# Narrowing prismatic cell selection down now...



## DIYguy (Sep 18, 2008)

I see a lot of battery activity from you Electriccar....  You're doing what I was doing a while ago. I went round and round and back and forth.... I finally settled on Calb. Of course you have to satisfy yourself.


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## gravelydude (Sep 6, 2008)

I am going through the same selection process myself right now. It is really great to have this forum as a sounding board. The experience and knowledge of everyone is a great asset to have before pulling the trigger on a $10,000 investment. My greatest concern right now is trusting a vendor. I think that TS or CALB is a good choice for me. I want to buy from someone that has stock, and knows what it is that they have. Being a retailer myself, I understand that everyone that hopes to stay in business has to make a profit (both today and in the future). So I am still lurking, learning, and hoping to not make a big mistake! Anyone have any specific vendor recommendations??

JACK


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## Tahoe Tim (Feb 20, 2010)

factory direct - Calib in Long Beach, Ca. 

It's your best shot that if you need to file a warranty claim during the 2 year warranty period they will still be at the other end of the phone...

No offense, but the importers in the US tarnished the market with the much publicized and STILL discussed fraud that took place almost a year ago.


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## dtbaker (Jan 5, 2008)

gravelydude said:


> Anyone have any specific vendor recommendations??


http://www.alliancerenewableenergy.com/ source a lot of cells and have a long record for delivery

EvolveElectrics.com retailers for them and may have stock

http://currentevtech.com has a short track record, but a stand-up owner who will play straight and let you know if he has stock ready to ship, or have to FOB china....


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## gravelydude (Sep 6, 2008)

Electricar--

Thanks for starting this thread and the info. I think that I may be more inclined towards the CALB cells as well, depending on availability.


Dan--

Thanks for the vendor info. I do wish there was a vendor closer to Florida.

Tim--

Thanks for the CALB tip. Did not realize that there was a direct US connection. I will investigate that.


JACK


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## ElectriCar (Jun 15, 2008)

dtbaker said:


> http://www.alliancerenewableenergy.com/ source a lot of cells and have a long record for delivery
> 
> EvolveElectrics.com retailers for them and may have stock
> 
> http://currentevtech.com has a short track record, but a stand-up owner who will play straight and let you know if he has stock ready to ship, or have to FOB china....


Thanks for your links. You guys make it all so easy! 

I'm thinking of going with this instead of the 180ah, since they don't make a 200ah. I'm wanting OVER 100 mile range. Heck if you're going to use it for a vehicle you may as well use it to the max! More importantly, *the higher the AH rating, the longer the life expectancy*. 0.3C on that battery would be 72A. All my driving but hills and acceleration would be less than that! 

I'm requesting a price from Keegan in Ca. along with info on what hardware comes with it.

ALSO OF NOTE: I'm going to see about getting a shipment COD. That's the way business used to be done a lot. I don't mind paying the freight up front but sending someone $10,000 BEFORE delivery is more risk than I'm prepared to take, witness the EVComponents fiasco. 

I'm satisfied there are lots of people who TRUSTED them with their money are now not even in an EV. And that is most unfortunate.


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## dtbaker (Jan 5, 2008)

ElectriCar said:


> ALSO OF NOTE: I'm going to see about getting a shipment COD.


I don't think any of them accept COD. The issue is that they can't afford to front the purchase w/ China to maintain stock. Alliance I think is the highest volume and has a pretty good chance of having some in the US rather than FOB china, but they didn't like to deal with credits cards even in the past because it nibbles into the margin too much. The other two are smaller but have established personal credibility.....


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> I'm thinking of going with this instead of the 180ah, since they don't make a 200ah.


They actually do make a 200 Ah ...http://cali-battery.en.alibaba.com/product/219196040-209626885/Lithium_ion_Battery_Cell_200AHA.html


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## Tahoe Tim (Feb 20, 2010)

Calib's ship hit the dock in LA today. I just got an email with a copy from the shipper. My cells should be here around Christmas

BTW - I had to mail a check in advance. (credit card is accepted too)


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## EVfun (Mar 14, 2010)

One pays their money and takes their chances  I went with Thunder Sky in large part because of the extensive documentation available on their web site.

I read over the information from Jack that ElectriCar linked to. It looks like the 180 ah CALB cells have an internal resistance of 0.94 milliohms and the 200 ah new Thundersky cells have an internal resistance of about 1.1 milliohms. Based on initial drop my 60 ah TS cells have an internal resistance of about 1.5 milliohms and that is plenty good for me. It allows 300 amp draws at slightly over 2.9 vpc. I haven't noticed any heat yet, but I've mostly just done a little playing around with the car while working on the car. What driving I have done has included a lot of full throttle blasts but little freeway driving.


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## ElectriCar (Jun 15, 2008)

Tahoe Tim said:


> Calib's ship hit the dock in LA today. I just got an email with a copy from the shipper. My cells should be here around Christmas
> 
> BTW - I had to mail a check in advance. (credit card is accepted too)


I love it that you're so trusting of someone but I just can't do that with that kind of money. Seriously. Lots of folks trusted EVC too and in the end several people got hosed, no product no refund. Screwed!

I'm talking to them about COD...CASH ON DELIVERY! He didn't know what that meant lol.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> They actually do make a 200 Ah ...http://cali-battery.en.alibaba.com/product/219196040-209626885/Lithium_ion_Battery_Cell_200AHA.html


Just received email from Keegan who said the 240Ah cell isn't made and after March the 200 & 210Ah won't be either. Wonder what they're replacing them with? 

I'm talking with them now but if they can't get the price where I want it I'm not going to buy now. As I understand it Calb doubled their sales and capacity to produce cells in 2010, currently have 1 automated line running now and are expecting to have 4 online at end of 2011 with much more capacity. So with so much capacity expected and other forecast of lower prices next year I may just hang in there a few more months. They say there are so many battery companies gearing up production capacity, even with the new cars hitting the market there expecting a market flood. 

I have one pretty highly respected mfg on this site already offering me a pack at just over $1/ah now but I don't know if I want to go that route yet, and it's not TS either. I may go with that company if Calb won't work with me as I'm ready to do this!


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## Tahoe Tim (Feb 20, 2010)

At some point you have to trust someone. The way I see it, no one is going to ship you a pallet of batteries COD. I certainly wouldn't if I were in the business. 

I am trusting that the CALB factory will not "screw" any customers and will be around should any warranty issues pop up. (You do realize that Calib is the CALB factory warehouse in the U.S., right?)

I wish you luck waiting for pricing to come down. It could go up with increased demand - supply and demand forces could result in the opposite effect you are hoping for. I have waited until the last minute to order my pack. My project is ready for the pack. Every month I wait I lose the fuel savings. When I ride my Zero S motorcycle in the summer I saved $100 a week over fueling up my F150 4x4. Even if I thought I could save 10% on my $6000 battery purchase, it's not worth waiting more than a month or two. At some point, you just have to jump in and start driving.


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## ElectriCar (Jun 15, 2008)

Hi Tim. I am in talks with two companies and hope to order this week or next. I'm hoping to get the price down a bit which I am confident to do so but will see. 

Re waiting. I'm already driving an ev and using lead and saving about 19 cents/mile. Just can't go very far and am waisting power heating the batteries every time I charge/drive. I'm at about 480wh/mile on average and am hoping for around 320 or less when done. But with a lot more power!


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Hi Tim. I am in talks with two companies and hope to order this week or next. I'm hoping to get the price down a bit which I am confident to do so but will see.
> 
> Re waiting. I'm already driving an ev and using lead and saving about 19 cents/mile. Just can't go very far and am waisting power heating the batteries every time I charge/drive. I'm at about 480wh/mile on average and am hoping for around 320 or less when done. But with a lot more power!


sent u a PM


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## ElectriCar (Jun 15, 2008)

Got it. Thanks. May go that route.


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## ElectriCar (Jun 15, 2008)

MORE HELPFUL INFO: After getting the specs on the new *HP 200Ah cells*, they fit right in my existing battery boxes. Two of them measure 10"W X 5.5" X 9.375"H, replacing one lead battery with room to spare! Carl Clark said he suggested to HP they modify the cases for this reason and they listened. Well it couldn't have been a better fit. 

I wanted the new batteries to have a half inch gap all the way around the box for a heating/insulating material. I'll have that with HP batteries. My battery boxes were made with batteries in rows of two on each side of the drive shaft. Now I can have 4 rows of cells with a 30mm gap for whatever between each set of two rows. There is one battery box like this on each side of the drive shaft. Gives me a total of 47 under the bed with NO mod to existing boxes and room to insulate/heat all the way around! *Total KW under bed: 30Kw*

With the Calb 180's odd dimensions, I struggled to get 48 total under the bed. Wouldn't have enough clearance in some directions for insulation without lots of steel bracket modifications and would have to make lots of shims/spacers to fit them all in. * Totak KW under bed: 27.6* and lots of cutting/welding/downtime to do.

Also of note, with a 1C discharge, the *HP cells outperformed the new TS and Calb and maintain over 3.2V at that rate for about 45 minutes.* HOWEVER this is from their data sheet so take that for what it's worth.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> MORE HELPFUL INFO: After getting the specs on the new *HP 200Ah cells*, they fit right in my existing battery boxes. Two of them measure 10"W X 5.5" X 9.375"H, replacing one lead battery with room to spare! Carl Clark said he suggested to HP they modify the cases for this reason and they listened. Well it couldn't have been a better fit.
> 
> I wanted the new batteries to have a half inch gap all the way around the box for a heating/insulating material. I'll have that with HP batteries. My battery boxes were made with batteries in rows of two on each side of the drive shaft. Now I can have 4 rows of cells with a 30mm gap for whatever between each set of two rows. There is one battery box like this on each side of the drive shaft. Gives me a total of 47 under the bed with NO mod to existing boxes and room to insulate/heat all the way around! *Total KW under bed: 30Kw*
> 
> ...


Yes, proper fit is a big deal for sure. I know it weighed heavily in my choice also. I think I spent an inordinate amount of time on my battery boxes, and really didn't want to have to hack them up too much. Like you, I also want some room around them for insulation.


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## ElectriCar (Jun 15, 2008)

Well after reviewing the Calb info again and the fact that their batteries typically have more charge than specified according to you guys, I'm going with them. Keegan had told me that but I discounted it as sales crap. 

I looked again at the layout of my battery rack with the dimensions of their 200AH units and I'll get them in but with a little less room for insulation than I wanted and NO CUTTING OR WELDING! I may go with that bubble wrap from radiantbarrier.com in addition to what I have now for insulation. And I got Keegan to come down a bit more on price than I expected.  

I'm so jacked about this I can't stand it but I've go to wait on that "slow boat from China" lol. He said I would have them by late February. They have a 10 day "spring" holiday of some kind and nobody apparently works then.


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## JRP3 (Mar 7, 2008)

The Chinese seem to have a 2 week holiday every 2 months where the whole country shuts down. It's really annoying since it seems to affect every order. On the other hand that might be the only thing that's prevented them from already taking us over


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## EVfun (Mar 14, 2010)

Most of those weren't actual Chinese holidays, just excuses by EVC to rip people off


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## JRP3 (Mar 7, 2008)

I've had the same issues dealing with 3 other orders, 2 directly with China. They seem to have a lot of holidays, or it's common practice to cover up any delays with the "holiday" excuse.


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## EVfun (Mar 14, 2010)

My comment was offered in the same vein as your comment. I have more than my share of black humor.



JRP3 said:


> On the other hand that might be the only thing that's prevented them from already taking us over


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## tomofreno (Mar 3, 2009)

> Well after reviewing the Calb info again and the fact that their batteries typically have more charge than specified according to you guys, I'm going with them.


 The 200Ah are out of production after March, right: 


> Just received email from Keegan who said the 240Ah cell isn't made and after March the 200 & 210Ah won't be either.


If a cell goes bad after that, how will you replace it?


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## valerun (Nov 12, 2010)

FWIW, after a month or so of reasonably deep research, I have too decided on CALBs. Picking up my cells in LA next week ;-)


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## ElectriCar (Jun 15, 2008)

tomofreno said:


> The 200Ah are out of production after March, right:
> If a cell goes bad after that, how will you replace it?


 I'm thinking the 200A cells not being made after March are the long & short models but I may be wrong. I need to find that out for sure. I'll ask him today when I talk to him later.

