# Shandong (HiPower), ThunderSky, VS CALB/SkyEnergy



## arddea (Jan 23, 2010)

Which cell are to buy and what are the communities experience with them?

I know their price points are ~ $.37/WH for ShanDong, ~$.40 / WH for ThunderSky and ~ $.45WH CALB/SE. 

My only experience with them are the 4.95AH Cells that ShanDong made for Valence's NGage System about 5 years ago, and at low C (.1 to 1) you can abuse the s#!7 out of them. The Ngages we use at work we do 2-3 Cycles a day at a DOD of >90% most of the units are still going stong and the 2 (we have had 5 out of 15 die) systems with failed cells that we dissected had failure relating to the Valence BMS' low charge cut off. 

According to Jack he sees a limit on the C potential of the TS batteries. 
(http://www.diyelectriccar.com/forum...formance-ac-motor-and-controller-42684p5.html)
According to lithiumstorage the TS has a ~10% DOA rate.
(http://lithiumstorage.com/index.php?main_page=page&id=15)

Has anyone used the ShanDong (HiPower) 3C batteries? 

Has TS improved their performance?

Is Caleb relay worth the 12.5% premium? Would you say that holds true with a 100 CELL system? AKA worth $1700 more.

Who can handle more abuse? 

For a HIPower 100 Cells it looks like their 12,000 (lithiumstorage.com)
For a ThunderSky Pack it look to be around 12,500 (Ev components) 
For a Sky Energy Pack it look to be around 13,500 (lithiumstorage.com) / 14,000 (Ev components) 

Has anyone made a purchase from lithiumstorage.com? 

Thanks for the input.


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## Tesseract (Sep 27, 2008)

To do a fair and meaningful test you would have to buy identical capacity packs from each manufacturer then run them through identical load cycles.

Who has the resources to do that?


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## major (Apr 4, 2008)

Tesseract said:


> To do a fair and meaningful test you would have to buy identical capacity packs from each manufacturer then run them through identical load cycles.
> 
> Who has the resources to do that?


I can do this. At least constant current discharge tests up to about 400 to 500 amps. I'm not set up to do load cycle or life testing, but can verify C rating at room temperature. I have the equipment and time resources. But do not have the money resources to buy batteries to test 

I made this offer to HiPowerKevin.


major said:


> Hi kevin,
> 
> I may be able to conduct tests of this nature. I have been doing this on some Kokam cells recently. See http://www.diyelectriccar.com/forums/showthread.php/lithium-battery-monitor-39708p2.html posts #16 - 20. I would need enough cells to make a 48 volt pack, 16 of your cells sounds about right. I do not work for nor am compensated by any battery maker or seller. I just test them and tell it like I see it. Contact me if you are serious.
> 
> ...


He and I had a few email exchanges about it. But I have yet to hear back from him yes or no. I am willing to extend this offer to the other guys. BTW, I could use a better current limit circuit 

major


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## dimitri (May 16, 2008)

> Has anyone used the ShanDong (HiPower) 3C batteries?


My sample of 4 200AH HiPower 3C cells should be arriving to US shore this week, then customs and ground shipping to my door, so hopefully within couple weeks I will report first results.

I will run them side by side with 160AH Thundersky cells, so we'll see how they will fight each other


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## Dalardan (Jul 4, 2008)

This thread is getting really interesting. If money is the only thing stopping those tests to be done, we need to know how much money is needed for them. I am surely not the only one with philanthropic ideas right now...

Random questions :
- Which capacities should be tested?
- How many batteries of each type and capacity should be tested?
- Should it be opened to other brands? (Headway, A123, Kokam, LifeBatt)

Quickly, for 1 x 100Ah of Thundersky, Sky Energy and HiPower, it should get around $400 + Shipping. I guess it should end up under $600 for the batteries. Not that hard to get, but not too extensive tests... Am I right? So we should specify the tests wanted, get a price tag for the batteries needed, readjust the testing parameters for real life  and then begin looking for sponsors. Maybe first a small test run with few batteries to try and see if it's worth it?

Keep on the discussion, the solution Major just proposed seems to me the easiest, fastest and least expensive one that I can think of.

Dalardan


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## major (Apr 4, 2008)

Dalardan said:


> Random questions :
> - Which capacities should be tested?
> - How many batteries of each type and capacity should be tested?
> - Should it be opened to other brands? (Headway, A123, Kokam, LifeBatt)


Hi Dala,

I'm set up to do 48V nominal up to 400, maybe 500 amps. The Kokams I am testing worked well as 14 cell batteries. They are 40 Ah, so I could get up to 10C, which is their "pulse" rating. I've had them up to 8C, 320 amps. If I had 200 Ah cells, I could only go to 2C.

I just tried a 24 volt (7 cell) test a few days ago, but my current limit circuit locked me out at 240A. We wanted to go higher, but the little bugger said no. On the other hand, I can go higher than 48 in voltage, maybe up to 200, but see no reason to. And I don't have that many cell loggers.

The TS and other such cells are a little lower in V/c, so I think 16 cells would make a good "48V" test battery. I'd like to stick with 40 Ah cells because it is easier for me to charge with the equipment I have.

14 to 16 cells tested also gives a good sample in my opinion. I can monitor each cell during the discharge test, and also on charge. I'll test anybody's battery. Only condition: No conditions. 

Bring 'em on 

major


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## EVComponents (Apr 20, 2009)

I have 100 Ah cells from ThunderSky and Sky Energy that we can use for testing. Manzanita Micro (Rich Rudman) has all of the equipment for testing. He has offered to do it if someone will contribute the cells.

I do not have any China Hipower 100 Ah cells for testing.
I requested samples from Kevin, but nothing has been offered.

If anyone wants to contribute 2 of the Hipower 100 Ah cells, I will contribute TS and SE 100 Ah cells.

Then I will take them all to Manzanita Micro (1 hr away from me) for testing. All results will be published.

Anyone have relatively new Hipower 100 Ah cells?


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## CroDriver (Jan 8, 2009)

I have tested A123 vs. Headway 10Ah vs. Headway 12Ah. I'll test Headway 8Ah P cells tomorrow.

Since I have no commercial interest in any of those brands I think that my results can be classified as independent tests.

I have to find the graphs and post them here tomorrow

Btw. Major, do you know if John Wayland will use the same Kokam cells you have used? I think that he got some fancy ultra high power cells.

10C doesn't look that impressive for Li-Po.


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## major (Apr 4, 2008)

CroDriver said:


> Btw. Major, do you know if John Wayland will use the same Kokam cells you have used? I think that he got some fancy ultra high power cells.
> 
> 10C doesn't look that impressive for Li-Po.


Hi Cro,

Don't know what John has. And 10C ? It is what it is. I have yet to go there. Just to 8C. And I have yet to see "pulse" defined in seconds, or would that be milliseconds? I know they get pretty warm at 8C after a few minutes  

Yeah, post up what you have, please.

Regards,

major


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## arddea (Jan 23, 2010)

Thank for the input. I was hope for some real world experiences (likes James comments) from people that have already used them. Testing is good and the data would, I think, help the community. I’m ordering a 90K motor, inverter, charger, DC-DC system from Dave and was hoping I could get the batteries to do some testing with at the same time. 

I am not “wealthy” or have a sponsor to be able to afford dropping 12-14 K on a pack just to find it cant sustain the 330 amps the inverter / motor can eat at max power, taking a dice throw on the motor / inverter is ouch enough as it is. 

I’m doing my first ICE to E conversion, but do have a back ground in electronics, and I’ve done ICE to ICE conversions before. I’m an aggressive driver and plan to have enough power to still pass on the 294 when need be. About 5 years ago I looked at doing a conversion, but everything was SLA and DC other then the just announced Tzero (Telsa) which on my 40K income is beyond my budget. I never liked the horrible cycle life of SLA and the inefficacy / (historical) reliability of DC. 

Luckily I do not have my glider yet and if it wasn’t for IL jacked up registration system I would build my own from the ground up modeled after the Countach (in IL you need a NHSTA COO or clean title / Vin to register). I’m currently looking at primarily a 70 - 72 914 or 98 or 99 (non guppy) Sebring convertible (I plan on getting one from Copart for its drive train anyway). The whole problem with the industries planned EVs is their visual repulsiveness, they are Vaporcars, or they are insanely overpriced, which is the reason I’m taking the jump and canceled my deposit with Aptera (VaporCar USA). It is almost as if the industry is trying to prove there is no demand by only offering the automotive equivalent of a 500lb pizza face, some truly desperate people who swallow the “Carbon Hoax”(1) lock, stock, and barrel will settle but most will look elsewhere. I plan for the finished unit to be my primary vehicle for the next 7 - 12 years (plausibly longer if i get a classic like a 914), unless I successfully build a power trailer I plan on keeping / rebuilding my current ICE 98 Sebring Convertible for the days I need to drive 75+ miles. 

(1) Note I use the term “Carbon Hoax” because the CO2 issue is no where near as bad as the CAP and TAXers would have you believe. Is our emissions bad, yes, are they world ending as the CAP and TAXer would have you believe, no. 
The real issue is we are post peak and the worlds oil should be directed towards things that truly need it like medicine and lubricants.


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## Tesseract (Sep 27, 2008)

Dalardan said:


> ...
> Random questions :
> - Which capacities should be tested?
> - How many batteries of each type and capacity should be tested?
> - Should it be opened to other brands? (Headway, A123, Kokam, LifeBatt)


Random answers:

- Don't think the capacity choice matters so much, but 100Ah and 200Ah would be a good start.

- Here is the crux of the problem. You need to test a whole lot more than 1 or 2 cells from each manufacturer. In order to draw any valid conclusions from random sampling of a population your sample size needs to be "statistically significant", and, among other things, the variation in observed parameters during testing dictates whether your chosen sample size will suffice. 

For example, say you were to going to determine the average skin color of people inhabiting the Arctic Circle. You could use a very small sample size because the only people that live there are the Inuit. Contrast that with the USA where, clearly, a sample size of 1 clearly won't give you meaningful results. Well, it's the same thing with these cells, or at least it has been with the Thundersky cells that have passed through Rebirth Auto. Actual capacity varies as much as 10Ah for a 160Ah cell while internal resistance varies as much as 3x (e.g. - one cell might be 7mΩ while the next measures 21mΩ). We are outright rejecting about 5% of the cells. 

Basically, with this kind of variation in such critical parameters as capacity and internal resistance you need to test enough cells to be able to draw a normalized distribution and determine a standard deviation. I don't think 16 cells will be enough, and even that amount will cost $2000 to $4000 per manufacturer depending on size. 

This is why I asked who has the resources to buy and test hard - possibly to destruction - a statistically significant number of cells from Thundersky, CALB/Sky Energy and HiPower?


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## Tesseract (Sep 27, 2008)

major said:


> BTW, I could use a better current limit circuit
> 
> major


Send me pics of your setup as well as important details like:

- the size of the bus bars/cables going from the IGBTs to the load bank (important, and must also included the actual outside diameter if insulated cable)
- switching frequency you want to operate at
- the IGBT part number
- the current limit range you want to accommodate

And I'll whip something up for you.


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## LithiumStorage (Feb 3, 2010)

Hi y’all! This is a cool thread. I have wanted to conduct a test like this, but the economy has been a drain on my resources, and I have a natural bias being a distributor for Hipower and CALB/SkyEnergy so any results I post would be automatically questioned. I had intended on buying a CBA III for testing and posting the results.

I suggest this test be performed on 100Ah cells because all three Chinese manufacturers produce a 100Ah cell and thus can be directly compared. I am interested in co-sponsoring this test by loaning out few Hipower cells (I would want them back afterwards). Would 2-16 cells be adequate for most folks to agree a credible test was performed? I don’t want to lend out cells so a novice can make a video of them exploding. What tests would be performed, and by who, and how should the results be best reported to benefit the most people (blog? ‘Sticky’ forum post? Email? Etc.)?

The Chinese get a bad rap for their products, but we shouldn’t judge a supermarket for a few bad apples. We should prove products for ourselves and pass that information on to help others. For example, I could use such results to post a chart on my website comparing all 3 brands against each other on internal resistance, C ratings, instantaneous discharge, etc., with performance graphs included for support.

If this test is going to be done, it should be detailed and comprehensive. I’d like to see a team with experience and good equipment manage this project. I think the EV community will really benefit from the reviews and results of this experience.

Mike Collier
President
Lithium Storage Incorporated
(801) 513-6610
www.lithiumstorage.com
[email protected]


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## hipowerkevin (Jan 14, 2010)

major said:


> I can do this. At least constant current discharge tests up to about 400 to 500 amps. I'm not set up to do load cycle or life testing, but can verify C rating at room temperature. I have the equipment and time resources. But do not have the money resources to buy batteries to test
> 
> I made this offer to HiPowerKevin.
> 
> ...


Dear Major, I feel sorry to you, for 48V100AH do cost some high and my boss still interesting in famous certificate much , I just can say thank you but can not really go with you.

As myself I do interested in comparision testing, and I have some thinks,

1. Take large AH single cell for testing is better, for we need to cut down the number of cells in total pack, less cells means higher corresponding, corresponding is very important for battery pack.
2. also concern as corresponding, As I know, my company Hipower, offer cells for battery pack in same batch. That means, If customer order the battery pack,
we would selecting cells in one batch, same batch offer same IR, and other paramaters, so cells have very high corresponding, because the matiral, temparature, even worker are same, We use this way keeping pack performance highly well to win large customer demand. 
3. I do not so agree as single cell testing, like IR, if one is 3.1 3.4 3.3 3.0 3.1 3.3, another is 3.3 3.2 3.3 3.2 3.4, I would perfer the second one even RI is higher.
As in our factory, if some one order battery pack, we would do cycle testing hundreds of cells in order to select the best corresponding cells make up packs.
4. performance could be done well but how to test life cycles ? I feel big big head :-(

I am interesting in this program and glad to offer my efforts, maybe I could cut the cost of Hipower pack a little 

sorry for my poor English level but selfly I think I am improving everyday a little


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## arddea (Jan 23, 2010)

Mike

This 


LithiumStorage said:


> I don’t want to lend out cells so a novice can make a video of them exploding.


Plus 6.4 and 7 on this:
http://lithiumstorage.com/index.php?main_page=page&id=23

All point to HI Power not being LiFePO4. The storage requirements, the exploding comments, and the low cycle life all point to the batteries being LiCo or a derivative of LiCo. 

Is it LiCo or some other extenuating circumstance that makes it look like a lower performing battery, AKA the life cycle is 100%DOD at 3C. 

Please advise.


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## MN Driver (Sep 29, 2009)

Which exploding comments are you referring to? The storage requirements might be conservative or the other LiFePO4 manufacturers may be exaggerating that aspect as it seems every independent test has found LiFePO4 and LiCobalt more or less unusable in an EV application at -40C temperatures due to the dramatic voltage drop, HiPower is at a conservative -20C rating, from peoples experiences here the Thunder Sky batteries do have heavy voltage drop at these low temperatures despite their -45C rating, TS charts are all at 0.5C. I couldn't say anything about cycle life though. They claim 1000+ cycle for 1/3C charge and 1/2C discharge. The charge/discharge rates aren't uncommon but the count is lower than that being provided in datasheets from other Chinese battery manufacturers.


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## LithiumStorage (Feb 3, 2010)

arddea said:


> Mike
> 
> This
> 
> ...


Thanks for checking out the data sheets on my website!

Hipower cells are LiFePO4. My comment about making videos of them exploding was made in sarcastic jest; I had recently watched an online video of a guy who put an excessively load high on TS (Thunder Sky) cells in hopes to make them pop. They eventually caught fire as he shot at them with a gun. I can't afford to have that kind of wasteful fun with Lithium; but I would be willing to let the loaned cells be subject to rigorous tests so long as there's a purpose.

As the first post in this thread inferred, you can be abit tough on CHP (China Hipower) cells and still expect performance. I think the point of this thread is that EV enthusiasts want cells that match their expectations and budgets and they mistrust the data provided.

Prices aren’t too complicated. So what about expectations then? I hear that CHP underestimates their specs and CALB overestimates them abit. I hear that TS cells have improved in quality. But rumors are simply rumors. There is a need for an unbiased perspective to test the top brands and measure them against each other. For example, maybe CALB cells really are 4C; someone building a Tesla type EV would need to know that. Or maybe a guy just wants to build an economical commuter and needs to know how TS compares to CHP on cost and performance.

To answer evcomponents, I can provide 2pcs 100Ah Hipower cells for such a test. But I want to know what tests are planned and if most folks with find such acceptable.


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## arddea (Jan 23, 2010)

MN Driver said:


> Which exploding comments are you referring to?


The quote from Mike at lithium storage. 



MN Driver said:


> The storage requirements might be conservative or the other LiFePO4 manufacturers may be exaggerating


No other LiFe battery manufactures states that you have to discharge the battery for storage. The chemistry of LiFe batteries is more stable than LiCo. LiCo suffers from self oxidation that prematurely ages them if stored at full charge so discharging for storage is necessary. So requesting a discharge for storage implies lower stability chemistry. 



MN Driver said:


> that aspect as it seems every independent test has found LiFePO4 and LiCobalt more or less unusable in an EV application due to the dramatic voltage drop.


??? Tell that to the Killavolt (Sp?), Tesla, BYD's and Thunder Skys on the road all ready. (wish I could import a BYD 6E just to scrap for parts) The voltage drop for the nominal ratings is less then FLA or SLA. The problem is if you do not read the documentation and overload the battery the drop in voltage and cycle life is sever. For example if you build a 72V DC car the minimum batteries used should be the 200AH if not 300 or 400s any lower capacity battery is heavily overloaded. 

LiCo is unusable in EV due to the explosion factor. Can’t wait till I hear a Tesla burned down someone’s house because they forgot to flush the antifreeze. (OK, that's a jealousy factor.)




MN Driver said:


> I couldn't say anything about cycle life though. They claim 1000+ cycle for 1/3C charge and 1/2C discharge. The charge/discharge rates aren't uncommon but the count is lower than that being provided in datasheets from other Chinese battery manufacturers.


 A properly designed system should be around .5C nominal under normal driving conditions. I’m looking at nominal current of 70A (at 65MPH) for my AC system with peak of 330A (hard acceleration from 20 to 105). The ideal battery would be the 150AH but the closest is the 160AH from calb at about 2X the cost of the 100AH TS or Hi Power. 

Most others excluding headway claim a 3000+ Cycle life to 80% SOC at nominal C at 80%DOD on LiFe batteries. Headway can be expected to be lower as they state 1000 cycles to 80SOC at 5C at 100%DOD.


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## LithiumStorage (Feb 3, 2010)

Again, the comment about Lithium cells exploding was an attempt at humor. I guess it didn't translate well... see post #17.


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## arddea (Jan 23, 2010)

Hey - Hey no offence you posted your response while I was typing mine to MN.
You have a link to that video?

The reason I started this is while doing research I noticed that no battery manufacture seems to set up the tests for an apples to apples comparison. 

For example Headway measures cycle life at 100%DOD 1C and lists the 1 C curve only with time units instead of capacity. Headway states the battery can handle a continuous discharge of 20C. Most people will use it at 3 – 5C why is there no data in this zone?.

Thunder sky lists the drain curves for .5c 1C 3C, and 5C but states the max continuous use is 3C no time limit on this 3C is there one? what use is the 5C then? Can they do 5C and if so how long is safe? The cycle power curve is listed for .5C at un-translated DOD up to 8000 cycles. They rate it for 3000 at .5C of 80 DOD. 

Calb lists the drain curves for .1c .5c and 1C. and a cycle life of 2000 at 80% DOD and 3000 at 70% DOD, they do not list a curve for 4C. 4C is not continuous. What is the continuous discharge?

HiPower has a barely readable drain curve for 3C states the nominal is .3C constant is 3C and a 5C 15 second pulse. It displays a cycle life of 1000 at an undisclosed C or DOD. This last part makes the HiP look very undesirable, but are we tying to compare bad apple to a good apple or compare a good apple to a good orange?

So I was hoping that people would share their experiences so others would have a clue.


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## MN Driver (Sep 29, 2009)

arddea said:


> ??? Tell that to the Killavolt (Sp?), Tesla, BYD's and Thunder Skys on the road all ready. (wish I could import a BYD 6E just to scrap for parts) The voltage drop for the nominal ratings is less then FLA or SLA. The problem is if you do not read the documentation and overload the battery the drop in voltage and cycle life is sever. For example if you build a 72V DC car the minimum batteries used should be the 200AH if not 300 or 400s any lower capacity battery is heavily overloaded.


I made a mistake when typing that up and meant to discuss the -40C temperatures as I thought you were discussing temperatures with storage requirements. Due to the dramatic voltage drop, HiPower is at a conservative -20C rating, from peoples experiences here the Thunder Sky batteries do have heavy voltage drop at these low temperatures despite their -45C rating, TS charts are all at 0.5C. Ideally the batteries should be heated, and like you said be setup for 0.5C cruising. It seems most people hear are running around 1C cruising and 3C, sometimes more for acceleration due to the high cost of cells. I didn't realize you were talking about the discharging recommendation for storage instead of temperature as you weren't initially specific about it. When you were talking about them exploding, I thought you meant you saw this in the spec sheet as you were talking about the spec sheet storage requirements in the same post.

LiFe chemistry may be more stable than LiCo but we don't know how much more stable. LiCo degrades with time, just sitting on the shelf at full charge at room temperatures in a garage they slowly decay. We don't have enough time on LiFe research to know in real life how these fair in this respect and other respects. HiPower is probably doing what many people here are doing, which is taking LiCo recommendations and using those to 'play it safe' to hopefully get the longest life. Others are listening to the battery manufacturers and making up their own stories along the way such as the one suggestion from a particular member to charge Thunder Sky cells at the 3C charging specification and completely disregard the max charge voltage specified by the manufacturer at the same time and also have trust that the cells specifying -45C will do just fine at high C amp draws. Some information is passed on, made up, grandfathered in, and doesn't have any independent testing to back it up. I'm just not buying your argument that HiPower cells are LiCo just because their spec sheet has a few red flags that were probably more or less just copy/pasted to cover their ass.

A realistic cycle life is the one thing that is hard for the average EV person to obtain, especially with the concern of internal resistance rising with age preventing the higher C draws necessary for vehicle acceleration. When we start with cells that seem to have an appropriate voltage sag at say 3C or 4C and we need 2C, we might be okay. If you need 3C as part of the design of a vehicle and the battery starts dropping too low in voltage and damages itself after 1000 cycles, you've got lost a pack. If you knew to expect that and compromised to make a system that ran 2C, then the cycle life obviously be longer. We just don't have the testing beyond .5C to know if after, say 3000 cycles at 70% DOD if we can still get our car up to speed on the highway. I'm with you on sizing the batteries to cruise at .5C, I also want to have a realistic 100 miles too so I can completely park my gasoline car or sell my car and borrow or rent someone elses when I need it for everything except for a road trip.

"You have a link to that video?"
It won't load for me right now but the link to it is right on the Thunder Sky site. It's been linked here more recently though, I believe it was a Youtube link. I'm pretty sure that Thunder Sky just took the Youtube video of someone short circuiting the cells and shooting them and uploaded it to their site. If I remember right, there was a fair amount of smoke and heat but I don't remember if there was fire.
http://www.thunder-sky.com/technical_en.asp?id=454&typeid=106&orderby=2

You've got good questions, one that most of us here are also asking. The chart showing 5000 cycles with 80% discharge capacity, since it correlates with the spec for 70% DOD, you could assume they are connected. The standard for Lithium ratings is 80% discharge capacity is the factor for cycle life testing.

For your questions about discharge rates, here is an answer from Thunder Sky from this thread http://www.diyelectriccar.com/forum...o4-real-world-experience-thread-24433p12.html



CroDriver said:


> I have already posted this mail a few times but looks like no one have seen it
> 
> Quote:
> Dear Mate,
> ...


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## hipowerkevin (Jan 14, 2010)

arddea said:


> Hey - Hey no offence you posted your response while I was typing mine to MN.
> You have a link to that video?
> 
> The reason I started this is while doing research I noticed that no battery manufacture seems to set up the tests for an apples to apples comparison.
> ...


Hello arddea,

I offer some info hope it may help you.

For high C discharge, it need consider the RI, the fast temperature uping of pole, and the inner matiral reaction.
For RI is most need to be considered, if large current output and still keep in low RI, that is good quality cells.
The fast temperature uping on bus bar connection, and pole, need to resolve, you can calculate the healing as I*I*R, you need cold down it.

And inner matiral reaction, most complicated, in high C discharge it may cause battery damage, as I know thundersky cell would swell, so we don't recommend to do that.
but please don't talk about small round cell, they have different inner structure, and if you make hundreds of small round cell for your pack, you would be crazy because of cells corresponding in pack. 

I have data report of 50AH cell test, we do different test and logged, but it is Chinese edition, hard for me to translate in English, you all know my pool English.  But I have offered the testing of 48V100AH pack testing data you may check, as 1C,2C,3C discharge and charging curve.

The extreme testing would be done by our customer as famous company,
They just testing by them self and make decision. 

For cycle as 8000 times, 5000 times, you just treat it as joke, we all do not believe.


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## JRP3 (Mar 7, 2008)

I think to keep costs down and make testing of high C rates easier the smallest sized cell should be used, maybe 40ah or so. I don't think you really need a large volume of cells to be meaningful if the cells each come with ah and resistance ratings. Try to get 2-4 cells of each brand matched for similar ah and resistance and see what they'll do. That should be plenty. If one brand of cells is significantly different than the others you could try testing additional cells to be sure.


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## hipowerkevin (Jan 14, 2010)

MN Driver said:


> "You have a link to that video?"
> It won't load for me right now but the link to it is right on the Thunder Sky site. It's been linked here more recently though, I believe it was a Youtube link. I'm pretty sure that Thunder Sky just took the Youtube video of someone short circuiting the cells and shooting them and uploaded it to their site. If I remember right, there was a fair amount of smoke and heat but I don't remember if there was fire.
> http://www.thunder-sky.com/technical_en.asp?id=454&typeid=106&orderby=2
> 
> ...


I completly agree with MN Driver, people should treat cell reasonable and not be cheat by make up story or data.

To realize that we do not recommend 5C, 8C continuous discharge, it would damage battery, we suggest below 3C, like 2C.
And for life cycle, how does it can reach 8000, 5000 times? just bragging.

As the second link, the salesman say 100AH cells discharge at 20C, did she really take resposibilty of her words? discharge at 20C would damage the inner of cell heavily! even they could done, but it is extremly test, not for nominal using!

However, I think the salesman should take the basic spirit, that is not cofuse or misunderstanding people. as some one who says the life cycle reach 8000 times, discharging at 20C of 100AH cells, not consider the damage but just take it as honour and advertising, also some time befor I see "50000AH" battery for submarine on thundersky website, I feel deep disappointed.

As Hipower battery, we all offer two years guarantee, but we just put
100%DOD life cycle 1000 times in specification, we do not make up datas,
but we would tell people if in 80%DOD it could reach 2000 times, we are honest. and we also offer real testing data of 48V100AH pack, could be download, such curves is well accord with our 3C discharge curve in specification.

Any way keep honest and brave, time would finally prove the truth.


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## Tahoe Tim (Feb 20, 2010)

Am I the only one tired of a certain manufacturer stonewalling proof of his products while putting down other brands?

"crazy" to use lots of small cells? I guess he's never heard of Tesla, Zero motorcycles, and other PRODUCTION vehicles.


I am wishing for a US manufacturer to step up and start making prismatic cells for public purchase. I see a market for Evs, golf carts, car batteries, etc.


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## MN Driver (Sep 29, 2009)

Tahoe Tim said:


> I am wishing for a US manufacturer to step up and start making prismatic cells for public purchase. I see a market for Evs, golf carts, car batteries, etc.


I think it's all labor costs, the process is automated but where things currently are, it requires enough human intervention to the point where it isn't like lead-acid where the human intervention time is so low to barely be a factor of the manufacturing cost. Once the R&D reaches the point where things aren't changing and the machines can be built to build these, quality check them, and box them, we will likely have a US manufacturer building them here and hopefully supplying them to us. GM is touting that their batteries and motors will be assembled here, but I'm pretty sure the cells will still be traveling across the ocean from LG Chem before they get packed into the pack by Compact Power Inc. in Troy, Michigan.

I wouldn't mind getting my hands on a pack from crashed cars in the junkyards, nice compact cells capable of crazy rates. I have a feeling these production packs from various EVs will be a very hot item, especially knowing the testing that GM is putting behind the platform and the warranty they are putting behind it.


----------



## hipowerkevin (Jan 14, 2010)

Tahoe Tim said:


> Am I the only one tired of a certain manufacturer stonewalling proof of his products while putting down other brands?
> 
> "crazy" to use lots of small cells? I guess he's never heard of Tesla, Zero motorcycles, and other PRODUCTION vehicles.
> 
> ...


