the Batteries and Charging forum. Some good ideas.


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## tomofreno (Mar 3, 2009)

> Some sort of time delay might be useful in this case, so that momentary drops to 2V do nothing but sustained 2.8V or so would trigger the alarm. Of course I have no idea how to implement that.


 I'm not sure this is what you want. If it only triggers at 2.8V at lower steady current draws, then you have very little energy left, and if you need to accelerate you will use most of it up. I think I would like something that says whoa, you've got energy left, but not enough to sustain that high discharge rate for very long!


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## JRP3 (Mar 7, 2008)

2.8 is probably too low, but if you knew when the lowest cell hit maybe 3V or whatever for a predetermined period of time as opposed to a short burst that should allow you to avoid disaster. Remember if you have properly sized your pack this should be a rare occurrence. I want the cells to last a long time as well, and I doubt I'll end up killing any of them, let alone 5, I was just pointing out you have some margin of error before you even come close to what you could spend on a BMS. If Dimitri or someone can come up with a simple cheap HLVC board that can't damage the cells if it fails that would be great. Even just LVC is all you might need.


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## Coulomb (Apr 22, 2009)

My AU$0.02: you seem to be wanting to use battery voltage as a sort of binary fuel gauge (above or not above "almost empty"). Voltage is a poor indicator of SOC, especially for Lithium.

The point of the LVC is supposed to be protection for the cells. It should tell the controller to back off current immediately (driver reaction time will likely be too slow). This is for unusual situations only, e.g. a weak cell, bad connection, or cell badly unbalanced with the rest of the pack. You don't want to use this every day, because it could take away power when you need it to avoid a collision.


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## JRP3 (Mar 7, 2008)

Problem is that a healthy cell with good charge may still drop below your threshold under hard acceleration, which is fine, but you don't want it cutting the controller at that point. Near the ends of the curve cell voltage does seem to be a good indicator of charge. You shouldn't rely on it as your fuel gauge, ideally you never get near it, but if you do you want a warning.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> Problem is that a healthy cell with good charge may still drop below your threshold under hard acceleration, which is fine, but you don't want it cutting the controller at that point.


Hmmm. Looks like we're in for a surprise, and some sort of adjustment to get the right compromise between cell safety and usability.

Our LV threshold is 2.5 V, and we're using Sky Energy cells, which supposedly go down to 2.0 V. Luckily, changing the LV threshold is a simple matter of replacing 208 SMD resistors!


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## JRP3 (Mar 7, 2008)

In his testing Jack seems to have concluded there is not much left below 3V and things start dropping quickly below that. If you're at 3V on low draw you're getting near the end. 2.5 seems too low, 2.0 much too low other than a momentary sag under high amps.


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## tomofreno (Mar 3, 2009)

> If you're at 3V on low draw you're getting near the end. 2.5 seems too low, 2.0 much too low other than a momentary sag under high amps.


 My cell that was at 1.8V charged to 3.0V in about 1 3/4 hour at 5A. If you are accelerating and pulling say 400A or 80x as much current, then you would go from 3.0V rest voltage to 1.8V rest voltage in about 1 1/3 minute.


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## tomofreno (Mar 3, 2009)

> but if you knew when the lowest cell hit maybe 3V or whatever


 I was thinking, the charger supplies current through the shunt so I can read DC current into the cells during charging on the TBS gauge. Then I can record time and know how much Ah charge I put into the cells. After I have gone through a couple charge/discharge cycles monitoring cell voltages, I should be able to identify the lowest capacity cell as the one with the largest voltage change during charging, and know it's capacity from the Ah data. Then I just enter this Ah capacity on the TBS gauge for the pack capacity, so it reads soc based on the capacity of this cell. If the cells remain fairly well balanced, I would not be in any danger of over-discharging this cell, or any others, if I stop driving by 20% soc. This should be quite safe if I monitor cell voltages at regular periods to see if capacities/and or balance have changed. If another cell should become the lowest capacity, I just enter its capacity in the TBS. If they become too imbalanced, I re-balance them by charging lower cells with a ps.

Tom


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## JRP3 (Mar 7, 2008)

I plan something similar, though I'll do my initial charging at 120 volts AC through a Killawatt meter and use those numbers times 90% to get actual DC energy used.


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## dimitri (May 16, 2008)

tomofreno said:


> I used to think that internal cell resistance could lead to imbalancing but then I realized that it can only affect energy required to move the charge, not how much charge moves into or out of the cell. That leaves only differences in capacity to lead to unbalance.


I still disagree with this, you seem to ignore the difference in heat dissipated by cells with higher IR, that heat is the energy lost, not used to drive and not recovered during charge, so this small loss will keep adding up with each cycle. True, charge and discharge move equal amounts of energy across all cells, but difference in heat losses due to difference in IR will evenually create an imbalance. I can't wrap my head around calculating this yet, my cells have approx 5 milliOhm difference in IR between best and worst cells, I need to turn this into Watts lost in heat on each cycle to see how much it adds up over long term.
Of course it doesn't help in my case since PakTrakr eats a little from some cells, so I have to manage imbalance even if there was no IR differences. I like PakTrakr, but I hate its many shortcomings.



> Dimitri, when does your LVC come on?


I have TS cells and my LVC is 2.6V , which I find perfect balance between not alerting too soon during occasional sags, yet decent enough alert to prevent damage. However, I think 50% throttle reduction is the key, it still lets you get out of traffic, but saves the cell from even deeper sag as you intuitively keep pressing the pedal regardless of buzzer ( ask me how I know this  )

My opinion : if you sag your cells so much that you hit LVC while over 30% of SoC, then you have bigger problems, like seriously undersized pack for your car 



> There is lots going on. Davide is working on a new, lower cost bms, Otmar is supposedly working on one, HPGC...I'll bide my time and check them out I think. 'Course all that could change in a few weeks if I find that cells aren't staying well enough balanced. Either way, I'd prefer not go without LVC and HVC for too long, just for more peace of mind. Have to wait and see how much of an issue balancing is.


EVen though I started the poll thread, I am not convinced that I can compete with all these guys, especially EV Power, which offers almost the same product as I have planned, although still at $16-$20 per cell. Low cost is the key, but high quality is also critical, and as we all know, managing both in one product is not easy.


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## tomofreno (Mar 3, 2009)

> I still disagree with this, you seem to ignore the difference in heat dissipated by cells with higher IR, that heat is the energy lost, not used to drive and not recovered during charge, so this small loss will keep adding up with each cycle. True, charge and discharge move equal amounts of energy across all cells, but difference in heat losses due to difference in IR will evenually create an imbalance. I can't wrap my head around calculating this yet, my cells have approx 5 milliOhm difference in IR between best and worst cells, I need to turn this into Watts lost in heat on each cycle to see how much it adds up over long term.


 My comment was that they all accumulate and loose the same amount of charge. But I don’t think consideration of energy shows an imbalance either. Due to current continuity all the cells will accumulate the same amount of charge during charging, and loose the same amount during discharge. The energy into the cells during charging will be different if they have different internal resistances. The charger has to do more work to move charge into the cells with higher internal resistance. A higher ir will result in higher voltage across the terminals of those cells for a given charging current. Work is the product of charge and voltage, so the charger does more work, expends more energy, charging these cells, while these cells accumulate the same amount of charge as the other lower ir cells. But the charger is doing more work because the cell is dissipating more energy during charging due to its higher ir. The cell voltage is higher precisely by the amount required for the charger to supply this extra dissipated energy. If this higher ir cell has the same capacity as other cells, its rest voltage (no current through the cell) will be the same as the others after charge (assuming they were balanced in voltage prior to charge), so it will have the same stored energy as the other cells, qV. Same charge, same cell voltage due to same capacity. The excess energy output of the charger was dissipated as heat. The energy from the charger is equal the total energy into the cell, the increase in potential energy of the charge plus energy dissipated as heat.

During discharge the higher ir cells have larger voltage sag than others for a given discharge current, so the charge in these cells falls through a smaller potential drop than other cells as it flows out of the cell. The same amount of charge flows out of each cell by current continuity, so you get less useful energy out of these cells. The rest was dissipated as heat in the cells due to higher ir. The cells have all lost the same amount of charge, so if they have the same capacity they will all have the same cell voltage (again assuming initial voltage balance prior to charging). They also have the same energy, qV'. Less useful energy was obtained from those with higher ir, but all lost the same total energy, equal to the useful energy extracted plus the energy dissipated internally in the cell. The voltage sags due to this internal energy loss. With no ir there would be no internal energy loss, all charge in all cells would fall through the same potential through a pair of cell terminals, and all cells would supply the same useful energy.

Tom


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## tomofreno (Mar 3, 2009)

I think I mentioned that I noticed my parking brake didn't work when the car started rolling out of the garage when I removed the blocks I had put against the tires. Seems you can't drive an ev without a parking brake since you can't just leave it in gear to hold it as I did when it was an ice vehicle. I thought I just needed to adjust the parking brake cable, but no, that didn't have an effect. I pulled the rear wheels and found the brakes are self-adjusting and the teeth on this self-adjusting mechanism were worn down so it didn't work any more. The rear brake shoes had little wear as a result. I ended up having to order this mechanism from the dealer, along with the spline nuts, $110.00 total. I liked the old castelated nuts with cotter pin better than the spline nuts like these that have a sleeve you bend down into a slot on the shaft with a hammer/punch. Lot cheaper to replace the cotter pin when you do a brake job, and you don't have to order those (I'm a fairly parsimonious myself JRP3 ). After install, the parking brake works.

I also installed a piece of 1/8" thick polypro under the engine compartment to protect the motor from water and gravel (I have a gravel driveway). I bolted the front edge to the bumper (tucked up over the bottom edge), and adapted two 1/8" steel L brackets, which I bolted to my rear motor mount bracket and a bracket on the transmission, to hold the rear edge of the polypro. Pretty solid. Will reduce air drag too - maybe 1/4%?

I also noticed that I actually had six low cells not four. The additional two were only at 3.15 and 3.2V though. I recharged five up to the voltage of the other cells. Haven't tried to recover the one at 0.67V. I likely will at some point, but would be wary of its behavior after discharge to so low a voltage.

Not much to do now but wait for a replacement cell from evcomponents, which they said likely won't be for another week or more.


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## tomofreno (Mar 3, 2009)

Not much to do but wait for evcomponents to answer my emails and phone calls from last week about the VBs and a replacement cell, so thought I would post a photo showing an under-the-hood view now that it is complete:









The controller is on the far left, mounted on the rear motor mount bracket. To its right is the Manzanita PFC30. The gray box on top the PFC30 contains an EKM meter that reads AC V, I, phase, power, and energy. The aluminum box to the right of the PFC30 contains the contactor and shunt on one side, and the relays and potbox on the other side. The black box on top is the cell heater controller. The black object to the right of the aluminum box is the DC/DC converter - next to the 12V battery. There are 8 SE180 Ah cells in the blue box in front of these components. The small gray box in front of the battery box contains the charging plug, a NEMA14-30. It is under the hood when closed. The brake vacuum pump is mounted to a plate bolted to the rear motor mount. It is mounted vertically, underneath the rear of the PFC30. Total weight on the front axle is around 30 lb more than stock. The rear axle has about 300 lb more than stock (28 cells back there). I have not modified the rear suspension, as I am well under the GVW, and the additional load is equivalent to two 150 lb people in the back seat.


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## JRP3 (Mar 7, 2008)

Good work, it looks nice and neat. Are you also using the Curtis 840 display? I'm interested in seeing how it's "estimated" amp draw compares to reality. I'm hoping to get by only using the 840.


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## tomofreno (Mar 3, 2009)

> Are you also using the Curtis 840 display? I'm interested in seeing how it's "estimated" amp draw compares to reality.


 Not sure what you mean by estimated amps. HPEVS told me the 840 reads out voltage and current. I asked for clarification whether that was battery or motor voltage and current, and they responded battery pack voltage, and CONTROLLER current. I assumed they meant controller rms output current. 
With regard to regen, I plan to see how it behaves as programmed for "moderate" regen, but I would like to have more control over regen. I would like a pot mounted in the dash and connected to the brake pot inputs on the controller (J27, J17, J18) so I can apply more for braking downhill (assuming there is capacity in the pack), and less when I want to coast, ie, I'd like to use it as a brake pedal. You could operate a pot off the brake pedal, but seems this would be difficult due to changes in pedal movement over time. Maybe you could operate a pot only over the "dead band", free play, of the pedal. Then it would could be varied by lightly depressing the pedal, and be full on when the pedal is pushed fully to engage the mechanical brakes. Would still need a way to disable when the pack is full, unless you can ensure it never will be. Once I am comfortable operating the car, I'll likely look into what changes in VCL this would require and how much the hand held programmer cost. Alternatively, I could send the controller back to HPEVS to have them reprogram it. You could also then connect a resistor and ssr driven by the HVC output in parallel with the pot to cut back regen at high soc. HPEVS said their bms would be ready after the holidays (the prototype is in a vehicle now) and will control regen, so I'll see what it offers too.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Not sure what you mean by estimated amps. HPEVS told me the 840 reads out voltage and current. I asked for clarification whether that was battery or motor voltage and current, and they responded battery pack voltage, and CONTROLLER current. I assumed they meant controller rms output current.


I can't remember exactly who phrased it that way, but I think in one of my emails to HPG discussing the 840 display they mentioned "estimated amps". I'll have to see if I can find it.


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## JRP3 (Mar 7, 2008)

In an email from HPG:


> We can load our generic software into the controller. This will give you: Motor RPM, estimated battery amps, Motor Temperature and Controller Temperature on the display.


 Your EKM is reading motor amps?


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## tomofreno (Mar 3, 2009)

> Your EKM is reading motor amps?


 No. It reads AC current, voltage, phase, power, and energy from the wall during charging. the AC goes through it to the charger. The TBS Ex-pert Pro reads DC current into and out of the battery pack using a 500A shunt. HPGC told me the 840 reads motor rpm, motor temperature, controller temperature, controller amps, battery volts. Maybe they measure current into the controller with some approximate method that gives an estimate of battery current? Unclear to me why they would have responded "controller current" to me instead of "estimated battery current".


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## JRP3 (Mar 7, 2008)

I don't know. Maybe you can compare your TBS current readings with the 840 and get some idea.


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## tomofreno (Mar 3, 2009)

> I don't know. Maybe you can compare your TBS current readings with the 840 and get some idea.


 I'll do that. I also have an Extech clamp meter with true rms current reading (been wanting something like it for years, finally pried open my wallet and bought one - also measures DC current and has all typical dvm functions plus temperature probe and IR temp). I'll compare the above two current readings to a reading from this clamped on one motor/controller cable. It also has "peak hold" so I can record max current output per phase of the controller during acceleration. I can also record this and voltage sag at different temperatures for input for Dimtri's boards. Sigh, wish I could get that cell from evcomponents...lots of data to take.


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## tomofreno (Mar 3, 2009)

I got tired of waiting for a replacement cell from evcomponents and made up a cable to bypass it in the pack. I removed all the VBs and connected up my now 35 cell pack. 

I also received my PFC30 back from Manzanita. They said it only had a blow fuse on the output, no other problems. I hooked it back up the same exact way as before and this time it worked fine! My EKM meter was showing 247VAC input at 12A setting. It pulled down to 238V at very roughly around 25A setting. I turned the amp dial all the way up and the EKM showed 238VAC/43A! At 35A the EKM showed a bit over 4kW going into the charger.

Then I took the car for it's first real drive - about 8 miles. It has good acceleration and driving it feels similar to before. Unfortunately the transmission still whines loudly as it did before. Regen is also disappointing. Going down an approximately 3% grade in second gear the max regen was about 15A! I never saw over 16A, and usually only 10 or less when stopping. I expected 50 to 100A going down a hill. It did slow the car fairly quickly though on flat ground, and held it back significantly down the hill. I'll have to check this out. Maybe I have something set wrong. Max current was a bit over 300A when I floored it on level ground, and between 40 and 60A cruising at a bit over 35 mph on very slightly rolling terrain. I was glad to see this, as it looks like normal driving will be quite easy on my 180Ah cells. Temperature read by the sensor on a cell clamp was 40F when I left, and 40F when I returned. The 12V auxillary battery was at 12.84V when I left and at 13.23V when I returned, so the DC/DC is working. The pack was at 116.1V when I left and at 114.8V when I returned. What fun! Lots of data to take now! Time to set up an appointment at DMV.


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## dimitri (May 16, 2008)

Congrats Tom, I bet you had a real EV Grin on your face today


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## JRP3 (Mar 7, 2008)

Good deal. Does the transmission whine all the time or just under load? Were you able to compare the 840 amps with your other amp gauge? How fast did you take it and how did it feel?


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## tomofreno (Mar 3, 2009)

> I bet you had a real EV Grin on your face today


 You bet!! I'll try to get you some voltage sag data this week.



> Does the transmission whine all the time or just under load?


 Under load. I put in a new clutch and throwout bearing hoping that might have been the cause. No such luck. 


> Were you able to compare the 840 amps with your other amp gauge?


 No. I thought of that after I returned home. I'll check it tomorrow. 


> How fast did you take it and how did it feel?


 I only drove on secondary roads, so about 45 mph. It's peppy there. I could accelerate quickly up to 45. I think it would hit 60 pretty quickly too. I only used second and third gears. The motor drops in rpm pretty quickly when you release the accelerator thanks to electric braking. I think HPGC set it up like a golf cart - lots of safety features in the controller to prevent you from destroying the motor. It may be they have limited the the current draw to protect the controller/motor and that's why I only drew around 300A when I floored it. Or it could be because the pack was at 40F. I drove it up about a 5% grade for a short way and it zipped right up. Before long I was just driving it like a normal car, nothing special, except less shifting. I like it!!


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## DIYguy (Sep 18, 2008)

tomofreno said:


> Front battery box (under hood) with 4 of 8 cells in place and battery heater visible on RHS. AC50 behind and below it, box for charging plug on the front of it:
> View attachment 4374


Hey tomofreno....what are you using for battery box heating pads there? 

Thanks


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## 80N541 (Jan 11, 2009)

so this is happy hour time !

congratulation for your first real drive


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## tomofreno (Mar 3, 2009)

> what are you using for battery box heating pads there?


Farnam heater pads and controller from kta-ev. Each pad is 35W, 10 pads connected in parallel to the controller which runs off 120VAC. The idea is to heat the cells to 50+F prior to charging so they take a charge better. It has been around 20F low at night for a couple weeks here now, so I'll be getting some data on how well this works.


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## paker (Jun 20, 2008)

tomofreno said:


> Y Before long I was just driving it like a normal car, nothing special, except less shifting. I like it!!


How do you like the controller? How configurable is it? You mat have talked me out of my idea of using an 11" DC motor.


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## tomofreno (Mar 3, 2009)

> How do you like the controller? How configurable is it? You mat have talked me out of my idea of using an 11" DC motor.


 Assuming you use an appropriately sized controller, you will get much more torque and power from an 11" DC motor than the AC50motor/1238-7501 controller I am using. The latter makes my car zip because it is light, about 2250 lb. A heavier car would be more sluggish, and limited by the relatively low constant power rating of this motor/controller. I assume you were considering 11" rather than 8" or 9" due to desire for more torque and power.

The controller is very configurable using Curtis' VCL code, but I have not looked into it much. You might try Brian at Thunderstruck EV. I think he has.


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## tomofreno (Mar 3, 2009)

I drove the car to dmv today and got my exemption from smog. There is no inspection other than to ensure there is no ICE. It was already registered, licensed, and insured prior to conversion. None of that changes. Just don't have to smog with registration each year now. NV is pretty loose. I took the highway and was surprised at how much acceleration the car had even at 60 - 70 mph. I Punched it at 70 mph in 4th gear and it accelerated pretty quickly to 75. You could feel it pick up immediately. I think it will do 90 mph easily - much faster than I want to be going in a little Swift.

JRP3, the 840 gauge current is similar to the current the TBS reads through the shunt, but maybe 5% or so higher. Difficult to tell exactly as it is constantly moving around due to changes in grade, bumps, my foot moving, etc. I'll look at it some more. I like the little optional push button selector for the 840. I mounted it in the dash next to the steering column, so it is convenient to scroll through the outputs of the 840.

I also made a couple other stops. Drove 22 miles total. Discharge current seemed to be about 108A at 60mph. I had estimated about 150A! I'm not certain it was level though. I need to run on a stretch in both directions. Too much traffic today. No problem accelerating out into traffic, or up a freeway on ramp. It scoots! I didn't want to go home. I got real comfortable driving it, since it is about like driving an automatic. No need to put in the clutch when stopping. Just shift into the gear you want to start out in after you have stopped, and I only used 2nd and 3rd most of the time. It will cruise nicely at 60 mph in 3rd at around 4000rpm with good efficiency.

I heated the pack this morning prior to charging. It started at 38F (28F in the garage) and heated at a bit better than 3F/hour, rising to 51F at 4 hours. Not exactly blazing, but ok. The IR temperature measurement on my Extech gave the same temperature on the top and sides of cells, and agreed pretty well with the sensor bolted on a battery clamp. I forgot to measure cell temperature after charging, but the ones in the rear box inside were at 76F after the drive, and the ones in the under the hood box were at 70F. It was about 45F outside.

I charged for maybe 2 1/2 hours this morning at 30A with no problems. I checked pack voltage, and spot checked cell voltages every 20 minutes or so, and charged to about 3.4V/cell. Charger seems to be working well now.

JRP3 was correct on which gets hotter - the controller. The motor was at about 60C when the controller was at 90C. I had the controller fan off - wanted to see how hot it would get. Will be interesting to see how much cooler it stays with it on (250cfm). I noticed pulling about 370A taking off up a grade, but most of the time, even with good acceleration it pulled less than 300A - and that for only several seconds typically. I wasn't burning rubber, but I was accelerating as fast or faster than most cars around me.


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## tomofreno (Mar 3, 2009)

I was thinking today that with an ICE when you are out of gas the car stops, and everyone accepts that. So why not set up the ev the same way? With that in mind, I will be setting up my TBS Ex-pert Pro gauge SOC alarm for 0% SOC. It's relay will put a low resistance in parallel with the throttle potbox so the car "will run out of gas" and coast to a stop when 0%SOC is reached. Except it won't really be 0% SOC, it will be about 20% SOC of my lowest capacity cell, because I will enter 80% of the capacity of this cell into the TBS as the Ah of the pack. SOC is based on discharge current from the pack and starting SOC after charge. The current is integrated to determine total charge lost over time. Voltage doesn't enter the equation, so sag is irrelevant, and how much charge is left is what you want to know. The driver can read SOC on the gauge display just like a gas gauge. When it is getting down around 10%, s/he knows better get "gas" fast. If not, it runs out, just like an ICE (carry a map of those charging stations). But the cells are fine, you reset the alarm, and slowly drive it to a charger or home. I'll also "bottom balance", so the SOC is representative of the SOC of all cells. I also intend to have HVLC to let me know if cell capacity has drifted lower (watching Dimitri's progress). 

Right now I have no bms. I'm just charging up to about 5% below max pack voltage by setting a voltage limit on the charger, and plan to discharge to about 30% SOC. I'm checking cell voltages after and before charge to ensure they are all still close in value. Took me less than 5 minutes to read them all and write them on a cell map today after charging. I'll do the same when discharged further to determine the lowest capacity cell.


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## JRP3 (Mar 7, 2008)

Great data Tom, and you're still one cell down, correct? Interesting to see how things change with an extra 3.2 volts, if it's even noticeable. The way you setup your SOC gauge seems like the right way to do it, no worry about voltage sag or temp changes, and plenty of reserve built in.


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## tomofreno (Mar 3, 2009)

> ...and you're still one cell down, correct? Interesting to see how things change with an extra 3.2 volts, if it's even noticeable


 Yes, and yes I expect it won't be very noticeable. It's less than 3% increase in voltage and energy. But of course the bigger the pack, the more cushion you can afford at top and bottom to keep your cells happy. 

I'll try to connect up the TBS relay to the PB6 this week. Dimitri, if you are out there, do you have an idea how much resistance I should put in parallel with the potbox to pretty much shut down the controller so the car won't move, and how much current the relay will have to handle? I'm guessing less than 10% of 5k, so maybe 300 Ohm? The TBS internal relay will handle 1A. I'll have to use it to drive another relay if more current is required. The TBS can also be set up to post a "Low" SOC alarm to the display at some selected SOC value. So it will act as a "gas" gauge displaying SOC, and give a warning you are low, and if you run out of "gas" you can reset the alarm and have a reserve to drive slowly to a charger if "empty" is say 30% capacity of the lowest capacity cell. 

It looks like I'll rarely go over 2C discharge current driving normally, and that for only several seconds during initial acceleration. Typical currents for longer time will be less than 100A or about 0.55C. The cells should be happy!


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## dimitri (May 16, 2008)

tomofreno said:


> I'll try to connect up the TBS relay to the PB6 this week. Dimitri, if you are out there, do you have an idea how much resistance I should put in parallel with the potbox to pretty much shut down the controller so the car won't move, and how much current the relay will have to handle? I'm guessing less than 10% of 5k, so maybe 300 Ohm?


Assuming your controller uses 3 wire potbox, when your pedal is high, potbox wiper is shortened to the lower end of potbox, so to mimick the same with relay, just put relay pair across the 2 potbox contacts, simulating high pedal. No resistor is needed. Resistor is only needed when you want to reduce available throttle range, in which case with 3 leg potbox you need to add 5K in series with high end and have it shortened by NC pair from the relay, so 5K is inserted into voltage divider when LVC hits. But since you want to "run out of gas" control, then just mimick high pedal. IMHO, its a bit risky. ICE car doesn't just suddenly cut out, it spurrs for a little while, so I think reduced throttle is safer overall. I wouldn't want to be in a car that just stops all of a sudden.

BTW, I sent you a PM few days back, did you get it?

Thanks


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## dimitri (May 16, 2008)

Doh, too little coffee this morning, I take back "no resistor" comment 

If driver floors the pedal it will shorten 5V supply to the ground 

I guess you can put 300-500 Ohm resistor across, but your controller will still operate at very low duty cycle, not a complete cut out. With too low value of resistor you might overload 5V supply in the controller.

I would use a trimpot and do some testing, since there is not much data for these AC controllers.

Hope this helps.


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## dimitri (May 16, 2008)

Actually, you can just use NC pair between high end of the potbox and controller's 5V supply. This way potbox gets cut off when NC opens and goes to zero safely, without compromizing 5V supply.

Sorry for multiple posts, ideas keep coming as I type


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## tomofreno (Mar 3, 2009)

> BTW, I sent you a PM few days back, did you get it?


 No. I'll check the spam folder. I have a two wire potbox with click "deadman" switch at high pedal. So I thought if I switch in a low R in parallel it would be low throttle. Maybe I should have it just reduce to 10 mph or so.


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## dimitri (May 16, 2008)

Hmm, I thought it was a 3 wire box. 2 wire box is a lot easier, just put 500 Ohm across with a relay for 10% max throttle.

It was a PM via Forum, I didn't think there was a spam filter on the forum...


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## tomofreno (Mar 3, 2009)

> Hmm, I thought it was a 3 wire box.


 It is, but they only use the wiper and one end on this motor/controller setup.


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## MN Driver (Sep 29, 2009)

Congratulations on getting the SwiftE moving, your progress is very encouraging to the rest of us. 90C is very hot, I'm curious what it's rated for but either way, it's nice to know you got it is peppy enough in the 60-70mph range and it got you to 75mph with power to spare. Are they programmed to power off on their own or do we need to watch them closely when doing a max speed test run? Do we have max temp specs for the motor and controller?


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## JRP3 (Mar 7, 2008)

Just found this in the manual

Storage ambient temperature range -40°C to 95°C (-40°F to 203°F)
Operating ambient temp. range -40°C to 50°C (-40°F to 122°F)
Internal heatsink operating temp. range -40°C to 95°C (-40°F to 203°F)
Heatsink overtemperature cutoff linear cutback starts at 85°C (185°F); complete cutoff at 95°C (203°F)
Heatsink undertemperature cutoff complete cutoff at -40°C (-40°F)
Tom you were pretty close to cutoff already  Hope that fan gives you some good cooling. They do mention the controller should be bolted to a larger piece of aluminum for heat dissipation.


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## tomofreno (Mar 3, 2009)

> Tom you were pretty close to cutoff already
> 
> 
> 
> ...


 It did cut back, as I was driving uphill toward home the last 1/4 mile. Ran fine today. With the fan on and similar conditions it never went over 41C. Still concerned about summer though. I spoke with HPEVSA today and he said you can just use a large heat sink of aluminum without a fan, but a fan gives far better heat transfer than just adding some more thermal mass, so I'll stick with it. It only draws 1.6A for 250cfm.


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## tomofreno (Mar 3, 2009)

Some good news and bad news today. First the bad. I over-discharged more cells - the rest that bad VB's had been installed on. I had planned to drive to about 3.0 to 3.1V per cell and then bottom balance. The good cells are sitting at 3.221 to 3.226V, but the ones VB's were on went to 0.75 to 1.9V. All cells started within 0.009V of each other worst case, so something is going on with the "bad VB cells". Dave Kois said he is hearing a similar story from others and evcomponents will replace them. I have the 5A ps on one now seeing if they will recover, but they seem to be significantly lower capacity than the other cells. I'm wondering if more VB's are bad, and I noticed it on these cells and not others because these were significantly lower capacity to start with. I'll check out the other VBs to see if this is the case. Hopefully I can recover the low cells enough to drive around with shorter range until the replacements show up.

Now the good news. I drove much more today to drain the cells down. I put a total of 71 miles on the car with one charge, and that charge was only to 117V/35cells or about 3.34V/cell! I estimate about 35%/65% highway/secondary road driving. I also punched it going up an on ramp, drew about 450A and had to hit the brakes to avoid running into the guy in front of me! It goes when I punch it! In 4th gear on the highway it jumps right up from 60 to 70 mph if I punch it, and it is still accelerating at about the same rate at 70 until I back off. As I said, the controller didn't go over 41C, and the motor was only around 30C max. All terminal connections were cool when I got home. I am very happy with the car's performance. It is considerably better than I expected.

The reason I called HPEVS was to see how to improve regen. He said I'll have to get a Curtis programmer, about $500.00, and can then use an external pot or a kit they will soon be selling. The kit uses a pressure transducer in the brake line to give more electric braking when you push harder on the brake pedal. I told him I don't like that as it wastes energy mechanically braking. I want a pot so I can adjust regen to some standard setting I like, and adjust it more if I want stronger braking on a big hill. The present adjustment works ok if you downshift when stopping, but I still get a max of only about 20A regen. And I have to mechanically brake on a hill, so I could be getting much better regen and saving my brakes.

Just checked, and after 45 minutes at 5A, the cell that was down to 0.75V when I returned home is now at 3V (edit: actually after sitting it "relaxed to about 2.9V, and required another 45 min to get to 3V, and it had recovered to about 1.2V before I started charging).


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## JRP3 (Mar 7, 2008)

Did you ask them why they set the regen so low? I thought with the proper plug interface you could use a laptop to reprogram the Curtis? I wonder if HPEV or one of the other HPEV dealers might rent out a programmer?


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## tomofreno (Mar 3, 2009)

HPEVS said they had "a bunch" of the programmers on order, so I think they prefer to sell them. But its a good idea and worth checking with other dealers.


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## 80N541 (Jan 11, 2009)

In that case, try to contact curtis directly
I don't know if it the same in US but in france, a non professional can buy the programmer, it's less expensive ^^


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## JRP3 (Mar 7, 2008)

Check out the PDF for the PC Programming Station software
http://www.curtisinstruments.com/index.cfm?fuseaction=cProducts.dspProductCategory&catID=7
They talk about different connection options. I'd think it would be cheaper to go this route, probably a better interface using a laptop than the little hand held programmer.


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## tomofreno (Mar 3, 2009)

The programming station would be great since I could datalog parameters while driving, but I expect it is more expensive than the hand held unit. I'll call today to see.


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## JRP3 (Mar 7, 2008)

I thought the Programming station was just software, and then you need the proper cables to interface with the controller? I'd think that would be cheaper.


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## tomofreno (Mar 3, 2009)

Talked to Bill at HPEVS today regarding programming. He said the PC based programming system is about the same cost as the hand held programmer. He has some in stock and said he would send me cost info. The PC based system doesn't permit datalogging, it has about the same capabilities as the hand held, but does permit you to receive controller software updates by email and upload them into the controller via a PC. He said its also a bit difficult getting the software set up properly. He thinks the hand held is easier to use.


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## tomofreno (Mar 3, 2009)

Oh, I also contacted Curtis, and they told be you have to purchase either programmer through a dealer, wouldn't tell me cost. They are such a customer service oriented company.


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## tomofreno (Mar 3, 2009)

Some data on cell heating in cold weather: I heated my cells to 65F yesterday and shut off the heaters at 7:30pm, when the garage (detached metal building) was at about 37F. This morning at 5:30am the garage was at 18F and the cells were at 42F. The combination of cell heat capacity and 1/2" polyurethane insulation in the metal boxes keeps them at a higher temperature than ambient fairly well. It seems they would be fine with the car parked outside for 8 hours per day if they were heated prior to leaving home. The heaters could be left on all night as they only use about 350W total, about 3A from the 120VAC outlet. Those in the lands of -40F will require more insulation though. 

A bit nippy working in the garage these days.


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## OHM (Jun 30, 2008)

We need some photos of the whole swiftE its such a nice sounding conversion that Im sure many will now consider low voltage AC as
a good option.

Can you put it up on the EValbum?

Also any updates on performance and range figures to compare to your
original data? It sounds like its better than originally anticipated.


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## tomofreno (Mar 3, 2009)

> We need some photos of the whole swiftE...


 You mean a photo of the outside of the car? Ok, but it just looks like a stock Swift or Metro:








I've been waiting to get more data on range and 0 to 60 before I post it in the Garage here and the Evalbum. All I have so far is 71 miles on roughly 15.6kWh or about 220wh/mile at roughly 35%/65% secondary/highway driving (about 60mph ave highway speed). But I didn't have my soc gauge calibrated so the estimate of energy use is only a guess based on high and low cell voltages. I have charged the cells that were discharged significantly lower than the others so they are balanced with the rest, and will charge up the pack today. It snowed about 10" here yesterday and is -5F (-21C) this morning so I don't think I'll be driving it for a while. I left the battery heaters on last night and they are at 58F this morning (thermostat set at 59F). It is warmer in the garage though, 0F.  I was planning on pulling the front bumper and putting insulation on the outside of the front battery box to reduce heat loss due to cold air flow around it while driving, but not today I think. Maybe this weekend when it is supposed to get to a balmy 40 hi/26 lo. 
Oh, here are some photos of the inside with the rear battery box repainted gray:















Performance seems as good or a bit better than I estimated as far as acceleration. Range is considerably better, I think likely because rolling resistance is lower than that predicted by the equation in Bob Brant's book. The wheels spin very freely, no brake drag, and it has radial tires. That range of 71 miles was with the tires still at about 28psi and the DRL (Daytime Running Rights) active. The manual says the DRL turns on the headlights at a bit less than low beam. I disconnected the DRL yesterday and put more air in the tires. 

I will record cell voltages after charging today to determine the lowest capacity cell, reset pack capacity on the TBS gauge to this value, and set the soc to "full", so I will get a good estimate of energy used on the next run. But I am running with 7 weak cells (all below 2V when others were at 3.24V) so not sure how that will affect things. I'll likely have to wait for replacement cells to get good range figures.


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## OHM (Jun 30, 2008)

I wondered why the weight was higher than the swifts and now its clear.
Its actually the heavier of the Suzuki hatchbacks sold here in Oz and rest
of the world markets ** Baleno** ( also avail in sedan and wagon).

Looks a very clean and aspiring conversion will look forward to your posts and experiences as I have been interested in the AC system you are running and also the non TS cells 

I know TS cells scored best in comparisons but what they have done
to past members of our community is criminal and should be treated
as such.


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## tomofreno (Mar 3, 2009)

An update: I found my skis, poles, and pack fit nicely in the back of the car,  and groceries too. I drove 25.4 miles today, maybe 15% on the highway, and used 47.8Ah or about 26.6% of 180Ah capacity. At this rate I should be able to drive about 67 miles to 30% SOC. This is about 215Wh/mile, and when I drove at about 35% on the highway I estimated about 220Wh/mile. Looking good! I am going to get the PC Programming station for the controller so I can re-program it to use a pot to control the regen. That should help the range a bit since even when I downshift I don't get more than about 20A of regen as it is currently set up, whereas I should get more like 150A. I'll likely leave it at one setting most of the time, but increase it as needed on hills to avoid using the mechanical brakes.

I have one cell that consistently reaches high voltage before the others. During charging it remains at about 3 to 8mV higher voltage up until around 3.37V or so then starts leaving the others behind. When it reached 3.66V the other higher voltage cells were at about 3.49V, and most were a bit over 3.48V. This is a cell that did not have a bad VB on it, nor has it been over-discharged. The lowest rest voltage it has seen is 3.228V. If it had lower capacity than the rest, I would expect it to discharge faster, but it does not. I also would expect it to have higher rest voltage than the others after charging, but it does not. The cells that over-discharged were all ones that had bad VB's on them, even though they were charged up about to the level of the other cells, prior to charging the entire pack. I don't know what is going on, but I sure will be glad when I get those replacement cells and have a cells that charge and discharge fairly closely together.


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## JRP3 (Mar 7, 2008)

Maybe you could try discharging the high cell a bit more than the others and see how it behaves? Basically bottom balance it. It sounds as if it has higher capacity than most and has not been discharged as deeply. If it is your highest capacity cell and was filled to the max when the VB's were on it will constantly be at a higher SOC than the rest of your pack.


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## tomofreno (Mar 3, 2009)

> Maybe you could try discharging the high cell a bit more than the others and see how it behaves? Basically bottom balance it. It sounds as if it has higher capacity than most and has not been discharged as deeply.


 Hmmm...it started at 3.338V before I started a "top off" charge this morning. Others were at 3.347 to 3.340. So if it had larger capacity I would expect it to be at lower voltage than the others. It seems it has smaller capacity, and "fills up" faster, but then if that is the case why does it always drop back down to the same rest voltage as the others after a few hours? This same cell was charged to 3.88V in the previous charge cycle, but it relaxed to the above 3.338 voltage afterwards - very similar to the others.

On another topic, I charged at 15A AC input current this last time. The TBS gauge showed 13.4ADC current into the pack. The EKM meter read 241VAC/15A into the charger, so about 170.4Vrms*10.6Arms = 1806W assuming power factor of 1. The pack voltage was about 119V, so 119*13.4 = 1595W, so looks like the charger efficiency was around 1595/1806 = 88.3%.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Hmmm...it started at 3.338V before I started a "top off" charge this morning. Others were at 3.347 to 3.340. So if it had larger capacity I would expect it to be at lower voltage than the others.


It was wasn't it? 3.338 is lower than 3.340. But I was thinking that it does have a larger capacity, and it was filled when hooked to the VB, so it should be at a higher SOC and would show a higher voltage, not lower. However I'm not sure resting voltage tells you much of anything after being off the charger for a while. If it's consistently showing higher voltage than other cells after discharging and reaches higher voltage when charging it sounds to me as if it's constantly closer to full. I'd try bottom balancing it a bit.


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## tomofreno (Mar 3, 2009)

> It was wasn't it? 3.338 is lower than 3.340.


 Sorry, that was a typo. Should have been 3.337 to 3.340. So there were some lower, but most had a bit higher voltage than that cell. But I think 2 to 3 mV difference is not significant.


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## tomofreno (Mar 3, 2009)

I looked back over the data and it appears this cell has a bit smaller capacity than the others. It consistently had a slightly larger change in rest voltage with charging, around 6 to 8 mV, and similar with discharging. It's not a big difference, but it doesn't take much to make it hit 3.6V faster during charging. It went from 3.51V to 3.66V in less than 10 minutes at 15A charging current (13.4A into the cells). It has a really steep curve near end of charge. I measured it at 3.51, stood there a minute or two, then measured it at 3.55, measured the two next to it, then it again, and it was at 3.66V. So there isn't much charge going into the cell from 3.5 to 3.66V. That makes me wonder what the significance of this "dynamic" voltage is. I don't understand it. But it is clear that these cells are quite stable and well-behaved if you just stay away from those steep parts of the V versus Ah curve.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> I looked back over the data and it appears this cell has a bit smaller capacity than the others.


Then it should be hitting a lower voltage sooner than all the rest, but if I understand you correctly it doesn't.


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## tomofreno (Mar 3, 2009)

> Then it should be hitting a lower voltage sooner than all the rest, but if I understand you correctly it doesn't.


 It charged to a higher rest voltage than the other "good" cells and discharged to similar or a bit lower voltage when starting from an initial discharge voltage similar to the other "good" cells in the few cycles I have done. The CHANGE in voltage is larger than that of the other "good" cells, which is why I said it seems to have smaller capacity. The cells that had the bad VBs and over-discharged behave somewhat differently, so my comment was meant to compare it to the other good cells. Btw, it is not as straight-forward to compare cell voltages as you might think. When recharging the bad VB cells at 5A, I charged them to about 0.015V higher voltage than the other cells 3 times before they relaxed to voltage within 4mV of the other cells. And I had to wait overnight to see what their rest voltage was, as it kept slowly creeping down for over 8 hours. Of course it is impossible to compare dynamic (during charging) voltages near the top end of the curve, above 3.5V, while charging at 15A or more as they are changing faster than you can measure more than a few cells to compare. Above 3.55V they change faster than that - or at least the one cell that has gone to over 3.6V did. I imagine cell voltages are quit different at the low soc end of the curve when drawing high discharge current, even if you "bottom balance". Life is a lot simpler if you just stay away from the low and high parts of the curve as you intend to do. There is hardly any charge and energy storage there anyway.


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## dimitri (May 16, 2008)

tomofreno said:


> Life is a lot simpler if you just stay away from the low and high parts of the curve as you intend to do. There is hardly any charge and energy storage there anyway.


Amen to that, but as you have found all cells aren't created equal and one can climb over max voltage even if you intentionally lower your overall charging voltage, so you keep lowering it just to protect one cell and lose few percentage points of your pack capacity in the process. This is why I still believe that even small amount of shunting at the top would be helpful to pull back those pesky cells while others are still charging.

And before someone reminds me that pack capacity is equal to smallest cell and there is no point of charging others more than that, as you are discovering, top voltage is not always a good indication of cell capacity and it doesn't always point out a smallest cell, there are more complex processes involved.


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## Voltswagen (Nov 13, 2008)

Dimitri
When I ordered my Lithiums (TS 160ah), I ordered 40 of them.
I plan on installing 36 of them in my Beetle and will then have 4 spares on the shelf.
These 4 spares will also give me the option of "culling out" some cells which may have low capacity or quick charging characteristics.
I think this is a good plan to try to bring the pack into better balance before first use.

Roy


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## dimitri (May 16, 2008)

Voltswagen said:


> Dimitri
> When I ordered my Lithiums (TS 160ah), I ordered 40 of them.
> I plan on installing 36 of them in my Beetle and will then have 4 spares on the shelf.
> These 4 spares will also give me the option of "culling out" some cells which may have low capacity or quick charging characteristics.
> ...


Having a few spares is a great option, I wish I had an extra $1000 when I ordered mine  , although one can argue that its a waste of cells. In my own pack of 40 TS160s if I had access to spares or ability to exchange some, there are 5 cells from apparenty a different production batch which appear to have slightly different curves, not enough to cause troubles, but only because I have BMS on them. Without BMS those cells would behave just like Tom described above. Since I don't have a luxury to adjust charger voltage with Zivan NG3, I have to use BMS anyway.

We can argue which is better, $1000 charger and $500 BMS or $2500 charger and no BMS, to each its own


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## Voltswagen (Nov 13, 2008)

I still think it's a good idea to have a few spares.
In addition to better balancing.......
With the extended life of these cells it's entirely possible say 5 years down the road to have some cells go bad. 
If the battery chemistry has changed again it might be very hard to replace those cells.


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## JRP3 (Mar 7, 2008)

Voltswagen said:


> With the extended life of these cells it's entirely possible say 5 years down the road to have some cells go bad.
> If the battery chemistry has changed again it might be very hard to replace those cells.


That's Jack's argument but I'm not sure I agree. As long as you replace a bad cell with something of equal or better capacity I don't see a problem with putting in a different cell.


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## JRP3 (Mar 7, 2008)

dimitri said:


> We can argue which is better, $1000 charger and $500 BMS or $2500 charger and no BMS, to each its own


Actually a PFC20 is about $2K, and since it's adjustable you don't have to buy a new charger if you change your pack voltage in the future.


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## Voltswagen (Nov 13, 2008)

John
Look at the evolution of computer engineering. How many CPU changes did we go thru? 286 -386 -486 - Pentium etc.
Not many 286 programs will run on today's computers.
What if down the road the nominal voltage changes? 
Is there anything about 3.2v which makes it forever?
And if larger voltages were produced, could we be sure they will be in multiples of 3.2?
I'm not arguing...just wondering.
Roy


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## JRP3 (Mar 7, 2008)

Most of the lithium chemistries come in around 3.2-3.6 for the last 20 years, so I think you'd be ok in that range. I don't see lithium going away any time soon, but I could be wrong. Who knows, in 5 years the $1k you spent on extra batteries might buy you so much more in better technology that you might want to put in a whole new pack anyway. Either way it's a gamble, I'm gambling that either I wont need a cell or if I do I can get one, or I'll upgrade the whole pack to an EESTOR


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## tomofreno (Mar 3, 2009)

> in 5 years the $1k you spent on extra batteries might buy you so much more in better technology that you might want to put in a whole new pack anyway


 I'm of that mind myself. There is a lot of work going on now on lithium-based battery chemistries. I'm guessing there will be significant improvements in 5 years, but who knows?


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## tomofreno (Mar 3, 2009)

Another data dump:
Drove some more today to give a total of 47.3 miles on the previous charge, then recharged. Cell voltages before recharge were all greater than 3.286V and the TBS showed 89.1Ah used, or about 50% discharge. The product of 89.1Ah and estimated average pack voltage of 114V (maybe overestimate due to sag) gives about 10.16 kWh, or 215Wh/mile. The EKM meter read 35.37kWh prior to recharge and 47.16 after, or about 11.79kWh. I estimated the charger efficiency at about 0.88 so multiplying by this gives about 10.4kWh, or 220Wh/mile. These estimates agree with earlier ones, so it seems the car gets around 220Wh/mile with around a 30%/60% mixture of highway/secondary road driving, with 60mph highway/35mph secondary. From the wall, including charger losses, it gets about 250Wh/mile.

I also measured current draw at three speeds:
30 mph: 45A
40 mph: 70A
55 mph: 105A (thought this seemed low so repeated it and got 138A, got about the same for the others)
I drove both directions on a stretch of road and averaged the two, then rounded up since it is difficult to keep the current and speed exactly steady. Then with 80% DoD or 144Ah the car should go about 3.2hr at 30mph or around 96 miles; about 2 hours at 40mph or 80 miles; and about 1.37hr at 55 mph or 75 miles (with corrected current this is 57 miles. All three ranges now agree well with my calculated estimates). The above 220Wh/mile for mixed driving indicates about 20,160Wh*0.8/220 = 73 miles (35 cells at nominal 3.2V). So it seems it should be pretty safe to drive 60 - 65 miles after a full charge. I almost never do this in a day though so I'll likely be charging at night to top off after a 40 to 60% DoD.

The weak cell started at 3.290V, with the other good cells at 3.294 +/-0.002V, and hit 3.475V when the other good cells were about at 3.421V on average, but they had maybe 0.014V spread, much more than when at rest. That was at 25A charging current. I backed off to 6.5A and the weak cell dropped to 3.417V, other good ones to 3.391V with only about a 2mV spread. I charged for a total of a bit over 15 minutes at 6.5A before the weak cell hit 3.611V and I shut off the charger, so there isn't much capacity up there. Probably more detail than anyone wanted to know, but I'm a data-driven kind of guy.


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## tomofreno (Mar 3, 2009)

Oh, one more thing, outside and garage temperatures were about 40F. Front box cells (in engine bay) were at 57F, mid box cells (sticking partially through the floor) were at 66-72F, and rear box cells (in the spare tire well, completely inside the car) were at 72F after returning from drive and prior to charging. After charging, front box cells were at 67F, and so were the others on average because I opened their lids during charging to cool them to the temperature of the front ones. That way, they won't be at a higher temperature than the front ones when the heaters kick on tonight. They likely won't kick on for 6 to 8 hours or so though as the cells drop very slowly in temperature in this balmy weather.

Also, I sized the PV array on my roof to power both the house and car. The house uses about 14 - 15kWh/day. The array generates about 40kWh/ day on a clear day in summer, and about 27kWh/day on a clear day in winter, so I figure around 25kWh/day on average counting cloudy days (about 255 sunny days/yr here). That gives about 10 -11 kWh/day for the car, or around 48 miles/day (NV Energy does not pay for excess power produced like they do in CA - and they get time-of-use rates, $0.30/kWh during production and $0.11/kWh at night during charging). I planned to add solar hot water if I needed more energy for the car, since hot water is likely about 30% of our house electric usage (electric hot water heater), but looks like we won't require it unless we start driving quite a bit more.