Valerun, good for you. If you're like me you can hardly wait!


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## DIYguy (Sep 18, 2008)

It may be a good idea to buy a couple spares also. I plan to use 65 and bought 67. Just a thought to consider.


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## ElectriCar (Jun 15, 2008)

Was going to go with 50 but I may cut back to 49 & keep a spare. 

Hey what kw charger are y'all using to charge lithium packs? I have a Zivan NG5 (5kw) but now with this pack it can charge at 1C. Zivan doesn't have a charger any larger unless it's used on a 3 phase breaker which is hardly anywhere for home use.

I'd like to put it on a 60-80A breaker. That would be 10-12kw, still a 3 hr charge if you run it low.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Was going to go with 50 but I may cut back to 49 & keep a spare.
> 
> Hey what kw charger are y'all using to charge lithium packs? I have a Zivan NG5 (5kw) but now with this pack it can charge at 1C. Zivan doesn't have a charger any larger unless it's used on a 3 phase breaker which is hardly anywhere for home use.
> 
> I'd like to put it on a 60-80A breaker. That would be 10-12kw, still a 3 hr charge if you run it low.


I have a 6 kw Elcon. I can run it on 240 or 120. I guess with the increased energy requirement... it will take some time to charge....
I'm not an electrician... but I don't think you can go that high on single phase.


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## ElectriCar (Jun 15, 2008)

I am and yes you can! If you go too high though it could cause you a problem with tripping the main breaker if you're total electric with the dryer, oven, water etc on. That would be about 60-70A plus your charger. Would be getting up there though as most homes are 200A main breaker and no larger. However I may upgrade to 3 phase or 400A eventually when I have more than one ev.


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## tomofreno (Mar 3, 2009)

> Hey what kw charger are y'all using to charge lithium packs?...I'd like to put it on a 60-80A breaker. That would be 10-12kw, still a 3 hr charge if you run it low.


 This one should do it, and only $4500.00 and 88 lb!

http://www.batteryspace.com/Smart-Charger-10KW-KP-N-series-for-SLA/Li-Ion/LiMnNi/LifePO4.aspx

A Manzanita PFC-75 would also do it, for only $4400.00.


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## Tahoe Tim (Feb 20, 2010)

My CALB 100AH pack is shipping next week too. Why do you need to charge do fast? 

I am struggling with the issue and have come to the conclusion, right or wrong, that I only need a charger large enough to charge my pack of 48 100AH cells in 10 hours. I have all night to charge or all day at work. Unless we could charge in 5 or 10 minutes, everything in between 10 minutes and 10 hours charge time is worthless in a daily commute car.

I realize that the CALB spec sheet states the maximum charge rate at 3CA and I read somewhere that there was a minimum but is there really a minimum charge rate?

What is the charger sizing formula?

Is it:
battery AH rating/recharge hours desired = charger amp rating
(ignoring losses of course)

plugging in my pack figures:
100ah/10 hours = 10 amp charger


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## ElectriCar (Jun 15, 2008)

Hi Tim. I'm shooting for 100 mile range or so. Unlike most ev's, this one is for my commute to work, then trips to customer plants, construction sites etc. So far I've driven my lead pack of 30 mile range or so up to 100 or so miles in a day before. Should I drive somewhere say 30 miles away and return, I'd like to charge it quickly in case I need to hop in and go again. 

Since I built my truck, the economy has been in the gutter. But being in the construction industry I see the economy's direction before it hits the news. Since this last election people evidently feel better, retail companies and home owners. Since around Thankgiving or so, we've seen an ever increasing list of new projects and phone calls for work. It's been the most since about 2007 and the economy if about to go in high gear. That means I'll be driving a ton, something I've not done since I built this truck.


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## MN Driver (Sep 29, 2009)

ElectriCar said:


> I am and yes you can! If you go too high though it could cause you a problem with tripping the main breaker if you're total electric with the dryer, oven, water etc on. That would be about 60-70A plus your charger. Would be getting up there though as most homes are 200A main breaker and no larger. However I may upgrade to 3 phase or 400A eventually when I have more than one ev.


I'd be all set with a 200amp main. I'm sitting happy with a 100amp main without a huge charger sitting on it. With 200amps, I could take a charger as big as they make them and still run the fridge, freezer, air conditioner, electric dryer, microwave, and toaster and still be okay.

I'd probably be okay with a 75 amp charger on my 100amp main as long as I'm careful about load balancing when charging. Not ideal but I don't see how a 200amp breaker would be that hard to work with.


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## ElectriCar (Jun 15, 2008)

Yea MN IF you watch things you could. If you don't want to worry with it you can upgrade your service. We did one this morning for a guy installing a heat pump for $950. About 3 years ago, we did them for $1200 or so but it would depend on labor rates in your area. Make a few phone calls if you decide to do it and compare prices. I'd suggest you do it soon though as this economy looks like it's revving up pretty fast.


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## valerun (Nov 12, 2010)

tomofreno said:


> This one should do it, and only $4500.00 and 88 lb!
> 
> http://www.batteryspace.com/Smart-Charger-10KW-KP-N-series-for-SLA/Li-Ion/LiMnNi/LifePO4.aspx
> 
> A Manzanita PFC-75 would also do it, for only $4400.00.


I am building my own charger, as are a few other people on this forum. Check out http://www.diyelectriccar.com/forums/showthread.php?t=36627. I am shooting for 50-60A on my 200V pack - fed from 220V mains. Part costs are ~$400 total (including the Arduino microcontroller, box etc). I estimate that once I get all the prep / prototyping work done, the next one can be assembled in ~20 hours (including time for sourcing parts). 

$5k for a charger is WAY too much IMHO...

I will be finishing my variation on the Simon's & Jack's design (see above thread) in the 1st/2nd week of Jan and will post all updates on the above forum.

V


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## ElectriCar (Jun 15, 2008)

valerun said:


> I am building my own charger, as are a few other people on this forum. Check out http://www.diyelectriccar.com/forums/showthread.php?t=36627. I am shooting for 50-60A on my 200V pack - fed from 220V mains. Part costs are ~$400 total (including the Arduino microcontroller, box etc). I estimate that once I get all the prep / prototyping work done, the next one can be assembled in ~20 hours (including time for sourcing parts).
> 
> $5k for a charger is WAY too much IMHO...
> 
> ...


Wow that is awesome. I have a background in electronics, building a few things from schematics for various projects so that would be awesome to build a charger. The computerized part is where I may hit a wall. If you guys are documenting things in detail then I may dive in and do one myself. 

Thanks so much for recommending! I didn't know a DIY charger was in the works here.


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## Tahoe Tim (Feb 20, 2010)

Electricar,
I guess we are in the same business and use. I plan to use mine all day to do estimates. My town is only 5 miles from one end to the other so my daily rarely goes above 40 miles. I have the mountains to deal with but my electric motorcycle does it fine. 

Don't come out here and do service changes! We charge $1900 on average including the required permit and changing out GFI's and smokies in the house. We do a ton of them. Most are old fuse style that were installed in the 50's. Our local power company requires us to move the new panel to the front of the garage within 3 feet of a plowed surface to make reading the meter easier


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## tomofreno (Mar 3, 2009)

> Our local power company requires us to move the new panel to the front of the garage within 3 feet of a plowed surface to make reading the meter easier


 How do you extend the existing wiring to the new meter? Seems like a mess - all those old wires ending where the old panel was mounted.


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## ElectriCar (Jun 15, 2008)

Wow, our utility company uses rf I believe to read the meter from their truck. And $1900? Whew! No I wouldn't charge that much I don't think.


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## Tahoe Tim (Feb 20, 2010)

Yep Tom, 
we have to run a 2 inch conduit down the side of the house or crawl under the house and extend all the circuits to the hew panel. We could leave a sub panel in the old location but if I am going to move it, why have breakers in a bad location that is piled up with snow?

It's an all day job for two guys.


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## ElectriCar (Jun 15, 2008)

Well that would be more than your price I suspect with NMB cable running $0.32/ft for 12/2. You know you're not supposed to have more than 4 NMB cables (9 current carrying wires) per conduit unless you derate them 50% which means several conduits in most panels to meet code. Man that would be some ugly stuff on the side of a home! Tim where do you live???


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## tomofreno (Mar 3, 2009)

> we have to run a 2 inch conduit down the side of the house or crawl under the house and extend all the circuits to the hew panel.


 You have to have some kind of enclosure in which to make all the splices from old to new wire extensions. How do you make the splices? Do you also move the power mast, or are the main power wires also buried and run to the panel?

He lives at Lake Tahoe in CA electricar.


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## Tahoe Tim (Feb 20, 2010)

We are required to move the meter panel and mast. We decide on the solution for each house. Sometimes it is easier to run a 100 amp sub feed back to the original meter location.

We just did one on Thursday with water in the original panel. The owner has "issues" with the lights dimming and them going so bright that they burned out the bulbs

He had one sub panel in ice and another screw in fuse type on the other side of the house. Also had the dryer and stove wired together!!!

We have a lot of home built cabins here in Tahoe. Was was OK in the past is a hazard today. Don't get me started on knob and tube systems and ungrounded houses.

We should un-hijack this thread


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## ElectriCar (Jun 15, 2008)

DIYguy. Have you received your cells yet? Just wondering how even your pack is charging. I got the data for mine and was comparing the numbers to yours. *My data for 50 200Ah cells shows an IR range from .25-.32mohm, about 28% variation but the AH range is very close at 217-219 or 1%. 
* 
At 350A, the difference in IR using those numbers would cause a voltage drop ranging from .0875V to .112V. But Charging at 30A would cause really NO difference in charge voltage. *I understand the cells will charge differently with different Ah as the smaller ones will fill up first. Just wondering how much difference this might be at the end of the charge cycle? *

Anyone else able to analyze this data?


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> DIYguy. Have you received your cells yet? Just wondering how even your pack is charging. I got the data for mine and was comparing the numbers to yours. *My data for 50 200Ah cells shows an IR range from .25-.32mohm, about 28% variation but the AH range is very close at 217-219 or 1%.
> *
> At 350A, the difference in IR using those numbers would cause a voltage drop ranging from .0875V to .112V. But Charging at 30A would cause really NO difference in charge voltage. *I understand the cells will charge differently with different Ah as the smaller ones will fill up first. Just wondering how much difference this might be at the end of the charge cycle? *
> 
> Anyone else able to analyze this data?


Hey guys. Sorry, was away at Silverstick (hockey tourney). No I won't be getting them for another 3 weeks or so. They are made and tested and have been transported to the Shenzhen port and will be loaded this weekend. I have only pics at this point... I also must get my Elcon charger modified for Li. I had better get this off to Greg McCrea. I still have to make some decisions about the algorithm. 

You got yours pretty quick. What did u end up buying?


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## ElectriCar (Jun 15, 2008)

I too have to send mine to Greg BUT FIRST I'm going to connect it to my pack and charge it up to see if I can get them to 3.5V or a little more without a cell spiking too high. I want to get a few cycles on it to be sure of the max voltage I can charge to first. 

I'm doing this because I fear having to send it back again if I need to lower the charge voltage since I'm not planning on a BMS.


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## DIYguy (Sep 18, 2008)

Since the chargers will hold 10 different algorithms, I was thinking to have several options including perhaps a few that would allow me to charge a pack with one or two cells more/less. (higher vs lower end voltage). This is still to be discussed...but I think there is some room for "options".

Regards,
Gary


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## valerun (Nov 12, 2010)

ok guys, picked up my 60 100AH cells today from CALIBPOWER warehouse. Yey! Keegan's awesome. Couple of pics for you. There are a bunch of pods sitting on the floor waiting to be shipped off in the next few days. He said the next shipment comes in mid-Feb.

According to the individual cell info sheets, IR is <0.5 mOhm, with ~20% spread; Capacity is ~108-110 Ah. Measured all 60 cells, all exactly 3.29V. Spec sheet calls for 10-second 800A draw (8C!). This is awesome - means that I can draw 136kW from my pack and still stay within manufacturer's specs! Will give my Soliton1 some workout 

Cheers,
Valery.


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## ElectriCar (Jun 15, 2008)

Oh thanks for rubbing it in! Mine will be on that next shipment. I had to sit at the office today twice totaling about an hour and a half charging so I could get to my next stop then back home. It's cold today and that really curtails my range.


