# Lithium cell abuse incidents?



## EVfun (Mar 14, 2010)

Did you remove the cell log 8s or modify them to load all 8 cells? I ask because unmodified they get the power to do their measuring from just the first 6 cells. It is a tiny bit of power but over time the upper 2 cells attached to a Cell Log 8 can get ahead of the rest. This could easily explain whey the last 2 cells went high at one point. I don't think it was high enough to do noticeable damage unless allowed to continue until the current was very low. 

I'm certainly interested in your experiences with LiFePO4 cells and charging (with or without a BMS.) I try to share mine. I think hearing real reports from on-road EVs is very important. We are getting to the point where we have a pretty good idea what to expect in controlled cycling.


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## Sun Motors (Aug 10, 2010)

No, I use only the first 6 meters on stock cell log 8s. The last 2 places are empty. They do have a drain of about 1ah/week which is not a problem when I leave the car idle for 2 weeks or so sometimes at about 60% SOC.

The over-charge incident happened just days after I got the batteries in the car for the first time.


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## mizlplix (May 1, 2011)

OK, Here goes...

After about 12-15 charge/discharge cycles, I needed to pull my 38 cell pack (of 130AH CALB's) down to 3.0/cell to set my ZEVA sensor.

I was doing daily short trips. The pack was down to 3.2 per cell. (I had just checked them individually and put a torque wrench to the strap bolts). 

I drove about 2 miles when the controller derated to 1000 RPM (set point for low voltage). So, I drove about 1/2 mile very gently to get to a secure pull-over spot. 

The sitting pack voltage said 2.54 volts per cell OR 96.6 volts total.

I dont know what the sag was, but the controller didnt shut off completely and the car accelerated from the last stop normally. So, from 3.2 volts per cell, (Just individually checked) to 2.555 volts per cell (also checked individually after). It took me less than 2 miles and 3 minutes driving time for the pack to somehow drop down to basically nothing. A real surprise for sure...... 

This tells me there is no real current under 3.2 volts per cell and everything I had read indicated 3.0 volts was the bottom for usable current. 

*NOTE: Up to that point, I had not driven the car lower than 3.3 Volts/cell.*

I still feel I should have had adequate current for a leisurely around-the-block spin (4 miles).

But, what happened, happened.

I called a friend-truck-rope and we went home.

It started charging normally (at 13.6 Amps). It took 14 hours to a green light (at 2.35 Amps). It read 3.85 volts at unplug. It read 3.65volts the next morning according to my lowest cell I have a meter on.

The car drove 11.5 miles and the controller shut down completely when I stopped at an intersection then took off hard. The sag was down around 2.45V/cell from the one glance I could get.

EDIT: I just read the faults stored in the controller. My 3 shut offs were all "encoder fault" and not part of the battery problem. Just wanted to set the record straight.

I shut off and reset the controller, The voltage read 3.35 Volts/cell. I drove home very gently and it acted normal, but if I pushed it any, it would sag down below 2.5 from a cruising voltage of 3.3

All cells check 3.29 -3.33 volts. (on a VTOM)

No loose connections. ("/# torque wrench)

They are on the charger ATM. Started out at 12.8 Amps

I have no answer why the pack went nuts the first time after 10-12 normal driving cycles. It always Accelerated hard and would go 48-55 miles per charge (stopping at 3.3 V) plus the sag was very small........

But now, I am thinking I have 1 or more capacity damaged cells limiting my range to 11.5 miles. 

I would consider a damaged contactor, but my lowest cell monitor is before all of that.

What is the best way to check the AH capy' of the individual cells?

TYVM, Miz


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## Sun Motors (Aug 10, 2010)

Hello,

Sounds like one or more of your cells have gone bad. 
Don't know the best way to figure the individual cell resistance. I get an idea of it by seeing the sag in voltage across all the cells under different amperage readings. for example the voltage readings are about 3.21v driving at 40 amp current and 3.09v at 100a at 80 degrees f. At 40 degrees f 100a current is reading 3.00v.

Do you have such a meter to read some cells at a time while under load?

GNN


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## JRP3 (Mar 7, 2008)

Maybe jack up the car, put it in gear, set the accelerator to turn the motor at low speed, and check individual cell voltages. Maybe set the E brake a bit to increase load. Or you can test groups of 4 cells at a time with a 12V load, like a headlight.
I agree that it sounds as if you have one or more bad cells.