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## paker (Jun 20, 2008)

tomofreno said:


> I drove both directions on a stretch of road and averaged the two, then rounded up since it is difficult to keep the current and speed exactly steady. Then with 80% DoD or 144Ah the car should go about 3.2hr at 30mph or around 96 miles; about 2 hours at 40mph or 80 miles; and about 1.37hr at 55 mph or 75 miles. The above 220Wh/mile for mixed driving indicates about 20,160Wh*0.8/220 = 73 miles (35 cells at nominal 3.2V). *So it seems it should be pretty safe to drive 60 - 65 miles after a full charge.* I almost never do this in a day though so I'll likely be charging at night to top off after a 40 to 60% DoD.


Thank you VERY MUCH! My everyday drive will be at 65-70 + MPH for 22 miles, and another 14 at 50-60 MPH to and from work. I've been reading as much as I could find about the Curtis - AC50 combo and it will probably be what I use.


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## tomofreno (Mar 3, 2009)

You will use considerably more energy at 65-70mph compared to 55mph due to drag force increasing as velocity squared as you likely know, so range will be shorter. I'll try to get some data at 65. If you use the AC50/Curtis 1238-7501 controller I recommend a fan on the controller, as it will get hot driving at 70 mph continuous in summer. HPEVS says a finned heat sink is good enough, but I am not so sure. I think this motor controller would give good acceleration in a vehicle a few hundred pounds heavier than mine (2250 lb), but will degrade as weight increases. HPEVS had talked about finding a higher voltage controller for their motors. You might check with them on progress if you plan a heavier vehicle. Might need to add a fan to the motor in that case to run higher continous power. Mine is staying cool now (<30C), but of course it is winter here with temps < 40F (4.4C).


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## tomofreno (Mar 3, 2009)

Added the car to the "garage" on this site, and to the evalbum now that I have some data on range, etc. Got a 0-60 time of about 20 seconds shifting from 1st through 4th. Didn't do very well shifting, and stayed in a couple gears too long so acceleration started dying, so likely could do a bit better. The current pegged at 500A a couple times (500A shunt), so likely pulled about the full 550 the controller will give. I had the Curtis gauge set to voltage, TBS set to current, and planned to record time, current, and sag, but only got two out of three. Hard to watch gauges, watch for other cars, and concentrate on shifting. I don't plan to attempt it again as I don't really care.

Also edited my post on range estimates. The current draw at 55 mph didn't make sense as it was not that much more than at 40 mph. Repeated all three speeds and got about the same for 30 and 40mph, but significantly more for 55 this time - 138A, which gives a range of about 57 miles at 55mph @ 80% DoD. I found that all the places I thought were level were not. Drove about 56 miles that day, most at 50-55mph and used 103Ah, or around 205Wh/mile. Current draw, range, and energy/mile are all in very good agreement with my estimates. The speadsheet I use is called "evcalculator" and can be downloaded at electricnevada.org. The data for the AC50 motor is for 96V in that spreadsheet, from Curtis dynomometer tests. I modified it for 115V, which gives the max 90 lb-ft torque out to 3500 rpm, then falls off at the rate in the spreadsheet (just replace 3000 with 3500 in the IF statement for Available Motor Torque in the section on the AC50 below about line 230). The higher voltage can overcome the back emf of the motor, permitting the max controller current and torque, out to higher rpm. The estimates using this are amazingly good, most less than 3% error. Got to be some luck involved. 

Finally got the time and voltage set on the Manzanita so that it shut off automatically last night when the weakest cell was at about 3.48V. This cell's voltage starts taking off once over 3.5. The charger timer comes on and it starts slowly backing off on current at about 119.2V. I don't quite get a full charge this way, but from measurement described in previous posts I think I could only get another 5Ah or so, or about 600Wh more pack energy before this cell hit 3.6V. I have more than enough range anyway discharging to 30% soc, so I may even back it off a bit more to be safe. I'll have to re-adjust when I get replacement cells and have the full 36 rather than 35 I am currently using.

I really like the TBS E-xpert Pro gauge. Finally got it set up to show "Full" automatically. You input the "float" voltage and current for the charger in cv mode, and elapsed time this must be met. I set the former to 119.5V and and latter to 9A for 30 sec. I have the "Low soc" alarm set for 35% soc, giving me about 9 miles range left at around 45mph to find a charging station or get home by 28% or so soc. It has 1A relays for triggering an external alarm on low soc, low voltage, and high voltage, and posts alarms on the display. There is a battery icon on the display that is filled with 5 bars when full, then 4, 3, 2, 1, and none. The empty icon flashes when the pack is "empty". Empty is defined by the "discharge floor" variable and operates off percent soc. So the way I have it set up it flashes empty at 35% soc, but I know I have 9 miles left to about 28% soc. Really nice, and easy to glance at the icon and bars. It also displays Ah used, %soc, voltage, current...


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## JRP3 (Mar 7, 2008)

Great data. I would think you might get better 0-60 by starting out in 2nd, to avoid one shift point, and maybe taking 3rd all the way to 60 to eliminate another? Or does power drop off too much in 3rd? What sort of RPMs can you get to in 3rd, and what's the top speed in 3rd?


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## dtbaker (Jan 5, 2008)

tomofreno said:


> Also, I sized the PV array on my roof to power both the house and car.


I didn't know you had PV as well! So do I.... must be something about the Swift mindset.  

But... I might add more after I build a SECOND EV !


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## tomofreno (Mar 3, 2009)

> I would think you might get better 0-60 by starting out in 2nd, to avoid one shift point, and maybe taking 3rd all the way to 60 to eliminate another? Or does power drop off too much in 3rd? What sort of RPMs can you get to in 3rd, and what's the top speed in 3rd?


 Yeah, I thought about that, but decided to use 1st because there seems to be lag for a second or two in 2nd before it really takes off. You probably are correct though, shifting eats up seconds, and the car slows down noticeably due to regen when shifting out of 1st, not so noticeable in higher gears. I think if I practiced a bit and started in 2nd I could get it down to 16-18 seconds. Peak power is at about 3500 rpm and occurs in 3rd at about 50 mph, and in 4th at about 65mph. But the power in 3rd is still higher than in 4th until right about 60mph, so I should have stayed in 3rd. If I did it again I would start in 2nd and shift to 3rd at 40mph, where the two power curves cross. Someone will likely protest that it is torque that matters not power, but it is not, it is torque AT RPM that matters and that is power. Btw, you can see graphs of the torque and power curves in the spreadsheet I mentioned. But they are for 96V for the AC50. Similar curves are there for 8" and 9" DC motors with a few different controllers.


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## tomofreno (Mar 3, 2009)

> I didn't know you had PV as well! So do I.... must be something about the Swift mindset.


 Just trying to lower my impact.


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## paker (Jun 20, 2008)

tomofreno said:


> You will use considerably more energy at 65-70mph compared to 55mph due to drag force increasing as velocity squared as you likely know, so range will be shorter. I'll try to get some data at 65. If you use the AC50/Curtis 1238-7501 controller I recommend a fan on the controller, as it will get hot driving at 70 mph continuous in summer. HPEVS says a finned heat sink is good enough, but I am not so sure. I think this motor controller would give good acceleration in a vehicle a few hundred pounds heavier than mine (2250 lb), but will degrade as weight increases. HPEVS had talked about finding a higher voltage controller for their motors. You might check with them on progress if you plan a heavier vehicle. Might need to add a fan to the motor in that case to run higher continous power. Mine is staying cool now (<30C), but of course it is winter here with temps < 40F (4.4C).


I'll be using a Honda CRX. I'm hoping to get it 2200 lb, or close, finished. 

Summer driving on I-4 is HOT. The part of central Florida I'm in is about the hottest area in the country. I'm thinking, if need be, I'll try machining something like a CPU water block.


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## tomofreno (Mar 3, 2009)

> I'll be using a Honda CRX. I'm hoping to get it 2200 lb, or close, finished.


 Should be good! 



> Summer driving on I-4 is HOT. The part of central Florida I'm in is about the hottest area in the country. I'm thinking, if need be, I'll try machining something like a CPU water block.


 Sounds like you know what you are doing and are willing to go to the lengths required to make it work. Be nice to see what you end up doing and how it works!


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## paker (Jun 20, 2008)

Have you done anything with the controller programming, or are you using factory settings?


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## tomofreno (Mar 3, 2009)

> Have you done anything with the controller programming, or are you using factory settings?


 I am currently using it as it arrived. Performance is fine, except for electric braking. I only get a max of about 20A regen, usually less than 15A. I recently ordered the 1314 PC Programming Station so I can improve this. It currently is under VCL control ("Brake Type 5"). I'll try leaving it that way and just change the "VCL Brake" parameter - have to talk to someone at HPEVS who knows the software. Later I may set it up for control by external pot changing to "Brake Type 3". That way I can increase regen if I like when going down a long hill so no mechanical braking is required, and more importantly I can set it up to cut off regen automatically using a relay and small resistance in parallel with the pot triggered by HVC signal. Overcharge with regen might be an issue if the car is charged at a significantly higher elevation. Say for example the car was driven to Truckee CA at 2000+ ft higher elevation, and charged close to full at the charging station there prior to heading back down. Otherwise it shouldn't be an issue, but I would like to make the car as foolproof and easy to operate as possible so my wife can drive it without destroying something - and she won't pay any attention to such considerations.


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## Guest (Dec 20, 2009)

JRP3 said:


> That's Jack's argument but I'm not sure I agree. As long as you replace a bad cell with something of equal or better capacity I don't see a problem with putting in a different cell.



The manufacturer is pretty emphatic about mixing cells with different chemistries or capacities. We're recommending a couple of cells from the same batcch as spares just to avoid having to replace the whole pack three or four years from now because you've lost one or two cells and they don't make them anymore.


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## Guest (Dec 20, 2009)

tomofreno said:


> Hmmm...it started at 3.338V before I started a "top off" charge this morning. Others were at 3.347 to 3.340. So if it had larger capacity I would expect it to be at lower voltage than the others. It seems it has smaller capacity, and "fills up" faster, but then if that is the case why does it always drop back down to the same rest voltage as the others after a few hours? This same cell was charged to 3.88V in the previous charge cycle, but it relaxed to the above 3.338 voltage afterwards - very similar to the others.
> 
> On another topic, I charged at 15A AC input current this last time. The TBS gauge showed 13.4ADC current into the pack. The EKM meter read 241VAC/15A into the charger, so about 170.4Vrms*10.6Arms = 1806W assuming power factor of 1. The pack voltage was about 119V, so 119*13.4 = 1595W, so looks like the charger efficiency was around 1595/1806 = 88.3%.


Nice conversion...

That does sound like a strange result if it is climbing fast during charge and the dropping back below the others after charge. But sometimes these cells "work in" and it sounds like you don't have many cycles on it. I would just keep an eye on it for 15 charges or so and see what shakes out. It very well may settle in.

Basically a 100% charged SE cell is 3.400 volts at rest. THat IS fully charged. The 3.6v is just a target voltage provided by the manufacturer to GET there. It' isn't a limit of anykind in truth. You can charge at 10 v per cell if you like and 3C. The problem is, there is then no way to TELL your getting close to full. So the 3.6v at 0.3C is given and it works just as well at 15 amps as 50 amps.

AFTER you charge, it is quite indicative. I like something around 3.35volts and it' sok if I never got everything charged up to the spec. But they do NOT like to be overcharged at all. So they should never show over 3.4000. When you shutoff the charger of course they will, but they should settle to something less than 3.40 within five minutes or so.

If it settles to something within range of the others, it's fine. The manufacturer says within about .1 volt, not .01 volt. So I think you're doing fine.

You said in an earlier post that there were some issues with the Curtis controller. Curtis controllers have always had heat problems and the book implies you need a 1/2 meter square sheet in ADDITION to their heat sink just for normal operation. What kind of temperatures are you seeing - or have you measured it? The upper limit is supposed to be 85C according to the book.

I'm thinking of building a glycol/water cooling system for mine. The Speedster will be about 2050 lbs and I just don't want heat issues. But the liquid cooling adds quite a bit of complexity and things to break. I'm not as far along as you with the AC50, and I just keep going back and forth over this liquid cooling thing. It may actually be easier to do than a fan and finned heat sink in some ways and look better as well. But I hate to agonize over it and then find the thing doesn't have heat issues anyway.

What are your further thoughts on the Curtis and the heat?

Again, congratulations. It looks like a winner....

Jack Rickard


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## tomofreno (Mar 3, 2009)

> What are your further thoughts on the Curtis and the heat?


I actually over heated the Curtis controller once. It was one of my first times out, testing at highways speeds from 60 to 75mph, and punching it to check acceleration there. Outside temperature was in the upper 40's (F). I have a 250 cfm fan blowing on the aluminum plate that comes with the charger, but had turned it off to see how it did without it. It remained less than 80C most of the time. I repeated this a couple days later with the fan on and the controller temp remained less than 40C. I think it will be ok in summer too with the fan on at speeds 55-60, but not so confident that you could do 75mph continuous in summer even with the fan. Maybe a big finned heat sink and fan. HPEVS claims a finned heat sink it enough. I'm not so sanguine. If you plan on punching it a lot and driving at 70+ regularly, the water is probably a good idea. The motor has not been an issue, but may be on hot days. I think a 250 - 300 cfm axial fan mounted in place of the rear end shroud would be more than sufficient.


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## tomofreno (Mar 3, 2009)

> Again, congratulations. It looks like a winner....


 Thanks, I am very happy with its performance - except for the low regen current, but I think that will be fixed soon. The acceleration in the 2050 lb speedster should be very good, and I would guess top speed close to 100 mph. I think the AC50 is a great choice for lighter vehicles.


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## JRP3 (Mar 7, 2008)

jrickard said:


> The manufacturer is pretty emphatic about mixing cells with different chemistries or capacities.


I don't see how it would matter, unless I'm missing something. As long as you use a cell that has the same or greater capacity and a similar voltage range, what would it matter? Even if you couldn't match a newer cell, running without one or two cells shouldn't cripple a vehicle. It might even be worth selling your pack assuming the rest of it is in good shape and putting the money into a whole pack of the newer technology. My guess is most people will weed out any bad cells or kill them through mistakes within their first year or so when replacements are still readily available. I just think there are a number of options other than purchasing extra cells.


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## tomofreno (Mar 3, 2009)

I repeated the 0 to 60 mph, shifting from 1st through 3rd and got 18 seconds this time. Starting in 2nd did not work nearly as well. This time I focused on shifting rather than looking at gauges, so I don't think it will do much better than that.


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## Voltswagen (Nov 13, 2008)

I guess I'm a dummy on this one as I have never fully understood the logic behind starting in 2nd gear. 

To me it would seem that no matter if it's an ICE or an Electric Motor it takes more energy to break inertia in 2nd than in 1st gear.
It's about ratios and weight, not propulsion choice.
Try to start out in 4th gear.......see what I mean?
The higher the gear ratio the more strain and energy it takes to get moving.

OK...slam me 

Roy


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## JRP3 (Mar 7, 2008)

In first gear, or any gear that isn't 1:1, you're giving up speed for torque multiplication. If you have enough torque to begin with you may not need the extra multiplication of first and you don't lose the time shifting if you can start in second. If you've ever driven a truck with a super low first and a big motor you almost never use first because you have to shift up almost immediately and you don't need the torque multiplication.


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## tomofreno (Mar 3, 2009)

> I guess I'm a dummy on this one as I have never fully understood the logic behind starting in 2nd gear.


 Well, the idea is that the available acceleration in 2nd gear, though lower than in first, is still pretty high, so maybe its better to start there and not loose the time shifting from 1st to 2nd. For example, the available acceleration at 10mph in 1st gear in the Swift is about 11.4mph/sec, whereas in 2nd it is 5.9mph/sec (calculated). It is enough lower in second that you don't loose enough time shifting from 1st to 2nd to make up the difference. It was very noticeably slower. Other cars with different gear ratios and motor torque may be behave differently.


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## Voltswagen (Nov 13, 2008)

Tom
What is your difference in amps drawn between starting in 2nd as opposed to 1st?


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## tomofreno (Mar 3, 2009)

> What is your difference in amps drawn between starting in 2nd as opposed to 1st?


 If I accelerate at the same rate in both gears, I use less current starting in 1st, up to around 15mph. I only start off in 2nd if I can accelerate more slowly than usual, or am starting off downhill because I like to try to keep the current below 200A. If there are a bunch of cars behind me I always start in first - and usually leave them behind. In that case I may draw close to 300A briefly. Rarely draw more than this except for when I was testing acceleration and 0 to 60.


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## paker (Jun 20, 2008)

At what RPM were you shifting at? High, 5000+-, or lower, 3000-3500?


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## tomofreno (Mar 3, 2009)

> At what RPM were you shifting at? High, 5000+-, or lower, 3000-3500?


 Around 5000.


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## tomofreno (Mar 3, 2009)

Here are the torque-speed and power curves for the SwiftE with 115V pack:
View attachment SwiftE torque.spd curves.pdf

View attachment SwiftE power curves.pdf

My goal was to shift just past the peak in the power curve for each gear, where power is still greater in that gear compared to the next one. The peak in the power curves occurs at a torque just above the "knee" in the torque-speed curve, where the product of motor torque and angular velocity is a maximum. These are from the spreadsheet ("evcalculator") posted at electricnevada.org, but modified to 115 pack voltage rather than the 96V used in that version. Note the curves are approximate due to a limited number of values used to generate them, and the curve fitting routine Excel uses. For example, the actual peak power is about 61 H.P. The motor rpm corresponding to mph can be seen in the spreadsheet (related by tire radius and overall gear ratios). In second gear the motor is at approximately 5000 rpm at 45mph, so you actually want to shift a bit before that, at around 35-40 mph where available power is higher than in 3rd gear. I haven't taken the time to check how accurately these curves reflect actual performance with much precision. It "feels" they are approximately correct when driving the car, ie, I feel the acceleration start falling at approximately the motor rpm expected from these curves.


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## tomofreno (Mar 3, 2009)

> ...the motor is at approximately 5000 rpm at 45mph, so you actually want to shift a bit before that, at around 35-40 mph


 That would be around 4000 to 4500 rpm approximately.


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## Guest (Dec 24, 2009)

paker said:


> I'll be using a Honda CRX. I'm hoping to get it 2200 lb, or close, finished.
> 
> Summer driving on I-4 is HOT. The part of central Florida I'm in is about the hottest area in the country. I'm thinking, if need be, I'll try machining something like a CPU water block.


We've been back and forth on this, but I think we're going to go ahead and do it. We've taken 2 sheets of 1/2 inch aluminum and cut them to the size of the Curtis 1238-7501 controller and drilled them for the mounting holes. We'll use a vertical mill to scribe a channel about 1/8 inch deep and 1/4 inch wide across the face in a serpentine form with two terminations on the same side.

We'll then put a little silicon along the sides of the channel and bolt the two pieces together. Tap and drill for 1/4 inch and install two AN6 x 1/4 NPT fittings.

We'll then use a radiator overflow as a tank, a small Bosche pump and a finned aluminum heat sink with some AN6 steel braided hose and AN6 fittings to rig it all up. I think this "chill plate" will allow us to get max performance from the Curtis and at the same time prolong its life. 

I detest the added complexity and expense, but these Curtis controllers have always been infamous for heat problems. I would say I hope that they've solved it, but the manual is pretty clear that it needs at least 1/2 meter by 1/2 meter additional heat sink. I'm planning to mount it kind of high in the car out of the weather and it will not have very good air flow there.

The Zilla is liquid cooled. The MES-DEA controller is liquid cooled. The new Netgain Controls controller is liquid cooled. There's a clue in here somewhere.

The heat capacity of water over air is well over 3000:1. Avoiding a liquid cooling system is probably an act of gravity defiance at this point. 

Jack Rickard
http://evtv.me


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## Guest (Dec 24, 2009)

Voltswagen said:


> I guess I'm a dummy on this one as I have never fully understood the logic behind starting in 2nd gear.
> 
> To me it would seem that no matter if it's an ICE or an Electric Motor it takes more energy to break inertia in 2nd than in 1st gear.
> It's about ratios and weight, not propulsion choice.
> ...


No slam. What you say makes sense. But it doesn't work out that way.

An ICE engine develops torque at very narrow RPM ranges. OFten high ones. The Porsche for example is at 4600 RPMS. I've got some MG's in teh same range. No power at low RPMs., lots of power at high RPM. So the gearing is of course designed for those engines.

Electric motor is all different. You have max torque from zero up to some value that would be considered very low for an ICE engine. On my Warp 9 at 120v, above about 3400 rpm it is truly gutless. At 2800 it pulls strong.

I think the AC50 is going to be the same, good torque out to about 3000 and trailing off badly after that.

In Speedster, we take off in 3rd gear and shift at 55 mph into 4th which gets us up to 95 mph.

In Speedster part duh, which is where the AC50 is going, we've actually regeared to the higher 3.44 R&P and as high a gearing as we could get in all four. The 4th will be 0.70. I think this will get us to 110 mph. And hopefully it will at least get 2nd gear into the game.

In 1st, currently, you are overrevving the motor almost immediately and lose all torque really at 7 or 8 mph. It is just unpleasant.

So what you say is entirely true. But in practice, the drive plants are just different in their RPM characteristics. I don't really like direct drive, and I do like using the transmissions, but they are geared for ICE and we have electric motors. So you will often find the lower gears essentially useless.

Jack Rickard
http://evtv.me


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## Voltswagen (Nov 13, 2008)

Jack
I perfectly understand what you are saying. Electric Motors develope full torque at 1 RPM. 
In a stock Beetle 4 speed transmission the largest difference between gears is 3.80 - 1st gear, 2.06 - 2nd gear. My Beetle is powered by a D&D ES-31B which is small in comparison to the Warp 9 and therefore developes much less torque. 
In my experience driving the Beetle about 1500 miles, when I startout in 2nd the vehicle doesn't pull strong like it does in 1st gear. And you are right, I have no doubt that in 1st I hit full torque early - I usually shift before 20mph.
It just doesn't seem to have as much strength to break inertia in 2nd tho I can go all the way to 30mph before shifting into 3rd.
Roy


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## tomofreno (Mar 3, 2009)

> It just doesn't seem to have as much strength to break inertia in 2nd


 That's because it has less wheel torque in 2nd at low rpm due to the lower mechanical advantage. The max torque of the motor is the same at lower rpm (below the "knee") regardless of gear you use, so you will get more wheel torque in lower gears which give greater mechanical advantage, but you need to shift at about the "knee" in the curve (or around the peak in the power curve), before motor torque decreases by more than the difference in mechanical advantage. If your 1st gear is geared really low, this might be at very low vehicle speed, like 10 mph or less, as JRP3's example of a low-geared truck. Just depends on the gearing and where the knee is for the electric motor you are using.


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## paker (Jun 20, 2008)

jrickard said:


> We've been back and forth on this, but I think we're going to go ahead and do it. We've taken 2 sheets of 1/2 inch aluminum and cut them to the size of the Curtis 1238-7501 controller and drilled them for the mounting holes. We'll use a vertical mill to scribe a channel about 1/8 inch deep and 1/4 inch wide across the face in a serpentine form with two terminations on the same side.
> 
> We'll then put a little silicon along the sides of the channel and bolt the two pieces together. Tap and drill for 1/4 inch and install two AN6 x 1/4 NPT fittings.
> 
> ...


I talked to a guy at Thunderstruck Motors about the Curtis controller and he said it could be mounted in the grill with a finned heatsink, but I don't think that would help if I'm stuck in traffic with the car in front blowing it's exhaust on my car, as well as the hot pavement.


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## MN Driver (Sep 29, 2009)

Paker, One thing to consider is your controller won't be generating heat at a standstill like an ICE engine since you have no need to idle, so it won't matter as much in that case, once traffic gets moving you'll be able to get the cooling air you need when you willl be using the power that will generate heat, so for cooling, Thunderstruck's idea might be fine.

I'd personally like to avoid putting the back of the controller in a place that, if something gets struck such as a deer or another car that it would be damaged. I've never had to deal with that but if I crushed a bumper, I'd rather just replace the bumper and not a spendy A/C controller too, if I could even manage to get it seperate from the motor. That's just my opinion though.

My plan would be to use watercooling if the controller can't keep cool with air cooling against a finned heatsink with either a blower or a standard fan. Jack, I think your plan for watercooling will work well, a quart of water, or whatever size overflow tank is probably fine. Usually in the computer processor overclocking field, the water will still eventually produce enough heat to where you need to cool the water, which is normally cooled through a radiator the size of a cars heater core with a fan on it. It seems a little backwards on first thought but water does have a great deal of thermal capacity but eventually it needs to be cooled. Does a quart have enough capacity to run through the capacity of your battery? Only testing would give us the answer. I personally would plan to cool that water off though.

My plan would be to have an aluminum block mounted to the controller with a back and forth groove for the water, which sounds like what Jack is doing, but then I'd route it directly through a radiator, probably getting one designed for computer overclocking as they have some serious heat dissipation abilities and have a minimal sized resevoir so that there is room for expansion. I'd probably run the system with a 50/50 mix of coolant to prevent it from freezing when I'm not driving as I come from a climate that would require it.


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## Coulomb (Apr 22, 2009)

MN Driver said:


> ... water does have a great deal of thermal capacity but eventually it needs to be cooled. Does a quart have enough capacity to run through the capacity of your battery? Only testing would give us the answer.


Actually, we can use science! A quart is about 0.9 litres; let's call it 1L with some capacity in the hoses. A kilowatt of heat will raise 1L of water 1°C in 1 second. Elsewhere it was stated that a high power controller will need to dissipate about 2kW peak. So at peak power, the water will be heating at 2°C per second. In half a minute, it will go from 25°C to 85°C, about where an ICE works. In another 10 seconds, it will be at 105°C, boiling.

Granted, you won't be using peak power for very long, but a single quart of water will only last you one high power acceleration. It will then take longer to cool down the controller plus water than the controller by itself.

So: you do need cooling! That's why water cooling, despite the 3000:1 difference in heat capacity that Jack mentioned, isn't an automatic winner. Eventually, you need moving air to get rid of the heat. The water is really just a "middle man", useful if you can cool the controller better elsewhere (at a radiator) than where it is. The same thing applies to motors: if your motor has lots of cooling fins, like an industrial AC does, and you have the space for fans nearby, then water cooling doesn't buy you anything except complexity and cost.

Remember that some Infernal Combustion Engines, like early Beetle engines, were actually air cooled. Granted, they were a lot of trouble, and for an ICE that generates ~~15x the heat that an electric motor does, and maybe 30x the heat that a controller does, it really is a lot easier to cool a radiator that is designed solely for cooling than an engine that has obstructions all over it. A 50 kW engine is producing 150 to 200 kW of heat. It's a different problem by far. (I'm pretty sure that a car can't get rid of the peak heat output of its engine continuously, or even for more than a few minutes.)


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## Guest (Dec 25, 2009)

paker said:


> I talked to a guy at Thunderstruck Motors about the Curtis controller and he said it could be mounted in the grill with a finned heatsink, but I don't think that would help if I'm stuck in traffic with the car in front blowing it's exhaust on my car, as well as the hot pavement.


My GUESS is that it probably would work fine. If you're stuck in traffic the heat is not great at all. Ambient heat isn't really what we're talking about. It's the heat of dissipation given off by the semiconductor power components. When you're stuck in traffic, you're not really generating any.

You do generate a LOT of heat accelerating and most particularly at continuous highway speeds.

In Speedster 1, we have an aluminum plate presenting partially below the car in the slipstream and a Kelly controller mounted on this somewhat higher. It seems to work fine. But the Kelly uses some pretty nice little MOSFETS. 

So if you have a grill, and mounted the Curtis on a piece of finned heat sink stock, I think it would work fine. We don't have a grill at all. What we do have is a kind of fiberglass shelf in the rear engine compartment, high in the car under the "hump" of the Speedster. No flow at all. That's where I would like to mount it ideally.

Ergo, my question "how much heat are you really generating" which is kind of a vague touchy feely kind of question. But the answer points toward the need for liquid coolant in my particular application.

Jack Rickard


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## Guest (Dec 25, 2009)

Coulomb said:


> Granted, you won't be using peak power for very long, but a single quart of water will only last you one high power acceleration. It will then take longer to cool down the controller plus water than the controller by itself.
> 
> So: you do need cooling! That's why water cooling, despite the 3000:1 difference in heat capacity that Jack mentioned, isn't an automatic winner. Eventually, you need moving air to get rid of the heat. The water is really just a "middle man", useful if you can cool the controller better elsewhere (at a radiator) than where it is.


Yes, that is what is planned. But I don't think we need much. First, we'll have an aluminum reservoir holding probably less than a quart. But it will dissipate some heat. Then we have a "cooler", essentially a little finned aluminum tank about a foot long and 2 inches in diameter that we'll mount down into the passing air slipstream. This is where the water is "cooled".

I think it will be more than adequate. I was actually considering using one of the computer units that mounts in a hard drive bay. Has the radiator, pump, and fan all in one small device. But i decided they might not be dependable over years of operation. A little Bosch pump is likely to last, and metal stainless or aluminum parts from Summit Racing are most likely to be trouble free and look kind of cool as well. Same with the AN fittings and braided steel hose. It's a little pricey, but should last and might as well LOOK like we know what we're doing anyway.
Jack Rickard
http://evtv.me


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## tomofreno (Mar 3, 2009)

Good points Coulomb. As you say, you are ultimately limited by forced convection for heat transfer, whether from a finned heat sink on the controller or a liquid-air heat exchanger. The latter typically has much greater surface/volume ratio though so greater heat transfer. If it is just a finned tank, the heat transfer will be similar to a finned heat sink on the controller of similar area, but sounds like Jack is just using it to get the heat sink where he can get air flow due to vehicle movement, passive cooling. Active cooling with a fan has the advantage that when you slow down or stop the controller continues to cool, and faster, since the heat load is lower. "Heat sink" is somewhat of a misnomer in this case, as it is more of a buffer, providing some temporary heat sinking as its temperature rises closer to that of the controller, and requiring heat removal to continuously remove heat from the controller with sufficient efficiency. It is more a low efficiency heat exchanger. Its heat capacity just smooths out the peaks in controller temperature due to momentary high heating during acceleration or short hill climbing.

For more efficient heat transfer you will want want high enough flow rate to give turbulent flow (high Reynolds number), breaking up the boundary layer between liquid and metal to increase the metal-liquid temperature difference at the metal surface.

You are pretty much stuck with the deltaT required for a given heat transfer rate for a given convective heat transfer efficiency, so I expect my controller temperature will climb with ambient temperature. I'm getting around 40C now with ambient of 40F, or 4C, so in summer with temperatures around 100F, 38C, I expect the controller will be around 34C warmer or around 75C. That's driving at about 60mph continuous. I would likely need to add some surface area to drive at 75mph continuously.


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## tomofreno (Mar 3, 2009)

My first data log using the Junsi Cell log8! Four cell voltages logged for a short drive.

View attachment file1, cell log.pdf


The first large dip just past 2min30sec is at about 145A max current, the next is at 97A max, the fairly flat, but slightly increasing section after this is going downhill with about 15A regen. The largest dip, just past 5min is accelerating with max of a bit over 300A. Cells were at about 65F when I left, outside temperature was about 18F. Rest voltages, cell 1 to 4, before departing were: 3.293, 3.292, 3.293, and 3.292V. TBS said 37% soc. This thing is great!


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## tomofreno (Mar 3, 2009)

Some more cell log 8 data. I left the "voltage accu", accumulated voltage (sum of all 4 cells) axis in on this one.
View attachment file2, cell log.pdf

These are from 4 cells in the front box, at 54F (compared to the other 4 at 65F in the rear box). Same drive, but accelerated a bit more this time and drew a max of a bit over 400A. The first kind of steadily decrease is driving along in 1st out the driveway and up a small grade, the next dip is at 124A max, accelerating from a stop sign. The two sharp big dips at just past 5min are due to accelerating from another stop sign at around 405A max in 1st and 416A max in 2nd gear. The two smooth sections with very slight increase in V, starting at about 3min20sec and 7min30sec are at about 16A max regen going down small grades. As I was going down the second grade the "Lo" alarm displayed, showing the pack was at 35% SoC. 

The minimum cell voltages (sampling at 1 hz) at the big dip at 416A are: 
cell1 cell2 cell3 cell4
2.887 2.931 2.875 2.866

The min voltages of the 4 cells in the rear box at 300A in the drive prior to this one were:
2.837 2.939 2.854 3.074

This seems to indicate that the temperature difference in the front and rear boxes has negligible effect on cell voltage sag, so no need to decrease it - as long as I keep them both above 55F anyway. Also one of the cells in the front box was discharged by a faulty VB to 1.80V and subsequently overdischarged to 0.753V REST voltage. Can you tell which one? Cell3. It seems to behave the same as the others. It was first recharged with a 5A power supply (3 or 4 times because it kept creeping back down significantly) to get it to within 8mV of the other cells. The pack has been through about 3 charge/discharge cycles since then and its rest voltage has been similar to the other cells (bit larger due to charging a bit higher with the ps). I wondered though, if it was sagging more because of the "spongy" way it acted when first recharged. Apparently not. Looks like I don't need that one replaced.

Also looks like I will be fine triggering "empty" at 35% soc, and driving another 8 miles or so at about 40mph to get home or to a charger. What great data for $28.00!


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## tomofreno (Mar 3, 2009)

This is the same data as in the last post (4 cells in the front box) but with the ordinate chopped off at 2.7V to magnify the voltage differences. The small increases in voltage due to regen and the cells recovering in voltage are now more visible.

View attachment file2, cell log, scaled.pdf


I'm learning a bit more about Logview. The menu item "max/min" gives the maximum, minimum, range, and average of each data set, in this case each cell, which makes it easy to compare sag:

cell1 cell2 cell3 cell4
max 3.275 3.294 3.278 3.294
min 2.887 2.931 2.875 2.866
range 0.388 0.363 0.403 0.428
ave 3.203 3.225 3.203 3.215

Cell4 is the cell that is always the highest in voltage during charging. All the cells that had defective VBs are lower in voltage by around 0.02V despite having been charged to within 0.008V of the other cells a few charge cycles ago. All cells were at <3.24V after the drive as can be seen at the end of the cell log data, but 2 hours later most were up around 3.291V.


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## lapwing (May 8, 2009)

Brilliant information. Thanks for posting. It makes so much difference to have actual data on how these cells perform.

Thanks.

It's interesting how little extra regen provides. Not really surprising. 

I hilly areas I would guess is would matter a lot more. Hills punish the batteries on the way up, and regen then matters on the way down.


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## tomofreno (Mar 3, 2009)

> It's interesting how little extra regen provides. Not really surprising.


 It should be. The regen on this controller is not set up properly. It should be giving over 100A regen when it is giving about 20A. It is set up under VCL (the Curtis programming language) with no input from an external pot. I recently purchased a programmer to change it.


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## lapwing (May 8, 2009)

tomofreno said:


> It should be. The regen on this controller is not set up properly. It should be giving over 100A regen when it is giving about 20A. It is set up under VCL (the Curtis programming language) with no input from an external pot. I recently purchased a programmer to change it.


I look forward to seeing the data when it's set up to Max potential. (5% capture is a number I see tossed around as a best to hope for improvement) I am sure it depends a hell of a lot on topography. My Prius is bloody hopeless at getting to the top of a hill with a full battery pack, with nowhere to put the regen available on the way down. I wish I had a manual override on the way up to use the juice in the battery. Better yet, would be if the car had GPS smarts and learned the energetic characteristics of the "standard" routes I drive. That way once a route is driven once "predictive" battery depletion and regen could be utilized. Alas my Prius is dumb.

Anyway looking again at your graphs, anything under the bar is a bonus. I would love to see bigger areas under that regen curve. Having had a look at Transit bus published bus data where stop-accelerate-stop cycles are pronounced there appears to be a fairly worthwhile amount of coulombs to capture. The most success I have read comes from combining a smallish super-cap bank with the batteries, though it is not just hooked up in parallel. Some other way of routing regen surges to the caps, and the batteries independently is implied, but not detailed. I guess it's all proprietary. It seems the real value of the super-caps is reducing the I/O power peaks to the batteries, thus stressing them less. 

Definitely lots of scope for innovation here.


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## tomofreno (Mar 3, 2009)

My understanding is that the Prius is designed to use the motor principally as an assist to the ICE during acceleration so that a smaller, lower energy consuming ICE can be used. It only needs a bit more power than required to push the car at constant speed on the highway, since the motor provides the extra "umph" to accelerate the car. But the motor isn't designed to drive the car on its own either, except at very low speeds for very short distance, since its main job is to assist the ICE. The battery pack energy storage doesn't need to be that large for this purpose, so it is much smaller than the pack in an all electric vehicle, and constrained by its bms to charge to something like 80% and discharge to maybe 30% to baby the pack for long life. I don't think it was ever intended to climb even a short modest grade (say 3%, 3/4 mile long) in all electric.

With regard to supercaps, there has been a lot of discussion on those. I was strongly considering them at first, but others convinced me that it is as, or more, cost effective to just buy higher Ah cells and larger Ah pack so the regen current and current during acceleration is not a large enough fraction of C to affect cell life. If supercaps were less expensive, that might be different. The former is also a heck of a lot simpler.


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## JRP3 (Mar 7, 2008)

More good data. Looks like a LVC of 2.8 wouldn't give you any false readings, or at least very few.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> Looks like a LVC of 2.8 wouldn't give you any false readings, or at least very few.


Well, for the first 12 or so minutes of driving, when the pack is new.


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## JRP3 (Mar 7, 2008)

Coulomb said:


> Well, for the first 12 or so minutes of driving, when the pack is new.


His first test said he started with SOC at 37%, which would be near the end.


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## tomofreno (Mar 3, 2009)

Cell log data while charging:

View attachment file3, cell log.pdf


Guess I'm going to have to disagree with Jack's statement in his last video that 3.4V is full after charging at 0.05C to 3.6V. Cell1 was charged to 3.77V, with current ranging from 9 to 4A during the last 25 minutes of charging, and its rest voltage this morning 18+hrs later is 3.350V. All the other cells in the pack are in the range 3.350 to 3.356. I'm guessing the 3.4V was measured within less than an hour after charge. Cell voltages tend to continue to move around for quite a while after both charge and discharge. 

Notice the initial rise in voltage of the 3 cells when the charger is turned on is different even though they are starting at similar voltages (edit: actually they all increase about 0.07V, the scales on the graph are different). Also, cells 2&4 start to rise more quickly in voltage toward the end, but then level out again, before starting back up. I think that is because they are at the very beginning of the exponential rise seen in cell1, but charger current is decreasing at this point delaying the rise, until they reach a higher soc where voltage increase overwhelms the decrease in charger current, and voltage starts going up more rapidly.

Cell1 is a cell that was discharged by a VB and overdischarged. All such cells have lower capacity than the others. They had been at lower rest voltage than the others, so another cell always hit HVC first, but I charged them individually to "bottom balance" before this last charge, and now they all hit HVC well before the others.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> Guess I'm going to have to disagree with Jack's statement in his last video that 3.4V is full after charging at 0.05C to 3.6V. Cell1 was charged to 3.77V, with current ranging from 9 to 4A during the last 25 minutes of charging, and its rest voltage this morning 18+hrs later is 3.350V. All the other cells in the pack are in the range 3.350 to 3.356. I'm guessing the 3.4V was measured within less than an hour after charge. Cell voltages tend to continue to move around for quite a while after both charge and discharge.


Ah, good to have that confirmed. I believe that Jack said that the voltage settled in about 5-6 minutes. I guess he just wasn't patient enough.

Do you know if cells 3 and 4 had similar SOC to start with? It looks like they mostly have different internal resistance. I assume that they would have been at similar temperatures. IR may vary more than capacity; I guess time will tell.

Great data; thanks for publishing!


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## tomofreno (Mar 3, 2009)

> Do you know if cells 3 and 4 had similar SOC to start with? It looks like they mostly have different internal resistance. I assume that they would have been at similar temperatures. IR may vary more than capacity; I guess time will tell.


 You mean cells 1 & 4? All were in same box at same temperature (55F), rest voltages prior to charging were 3.294 cell1, 3.296 cell2, 3.294 cell4. Now that I look at the graph more closely, the apparent difference in initial voltage increase is just a result of the difference in scales used on the 3 cell y axes. The actual voltage increase is about 0.07V for all three. Sorry for the misleading comment.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> the apparent difference in initial voltage increase is just a result of the difference in scales used on the 3 cell y axes.


Oh, brilliant! Sorry, I wasn't expecting that. I hope that "feature" can be turned off... Or is that excel (or similar) doing the autoscaling for you?


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## maxvtol (Nov 11, 2009)

Tom, 
Very nice build, thanks for all the good info.

I'm in the design stages and looking an nearly the exact motor and battery setup, but my car is about 500 lbs heavier. 

My calculations for acceleration are similar to yours at electricnevada.org, showing your 0-60mph should be closer to 13 or 14 sec. Is the regen when you let of the accelerator the main reason, or are there other reasons it's taking 18 sec?

My calculations also show I would be better off spending ~$400 on 2 extra batteries than on a aluminum flywheel for a faster 0 to 60 time (by 1.0 sec vs 0.2 sec respectively). Do you think after the recharge the controller could handle the voltage of 38 batteries? It looks like the batteries would be under 130v after just a few minutes when the charger is removed.

Thanks,
Joe Davis


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## tomofreno (Mar 3, 2009)

> My calculations for acceleration are similar to yours at electricnevada.org, showing your 0-60mph should be closer to 13 or 14 sec. Is the regen when you let of the accelerator the main reason, or are there other reasons it's taking 18 sec?


 I think that maybe it is due to the way the controller is programmed. I purchased a programmer but have a communication problem with the controller, and HPEVS asked me to wait for help until after the first, as they have a bunch of tax rebate jobs to finish. There is quite a bit of flexibility in how the throttle is set up with Offset, Deadband, and Map parameters, so it might be improved.



> Do you think after the recharge the controller could handle the voltage of 38 batteries?


 I think so, the cells usually drop to less than 3.34V within 10 minutes after charging. 

Glad to have someone check my calculations! They seem fairly good insofar as the spreadsheet predicts range and current draw at various speeds very well. If you use 38 cells that should give about 122V nominal which is about 35% higher voltage than the dyno data in the spreadsheet. I would expect you would have the full 90 lb-ft torque out to about 4000 rpm then, which will help a lot accelerating at speeds over 50 mph. Good luck, and let me know how it works out.


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## maxvtol (Nov 11, 2009)

Thanks Tom.
Please post a 0 to 35 and 0 to 60 when you get the controller dialed in. I'd be interested in how close our calculations are. I couldn't tell from your sheet where your shift points would be, but using your weight and gear ratios mine shows if you start at 1st and shifted to the next gear around 3800rpm, you should be at 60mph in 4th in about 14 seconds. 

I was hoping for a sub 15 sec 0 to 60mph on my car, but my calcs show mine would be about 17sec with 36 batteries. If the AC50 is slower than that, I'll probably go DC with higher voltage and bigger controller. 

I'll definately post once I get closer. I just bought a donor and want to do some custom work to it before I get the motor. 

Joe


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## tomofreno (Mar 3, 2009)

> I was hoping for a sub 15 sec 0 to 60mph on my car, but my calcs show mine would be about 17sec with 36 batteries. If the AC50 is slower than that, I'll probably go DC with higher voltage and bigger controller.


 An 8", or in your case 9" DC motor with at least a 650A (2 min rating) controller would definitely give you more acceleration. I was planning on going that way until I found out about the AC50. I wanted electric braking and didn't want brushes/commutator. The latter work well of course, its just a distaste on my part. I don't think there is any way you will meet your acceleration goal with a 500 lb heavier vehicle and the AC50. Another consideration is that you will have to do a good job cooling the controller to run that weight, and I assume larger drag force, vehicle at sustained 60-65 mph. HPEVS had mentioned working with another controller manufacturer on a higher voltage controller, but I don't know if anything came out of it. 

In the version of the spreadsheet I modified for 115V pack, I also calculate available acceleration in mph/sec from the difference in available and required torque at each speed. From this I estimate my shift points with a 115V pack would be at about 25, 45, and 55 mph in 1st, 2nd, and 3rd. In actual driving it seems to maintain strong acceleration in 2nd up to about 5000 rpm and 45mph (maybe 5200 rpm) before it starts to fade. The most time lost in 0 to 60 is from 50 to 60 mph. The peak power of around 60 H.P. is just not enough to give high enough WHEEL torque at that speed range - because either rpm is too high in second or mechanical advantage is too low in 3rd. You need more power in that range. I expect the same for the smaller Azure Dynamics AC motor/controllers, although the AC24LS is better than the AC24, and should be stronger than the AC50/Curtis at higher speeds if run in Y configuration with a higher voltage pack. Adds expense though. I'm not aware of anything available to the diyer in AC with enough power to meet your acceleration goal. (Edit: Sorry, there are the Siemens AC motors and controllers available at Metric Mind and HEC, they don't usually come to my mind because of the price)


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## JRP3 (Mar 7, 2008)

Victor doesn't seem to be carrying Siemens any longer. What is really needed is around a 200 volt 700 amp controller for the HPEVS motors. Supposedly Sevcon has these but they are as yet unavailable.


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## maxvtol (Nov 11, 2009)

Re-entered your info in my spreadsheet this morning and got the same shift points as you, with 60mph in 3rd, don't know what I used last night, but it's encouraging that our numbers are close. You still should be able to get close to 14sec in 0 to 60mph. 

My parameters to keep the "fun factor" in driving is 0 to 35mph 5 sec desirable, 6 seconds acceptable and 0 to 60mph 13.5 sec desirable, 15 sec acceptable. Looks like the 0 to 60mph is a miss with the AC50 and right at 6 sec in the 0 to 35mph for my application. I could live with a slightly lower 0 to 60mph but if the 0 to 35 is a miss, then the AC50 is a no go. I'm hoping to chop out a couple hundred pounds with modifications, so my numbers may improve a little. 

I would love an AC for all the reasons you stated, but if the AC50 can't match our numbers, I'll definately go DC (mostly because I can just add a few batteries to get the extra range vs a much higher AC priced motor). I'll be following your thread with great interest.


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## tomofreno (Mar 3, 2009)

I put a bike rack and bike on the back of the car and drove about 30 miles round trip to bike ride in another valley. I used about 270 Wh/mile. Earlier I had driven to the same area sans bike to do some test driving and got about 205 Wh/mile, so additional drag caused by the bike apparently increased energy/mile by about 30%!


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## JRP3 (Mar 7, 2008)

I can imagine the bike would mess up the aerodynamics quite a bit.
I have a question, on the Curtis wiring harness there is an orange wire that is not shown in the diagram and I assume is not used. It goes into pin 3 on the connector. Do you know what it is?

Also, what did you use for a 10 amp fuse on the pack voltage to relay blue wire?


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## tomofreno (Mar 3, 2009)

> I have a question, on the Curtis wiring harness there is an orange wire that is not shown in the diagram and I assume is not used. It goes into pin 3 on the connector. Do you know what it is?


 I called HPEVS on this and confirmed it is not used - said he included it by mistake.


> Also, what did you use for a 10 amp fuse on the pack voltage to relay blue wire?


 Just a 1/4"dia x 1 1/4" long fast blow 10A fuse and cartridge type fuse holder, both from Radio Shack. I figure the relay uses much less than this.

Sounds like you are hooking things up. When do you expect to be able to drive it?


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## tomofreno (Mar 3, 2009)

JRP3, didn't you say you were using a tank type heater? What do you use for a fluid pump?


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## JRP3 (Mar 7, 2008)

I'm trying to do as much wiring on a board in the house, then I'll run outside and bolt it on top of the motor and hook up the motor and battery wiring. Trying to minimize my outdoor time as it's about 15F right now and not looking to get much warmer. Then I'll throw in 96 volts of lead acid for the 3 mile drive to work so I can get it in the shop. Might have to wait a few days for clear roads as the nearly bald 60 series tires won't do too well.
I used this Surflo pump, or will use as I haven't hooked it up yet:
http://www.adventurerv.net/shurflo-nautilus-single-station-water-pump-gpm-p-1713.html


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## tomofreno (Mar 3, 2009)

> I used this Surflo pump, or will use as I haven't hooked it up yet


 Thanks for the link. I was looking at this same pump, but it was $49.99 where I was looking. I would guess 1 gpm would be plenty. Do you plan to use a small expansion tank, or just fill the lines, core, and pump to overflowing to get air out, and assume negligible expansion over the temperature range used?


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## tomofreno (Mar 3, 2009)

Fifteen is too cold to work! I had a hard enough time working at 30F.


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## JRP3 (Mar 7, 2008)

Yes and right now it's 11  I may end up renting a tow dolly, but since the car is so low and not running it will take some work just to get it on the dolly. Guess I'll be waiting till things warm up a bit, I'm not looking to drive this much in the winter anyway. 4 wheel drive is often needed here and my ICE RAV4 handles that for me, and I don't want to salt up the Fiero after all this work.
So far I just filled everything up to overflowing a couple of times and it seems to work well, no tank. I am thinking of adding a remote radiator fill cap like this one
http://www.siliconeintakes.com/product_info.php?products_id=1064
This would provide pressure relief and easier air bleeding.
Adding a tank would allow longer run time after preheating when plugged in but would take longer to warm up on it's own, so for now I'll try tank less.


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## tomofreno (Mar 3, 2009)

What do you think about long term reliability of the pump at those fluid temperatures?


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## JRP3 (Mar 7, 2008)

I don't know exactly what temperatures it will see but plumbing it after the heater core and before the heater should mean most of the heat is gone before it gets to the pump. If the pump is still seeing hot water that would suggest to me the flow should be restricted more so that the heat can be extracted by the heater core more effectively.