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## dtbaker (Jan 5, 2008)

sweet, so what was the final price?


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## JRP3 (Mar 7, 2008)

valerun said:


> According to the individual cell info sheets, IR is <0.5 mOhm, with ~20% spread; Capacity is ~108-110 Ah.


Nice grouping, but WTF is going on with capacity? Cells more than one year newer than mine with slightly LESS capacity in the same form factor? No improvements? Are they offering larger capacity cells in the same case, like 120's or something?


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## ElectriCar (Jun 15, 2008)

Baker, $1.21ah. 

JRP3, my 200Ah are measuring 217-219, nearly 20% (oops it's nearly 10%) bonus! So what did your 100's measure new? Were they more than 20%?


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## JRP3 (Mar 7, 2008)

Mine were 110-114. In fact the entire shipment of 214 100ah cells were in that range.


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## Duncan (Dec 8, 2008)

Speaking as a Quality guy 
for a 100Ah (or oranges) product 
108-110 is better than 110 - 114, 
less spread and nearer the drawing target - sounds like their process is improving!


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## ElectriCar (Jun 15, 2008)

Calb intentionally adds a little capacity so that in a few years when capacity is reduced due to aging you'll still have rated Ah. That speaks to their desire to satisfy the customer with a quality product. 

My 200Ah cells came in at 216-218Ah, 1% variation, so they could be getting better, more uniform in their manufacturing.


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## JRP3 (Mar 7, 2008)

Duncan said:


> Speaking as a Quality guy
> for a 100Ah (or oranges) product
> 108-110 is better than 110 - 114,
> less spread and nearer the drawing target - sounds like their process is improving!


Yes it's better but it may just be better sorting, not production. Two years ago we saw them go from 90ah to 100ah in the same case size, now we are seeing slightly less after two years of production? I was hoping, and expecting, that by now we'd be seeing 110ah cells being sold in the same form factor, with close to 120ah actual capacity.


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## ElectriCar (Jun 15, 2008)

It's probably not a good idea to switch to a smaller package until there is a large reduction in needed space. If they cut the package dimensions by 5-10% and you need a replacement cell or such, you'll have to make adjustments to fit it into the pack properly, ie it may shrink in height 5mm. Now your connections are not in alignment. Just my thinking. Once there's a huge difference then it makes sense to update the package.

From what I read a month or so ago, there may be a 10 fold increase in capacity in the next couple of years. Then you could put a huge pack in a small space.


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## JRP3 (Mar 7, 2008)

They didn't switch package size, they were simply able to put more into that same package since the technology and manufacturing were progressing. For a while they sold both the 90's and the 100's but the 100's quickly took over for obvious reasons. I don't put much into projections of future capacity, I'd much rather see real world examples that I can buy. For the past two years density of the TS and CALB prismatics seems to have stagnated, not a good sign. TS looked as if they were making good progress with their 200ah cell in the 160ah case but they've stopped making those as they had poor yield. I know CALB is supposed to have some new cells coming out soon so maybe we'll see advancements with those.


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## tomofreno (Mar 3, 2009)

> Speaking as a Quality guy for a 100Ah (or oranges) product 108-110 is better than 110 - 114, less spread and nearer the drawing target - sounds like their process is improving!


 I agree Duncan, but then we are comparing two different sample sizes (JRP3's sample is larger than his pack), with the larger variability in the larger sample size as would be expected even if the population variability is unchanged. I expect no or incremental change from TS and CALB in their current prismatic cell technology - mainly just improved process control with tighter control of Rs and capacity. A large change in energy and/or power density will likely require a different approach. I don't expect to see such a product in volume production for at least 8 years, and that is if there is a breakthrough in the next 4-5 years - hard to schedule those.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> I expect no or incremental change from TS and CALB in their current prismatic cell technology - mainly just improved process control with tighter control of Rs and capacity. A large change in energy and/or power density will likely require a different approach. I don't expect to see such a product in volume production for at least 8 years, and that is if there is a breakthrough in the next 4-5 years - hard to schedule those.


How about now?  150 C rated Lipoly http://www.maxamps.com/Lipo-6500-222-Pack.htm


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## tomofreno (Mar 3, 2009)

I'd like more than a 300 cycle warranty. Do you know what "true 150C capacity" means?


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## DIYguy (Sep 18, 2008)

ya, no kidding. Crazy C rating though, u must admit. Pretty sure the wiring wont support that either..... still interesting advancement of A123 cells ( I think)


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## tomofreno (Mar 3, 2009)

> still interesting advancement of A123 cells ( I think)


 Oh, I thought they were lithium polymer, more like Kokam cells.


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## pm_dawn (Sep 14, 2009)

These Lipos at maxamps:
http://www.maxamps.com/Lipo-10000-222-Pack.htm

Has the highest energy/weight ration I have seen.
181 wh/kg

If they are true about tested to 11,000mah they are actually 200wh/kg

But boy they are expensive.


Regards
/Per


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## tomofreno (Mar 3, 2009)

> A large change in energy and/or power density will likely require a different approach. I don't expect to see such a product in volume production for at least 8 years, and that is if there is a breakthrough in the next 4-5 years


 I should have elaborated: at low cost, long lifetime, and high quality.


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## valerun (Nov 12, 2010)

DIYguy said:


> How about now?  150 C rated Lipoly http://www.maxamps.com/Lipo-6500-222-Pack.htm


Very cool but 6.5AH*150C=~1000Amps through a 12 gauge wire they put on these things???!!! That's a 1.5-2V drop on 8-12 inch leads alone - or 2kW dissipation! I doubt they will be able to handle this for more than 1 sec or so...


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## corbin (Apr 6, 2010)

This might be a silly question, but how do you measure the Ah in a single cell to see what it is actually at?

corbin


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## JRP3 (Mar 7, 2008)

You can't really. You either have to pull charge out of it and measure how much comes out of it till voltage signifies empty or put charge into it and see how much it takes till voltage signifies full.


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## dimitri (May 16, 2008)

JRP3 said:


> You can't really. You either have to pull charge out of it and measure how much comes out of it till voltage signifies empty or put charge into it and see how much it takes till voltage signifies full.


So you just measure A ( amps ) and h ( time that passes while amps flow ) and multiple to get Ah. Why do you say you can't really? 

You meant to say you can't measure it immediately, right?


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## corbin (Apr 6, 2010)

JRP3 said:


> You can't really. You either have to pull charge out of it and measure how much comes out of it till voltage signifies empty or put charge into it and see how much it takes till voltage signifies full.


That's sort of what I figured; so people who report the Ah for their cells are just reporting what the manufacturer says they hold.

corbin


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## JRP3 (Mar 7, 2008)

You got me


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## JRP3 (Mar 7, 2008)

corbin said:


> That's sort of what I figured; so people who report the Ah for their cells are just reporting what the manufacturer says they hold.
> 
> corbin


Or they are using an Ah counter while the cells discharge and/or charge.


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> Or they are using an Ah counter while the cells discharge and/or charge.


My plan. I want to KNOW how much is left in the tank, not rely on a BMS to save me.


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## dimitri (May 16, 2008)

ElectriCar said:


> My plan. I want to KNOW how much is left in the tank, not rely on a BMS to save me.


Do you mind sharing make/model of AH counter which has configurable setting to trip a relay at specific AH count to stop the charger? Just curious how this plan can be implemented in reality. I happen to use both BMS and AH counter, but my AH counter can't control the charger.


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## JRP3 (Mar 7, 2008)

Couldn't you set the relay in the EV Display to control the charger?


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## tomofreno (Mar 3, 2009)

I think electricar was speaking more of discharge and LVC. He would like to watch Ah used and stop before he hits LVC I think. Maybe he also plans to stop the charger manually when Ah used hits zero.


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## dimitri (May 16, 2008)

tomofreno said:


> Maybe he also plans to stop the charger manually when Ah used hits zero.


This implies spending nights in the garage, I doubt anyone plans for that


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## tomofreno (Mar 3, 2009)

> This implies spending nights in the garage, I doubt anyone plans for that


 I've done it a number of times myself. Just hang a timer around my neck set for Ah used/charge current, work at my computer until the timer goes off, then walk out and shut off the charger. No big deal. Actually, I usually did it so I could check cell voltages near end of charge. I like Frodus' plan of logging them. Looking forward to seeing some data.


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## dimitri (May 16, 2008)

JRP3 said:


> Couldn't you set the relay in the EV Display to control the charger?


Theoretically, yes. Practically there are reasons why I would not want to short of complete redesign of the device. That is why I am curious if there is an existing AH counter that can trip relays on "full" and "empty".

Still, even with AH count and deliberately pulling down charger voltage ( which happens to require very expensive charger ) I do not see the idea of never overcharging smaller cells working long term in real life. It a sound theory, but my personal experience speaks against this approach. To each his own I suppose. I don't know how you manage to get all cells above the "knee" for decent "full" SOC, yet keep smallest cell under safe voltage limit. I would never trust the charger with manual knobs to do this job.


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## JRP3 (Mar 7, 2008)

I don't get them all above the knee, just the smallest ones, which is all that matters since I can't get more capacity than they have. All my cells are normally undercharged, some a little more than others.


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## ElectriCar (Jun 15, 2008)

You stop charging before full at a point below where the first cell tops out, no overcharge. You stop discharging before you run out. The Ah counter knows your pack capacity & it's used to prevent over discharge.


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## MN Driver (Sep 29, 2009)

Some cells have an emphasis on power over energy and the volume might remain the same but provide something different such as better discharge performance, better cycle life, or something similar to that. It seems that LiFePO4 hasn't made too many advances, for the past few years I haven't seen much out of A123 except for releasing their pouch cells which just seem to be a different form factor than their other cells. It seems that Lithium Polymer cells are reaching new heights with both energy and power density, maybe even lifetime.

I like LiFePO4 and would like to use it since it seems fairly abuse tolerant, promises for a very long cycle life, comes in easy to position and wire large format packages, and comes at a price that is reasonably affordable for what we get.


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## valerun (Nov 12, 2010)

dimitri said:


> Theoretically, yes. Practically there are reasons why I would not want to short of complete redesign of the device. That is why I am curious if there is an existing AH counter that can trip relays on "full" and "empty".
> 
> Still, even with AH count and deliberately pulling down charger voltage ( which happens to require very expensive charger ) I do not see the idea of never overcharging smaller cells working long term in real life. It a sound theory, but my personal experience speaks against this approach. To each his own I suppose. I don't know how you manage to get all cells above the "knee" for decent "full" SOC, yet keep smallest cell under safe voltage limit. I would never trust the charger with manual knobs to do this job.


Hi Dimitri - could you explain what you mean by 'pulling down charger voltage'? I am designing & building my own charger right now (inspired by http://www.diyelectriccar.com/forum...ld-your-own-intelligent-charger-36627p32.html) and am definitely thinking of building an AH counter into it...

Thanks!
Valery.


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## dimitri (May 16, 2008)

ElectriCar said:


> You stop charging before full at a point below where the first cell tops out, no overcharge.


Again, you quote excellent theories, no argument at all, but tell us how you will actually do it in real life, repeatedly producing same result every day for several years, only having DVM at your disposal and without moving your bed permanently in the garage. I want to hear specific make/model/price of all equipment involved and how it all ties together to implement that great theory you keep repeating.

I only know of 2 people who have actually done it for any meaningful time periods, JRP3 and Jack. 1000 others just blindly repeat the theory and PLAN to do it themselves. Lets put down in very detail HOW this will be done, what equipment and what cost.

If you can prove that it can be done safely and reliably and at lower cost of time and money over long time period compared to what I am doing now, I would happily join the BMS'less club in my next EV conversion.


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## JRP3 (Mar 7, 2008)

There is a learning curve and some tweaking involved but the more closely matched your cells are the easier it is. Recent purchasers are getting cells grouped within 2% or less in capacity which makes individual cell voltages close enough that pack level voltage is an accurate indicator. I think you are dealing with a poorly matched pack and you need a BMS to deal with the outliers.


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> There is a learning curve and some tweaking involved but the more closely matched your cells are the easier it is. Recent purchasers are getting cells grouped within 2% or less in capacity which makes individual cell voltages close enough that pack level voltage is an accurate indicator. I think you are dealing with a poorly matched pack and you need a BMS to deal with the outliers.