Sorry Tahoe, I just want to say if large battery pack like 288V200AH pack, using small round cell is not so well, because the it is hard to control the corresponding of cells, slightly vlot defference and RI, would low down the battery performance. 
Also I do not trust on life cycle about 8000, 5000 times, and I may not so good know EV or batteries, I just want to learn.


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## Matthijs (Jun 19, 2009)

Don't we have testing results from AndyH over at the endless-sphere? 

http://www.endless-sphere.com/forums/viewtopic.php?p=228297#p228297


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## Matthijs (Jun 19, 2009)

Tahoe Tim said:


> Am I the only one tired of a certain manufacturer stonewalling proof of his products while putting down other brands?
> 
> "crazy" to use lots of small cells? I guess he's never heard of Tesla, Zero motorcycles, and other PRODUCTION vehicles.
> 
> ...


Nope he is spamming the sphere as well. http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=17285


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## EVComponents (Apr 20, 2009)

arddea said:


> The reason I started this is while doing research I noticed that no battery manufacture seems to set up the tests for an apples to apples comparison.
> 
> So I was hoping that people would share their experiences so others would have a clue.


We seem to be discussing ThunderSky, CALB (Sky Energy), China Hipower and Headway.

Of those four brands, we offer three of them (not China Hipower). So I can comment on only the three that I have experience with.

ThunderSky is far and away the volume leader for us. In general customers have more confidence in that brand because they have been around over 10 years. Their performance and specs have improved dramatically in the past 12 months. We have had very few warranty claims in the past year. Approximately 1/10 of 1%. 1 out of 1,000 cells require warranty replacement.

Besides reliable performance, the strapping hardware from ThunderSky is much more user friendly. The CALB (Sky Energy) cells have poorly designed hardware to compress the cells together. 

At the company level, ThunderSky appears to have their act together in terms of production and delivery. They are much easier to deal with. We have constant problems dealing with CALB (Sky Energy).

Headway is a different type of cell for higher performance, higher discharge rates. This is appropriate for electric scooters, bikes, motorcycles, etc. The 38120 P cells (8 Ah) are good for drag racing with 40 C discharge rates. Mike Willmon is building a drag racing pack for the Crazy Horse Pinto with 500 of the P cells.

I have no experience with the China Hipower cells. They had a poor reputation in the past. But they might have improved. 

I am willing to send their 100 Ah cells for testing to Manzanita Micro for comparison testing versus a ThunderSky 100 Ah and a CALB 100 Ah. Someone (Kevin or Mike Collier) will have to agree to submit two China Hipower cells at their own expense. 

Rich Rudman (3rd party) of Manzanita Micro will do the testing for everyone and publish the results.


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## JRoque (Mar 9, 2010)

Jim, in a forum that at times seems to be dominated by commercial interests where "my" product is better than "your" product, it's refreshing to see you post something like this. Completely unbiased with full disclaimer. Not very many businesses will disclose this type of inside information so openly with the idea of helping their customers make the right choice. I mean, you sell the other products too and while you're not bashing them, you're sharing your experience as to which one you think it's best. Coming from a potential customer, that's greatly appreciated.

Back to topic: I understand that from a battery proper care and feed point of view, you want to be as granular as possible, perhaps down to a single cell. You want to monitor and charge them individually to extend their useful life and whatnot. But, from a whole system view, where losses and potential issues between connections, monitoring requirements, etc, what is the break point for cell group sizes? 

Example, if I wanted to build a ~120V pack, should I do 10ea 12V batteries or 37ea 3.2V cells? At what point does the individual cell granularity is overshadowed by the 12V convenience? This assumes the 12V battery would be factory shipped with welded cell connections, hence avoiding interconnection issues, and bound together to prevent bulging, etc.

Regards,
JR


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## AndyH (Jun 15, 2008)

Matthijs said:


> Don't we have testing results from AndyH over at the endless-sphere?
> 
> http://www.endless-sphere.com/forums/viewtopic.php?p=228297#p228297


I posted the info here first, actually...
http://www.diyelectriccar.com/forums/showpost.php?p=166242&postcount=16

I realize it's only one cell, and limited to 130A discharge, but it's a start. 

Andy


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## AndyH (Jun 15, 2008)

EVComponents said:


> <snip>
> I have no experience with the China Hipower cells. They had a poor reputation in the past. But they might have improved.
> 
> I am willing to send their 100 Ah cells for testing to Manzanita Micro for comparison testing versus a ThunderSky 100 Ah and a CALB 100 Ah. Someone (Kevin or Mike Collier) will have to agree to submit two China Hipower cells at their own expense.
> ...


I have the trio of cells that I bought from you in December - 100Ah TS YPO4, SE, and HP. They have four cycles on them - they were used to generate the 50A, 100A, and 130A curves that have already been posted here.

I'll send the three to you or Rich if you can use them. If you only need the HP cell, that's fine too.

Andy

ahecker (at) rechargeablelithiumpower.com


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## LithiumStorage (Feb 3, 2010)

AndyH said:


> I posted the info here first, actually...
> http://www.diyelectriccar.com/forums/showpost.php?p=166242&postcount=16
> 
> I realize it's only one cell, and limited to 130A discharge, but it's a start.
> ...


These tests were performed with the 2009-type 1C Hipower cells and not the newer 3C cells right?

I'm sure that Manzanita Micro is qualified to perform the tests, but half the point of this exercise is to get results without commercial bias; otherwise the Chinese would be the best source for information. Manzanita Micro lists evcomponents as their top distributor of their products...I don't think that's commercially removed enough from the source.

Anyone else interested in taking on the testing?


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## JRP3 (Mar 7, 2008)

I don't think EVC cares one way or the other. If the Hipower cells test well I think James would carry them. Where's the conflict?


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## major (Apr 4, 2008)

LithiumStorage said:


> Anyone else interested in taking on the testing?


Look at posts #3 and 6. I've got some different test equipment, but am willing to do it. No takers. Go figure 

major


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## LithiumStorage (Feb 3, 2010)

JRP3 said:


> I don't think EVC cares one way or the other. If the Hipower cells test well I think James would carry them. Where's the conflict?


I completely agree. And anyone can do the testing with the right equipment. My hope was to have someone/business not commercially related to the sources do the testing. Otherwise someone will always claim bias.


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## hipowerkevin (Jan 14, 2010)

AndyH said:


> I posted the info here first, actually...
> http://www.diyelectriccar.com/forums/showpost.php?p=166242&postcount=16
> 
> I realize it's only one cell, and limited to 130A discharge, but it's a start.
> Andy


Hello Andy,

I am sorry you got the capacity type, only offer 1C continous, its advantage is smart size and weight.
I offer the new type picture, you may check.
take care that *the slide side have horizontal bar* on it, but capacity type is total smooth.









Comparison, from the datasheet of two types,









and the comparsion table, It seems can not support the table,
you may visit:
http://spreadsheets.google.com/ccc?key=0AsrI5a1wMrabdGNVaHl4ODlIX3N4NXh4VTFRMExOTnc&hl=en
Hope those works.


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## AndyH (Jun 15, 2008)

LithiumStorage said:


> These tests were performed with the 2009-type 1C Hipower cells and not the newer 3C cells right?


Correct



LithiumStorage said:


> I'm sure that Manzanita Micro is qualified to perform the tests, but half the point of this exercise is to get results without commercial bias; otherwise the Chinese would be the best source for information. Manzanita Micro lists evcomponents as their top distributor of their products...I don't think that's commercially removed enough from the source.
> 
> Anyone else interested in taking on the testing?


Any of your commercial bias affecting your thoughts on EVC and/or MM's perceived bias?  Great way to add a bit of FUD to the efforts of a company that has been found so far to be above-board in their EV advocacy and support...

One of the first things I do when evaluating a cell, manufacturer, and retailer is a quick look at the product and compare it to the puslished specs. In this specific instance, and up to the 130A limit of my equipment, I found that HP's info was accurate - as was TS and SE.

When I walk into Sears I don't expect any of them to kiss my heiney as part of selecting a dish washer. I also don't expect anyone from a Chinese (or Korean or German...) manufacturer to swim their product on their back for my free in-home trial. If I do my job right, coordinate with the company, and feel good about the product meeting my needs, I buy it. If not, I look elsewhere.

I frankly don't think it's Kevin's job to give anyone anything free. When I want to compare cells I either find existing info that I trust or I buy the cells, buy the equipment, do my work, and see what I see.

Andy


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## major (Apr 4, 2008)

LithiumStorage said:


> My hope was to have someone/business not commercially related to the sources do the testing. Otherwise someone will always claim bias.


AndyH can go up to 130A and I can go to 500A. What's your problem? AndyH seems willing and I know I am.

BTW AndyH, I like your test results as posted. Keep up the good work 

major


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## LithiumStorage (Feb 3, 2010)

AndyH said:


> Any of your commercial bias affecting your thoughts on EVC and/or MM's perceived bias?  Great way to add a bit of FUD to the efforts of a company that has been found so far to be above-board in their EV advocacy and support...


I have no issue with EVC or MM and was not insinuating anything against them. My concern is having anyone with a related commercial interest in the sale of these brands also performing the testing. major seems like a good candidate.


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## MN Driver (Sep 29, 2009)

Kevin, thanks for letting us know how to tell the difference. It's good to have the clarification that those cells previously tested were the capacity cells instead of the power cells. I'm as interested in the results as anyone else is.


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## EVComponents (Apr 20, 2009)

JRP3 said:


> I don't think EVC cares one way or the other. If the Hipower cells test well I think James would carry them. Where's the conflict?


That is exactly correct.

If China Hipower tests well versus TS or SE and is price competitive, we would be offering them.

Prior testing has shown China Hipower to be a lesser cell but about the same price. So there has not been any reason to offer those cells.

But most companies do improve their products over time.
If the China Hipower cells have improved, we can always add them to our website and start importing the cells in volume.

But I am not going to risk any capital on importing China Hipower cells until I learn more.
Just my opinion.


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## Guest (Apr 7, 2010)

Tesseract said:


> To do a fair and meaningful test you would have to buy identical capacity packs from each manufacturer then run them through identical load cycles.
> 
> Who has the resources to do that?


Actually, I'm working on it at the moment. But I don't think you need to do that.

I have three DIFFERENT sized cells = all in the same physical package by size and weight. One is a TS 160AH, one a CALB 180AH, and the last a TS-200AH all in exactly the same form factor.

Here's the test scenario. I'm doing a 1C discharge to 100% immediately followed by a 1C charge back to 0%DOD. This is done at 1C, so 160 amps for the 160AH cell, and 200 amps for the 200AH cell. 

I'm actually counting amp hours, and I specifically want to be able to compare them. So, I'm taking voltage and temperature measurements every 4 AH on the 160 AH cell, 4.5 AH on the 180 AH cells, and every 5AH on the 200 AH cells. This represents an identical DOD at any point on any of the cells.

So that's how you compare different sized cells. I tried doing this by time, but I just wasn't precise enough. I've kind of cobbled together an Arduino current and AH counter that measures pretty nicely with my lab stuff, and it has enabled the whole thing. I've got 3000 watts of quite accurate constant current load is the other trick, and yes, that was a little expensive.

Working on graphing the data now. Should have something posted here this week.

Jack Rickard


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## AndyH (Jun 15, 2008)

What's your goal for this evaluation, Jack? What are you hoping to prove or disprove?

[edit] And how is your process different than simply connecting the cells to your West Mountain equipment and simply letting the machine run a continuous discharge while logging voltage, current, and temperature every second during discharge? The CBA with pro software can also log the charge portion. I frankly don't see any value to limiting data collection to 4 or 5Ah resolution.[/edit]

Andy



jrickard said:


> Actually, I'm working on it at the moment. But I don't think you need to do that.
> 
> I have three DIFFERENT sized cells = all in the same physical package by size and weight. One is a TS 160AH, one a CALB 180AH, and the last a TS-200AH all in exactly the same form factor.
> 
> ...


----------



## AndyH (Jun 15, 2008)

hipowerkevin said:


> Hello Andy,
> 
> I am sorry you got the capacity type, only offer 1C continous, its advantage is smart size and weight.


Hi Kevin,

No need to apologize. I bought exactly the cell I wanted to test, which was your 1C product.

I did the cell side-by-side evaluation because, frankly, I didn't think your cell was going to compare with Thunder Sky and Sky Energy/CALB.

I'm part of a group that includes at least six people using your early 1C cells in factory-produced Ford Ranger trucks. They're using your early cells primarily because they're inexpensive and because they can get 100 cells inside the Ford battery box.

While the cells look less capable on paper, and my load testing and internal resistance measurements confirm that the TS and SE cells perform better on the bench, I cannot deny that in the 'real world' the cells seem to work in an AC EV application - considering that one of the Ranger owners has a bit over 9000 miles on the pack - and that's with 2C/200A at the pack for acceleration and a bit less for regen.

I wish you well wiith your new factory and new cells!
Andy


----------



## Guest (Apr 8, 2010)

AndyH said:


> What's your goal for this evaluation, Jack? What are you hoping to prove or disprove?
> 
> Andy


Hmmm. Well the first topic is tidings of great joy. We have climbed from 160 Ah to 200 Ah in precisely the same weight and dimensions in 18 months, and the price has held almost exactly the same.

There are a lot of questions related to heat gain. One of the things we're doing with this is measuring the temperature somewhat accurately between two cells while doing a 1 hour continuous 1C drain.

And there are a lot of questions we receive about how these cells operate under load. You have a couple of guys on this forum that are propounding that these cells cannot be operated at 3C at all - and posing as knowledgeable BMS designing typing geniuses.

We are going to baseline these three cells at 1C - broadly establishing their similar nature. Then we are going to do a 3C pulsed test on the CALB 100Ah cells with pulses ON for a couple of AH and then OFF for a fixed time period, measuring voltages at the END of the draw period and the end of the rest period. This will show voltage sag at 3C, temperature gain at 3C, and roughly approximate a driving cycle.

So I suppose we are going to "prove" that they can do 3C. The largest value to it I think is that most users simply don't have a way to load these cells in the garage at these levels, and accurately measure voltage, current or temperature while doing so. So we're going to do that.

There is also some continuing enormous confusion about the charge process. In our 1C tests, we are also charging the cells at 1C and the voltage goes quite beyond the charge voltage listed on the spec sheet. We're actually counting the AH out of the cell and again back in to avoid overcharging the cells. At the completion of a 200A charge cycle providing a 1 hour charge of the cells, you will see that they settle down to the normal 3.35 v per cell at the end, despite having a "charge voltage" quite over 4.5 volts along the way.

Oh, and I'm going to show what a battery looks like if you overcharge it signficantly even at low currents past the fully charged point. It's a work of art actually.

Jack Rickard


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## GerhardRP (Nov 17, 2009)

jrickard said:


> We are going to baseline these three cells at 1C - broadly establishing their similar nature. Then we are going to do a 3C pulsed test on the CALB 100Ah cells with pulses ON for a couple of AH and then OFF for a fixed time period, measuring voltages at the END of the draw period and the end of the rest period. This will show voltage sag at 3C, temperature gain at 3C, and roughly approximate a driving cycle.


You are providing a great service, Jack.

Let me add a tweak to your protocol: Instead of having a complete rest between pulses, go to the discharge rate which will make the complete test last one hour, having drawn the rated Ah during that time. Then we have the difference between 1C and, as you say, a normal one hour drive [=100km at highway speeds] at an average of 1C with 3C or higher pulses included.

Gerhard


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## AndyH (Jun 15, 2008)

jrickard said:


> Hmmm. Well the first topic is tidings of great joy. We have climbed from 160 Ah to 200 Ah in precisely the same weight and dimensions in 18 months, and the price has held almost exactly the same.


Gotta love it when product evolution continues to happen as it has for thousands of years. 



jrickard said:


> There are a lot of questions related ...
> 
> We are going to baseline these three cells at 1C - broadly establishing their similar nature. Then we are going to do a 3C pulsed test on the CALB 100Ah cells with pulses ON for a couple of AH and then OFF for a fixed time period, measuring voltages at the END of the draw period and the end of the rest period. This will show voltage sag at 3C, temperature gain at 3C, and roughly approximate a driving cycle.
> 
> So I suppose we are going to "prove" that they can do 3C.


Someone on this forum has already posted data from TS that shows the ability and limits of up to 10C pulses. I guess confirming that would be useful.



jrickard said:


> There is also some continuing enormous confusion about the charge process. In our 1C tests, we are also charging the cells at 1C and the voltage goes quite beyond the charge voltage listed on the spec sheet.


If you're charging with the CC/CV process specified for LiFePO4 then cell voltage will not rise above the transition point. One can do that with a current limited power supply. Dial in the voltage - say 3.6V - and that defines the highest voltage point. Dial in the 1C charge current and let er rip. As the cell approaches full, current will continue to drop until reaching the .001-.002C rate specified by the manufacturer at the specified temperature.

If your cell voltage is rising above your set voltage during charge, then you're either not using a current-limited power supply or are testing something other than a standard charge. Either way, chances are very good that you're damaging cells. And that's supported by your statement that your cells bleed-down to 3.35V after charge.

Andy


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## Tesseract (Sep 27, 2008)

jrickard said:


> Actually, I'm working on it at the moment. But I don't think you need to do that.
> 
> I have three DIFFERENT sized cells = all in the same physical package by size and weight. One is a TS 160AH, one a CALB 180AH, and the last a TS-200AH all in exactly the same form factor.
> ....


Do I understand correctly that you are testing just one cell of each capacity?




jrickard said:


> ...
> And there are a lot of questions we receive about how these cells operate under load. You have a couple of guys on this forum that are propounding that these cells cannot be operated at 3C at all - and posing as knowledgeable BMS designing typing geniuses.
> ...


Is this sort of personal attack really necessary to make your point? I mean, either the data will support you or it won't.


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## Guest (Apr 8, 2010)

GerhardRP said:


> You are providing a great service, Jack.
> 
> Let me add a tweak to your protocol: Instead of having a complete rest between pulses, go to the discharge rate which will make the complete test last one hour, having drawn the rated Ah during that time. Then we have the difference between 1C and, as you say, a normal one hour drive [=100km at highway speeds] at an average of 1C with 3C or higher pulses included.
> 
> Gerhard


It's a good idea. I was going to do 30 seconds on and a minute off, which would basically work out the same at 3C - 20 minutes draw, 40 minutes rest over the course of an hour. But to be a little more accurate, we were going to fix what the AH should be in 30 seconds. It turns out to be .8333AH which is difficult to deal with.

At the moment, i"m leaning toward doing 100 1AH pulses with a 60 second rest between each. This is a little over the 30 seconds continuous rating, but not by much.

You might find it interesting that I'm combining a couple of tests here. I've been testing an Arduino/Hall Effect current sensor scheme for measuring current and AH. But we're also building a contactor for the Speedster Part Duh.

The Curtis controller actually does its own precharge and then activates the contactor with a relay activation signal from the controller. This circuit prefers a 24v coil.

I found a kind of interesting device. It's a Gigavac relay that features a kind of bus bar connection I find much more attractive than the wee little hex bolts on the Kilovacs. This bus bar allows it to dissipate quite a bit of heat. I put TWO of them in series and connected the busbar with a piece of 20mmx10 mm copper bar.

These relays are quite lower profile, allowing me to put them in an aluminum enclosure. By having 2 12v coils in series, I kind of match up to the 24v coil spec for the Curtis 1238. But it also gives me two contactors in series, an added safety consideration. In fact, Australia, I'm told, no longer requires a cockpit kill switch if you use two contactors in series.

The rating is 350Amps and we will do as high as 550 amps in the car. I think the addition of the copper bus bar will aid in heat dissipation and this will all work pretty well. But it rather brings up the question.

Generally, we don't really "break" the high currents the Kilovacs are spec'd for anyway. You normally shut off your ignition, and thus your contactor, once parked. You aren't really drawing anything at the time. How do we know it will actually brake a current load without arcing and welding the contacts?

So in my initial tests I've used this contactor box to break the 300 amp flow into the load - about 200 times. It is an enclosed unit, so I can't really open it up and inspect the terminals without destroying the contactor, which is $141. I'm not THAT curious. But I'm pleased to report that both relays seem to be working quite well after a couple of hundred disconnects with an absolutely measured 300 amps going through them at the time.

I'm kind of growing in confidence these units could actually interrupt a max current event.

So that's how we'll do the test. I have a switch to the 2 coils in series and a 24 v power supply. If I throw the switch, it energizes and connects four cells in series to the constant current load at 300 amps. If I flip it back, it disconnects them. We'll do that another 100 times in the data logging test itself.

I'll either be installing a known proven good contactor box in the Speedster Duh, or perhaps one I've already worn out. I'm not certain which.

Jack Rickard


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## AndyH (Jun 15, 2008)

jrickard said:


> ... that these cells cannot be operated at 3C


As already stated, Jack, the cells CAN be operated at 3C and higher rates - but the voltage sag gets really ugly at 3C and higher - especially in cooler weather. The voltage drop can be enough to hit controller shut-down on hard acceleration with a cold pack.

But I think the real reason for the reluctance to explore higher discharge rates is related to cell life. It's well known that Li-based cells give up some of the life when they're overcharged, over discharged, and discharged at a high rate. One example:









Some Li-Ion/LiFePO4 background for you:

http://focus.ti.com/lit/an/slua443/slua443.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/22191a.pdf
http://www.thunder-sky.com/pdf/IM.pdf
http://helifreak.com/showthread.php?t=40579
http://www.intersil.com/products/deviceinfo.asp?pn=ISL9219
http://www.powerstream.com/li.htm
http://grouper.ieee.org/groups/1625/
http://www.buchmann.ca/Chap4-page9.asp

Andy
http://www.batteryuniversity.com/images/parttwo-34.jpg


----------



## Guest (Apr 8, 2010)

AndyH said:


> If your cell voltage is rising above your set voltage during charge, then you're either not using a current-limited power supply or are testing something other than a standard charge. Either way, chances are very good that you're damaging cells. And that's supported by your statement that your cells bleed-down to 3.35V after charge.
> 
> Andy


A lot of misinformation there. But do let me explain. The power supply specifically is a Lambda lab supply of 2000 watts. It can provide power in either constant current or constant voltage as I like. We did the charge test at a constant current of 200 amps on a 200 Ah cell, 180 amps on a 180 amp cell, and 160 amps on a 160 Ah cell - kind of what 1C charging is all about. 

But that's not the point. There is a strong misunderstanding of what that Spec curve is, and again, you've proven that it is an ongoing misunderstanding. There is no magic in the terminal voltages at all. The battery doesn't care what the terminal voltage is and never did. 

IF you did a constant current charge to the given spec voltage, and switched to a constant voltage source at that voltage and held until the current diminished to some low value (0.05C is the spec I think), you would fully charge the cell. That terminal voltage has NOTHING to do with the voltage of a fully charged cell, which in all cases of LiFePo4 is 3.4v, whatever the manufacturer states as the "nominal" voltage. 

It's actually kind of hard to actually reach precisely 3.4v without overcharging it a bit. If I see somewhere between 3.35 and 3.38 I'm pretty happy with it on the bench, though I would never charge to that in a car.

In any event, after charging the cells the voltage WILL bleed down to about 3.35v if the cells are NOT damaged. If they linger for more than a few hours, you kind of have a problem, though I've noticed the new Yttrium cells do linger longer than the others. This is surface charge which should dissipate. If you put a very light load of a few amps for a couple of minutes, it will certainly bleed off.

I had this argument once with a guy on the Endlessly Boring Sphere forum. I don't suppose it was you? Turns out he was faking his data outright and selling BMS systems on the side.

In any event, the theoretical fully charged voltage on the cell is 3.400v and the practical voltage you will see is somewhere between 3.35 and 3.38 unless you really run it down to zero amps over a day or so. 

The 3.6v, 4.00v, or 4.25 volts are simply calculated CC/CV curves to GET you fully charged using something that is easy to measure, current and voltage. You can derive such a curve at ANY voltage. The cell doesn't care what the voltage is, or apparently the speed of energy absorption up to I'm told 3C. At that point there are simply some temperature issues.

So we were demonstrating a 1C charge. And using AH to count down and back up. As there is a minor loss in the round trip, a little over an AH, we wind up stopping safely before fully charged.

And yes, of course we fall back to the proper voltage. And the cells are quite fine thank you.

You can recharge your car in an hour.

By spec, at the sacrifice of some cycle life, you can do it in 20 minutes.

THat's one of the things I'm trying to demonstrate here.

Jack Rickard


----------



## Guest (Apr 8, 2010)

AndyH said:


> As already stated, Jack, the cells CAN be operated at 3C and higher rates - but the voltage sag gets really ugly at 3C and higher - especially in cooler weather. The voltage drop can be enough to hit controller shut-down on hard acceleration with a cold pack.
> 
> But I think the real reason for the reluctance to explore higher discharge rates is related to cell life. It's well known that Li-based cells give up some of the life when they're overcharged, over discharged, and discharged at a high rate. One example:
> 
> ...


That's why I do the videos. There are so many of you guys typing misinformation so furiously. It WAS you on Endless sphere with the faked data on surface charge dissipation wasn't it?

Jack Rickard


----------



## Guest (Apr 8, 2010)

AndyH said:


> As already stated, Jack, the cells CAN be operated at 3C and higher rates - but the voltage sag gets really ugly at 3C and higher - especially in cooler weather. The voltage drop can be enough to hit controller shut-down on hard acceleration with a cold pack.
> 
> But I think the real reason for the reluctance to explore higher discharge rates is related to cell life. It's well known that Li-based cells give up some of the life when they're overcharged, over discharged, and discharged at a high rate. One example:
> 
> ...


This IS the guy from endlessly-boring sphere. Let me alert you people, he was busted outright FAKING data. He sent me some graphs trying to demonstrate something idiotic. It caught my eye over THIS issue of surface charge dissipation and I started questioning his data. He informed with GREAT authority that the cell somehow has a higher than theoretical terminal voltage when it's new and that if you do fall back to 3.4 volts you have damaged the cell. 

He was persuasive enough that I spent about 5 hours manually testing this like a moron. Of course it was not only not true, but the only way I could actually GET his results was to grossly overcharge a Sky Energy cell (out another $110 on this idiocy) and then indeed I did get it to hang at 3.65 volts. Of course the cell was ruined.

So I simply started to question how he derived this data for these pretty graphs. I got some vague allusions to an "automated system." I gave him my data, using his test scenario, and pointed out that I got exactly the OPPPOSITE result. This is a mystery that has to be resolved. I asked him to do some manual tests to try to duplicate HIS results without the automation, so I could verify.

Instead of collaborating, he informed me I was a jerk and he was adding my e-mail address to his SPAM folder (at least not a death threat eh).

I'm adding a copy of my e-mail of last January. As it turns out, his buddy makes BMSs. He is the main touter and salesman. They run the Endless Sphere forum to sell these things. And he routinely publishes graphs with faked battery data in them. 

Here was my e-mail with the data I generated after several hours of trying to duplicate his:


Ok, I think I've got it. No, we're not talking the same language at
all. The remaining graphs are really not very interesting to me. As
I said, they indicate almost EXACTLY the opposite of your
interpretation and are entirely normal. The more you try to fix em,
the more damage you'll do.


What has had me going in circles is this:


>
> The TS100 bleed image is a new TS 100Ah cell charged to 4.2V and allowed to
> sit for 24 hours with no load. A more experience cell will bleed to a lower
> voltage; a damaged cell will bleed to a much lower voltage - like my used
> and abused PSI cell chart.
>
> We agree that a fully charged cell will bleed down a bit when charge current
> is removed. And though I don't know where you got the 3.4V number, I think
> we can agree that a cell with a resting voltage below 3.4 is probably not
> fully charged.
>
> Back to page 1: This 30 minute shapshot is after the TSL charger was
> disconnected from the pack. The cells that are full but were pushed into
> the 3.6V range are bleeding down. The low cells - as low as 3.27V - are
> just sitting there. This is static data.

Your claim is that the cells remain at higher voltages and do not
descend to their natural static voltage and yes 3.4 is definitely the
fully charged voltage of the cell.
You went ON to say that they would fall to that level IF they had
already been damaged but that I would never see that with a good cell.

This is an amazing statement, and would indicate that I've seriously
overlooked an amazing fact for a long period on a LOT of cells.

Five hours of watching paint dry later:

Cell 1 is a brand new out of the box Thundersky TS-LFP90Ah cell
Cell 2 is a thoroughly experienced bench test cell thought to be still
in good shape but run quite a bit on the bench - same specs
Cell 3 is a TS LFP160Ah cell intentionally overcharged for one hour at
5.5 v. Pronounced swelling. Recompressed between two steel plates on
a bench vise and confirmed to have diminished capacity to 128 AH from
the original 164Ah.


All three cells were charged to an identical 4.1936 volts to 4 amps
and then the power removed.