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## tomofreno (Mar 3, 2009)

I drove a bit over 65 miles round trip yesterday. About 70% at 50 mph and the rest at around 35 - 45 mph. I didn't use the heater or lights. Used 114Ah, or about 64% DoD, and 1.75Ah/mile. That gives around 200Wh/mile guesstimating an average pack voltage of 114V. The difference in EKM meter readings before and after re-charge was 14.52kWh, or about 223Wh/mile from the wall. Outside temperature was in the low 20's (F) on the first half of the trip in the morning and around 38F on the return. Cell temperature was 60F when I left in the morning. Unknown in the afternoon after sitting outside for about 7 hours, but was about 49F when I returned home, so maybe they got down in the high 30's. I didn't notice any difference in performance with the cells colder. Forgot my cell log 8 though, so don't know how sag differed.


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## dimitri (May 16, 2008)

tomofreno said:


> I didn't notice any difference in performance with the cells colder. Forgot my cell log 8 though, so don't know how sag differed.


Tom, other than cell loggers, do you have overall pack voltage visible while you drive? I am surprised you don't notice the sag and less performance with cold pack. Mine is too obvious to miss. Perhaps SE cells are better at low temps, or maybe because they are new, or maybe I have crappy cells, don't know. I have a few weak cells which sag to 2.6V, but even my good ones sag to 2.9V and its very noticeable on the voltmeter even without looking at cell level data.

Thanks


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## tomofreno (Mar 3, 2009)

> Tom, other than cell loggers, do you have overall pack voltage visible while you drive? I am surprised you don't notice the sag and less performance with cold pack. Mine is too obvious to miss. Perhaps SE cells are better at low temps, or maybe because they are new, or maybe I have crappy cells, don't know. I have a few weak cells which sag to 2.6V, but even my good ones sag to 2.9V and its very noticeable on the voltmeter even without looking at cell level data.


 Yes, I can read pack voltage on both the Curtis and TBS gauges. The lowest voltage I saw was 109.4V, or about 3.1V/cell going up an about 3% grade at about mile 64 on the return, pulling about 165A max. Can't say of course how much of that sag was due to any one or more cells being significantly lower than others. I had planned to clip on the cell logs on the return trip to examine this but forgot them. Ah well, next time. I rarely see the the pack voltage drop below 110V, or 3.14V/cell during normal driving, which means pulling around 2C or less during acceleration and no less than around 40% soc. I'm still running on 35 cells, as I haven't received replacements yet.


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## dimitri (May 16, 2008)

Thanks, so I guess you aren't hitting 3C that often since your car is light and you have larger cell size and your cells are new, so you don't see much sag. I don't see much trouble at 1C-2C , only at 3C it becomes obvious. I am coming to a conclusion that constant 3C rate in TS datasheets is bullshit, they seem to degrade faster if you pull 3C often, even if its only for 5-10 seconds at a time. Maybe I just have exceptionally crappy cells, but more likely TS datasheet is full of crap.

Again, its not all cells, but seems to be about 10% of them at least.

I should have gotten 45 180AH cells instead of 40 160AH cells for my car, oh well, lessons learned for the next time


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## tomofreno (Mar 3, 2009)

> I am coming to a conclusion that constant 3C rate in TS datasheets is bullshit


 The question is what does that 3C rating mean? That the cell won't blow up or melt at 3C, that its lifetime will not be affected regularly hitting 3C, that lifetime will be affected if you drive it to 3C more than a few times...? Most people seem to assume it means there is no effect whatsoever on lifetime if a cell is repeatedly driven to 3C discharge. But the spec does not explicitly say that. You don't really know what it means as it is not spelled out. The devil is in the details.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> I drove a bit over 65 miles round trip yesterday. About 70% at 50 mph and the rest at around 35 - 45 mph. I didn't use the heater or lights. Used 114Ah, or about 64% DoD, and 1.75Ah/mile. That gives around 200Wh/mile guesstimating an average pack voltage of 114V. The difference in EKM meter readings before and after re-charge was 14.52kWh, or about 223Wh/mile from the wall. Outside temperature was in the low 20's (F) on the first half of the trip in the morning and around 38F on the return. Cell temperature was 60F when I left in the morning. Unknown in the afternoon after sitting outside for about 7 hours, but was about 49F when I returned home, so maybe they got down in the high 30's. I didn't notice any difference in performance with the cells colder. Forgot my cell log 8 though, so don't know how sag differed.


Very nice! Do you have the heating pads working? Were u not using them on this trip?

Cheers,
Gary


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## JRP3 (Mar 7, 2008)

I think the SE cells are supposed to be better in the cold than the TS cells, or at least the older TS cells before they added yitrium.


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## dimitri (May 16, 2008)

JRP3 said:


> I think the SE cells are supposed to be better in the cold than the TS cells, or at least the older TS cells before they added yitrium.


Is there any data to support this theory? There is even less info published on SE cells than TS cells, and even TS data is sketchy at best. Everything has to be discovered by trial and error  . Oh well, we are early adopters, so we get to uncover things for others to come....


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## JRP3 (Mar 7, 2008)

I can't point to any actual data, that's just information I've read at various places.


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## tomofreno (Mar 3, 2009)

> Do you have the heating pads working? Were u not using them on this trip?


 Yes, they are working. I only use them when the car is parked, plugged into 120VAC. Between the heat capacity of the cells, heat generated while driving, and the box insulation the cells remain warm while driving. I'm usually not parked away from home that long so they don't usually cool down that much.


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## tomofreno (Mar 3, 2009)

Got my programming software communicating with the controller today thanks to help from HPGC. I think I see one reason why acceleration was not as good as expected. The forward_map parameter is set to 35%:

*Forward Map *0–100 % Modifies the vehicle’s response to the throttle input. Setting the throttle. _Forward_Map 0–32767 _map at 50% provides a linear output response to throttle position. Values below 50% reduce the controller output at low throttle settings, providing enhanced slow speed maneuverability. Values above 50% give the vehicle a faster, more responsive feel at low throttle settings.

Not sure what is limiting regen yet. The regen_current_ limit parameter is at 100%. Might be the neutral_braking parameter, which is set at 10%. Hope to get some answers from HPGC tomorrow. They are really busy. Nice software. Very easy to use, easy to edit parameters. Still much to learn, but I like that.


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## GizmoEV (Nov 28, 2009)

tomofreno said:


> Not sure what is limiting regen yet. The regen_current_ limit parameter is at 100%.


Is it possible that you want the regen_current_limit parameter to less than 100%? Maybe it is limiting regen current as much as possible without totally disabling regen.


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## tomofreno (Mar 3, 2009)

> Is it possible that you want the regen_current_limit parameter to less than 100%? Maybe it is limiting regen current as much as possible without totally disabling regen.


 Possible, but no, the manual says:
Regen Current Limit, 5–100 %: Sets the maximum RMS regen current, as a percentage of the controller’s full rated current. The regen current limit applies during neutral braking, direction reversal braking, and speed limiting when traveling downhill.

That last one, speed limiting when traveling downhill is what I'm interested in. From this, I would guess neutral braking doesn't affect it. Have to talk to someone who knows.

I think the throttle_map parameter value of 30% is why I have to push the accelerator pedal halfway down before I get much acceleration, so I'll likely change that to 50% - 60% so it is linear or a little greater acceleration during the first half and see how I like it. I don't want it set up so it jumps when you touch the pedal, but it feels spongy now.


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## maxvtol (Nov 11, 2009)

Sorry if I missed in earlier posts, but how are you applying regen? Pot or switch on brake pedal or manually?

Lots of parameters in that manual, that could keep you busy for awhile.


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## tomofreno (Mar 3, 2009)

> Sorry if I missed in earlier posts, but how are you applying regen? Pot or switch on brake pedal or manually?


 None of the above. It is under VCL control by the VCL_brake variable. There is no input to pins 17&18 on the controller. I ended up setting the neutral_braking parameter to 20% to give some coasting, but limit speed downhill acceptably. After playing with it, I think pot input to change the amount of braking would only be useful on an unusually steep hill, and you change how much you coast by shifting to a higher or lower gear, or taking it out of gear. So I likely won't add a pot.



> Lots of parameters in that manual, that could keep you busy for awhile.


 Yeah, keep me off the streets. Most of them aren't of much interest though. I'll likely tweek the drive and regen limiting map parameters, and maybe a couple other things to see what effect they have and tune it to my preference. I'm happy with the performance now, but its interesting to explore effects.


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## JRP3 (Mar 7, 2008)

So how much regen are you seeing now?


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## maxvtol (Nov 11, 2009)

And is the Overvoltage on the Battery menu perhaps limiting the regen? 

_Overvoltage protection cuts back regen braking to prevent damage_
_to batteries and other electrical system components due to overvoltage._
_Undervoltage protection prevents systems from operating at voltages below_
_their design thresholds._
_Overvoltage = Either Max Voltage (see voltage ratings table) or User Overvoltage × Nominal Voltage, whichever is lower._​ 
The table voltage of 105v would be lower than Nominal x User Overvoltage, so hope that's not it, or at least it could somehow be changed or upgrade to a higher voltage pack. ​


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## tomofreno (Mar 3, 2009)

> So how much regen are you seeing now?


 About twice as large max Amps as before.


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## tomofreno (Mar 3, 2009)

> The table voltage of 105v would be lower than Nominal x User Overvoltage


 The table in the manual doesn't include settings for the -7501 controller. The nominal_voltage parameter is set at 96V, which is not in the table. I think max voltage for the controller is probably 134V since the user_overvoltage parameter was set at 140% which is about 134.4V. I set it back to 124% to avoid overcharging my cells.


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## EV-Eric (Jun 21, 2009)

I have been following you progress and I have to say it’s outstanding! The data you provide is also very informative.

I’m actually looking for some specific information you may already have, possibly provided.

Do you have teh current draw on your battery pack? This would be the current the AC controller is drawing from your pack, not what the motor is using. I’m not totally clear the current you state is from the battery pack or the motor.

I would be very interested in the current draw (battery pack) at say… 5mph, 25mph, 45mph and 65mph on a flat street, but would be grateful for any real world measurements.


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## tomofreno (Mar 3, 2009)

> I would be very interested in the current draw (battery pack) at say… 5mph, 25mph, 45mph and 65mph


 See post #202 in this thread for currents at 30, 40 and 55 mph.


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## tomofreno (Mar 3, 2009)

I've played around with parameter settings for a bit now. I changed throttle_forward_map to 65% to get more responsive accelerator pedal. Feels more like what I am used to in an ICE now, little push gives good acceleration. Before it felt like I had to push the pedal half way down to get the car to move at all. I changed Accel_Rate under Torque Mode to 0.5 sec from 1.0 sec and the Throttle_Forward_Deadband to 0.25V from 0.5V to try to improve response and shave a hair off 0 to 60 time. There was nothing to be gained under Drive_Limiting_Map as all parameters were already at 100%. I did 0 to 60 in about 17 seconds with this, might have shaved off that second only because I am getting more comfortable with the car. Not going to do better I think. That's much faster than normal acceleration in traffic anyway. If I had a smoother shifting car I might shave another second or so. The Swift does not shift very quickly from 1st to 2nd - not a high end vehicle you know.

Neutral_Braking ended up at 22% which permits me to coast down most hills at or near the speed limit in an appropriate gear without using mechanical brakes, and gives a max of around 45A regen depending on grade and vehicle speed. So the comment earlier by a viewer that you don't get a lot of regen is correct. You can set it higher to get more max current, but you just slow down faster. There is only so much kinetic energy available to convert. It is significant, but nothing approaching the magnitude of current used going up the hill. I get about 40 - 45A going down a hill at 50 mph that I use 180 to 220A going up at 50 mph.

I set User_Voltage to 124% to avoid overcharging with regen. This and HVC (yet to get) should protect the cells well. I'm driving the car regularly now. It has become quite routine. Fun to drive, good response, handling about the same as before conversion (only added about 350 lb to curb wt). Charging is also routine. Plug in the charger, go out 3 - 4 hours later, depending on DoD, and unplug it. The timer kicks on at about 117.5V and times out when the highest voltage cell is at about 3.42V. Might seem low, but I can only put about 5Ah more charge in before this cell hits 3.6V. I could tweek it a bit higher but it doesn't seem worth it as it is only about 3 miles worth of charge, and I have plenty range. 

I typically don't drive enough to require charging every day. Sometimes each day for a few days, other times every 2nd or 3rd day. I'll drive it even less in summer as I ride my bicycle for many trips then (more fun). At most, I head for home when the last bar on the TBS starts flashing indicating I am about to run out of energy, which is really 35% DoD. I can drive around 6 - 8 miles I think from the time this last bar starts flashing to when it disappears. Then I can drive another 8 or so at around 40mph and be a little under 30% soc. Its like getting to know the gas gauge in a new-to-you ice, you learn about how far you can go when near empty. The most I have used is 114Ah on one trip of 65.1 miles, most at 50mph, the rest at 35 to 45mph. Got 1.75Ah/mile and about 200Wh/mile on that one (little stopping, just cruising). Its a delight.


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## Kelmark (Oct 26, 2009)

Tom,
I have been watching your EV build with great enthusiasm you have provided outstanding data. Earlier there was some discussion that HPEV was looking at a higher voltage controller to use with the AC-50 motor. Do you know if there has been any progress or who I might e-mail to get more information? 
Also do you know if the controller below would work with the AC-50? It has the cooling system built in and similar compared to Curtis, it is listed at 80V nominal with 116V max with 600 amps for 1min for better acceleration! Also I could not find, continues amp rating, for the Curtis controller but the Sevcon is rated for 240 cont. which should be enough to handle highway speeds without getting hot I would think. I am trying to get prices now, but thought I would pick your brain while I am waiting.
Sevcon “espAC” 80V Single Traction 600/240 Amp controller with the fan cooling http://www.sevcon.com/pages/espac.html
One more thing I wanted to ask, I am converting a VW based kit car that has a stock 1978 4spd Transaxle. I will be having it rebuilt but was wondering if I should change some of the gear ratio’s to optimize acceleration, best 0-60, or leave everything stock? I know you have I nice spreadsheet made up but I am not sure how to read it to compare acceleration, I think it is more for range. Top maintained speed needed is 70mph but I not to worried about how fast it goes from 60-75 and I live in Kansas so I don't have alot of hills. Tire size can vary between 24min-27max dia. to dial it in. Finished weight of the car will be <2,000 pounds. Any help would be appreciated. 
Respectfully, 
Jacob Blake 
USNR


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## Voltswagen (Nov 13, 2008)

Jacob
I have 2 Beetles 73 & 77. I installed a Freeway Flyer Trans in the 73 from Car Craft in Riverside, CA and it has performed well for over a year now.
http://carcraftstore.com/stockandhdtransmissions-swingandirs.aspx

First, second and third gears are stock ratios...... 
The fourth gear is taller changing the stock ratio from 0.89 to 0.82
This trans drops my rpm's at 65mph from 3200 to about 2700 in the ICE powered 73.
My 77 is an EV but I dont drive many highway miles so I left that trans stock.
If you drive lots of highway miles the Freeway Flyer will reduce your rpms.


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## Kelmark (Oct 26, 2009)

Voltswagen said:


> Jacob
> I have 2 Beetles 73 & 77. I installed a Freeway Flyer Trans in the 73 from Car Craft in Riverside, CA and it has performed well for over a year now.
> http://carcraftstore.com/stockandhdtransmissions-swingandirs.aspx
> 
> ...


Voltswagen thanks for the feed back,

I was thinking of going with something like: HD Comp Transmissions are available that come with: Super Diff, HD Side Cover, Welded Hubs, Steel Shift Forks, Hardened Keys and Close Ratio gears. With the exception of fourth gear, this should be at 0.82 for interstate travel. Or I can change the ring and pinion to 4.86 and go a little taller than .82 for forth. Not sure what’s better or cheaper.

Now if I can figure out what the ratio is for 1, 2, and 3 along with the stock ring and pinion. I am not sure what they mean when they say closer (vague)? 

The reason I am asking is to determine approximate acceleration rates and shift points at motors peak power which is around 3,200 RPM. I’m trying to maximize acceleration 1-3 gears with 4th for interstate (70mph). Am I on the right track or wasting money?

What tire diameter do you have on your 73?

Respectfully,

Jacob Blake
USNR


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## tomofreno (Mar 3, 2009)

> Earlier there was some discussion that HPEV was looking at a higher voltage controller to use with the AC-50 motor. Do you know if there has been any progress or who I might e-mail to get more information?


 I see you found the thread on these controllers that JRP3 started. That's as much as I know. The nominal voltage for the Curtis 1238-7501 is 96V not 80V. It's max voltage is around 134V I think. So the Sevcon might be a bit higher power. The higher voltage with the Curtis will give you a bit better acceleration at higher speeds. I don't think the Curtis will handle 240A continuous without overheating, so the Sevcon looks better in that regard. I use around 150-160A at 60mph on level ground. A < 2000 lb VW should use less. 



> I know you have I nice spreadsheet made up but I am not sure how to read it to compare acceleration


 Check the "New EV Calculator" thread (9-29-09) under the "Technical Discussion" forum. Might get him to run some calc's for you to find optimum gearing.



> motors peak power which is around 3,200 RPM


 The rpm where you have peak power will depend on your pack voltage. Mine is about 115V nominal which gives peak power at around 3500-3600 rpm - you have more voltage to overcome the motor back emf, so can maintain the 90 lb-ft out to higher rpm. Even past this peak power point you have higher power in that gear for a several hundred rpm more compared to the next higher gear (click on the tab AC50, Power at the bottom of my spreadsheet to see motor power versus vehicle speed - you can relate this to motor rpm by looking at the spreadsheet - "data" tab). For max acceleration I don't shift until around 4800 - 5000 rpm - a little over 40 mph in 2nd and around 57-58 mph in 3rd. 

Thanks for the kind words. I'm trying to get some data out so people can get some idea of what to expect - rather than just using different ev calculators unaware of their accuracy.


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## Voltswagen (Nov 13, 2008)

Jacob
My 73 wheels are 17" but standard height. (28" I think?) I used a lower profile tire to maintain the stock diameter.
I really don't think you need a competition trans. The first 3 gears in the stock VW trans are sufficient.


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## Dave Koller (Nov 15, 2008)

Thanks for your posts Tom - Real world data !!!


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## Kelmark (Oct 26, 2009)

tomofreno said:


> Neutral_Braking ended up at 22% which permits me to coast down most hills at or near the speed limit in an appropriate gear without using mechanical brakes, and gives a max of around 45A regen depending on grade and vehicle speed. So the comment earlier by a viewer that you don't get a lot of regen is correct. You can set it higher to get more max current, but you just slow down faster. There is only so much kinetic energy available to convert. It is significant, but nothing approaching the magnitude of current used going up the hill. I get about 40 - 45A going down a hill at 50 mph that I use 180 to 220A going up at 50 mph.


Tom,

I thought this kit had two regen features; one when you let of the gas (neutral braking), and the other when you press the brake pedal? Is this not the case? And if it does have both features what amps are you getting from when you hit the brake pedal? I would think it would be allot more than the nuetral braking.


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## tomofreno (Mar 3, 2009)

> I thought this kit had two regen features; one when you let of the gas (neutral braking), and the other when you press the brake pedal? Is this not the case? And if it does have both features what amps are you getting from when you hit the brake pedal? I would think it would be allot more than the nuetral braking.


 That is correct, i.e. the controller has this capability, but it did not come wired for input from an external pot (pins 17&18) from HPGC. You can add a pot and wires/connector pins, but it didn't come with it. HPGC/HPEVS told me they developed an input for this using a pressure transducer mounted in a brake line so that increasing pedal pressure gives more electric braking (above the neutral braking). However, they said it is difficult to find fittings and the right transducer for a given vehicle, so they only offer it to OEMs. Too difficult to offer kits for different ev's. It would be nice to have since it would act as power brakes, decreasing stopping distance, and also decrease wear on mechanical brakes. The plumbing job would have to be tight and reliable because they said the brake pressure is around 500 to 700 psi. The problem with using a pot driven off the brake pedal motion directly is brake pedal travel drifts over time. But maybe that doesn't matter so much, you would still get electric braking, and it seems you could lightly touch the pedal to increase electric braking without engaging the mechanical brakes significantly. Maybe a rotary pot with a lever on it that rides against the brake pedal, with lever length determining the total possible rotation of the pot.


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## Kelmark (Oct 26, 2009)

Couldn't you set it up like neutral braking 22%, braking 40% (triggered off brake light sensor) for non-OEM vehicles? Then with the software it can be adjusted as needed. I might just ask them for their transducer though, it can't be that hard to get fittings, and besides most brake lines are fairly standardized. If you order from them is the wiring an option?


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## tomofreno (Mar 3, 2009)

> Couldn't you set it up like neutral braking 22%, braking 40% (triggered off brake light sensor) for non-OEM vehicles?


 You could set up for a constant input to the brake input pins if you like. It requires a resistance of the correct value for percentage braking you want. Don't know what you mean that it can be adjusted with the software, also don't know what you mean by brake light "sensor".


> I might just ask them for their transducer though, it can't be that hard to get fittings, and besides most brake lines are fairly standardized.


 I don't think they will sell you a transducer, as they don't know what model is required for your car to give the proper signal level. 



> If you order from them is the wiring an option?


 Don't know. They might be willing to include the additional wires in the harness, or, they might just make up standard harnesses and not be interested in one-offs for diyers.


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## Kelmark (Oct 26, 2009)

tomofreno said:


> Don't know what you mean that it can be adjusted with the software, also don't know what you mean by brake light "sensor".


I just thought it would have been nice if it was set up for when you push the brake and the brake light switch (sensor was not correct terminology) closed, lighting up your brake lights it also could have engaged the regen braking that could have been an adjustable setting in the controller.

Sorry, allot of could have's but I am interested in getting the most out of the regen. And in Kansas we don't have allot of hills to use the neutral braking on.


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## JRP3 (Mar 7, 2008)

If you don't have hills you probably won't have much regen available anyway.


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## tomofreno (Mar 3, 2009)

> I just thought it would have been nice if it was set up for when you push the brake and the brake light switch (sensor was not correct terminology) closed, lighting up your brake lights


 I see. Yes it would, but then when you engine brake in an ICE vehicle they don't light. Would be good though. You get neutral braking/regen any time you take your foot off the accelerator. How much depends on how aggressively you set it. I notice Brian said he was getting up to 100A and didn't have to use his mechanical brakes much at all. When you set it that strong the car slows very rapidly when you release the accelerator and you get a short burst of fairly high current. With it set this aggressively, I found I had to leave my foot on the accelerator going downhill to maintain speed. I might draw very low amps, but I didn't get regen. I preferred to set it less aggressively so I could find an appropriate gear for the grade to maintain speed with my foot off the accelerator, and get regen all the way down. Just depends on what you want. It helps much more with braking when set aggressively - like power brakes. I downshift to get a similar effect, but not as strong.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> If you don't have hills you probably won't have much regen available anyway.


What about stop lights and intersections? You can get back a proportion of the energy used to get up to speed.

The regen from this sort of stopping is surely what makes hybrids more efficient with city traffic than with highway driving, where essentially the only regeneration is from hills.


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## JRP3 (Mar 7, 2008)

Being able to shut off the motor when stopped is probably the major boost for hybrids in city driving. Gentle driving in the city is probably the best way to get range in the city, no matter what you drive. I doubt you'll get much regen from stopping on the flat at 30 mph or less.


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## GizmoEV (Nov 28, 2009)

What about doing what Victor at Metric Mind did on his ACRX? He put a linear pot on the gear shift lever. This is easily controlled with one finger and the regen is then variable.

I have a less smooth way of doing the same thing on my Gizmo where I hit a button which turns my throttle trigger into a regen trigger until I hit the button again or I hit the brakes. In my case I use the regen to save my brake pads more than the energy I get back. Below about 10mph it actually takes energy out of the pack for "regen," upto about 40A when I'm at about 4mph. This might be because of running a SepEx system and not an AC system.


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## frodus (Apr 12, 2008)

does the curtis allow you to change regen on the fly without having to reprogram the VCL code?


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## tomofreno (Mar 3, 2009)

> does the curtis allow you to change regen on the fly without having to reprogram the VCL code?


 Only by using an external pot as gizmo described. Mine is currently set up as Brake_Type 5 so braking/regen is determined by the VCL variable VCL_Brake. I can only vary it by changing the Neutral_Braking parameter with a programmer, and then it is fixed at that value. You can also use an external pot and Brake_Type 2 to vary braking/regen "on the fly". I believe in this case the Neutral_Braking parameter will determine how much braking you get if there is no signal from the pot, but not sure. That is why I was thinking of actuating a pot off the brake pedal. I would leave the Neutral_Braking parameter as I have it, and slightly depress the brake pedal (mostly over its free travel) if I want more em braking. This would also light the brake lights. One issue would be finding a pot that would give the resistance range required with the given amount of pedal travel. Don't really know if it is feasible to set it up this way, may be unforseen issues. I originally planned to use a pot like Victor, but now think I don't want to have to mess with adjusting it. I just shift gears to find one I can coast down a given hill at about the speed limit, avoid mech braking, and get regen. Downshifting doesn't stop you fast like aggressive em braking would though, so would be nice to be able to increase it with the brake pedal for sudden stops or just final stops at stop lights. HPGC says that is how the pressure transducer works - neutral braking plus more em braking when stopping.


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## tomofreno (Mar 3, 2009)

> Being able to shut off the motor when stopped is probably the major boost for hybrids in city driving.


 That and the fact that the electric motor/controller combined efficiency is around 60 -80% compared to less than 20% for an ICE when accelerating from a stop.


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## few2many (Jun 23, 2009)

What I got from the curtis site and manuals is that there is off pedal regen and support for a brake pedal pot, similar to the accel pot, but controls braking amount by regen, or vice versa. As kelmark mentioned, setting up the brake pedal to send the signal for regen and use a resistor to control the amount of regen required would be fine. 
Would this would act in place of the brake pedal pot? 
So you press the brake enough to actuate the lights and regen, press a little harder if you actually need mech brakes? 
Or just set up the off pedal regen strong and let off the accel slow and easy?
I think having the brake pedal actuate a pot, then the mecanical brakes or a hand operated brake pot might raise some safety concerns, especially where "panic" stops are concerned.


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## Dave Koller (Nov 15, 2008)

tomofreno said:


> You can also use an external pot and Brake_Type 2 to vary braking/regen "on the fly".


I am looking for an old hydraulic resistance sensor... It could go on the master cylinder and give you a resistance for the amount of pressure - it is a hydraulic device used in industry on rams to prevent over "pushing" or stop at a certain pressure ... But I can't find my source ! Thought that might be easy - Anyway, all the regen has a great benefit and makes me want to build with AC next time.. We have run a few threads on over-rev and AC regen does fix that!!


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## tomofreno (Mar 3, 2009)

I said you would use brake_type 2 with a pot, but it looks like you would use brake_type 3 for a two wire pot to pins 17&18. Brake_type 3 is used for single ended 3 wire pot, 0 to 5V, or current input. It doesn't specify current level.



> I think having the brake pedal actuate a pot, then the mecanical brakes or a hand operated brake pot might raise some safety concerns, especially where "panic" stops are concerned.


 You have to push the brake pedal to actuate the mechanical brakes anyway, the pot would just add em braking to this. _But I do agree that a great deal of caution should be used in messing with the brake system._ That is why I thought it would be good to leave the mechanical braking hydraulic system alone, and just adding something like a pot to add electric braking. If the latter fails for some reason, the mechanical brakes still work as usual. But if you become accustomed to having the electric braking help stop the vehicle, and it fails, you may well not have left enough space to stop in time, so it could be dangerous. I wonder if liability is the real reason HPGC doesn't want to sell pressure transducer-based kits.



> I am looking for an old hydraulic resistance sensor


 Seems like it would be a good solution if you can find one with the required resistance range for your brake pressure range. Something like this or a pressure transducer seems like the slickest solution, but there may be unforeseen issues. This pressure transducer looks like it may work: 
http://www.omega.com/ppt/pptsc.asp?ref=PX309-5V
But it cost $225.00. A tee would need to be added at the master cylinder output so this could be teed in...would have to find appropriate fittings to give highly reliable connections. It does make me very nervous messing with the brake system, so not sure I will try it.


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## maxvtol (Nov 11, 2009)

tomofreno said:


> Don't really know if it is feasible to set it up this way, may be unforseen issues. I originally planned to use a pot like Victor, but now think I don't want to have to mess with adjusting it. I just shift gears to find one I can coast down a given hill at about the speed limit, avoid mech braking, and get regen. Downshifting doesn't stop you fast like aggressive em braking would though, so would be nice to be able to increase it with the brake pedal for sudden stops or just final stops at stop lights. HPGC says that is how the pressure transducer works - neutral braking plus more em braking when stopping.


Seems to me your neutral braking setup is the way to go. 

If you use a pot or switch with a set resistance on the brake pedal, wouldn't the car slow down differently in 1st gear vs 3rd gear? Seems like you would get a different stopping experience depending on what gear you're in, and not very natural feeling.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> This pressure transducer looks like it may work:
> http://www.omega.com/ppt/pptsc.asp?ref=PX309-5V
> But it cost $225.00. A tee would need to be added at the master cylinder output so this could be teed in...would have to find appropriate fittings to give highly reliable connections. It does make me very nervous messing with the brake system, so not sure I will try it.


Right. So why not use the pressure that already is transmitted to the brake pedal, which the user is already used to? A tough, thin strain gauge ought to do it, somewhere between the brake pedal and the slave cylinder.

Even if it's essentially a pedal position sensing system, I think it would be okay, even though brake pedal positioning will drift with time. The driver will get the feedback from the movement of the car, and the movement of the windshield relative to his/her nose . Certainly, actual pressure senitivity would be better, even though it means light use of mechanical brakes for the lightest braking.


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## Dave Koller (Nov 15, 2008)

tomofreno said:


> Seems like it would be a good solution if you can find one with the required resistance range for your brake pressure range. Something like this or a pressure transducer seems like the slickest solution, but there may be unforeseen issues. This pressure transducer looks like it may work:
> http://www.omega.com/ppt/pptsc.asp?ref=PX309-5V
> But it cost $225.00. A tee would need to be added at the master cylinder output so this could be teed in...would have to find appropriate fittings to give highly reliable connections. It does make me very nervous messing with the brake system, so not sure I will try it.


I agree now - they "use to be" 49 bucks  Gad it's like the price of gas! Keeps going UP .. Coulomb's strain gauge sounds less expensive BUT maybe they have gone UP also!


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## rctous (Jun 18, 2008)

tomofreno said:


> I see. Yes it would, but then when you engine brake in an ICE vehicle they don't light. Would be good though. You get neutral braking/regen any time you take your foot off the accelerator. How much depends on how aggressively you set it. I notice Brian said he was getting up to 100A and didn't have to use his mechanical brakes much at all. When you set it that strong the car slows very rapidly when you release the accelerator and you get a short burst of fairly high current. With it set this aggressively, I found I had to leave my foot on the accelerator going downhill to maintain speed. I might draw very low amps, but I didn't get regen. I preferred to set it less aggressively so I could find an appropriate gear for the grade to maintain speed with my foot off the accelerator, and get regen all the way down. Just depends on what you want. It helps much more with braking when set aggressively - like power brakes. I downshift to get a similar effect, but not as strong.


But that 100 amps is if you take you foot 100% off the gas pedal,if you just de celerate slowly the regen is very low it is very cool actually now that I am getting used to it. Heck it can be at coast if the foot is in the right position on the pedal then back off a bit more re gen kicks in from 0% - 100% and every level in between, its all about FEEL,, the controller turns on the brake lights every time it goes into any amount of regen, it seems to regen all the way to about 5 mph. This is a setting I can also adjust.

I do not have exact stats yet but I suspect the regen will add significant range to the drive,, not 3-5% like I have been hearing, I am guessing lots more ( hoping any way)

also I will probably bump the regen up to 120 amps for even more,, the max is 150amps that may be a bit too much for my little 60 AH batteries

Brian


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## tomofreno (Mar 3, 2009)

> But that 100 amps is if you take you foot 100% off the gas pedal,if you just de celerate slowly the regen is very low it is very cool actually now that I am getting used to it.


 Yes, I was playing with this yesterday - since you had said "it was all in the gas pedal". I found I could get regen with the throttle just slightly depressed, and vary the amount very slightly, because it is VERY touchy now due to the way I have set up the throttle_map parameter and neutral_braking. I'm going to increase neutral_braking to around 35 - 40% (22 now), and make the throttle less aggressive to see if I can then control regen with the throttle more easily. Would be nice if this is not too touchy, because then I could do as you say, ease off the throttle to control regen, and release it to get aggressive stopping with electric braking, using mechanical brakes very little for most stops. 

The problem with how I have it set up currently is that many people (apparently with no concern for energy use) continue driving fast until almost to a stop light, then aggressively brake to stop. If I stop more gradually with electric braking I impede traffic - well not really as they aren't going anywhere 'till the light changes, but you know what I mean. Some get quite angry, accelerate around me, then hit their brakes hard a few seconds later to stop for the light (yes, we could argue who is "right" here, but lets just stick to more objective matters such as how to vary electric braking). It would be nice to be able to vary how aggressively I stop with electric braking depending on the circumstances - i.e. drive defensively. I think I would get about the same regen regardless, just different current and time, and I could pace myself with traffic flow. However, this could be quite dangerous for someone not used to it, since if they release the throttle they would decelerate very quickly. If one of those aggressive drivers is right behind them... so I'm not sure about this being the way to go. 

With regard to how much energy regen supplies, I seem to get regen as long as the car is moving and my foot is off the throttle - even as I coast to a stop in my garage. I would guess it is significantly less than 10% energy added though. Current can be fairly high, but time is usually very short (50A for 15 seconds is about 0.21Ah) unless going down a hill, and the more aggressively you set it the faster you stop. Going down an approx 1 mile long hill at 55 - 60mph I got a bit over 50A for about 1 minute, ~0.8Ah. That is the most regen I've had. 'Course it required about 250A for a bit longer time (slower speed) to get back up that hill.


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## rctous (Jun 18, 2008)

tomofreno said:


> However, this could be quite dangerous for someone not used to it, since if they release the throttle they would decelerate very quickly. If one of those aggressive drivers is right behind them... so I'm not sure about this being the way to go.


The learning curve is about 3 brake stops, and very very very very controllable and if ya ever need to brake real hard 1/2 of the work is already done before the right foot even hits the brake pedal.

Did I mention very?????????

Brian


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## tomofreno (Mar 3, 2009)

> But that 100 amps is if you take you foot 100% off the gas pedal,if you just de celerate slowly the regen is very low it is very cool actually now that I am getting used to it. Heck it can be at coast if the foot is in the right position on the pedal then back off a bit more re gen kicks in from 0% - 100% and every level in between, its all about FEEL,, the controller turns on the brake lights every time it goes into any amount of regen, it seems to regen all the way to about 5 mph. This is a setting I can also adjust.


 I increased the neutral_braking parameter to 50%, decreased the throttle_map parameter to 50% (so throttle less touchy) and found it works as you said. I can control the amount of electric braking/regen with the accelerator pedal, and over 90% of stopping is done purely with electric braking. Cool! I can now pace my stopping with traffic by easing the accelerator as required to get the amount of electric braking I need to keep pace, and release the accelerator completely to stop more quickly when I get close to the light - as if I were applying my mechanical brakes. On flat ground the electric braking stops me completely, I only have to touch the mechanical brakes to stop the car from barely rolling at less than the speedo will register. Works really slick, using regen to stop, and getting almost no wear on my mechanical brakes as I had hoped! Of course I still get about the same amount of regen current going down a hill at a given speed as before. The difference is I ease back on the accelerator to coast down at the speed limit and provide regen to the pack, but now I can tailor as needed without using my mechanical brakes at all on steeper grades, maximizing regen. If there is a stop sign or light at the bottom I back my foot off the accelerator to get a larger burst of regen and provide most of the stopping of the car. As Brian said, you hardly use the mechanical brakes at all. I'll never need to do a brake job!

I have no interface to my brake lights, but HPGC said they would modify the software to provide a signal and email me a copy. I can download it and load it into the controller using the PC Programming Station software. Then I should have a signal from the controller to drive a relay connected in parallel with my brake light switch. Woohoo!!


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## Dave Koller (Nov 15, 2008)

Yep ! All the problems seem to melt away with regen ...

Too late to start up a new car but this has been a good show - keep filling my head


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## rctous (Jun 18, 2008)

tomofreno said:


> I increased the neutral_braking parameter to 50%, decreased the throttle_map parameter to 50% (so throttle less touchy) and found it works as you said. I can control the amount of electric braking/regen with the accelerator pedal, and over 90% of stopping is done purely with electric braking. Cool! I can now pace my stopping with traffic by easing the accelerator as required to get the amount of electric braking I need to keep pace, and release the accelerator completely to stop more quickly when I get close to the light - as if I were applying my mechanical brakes. On flat ground the electric braking stops me completely, I only have to touch the mechanical brakes to stop the car from barely rolling at less than the speedo will register. Works really slick, using regen to stop, and getting almost no wear on my mechanical brakes as I had hoped! Of course I still get about the same amount of regen current going down a hill at a given speed as before. The difference is I ease back on the accelerator to coast down at the speed limit and provide regen to the pack, but now I can tailor as needed without using my mechanical brakes at all on steeper grades, maximizing regen. If there is a stop sign or light at the bottom I back my foot off the accelerator to get a larger burst of regen and provide most of the stopping of the car. As Brian said, you hardly use the mechanical brakes at all. I'll never need to do a brake job!
> 
> I have no interface to my brake lights, but HPGC said they would modify the software to provide a signal and email me a copy. I can download it and load it into the controller using the PC Programming Station software. Then I should have a signal from the controller to drive a relay connected in parallel with my brake light switch. Woohoo!!



told ya so I told ya so

LOL

it is cool,, very cool

definately need the controller to help with the brake lite,, I guess in the mean time you could add a simple switch to the "gas pedal" have it activate from 10% to 50% pedal throw, that would be pretty simple and the end result is the same.

Brian

B


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## Kelmark (Oct 26, 2009)

tomofreno said:


> I increased the neutral_braking parameter to 50%, decreased the throttle_map parameter to 50% (so throttle less touchy) and found it works as you said. I can control the amount of electric braking/regen with the accelerator pedal, and over 90% of stopping is done purely with electric braking. Cool! I can now pace my stopping with traffic by easing the accelerator as required to get the amount of electric braking I need to keep pace, and release the accelerator completely to stop more quickly when I get close to the light - as if I were applying my mechanical brakes. On flat ground the electric braking stops me completely, I only have to touch the mechanical brakes to stop the car from barely rolling at less than the speedo will register. Works really slick, using regen to stop, and getting almost no wear on my mechanical brakes as I had hoped! Of course I still get about the same amount of regen current going down a hill at a given speed as before. The difference is I ease back on the accelerator to coast down at the speed limit and provide regen to the pack, but now I can tailor as needed without using my mechanical brakes at all on steeper grades, maximizing regen. If there is a stop sign or light at the bottom I back my foot off the accelerator to get a larger burst of regen and provide most of the stopping of the car. As Brian said, you hardly use the mechanical brakes at all. I'll never need to do a brake job!
> 
> I have no interface to my brake lights, but HPGC said they would modify the software to provide a signal and email me a copy. I can download it and load it into the controller using the PC Programming Station software. Then I should have a signal from the controller to drive a relay connected in parallel with my brake light switch. Woohoo!!


Tom,

Glad to hear that you got the regen working better in your Swift. I will probably do the same instead of messing with the brake pedal control. 

Another question, I was wondering does the Curtis controller have any way to use factory cruise control. I hate watching my speed all the time and have gotten addicted to using cruise... So it would be a really nice feature. 

Jacob
USN/USNR


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## rctous (Jun 18, 2008)

jacob where about in Kansas are you??? I am in Prairie Village

B


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## Kelmark (Oct 26, 2009)

rctous said:


> jacob where about in Kansas are you??? I am in Prairie Village
> 
> B


 
Just south of Salina in Mcpherson.


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## tomofreno (Mar 3, 2009)

> I was wondering does the Curtis controller have any way to use factory cruise control.


 I don't expect so. I think if it is possible, it would have to be done using throttle type 5 and writing VCL code to implement it, since you would need feedback on vehicle speed and some "smarts" to know how to vary the throttle based on it. Seems you need speedometer input for the former since motor rpm at a given vehicle speed will be gear dependent - unless you have direct drive. I really like cruise control for long trips on open highway. However, most of my local driving is in traffic, even when traveling 25 miles on highway, so I couldn't use cruise control very effectively - but that is probably over 90% of my driving.


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## MN Driver (Sep 29, 2009)

tomofreno said:


> I increased the neutral_braking parameter to 50%, decreased the throttle_map parameter to 50% (so throttle less touchy) and found it works as you said. I can control the amount of electric braking/regen with the accelerator pedal, and over 90% of stopping is done purely with electric braking. Cool! I can now pace my stopping with traffic by easing the accelerator as required to get the amount of electric braking I need to keep pace, and release the accelerator completely to stop more quickly when I get close to the light - as if I were applying my mechanical brakes. On flat ground the electric braking stops me completely, I only have to touch the mechanical brakes to stop the car from barely rolling at less than the speedo will register. Works really slick, using regen to stop, and getting almost no wear on my mechanical brakes as I had hoped! Of course I still get about the same amount of regen current going down a hill at a given speed as before. The difference is I ease back on the accelerator to coast down at the speed limit and provide regen to the pack, but now I can tailor as needed without using my mechanical brakes at all on steeper grades, maximizing regen. If there is a stop sign or light at the bottom I back my foot off the accelerator to get a larger burst of regen and provide most of the stopping of the car. As Brian said, you hardly use the mechanical brakes at all. I'll never need to do a brake job!
> 
> I have no interface to my brake lights, but HPGC said they would modify the software to provide a signal and email me a copy. I can download it and load it into the controller using the PC Programming Station software. Then I should have a signal from the controller to drive a relay connected in parallel with my brake light switch. Woohoo!!


As you said right before this post, it does help with recovering the energy involved with 'being nice' with the drivers who more or less 'speed up to stop' when arriving at a stop light that will still be red while they continue at highway speeds towards it. I'm with you on that, I like to coast a bit so I have some speed when it turns green but most people don't realize the savings.

Be careful however with the regen on the gas pedal, especially if you set things up too aggressively. I'll quote what Victor T from Metric Mind said:



> - Off-throttle regen, where you'd set middle of throttle pedal position as "neutral" (coasting) and from that position fully depressed is 100% acceleration demand and fully released - 100% regen demand (so one pedal operation) almost got me into big trouble. IT may be OK for someone just learning to drive, but such setup is very different from conventional, and if your hands and feet in emergency operate vehicle quicker than brain thinking about it, you won't like such change. It is re-learning to drive. Once I drove on a freeway evaluating such set up. First, I noticed I have to freeze my foot in strictly one position as I drive, no stretches, no movements. I had to take something from behind my seat while cruising on a freeway, and to reach far corner I had to stretch my body body took my foot off the accelerator pedal for 2-3 seconds - action I never think about as it would not be noticeable for "normal" setup. Well, it was equivalent to slamming brakes 100% while in the middle of freeway and no one in front of me, so no one behind would expect such a stunt. And, I wasn't consciously braking, the effect was as if some one slams on the brakes for you without any warning. The rear of the car breaks loose, I'm thrown toward wind shield and intuitively as in any emergency situation, before my brain assess the situation, my right foot goes from already 100% braking accelerator to real brake pedal, compounding effect. Now the car really grips the road, scarring me out of my pants! Mind you, I had about 450kg (1,000 lb) of lead in the car at that time (I think around 2002). It would take thinking twice to realize that to rectify situation I had to slam on "gas". Anyway, I'm coming to a complete sketching stop in the middle lane of I84 freeway. I was LUCKY - no one was following me on my lane, and I noticed couple of by-passers looked at me as if I was total moron (and I probably was!). This was first and last time I tried off-throttle regen. You may like it, but it would take a lot of money to make me do it again...


 http://www.metricmind.com/audi/10-shifter.htm

He had his set very aggressively but it makes a point, if the regen ever catches you off guard it could lead to a fairly disastrous outcome.

I like the idea of a spring loaded potentiometer that he mounted to the gearshift in his Honda CRX where it won't be active during the seasons with ice and snow, as I live in Minnesota and we have slippery conditions now, I'd hate to be entering a turn and having my front tires lock up due to regen. Just like those with the Honda Insight who manually control their hybrids electric assist and regen, I'd like to do the same if I had an electric car with regen. I suppose I am more of a coasting driver though that when I come across a slight downhill that I can use the speed and it won't bring me to an excessive rate of speed, I let it happen and would like the movement downhill to be natural. I suppose neutral achieves this but it feels like too much clutchwork. I also don't like the brake pedal idea because I like my brake pedal to have its natural balance of front and back, especially in the winter and don't want to use friction braking when I really would rather regenerate as much as possible.

Of course this is just my humble opinion, put out there for discussions and thoughts. Life would be boring if we all did things the same.


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## JRP3 (Mar 7, 2008)

From his description I don't think Tom's motor has any where near the intense regen Victor is talking about. On the other hand my understanding is that Tesla and Mini both have strong off throttle regen and people seem to get used to it.


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## tomofreno (Mar 3, 2009)

> He had his set very aggressively but it makes a point, if the regen ever catches you off guard it could lead to a fairly disastrous outcome.


 I don't have it set nearly that aggressively. There is no reason to do so. One of the first things I did when I reset it was take my foot off the pedal at 40 mph to see what it did. It wasn't dangerous deceleration, and certainly nothing like he describes.


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## rctous (Jun 18, 2008)

tomofreno said:


> I don't have it set nearly that aggressively. There is no reason to do so. One of the first things I did when I reset it was take my foot off the pedal at 40 mph to see what it did. It wasn't dangerous deceleration, and certainly nothing like he describes.


neither is mine


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## tomofreno (Mar 3, 2009)

> From his description I don't think Tom's motor has any where near the intense regen Victor is talking about.


 That's right, though you could certainly set it up that way. Just set the neutral_braking parameter to 100%. I don't know why anyone would though. Besides the behavior Victor described, it would make it quite difficult to shift gears, and very jerky, as the car would very abruptly decelerate when you released the accelerator to shift. You don't gain anything in regen setting it that way, it just stops the car much faster and gives a much larger magnitude but much shorter duration regen current spike. The integral over time, charge, is about the same except for efficiency differences.

You do of course have to explain it to a new driver and have them drive it for a bit with no traffic to get the feel. But it doesn't take long as Brian said, a few stops/starts and it feels natural and convenient - just ease off the acclerator to slow down, and release it more to slow down more quickly. It makes me feel like I have really good control of the car. It could definitely be a problem on icy roads due to braking with only the front (drive) wheels. If I have to do that, I'll likely set neutral_braking back down to 20% or less. I drove on packed snow/ice with it set there with no problems.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> One of the first things I did when I reset it was take my foot off the pedal at 40 mph to see what it did. It wasn't dangerous deceleration, and certainly nothing like he describes.


What if you happen to be driving on ice though? I guess if you know in advance that the conditions are treacherous, you could switch off regen altogether, or switch it to a very mild rate (say 10%, or whatever is similar to ICE compression in top gear).

I live in sunny Queensland , so I know nothing about driving on ice or snow.


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## tomofreno (Mar 3, 2009)

> What if you happen to be driving on ice though?





> It could definitely be a problem on icy roads due to braking with only the front (drive) wheels. If I have to do that, I'll likely set neutral_braking back down to 20% or less.


It snowed a couple inches last night and stuck on the roads due to cold temps here, so I actually got to test this a bit. It was no problem stopping with electric braking. I just eased off the throttle and stopped gently, as I would using the mechanical brakes on snow. Sure, if I tried to stop quickly, large change in momentum, the coefficient of friction would be too small to supply the necessary force on the wheels, but that's true of mechanical braking also. Mechanical braking does have the advantage of applying to all 4 wheels, and ABS is even better. Driving cautiously and defensively I had no problem. Ice would be much worse of course. Don't think I would try it. I don't like to take my ICE on ice either.


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## Kelmark (Oct 26, 2009)

Tom you have posted your 205 wh/m for 50mph I am curious to see what you get at around 25-35mph.


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## tomofreno (Mar 3, 2009)

> Tom you have posted your 205 wh/m for 50mph I am curious to see what you get at around 25-35mph.


 I haven't driven very far at either of these speeds to get an energy/mile estimate. All I can say is I measured 45A at 30 mph and 70 at 40 mph, which agree well with calculated estimates. Linearly interpolating between the two gives 57.5A at 35 mph. That gives 57.5Ah to go 35 miles at 35 mph, or 1.64Ah/mile. Average pack voltage is typically around 114V at currents in this range, so that would be roughly 187Wh/mile. My spreadsheet predicts about 190 in 2nd gear. That would be cruising at constant speed. The spreadsheet usually estimates a bit high, so I would guess 190 is an upper limit, 180 -185 more likely. The current and energy usage don't seem to increase with vehicle speed as I expected. It seems it cruises at 50 mph very efficiently - I seem to use less energy this way than when doing mixed driving around town, but it is hard to tell since trips are usually a mix, even if most is at 50-55mph.