Mine are 1%. What are TS? HP? I picked a high quality product, which is where you want to start anyway. 

Dimitri if you've followed my writings you know I post what I find and know about. I do it TOTALLY because I want to help people get to where I'm at, solve the problems they're facing if I can. I don't have anything to sell and don't charge consultation fees.

I've been working on my game plan seriously for a month or so and dabbled back and forth for the last couple of years. I have an EV so I have some experience with them. I have an education in electronics and years of field experience in development and repair. I know what you can do with it, good or bad and it's limitations. I've designed circuits, some of which didn't quite do what I expected, most did it faithfully. 

When I get it all worked out and running, I'm sure it will be posted on here over time, though most of my plan has already been posted here and there.


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## DIYguy (Sep 18, 2008)

dimitri said:


> I only know of 2 people who have actually done it for any meaningful time periods, JRP3 and Jack. 1000 others just blindly repeat the theory and PLAN to do it themselves. Lets put down in very detail HOW this will be done, what equipment and what cost.
> 
> If you can prove that it can be done safely and reliably and at lower cost of time and money over long time period compared to what I am doing now, I would happily join the BMS'less club in my next EV conversion.


I'm not interested in "piling on" either side. Some random thoughts/brain dump follows. 
My reading has lead to better understanding of what is required,.... as for attaining it, as Dimitri challenges... it may be tough. 
Even though I have not done it... I'm pretty sure I could be successful without a BMS. That said, I don't want to live in my garage nor do I want to worry when I plug in my truck. 
Bottom balancing makes a lot of sense to me, personal opinion. 
The BMS world is pretty full of choices.... and I think the MiniBMS is a pretty good value and does the basics required. 
I went to a fair bit of trouble to buy a pack that is as closely balanced as possible as I think this is a good thing regardless of BMS or not. 
Like some others, I think leaving some headroom at the top is a good idea, especially since there is little energy stored here.
What I think may work is a bit of a compromise. I think a decently balanced pack (preferably bottom) could be managed quite well by selecting a "control group". .. meaning several cells... perhaps 4 - 6, that could be used to control the charger...and also play a role in LVC. Even this solutions is not for the "install and forget" type of user, periodic checking of pack condition is still important. 
While there are several ways to do this with available components... I haven't really found one that I would go with... yet. A small parasitic load on the control group may be manageable, but not my first choice. Especially if the car was not used for a while. This just forces more imbalance without shunt balancing (which I would rather not do since it forces top balance) Separate power supply would be best. 
So....for me, the jury is still somewhat out. I like Dimitri's challenge. DTBaker got me thinking more along this line also with his Set and forget charger thread. JRP has helped me better understand how a pack behaves without a BMS. So thanks to all u folks.
PS... I do recall another fellow that ran without a BMS successfully. One of the first I recall... lots of folks thought he was way out at the time... lol I think it was the chap from Detroit who had a motorcycle then bought the Blackhawks. . . could be wrong here..... Last time I recall asking, all was well there.
BTW, save your typing... I'm not really looking for any black eyes this morning... 
Cheers,
Gary


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## JRP3 (Mar 7, 2008)

I toyed with the idea of just monitoring a few cells but found it wasn't necessary. As I've mentioned you could break the pack into 2 or more sections and monitor them individually for finer resolution but I don't think it's necessary either.


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## dimitri (May 16, 2008)

valerun said:


> Hi Dimitri - could you explain what you mean by 'pulling down charger voltage'? I am designing & building my own charger right now (inspired by http://www.diyelectriccar.com/forum...ld-your-own-intelligent-charger-36627p32.html) and am definitely thinking of building an AH counter into it...
> 
> Thanks!
> Valery.


Its the key to BMS'less approach. You build your pack and bottom balance it, then you have to find exact point where to stop your charger when smallest cell in your pack goes over the "knee" voltage, while others are potentially still below or at the knee. That is assuming you plan to stop the charger based on pack voltage since you refuse to monitor individual cells due to spaghetti wiring and extra BMS cost. Perfectly valid reasoning, no objections. So, lets put that in numbers using round but typical pack size for illustration point.

50 cells of 100AH with 2% spread, i.e. one or more cells will be at 98AH somewhere in the pack. Lets assume 3.5V knee and desired max voltage 3.9V to be safely under 4 volts. You are charging at bulk CC rate of 20Amps, most of the time in bulk phase ( several hours potentially in the middle of the night while you stare at the back of your eyelids in the bedroom ) pack voltage will be slowly rising to 50*3.5V= 175V. Nothing exciting happens until this point since all cells are below the knee. Now, that 98AH cell reached the knee and its voltage starts rising quite fast at 20Amps rate, but others still have 2 AH to go, which means 6 minutes at 20Amp rate. Your safety margin on 98AH cell is 0.4V ( 3.9-3.5 ). So, you must have your charger go from full 20Amp CC mode to CV mode in the range from 175.0V to 175.4V !!!! You must have this precision at full range of ambient temps from freezing winter to hot summer. I am sure you are capable of designing a charger that will do that every day for 10 years, but I am not and there isn't one on the market with reasonable price tag that can do this. Brusa costs its weight in gold and Manzanita is not cheap either and I hear its not so precise to be completely trusted in described conditions ( nothing against Manzanita people, just stating facts ).

So, what do you do to address the challenge? You reduce CV limit to increase safety margin, simple, right? Well, since the curve is so flat, if you reduce CV by 1-2 Volts, you can potentially lose a good chunk of usable capacity, which brings a question of useful range and the cost of the battery that you lug around but not fully using. Is it worth it for you? Maybe yes maybe no, certainly not for me.

If someone doesn't appreciate significance of 6 minutes of 20Amp charging of an already full 100AH cell, I guarantee that cell will be dead within a dozen times you do such thing. I know it for a fact. Every time you overcharge by even tiny amount, you reduce capacity by tiny amount, increasing the 2AH spread little by little, making the problem worse and worse every time it happens. Every AH you lose on one cell is AH lost on the whole pack until you have no choice but replace that cell. Then next smallest cell takes its place and the story goes on.

So, if voltage margin is too small, lets forget it and use AH count to stop the charger. There isn't a device on the market that does it yet, so you will build one for yourself, while others will be PLANNING or WAITING for you to sell it to them, but only if its dirt cheap, yet 100% reliable and feature rich, otherwise they'll keep whining.

Well, in order to properly count AH you must have very precise current sensor in the whole range of measurement, or multiple sensors with different ranges and complex computation scheme to keep track of their data. Even if you are off by 0.1% the error marging will add up to 10% in just 3 months, unless you have some frequent calibration routine based on voltage, which brings us back to pack voltage monitoring.

I spent last 2 years contemplating every single aspect of these issues, designed and tested multitude of approaches. Its all about compromises, there is no holy grail. I chose my compromises and make my decisions based on those, others have gone their routes. Every route had sucesses and failures, nothing is perfect.

I have no doubt that you are capable of building a system that will work for you just like I built one that works for me. As for everyone else watching TV shows and repeating every word, please actually build something that works and show your results before you claim you found a holy grail and honestly report all pros, cons and mistakes you learned from and how much it all costs. I'm sure 5 years down the road we will have enough data to have more or less standard approach to EV conversions and will look back at these threads and have a good laugh.


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## dtbaker (Jan 5, 2008)

how about this for an inexpensive fail-safe... even with an cheap charger, even without a BMS...

If you have an ah counter, which you really should with Li, zeroed after your first monitored charge where you can hover over the pack, and check every cell with multimeter to stop charge as soon as the first cell hits the knee and heads up past 3.7...

then after use, you know how many ah you consumed per the meter. When you start charging you can see how many ah per hour you are actually getting into your pack... if you are charging from 110vAC, you can just get a cheap little timer and set the hours of charge a little less than the calculated time to full charge and it will click off without ever having to rely on the charger being very accurate or cells perfectly balanced.

this does not protect the BOTTOM end, where you have to keep an eye on ah consumed, and be sure not to go to close to full capacity use since you are starting with a purposely less than full pack initially....


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## dimitri (May 16, 2008)

To focus on some challenges in AH counting, which may seem trivial until you actually try it. 

- device must be powered at all times so it won't lose the counter data. If its part of the charger or motor controller where current sensing is already taking place and counting Amps seems logical inside those devices, then you must design a way for AH count to be kept while mother device ( charger or controller ) is powered off. Alternative is to frequently write AH count to NVRAM, but this approach has its own issues.
- zero point must be extremely precise. EV spends 90% of its time sitting idle. If you count even tiny amount of current during this time, long term the counter will be way off.
- end point calibrations ( either at empty or at full ) must be done frequently and automatically otherwise you can't trust the counter long term.
- self discharge and inefficiencies must be calculated for, or the counter will drift off fast.

When I set off to design affordable EV Display I had to discover and deal with all above points. I had to make several compromises to reach somewhat acceptable end goal, which is far from perfection, but works for me and few others. It will not work for everyone due to those compromises.

Given those issues and compromises there is no way in hell I can trust to charge my pack based on AH count alone, but in combinations with other safety checks it might be helpful.


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## dtbaker (Jan 5, 2008)

dimitri said:


> To focus on some challenges in AH counting, which may seem trivial until you actually try it.
> 
> - device must be powered at all times so it won't lose the counter data.
> - zero point must be extremely precise. EV spends 90% of its time sitting idle. If you count even tiny amount of current during this time, long term the counter will be way off.
> ...


all points right on...

I absolutely agree that the counter system needs to be 'always on', needs occasional reset, and should be used in combo with other protection like normal charger sensing/curve and pack low-voltage display/warning.

I do have a question as to whether a Hall effect amp counter is more or less accurate than a shunt-type connector, especially at the lower end of charge/discharge amps. Can you shed some light on the pros-cons of sensing amps as the charger flips from CC to CV and the amps start dropping?


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## dimitri (May 16, 2008)

Regardless of the sensor type you have to look at actual datasheets for specific sensor model and see its precision at full range of ambient temps, then take worst case scenario. But, that's only beginning.
Next step is A/D conversion. What is the resolution and precision of your chip? I used 10 bit Atmel which was a huge compromise. In retrospect I wish I had 16 bit AD chip at my disposal. Current sensor must be bidirectional with large scale, I used -600A/+600A, which means 1200Amp full scale, which means 1.2Amp resolution at 10bit AD conversion. This is the weakest point of my EV Display, I am not hiding it from anyone. Alternative is to use 2 sensors, one for charge and one for discharge, but it complicates the device and adds cost.

To have a solid zero point you must discard smallest reading as noise, which makes final resolution even worse. Another compromise.


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## dtbaker (Jan 5, 2008)

dimitri said:


> Regardless of the sensor type you have to look at actual datasheets for specific sensor model and see its precision at full range of ambient temps, then take worst case scenario. But, that's only beginning.


... a lot deeper swamp than I want to step into for sure.  It would be interesting to do a third-party test of the available multi-function instrumentation available; like a 'consumers report' test for us.... I wonder if Jack has done/published any side-by-side omparisions bench testing various models under various conditions?

I'd be VERY curious to know how my 'Cycle Analyst' stacks up against the others so I can make an informed choice for my next EV....


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## dimitri (May 16, 2008)

dtbaker said:


> I wonder if Jack has done/published any side-by-side omparisions bench testing various models under various conditions?


That's not really his style, there is not much drama in that and TV shows without drama tend to be even more boring 

I already regret spending time to type above couple posts, knowing that most people won't read them for lack of drama and boring details. Next the posts will drift down to no man's land ( aka 2nd forum page ) and be lost in endless threads asking same stuff over and over again. There hasn't been anything really new posted in months, yet we keep repeating same stuff again and again.

A month from now someone will start a new post asking how to manage a pack without BMS, round and round we go....

Geez, why I am so pessimistic lately, must be getting old...


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## JRP3 (Mar 7, 2008)

dimitri said:


> 50 cells of 100AH with 2% spread, i.e. one or more cells will be at 98AH somewhere in the pack.