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## EVfun (Mar 14, 2010)

Run the car down to the point where you are having the problem, but not further than you previously have (let's find a problem, not create one.) Park it and check (and record) the voltage of each cell. If it gives you nothing you need to test with some load. If you have a DC>DC converter turn everything on and let it impose a couple amp load. Check the voltage at every cell with a little load. A cell going over the curve to dead should be easy to spot. If you can't you need a bigger pack load and try measure the voltage at every cell again. Something is going low, perhaps even going into reversal, to cause such a sharp voltage drop-off. Household incandescent lamps work well for 120 volt loads but fail pretty quick at 130 volts. Heaters make great loads, but the fans in most need to be separated so they can run on 120 vac. Many hair dryers are the exception, where universal fans are common (but the switch cannot be used to turn it off!!)


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## GizmoEV (Nov 28, 2009)

Miz,

Did you clean all the terminals just before connecting the straps? I remember Bill Dube saying something about his rig did something similar and found that the contacts had all gone high resistance. Cleaning all the terminal tops and reassembling things fixed the problem. I'd put a layer of NO-OX-ID on the terminals too.

To narrow down the culprit if it is a single cell just install a Batt-Bridge device like I have on my pack or use two volt meters you can watch while you drive. Once you know which half the problem cell is in use the two volt meters on that half and so on until you narrow down where the cell is.


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## mizlplix (May 1, 2011)

Thanks for the ideas, guys.

I did clean the connections when I installed my pack. I also sprayed "Clear Ignition sealer" on the connections to seal the air out and hopefully any future oxidation.

I did a half-assed balance when I received the cells by putting them all in parallel for a week. When I unhooked them, I waited 24 hours and did a standing voltage test. They were all at 3.10/cell. SO, some sort of "balancing" did take place.

After installation, I did a charge cycle and all were really close together. I charged and drove again, I did another cell/voltage test. 3 were off a little (.08 volts) .

Consistently they are close together when 1/2 discharged and the same 3 are split when charged. I have about 5 cycles on them.

All discharge cycles were 2/3 pack and never more. (about 40 miles at most)

THEN, I needed to run them down to the safe minimum (for me) of 3.0 volts to calibrate my ZEVA device. I carefully drove short distances and kept checking my voltages.

I got down to 3.2 (Some were 3.175 and some were 3.209). and tried to drive around the block. After 1-2 miles, the car lost power and I coasted to the side of the road. The voltage read 96.9 Volts. ( roughly 2.55v/cell)

How in the hell did it go from 3.2v down to 2.5v in 1-2 miles? There has to be a really weak cell. Like maybe 100AH or less. (I had never ran the pack that low before.)

I towed it 1/2 mile to home and checked all cells. NONE were under 2.5V but all were 3.1 and down.

I have given them a full charge and the car drove 11.5 miles and stopped.

I charged again, it went 18 miles.

I now have given them a "full" charge and am now manually balancing them all to the lowest cell voltage and will recharge them after.

Yes I have at least one that sags horribly under a 100 amp test load. Maybe as many as 3 cells that sag a lot. I will lose 1 maybe as many as 4 cells.....

Everything was fine until I attempted to run the pack down lower and the first time the cells were required to really perform near their claimed capacity, the weak ones are showing up. There are a lot of them it seams.

There are a couple of us here on the forums that bought CALB cells at the same time. Two of us bought the same 130AH size. Both of us had a similar problem almost on the same week. One pack has a BMS and one is manually monitored.

Our cells were some of the last of the "old" type out of the warehouse before the new ones started selling. As my cells perform all erratically, I can only conclude that I got what ever was there and went into the crates.

I will post after top balancing and hopefully, I will get back to my former mileage, but at this point I am doubtful.

miz


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## JRP3 (Mar 7, 2008)

I remember the rather large spread in resistance numbers when you got your pack, and the different colored casings.


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## mk4gti (May 6, 2011)

Keeping an eye on this thread as a few of us "end of production" 130ah owners seem to have got "floor scraps" to quote another member on here.


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## mizlplix (May 1, 2011)

update: 

JR: you remembered correctly. I was not really pleased at the time, but that was what I got. They were about the only real game in town.

From the "event" (what ever happened);

I have charged the pack fully. It had a wide voltage difference, cell-to-cell. (3.355 to 3.500), 

So I pulled the individual cells down to 3.350VDC and recharged the pack.

They still vary from 3.375 to 3.580 or so. I have about half of them pulled down to 3.375Volts(I will do the rest tomorrow) and plan to charge them again. 

I guess I will keep doing this until I get some sort of parity.

How close do I try to get them? within .01? or closer like .005 ?

Also: What is the most affordable cell minder (that works) that will top balance every time I charge?