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## tomofreno (Mar 3, 2009)

I'm getting better range now that I increased neutral braking. I did a duplicate trip of exactly the same miles, 54.4, but with my bike on the back of the car, and used almost the same charge and energy as I did without the bike: 200 Wh/mile, 1.76 Wh/mile w/o, 203 Wh/mile, 1.78 Wh/mile with. Before adjusting the braking I had seen a significant increase in charge and energy usage with the bike on the back (drag force, much of the trip is at 50-55 mph). Previously I used my mechanical brakes quite a bit when stopping, especially if I had to stop more quickly for a sudden light change. Now I can stop almost completely with electric braking, and get currents well over 100A briefly. Yesterday a light turned red when I was roughly 300 ft away going 50 mph. I took my foot off the accelerator while in 3rd gear, then downshifted to 2nd after slowing to around 35 mph. When I got to the intersection, the car was barely rolling, less than 5 mph, and I lightly touched the mechanical brakes to stop. I also get more going down hills, as I can control it better with the accelerator pedal so the car remains moving at the speed limit for a wide range of grades.


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## TheSGC (Nov 15, 2007)

How are your battery heater pads working out?


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## Guest (Jan 30, 2010)

tomofreno said:


> Cell log data while charging:
> 
> View attachment 5335
> 
> ...


The 3.4v really isn't "Jack's" number. That's the "float voltage" on the spec sheet for several LiFePo4 cells and it really is the fully charged voltage of such a cell. 3.35, while pretty close, indicates a very slight undercharge. I would offer that had you continued from the 4 amps on down to zero, the voltage a few hours later would have been right at 3.4 volts. 

That said, FULLY charging the cells for a car really isn't the objective. Safely charging the cells, particularly in series is. I like to see mine about 3.33 v on average after charging and a 3 hour rest. As I have said many times, gaining that last Ah in charging is a losing game. You get little range from it, and it has the potential to hurt your cells. The more you undercharge the cells, the longer they last.

Jack Rickard
http:/EVTV.me


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## Guest (Jan 30, 2010)

Kelmark said:


> Voltswagen thanks for the feed back,
> 
> I was thinking of going with something like: HD Comp Transmissions are available that come with: Super Diff, HD Side Cover, Welded Hubs, Steel Shift Forks, Hardened Keys and Close Ratio gears. With the exception of fourth gear, this should be at 0.82 for interstate travel. Or I can change the ring and pinion to 4.86 and go a little taller than .82 for forth. Not sure what’s better or cheaper.
> 
> ...



Gear ratios can drive you crazy. For Speedster part DUH, we are going to a 3.44 R&P and 4th gear will actually be 0.70. This transmission was built for us by Longstreet.

My experience with the first Speedster with a Warp9 is that the RPM range of the electric vehicle is best at 0-3000rpm and the VW transaxles, particularly close ratio sets, are for 4600rpm type ICE engines. The much taller gear set of 3.44 and 0.70 should move us further DOWN in RPM more into the torque band of advantage for electric motors.

Jack RIckard
http://EVTV.me


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## maxvtol (Nov 11, 2009)

jrickard said:


> Gear ratios can drive you crazy.


Gear ratios are simple, you want the most torque at the wheel for maximum acceleration, not at the motor. ie For my application at 35mph, in second gear with a final ratio of 8.39 and motor torque of 74.3ft lbs @ 3917 rpm would give a wheel torque of 623.8ft lbs vs 3rd gear with a final ratio of 5.36 and a motor torque of 100.1ft lbs @ 2501 rpm gives a wheel torque of 536.5ft lbs. The motor torque peaks out at 3000 rpm, but in this example it would be better to leave it in 2nd gear well past the motor peak torque for best acceleration. 

For efficiency at cruise, you would just want the motor to operate at its most efficient rpm at the speed you're cruising at, very simple. 

Tom has a good spreadsheet for calculating these numbers. I also have one geared more towards optimum shift points for maximum acceleration, if anyone is interested. 

Now finding a decent motor chart for torques, efficiencies, etc. at different rpms, THAT'S what drives me crazy.


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## Guest (Jan 30, 2010)

maxvtol said:


> Gear ratios are simple, you want the most torque at the wheel for maximum acceleration, not at the motor. ie For my application at 35mph, in second gear with a final ratio of 8.39 and motor torque of 74.3ft lbs @ 3917 rpm would give a wheel torque of 623.8ft lbs vs 3rd gear with a final ratio of 5.36 and a motor torque of 100.1ft lbs @ 2501 rpm gives a wheel torque of 536.5ft lbs. The motor torque peaks out at 3000 rpm, but in this example it would be better to leave it in 2nd gear well past the motor peak torque for best acceleration.
> 
> For efficiency at cruise, you would just want the motor to operate at its most efficient rpm at the speed you're cruising at, very simple.
> 
> ...


I don't agree. It's simple if you're simple. I would point to the many many gear ratio changes offered by OEM automotive manufacturers over the years on the same basic make and model - never mind the options offered on the same car in the same year. 

Yes, it's very easy to calculate. But the calculation tells you very little about how the car will feel and perform unfortunately. 

In any event, the higher gears seem to work better with the electric motors, as the torque on the motors falls off badly in the RPM range that ICE engines typically make their best power. In the Speedster, we take off in 3rd gear, and shift to 4th at 55 mph. At about 95, it simple runs out of power, and we're doing 4000 rpm. If I could move that down to 3000 rpm, we would see a big improvement because of the torque curve of the Warp9.

At those speeds, it's not that the Warp9 can't make enough power, it's that it can't make it at that rpm.

Jack Rickard


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## maxvtol (Nov 11, 2009)

I don't want to turn Tom's thread into arguing physics. 

But your subjective "feel" and actual performance are 2 different things. Yes, GM still uses engineers to tune their cars by subjective feel to give a desirable driving experience, not by what may be optimum on some spreadsheet or test result chart. 


jrickard said:


> I don't agree.


 With what? I'll give you that what "feels" right may not be optimum performance. But if you take actual test results and compare them with engineering calculations they will be close, maybe not exactly, but close if you have been given the correct data. That's what engineers do. 

But if you don't agree with physics, well I'll leave that one alone.


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## Guest (Jan 30, 2010)

maxvtol said:


> I don't want to turn Tom's thread into arguing physics.
> 
> But your subjective "feel" and actual performance are 2 different things. Yes, GM still uses engineers to tune their cars by subjective feel to give a desirable driving experience, not by what may be optimum on some spreadsheet or test result chart.
> With what? I'll give you that what "feels" right may not be optimum performance. But if you take actual test results and compare them with engineering calculations they will be close, maybe not exactly, but close if you have been given the correct data. That's what engineers do.
> ...


It is not so much that I disagree with physics, I disagree with your presentation of it. And no, GM engineers don't just do it by feel. But the ratios change a lot across the years and across the models because what they calculated turned out not to work quite as well as they thought. Now I know you think you've invented it, but I will reiterate again, it just doesn't work out the way you think.

If you want to wrap your own personna around the concept of physics and the laws of the universe, I'm not going to challenge you because it is nonsense. But you can "calculate" forever, it isn't going to precisely turn out that way.

Jack Rickard
http://EVTV.me


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## maxvtol (Nov 11, 2009)

Sorry if I offended you Jack, or anyone else on this thread with my presentation of my "concept of physics and laws of the universe." 

I'll just state my case and be done. I use to work for GM 25 years ago as an engineer, and still have friends that work there. No, they don't just do it by feel, I said they tune it by feel. There are many reasons for gear changes, performance, milage requirements, as well as a better driving experience. Even with today's with sensor technology, they still tune the cars by feel. If they didn't get it right, it's more likely because the customer didn't like it, not because it didn't perform (objectively) the way the thought. 

If you give me an engine chart with gear ratios and some other relavent data, I'll tell you where to shift for maximum performance. If your car represents the input data, I'll be close. Whether you like the way it feels or not is something I can't predict.


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## Guest (Jan 30, 2010)

maxvtol said:


> Sorry if I offended you Jack, or anyone else on this thread with my presentation of my "concept of physics and laws of the universe."
> 
> I'll just state my case and be done. I use to work for GM 25 years ago as an engineer, and still have friends that work there. No, they don't just do it by feel, I said they tune it by feel. There are many reasons for gear changes, performance, milage requirements, as well as a better driving experience. Even with today's with sensor technology, they still tune the cars by feel. If they didn't get it right, it's more likely because the customer didn't like it, not because it didn't perform (objectively) the way the thought.
> 
> If you give me an engine chart with gear ratios and some other relavent data, I'll tell you where to shift for maximum performance. If your car represents the input data, I'll be close. Whether you like the way it feels or not is something I can't predict.


We seem to have "shifted" into agreement. My point was that I can calculate until I'm blue, I've found that it is all different in the car.

The wider point is that all these drive trains are of course designed for ICE engines. We have some different characteristics. ANd while all EVers seem to be proud of the wider RPM band, it is generally a LOWER RPM band and most of our motors top out at about 3500. 

On the Speedster, 1st and 2nd immediately get you into a high rpm area that feels terrible. So we take off in 3rd and shift to 4th at about 55 mph.

We have gone to a taller ring gear (3.44) and a much taller gear set with 4th at 0.70 in an attempt to get 1 and 2 back in the game, and maybe get a bit more top end speed.

Whether this will all work or not remains to be seen. Speedster part DUH will also use the AC50 and Curtis controller, so I've been following Tom's thread pretty closely. 

I'm learning a lot about regen, though I've remained mostly confused. We were going to tie it to the brake light signal, and mostly like to coast where we can. So this talk of accelerator regen has me a little thrown. What are the basic setup numbers for it in your car Tom?



Jack Rickard
http://EVTV.me


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## CroDriver (Jan 8, 2009)

Jack, how much voltage does your motor see?

Maybe you could get some more power in the high RPM's by "overvolting" it


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## Guest (Jan 30, 2010)

CroDriver said:


> Jack, how much voltage does your motor see?
> 
> Maybe you could get some more power in the high RPM's by "overvolting" it


A lot going on here. I can get higher RPM by increasing the voltage, but that doesn't do much to change the torque curve. In any event, that applies to DC series motors.

For Speedster Duh we are going to use an AC induction motor. The input voltage is not tied to rpms in that case.

The voltage and current of course define the power available to the 3 phase controller, but they don't really have anything to do with rpm.

Jack Rickard


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## maxvtol (Nov 11, 2009)

jrickard said:


> On the Speedster, 1st and 2nd immediately get you into a high rpm area that feels terrible. So we take off in 3rd and shift to 4th at about 55 mph.
> 
> We have gone to a taller ring gear (3.44) and a much taller gear set with 4th at 0.70 in an attempt to get 1 and 2 back in the game, and maybe get a bit more top end speed.


The older VW transaxles used 1st and 2nd to get you off the line, 3rd and 4th were mainly for economy and top speed (for a small ICE). I didn'nt like the way my VW dunebuggy shifted (30+ years ago) so check into "close ratio" gears, if you haven't already. They lower 3rd and 4th instead of raising 1st and 2nd, so it may not be what you want if your looking for top speed, but it feels (and performs, acceleration wise) much better. If your raising your final drive, it might be worth a look. Just check out any "hot VW" magazine or any VW dunebuggy website.


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## few2many (Jun 23, 2009)

Hey Tom, have you considered that youre off pedal/nuetral regen may be too high? You sound like you slowing down pretty fast and getting some good regen. Maybe too fast! Youre slowing down as if brakes are applied, but they arent, so no brake lights. Are you worried about someone rear-ending you?


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## Guest (Jan 31, 2010)

maxvtol said:


> The older VW transaxles used 1st and 2nd to get you off the line, 3rd and 4th were mainly for economy and top speed (for a small ICE). I didn'nt like the way my VW dunebuggy shifted (30+ years ago) so check into "close ratio" gears, if you haven't already. They lower 3rd and 4th instead of raising 1st and 2nd, so it may not be what you want if your looking for top speed, but it feels (and performs, acceleration wise) much better. If your raising your final drive, it might be worth a look. Just check out any "hot VW" magazine or any VW dunebuggy website.


I guess I'm not communicating very well here. YES, the close ratio gears felt BETTER with an ICE engine. With an electric motor, they do not. We need ratios that are FURTHER APART as we have a wide RPM range. 

The axle we had made, basically used the OLD VW transaxle ratios from years ago that most people had abandoned over time in favor of the close ratio gears. They're pretty rare, but they're still around. And the guy at Longstreet chased some down for us and made us up an axle. I'm looking for a big improvement by going the other direction from close ratio. We're going to higher gearing and wider spacing. 

Hopefully, this will at least get 2nd gear into the game and perhaps a little higher top end. In this way, we'll have a three speed instead of a two speed - given four to choose from.

Jack Rickard


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## tomofreno (Mar 3, 2009)

> I also have one geared more towards optimum shift points for maximum acceleration, if anyone is interested.


 Sounds interesting, I'd like to take a look at it to see what I can learn.


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## tomofreno (Mar 3, 2009)

> How are your battery heater pads working out?


 Good. Holding the cells right at the setpoint of the thermostat, even at 0 F ambient.


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## tomofreno (Mar 3, 2009)

> But the calculation tells you very little about how the car will feel and perform unfortunately.


 My car seems to behave pretty much as I expected from the available power versus speed curves, and estimates of available acceleration from the difference in available and required torque. I sometimes start off in 2nd gear, but initial acceleration is noticeably slower than starting in 1st. Starting in 3rd is slower still. Not enough mechanical advantage for the available motor torque. As you say there are many gear ratios available. How a given car behaves depends on the specific ratios and the available motor torque and power, which of course also depends on the motor controller used.


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## Coulomb (Apr 22, 2009)

few2many said:


> Are you worried about someone rear-ending you?


I believe that the Curtis 1238-7501 has a wire you can hook up to a relay to cause your brake lights to come on with neutral regen. So that works around that problem.


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## Voltswagen (Nov 13, 2008)

I have a D&D ES-31B motor mated to a stock Beetle manual transmission.
I have also found that starting in 2nd gear noticeably reduces the mechanical advantage owing to the small size of my motor.
If I had a Warp 9, the extra torque would probably allow me to start in 2nd.
I do use all 4 gears and have found that crusing at about 40mph in 4th gear only draws 50-60 amps on a level road which I think is quite economical.
Just my own un-scientific observation.
Roy


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## tomofreno (Mar 3, 2009)

> I believe that the Curtis 1238-7501 has a wire you can hook up to a relay to cause your brake lights to come on with neutral regen. So that works around that problem.


 Mine does not. HPGC said they could modify the VCL to operate the brake lights, I guess through one of the controller DO's, but they haven't gotten to it yet.


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## JRP3 (Mar 7, 2008)

I suppose you could simply wire a second brake light switch to the accelerator pedal such that when you lift off enough to get regen the switch is engaged and the brake lights come on. Or just move the existing brake switch to the accel pedal, though that may not pass an inspection.


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## tomofreno (Mar 3, 2009)

> What are the basic setup numbers for it in your car Tom?


 Throttle_Map = 50%, Neutral_Braking = 50%. Free coasting is usually less energy efficient than controlling speed with neutral braking unless you can exceed the speed limit, are not impeded by other cars, and can continue to freely coast until you slow down enough to require some energy input to continue at the speed limit or traffic speed. In that case you can just freely coast down a hill until the car slows then depress the accelerator to maintain the desired speed. I find I can rarely do this for one or more of the above reasons, so rather than touch the mechanical brakes to slow the car, I ease off the throttle to apply the required amount of neutral braking to continue at the speed limit or maintain pace with traffic, generating a bit of current into the batteries in the process, rather than dissipating that energy as heat in the mechanical brakes. I also do almost all my stopping with neutral braking normally. I just ease off the throttle to slow at the pace of most of the cars around me, then when close to the intersection I release the throttle which brings me to almost a complete stop, again sending some current to the batteries rather than dissipating the energy as heat. It may sound strange since it is not what you are accustomed to, but after a very short time it feels completely natural and mechanical braking seems kind of primitive. You can of course still coast freely by either taking the car out of gear, or by leaving it in gear and releasing the throttle to the point where regen current reads about zero. Control of the car's speed is almost all by your right foot.


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## tomofreno (Mar 3, 2009)

> I can get higher RPM by increasing the voltage, but that doesn't do much to change the torque curve.


 Higher voltage will change the torque curve somewhat for the 1238-7501/AC50 combination by extending the maximum available torque, limited by the maximum controller current, out to higher rpm. For example, for the above controller the max 2 minute current is 550A giving about 90 lb-ft torque from the AC50. At 96V nominal pack voltage it can supply this torque out to about 3000 rpm, but at 115V nominal pack voltage it can supply it out to about 3500-3600 rpm, due to more voltage to overcome the back emf of the motor.


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## tomofreno (Mar 3, 2009)

> For Speedster Duh we are going to use an AC induction motor.


 Keep in mind that an AC motor doesn't have full torque immediately from a dead stop like a series DC motor does. An AC motor develops torque through slip, the difference in angular velocity of the mmf field of the field windings and the rotor. If you start in a higher gear, with less mechanical advantage, the motor has to develop more torque to give similar torque to the wheels as in a lower gear. It has to develop more slip to do this, so there is a bit of a lag, hence lower initial acceleration. I'm guessing that is why Brian's acceleration is a bit slow below about 5 mph with his direct drive AC motor - lot of torque and slip required to start.


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## tomofreno (Mar 3, 2009)

> I suppose you could simply wire a second brake light switch to the accelerator pedal such that when you lift off enough to get regen the switch is engaged and the brake lights come on.


 Yes, I could do something like this which would give some warning, if not precise, and I will if I can't get it done through VCL. The VCL would be better as it should put out a signal whenever neutral braking is applied. I also contacted tech support at Curtis to see how this can be done. I generally don't drive in heavy traffic, and most of the time there is no one close behind me when I stop, so it hasn't been a pressing issue so to speak. If I were ordering an 1238-7501 now though, I would ask to have this in the VCL code and wiring harness.


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## Jimdear2 (Oct 12, 2008)

tomofreno said:


> Mine does not. HPGC said they could modify the VCL to operate the brake lights, I guess through one of the controller DO's, but they haven't gotten to it yet.


Just a thought from a non electronics guy. Please don't flame if this is stupid.

Could you use a parallel circuit from controller to motor with a relay and diodes that would see when the motor went into regen. The diodes would allow current flow in one direction, operate the relay and turn on the brake lights.


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## maxvtol (Nov 11, 2009)

tomofreno said:


> Sounds interesting, I'd like to take a look at it to see what I can learn.


PM sent. It could probably use a little tweaking on the motor torque vs rpm curve (it's only for the AC50 now, I haven't tried Warp 9 motor), I would value your input on how battery voltages and controller amps affect the curve, and how AC & DC motors differ in this respect.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> Keep in mind that an AC motor doesn't have full torque immediately from a dead stop like a series DC motor does.


I don't believe this statement applies to all AC motor controllers. Industrial controllers usually have a feature called something like "torque boost" that allows more torque at low speeds, by increasing the voltage to the motor over the standard volts per hertz "constant". Danfoss controllers can reportedly boost low speed torque by up to 4x. I don't pretend to understand how it works, but it seems to be real.

Curtis don't seem to make many AC controllers, and those they do seem to be intended for the forklift market, so maybe they don't have this feature in their software as yet. But presumably the eventually will, and it presumably would be field upgradeable, so Tom could get the benefit of this in the future.

Even without torque boost, an AC motor would presumably be able to start from 0 RPM at full (nearly breakdown) torque, merely by giving plenty of slip (at 0 RPM, all the applied frequency is slip). So surely it would have constant torque down to speed zero, at the very least.

DC motors would be similar, it seems to me, since at low speed they would be controller current limited. So both motors would see maximum torque from 0 RPM up to a certain point (nominal frequency for an AC motor, where you usually run out of voltage), and where the controller comes out of current limit for a DC motor. At high RPMs, torque from the DC motor would be less than from the AC, since the DC motor doesn't have slip to force more current.

With torque boost, the AC motor could presumably have even more torque at low speeds, even though I don't understand how an AC motor could exceed breakdown torque. (I think that perhaps the higher voltage gives it a different torque curve with a higher breakdown torque).

My apologies if this is covered by the many "AC vs DC" threads, though I'd appreciate a pointer to one.


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## Coulomb (Apr 22, 2009)

Jimdear2 said:


> Could you use a parallel circuit from controller to motor with a relay and diodes that would see when the motor went into regen. The diodes would allow current flow in one direction, operate the relay and turn on the brake lights.


Not a stupid suggestion at all, but as far as I can see, it won't work. AC motors are driven with AC voltage, which looks much the same in regen as it does in traction or coasting. You'd really need to compare the zero crossings with information about position from the shaft encoder / resolver. That's not impossible, but a lot harder than just a few diodes, resistors, and a relay.

Your idea would work on a DC motor, although on the common series wound DC motors, you usually need a contactor to reverse the field anyway, so you could just parallel that contactor with a (relative to the field contactor) small relay for the brake lights.

Your idea would work well on a separately excited DC motor; you could just detect that the motor armature was more positive than the battery. You'd need an amplifier, since the difference would be in the hundreds of millivolts (I'm guessing, and that's if there is a shunt to measure this voltage across), and you'd need at least 5 V, probably 12 V, to drive the relay.

Really it's the power flow direction that you need to detect.


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## Jimdear2 (Oct 12, 2008)

Coulomb said:


> Not a stupid suggestion at all, but as far as I can see, it won't work. AC motors are driven with AC voltage, which looks much the same in regen as it does in traction or coasting. You'd really need to compare the zero crossings with information about position from the shaft encoder / resolver. That's not impossible, but a lot harder than just a few diodes, resistors, and a relay.
> 
> Your idea would work on a DC motor, although on the common series wound DC motors, you usually need a contactor to reverse the field anyway, so you could just parallel that contactor with a (relative to the field contactor) small relay for the brake lights.
> 
> ...


Thanks for the information. If I keep learning little bits like this in another 50 or 100 years I might know something. 

Another stupid question. In an AC system would the power flow changing direction change the magnetic field polarity in the power leads and if it does would that be detectible.

Thanks again,
Jim


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## Coulomb (Apr 22, 2009)

Jimdear2 said:


> In an AC system would the power flow changing direction change the magnetic field polarity in the power leads and if it does would that be detectible.


Certainly the magnetic field due to currents in cables is measurable; there are hall effect and other sensors for this very purpose. Clamp-on ammeters use the same principle.

But again, the magnetic field, as with the voltage and current, is changing direction all the time. All three wires connecting to the motor terminals are alternating at up to over a hundred cycles per second. You have to figure out the relative frequency of the applied voltage to the mechanical frequency, to figure out if the slip is positive or negative, i.e. the rotating magnetic field is trying to speed up or slow down the rotor.

You could figure out the power flow direction by considering the relative phase of the voltage and current into the motor. After all, that's how AC power meters work. I'd say a quad op-amp and a handful of parts could detect when the power flow direction is over a certain threshold in the regenerative direction.

Think of it this way: in an ideal AC motor, when coasting (spinning with no load), it will be drawing purely imaginary power to maintain the field. So the voltage and current will be 90° out of phase (less than 90° in a real motor, to power the various losses). When motoring, there will be more in-phase current, so the phase angle between voltage and current will decrease. When regenerating, there will be more out-of-phase current, so the phase angle will increase. At 100% regeneration in an ideal motor, the voltage and current will almost be 180° out of phase: as the voltage peaks, the current will peak but running in the opposite direction. There is still imaginary power being drawn to power the field, so that's why even at full regen and no losses, the phase difference will still be less than 180°.

Edit: idle -> coasting


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## tomofreno (Mar 3, 2009)

> PM sent.


 Thanks! I'll take a look!


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## tomofreno (Mar 3, 2009)

> I don't believe this statement applies to all AC motor controllers. Industrial controllers usually have a feature called something like "torque boost" that allows more torque at low speeds


 You may well be correct. I don't know much about it. Plus, I would expect slip would develop quite quickly.


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## Kelmark (Oct 26, 2009)

jrickard said:


> Gear ratios can drive you crazy. For Speedster part DUH, we are going to a 3.44 R&P and 4th gear will actually be 0.70. This transmission was built for us by Longstreet.
> 
> My experience with the first Speedster with a Warp9 is that the RPM range of the electric vehicle is best at 0-3000rpm and the VW transaxles, particularly close ratio sets, are for 4600rpm type ICE engines. The much taller gear set of 3.44 and 0.70 should move us further DOWN in RPM more into the torque band of advantage for electric motors.
> 
> ...


I went back and forth on this until I just ordered the stock gear ratio but in sport setup so it was beefed up a bit. I figured I would dial it in with the tire size from there.

I want to be in the 4,600 rpm range to get the max torque multiplication for acceleration from 0-60, and I thought electric motors were more efficient at their upper rpm band. 

Besides I am looking to use either the AC-50 kit if they come up with a 144v controller or the AC24ls @ around 400V if they don't by the end of this year. A DC system probably works better with higher gears because they have more torque in the lower rpm band.

You can check out my build site “Kelmark Solar Series Hybrid”


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## Kelmark (Oct 26, 2009)

Tom,

I have been looking into this new controller to use with HPEV's AC-50 motor.

http://www.emduro.eu/index.php?option=com_content&view=article&id=10&Itemid=33

If it can run at 144V and 650 amps what do you think that will relate to in torque and to what RPM? Also I am not sure why they have 50KW on their site. Shouldn't it be higher? 

They say they have a set of Lifepo4 in route so they can start testing. I will post the results when I get them if your interested.

Respectfully,

Jacob Blake


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## tomofreno (Mar 3, 2009)

> If it can run at 144V and 650 amps what do you think that will relate to in torque and to what RPM?


 Well, I think 650 versus 550A max should give about 106 lb-ft torque at lower rpm with the AC50 (90 with 550A), and I would guess that with 144V you should be able to get max torque out to about 4500 rpm, EXCEPT that I don't think the controller has the power to do that, since it says it is 50kW, or about 67 HP. I expect this is peak power, but I am not sure. If it is continuous that is very different. I can get up to about 45.5kW or 61HP peak with the Curtis controller with my 115V pack, so I don't think this controller would give that much better performance as far as torque at higher rpm. The Curtis was not designed for this much power however, since they say it is for a max nominal 96V system. Looks like this one might be capable of providing higher sustained power without overheating, like cruising at 70 mph. Would need to find out more about it, like its continuous power rating.


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## Kelmark (Oct 26, 2009)

tomofreno said:


> Well, I think 650 versus 550A max should give about 106 lb-ft torque at lower rpm with the AC50 (90 with 550A), and I would guess that with 144V you should be able to get max torque out to about 4500 rpm, EXCEPT that I don't think the controller has the power to do that, since it says it is 50kW, or about 67 HP. I expect this is peak power, but I am not sure. If it is continuous that is very different. I can get up to about 45.5kW or 61HP peak with the Curtis controller with my 115V pack, so I don't think this controller would give that much better performance as far as torque at higher rpm. The Curtis was not designed for this much power however, since they say it is for a max nominal 96V system. Looks like this one might be capable of providing higher sustained power without overheating, like cruising at 70 mph. Would need to find out more about it, like its continuous power rating.


Here is quote from the e-mail;

"Our controller capable to drive from 0 to 400Hz so max rpm is 8x motor rpm at 50Hz. Maximum torque is constant until maximum 50KW power. Continuous maximum power is about 30KW so 40 bhp. Our system maximum voltage rate is 144V, cut off is voltage if I remember correctly is 175V. Yes our system is watter cooled, bu we don't add any kit for it it is all designers choice."

You probably understand this better than me.


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## tomofreno (Mar 3, 2009)

> Our controller capable to drive from 0 to 400Hz so max rpm is 8x motor rpm at 50Hz. Maximum torque is constant until maximum 50KW power. Continuous maximum power is about 30KW so 40 bhp.


 The continuous power is about twice the rating of the AC50 continuous power, but you could likely increase the latter quite a bit with a blower blowing into the back of the motor. With that continuous power and your light car you should be able to cruise at 75 - 80 mph no problem (if you can keep the motor cool) . I expect acceleration to 60 mph would be maybe only 15% better than with the Curtis 1238-7501 though due to the 50kW max power limit.


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## Guest (Feb 6, 2010)

tomofreno said:


> Well, I think 650 versus 550A max should give about 106 lb-ft torque at lower rpm with the AC50 (90 with 550A), and I would guess that with 144V you should be able to get max torque out to about 4500 rpm, EXCEPT that I don't think the controller has the power to do that, since it says it is 50kW, or about 67 HP. I expect this is peak power, but I am not sure. If it is continuous that is very different. I can get up to about 45.5kW or 61HP peak with the Curtis controller with my 115V pack, so I don't think this controller would give that much better performance as far as torque at higher rpm. The Curtis was not designed for this much power however, since they say it is for a max nominal 96V system. Looks like this one might be capable of providing higher sustained power without overheating, like cruising at 70 mph. Would need to find out more about it, like its continuous power rating.


The AC controllers are a bit different than the DC controllers in a couple of curious aspects. There is no particular requirement to have the maximum voltage from the pack at all connected to the voltage applied to the motor windings. The speed of the motor is a function of frequency, and the torque of current. In DC motors speed is a function of voltage, and similarly torque of current.

So having a 144 volt pack reduces the amount of current necessary to the controller. But the controller has to form three broadly sinusoidal waveforms at a specific frequency and phase angle. If he can do 650amps in the motor windings, but with a 50 kw power limit, that implies an rms value of 77 volts.

Similarly the Curtis. You say it will do 45kW at 115 volts. But the max current on your controller is 550 amps. At 115v that would be 63 kW in a DC world. 

Most of these AC controllers are using low resistance MOSFETS instead of IGBT and while they offer a number of advantages, anything approaching 200v limit starts to get to be very expensive. That's the reason for these lower cutoff voltages than we're seeing with the older higher voltage AC systems. The MOSFETS have some serious advantages in power dissipation and switching losses, but just aren't available in higher voltages as yet.

But I'm guessing.......

Jack Rickard


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## Grant_NZ (May 28, 2008)

Hi guys, this seems promising for a 160 volt system, 50 batteries, however some questions come to mind;

If it has regen, which I'm guessing it would being an AC controller, if your batter pack was 160v which they say it can take and regen was applied, would the over current protection kick in shutting the motor or regen off? or would it be safer to stick to144? 

Also I take it this is designed specifically for the AC55 or can it be used for other AC motors? I was always under the impression AC controllers were designed for specific motors..?

Thanks
Grant


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## Guest (Feb 6, 2010)

Grant_NZ said:


> Hi guys, this seems promising for a 160 volt system, 50 batteries, however some questions come to mind;
> 
> If it has regen, which I'm guessing it would being an AC controller, if your batter pack was 160v which they say it can take and regen was applied, would the over current protection kick in shutting the motor or regen off? or would it be safer to stick to144?
> 
> ...


I'm not advocating this system, or indeed know anything about it except what is on the web site.

That said, you are quite correct. In the past, AC controllers had to be specifically set for a particular motor. This has become a set of variables for obvious reasons. And now it seems that some of the controllers, including the Curtis, are "easy setup." And that is kind of morphing into "adaptive controllers" that can "learn" the motors. 

It's in kind of a changing state, so there aren't any guarantees all around. But it is clear the old days of having to have an engineeered "set" of motor and controller are gone. How much trouble/how well they adapt to motors is another matter. I wouldn't buy one without some indication someone had successfully used THAT motor with THAT controller.

Jack RIckard
http://evtv.me


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## Coulomb (Apr 22, 2009)

Grant_NZ said:


> Hi guys, this seems promising for a 160 volt system, 50 batteries, however some questions come to mind... or would it be safer to stick to144?


Unless you are really pressed for voltage headroom (as Tom of Reno was), I'd stick to 45 cells, for exactly the reason that you state: to get decent regen into a Lithium cell, they will go to about 3.6 VPC, certainly 3.5 VPC. So with a controller limit of 160 V, you'd want a maximum of about 160/3.5 = 45 cells, or 144 V nominal. You still have to disconnect your controller when charging, since assuming you charge to 3.6 VPC, that would be 45 * 3.6 = 162 V, and if you occasionally charge to 4.0 VPC, that's 180 V. It most likely is not a good idea to exceed the input voltage, even when not operating the controller.

Tom's controller has about a 130 V limit, and he's sticking to 35 or 36 cells (sorry I can't remember which); with 36 cells that allows 130/36 = 3.61 VPC for regen.

So if you wanted about the same safety/regen margin as Tom, that would mean a maximum of 160/3.6 = 44 cells, or 44 x 3.2 = 141 V nominal.

The voltage limits become painful for AC controllers. It's only been with the advent of the 1238-7501 that it's even been reasonable at all. That was the genius of HPGC - to get Curtis to make a higher voltage controller. Just a little higher again (which this Lithuanian controller promises) is better again, and a limit near 200 V would be better again. But that's where the cost of MOSFETs starts getting ridiculous, and there needs to be a very healthy voltage margin with all the spikes that controllers have to deal with all day every day.


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## Coulomb (Apr 22, 2009)

jrickard said:


> The AC controllers are a bit different than the DC controllers in a couple of curious aspects. There is no particular requirement to have the maximum voltage from the pack at all connected to the voltage applied to the motor windings.


Well, if you assume sine wave voltages, then the maximum you can produce without a boost design is 1/√2 times the input voltage, or about 102 VRMS less voltage drops. This is assuming that they know how to do the "neutral wobble" technique; otherwise it's worse, something like 1/√3 of the input voltage, or 83 VRMS less voltage drops.



> The speed of the motor is a function of frequency, and the torque of current. In DC motors speed is a function of voltage, and similarly torque of current.


Voltage is closely related to frequency (speed) for both AC and DC motors, essentially because back EMF is proportional to speed, and you can't exceed back EMF by very much (AC or DC) without excessive currents flowing.



> If he can do 650amps in the motor windings, but with a 50 kw power limit, that implies an rms value of 77 volts.


That would be so if there was only one winding. The problem is that there are so many ways of measuring current into 3 wires. You could add the magnitudes, or add the currents vectorially (but that would usually result in zero), or the usual method is RMS line current. With a 3-phase load, depending on whether the load is connected in delta or star (Wye in the US), either the current or voltage is √3 less than the line current or voltage, so overall you end up with line voltage times line current times √3 as the resultant power. So if the maximum RMS current is 650 ARMS per phase, the line voltage (phase to phase) would be 50,000 / 650 / √3 = 44.4 VRMS. But it should be capable of about 100 VRMS. So yes, there is something fishy about these figures.

So maybe the 650 A figure is the current limit of the MOSFETs, i.e. the peak of the AC current sine wave. Then the RMS current would be 650/√2 = 460 ARMS, so with 100 VAC phase to phase, it would be capable of 100 * 460 * √3 = 80 kW. Or working backwards, the voltage must be 50,000 / 460 / √3 = 63 VRMS phase to phase. I can't make that fit sensibly either.

Maybe they're thinking battery sag, and expecting the battery voltage to sag to 5/8th of nominal? It seems a bit extreme.

So Jack we are in agreement to this extent: the provided figures don't add up. Unless the 50 kW is a cooling limitation, but we're told elsewhere that the continuous power is less than 50 kW, and usually any controller can output its theoretical maximum for short periods of time, before the silicon gets too hot.



> Similarly the Curtis. You say it will do 45kW at 115 volts. But the max current on your controller is 550 amps. At 115v that would be 63 kW in a DC world.


115 VDC is enough for some 115/√2 = 81.3 VAC, call it 80 VAC with voltage drops. With 550 ARMS per phase output, that's 80 * 550 * √3 = 76 kW.

So I actually think that the 550 A limit on the Curtis is on the DC side, so I think that Tom expects his batteries to sag a lot at peak currents. So 45000 / 550 = 81.8 V, or 2.27 VPC (assuming 36 cells), neglecting voltage drops in cabling.

Hmmm. If I go back to the nominally 144 V controller and use 2.27 VPC and 45 cells, I get 102 VDC, enough for about 72 VAC before voltage drops. That's getting closer to the 63 V I calculated. Using 2.0 VPC, I get 90 VDC and 63.6 VAC... maybe that's it: severe battery sag assumed. That's most unlike any existing controller's marketing! Usually, the controller figures will be optimistic in the extreme.

I actually suspect a goof in their maths somewhere (or mine of course), but without more details, it's very difficult to guess where it is.


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## Grant_NZ (May 28, 2008)

jrickard said:


> ...now it seems that some of the controllers, including the Curtis, are "easy setup." And that is kind of morphing into "adaptive controllers" that can "learn" the motors.


Thanks Jack, no stress I totally understand you've just discovered this yourself 

By learning I take it they would have a list of basic motor functions which you could the alter/program according to your motor requirements? If so thats pretty cool and moving in the right direction for this type of industry 



jrickard said:


> I wouldn't buy one without some indication someone had successfully used THAT motor with THAT controller.


So when did you say you were going to be the tester/guinea pig?



Coulomb said:


> Unless you are really pressed for voltage headroom (as Tom of Reno was), I'd stick to 45 cells, for exactly the reason that you state: to get decent regen into a Lithium cell, they will go to about 3.6 VPC, certainly 3.5 VPC....


Thanks Coulomb, understood and good advice. There will be plenty of room for cells and reducing to 45 will save on the pocket. 

Grant


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## tomofreno (Mar 3, 2009)

> If it has regen, which I'm guessing it would being an AC controller, if your batter pack was 160v which they say it can take and regen was applied, would the over current protection kick in shutting the motor or regen off? or would it be safer to stick to144?


 On the Curtis controller you can change the parameter user_overvoltage to avoid overcharging with regen. It is set as a percentage of the nominal_voltage parameter, which is the nominal pack voltage. Of course it doesn't protect against overcharging an individual cell should it become significantly unbalanced for some reason. I don't think that is very likely until maybe the pack gets quite old, and you should be checking voltages periodically anyway to watch for this, or have a bms with HVC interfaced to the controller. Even then, you could set the parameter much lower to ensure you don't overcharge. I've not found overcharging with regen to be an issue so far. 



> So I actually think that the 550 A limit on the Curtis is on the DC side, so I think that Tom expects his batteries to sag a lot at peak currents.


 The max power I reported is shaft power (product of motor torque and angular velocity), not what theoretically goes into the controller. The dynomometer data for the motor/controller show a max 50 HP shaft power for a nominal 96V pack. I just scaled that for a 115V nominal pack. The lead acid 96V pack sagged to 85V at high currents, so likely the power is a bit higher with LiFePO4. As I've warned before though, you can't run the Curtis controller at that peak power, or close to it, for very long without the controller overheating. I have a 250 cfm fan blowing on the aluminum plate that the controller came mounted on, but I don't think that will be sufficient to run at even 60 mph continuously at summer temps around 100 F. The controller is the achilles heel of this setup. I sure would like to find something that can run at higher continuous shaft power. The website for this other controller claims 30kW continuous, but it is not clear what that is, i.e. if it is shaft power, more likely it is an estimate based on the power the mosfets can handle as Coulomb suggested. They use water cooling, so there is a potential for greater heat transfer, but there is no spec for the required heat removal, so you don't know what size liquid-air heat exchanger is required - unless it is 30 kW. I think you don't know what you are really getting with that controller with the info given. Nor do you know reliability, parts availability, service, etc. Could work out well, dunno.


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## JRP3 (Mar 7, 2008)

I wonder if water cooling would actually be more efficient or not. Thinking of a cool plate for the Curtis. Ultimately all water cooling does is move the heat to be dissipated in the air somewhere else and give greater surface area with a radiator. Maybe a finned heatsink and a more powerful, possibly ducted, fan would do just as well. Would a small pump and large enough radiator that didn't need a fan take less energy? I'm sure there's a formula somewhere.


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## tomofreno (Mar 3, 2009)

> Ultimately all water cooling does is move the heat to be dissipated in the air somewhere else and give greater surface area with a radiator. Maybe a finned heatsink and a more powerful, possibly ducted, fan would do just as well


 It would be difficult to match the performance of a liquid/air heat exchanger due to the large surface area, but the finned heat sink/fan would be sufficient, and easier to implement, if you could make it large enough. I don't have enough space for that. I think I'll likely have to mill a fluid channel and periphery o-ring groove into the back of the controller aluminum plate and bolt a 1/4" thick aluminum plate with fluid fittings to it. I can fit this in the same space I am currently using, and mount a large heater core from a junkyard and fan for heat exchanger remote from it - similar to what Jack is doing, probably for similar reasons.


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## tawright (Dec 30, 2009)

What about the same liquid cooling system you would find on some high end gaming PC's? I believe it is a closed system and it may be just what you are looking for.

Tom


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## Guest (Feb 8, 2010)

tomofreno said:


> It would be difficult to match the performance of a liquid/air heat exchanger due to the large surface area, but the finned heat sink/fan would be sufficient, and easier to implement, if you could make it large enough. I don't have enough space for that. I think I'll likely have to mill a fluid channel and periphery o-ring groove into the back of the controller aluminum plate and bolt a 1/4" thick aluminum plate with fluid fittings to it. I can fit this in the same space I am currently using, and mount a large heater core from a junkyard and fan for heat exchanger remote from it - similar to what Jack is doing, probably for similar reasons.


Actually I hadn't thought of milling right into the Curtis plate. Good idea. I am using two half inch plates that will have a serpentine milled into the face of each, matching of course. The plates will be bolted together with some silicon around the milling and two holes drilled/tapped for 1/4 inch. I have two 1/4NPT to -AN6 fittings that will screw into this. 

I get a little carried away with this stuff. If you go to Summit Racing's web site, you can spend an unlimited amount of money on fill bottles, braided steel hose, heat exchangers, and pumps. 

Here's the real issue. I've been bitten by this a couple of times. We build an electric car, but we have no experience or "known good car" to compare it to. It feels like it feels.

I had a Kelly controller on the Speedster with the Low Voltage entry set to high. I would press on the accelerator, and as the pack voltage sagged, it dipped below this level. The Kelly doesn't cut out, it just current limits in that case. So I would get a pretty smart jump out of the gate, but then acceleration wasn't quite what I had hoped for. 

After driving this way a couple of weeks, I got a little smarter about the batteries and adjusted the low voltage cutout on the Kelly to a much lower value. I nearly went through a fence and wall the next time I stepped on the accelerator. 

Reading through the Curtis manual, I'm getting the same sense. It current limits at 85C. These controllers are getting to be TOO GOOD for our own good. I could have a heat problem FOREVER and never know it. The controller would simply limit its output to stay below 85C. How would I know it was limiting?

Well, it does have a CAN bus and RS-232 output and I should probably develop something to monitor that. 

But right off the bat I want to take heat off the table. And I will do it with water. I do NOT agree JRP that heat is heat and water and air are all the same thing. Water is about 3000x more effective at removing heat. All I want is to get it off that controller heat sink. What happens then is moot to operation to some degree. But the short answer is that the hoses will cool it, the fill bottle cools it, the pump cools it, and the remote finned heat sink cools it.

As Tom says, I actually have a LIMITED amount of room around the controller for fans and heat sinks, but if I can pipe it away, there are all sorts of places to hang a pump and a heat sink. Placing the fill bottle artfully where I can easily get to it, is a bit of an issue, but nothing heroic.

So I have an 18 inch long 3 inch diameter finned heat sink that I'll hang UNDER the car in the passing air. At that point I am REALLY into overkill on this thing I feel. 

Part of this is that it isn't a great deal of absolute heat energy to begin with . The problem is its concentration. You have a high temperature in a very local area - the surface of the MOSFET. This is removed with the heat sink plate, but not far enough. There is enough total energy to heat the heat sink. 

But if I can move it away quickly, and water is the way to do that, to a much larger degree than air, the total amount of heat generated is not a problem. It is nothing like a "radiator" on a car for example. 

So I'm going to a water system for the Speedster part DUH in the hopes that I don't go into current limit over temperature. Looking at this motor, and this controller, and the specs on both, and the description of performance Tom is posting, and the car size he has, I'm not able to put all this together. Something isn't right here. This motor is the size of a Warp 9. This controller should be able to do 550 amps at 115 volts. This car doesn't weigh any more than the speedster. 

Now without being there, I just can't be sure enough to offer Tom any advice on this. But it has me going to water cooling. I'm guessing, and only to myself, that he's in thermal current limit on his controller. And it's doing such a good job of it, he can't tell.

The biggest problem I've had developing electric cars, is I don't know how they're supposed to work when I'm done. We don't have a "go by" to go by. 

We installed the water heater in the Mini and I have to confess I was a little disappointed in the output. It was working well and heating, but not by as much as I had hoped. But oh well. It's in.

I later did some measurements of current when we got the EVision installed, and with the heater on we were only drawing about 4 amps at 375 volts. It's supposed to be a 4kw heater. So it should be drawing over 10 amps. How can this be? We asked Victor about it, and he told us to send it back and he'd put it with all the others he was shipping back to MES-DEA with faulty controllers. He sent us a new one and it works GREAT. This car will be warm and toasty in MINUTES in the dead of winter. I THOUGHT it was working properly, but just a little bit disappointed. Turns out it was NOT working properly, and when we put a new one in, it blew me away. Draws a little over 10 amps just as it should.

So I'm looking at this Curtis, and the size of the unit and the heat sink, and I want to mount it up in the humpback of the Speedster part DUH, (which we received the roller Friday and is IT GORGEOUS). I can do a pretty big aluminum plate under it, and yes, we could mount a fan, which would be kind of noisy. But the fan would take up room there and I don't have much. So we're probably going to the added expense, complication, and maintenance issue of a water system.

The MES-DEA 200-250 we use in the Mini, AND the TIMS 600 controller, are both water cooled. The Zilla is water cooled. The new Netgain Controller is water cooled. The Tesla limped back to the pits after 3 laps with a heat issue (air cooled). The Mini-E has had some heat issues (air cooled). 

My general sense is that the future for us in electric cars is AC with regen, and water cooling, and I need to get over it on the water cooling. So we're ordering Summit Racing parts and trying to do the trickest system we can - in the hopes of avoiding maintenance issues by using lots of machined aluminum and braided steel hose with expensive AN fittings.

Jack Rickard
http://EVTV.me


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## frodus (Apr 12, 2008)

If anyone is interested in water cooled plates for the Curtis 1238 that will be about 3/8" thick, PM me, I have a contact that is making a few. We can also help source motorized pump/radiator. Mine is for a bike, so its minimal in size.


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## John (Sep 11, 2007)

JRP3 said:


> I wonder if water cooling would actually be more efficient or not. Thinking of a cool plate for the Curtis. Ultimately all water cooling does is move the heat to be dissipated in the air somewhere else and give greater surface area with a radiator. Maybe a finned heatsink and a more powerful, possibly ducted, fan would do just as well. Would a small pump and large enough radiator that didn't need a fan take less energy? I'm sure there's a formula somewhere.


Air weighs about 1.2 kg/m^3 and water of course weighs 1000 kg/m^3. This works in waters favour as you can put a much higher mass of it close to the bits you want to cool. About 830 times as much by volume. Also the specific heat of liquid water is about 4.2 kJ/kg.K compared to airs specific heat of about 1 kJ/kg.K. That is to raise the temperature of one kilogram of water one degree Centigrade (Kelvin) takes 4.2 kilojoules of energy. So water by weight absorbs about 4 times as much energy for any given temperature rise as air. If you figure that by volume you get 3500 times the energy absorption from any given volume of water over air. Given the specific heat capacity of both mediums if it took the same energy to move the same mass of each water would still win by a considerable margin.


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## JRP3 (Mar 7, 2008)

tawright said:


> What about the same liquid cooling system you would find on some high end gaming PC's? I believe it is a closed system and it may be just what you are looking for.
> 
> Tom


I would guess that they are much smaller than what is needed but I could be wrong.


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## tomofreno (Mar 3, 2009)

> Now without being there, I just can't be sure enough to offer Tom any advice on this. But it has me going to water cooling. I'm guessing, and only to myself, that he's in thermal current limit on his controller. And it's doing such a good job of it, he can't tell.


 Jack, the Curtis 840 gauge that comes with the motor/controller reads out both motor and controller temperatures, so it is easy to check if you are over-heating. I drove about 5 miles at 60 mph today while watching the controller temperature (motor is always much cooler). Max was 33C, reached after a few miles. Ambient was about 40F or 4.4C. If we assume the temperature difference between controller and ambient will be similar in summer, then on a 100 degree day the controller would be around 73C. I have had the controller up to its overheat temperature, but that was with the cooling fan OFF, no additional cooling plate other than the aluminum plate that came with the controller, and after doing a couple zero to 60 runs, and driving along at 70 to 75 mph for several miles. Ambient was pretty cool, less than 30F I believe.

I think JRP3's point is that even if you remove the heat from the controller with water, you still rely on air to remove the heat from the water, you are just doing it further down the line so to speak. That is an advantage though when you don't have much space. I see your point though, that you can get more heat removal close to this spatially small source (mosfets) with water. I think a larger finned heat sink and fan would work fine for speeds less than 70 mph, I just don't have space for it.

Yes, if you don't have good instrumentation it is hard to tell what is going on. And without a programmer or PC Programming Station for the Curtis, you don't know what the parameter values are, and cannot change them.


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## tomofreno (Mar 3, 2009)

> I would guess that they are much smaller than what is needed but I could be wrong.


 I would guess by more than an order of magnitude. I expect tens of watts from a microp and around 1kW from the controller at highway speeds.


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## JRP3 (Mar 7, 2008)

Jack, as to the Tesla overheating, I'm not sure which Tesla under what conditions you are referring to, but under daily spirited driving I'm not aware of any issues. I think it's worth noting that the most powerful production EV is air cooled, and other than drag strip passes heat has not been an issue.
I agree that water can more quickly remove heat, and if there is no room for fans and heatsinks it's really your only option. I'm just wondering if a large enough heatsink and a fan might be enough. As long as you keep below cutoff temp that's all the cooling you need. I have the room so I guess I'll find out.