Most packs with tolerances that close will have a number of cells at 98AH, not just one or two, so the voltage rise of the pack will more accurately reflect what is happening at the cell level. You are correct that you can't expect a charger to react to 0.4V but in reality you're going to have a bunch of cells climbing in voltage together. If you have one or two outliers it does become more difficult and you either need a BMS or replace those cells. My cells range from 110-114AH but there are enough of them near 110 that pack voltage can be used as a good indicator as long as I leave some capacity on the table, which is better for the cells anyway. BMS's exist to compensate for differences in the cells, as those differences become smaller so to does the need for a BMS become smaller. If over time the cells drift farther apart during use as some suggest then a BMS may indeed be a necessary item. Of course the closer the pack is to begin with the less likely we'll see differences as they age. We probably won't know the real answer for a few years.


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## azdeltawye (Dec 30, 2008)

dimitri said:


> Do you mind sharing make/model of AH counter which has configurable setting to trip a relay at specific AH count to stop the charger? ....


 
As I have mentioned before. The BRUSA BCM400 will do this. It has two fully programmable outputs which you can drive gauges, relays, lights etc. It works like a champ!

See thread: 
http://www.diyelectriccar.com/forums/showthread.php?t=53477

See attached instruction manual pdf.


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## dimitri (May 16, 2008)

azdeltawye said:


> As I have mentioned before. The BRUSA BCM400 will do this. It has two fully programmable outputs which you can drive gauges, relays, lights etc. It works like a champ!
> 
> See thread:
> http://www.diyelectriccar.com/forums/showthread.php?t=53477
> ...


Ah, yes, thanks Darren! As someone who attempted to design a similar device I can tell you that this unit is a holy grail of AH counting. I have not used it myself, but after reading user manual it looks absolutely perfect! 

Being BRUSA of course means it costs its weight in gold, just like their chargers. $700 a piece, OUCH!!!

So, Darren, how do you like it? Any cons? Can you trust it to stop the charger reliably? Please share your experience. I'm interested how well autoreset works and how solid is the zero point and smallest currents it registers.


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## DIYguy (Sep 18, 2008)

dimitri said:


> So, Darren, how do you like it? Any cons? Can you trust it to stop the charger reliably? Please share your experience. I'm interested how well autoreset works and how solid is the zero point and smallest currents it registers.


subscribing..... 

I see there are different models... care to comment on any of these Darren? (I didn't look at the differences)


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## ElectriCar (Jun 15, 2008)

I think the AH counter needs to be auto reset at charge complete. That will cover any cumulative counting errors. 

And at $700 for the Brusa, if it does what I want it to do and there's not another option then Brusa I will buy. I do want to protect my pack but do the least intrusive most passive manner possible.


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## azdeltawye (Dec 30, 2008)

dimitri said:


> ...
> So, Darren, how do you like it? Any cons? Can you trust it to stop the charger reliably? Please share your experience. I'm interested how well autoreset works and how solid is the zero point and smallest currents it registers.


So far I am very happy with the performance of the BCM400. Like I mentioned before, the accuracy is on par with my fluke clamp on ammeter. No problem with zero point wandering - once I open the main contactors on the pack, it’s a rock solid 0 Amps! Minimum current measurement is 0.5A with the large shunt (500A cont. / 1250A peak). There are smaller shunt options available which result in higher resolution down to 0.02A.

So far to date I have logged 170 charge cycles and every time the difference between Ah in and Ah out is negligible - see attached spreadsheet columns K & L. The only exceptions are the two times I top-balanced on (11/6/2010 & 12/4/2010) where I put an extra 4.15 and 1.9 Ah respectively into the pack. Normally I keep the battery charger set to 3.55V per cell which stops the charge cycle before any of the shunts turn on. 

The auto-reset works great when the Ah count is negative (more Ah in than out) but some times I will have to manually reset the gauge when the Ah count is 0 or non-negative. If I were to crank up the charger a tad, then it would consistently trip the auto-reset every time but I like to keep well away from the point where cell voltages rise rapidly... 


I only have two complaints about the Brusa BCM400 multi-function meter: 

Not enough programmable outputs. It only has two. One I am using for battery amps and the other is being used to drive the factory gas gauge with the net Ah count for at-a-glance SOC. 
The cost – at $700EUR which is about $920US at today’s exchange rate.


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## azdeltawye (Dec 30, 2008)

DIYguy said:


> .....
> I see there are different models... care to comment on any of these Darren? (I didn't look at the differences)


BCM100 measures net Ah only
BCM200 measures V, A, Ah in, Ah out, Ah net, Wh in, Wh out, and three temp sensor inputs
BCM400: same as 200 but with two programmable outputs

They also are available without a case for installation inside instrument cluster.


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## ElectriCar (Jun 15, 2008)

azdeltawye said:


> The auto-reset works great when the Ah count is negative (more Ah in than out) but some times I will have to manually reset the gauge when the Ah count is 0 or non-negative. If I were to crank up the charger a tad, then it would consistently trip the auto-reset every time but I like to keep well away from the point where cell voltages rise rapidly...


 
Question, is the AH reset function programmable to reset at a certain voltage or resetable with an input to it from the charger or other relay contact?


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## azdeltawye (Dec 30, 2008)

ElectriCar said:


> Question, is the AH reset function programmable to reset at a certain voltage or resetable with an input to it from the charger or other relay contact?


No, the auto-reset only occurs when the net Ah count goes negative. 

You can enable the auto-reset hysteresis option which desensitizes the auto-reset function by requiring greater than 1 A flowing out of the pack while the Ah count is negative.


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## tomofreno (Mar 3, 2009)

> I only know of 2 people who have actually done it for any meaningful time periods, JRP3 and Jack.


 I did it for about 3 months, but maybe that is too short to be a meaningful time period to you. As I've said several times, I certainly don't think it is for everyone, but it is doable. It requires conservative use of the pack, discipline, and the willingness to spend the necessary time. Essentially you are the bms, and your reliability depends on your discipline. All it takes is to get distracted once...As I mentioned in a previous post in this thread, the way I did it was to use a simple kitchen timer hung around my neck set for Ah used/charge current. Actually I set it for about 3-5 minutes less than this to give time to take some dvm measurements before the estimated end of charge. I bottom balanced the pack and identified the lowest capacity cells, the ones that hit HVC first. When the timer went off I walked out with my dvm and measured voltage on the lowest cap cells to decide whether to shut off the charger or let it continue a bit more.

If the starting temperature of the cells and charge current setting are always the same, the Manzanita voltage limit and timer can be tweeked so it shuts off when the lowest cap cells hits the voltage you desire +/- about 0.02V quite repeatably. But if either of those variables changes even a bit, it will charge more or less. That is why I checked with the dvm.

After that 3 months I added the most excellent minibms.  As I've also posted before, I use it as backup. I ordered it sans shunts, for HVC/LVC only. I spoke of monitoring with the dvm in past tense above, but actually I still do it because it just isn't much of a chore for me and I don't trust any charger or bms completely. I've posted here on bms failures I have had, and how the Manzanita shut off varies with those above two variables, as well as starting SOC if it is too high for the charger's timer to time out after its voltage limit is hit. Because of that, charging at the same current setting in the evening in winter when the starting cell temperature is always at the setting of the thermostat of the cell heater controller is straightforward. The charger shuts off right about at what I have chosen as full charge (3.45V on the low capacity cell). 

Yes, the other cells are not up to that voltage, but as JPR3 said, and you know, it doesn't matter, that is as much as you can get into/out of the bottom balanced pack. If you top balance the converse is true, you get them all to the same high voltage, but you can only discharge until the lowest cap cell gets to 2.5V or whatever the low voltage limit is for your cells, so same limitation. Cell starting temperature varies a lot in summer, so the charger cannot be counted on to shut off at the right time. Then it is up to me and my trusty timer, or the minibms.

I measure the voltage of ALL cells about every month or less to ensure the HVC cell hasn't changed. It has twice in a bit over one year, 7500 miles. Once when I individually charged some replacement cells - one of them became the HVC cell, and once when I over-charged a couple cells to about 3.95V - one of those then became the HVC cell (Why overcharged? Something took out the Lm339 chip on the minibms main board, the cell temperature was warmer than usual, and at the last minute I decided, well maybe I should check with my dvm just to be sure...). Other than that, the voltage balance of the 32 original cells hasn't changed appreciably. Three of the 4 replacement cells seem to like to stay about 0.02V lower than the others (I discharged the one that was temporarily hitting HVC first a bit, the fourth is staying within about 0.005V. That is checked at 28-30% SOC, which admittedly is not down below the knee where you would see more variation. It is ok for me though, since I never go below that SOC, and usually recharge at 35% SOC or greater (The TBS gauge "empty" alarm is set for 35% SOC). They are also within that range right before end of charge, actually a bit closer. You really get to know your pack when you spend a bit of time with it with a dvm.

If you are just starting off with a new pack, you don't know all the above very well so you have to be very diligent and check the cell voltages multiple times during charging. It is easy to see how someone could mess up and overcharge some cells as Travis described if they aren't careful and diligent. Similarly, you have to be very careful during discharge, because that voltage versus Ah cliff at the end is very steep. Boom! Suddenly there is a lot more voltage sag and some cells are at LVC when the pack voltage looked great 1 mile ago. After a few months it gets to be routine.

So which is more reliable you, a given version of bms, or the charger shut off? None are reliable enough for me, so I use all three, and hope at least one works. Could I see your wife doing this? Ha! You have to decide what will work for you and anyone else who will be using the vehicle.

As far as bms reliability, if it is well designed, has enough redundancy and safety features built into it, and is well installed, it should be very reliable. The space shuttle electronics were reliable (if not the tiles). Those if's present opportunity for failure.

Edit: Ok Jack, I spent about 25 minutes writing this, and my build thread has as much or more data than any other on this forum, so I expect you to make good on your boast to provide lots of data. I also expect Travis to present data from his Elithion/bluetooth/Android.


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## dimitri (May 16, 2008)

Tom,

you and I agree on most things and have mutual respect, so please don't take following question as attempt to disprove anything or change anyone's mind. Try to look back at everything you done and learned so far and with truly open mind tell me, would it not be easier and safer to simply top balance your pack, with all the rest being the same? I follow all your posts and compare your experience with mine and I can't shake off the thought that if I was to bottom balance my pack I would have followed your every step in managing my pack, yet my daily routine for past year seems a lot more relaxed and I hardly even think about my pack anymore. Granted I do monthly or bi-monthly health check, which in my case takes 5 minutes of observing all red LEDs just before my charger stops and then I am off duty for another month or 2. I have not touched my cells with DVM for many months now.

Again, not saying my way is THE way, my car might fail any day, anything is possible, just trying to compare 2 relatively similar conversions by 2 relatively similar people, taking 2 different approaches to battery management.


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## dtbaker (Jan 5, 2008)

I just have to echo Dimitri here... not that bottom balancing can't be a good strategy if you have long range requirements and you plan on wanting to be safe at max DOD.

I keep thinking that in many cases, since all the chargers work by sensing total pack voltage for the switch from CC to CV at the upper knee;it reduces the chance of a BMS trying to catch and handle out of balance cells at the end of charge if the cells are balanced at the end of charge....

I mention only to verify my logic where I want to increase the chances of my charger handling the end of charge as it is designed without a lot of daily manual intervention. It seems that if cells are initially top balanced, then the charger will catch the pack voltage and switch to CV unless and until the cells drift out of balance... which apparently takes a long time.


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## JRP3 (Mar 7, 2008)

As someone with a bottom balanced pack without a BMS I will agree that top balancing would be easier, no doubt, and next year I may experiment with that method. However, without a BMS, top balancing has more potential to kill a cell during discharge at 100's of amps. I can say that I'm not quite as diligent as Tom at monitoring but I believe I use a shorter CV time of 15 minutes than he does so there is less time at reduced current and my pack is charged to a lower SOC. I also have smaller cells so at the same current my C rate is higher which drives the voltage higher at a given SOC, which further undercharges the pack as I mentioned in the other BMS thread.


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## MN Driver (Sep 29, 2009)

JRP3 said:


> As someone with a bottom balanced pack without a BMS I will agree that top balancing would be easier, no doubt, and next year I may experiment with that method. However, without a BMS, top balancing has more potential to kill a cell during discharge at 100's of amps. I can say that I'm not quite as diligent as Tom at monitoring but I believe I use a shorter CV time of 15 minutes than he does so there is less time at reduced current and my pack is charged to a lower SOC. I also have smaller cells so at the same current my C rate is higher which drives the voltage higher at a given SOC, which further undercharges the pack as I mentioned in the other BMS thread.