Miz


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## jeremyjs (Sep 22, 2010)

mizlplix said:


> update:
> 
> JR: you remembered correctly. I was not really pleased at the time, but that was what I got. They were about the only real game in town.
> 
> ...


Isn't it near impossible to to balance a pack on the flat part of the curve? If you're top balancing them, why not just get a single cell charger, and take them all up to 3.65v with the recommended cutoff current for the initial balance?


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## JRP3 (Mar 7, 2008)

I think Dimitri's Clean Power Auto BMS http://www.cleanpowerauto.com/MiniBMS.html is the lowest per cell cost that can top balance, and, it seems more importantly for you, can also signal a low voltage at the cell level to limit discharge. There may be others, I'm not really up on the BMS scene. At some point you need to find which cells are the weak ones and by how much since they are limiting your range. Are you going to try to make a claim with CALB? At least one representative of theirs has stated you should not have gotten such a mixed set, and that the cells are no longer in production.


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## JRP3 (Mar 7, 2008)

You don't want to take CALB's to 3.65, and there is no reason to. 3.5 or so is far enough into the curve to get an accurate balance.


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## mk4gti (May 6, 2011)

jeremyjs said:


> Isn't it near impossible to to balance a pack on the flat part of the curve? If you're top balancing them, why not just get a single cell charger, and take them all up to 3.65v with the recommended cutoff current for the initial balance?


My thoughts exactly... After 3.6v it climbs very fast.
Many brag about their cells being .001v apart; not sure if that level of precision is required when top balancing and having a bms...

I run the mini-bms and it's been good so far.


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## mizlplix (May 1, 2011)

you can tie cells in parallel in almost any state of charge as long as they are close and SOME balancing will take place.

http://liionbms.com/php/cell_prebalancing.php

Excerpt:

"If you connect all the cells directly in parallel with each other, you will allow their voltages to equalize. Their terminal voltages will be identical (because they are connected in parallel), though, initially their OCVs will be different (because initially their SOC levels are different), which will force charge out of the cells with higher SOC, through the common connection, and into the cell with lower SOC.
Initially, the current will be high (10s or 100s of Amps), but will soon decay exponentially; the current removes charge from the most charged cells, and places it in the least charged ones. Eventually (in a matter of hours to a few days), the SOC of all the cells will be equal, therefore all the OCVs will be equal (and equal to the terminal voltage), and the current will drops to practically zero.
At that point, the cells are balanced."

I initially did mine at 3.10V or so. It worked for a while, but Something unbalanced them in 5 cycles. Now I am doing it again.

If I bought a single cell charger, it would bring them to their own full charge, not necessarily balanced with each other and I would have to still tie them in parallel again at some point to do a true balance.

Those guys sort of know what they are about.

Miz


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## JRP3 (Mar 7, 2008)

Actually David Andrea from elithion has repeatedly shown he really doesn't know a lot about the behavior of lithium cells, and when he posted his youtube videos that were full of errors and was corrected, he deleted all comments and disabled commenting. Remember, he's selling a product, and expensive one at that. 
If you want a good balance, either top or bottom, then do the balancing at the top or bottom.
Worth noting that many of us have had a balanced pack stay that way for years, without every paralleling the entire pack.


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## mizlplix (May 1, 2011)

Oh, My charger is set to go green at 133V (3.5/cell) I am OK with that even if it drops to 3.44 or so over night.

Mostly it starts charging at 13.4 Amps and when it goes green it is usually charging 2.8Amps. 

I will try to get them within .008V. of each other before I drive. 

I am watching them for voltage drop while I am balancing them. 

What would be a good voltage drop on one cell at a 25 AMP load?

Miz


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## JRP3 (Mar 7, 2008)

I can't give a number off the top of my head but I'd look for relative variations between cells to pinpoint potential bad ones. It might take a larger load to show up clearly though.


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## Ziggythewiz (May 16, 2010)

25A is pretty low. I've recorded a drop of .01 vpc at 14A and .06 at 53A for 40AH cells.


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## dladd (Jun 1, 2011)

mizlplix said:


> What is the best way to check the AH capy' of the individual cells?
> 
> TYVM, Miz


It's a hell of a lot of time and work, but you could cycle test each cell with a Powerlab 6 (or 8) if you really wanted to know the capacities and IR's. I did it with my cells, and was able to pinpoint a few that were significantly weaker than the others. It took me about 3 weeks or so to test my 48 130ah cells... 

You could also buy and temporarily install a Cellog8s and move it around your battery pack until you find the cells that are sagging under load. I plan to do this soon, but have not yet. It doesn't tell you capacity, but will tell you which cells are causing a low voltage alarm under load.