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## JRP3 (Mar 7, 2008)

Tom, or anyone else using SE cells, did you end up with two different bolt head sizes for the cell terminals? Same shank and thread but some bolt heads are 13mm and some are 14mm, annoying to keep switching wrenches when bolting up the pack.


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## tomofreno (Mar 3, 2009)

> Tom, or anyone else using SE cells, did you end up with two different bolt head sizes for the cell terminals?


 Yes. Its a pain swapping sockets as you go around tightening. Thought I was the only one...


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## MN Driver (Sep 29, 2009)

tomofreno said:


> I would guess by more than an order of magnitude. I expect tens of watts from a microp and around 1kW from the controller at highway speeds.


To put it into perspective, overclockers using water cooling have quad-core chips that use around 150 watts. I have a buddy who uses a system that I've checked out the radiator filled with water fits 2 120mm fans on it and the radiator itself is about as thick as the fans. The fans are slow speed fans(1800 rpm I think) but have enough pitch to make his entire system silent. The water is measurably at ambient temp going into the processor cooling water block. He has tried to use a heater core from a car but they aren't design to exchange that much heat and it didn't work very well in comparison because they are designed so that they don't put out a level of heat that will cool the engine below operating temperature in the winter as that would be undesirable.

I suppose with more air flow one of these overclocking water radiators could do the job if it can keep 150 watts near ambient, it would probably do well decently with 1kw, just not cooling to ambient. Either that or you could snag an oil cooler or transmission cooler(same thing) that is designed strong and to put attached in front of a normal radiator and put it on the front of your car and could probably call it good as that will do -much- better than the manufacturer recommended 'put a bigger hunk of aluminum on there to sink the heat'.


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## Guest (Feb 9, 2010)

JRP3 said:


> Tom, or anyone else using SE cells, did you end up with two different bolt head sizes for the cell terminals? Same shank and thread but some bolt heads are 13mm and some are 14mm, annoying to keep switching wrenches when bolting up the pack.


Yes, what is that about? Why did the ship two different head sizes? I too thought it was a mistake and just me.


Jack Rickard
http://EVTV.me


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## Guest (Feb 9, 2010)

JRP3 said:


> Jack, as to the Tesla overheating, I'm not sure which Tesla under what conditions you are referring to, but under daily spirited driving I'm not aware of any issues. I think it's worth noting that the most powerful production EV is air cooled, and other than drag strip passes heat has not been an issue.
> I agree that water can more quickly remove heat, and if there is no room for fans and heatsinks it's really your only option. I'm just wondering if a large enough heatsink and a fan might be enough. As long as you keep below cutoff temp that's all the cooling you need. I have the room so I guess I'll find out.


There was an article about a Tesla Roadster owner going to a local sports car race - lap race type of deal. He did three laps and limped back to the staging area. Tesla's reaction was to note that these "sports cars" were designed for normal daily driving, not racing. It was purely a heat issue. The car recovered in minutes.

It was of course the Power Electronics Module. It's air cooled, and up front. But it apparently went into limp mode when the temperature got too high.

http://fuel-efficient-vehicles.org/energy-news/?p=836

Jack Rickard
http://EVTV.me


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## JRP3 (Mar 7, 2008)

jrickard said:


> Yes, what is that about? Why did the ship two different head sizes? I too thought it was a mistake and just me.
> 
> 
> Jack Rickard
> http://EVTV.me


I wondered if they maybe sent different sizes for the + and - terminals, but only 1/3 of my bolts are the larger size. I actually went anal retentive and switched all the large bolts to one of my 12 cell packs so I won't have to mess around with swapping sockets during future maintenance.


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## Jimdear2 (Oct 12, 2008)

JRP3 said:


> I wondered if they maybe sent different sizes for the + and - terminals, but only 1/3 of my bolts are the larger size. I actually went anal retentive and switched all the large bolts to one of my 12 cell packs so I won't have to mess around with swapping sockets during future maintenance.


As I remember, this is something that goes back to the 60s. There was an arguement between Japan and other countries about metric standards. Thread pitch, bolt strength and bolt head size were amoung the points of difference. One specific arguement I heard on bolt head size was that a 1/2 inch wrench would fit a 13 mm hex and vice versa, where as a 9/16 to 14 mm the match up wasn't so good. Also if a standard was adapted a lot of good tooling wopuld need to be discarded

I don't think a univerisal standard was ever adopeted. Japan adopted the Japan Industrial Standard (JIS) A lot of the others did not.

The last Chinese scooter I put together had both 14 and 13 mm hex 8 mm bolts on it. Probably the mainland people are used to the situation and deal with it 

The 13 mm hex mostly won out in general use, but you will still see 14 mm heads on a lot of mainland stuff. You will even find 12 mm Hex on some 8 mm bolts. 

The situation you guys are running into is probably a case of lowest bid suppliers to the battery manufacturers.

A thought to pass on to the battery importers when you break up the shipments TRY (I know it will cost time = money) to sort through the hardware and get a common bolt size with every individual shippment.


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## JRP3 (Mar 7, 2008)

A thought on brake light triggering during regen. The 840 display lights the third green LED during regen, so whatever triggers that LED could be tapped to trigger the brake light.


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## tomofreno (Mar 3, 2009)

> The 840 display lights the third green LED during regen, so whatever triggers that LED could be tapped to trigger the brake light.


 That is what I thought too, and mentioned it to HPGC, but they said they would have to customize the software to provide the function. Don't know why, unless they think the current drive for that signal is too low to drive a relay. It might work with a mosfet relay that only requires about 15mA input. I could use that to turn on a larger relay to drive the brake lights. HPGC recently verified that they will send me the software, but it might be a while as they are swamped. 

I've been thinking more about this too, and wondering if it is a good idea to have the brakes lights come on every time regen kicks in. They will be flashing on quite a bit in that case - when I back off the throttle to go around a bend, when I drop down a small grade and ease off the throttle to maintain the posted speed limit, and all the way down a larger hill. When I drive my Isuzu pu I engine brake regularly to hold speed on a hill, back off the throttle to slow for a bend, and down shift to stop. It is very similar to what I am doing with regen, and not that much weaker an effect. I've never had a problem doing this. I've also not had a problem with the electric car. I've been watching in my mirror when I stop for a light, and as soon as I slow down with regen the car behind me backs off if they were following closely, but usually they weren't and they just slow down at the same pace. Of course if someone is following closely I don't slow quickly - unless I have to because a light suddenly changes. Not sure all this fuss is warranted.


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## GizmoEV (Nov 28, 2009)

I believe that the Tesla turns on the brake lights if the regen is causing the car to physically slow down. I remember reading it on one of their blogs a couple of years ago. It may be that it lights them if the car is slowing faster than it would coasting on level ground or something. It seems that it wouldn't be too hard to program this into the controller since I'm sure the controller knows the motor rpm.


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## JRP3 (Mar 7, 2008)

It may not be that much of a concern as you say, certainly using aggressive down shifting and engine braking in an ICE has never been a concern. Maybe the answer would be an accelerometer, or deccelerometer, set to a certain value.


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## tomofreno (Mar 3, 2009)

I drove 60.9 miles today, about 3/4 of it at 50 to 57 mph, and used 102.1 Ah, or 1.68 Ah/mile and about 193 Wh/mile. I added a new 36th cell to the pack recently and the pack voltage remained at 115 +/-3V on the return half of the trip on the freeway where fairly flat. Coming up an about 3% grade in the last mile voltage dropped to about 114V when drawing 192A. Rest voltage was about 120.6V after charge and before the trip. 

I charged the new cell to 3.310V initially (rest voltage about 15 minutes after charging) to match the neighboring cells which were 3.308 to 3.311V, then charged the pack. But as usual, the cell dropped further in voltage, and a day later was about 0.01V lower than the neighboring cells. After the drive it was about 0.017V lower, so I charged it at 5A with a power supply to about 0.08V higher than the other cells. Will check it in the morning after it has "relaxed" to see if I need to charge it more. This is typical. I've found I have to charge, charge, and recharge a cell to get it to match others in the pack, because it keeps relaxing back down to a lower voltage for hours after a charge. I data logged this cell and the neighboring 5 cells voltage on the trip, and sag seems similar for all, just an offset since the new one is lower in voltage. It remained above 3.1V for even the deepest current draws though (only about 250A). I preheated the cabin with a ceramic heater for about 45 minutes prior to the trip, and only used the car heater for about 10 minutes as it was warm enough to go without. So about 1/5Ah.


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## tomofreno (Mar 3, 2009)

The datalog below is from the second half of the 60 mile trip. I was incorrect on the low cell voltage. As you can see it actually got down to about 2.97V, not 3.1. That is at 0.5 second resolution. It appears to sag a bit more than the other cells, but the difference in voltage is mostly an offset I think. After charging it last night it settled at 3.300V this morning, with neighboring cells at 3.302V. Under 30A charge it is about 0.01V higher than those same neighboring cells now, so there is some difference. The other cells track each other very well. You can see the cells slowly recovering back up to higher voltage at the end of the datalog while the car is sitting idle. Unit of the abscissa is Second, ordinate unit is Volt. Six cells total, cell 3 is the new one.

View attachment file9, 2.11.10.pdf


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## tawright (Dec 30, 2009)

What batteries are you using? Is the specs at the beginning of the thread still what you are using?


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## tomofreno (Mar 3, 2009)

> What batteries are you using? Is the specs at the beginning of the thread still what you are using?


 SkyEnergy 180Ah. Yes.


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## tomofreno (Mar 3, 2009)

I did an inadvertent test of the controller user_overvoltage parameter earlier this week. I forgot I had it set at 124%, and nominal_voltage was set at 96V. After I added the 36th cell and charged the pack, the voltage was 120.6V, exceeding the 119V user_overvoltage. I pressed the accelerator and nothing happened. Turned the ignition off and back on, pressed again. Nothing at first, then it took off out of the garage. Stopped and shifted, pressed the accelerator, nothing. Off/on, pressed again, it took off. I did some circles around the drive then headed out for a test drive without stopping, since by then it hit me that user_overvoltage was probably too low, but I couldn't remember what I set it at. Sure enough, no regen on the test drive. Current meter showed the usual -0.7A, (DC/DC converter load) when I released the acclerator. It was funny, because I was so used to the car slowing with regen, it felt like it was taking off when I released the accelerator, rather than just coasting. Went home, set user_overvoltage to 128%, ensured everything else was unchanged, and went for another drive. Everything worked fine.


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## JRP3 (Mar 7, 2008)

What was the factory nominal and over voltage setting?


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## tomofreno (Mar 3, 2009)

> What was the factory nominal and over voltage setting?


 nominal_voltage = 96V, user_overvoltage = 140%.


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## JRP3 (Mar 7, 2008)

So does that mean if you increase the user voltage and/or the overvoltage percentage you could run higher voltage, or are those the max settings allowed by the software? Or is there a hard shutdown built into the controller that over rides these settings?


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## few2many (Jun 23, 2009)

If you increase the user volage, does the over voltage drop by default, keeping approx 135v as the max?
or is this something you can adjust and blow things up?


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## tomofreno (Mar 3, 2009)

> If you increase the user volage, does the over voltage drop by default, keeping approx 135v as the max?


 I don't think so , but haven't tried it.


> or is this something you can adjust and blow things up?


 My understanding is the controller just will not operate at voltage above its max voltage rating, which is nominally around 130 - 135V I think for this controller (I think HPGC told JRP3 they had run the controller at as high as 134V). The user_overvoltage parameter permits the user to define the max voltage at a lower value (for example, 122.9V as I set mine up). This effects both max operating voltage and the cutoff voltage for regen. I don't know how high you can go in voltage without damaging the controller. Why 122.9V? Because that is an integer percentage (128%) of 96V, and corresponds approximately to the pack voltage with 35 cells at 3.414V and one at 3.6V. My weakest cell hits 3.6V when most others are at about 3.43V. Gives me a little safety factor, and is high enough to ensure it won't cut in during normal vehicle operation.


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## tomofreno (Mar 3, 2009)

> So does that mean if you increase the user voltage and/or the overvoltage percentage you could run higher voltage, or are those the max settings allowed by the software? Or is there a hard shutdown built into the controller that over rides these settings?


 The manual for the Curtis controller gives a little table on page 55 that lists voltage ratings. The leftmost column lists nominal voltage range, and the rightmost column lists max voltage. Below the table it states: "Overvoltage: Either Max Voltage (see voltage ratings table) or User Overvoltage*Nominal Voltage, whichever is lower." My experience described in the earlier post infers the controller doesn't operate when there is an Overvoltage condition as defined above.

Unfortunately the manual I have (draft 17 November 2006) evidently does not cover the 1238-75xx controller, as its upper limit in nominal voltage is 96V according to HPGC, not 24 - 84V listed for nominal_voltage allowable range on page 55.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> The manual for the Curtis controller ...
> 
> Unfortunately the manual I have (draft 17 November 2006) evidently does not cover the 1238-75xx controller, as its upper limit in nominal voltage is 96V according to HPGC, not 24 - 84V listed for nominal_voltage allowable range on page 55.


The 1238-75xx seems to be a different beast to the other 1238 series, hence even Curtis people not believing it exists, etc. On the Curtis controllers page, there is a separate "overview" PDF (they call it a data sheet) for the 75xx:

http://www.curtisinstruments.com/in...ducts.DownloadPDF&file=50175_1238-75_RevC.pdf

There, on page 2 of 4, it states "Battery Voltage V" as "72-96". I've heard the figure 108 V nominal mentioned for this controller, but it looks like Curtis don't use this figure. I think I saw it on some retailer's web site; perhaps that was before this "data sheet" came out.

It would be nice to find the proper manual for the 1238-75xx models, or for Curtis to update the existing manual to cover this model. Tom, where did you get your 55+ page manual from? Or are you talking paper not PDF?


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## tomofreno (Mar 3, 2009)

> I've heard the figure 108 V nominal mentioned for this controller


 You cannot set nominal_voltage over 96V, not even 97V. I tried.



> Tom, where did you get your 55+ page manual from? Or are you talking paper not PDF?


 PDF, http://www.thunderstruck-ev.com/AC_drive_performance.htm 

btw, the max torque is 90 lb-ft (@550A), not 115 as stated on this page. I know HPGC had said people were using this motor/controller with 108V, so that may be where the 108V came from.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> PDF, http://www.thunderstruck-ev.com/AC_drive_performance.htm


Ah, thanks, Tom. Here was me thinking that the manufacturer (Curtis) would supply the manual. What was I thinking?

It seems that the 550 A limit quoted really is RMS motor current, presumably per-phase (but that isn't stated).

So the peak power is about 130/√2 * 550 * √3 = 87 kW, call it 80 kW with voltage drops and battery sag.

I note that 130/√2 * 550 is 50.5 kW, so maybe this is where the 50 kW peak (electrical) power number (that I hear frequently) comes from (someone forgetting to multiply by √3 because of 3 phases, and either voltage or current being reduced by a factor of √3 depending on whether it is wired in star (wye) or delta respectively). 80 kW electrical translates to some 72 kW mechanical, using a motor efficiency of 90%.

This controller is in a small package, the same as the other 1238 series I'm guessing, so cooling will be a real issue, but it looks like it's capable of good performance if you can keep it cool, and can keep the pack voltage up near the limit.


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## tomofreno (Mar 3, 2009)

> So the peak power is about 130/√2 * 550 * √3 = 87 kW, call it 80 kW with voltage drops and battery sag.


 I just go by shaft power. With a nominal 115V pack (36*3.2V) sagging to maybe 111V at 550A and full charge (~120V) I estimate max torque of 90 ft-lb is available out to about 3900 rpm or so, since the dyno (from HPGC, taken by Curtis) data showed 90 ft-lb out to about 3000 rpm with a 96V pack sagged to 85V: 3000+3000*(111-85)/85 ~ 3900. Using 90 ft-lb = 122 N-m, gives 122*3900*2pi/60 = 49.8 kW = 66.7 H.P. I haven't seen the 50kW figure quoted before, only 50 H.P., which was about the peak for the dyno data (51). Thunderstruck states 48 H.P. with 108V, which is an underestimate of power. It would actually be around 60.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> I just go by shaft power. With a nominal 115V pack (36*3.2V) sagging to maybe 111V at 550A and full charge


Yes, of course, I shouldn't use 130 VDC, since it will allow absolutely no regen. Let's take your 111 VDC as a maximum usable figure with a real-world battery.
So that's some 78 VAC, call it 75 VAC with IGBT and cable voltage drop. 75 * 550 * √3 = 58 kWe. Using 90% efficiency, that's some 52.5 kW mechanical.



> Using 90 ft-lb = 122 N-m, gives 122*3900*2pi/60 = 49.8 kW


That's pretty close to what I got. So it looks like this motor is getting close to the maximum you could expect from this controller. I suspect a higher power controller could get a fair bit more out of this motor.



> I haven't seen the 50kW figure quoted before, only 50 H.P.,


Oops, that's probably me misremembering the figure, sorry.



> Thunderstruck states 48 H.P. with 108V, which is an underestimate of power. It would actually be around 60.


Yes, it's so unusual to see a supplier underestimating power. I suspect a typo or similar.

Edit: Oops! I've just realised that we're still talking different mechanical power. I'm talking power from the motor (as specified by the industrial AC controllers that I'm a little more familiar with); dynos are about power at the wheel (correct me if I'm wrong there). I could easily expect 10-15% loss through the transaxle, so that would bring the 52.5 kW down to say (using 12.5%) 47 kW. Probably the motor or transaxle is a little more efficient than I guessed. So yes, this combination seems to be controller limited, but the controller limit is pretty reasonable.


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## JRP3 (Mar 7, 2008)

This guy could probably do a custom liquid cooled inverter for the motor http://www.rinehartmotion.com/
HPG mentioned a max of 200 volts for the motor, which would stretch the torque curve out nicely I'd think. 600-700 amps, 200 volts, wheeeee


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## tomofreno (Mar 3, 2009)

> This guy could probably do a custom liquid cooled inverter for the motor http://www.rinehartmotion.com/
> HPG mentioned a max of 200 volts for the motor, which would stretch the torque curve out nicely I'd think. 600-700 amps, 200 volts, wheeeee


 Probably, but for how much? With a 700A, even 150V controller the motor would power a 3000 lb vehicle with good acceleration. That would give about 115 ft-lb out to around 4800 rpm, about 78 kW or 105 H.P. This motor needs quite a bit of current to get much low end torque, higher voltage doesn't help you there. So I think that 800A and 140V would give better overall performance in something like a Corolla or Spectra. It would be nice if HPGC would make a motor with different windings for higher voltage/lower current, say more like the Azure motors at around 300V, so you could use battery currents less than around 250A. Of course then you would need a high voltage controller. The problem with higher currents is then you need higher Ah cells to avoid larger than 3C currents. Something like 260Ah or more, which are more difficult to fit in a vehicle. Easy to see why so many go with DC.


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## CroDriver (Jan 8, 2009)

maxvtol said:


> Now finding a decent motor chart for torques, efficiencies, etc. at different rpms, THAT'S what drives me crazy.


http://www.diyelectriccar.com/forums/showthread.php?t=41328

http://kostov-motors.com/files/productattachments/21df9baa0453d539f868d9041f11e4a6_S400F01.pdf

http://kostov-motors.com/files/productattachments/04a1d5e7278db48475f2aa409b5df5ce_S192F01.1.pdf

http://kostov-motors.com/files/productattachments/da0012f5e806b95241ea09d19be9abe3_11-192V.pdf

http://kostov-motors.com/files/productattachments/1c7d6f1e0a80d760104fb0d617e9bcda_11-168V.pdf


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## JRP3 (Mar 7, 2008)

tomofreno said:


> The problem with higher currents is then you need higher Ah cells to avoid larger than 3C currents. Something like 260Ah or more, which are more difficult to fit in a vehicle. Easy to see why so many go with DC.


That's why I was thinking between 600-700 amps, a 200ah cell could handle that pretty easily, and the higher voltage helps compensate for voltage sag as well as letting you rev higher while still providing torque.


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## Kelmark (Oct 26, 2009)

JRP3 said:


> That's why I was thinking between 600-700 amps, a 200ah cell could handle that pretty easily, and the higher voltage helps compensate for voltage sag as well as letting you rev higher while still providing torque.


Tom,

I would think that even keeping the amps the same and having the torque band increased by going to around 160V would allow you to use lower gearing and still acheive better acceleration you might be able to take the peak RPM up a bit as well (8000). I agree 650A is about max until 5c cont. batts become more affordable. Still waiting for more info on the AC-144-50 kit I hope it turns out to be as good as they say.

Jacob


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## maxvtol (Nov 11, 2009)

Thanks CroDriver. Actually found your thread in my search of motor torque curves. 

With the help of major, and Tom, I put together a spreadsheet that gives an idea of how an ev might accel with different motors/controller volt/amps. Check out the link in my signature. 

I think I see what Jack was trying to say about spreading the gears out. My fastest accel to 60mph with a WarP 9, 1000amp controller, ~ 108v and 540amp battery limit was using 1st, 3rd, and 5th gears, in part because of shift times. But that's not the case with the AC 50 using it's present controller, using 1st, 2nd, and 3rd gets me there faster (though at a much slower time).

Unless the AC 50 gets a better controller, I'll be using a DC motor for better performance.


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## tomofreno (Mar 3, 2009)

> I would think that even keeping the amps the same and having the torque band increased by going to around 160V would allow you to use lower gearing and still acheive better acceleration


 Yes it would. A significant part of my 0 to 60 mph time, about 8.5 sec, is spent going from 40 to 60, and higher voltage would help. However, I was thinking of a heavier car like a Corolla. That would require higher voltage, and more current at the low end for greater torque. I don't think 650A, which gives about 106 ft-lb torque, would give good enough acceleration for many - like maxvtol. Would sure make the Swift jump though.

What is the AC-144-50? 144V? Haven't heard about that.


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## JRP3 (Mar 7, 2008)

A while back HPG was talking about working on a 144 volt controller for their motors. Haven't heard any updates on it though.


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## Kelmark (Oct 26, 2009)

tomofreno said:


> Yes it would. A significant part of my 0 to 60 mph time, about 8.5 sec, is spent going from 40 to 60, and higher voltage would help. However, I was thinking of a heavier car like a Corolla. That would require higher voltage, and more current at the low end for greater torque. I don't think 650A, which gives about 106 ft-lb torque, would give good enough acceleration for many - like maxvtol. Would sure make the Swift jump though.
> 
> What is the AC-144-50? 144V? Haven't heard about that.


We were talking about this system before, it is scheduled to be available May of this year.

http://www.emduro.eu/index.php?option=com_content&view=article&id=10&Itemid=33

I have been talking with Lauris about it and he says the operating range 120-160V but the voltage cutoff is around 175V. I think I could get 160 nominal and leave a little room for regen. He also said that it can go up to 650Amp. When I asked if the 50kw limit could be pushed to around 55kw this is what he said. "Also from other mail you were asking about making our controller more powerful. It has some extra power, but are keeping it for safety at least with current system design."

Here is some more information I got but I am still waiting for their dyno results and graphs that they should be sending me as soon as they complete testing.

Lauris wrote,"In our system torque depends on used AC motor, since all our motors are rewound 3-phase AC asynchronous industrial motors, and torque will be same as motor had before rewinding. Max rpm also depends on used motor. Our controller capable to drive from 0 to 400Hz so max rpm is 8x motor rpm at 50Hz. Maximum torque is constant until maximum 50KW power. Continuous maximum power is about 30KW so 40 bhp." 

I am not sure if this means the controller could be used with a higher torque motor than the AC-50 by HPEV.


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## tomofreno (Mar 3, 2009)

> We were talking about this system before, it is scheduled to be available May of this year.


 Oh. I thought you were talking about something new from HPGC. Do you know the price of this controller? 

Torque increases fairly linearly with current for a given motor, so I would guess the AC50 would have around 90*650/550 = 106 ft-lb torque with this controller.


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## Kelmark (Oct 26, 2009)

tomofreno said:


> Oh. I thought you were talking about something new from HPGC. Do you know the price of this controller?
> 
> Torque increases fairly linearly with current for a given motor, so I would guess the AC50 would have around 90*650/550 = 106 ft-lb torque with this controller.


They give an approximate starting price of $3,500 to $4,000 for the kit he said he can sell the controller seperate but I am not sure on the price yet. 

Another kit I just found was here;

http://www.leomotors.com/

It is a 60kw system and more expensive, I just e-mailed them to get more info and some pricing. I saw in a press release that the kit includes a 16KWH pack with density similar to kokam, charger, BMS, motor and controller for $20,000 still waiting for word from a company representative. They say that you can get about 80mile range and 0-60 in 6.5 seconds with this kit. For extra you can upgrade to the 30KWH pack.


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## Grant_NZ (May 28, 2008)

Kelmark said:


> It is a 60kw system and more expensive, I just e-mailed them to get more info and some pricing. I saw in a press release that the kit includes a 16KWH pack with density similar to kokam, charger, BMS, motor and controller for $20,000 still waiting for word from a company representative. They say that you can get about 80mile range and 0-60 in 6.5 seconds with this kit. For extra you can upgrade to the 30KWH pack.


That is tempting if the quality is there. Did they give you a price also for the 30kwh kit?


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## Kelmark (Oct 26, 2009)

Grant_NZ said:


> That is tempting if the quality is there. Did they give you a price also for the 30kwh kit?


No response to my e-mail yet, I don't even know if they sell to individuals or not. But I have read allot of press releases with positive remarks.


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## tomofreno (Mar 3, 2009)

I drove around 10 miles yesterday at about 55 - 58 mph and the controller temperature settled at 64 C. It was about 52 F or 11 C outside, so around a 53 C delta between controller and ambient. That is with a 250 cfm fan blowing on the aluminum plate on the controller. Doesn't look good for high summer temperatures. I'm very interested in hearing what controller temperature Jack can maintain with water cooling.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> I drove around 10 miles yesterday at about 55 - 58 mph and the controller temperature settled at 64 C. It was about 52 F or 11 C outside, so around a 53 C delta between controller and ambient. That is with a 250 cfm fan blowing on the aluminum plate on the controller. Doesn't look good for high summer temperatures. I'm very interested in hearing what controller temperature Jack can maintain with water cooling.


hhhmmm, this IS interesting. With my new hood scoop pushing air over the heatsink, the controller is not even warm to the touch after driving. I just got an infrared temp thing (cheap), so I will check next time out. But, my longest sustained pull on normal trips is a 3 mile pull at 45-50mph on a 2-3% uphill... a steady 200-300 amps since I have only 96v right now (less w/ FLA sag).

http://www.envirokarma.org/ev/gallery/100101_wscoop.htm


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## Dave Koller (Nov 15, 2008)

Tom
Do you have room to bolt a finned heat-sink to that plate?


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## dtbaker (Jan 5, 2008)

Dave Koller said:


> Tom
> Do you have room to bolt a finned heat-sink to that plate?


I got mine from heatsinkusa.com....


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## Dave Koller (Nov 15, 2008)

Nice!

This is on my Curtis:


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## dtbaker (Jan 5, 2008)

looks like a similar heat sink... do you have it mounted vertically? moving any air over it?


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## Dave Koller (Nov 15, 2008)

dtbaker said:


> looks like a similar heat sink... do you have it mounted vertically? moving any air over it?


 Horizontal - over a 4" hole in my Plexiglas - with a fan that is on with key and on for several minutes AFTER the key is off.. Air is forced up and out both ends.. I'll try to find that picture but don't want to hijack the thread ... So I will post it on my thread...


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## tomofreno (Mar 3, 2009)

> Do you have room to bolt a finned heat-sink to that plate?


 No, unfortunately I don't. That and the fan (or two) would probably be enough. The only reason I am considering water cooling is I don't have the space for the finned heat sink.

Edit: Well, I think I might be able to fit a heat sink if I remove the steel plate from the rear end of my motor, cut it off and mount the controller differently. The rear motor mount bolts to this plate. I extended the plate up beyond this bolt point so I could mount my controller on it. I don't have space for a heat sink with this because the controller runs into the side of the car if I move it out to insert a heat sink. If I could shift the controller forward and up a bit I could move it out further to insert a heat sink. It will be very close to hitting the hood if I move it up much, so I'll have to measure and see if it can be done. I would have to cut off the plate extension to prevent interference with the mounting of the controller/heat sink this way. I think I could just block up the rear of the motor to remove the rear mount and plate to cut the plate off, and not have to disturb anything else. Sure would be easier to add a heat sink with the current fan than using water, and I think that would suffice. But I have to be able to fit it in and have the hood close.


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## tomofreno (Mar 3, 2009)

It will fit! If I cut off the plate and mount the controller differently (horizontal tilted up toward firewall), I have space to fit the controller with 10" heat sink with 2.5" tall fins from heatsinksusa and two 250 cfm axial fans with faces against the fins of the heat sink. Thanks for the link to the inexpensive heat sinks Dan. Thanks for the photos Dave. I had resigned myself to using water, but because I already have the two fans and the heat sink is less than $40.00, I got out the tape measure and said there MUST be a way to do this. It won't be that difficult, block up the rear of the motor, remove and cut the plate, bolt aluminum angle to the top of it and some angle brackets to the side of the car to mount the controller/heat sink/fan stack, make up some new motor to controller cables and be ready to go. I will have to cut off some of the fins on one corner of the heat sink to clear, but not a lot. Ordering the heat sink now!


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## dtbaker (Jan 5, 2008)

cool, and if you use a sexy hood scoop and duct the air over the heat sink, you wont need any fans! But be sure you've got a plan for where the possible rain/snow will drain thru.... BTW, I got much shorter fins... I think they are only about an inch or so. Aligning them vertically gives the best natural convection.


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## Guest (Feb 22, 2010)

maxvtol said:


> Thanks CroDriver. Actually found your thread in my search of motor torque curves.
> 
> With the help of major, and Tom, I put together a spreadsheet that gives an idea of how an ev might accel with different motors/controller volt/amps. Check out the link in my signature.
> 
> ...


That's very interesting. So you compared the Warp 9 to the AC-50 in the same car? And you see noticeably better performance with the Warp 9.

This is kind of disappointing. I don't have the AC-50 installed yet, but I was hoping for at least the same performance. We have very good accel with the Warp 9 and a top speed of 95 mph.

As to the gearing, yes, it is pretty simple. The torque curve starts falling off at 3000 rpm - either motor. If at higher speeds you can keep that rpm down below 3400 or so, you have more torque available. Right now, I think I'm topping 4000 rpm at about 75 mph. So by going to higher gearing, we can move the whole range down in rpm. That gets 2nd gear into play. Maybe even makes first gear a bit useful.

But I'll be disappointd if the AC-50 doesn't match the feel of the Warp9.

Jack Rickard


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## Kelmark (Oct 26, 2009)

jrickard said:


> That's very interesting. So you compared the Warp 9 to the AC-50 in the same car? And you see noticeably better performance with the Warp 9.
> 
> This is kind of disappointing. I don't have the AC-50 installed yet, but I was hoping for at least the same performance. We have very good accel with the Warp 9 and a top speed of 95 mph.
> 
> ...


From what I have seen and read the AC-50 is comparable to the Warp9 when ran at 500A if someone was to run the Warp9 at 750A or 1000A they would get substantially better acceleration out of the the Warp9. 

On the other hand when comparing at 500A the AC-50 will handle hills better, is more efficiant, and gets regen. The AC-50 is limited by the controller so soon you might be able to upgrade to a 650A 144V controller which will help the performance a bit.

Of course this is just from my research, Tom can give you better perspective because he is already running it in his car.


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## Guest (Feb 22, 2010)

Kelmark said:


> From what I have seen and read the AC-50 is comparable to the Warp9 when ran at 500A if someone was to run the Warp9 at 750A or 1000A they would get substantially better acceleration out of the the Warp9.
> 
> On the other hand when comparing at 500A the AC-50 will handle hills better, is more efficiant, and gets regen. The AC-50 is limited by the controller so soon you might be able to upgrade to a 650A 144V controller which will help the performance a bit.
> 
> Of course this is just from my research, Tom can give you better perspective because he is already running it in his car.


Well that's the problem. It's all from what you've seen and read. I try to avoid "typing myself smart." i have seen and read as well. But MaxVTOL seemed to imply he had run the two motors in the same car. That's the best way I know of to compare them. Tom's not run the Warp9 in his car. I've not run the AC-50 in mine (yet). So I was kind of lunging at the concept that someone had run the two motors in the same car. 

In reviewing his post, I may have read something into it that wasn't there. It seems he was comparing in a spreadsheet calculation. Duh. 

Yes, by the torque curves they should both put out about 115 ft lbs at 500 amps. And that's about all the power I'm likely to apply to either one. 

Jack Rickard


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## tomofreno (Mar 3, 2009)

> But I'll be disappointed if the AC-50 doesn't match the feel of the Warp9.


 This is what I would expect for a Warp9 with a high current controller like a Zilla, Soliton, or new Netgain. No way the AC50/Curtis can match that torque and power. As far as running the motor at lower rpm for higher torque, that only works if you don't loose more in mechanical advantage than you gain in motor torque, since wheel torque depends on both. If you run at 3:1 rather than 6:1 to decrease motor rpm at a given vehicle speed, then motor torque at the rpm with 3:1 has to be more than double that at the rpm with 6:1 to see an increase in wheel torque and tractive effort. I agree with Joe that the AC50 needs a higher current and voltage controller to give the performance he wants.

The Curtis/AC50 with 115V pack may give higher wheel torque than the Warp9/1000A controller at higher motor rpm, like over 3500 rpm, maybe as much as 50% more, but it will have much less at less than 2500 motor rpm - like 1/3 as much. This is for the same pack voltage.

If you compare the AC50 to the Warp9 with Curtis 500A controller, then yes, the AC50 should give similar performance. You can see that in the torque and power curves in my spreadsheet.


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## maxvtol (Nov 11, 2009)

jrickard said:


> In reviewing his post, I may have read something into it that wasn't there. It seems he was comparing in a spreadsheet calculation. Duh.


It's a calculation with a 1000 amp controller on the Warp 9 and a battery limit essentially the same as the AC 50. If I understood major correctly, the DC controller can apply 1000 amps to the motor until the battery limit is reached, then there is a constant power section of the motor curve, then it drops off ~ 3100 rpm. So if major is correct, there should be much more off the line acceleration with the WarP 9 than the AC 50. But the AC 50 torque doesn't drop off as sharply around 3100 rpm, so top speed should be slightly higher with the AC 50.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> The Curtis/AC50 with 115V pack may give higher wheel torque than the Warp9/1000A controller at higher motor rpm, like over 3500 rpm, maybe as much as 50% more,


Right - because the torque of series DC motors drop off rather more quickly at higher speeds, right?


> but it will have much less at less than 2500 motor rpm - like 1/3 as much. This is for the same pack voltage.


I wonder if you can help me understand that, please. For both controllers at near maximum power, the DC controller will be putting out close to maximum voltage, though with 2500 RPM it's presumably limited to about 80% of pack voltage. Current will be controller maximum, which we're taking as 1000 A here.

The AC controller will be limited to about 0.717 of the pack voltage, call it 70%, because of the RMS to peak ratio of sine waves, and the way that 3-phase is typically synthesised utilising neutral wobble. The 550 A RMS per phase current limit translates to the equivalent of some 1.73 times 550 A (3x with 3 phases, and a factor of √3 because of the current splitting with delta connections, or voltage splitting with star connections). So that's about 950 ADC equivalent. So I'd expect the torque from the motors, given similar gearing, to be about the same, with the 5% higher electrical power swallowed by the approximately 5% lower efficiency.

But the 70% voltage factor means that the AC motor needs something like a 45% higher (less tall) gearing, to run out of voltage, and hence have power plateau or worse and torque decrease, at about the same speed. I would expect the AC motor to decrease torque more gracefully when it runs out of voltage, as mentioned above.

So the total AC multiplier for the same current is about √3/√2, or some 1.23. So 550 A per phase would (if I am right) be comparable with 1.23*550 ~= 675 ADC, neglecting efficiency considerations. So there's the 1000/675 = 1.48 ratio, call it 1.45 with a slight efficiency gain for the AC motor.

So with all these assumptions and the 550 ARMS vs 1000 ADC controllers, I would expect the low speed performance of AC to be of the order of 45% worse. Simply because the AC motor is getting something like 48% less power. But where does a factor of 1/3 come in?

The 45% figure is quite a lot, and closer to the 1/3 than I thought it would be before doing the numbers.


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## tomofreno (Mar 3, 2009)

> Yes, by the torque curves they should both put out about 115 ft lbs at 500 amps.


 No, they don't. The AC50 only has 90 ft-lb torque with 550A. Source: Curtis dynomometer data obtained from HPGC. Edit: The HPGC AC31 actually has higher torque than the AC50 at lower rpm, just under 100 ft-lb. I asked HPGC about this and they said they traded off some starting torque for higher running torque (torque at higher rpm) - that's where details of the windings comes in. The AC31 only has this torque out to about 1800 rpm.


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## tomofreno (Mar 3, 2009)

> Right - because the torque of series DC motors drop off rather more quickly at higher speeds, right?


 Yes. At least that is my understanding.


> The 45% figure is quite a lot, and closer to the 1/3 than I thought it would be before doing the numbers.


 You put a lot more into this than I did. I am just going from the dyno data for the AC50, and it shows a max of about 90 ft-lb torque at 550A. The curve for the ADC FB1-4001 shows 240 ft-lb at 1000A. This is about 2.7 times the torque of the AC50. I just rounded to 3x since those three high current controllers can put out more than 1000A. 

The motors are close to the same diameter so you might expect similar torque for similar currents. But it depends on the length of the windings too, and the ADC and Warp9 motors are considerably longer than the AC50. You would have to know the details of the windings to make a meaningful comparison. I just go by the published curves.


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## karlos (Jun 30, 2008)

Hi Tomofreno, it's been good value to follow your thread thanks.
How do you or anyone else feel the HPGC AC50/Curtis 1238-7501 package would go in a Toyota MRS 99 model? I don' expect a performance car out of the combination but if I could cruise at 110kmh/68mph with a little extra, that would be great.


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## JRP3 (Mar 7, 2008)

I would think it would work pretty well.


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## karlos (Jun 30, 2008)

JRP3 said:


> I would think it would work pretty well.


Thanks for the confidence JRP3, I don't want to hijack the thread but there is plenty of experience with this package here. Now if there was a controller with a little more voltage for the motor.... but for the price this package seems about as good as it gets for AC of this size.


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## JRP3 (Mar 7, 2008)

karlos said:


> ... but for the price this package seems about as good as it gets for AC of this size.


That about sums it up.


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## tomofreno (Mar 3, 2009)

> How do you or anyone else feel the HPGC AC50/Curtis 1238-7501 package would go in a Toyota MRS 99 model? I don' expect a performance car out of the combination but if I could cruise at 110kmh/68mph with a little extra, that would be great.


 Hi Karlo, the source I found gave the curb weight of the MR-S as 2200 lb, about 300 lb greater than the Swift. The MR-S likely has low drag so I would guess performance similar to the Swift. It won't match the original 0 to 60 mph time of 8 seconds, more like 18. The Swift has more than enough pickup for normal driving though, including on the freeway. I have no problem passing someone going 60 mph. I don't know about cruising at 68 mph for say 20 minutes or more though. You will definitely need a finned heat sink and fans on the controller to do that, but even then you may have problems with overheating on hot days. I haven't driven the Swift in hot summer weather so I don't know, but my experience on 50 F (10C) days makes me think that may be pushing it even with the heat sink/fans. I'll be installing a heat sink and fans within another few weeks and will report on how much it lowered the temperature difference between controller and ambient. I agree the AC50/Curtis controller is the best available for the money for AC. Too bad there isn't a bit higher voltage and current controller. If you want higher acceleration I think DC is the only option now, unless you can get AC Propulsion, Calmotors or someone similar to sell you an AC motor&controller for $15k or more.


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## karlos (Jun 30, 2008)

tomofreno said:


> Hi Karlo, the source I found gave the curb weight of the MR-S as 2200 lb, about 300 lb greater than the Swift. The MR-S likely has low drag so I would guess performance similar to the Swift. It won't match the original 0 to 60 mph time of 8 seconds, more like 18. The Swift has more than enough pickup for normal driving though, including on the freeway. I have no problem passing someone going 60 mph. I don't know about cruising at 68 mph for say 20 minutes or more though. You will definitely need a finned heat sink and fans on the controller to do that, but even then you may have problems with overheating on hot days. I haven't driven the Swift in hot summer weather so I don't know, but my experience on 50 F (10C) days makes me think that may be pushing it even with the heat sink/fans. I'll be installing a heat sink and fans within another few weeks and will report on how much it lowered the temperature difference between controller and ambient. I agree the AC50/Curtis controller is the best available for the money for AC. Too bad there isn't a bit higher voltage and current controller. If you want higher acceleration I think DC is the only option now, unless you can get AC Propulsion, Calmotors or someone similar to sell you an AC motor&controller for $15k or more.


Thanks for the feedback Tomofreno, I have been considering a lot of options including the Swift and the MX5. There are a lot of motors I have considered as well, even the motorcycle hub motor by Enertrac and fitting them inboard (4 of them) on something like a 4WD swift but the RPMs were not enough. Motors of considered are UQM, Tai'an Taishan, Brusa, Agni and others. 
I notice the later model Swifts are a similar weight to the MRS I was thinking of. I really want to get started soon so am trying to nail a plan down!


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## tomofreno (Mar 3, 2009)

> Tom's not run the Warp9 in his car.


 I got some data on this. I gave a little presentation to the local club on my car last night and a guy there converted a Ford Festiva (curb weight about 1800 lb) using an Advanced DC 9" motor, Zilla 1k controller, and 156V pack of gel lead acid batteries for finished weight of about 3000 lb. It does 0 to 60 in 7 seconds.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> I got some data on this. I gave a little presentation to the local club on my car last night and a guy there converted a Ford Festiva (curb weight about 1800 lb) using an Advanced DC 9" motor, Zilla 1k controller, and 156V pack of gel lead acid batteries for finished weight of about 3000 lb. It does 0 to 60 in 7 seconds.


cool, I wonder how fast it would be if he switched to Li and dropped a bunch of weight!

On a more technical note, do you know whether he beefed up the transmission/drivetrain/motor mounts to handle the extra torque? He's gotta be pushing twice the torque of the ICE off the line to ge moving that fast!


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## tomofreno (Mar 3, 2009)

> On a more technical note, do you know whether he beefed up the transmission/drivetrain/motor mounts to handle the extra torque?


 Dunno, didn't get into that detail. He did have to beef up the suspension to handle the battery weight. Don't know what he did for brakes either, 3k lbs would be hard to stop with little Festiva brakes.


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## tawright (Dec 30, 2009)

tomofreno said:


> I got some data on this. I gave a little presentation to the local club on my car last night and a guy there converted a Ford Festiva (curb weight about 1800 lb) using an Advanced DC 9" motor, Zilla 1k controller, and 156V pack of gel lead acid batteries for finished weight of about 3000 lb. It does 0 to 60 in 7 seconds.


 How many batteries did he squeeze into that car? And are gel lead batts better than AGM or are they the same? 

Tom


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## Guest (Feb 26, 2010)

tomofreno said:


> Yes. At least that is my understanding.
> You put a lot more into this than I did. I am just going from the dyno data for the AC50, and it shows a max of about 90 ft-lb torque at 550A. The curve for the ADC FB1-4001 shows 240 ft-lb at 1000A. This is about 2.7 times the torque of the AC50. I just rounded to 3x since those three high current controllers can put out more than 1000A.
> 
> The motors are close to the same diameter so you might expect similar torque for similar currents. But it depends on the length of the windings too, and the ADC and Warp9 motors are considerably longer than the AC50. You would have to know the details of the windings to make a meaningful comparison. I just go by the published curves.


I'm a little lost here. But it sounds like apples to oranges to peanuts. I have a 1000 amp controller on the Speedster. But it doesn't draw 1000 battery amps. I guess I'm just not smart enough to calculate a comparison between controller amps to the motor between an AC 3-phase controller and a DC controller. I thought I was. But after reading all this, I must be terribly confused....

I can do about 540 battery amps on the Kelly with Warp9. I would be surprised if this package draws less. But it's a sufficiently interesting question, and they are sufficiently similar sized motors, that when we get the Speedster part DUH completed, I'm just going to run them down and put them on the dyno and get some real numbers. We'll see.

Jack Rickard
http://EVTV.me


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## maxvtol (Nov 11, 2009)

As it was explained to me how you can get more amps at the motor than coming from the battery, current multiplication. 


major said:


> You may be looking at motor current, which will be high at high torque regardless of RPM. But battery current will be lower than motor current at lower RPM because the motor voltage is lower than battery voltage. The controller is acting similar to a transformer giving you current multiplication at reduced voltage output.


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## JRP3 (Mar 7, 2008)

But at full throttle the controller isn't PWMing the voltage, so other than losses, you should have full voltage to the motor, and full current that the batteries can deliver.


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## tomofreno (Mar 3, 2009)

> How many batteries did he squeeze into that car? And are gel lead batts better than AGM or are they the same?


 156/12 = 13 batteries, they are AGM.


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## tomofreno (Mar 3, 2009)

> I guess I'm just not smart enough to calculate a comparison between controller amps to the motor between an AC 3-phase controller and a DC controller. I thought I was. But after reading all this, I must be terribly confused....


 If you think you see something wrong with the reasoning, please explain.


> when we get the Speedster part DUH completed, I'm just going to run them down and put them on the dyno and get some real numbers. We'll see. what it is.


 It will be good to get more data. I think the comparison of the Swift and the Festiva already give us a good indication of the difference.


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## tomofreno (Mar 3, 2009)

> But at full throttle the controller isn't PWMing the voltage, so other than losses, you should have full voltage to the motor, and full current that the batteries can deliver.


 If the motor had neglible back emf, i.e. at extremely low rpm. The voltage input to the motor in this case is pack voltage - back emf. The latter increases with motor rpm.


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## JRP3 (Mar 7, 2008)

I was thinking full throttle take off, wouldn't you get full amps and full voltage, or pretty close to it?


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## Coulomb (Apr 22, 2009)

tomofreno said:


> If the motor had negligible back emf, i.e. at extremely low rpm. The voltage input to the motor in this case is pack voltage - back emf.


Err, no. The whole voltage from the output of the controller is input to the motor. It's pack voltage minus back emf that exists across the armature and field resistance to set the current (thinking series DC here, it's easier).

In fact, that difference across the armature is essentially all copper loss, so the voltage available to power the vehicle is essentially the back EMF... someone please correct me if I'm wrong here.

My understanding is that even at full power (1000 A or whatever), the voltage across the armature and field is still pretty low, of the order of a few volts. So considering volts-to-motor = pack voltage less sag and losses is pretty reasonable at maximum PWM.

You may be thinking of how it gets harder to _make_ a series DC motor keep drawing full current as the speeds (and hence back EMF) rise. So with a 156 V pack and a high speed on your motor, you may have 130 V back EMF, and with not quite 100% PWM and controller and cable and motor losses, you might need 150 VDC at the input to the controller, but at 1000 A the pack just can't do it, sags to say 135 V so the motor only sees say 131 V from the controller, and won't draw 1000 A with only a single volt across the armature and field. So the motor current goes down, which makes the back EMF go down, and it settles to an equilibrium somewhere short of maximum power.

This lack of power is a result of back EMF, but not because back EMF subtracts from the pack voltage to "give what's left" to the motor. What's left goes to the losses.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> But at full throttle the controller isn't PWMing the voltage, so other than losses, you should have full voltage to the motor, and full current that the batteries can deliver.


Yes, correct. At full PWM, the motor is essentially across the pack, or since the maximum PWM may be 95%, close to it. (Maybe DC controllers can do 100% PWM, where the switch stays on).

But we were comparing with AC at one point; for an AC controller at maximum voltage output, it's still PWMing the DC from the pack to sine wave AC for the motor. (For the case of brushless DC, it may be something between sine and square waves, I'm unclear on that point), but it has to be AC.

For induction motors, the output voltages (phase to phase) are sine waves, and it turns out that with neutral wobble, you are getting at best 1 divided by the square root of 2 (0.707) of the input DC as RMS AC output. So for a 115 V pack input sagging to say 105 V (total guess), the RMS voltage output will be 74 VAC (less IGBT voltage drops).

This is more than made up for by the fact that there are three outputs, not one. You end up with a square root of 3 because either the voltage or current gets split with the delta or star connection.

The long and the short of it is that a DC controller flat out is like a transformer with a 0.95 turns ratio (almost full pack voltage to the motor, and a little more than pack current to the motor).

An AC controller flat out is like a DC to AC transformer that multiplies the pack voltage by about 0.70 (VRMS), but each motor wire gets about .82 (√2/√3) of the pack current (as RMS AC).

For the case of the Curtis 1238-7501 with 105 VDC input and 550 ARMS per motor wire, it will be drawing about 1.23 (√3/√2) * 550 = 675 ADC at 105 VDC, for an electrical input of about 71 kW (neglecting switch voltage drops and losses).

For the 9" with 156 VDC and Zilla 1K, supposing the gels sag to 130 V at 1000 A (is that reasonable?), and assuming that you can get most of that 130 V at the motor with 1000 motor A and say 950 pack amps, that would be 123 kW electrical into the Zilla. Let's call it 117 kW with 5% less efficiency for DC.

So that DC motor may be getting 65% more power input at maximum PWM. Not quite apples to peanuts, put perhaps apples to plums...  The Zilla is a pretty large controller compared to the Curtis 1238-7501. And 156 V is 35% more than 115 V, even though the 156 being supplied by lead will sag more.