Yeah, you wouldn't want to top balance without using a method low voltage cutoff or some other way to quickly know that one cell is suddenly taking a voltage plunge so you can take immediate action. ...either that or you are driving watching Ah but unless you know how much you have total, that might be a bad idea. With seeing discharge curves and less capacity available when it is cold, I can't imagine that I could trust Ah alone if I wanted to make a trip that would use, say 80% of the pack capacity out of the blue when I might want to normally use 50% on a daily basis.

You -could- do something like what Rickard suggests with his 1/2 pack voltage comparison hysteresis monitoring, but instead when a cell takes a dive to set up some alarm or shutoff indicating that a cell is dropping off. Whether or not you react quickly and have the voltage sensitivity right could be life and death for the cell though. If someone was driving they would likely know they were running low and wouldn't put themselves in a compromising driving position where it would be a problem if someone was smart about it.

Possible a half pack, third pack, or quarter pack monitoring that can see the difference when one cell take a hike up the 'knee' to cutoff charging? The difference you would need to monitor would have to be small though .4v or probably less ideally to catch one at 3.5 and another at, say 3.9v or the group at 3.6 and one at 4v. All depends on the charge curve of the cells.


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## JRP3 (Mar 7, 2008)

Yes I've considered half or quarter pack monitoring as well, probably quarter pack would be as fine a resolution as you really need for protection. As I'm more aware of my daily range needs and what the car can deliver I feel more confident that I could use top balancing with AH counting to good effect. The real key of course is a closely matched pack, and then it matters less if you're top, bottom, or middle balanced, they all reach the same state close enough that no individual gets out of line.


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## DIYguy (Sep 18, 2008)

Since this thread is kind of bouncing all over the place... I'll throw this in here.... Moderator....feel free to move it if u like. There is so much functionality with this thing, I'm not even going to start to list everything. That said, charger control was brought up as well as split pack monitoring, driving fuel gauge SOC and WHOLE Bunch of other stuff... and it looks kewl too. I didn't do a search on here to see if/where it has been discussed b4...so, ... sorry if it has... 
http://www.metricmind.com/data/evision_manual.pdf


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## dimitri (May 16, 2008)

I looked at EVision over a year ago and it didn't seem to be cost effective at the time. This new version seems to be a dramatic improvement in design and features, definitely looks awesome. Costs about the same as BRUSA and has similar features, although looks sexier to me. Definitely a top dog, no competition with low cost stuff I make


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## DIYguy (Sep 18, 2008)

dimitri said:


> Costs about the same as BRUSA and has similar features, although looks sexier to me.


Are you kidding me? lol Cost may be similar...but the functionality is not even close for the BRUSA unit. This thing does everything but wipe ur nose....

Main specifications are listed below.​ Measured and displayed parameters:
Traction battery:


Instantaneous traction pack voltage, V
Instantaneous driving current in or out, A
Instantaneous charging current, A 
Instantaneous power in or out, kW
Running Coulomb capacity Ah
Running energy, kWh
Running State Of Charge (SOC), %
Temperature (highest of 2 zones), °F or °C1
Indication of direction of battery current, OUT (drive) or IN (regen or charging) 
Battery Cycle counter, full cycles
Traction battery imbalance detection and measurement
TTF (Time to Full) estimation in charging mode
Indication of charging status
Automatic drive/charge/idle mode detection
 Auxiliary 12V battery:


Instantaneous voltage (V)
 Vehicle:


Current vehicle speed1
Energy consumption, Wh/mile and/or miles/kWh1
Odometer and Trip Odometer function1
DTE (Distance to empty) estimation1
Night time display dimming and HMI illumination
Sleep with wake up on ignition or charge
No power consumed from onboard auxiliary 12V battery, no such battery is required for full functionality.
Power steering pump programmable drive
 Instrument


Streaming running data out from the serial port
Download and Upload instrument configuration parameters, user preference, battery and vehicle parameters
Long retention of internal RTC setup for correct time stamping without power applied (~ 1 week).
 External controls:


Stock analog fuel gauge drive
Charger disconnect Itimer
Power Steering pump control (OEM option only)
 1Configurable for using Imperial or Metric units.


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## tomofreno (Mar 3, 2009)

> Try to look back at everything you done and learned so far and with truly open mind tell me, would it not be easier and safer to simply top balance your pack, with all the rest being the same?


 Well, I haven't done much balancing other than the initial bottom balance of all cells, then balancing the 4 replacement cells when I put them into the pack. Like I said, I've not balanced the original other 32 cells other than that. I occasionally discharge to 30% SOC and check cell voltages, but they (the 32) have always been very close with no need to balance them. 

I would have purchased the minibms with shunts but I didn't think they would do me much good. The shunts turn on at 3.5V, and HVC shuts down the charger at 3.6V. If I could always charge at the same cell temperature and charge current, I could tweek the Manzanita V limit and timer so it cut back to < 2A by the time a cell hit 3.5V, giving them some time to balance before one hits 3.6V. But that's not the way it works. When cells are warmer, the charger will hit its V limit later, and will still be charging at 15 - 25A when a cell hits HVC. The amount of balancing before the bms shuts off the charger is tiny in this case. If I could set it up like your Zivan, then yes I would use the shunts. I think they are safe, since they are low power and fused. I definitely think anyone who wants to not be bothered with monitoring a pack in any way should use shunt balancing. 

But you know, I've had two bms failures (only one with the minibms as mentioned above - still not sure what took out the LM339 chip, but voltage spike seems likely). The first one drained 6 cells. I was just starting to get complacent when the second one happened. When that happens to you it is very difficult to get yourself to completely trust any bms (Edit: I think I should add here: that doesn't mean I think it is better to operate without one. It simply means I think I need one, but I don't expect it to never fail). I think I would check cells no matter what I was using. The UPS on my pc beeps every once in a while indicating a line voltage change. What if I get another voltage spike while charging? It takes me 5 minutes or less to go out and check my lowest capacity cell with my dvm near end of charge. That is cheap insurance.



> I keep thinking that in many cases, since all the chargers work by sensing total pack voltage for the switch from CC to CV at the upper knee;it reduces the chance of a BMS trying to catch and handle out of balance cells at the end of charge if the cells are balanced at the end of charge....


 Not sure what you are saying here Dan. Even if you top balance the bms is going to shut down the charger when it detects HVC. Maybe you are thinking your charger will neatly charge all cells exactly to the voltage you want each time. Maybe. Mine will not do that as I explained above.

Perfect for me would be a well-matched pack in cell capacity and Rs, a charger that held pack voltage exactly constant once CV mode was entered and throttled back current to hold that voltage, and a simple inexpensive bms with HVC, LVC and shunt balancing. I think the bms would almost never shut off the charger, the charger would just time out, and the bms would do hardly any balancing, so it would mainly just be insurance. Would I stop checking with a dvm then? Maybe after a year or so if there were no problems.


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## tomofreno (Mar 3, 2009)

> Are you kidding me? lol Cost may be similar...but the functionality is not even close for the BRUSA unit. This thing does everything but wipe ur nose


 I find all those features are cool for about 2 months, then you just drive the car and don't pay any attention to that stuff except the Coulomb counting to know when you need to charge.


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## JRP3 (Mar 7, 2008)

I agree, though the split pack monitoring is a nice feature.


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## JRP3 (Mar 7, 2008)

tomofreno said:


> Perfect for me would be a well-matched pack in cell capacity and Rs, a charger that held pack voltage exactly constant once CV mode was entered and throttled back current to hold that voltage


To me this is really where effort should be focused. With an accurate voltage metering and clamping to hundredths of a volt a well matched pack should easily be controlled by the charger.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> I find all those features are cool for about 2 months, then you just drive the car and don't pay any attention to that stuff except the Coulomb counting to know when you need to charge.


maybe some of them... here is how Rickard described the split pack monitor....

"Now here's one that DOES tell me something. I've got two voltages, the top half of the pack and the bottom. On the EVision these are compared and a little LED gage around the gauge displays top dead center if both half-packs are exactly equal. If one is greater than the other, it moves a dot to the right or left. 
NOW I have an indication I can use. Full acceleration, the dot moves a dot or two left or right. I'm a little out of "balance" between the two halves. But if the dot moves a quarter around the circle, I'm way out. All the cells should be reacting to the same load in about the same fashion, to a tenth of a volt anyway. At the stoplight, I should be balanced between the two halves. At 500 amps, I should be balanced between the two halves. In fact, if it is DIFFERENTLY balanced at the stoplight and under acceleration, by more than a dot or two, that tells me something is wrong."

What about turning off the charger? Several ppl are interested in this feature.

Reading Voltage, Current, SOC etc.. are all the main items...perhaps you were referring to the other features beyond the basic ones?.. not sure here. 

What about an indication of your 12 volt battery? Wouldn't look at it? hmmmm

Speedometer? Odometer...maybe the stock ones work... but I guess for some folks...?

Power steering pump drive? 

Battery temp?

What about time to full estimation?... I guess after you charged enough times from different SOC or had a AH counter, maybe not.... but I recall wondering a lot of times when I was charging and wanting to make multiple day trips.... how long.....I dunno...

You can drive your stock fuel gauge for a quick reference also... I see lots of folks looking to do this..

There's more....ok... what is there to get tired of here??? 

I thought of something... the price... lol, ...


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## ElectriCar (Jun 15, 2008)

Yea I like the evision. And the fuel gauge feature as I'm planning to do that very soon. The other is the oil pressure gauge. It registers up to 80 and I've been thinking about using it as an ammeter somehow.


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## DIYguy (Sep 18, 2008)

I bought 18" rims and tires off a 2005 Mustang GT for my truck... (looks pretty nice too ). These came with the pressure bands inside. Been thinking of the wireless setup to monitor tire pressure. I am always checking this and I love this feature on my Buick Enclave. Looks like the Evision can do this also... .kewl I know I would use this a lot.


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## tomofreno (Mar 3, 2009)

> There's more....ok... what is there to get tired of here???


 For me, most of it. My TBS gauge has many of those features, not energy, not the comparison of pack halves...I ignore most of it. I didn't even hook up the 12V auxiliary battery to it. I am using the original 12V sla battery that was almost new when I bought the donor. It has way more capacity than required for the little load I put on it. I can see if the DC/DC is working by just observing the current out of the pack on the TBS when I turn on the ignition. Once in a while I take a few seconds to put my dvm probes across the 12V battery terminals to check it while I am checking cells (too much effort for some I know). 

Knowing energy in/out of the pack is nice, but not a must have. I datalogged pack voltage and current from the TBS with a sample rate once per half second, and multiplied V and I point by point to determine energy used over a 50+ mile route. It agreed to within a percent or so of just multiplying the average pack voltage by Ah used. Evidently because the V versus Ah curve is so flat, and V sag during acceleration occurs over such a small fraction of the running time. I almost never look at pack voltage, but then I have over and under voltage limits set on the controller, alarms set on the TBS, and LVC with the minibms. To me, that beats trying to watch a bunch of readouts while I am driving. I guess if you think comparing voltage on pack halves is good enough in place of HVC/LVC that feature would be worthwhile. I'm not convinced it is. At what difference do you take action? Do you continue watching it regularly after a few uneventful months? I'd rather use the controller limits and alarms so I can concentrate on driving rather than watching readouts. I glance at pack current and the little bars on the TBS representing remaining Ah used, that's about it. I watched rpm too until I got a feel for it and no longer need to see it. When I first started I datalogged and watched a bunch of stuff, until I got bored. It is like Jack R. said a long time ago about checking cell voltages each charge, its boring, they never change.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> I bought 18" rims and tires off a 2005 Mustang GT for my truck... (looks pretty nice too ). These came with the pressure bands inside. Been thinking of the wireless setup to monitor tire pressure. I am always checking this and I love this feature on my Buick Enclave. Looks like the Evision can do this also... .kewl I know I would use this a lot.


Camping World sells a 4 tire setup to put on your camper in case of tire issues. It has some sort of remote monitoring. Check it out.


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## DIYguy (Sep 18, 2008)

tomofreno said:


> My TBS gauge has many of those features, not energy, not the comparison of pack halves...I ignore most of it.


Thank Tom. What model are you using?