CELL 1

1 minute 4.03v
2 minute 3.93 v
3 minute 3.87v
4 minute 3.82v
5 minute 3.79v
6 minute 3.77v
7 minute 3.74v
8 minute 3,73 v
9 minute 3.71v
10 minute 3.70v
60 minute 3.45v
75 minute 3.43v
90 minute 3.42v
105 minute 3.41v
120 minute 3.41v
180 minute 3.40v
195 minute 3.40v

Cell 2 "Experienced"

1 minute 4.05v
2 minute 3.96 v
3 minute 3.89v
4 minute 3.85v
5 minute 3.81v
6 minute 3.78v
7 minute 3.76v
8 minute 3,75 v
9 minute 3.73v
10 minute 3.72v
60 minute 3.47v
75 minute 3.45v
90 minute 3.43v
105 minute 3.41v
120 minute 3.41v
180 minute 3.40v
195 minute 3.40v

Cell 3 "Known damaged"

1 minute 4.02v
2 minute 3.94 v
3 minute 3.88v
4 minute 3.84v
5 minute 3.81v
6 minute 3.80v
7 minute 3.78v
8 minute 3,76 v
9 minute 3.75v
10 minute 3.74v


I did not bother to continue the checks on Cell 3. Clearly there is
no difference between BRAND NEW, experienced, and known damaged in the
bleed off of surface charge. And they all wind up at 3.40 vdc if
properly charged to manufacturers maximum charge. You did not run the
test long enough, and you drew some BIZARRE (albeit interesting if
true - you had me going there) conclusions. There is nothing wrong
with my cells except for cells I've tortured to death on purpose.
They behave EXACTLY as I described, though I may have exaggerated with
the "within just a few minutes" it's more like 180 minutes to
completely bleed off the charge voltage. But exactly as described.

Now your charts and charging. First, there is not enough energy
between the "fully charged" condition and what you're showing to
bother with. In fact, by sacrificing that bit of extra range, you
will dramatically prolong the life of your cells. Your STRONGER cells
are the ones lagging at the bottom. It is a long flat curve followed
by a steep hill climb. Theyh haven't started the climb yet because
they are larger capacity cells.

Your attempts to balance the cells are also not productive. While I
charge a bit at 200 amps, series packs in car sizes are difficult to
charge without heavy equipment much past 15 or 20 amps at a time. But
I routinely draw 540 amps from the cells on the freeway, and have for
over a year - NO BMS and NO BALANCING. If you would take the time to
watch the videos, you'll find that I did simulate a top balancing
regime on a GEM and was able to destroy 3 cells in a week with this
technique. The cells really don't care about charging and the
overcharging you all are striving to avoid is not as damaging as you
apparently think. It ain't any good for them, but one of the cells I
just tested to disprove your interesting but not very accurate theory
was overcharged for an hour at 5.5v AFTER being fully charged. It
swoll up like a football. But it's still useful around the shop. The
thing will do 128 amp hours now and put out a couple or 300 amps at
the drop of a hat.

What can KILL a cell irrecoverably and without recourse, useful only
as a door stop is cell reversal under load. This is NOT what you all
are describing. The cell hasn't just fallen. It's fallen behind the
others in the pack, and thehy are now driving 500 amps through the
cell violently. This is because one cell reached the knee of the
curve in advance of the others, because of differing cell capacities.

If you DON'T balance at all, and try to stay at least below 90%DOD,
it's not much of a problem. But if you TOP balanced, instead of
splitting the differences top and bottom, you are lining them up at
the top and putting ALL the difference at the bottom, where the damage
can be done at high current levels.


So, I only balance when marrying in a new cell. I CHECK balance
periodically, at the bottom. And I intentionally undercharge the
cells to an average voltage of 3.65 KNOWING FULL WELL that some are
not getting a maximum charge, and knowing that a few are going to be
climbing that wall up pretty close to 4v. But on average, it extends
the life of the pack and avoids the problems of overcharging any one
cell. I've got 7700 miles on the Speedster in a year, and routinely
HAVE taken it down to 95% or more DOD. The 80% mark comes in about an
85 mile range. The longest I've driven it is 107 miles.

The concept of a DAMAGED cell reaching it's natural static voltage but
a NEW cell not, complete with definitive graph, was interesting. But
not very. Try your test again on a NEW cell and a DAMAGED cell and
run it for 180 minutes and report those results. I think you'll find
a very different story from what you have put out here.


----------



## JRoque (Mar 9, 2010)

> It WAS you on Endless sphere with the faked data on surface charge dissipation wasn't it?


Jack, you're so charming some times  ...and that's fine, too.

I'm far from an expert but I've always charged my batteries with both CC/CV loops. They simply switch from primary control source to secondary but they're both always there. You wouldn't want to charge CC and not watch your voltage, for example.

JR


----------



## Guest (Apr 8, 2010)

JRoque said:


> Jack, you're so charming some times  ...and that's fine, too.
> 
> I'm far from an expert but I've always charged my batteries with both CC/CV loops. They simply switch from primary control source to secondary but they're both always there. You wouldn't want to charge CC and not watch your voltage, for example.
> 
> JR


You're quite right. But do you understand why? IF you could monitor AH in and out, you can charge at quite high voltage and current levels. If you cannot, you use the CC/CV technique and do it the normal way because that's all you have. 

The batteries don't care. You CAN charge them at 1C or even 3C and you do not HAVE to mind the voltage at all, as long as you don't overcharge them. If you're not monitoring voltage, how do you know? Well, you have to count coulombs. 

The batteries don't care much how you get there. My point is the voltage never was what mattered, it's simply a handy technique to get to full charge. But you can certainly charge at higher voltages and currents, as long as you know somehow where to stop. 

It won't "damage" the cells per se. It may wear on them a little.

Jack RIckard


----------



## Guest (Apr 8, 2010)

It's generally about quick charging. It's coming. And I think I'll like it. If all of this seems too unreal, see Manzanita's web site. True, it is beyond even my means. But they are now offering a 225 amp charge system. Basically 3 PFC75's on a 3-phase hookup with cooling.

Of course, it's $24,000. We recently mentioned an AkerWade system to do the same thing. It IS going to be available, and quick charging is quite real. And it has a use. WIth basically a controller much like the one in your car and a mother bank of batteries in your garage, you could do it now. 

The question is how will the batteries react. Basically, you need an AH counter and you probably need to stop short of a full charge. But we are demonstrating that you can charge cells at high currents without destroying or damaging them. 

Would I do it every day? I don't need to do it every day. But it extends the utility of the car to be able to. If I did want to drive to ST. Louis, and there was a place I could charge the car in 30 minutes along the way, I would want to do it. If I could count coulombs, and do an 80% charge, that's probably what I'd opt for.

I see AH as the proper metric ultimately for all of it. It is the equivalent of the gallon. Ultimately kWh are even better.

Jack RIckard


----------



## JRoque (Mar 9, 2010)

Hey Jack, let's see how far I can get into this before I get zapped (no pun intended).... again, I'm no expert.

I always thought you had to watch your voltage, too, so it's not just pumping amps and keeping that below the rating. Parameters to watch are:

- Current
- Voltage
- Temp
- Time

Here's how I've known it, and you're suggesting it can be different to accelerate charging:

You start applying a max current while watching voltage since the bat can be already charged and not present too much of a load. Yes, you could read the voltage before the charging cycle starts but temperature and recent drain/charge might skew that.

You continue with your constant current for a given time period. You don't just measure current alone because bats need that nice current flow in to break crystal forming. You also watch your voltage so it doesn't exceed the breakdown point.

After a given time period (an hour or so for some chemistries), you switch to constant voltage and let the current roll off.

All the while, you're watching the battery temperature since it will also be an indicator of when to break the charging cycle. This is why it's not a good idea to charge while the battery is hot, either by recent use, charge or ambient.

On the flip side of this, you (and I have read bits on this elsewhere too) say that I can pump as much voltage - within reason I assume - into the battery as long as I keep the charging current below rating, true?

Hmmm, this is kinda off main topic. Maybe I should move this to another thread.

JR


----------



## AndyH (Jun 15, 2008)

jrickard said:


> Instead of collaborating, he informed me I was a jerk and he was adding my e-mail address to his SPAM folder.


I see you choose to represent personal communications the same way you work with battery data. So be it.

If I didn't 100% believe you had the right to speak, I would not have served in this country's uniform for more than 21 years. That being said, I believe I have earned the right to not be subjected to some of the more coarse portions of your personality in my personal inbox. After requesting three times a reduction in personal attacks, I informed you that I no longer wanted to converse with you.

You chose to berate 30+ year electrical engineers with many years' experience with LiFePO4. You also chose to ignore my thoughts on management - which I learned from engineers that make and test the cells. That's fine! Each of us is free to speak and free to selectively listen.

But I trust you'll not take it personally if I choose to learn cell management from cell manufacturers and PhD EEs rather than people that make videos.

Unsubscribed.

Andy


----------



## Guest (Apr 9, 2010)

JRoque said:


> Hey Jack, let's see how far I can get into this before I get zapped (no pun intended).... again, I'm no expert.
> 
> I always thought you had to watch your voltage, too, so it's not just pumping amps and keeping that below the rating. Parameters to watch are:
> 
> ...


You're understanding of charging basics is quite good JR. The only thing that I would take exception to is the temperature. This is a hold over from lead acid battery thinking. It makes sense that it would also apply to LiFePo4, and undoubtedly in extremis it does. But in practice it doesn't matter much as the operating temperature of the cell is up to about 85C, and you never see that in even extreme ambient temperatures and extreme charge currents. So as a practical matter you can ignore it.

The CC/CV charge curve is just the way to do it, and in fact, the more exotic forms of that with multiple stages and absorption phases and so forth do not seem to render any advantage with these cells. They do not sulfate. It is NOT important that they be fully charged each time. And so a lot of the woof and lore of lead acid CC/CV charge curve magic sauce simply doesn't do anything. A very simple CC/CV charge curve works superbly.

The overriding caveat is that you are simply better off with a series pack to charge to an undercharged average cell voltage for your curve rather than the spec voltage. The 4.25v for Thundersky cells, for example, in series strings of over about five, we charge to 3.65v. In fact I have a THundersky 72v charger and it is hardwired for 87v - no adjustments in the device at all, which works out to 3.625v.

So if you charge at the spec standard current of 0.3C or 0.5C and you charge at that current to reach the voltage (let's say my 3.65v) you will have a string of slightly undercharged cells that will read somewhere in the 3.33-3.36v range after the charge is complete and the surface charge has dissipated.

NOW. Let's talk about higher currents.

The voltage and current on the spec sheet charge curve is ONE way and a GOOD way to get to a fully charged cell of just under 3.4000 v. It is not the ONLY way. In fact there are a million ways.

The charge process is basically putting energy into the cell. As long as lithium ions can be recombined readily, it will take it. And the manufacturer SPECIFICALLY tells us that it will take it safely at rates up to 3C.

It is very easy to measure voltage. It is somewhat easy to measure amperage. It is really only a step further to integrate AH from amperage and time.

IF you can measure AH, you can quite safely charge at very high currents, and certainly, we are told, up to 3C - but the overcharge restriction still applies. THE VOLTAGE DOESN"T. Actually it never did. It DESCRIBED a charge curve that would get you to 100% charge. If you EXCEEDED the voltage using that charge curve, you would have OVERCHARGED the cell which does the damage. But the terminal voltage itself never damaged anything - the continued application of power beyond the available lithium ion population caused the damage.

By counting AH, you can recharge at very high currents and stop the charge process before you have overcharged the cell. Because the LiFePo4 cells are really comparatively efficient, you can actually come quite close. I have taken 200AH out of a cell at 200 amps, and put 200AH back into the cell, again at 200 amps, and then rested the cell. Somewhat later, I put a standard charge curve on the cell at 0.3C. It absorbed an additional 1.35AH. 

Do I advocate doing this to your cells on a daily basis? Probably not. But in practice, if you have the power available, and need to quickly charge the car, you could for example very safely put 80% of the AH used back into the car at currents up to 3C. In doing this, even your terminal voltage won't exceed the given values. But you can do it up to 99.4%, with terminal voltages quite exceeding the values, and no harm to the cell is apparent. I've done it. And we'll probably tape it next week. 

I'll probably also show some melted slag I produced at 3 AMPERES.

Jack Rickard


----------



## Guest (Apr 9, 2010)

So I guess by showing melted slag, I've proven your point on temperature. Yes, if you overcharge for several hours, even at very LOW currents, it will go into thermal runaway and literally melt the battery into slag with very high levels of heat.

(I've done that too).

Jack Rickard


----------



## JRoque (Mar 9, 2010)

Excellent information, Jack, thanks. I'll keep this handy when working on my charger.

My hang with temperature comes from experience with NiMH and how a relatively small change in temperature is indicative of end of charge cycle. I'm glad LiFePO4 has done away with that, practically speaking.

Ah charging shouldn't be too difficult given voltage, current and time values plus knowing the battery rating. I do something like that on a charger a built some time ago.

Ok back to regularly scheduled program. Anyone ready to post 'who's best' battery charts?

JR


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## eva-michael (Apr 13, 2010)

In the middle 2008, I have ever gone to the factory of Hipower. At that time they didn't show me as "a busy factory". Also the sample I get from them at that time do not provide us a performance which will make us satisfied. At that time when I ask them to send a pack sample, they just send me some cells which are combined by some poor quality wires. Anyway I dont contact them anymore after that. Maybe they get improvement............
Last: Hipower is also one of lithium factory which China goverment pay emphasis on its development as TS. They are in same energy project of the goverment.


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## JRoque (Mar 9, 2010)

Calling on Jack:

I just watched your EVTV show for April 16, 2010. A great amount of excellent information there with no perceivable bias just like we like it. When I opened this "Batteries and Charging" forum to post this, I looked at the questions being posted and thought, hmm, these guys need to watch your show. Almost all of them could be answered by watching your demo. Thanks for that.

Now, you flew by a comment on how Lithium batteries don't like or need floating charges and I'm curious about that. Why not? If I hold the battery "charged" voltage constant, the current will taper off and you can hold this voltage indefinitely as the battery will (should) not absorb anymore current. If you keep this voltage constant, any cells that have not fully charge yet will continue to do so until all cells in your battery pack are balanced. 

Let me disclose that I believe the whole balancing of cells thing is a bit overrated. As I understand it, batteries will settle in their own charge/discharge cycle as they typically exhibit slight internal resistance and chemical variations between them. So, with all system things equal, if a cell doesn't come up to it's specified charge voltage that means that it has resistance or chemical differences with it's mates. You carefully balance them out and as soon as you put them to use, they're off balance again. If their higher resistance prevented them from reaching fully charged voltage, the same resistance will keep them from discharging fully compared to others.

On the flip side, if you have one cell that gets to it's charge voltage quicker than the rest, you only risk damaging that cell if your charge voltage (from your charger) is greater than your cell's charge voltage spec. No? That's why I believe "floating" the charger at the cell's charge voltage is important if you want to balance out your pack.

While I do see the merits of your proposed Ah charging concept, I'm still trying to wrap my lead acid head around that. Perhaps the crux of it all is that LI batteries continue to absorb current even after they're been charged, in which case constant voltage is irrelevant... but you tell me.

Ok, shoot away!!

JR


----------



## Guest (Apr 21, 2010)

Yes. We have finished the 1C segment. I'm going to start work today on the 3C segment. I've already done some tests, but we're going to go through kind of the same thing but with PULSED 3C for a couple of amp hours with a rest bettween each.

The current stuff is most available on my blog at http://jackRickard.blogspot.com/

This contains not only the video, but the graph images and a link to the actual Microsoft spreadsheet.

Float. Balancing. Etc. I confess to not know a whole lot about it. However.

My BELIEF is that the constant voltage phase of the charge curve is actually very important and this is where the inclination to self balancing, which is a very mild inclination, occurs. You charge at high currents, and when you reach the spec voltage, 3.6v for SE or 4.0v for new TS cells, you hold it there. We actually use 3.5 and 3.65. As the battery charge state increases, the current will naturally decrease. You do this to a low value.

I'm with you so far.

Now the concept of "float" in batteries is that you leave a trickle charge on that maintains the cells at their open circuit terminal voltage. For LiFePo4 this is 3.4 volts. But the reason you usually do this is to maintain batteries that are not used over time.

We're specifically advised by the manufacturer that if the cells are not to be used for some time, they be discharged to 55-60% charge for that period.

This kinda/sorta makes sense. Every single test we do seems to emphasize that these cells will last longest and work best in the middle of their charge discharge curve. In other words, if you had the cell at 50%, charged it to 51%, and discharged it to 49%, you could probably repeat this for 10 million cycles with no loss in capacity. Of course you're not using any capacity and that's not what we need these cells for. But it is a concept worth understanding. Very unlike NiMH, NiCAD, and most specifically unlike PBa cells, these cells do not like the extremes. Overcharging hurts. Overdischarging hurts. And if you work back from those too ends, the logically extremis is dead in the middle.

So you don't really float charge the cells at the 3.4volt level. You fully absorb during constant voltage until the current diminishes to a very low level, and then drop it. As a practical matter, you will wind up with 3.35v after a few hours. 

Ergo my comment that "float doesn't precisely make sense with these cells." For storage you do NOT want them at 100% charge - better 55% charge to allow the minor self discharge they will exhibit.

But I also constantly see people trying to use Zivan's and simple chargers and simply cut off the charger when the cell reaches a voltage level. This is wrong. As you describe, you DO need the CV stage and probably need it more than the CC stage. I would rather bring it instantly to spec voltage and hold it there until current gradually drops to zero.

Point of the video is that ultimately you are just putting power in. If you could do that accurately without using the curve, you can do it. But ideally, you would do 80% of it fast charge, and top off with a standard curve to affect this CV stage, where I do think some minor adjustment between the cells occurs, effectively accomplishing some balance. Through enough charge and discharge cycles, they will become more closely aligned in both balance and even capacity I think.

Jack Rickard
http://EVTV.me


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## david85 (Nov 12, 2007)

Jack, what you just described is how the Hipower chargers work for me. Only difference is I also have a BMS that "burns off" the higher cells as they approach 3.65V and above. There is some natural inclination for the cells to self balance under these conditions, but it is very small.

Once it gets to float charge, the voltage from the charger gradually drops and the BMS has an easier time micro adjusting the cells. Repeated cycling like this does bring the batteries within excellent balance relative to each other. It's been a little harder doing this on the big pack than the small one, but I everything does seem to be charging closer togother as I cycle deeper each time.

So far the setup seems to work very well.


----------



## ElectriCar (Jun 15, 2008)

So has the comparison testing been derailed? I've looked at the self stated cycle life and IR values of TS, SE and Hi Power but TS doesn't post it's IR values that I can find. 

So far what I've found is HI Power IR is <2 mohm, SE is <1 mohm. 

TS has the highest life cycles it seems but has higher sag values = higher IR value = more energy wasted charging and discharging. 

SE stated nom. voltage is 3.4, TS and HP is 3.2

Cycles: HP says >1000 to 100%DOD, TS >3000 to 80%, SE >2000 to 80%

HP seems to be interested in a low IR or RI, however it should be labeled, thus the use of the HUGE terminals. 

From a MFG self posted data perspective I'm inclined to go with HP if as Kevin says they could say at 80% HP could post 2000 cycles. 

I just hope someone will test them all with a decent number of cells of the size typically used in an EV. 

I want to go with the 160-200ah to keep discharge <3C and have a long range. Also want a low IR as I don't want to waste energy on internal battery voltage drop. That's comparable to having an engine running rich or more like having the brakes dragging. It's wasteful.


----------



## major (Apr 4, 2008)

ElectriCar said:


> So has the comparison testing been derailed?


Hi Electri,

Nobody was willing to take me up on my offer. And I have not seen any other objective test comparisons.

I want to warn you that manufacturers' specifications can be misleading, to say the least. I won't go so far as to say they are false. But the numbers representing attributes can be different from what you may interpret. Meaning they are not certified to any unified standards to my knowledge.

I have tested internal resistance and capacity on one type of Lithium cell and it conformed fairly well to the specification. However the bulk of my battery test experience has been with Pb-Acid and there rarely did an actual measured internal resistance at DC load meet the manufacturer's specification. And capacities varied all over the place.

I have not done life testing or temperature dependency tests. 

I realize that a set of Lithium cells is a large expense for an individual and commend you for your research. But I think you may do better researching the integrity of the dealer and company, and the user base for the product. Afterall, can you actually verify the internal resistance of the cells you buy? And how long is the warranty period compared to the life cycle specifications? Could you document your DOD and number of cycles to make a claim after you have 15 or 20% of the cells go south in 18 months? 

I don't have the answer for you. Just wanted to you to know my concerns. 

I've been busy with some non-battery related projects. But intend to get back to my battery testing next month. 

Regards,

major


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## ElectriCar (Jun 15, 2008)

Major, Jim at EVComponents on page 3 of this thread said they would volunteer Thundersky and SkyEnergy cells for another company for testing. Maybe you could talk to him about it.

RE the internal resistance, I read in another thread that FLA has an IR of .003-4 ohms. Compare that to SE being <.001 and HP being <.002. Though those numbers appear close and only .001-2 difference, actually those are HUGE differences from the lowest to the highest. 

Lets look closer. At 500A you're looking at a voltage drop of 1.5-2.0V (25-33%) on a 6V FLA, 1V or 31.25% for the HP and 0.5V or 15.6% for the SE unit. 

This leaves the resulting voltage to the controller from the pack on my 144V system at: 
95-108V for the FLA (my current battery) Variation may be due to operating temp???
99V for the HP (only better than some flooded batteries)
121.5 for the SE (blows away everything!)

THAT IS HUGE to say the least!

Again, this is based on their stated IR for the li batteries.

And if you test the batteries at a known current draw, can't you calculate the IR based on the voltage on the battery at that point?


----------



## major (Apr 4, 2008)

ElectriCar said:


> And if you test the batteries at a known current draw, can't you calculate the IR based on the voltage on the battery at that point?


Well, I test the internal resistance between two load points so I don't have to use the open circuit voltage which can be dubious. Like at about 1C and 2C. Take the difference in voltage and divide by the difference in current. And then double check it at 2C and 4C. But I don't think this is how battery manufacturers determine it 

I am not about to call Jim at EVComponents with all that is happening there


----------



## MN Driver (Sep 29, 2009)

Quotes are from ElectriCar and are clipped a bit, going to the original a few posts back has more info to put this into context.

'So far what I've found is HI Power IR is <2 mohm, SE is <1 mohm.'

That is a big difference, like major said it all depends on how it was tested and it's hard to tell if it was right off a charge or at 50% SOC or some kind of weird average. Since IR increases as you discharge the pack, it makes things a little difficult to work with. Temperature is huge too, we don't know what the manufacturers are using for temp when fabricating a number. I look at the discharge graphs where SE and TS are put together and it looks like SE is the IR winner.

'TS has the highest life cycles it seems but has higher sag values = higher IR value = more energy wasted charging and discharging.'

I've also read that using a similar high C rating with a battery with higher IR is likely going to cause the battery with higher IR to last a shorter period of time. TS likely rates their cells at 0.5C which is their specified standard discharge rate at a standard but unknown temperature, who knows if there is any truth to it. Based on FMA's paper on A123 cells, it seems if you drive batteries of this chemistry beyond 60c in temperature that you shouldn't expect 1,000 cycles. Based on the 200amp discharge and subsequent charge of the TS 160Ah cells by Jack Rickard, the rise to just over 130F leads me to either not run them on too high of a C rate or at least wait until they have cooled off before charging. Cooling the pack would be a good idea but getting the center of a cell cooled off when you only have access to its thick plastic shell is limiting. Since the test started at 75, if it was 85 these cells would be hotter than I'd want them to be on a regular basis. Usually people don't discharge them all the way and follow the manufacturers directions by not letting them get to 4.4 volts, which also caused temperature to spike a little during the charge but it all depends on how temperature looks in someones own usage. I'm planning on doing a constant discharge of 1.5C from 40Ah cells, Sky Energy rates the 40Ah cell at <1.5m ohm and larger cells at <1m ohm but based on the performance I've seen with Thunder Sky, I'd like to go with Sky Energy. I know someone who has pulled an average of 1.5C draining the pack in 40 minutes for the 1C(3C 15 second burst, cells show standard discharge and charge rates at 1/3C though) Hi Power 40Ah cells and subjects them to a 50 amp intermittent charge with regen when slowing down. They've survived the abuse and they've been used for nearly a year and a half and only one cell out of 50 failed after swelling and the IR make the cell functionally useless but the rest of the pack is doing well. It's apparent some things can be stretched.

'SE stated nom. voltage is 3.4, TS and HP is 3.2'
LiFePO4 is 3.2 A123, LiFeBatt and a few others claim 3.3 but it is more of a marketing gimmick. I haven't seen SE state a nominal voltage of 3.4 volts, possibly getting confused with the float voltage, which is a little odd as I don't see why anyone would ever float charge a lithium battery. It's clear that SE isn't 3.4 volts nominal because their 1C chart shows it dipping to 3.2 volts pretty much immediately, nominal is supposed to express average voltage during discharge.

'Cycles: HP says >1000 to 100%DOD, TS >3000 to 80%, SE >2000 to 80%'
I don't trust battery manufacturers with these numbers. It seems evident based on peoples experiences that TS has fudged the high rate discharge graphs and in the past has lied about the capability of their cells, especially early to middle portion of the last decade. Cycle life is difficult to verify and I speculate that it is heavily dependant on how they are treated, temperature, discharge, charge rates, voltage limits of operation, probably more to this too, maybe calendar life issues like Lithium Cobalt but I can't say anything about that since it hasn't been 7 years yet which is the amount of time a Lithium Cobalt ThunderSky lasted before it's internal resistance rose to the point where the cells were not usable at the needed rates. They were bought in a 2005 group buy.

'HP seems to be interested in a low IR or RI, however it should be labeled, thus the use of the HUGE terminals.'
I think everyone aiming for the EV market has that goal, I'm surprised that the huge 800Ah ThunderSky batteries state a pulse discharge of 20C with just an extra set of the same terminals, I'm sure 16,000 amps would melt them in a short period ever so slightly longer than instantly. I'm not sure if they thought of that before they published the same specs for all cells from 40Ah and up.

'From a MFG self posted data perspective I'm inclined to go with HP if as Kevin says they could say at 80% HP could post 2000 cycles.'
Seems reasonable

I just hope someone will test them all with a decent number of cells of the size typically used in an EV. 
For now we are stuck with the experiences of those using them, it doesn't help as much as it could now as it would 5 years down the line when people have tens of thousands of miles on them or ideally over hundred thousand so we can beat the RAV4's NiMh battery lifespan, people have over 100k miles and coming up on a decade in a couple of years and still get over 100 miles of range with them, hoping we can experience the same sort of life.

'I want to go with the 160-200ah to keep discharge <3C and have a long range. Also want a low IR as I don't want to waste energy on internal battery voltage drop. That's comparable to having an engine running rich or more like having the brakes dragging. It's wasteful.'
I feel the same sentiment. You might waste a little more at 3C but outside of the short period of acceleration, the average drop at your rate while at your constant speed is the one to look at, finding a 1C chart for TS and SE can be found, I'm sure there is probably an independant one of Hi Power cekks somewhere too.


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## ElectriCar (Jun 15, 2008)

"Since IR increases as you discharge the pack, it makes things a little difficult to work with."

Does IR increase or are you thinking of the internal voltage increase? I would think that the resistance stayed the same but since E=IXR (Volts = Current X Resistance), as current increases the voltage drop (voltage consumed by the battery IR) as we call it would increase. Increasing current flow through the battery is the main cause of sag due to the IR.

That's why testing needs to be done, extensive testing. If I were a battery company, I would do my own testing and if my battery clearly was the better battery I would scream it from the roof tops! Why they don't do this is beyond me.


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## EVfun (Mar 14, 2010)

MN Driver said:


> Quotes are from ElectriCar and are clipped a bit, going to the original a few posts back has more info to put this into context.
> 
> "SE stated nom. voltage is 3.4, TS and HP is 3.2"
> 
> LiFePO4 is 3.2 A123, LiFeBatt and a few others claim 3.3 but it is more of a marketing gimmick. I haven't seen SE state a nominal voltage of 3.4 volts, possibly getting confused with the float voltage, which is a little odd as I don't see why anyone would ever float charge a lithium battery. It's clear that SE isn't 3.4 volts nominal because their 1C chart shows it dipping to 3.2 volts pretty much immediately, nominal is supposed to express average voltage during discharge.


Before Sky Energy was renamed CALB the cells where advertised as being 3.0 volts. Just thought I'd toss in a little history


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## MN Driver (Sep 29, 2009)

"Does IR increase or are you thinking of the internal voltage increase? I would think that the resistance stayed the same but since E=IXR (Volts = Current X Resistance), as current increases the voltage drop (voltage consumed by the battery IR) as we call it would increase. Increasing current flow through the battery is the main cause of sag due to the IR."