The MiniBMS technically top balances, but it's such a small amount of balancing (especially if you are only charging to 3.5vpc) that you really have to manually balance them before installing it.


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## nucleus (May 18, 2012)

*David Andrea of elithion*



JRP3 said:


> Actually David Andrea from elithion has repeatedly shown he really doesn't know a lot about the behavior of lithium cells, and when he posted his youtube videos that were full of errors and was corrected, he deleted all comments and disabled commenting. Remember, he's selling a product, and expensive one at that.
> If you want a good balance, either top or bottom, then do the balancing at the top or bottom.
> Worth noting that many of us have had a balanced pack stay that way for years, without every paralleling the entire pack.


I remember him going on about Lithium cells self-discharging and drifting. Complete silliness. I never saw his youtube videos though, I look forward to seeing those, they should be pretty amusing.

And he was the guy who "wrote the book" on batteries and bms systems. Ha!

Nucleus


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## EVfun (Mar 14, 2010)

mizlplix said:


> If I bought a single cell charger, it would bring them to their own full charge, not necessarily balanced with each other and I would have to still tie them in parallel again at some point to do a true balance.


You shouldn't. LiFePO4 cells have little to no self discharge. If you disconnect the pack at the ends and insure there is absolutely no load then you can take any quality, repeatable charger, and bring them all up to 3.6 volts at some determined current level (the same cut-off current for each cell) and move on to the next cell. I would go back after all are done and do it again, but the second round should be something you can do in a day or two (depending on just how low the charger current limit is.) This way the pack can remain in series the whole time and you can match up the cells.

I also suspect you can find any trouble cells pretty easy with just a 2 amp load if you first drive right to the voltage sag cliff. When the pack is doing that the voltages without a load may still be nearly the same, but any load should show the low ones. Record the no load and under load voltage and you should see it. If not right away then within an hour or two. Once a cell is empty the voltage will collapse with any load. This would be a lot quicker and easier (bigger sag) if you have a 10 amp load. I took a $15 cheap heater apart and brought out a second set of wires from the ceramic heaters to connect to the pack while the fan remains powered by the mains.


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## mizlplix (May 1, 2011)

Update:

After about 7 cycles of pulling down the high cells and charging the pack to the "green" light, I am getting them a LOT closer to being even.

I still am doing cycles though. I want to see them as close as I can get them.

My cell loading device is a 100amp (at 12VDC) lead/acid battery load tester from Harbor freight. I have two of them, one is Harbor freight the second is NAPA. They both are close to 25 amps @ 3.5 VDC as measured by my Amp-Clamp. I have a VTOM wired to them to read real time volts as loading and resting. That way I can get 3 digits after the decimal. 

When the cells were in a lower state of charge(3.2Volts) they would sag a whole volt, but at 3.4 volts the sag is half that. 

I am shooting for a finished voltage of 3.45 (after sitting) with an even sag for all cells. Then will drive the car to see if my cells perform as good as they originally did, mileage wise.

I still do not have an explanation for my "event" except that the cells seem to be a lot less usable capacity than advertised. Time will tell. 

Later, Miz


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## Ziggythewiz (May 16, 2010)

3.4 is full, so you shouldn't be able to get higher than that after sitting. I think mine are 95-99% full and sit at 3.35


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## JRP3 (Mar 7, 2008)

Chances are you have some damaged cells. Without monitoring them during discharge, or bottom balancing them and monitoring them during charge, you won't know. Since it's easier to monitor during charging than driving, that's a good reason to bottom balance first, even if you intend to use top balancing eventually.


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## mizlplix (May 1, 2011)

Sorry, those are just off the charger voltages.

My charger finishes at 133 volts/38 cells=3.50volts per cell.
They seem to settle down to 3.40v to 3.47v 

One step down in the charger is to 129.5 volts/38 cells=3.40 per cell

Are you recommending I do that instead?

As I continue to knock down the high ones, they are all doing much better for sag.

They are acting more normally now than even two days ago. I am still looking for that "bad one" that started the whole thing. I have it narrowed down to three suspects. I am going to keep my eye on them as I get back into regular driving. 

Thanks, Miz


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## EVfun (Mar 14, 2010)

133 volts for 38 cells is what I am currently using.


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## Ziggythewiz (May 16, 2010)

I've heard they shouldn't settle above 3.4, so I'd turn that down a bit. Mine are balanced now at 3.38V, but I only plan to take them to 3.33 (~90%) in regular use.


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