Cheers,


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## DIYguy (Sep 18, 2008)

azdeltawye said:


> BCM100 measures net Ah only
> BCM200 measures V, A, Ah in, Ah out, Ah net, Wh in, Wh out, and three temp sensor inputs
> BCM400: same as 200 but with two programmable outputs
> 
> They also are available without a case for installation inside instrument cluster.


Yes, thanks very much for that.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Camping World sells a 4 tire setup to put on your camper in case of tire issues. It has some sort of remote monitoring. Check it out.


OK thanks, I'll check that out.


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## dimitri (May 16, 2008)

I concur with Tom. I started my conversion with same percieved needs to have as much data as possible because I was stepping into unknown territory. Spent $$$ on paktrakr, etc. Watched voltages, logged data, etc. When failures happened, watching data did nothing to address/prevent failures. So, I scraped everything and built a simple system which watches for LVC/HVC only and takes action without me having to watch for anything. Watching real time voltage data is useless, logging is hardly useful, knowing voltage between LVC and HVC is utterly useless. For past year all I do is watch real time current in the corner of my eye and AH count, the rest is watching the road and listening to radio.

When I keep stating my experiences over and over, people who just forked $$$ for their cells don't believe me and call me names, whatever, I'm not offended, I don't blame them either. Just don't expect me to keep repeating same info if you didn't believe me the first time.

When you don't know what you need you tend to want everything, so you can later decide what you needed for yourself. That's logical, but it costs $$$. You don't believe that you need a simple system with less points of failure, fine, go buy expensive one, it will likely work great too, and if you are data junkie you will enjoy it. I personally am not a data junkie, so I offer a simple solution that I proved for myself. I can't prove it any other way.

I find it amusing when people say that vendors must prove it to them. When I go to Home Depot I don't ask them to prove shit to me, I chose to buy what I think is right. If I ask them a question, they give me verbal answer and its up to me to believe them or not. If product I bought in Home Depot killed something in my house, I doubt Home Depot will be held responsible. What's up with all these unreasonable demands to prove stuff? We all have reputations, I cherish mine, whatever it might be. If my word is not enough, please, be my guest and look elsewehere.

Sorry for the rant.


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## dimitri (May 16, 2008)

Above rant was meant to cover subjects in both BMS related threads, which are now too mixed up to tell them apart  and I was not pointing to anyone in particular, no offense to anyone. Peace


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## DIYguy (Sep 18, 2008)

I guess not everyone's desires, needs, likes are the same. It's all good. 

I do have an ev and a monitor also, with lots of info. I already know what is important to me. I just like to listen to others and compare. 

I think there is a difference with functionality regarding this gizmo though. It doesn't just flash numbers at you. It actually has a number of other functions including control of some sub systems. 

I don't really like the price though.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> I guess not everyone's desires, needs, likes are the same. It's all good.
> 
> I do have an ev and a monitor also, with lots of info. I already know what is important to me. I just like to listen to others and compare.
> 
> ...


I assume you're on the Evision still...

*And Tom, the TBS monitors I looked are rated at <100V. I guess you have some sort of work around that, prescaler or such?
*


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## tomofreno (Mar 3, 2009)

> Thank Tom. What model are you using?


 This one:
http://evolveelectrics.com/E-Xpert Pro.html
The Xantrex LinkPro is the same thing I believe. It is made by TBS. For a while Xantrex was the only U.S. dealer, now there are a number.
You can see 3 of the "bars" I mentioned in the photo. There are 5 total, each about 20% of what you define as cell capacity. It also reads out Ah used and % SOC. I record the former each charge, but just glance at the bars when driving. I am not saying this is better than the EVision. The EVision obviously has more functionality, and it has a good reputation. I'm just saying I don't use all that functionality. Some may. 

Regarding voltage, I use the TBS 5:1 voltage prescaler. EVWorks and Belltronics both sell a 10:1. See:
http://www.belktronix.com/LinkProAdapter.html


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## JRP3 (Mar 7, 2008)

I'll chime in agreeing with Tom and Dimitri, you think you want all information possible but after actually using the vehicle you realize you don't need it. I have my EV Display set to show pack SOC and current and I usually leave my Curtis 840 display showing voltage, though I do cycle it to show motor and controller temps once in a while. Most of the time I'm looking at current since that tells me how efficiently I'm driving, then I'll check SOC once in a while to keep an eye on range. 
I will disagree with Dimitri on the usefulness of knowing voltage since I did drive for a while with no SOC gauge and only used voltage and the trip odometer to estimate SOC and it worked fairly well with a bottom balanced pack. It was easy enough to lift off the throttle to check unloaded voltage to get a sense of pack SOC nearing the bottom.


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## dimitri (May 16, 2008)

JRP3 said:


> I will disagree with Dimitri on the usefulness of knowing voltage since I did drive for a while with no SOC gauge and only used voltage and the trip odometer to estimate SOC and it worked fairly well with a bottom balanced pack. It was easy enough to lift off the throttle to check unloaded voltage to get a sense of pack SOC nearing the bottom.


Totally agreed, my comment was in context of having automatic HLVC controls in place and having SOC meter based on AH count. Only under these conditions voltage reading becomes irrelevant. If you have nothing else, then voltmeter is better than nothing.


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## DIYguy (Sep 18, 2008)

The Wayland summary..... http://www.metricmind.com/testimonial_letter.htm


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## JRP3 (Mar 7, 2008)

It's almost a grand too. Nice gauge, but no thanks. The EV Display already gives me more data than I need, for less than $200.


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## DIYguy (Sep 18, 2008)

JRP3 said:


> It's almost a grand too. Nice gauge, but no thanks. The EV Display already gives me more data than I need, for less than $200.


I'm not trying to sell u one JR. lol.. I think it's too much also. (but's it's not just a gauge, and it doesn't have the same functions as suggested). I actually bought the Cycle Analyst and I think it is fine as well. 
I may be looking for redundancy in charger control (timer) though as well as a fuel gauge driver and wireless tire pressure monitor. Even adding all of these up...it's still more than I wanna pay. ... but if I hadn't bought the CA.....maybe??? Also, I will be putting in an MR2 power steering pump this winter and I'm starting to wonder what this thing will do wrt driving the pump motor. Suppose to be pwm control...so maybe inverse proportion to speed or something??? no info in manual that I could see. just keepin it real...... 

hmmmm. It does cruise control also. (not too sure how tho). I know, I know, ur not interested... lol


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## valerun (Nov 12, 2010)

JRP3 said:


> Most packs with tolerances that close will have a number of cells at 98AH, not just one or two, so the voltage rise of the pack will more accurately reflect what is happening at the cell level. You are correct that you can't expect a charger to react to 0.4V but in reality you're going to have a bunch of cells climbing in voltage together.


ok guys, I've actually decided to test all this by charging one of my 100AH CALB cells I just bought. I have set the charger to CC mode without voltage cutoff to simulate the condition Dimitri described. Charge current 0.1C. Attached is the chart of voltage by SOC.

For the following analysis I am assuming you want to switch to CV mode when the smallest cell reaches 3.6V, and that you want to allow no more than 0.1V over-voltage on that cell. At 3.6V, the first derivative of the cell voltage is ~0.2V/% SOC, meaning that another 0.5% SOC will drive 0.1V over-voltage. Assuming the WORST case that ALL other cells in a 60-cell pack are 2% bigger (112AH), we go back from 99% SOC to 97% and see that the derivative there is ~0.015V/%SOC. Therefore, same 0.5% SOC change will result in 0.015V/%*0.5%*59(remaining cells)=~0.45V rise in the rest of the pack. 

In other words, for my 100AH CALB cells, I will see 0.55V total pack voltage rise for every 0.1V rise of the smallest cell once it crosses 3.6V. 

Note that the same analysis for 3.5V CV switch produces a different result - in that case, I will see ~1V total pack voltage rise for every 0.1V rise of the smallest cell once it crosses 3.5V. For 3.45V, it's 2.5V for every 0.1V.

Conclusion:
for CV cutoff at 3.5V and safety margin of 0.2V on the smallest cell, the charger has to be able to detect a change in the total pack voltage of 2V. This is ~1% rise of the total pack voltage at that point. Should be quite detectable with any ADC over 9 bit resolution. Also remember that the pack is still charging at CV 3.5V so you are not really losing any more than 1% of the capacity in the end.

The reality will be even more forgiving as the cells' capacity is likely distributed around the mean and therefore in a sample of 110-112AH, the average is around 111Ah, hence you can probably safely multiply the above voltage sensitivity required by 2.


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## JRP3 (Mar 7, 2008)

If you think it's best to leave some unused capacity in your cells plus give yourself a greater safety margin you can go into CV mode somewhere around 3.45, or just skip CV mode and stop charging at 3.45. This assumes a higher charge current which will push the voltage higher than the 10 amp current you used.


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## ElectriCar (Jun 15, 2008)

I want to stop charging mine at a point just before they start to spike. Only thing is I wonder how precision my Zivan NG5 is and whether it's capable of stopping the charge a say 3.45 or 3.42 or whatever I set it for. Being my charger must be sent off for changing charge voltage parameters, I found a way to override the thing if I want it to stop at a lower level.

I found this for a LV/HV shutdown. It has a digital display on the front, led's for both alarms and is rated for transportation duty from what I gathered on the spec sheets. I emailed them for a price, couldn't find one on the web.

I also found one by ABB, a well known German controls company but you must use one for HV and another for LV if you want to do both at about $135USD each.

Both also have a delay function, both on and off.


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## DIYguy (Sep 18, 2008)

anyone wants into Lifepo and doesn't have enough $$ check this out... 
(just posted today) ...hurry up!  http://www.ssinc.us/forum/forum_posts.asp?TID=314&pid=582#582


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> I found this for a LV/HV shutdown. It has a digital display on the front, led's for both alarms and is rated for transportation duty from what I gathered on the spec sheets. I emailed them for a price, couldn't find one on the web.


Isn't that for 3 phase AC use?


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> Isn't that for 3 phase AC use?


Oops. That's the one above it. Same thing, different systems I believe. Here is the correct one, VME421H-2. I spoke to one of their guys yesterday. He said ALL settings are independant but for the hysteresis being common to both alarms. It is variable up to 50% he thinks. There are two separate contacts. And I like the digital display but not sure what it can display. Whatever the case, it will be tucked away under the hood somewhere.

So it can be used for HV disconnect if charger fails or in the case of mine that has to be reprogrammed to make a change, (Zivan NG5) I could set it to interrupt the charger at a little lower voltage than the charger setting. I could also use the undervoltage to shut the truck down or turn on a warning light, ie the low fuel light if I had one. 

If I go this route, I overall will have 3 voltage trip points. One or HV, one for low fuel warning probably at 3.0V/cell, and the third to kill the vehicle at some point less than that. In this setup it will behave the same way a petrol fueled vehicle would if you ran out of gas. For the third trip point, I'll add another single alarm unit from ABB which I think I also posted a link to.

The Bender unit I found out yesterday is $245, the ABB is $135 then an Ah counter of some sort, likely the Evision would complete the setup providing an Ah counter and SOC gauge using my existing fuel gauge. With this setup, I would have voltage stops in place for extremes, Ah data and a visual indicator comparing the two halves of the pack against each other. This is still up in the air for me. All for around $1500 *with only one wire in the middle of the pack* for the split pack feature of the Evision*.* The other wires can be connected under the hood to the pack conductors. And yes I know there are BMS systems cheaper but $ isn't my objective.

I may just stick the pack in and run for a while, be the BMS myself and gather data to see if this is workable or not. Sticking to a moderate operating range on discharge and charge I think may work well.

Any thoughts on it?


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> Any thoughts on it?


Do you even have to ask my thoughts on it?  One thing I don't like about your LVC plan is to disable the vehicle completely, unless you really can't trust yourself to heed the warnings. If it glitches on you it could leave you stuck in a bad place at a bad time. A really loud annoying buzzer that can't easily be disabled would probably be better.


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## corbin (Apr 6, 2010)

ElectriCar said:


> The other wires can be connected under the hood to the pack conductors. And yes I know there are BMS systems cheaper but $ isn't my objective.


What is your main objective?