The other way to look at a 550 ARMS controller is as if it was a 1.225 * 550 = 674 ADC controller. So the Zilla has 1000/674 = 1.48 times the current capability. Then there is the 130/105 = 1.24 times the pack voltage, for a combined advantage of 1.24 * 1.48 = 1.84x advantage; the rest are efficiencies and rounding errors (I hope).

All this is purely academic of course; Jack, if you can put the machines on the dyno, then we can get an idea of what it is like at partial "throttle" as well, how they compare at higher speeds, etc etc.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> I was thinking full throttle take off, wouldn't you get full amps and full voltage, or pretty close to it?


You'll get full motor current, but unless the wheels are slipping, the motor voltage will be way less, so the pack current will be way less. Surely someone can answer this... what proportion of maximum motor current do you see with a full throttle take off? Would it be as much as half? A quarter? Assuming you can get a reading at say 10% of full motor speed.


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## Tesseract (Sep 27, 2008)

jrickard said:


> I'm a little lost here. But it sounds like apples to oranges to peanuts. I have a 1000 amp controller on the Speedster. But it doesn't draw 1000 battery amps. I guess I'm just not smart enough to calculate a comparison between controller amps to the motor between an AC 3-phase controller and a DC controller. I thought I was. But after reading all this, I must be terribly confused....
> 
> I can do about 540 battery amps on the Kelly with Warp9. ...


If you measure 540A on the battery side when the motor current is 1000A then that means the duty cycle is 54%. Conversely, average motor voltage will be 54% of the battery voltage because, of course, power is always conserved. 

For a 3ph. motor things get a little trickier as there are two different ways to wire the windings - star or wye and delta - but assuming the windings are fed the proper voltage/frequency for the respective configuration (e.g. - 240V/60Hz) then the battery current will be 1.73x/1.414 (3^0.5/2^0.5) the current flowing in any one phase. E.g. phase current = 500A then battery current will = 612A.


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## Coulomb (Apr 22, 2009)

Tesseract said:


> ... the battery current will be 1.73x (3^0.5) the current flowing in any one phase. E.g. phase current = 500A then battery current will = 865A.


Um, aren't you assuming than the output voltage (RMS AC) is the same as the input (DC) voltage? With wide open throttle (WOT), there will be a 1.414 (2^0.5 or √2) factor less RMS voltage on the output that the DC input. So as I calculated earlier, the pack current will be √3/√2 times one of the motor's line current, neglecting losses.

[Edit: Tesseract has now edited his original post, to take the DC->RMS AC conversion into account.]

For less than WOT, there will be an even larger ratio between pack voltage and motor RMS voltage.

I prefer not to use the term "phase current", as that usually means the current in one of the phase windings, which is equal to the line current for star/wye connections, but 1/√3 of the line current for delta connections. Line current and line (phase to phase) voltage seem to the the standard.


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## major (Apr 4, 2008)

Coulomb said:


> So as I calculated earlier, the pack current will be √3/√2 times one of the motor's line current, neglecting losses.


My experience with battery fed inverter induction motor drives is that the motor phase current (RMS) is approximately equal to the battery current at base frequency. This is from a vehicle under maximum acceleration and is the maximum battery current and maximum motor current for the event.


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## tomofreno (Mar 3, 2009)

> You may be thinking of how it gets harder to _make_ a series DC motor keep drawing full current as the speeds (and hence back EMF) rise. So with a 156 V pack and a high speed on your motor, you may have 130 V back EMF, and with not quite 100% PWM and controller and cable and motor losses, you might need 150 VDC at the input to the controller, but at 1000 A the pack just can't do it, sags to say 135 V so the motor only sees say 131 V from the controller, and won't draw 1000 A with only a single volt across the armature and field.


 That's what I was thinking. I think of the time varying current in the rotor inducing an emf in the stator, and the voltage output of the controller having to be larger in order to have current flow into the stator.



> So the motor current goes down, which makes the back EMF go down, and it settles to an equilibrium somewhere short of maximum power.


 I see. Thanks.



> So that DC motor may be getting 65% more power input at maximum PWM


 Well yeah, that was the point:


> This is what I would expect for a Warp9 with a high current controller like a Zilla, Soliton, or new Netgain. No way the AC50/Curtis can match that torque and power.


 Jack said he was disappointed to hear the Curtis/AC50 wouldn't give similar performance to the Warp9. But Joe was using a 1000A controller with the Warp9 in his spreadsheet, not a 500A. That's why I said no way the Curtis/AC50 can deliver that kind of torque and power. Sure its not the difference in motors, rather the controllers. I guess maybe that's what Jack meant with his apples, peanuts remark.


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## maxvtol (Nov 11, 2009)

If the dyno for the AC50 is accurate, and using Jack's new gearing on Speedster part DUH and similar weights etc, optimistically 0-60 mph calculate to be 14+ seconds. Not bad in my book, but not the 8 seconds I think I heard on one of the videos for Speedster 1. 

Be interesting to see what the real results turn out to be.


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## tomofreno (Mar 3, 2009)

I installed the minibms and got some immediate results. I charged at lower current than normal for a short top off charge, and the charger ran too long and drove a cell to high voltage. The minibms shut down the charger. I could tell because when the timer on the charger times out and stops the charger the blue timer light stops flashing and stays on. In this case the timer light was still flashing when I walked out to check it, indicating the timer hadn't timed out yet - but the charging current was zero. 

Then today I headed out with this full charge and as I neared the bottom of the hill the buzzer went off. Regen had driven a cell to high voltage. This repeated 2 more times during the drive. It even did it after I had driven about 3 miles, stopping and starting at a few stop signs/lights, when I stopped fairly quickly for a light. I was watching the pack voltage on the Curtis 840 gauge and it hit only about 121.5V max (121.5/36 = 3.375V). So I have a cell that is considerably lower capacity and/or higher resistance than the others (they are fairly well balanced at around 3.18V). I've probably been doing this all along and didn't know it. It was easily stopped by just touching the mechanical brakes. I'll have to set the user_overvoltage lower in the controller sw. I have it at 122.9V now. Also will have to set the voltage limit on the charger a bit lower I guess. I've thought of replacing my weakest cell, but it hasn't been over-discharged nor over-charged (other than a bit with regen I guess), and it also serves to protect my other cells from over-charging. It is not limiting my range enough now to be an inconvenience.


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## JRP3 (Mar 7, 2008)

This didn't show up in any of the Cell log8 data? You don't have any cells left that were affected by the VB's?


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## tomofreno (Mar 3, 2009)

> This didn't show up in any of the Cell log8 data? You don't have any cells left that were affected by the VB's?


 I don't normally have the cell log8 hooked up. The reason the charger ran too long is I was charging at a different current than I normally use, and the timer and voltage limit were not set up for it. I knew that, and was checking voltage with a dvm, but waited a minute or so too long. I probably would have caught it close to 3.6V, as it had been at 3.46V about 8 minutes earlier. As I mentioned before, you have to set up the timer and voltage limit to shut the charger off before the lowest capacity cell hits high voltage. I have it set up pretty close. It usually shuts off at about 3.46 to 3.5V or so on that cell, but charging at a lower current it didn't time out in time. That's one of the reasons I gave for needing HVC. An opportunity top-off charge, charging at a different current, or at different temperature may well result in the charger not shutting off in time to avoid an HVC if you have it set up that close. If it is only charging to 90% it shouldn't be an issue. I can't set it up for that and have enough range for some longer trips though. You have way more capacity than you need so you can easily set the voltage limit of the charger so it isn't ever an issue - unless a cell goes way out of wack.

I have a few cells left that were affected by the VBs. They were discharged a bit below 2V and are weaker than all my other cells but one. Seems that one was at the bottom of the distribution of capacity right out of the box. That one has always hit HVC first (other than ones affected by VBs that have been replaced) with the pack balanced around 3.1 to 3.2V. Of course I don't know which cell caused the HVC alarm, so it may have been another cell with higher resistance, but that should show up during charging, and they all seem to show about the same voltage rise when the charger is turned on. I suspect it is that low capacity cell, which is close enough to the exponential rise part of the curve that a burst of 80 - 110A regen drives it up the curve to HVC because of the higher resistance at that soc. 

I could replace it and the other VB affected ones to increase pack capacity, but like I said they are not impacting my range enough that it is a big problem, and they protect my other cells. None of the other cells have ever been over 3.43V or under about 3.25V. So I'll just run these until they become a problem. They are my sacrificial lambs, protecting the rest of the pack from overcharge/discharge.


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## Tesseract (Sep 27, 2008)

Coulomb said:


> Um, aren't you assuming than the output voltage (RMS AC) is the same as the input (DC) voltage? With wide open throttle (WOT), there will be a 1.414 (2^0.5 or √2) factor less RMS voltage on the output that the DC input. So as I calculated earlier, the pack current will be √3/√2 times one of the motor's line current, neglecting losses....


D'oh... yes, I did forget the Peak -> RMS conversion. Will correct my original post.


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## tomofreno (Mar 3, 2009)

I connected the Junsi Cell log 8 to four of the cells in the front box to see if I was correct as to which cell was hitting HVC and setting off the buzzer during higher regen current events after a full charge. I was wrong. It is a "new" cell from evcomponents recently installed in the car to replace a cell that had been discharged by a VB. It is cell 3 in the graph. I have never seen anything this bad. Even a cell that was drained to 0.67V, when recharged gave much better initial performance than this, but kept dropping in voltage with use. Another cell that was discharged to about 0.75V performs far better than this one - it is cell 3 in post 242 in this thread, and performs similar to other cells. The terminals were not warm after the drive, and torque checks fine, so I don't think it is due to poor terminal connections. I guess I better test the other three cells I recently received from evcomponents and see how they are performing. This is very upsetting. Edit: I forgot to mention that cell 1 is also a "new" replacement cell, and it appears to be fine, behaving similar to cells 2 and 4. Damn I hate to have to take that all apart again to get at one cell.
View attachment Cell log 8, 2.28.10.pdf


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## Coulomb (Apr 22, 2009)

tomofreno said:


> I was wrong. It is a "new" cell from evcomponents recently installed in the car to replace a cell that had been discharged by a VB. It is cell 3 in the graph. I have never seen anything this bad.


Wow. Talk about not playing as a team member.

One thing that comes to mind is that despite the open circuit cell voltage, this cell may be at a significantly lower SOC than the rest of the pack, and simply needs a good initial charge, perhaps holding 3.60 V for some hours, rest for a few more hours and overnight if possible, then discharging it to get it to the same O/C voltage as the rest of the pack.

The other thought I have is that maybe there is something to the idea that cells really do need "breaking in" for a few cycles. Obviously your other cells are well and truly broken in now, and you may not have noticed the effect so much when they were new, since they all would have been a bit weak at the same time, and you were probably not used to the pack yet, so you didn't know what to expect. Plus, you were probably rather cautious with the pack early on.

So I think it's a bit early to say for sure that this is a bad or even a significantly different capacity cell.

I guess the two main options are to exercise it (and its brothers from the same batch) on the bench, or to baby the cells rather carefully in the vehicle for a while, perhaps taking shorter trips (if that's possible or convenient), and/or going easy on the acceleration and regenerative braking.

I hope they come good for you in short order.


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## tomofreno (Mar 3, 2009)

> So I think it's a bit early to say for sure that this is a bad or even a significantly different capacity cell.


 Cell 1 was installed at the same time, why doesn't it require "breaking in"? Cell 3's rest voltages track with the rest of the pack, before and after charge. How can it be at a different state of charge but have similar voltage to other cells? The big swings in voltage from over 3.6V to almost 2.7V indicate much higher internal resistance to me.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> Cell 1 was installed at the same time, why doesn't it require "breaking in"?


Ah, I didn't know that cell 1 was another replacement. It does seem to match the others much better than cell 3, so yes, at this stage, it does look as though 3 is faulty, or at least very different.

There is still a chance that cell 1 got some "exercise" (perhaps some testing by EV components?) that cell 3 didn't, but I agree that this seems unlikely.



> Cell 3's rest voltages track with the rest of the pack, before and after charge. How can it be at a different state of charge but have similar voltage to other cells? The big swings in voltage from over 3.6V to almost 2.7V indicate much higher internal resistance to me.


Yes, its internal resistance is presently much higher than the others. However, internal resistance increases when SOC is very low (and very high), so I'm open to the possibility that a few cycles might still bring it into line with the others.

IR also increases with lower temperature, but I assume that now that it's installed in the pack, it would have well and truly matched the others for temperature (even deep internally) by the time the data logging was done.


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## JRP3 (Mar 7, 2008)

Did your new cells come with a data sheet showing resistance, capacity, and bar codes? My initial 34 cells did, but the two extra cells I added to the pack did not. More cost cutting by SE/Cama, drop in QC?
During your high regen incidents, were you using your heater, and if not did you think to try turning it on to prevent overcharge?


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## tomofreno (Mar 3, 2009)

I had forgotten I data logged the first cell I replaced as soon as I installed it, to see if the new cells behaved similar to the existing ones. I data logged it and its 5 neighboring cells. As you can see in the graph, it (cell 3) was not quite balanced to the other cells (the flat part of the curves to the left is at rest voltage), but its voltage changes are similar. It looks fine. According to my log book I charged it with a power supply after this to bring it into balance. So I only need data on one more cell. I'll get that tomorrow. This data was taken when the cells were at about 30% DoD.
View attachment cell log 8, 2.11.10.pdf


It seems this is the kind of behavior (the "bad" cell) Dimitri has been complaining about on 3 of his cells.


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## tomofreno (Mar 3, 2009)

> Did your new cells come with a data sheet showing resistance, capacity, and bar codes?


 No. Nothing. Edit: there is a Q on each of the cells, indicating they are from the same lot I guess.


> During your high regen incidents, were you using your heater, and if not did you think to try turning it on to prevent overcharge?


 No I wasn't. It might. You can see in the graph that the time the cell is at high voltage during regen is quite short - and only on larger regen bursts. The buzzer only stays on about 2 - 4 seconds. Touching the brakes makes it go off immediately. That's not a big problem, but the large voltage swings of the cell are. I'm glad I haven't taken any longer trips since I installed it. It is swinging down to almost 2.7V when it is at about 70% soc - and current draws in this data are less than 1.5C.


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## GizmoEV (Nov 28, 2009)

This may not be it but is it possible that a high resistance connection to the cell could make it act this way? I ran a tap down each of the posts on my cells and cleaned the tops of each post before hooking it up. To clean the top of the posts I ran a very fine mill file across the top of each post. During this process I found three where the aluminum nut hadn't been turned tight enough so that the top of the post was below the aluminum nut.


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## tomofreno (Mar 3, 2009)

> This may not be it but is it possible that a high resistance connection to the cell could make it act this way?


 Its possible, but I don't think it is the cause:


> The terminals were not warm after the drive, and torque checks fine, so I don't think it is due to poor terminal connections.


 All terminals were sanded with #600 carborundum, wiped clean, and given a thin coating of Noalox prior to fastening connections. Though having similar rest voltage, the cell shows higher voltage under charge at 30A than other cells with dvm probes directly on the terminals, and reads the same voltage (as on the terminals) with probes on the straps (to three decimal places).


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## dimitri (May 16, 2008)

tomofreno said:


> It seems this is the kind of behavior (the "bad" cell) Dimitri has been complaining about on 3 of his cells.


Its exactly the same behavior I observe on my weak cells, however, mine got to this point over the course of a year and mostly evident during cold days. We had a much warmer day last week and my cells performed much better, although weak cells still stand out from the rest of the pack by far.

There is no doubt you have a weak cell and should pursue the replacement while you have the warranty.


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## major (Apr 4, 2008)

major said:


> My experience with battery fed inverter induction motor drives is that the motor phase current (RMS) is approximately equal to the battery current at base frequency. This is from a vehicle under maximum acceleration and is the maximum battery current and maximum motor current for the event.


Here is a chart from a dyno run:


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## maxvtol (Nov 11, 2009)

major said:


> Here is a chart from a dyno run:


OMG! It's "sideways", you feeling ok?

You got any of those for dc matched with a controller?


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## major (Apr 4, 2008)

maxvtol said:


> OMG! It's "sideways", you feeling ok?


Got out of the wrong side of the bed this morning. And besides that, it's not a torque curve 



> You got any of those for dc matched with a controller?


No, but I think Tesseract and Qer posted some in their controller thread. Guys?

major


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## maxvtol (Nov 11, 2009)

Is that the AC 50 motor, and was there any battery limits set up?


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## tomofreno (Mar 3, 2009)

Logged data on the fourth and last replacement cell today. It is cell 1 in the graph. Its voltage is being pulled down a bit lower than the other cells but it looks ok. So seems there is just one defective cell. Unfortunately it is in a set of four in the most difficult to access location.
View attachment file 11, 3.1.10.pdf


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## major (Apr 4, 2008)

maxvtol said:


> Is that the AC 50 motor, and was there any battery limits set up?


Hi max,

I assume you're talkin' to me. No. And no. It was a special which belongs to a client and so does the data we collected. I just posted up what I considered non offensive current traces to show the relationship between AD and DC current on a DC fed inverter driven induction motor at a maximum torque command versus speed. Base speed in this case was around 5500 to 6000 RPM. Seemed like there was some confusion about the subject a page or two ago. This also corresponds well to vehicle data collected years ago when we had a competition car.

Now back to the Li cell discussion which I find very interesting. I've been running some discharge test on LiPo cells. Have a 14 cell battery. So far, I've done constant current from 2C to 8C. I have 2 CellLog8s. Lost the USB port on one when we connected it to the computer while still on the battery. Ordered and waiting on replacement. Nice little devices.

I see some deviation cell to cell, but nothing like Tomo sees on that one. Looks like a stinker to me 

Regards,

major


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## Coulomb (Apr 22, 2009)

major said:


> Here is a chart from a dyno run:


Thanks, Major!

It had me puzzled for a while, then I remembered that I have been neglecting magnetising current (imaginary current for the field). As Major will know, this current more or less circulates from the controller to the motor without costing much in the way of battery current, and doesn't contribute to torque production.

So I believe that my calculations are correct, given the unrealistic assumption of negligible field excitation. Even though the current is "imaginary" from a power transfer point of view, it is quite real in the sense that it takes away from the torque-producing-real-current driving capability of the controller's switches.

Taking field excitation into account, the approximation motor line current ~= battery current seems reasonable, and is much easier to remember.

It also means that a 550 A RMS per motor line controller (such as a Curtis 1238-7501) is roughly comparable to a 550 A DC controller, which is even easier to remember. And makes the Zilla to Curtis comparison even less of a level comparison.

That also highlights a difference between series DC and induction AC motors. In a series field DC machine, the power for the field takes away from armature voltage, and hence motor speed, at high power. For an AC machine, the field current takes away from the controller's current capability, and hence motor torque, at high power. Also, since the AC motor's field is energised from imaginary current, the battery power that ends up heating the field windings is quite low compared to the battery power needed for the field of a series DC motor. This may where most of the ~5% efficiency advantage for an AC motor (over a series DC say) comes from (though commutation losses would also be a significant point of difference).

Now back (closer) to the topic.


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## tomofreno (Mar 3, 2009)

> Lost the USB port on one when we connected it to the computer while still on the battery.


 Yeah, I lost one by hooking it up while AC was connected to the un-isolated Manzanita charger. I dropped a clip/lead and it touched the steel battery box. I make sure AC is not connected when hooking up a cell log now, and also leave the cell log8 disconnected while hooking up the leads, check everything, then press the connector on.


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## tomofreno (Mar 3, 2009)

My ahem, apologies to evcomponents and Sky Energy. That cell is fine. The uh, ahem, connections were loose.  Uh yeah, just uh, finger tight.  Don't know why I didn't measure a different voltage between the terminals versus between the straps when charging at 30A, but the graph of the same four cells is attached, and you can see cell 3 is just fine. Must have gotten distracted...
I don't have to pull that cell!!!
View attachment cell log file 3.2.10.pdf


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## JRP3 (Mar 7, 2008)

It happens. Embarrassing but easier to deal with than a bad cell  I was starting to worry that Q.C was slipping at SE, but it's just your Q.C.


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## MN Driver (Sep 29, 2009)

Tom, good to know everything was figured out with the cell. It makes life easier when you don't need to swap out the cell. It's nice to know that you can go back to doing other things with your EV without worrying so much about one cell being different than the rest.


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## tomofreno (Mar 3, 2009)

Dusty around here! Thought I would post some data on cell voltages and give a little summary since it has been a while.
This is what I call a "cell map", a record of measured cell voltages in the three boxes in the car. I hadn't done one of these for over a month, so thought I would check. Top is the front box under the hood, middle is the main box where the rear seat was, and bottom is the rear box in the spare tire well. This first image is measured voltages after putting 54.1 miles on the car after a charge:







Sorry for the small size, best I could do. The numbers are of course the measured cell voltages. They were measured after the last ~ 25 mile trip on the latest charge, and the car had been sitting for a bit over an hour. The four R's indicate replaced cells. Three of these are in the front box, and one in the main box. These cells were added to the pack recently to replace some that had been over-discharged. The "OD" indicate three other cells that had been over-discharged, but have not been replaced, as they are performing similar to the other cells. Two of these are in the front box, and one is in the main box. These seven cells have been charged individually with a 5A power supply in the past to match them to the rest of the cells. It is difficult to get them exactly matched as they continue to decrease in voltage for hours after charging, and I typically don't want to spend the time fiddling to get them matched just right. The other 29 cells have never been individually charged or balanced. I am using a minibms, but without shunts. Notice how closely these 29 cells match. They are all between 3.294V and 3.296V. 

After those measurements I individually charged the four replacement cells and measured their voltages about 1/2 to 1 hour afterward (depending on the cell, last one charged was measured just 1/2 hour afterward) as indicated on the map. Charging times varied from 1 hour to 35 minutes. I have learned to charge them up around 0.01V above the other cells to account for decrease in voltage after charge over time. This 0.01V difference is measured shortly after the is charger turned off. The cell map below shows the measured cell voltages the next morning after sitting over night:







Amazing huh?! They are all within +/- 0.002V range, all but one within +/-0.001V range! Looks like I guessed well on how much to charge the replacement cells that were lower. Also notice the cells are at a bit higher voltage than the day before. This is typical. They continue to "recover" to slightly higher voltage for hours after use.

The first map gives the ev miles on the car to this point: 1663 miles, and approximate number of charge cycles: 37 (thought I had more than this, but my notes indicate not). So the 29 cells that have never been over-charged, over-discharged, balanced, or individually charged for that time are all within 0.001V of each other.

The car is working great, and is a joy to drive. The minibms continues to work, and shut off the charger occasionally when it fails to time out in time. Charging is pretty easy because of this. I just plug it in, estimate charging time from Ah used/charging current, go out an check it about that time, and unplug it shortly afterward, as it takes a bit longer than this estimate due to throttling back of charge current toward the end.

As the weather warms, the car seems to have a bit more zip (or maybe just feels that way because it is spring), and my energy/mile has gone down somewhat. Maybe because the drive train is less "stiff". As the first cell map shows the charge/mile on this latest run was 86.1/54.1 = 1.59 Ah. Pack voltage while driving is typically around 116V to 118V with 36 cells, so energy/mile was about 117*1.59 = 186 Wh/mile. I only drove on the freeway for maybe 10 of the 54 miles, another 15 or so at 50 mph, and the rest "in town" at 25 to 40 mph. There typically isn't much voltage sag on the pack because I only draw around 150A, 0.83C, on the freeway at 60 mph, and far less otherwise. After full charge it typically is at around 121V rest voltage, and remains mostly between 116 and 118V for at least the first 40 miles during driving, dropping to around 114-115V during acceleration with current around 1C, and maybe 112 -113V with current of 1.5C (these are approximate, I only look at the voltage occasionally). At 1.5C during acceleration I typically leave most other cars behind.

I also noticed an increase in range after adjusting the neutral_braking controller parameter to 50% to increase regen and electric braking. After this 54 mile run I still had 2 out of 5 bars showing on the TBS gauge, so over 20 miles left to 35% SOC (20.76Wh pack), which is what I defined as "empty" on the TBS. As I've stated before I hardly use my mechanical brakes. I've become pretty good at coming to a complete stop at stop lights and stop signs using only electric braking to maximize the energy recouped. Regen current is typically 80A or less. If I completely release the accelerator pedal while going 40mph in 2nd gear, it might jump up to 130 - 150A briefly. If I do that in third gear at 50 mph it might jump to around 110-120A briefly. Typically it is less than 80A though, usually 30 to 60 through most of the slow down approaching a light, so less than 0.4C. Because of this, and the fairly low discharge currents, I expect the cells to have a long lifetime. We shall see.


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## JRP3 (Mar 7, 2008)

Great data as always. In my limited parking lot antics I've seen around a max of 50 amps of regen on the flat if I quickly let off the throttle in second gear around 35-40mph. I'll probably want to bump that up a bit as the car takes a while to slow to a stop on regen alone.


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## Kelmark (Oct 26, 2009)

Tom,

I was wondering if you have or could make a video of your car driving. I know I would be interested in seeing it along with many others that are interested in buying the AC-50 kit. Things I would like to see are;

A short clip from inside while driving up to 65mph cruise with a look at amp draw occasionally.

Another suggestion is a short clip looking around the car at the installation.

Also, an acceleration clip preferably against another car like a newer ford focus 0-50mph on a back road.

This would give us a good look at the system that words can’t always portray.


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## raymond.nl (Mar 17, 2010)

Kelmark said:


> Also, an acceleration clip preferably against another car like a newer ford focus 0-50mph on a back road.


Even better: tape a GPS logger to the roof of the car, make a few
0-60 runs and post the GPS logger data to the net!

Please?


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## Mesuge (Mar 6, 2008)

tomofreno said:


> I really like the TBS E-xpert Pro gauge.


Isn't it basically just re-badged "next gen/usb output" version of E-meter aka Xantrex Link10/Pro? The prefered e-conversion (& home solar) gauge of the 1990s-early 2000s (reminder for the young ones hah). TBS does provide some basic user software nowadays:

http://www.tbs-electronics.nl/products_expertpro_rs232.htm
http://www.tbs-electronics.nl/products_dashboard_features.htm
(this stock software might come handy if you plan to use winbased carputer, i.e. RoadRunner frontend,
you just plug it along side your mp3, RDS radio, weather info, navigation, .. tabs)

http://www.xantrex.com/web/id/274/p/2610/pt/7/product.asp
http://www.xantrex.com/web/id/274/p/docs/pt/7/product.asp
Comm. interface spec./protocol here (pdf): http://www.xantrex.com/web/id/2611/docserve.aspx 
Tim Nolan explained the basics of comm. operation of this E-meter here (pdf): http://web.archive.org/web/*/http://www.timnolan.com/hparticle/Nolan74.pdf












But, you might recall Peter Ohler's neat application EVDash for Palm handhelds, the major benefit, was that you can list through several display tabs, change settings (Peukert), log data/watch graphs, compute various e-driving critical data on the fly etc. The demo works, I looked at the source code and had problems compiling it, missing libraries, this is quite a bit dated software platform. But some more skilled codies could surely easily transfer in into the more contemporary world of pocketpc, winmobile, smartphones, iphones, portable linux distros, java touchscreens and what have you. Or just inspired by the functionality and structure of it, write it from the scratch:

http://www.ohler.com/palm/EV1Dash.html
http://www.ohler.com/palm/EVDash.html
http://www.ohler.com/downloads/index.html#EVDash

Haven't check it yet, but the data export format for TBS is likely to be the same or very similar to Xantrex/Link10. You need a prescaler for the max 175VDC (1:5) from TBS, or there is even 350VDC (1:10) 3rd party unit from the aussies: 
http://www.evworks.com.au/index.php?category=12
Belktronix offered 500VDC scaler: http://www.belktronix.com/link10.html
How to safely wire it to shunt/fuses: http://www.masonclan.org/EVConversion/EVS-10Project9.html

You don't need the additional payware usb comm kit (with insulation box) in case you manage to read its RS232 output talk, it shouldn't be password protected or coded, just set (I believe mod 0) for spitting raw data over RS232, read manuals for TBS and Xantrex. This would make for nice alternative to 2-3x more expensive Evision gauge, which is more precise and feature rich, without any handhelds attached.


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## tomofreno (Mar 3, 2009)

> I was wondering if you have or could make a video of your car driving.


 Going to be a challenge since I don't have a video camera. I don't have a GPS either. Maybe I can borrow one.


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## Dave Koller (Nov 15, 2008)

Mesuge said:


> Isn't it basically just re-badged "next gen/usb output" version of E-meter aka Xantrex Link10/Pro?
> 
> Haven't check it yet, but the data export format for TBS is likely to be the same or very similar to Xantrex/Link10. You need a prescaler for the max 175VDC (1:5) from TBS, or there is even 350VDC (1:10) 3rd party unit from the aussies:


I wrote two freeware programs over the years for link10.. One DOS (lol yes DOS) in assembly - and one with a few bells an whistles... that one in VB.
http://www.grassrootsonline.com/public/linkit.tpl still has Dos Version..

The Vb version was used by Xantrex / Trace techs...

Never tried them on USB serial ports - they need a serial input!

edit: I found VB there also http://www.grassrootsonline.com/public/vblinkit.zip

take it easy on the server as it has limited bandwidth!


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## Mesuge (Mar 6, 2008)

Hi Dave, thanks for your input, I do recall your DOS progiee, but not that VB version, which looks fairly advanced (just installed it on winXP), it offers various graph plotting options, alarm settings etc., quite impressive! I'll have to fix some tbs/xantrex setup to try if their newest firmware didn't introduce some small variations into the data stream. Are there more people owning this recent generation of tbs/xantrex e-meters besides Tomofreno, not the 1990s first gen of Xantrex Link 10 E-meter?

screenshot as attachment:


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## tomofreno (Mar 3, 2009)

So would Dave's VB sw work with a simple connection from the RS232 output on a PC and the (looks like in photo) J connector on the TBS? If so, which pins? Data logging voltage and current along with GPS data would be cool, as you could plot your course and calculate power use at all points along it to see what power you use on level ground and various grades. You could also determine an "average grade", positive for net uphill, negative for net downhill, for distance traveled, and estimated range remaining for that average grade and average speed to that point. Anyone know the cost of the TBS sw/interface?


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## Dave Koller (Nov 15, 2008)

tomofreno said:


> So would Dave's VB sw work with a simple connection from the RS232 output on a PC and the (looks like in photo) J connector on the TBS? If so, which pins? Data logging voltage and current along with GPS data would be cool, as you could plot your course and calculate power use at all points along it to see what power you use on level ground and various grades. You could also determine an "average grade", positive for net uphill, negative for net downhill, for distance traveled, and estimated range remaining for that average grade and average speed to that point. Anyone know the cost of the TBS sw/interface?



Tom
Graphing is in 15 min blocks LOL it was for reading *solar/wind* at the time !
It will store each minute (yep minute) as if I stored for Solar/wind for a 
24 hour day the files would scare you.. (60 x 60 x 24 hrs..)

It's use in EV might be limited... I have the source code somewhere if we find it useful on the TBS it could be rewritten to provide a more EV friendly data. ( In my spare time  ) As always it would be freeware....


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## Mesuge (Mar 6, 2008)

tomofreno> if you had followed the links provided.. or just google .. the OEM interface of TBS/Xantrex is around $150 (usb isolated conn. box + CD), which is a bit steap. Otherwise the null modem cable or adapter needed for the serial rs232 connection only is around $2-3 bucks, but ask some IT friends, many freebies around in their bins.

Dave> thanks, any functional upgrades to your application along the lines of Ohler's EV1/Dash would be greatly appreciated..


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## Dave Koller (Nov 15, 2008)

Mesuge said:


> Dave> thanks, any functional upgrades to your application along the lines of Ohler's EV1/Dash would be greatly appreciated..


Peter and I have communicated in past...

So my question is Does the TBS have the same data stream? And is it sold anywhere in the US? I might get one to tinker with for you.

http://www.evworks.com.au/store/datasheets/EVWorks - Fuel Gauge Driver.pdf

like the above fuel gauge also!


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## Mesuge (Mar 6, 2008)

Dave, the word on the street is that TBS (Netherlands, EU) is the original designer/manuf. of these E-meters (Link10, LinkPro/Expert-Pro), Xantrex just rebadged it for U.S. market, or is it the other way around, lol? Seriously, they should be exactly the same product, however they might be shipped with different firmware versions, but I'd give it a very low probability since this latest generation (LinkPro/Expert-Pro), has been there for few years. There is some informed speculation and practical experience from these meters on EVDL: http://www.diyelectriccar.com/forums/showthread.php/evdl-ts-lfp260-pack-capacity-test-31531.html

btw. here is a related line of these meters - XBM undergoing some surgery:
http://biankablog.blogspot.com/2009/12/going-electric-repairing-zantrex-xbm.html


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## tomofreno (Mar 3, 2009)

> Dave, the word on the street is that TBS (Netherlands, EU) is the original designer/manuf. of these E-meters (Link10, LinkPro/Expert-Pro), Xantrex just rebadged it for U.S. market


 Correct. I exchange emails with TBS looking for a U.S. distributor for their gauge and they told me Xantrex. I purchased from evworks in AU because I could get the voltage adapter with it.


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## dimitri (May 16, 2008)

Here is the US distributor...

http://www.evolveelectrics.com/E-Xpert%20Pro.html


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## tomofreno (Mar 3, 2009)

Finally got around to remounting the motor controller with a heat sink. The heatsink is 10" wide x 11" long with 2.5" tall fins and 3/8" base. The controller is a bit narrower and 10.8" long. I didn't have a lot of room to mount these with a fan on the heat sink, but after measuring and re-measuring I convinced myself it would fit here, with the fan just above the chassis down near the motor, and heat sink/controller mounted tilted toward the front of the car with a bit more than 1/3 of their width over the fender:









There is a 1/4" steel plate that bolts to the back of the motor, and 2" steel angle which bolts to the plate and the motor mount just at the bottom of the photo. These were removed to do a test fit when this photo was taken. The aluminum tray bolts to this plate through aluminum angle. The plate used to extend up well above the tray, and the controller was bolted to it, edge up. 

It is a difficult place to measure, but I thought it would fit if I cut off 9 of the heat sink fins at an angle to clear the fender, and removed 1" off the fins at the back end. I got a quote from a machine shop for $200.00 to make those cuts. So I picked the heat sink up from them, stopped at Apex Saws on the way home, bought 2' of 1/2" band saw blade for $10.00, and made a bow saw with some old wheel barrow handles I had salvaged. Made the cuts in under 2 hours (also cut off the front corners to attach angle brackets):







Not bad, $95.00/hour including the blade.
I bolted the heatsink, fan, and controller together to see if the assembly would fit:







It fit in the space as expected, and looked as if it would not interfere with the hood, so I proceeded to make the mounting brackets, and cut off the steel plate so its top edge would be flush with the aluminum tray because the heat sink had to extend over the tray by about 3/4". It only took about 15 minutes to cut off that 10.5" wide, 1/4" thick steel plate with the bow saw. That sucker cuts! 
Got everything finished today:







I put red flex tubing on the motor and battery cables. That gray stuff at the cable ends is the heavy flexible plastic conduit sold at Home Depot and Lowes. I put a cut through the length of each piece, and cut out some of the bottom so I could force it on over the terminals and cable lugs so they cannot be touched. Not much danger there really. But if by some chance the key was left on, and you put a body part across the B+ and B- terminals on the controller front...  
The bottom of the heat sink was not flat. It had a rounded W shape, but I liberally applied heat sink compound to it and spread it around before bolting the controller to it.
No data on temperature yet. We had snow flurries most of today, same forecast for tomorrow. But Friday it is supposed to clear up and get to about 60F, so I'll be able to see how it does then. Of course the real test will be this summer, but I think it will remain significantly below its 85C max temperature. The motor max is 120C, and I've not seen it above about 40C during highway cruising at 55-60 mph with 70F (21C) outside temp.


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## JRP3 (Mar 7, 2008)

Nice work Tom. Great idea on the bow saw, how about a picture of that?


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## tomofreno (Mar 3, 2009)

> Here is the US distributor...


 Great, they finally got one besides Xantrex! It is well worth $250.00 to have Ah used and SOC.


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## dimitri (May 16, 2008)

tomofreno said:


> Great, they finally got one besides Xantrex! It is well worth $250.00 to have Ah used and SOC.


I agree. Since I am sick and tired of my PakTrakr and the only true SoC gauge method is AH counting, I am working on my own EV Display design to compliment my MiniBMS. 

Imagine that PakTrakr and TBS Gauge met in a bar and had too much to drink .... their bastard child would be my EV Display... 

Its based on Arduino and uses 2x8 character LCD display and hall effect sensor to measure AH in and out, along with pack voltage and temperature, so AH can be temperature compensated, to show true fuel gauge in summer and winter.

I already have a working prototype, just polishing some code before I put it in the car for road testing. I'll probably start a thread on it once I have something to show.


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## tomofreno (Mar 3, 2009)

> Great idea on the bow saw, how about a picture of that?











Scrounged some baling twine from out by the garden for the tensioning.
Mortise and tenon at the joints between the cross piece and handles. Quick to make and work well. Those 9 fins had to be cut from the side - so cutting through 11" thick aluminum. They are around 0.1 thick, so together it is equivalent to about a 1" deep cut into 11" thick aluminum. The saw accomplished it handily.


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## Dave Koller (Nov 15, 2008)

Now that is a Saw - nice job Tom!


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## JRP3 (Mar 7, 2008)

DIY at it's finest


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## procupine14 (Mar 17, 2010)

JRP3 said:


> DIY at it's finest


 
I agree with you on that!


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## tomofreno (Mar 3, 2009)

Went for a drive today to test the new heat sink addition. Outside temperature was 63 F (17C). I drove around town first to run some errands then about 10 miles at 50 mph. The controller stayed at 39 C while going 50 mph. Up a 3/4 mile long hill pulling about 250A at 50 - 55 mph the controller temp rose to 45C and dropped to 41C by the bottom on the other side. I then turned off on a back road and drove about 6 miles at 45 mph. Controller temp dropped to 39C shortly after turning off and continued dropping, settling at 33C, at which point I stopped. The motor was also at 33C at this point. On the return trip, going up the hill the other way is not as steep, so pulled about 170A and the controller got to 39C, and cooled to 31C by the time I reached bottom on the other side. I then drove at 55 mph for 8 miles. The motor remained at 31C and the controller at 33C. I then stopped at a long stop light and the motor temp climbed to 36C and controller to 38C, so I guess I am getting significant air flow to the controller heat sink while driving. The motor cooled to 33 C and controller to 34C within a few miles afterward cruising at 50 mph. 

The largest temperature difference between ambient and controller was 28C when pulling 250A on the hill. So at ambient of 100F (38C) I would expect about 66C controller temp in this case, and only about 54C when driving on level ground at 55 mph. Both well below the 85C limit. The motor should remain way below its 120C limit.

Some time in the next few days I'll go out on the interstate and see what temperature I get cruising at 65mph for about 8 miles.

Washed and waxed it when I returned to get ready to have it on display at the Earth day festival tomorrow.


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## JRP3 (Mar 7, 2008)

Nice, seems as if that should be plenty of cooling. Is that with the fan running? So far with my setup I've seen a max controller temp of 45C when it was near 70F, 21C, outside, but that was not an extended run.


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## Guest (Apr 24, 2010)

tomofreno said:


> Went for a drive today to test the new heat sink addition. Outside temperature was 63 F (17C). I drove around town first to run some errands then about 10 miles at 50 mph. The controller stayed at 39 C while going 50 mph. Up a 3/4 mile long hill pulling about 250A at 50 - 55 mph the controller temp rose to 45C and dropped to 41C by the bottom on the other side. I then turned off on a back road and drove about 6 miles at 45 mph. Controller temp dropped to 39C shortly after turning off and continued dropping, settling at 33C, at which point I stopped. The motor was also at 33C at this point. On the return trip, going up the hill the other way is not as steep, so pulled about 170A and the controller got to 39C, and cooled to 31C by the time I reached bottom on the other side. I then drove at 55 mph for 8 miles. The motor remained at 31C and the controller at 33C. I then stopped at a long stop light and the motor temp climbed to 36C and controller to 38C, so I guess I am getting significant air flow to the controller heat sink while driving. The motor cooled to 33 C and controller to 34C within a few miles afterward cruising at 50 mph.
> 
> The largest temperature difference between ambient and controller was 28C when pulling 250A on the hill. So at ambient of 100F (38C) I would expect about 66C controller temp in this case, and only about 54C when driving on level ground at 55 mph. Both well below the 85C limit. The motor should remain way below its 120C limit.
> 
> ...



VERY interesting data Tom. My water system may be overkill. But on the other hand, I don't have room for the quantity of aluminum your photos showed. It looks like you've got controller temp in hand.

Jack Rickard


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## Guest (Apr 24, 2010)

dimitri said:


> I agree. Since I am sick and tired of my PakTrakr and the only true SoC gauge method is AH counting, I am working on my own EV Display design to compliment my MiniBMS.
> 
> Imagine that PakTrakr and TBS Gauge met in a bar and had too much to drink .... their bastard child would be my EV Display...
> 
> ...


That's pretty much what the world needs right now actually. I did the same thing with an Arduino and two LEM HASS sensors. The 200-s and 50-s actually use the Arduino 5v to power them. I did learn a couple of things:

1. The 5v power supply on the Arduino is inadequate. As the 5v sags, it is ALSO the reference for the ADC and your measured currrent will vary correspondinly. You need an additional 5v regulator capable of at least an amp.

2. The Arduino is great. But the inputs are in no way protected. I put mine in the Mini and it ran 22 miles and then blew up entirely from the noise put out by the controller. Needs 5v Zeners on the ADC inputs.

3. Sparkfun sells a GPS module called the VENUS. I've already done the code for reading it. You can have it. The VENUS does 10Hz reads, and it will live with 5v serial. So it's easy to interface. With the GPS, you get speed. If you count millis between GPS reads, you can integrate distance. Once you have distance, and AH, you can do Miles to Empty. 

Jack Rickard


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## Guest (Apr 24, 2010)

tomofreno said:


> Went for a drive today to test the new heat sink addition. Outside temperature was 63 F (17C). I drove around town first to run some errands then about 10 miles at 50 mph. The controller stayed at 39 C while going 50 mph. Up a 3/4 mile long hill pulling about 250A at 50 - 55 mph the controller temp rose to 45C and dropped to 41C by the bottom on the other side. I then turned off on a back road and drove about 6 miles at 45 mph. Controller temp dropped to 39C shortly after turning off and continued dropping, settling at 33C, at which point I stopped. The motor was also at 33C at this point. On the return trip, going up the hill the other way is not as steep, so pulled about 170A and the controller got to 39C, and cooled to 31C by the time I reached bottom on the other side. I then drove at 55 mph for 8 miles. The motor remained at 31C and the controller at 33C. I then stopped at a long stop light and the motor temp climbed to 36C and controller to 38C, so I guess I am getting significant air flow to the controller heat sink while driving. The motor cooled to 33 C and controller to 34C within a few miles afterward cruising at 50 mph.
> 
> The largest temperature difference between ambient and controller was 28C when pulling 250A on the hill. So at ambient of 100F (38C) I would expect about 66C controller temp in this case, and only about 54C when driving on level ground at 55 mph. Both well below the 85C limit. The motor should remain way below its 120C limit.
> 
> ...


Tom:

Went back and reviewed your photos. It looks like a fantastic job on a LOT of heatsink. And I'm wondering about the amp investment in the fan. Would it be at all interesting to do a brief test at identical runs fan ON, and fan OFF to determine what effect the fan is having on the controller temperature?

Jack Rickard


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## JRP3 (Mar 7, 2008)

Definitely. If I start seeing elevated temps on my simple 1/4" x 12" x 20" flat mounting plate I'll start by simply adding a fan to that and see what happens. Jack you and I are working at opposite ends of the spectrum, you're probably overkill and I may be underkill. Hopefully no deaths in either case


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## tomofreno (Mar 3, 2009)

> Is that with the fan running?


 Yes. So I was surprised that the controller temp climbed while sitting at the light. I thought the 260 cfm fan would be the largest source of air flow. But the front inner corner of the heat sink is positioned about 3/8" to the side of the front battery box, and about 1/4" ahead of the rear edge of it. It is mounted so the fins are oriented along the car front to rear axis, so air moves around the box and through the opening between the box and chassis right through the fins of the controller. The motor could obviously be pushed more temperature wise. The controller is still the limiting factor.


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## Guest (Apr 24, 2010)

JRP3 said:


> Definitely. If I start seeing elevated temps on my simple 1/4" x 12" x 20" flat mounting plate I'll start by simply adding a fan to that and see what happens. Jack you and I are working at opposite ends of the spectrum, you're probably overkill and I may be underkill. Hopefully no deaths in either case


I don't think there's a wrong answer here JRP. IT's a matter of degree and mission. We're trying to prototype a car that Special Editions can build and sell. This is a new controller, but it is a Curtis. They have had heat issues in the past and most of the Curtis failures I think are simple heat issues. If I had a forklift as a heat sink it might not be a problem. 

We want it to be bulletproof and in trying to envision how to make the drive train last a half a million miles heat is what I came up with. But it's kind of like the BMS thing. If my water pump goes out after 10,000 miles we did no good. In fact, we did harm. So I'm looking at a $200 Meziere again.

The air cooling is just much simpler and better in all respects. In fact simple and better are in the following order.

Large plate area - no fan.
Smaller plate area with fan.
Chill plate and water system.

We simply don't have room physically for 1 or 2 without putting the controller in the front and running long cables to the motor in the rear. If you do, it is superior in every way.

But I am curious to know the delta fan/no fan for a given heat sink. I think the fan is probably important. But I do a lot of thinking that doesn't amount to much when you get down to cases.

Jack Rickard
http://EVTV.me


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## tomofreno (Mar 3, 2009)

Did some more testing today. I drove at 65 mph until the motor and controller reached steady state temp, which only took about 4 miles. The motor got to 38 C, and controller got to 41 C. They climb quickly at first, but then just seemed to clamp at these temps. Apparently heat loss by forced convection equals heat into the sink from the controller at this point. I then pulled off the highway, turned around and drove back the other way for about 6 miles at 65 mph, temperatures were the same.



> Would it be at all interesting to do a brief test at identical runs fan ON, and fan OFF to determine what effect the fan is having on the controller temperature?


 After the above, I pulled over and turned off the fan on the heat sink (switch is under the hood), then continued driving at the same speed. The controller maxed at 43 C, only 2 C higher! I then slowed to 55 mph and the motor settled at 38 C and controller at 40 C. When I stopped at a light the controller did heat up faster than with the fan off, reaching 48 C. I pulled off and turned the fan back on when it was at 47 C, and it cooled to 44 C in about 20 seconds. So the fan mainly helps when the vehicle is stopped, with no other source of air flow across the heat sink, but is not significant otherwise. 

Outside temperature was 67 F or 19.4 C, so at 48 C the temperature difference between heat sink and air was about 29 C. Then at 100 F or 38 C air temp, the controller might be expected to get to about 67 C. That is with the fan off, sitting at a stop light after driving 55 to 65 mph. 

When I returned home the motor was at 36 C as I pulled in the driveway. When I stopped in the garage it quickly climbed to 61 C, so its fan has a very big effect. Batteries in the front box were at 77 F and those in the mid box were at 86 F (they started at 60 F) upon return. No terminals on any cell or on the controller were at all warm to the touch, felt like ambient. 

Because the heat sink is beside the front battery box with fins parallel to air flow, air will flow through the opening between the box and chassis and through the fins. The fan has little effect compared to this. It is evidently a much larger mass flow across the fins - at least at 55 to 65 mph. Might see a bigger effect from the fan driving in town at 25 to 35 mph, and frequent stopping at lights. Of course there wouldn't be near as much power dissipated by the controller in that case so maybe the difference in temperature wouldn't be significant. The car used an average of about 169A at 65 mph, but my bike and rack were on the back which adds drag. Drove a bit over 48 miles, and was at 48% soc upon return. The heat sink fan only draws 1.6A (edit: Wasn't thinking here. That is its current draw from the 12V battery, so about 1/10 that from the pack).


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## tomofreno (Mar 3, 2009)

> It looks like a fantastic job on a LOT of heatsink.


 There were a total of 24 fins, 11" x 2.5". I cut 9 off at an angle leaving about half of each. Also cut all fins off by 1" in length. So 15 x 10 x 2.5 = 375 square inches, times two sides of each fin gives 750 square inches. And 9 x 10 x 2.5 = 225 square inches ( 9 half fins, two sides, 1/2 x 2 = 1). So 975 square inches total, or 6.8 square feet, minus the bit I cut off at the front corners.


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## JRP3 (Mar 7, 2008)

jrickard said:


> I don't think there's a wrong answer here JRP. http://EVTV.me


Actually I think there might be, and I think it's mine. Yesterday I did 20 mile round trip in and out of town, return trip being mostly uphill all the way. A 1 mile steep grade at 55mph followed by about 6 miles of moderate uphill at the same speed left me with a 54C motor temp and 66C controller temp, air temp around 18C, 65F . My mid engine Fiero with a belly pan doesn't give good airflow to the motor and controller, my controller plate is right over the motor, plus I've been trying to seal off the engine compartment to eliminate dust and water. Obviously I'm going to have to concentrate on managing airflow in and out a bit better and will probably need a fan.