What I meant was a battery at 20% state of charge is going to sag more than one that is fully charged, there is just not as much power to hand out anymore towards the end.

"That's why testing needs to be done, extensive testing. If I were a battery company, I would do my own testing and if my battery clearly was the better battery I would scream it from the roof tops! Why they don't do this is beyond me."

Well, they do, but we never believe them. HP and TS posts high current discharge charts but we are trying to verify their information through an independant test that isn't paid for or done by them. We know from the past that TS has lied to us and it is apparent they still do based on the charts they provide. The more respected and powerful battery companies don't seem to put discharge charts and sometimes don't put their specs out there, for example the A123 20Ah pouch packs don't come with any sort of datasheet, we had to come up with that ourselves.


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## Guest (May 14, 2010)

david85 said:


> Jack, what you just described is how the Hipower chargers work for me. Only difference is I also have a BMS that "burns off" the higher cells as they approach 3.65V and above. There is some natural inclination for the cells to self balance under these conditions, but it is very small.
> 
> Once it gets to float charge, the voltage from the charger gradually drops and the BMS has an easier time micro adjusting the cells. Repeated cycling like this does bring the batteries within excellent balance relative to each other. It's been a little harder doing this on the big pack than the small one, but I everything does seem to be charging closer togother as I cycle deeper each time.
> 
> So far the setup seems to work very well.



I can only offer that it will work better after you remove it from the vehicle and bury it in the back yard.

This will prevent some other poor hapless yuck from discovering it in a landfill somewhere, extracting it, and trying to use it on THEIR car.

Jack Rickard


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## Guest (May 14, 2010)

ElectriCar said:


> "Since IR increases as you discharge the pack, it makes things a little difficult to work with."
> 
> Does IR increase or are you thinking of the internal voltage increase? I would think that the resistance stayed the same but since E=IXR (Volts = Current X Resistance), as current increases the voltage drop (voltage consumed by the battery IR) as we call it would increase. Increasing current flow through the battery is the main cause of sag due to the IR.
> 
> That's why testing needs to be done, extensive testing. If I were a battery company, I would do my own testing and if my battery clearly was the better battery I would scream it from the roof tops! Why they don't do this is beyond me.


I'm not a battery company, but I've done plenty of testing. No, the IR increases somewhat dramatically as you move down the discharge curve. That is holding the current output steady, the voltage sag between open circuit and loaded increases. 

What this basically means is that internal resistance as a measure of anything in operation of LiFePo4 cells is broadly nonsense. It might be useful in comparing different cell manufacturers offerings and implies the ability, with lower IR, to deliver higher currents continuously. Beyond that, I've found no use for it.

But they talk about it in these forums almost constantly, as if it means something. 

Jack Rickard


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## david85 (Nov 12, 2007)

jrickard said:


> I can only offer that it will work better after you remove it from the vehicle and bury it in the back yard.
> 
> This will prevent some other poor hapless yuck from discovering it in a landfill somewhere, extracting it, and trying to use it on THEIR car.
> 
> Jack Rickard


um, ok...

Can you tell me why you think its a bad idea?


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## Jan (Oct 5, 2009)

david85 said:


> um, ok...
> 
> Can you tell me why you think its a bad idea?


Checking if I understand his point of view well:

You're top balancing every time you charge your pack. All cells wil be brought to their maximum capacity. 

In an already balanced pack this has no advantage, because the weakest cell(s) will still get as first at their LV cut off. And makes the whole pack unsuable. The weakest cells will always determine your total pack power, whatever charge method you choose.

The disadvantage is that all your cells are every time charged to their limit. And the weakest a little beyond.

What I understand from lithium for long life is to stay away from the bottom, but also the top. Storage seems to be the best around 60% charge.

Better to charge untill the first cell reaches it's max capacity, and stop discharging when it reaches its LV cut of. This way not only the weakest cell will get less stress, but all good/better cells will not stressed att all, and all will live longer.

If I understand well, and Jack's wright, I want a BMS that monitors all cells, and cuts the charger off if the first reaches its high voltage. No balancing. No smart tricks while charging. 

If I understand all well, the balancing will automaticly take place while discharging. The cells with the highest voltage will add a lot more to the total pack power than the once with a lower voltage. So the fullest cells will discharge the quickest.


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## Tesseract (Sep 27, 2008)

jrickard said:


> What this basically means is that internal resistance as a measure of anything in operation of LiFePo4 cells is broadly nonsense. It might be useful in comparing different cell manufacturers offerings and implies the ability, with lower IR, to deliver higher currents continuously. Beyond that, I've found no use for it.
> 
> But they talk about it in these forums almost constantly, as if it means something.


Variations in IR from cell to cell are, in my opinion and experience, an excellent indicator of manufacturing consistency. I've noticed a 4:1 spread in the internal resistance of ThunderSky 160Ah and 200Ah (old style) cells right from their shipping crate. I agree that for such a test would be more meaningful if all the cells were at exactly the same state of charge, but a 4:1 variation right out of the box is breathtakingly bad regardless.

In stark contrast are A123's cells. I've been testing 40 of the 2.2Ah size for a side project and found them to be unbelievably consistent both in IR and capacity. They easily deliver 50C for 5 seconds and internal resistance measured 8-9mΩ across the lot. That's pretty damn good compared to the 1-4mΩ range of the 70-90x larger Thundersky's.

Additionally, it is also pretty obvious that cells with a higher IR will convert more of their stored energy into heat during discharge. 

For example, at 200A a cell with an IR of 1mΩ will sag 0.2V and produce 40W of heat while one measuring 4mΩ will sag 0.8V and produce 160W. One may surmise, then, that a pack comprised entirely of cells measuring 4mΩ will stay in much better dynamic balance (ie - during the middle of the discharge curve, not at the ends) than one comprised of a mishmash of 1mΩ to 4mΩ cells, even if the latter has lower total losses.

So, is it useful to know what the internal resistance is? I think so; you don't, but I provided some reasoning and data why I think that while you just accused everyone here of being navel-gazing idiots. That might be true, but it's not a particularly compelling argument in my book.


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## JRP3 (Mar 7, 2008)

I recently had an incident that showed why bottom balancing is a really good idea. Because of some changes I made to the controller I have been driving my vehicle much more aggressively, because it's more responsive. That, coupled with some cold weather, led me to overestimate my remaining range. I was a few miles from home and suddenly my voltage was quickly dropping. Since it was mostly flat with some downhill I thought I'd push it. The controller cut back quite a bit but I was able to limp home. Saw 64 volts under load, 1.77V per cell. When I got home cells were resting at 2.4V and climbing quickly. I may have lost a few cycles in the long run but no single cell was driven near zero. If I had done this with a top balanced pack you can be sure some cells would have been ruined.


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## Jan (Oct 5, 2009)

JRP3 said:


> If I had done this with a top balanced pack you can be sure some cells would have been ruined.


I understand, but you took the risk to kill the whole pack. If you couldn't have limped the whole way home. You gained nothing with your risk, but could have lost the whole pack. I don't like that whole limping idea.


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## etischer (Jun 16, 2008)

Slightly damaging all cells by bottom balancing, vs. killing 1-2 cells by top balancing, I don't know which is better. I prefer option 3, using a BMS and not killing any cells (top or bottom balanced). As Jan points out, hopefully you didn't kill the whole pack, time will tell. 








JRP3 said:


> I recently had an incident that showed why bottom balancing is a really good idea. Because of some changes I made to the controller I have been driving my vehicle much more aggressively, because it's more responsive. That, coupled with some cold weather, led me to overestimate my remaining range. I was a few miles from home and suddenly my voltage was quickly dropping. Since it was mostly flat with some downhill I thought I'd push it. The controller cut back quite a bit but I was able to limp home. Saw 64 volts under load, 1.77V per cell. When I got home cells were resting at 2.4V and climbing quickly. I may have lost a few cycles in the long run but no single cell was driven near zero. If I had done this with a top balanced pack you can be sure some cells would have been ruined.


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## JRP3 (Mar 7, 2008)

I'm not suggesting limping is a good idea or should be a regular practice, just pointing out that by bottom balancing I didn't kill any cells, but certainly would have in the same situation with top balancing. Even before going to such an extreme a top balanced pack could have had some individual cells damaged at low pack SOC. A BMS would not have made any difference in this situation unless it left me stranded on the side of the road and unable to drive the vehicle.


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## JRP3 (Mar 7, 2008)

Also, we don't know if any significant damage was done at all. Very little current was flowing since the controller was cutting back and resting voltage was higher than 2.4 volts per cell. I should have waited a few minutes before charging to see where they would have settled. Maybe next time


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## Guest (May 14, 2010)

Tesseract said:


> Variations in IR from cell to cell are, in my opinion and experience, an excellent indicator of manufacturing consistency. I've noticed a 4:1 spread in the internal resistance of ThunderSky 160Ah and 200Ah (old style) cells right from their shipping crate. I agree that for such a test would be more meaningful if all the cells were at exactly the same state of charge, but a 4:1 variation right out of the box is breathtakingly bad regardless.
> 
> In stark contrast are A123's cells. I've been testing 40 of the 2.2Ah size for a side project and found them to be unbelievably consistent both in IR and capacity. They easily deliver 50C for 5 seconds and internal resistance measured 8-9mΩ across the lot. That's pretty damn good compared to the 1-4mΩ range of the 70-90x larger Thundersky's.
> 
> ...


I agree with your reasoning well enough. As I said, it does imply the ability to produce current. I was referring to measuring it as a practical indicator across the discharge curve.

I cannot duplicate your wide span results on the Thundersky cells. And I'm finding the SE cells very very close right out of the box. The SE cells seem very nicely matched at about 1 mohm.

I have discontinued any testing of A123 cells over a year ago. I have about 450 of them still in the box in the garage if you're at all interested.

I didn't say or imply that anyone was naval gazing. But there is a preoccupation with IR and I don't find it a very useful measurement. Explaining what it IS (again) won't help (again). You're mileage may vary.


Jack Rickard


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## Guest (May 14, 2010)

Jan said:


> I understand, but you took the risk to kill the whole pack. If you couldn't have limped the whole way home. You gained nothing with your risk, but could have lost the whole pack. I don't like that whole limping idea.


Yes, well a lot of finger wagging accomplishes nothing. It's a car. It happens. It's kind of like running out of gasoline. If you've never done it raise your hand. It will happen within the next week as soon as you brag on it.

And yes, the disconnect again is that even limping, and sometimes especially limping, as the voltage sags the current goes up. If you are top balanced and have a too ragged edge at the bottom, you can drive a cell into reversal and you just lose it. IF they are all marching in line, you don't actually kill the whole pack. You just can't drive.

This is not a theory Jan. I demonstrated EXACTLY how to destroy a cell three consecutive times in a row and did a video on it and showed the cells. Simply top balance them, and then drive to a low level, and you lose a cell, voila. It's demonstrable and repeatable.

Jack Rickard


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## Guest (May 14, 2010)

etischer said:


> Slightly damaging all cells by bottom balancing, vs. killing 1-2 cells by top balancing, I don't know which is better. I prefer option 3, using a BMS and not killing any cells (top or bottom balanced). As Jan points out, hopefully you didn't kill the whole pack, time will tell.


I would expect he didn't "kill" the pack. He aged it some. You get more cycles by not doing that. And certainly by not doing it routinely. But I would predict NOTHING dire comes of it and if he does it once a month forever nothing dire will come of it.

I love the "only time will tell" proviso. It's so flexible and so ass covering. Big debate on ev-tech about cell drift. They're sure they drift. And something must be done now. The reason I can't detect it is that it just takes several years to show up. Well, if it takes several years, why am I worrying about it? Wouldn't a thorough check annually then cover it.? Why do I need a BMS to check it every night?

It's true they either drift or they don't drift. If they drift over the course of years why is it an emergency?

If you diminish your pack life that's bad. Of course, if you get 10X the pack life of lead acid anyway, how bad is it? Let's say for the sake of argument, that through this careless wanton waste, done monthly, JRP reduces his cycle life from 3000 cycles to 80% capacity down to 2865 cycles to 80% capacity. As opposed to the 350 he would have gotten from the very best Trojans? And yes, who is paying for those precious 135 cycles?

If on the other hand, it reduces it from 3000 to 1200, it's more of an issue.

If it takes a sufficient amount of "time to tell" then its not really an issue at all.

Understand that what you are saying is more or less true and I agree with you. But I might suggest that the scale of it is not what you are picturing.



Jack Rickard


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## Guest (May 14, 2010)

JRP3 said:


> Also, we don't know if any significant damage was done at all. Very little current was flowing since the controller was cutting back and resting voltage was higher than 2.4 volts per cell. I should have waited a few minutes before charging to see where they would have settled. Maybe next time


I do this perhaps more on purpose than you do. You will see the same ragged edge you see at the top if you've done no balancing, a less extreme ragged edge than at the top if you bottom balanced, and a train wreck if you topped balanced. But it's a good time to go through the cells and write down all the voltages and look em over. Some recover more quickly than others and the slow and the halt can be marked to keep an eye on them.

Surprisingly, they seem to just stumble on as the slow and the halt, but still work well enough, particularly in the middle of the curve.

I have STILL not had a cell fail in routine use. I've had ONE fail on the very first discharge and that was done with a 4kw heater and their wasn't even a motor in the car at the time. That was a single cell on the Mini. Actually, it recovered to some degree and I use it around the lab to power minor things. 

I've failed two by simply adding cells without marrying the new (8) cells into the pack properly. And of course 3 in the GEM with the infamous top balancing demonstration.

All the rest were overcharged or overdischarged in the lab. Sometimes on purpose. And sometimes after being distracted and forgetfully overcooking or overdischarging cells.



Jack Rickard


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## dexion (Aug 22, 2009)

If anyone is interested (or has the time to test further I dont) I noticed an interesting effect with my new pack of cells. I charged them all up initially with a power supply . Then used my new charger which charges to 168V cc then cv. Cells were pretty good one at 3.7 (blackhawks are 3.85 max) a few at 3.62 several around 3.5 and several around 3.45.

My new charger maxes at 168VDC it then does the cv stage. 
It took about an hour at cv to go green.

I ran about 10ah out of it with the cars heating system
Put the charger on and it was cv about 15 minutes until going green.

hmm I thought. Looked at the cells. Max cell was 3.62 (the one that was 3.7) and the other 3.6's were about 3.57. The other low ones went up a bit. 

so, I repeated the experiment 4 more times. Removing 10 amp hours (100ah cells) and then charging it back up. So i did (5) 10 amp discharge/charge cycles (plus the 
initial charge to 168V) they are now closer. Max being 3.55 min being about 3.47 at the end of the cc state (which is lasting about 5 minutes now Its only a 10amp charge output so its pretty close when the cells get up to 3.5V theres not too much left.)

To me this seems like it doesnt really matter where one ballances (unless you ballance every charge cycle) since they will all drift closer together every charge as long as you dont go too far on either side of the curve (with new cells anyway.) Unless 10% of the cell isnt far enough so see some sort of drift. But my TS cells are two years old and have several 100 cycles on them they stayed very close together as well (or charged closer together over time.) I really used about 60% of the pack maximum 99% of the time. I had 2 discharges to 80% and thats it. Anyone else messed with shallow discharges and charges and see the same thing? The manufacture wanted 30 shallow (say under 30% out of the pack) discharges before I hammer them. So I am going to do this over the weekend I will see if they stay or go closer or whatever they do. But the pack was fairly close to start out with.


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## EVfun (Mar 14, 2010)

JRP3 said:


> I recently had an incident that showed why bottom balancing is a really good idea. Because of some changes I made to the controller I have been driving my vehicle much more aggressively, because it's more responsive. That, coupled with some cold weather, led me to overestimate my remaining range. I was a few miles from home and suddenly my voltage was quickly dropping. Since it was mostly flat with some downhill I thought I'd push it. The controller cut back quite a bit but I was able to limp home. Saw 64 volts under load, 1.77V per cell. When I got home cells were resting at 2.4V and climbing quickly. I may have lost a few cycles in the long run but no single cell was driven near zero. If I had done this with a top balanced pack you can be sure some cells would have been ruined.


However, if you used a cell level monitoring system like EVworks or Clean Power Auto regulators you would be equally able to catch just a single low cell and turn down the power. Since the average pack voltage would have been higher (just the first few smallest cells crying) the amp hours used to crawl the last bit home would be been less so the risk of damage could have been even lower.


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## JRP3 (Mar 7, 2008)

dexion said:


> Anyone else messed with shallow discharges and charges and see the same thing?


With my mostly shallow, and a few deep, (one really deep  ), cycles my cells already seem to be getting closer together, at least at the top. I don't know if the closer finishing voltages I'm seeing mean they are farther apart at the bottom. On my super deep discharge they seemed very close but as I mentioned the voltages were still rising. I'll have to check them at rest next time I do a deep discharge.


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## JRP3 (Mar 7, 2008)

EVfun said:


> However, if you used a cell level monitoring system like EVworks or Clean Power Auto regulators you would be equally able to catch just a single low cell and turn down the power. Since the average pack voltage would have been higher (just the first few smallest cells crying) the amp hours used to crawl the last bit home would be been less so the risk of damage could have been even lower.


 Why would the average pack voltage have been higher? My cells were all even at X voltage, in your example at the same X voltage some cells would be lower and some would be higher. I don't need a cell level monitoring system since by bottom balancing voltage has meaning at the low end. My only problem was a false assumption as to how much range I had left and not paying attention to voltage readings, mostly because I was distracted playing with the programmer cycling through various controller parameters. What I really need is an Ah/Wh counter. That would have shown me that all my aggressive driving had used more capacity than I realized.


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## EVfun (Mar 14, 2010)

JRP3 said:


> Why would the average pack voltage have been higher?


Because bottom balancing, by nature, means the cells with slightly larger capacity are left slightly undercharged. The cells within the last few percent of dead are the ones with the excess (and potentially damaging) voltage sag.


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## JRP3 (Mar 7, 2008)

Hmm, I'm not seeing it. Let's take two simple 2 cell packs, one bottom balanced, one not. Discharge both packs to 6 volts, bottom balanced pack is 3 volts per cell, top balanced pack could be 2.8 and 3.2. Keep discharging them and you'll kill the low cell in the top balanced pack before the cells in the bottom balanced pack.


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## JRoque (Mar 9, 2010)

Hi. Most agree that here's nothing like charging your cells individually. You get full control over volt and current (and temp) and can really baby each of them. But, we string them together so charging each cell is not practical. 

Take the drawing below. If each cell is 3.2V when I put 5 of them in series, I get a 16V pack. I want to charge this horribly "unbalanced" pack to 3.4V per each cell so I set my charger to 3.4 * 5 = 17V output.

Cells B and E, the ones with the lowest charge voltage, will draw the most current while cell C will barely draw anything because it is already at 3.2V. Once cell C reaches 3.4V it will not draw any current - in practice it will probably approach 3.4V but never reach it. Other cells will continue to draw current from the charger until they too reach 3.4V. My charger continues to delivery 17V while it's current output drops as cells charge. My charge cycle ends when current draw drops below a certain level, probably determined by cell and system resistance.

How am I doing so far? If the above is true then why do I need a BMS or worry about balancing my cells? If my charge cycle, which is also timed, does not finishes at the expected low current, I know there's a problem child in the pack. But otherwise, every cell should have more or less the same charge at the end of the cycle. I might want to check each cell voltage once a month to get reassurance but even that is likely not needed.

JR

PS: wow, I don't get the bottom balancing concept at all. I need to read on that.


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## EVfun (Mar 14, 2010)

JRP3 said:


> Hmm, I'm not seeing it. Let's take two simple 2 cell packs, one bottom balanced, one not. Discharge both packs to 6 volts, bottom balanced pack is 3 volts per cell, top balanced pack could be 2.8 and 3.2. Keep discharging them and you'll kill the low cell in the top balanced pack before the cells in the bottom balanced pack.


Do you agree that bottom balancing, by nature, means that the stronger cell is left less than completely full? 

Looking at the 2 cells bottom balanced you are correct, both drop to 3.0 volts after "x" amp hours are removed. You can recharge and repeat this process and get the same result repeatedly. 

Next, recharge and then top balance the 2 cells. You will have to put a little extra into the stronger cell to bring it up to a top balanced state with the other one. Be sure to add the cell monitors to the 2 cell pack and rig it up to stop the discharge when the first cell reaches 3 volts. The discharge stops when the first cell reaches 3.0 volts while the other may still be at 3.2 volts. You cut off at 6.2 volts while still removing the same number of amp hours. The available amp hours in a series pack is always set by the smallest cell (the cell that didn't need extra charge to reach a top balanced state.)

Without some type of cell monitoring you become the monitor that regularly checks to make sure the cells remain (bottom) balanced. With a single wire loop monitor system that is isolated from the traction pack you can catch, and take action, when any one cell in a series string gets out of line on either charge or discharge. A simple one wire loop is still a hobbyist level way of handling things, but it is one step up because bottom balancing and using pack voltage catches the cell that fails after it get over-discharged and/or charged over a safe voltage. The monitor will let you know one is starting to loose capacity before you kill it dead.


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## EVfun (Mar 14, 2010)

JRoque said:


> Take the drawing below. If each cell is 3.2V when I put 5 of them in series, I get a 16V pack. I want to charge this horribly "unbalanced" pack to 3.4V per each cell so I set my charger to 3.4 * 5 = 17V output.
> 
> Cells B and E, the ones with the lowest charge voltage, will draw the most current while cell C will barely draw anything because it is already at 3.2V. Once cell C reaches 3.4V it will not draw any current - in practice it will probably approach 3.4V but never reach it. Other cells will continue to draw current from the charger until they too reach 3.4V. My charger continues to delivery 17V while it's current output drops as cells charge. My charge cycle ends when current draw drops below a certain level, probably determined by cell and system resistance.
> 
> How am I doing so far?


That is not what will happen. In a series string all the cells will take the same current because they have no choice. The cell voltages will remain all over the place and it it likely the cell that fills first will go well over a safe voltage and end up damaged. Battery regulators, that can bypass current around an individual cell starting at some preset voltage, can help bring the cells into line. However, the need for battery regulators with Lithium is quite in dispute. Once balanced (either top or bottom) they seem quite inclined to remain balanced. Cells do eventually wear out or get damaged so I tend to think something should be watching them regularly, and that could be the user. It seems clear that over-voltage and under-voltage events can destroy a cell quickly (in some cases immediately.)


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## JRP3 (Mar 7, 2008)

JRoque said:


> Cells B and E, the ones with the lowest charge voltage, will draw the most current while cell C will barely draw anything because it is already at 3.2V. Once cell C reaches 3.4V it will not draw any current - in practice it will probably approach 3.4V but never reach it. Other cells will continue to draw current from the charger until they too reach 3.4V. My charger continues to delivery 17V while it's current output drops as cells charge. My charge cycle ends when current draw drops below a certain level, probably determined by cell and system resistance.


That's not what happens though. The 3.4V cell will be driven even higher as the other cells continue to charge, it doesn't stop taking charge just because it's at 3.4 volts. That's why you either need a BMS that burns off extra current from higher cells, or you simply set your charger voltage such that it shuts off when your first cell hits about 3.4 volts and you live with the other cells slightly undercharged. That's where bottom balancing comes in, you balance your cells so they all hit empty at the same time and live with most of them never being full, which is not a bad thing. You'll never get more range than your smallest cell can provide anyway.


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## JRP3 (Mar 7, 2008)

EVfun said:


> Do you agree that bottom balancing, by nature, means that the stronger cell is left less than completely full?


Of course.



EVfun said:


> Next, recharge and then top balance the 2 cells. You will have to put a little extra into the stronger cell to bring it up to a top balanced state with the other one. Be sure to add the cell monitors to the 2 cell pack and rig it up to stop the discharge when the first cell reaches 3 volts. The discharge stops when the first cell reaches 3.0 volts while the other may still be at 3.2 volts. You cut off at 6.2 volts while still removing the same number of amp hours. The available amp hours in a series pack is always set by the smallest cell (the cell that didn't need extra charge to reach a top balanced state.)


Yes, but in an EV sized pack you'll see a very small difference in average pack voltage, unless your cells are very different in capacity. For the price of even the cheapest BMS, other than DIY units, you can buy a number of extra cells to add much more range to your pack.


EVfun said:


> Without some type of cell monitoring you become the monitor that regularly checks to make sure the cells remain (bottom) balanced. With a single wire loop monitor system that is isolated from the traction pack you can catch, and take action, when any one cell in a series string gets out of line on either charge or discharge. A simple one wire loop is still a hobbyist level way of handling things, but it is one step up because bottom balancing and using pack voltage catches the cell that fails after it get over-discharged and/or charged over a safe voltage. The monitor will let you know one is starting to loose capacity before you kill it dead.


Just to make my position clear, I'm not completely against cell level monitoring, but it has to make sense, and dollars. If the BMS cost is equal to or more than a few more cells, I'll get more range by purchasing more, or larger, cells. Ultimately I don't think a BMS is to save cells, it's to save money because cells are expensive. If the BMS costs too much it just makes more sense to buy more capacity and skip the BMS.


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## EVfun (Mar 14, 2010)

JRP3 said:


> Just to make my position clear, I'm not completely against cell level monitoring, but it has to make sense, and dollars. If the BMS cost is equal to or more than a few more cells, I'll get more range by purchasing more, or larger, cells. Ultimately I don't think a BMS is to save cells, it's to save money because cells are expensive. If the BMS costs too much it just makes more sense to buy more capacity and skip the BMS.


My BMS costs about 18% of the cost of each cell. It may allow me to save cells, if they get out of balance for any reason (including operator error) or slowly loose capacity as they age. More importantly, it will prevent over-voltage events from happening in my garage. I've seen the tests, "they don't catch fire," O.K... These are a number of controlled tests, you can continue testing that theory in your garage if you would like. It is your garage. I don't want to continue the testing on long series strings in my garage while I sleep. I want both over and under voltage monitoring because those are the only 2 ways I've outright killed batteries in an EV. Others have died due to age, I've been doing this with lead since 1999.

At the simplest level a Lee Hart Battery Bridge running opto-isolators would likely function as a sufficient under and over voltage detector. I want more experience with Lithium before I'm ready to rely only on comparing the voltage between the top half and bottom half of the pack. Still, such a system should be less than $10 in parts.

Did you notice the similarity in the first couple of sentences in each of our replies to JRoque?


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## JRoque (Mar 9, 2010)

> That is not what will happen.





> That's not what happens though.


I gotta stop posting musings past my bedtime. My scenario works with paralleled batteries, not series where current is equal.

I assume that by 'burning off extra current' you mean bypass the battery after it reaches certain voltage, right? That is, if you want to continue charging beyond that point. And I can see how you would use bottom balancing to equalize them. What do you use to bypass the batteries? Zener? 

JR


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## JRP3 (Mar 7, 2008)

EVfun said:


> My BMS costs about 18% of the cost of each cell.


That's still too much. For the same price you could have an 18% larger pack, which means lower C rates at all times, shallower discharges for the same distance, increased usable range if you want it, and extra safety margins in the top and bottom ends of the cycle. Given the choice, for the same money, I'd rather have a larger sized pack than a smaller pack with a BMS. For reasons outlined above I think the larger pack will likely have an easier life and last longer. If for some reason you must size your pack such that you will be pushing it to the limit on a regular basis then yes you probably need a BMS.


EVfun said:


> It *may *allow me to save cells, *if *they get out of balance for any reason (including operator error) or slowly loose capacity as they age. More importantly, it will prevent over-voltage events from happening in my garage. I've seen the tests, "they don't catch fire," O.K...


Slightly undercharging and occasional bottom balancing also serves the same purpose, for zero cost, and not much time. A number of us are seeing the cells get *closer* over time, not farther apart. Certainly this trend could reverse but as of yet we haven't seen it.



EVfun said:


> Did you notice the similarity in the first couple of sentences in each of our replies to JRoque?


Yes, you were faster than I was


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## Tesseract (Sep 27, 2008)

JRP3 said:


> That's still too much. For the same price you could have an 18% larger pack, which means lower C rates at all times, shallower discharges for the same distance, increased usable range if you want it, and extra safety margins in the top and bottom ends of the cycle. ...


This argument is a bit of a red herring as it _assumes_ that you can actually _fit_ more cells onto the vehicle - a recursive situation soon develops. The converse argument - that by having a BMS you can more fully utilize your existing pack and thereby drive farther - is an interesting one, though, and does not suffer from recursiveness.

Let's say you have a 10kWh pack without a BMS and to protect against cell damage you only use 60% of that capacity, or 6kWh. Let's say you bought this pack at the bargain basement never to be seen again price of $1.10/Ah, for a total cost of ~$3438. You can only use 6kWh, though, so your _effective_ cost is $5730. Now, let's say with a BMS you feel comfortable using 80% of your pack now, making the effective cost $4298. If the BMS for this pack costs less than $1432 it's an economically superior solution.