If it is to monitor SOC and Ah, and cost isn't that much of an issue, why don't you just get the Elithion Lithumate BMS? The SOC output can be wired to your fuel tank gauge, there is a SOC display option, and it has charge and discharge limits. I'm curious what you are looking for.

corbin


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> Do you even have to ask my thoughts on it?  One thing I don't like about your LVC plan is to disable the vehicle completely, unless you really can't trust yourself to heed the warnings. If it glitches on you it could leave you stuck in a bad place at a bad time. A really loud annoying buzzer that can't easily be disabled would probably be better.


My thoughts on that are to make it like a petrol powered vehicle, should the wife or such drive it. You have a warning with ample capacity to get back or to a charging station. Someone WILL continue to drive it, even owners who know better at some point or other. They've done it on this forum!

I also fly planes. The #1 cause of small plane crashes is running out of fuel believe it or not! They push it. The gauges will be on E but they think "I only have X miles to go and I can make it and glide if I need to."


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## ElectriCar (Jun 15, 2008)

corbin said:


> What is your main objective?
> 
> If it is to monitor SOC and Ah, and cost isn't that much of an issue, why don't you just get the Elithion Lithumate BMS? The SOC output can be wired to your fuel tank gauge, there is a SOC display option, and it has charge and discharge limits. I'm curious what you are looking for.
> 
> corbin


I want a system benign and less likely to cause cell death or fire. As the saying goes "First do no harm". I think it's a medical expression.


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## ElectriCar (Jun 15, 2008)

Oh yea, JRP3, if I connect the circuit to kill the controller I can also work around it if I'm certain I can make it safely!


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## JRP3 (Mar 7, 2008)

ElectriCar said:


> Oh yea, JRP3, if I connect the circuit to kill the controller I can also work around it if I'm certain I can make it safely!


Yeah that's not a bad idea, especially if others will be driving the vehicle. I was one of those who pushed the pack and limped home, but with the bottom balanced pack and a controller that cut back on current when the voltage dropped low enough I did no damage.


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## corbin (Apr 6, 2010)

ElectriCar said:


> I want a system benign and less likely to cause cell death or fire. As the saying goes "First do no harm". I think it's a medical expression.


So, specifically, you are worried about a fire caused by over charging, correct?

You could probably use the Elithion BMS, but set the cell voltage limits really high, so it never shunts off excess voltage when charging. You could then charge as you normally would (i.e.: not controlling the charger with the BMS). You could then use the monitoring and low-voltage warning features of the BMS.

corbin


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## JRP3 (Mar 7, 2008)

He may also be concerned with a faulty BMS module draining a cell, that is one of my concerns.


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## corbin (Apr 6, 2010)

JRP3 said:


> He may also be concerned with a faulty BMS module draining a cell, that is one of my concerns.


Ah, good point…but that won't cause a fire, right? Just kill-a-cell.

corbin


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## JRP3 (Mar 7, 2008)

Right. It's happened to a few already. My worst nightmare, paying for cell protection that kills my cells


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## ElectriCar (Jun 15, 2008)

JRP3 said:


> He may also be concerned with a faulty BMS module draining a cell, that is one of my concerns.


 Ding Ding! Yes that's one thing of many. Every device attached to the pack is a potential issue. 

I may decide one day I should have a BMS. I have a PakTrakr now and it's garbage. It's basically been useful as a SOC gauge but due to it's poor design it has a history of noise related issues. It did lead me straight to a failed lead battery recently though. But I'm going to try and do without one. 

I think I'm going to order the Bender relay I mentioned earlier here at post 143 for HV and LV cut out. 

Got my tach in today but the inductive pickup I ordered isn't a proximity switch but is intended to run a coil wire through it to pick up the ignition pulse.


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## valerun (Nov 12, 2010)

Hi ElectriCar, 

yes, I agree that making the car as failure-proof as possible is a great idea. I expect my car to be driven by my wife and maybe my son. I am also starting a conversion business here in the Bay Area so even more reason for that.

However, I do think you need to take both voltage and current into account here. I am a big fan of jrickard on this - just cell voltage means close to nothing in a dynamic system under load. Example: my CALBs are rated for 10s 800A burst. They also have ~0.5Ohm IR -> hence 0.4V drop at that current. If they are partially discharged already at 3.1V, that pulls them down to 2.7V and undervoltage protection would kill the power - from the perfectly fine and well-operating pack... 

So the right protection would be an undervoltage cut with threshold dependent on the pack current. The slope constant would be based on IR of the cells. This is what I am planning to do for my conversions using all the intelligence left over from my charger controller - will post the results here.

V


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## ElectriCar (Jun 15, 2008)

valerun said:


> So the right protection would be an undervoltage cut with threshold dependent on the pack current. The slope constant would be based on IR of the cells. This is what I am planning to do for my conversions using all the intelligence left over from my charger controller - will post the results here.
> 
> V


You lost me there brother. 

I wonder if most BMS just measure cell terminal voltage which is not indicative of SOC? I know some use a time delay to help eliminate false cutouts. Though better than a terminal voltage based cutoff, it can't compensate for a long slow uphill climb etc.

How can you know the SOC of each cell? That would be ideal but we don't live in an ideal world.


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## valerun (Nov 12, 2010)

ElectriCar said:


> You lost me there brother.
> 
> I wonder if most BMS just measure cell terminal voltage which is not indicative of SOC? I know some use a time delay to help eliminate false cutouts. Though better than a terminal voltage based cutoff, it can't compensate for a long slow uphill climb etc.
> 
> How can you know the SOC of each cell? That would be ideal but we don't live in an ideal world.


sorry ;-). yes, exactly - voltage-based SOC indicator can only work in a lightly loaded circuit. To work in a heavily loaded circuit, cutoff voltage has to be adjusted based on real-time current flowing from the pack. Don't know if there are any systems out there that do that already...


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## DIYguy (Sep 18, 2008)

just wondering if LVC control based on voltage alone would work ok with a delay. I know what you are getting at... but the 10C wont be goin on for long... and while voltage under load means little... resting or low-load voltage means a-little-more. Why not just use a delay of 10-12 seconds or even 15 for this and not worry too much about adding in the the complexity of current and IR? Just asking....


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## JRP3 (Mar 7, 2008)

I agree with a longer delay and maybe even a lower voltage number. I took my pack to 1.77V under load once, which sprung back to 2.45V and rising when stopped, with no problems other than a deep DOD. Wouldn't suggest doing it all the time of course.


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> just wondering if LVC control based on voltage alone would work ok with a delay. I know what you are getting at... but the 10C wont be goin on for long... and while voltage under load means little... resting or low-load voltage means a-little-more. Why not just use a delay of 10-12 seconds or even 15 for this and not worry too much about adding in the the complexity of current and IR? Just asking....


Guys I'm of the opinion that with a low C discharge, a LV cutout will be fine with a bottom balanced pack. However Mike P has me wondering about what to do long term, ie will this be fine as ir builds upon aging will it become an issue and what are the consequences? 

I'm still considering a BMS but if I can do no harm without one, I'm much more happy with that. I still think the split pack monitor is a viable option. Maybe Jack will be reporting back as he installed the Evision in his speedster just recently. I just feel that for Metric Mind to go through the trouble to add this feature it must be pretty useful. 

I guess you saw the new thread I started hoping to get data from BMSless users, experiences, regrets etc.


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## DIYguy (Sep 18, 2008)

ElectriCar said:


> Guys I'm of the opinion that with a low C discharge, a LV cutout will be fine with a bottom balanced pack. However Mike P has me wondering about what to do long term, ie will this be fine as ir builds upon aging will it become an issue and what are the consequences?
> 
> I'm still considering a BMS but if I can do no harm without one, I'm much more happy with that. I still think the split pack monitor is a viable option. Maybe Jack will be reporting back as he installed the Evision in his speedster just recently. I just feel that for Metric Mind to go through the trouble to add this feature it must be pretty useful.
> 
> I guess you saw the new thread I started hoping to get data from BMSless users, experiences, regrets etc.


Mike's still an OMG u'll be sorry BMS guy remember...  (sorry Mike) (not really) lol
Do you really think there are more people just waiting to chime in on your new thread that u didn't already know about?? lol


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## ElectriCar (Jun 15, 2008)

DIYguy said:


> Mike's still an OMG u'll be sorry BMS guy remember...  (sorry Mike) (not really) lol
> Do you really think there are more people just waiting to chime in on your new thread that u didn't already know about?? lol


Who knows? Just had a thought and posted it. Still working and in a hurry to boot!


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## valerun (Nov 12, 2010)

DIYguy said:


> just wondering if LVC control based on voltage alone would work ok with a delay. I know what you are getting at... but the 10C wont be goin on for long... and while voltage under load means little... resting or low-load voltage means a-little-more. Why not just use a delay of 10-12 seconds or even 15 for this and not worry too much about adding in the the complexity of current and IR? Just asking....


yes, maybe 15-20 sec might work. Just have to be careful with those long hill climbs ;-))


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## JRP3 (Mar 7, 2008)

DIYguy said:


> Do you really think there are more people just waiting to chime in on your new thread that u didn't already know about?? lol


Really, how many more BMS threads do we need?


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## DIYguy (Sep 18, 2008)

JRP3 said:


> Really, how many more BMS threads do we need?


What does BMS stand for again????


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## MN Driver (Sep 29, 2009)

2 volts is as low as I'd take LiFePO4. If you go lower in voltage, you either have an undersized pack, you are pulling too much amperage at a low ambient temperature, your state of charge is too low, you have a cell with bad IR either due to premature aging or it being a bad cell in general(which I would personally replace), or you are using the pack for racing or very short bursts and don't care so much about cycle life.

These cells generate way more heat down at 2 volts and if your SOC is low you should be driving more gently by that time anyway since they generate so much more heat(relatively) when you pull enough amperage to drop them down to 2 volts.

If anyone is seeing under 2 volts at 30% SOC or higher with acceleration current on a non-frozen day or 20%+ on a room temp day, I'm interested in hearing from you about the C rate you are drawing and at what temperature. I'd personally go with 2 volts, i don't see anyone hitting that point unless they are scraping the bottom of their pack or ragging on it pretty hard. If you think 2 volts is too low, the reason why I don't think so is because this is a damage preventing point and the cells likely won't fry on you at this point but lower and it becomes likely much sooner. I'm not convinced that they are okay to be pulled down to zero volts at amperage, even if they don't cross to negative voltages. Most lithium cobalt battery damage that I've seen first shows up as high IR, based on TS/Winston data, I think its the same for LiFePO4 so I'd like to avoid dragging the anchor with these batteries.


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## valerun (Nov 12, 2010)

Hi Guys, 

just came across a new LiFePo4 battery manufacturer in China. They are not selling in the US yet. My friend is thinking about becoming a distributor. I wonder if there is a good demand for something like this:

Prismatic cells capacity ranges similar to CALB or TS. However, performance more like Headway if not better. See below:
•	Super fast 6C-12C charging – useful for fast-breaking regen
•	Continuous 20C discharge
•	2,000+ cycles at 2C continuous discharge, 1C charge
•	~900 cycles at 7C continuous discharge, 2C charge
•	Price: $2 / Ah

What do you think?

Thanks,
Valery.


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## JRP3 (Mar 7, 2008)

Interesting. What sort of wh/kg and wh/l?


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## valerun (Nov 12, 2010)

JRP3 said:


> Interesting. What sort of wh/kg and wh/l?


similar to CALB/TS, maybe 10% better, not more. Power density is the main benefit. Basically, similar characteristics to Headway 8Ah fast discharge but in a prismatic form


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## ElectriCar (Jun 15, 2008)

8ah? The plastic housings will take up a lot of space to have a pack of any size. Evidently the size of the package has an effect on C numbers due to the diminished ability to shed heat. Plastic is a poor heat conductor. If they put our prismatics in a tin they would be higher rated I suspect.


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## valerun (Nov 12, 2010)

ElectriCar said:


> 8ah? The plastic housings will take up a lot of space to have a pack of any size. Evidently the size of the package has an effect on C numbers due to the diminished ability to shed heat. Plastic is a poor heat conductor. If they put our prismatics in a tin they would be higher rated I suspect.


sorry didn't make myself clear - the capacities are similar to TS/CALB (100, 130Ah, etc). The fast-charge/discharge characteristics are similar to Headway 8ah.


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## JRP3 (Mar 7, 2008)

The numbers are good, except for price. Truth is the CALB and TS cells are good enough for most conversions but I can see some builds that might be worth spending the extra money for better C rates and slightly better density.


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