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## Guest (Apr 25, 2010)

JRP3 said:


> Actually I think there might be, and I think it's mine. Yesterday I did 20 mile round trip in and out of town, return trip being mostly uphill all the way. A 1 mile steep grade at 55mph followed by about 6 miles of moderate uphill at the same speed left me with a 54C motor temp and 66C controller temp, air temp around 18C, 65F . My mid engine Fiero with a belly pan doesn't give good airflow to the motor and controller, my controller plate is right over the motor, plus I've been trying to seal off the engine compartment to eliminate dust and water. Obviously I'm going to have to concentrate on managing airflow in and out a bit better and will probably need a fan.


A 1 mile steep upgrade at 55 is a pretty strenuous test. 66C is well within the 85C current limitation point. Of course, a 48C gain on a 40C day might well put you over. But that's on a pretty warm day, and assumes the same heat gain. Under most conditions you'll encounter, you've got it covered.

But yeah, fans are inexpensive and use little power on balance. If your plate is right over your motor, I'd be looking for some way to get the same flow to cool two devices.

Jack


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## Guest (Apr 25, 2010)

tomofreno said:


> Did some more testing today. I drove at 65 mph until the motor and controller reached steady state temp, which only took about 4 miles. The motor got to 38 C, and controller got to 41 C. They climb quickly at first, but then just seemed to clamp at these temps. Apparently heat loss by forced convection equals heat into the sink from the controller at this point. I then pulled off the highway, turned around and drove back the other way for about 6 miles at 65 mph, temperatures were the same.
> 
> After the above, I pulled over and turned off the fan on the heat sink (switch is under the hood), then continued driving at the same speed. The controller maxed at 43 C, only 2 C higher! I then slowed to 55 mph and the motor settled at 38 C and controller at 40 C. When I stopped at a light the controller did heat up faster than with the fan off, reaching 48 C. I pulled off and turned the fan back on when it was at 47 C, and it cooled to 44 C in about 20 seconds. So the fan mainly helps when the vehicle is stopped, with no other source of air flow across the heat sink, but is not significant otherwise.
> 
> ...


An EXCELLENT report and very informative. Thanks Tom. With that much heat sink and fan and those temps, I'm feeling better about the chill plate and motor fan we are adding. It's probably overkill, but it's not overkill in vain.

And I think it's safe to assume that without some form of heat sink, this controller would indeed have potential temperature issues. I guess I'm seeing the fan as not particularly useful at these temperatures. You are quite under the 85C assuming you are measuring right at the interface. 

I'd probably put it on a manual switch or a little thermoswitch to cut it in at some higher ambient temperature only. In fact, I may do that on my pump on the liquid system.

At $78, it's not precisely a steal. But it's quite overdesigned for this application, thanks to the H2O hydrogen-whackos. http://cgi.ebay.com/DC-Motor-Contro...ltDomain_0&hash=item2559e67131#ht_1897wt_1167

Jack Rickard


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## tomofreno (Mar 3, 2009)

> You are quite under the 85C assuming you are measuring right at the interface.


 I'm reporting motor and controller temperatures from the Curtis 840 gauge. I assume (bad thing to do) that the temperature sensor is inside the controller near the devices. I don't know where the motor temp sensor is.


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## Guest (Apr 25, 2010)

tomofreno said:


> I'm reporting motor and controller temperatures from the Curtis 840 gauge. I assume (bad thing to do) that the temperature sensor is inside the controller near the devices. I don't know where the motor temp sensor is.


I'm sure the motor temperature is taken at the encoder. That's the only possible connection. This is perfect. Wherever the controller sensor is, it almost has to be the same one used to go into current limit, which is what we are trying to avoid.

Most excellent.

Jack Rickard


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## JRP3 (Mar 7, 2008)

I too am reporting the 840 gauge data. It's great to have all that data built in and included in the package, though it would be nice to have it all displayed at once.


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## tomofreno (Mar 3, 2009)

I am getting considerably better range with the warmer weather, 65 to 70 F. I drove on secondary roads mostly at 35 mph for about 19 miles yesterday, then today I drove 60 mph on the freeway for about 8 miles, then on secondary roads, for a total of about 41.9 miles total and used 61 Ah charge, or about 1.46Ah/mile. In the winter I was averaging about 1.7 to 1.8 Ah/mile. The cells are 180 Ah, so I was at about 66% SOC after driving about 42 miles. In winter I was getting about 12 to 13 miles per bar on the TBS battery icon with 5 bars total, mixed driving. Now I am getting 16 to 18 miles per bar indicating 80 to 90 mile range at 80% DoD, though I haven't driven that far to test it.


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## tomofreno (Mar 3, 2009)

A bit over 2600 miles on the car now. Drove 55.3 miles yesterday, about 22 miles at 50 mph, 14 at 60 mph, the rest at 30 to 40 mph, half with the headlights on (original lights). used 88.9 Ah so was at about 50% DoD afterward. Took 11.56 Wh to recharge. The charger efficiency at 30A was previously estimated as 0.94 (from TBS and EKM readings), which gives an estimate of 10.87Wh/55.3 = 196 Wh/mile, 209 Wh/mile from the wall. Seems to be holding a bit more charge and using less energy in the warmer weather. 

Checked cell voltages before recharging, and all 8 in the rear box were at 3.299V, 19 at 3.299V, 1 at 3.296V in the middle box, 1 at 3.000V (edit:3.300V, not 3.000), 4 at 3.299V, 1 at 3.298V and 1 at 3.296V in the front box. The lower voltage cells are replacements that were charged some time ago to match the other cells. The 4th replacement cell is one of those at 3.299. The other cells have never been individually charged or "balanced."


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## Coulomb (Apr 22, 2009)

tomofreno said:


> ... 1 at 3.296V in the middle box, 1 at 3.000V,


Did you mean 3.300 V for that one? Otherwise, it's a long way out of balance compared to the others.


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## tomofreno (Mar 3, 2009)

> Did you mean 3.300 V for that one?


 Yes, sorry.


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## tomofreno (Mar 3, 2009)

Drove a bit over 3 miles up an about 5.8% grade (according to topo lines on google maps) at about 50 - 53 mph and about 60F (16C) outside temperature. Motor settled at 36C and controller at 41C. Pulled 240 to 270A on the way up (slope varies a bit). Regen was around 70A most of the way down. Didn't have anything to measure cell temperature when I stopped at the top, but cell terminals felt like ambient temperature, not at all warm. 

Also saw the highest regen to date, 192A, when I completely released the accelerator to stop for a sudden light change while going about 52 mph in 2nd gear. I've been driving at 50 - 55 mph in 2nd gear lately rather than 3rd since the higher motor rpm, about 6200 at 55 mph, keeps the motor a bit cooler. The controller cuts back at around 6400 rpm to protect the motor. Current draw seems to be about the same as driving at the same speed in 3rd.


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## JRP3 (Mar 7, 2008)

I too have been using mostly second gear for all my driving lately, including long uphill pulls. It seems to give a good combination of performance and regen.


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## tomofreno (Mar 3, 2009)

> I too have been using mostly second gear for all my driving lately, including long uphill pulls. It seems to give a good combination of performance and regen.


 What is your top speed in 2nd? What motor rpm do you have at 55 mph? I was concerned with running it regularly at 5900 - 6200 rpm, but it runs cooler that way, and as you say gives good acceleration, and deceleration with regen.

I was happy to see there was no sign of over-heating of anything in that hill run. That was only about 1000 ft change in elevation. Maybe I'll get the nerve sometime to try the about 4300 ft change in elevation from the valley floor to the 8994 ft pass.


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## JRP3 (Mar 7, 2008)

Fastest I've gone in second so far is 60mph at a little over 5800 RPM, so probably around 65mph max. This car could be quite practical with a single speed gear reduction equal to second. I was thinking of possibly boosting the max motor RPM to 7K but I don't really need it and assume they had a good reason to keep it at 6500. I probably will try adding one more cell to the pack, I do love the way it feels fresh off the charger


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## tomofreno (Mar 3, 2009)

> Fastest I've gone in second so far is 60mph at a little over 5800 RPM, so probably around 65mph max.


 It has a bit higher gearing than the Swift. I am at about 6200 - 6300 rpm at 55 mph.


> This car could be quite practical with a single speed gear reduction equal to second.


 That is what HPEVS is doing with the Wheego Whip Life, and why its top speed is limited to about 67 mph. With that gearing I would think initial acceleration from a stop would be a bit sluggish though. There is a big difference in initial acceleration in 1st versus 2nd in my car.


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## JRP3 (Mar 7, 2008)

It's really not bad at all, especially on the flat, and if you get aggressive with the go pedal. I do have a bit more peak torque than you do, though it does drop off sooner.


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## tomofreno (Mar 3, 2009)

My remark on acceleration was with regard to the Wheego, which has higher gear ratio, not your car. Still, after one scary left turn in fast traffic in second gear where acceleration was barely sufficient, I use first gear whenever I think I may need to scramble. Normally second is fine, but not when I have to accelerate fast.


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## MN Driver (Sep 29, 2009)

tomofreno said:


> It has a bit higher gearing than the Swift. I am at about 6200 - 6300 rpm at 55 mph.
> That is what HPEVS is doing with the Wheego Whip Life, and why its top speed is limited to about 67 mph. With that gearing I would think initial acceleration from a stop would be a bit sluggish though. There is a big difference in initial acceleration in 1st versus 2nd in my car.


The only issue as far as motor life is concerned that I can see, would be bearing wear issues, since they are sealed you can't replace their grease or check them. From the guys on ES, it seems they think they aren't too hard to change out. For what it's worth, there are other HPEVS motors that go up to 8k RPM if I recall correctly, and someone here once mentioned that they capped it at 6500rpm because they didn't think there was any additional useful power any higher.

Considering that the power has dropped off at the higher RPM range, if you are hanging at 6300rpm and need to accelerate hard to pass someone, which gear are you going to for max acceleration, 3rd or 4th?

My current donor prospect, the 2000 Honda Insight that I'm driving now, hits 70 at 6000rpm, so 55mph would be about 4700rpm.
The issue that I see with it is with heavy regen in 2nd gear, some people have had issues with the input shaft bearing since the bearing they used seems to wear out over time with the amount of 'reverse' torque involved. Some of the guys on the Insight forum think that there may be a better bearing to swap it out with rather than putting in the same replacement bearing from Honda.
I originally thought that I'd be using third gear for best acceleration on the highway if I went with the AC50, now I'm wondering how much power is available at those higher speeds? Is there enough passing power to be comfortable at, say 65mph if needed? I consider the smaller powerplant of the 1700 pound Insight and it seems like it would be more than sufficient to have an AC50 but the Swift is fairly close to make a comparison.


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## tomofreno (Mar 3, 2009)

> Considering that the power has dropped off at the higher RPM range, if you are hanging at 6300rpm and need to accelerate hard to pass someone, which gear are you going to for max acceleration, 3rd or 4th?


 Third. I've only used 4th once, at 65 mph. It accelerated well from 65 to 75 mph in 4th, and would have kept accelerating - I had plenty throttle left. I just stopped there. Now that I am running it up to higher rpm I would just leave it in 3rd up to about 70 mph. Required power should exceed available power much above that, so I would have to shift into 4th to go faster. Fourth should take me to about 85 mph, then I should have to shift to 5th.


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## tomofreno (Mar 3, 2009)

Yesterday I drove at average speed of 38 mph 6.3 miles up a 1600 ft change in elevation (low speed due to lots of switchbacks), about 4.8% grade, with outside temperature of 91 F. Motor/controller start temperatures were 55/53 C (drove about 7 miles to get there), and at the top were 61/56 C (max motor is 120 C, max contr is 85 C). Cell temp was 94 to 96 F at bottom and 95-97 F at top (measured with IR sensor on Extech EX830). These are in insulated boxes, but I had a 160 cfm bilge blower circulating air through the boxes (too noisy, need to get a different fan with lower tip speed). Current draw going up was about 135 to 210 A. Pack V going up was 114V at 200A draw, and 115V at 170A (about 119.7V at rest at this point). Current draw ranged from about 135A to about 210A, about 160 ave. Regen going back down was 21% of Ah used going up - used 25.6 Ah going up, gained 5.5 Ah going down. Did not use the mechanical brakes at all going down. 

Over 3k miles on the car now, and no problems with the motor/controller.


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## JRP3 (Mar 7, 2008)

So the question is did you use regen at all on the way up, slowing down for curves and such? Jack might think that a non regen vehicle was more efficient on the way up and therefore the overall AH's would be less. What's your normal AH/mile consumption? Hope you don't mind I copied your trip onto Jack's blog.


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## CroDriver (Jan 8, 2009)

JRP3 said:


> So the question is did you use regen at all on the way up, slowing down for curves and such? Jack might think that a non regen vehicle was more efficient on the way up and therefore the overall AH's would be less. What's your normal AH/mile consumption? Hope you don't mind I copied your trip onto Jack's blog.


Why would a non-regen EV be more efficient?


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## JRP3 (Mar 7, 2008)

To get the full story you need to read the latest blog from Jack Rickard at EVTV.ME There's a huge debate, and I'm all up in it  Basically Jack did some trips with and without regen and got better numbers without regen. He then concluded regen is no good. I'm not yet convinced, it may not give as much as was assumed but I think a different driving style may get more out of it than coasting and brakes.


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## CroDriver (Jan 8, 2009)

JRP3 said:


> To get the full story you need to read the latest blog from Jack Rickard at EVTV.ME There's a huge debate, and I'm all up in it  Basically Jack did some trips with and without regen and got better numbers without regen. He then concluded regen is no good. I'm not yet convinced, it may not give as much as was assumed but I think a different driving style may get more out of it than coasting and brakes.


OK, I kind of understand why someone wouldn't like to have a BMS in his car but I can't possibly find a logical reason why the same car with regen turned ON would be less efficient than with regen turned OFF. I'll try to find time to read Jacks thoughts on this...


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## JRP3 (Mar 7, 2008)

My take on it is that Jack is used to driving an EV without regen, and is used to coasting a lot, which is more efficient than regen. When he put regen on the accelerator pedal he wasn't used to it, couldn't easily find the neutral position for coasting so he was using regen when he normally would coast. When he put regen on the brake pedal it's keyed into his brake line pressure which means he's not getting max regen since he's also using brakes at the same time. He also doesn't have any steep hills in his area.


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## Dave Koller (Nov 15, 2008)

Regen in the flatlands is not the same as Regen in the hills.. or stop and go - think it is all relative. In my case it is not good as my age means I went to school "uphill" both ways... unlike Jack


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## tomofreno (Mar 3, 2009)

> So the question is did you use regen at all on the way up, slowing down for curves and such?


 Yes I did. There are many, many curves, some quite hairpin. Electric braking was very handy in slowing for them. I didn't have an easy way to quantify the amount of regen though. No problem putting it on Jack's blog, thought of doing that myself so he would have the data - but was unaware of the debate. 

To answer your other question, my usual Ah/mile at 35 mph on level ground in summer would be around 1.3 I think.



> Basically Jack did some trips with and without regen and got better numbers without regen. He then concluded regen is no good.


 I've done this too, and gotten the opposite result. I drove an about 5 mile loop with about 6 stop signs and a few small hills. Car charged to the same level before each trip. With regen I used about 12% less Ah. Results will depend on terrain, speed, stop/starts...I tried to accelerate as much the same as possible in both runs. With regen turned off I drove as if hypermiling, coasting as much as possible while not dropping too far below the speed limit - except to stop at the stop signs of course.

I agree with your explanation of Jack's regen experience. I think he doesn't know how to use it, and having it on the brake pedal makes it difficult if not impossible to use efficiently. Much better to use the neutral_braking parameter as you and I are I think, and just accelerate, coast, and declerate with the accelerator pedal. I really like it! He may also have his accelerator input programmed too touchy to control it well. A guy here that has one of Ford's original ev pickups had turned regen off for similar reasons - but he drove it as if it were digital, max regen or none at all, rather than using it to finely adjust his speed as required by easing the accelerator pedal as required. He complained that regen just stops the vehicle immediately. Jack is likely doing something similar, plus engaging the mechanical brakes somewhat.

I mean, come on, you have to repeatedly slow, and stop the vehicle while driving. How could it be more efficient to do this with friction than with regen? I can coast right along side of him at the same speed by easing my acclerator back, and when he touches his brakes to slow for a curve, or stop for a stop sign, I ease off the throttle more and get some energy back in the cells. Both cars remain side by side, one converts kinetic energy to heat to slow, the other converts some of that kinetic energy to potential energy in the cells. The one that converts kinetic energy to heat is more efficient??  And yes, I can pace him exactly, its all in the accelerator pedal. I do it every day, pacing traffic.

I thought I would have people riding my bumper going up the hill, but it turned out to be the opposite.


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## paker (Jun 20, 2008)

Jack explained that on the second speedster he used regen working with the brake pedal, working with the accelerator, and off. 

The mini cooper has a switch that turns regen on and off. Only two options. The mini cooper's regen is on through the brake.

The results for both cars were virtually the same with both cars driven in a 45 mile course.


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## tomofreno (Mar 3, 2009)

Drove up to Mt. Rose summit today. 19.3 miles (~32 km) from the bottom on S. Virginia St., 4594 foot (~1400 m) elevation gain, about 4.5% grade average. Used 65.1 Ah going up, at about 40 to 45 mph. Outside temperature at start was about 75 F, cooler at the top. Motor/controller temps at top were 53 C/48 C. Forgot to record Ah at the summit after climbing about 500 ft in elevation from the other side, so didn't get accurate regen Ah on the way down. No use of mechanical brakes on the way down, just electric braking, except near the bottom where I stopped for a traffic light. Edit: its worth noting that it is not at all unusual to smell burning brakes from cars in front of you going down this hill, as there is repeated braking on steeper parts and at hairpin switchbacks. Round trip from home was about 48 miles. Total Ah used for the 48 miles was 76.2 or about 42% DoD.


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## tomofreno (Mar 3, 2009)

> The results for both cars were virtually the same with both cars driven in a 45 mile course.


 Thanks Paker. Must be a very flat course with little or no traffic and few stops, or stops he can just coast up to, and end up at very low speed as he nears the stop. If you have to slow down and speed up regularly due to traffic modulation, maintain the speed limit up to within a reasonable distance of stop signs due to traffic pace, stop repeatedly, go up and down hills, and you control the accelerator pedal carefully to provide only the amount of current draw or current into the cells (regen), that is required to hold the car at the speed limit or pace traffic, I am confident you won't get Jack's result. I don't. 

Edit: If on the other hand you use the accelerator pedal more coarsely, you will modulate the kinetic energy of the vehicle more than if you just coasted and applied mechanical braking sparingly. In this case it could be more inefficient using regen. But if the change in kinetic energy of the vehicle is the same using both methods, then the same kinetic energy is converted, and one method (regen) stores some of that energy rather than dissipating it as heat, so it will be more efficient, even if only a little. It cannot be less efficient in this case. The modulation in K.E. may not be noticeable to the driver if he is backing off on current a bit too much, so slowing the car just a bit too much, then pressing the accelerator a bit more than he had it before releasing, putting more current into the motor, but not enough more to give noticeable acceleration...continually modulating like this could be less efficient than coasting and carefully braking because, not only is the KE of the vehicle modulating slightly, energy is wasted as heat in each cycle due to motor, controller, and drive train inefficiency.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> The modulation in K.E. may not be noticeable to the driver if he is backing off on current a bit too much, so slowing the car just a bit too much, then pressing the accelerator a bit more than he had it before releasing, putting more current into the motor, but not enough more to give noticeable acceleration...continually modulating like this could be less efficient than coasting and carefully braking because, not only is the KE of the vehicle modulating slightly, energy is wasted as heat in each cycle due to motor, controller, and drive train inefficiency.


Which is pretty much what Jack is describing. I wonder if he has his throttle parameters set too tightly, can't remember the exact values off hand, but throttle ramp, throttle release rate, etc. Also I think he's using a Kelly throttle like mine, and mine has very stiff springs that do make it a bit hard to control, I plan on changing mine. However that doesn't address his brake only regen drives which also show less efficiency. Supposedly he has it set so the first bit of pedal travel is regen only, so that's a puzzler.


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## paker (Jun 20, 2008)

tomofreno said:


> Thanks Paker. Must be a very flat course with little or no traffic and few stops, or stops he can just coast up to, and end up at very low speed as he nears the stop. If you have to slow down and speed up regularly due to traffic modulation, maintain the speed limit up to within a reasonable distance of stop signs due to traffic pace, stop repeatedly, go up and down hills, and you control the accelerator pedal carefully to provide only the amount of current draw or current into the cells (regen), that is required to hold the car at the speed limit or pace traffic, I am confident you won't get Jack's result. I don't.
> 
> Edit: If on the other hand you use the accelerator pedal more coarsely, you will modulate the kinetic energy of the vehicle more than if you just coasted and applied mechanical braking sparingly. In this case it could be more inefficient using regen. But if the change in kinetic energy of the vehicle is the same using both methods, then the same kinetic energy is converted, and one method (regen) stores some of that energy rather than dissipating it as heat, so it will be more efficient, even if only a little. It cannot be less efficient in this case. The modulation in K.E. may not be noticeable to the driver if he is backing off on current a bit too much, so slowing the car just a bit too much, then pressing the accelerator a bit more than he had it before releasing, putting more current into the motor, but not enough more to give noticeable acceleration...continually modulating like this could be less efficient than coasting and carefully braking because, not only is the KE of the vehicle modulating slightly, energy is wasted as heat in each cycle due to motor, controller, and drive train inefficiency.


Jack's first video driving the speedster showed him driving in town, with traffic, going around curves, up and down hills, and freeway driving.
The second video when was driving the mini didn't take an hour showing the entire route. He acknowledged the variables of every drive due to traffic and traffic lights, but came to the same conclusion about regen.


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## tomofreno (Mar 3, 2009)

> Supposedly he has it set so the first bit of pedal travel is regen only, so that's a puzzler.


 Emphasis on _supposedly. _How did he verify the mechanical brakes are not partially engaging with this initial pedal displacement? My experience in adjusting brakes with a car on jack stands is if they are adjusted normally, i.e. small pedal displacement before engaging, they do drag with just pressing the pedal over its low resistance range. I would guess if Jack put a thermocouple on the pad he would see temperature rise when he did this.

My, and others results don't agree with Jack's. For example, I posted a quote from a RAV4 owner in Florida on another thread here who did the same test, with regen, with regen turned off, and with regen was considerably more efficient. I expect the difference in Jack's and others results can be explained by the above, brake drag with partial pedal displacement, and too coarse movement of the accelerator pedal resulting in repeated modulation current into/out of the motor and vehicle kinetic energy. I can control current to within a few amps with my pedal. I can hold it on zero, increase to -2 or -3A (current out of pack), or decrease to 2 or 3A regen. During normal driving it will move all around due to changing traffic pace, changes in slope, etc, as I keep pace with traffic, but I can hold it very steady if I want, and let the car's speed vary with changes in slope instead.


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## tomofreno (Mar 3, 2009)

From Fred Ungewitter on EVDL, May/5/2010, "regen revisited":

Even though a number of posts have suggested that regen is of little value in a flat terrain such as much of Florida, our experiences have been all positive. It's a Rav4EV, so the factory/designers did the engineering, not me or a converter/builder. 

A switch on the shift lever (EB, ostensibly engine braking) and a gear position (B, Big Braking) gives us three levels of regen. The EB switch is left engaged all the time, and takes effect when one lifts one foot from the go-pedal. Approaching an intersection at reasonable speed, and having the light change is something we both dislike, but that's when the B position makes for some serious power to the pack. It's akin to a Jacobs Brake on a semi-truck, only they don't get energy back in the deal. Even if the shift lever is left in B, the power application is normal when the pedal is depressed, but very noticeable when the pedal is lifted. 

We have installed a Palm based energy monitoring system, tapped into the OBDII connector, which displays all manner of useful numbers and graphs and flashing things. This last sequence of use allowed me to monitor the entire energy consumption as well as the energy put back into the pack. On a 77 mile trip, slighly more than three thousand watt-hours was regen'd back into the pack. Since we have nothing in the way of elevation, it's all from the EB and B settings. I don't have the total energy consumed, but my calculator still displays the 167 watt-hours per mile calculation from using the regen, and the 208 watt-hours per mile without it. 

We are reserved in power application, as there is a great little bar graph on the display which goes higher as the pedal goes deeper. Conservative driving, keeping a five-mile eye ahead and letting everyone else pass us makes for extremely economical EV enjoyment.


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## JRP3 (Mar 7, 2008)

I didn't think the RAV4EV had a way to disable regen completely? I thought you could increase it with the EB and B switches but it was still there to some degree without?


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## tomofreno (Mar 3, 2009)

Passed a milestone of sorts on 7/29/10, one MWh of energy used in the car (from the wall). Total of 4591 miles for 1002.78 kWh, or 218 Wh/mile average, from the wall. Assuming about 94% charger efficiency (measured before), thats about 205 Wh/mile average, over half of which was in colder winter temperatures, with cells heated to 55 to 60 F. The energy is recorded by an EKM meter at the input to charger.

Still running well. The brake vacuum pump overheated as described on another thread here. The manufacturer has been very helpful. Thinks it was due to a vacuum leak which caused the pump to run too long. Sending me some oil, new relay (it stuck closed once), and new pump muffler (melted somewhat). Will have to test for a leak. 

Otherwise the car is doing great - drove up Mt. Rose again today at about 40-45 mph (about 19 mile, 4500-4600 ft elevation gain, no problem. Mechanical brakes still work, just have to push harder, and I don't use them much anyway, mainly regen braking.


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## JRP3 (Mar 7, 2008)

That's great efficiency, what do you think your overall average speed was for those miles? Mostly in the 40-45 range?


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## tomofreno (Mar 3, 2009)

> That's great efficiency, what do you think your overall average speed was for those miles? Mostly in the 40-45 range?


 I would guess so. Difficult to estimate. Sometimes I drive into town on secondary roads at 35 mph, other times take the highway at 55-60 mph. A significant amount is driving to a place about 18 miles away at mostly 50 mph with my bicycle and rack on the back. Also some longer trips on the highway at 55-60.


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## belair (May 24, 2010)

JRP3 said:


> Which is pretty much what Jack is describing. I wonder if he has his throttle parameters set too tightly, can't remember the exact values off hand, but throttle ramp, throttle release rate, etc. Also I think he's using a Kelly throttle like mine, and mine has very stiff springs that do make it a bit hard to control, I plan on changing mine. However that doesn't address his brake only regen drives which also show less efficiency. Supposedly he has it set so the first bit of pedal travel is regen only, so that's a puzzler.


 
Which throttle do you plan to use? The Curtis type with Hall effect is what I have planned but obviously an important piece.


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## JRP3 (Mar 7, 2008)

I used a Kelly 0-5K foot pedal because I didn't have a programmer, I would have preferred a hall effect, especially since I've had to replace the Kelly twice already. I plan on changing the springs out to softer ones if I can find them.


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## bensbarrels (Aug 22, 2010)

Hi Tomo,
im doing a similar conversion but with a toyota corolla.
where did you get your curtis heatsink from?


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## tomofreno (Mar 3, 2009)

Hi Ben,

At www.heatsinkusa.com. Hope it goes well!


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## Jimdear2 (Oct 12, 2008)

Another source 

EeBay search Aluminium Heat Sink

1200 hits on the first page I found this 

http://cgi.ebay.com/Aluminum-Heat-Sink-13-3-4-x-6-3-4-x-1-1-2-/350385473628?pt=LH_DefaultDomain_0

good luck
Jim


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## tomofreno (Mar 3, 2009)

Since this thread has been revived, I thought I would post about a throttle problem. It appears my PB6 is on its way out. I can't describe it any better than this guy did on EVDL:

"I am trying to find out if anyone has had any luck in finding potentiometers that do not degrade with heavy use. I have tried the Curtis PB-6, a Chinese copy of the PB-6, and the Logisystem potboxes. All have suffered from the same degradation over time and last no more than 6-8 months in heavy city and suburban driving (about 100 miles a week in stop and go traffic). The Logisystems potbox lasted only 2 months, the Curtis about 8 months, and the Chinese copy has been in for 6 months and showing signs of degradation. Initially all the potentiometers have a steady increase in resistance with the movement of the arm. However, the pots become progressively “jumpy,” making driving difficult. I have measured the resistance and find that any small movement of the arm makes the resistance go up much higher for second and then come down to what it should be. For example, if I have the arm in a position that provides 1000 Ohms of resistance and move it just a few degrees the resistance jumps to 2500 Ohms before coming back down to 1200 Ohms. This type of jump occurs at any setting of the arm and is not related to the controller. I have measured this jump when the pot boxes are disconnected from the controller as well."

Also, this is the same type of symptoms described for a faulty tps, and it is said that it significantly increases fuel consumption, as you would expect since it is continually modulating the vehicle's energy.

Anyone found a better solution than the variable resistor potboxes? Not sure I can use a Hall Effect type on my Curtis 1238-7501 controller, and if I can, I would have to supply 5V to it.

The PB6 has been slowly getting worse over the last few weeks. I will have to replace it soon as it is starting to be more and more jumpy. It has a bit over 8 months on it - same as the guy above says.


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## GizmoEV (Nov 28, 2009)

Have you tried to do something like this: http://picasaweb.google.com/lh/photo/sby8m0mJDgKUTfUMTvYoVA?feat=directlink

I thought Evenetics had a throttle too but I can't find it.


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## bensbarrels (Aug 22, 2010)

Hi tomo,
Thanks for the reply.
Regarding the throttle, Im going to use a Hall effect throttle, and will last for ever!! as there are no mechanical wear, except the hinge ofcourse. 

A local mob around my way makes the hall effect boxes, here is the web site, http://www.evworks.com.au/index.php?category=4
these guys are just up the road from me here in Perth (Australia).
all you will need to do is program your Curtis for this style of throttle and away you go.

I deal with allot of industrial remotes and industry is heading this way because of reliability.


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## bensbarrels (Aug 22, 2010)

Tomo,
regarding the 5V supply, its realy easy to find a 1A 12 to 5V regulator, about $12AU. 
youy can get them in a 3 pin configuration, so GND +12V and then 5v out to the hall sensor. just heat shrink and cable tie where convenient.


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## JRP3 (Mar 7, 2008)

I'm on my third Kelly pot, same problems, makes the car rather jerky to drive, ohm readings go up and then drop down a bit. Meanwhile the $30. trigger throttle on the AMPhibian is still going strong after two years. It certainly doesn't see as much use as a normal throttle but I've used it as a replacement each time the Kelly has gone bad and I've probably used it as much as the three Kellys.
EVnetics does make a throttle using a good auto TPS. Unfortunately all of the TPS's I've seen don't use a male shaft so you can't use one to replace the one in the PB6.
The Curtis manual says a hall effect will work if you reprogram it, and I'm considering it.


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## tomofreno (Mar 3, 2009)

> The Curtis manual says a hall effect will work if you reprogram it, and I'm considering it.


 Are you referring to the "wig wag" throttle type4? The Hall Effect from evworks would bolt right in to replace my PB6. Just have to figure out how to set it up/re-program the controller.


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## JRP3 (Mar 7, 2008)

That's what I was thinking of, but looking at the description again it looks as if it reverses the motor below a value of 2.5 volts, if I understand it correctly:


> Type 4 throttles operate in wigwag style, and are appropriate only for the
> drive throttle. No signals to the controller’s forward and reverse inputs are
> required; the direction is determined by the wiper input value. Only 0–5V
> voltage sources and 3-wire potentiometers can be used as Type 4 throttles. The
> ...


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## tomofreno (Mar 3, 2009)

Oh, maybe you are referring to throttle type 2:

"Throttle Type 2
With these throttles, the controller looks for a voltage signal at the wiper input.
Zero throttle request corresponds to 0 V and full throttle request to 5 V. A variety
of devices can be used with this throttle input type, including voltage sources,
current sources, 3-wire pots, and electronic throttles. The wiring for each is
slightly different, as shown in Figure 5, and they have varying levels of throttle
fault protection.
When a voltage source is used as a throttle, it is the responsibility of the
OEM to provide appropriate throttle fault detection. For ground-referenced
0–5V throttles, the controller will detect open breaks in the wiper input but
cannot provide full throttle fault protection."

Not sure about the "full throttle fault protection."


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## JRP3 (Mar 7, 2008)

Actually I think type 2 might be the correct setting:


> With these throttles, the controller looks for a voltage signal at the wiper input.
> Zero throttle request corresponds to 0 V and full throttle request to 5 V. A variety
> of devices can be used with this throttle input type, including voltage sources,
> current sources, 3-wire pots, and electronic throttles. The wiring for each is
> ...


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## JRP3 (Mar 7, 2008)

Ha, we're cross posting


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## tomofreno (Mar 3, 2009)

Hi Bensbarrels,

Thanks for the tips on the throttle and 5V regulator. Now I need to determine what Curtis means by "appropriate throttle fault protection."


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## tomofreno (Mar 3, 2009)

> Ha, we're cross posting


 Yeah, if you look at the schematic just below this text in the manual, the one on the left shows a "sensor". Looks like you need a 5V source to the Hall Effect sensor, ground to pin 7 and the variable voltage output of the sensor to pin 16 on the controller. This gives you the same variable voltage signal into pin16 that the wiper on a throttle pot gives. Need to figure out throttle fault protection though.


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## bensbarrels (Aug 22, 2010)

Tomo,
There are many ways to protect yourself from the Prius (full throttle) fault! 
I have seen the following combinations,
dual pot
dual pot plus pedal switch
single pot plus pedal switch
single pot plus 2 pedal switches
CAN throttle

I think we need a solution that does not need a processor to sort the logic out, most of the above will need some sort of ECU.
I think the simplest would be a pedal switch that is actuated when throttle is asserted. This means on a fault and full throttle is asserted, the operator just simply removes his foot from the pedal and the switch cuts the throttle input.
I think this would significantly reduce the probability of an accident happening.


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## JRP3 (Mar 7, 2008)

Yes I assume all you need is something that switches off the 5V. A brake light switch on the pedal would probably work, maybe another toggle switch on the dash for backup.


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## tomofreno (Mar 3, 2009)

> Yes I assume all you need is something that switches off the 5V.


 Why not use a microswitch on the throttle similar to the "deadman" switch on the PB6? The latter is connected between 12V (pin 25) and pin9 on the controller, which is labeled "interlock". Could use the same 12V for input through the microswitch to the 5V regulator chip mounted in a box next to the throttle - as long as it is low enough current draw. The microswitch would open when the throttle is released. I like the idea of a dash mounted switch in series with this as a backup. That way if the pedal sticks down, you can switch it off (provided you can think that well in a panic).


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## tomofreno (Mar 3, 2009)

The Hall Effect throttle sold by EVWorks has a microswitch on it which can be configured N.O. or N.C. Looks like pin 7 (ground) on the Curtis controller is only used by the motor encoder. Probably can tap into this wire at the controller connector for the Hall throttle ground. A wire from pin 16 is already there connected to the present throttle. Could just clip the wire from the present throttle to pin 18 at the controller connector, and connect it to the wire to pin 7. Then no need to run new wires from controller to throttle through the harness. Need to find one of those 5V regulator chips. I can pick up 12V for it from the red wire to the microswitch on the present throttle. Looks pretty easy since the EVWorks throttle is a bolt-in replacement for the present PB6, and all the wires I need are already there at the controller, except for the emergency off dash switch. Anything I am missing?

Oh, I also found a Honeywell conductive plastic rotary pot in the Mouser catalog (pg 694) that states lifetime as 100,000 cycles. Cost is about $11.00. There is another Honeywell "economical" conductive plastic pot that lists electric vehicles for one of its applications for about $7.00, but only 25,000 cycles. Might be easiest to buy a few of the $11 pots if they really last 100k cycles.


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## JRP3 (Mar 7, 2008)

Are those pots the same degree of rotation as the Curtis, or would you need to get a higher value and only use part of the throw?


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## Dave Koller (Nov 15, 2008)

tomofreno said:


> Oh, I also found a Honeywell conductive plastic rotary pot in the Mouser catalog (pg 694) that states lifetime as 100,000 cycles. Cost is about $11.00. There is another Honeywell "economical" conductive plastic pot that lists electric vehicles for one of its applications for about $7.00, but only 25,000 cycles. Might be easiest to buy a few of the $11 pots if they really last 100k cycles.


Pay $25 and get "military grade" or at least "industrial grade" ...
JRP3 is right, the throw is about 270 degrees.... so gearing or using less of higher value pot may work or dual pulley with aircraft cable/clock spring as in a "string" pot....


http://www.diyelectriccar.com/forums/showpost.php?p=154862&postcount=13

(above edit - I knew we had talked about this before!!)


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## tomofreno (Mar 3, 2009)

> Are those pots the same degree of rotation as the Curtis, or would you need to get a higher value and only use part of the throw?


 It is a Honeywell/Clarion industrial potentiometer with 312 degree rotation. My PB6 appears to be about 45 degree rotation, so a 25k pot would give me about 3.6V (edit: 2.6V). The max throttle voltage setting in the controller software is 3.5V, which agrees well with this, so I think that is what is used. Honeywell part number is 380C325K with 22.23 mm long shaft, which looks about right. I would still like to use the EVWorks Hall Effect throttle, but I ordered one of these pots anyway just in case mine starts getting really squirrely. It may take me a bit longer to get an EVWorks installed since I am still going over details. Do you have any experience with Hall Effect throttle installation Dave?


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## tomofreno (Mar 3, 2009)

I just received this response from HPEVS on a Hall Effect throttle:

" For a hall style throttle you will use pin 26 for your 5 volt supply, pin 7 for ground & pin 16 for your input to the controller. You will use Throttle Type 2 with this set up."

Both pins 7 and 26 are used by the motor encoder, so could tap into those wires at the connector on the controller.


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## Dave Koller (Nov 15, 2008)

tomofreno said:


> Do you have any experience with Hall Effect throttle installation Dave?


I tried an experiment with Arduino micro and input voltage from a Hall Effect thru the processor and out a Digital to analog circuit, smoothed out the steps with a filter it worked BUT I am not sure of the current rating on some controllers - at the low end... Just sort of a test... But it did seem to work. I also played with inline linear pots used in robotics BUT THEY are expensive but take a beating - you can get them in different throw lengths and Ohms...

I wondered how a light dependent resistor in a slide tube with a constant current led light source would do - sort of an trombone effect lol.. BUT no wipers to grit or wear out ,,, but output to leds change too over time - 

even a circle with a varying slit and light source to light dependent resistor ..
I know CDS deteriorates over time - so I am leary of them....

There was something else beside the "string" pots but I gotta run have a XC running meet tomorrow with all the kids - I have about 50 out - so I need to get some roster stuff out of the way


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## JRP3 (Mar 7, 2008)

I was wondering if changing the Forward Max setting in the Curtis might smooth out your throttle. I think it's set at 3.5 for full throttle, if you set it to 4.5 or so you'd get a longer throw of the pot and might be using more of a different section on it.


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## tomofreno (Mar 3, 2009)

> I was wondering if changing the Forward Max setting in the Curtis might smooth out your throttle. I think it's set at 3.5 for full throttle, if you set it to 4.5 or so you'd get a longer throw of the pot and might be using more of a different section on it.


 Well, I don't know what voltage corresponds to full throttle position now. I assumed that 3.5V was full throttle. I measured full throttle resistance at 4.84kV, so with the above assumption, 45 degree rotation of a 312 degree 25kOhm pot would give me about 2.6V full throttle, so I thought I could use that and reset max voltage. The other choice would have been a 50k pot, which would give too high voltage. If full throttle is actually something like 4 or 5V I could do as you say, or maybe I could set max voltage lower now so I use less of the pot. I may try some different max throttle voltage settings and see what it does. But I'll have an EVWorks Hall Effect throttle in another week or so.


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## tomofreno (Mar 3, 2009)

Been a while. I had to send my charger back for repair, so I took the opportunity to replace my PB6 throttle pot, which had been jumpy during the hotter summer weather, with a Hall Effect throttle from evworks which is a bolt-in replacement for a PB6 - also can be purchased here I later found: http://shop.transatlanticelectricconversions.com/main.sc
I connected the throttle to 5V and I/O ground on the Curtis 1238-7501 controller, and to the minibms main board with a resistive divider per Dimitri’s schematic for Hall throttle connections. The 10k divider pulled down the throttle max output voltage from 4.73V to about 3.45V, so I replaced it with two 100k resistors I happened to have. With these max output is 4.66V. Re-programmed the controller to throttle type 2, and everything works fine, including the half throttle and buzzer alarm from the minibms for an LVC event (simulated by breaking the chain while driving).

Also replaced my anemic heater before winter arrived. I purchased two of these at Lowes for $21.00 each:







They are 1500W heaters, but the element is considerably smaller (Edit: 3.5" wide x 3.9" + terminal length) than the one I had in the car, so I could fit two of them in side by side in place of the original core. I also looked at re-installing the original core, and using two 1500W hot water heaters with pump, thermostat and remote filler cap, similar to what Brian and JRP3 did. I was limited to using 1500W heaters due to a nominal pack voltage of 115V (larger wattage heaters are 240V). So I figured 3kW heat generated inside the car is better than 3kW generated outside in the cold under the hood and pumped in with losses, and it is also cheaper.

I made a holder for the two heaters, with them insulated from each other (that thin white strip down the center), out of Teflon (working temperature of 500 F):








And inserted into the heater housing in place of the original core:















Using two has the added advantage of larger area and more air flow through them compared to the former single ceramic heater element.

Before installing I measured output of one heater plugged into the wall with its fan on “high” as 1460W. Resistance of the two heaters in parallel was 11 Ohm at room temperature of about 85 F, and after heating with a heat gun briefly, 5 Ohm. The typical U-shaped curve for resistance versus temperature, which is nice, since the higher resistance of the “cold” heater limits the initial surge current. 

After installing the heater and putting everything back together I tested the heat output. Boy, I have heat now! I measured current into the heaters with an Extek EX830 meter. The pack was at about 44% SOC, and 116V. With blower on high: 27.2A, 116V, 3155W, blower on medium: 26.2A, 116V, 3039W, blower on low: 24.8A, 116V, 2877W! Don’t know how this will affect the life of my P&B relay which is rated for only 20A, 120VDC, but expect reduced life. I am using 30A slow blow fuses, so should be ok, but may have to upgrade to automotive type fuses of higher value. I would appreciate a link if anyone knows of a more beefy relay or small contactor (space limited). Will be interesting to see how well it works when it is 15 – 20F outside. At 26A, that’s 26Ah/hr, so will decrease my range around 30% or so if left on constantly. I will still preheat the car first with a normal ceramic heater before leaving the garage, then expect I will run the heater for 10 minutes or so, turn it off but leave the blower on ‘till the heater cools, and turn the heater back on when I get cold, so I expect maybe a 15% hit in range.

Also re-programmed the _Gear_Soften_ parameter from 15% to 5%, and it made a big difference in acceleration. The higher this parameter, the more slowly torque is increased initially, kind of like slipping the clutch, or an ICE revving up. At 5% the max torque is immediate, more like a series DC motor. Felt like being shot out of a slingshot in first gear compared to how it behaved before. I think this is likely why I didn't quite get the 0-60 mph time Maxvtol's spreadsheet predicted. Now when I punch the throttle, the car jumps.


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## maxvtol (Nov 11, 2009)

Nice work Tom. 

On the relay, if you have heaters in parallel, do you have enough room to add another similar relay, split up the amps?

If not, maybe under the Power Relay section http://relays.tycoelectronics.com/pnb.asp . Looks like the ones we use in HVAC. Automotive or marine type relays might be smaller, but not too familiar with those. 

Cool to know on the acceleration. Rickard's numbers were similar on my spreadsheet with his Speedster DUH, but don't know why his was faster with taller gearing than a lighter Spyder with the exact same motor and battery setup. Let me know if you ever run any acceleration times.


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## JRP3 (Mar 7, 2008)

Nice job on the heater install. Do you have room for one of the short Kilovac 200 contactors?
Hear anything from Rich on the charger status? I was wondering if you ever shut down the charger when it was still hot, I try to leave mine running on zero amps for a bit to cool it down, don't know if it makes any difference or not.


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## tomofreno (Mar 3, 2009)

> On the relay, if you have heaters in parallel, do you have enough room to add another similar relay, split up the amps?


 No, but I think I may have room for the P30 in the link you gave. Thanks!


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## tomofreno (Mar 3, 2009)

> Nice job on the heater install. Do you have room for one of the short Kilovac 200 contactors?


 I would rather use a DPST to disconnect both pos and neg connections as the present P&B relay.



> Hear anything from Rich on the charger status?


 Yeah, rather embarrassing. It was the charger relay. Rich said only one side was tripped so it had to be pushed harder than normal to reset it. He just pushed hard to fix it or break it and replace it. I thought it looked higher than normal, and applied what I thought was the force I normally apply to reset a tripped breaker, but didn't want to push too hard for fear of breaking it. I don't know why one side tripped.


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## JRP3 (Mar 7, 2008)

Oops.....


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## Coulomb (Apr 22, 2009)

tomofreno said:


> No, but I think I may have room for the P30 in the link you gave. Thanks!


I don't think that those relays are rated for switching DC. You need DC rated contacts. Interrupting 20 ADC at 120 VDC or so is really hard on contacts.

For example, the T92 series, which mentions DC in the title, has

40A @ 277VAC, resistive; 6K Ops. (Flange Mount);
30A @ 120/277VAC, resistive;
10A @ 600VAC, resistive;
1 HP @ 120VAC, 3 HP @ 240VAC;1.5 HP @ 480VAC, 1.5 HP @ 600VAC
110 LRA, 25.3 FLA, @ 240VAC with DC coil(1);
60 LRA, 14 FLA @ 240VAC with AC coil;
3A @ 240VAC pilot duty;
20A @ 28VDC;

So you need something a lot stronger than one capable of 30 A @ 277 VAC. Possibly with magnetic blowouts.


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## tomofreno (Mar 3, 2009)

> Possibly with magnetic blowouts.


 Yeah, I've been trying to find something with that. I found one on the Curtis website, and asked Wistar (kta-ev) if he could order it, but he wasn't able to find anyone at Curtis familiar with that relay, or who could even locate one. Strange. I may do what another ev'er here did - made his own by adding a magnet to a relay like the P&B I have. He is switching 156V with it for his 2400W heater and said it arced like crazy before he added the magnet, but now doesn't arc at all. I may see him tomorrow at an EVent, if so I'll find out where he got the magnet. Just need the right magnitude B field parallel to the contacts so the electrons precess around the field lines out to the side.


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## gdirwin (Apr 7, 2009)

Quick question on your heater install - how do you control the SSR relays?

I have been struggling with the best way to do this... See thread here about using a PWM controller to get a variable output (instead of on/off control):
http://www.diyelectriccar.com/forums/showpost.php?p=203978&postcount=24


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## tomofreno (Mar 3, 2009)

> Quick question on your heater install - how do you control the SSR relays?


 I am not using any solid state relays. I use a Potter & Brumfield mechanical relay purchased from kta-ev, 120VDC/20A. It is simple on/off. There is only slight variation in heat with blower setting. I don't expect I'll need more control than that, as I can just cycle it on/off to control cabin temperature. My problem last winter was not getting enough heat. Have you found an ssr that will switch 30ADC at 120VDC with 12VDC control?


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## tomofreno (Mar 3, 2009)

I found some 250V/25A DC SPST N.O. Omron relays that are only 2.36" long, 2.28" high, and 1" wide:
http://www.omron.com/ecb/products/dry/3/g9eb-1.html
I could fit two of these in place of the P&B relay I am currently using. I would be slightly over the current rating at 26-27A, but at less than half the voltage rating, so would be ok if heat dissipation is the limiting factor. What do you think?


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## JRP3 (Mar 7, 2008)

Is heat dissipation the limit or breaking the arc? In either case I'd think the lower voltage would keep you in spec.


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## maxvtol (Nov 11, 2009)

We always used the amp rating to pick a contactor/relay as long as the voltage rating was high enough (but would it be the same for DC?)

If you're using 2 relays, wouldn't that be ~3kw/120v/2=12.5amps for a parallel circuit? I would think that would be plenty.


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## Coulomb (Apr 22, 2009)

maxvtol said:


> If you're using 2 relays, wouldn't that be ~3kw/120v/2=12.5amps for a parallel circuit? I would think that would be plenty.


Well, it might be if he was wiring the two relays in parallel to share the current. But I believe he wants to switch both legs, effectively putting the relays in series, so that when the relays are off, there is nothing in the cabin that connects to either end of the pack. I can understand that desire.

But even there, paralleling the contacts... I think the contacts will disconnect at slightly different times, so the last one to break will carry all the current anyway.

Same thing with the contacts effectively in series; one will break first, do all the hard work, and the other will have no current to interrupt. Maybe there will be a time when there is an arc across both contacts, so the energy of the arc is shared between them, making it easier for the pair to break the current.

Tricky things, are DC contacts.


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## maxvtol (Nov 11, 2009)

I thought it was 1 relay for each heater 1.5kw each, maybe I just misunderstood.


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## tomofreno (Mar 3, 2009)

> But I believe he wants to switch both legs, effectively putting the relays in series, so that when the relays are off, there is nothing in the cabin that connects to either end of the pack.


 Correct, so as you say one or the other will break the circuit first. But do these sealed gas-filled relays arc? I don't know, but guessed they filled them with an electronegative gas like SF6 to snuff arcs (same as used in large transformers). I wondered what limits the rating, heat dissipation or arcing? If the latter, seems that would depend more on voltage, and an 8% increase in current wouldn't make much difference.