Simple as that. Y'all can argue til your blue in the face about BMS vs. no BMS, but until you determine the economics of the two setups your arguments have no merit whatsoever; they are just opinions, and not particularly well-informed ones at that.


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## Guest (May 15, 2010)

One shorted wire in that mess of BMS wires and the economics are out the window. Hands down. Argue that! I'd rather not have all that wire. I know first hand that skinny tiny wires can and do short out and then you will have trouble. Just more you have to monitor. 

How about a WMS (wire management system) for the BMS 

Pete


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## Guest (May 15, 2010)

Economics is only for those selling something. If I was concerned with economics I'd not buy any vehicle because economically it makes no sense. I could by the cheapest car or one way more expensive because I can afford to buy it. So if one chooses to do BMS vs NO BMS then its just a choice. Not economics. It's economics for the seller because he is trying make money. I'm not trying to make money and I don't care if I spend the money. I like the idea of no BMS. Easier on the batteries. Less stress. Sure the BMS may monitor the max and minimum but it still is a stress on the battery. No argument there. 

Pete


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## Guest (May 15, 2010)

Smaller wire harness too and much safer. No WMS needed.


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## JRoque (Mar 9, 2010)

Hi. This thread has drifted from main topic slightly  

Would "skinny tiny wires" burn in case of short? How about making the BMS so it measures locally, right on the battery, across high impedance inputs and then send the result over an isolated bus back to the BMS central unit? Not sure what that would do to the budget but it would keep the risk to a minimum.

So, do you burn off the extra charging voltage with a zener across the battery or how?

JR


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## Guest (May 15, 2010)

Small wires can burn. Can you say fire! Oooops now all that investment is up in smoke and hope the hell you are safe. I had an old VW burn once and it takes less than a few minutes to engulf the vehicle. You don't have time to try to rescue anything except your self and maybe if your lucky a few items within reach before acrid smoke moves you out. Sorry but electrical fires are NO JOKE. Don't care if you have an extinguisher either. Electrical fires are fast and deadly. The less wires the better. There is always that danger but why make it riskier. There is way more than just wires on the BMS systems being built and sold and everyone works different and is put together different and you have no clue if it really will save your batteries in the long run. 

Less power in and out of a battery with no BMS will extend the life. No complex wires and maybe the cost of an extra one or two batteries. Maybe. So charge to 3.9 instead of 4.2 volts. Set your cut of higher than the recommended and you will extend the life. Hands down. 

What is a BMS and what exactly will it do for you're pack? I know they can be very expensive. Lots of guys trying to sell wares is more what I see. Mine is better but you NEED one. Get mine. No get mine, No mine is better because it does X and yours does not. Your all wrong, mine is required because I won't guarantee the batteries if you don't use it. 

Go figure that mess out.


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## EVfun (Mar 14, 2010)

gottdi said:


> One shorted wire in that mess of BMS wires and the economics are out the window. Hands down. Argue that! I'd rather not have all that wire. I know first hand that skinny tiny wires can and do short out and then you will have trouble. Just more you have to monitor.
> 
> How about a WMS (wire management system) for the BMS
> 
> Pete


The cell monitors are on the cells, the circuit board fits between the posts. The output of the monitors is a single loop normally closed circuit. One monitor wire comes off each end of the pack goes back to the monitor control board. This is part of the vehicles 12 volt system and shorted is the natural state (the power into this loop is resistor restricted to just milliamps.) Any open circuit indicates fault and shuts down the charger or signals the controller to back off.


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## EVfun (Mar 14, 2010)

JRP3 said:


> Slightly undercharging and occasional bottom balancing also serves the same purpose, for zero cost, and not much time. A number of us are seeing the cells get closer over time, not farther apart. Certainly this trend could reverse but as of yet we haven't seen it.


Not exactly. In the event of uneven cell wear, cell failure, or user balancing error your method only catches the problem *after* a cell is taken outside of its safe voltage range and quite possibly destroyed. A management system alerts *before* the voltage of any cell leaves the safe range.


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## Guest (May 15, 2010)

EVfun said:


> Any open circuit indicates fault and shuts down the charger or signals the controller to back off.


And you go out to your car and can't get to work because your pack did not charge. Ouch. 



I have seen a rise in BMS systems and all state that theirs are the best. All are expensive. If I don't NEED them why use them.


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## Tesseract (Sep 27, 2008)

gottdi said:


> Economics is only for those selling something.


Economics is for _everyone_ and applies to _everything_. When you weigh the _price_ of something vs. its _utility_, you have made an economic assessment, and if you act upon that assessment you have made a _decision_.



gottdi said:


> If I was concerned with economics I'd not buy any vehicle because economically it makes no sense.


If you think your time has no value then probably not. Perhaps riding the bus and occasionally renting a vehicle makes more sense. If you live in a very densely populated city with a vast array of public transportation and very little parking - e.g., New York City and London - then it might not be economical to own a car unless your time is so valuable that the extra minute or two spent walking to a subway station "costs" you more than parking, insurance, etc.



gottdi said:


> So if one chooses to do BMS vs NO BMS then its just a choice.


Not sure what point you are trying to make here, but it appears that you didn't read the example in my previous post...

Setting aside the rather contentious issue of balancing, a BMS at its most basic ought to warn you when a cell is outside of its allowed voltage range. If you only use that information to immediately stop driving so as to protect the offending cells then you might not derive any utility whatsoever from your expenditure. If, as I proposed in my previous post, you use the BMS to extend the range which you can drive without worrying about killing a cell then you have derived some benefit which may, in fact, exceed the cost of the BMS compared to the greater range you can extract from the same amount of batteries.



gottdi said:


> I like the idea of no BMS. Easier on the batteries. Less stress. Sure the BMS may monitor the max and minimum but it still is a stress on the battery. No argument there.


How in the world did you conclude not only that a BMS is stressful on the batteries, but that there is "no argument" about this rather bold statement?


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## EVfun (Mar 14, 2010)

gottdi said:


> And you go out to your car and can't get to work because your pack did not charge. Ouch.


I trust my wiring more than I trust any battery. After all, we know a battery will fail, it is only a matter of time (NiFe almost defy that.)

I guess the alternative is to drive half way to work and then find out one of the cells is taking a dump. Now you get a towing bill and you are late for work. I would rather take a small risk of false charge termination. It means I find out something has gone wrong while I am in my garage instead on the road. It also means that when something really does goes wrong in the pack it wasn't one cell going to 8 volts while the rest where still at 3.5 (see paragraph 1 )


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## Guest (May 15, 2010)

JRP3 said:


> Why would the average pack voltage have been higher? My cells were all even at X voltage, in your example at the same X voltage some cells would be lower and some would be higher. I don't need a cell level monitoring system since by bottom balancing voltage has meaning at the low end. My only problem was a false assumption as to how much range I had left and not paying attention to voltage readings, mostly because I was distracted playing with the programmer cycling through various controller parameters. What I really need is an Ah/Wh counter. That would have shown me that all my aggressive driving had used more capacity than I realized.


JRP. I'm gradually becoming a fan of the Xantex ProLink. It is fairly inexpensive ($250 on eBay), it does a good job of measuring current, gives me AH IN and OUT totalized which you need with regen or to monitor charging, and it is a pretty simple connection. It uses a 50mv 500A shunt and I have three wires to the shunt connected to the negative terminal of the pack, and 1 wire connected up the string 10 cells. This lets me use the voltage input to monitor 10 cells and power the unit. So it shows 33.25 volts when my average cell level is 3.325. You can monitor the entire pack voltage by using a very simple voltage divider/scaler.

It even has an internal relay you could use to disable your controller or decrease throttle voltage at some defined level of discharge based on AH.

We're probably going to use this in Speedster Part Duh and put off our more advanced plans for graphical instrumentation until Speedster Tres.

Jack Rickard


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## JRP3 (Mar 7, 2008)

Tesseract said:


> This argument is a bit of a red herring as it _assumes_ that you can actually _fit_ more cells onto the vehicle


I did state that if for some reason you cannot use a slightly larger pack, either larger cell size or number, and you must use the pack to it's full extent, then you probably need a BMS.


Tesseract said:


> Let's say you have a 10kWh pack without a BMS and to protect against cell damage you only use 60% of that capacity, or 6kWh. Let's say you bought this pack at the bargain basement never to be seen again price of $1.10/Ah, for a total cost of ~$3438. You can only use 6kWh, though, so your _effective_ cost is $5730. Now, let's say with a BMS you feel comfortable using 80% of your pack now, making the effective cost $4298. If the BMS for this pack costs less than $1432 it's an economically superior solution.


That's not even close to a realistic scenario. With a bottom balanced pack and a slight undercharge for all the cells except your smallest capacity cell, which will limit your range with or without a BMS, you can safely use 80% or more of the pack capacity, about as much as you'd want to use for long life with or without a BMS. If you can use the BMS money for more or larger cells then you get to draw lower C rates and cycle the cells less deeply for the same money.


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## Guest (May 15, 2010)

EVfun said:


> That is not what will happen. In a series string all the cells will take the same current because they have no choice. The cell voltages will remain all over the place and it it likely the cell that fills first will go well over a safe voltage and end up damaged. Battery regulators, that can bypass current around an individual cell starting at some preset voltage, can help bring the cells into line. However, the need for battery regulators with Lithium is quite in dispute. Once balanced (either top or bottom) they seem quite inclined to remain balanced. Cells do eventually wear out or get damaged so I tend to think something should be watching them regularly, and that could be the user. It seems clear that over-voltage and under-voltage events can destroy a cell quickly (in some cases immediately.)


This is nonsense for several reasons.

First, the cell variation in capacity you are envisioning just isn't there. The variation is typically less than 2%. Second, we dont' charge to the "max votlage" at all. On a series string, we'll charge to an average 3.65v and in fact that's what Thundersky charges to.

The result is that the cells do vary in voltage at the end of charge, with some above 3.65 and some below. But the range is more like 3.58 to 3.82. Note that NONE of them have to go over 4.2.

If you top balance, you exacerbate the variation at the DISCHARGE end. The problem with this is that we can often discharge at 500 amps, while we're charging typically at 20. Worse, we're busy driving a car. The cell damage can happen in seconds.

If you bottom balance, that pretty much exaggerates the cell differences at the top, no sin actually. But when reaching discharge, they all get there together.

We don't do either. The only time we "bottom balance" is to marry a new cell or an additional cell to an existing pack.

But if you must balance, you really should do it at the bottom. That it is EASIER to do it at the top doesn't change the physics at all.

Even the concept that in an ideal world, we would simply charge each cell individually to the maximum 4.2v is something I would take strong exception to. In the first place, you gain trivially little in charging to a voltage of 4.2 instead of 3.65. Truly, very near nothing. But more importantly, you can't drive your car past the end of capacity of whatever cell exhibits the least capacity cell in the pack ANYWAY. Once the first cell goes over the discharge knee and starts the plunge YOU ARE TRULY DONE. And if you have top balanced, with seconds you have truly lost your cell. How much energy remains in the very carefully charged cells of greater capacity does you NO good at all. All you did was stress the cell a bit to achieve not a single yard further range.

Even Thundersky is explicit on this topic. They tell us that by charging to 4.10 instead of 4.2 you can extend the cycle life of the cell. This actually is the mirror image of the cycle life extension you get by discharging to 70% instead of 80% and it is substantial. You get a 50% longer life for 10% less discharge. And it works as a mirror image on the CHARGE side as well.

There is simply no purpose to "fully charging" these cells and indeed you diminish the life of your pack demonstrably by doing so. It is a lead acid concept from start to finish and simply does not apply to LiFePo4 cells. Period.

My approach is to charge until all cells have basically just barely turned the knee on the charge curve and are starting up the wall. At that point there is NOTHING good going to come from continued charging. i wont' get more range. I'll get less cell life. It's just a loser. 3.65 works. 3.60 would work better. 3.50 would work better yet but we are leaving a significant amount on the table at that level - though undeniably extending the life of the cells.

SE's are a little flatter. I'm trying to get away with 3.5v there but I may fall back to 3.45 at the first sign of trouble.

Jack Rickard


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## JRP3 (Mar 7, 2008)

With my SE's at first I had one cell that would start to shoot up near the end so I backed down the charger to a 3.45 average. Now they seem to be finishing closer to one another and I'm moving closer to a 3.5 average.
This same cell used to sag more under load as well and I was thinking of replacing it, but now it seems to be more in line with the others. I'll have to keep an eye on it but it seems to be improving slightly with use.


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## EVfun (Mar 14, 2010)

jrickard said:


> This is nonsense for several reasons.
> 
> First, the cell variation in capacity you are envisioning just isn't there. The variation is typically less than 2%. Second, we dont' charge to the "max votlage" at all. On a series string, we'll charge to an average 3.65v and in fact that's what Thundersky charges to.
> 
> The result is that the cells do vary in voltage at the end of charge, with some above 3.65 and some below. But the range is more like 3.58 to 3.82. Note that NONE of them have to go over 4.2.


I've snipped off a bunch to just look at that. The example that was given was specifically cells that where well out of balance. So, what I described is what would happen.

Charging a 40 cell pack to 3.65 vpc can also be 39 cells at 3.6125 volts and 1 at 8.00 volts! Because it hasn't happened yet doesn't mean it won't happen eventually. Cells will, in time, fail. If they are going to charge in my garage while I sleep I want something to watch for that. Hopefully it won't happen until they have 3000 cycle on them but there are few (any?) TS or SE powered EVs with that many cycles on their packs (and the cells seem to have changed quite a bit over the last 2 years too.)

As far as the part about using regulators to bring a pack into line, that is *one* cycle in the packs life. I specifically mentioned that there are doubts about the ongoing value in it. TS still recommends an initial charge to 4.1 volts. With a battery monitoring system you can also detect one cell going below a safe voltage just as quickly and easily as all the cells going below the safe voltage.

I am trying to make a distinction here between battery management and battery regulation. Battery management need not involve any method of equalizing the cells. It is about knowing what is going on at the cell level. Battery regulation, dissipative regulators being the most common version, acts on the individual cells.


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## Guest (May 15, 2010)

Tesseract said:


> This argument is a bit of a red herring as it _assumes_ that you can actually _fit_ more cells onto the vehicle - a recursive situation soon develops. The converse argument - that by having a BMS you can more fully utilize your existing pack and thereby drive farther - is an interesting one, though, and does not suffer from recursiveness.
> 
> Let's say you have a 10kWh pack without a BMS and to protect against cell damage you only use 60% of that capacity, or 6kWh. Let's say you bought this pack at the bargain basement never to be seen again price of $1.10/Ah, for a total cost of ~$3438. You can only use 6kWh, though, so your _effective_ cost is $5730. Now, let's say with a BMS you feel comfortable using 80% of your pack now, making the effective cost $4298. If the BMS for this pack costs less than $1432 it's an economically superior solution.
> 
> Simple as that. Y'all can argue til your blue in the face about BMS vs. no BMS, but until you determine the economics of the two setups your arguments have no merit whatsoever; they are just opinions, and not particularly well-informed ones at that.



As always, you've shot yourself in the foot Tesseract. It IS as simple as that. ANd yes you CAN argue till your blue in the face. And iT DOES come out the same way. Your arguments have NO MERIT WHATSOEVER. They are just OPINIONS, and in your case peculiarly DISINFORMED ones at that.

For $1432 you can buy another DOZEN CELLS TO REPLACE ALL THE ONES THAT NEVER DID GO BAD ANYWAY!!!.

It indeed IS recursive and circular. A blue elephant gun. As along as we don't SEE any blue elephants, the gun MUST be working and is well worth the $1432.

In REAL WORLD PRACTICE - you can drive a car quite without a BMS and it is just not that hard to check the voltages manually and verify over and over and over and over, as many times as you like, that you STILL don't need a BMS. This isn't a theory. It's not YOU typing yourself smart into a computer screen.

There is another side to the BMS thing that every time I bring it up everyone mumbles off into the bushes. THEY BURN CARS TO THE GROUND.

Here's my favorite poster child photo:










Do you know why I'm so enamored of this photo? It encapsulates about a dozen different things into the same graphic image. As I see it, one of the more popular, albeit expensive BMS's on the table is the Elithion. It's designed by a guy named David Andrea.

Mr. Andrea used to be with a company called Hybrids PLus. This is a car they converted to plug-in in Colorado. I still have a home there. This one caught fire WHILE GOING DOWN THE HIGHWAY with some of Mr. Andreas very personal work in it.

Not only did it burn completely, and fortunately the driver was able to pull over and get out of the car before serious injury, but it was of course traced directly to Hybrid Plus's module of A123 cells.

Had a conversation with A123 a couple of weeks ago. I'm kind of interested in their 20 Ah pouch module they have now. It is going int he Fisker etc. The HEAD of the company discussed this with me by telephone and noted that we, nor anyone else would EVER get one of these cells, without buying a full battery module designed and built by A123. And guess what the reason was?

Their experience with THIS fire and THIS Hybrids Plus company. They had a six month nightmare of damage control and BELIEVE TO THIS DAY that this incident is why they lost the contract with GM to LG Chem.

Meanwhile YOU and DAVID and a host of others, are basically DEFRAUDING interested, enthusiastic, and well meaning individuals who want to build their own electric car into buying these piece of shit BMS systems that regularly CAUSE fires, not cell damage, not the loss of a couple of batteries, but LIFE THREATENING FIRES - all in the name of preventing them. And you 've done a good enough job selling this crap that people are buying it to PREVENT them and argue your nonsense for you in forum after forum after forum. 

I"VE HAD IT AND I"M CALLING YOU ALL OUT FOR THE CHARLATAN PATENT MEDICINE SNAKE OIL SALESMEN THAT YOU ARE. I have measured, I have reasoned, and I have demonstrated. Using the best equipment and best principles. But I cannot overcome the greasy greedy desire to milk a few ducats from your fellow men that you people ooze.

What's so pathetic is that it isn't either an imaginative or a big crime. The guys doing this are so small potatoes they don't even really make any real money at it. Just grubbing in the grass for lost quarters, nickels and dimes.


OF COURSE it is nice to be able to MONITOR your cells. Measure to your hearts delight - its part of the learning process which is a great deal of why most people do this in the first place. A device that makes it easier to this, and in the process FIRST DOES NO HARM - safely, is broadly celebrated and welcomed by the entire community.

YOU CAN TELL THE DIFFERENCE. If the sales pitch comes with a dire warning of all that will befall you if you don't buy a BMS, preferabley THEIR BMS, 
RUN don't WALK in the other direction.

IT MAKES SENSE. But it isn't true. And it IS the economics. This clown wants you to spend as much as TEN MORE CELLS would cost to prevent you losing A CELL.

AND he'll burn your car to the ground while cashing the check.

If you think I was a thorn in your side before, you've seen nothing. I'VE HAD IT. I'M CALLING YOU OUTSIDE. Bring a friend. Bring a lunch. Bring a lawyer. I don't care. We're hookin em up. Lockin horns. No more Mr. Nice Guy.

YOU will CEASE abusing my people NOW Pharoah. No more bricks without straw.

Jack Rickard - served flamin hot.


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## Guest (May 15, 2010)

EVfun said:


> I've snipped off a bunch to just look at that. The example that was given was specifically cells that where well out of balance. So, what I described is what would happen.
> 
> Charging a 40 cell pack to 3.65 vpc can also be 39 cells at 3.6125 volts and 1 at 8.00 volts! Because it hasn't happened yet doesn't mean it won't happen eventually. Cells will, in time, fail. If they are going to charge in my garage while I sleep I want something to watch for that. Hopefully it won't happen until they have 3000 cycle on them but there are few (any?) TS or SE powered EVs with that many cycles on their packs (and the cells seem to have changed quite a bit over the last 2 years too.)
> 
> ...


This is all theory. I would offer a different one. It won't go to 8v. It won't even go to 2.0 v when it fails. I have failed cells. And that's what they do under charge. You're simply fabricating a theoretical scenario no one has seen every anywhere.

In fact, I have overcharged cells to the point of burning them into slag. They never went to 8 v. Again, there is widespread confusion between voltage and state of charge. This is because the most convenient thing we have to measure SOC is voltage. But it's not because they are one and the same.

Now here's some FACTS not theory.

1. I have purposely overcharged cells until they melted into slag and they never reached 8v.

2. I have published VIDEO of me taking a cell to 8v while charging without any damage to the cell at all.

So I'm having a hard time following your theoretcal area of concern.

I know you find it hard to believe item 2. But it demonstrates the disconnect between cell terminal voltage WHILE CHARGING and SOC. What Thundersky gives you with 4.2 v, or now 4.0 v, is a DESCRIPTION of a CHARGE curve. IF you add energy to a cell, electrical current, until what YOU MEASURE as the cell terminals is 4.0 v, and AT THAT POINT switch to holding it at 4.0v, until it will TAKE NO MORE ENERGY without RISING beyond the 4.0v, you have come pretty close to fully charging the cell. By the way, the fully charged CELL VOLTAGE of a LiFePo4 cell was and always has been without change 3.4v.

So the charging voltages you hold so sacred are really a measurement you can take, and if you follow this, you will successfully charge their cells. It never was the cell voltage. It has nothing to do with overcharge and undercharge. It is a description of a PROCESS, a RECIPE if you will, to get there.

They also tell you that you can safely charge at 3C. Well now how can this be? In order to force 3C current into the cell, you have to apply a much larger voltage than the cell voltage, to attain that current flow. Your MEASURED VOLTAGE will be quite beyond 4.2 volts and indeed I've run it up to 10 volts or 12 volts with no cell damage. HOw can this be so?

Well the cell wasn't fully charged. It was about half charged. And in fact, I wasn't even doing 3C. I was doing 200 amps. And it works fine. Because this measured voltage never did have anything to do with SOC. Since I was measuring AH in and out, I knew where the SOC was to a pretty good degree.

IT is quite true, that if you shunt current around the cell and do not allow it to rise above 4v, while continuing to charge the other cells, that that cell will not be overcharged. Of course, the nature of semiconductors is that the 45 cent mosfet you are using is much more likely to fail than the cell is. And when it does, it typically fails in thermal runaway. The hotter it gets the more it shunts and the more it shunts the hotter it gets.

So you're doing all this because you don't want to burn your garage to the ground while you're sleeping. And your $1800 BMS is what sets the garage on fire. Help me with this, because this is NOT theory it has happened to severla people.

As to the monitoring of voltage of LiFePo4 cells. Both in theory and in practice how can I be against this? It's like being against puppies and apple pie. Yes, measure all you want. Buy any device that makes it easier. But try to use devices that won't themselves do harm. I DID just start a fire in my Speedster using a very innoicent Cell Log 8s thingy and indeed the Cell Log wasn't the problem. The connector kind of vibrated loose while driving, built up a little heat, and softened. To adjoining wires made contact, shorting a cell. This fried all the insulation off the wires in a second and a great plume of smoke rose from beneath the hood.

Thankfully, I was not asleep in the house, I was just pulling into the driveway. I opened the hood, waved off a little smoke, and could SEE the bare wires glowing red. I took a pair of snips and cut the wire. 

So even the most innocuous looking thing I can imagine - used to read 8 cell voltages at a time, got tangled in its own spagghetti wiring and did indeed start a fire, albeit a small one. Had this happened in the garage while I slept, it could have been indeed a tragedy.

So if the very WIRING to do this is dangerous, by the way the Cell Log 8S is still operational, how are you going to do all this monitoring without wiring. You need to fuse each wire at the terminal location. Don't use cheap fuses. Use good, automotive inlines that are thoroughly insulated and weather proof. And unfortunately, a little wobble in the fuse and you have heat. And a little heat and you have...... and so it goes.

I'm not conceptually opposed to monitoring. But as a practical matter, it is difficult. In truth, there are SO many cells in the Mini (112) and some are in such inaccessible areas, that I have indeed spaggehetti wired it. No I didn't fuse it. I did use a series of very EXPENSIVE Amphenol MILSPEC 19 pin metal round connectors with heat shrink on every terminal. But I still live both in fear and in the sure knowledge that all my monitoring is basically for naught, while all that wiring weighs 40 lbs and might burn my car down.

NO BMS is connected to it. I have a little test set I made that plugs into it and allows me to scan through the cell voltages. I can even put a little charge on an individual cell or bleed a little off with a 0.5 ohm 50 watt resistor. I recently mated TWO Cell Log 8S to a plug that screws into any of them. But none of that resides in the car. It is disconnected all the time. I plug it in to measure. I disconnect it when I'm done.

Jack Rickard


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## Guest (May 15, 2010)

> How in the world did you conclude not only that a BMS is stressful on the batteries, but that there is "no argument" about this rather bold statement?


Well that is a simple one to answer. I never said the BMS was the stress but that using a BMS to maximize the utter limits of the battery as you suggest it is the problem. That kind of use is abusive and more than likely will destroy a batter well before it's time. Using the batteries in this capacity is the only reason you'd need to monitor your batteries to the enth degree to prevent battery failure. But with all those connections and wires from each BMS connection leaves you open for disastrous and deadly fire risk. I'd prefer to not take that risk thank you much. Been to close to a few fires in my life. Not a pleasant thought. 

Here is some stuff to think about. I have been driving the lowly VW around for many years and had plenty of stock engines. When I drove that engine as though it was a sports car with a potent engine I killed the engine prematurely. However when I built an engine with more power and ooomph I was able to go play with my lowly VW and have some fun too and the engine stayed alive for a very very long time. I never had to stress the engine out and when I needed that tiny bit of extra I had it. No muss no fuss and no danger of blowing my engine. But the stocker stressed to the limits will blow. A blown engine can cause a fire too. I'd prefer to not blow my pack and would rather spend a few more bucks for a performance pack and have more than I need rather than stress to the limits the bare minimum. Same goes for my controller. My controller is rated for 156 volts and 700 amps. I prefer to keep it below that and let my controller live a good happy long life rather than stress out the controller at its limits. . 

It's that simple and easy to be safe and have fun too. 

Pete


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## Guest (May 15, 2010)

gottdi said:


> Small wires can burn. Can you say fire! Oooops now all that investment is up in smoke and hope the hell you are safe. I had an old VW burn once and it takes less than a few minutes to engulf the vehicle. You don't have time to try to rescue anything except your self and maybe if your lucky a few items within reach before acrid smoke moves you out. Sorry but electrical fires are NO JOKE. Don't care if you have an extinguisher either. Electrical fires are fast and deadly. The less wires the better. There is always that danger but why make it riskier. There is way more than just wires on the BMS systems being built and sold and everyone works different and is put together different and you have no clue if it really will save your batteries in the long run.
> 
> Less power in and out of a battery with no BMS will extend the life. No complex wires and maybe the cost of an extra one or two batteries. Maybe. So charge to 3.9 instead of 4.2 volts. Set your cut of higher than the recommended and you will extend the life. Hands down.
> 
> ...


You're all over it. I couldn't say it better myself and I DID try....

Jack Rickard


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## Qer (May 7, 2008)

jrickard said:


> There is another side to the BMS thing that every time I bring it up everyone mumbles off into the bushes. THEY BURN CARS TO THE GROUND.


That's a bold statement. All caps too. Impressive.



jrickard said:


> Mr. Andrea used to be with a company called Hybrids PLus. This is a car they converted to plug-in in Colorado. I still have a home there. This one caught fire WHILE GOING DOWN THE HIGHWAY with some of Mr. Andreas very personal work in it.


Yep. But actually not because of the BMS.

http://www.evworld.com/library/prius_fire_forensics.pdf

The reason the Prius caught fire was because the battery packs weren't correctly connected. From the document (page 18):



> The inspection of the battery led to the conclusion that the fire was most likely the result of a loose connection, probably at the right-hand side of the Bottom Rear battery. This connection was found to have a nearly 0.1” gap between the bolt head and the lug (Figure 22).
> 
> As can be seen in the photo, this assembled joint was found with the bolt screwed only partially into the nut. It is unlikely that this occurred during either of the vehicle or battery inspections as it required wrenches to remove the nut from the bolt. More likely, this was a result of a) the lack of a locking device to prevent the bolt from backing out, b) the lack of a spacer between the fuse blade and the lug which placed the plastic of the clamshell housing in compression between the two and c) vibration from normal vehicle operation causing the bolt to back off from its original installed position. This joint was found to have approximately 0.16” clearance in the assembly. Assuming that the clamshell plastic was nominally 0.06” thick, the clearance at the time of the fire would be approximately 0.1”.
> 
> As a current-carrying joint becomes loose, the resistance of the connection increases. The power dissipated in heat by a resistor is given by P=I2R. Therefore, a doubling of the resistance increases the power dissipated by heat by a factor of two. The battery pack will experience a maximum discharge current somewhere near 100A during normal driving. Given that the power dissipated by heat is proportional to the square of this current, an increase in resistance to even a few Ohms will result in extreme heat generation. Experience shows that loose connections can lead to temperatures over 250°F.


The construction of the pack was also a cause:



> It should be noted that there was likely an additional source of heat generation. Due to the placement of the connecting tab at the edge of the Nickel sheet and the layout of the 10 cells in each parallel group, the cell closest to the tab would experience a higher current throughput than the rest of its parallel group mates. This additional current would tend to make this cell run warmer than the rest. Therefore, the cell in the Top Front battery where the tab was located would have been running warm to start with, and would be the first to receive heat conducted via the Cross Connect Cable, through the fuse and into the tab.


So the pack was badly built where the cells weren't sharing the current evenly and where especially one cell were quickly heated up by the bad connection. Perfect recipe for a catastrophe. Further on:



> Once the cell built up enough pressure, the pressure vent ruptured and the contents of the cell were ejected with great force; enough to rip the tab off the end of the sheet (the fuse was captured inside the clamshell next to the cells), to pull the Nickel sheet off several adjacent cells and to punch through the plastic clamshell cover (likely softened due to the heat). See Figure 23.
> 
> It is likely that the tab on the Nickel sheet was ripped off first as there is evidence of melting, a sign that current was passing through this area which resulted in arcing as the tab became separated from the sheet. With the first cell ruptured, an amount of electrolyte would have spilled out of the cell can. Any arcs or sparks in the area would have caused the electrolyte to burn which in turn would cause the foam behind the fuse to burn. When the first cell ruptured, pieces of the foil roll may have become separated from the roll and come in contact with the next adjacent cell. This cell is part of the next series group of 10 in parallel. As such, contact between these two cells would have caused a short circuit between these two series groups and all the current would have flowed through these two cells. This is the likely cause of the cell at the corner where the Nickel sheet is separated. Such high current would have caused the Nickel sheet to melt (1560°C), acting as a fuse for the rest of the parallel group.


In Appendix D (same pdf) "Battery Pack Design Safety Guidelines (DRAFT)" from A123 systems is included and on page 3 in that appendix A123 states:



> A battery pack should be equipped with a battery management system to operate the pack properly and to shut down the pack in case of internal or external abusive conditions. The battery management system should provide the following:
> 
> * Minimum and maximum voltage limits should be included in the algorithms to prevent abuse from overcharge and overdischarge.
> 
> ...


That's the only mentioning of a battery management system I could find. There is not one single mentioning of "battery management system" or "bms" being part of the series of events that caused the accident. I can therefore only draw the conclusion that your bold statement that battery management systems are a fire hazard is false and that you probably owe Tesseract an apology for your unfounded personal attack.

Just my humble two cents, of course.


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## EVfun (Mar 14, 2010)

jrickard said:


> So you're doing all this because you don't want to burn your garage to the ground while you're sleeping. And your $1800 BMS is what sets the garage on fire. Help me with this, because this is NOT theory it has happened to severla people.
> 
> As to the monitoring of voltage of LiFePo4 cells. Both in theory and in practice how can I be against this? It's like being against puppies and apple pie. Yes, measure all you want. Buy any device that makes it easier. But try to use devices that won't themselves do harm. I DID just start a fire in my Speedster using a very innoicent Cell Log 8s thingy and indeed the Cell Log wasn't the problem. The connector kind of vibrated loose while driving, built up a little heat, and softened. To adjoining wires made contact, shorting a cell. This fried all the insulation off the wires in a second and a great plume of smoke rose from beneath the hood.


Why the spaghetti? I'm not real keen on bringing out small wires from each cell to anywhere (espcially without fuses )

Look at the loadless miniBMS. It is a pretty good example of cell level monitoring without a bunch of small wiring. I have no financial stake in Clean Power Auto, but it is an example of what I am talking about. The spaghetti is replaced with a single wire from cell to cell that only carries limited amount of current and is part of the vehicles 12 volt electrical system. Watch that loop and if it goes open then a cell went over or under the safe voltage range. Let the user figure out which one. Trust but verify. There are very few EV packs with 2000+ cycles on them so we don't know the real end of cell life issues yet.


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## Guest (May 15, 2010)

> Trust but verify.


Well that is stupid. If I can't trust why have it to begin with? I will just manually check every once and awhile. 

Pete


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## Tesseract (Sep 27, 2008)

jrickard said:


> As always, you've shot yourself in the foot Tesseract. It IS as simple as that.


Good thing I have two... feet, that is. Another opportunity awaits!



jrickard said:


> It indeed IS recursive and circular. A blue elephant gun. As along as we don't SEE any blue elephants, the gun MUST be working and is well worth the $1432.


No, the argument I was making was that given a situation where one has installed the maximum number of cells in their vehicle, adding a BMS which merely monitors cell voltage _may_ allow you to safely extract more range from said pack. JRP3 thinks my example of going from 60% utilization to 80% is unrealistic and provided a reasonable counterargument. You argued in an unrelated post that knowing the number of Ah would effect the same result. I have no problem with either counterargument and accept their merits.

What I don't accept as a valid counterargument is a purely ad hominem attack completely devoid of any factual basis. That does not impress me much.



jrickard said:


> In REAL WORLD PRACTICE - you can drive a car quite without a BMS and *it is just not that hard to check the voltages manually* and verify over and over and over and over, as many times as you like, that you STILL don't need a BMS. This isn't a theory. It's not YOU typing yourself smart into a computer screen.


Well, checking cell voltages manually is still a _battery monitoring system_. It just happens to be a particularly labor-intensive one.



jrickard said:


> There is another side to the BMS thing that every time I bring it up everyone mumbles off into the bushes. THEY BURN CARS TO THE GROUND.


Well, I suppose anything's possible, but that particular vehicle had a problem with the battery interconnects, not the BMS, IIRC. So, you might want to find a better example if fear-mongering is your goal.

Furthermore, is not your main issue with unprotected shunting? This type of problem could be prevented by putting a PTC fuse in series with the shunt resistor(s). Or by not shunting at all - I happen to think your argument against shunting is quite persuasive. Your manner in making that argument leaves much to be desired, but, well... 



jrickard said:


> Meanwhile YOU and DAVID and a host of others, are basically DEFRAUDING interested, enthusiastic, and well meaning individuals...
> OF COURSE it is nice to be able to MONITOR your cells.


We don't sell a BMS and I doubt EVnetics ever will because the price vs. liability equation pretty much sucks. I did design one, but it is only for our own in-house use and to satisfy the demands of a particular European client. So, who am I defrauding, and what snake oil am I peddling? Gee, I guess I'm defrauding myself with my own snake oil. I should sue myself for damages!



jrickard said:


> If you think I was a thorn in your side before, you've seen nothing. I'VE HAD IT. I'M CALLING YOU OUTSIDE. Bring a friend. Bring a lunch. Bring a lawyer. I don't care. We're hookin em up. Lockin horns. No more Mr. Nice Guy.


Well, at least make it entertaining.


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## Tesseract (Sep 27, 2008)

gottdi said:


> Well that is a simple one to answer. I never said the BMS was the stress but that using a BMS to maximize the utter limits of the battery as you suggest it is the problem.


Actually, that is exactly what you said: 



gottdi said:


> I like the idea of no BMS. Easier on the batteries. Less stress. Sure the BMS may monitor the max and minimum but it still is a stress on the battery. No argument there.


But thanks for the clarification.

That said, I agree with you up to a point... that using a BMS to extract more range from a pack might reduce the cycle life. Having an extra 500-1000 cycles might be more valuable to one person; being able to drive 10-20% farther, without destroying cells, might be more important to another. I pointed this out as something to consider, I don't really care one way or the other except that I think given the expense of the cells, and the difficulty in obtaining replacements, that it seems most prudent to monitor cell voltages or, at least, total Ah, if you have an LFP pack.


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## Guest (May 15, 2010)

If you find you need 10% more then you did not plan your conversion very well. Just go get a few more batteries. It will give you more available power, distance and cycle life. Far easier on the batteries than spending $2k or more to monitor and stress out your pack that you will need to replace sooner. Poor economics if economics come to play the way that was described earlier to correct my post. 

Cheaper over all to just add a few more batteries. Most folks could fit more. If not then you need to live within the limits of your pack. I guess it is the choice of each person to stress the pack and replace it sooner than later at a greater expense. May even need to replace single cells during that time and really spend the money. 

Be smart, be easy on your investment and enjoy. Build to your needs. Plan smartly.

Pete 

PS. It is actually more prudent to make sure you don't stress your batteries into early failure. It is also more prudent to have a couple more on standby just in case a battery does fail. No matter if you have a BMS or not some batteries will fail. No amount of monitoring will change that fact. It just might allow me to remove it sooner. I can do that by manually monitoring the pack on a weekly or monthly basis.


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## Qer (May 7, 2008)

gottdi said:


> I can do that by manually monitoring the pack on a weekly or monthly basis.


Works for you, me and other hobbyists, sure. Doesn't work for Mr Average Commuter that only open the hood for adding washer fluid.


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## Guest (May 15, 2010)

Qer said:


> Works for you, me and other hobbyists, sure. Doesn't work for Mr Average Commuter that only open the hood for adding washer fluid.


I won't disagree with that. Now how to do a monitoring system SAFELY and one that does not break the bank to buy and one that will work for those who know nothing. 

My computer has a monitoring system and keeps the battery properly charged. It won't let me overcharge or take my battery to it's death. That is what a charge program is used for and a limit on the controller. If there is a problem you will see a reduced range and you can then have your pack checked to be sure all cells are within limits. 

Still no need for super complex systems. I never physically check my battery on my computer and so far has performed flawless and for the first time I have a battery that is still within it's new power range and it's two years old. Most old computers that used old lithium have died within that time and have had to replace the pack. No complex system but less battery use time. That is the all that is needed for any non techie. So a well done charge cycle and a controller that limits my discharge per driving cycle and enough batteries in the pack to give maximum charge cycles or more and a limit on the controller that says enough and my controller does that and the charger does the charge.

That is as simple as you will get for anyones needs. If your not smart enough to have something checked if normal parameters are not happening then you don't belong in the car. 

I will stick with a good charge cycle and a controller that will limit my power usage per charge. When I can't get my average I will check the pack or have it checked. 

It may be just fine but my driving style has changed. 

Or my tires are low. No different than any other car. Simple. 

KISS still applies.


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## Tesseract (Sep 27, 2008)

gottdi said:


> If you find you need 10% more then you did not plan your conversion very well.


Once again, no argument from me on this, but to clarify the math of my original example, going from a 60% DoD to an 80% DoD is a range increase of 33%. Even going from 60% to 70% is an increase of ~17%. It's sorta like the stock market... you have to gain 100% to make up for an earlier loss of 50%...



gottdi said:


> Far easier on the batteries than spending $2k or more to monitor and stress out your pack that you will need to replace sooner. Poor economics if economics come to play the way that was described earlier to correct my post.


And again I agree, but who says you have to pay $2k? Dimitri's Mini-BMS seems extremely reasonable at $12 per cell + $30 for the head unit and you can skip having the shunt option installed. No spaghetti wiring, either. You can monitor a 60 cell pack for $750, or the cost of about three 160Ah cells shipped



gottdi said:


> PS. It is actually more prudent to make sure you don't stress your batteries into early failure.


And yet again I agree; too bad we don't always plan ahead so well. Heck, just the other day I ran out of gas while on the interstate because I was in too much of a hurry to make it to a meeting so didn't stop to fill up beforehand. Wow, what an embarrassment. You know what else? Running out of gas has the exact same consequences as running out of battery!


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## Qer (May 7, 2008)

gottdi said:


> My computer has a monitoring system and keeps the battery properly charged. It won't let me overcharge or take my battery to it's death.


Yep, but it's a rather stupid system. Most laptop BMS simply solves the problem of balancing by cutting the high current charging when one cell reaches max voltage and then trickle charge the pack until all the batteries are fully charged. That's why it might take up to 24 hours to reach 100% in the pack the first time you put it to use. Now, my laptop battery is 72 Wh where a LiFePO4 pack for an EV will probably be at least a factor 200 larger. Might take a while to balance that by trickle charging it. 

But you're quite right that a BMS in an EV doesn't have to be more complex theoretically. The problem is that it has to handle vibration, a bigger temperature span, higher voltages (which means opto insulation or similar), be physically tough etc. Of course, the day someone starts to produce EV's on a big scale (like laptops are nowadays) the BMS will drop in price, but as long as EV's, and their components, are more or less hand made the price tag will reflect that.


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## EVfun (Mar 14, 2010)

gottdi said:


> Well that is stupid. If I can't trust why have it to begin with? I will just manually check every once and awhile.
> 
> Pete


No, blind trust is stupid. I don't blindly trust either the BMS or the cells!

"I will just manually check every once and awhile." = Verify
With no BMS what you must be doing in between those manual checks = Trust
And yet you start by calling "Trust but verify" stupid.


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## Guest (May 16, 2010)

Qer said:


> That's the only mentioning of a battery management system I could find. There is not one single mentioning of "battery management system" or "bms" being part of the series of events that caused the accident. I can therefore only draw the conclusion that your bold statement that battery management systems are a fire hazard is false and that you probably owe Tesseract an apology for your unfounded personal attack.
> 
> Just my humble two cents, of course.


I never said the BMS burnt the car to the ground. I said David Andrea's battery module design burnt it to the ground. He NOW designs BMS systems. And A123 won't sell any of us an individual cell because of this experience.

What wasn't said in the report was that the battery module DID have a BMS system, and it did nothing to prevent the fire. The actual breakdown was blamed on a misplaced washer, which caused stress on a connection, which then caused heat, which somehow caused adjacent cells to go thermal, etc. etc. And it is all admittedly speculation by A123, albeit probably pretty good speculation.

But no, no BMS is blamed directly for the fire. The Battery module design and assembly both took hits in the report and they were almost entirely the work of Andrea, now one of the principle BMS salesmen. But his reputation is not stellar in the OEM community and I can tell you it isn't very good with the highest management levels of A123.

Jack Rickard


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## Guest (May 16, 2010)

Tesseract said:


> Economics is for _everyone_ and applies to _everything_. When you weigh the _price_ of something vs. its _utility_, you have made an economic assessment, and if you act upon that assessment you have made a _decision_.
> 
> 
> 
> If you think your time has no value then probably not. Perhaps riding the bus and occasionally renting a vehicle makes more sense. If you live in a very densely populated city with a vast array of public transportation and very little parking - e.g., New York City and London - then it might not be economical to own a car unless your time is so valuable that the extra minute or two spent walking to a subway station "costs" you more than parking, insurance, etc.


I'm sure we all need a rambling lesson on economics. I'm more of the point of view that it seems there are plenty of people who no the cost of everything, and the value of nothing.

My time? Interesting observation. Not much discussed. Let me posit another way of thinking. I would love to have a BMS that monitored my system and did all of this for me, at a reasonable price and without posing more danger to the vehicle than it is supposed to prevent. 

If I had one, I would be relieved of all this checking. In fact, I could let the BMS do it. And in fact I would know very little about my pack, how it was working, or even whether a BMS was necessary or "doing a great job."

It will surprise you that I myself have designed two. They just never made it into a car. Along the way, since I didn't have one, I just had to use a voltmeter. And eventually an AH counter. And a little idiot balance meter. And so forth. But since I was operating all this, I got pretty familiar with what happened at the end of a charge. What happened after a short drive. What happened after a long drive and what happened if they were driven to nearly 100% discharge.

And it didn't match anything you were saying. And it didn't match anything I was reading on these forums. And it didn't match anything I was reading in Thundersky forum. 

So I must be doing something wrong.

So I've tried various ways of doing it. And as it so happens, what I was doing wrong was reading all this bullshit online.

My point is, to automate something you first have to know what you want it to do. The standard progression is to take a repetitive manual task that is deemed necessary, but labor intensive, and automate it. The BMS design process seems to be more akin to build it, then see if anyone will buy it, and then we'll see if it actually does anything.

You will know more from just doing it manually. But the truth appears to be that if you do it long enough, you'll notice you don't really need to do it at all.

There is no management. There's no management necessary. They die from overdischarge. And they die from overcharge.

I SUSPECT the disconnect is simply a function of too much community knowledge base in lead acid. If you overcharge ALL of your batteries to get them equalized, and if you don't do this they all wander off into the weeds and get lost, and you do that long enough, after awhile you don't think of it as overcharging at all. It's properly managing.

New cell. It doesn't like overcharging. I've had some englightenment by going back over the discussions from several years ago where several people "got burned" on a buy of early Chinese cells. Those damn Chinese.. In retrospect, these guys appear to have been overcharging from the get go, trying to save these cells using all the techniques they knew would work. And when they didn't, incredibly assumed the cells were faulty.

They don't like to be overcharged. They become wounded from a little bit of it. They die from very much of it at all.

So the technique I have found works very well is to UNDERCHARGE them. And because of the odd structure of the charge curve, this is not only easy to do, but your 10% is simple typing into the screen with no data at all. There is no 10% penalty. Your discussion of this is moot. It's 2% I might go along with 3%. The amount of energy to go from a 3.65 v average to a 4.1 or 4.2 average doesn't amount to a hill of beans. A mile of range -----perhaps....downhill range.... with a wind at your back.....in a tall, sail shaped car.....with one wheel.....maybe.

I go weeks with no monitoring. Then I monitor every day. There's no difference.

Right now, because of a stupid discussion in ev-tech, I'm busily writing down 32 voltages each day, along with temperature and the average voltage of 10 different cells in the same pack, and the pack voltage several hours after charging. I've got this going into a spreadsheet that calculates the high cell, the low cell, the average cell voltage, the span from lowest to highest, and the total of the variance of each/all cells from average. This will take then a couple or three months. I think by graphing the span and the totalized variance over time and temperature, we will pretty much prove or disprove this "cell drift" theory. 

But its a good bit of work. I assure you it is easier for some smart ass to type in the theory of cell drift, complete with an entire little world built around it, and of course requiring a BMS system solution, than it is to determine if it actually exists.

Jack Rickard


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## Guest (May 16, 2010)

Tesseract said:


> Simple as that. Y'all can argue til your blue in the face about BMS vs. no BMS, but until you determine the economics of the two setups your arguments have no merit whatsoever; they are just opinions, and not particularly well-informed ones at that.





Tesseract said:


> What I don't accept as a valid counterargument is a purely ad hominem attack completely devoid of any factual basis. That does not impress me much.


Ok, get me straightened out here. 

(A)You love ad hominem attacks and think they are a useful tool in these dicussions. 

Or

(B) you DON'T like ad hominem attacks and you aren't impressed by them very much.

Or more likely 

(C) It's ok for YOU to use ad hominem attacks because you are in the right and all us fools should clearly see that, but if anyone else stoops to that you're not impressed and they should be ashamed of their behaviour. 

Or what....

I just want to get a clear understanding of your concept of the rules you use in these things Jeff....

Jack Rickard


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## Guest (May 16, 2010)

Tesseract said:


> And again I agree, but who says you have to pay $2k? Dimitri's Mini-BMS seems extremely reasonable at $12 per cell + $30 for the head unit and you can skip having the shunt option installed. No spaghetti wiring, either. You can monitor a 60 cell pack for $750, or the cost of about three 160Ah cells shipped


Dmitri's system is one of the more innocuous and less expensive systems available. But I have 112 cells. And they are 100AH. And so we're talking 
$1400. That's more like 12 cells. 

So far, we're at 1000 miles and I haven't lost a cell. At this rate, I'm good for 12,000 miles, if I DO lose a cell per thousand. Of course, if we don't lose one for the next thousand, we go to 24,000. And I guess if I make 3000 miles with no cell lose, what do we figure then? 36,000 miles without BMS before I run out of my 12 spares.

How far do you want to take this concept of "economics". Ultimately, it is more economical to buy gasoline and forget the whole thing. 

The problem is not only does it cost 12 cells, but I have this little "thing" sticking up on top of each cell. And I have 112 of them. And any one of them might fail and cause more trouble than a failed cell would.

More likely, it fails and while I THINK my blue elephant gun is working there to protect me, come to find out there were elephants just beyond ear shot gathering and painting themselves a hideous shade of blue, readying for the attack. And it made not a peep. I find out via the olfactory sensation of burning insulation.



Tesseract said:


> And yet again I agree; too bad we don't always plan ahead so well. Heck, just the other day I ran out of gas while on the interstate because I was in too much of a hurry to make it to a meeting so didn't stop to fill up beforehand. Wow, what an embarrassment. You know what else? Running out of gas has the exact same consequences as running out of battery!


Well, not exactly. At its most basic, if you run out of gas in an electric car, you get to buy a new pack. In a gasoline powered car, you have to go get a gallon.

But that's the heart of it. How do daughterproof the car so you can let her use the car without worrying that she'll cost you $10K in batteries.

Right now we're going with a Xantrex and tying the alarm to a relay to cut the throttle voltage to 25%. That should limit speed to about 25 miles an hour full throttle. While she might ignore lights buzzers, etc. She will notice something's different with a top speed of 25. I might make it 20.

I would sure like to see all the BMS effort cease and refocus on instrumentation. I'd love some pretty gage "skins" on a 7 inch display where I knew AH used, maybe MILES TO EMPTY. Speed, rpm, instantaneous current draw, pack voltage, and yeah maybe a basic indication that the pack is GOOD, questionable, or BAD.

Jack Rickard


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## Qer (May 7, 2008)

jrickard said:


> I never said the BMS burnt the car to the ground.


Oh yes, you did:



jrickard said:


> There is another side to the BMS thing that every time I bring it up everyone mumbles off into the bushes. THEY BURN CARS TO THE GROUND.


So it's possible it wasn't what you meant, but that's they way you phrased it and the way I therefore interpreted it.



jrickard said:


> I said David Andrea's battery module design burnt it to the ground. He NOW designs BMS systems. And A123 won't sell any of us an individual cell because of this experience.


And thus BMS in general is a bad thing?



jrickard said:


> What wasn't said in the report was that the battery module DID have a BMS system, and it did nothing to prevent the fire.


Very true, but it still only proves that the BMS in this situation failed to avoid the catastrophe, not that BMS in general is worthless or a fire hazard in themselves. In this case the fire would have happened even without a BMS.



jrickard said:


> The actual breakdown was blamed on a misplaced washer, which caused stress on a connection, which then caused heat, which somehow caused adjacent cells to go thermal, etc. etc. And it is all admittedly speculation by A123, albeit probably pretty good speculation.


Well, look at the pictures in the pdf. I'd say the speculations are pretty darn good but as in all post mortem-analysis it's of course close to impossible to be 100% sure.



jrickard said:


> But no, no BMS is blamed directly for the fire. The Battery module design and assembly both took hits in the report and they were almost entirely the work of Andrea, now one of the principle BMS salesmen. But his reputation is not stellar in the OEM community and I can tell you it isn't very good with the highest management levels of A123.


Considering how the pack was constructed, I can see why. It still only indicates that it's probably a very bad idea trusting his BMS, although it's possible that his BMS-design is better than his pack-design (even though I personally wouldn't bet a pack on it...).

However, I'd still prefer if you'd back off and stopped calling people names when they don't agree with you. Everyone's entitled an opinion and even if you think they're wrong I'd say that words like "charlatan", "rambling lesson", "jerk" etc isn't very convincing. You do have some good points in your reasoning but right now there's a risk they're getting lost due to your verbal flailing and general bad attitude.

A pity, really.


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## Tesseract (Sep 27, 2008)

jrickard said:


> Ok, get me straightened out here.


Easy. You left off just one tiny bit of that quote which totally changed the context:



Tesseract said:


> Simple as that. Y'all can argue til your blue in the face about BMS vs. no BMS, but until you determine the economics of the two setups your arguments have no merit whatsoever; they are just opinions, and not particularly well-informed ones at that.


Specifically, the  .

That smiley was to let JRP3 (and anyone else) know that my giving him a hard time was all in good fun. JRP3 knows my sense of humor and has publicly stated his appreciation of it. You don't know me from, well, Jack, and should probably keep your fingers to yourself if you find apoplexy imminent upon reading something I wrote, especially if it wasn't addressed to you in the first place.

So, this was not an ad hominem attack at all, which sort of renders the rest of your post with all its rhetorical questions moot. You totally lost the moral high ground, anyway, when you flamed me in response to what you perceived to me "starting it". Ever heard that chestnut of moral wisdom, "two wrongs don't make a right"?

But this isn't the first time you've resorted to what any _teen_ would recognize as cyberbullying because someone had the temerity to disagree with your "Decrees".

As I've said to you before, Jack, use reason and data to make your arguments, not invective. Calling someone names does not make your position any more credible; indeed, it has the exact opposite effect.


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## Guest (May 16, 2010)

Tesseract said:


> Easy. You left off just one tiny bit of that quote which totally changed the context:
> 
> 
> 
> ...



Ok. I get it. It's  which is really C: but with a smiley face? AND you shamelessly continue the attack in the same message?

So YOU can attack personally, but the rest of us should do what? Lean on moral wisdom and avoid doing it to prevent the occurrence of TWO wrongs?????

I'll predict you'll be much easier to deal with AFTER your adolescence....

People who use smiley faces to justify spectacularly poor behavior are generally morons....

If it wasn't addressed to me in the first place, and was meant as private communication to JRP, then why wasn't it sent by private e-mail? You drop a bomb in a public forum sport, you have to deal with the debris. You made an ass of yourself in public, pretty much swamping any point you were so ineptly trying to make, and in the process of backpedaling furiously, you're main point now is that whatever you say is really not what you said, because you typed in a smiley face??

Apology accepted......I think.....

Jack Rickard



Jack Rickard


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## JRP3 (Mar 7, 2008)

jrickard said:


> JRP. I'm gradually becoming a fan of the Xantex ProLink. It is fairly inexpensive ($250 on eBay), it does a good job of measuring current, gives me AH IN and OUT totalized which you need with regen or to monitor charging, and it is a pretty simple connection. It uses a 50mv 500A shunt....


I've looked at the Xantrex/TBS. A bit pricey, and I don't like shunts. In the DIY spirit I'm interested in Dimitri's Ah/Wh meter which uses a hall effect, reads in and out, can do Ah or Wh, and can be temperature adjusted:
http://www.diyelectriccar.com/forums/showpost.php?p=181468&postcount=62


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## Guest (May 16, 2010)

Qer said:


> Oh yes, you did:
> 
> 
> 
> So it's possible it wasn't what you meant, but that's they way you phrased it and the way I therefore interpreted it.


Errr..Oh, NO, I didn't. I said BMS's burned cars to the ground and I believe they do.

In this particular case, I was trying to establish the connection between a person who had designed a plug-in battery system for a Prius that burned one to the ground so badly that a major battery supplier will never sell battery modules to the conversion community. AND as the winds of irony would have it, has NOW designed a BMS which is probably the leading solution on the ground. 

I say this, because in the irony of ALL ironies, I'm getting almost daily calls from people to ME asking for help in the apparent nightmare of installing it? I appear to be the only sucker on the planet who has not drunk of the BMS koolaid, and not one or two, but easily eight or ten calls and e-mails asking for help installing one????? 

I've talked to them. It isn't a joke. They're sincere.




Qer said:


> And thus BMS in general is a bad thing?


To put a broad point on it, yes. It is. 

Actually there is no "BMS in general". There are available BMS systems. Every one I've seen is a bad idea. Everyone I've bought has been a bad idea. Every one I've myself designed has been a bad idea. And every one I've seen described is a bad idea, with one lone exception, which in general doesn't appear to work in the noisy environment of a car.


And I believe that to be true without regard to economics. I do not insist that things work economically to work in general, and if I did, I certainly would not be converting perfectly good, and in one case, brand new, cars to electric drive in the first place.

But the discussion, now that Mr. Tesseract has sold 30 controllers and thus qualifies as a business/economics wunderkind, centered on the supposed economic considerations of a BMS. And lost in the As, the Bs, and the Cs of smiley faces and personal attacks, is that his point on economics fails entirely, because of their reliance on fantasy numbers. And indeed, if economics were the overriding concern, BUT you did a car conversion anyway AND you paid 3X more for LiFePo4 cells instead of lead acid, then a BMS still doesn't work and is in general, a very very bad idea and does indeed have the potential to 

BURN YOUR CAR TO THE GROUND. 

Ironically, no one having more experience in doing so, than the designer of what is apparently the most popular BMS solution currently extant. 



Qer said:


> Very true, but it still only proves that the BMS in this situation failed to avoid the catastrophe, not that BMS in general is worthless or a fire hazard in themselves. In this case the fire would have happened even without a BMS.


I know you believe this makes sense. And I'm sympathetic. But it has too much surmise and an appeal to logic simply doesn't make it therefore true.

The thinking process is too complicated. His was. Yours is. Ergo the situation. This module was a fire hazard in and of itself. The BMS purported to protect it did nothing. The BASIC CONCEPT is inherently flawed, by numbers and human frailty. It's an entirely other subject, but it goes to the process, the thinking, and the people involved. Again, I'm the only buffalo NOT going over the cliff on this one. I know Tesla does it. I know AC Propulsion does it. But it has to fail and it has to keep on failing. 