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## tomofreno (Mar 3, 2009)

Gdirwin gave links to two ssrs that should work well for much lower cost than the Omron relay in post#27 here:
http://www.diyelectriccar.com/forums/showthread.php/pwm-controller-ceramic-heatersi-39023p3.html


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## resago (Sep 28, 2010)

tomofreno said:


> Yes, I could do something like this which would give some warning, if not precise, and I will if I can't get it done through VCL. The VCL would be better as it should put out a signal whenever neutral braking is applied. I also contacted tech support at Curtis to see how this can be done. I generally don't drive in heavy traffic, and most of the time there is no one close behind me when I stop, so it hasn't been a pressing issue so to speak. If I were ordering an 1238-7501 now though, I would ask to have this in the VCL code and wiring harness.


i know i am responding to an old post, but.

it would be a simple program change to make the brake light relay come on for anything over 50AMP regen. this is really what you want. brake light needs to be a function of stopping, not throttle position or slight regen.


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## tomofreno (Mar 3, 2009)

> it would be a simple program change to make the brake light relay come on for anything over 50AMP regen. this is really what you want. brake light needs to be a function of stopping, not throttle position or slight regen.


 Right now there is no brake light relay, just a switch that works off the brake pedal. I could put a relay in parallel with this switch to the brake lights. What lines of VCL code would you add, and where in the code?


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## tomofreno (Mar 3, 2009)

This is some data on battery pack voltage, current, and charge as a function of time during a 58 mile test run over varying terrain and speeds. The battery pack parameters were datalogged using the "communications" kit for the TBS gauge and a laptop. The altitude and vehicle speed were recorded with a gps datalogger. 

The first ~ half of the run was mostly on secondary streets with multiple stop signs, and one fairly good hill. I live between two mountain ranges, so regularly go up much higher, but this is typical of driving around in the valley. The second ~ half is driving on the main highway down through the valley, with gently rolling terrain. 

Regen spikes (positive current) are due to slowing due to a vehicle in front of me, slowing for a turn or curve, entering a lower speed zone, or stopping for a stop sign (can see these best on the speed graph), more extended ones are when going downhill. Negative current spikes are acceleration from a stop, traffic pace picking up, entering a higher speed zone, passing another vehicle, or change in grade. The power graph is just a plot of the product of pack voltage and current. 

The route was a closed path, so net altitude change of zero. I tried to maintain current of 200A (fairly typical traffic acceleration rate) or less during acceleration for consistency, but went to 300A on one where I got tired of waiting and had to accelerate faster to pull out into traffic. It is very difficult to hold the current steady during acceleration as it increases as vehicle speed and motor rpm increase. As a result the current fluctuates as I keep trying to ease the throttle to stay around 200A, then ease off further to maintain contant speed. This, coupled with almost constant small variations in grade, and some traffic speed variation, result in the noisy current and voltage.

View attachment testrun1, voltage.pdf


View attachment testrun1, current.pdf


View attachment testrun1,battpower.pdf


View attachment testrun1, charge.pdf


View attachment testrun1, altitude.pdf


View attachment testrun1, speed.pdf


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## major (Apr 4, 2008)

tomofreno said:


> This is some data on battery pack voltage, current, and charge as a function of time during a 58 mile test run over varying terrain and speeds.


That is really nice data. Good regen also. I wonder if you could take a spreadsheet of the current or charge and integrate the regen charge and see as a percentage of total charge used for the entire cycle. I just wonder if that would be like 3% of Ahr returned to the battery or 10%. 

major


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## resago (Sep 28, 2010)

I notice your voltage never went above 124V, ever though about adding another battery?

Whats the current effective range?


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## tomofreno (Mar 3, 2009)

> I wonder if you could take a spreadsheet of the current or charge and integrate the regen charge and see as a percentage of total charge used for the entire cycle. I just wonder if that would be like 3% of Ahr returned to the battery or 10%.


The data was saved as csv files and imported into Excel, so yes I can do that. Sample rate was one data point per second for the battery data, so assuming each value of current measured was the value for about 1 second, summing all the positive values gives the charge put into the pack in A-sec. Similarly summing all the negative values gives the charge discharged from the pack in A-sec. Dividing by 3600 sec/hr converts these to Ahr. I did this and got 101.316 Ah discharged, and 10.058 Ah regen'ed into the pack. The difference is 91.26 Ah, which agrees well with the final Ahr used reading of 91.3 Ah. The regen as a percentage of the charge discharged from the pack is then 9.93%. Multiplying each of these charge columns by the voltage column gives 11571 Wh discharged, and 1199 Wh regen'ed into the pack, and percentage 10.4%, due to the higher pack voltage during regen.

I should add: I used 204.8 Wh/mile (energy measured by EKM meter on AC input to the charger) from the wall for the above 58 mile run. If I assume about 94% charger efficiency, that is about 193 Wh/mile.


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## tomofreno (Mar 3, 2009)

> I notice your voltage never went above 124V, ever though about adding another battery?


 No. You never did answer my question on how to add software to turn on the brake lights.


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## major (Apr 4, 2008)

tomofreno said:


> The regen as a percentage of the charge discharged from the pack is then 9.93%.


Cool  A little higher than I would have guessed. Nice to see real data.


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## maxvtol (Nov 11, 2009)

I wonder if you plotted voltage drop vs amps (or C probably better) at certain DOD you could start to see how the batteries are holding up over time. If you could somehow keep track of # of cycles at an average DOD that would be cool, too. If the plot looked linear over time, maybe you could tell what the useful life of the batteries would be. 

I noticed the voltage drop on the AGMs on my e-bike at 1C and 2C at around 50% DOD is really starting to drop more (after about 1.5 years of use). I would think the same principle may apply to Lithiums.


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## resago (Sep 28, 2010)

sorry, I'm not familiar with the language curtis uses, I am a programmer though. It would take all of 30 seconds for curits to add the code, since they are already estimating the amps out and can activate an unused pin for a light.


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## tomofreno (Mar 3, 2009)

> sorry, I'm not familiar with the language curtis uses, I am a programmer though.


 That is the problem. Sure it is simple if you are familiar with the code, and there are DO's available to use. But I am not. I asked HPEVS to do it maybe 8 months or so ago. They recently said they are "completely redoing" the software, and this will be in it. Btw, the reason I don't add another cell is it doesn't seem worth it to gain 4% more range (3 miles or less beyond the present about 75 at 35% DoD).


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## JRP3 (Mar 7, 2008)

I'm actually going to try adding a cell, not so much for the range, but to keep the voltage higher during acceleration. I'll have to use the brakes more when the pack is cold to avoid overvolting, but once they start salting the roads here I won't be driving it anyway. Since you have larger cells you'll see less voltage rise on regen so you probably won't have any problems with overvoltage.


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## GizmoEV (Nov 28, 2009)

JRP3, do you really regen that much to put more in than you take out to get to your first point of regen? Even when I used to charge to 4vpc the voltage always dropped to 3.35vpc or lower by time I reached 25mph and never went back over about 3.4vpc even with over 100A regen current. I'll be surprised if you have to worry about it unless you live up a long steep hill.


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## tomofreno (Mar 3, 2009)

> Cool  A little higher than I would have guessed. Nice to see real data.


 Well, all I would have to do is drive up hill faster and the percentage would drop. I drove at the posted speed limits or a bit above. But as you know, regen as a percentage can vary all over depending on the terrain, number of stops, how fast you drive...I would say around 10% is pretty typical for me. I think I typically get back around 15-25% what it took to go up a hill when I come back down - but haven't checked that yet with data logging, just watched Ah used. HPEVS said the AC50 was optimized for running torque. It is not a very good generator.


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## tomofreno (Mar 3, 2009)

> I'm actually going to try adding a cell, not so much for the range, but to keep the voltage higher during acceleration.


 Do you think it will make that much difference? 3.2/115 = 2.8% How much sag do you get at 300A - or are you pulling 400A from those 100Ah cells?


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## JRP3 (Mar 7, 2008)

GizmoEV said:


> JRP3, do you really regen that much to put more in than you take out to get to your first point of regen? Even when I used to charge to 4vpc the voltage always dropped to 3.35vpc or lower by time I reached 25mph and never went back over about 3.4vpc even with over 100A regen current. I'll be surprised if you have to worry about it unless you live up a long steep hill.


I have many long steep hills and routinely push the cells to 3.5 in the morning on a cold day, sometimes 3.55 which is 128 volts. I can push over 200 amps for a few seconds which is 2C for my 100 amp cells, you get some voltage rise with that.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Do you think it will make that much difference? 3.2/115 = 2.8% How much sag do you get at 300A - or are you pulling 400A from those 100Ah cells?


Who, me?  Sometimes I pull 550amps  But even in normal driving as it gets colder the voltage sags more so I pull more amps to get the same power. You're right it won't be much but I feel like experimenting. I'm actually going to play with 2 more cells to see how that affects acceleration but I don't expect to be able to keep them both hooked up. Might look into adjustable regen, it would be neat to vary regen according to voltage to keep me under the cutoff.


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## GizmoEV (Nov 28, 2009)

JRP3 said:


> I have many long steep hills and routinely push the cells to 3.5 in the morning on a cold day, sometimes 3.55 which is 128 volts. I can push over 200 amps for a few seconds which is 2C for my 100 amp cells, you get some voltage rise with that.


I have buddy paired 100Ah cells so I'm only doing 0.5C which might explain my low voltage rise. With less than 1000lbs to slow down I don't have much stored energy compared to your car.

I've read that as the temperature drops the ending voltage is supposed to be increased similarly to what is done with lead-acid batteries. I'm wondering if the 3.55vpc terminal voltage is actually lower in the cell. Are you at the limit of your controller voltage? On my Sevcon the regen will back off when it reaches a high voltage point and will cut off all together if necessary to keep the batteries from going over the max voltage set point. Maybe you controller has such a setting.


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## JRP3 (Mar 7, 2008)

Controller limit is supposed to be somewhere around 130 volts, I don't know if it will try to limit regen if it gets too high but I don't think so. I've had a few controller shutdowns but I'm not convinced they are from high voltage. I think for some reason the main contactor opens up which then causes a voltage spike and gives a high voltage error, but pack voltage has not been out of range when this happens.


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## tomofreno (Mar 3, 2009)

The Swift recently passed the one year mark:

Total EV miles: 7471
Total kWh from wall (EKM meter): 1615
Wh/mile: 216, from wall
Maximum distance driven between charges: 75.1 miles, about 2/3 at lower speeds so only 64% DoD.

Roughly half of total miles were driven at 50-60 mph, half at 30-40 mph. Maybe 1/4 of trips with bike on back and mostly highway driving (higher drag).

Recently changed motor max speed to 8000 rpm from factory setting of 6500 (HPEVS said no problem, just increased the value in my software). I used to hit 6500 rpm at about 30 mph in first, 58 mph in second, and feel the car drag as the controller limited current. Now can go to about 38 mph in first and 70 mph in second gear. Two results from this: (1) Now do almost all driving, including on highway at 60-65 mph in second, only use first for fast acceleration, (2) better acceleration since now can accelerate to over 30 mph in first gear putting me further up in the power band for second gear. I Get stronger pulling all the way to 70 mph as a result. 

Also changed the Gear_Soften parameter to 0% to get linear acceleration (Adjusts the throttle take-up from linear, 0% setting, to an S curve. Larger values create softer throttle take-up.) Was at 1.0 from factory, changed to 0.4 a while back, so not a huge change.

Also changed the Acceleration_Rate parameter to 0.2 seconds (sets the rate, in seconds, at which the motor torque increases to full when full throttle is applied). Was at 0.5.

Definitely more peppy acceleration with these changes - 8k rpm had the largest effect. One of these days I will redo the 0 to 60 mph time with datalogging to check improvement. Expect it will match Maxtvol's spreadsheet value well now (about 15 seconds if I recall correctly).

I now drive more in first gear, and noticed that going up the hill to my house now at 25-30 mph in first gear (25 mph speed limit) both green LEDs are lit on the Curtis gauge indicating good efficiency, whereas before in second gear only one would be lit. 

The CALB cells are still behaving well. I have not balanced the original 32 cells which remain closely matched, and last balanced the 4 replacement cells in early August/2010. They are staying at about 0.02 - 0.025V lower than the other cells (Edit: at about 63% DoD).


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Total Wh from wall (EKM meter): 1615


Either you've had a breakthrough in efficiency or that's a typo. 
Interesting that you still have good power above 6500RPM in second for highway cruising. My AC31 might do 75 in second with higher RPM but probably not up a decent hill. I'll have to wait until the snow and salt are gone around here to try it. By then the higher voltage higher amp Curtis may even be out. I do wonder how our transmissions will hold up constantly running at higher RPM's, I guess we'll find out.


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## tomofreno (Mar 3, 2009)

> Either you've had a breakthrough in efficiency or that's a typo.


 Its the new magnetic levitation. Thanks, will edit that.
Yeah, I've wondered about the transmission...the original ice had max power at 6k rpm though, so I hope I'm not pushing it too much if I stay under 7.5k, which permits me to go up to 65 mph in second. Maybe it wasn't designed to handle such a high duty cycle at that rpm though. Will find out as you say. 

I drive a stretch of highway frequently that has 50 mph limit, but most drive 55-60. I drive about 55 to pace traffic, which is about 6300 rpm, so it was always a pain watching the rpm so I didn't creep over 6500. Nice to not have to do that now. That was my main motivation for changing it. The strong acceleration up through 30 mph in first is a bonus. It used to die as low as just over 25 mph as the controller cut back current as it approached the 6500 rpm limit - and the faster I accelerated the lower the rpm the controller would start limiting, as low as 5900 rpm. Didn't see that effect in higher gears. I guess because rpm doesn't climb as fast in those. As a result, I was missing some of the power band in first.


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## tomofreno (Mar 3, 2009)

> My AC31 might do 75 in second with higher RPM but probably not up a decent hill.


 There will be a difference in power at higher rpm between the AC50 and AC31 due to the difference in base speeds - 1800 vs 3000 with 96V. I had no problem passing someone on the highway accelerating from about 55 to 67 mph in second. I backed off on the accelerator at that point when I saw rpm at over 7800.


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## maxvtol (Nov 11, 2009)

JRP3 said:


> I do wonder how our transmissions will hold up constantly running at higher RPM's, I guess we'll find out.


When we estimated the fatigue life of the gear teeth, the face velocity of the gear does come into play. If they are heafty enough, it shouldn't be too much of a problem. But I don't know that I would run them up into the redline too much. The gears probably weren't designed to take a lot more than the original engine could dish out, and still last. If you're using thinner oil in the transmission, that won't be real helpful at higher rpm.


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## tomofreno (Mar 3, 2009)

> If you're using thinner oil in the transmission, that won't be real helpful at higher rpm.


 I'm using Mobil 1 LS 75W-90 Synthetic Gear Lubricant. Although max power of the original ice was at 6k rpm, it wouldn't have been driven at that rpm often. Hmmm, maybe I better not make a habit of driving around at 6 - 7k rpm in second. It does have higher wheel torque in third above about 45 mph, but the motor runs cooler in second at higher rpm. The motor never did get all that hot, so not really a good reason to drive there. But then, I wonder about all the conversions done using Azure Dynamics motors that operate to even higher rpm.


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## maxvtol (Nov 11, 2009)

tomofreno said:


> But then, I wonder about all the conversions done using Azure Dynamics motors that operate to even higher rpm.


Yeah, it may not be an issue. Load is another factor on fatigue life, so it balances velocity to a point, but there is a limit to speed. Some of those transmissions are built unbelievably tough.

Just seems engines, motors, etc I'm familiar with, that are built to last, spin at less than 4k rpm. Guess I would just want to know something is designed to spin faster if I were going run it at high speed for long.


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## Coulomb (Apr 22, 2009)

tomofreno said:


> But then, I wonder about all the conversions done using Azure Dynamics motors that operate to even higher rpm.


Here is one datapoint:



> Incredibly, the old Porsche gearbox survived being driven in first gear (and at up to 12,000 rpm) for no less than 60,000 kilometres!


From The Electric Porsche (Autospeed article).

Maybe first gear is a special case (only designed to run for short periods of time in first?), or maybe it's the 12,000 RPM, or the fact that this is a 150 kW conversion. But 60,000 km (37,500 miles) is not a great lifetime for a gearbox, especially one from a Porsche.

Still, if it comes for free with the donor vehicle, and works for a few years, you can be saving up for that custom gearbox with the dry sump, special lubrication pumps and the six thermocouples (see linked article) while you wear out the original gearbox.


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## MN Driver (Sep 29, 2009)

From my understanding of lubricants. You might be speeding up the shear losses on your lubricant quicker as there is more shear involved based on the amount of times the lubricant gets squeezed between the gears. This isn't really an issue IMHO because it would mean that your fluid would thin out twice as fast at 6000RPM than 3000RPM which would simply be a change in lubricant intervals, run it half as long as you otherwise would. For a more shear stable fluid it might not be too much of an issue. Since heat is typically generated with torque in a transmission the transmission might even run cooler at a faster speed in every place where the speed isn't fixed to the drive wheel speed(such as the differential).

For what it's worth, I couldn't stand synchronizer performance in my 95 Geo Prizm(no longer my daily driver) that uses 75w-90 gear oil when using a synthetic. Tom, I didn't know that the Mobil 1 you are using was even rated for use in anything other than a differential or other purely geared application, do your synchros work well with it?

"It used to die as low as just over 25 mph as the controller cut back current as it approached the 6500 rpm limit - and the faster I accelerated the lower the rpm the controller would start limiting, as low as 5900 rpm. Didn't see that effect in higher gears. I guess because rpm doesn't climb as fast in those. As a result, I was missing some of the power band in first." Good to hear, I'm sure none of us knew that it was limited right before the cutoff. Was the old 6500RPM cutoff very jerky?

Thanks for sharing your new settings with us.


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## JRP3 (Mar 7, 2008)

Mine is very smooth at the cut off, power just drops as the rpm climbs and you simply can't push it above 6500.


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## Coulomb (Apr 22, 2009)

JRP3 said:


> Mine is very smooth at the cut off, power just drops as the rpm climbs and you simply can't push it above 6500.


Interesting. It looks like the power ramps from 100% to 0% over the range of speeds from about 90% to 100% of the limit parameter. (5900 to 6500 RPM is 600 RPM, about 10% of the 6500 RPM limit).

I guess that's better than ramping from 100% to 0% over 1 or even 10 or possibly 100 RPM; it would be too jerky and unstable near the limit.


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## tomofreno (Mar 3, 2009)

> I didn't know that the Mobil 1 you are using was even rated for use in anything other than a differential or other purely geared application, do your synchros work well with it?


 Yes. I didn't research lubricants, just bought what the guy at Kragen recommended based on the lubricant the Swift manual spec'ed. I may well change to Royal Purple though, as from what I've heard it is used in race cars. Anyone know anything about it?



> Was the old 6500RPM cutoff very jerky?


 No, smooth as JRP3 says. It just feels like something is holding the car back, as acceleration is smoothly, but quickly ceased. I did have it up to over 6700 rpm in second gear without noticeable limiting by the controller, so like I said it doesn't limit the same in second as in first. I would guess that it might be looking at the derivative of rpm as well as rpm value to determine when to start limiting. In second I would approach the 6500 limit quit slowly, just drifting up as I was cruising along, whereas in first I approach it very rapidly during acceleration.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> I may well change to Royal Purple though,


I used royal purple in the tranny when I re-filled. I had to put something in after I pulled the CV loose and a bunch of oil leaked out while I removed the ICE motor. No problems, but I dunno if it is that much better than anything else.


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## tomofreno (Mar 3, 2009)

After a little googling, it appears that Mobil 1, Royal Purple, and Amsoil are all considered very good, so I will likely just leave the Mobil 1 in there.


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## tomofreno (Mar 3, 2009)

Been a while...had to dig down to page 31 to find this.


Two years now since the Swift was converted to an ev.
Total EV miles: 14,617
Total kWh from wall (EKM meter): 3159.81
Wh/mile: 216, from wall


After one year, on 12/5/10 I reported:
Total EV miles: 7471
Total kWh from wall (EKM meter): 1615
Wh/mile: 216, from wall
Here: http://www.diyelectriccar.com/forums/showpost.php?p=215094&postcount=635


So despite upgrading the cabin heater to 3.1kW from about 1kW back in 4/2010, energy/mile has not changed. Probably because the amount of driving I do with the heater on is a small fraction of total miles driven, and I usually only leave it on for 10 minutes or so, then off a while, back on...and on sunny days in the high 30's F or above I don't use it at all, the sun heats the car enough.


I recently logged some cell voltages to see how they were behaving:
View attachment Cell log 8 data, 11.13.11.pdf

I selected this group of 5 because it includes the highest voltage cells as well as one of the lowest. The voltages given are at end of charge while still charging at about 0.5 A gauge reading. I ran the pack down to 30% SoC, then did some accelerations to check relative sag of the cells. All seem to be holding up well, staying up above about 2.85V at 521A or 2.89C discharge.


I had one cell (a replacement of one of the originals) that was at 3.375V on this charge cycle. It has always stayed lower than the other cells. I charged it 35 minutes at 3.8A, or 2.22Ah, to get it to 3.450V. The rest ranged from 3.404V to 3.550V. I bled some higher ones down after this to reduce the spread down to about 0.03V at end of charge. 

I added shunts to the minibms modules some time ago thinking I would top balance the cells and keep them that way by charging until they were all shunting each time, but decided I didn't want to charge my cells up to the 3.5V shunting voltage each time. I don't see much point in worrying about balancing often since that low cell at 3.375V was only 2.2Ah different than the highest cells, and you can see on the cell log data despite a spread of 0.09V at end of charge they all behaved very similar. In fact the voltage spread among them even at the highest discharge current is less than the 0.09V. I think the voltage spread on the exponential part of the curve is not very representative of how cells behave over the rest of their operating region. I would guess there are different internal mechanisms driving that voltage difference on that part of the curve compared to the flat part where they are only partially charged.

The cells have drifted apart a bit. The first year the spread was usually less than 0.01V near end of charge (except for the 4 replacements). I do charge to where the highest 3 to 5 are shunting once in a while, so get a little balancing that way.

No issues with the car over the past year. No down time.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> Two years now since the Swift was converted to an ev.
> Total EV miles: 14,617
> Total kWh from wall (EKM meter): 3159.81
> Wh/mile: 216, from wall
> ...


wow, that is awesome! very interesting to me that your Whr/mile number is significantly better than mine. your AC50 motor/controller must be kicking back in more regen than I would have expected. Last time I let my kill-a-watt meter on the outlet total up kWhr from the wall for a 1000 miles I think my average was around 290 Whr/mile, so your 216 whr/mile at the wall is pretty darn great at showing what you are getting for regen!

My vehicle 're-birthday' is in March, so we'll see how its doing then.... I am loving the Lithium, thats for sure.


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## CroDriver (Jan 8, 2009)

Nice data, thanks for sharing.

How are you logging the current to compare it with the voltages?

Do you calculate the SOC while driving? Or you're just watching the voltages?


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## dtbaker (Jan 5, 2008)

CroDriver said:


> Do you calculate the SOC while driving? Or you're just watching the voltages?



watching voltage won't give you much idea of SOC.... you have to watch amp-hr to figure your DOD. 

I have my cycleAnalyst set to display the net aHr in the default, along with the instantaneous voltage and amps. My cells are 100ah, so its easy to just read the ahr and consider it the direct DOD%. If I had some other size cell I'd have to do math because the CycleAnalyst does not have a bar display for SOC like the evDisplay.


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## JRP3 (Mar 7, 2008)

dtbaker said:


> w your 216 whr/mile at the wall is pretty darn great at showing what you are getting for regen!


There could be other differences that could also be a factor, rolling resistance, driving style, temperatures, etc. I don't know if I'd attribute it all to regen.


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## tomofreno (Mar 3, 2009)

> How are you logging the current to compare it with the voltages?


 With a notebook on my lap and writing down the max current value displayed on the TBS ExpertPro gauge when I accelerate. I have also data logged it with the TBS using the software they sell to do so. I bought the software here: http://evolveelectrics.com/ (scroll down) I think Dimitri now offers output from the EV Display for data logging too, but not certain (EV Display didn't exist in 2009 when I purchased the TBS gauge - even the TBS didn't in the US, had to buy it from evpower in Australia)

Easier to just grab a notebook and watch the gauge if I just want to record max currents.



> Do you calculate the SOC while driving? Or you're just watching the voltages?


 I use the TBS for SoC.

Edit: Btw, TBS is on your side of the pond: http://www.tbs-electronics.nl/ Nice folks too.


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## tomofreno (Mar 3, 2009)

> There could be other differences that could also be a factor, rolling resistance, driving style, temperatures, etc. I don't know if I'd attribute it all to regen.


 Agreed. I'm sure some is due to regen, but no idea how much. I presented data here: http://www.diyelectriccar.com/forums/showpost.php?p=208326&postcount=618 and here: http://www.diyelectriccar.com/forums/showpost.php?p=208464&postcount=621 for what is a fairly typical drive for me, which showed about 10% regen.


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## tomofreno (Mar 3, 2009)

Another year...3 years now since the Swift was converted to an ev.
Total EV miles: 22,456
Total kWh from wall (EKM meter): 4861.89
Wh/mile: 216.5, from the wall, around 200 Wh/mile excluding charger losses, about the same it has been each year.

Only one issue this year. A battery heater failed open circuit this fall. It was the one under the cell group that had the heater controller thermocouple on it, so the rest got heated to around 100 F before I discovered it next morning. No damage done. 

Decided to check and redo all heaters. Made aluminum pans that fit tightly into the boxes against the insulation, with heaters taped to the bottom of the pans under each cell group with aluminum tape. bolted aluminum angle to the top side of the pans to help hold the cell groups in position. Strapped cells down tight, nothing seems to be moving over the last few weeks. Heaters should be ok now without the cell ribs scrubbing on them.

Also added 86 F N.C. thermal switches, one in each battery box, mounted to a cell terminal on a tab. Wired AC supply to heater controller through them. There can be up to 21 F difference in open/close, and operating temperature is only accurate to +/-5F according to documentation. At least one seems to be opening at mid to high 70's and it appears all are not closed until around 70 F, which is fine since I am using a heater controller setpoint of 65 F. When I come home from a longer drive and plug in the heater power there is no power to the heater controller until later that night when the cells have cooled. Next morning they are all right around 65 F. Should be no more overheating if the tc fails or the heater fails again.

No noticeable change in range. Only test I've done is the usual drive to around 28-30% SoC, then floor it to draw 550A (3C) and see if the minibms LVC alarms (threshold 2.8V for 4 seconds). Never has so far.

Other than that just drive, charge, drive, charge...


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## Ziggythewiz (May 16, 2010)

Always good to hear updates after years on the road


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## Zappo (Sep 1, 2011)

Very awesome. Are the batteries still staying pretty well balanced?


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## tomofreno (Mar 3, 2009)

Zappo said:


> Very awesome. Are the batteries still staying pretty well balanced?


 I have had a minibms installed and the charger limit voltage is set so they get about 15 minutes of balancing most charges, so yes they are balanced. 

I ran bottom balanced without a bms for several months back in 2010. Then I added the minibms without shunts for HVC and LVC functions as backup to help prevent over charging or over discharging. After a bit over a year I started seeing some drifting of cell voltages resulting in more spread near end of charge than I had seen prior to that, but not enough to effect range. 

I decided to add shunts, top balance, and do a little balancing most charges. It has worked trouble-free for over 1 1/2 years now, to the point that I no longer check cell voltages with my dvm, just check how many are shunting at end of charge once in a while.

Like I've said here a number of times, you may see some drift after over a year of running if you charge most days, but likely not enough to effect range, and detectable only on the exponential part of the charge curve or discharge curve. I think you can run any of the above 3 ways without issues for a while with differing amounts of care. Not sure what happens after many years operation. 

I've verified many times by measurement that my 180Ah cells can differ in SoC by 2 or 3 Ah and differ in voltage no more than 1 or 2 mV on the rest of the charge/discharge curve. That SoC difference is not enough to effect range significantly, but that is the scale of difference most people with top balanced packs are talking about when they say their cells are out of balance - probably less than 1Ah in many cases. 

I think a good part of the divergence in cell voltages once they are on the exponential part of the curve is due to differences in internal resistance due to scarcity of sites for intercalation at that point of cell SoC, which differs from cell to cell. Though the differences in cell V may be on the order of several tens mV on that part of the curve, I think the SoC differences are quite small. I think WHEN cells reach that part of the curve is mainly a function of SoC. So I think shunt balancing does balance the cells quite well, with just minor differences, probably less than 1/3Ah, due to the different ir on that part of the curve.

Bottom line is that 1 or 2 Ah difference doesn't matter, so imo most debates of such unbalancing is a waste of time.


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## MN Driver (Sep 29, 2009)

I like the 216.5wh/mile from the wall figure, great number. Is this with standard driving or do you do a bit of hypermiling here and there. I'm curious because I haven't converted my 2000 Insight yet and I do a bit of hypermiling with it, mostly coasting and timing traffic lights when it wouldn't disrupt traffic, I make it a point not to bother others around me. If you aren't hypermiling, I'm figuring getting better than 160wh/mile, maybe even from the wall, might be possible.


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## dtbaker (Jan 5, 2008)

MN Driver said:


> I like the 216.5wh/mile from the wall figure, great number. Is this with standard driving or do you do a bit of hypermiling here and there. I'm curious because I haven't converted my 2000 Insight yet and I do a bit of hypermiling with it, mostly coasting and timing traffic lights when it wouldn't disrupt traffic, I make it a point not to bother others around me. If you aren't hypermiling, I'm figuring getting better than 160wh/mile, maybe even from the wall, might be possible.


I've checked several times... my Swift seems to pull an average of 300 watt-hr/mile from the wall (including all charger losses). I suspect I have a little brake drag in the front, but not terrible. This is NOT hypermiling, but just average around-town daily driving...


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## tomofreno (Mar 3, 2009)

MN Driver said:


> I like the 216.5wh/mile from the wall figure, great number. Is this with standard driving or do you do a bit of hypermiling here and there. I'm curious because I haven't converted my 2000 Insight yet and I do a bit of hypermiling with it, mostly coasting and timing traffic lights when it wouldn't disrupt traffic, I make it a point not to bother others around me. If you aren't hypermiling, I'm figuring getting better than 160wh/mile, maybe even from the wall, might be possible.


 I don't hypermile, but I do use regen for most of my slowing and stopping, applying mechanical brakes typically when regen current is less than 15A, sometimes not at all. I pace traffic. Many times I accelerate a bit faster than other cars from traffic lights because I don't want people to think electric cars are slow. 

Typical driving is a 30 - 35 mile round trip mostly at 50 - 55 mph with my bicycle and rack on back, which increases drag. Or about 40 miles round trip at 40 - 45 mph with 4500 ft elevation gain, and back down (did that a lot this past summer). Or 15 - 20 miles at 35 mph on secondary roads. Or 12 miles round trip at 60 - 65 mph plus another 8 miles at 35 mph. I would guess my average speed overall is around 40 - 45 mph. My yearly average from the wall as measured by the EKM meter at the input to the charger has been the same each of 3 years, 216 Wh/mile. It checks with my Ah usage according to the TBS gauge, which is typically about 1.6 at 35 - 40 mph and about 1.8 Ah/mile at 50 - 55 mph. Multiplying by nominal pack voltage of 115V gives 184 - 207 Wh/mile.
Edit: I should mention that I don't use my cabin heater that much. Not at all if it is above 35 F and sunny, and typically just for 10 minutes or so to warm the car during a typical drive. It heats the car quickly and it will remain warm enough for a while unless ambient is in the teens or lower and I am traveling at higher speed on a highway.


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## tomofreno (Mar 3, 2009)

dtbaker said:


> I've checked several times... my Swift seems to pull an average of 300 watt-hr/mile from the wall (including all charger losses). I suspect I have a little brake drag in the front, but not terrible. This is NOT hypermiling, but just average around-town daily driving...


 Seems high. At 60 mph I use about 250 Wh/mile.


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## dtbaker (Jan 5, 2008)

tomofreno said:


> I don't hypermile, but I do use regen for most of my slowing and stopping, ... 216 Wh/mile.


right.... you have AC motor, mine is DC w/o regen, explains a lot of the difference probably why I am much closer to 300 Wh/mile average. 


d


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## tomofreno (Mar 3, 2009)

dtbaker said:


> right.... you have AC motor, mine is DC w/o regen, explains a lot of the difference probably why I am much closer to 300 Wh/mile average.
> 
> 
> d


100*(300 - 216)/216 = 39%, Doesn't explain that much. A roll down test would tell you if your rolling resistance is high (from brake drag).


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## dtbaker (Jan 5, 2008)

tomofreno said:


> 100*(300 - 216)/216 = 39%, Doesn't explain that much. A roll down test would tell you if your rolling resistance is high (from brake drag).


I would love to be able to quantify whether my rolling resistance is near to as good as can be expected, or if we are measuring differently or what to account for that difference.

can you suggest a repeatable procedure we could compare with? I just cant think of a way to get the wheels spinning in neutral to a specific repeatable speed up on a jackstand....

when I look at the kW output instantaneously on a flat road at 35 mph, I see a fairly low output that would come out closer to your numbers, but then when I measure from the wall w/ kill-a-watt meter it has come out closer to 300 whr/mile.

I do know that my front wheels seem to get warm to the touch after just a few miles of driving even when I m not braking much. I also know that my extension cord gets pretty warm at the plug ends when charging, so maybe I am losing a lot to the charger/cord.....


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## JRP3 (Mar 7, 2008)

One way would be to take a torque wrench, probably an inch/lb beam type, and use it to rotate each wheel and compare the figures, which should point out any excessive drag.


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## Ziggythewiz (May 16, 2010)

dtbaker said:


> when I look at the kW output instantaneously on a flat road at 35 mph, I see a fairly low output that would come out closer to your numbers, but then when I measure from the wall w/ kill-a-watt meter it has come out closer to 300 whr/mile.


If you have an AH counter to compare with the KAW you could see how much is lost to the charger/cords.


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## evmetro (Apr 9, 2012)

The Swifte may have a much better alignment as well. That is an excellent idea about checking out the resistance with an inch lb torque wrench and I am going to do that to my metro as well. A crappy alignment however, could potentially give you much more rolling resistance than a few inch pounds of brake drag.


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## dtbaker (Jan 5, 2008)

JRP3 said:


> One way would be to take a torque wrench, probably an inch/lb beam type, and use it to rotate each wheel and compare the figures, which should point out any excessive drag.


hhhmmmm, I just got a small one for the battery bolts.... I'd like to have a repeatable 'driver' so other people could compare and report. I dunno what 'normal' is.... maybe I can spin the wheels with a cordless drill or something and get a reading with the torque wrench....

I did have the vehicle 4-wheel aligned, and tread wear is even, so I think that is probably 'ok'.

I suspect drag, especially in the front, as there is audiblevisible drag when spinning ft wheels up on jackstands. The rear wheels spin very freely, but they are drum and not the drive wheels. Hard to tell..... but the fact that front wheels heat up after driving a couple miles is an indicator that some watts are dumping from brakes right on out thru calipers/bearings/wheels....


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## evmetro (Apr 9, 2012)

I can check out some front wheel spinning torques for you tomorrow. I have six metros, so I will see if I can get us some averages. This may be helpful for all of us with electric metros. Do you have a build thread? I don't want to hijack the swifte thread but I may be able to help you on your heat problem...


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## dtbaker (Jan 5, 2008)

evmetro said:


> I can check out some front wheel spinning torques for you tomorrow. I have six metros, so I will see if I can get us some averages. This may be helpful for all of us with electric metros. Do you have a build thread? I don't want to hijack the swifte thread but I may be able to help you on your heat problem...



that would be awesome.... lets start a specific thread in 'technical discussion' on 'brake drag' or something similar... Having a little comparative info on Metros would be great, and in a more general case I think the topic of checking (and fixing) brake drag is a valuable general topic!

I didn't start a specific build thread on MY Swift because I concentrated that off-formum on my personal website. I did start a couple narrow-topic threads in tech discussion, and this looks like another really good one!

Please include your procedure for taking measurements, and perhaps we can have a semi-scientific duplication of test procedure!


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## JRP3 (Mar 7, 2008)

dtbaker said:


> hhhmmmm, I just got a small one for the battery bolts.... I'd like to have a repeatable 'driver' so other people could compare and report. I dunno what 'normal' is.... maybe I can spin the wheels with a cordless drill or something and get a reading with the torque wrench....


What I'm suggesting is using the torque wrench to rotate the wheel and see how much force it takes. I don't know why you'd want to spin the wheel with a drill.


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## tomofreno (Mar 3, 2009)

Hmmm, I don't have an in-lb torque wrench, only ft-lb which wouldn't show anything. My wheels turn really easy when jacked up, and spin for while. Be interesting to see what you guys find.


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## dtbaker (Jan 5, 2008)

JRP3 said:


> What I'm suggesting is using the torque wrench to rotate the wheel and see how much force it takes. I don't know why you'd want to spin the wheel with a drill.




because the torque it takes to spin it at some steady rpm is better than the force it takes to start it up from zero which depends on other stuff like mass and acceleration.....


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## JRP3 (Mar 7, 2008)

Mass will be the same for all your wheels, so any difference in force needed to get it turning would show up difference in resistance. Besides once you get it moving slowly with the torque wrench just keep it spinning at that speed and read the value. I can't quite see how you could get a reading if you spun it faster with a drill or something?


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## dtbaker (Jan 5, 2008)

JRP3 said:


> Mass will be the same for all your wheels, so any difference in force needed to get it turning would show up difference in resistance.


I am looking for a repeatable procedure that other people can do so we can compare differences between vehicles. probably are small differences in getting wheels up to speed depending on steel/aluminum wheels, tire size, etc. For this particular issue, I don't really care about the force required to get the wheel turning, I want to measure the drag.



JRP3 said:


> Besides once you get it moving slowly with the torque wrench just keep it spinning at that speed and read the value. I can't quite see how you could get a reading if you spun it faster with a drill or something?


expecting small differences that could well be masked if reliant on individual feel and ability to maintain steady force by hand. I'm not looking for fast, but some way that would be steady and hopefully able to be duplicated by other people.

I suspect this difference is only inch-ounces between a 'good' car with normal disc brakes in good condition, and one that has a little drag. Next step of course is how to reduce or eliminate brake drag cost effectively.


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## John (Sep 11, 2007)

Brake drag is liable to manifest itself as a variable torque rubbing for only part of the rotation of the wheel. Brakes are seldom perfect and would normally have a bit of run out. Bearing problems would change quite a bit depending on the loading conditions on the wheel. Torque wrenches are quite long so you would need fairly tall jack stands to see a complete revolution. If you put the torque wrench on a wheel nut the distance from the wheel nut to the center of the wheel would either add to or subtract from the moment arm (depending on which way around the torque wrench was) altering the reading.


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## z_power (Dec 17, 2011)

How about measuring motor current with car on jackstands?
First test possibly shortly after drive (warmed up oil and grease), then remove brake pads and measure again? Just note the motor current at, let's say 20 mph speedometer reading in both cases...


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## JRP3 (Mar 7, 2008)

John said:


> Torque wrenches are quite long so you would need fairly tall jack stands to see a complete revolution.


Inch pound wrenches are not that long.


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## dtbaker (Jan 5, 2008)

z_power said:


> How about measuring motor current with car on jackstands?
> First test possibly shortly after drive (warmed up oil and grease), then remove brake pads and measure again? Just note the motor current at, let's say 20 mph speedometer reading in both cases...



hhhmmmm, this might just be the winning idea. not motor current since different people have difference voltage packs, but kW expended to hold speed steady up on jackstands with and without brakepads might just show as a meaningful/measurable difference in kW on the Cycle Analyst or other meters like evDisplay that can show kW!


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## Electroid (Nov 23, 2012)

dtbaker said:


> I would love to be able to quantify whether my rolling resistance is near to as good as can be expected, or if we are measuring differently or what to account for that difference.
> 
> can you suggest a repeatable procedure we could compare with?


my suggestion would be to find a flat road, get the car up to some specific speed then see how far it takes it to coast to a stop.

this would not be precise but would give you a ball park figure, to compare,
if your just trying to tell if your making improvements, I would find a hill that leads to a flat road, mark a starting point then roll your car down the hill, mark the spot where it stops. make your adjustments then see if you can beat your previous mark.


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## Tesseract (Sep 27, 2008)

z_power said:


> How about measuring motor current with car on jackstands?....


Nope - can't do that with an induction motor because a certain amount of the phase current rating goes to inducing the field in the rotor. This current basically sloshes back and forth between the stator windings in the motor and the DC link capacitance in the inverter, so the only current drawn from the battery pack to maintain the field is that required to overcome losses in the inverter and motor (a few percent, say).

Thus you really want to look at battery current if you are trying to compare how changes to the vehicle affect efficiency.


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## z_power (Dec 17, 2011)

Tesseract said:


> Nope - can't do that with an induction motor...


I forgot about AC induction motors, only thought about "ordinary" DC systems...


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## tomofreno (Mar 3, 2009)

Four years now since the Swift was converted to an EV.
Total EV miles: 29,148
Total kWh from wall (4 yrs, EKM meter): 6272.79
Wh/mile: 211 from the wall for this year, so a bit under 200 Wh/mile excluding charger losses. Bit lower than previous years (216). Maybe because I blocked off the front grill late in 2012, and increased tire pressure from 30 to 38 psi, or maybe milder weather, less cabin heating...
No noticeable change in range or performance. 

I did some upgrades this year. The Manzanita PFC30 was replaced with an EMW charger: 









I had to relocate my EKM meter since this charger is taller than the PFC30 (had it on top the PFC30), so I mounted it on the firewall with a clear cover so I can read the LCD without opening a lid (it's behind the charger in the photo). You can see a triplet (red, black, green) of Anderson connectors (75A) on the LHS and RHS of the EKM box. Can also see there is a double Anderson connector (120A) on the charger output to connect to the battery pack. These permit me to easily disconnect AC input and DC output from the chargers to swap one out for the other. I carry the Manzanita on the back floor of the car on longer trips just in case. The Anderson connectors on the RHS permit me to swap AC input between two charge ports, a Marinco 50A and J1772 (described below). The Marinco permits charging at higher current than the J1772 at home or an RV park.

I replaced the 30A charge plug with this 50A Marinco plug:
http://www.hardwaresales.com/electrical/cep-marinco-6365m-male-plug-50a-twist-lock-connector.html

It is mounted on the front side of the front battery box where the 30A was, with 8AWG power cord to the EKM: 









I also added a J1772 charge port in the gas fill door:









I had originally purchased the port mounted in a box from tucsonev with a diode/resistor circuit and switch to pull down the EVSE square wave to 6V to trigger its power relay. Pulling it apart and soldering a new longer cord and ground, pilot, and proximity wires on it was easy, as it is held together by only one screw on the backside as shown in this photo with the front half removed:









The wires are inserted into a “solder cup” in each pin so it was relatively easy to remove the old and solder in new ones using a heat gun, then insert them back in the plastic. The back of the port is sitting right out in the wheel well where it is exposed to the tire throwing water and gravel on it, so it had to be in a watertight case. I used some 2” plastic drain pipe with caps on each end:








The grey flange was made from the box the port was formerly mounted in. The back part with flange was positioned in the wheel well, then the wire was fed into the “liquidtight” hose connected to the drain pipe flange (grey parts on LHS) with the wires soldered to the port. The grey flange was then bolted up to the port flange through the car body with neoprene gaskets in between:







http://www.evalbum/3060


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## dtbaker (Jan 5, 2008)

sweet! nice to see your build humming along..... I enjoy seeing your average consumption hanging right in there, predictably slightly better than mine (having a DC motor). 

I haven't put as many miles on my Swift this year as I can't help driving the Miata when I don't need the space for more than one passenger or large cargo items. 

How about status of batteries? Have you seen any evidence of imbalance or reduction in capacity?


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## JRP3 (Mar 7, 2008)

Glad to see the SwiftE is still going strong. Why the switch to the EMW charger?


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## tomofreno (Mar 3, 2009)

dtbaker said:


> ...How about status of batteries? Have you seen any evidence of imbalance or reduction in capacity?


 No, the shunts on the minibms do a little balancing on full charges. I try and do full charges most of the time for that reason. No noticeable change in range.


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## tomofreno (Mar 3, 2009)

JRP3 said:


> Glad to see the SwiftE is still going strong. Why the switch to the EMW charger?


 To reduce my dwell time at public EVSEs. I usually go for a hike or bike while I leave the car charging at a public EVSE (that is typically the only reason I go far enough from home to need to use an EVSE), so rather than leave it plugged in for the full time I'm gone, I can set it to charge at the max power the EVSE permits, and leave a note on the windshield that it is ok to unplug me after x hours - with x typically less than 2 for a full recharge. Can also charge at up to 90A DC (C/2) at home if I need to quickly recharge, or extend my range by about 16 miles by charging at an EVSE for 30 minutes, but those events are rare.
Edit: it also gave me something to do and I learned a bit about Arduino. The car is so reliable there is nothing to work on unless I just tinker with stuff.


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## evmetro (Apr 9, 2012)

Nice work! I especially like seeing nice work to metros/swifts!


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## tomofreno (Mar 3, 2009)

It didn't take long for me to get tired of plugging/unplugging that triplet of 75A Anderson connectors used to connect the charger to the 50A Marinco plug or J1772:







so I purchased one of these and installed it:
http://www.onlinecomponents.com/magnecraft-schneider-electric-w199apx15.html?p=29816731
It has a 240VAC coil. The Marinco input is also connected to the coil, so default is J1772 input. No more connecting to an EVSE or 50A and wondering why the charger didn't come on...Damn, forgot to switch connections!


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## tomofreno (Mar 3, 2009)

Five years now since the Swift was converted to an EV. 
Total EV miles: 37,337
Total kWh from wall (5 yrs, EKM meter): 8206
Wh/mile from wall this year:236
Wh/mile 5 year average: 220
Charger is about 91% efficient, so about 200 Wh/mile excluding its losses.

Got cheap "City Star" tires from Les Schwab this year and noticed my range decreased a bit from what I had with Michelin X tires. Also doing more highway driving/longer trips now that there are more charging stations around 50 miles from home. These two may explain the higher energy/mile this year.

Over 200 charges on EMW charger without problems (replaced Manzanita PFC30 with it about a year ago).
[FONT=&quot]Hot tub timer turns on power at midnight, turns it off at 4:00 am. Charge at 0.3C CC, to 0.05C CV. Power is off and TBS gauge is flashing "full" in the morning. Cell voltages are 3.49 < V < 3.54 near end of charge (shunt turn-on voltages are 3.50 +/- 0.02V), red LEDs on minibms boards are all on for the last 5 or so minutes of charging (I check them a few times per year). Pack rest voltage after an hour or so is always 120.3 to 120.4V or 3.34V per cell.
[/FONT][FONT=&quot][FONT=&quot]Over 830 charge cycles total in 5 years.

Around 25 - 30 trips up the 4500 ft elevation gain into the mountains this year, about the same as in other years.

No noticeable loss in range, no problems. 
Same motor, controller, batteries, DC/DC, relays, etc for 5 years.
Nice car.

www.evalbum.com/3060
[/FONT][/FONT]


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## JRP3 (Mar 7, 2008)

SwiftE still plugging along


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## tomofreno (Mar 3, 2009)

The Swift passed 40,000 miles as an EV yesterday. 


Went on a trip of 138 miles total. Stopped at mile 60 to charge for 30 minutes while I got some coffee on the way out, and continued to mile 69. Stopped at the same place again on the return to charge for a bit under 2 hours while I walked to a nearby restaurant and ate dinner. Used 66% charge or 13.7 kWh on the way out 60 miles to the first charge. This included climbing 9.5 miles up 2500 ft elevation gain, which alone used about 5 kWh. Used 53% charge or about 11 kWh on the drive back. Most was at posted speeds of 45 to 65 mph, but several miles through a couple towns with lots of traffic lights dropped average speed so the 60 miles took about 1 ½ hours each way. Very windy day (gusts to 70 mph on the pass). A 5 mile stretch of highway was closed to trucks, as some semi’s have been blown over there in the past.


A bit over 5 ¼ years as an EV.


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## Moltenmetal (Mar 20, 2014)

Tomofreno, thanks so much for continuing to post this data! You should be VERY proud of what you've achieved with this!


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## snoro (Jul 21, 2009)

I noticed that you are using MiniBMS. Since I plan to use them, I would like to have your opinion. Do you like them. Your advice is welcome.
Thanks


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## Moltenmetal (Mar 20, 2014)

Wonderful results- you have much to be proud of!

I also have miniBMS on my E-Fire and have nothing but good things to say about it. Reasonable price, basic features, and do far, very reliable too.


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## tomofreno (Mar 3, 2009)

snoro said:


> I noticed that you are using MiniBMS. Since I plan to use them, I would like to have your opinion. Do you like them. Your advice is welcome.
> Thanks


It works well. I've had some issues over the years but Dimitri has addressed those. These were mostly noise immunity problems on the main board due to using it with unisolated chargers - Manzanita and EMW. The latest main board works well. I've run the EMW up to 9kW into the pack several times without issues. Cell level boards have always worked. I like it because it is it has seveal features to make it fairly bullet proof.


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## tomofreno (Mar 3, 2009)

Moltenmetal said:


> Wonderful results- you have much to be proud of!
> 
> I also have miniBMS on my E-Fire and have nothing but good things to say about it. Reasonable price, basic features, and do far, very reliable too.


 Thank you molten. Its still running just fine, still my daily driver.


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