When you put a whole bunch of itty bitty batteries together, and then you draw a BIG chunk of current (power) out of them, as a group, you have set up basically not just a problem, but a kind of super-elegant form of fireworks. 

I really don't have to know the details of how you prevented catastrophe, or what a marvelous engineer you are. At a glance I can tell you this just won't work, and if it appears to work for awhile, it won't continue. 

First are the connections. We have no magic nickel sheet. What we have inherent in the batteries are dissimilar metals. Strong connections, or weak ones, are subject to a couple of things to note, and this applies quite to the larger prismatic batteries and YOUR packs as well. 

Dissimilar metals, in the presence of an electrolyte, form what can best be described, ironically, as a BATTERY. And it causes its own minor flow of electrons. This causes corrosion. Corrosion causes resistance. Resistance with current through it causes heat. Heat causes further erosion and corrosion. ANd you have a kind of slow motion thermal runaway. 

There are materials that act to seal the connection from the most commonly available electrolyte (water) and it's much more powerful related electrolyte (salt water) and in the process act as a sacrificial electron donor to minimize the change of a metal into an oxide - the corrosion. They are partially effective if properly applied.

The next problem is heat. No matter how tight the connection, there is a bit of a voltage drop across it and a little bit of heating involved just from passing electrons down the pike. At the currents we are talking, it is quite substantial. And dissimilar metals expand in the presence of heat, well, dissimilarly. Each have a different expansion coefficient. When we accelerate, we draw current, and heat. And when we cease acceleration, we cease drawing current, and we cool. And we do this not just with every driving cycle, but with every press of the pedal. 

So these connections are constantly expanding and contracting mechanically. This causes them to loosen. And this causes greater heating. Again, from an entirely second source we have a slow motion thermal avalanche or cascade event.

That all assumes that the connections were made correctly in the first place. And all the nature of numbers is against there being made correctly in the first place. These modules are not produced in sufficient numbers that heavy automation can be brought to bear. They are mostly assembled by humans.

It is boring and repetitive work. So if you had truly excellent humans, properly trained and over-supervised, with QC checks at every step, the sheer number of connections (two thousand, five thousand, ten thousand and more) works against you. But as it is boring and repetitive work, it is rare for truly excellent humans to be doing it. Most companies at this point can't even get a warm body to pee in a cup without screwing it up - at any labor price. Basically if you are drug free and don't have a job in America today you apparently don't want one.

(continued)


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## Guest (May 16, 2010)

Do I exaggerate? If any of you have problems getting a GOOD paying job, and are actually drug-free, trot yourself down to ANY major or even significant aviation maintenance facillity in the country and tell them you wish to speak to someone in the avionics department. If you know to say avionics and it is spelled A-V-I-O-N-I-C-S, as in avionics, they will show you right back. When you get there, immediately confess that you know ABSOLUTELY NOTHING, not only about avionics, but about electricity. And that you actually have obsessive fear of all things electronic. And that you literally could not put two batteries in a flashlight and get it right before the third try. But add that you DO know how to work a wristwatch and COULD if it was REALLY important show up on time, and that you THINK you MIGHT have about a 30% chance of passing a piss test if you had a couple of months notice, and see what happens.

They'll immediately try to negotiate you down of course. Not in pay, but on the two months notice on the piss test. They'll interview you of course. But the interview will be about how you think you'll do on the piss test with say 6 weeks notice? Or 4 weeks?

If you implied you were of such brazen personal courage that you could take one today, they would probably discontinue the interview about the avionics job. They'd want you to talk to some other people about what city you wanted to RUN an avionics shop in. And they'll probably have several for you to pick from.

Well, I'm off on a riff about employment prospects, and here, I haven't had a job for the last twenty years so I clearly don't know anything about it. Let the attacks begin....there's some meat for you Tesseract. If you can't slash and burn with that softball, you ain't a player.

To bring it back home, the basic concept of making big modules from tiny little cells is bad medicine. The contact problem is bad enough INSIDE the factory made and quite automated cells themselves. Making a module out of them with thousands of connections is nonsense pure, simple, and distilled.

And I would encourage anyone with a pack of large prismatics to take a half inch wrench, put some heat sink over the handle and hit it with a heat gun, and then go around and just gently tug on each of those M8 terminal bolts. If you haven't done it for awhile, you're in for a pretty alarming surprise.

And so in my very simple world, imagine what just the addition of a little tab , of the very finest material that 0.05 cents can purchase, does to that terminal connection, so that a BMS might live. I haven't got time really to go over your amateur schematic diagram. I know you've just doubled the problem at the terminal without adding any electronics. Put a wire on the tab, and I can show you how to start a fire.

And to all those who have expressed concern, my sincere thanks. My hands are really healing quite well at this point and I think they'll be fine. My budding career as a men's hand model is probably ended, but they work fine already. The pain really was never that big a deal. More embarrassed than anything else. 



Qer said:


> Well, look at the pictures in the pdf. I'd say the speculations are pretty darn good but as in all post mortem-analysis it's of course close to impossible to be 100% sure.


Where do you think I got the photo? Do you honestly believe I haven't read the PDF? About a dozen times. Would it surprise you that I see things in it you don't? Would it surprise you I have eight or nine of these? Would it surprise you that in almost every case the owner does NOT believe the BMS did it? It happened generally right after he installed the BMS. It happened at night when he wasn't there but it was charging And he's pretty sure it was "something that just went wrong with one of the cells"? And would it surprise you that in some cases the insurance company does actually pay for at least part of the damages?

And would it surprise you if I in reading the account view it a little differently. The latest was called to my attention by the receipt of a plaintive plea from a supplier to please, please use a BMS to AVOID what happened to the following poor, poor soul. Photos were attached. The battery supplier claims it was just a bad short to the frame and poor construction. Tracked all this down through the supplier to the guy to the photos, and lo and behold, there on the top of each cell was a little burned black circuit board. (everything was burnt). What's this? A meal timer? Digital watch? Perhaps a weather radio? Hookup for the IPOD?

Do I know the BMS caused it? No. I know we were TOLD that he didn't even HAVE a BMS. I know we were told we were to immediately purchase one, to prevent such an unfortunate event. And I know it was all bullshit. But I don't know that the BMS caused the fire.

I know Roger Heckenroth burned a car to the ground so badly it took his garage to the ground with it, melted the glass in the doors, and melted the transmission to slag. He does not believe it was the BMS. In fact he designed and built that shunt BMS with his very own hands. He put it on a dumb charger with the BMS to handle all the thinking and went to bed. He knows from a neighbor that three hours later everything was fine. But somehow, somewhere in the late night, after a full charge would have been reached, something happened probably inside one of the CELLS and it burned up his car, his charger, and his BMS. Those damn Chinese again....

No, I do not know it was the BMS. It appears to have been at the end of the charge cycle. With a newly deployed shunt balancing BMS. But he might be right. Maybe these cells just spontaneously burst into flame. It could be.

I've studied these intently and for years. You mockingly ask if I have read the PDF? Boy, do I stand corrected here. It just never quite occurred to me to read the damn thing while I was stealing the photo....

And you say I don't talk nicely? I'm not sufficiently genteel for your tastes? I should mind my manners.... I'll try really really hard....maybe I can get a lesson on conversion economics, from a hardware vendor perhaps, and get him to throw in a quick bonus lesson on online etiquette. Yes, it is true that I was writing FORUM software in 8088 ASSEMBLY LANGUAGE twelve years before either of you had your FIRST encounter with the Internet, but one can always learn a little more, cannot one? I should be more polite when challenging people championing costly BMS systems to the clueless and concerned all the while they are 

BURNING CARS TO THE GROUND.

Meanwhile, why don't you scan through this message, tweak and twiddle. Find a few mispellings. Maybe what YOU think is an overstated case. Be coy. Pleading. Accusing. And most of all dismissive. Because as we all know in the forums, we can always VOTE and change the entire reality of it all. If we type enough, we'll get really really smart. And of course, if all else fails, remember EVERYONE IS ENTITLED TO THEIR OPINON. Chant that about seven times to yourself. It starts to have a hypnotic rhythm doesn't it? Almost metronomic, or maybe metromoronic, I forget which. But it's apparently a very important concept. I never get what it has to do with, but it is apparently hypnotic in its allure.

It IS a pity. Really. I'd actually go further. I think the word you're searching for is "pathetic." It's like pity, but more emphatic.

Jack Rickard


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## Guest (May 16, 2010)

JRP3 said:


> I've looked at the Xantrex/TBS. A bit pricey, and I don't like shunts. In the DIY spirit I'm interested in Dimitri's Ah/Wh meter which uses a hall effect, reads in and out, can do Ah or Wh, and can be temperature adjusted:
> http://www.diyelectriccar.com/forums/showpost.php?p=181468&postcount=62


Really. I wasn't aware he was working on one. I've done such with an Arduino. But I just didn't protect the ADC inputs and the TIMS600 was putting out so much noise it quit in the car after 22 miles. I used two hall effect sensors and a GPS module. IT was actually giving me miles to empty, VERY accurate current measurements, and spitting out serial data that could be used with a GUI. I intended to finish it. But I need something for Part Duh. I was unaware Dmitri was working on such. The Xantrex is not that expensive compared to most of the instrumentation out there. The EVIsion was too complicated to install and $785. The Xantrex is an easy install and $250. I would be surprised if someone could do something interesting for less than that.

I don't think temperature adjust is much of a useful feature. But the rest sounds good. THIS is where the emphasis should be to my way of thinking. Instrumentation. I look at the gorgeous displays in the NIssan Leaf and Chevy Volt and think, "its all software. Somebody should be doing this."


jack Rickard


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## tomofreno (Mar 3, 2009)

> I've looked at the Xantrex/TBS. A bit pricey, and I don't like shunts. In the DIY spirit I'm interested in Dimitri's Ah/Wh meter which uses a hall effect, reads in and out, can do Ah or Wh, and can be temperature adjusted:


 As some of you know I am using the TBS and like it - depend heavily upon it for a "fuel" gauge. I also like the little 5 bar display for soc, since it is very easy to see approximate soc at a glance. What I don't like is it does not have Wh like the evision does and Dimitri's gauge will. I can get average Wh over a charge cycle from the EKM meter, but it would be nice to be able to track Wh used over a given stretch of road (at high speed, on a hill etc). Presently I estimate that by watching both current and voltage and making some mental estimate of average voltage - it doesn't change much at all on a given shorter stretch, so likely less than 2% error, but the error is larger on longer stretches where terrain varies. The temperature compensation should be good, since in winter, with cells heated to 60F I was getting about 12-13 miles per bar on the TBS. Now, with cells at 70 - 85F I am getting more like 14 - 15 per bar. One bar is 20% charge, and "empty" is set up as 35% soc on mine - which is another nice feature, being able to define "empty" as you like. Then you can just tell someone unfamiliar with the car to not drive it further once the last bar disappears, and they have x miles per bar. The gauge is made by TBS, Xantrex is a U.S. distributor. Beltronix is another, and sells the voltage adapter as well.


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## ElectriCar (Jun 15, 2008)

I don't know Jack but I like his writing! He may get a little over stimulated reading folks comments but his replies nonetheless are a must read for me! 

So Jack, keep it up. I've read every word you've written on this thread. Though one needs a cup of coffee and sit a spell to read your retorts, I do glean bits and pieces of useful info about all this BMS stuff. To BMS or not to BMS, that is the question and I think your knowledge and experiences are very helpful!

And yes I agree, drawing LOTS of current through lots of itty bitty batteries cobbled together is a fire waiting to happen. Seriously, people are doing things with batteries and cables totally devoid of electrical wiring knowledge, practices and experience, and that truly is a recipe for BURNING THINGS TO THE GROUND! 

I'm satisfied that by learning to fuse wires, properly make high current connections and check them periodically would eliminate a lot of fires.

And out of curiosity Jack, are you familiar with Arc Fault breakers? It occurred to me that possibly the electronics in them could be used in a pack to monitor arcing of loose connections. It would take some knowledge of the electronics but with that knowledge and a good hack, I think it could work to prevent meltdowns.


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## ElectriCar (Jun 15, 2008)

Yo. Jack. You asleep??


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## Guest (May 19, 2010)

He's working on his two active conversions rather than being here listening to us.


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## Guest (May 19, 2010)

gottdi said:


> He's working on his two active conversions rather than being here listening to us.


Yah. Kind of got my hands full this week. I'm pleased you all enjoy my rants. I do have some experience with arc-fault interrupt circuit breakers in housing renovations I've done. None of them good actually. And I've not seen any available at EV useful currents. 

That is not to say it's not an idea. I guess I think an arc-fault interrupt circuit would be late to the party in detecting increased temperatures across poor or lose connections, but that take might be hasty. It would require some experimentation. 

String of cells. 300 amp load. Put a thermometer on a connection and start loosening. See if the arc fault trilps before you blow the thing up. Or better, as soon as the temperature begins to rise. I guess I think it will go either too early or too late, and there won't be a way to tune it.

Yes, we have our hands full. I'm trying to learn how to make battery boxes out of carbon fiber/kevlar hybrid. Our first was ugly, but 3 lbs and holds 126 lbs of cells quite securely.

Our second looks a little better.

I've bought a GMC 2500 STX Rally van that started life as an electric G-VAN. GM/Conceptor/SoCal Edision manufactured 600 of them in 1991. We're going to remove 3200 lbs of lead and frame and replace with 800 lbs LiFePo4. It uses a 391 lb Sepex motor and features regenerative braking.

We're also lining up for a Smart for Two project. These little cars are going for cheap right now. You can pick up pretty low mileage units on eBay in the $7000-$9000 range. The fascinating thing about these revolves around a couple of oddities. They are terrifically small. Too small to actually be a car. And they have all the creature comforts we've come to expect in a car. A/C, heat, nav, keyless entry, power windows, heated seats, etc. It's kind of like going to a Mercedes dealer and asking for 1800 lbs of Mercedes, thinly sliced and wrapped to go.

And we're of course playing with instrumentation. Quite enthused about the Cycle Analyst until I received it. Very poor current accuracy and missing some obvious things in code - debounce on the switches most notably.

BUT found some fascinating little high quality voltmeter displays at LASCO ELectronics.

The Mini is a LOT of fun to drive. We still have some issues that will require some microcontroller CAN bus things that may take awhile - tachometer, system fuel gage, waking up the EPAS steering, etc. Also having some issues with the Masterflux Sierra air conditioning compressor.

I'm recording 32 cell voltages each morning after charging overnight. I think I've got a "cell drift" test scenario worked out. It's largely a specious and circular argument, but there is a germ of a question buried in all the online BS about this. My curiosity is up anyway. It will take a month or so to come up with a meaningful data set. But the results might be interesting. Or they might be nothing...


So yes, we're still working on the Mini, and have two others in process. We'll see what happens.

Jack Rickard


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## Guest (May 19, 2010)

Jack,

What type of motor are you thinking for the Smart? I'd think a nice small AC with lithium of course. I'll be watching for that in the future. 

Pete


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## Guest (May 19, 2010)

gottdi said:


> Jack,
> 
> What type of motor are you thinking for the Smart? I'd think a nice small AC with lithium of course. I'll be watching for that in the future.
> 
> Pete


Pete - its a little early for all that actually. I don't know exactly how this is going to turn out . But there's a European team that has successfully converted a 450 to electric drive with a pretty neat package - http://www.electro-vehicles.eu/shop/details.asp?prodid=EVE03&cat=0&path=53.

They are kind of working with us on a 30kw version with the necessary changes to fit a 451 - the 2008 we bought on eBay....

They do a kind of busy box with Curtis 1238 in it and a little AC motor. I thought the 15kw would be ideal but they have talked me into the 30 kw. I still think they just dont' have the 15kw set up right. We're not going to race the things.

I like high end projects. A segment of our viewership want's to do things at the sub $75K level. We're trying to find some viable things where you wind up with a cool ride and a fun project in the $25K range. It's kind of hard.

I'm never going to be onboard the "convert junk to electric junk" ship, But I have some ideas.

Jack Rickard


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## tomofreno (Mar 3, 2009)

> They are kind of working with us on a 30kw version


 This with the Mes-Dea TIM400 looks interesting for something like a Civic or Corolla - especially now that the Euro is falling.


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## Jan (Oct 5, 2009)

Jack,

Maybe you've explained it, but I'm not in the mood to read all that flaming.

But why is limping home with a bottom balanced pack not a serious risk? OK, I understand you'll probably will not distroy the weekest cells. Alone.. But why won't you distroy the whole pack?


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## JRP3 (Mar 7, 2008)

In my case for two reasons:
1. The controller cuts back as voltage drops so you pull fewer and fewer amps from the pack. Eventually the car will stop moving, before the cells go to zero. You can adjust when this happens, at least with the Curtis 1238.

2. SE/CALB lists 2.0 volts as the bottom for their cells, which is most likely resting voltage. My cells were at 2.4 volts and climbing when I got home and stopped. Very likely little to no damage at all was done to my pack other than a deep discharge.


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## Jan (Oct 5, 2009)

JRP3 said:


> In my case for two reasons:
> 1. The controller cuts back as voltage drops so you pull fewer and fewer amps from the pack. Eventually the car will stop moving, before the cells go to zero. You can adjust when this happens, at least with the Curtis 1238.
> 
> 2. SE/CALB lists 2.0 volts as the bottom for their cells, which is most likely resting voltage. My cells were at 2.4 volts and climbing when I got home and stopped. Very likely little to no damage at all was done to my pack other than a deep discharge.


Thanks JRP. So, if they are bottom balanced and you set a correct cutoff voltage in your inverter/controller it's ok. I thought of limping home is going as far as you can. Not untill the controler cuts off, but the batteries are dead. And hoping that you get home before this happens.


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## Guest (May 20, 2010)

Jan said:


> Jack,
> 
> Maybe you've explained it, but I'm not in the mood to read all that flaming.
> 
> But why is limping home with a bottom balanced pack not a serious risk? OK, I understand you'll probably will not distroy the weekest cells. Alone.. But why won't you distroy the whole pack?


If you want to know, you'll have to enjoy the fire as well. The cell failure is caused by cell reversal. The cell reversal is caused by the other cells still putting out high current levels through a cell that is below voltage. This immediately, (in seconds) drives the individual cell to zero.

If all cells are more or less balanced at the bottom, the voltage of the entire pack sags more or less equally, and it can't develop those high currents through a weak cell - in theory. At some point of course, one cell will give up the ghost first, but you will be crawling down the road by then with no protection at all.

As JRP notes however, most controllers have a low voltage limit. If the whole pack sags to that , you start limiting current from the pack anyway and at some point the controller just shuts you down.

THIS by the way, gets more people on controller setup than anything else. It got me big time. It works so well, you think its working and it very much is not. 

The basic scenario is that you put in a voltage that would be low voltage at static voltage. Let's say I don't want to go below 2.8 v per cell. So I have 40 cells for example, and I set the low voltage value to 112v. 

I drive the car, and everything works BEAUTIFULLY. Ok, the acceleration on takeoff is not what I was hoping for, but really is quite acceptable and I'm ok with it.

A few weeks later, I just try changing the low voltage to 80v. I step on the accelerator lightly and suddenly eSpeedster is squalling tires and taking off into the fenceline. 

What happened?

These things operate so well they are magical - magically misleading. I had set the thing to 112v. When I step on the accelerator, we are not TALKING about static voltage. It is measuring whatever voltage there is. And these cells DO sag in voltage to produce those high currents. When I accelerated, it produced plenty of current right up to the millisecond where it reached 112v. It then reduced the current until it was at 112.001. And everytime it increased the current where the voltage sagged to 112, it would current limit. Doing it a couple hundred times a second, the effect was to limit the current perfectly to what would maintain 112v. 

Happily, I notice I really just don't ever go below 112v.

When I set it to 80v, all of a sudden I get full current down to 2.0v per cell. And there was a LOT more current available. So the performance shoots up.

I've had two people with performance problems THIS week including the ugliest XPrize entry in the universe. GREAT acceleration now. Simply by changing the low voltage cutoff on their controller.

Makes me wonder how many people are out there, slightly disappointed in the initial acceleration but more or less happy with their cars, that without realizing it have hobbled the car with this one controller value.

In any event, if you are pretty well balanced at the bottom, you'll hit the controller current limit before you kill a cell. And really we don't bottom balance unless we're adding cells to a pack or replacing them. It isn't so much that you should bottom balance. It's that you should NOT top balance. It exaggerates the capacity differences at the bottom and CAUSES the problem where there really wasn't one. All in the name of protecting the batteries?

I demonstrated this on camera. I duplicated it three successive times. I showed you how you could duplicate it yourself - quite manually and to your own satisfaction. THERE IS NOTHING MORE I CAN DO. 

But if you encounter someone designing and selling a battery management system that top balances cells, I can assure you you have just seen in real time and up close, someone who DOES NOT KNOW ANYTHING ABOUT LIFEPO4 cells and particularly about their use in a traction application. It's not a debate. We don't get to all vote. It doesn't matter what anyone's "opinion" is. It's empirically demonstrable and has been empirically demonstrated. It is reproducible 100% of the time, by anyone with a very minimal amount of test equipment.

If they INVENTED the cells and their name is Goodenough, that's still not good enough. It doesn't change a thing.

That it is much easier to balance cells at the top is barely interesting. The chemistry of these cells is sort of ambivalent about how hard or easy your life is.

That you MEANT WELL when buying the system is barely interesting. I've got a garage full of stuff that's almost the right size. I meant well every time.

That the designer MEANT WELL when he sent the boards off to Sunstone and MEANT WELL when he cashed your check - doesn't matter.

That in your opinion you WISH it were otherwise - sorry, no change. I can't make it be what it aint' going to be.

That you don't like my flames on the topic - I'm actually NOT even sorry. No change.

1. You don't need to balance at all unless you are modifying your pack.
2. Don't overcharge your cells.
3. Don't overdischarge your cells.
4. There is no 4.

Cell life is an almost exponential function of how far you remove your operations from the TWO ends of the discharge curve.

Cell FAILURE is so rare as to be a non-issue. Even under EXTREME current loads. You basically have to have overcharged or overdischarged to get one to fail.

What about cell drift? I dunno. In a year and a half and 10,000 km I haven't had enough of it yet to be able to measure it with test instruments.
Maybe. But then how serious a problem is it going to be if I only have to deal with it every other year?

Jack Rickard


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## Guest (May 20, 2010)

JRP3 said:


> In my case for two reasons:
> 1. The controller cuts back as voltage drops so you pull fewer and fewer amps from the pack. Eventually the car will stop moving, before the cells go to zero. You can adjust when this happens, at least with the Curtis 1238.
> 
> 2. SE/CALB lists 2.0 volts as the bottom for their cells, which is most likely resting voltage. My cells were at 2.4 volts and climbing when I got home and stopped. Very likely little to no damage at all was done to my pack other than a deep discharge.


I would like to offer a modest, but I think important to note correction here. What CALB lists is a 2.0 v cutoff voltage at the STANDARD DISCHARGE RATE.

It is possible, usually toward the end of the ride, but still possible to draw enough current to sag those cells well below 2.0v, with NO DAMAGE TO THE CELL AT ALL. 

Yeah, I know you all don't believe me. I do need to get those 3C tests on video and get them out. But it is true. These spec sheets are a little weeny to interpret. The 3.6v is at the standard charge rate. The 2.0v is at the standard discharge rate. Neither necessarily holds true at a different current rate. IF you are discharging at 0.5C (I think) and you reach 2.0v while doing it, that is DEFINED as the "cutoff voltage".

That does not mean that the terminal voltage measured at the cell cannot go below 2.0v. I know "cutoff" sounds rather emphatic. But in reality it isn't.

It's just a defined data point. They guarantee their cell is still good at 2.0v and 0.5C. But they go together. At 0.2C and 2.1 v you may already be in the danger area. And at 2C and 1.9v you may well NOT be in the danger area.

Which goes to the LVC monitoring disconnect I've had all along. You're monitoring for WHAT and you're going to do WHAT with the information?


And it is intensely variable by CAR not by cell. My 375 mini does about 362 amps max and most of the time will go down a level road at 70 mph and 75 amps quite happily.

The speedster is 120v and more like 550 amps to get up to highway speeds.

Both use cells of around 100 Ah. The mini is 100Ah CALB and the Speedster is TWO strings of 90AH in parallel. So you're going to design a LVC monitor to do what about what? If you don't know what my current draw is, and you don't know what my AH capacity is, how did you get so smart to determine what the voltage level should be that you're monitoring for?

The answer is that when designing and selling a blue elephant gun, the bullet size doesn't matter, the caliber doesn't matter, the powder charge doesn't matter, and the accuracy doesn't matter. It just matters that you do a good job of making sure people know just how much damage a blue elephant can do....

Jack Rickard
Living BMS free - one day at a time...


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## Jan (Oct 5, 2009)

OK, Jack. You made your point very clear.


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## david85 (Nov 12, 2007)

Low voltage "cut off" is something I've been wondering about myself actually since current draw can vary widely and that affects measured voltage.


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## Jan (Oct 5, 2009)

david85 said:


> Low voltage "cut off" is something I've been wondering about myself actually since current draw can vary widely and that affects measured voltage.


With the arduino Jack build and knowing the behaviour of the batteries you can cut off. Without measuring the drawn amperages it's pretty useless.


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## Guest (May 21, 2010)

Jan said:


> With the arduino Jack build and knowing the behaviour of the batteries you can cut off. Without measuring the drawn amperages it's pretty useless.


Truly so. It is information. But it's not very useful. The back workshop is one environment, a car going down the road a very different one. Currents all over the place, voltages all over the place, and again, you're going to measure WHAT for WHAT and do WHAT with the information.

About what we're left with is Amp Hours. We can measure that fairly well. We know roughly our capacity. If we're shooting for 80%, and we're +- 3%, as the capacity changes a bit over time, oh well.

Jack Rickard


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## Jan (Oct 5, 2009)

jrickard said:


> Truly so. It is information. But it's not very useful. The back workshop is one environment, a car going down the road a very different one. Currents all over the place, voltages all over the place...


How come? Is it your dc-dc converter? Where do the arduino destroying currents come from? I understand Arduino's don't like voltage above 12v for long. It can take peaks upto 20v, but not long. 



> and again, you're going to measure WHAT for WHAT and do WHAT with the information.


If you want a LVC. If you just keep an eye on the kWh or Ah meter, it's not really necessary. Or if you don't trust that meter completely. 

Another thing: You should fire that guy that made those battery boxes for Porsche part duh. They are really to ugly.


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## MN Driver (Sep 29, 2009)

Jan said:


> Another thing: You should fire that guy that made those battery boxes for Porsche part duh. They are really to ugly.


...uhh, I think Jack said, in the video, that he made them himself. I don't think he cares what they look like, he talked about how he just wanted something functional and it was all experimental and he was satisfied with the results.

This reminds me of woodworking, you can make the back side of a homemade nightstand nice and smooth working your way up the grits with sandpaper, but in the end, why would you? You will never look at the back when it is always against the wall. Most people don't stare at their batteries, they just drive their car.


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## roger (Jan 24, 2010)

jrickard said:


> If you want to know, you'll have to enjoy the fire as well. The cell failure is caused by cell reversal. The cell reversal is caused by the other cells still putting out high current levels through a cell that is below voltage. This immediately, (in seconds) drives the individual cell to zero.
> 
> If all cells are more or less balanced at the bottom, the voltage of the entire pack sags more or less equally, and it can't develop those high currents through a weak cell - in theory. At some point of course, one cell will give up the ghost first, but you will be crawling down the road by then with no protection at all.


 
Jack,

can you please say how to make initial bottom balance to the cells with minimal equipment? I know you showed this on video but I´m unable to view your videos because my internet connection is too slow.

thank you 

Roger


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## JRP3 (Mar 7, 2008)

roger said:


> Jack,
> 
> can you please say how to make initial bottom balance to the cells with minimal equipment? I know you showed this on video but I´m unable to view your videos because my internet connection is too slow.
> 
> ...


Here is one way. I drove around till my pack was around 3.10 per cell, then I took a 12VDC headlight and hooked it up to 4 cells in series at a time until they all approached 3.05 or so. Then I used a bottom balancer circuit from Dimitri set to 3.00 on each individual cell. You could also use a 3VDC flashlight bulb to do something similar, though you'd have to monitor closely so it didn't drain the cell too low.


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## Guest (May 22, 2010)

Jan said:


> How come? Is it your dc-dc converter? Where do the arduino destroying currents come from? I understand Arduino's don't like voltage above 12v for long. It can take peaks upto 20v, but not long.
> 
> 
> 
> ...


Well I was referring to the problem of being about to use the LVC information as it was a moving target. As to the Arduino, no the problem is on the 0-5V ADC inputs. They can't take transient peaks. You have to guard them with a Zener or other device, and that complicates the measurement somewhat.

I think my battery boxes are a work of art. Of course, I also don't think I'm building a piano.

Jack Rickard


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## Guest (May 22, 2010)

roger said:


> Jack,
> 
> can you please say how to make initial bottom balance to the cells with minimal equipment? I know you showed this on video but I´m unable to view your videos because my internet connection is too slow.
> 
> ...


Minimal test equipment. Hmmm. Ok. Go on a long drive. When you're nearly empty go home. When you get there, use a voltmeter to measure your cell voltages. If they are above 2.8 static, go drive around the block once and measure again. When they are about 2.8 park it.

Take a 0.5 ohm 50 watt resistor and wire it with a couple of aligator clips. Go through and find any cell above 2.8 v and connect the clips across the cell for 20 seconds. Then disconnect and wait 20 seconds. Remeasure the cell. Repeat until it reads 2.8 volts.

For any cell with a voltage less than 2.8 volts, take a 12v battery and connect the terminals with alligator clips for 20 seconds. Disconnect and wait 20 seconds. Then remeasure. Repeat as necessary.

Charge car normally to average 3.65v x number of cells. 

Repeat this procedure every 2-5 years as necessary.

You can use an automotive light bulb in place of the resistor, but it might take longer than 20 seconds.

Jack Rickard


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## roger (Jan 24, 2010)

Jack and JRP, thank you for description. I think by using Dimitris boards without top balancing option only detecting LVC/HVC event, simple SOC meter and your bottom balancing method I´m on a very safe side. 
Regarding your discussion about conversion of a smart I have this link:http://www.bea-tricks.de
They offer a kit with AC motor, but as I mean with disabling automatic gearbox too.

Roger


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## Jan (Oct 5, 2009)

jrickard said:


> As to the Arduino, no the problem is on the 0-5V ADC inputs. They can't take transient peaks. You have to guard them with a Zener or other device, and that complicates the measurement somewhat.


What ADC measuring do you do, that can give such spikes? 

It's hard to protect. Analog optical isolation is very expensive. If they're just spikes a zeener could work. But are they spikes?


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## Guest (May 23, 2010)

Jan said:


> What ADC measuring do you do, that can give such spikes?
> 
> It's hard to protect. Analog optical isolation is very expensive. If they're just spikes a zeener could work. But are they spikes?


Well, I think so. WHo knows. The TIMS600 was putting out a lot of noise. The negative pack cable ran through the Arduino box and two LEM HASS hall effect current sensors were there. The LEM HASS outputs go to the 5v ADC inputs. And they were blown. 

Again, on the bench it works great. In a car, a bit of a problem. Test test test test.

I think simple 5v zeners would have avoided this.

Jack Rickard


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## Jan (Oct 5, 2009)

jrickard said:


> Well, I think so. WHo knows. The TIMS600 was putting out a lot of noise. The negative pack cable ran through the Arduino box and two LEM HASS hall effect current sensors were there. The LEM HASS outputs go to the 5v ADC inputs. And they were blown.
> 
> Again, on the bench it works great. In a car, a bit of a problem. Test test test test.
> 
> ...


Why don't you connect the TIM600 serial to the Arduino? It should give you current drawn. I don't know how. But there are parameters to collect it. If a PC software program can do it, you can do it. If the userguide doesn't provide enough info, you could put a sniffer on the com port to crack the protocol.

Or is it that the TIM600 measuers the AC current to the motor? And I suppose you want the battery current..?


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## Guest (May 24, 2010)

Jan said:


> Why don't you connect the TIM600 serial to the Arduino? It should give you current drawn. I don't know how. But there are parameters to collect it. If a PC software program can do it, you can do it. If the userguide doesn't provide enough info, you could put a sniffer on the com port to crack the protocol.
> 
> Or is it that the TIM600 measuers the AC current to the motor? And I suppose you want the battery current..?


There's a lot going on there. The TIMS600 does actually have two hall effect current transducers in it, one on each of two phases from the controller to the motor. This is to track phase current, and has little to do with battery current.

The original purpose of the Arduino was actually to provide a PWM output to drive an ancient Porsche fuel gage, based on AH/SOC. I added a Venus GPS module and got speed and so integrated distance. So it was showing current, AH, SOC, miles driven, Miles to Empty, and speed. 

It was of course by this time a spaghetti mess on the little shield board I was using. But I simlpy hadn't gone to the trouble to guard the ADC inputs. 

It's kind of an iterative process. If none of that's going to work sufficiently well to be useful, there's not much point in pursuing noise issues. But it worked well enough, and I may redo it with a little more attention.

But there is so much going on and so much avaialble. I like the Arduino, but it is a little raw circuitry wise. I found a device that will do 8 ADC inputs single ended or 4 differentials. It transmits the data by bluetooth Class 1 - 100 meters. Better, these are much more accurate 16 bit inputs.

So I'm starting to see a larger and more modular system. If I wired this ADC to measure the current outputs from separate LEM HASS 50 and LEM HASS 150 hall sensors, upper half pack voltage, lower half pack voltage and did them with diff pairs, I would really have all the data I needed from the batteries and everything would be quite isolated. Spread spectrum is the ultimate isolator.

Now, consider a serial port to bluetooth adapter that fits ANY serial output controlller.

Now consider a GPS unit with bluetooth output.



And finally, a little fanless Linux Pico ITX box, connected to the VGA and USB inputs of a car stereo with 7inch touch screen.

At this point we have pretty much all the necessary hardware. to collect all this data into a central box capable of good display output resolution and on a display I don't really have to fit to the car. 

So I'm thinking a kind of modular bluetooth network with various sensors, a CAN bus tie in, etc to gather data into a small LInux box and display it on screen. At that point, it's pretty much software to display it and it would be quite extensible or modifiable to include various controller outputs.

So the Arduino thing kind of grows as you chew on it.

And yes, I DO think you can do a better car than the Nissan Leaf for 25K, but it needs a snazzy instrumentation system like the Nissan Leaf.

Jack Rickard


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## JRoque (Mar 9, 2010)

> And finally, a little fanless Linux Pico ITX box, connected to the VGA and USB inputs of a car stereo with 7inch touch screen.


Jack, I like where you're going with that. I thought about a 7" monitor with a separate computer but decided a mini-PC running WinCE or Android would be neater. Because my convert car is so small already (and I ain't getting any smaller myself), I finally went for a radio/monitor/GPS all in one last night: http://www.mp3playerstore.com/stuff_you_need/dvd/IN-723GPS.html. I'll be working on that UI when it gets here. 

Before you jump out of your chair, I will NOT be running any vital processing on a Windows PC... no way. All processing with be done on a micro and sent over serial (USB) or bluetooth to the display. It's just easier to write a UI on WinCE than developing something from scratch with an MCU (I'm hoping).

You can pickup a standalone unit (sans radio, dvd, toaster, etc) for about $175 on eBay or about $100 if you don't care for an integrated GPS (and add Wifi in the process). I paid $200 for the all in one unit.

JR


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## JRP3 (Mar 7, 2008)

jrickard said:


> And yes, I DO think you can do a better car than the Nissan Leaf for 25K, but it needs a snazzy instrumentation system like the Nissan Leaf.
> 
> Jack Rickard


Total cost, including donor, (not some junk 10 years old or more), AC motor, 100 mile range, 5 passenger, for 25K? Sounds like your next project for the TV show.


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## david85 (Nov 12, 2007)

Whats wrong with 10 years old? most cars are still in reasonable shape at that age. At least they are in my area


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## MN Driver (Sep 29, 2009)

I specifically buy cars at the 10 year mark, if the purchase price is right, sales tax is only $10 in the state of Minnesota. The two cars I currently own were bought at the 12 year mark and my current at the 10 year mark, even though it's 10 model years, it's not officially 10 years old. There are plenty of great cars that are 10 years old. My definition of a 'junk' car to convert is one that has started rusting and will look like crap in 5 years requiring you to swap all the components into a different body. ...either that or it is a car nobody likes, is really ugly, has collision damage, or is not reliable in ways other than engine issues. Since my car is aluminum, body rust wouldn't be a concern for an EV conversion built to last.


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## JRP3 (Mar 7, 2008)

david85 said:


> Whats wrong with 10 years old? most cars are still in reasonable shape at that age. At least they are in my area


Nothing at all necessarily, but for my $25K "challenge" to make a comparable EV to the Leaf it needs to be a more recent vehicle in very good shape. Some $800 beater doesn't count.


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## JRP3 (Mar 7, 2008)

MN Driver said:


> I specifically buy cars at the 10 year mark, if the purchase price is right, sales tax is only $10 in the state of Minnesota.


See above post. I have nothing against using older vehicles, heck my two conversions were an '88 Fiero and a '75 Attex.


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## MN Driver (Sep 29, 2009)

JRP3 said:


> Nothing at all necessarily, but for my $25K "challenge" to make a comparable EV to the Leaf it needs to be a more recent vehicle in very good shape. Some $800 beater doesn't count.


The painful part of that is when you buy a car from a major auto manufacturer you pay for the engine. Same goes with a used car and used engines don't go for much unfortunately so you never get enough back to roll around to the positive side.

Auto manufacturers have the advantage of very high volume pricing and they don't have the cash of the engine in it like us doing conversions do. We can get nice motors and controllers but the nicer used AC stuff that can be matched together just isn't available on ebay, it's mostly forklift grade stuff.

The only car manufacturer grade components that I can think of is the Brushless DC motors and controllers ripped out of the Toyota Prius(don't forget to bring the transmission with) or Ford Escape. The Ford Escape's electric powertrain should be enough for a small car, the Prius powertrain will be hanging at its limits and needs some welding to work without the ICE. If those components could be made to fit, the options get much cheaper. I've seen on other forums where people have figured out how to control the Prius motors outside the car so it can be done, just needs to be fit into a vehicle.

It's definitely a good challenge, won't be a new car for sure though but I really think that 25k for a nice car isn't too hard to accomplish. My personal goal is to be under 200Wh/mile and a small car is perfect utility for me so it's a bit easier as finding a great condition car 10 years or less isn't too hard, just need to find a light aerodynamic one to keep the battery costs low while providing good range. The donor cost is such a small part of it.


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## jackbauer (Jan 12, 2008)

Why not consider a dc sepex? That can do regen. Kostov do a line of interpoled sepex motors and paul holmes is closing in on a sepex option for the revolt controller.


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## JRP3 (Mar 7, 2008)

1. I've never seen a sepex controller with more than 120 volts. If MPH comes up with one great, but it's not here yet.

2. It still has brushes so it's not as maintenance free as AC.

3. Leaf uses AC so the conversion has to use AC.

My challenge, my rules


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## MN Driver (Sep 29, 2009)

I'm not too well versed on SepEx but I thought that the adjustable field excitation voltage might allow for better performance with lower voltages. This might not be true but I'm not sure. There are less field losses though(I've read 75% less loss through the field windings, I could be, and probably am wrong) with SepEx and it is slightly more efficient due to that. It's brushed and since regen pushes power through the same brushes it is possible that they may wear out that much sooner with regen. Granted with large enough brushes I'm sure 50k miles is still possible. ...again not a SepEx expert by any means.

SepEx performance is still under development as jackbauer mentioned above but I don't see any performance solutions available today. ...maybe next year?

I still might err on the side of Brushless DC or AC, seeing the Colossus liquid cooled modular motor development on ES, if they can figure out a controller for it, I might take a swing in that direction. It makes everything else look like a joke except I can't figure out how their no-load amperage is nearly a 2 digit number, it makes me question the efficiency since I've got a cheap brushed DC motor about the same size that spins 48 volts at .7 amps but I suppose it's all about the quantity of magnets and potential power in there. Some of these high powered small RC-style and ebike brushless DC motors can be noisy little beasts though. They don't have regen solutions for their controller, even though it's possible with the motor since it is brushless DC.


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## Jan (Oct 5, 2009)

jrickard said:


> There's a lot going on there. The TIMS600 does actually have two hall effect current transducers in it, one on each of two phases from the controller to the motor. This is to track phase current, and has little to do with battery current.


Are you sure, this has little to do with battery current? Why isn't this the same? 



> It was of course by this time a spaghetti mess on the little shield board I was using.


I have exactly the same with my conversion. I'm restaurating a '77 Landcruiser. And if the weather is not so nice I'm busy rebuilding the gauges to EV gauges. Also with an Arduino. It's quite a mess now, and I'm going to redesign it. 



> But I simlpy hadn't gone to the trouble to guard the ADC inputs.


I will take serious attention to this.

Thanks Jack.


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## Bowser330 (Jun 15, 2008)

JRP3 said:


> Total cost, including donor, (not some junk 10 years old or more), AC motor, 100 mile range, 5 passenger, for 25K? Sounds like your next project for the TV show.


FYI the Leaf is based on the EPA LA4 aka UDDS drive cycle which simulates stop n go traffic at an average speed of about 20mph (see picture)

I am not sure if anyone knows yet what the highway speed (70?) range is...


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## JRP3 (Mar 7, 2008)

True the average speed is low but all that stopping and starting is not exactly efficient. I'd consider mostly steady state driving with 45-50 mph average speed to be a reasonable test for general usage.


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## Guest (May 26, 2010)

JRP3 said:


> Total cost, including donor, (not some junk 10 years old or more), AC motor, 100 mile range, 5 passenger, for 25K? Sounds like your next project for the TV show.


You know, I'm tempted to take the challenge. But there's one thing you're overlooking. Your asking for a competition between a conversion car, and a press release.

This has driven this world for years. That's what I've been saying. What Aptera? What Phoenix? What Zenn? They DO NOT EXIST. They only EVER existed as a press release.

Right NOW, the Nissan Leaf is a press release. They have not sold a single car. 
The "specs" are printed on paper and the world wide web. There are no cars with those specs.

And as we have seen from Chevrolet, Nissan, and BYD, press releases can be updated and upgraded by another press release. A production date can be changed by press release. A delivery date can be changed by press release. All specifications subject to change - by press release.

You guys are driving cars. Cars have problems. Press releases are pretty much problem free.

We went through this with the Internet for over a DECADE. Broadband from huge corporations was just around the corner - NEXT year for over a dozen years. I started a trade show and publishing business, grew it for 12 years, and SOLD it before it happened. ANd for many rural areas of America, it still hasn't happened YET 12 years AFTER I sold it.

Yes, the EV component suppliers and all hobbyist converters should immediately panic and run for the exits because there is a Nissan Leaf hiding behind door number two and we're only moments away from you having one.

Get your reservation in now - only $99 reserves your spot.

Now what happens when they DO finally introduce this, sell 30,000 of them, and can't give em away after that? Is it the end of the electric car AGAIN?

This is a much longer and dirtier road than you might imagine - in just so very many ways.

Meanwhile it is VERY cool to press the accelerator on the Mini.

Jack Rickard


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## Guest (May 26, 2010)

JRP3 said:


> True the average speed is low but all that stopping and starting is not exactly efficient. I'd consider mostly steady state driving with 45-50 mph average speed to be a reasonable test for general usage.


And yes, we're not totally committed to the idea, but I do confess some fascination with the Smart for Two. It is a tiny car, but it has all the stuff, stereo, power windows, keyless entry, wipers, bluetooth, heat, airconditioning, just like a car. 

I bought a 2008 on eBay for $9000 - about $10K delivered.

I'm thinking we can be on the road for $25K total. 

It won't have 5 seats. It won't go 100 miles. I'm picturing 2 seats and 50 miles.

But it should be kinda cute. It would be economical to do as a conversion and to operate. It's very very small.

As I say, I haven't committed to it yet. But it's appealing.

Jack Rickard


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## JRP3 (Mar 7, 2008)

jrickard said:


> You know, I'm tempted to take the challenge. But there's one thing you're overlooking. Your asking for a competition between a conversion car, and a press release.


OK, you can wait until they've actually sold some before you start the challenge. That's in your favor as batteries may even be a little cheaper and a little better by then.


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## JRP3 (Mar 7, 2008)

jrickard said:


> And yes, we're not totally committed to the idea, but I do confess some fascination with the Smart for Two. It is a tiny car, but it has all the stuff, stereo, power windows, keyless entry, wipers, bluetooth, heat, airconditioning, just like a car.
> 
> I bought a 2008 on eBay for $9000 - about $10K delivered.
> 
> ...


That sort of proves my point. It falls well short of the Leaf, or at least the press release Leaf as you say. I'm not a big fan of the Smart for a conversion as I'd imagine fitting cells would be a challenge.


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## MN Driver (Sep 29, 2009)

I think one of my biggest concerns regarding the topic of non-DIY solutions is that if you need to ever replace the battery, they've got things so shoehorned and compact by design that it would be extremely difficult to get non-OEM replacements into the OEM space. Especially if car manufacturers go the way of the ~220 cells in a tunnel type design the Volt is throwing together. At least with the Leaf it looks like we might be able to work with the pouch cells. ...beyond the physical batteries though if the computer system in the car turned off the battery pack for a fault, getting it turned back on or having it agree with a new pack might not be as simple as it would be for a DIY solution.

With DIY, it's a simple swap, just make sure you've got the max voltage in spec with your design requirements, equipment, capacity, C ratings, cycle life desires, any other details taken care of, then everything can fitted, connected up and ready to go.

As far as small cute cars go, I wouldn't mind doing a conversion of a Fiat 126. It's not new, doesn't have the amenities but it's a light weight small car at around 1400 pounds pre-conversion, but it isn't necessarily the unwanted rusty ugly junkbox that someone bought for $300. ...but both it and the Smart have aerodynamic issues that negates their weight savings and the range might not be the best on the highway as a more aerodynamic vehicle. ...but then again, we've got a van conversion going on, which is a heavy fist in the wind, a good proof of concept and useful if you have purpose for the room otherwise it's a pricey adventure. Many people turn to the older cars due to their lighter weight. Safety equipment and crash standards add a significant amount of weight to a vehicle. In the 90's it was simple to find a car under 2000 pounds. In the 2000's and this year, I might only be able to count the cars under 2000 pounds on a single hand which makes a cheaper 100 miles on the highway conversion a little more difficult. My 100 miles on the highway would be my personal goal, getting 100 miles with another method is respectable too as long as it isn't happening at 30mph the whole way on the flat because that ideal situation isn't applicable to very many people at all.


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## etischer (Jun 16, 2008)

JRP3 said:


> Total cost, including donor, (not some junk 10 years old or more), AC motor, 100 mile range, 5 passenger, for 25K? Sounds like your next project for the TV show.


I beat your challenge =)

2001 Passat (not a beater)
5 seater (bigger than the leaf)
80kw (more power than the leaf)
AC motor
100 mile range (haven't tested, but 32kwh should just barely get me 100 freeway miles)

total cost 27,431. This is after taxes, and before my $3000 rebate. 

before taxes, and after rebate, my cost is around $22K


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## Guest (May 26, 2010)

etischer said:


> I beat your challenge =)
> 
> 2001 Passat (not a beater)
> 5 seater (bigger than the leaf)
> ...


So if its already beat, where's the challenge?

Cars are kind of an individualistic thing. If Nissan DOES actually deliver a battery electric car, I see that as enormous validation and hope them every success. That wasn't my point. In fact, if it would sell well, I think this could be a great boon for the concept of electric cars. But I hardly believe it will lead to a one model nation.

Similarly, I think a lot of people are going to be further attracted to electric cars, but the brain immediately goes to the kind of car they've always wanted, but better electric.

I'm driving cars now that are operating beyond my wildest expectations while working on them. So what is the Nissan Leaf to add for me? Here's the list:

1. Better instrumentation. Tie all the available CAN info on the car with such things as voltage and AH and tell me what my state of charge is, how much is remaining, how many MILES can I drive the way I'm driving. And it SHOULD be in a futuristic eye pleasing touch display. But I want one of those for MY car.

2. Better cheaper batteries. More power. More range. Less money. Less weight. Less volume.

3. Drive train power electronics. AC Propulsion has one part of this right. An AC inverter and a battery charger are the same thing in reverse. Throwing out lesser voltages such as 5vdc and 12vdc go without saying. It should all be in one box.

4. Carbon fiber. More and more widely available body panels for existing cars that are lighter in weight.

The reason many do not feel they can produce as good a car as an automotive manufacturer is the availability of components. I think as major automakers produce electric cars, those components will become increasingly available. And the conversion process will become similarly easier.

Jack Rickard


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## GerhardRP (Nov 17, 2009)

jrickard said:


> The reason many do not feel they can produce as good a car as an automotive manufacturer is the availability of components. I think as major automakers produce electric cars, those components will become increasingly available. And the conversion process will become similarly easier.


Here is an article about Nissan's groundbreaking for battery plant in Tennessee titled "Nissan sees battery costs falling in 3-4 years"
http://www.reuters.com/article/idUSN2619064520100526


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## JRP3 (Mar 7, 2008)

etischer said:


> I beat your challenge =)


You got me, but you cheated, you built your own controller, plus got a deal on a motor that is no longer available. I was thinking of mostly off the shelf parts that most converters would use.


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## tomofreno (Mar 3, 2009)

> You got me, but you cheated


 Would that we could all "cheat" like that. 

A couple things a manufactured ev offers that a conversion by someone here likely doesn't is a written warranty and service support at multiple centers.


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## JRP3 (Mar 7, 2008)

Mine has full service support, by me, 24 hours a day, any location


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## JCR (Nov 26, 2009)

EVComponents said:


> I have 100 Ah cells from ThunderSky and Sky Energy that we can use for testing. Manzanita Micro (Rich Rudman) has all of the equipment for testing. He has offered to do it if someone will contribute the cells.
> 
> I do not have any China Hipower 100 Ah cells for testing.
> I requested samples from Kevin, but nothing has been offered.
> ...


I have two 48 volt x 100 AH Battery Packs from HiPower I would consider for testing. As you know this means there are 3.2 volt x 16 cells for each battery pack.

[email protected]

JCR


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## kroesche (Aug 31, 2009)

Hi. I know this thread was originally about comparing battery vendors, but it kind of wandered around and I have some questions about the balancing discussion.

With regard to the discussion about top balancing vs bottom balancing, I completely understand the concept and the arguments being made. In fact the bottom balancing argument is consistent with a presentation I saw from the battery group at my employer, a very large semiconductor company.

But what was lost on me in the whole discussion was how do you actually bottom balance. I see all the stuff on top balancing - float charge, shunts, charge transfer etc. But how do you bottom balance. Do you run the pack almost dead and then drain the "high" cells some more? Or are you saying that it just bottom balances as a side effect of the way you are charging it (not overcharging) and you dont need to do anything special to actually perform the balancing?

And about the Smart car ... I bought a fortwo earlier this year to have a daily commuter while my conversion was in progress. I really like it and have no regrets at all about buying it. It is a lot of fun to drive and makes people smile (as far as I know). It would be cool if it was electric but I am not even close to thinking about tearing it up until it ages quite a few years and miles.


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## JRP3 (Mar 7, 2008)

kroesche said:


> But how do you bottom balance. Do you run the pack almost dead and then drain the "high" cells some more


Yup. I ran my pack to about 3.10 per cell, used a 12 volt headlight on 4 cells at a time to take them closer to 3.0, then used a resistor circuit to take each cell to exactly 3.00 volts automatically, but could have done it manually with a 3 volt flashlight bulb or something similar.


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## ewdysar (Jun 15, 2010)

What ever happened to the comparison of LiFePO4 batteries from different manufacturers? Way back when the pages of this thread were in the single digits, somebody published load test results from 1 cell from each of three companies. The results were different enough to be significant, in my opinion. Has anyone done any follow up testing? Or collected real-world objective data comparing different brands of the same rated capacity cells? 

And please, before this thread gets hijacked again, if you want to discuss pack balancing or the trials and tribulations of whether to BMS or not BMS, consider starting another thread to collect those thoughts.

Thanks,
Eric


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## ElectriCar (Jun 15, 2008)

Bump. Good thread but windy. Would be nice to shorten it a bit.


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## mszhao (Oct 17, 2009)

it is not easy to say which one is the best.
there are many aspects to evaluate a supplier.
which point do you most care about?
then you can compare them and see which is most suitable for you.
and only good batteries is not enough,you also need to consider a effective charger and BMS.


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## motor guy (Dec 17, 2008)

hello all.
ive been reading all of these posts, and to be fair to all battery manufactures, test of 2 or 3 or 4 cells is not much of a test.you could have 1 weak cell out of 4 cells and give you bogus readings..
to make a fair test there needs to be more cells.
we have 48 hi power cells on our truck, with a reap systems bms. once you start exercizing the batteries and charging the batteries you find out which ones are weaker than the others. but you need a good battery management system. and some type of on screen read out to give you a good visual.
you can have all the cells charge up to set voltage and when you are discharging the cells, and after the voltage lowers in the cells, some cells might not have the same substianable charge/or reserve. that is just chemistry/or quaility control.
remember that batteries are biult by humans.
we have went 95.5 miles per charge with our truck, we went and weighed it today and it weighed 4120 lbs.

thanks kevin


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## Guest (Oct 28, 2010)

Show your car, show your work, show your results. Talk is, you know, cheap.


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## motor guy (Dec 17, 2008)

hello all

to see our truck, please go to our web site; topekaelectricmotor.com
you can see phase 1 with the lead acid and phase 2 with the lithium.
if you need more data you can call carl at the electric car co. 1-801-566-7744. on 10-18-10 he was at our shop and did a video of what the truck is and how it runs. he is getting it ready to be put on utube, for all the non-beleavers.
our ph# at topeka electric motor repair is 1-785-233-4750.please feel free to contact me.
thanks kevin


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## motor guy (Dec 17, 2008)

hello all.
like i have mentioned before we are in the early stages of our second build, this is going to be a 1/2 ton truck,automatic. we are designing a ac motor for this build.
we will keep all informed as we go along. 
or call 1-785-233-4750.
thanks kevin


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## Guest (Oct 28, 2010)

Very nice conversion. Any trouble with stripped out connectors or bolts on the batteries? 

Pete


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## JRoque (Mar 9, 2010)

Hello Kevin, which AC motor are you planning on using? Is it an off the shelf industrial type that you're rewinding or a commercial solution? I'm jumping the gun with these but I'm very interested if you say "rewound" motor. I'll have some questions on that and you might need your own thread to discuss the details  

JR


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## motor guy (Dec 17, 2008)

hello jr.
this is not a rewind,this a brand new design.we should have the drawings in about 10 days, with the specs.
then we will have 1 built and test.
i dont mean to be rude,but we cant persay let the cat all the way out of the bag.
if we give the specs out, there will be lots of talk and speculation.before it is even built.because when this works it will be a big positive for the ev world.
please be patient.
thanks kevin


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## JRoque (Mar 9, 2010)

Excellent Kevin that's great news! Don't forget to open a new thread so we can ask questions. I understand you want to keep it under wraps while it's still in development. 

As for being "rude", ha! Check out the "chit-chat" section of this forum to see what true rudeness looks like. I'm looking forward to your AC motor spec post.

JR


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## Guest (Oct 29, 2010)

Well you done it now. The cat is out. Have another look in the bag.  So a new design you say. Should have just kept it under wraps because now many if not most will hammer it because it is another promised dream that has yet come to pass and it comes with a claim of changing the EV world. Can't blame us if we begin to hammer the claim. I will be the first. The conversion is great, don't get me wrong there but making claims is a load of crap. You need to do it under wraps and if you find during the testing it WILL change the EV world then you go into actually making the item then do a full public test where all can verify the validity then go from there. Letting the cat out too early will only hurt and if it does not come to fruition your integrity will be challenged at all points down the road. Gotta keep things like this quiet. Only bring it out when ready. It is not ready. Drawings are not ready. It must be produced. No youtube hacks or parlor tricks either. 

Pete


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## the Brutus (Dec 9, 2009)

[/QUote]
I would sure like to see all the BMS effort cease and refocus on instrumentation. I'd love some pretty gage "skins" on a 7 inch display where I knew AH used, maybe MILES TO EMPTY. Speed, rpm, instantaneous current draw, pack voltage, and yeah maybe a basic indication that the pack is GOOD, questionable, or BAD.

Jack Rickard[/QUOTE]

Hi All, 

Without wishing to start WW3, I have a little Guantou BMS that actually does all of this, with a 5" screen. SOC, in/out, amps, and the cell voltages, right there for you to see.

http://guantuopower.en.made-in-chin...pr/China-Lithium-Battery-GTBMS005A-MC11-.html

The damn thing did cost a couple of grand though, and has some spaghetti.

but I dig the touch screen, and the fat that I get rid of ALL the gauges.

b.


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## CroDriver (Jan 8, 2009)

> Hi All,
> 
> Without wishing to start WW3, I have a little Guantou BMS that actually does all of this, with a 5" screen. SOC, in/out, amps, and the cell voltages, right there for you to see.
> 
> ...


Looks like a ThunderSky BMS system. I haven't heard anything good about it...


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## the Brutus (Dec 9, 2009)

CroDriver said:


> Looks like a ThunderSky BMS system. I haven't heard anything good about it...


LOL, then perhaps I'm about to get an education from the little bugger of a thing. Here's hoping that it's not all bad, either.....

b.


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