# Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.



## Jayls5 (Apr 1, 2012)

I purchased an EV motorcycle that had 10 of these:
http://www.evsource.com/datasheets/BatteryData/CALB_SE100AHA.pdf

They are several years old, but all were resting around 3.2v upon purchase. I am currently hooking 5 of them up in parallel and charging it with my hobby charger.

My initial concerns: With 5 of them in parallel, I can barely get 12A charge rate before hitting CV mode (set at 3.6v).

This seems like a fairly low charge current on what is essentially 500 AH while wired this way. Are these cells super old, or is this expected behavior for a saggy large size LiFePO4 prismatic chemistry?


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## onegreenev (May 18, 2012)

Jayls5 said:


> I purchased an EV motorcycle that had 10 of these:
> http://www.evsource.com/datasheets/BatteryData/CALB_SE100AHA.pdf
> 
> They are several years old, but all were resting around 3.2v upon purchase. I am currently hooking 5 of them up in parallel and charging it with my hobby charger.
> ...


The closer to fully charged they are the less amps will be going into them. So you hit the constant voltage. Hobby charger? Which one? Not all Hobby Chargers can do super high current on a large capacity cell. Charge them up then run them down then charge them up again. But run them in your bike. Be sure they are all charged equally. Bottom balance them then charge them connected to your bike. You may want to check the capacity. They look like my CALB 100ah cells. Good quality cells. Does your bike have a proper charger for these batteries?


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## dcb (Dec 5, 2009)

I would test them individually first, assuming you have some means of measuring high current and/or low resistance. A bit of wire in a bucket of water would work fine at 3.2v as a resistor, if you can get it to .032 ohms (i.e. with a wire resistance chart and some thick leads) it should draw 100 amps.

Then monitor the voltage drop (at the battery terminals), and you can compute the internal resistance.

Dont keep it on test long.


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## Jayls5 (Apr 1, 2012)

onegreenev said:


> The closer to fully charged they are the less amps will be going into them. So you hit the constant voltage. Hobby charger? Which one? Not all Hobby Chargers can do super high current on a large capacity cell. Charge them up then run them down then charge them up again. But run them in your bike. Be sure they are all charged equally. Bottom balance them then charge them connected to your bike. You may want to check the capacity. They look like my CALB 100ah cells. Good quality cells. Does your bike have a proper charger for these batteries?


I'm charging with this:
https://hobbyking.com/en_us/turnigy-mega-400w-v2-lithium-polymer-battery-charger-version-2.html

It's a good CC/CV charger with 20A charge current capability, and CV mode starts at 3.6v.

The prior owner accidentally left his bike on, and it self discharged to the point that two of the 12 cells died - which saved the other 10. He was using a bulk series charger, which obviously over-volt the remaining ten cells if I attempted to use it.

Thus, the hobby charger is being used. I wired in parallel to top balance them. I have no interest in bottom balancing because the charger I eventually plan to use will always ensure each is individually charged to the correct voltage, so there's no risk of over-charge from varying capacity or IR. I'd just have to watch it on the low-end while in use for a weak cell. I'd do at least 1 test of each at full discharge to establish what kind of capacity I'm working with to see if there's a dud or two in there.

I mainly made this post because I'm perplexed that it can only be receiving 11-12A charge rate on a 500 AH bank, then immediately fall back to the 3.35v range. Do these cells not actually rest at their peak charge voltage?


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## dcb (Dec 5, 2009)

if they have high internal resistance, like .05 ohms, it will raise 1/2 a volt when you pump 12 amps into it. so 3.2v is 3.7.

You need to test them INDIVIDUALLY, but it doesn't look so good.


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## Jayls5 (Apr 1, 2012)

dcb said:


> if they have high internal resistance, like .05 ohms, it will raise 1/2 a volt when you pump 12 amps into it. so 3.2v is 3.7.
> 
> You need to test them INDIVIDUALLY, but it doesn't look so good.


Yeah... I'm thinking these are going to basically be UPS batteries at this point.

I was thinking there's no way a 0.24C charge rate should make them go from 3.3v to 3.6v. I deduced it had to be IR, unless there was something functionally different about large size LiFePO4 prismatic cells behave that I wasn't aware of.

Another anomaly: If you test the voltage of the bank of cells, it's lower at the opposite end of the chain from where I'm charging. I was under the impression these should all be the same in parallel. They're all interconnected with standard looking copper bus bars, which I even sanded down old corrosion to ensure good contact.


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## nucleus (May 18, 2012)

After you charged them what was the resting voltage?


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## dcb (Dec 5, 2009)

Jayls5 said:


> Another anomaly: If you test the voltage of the bank of cells, it's lower at the opposite end of the chain from where I'm charging. I was under the impression these should all be the same in parallel. They're all interconnected with standard looking copper bus bars, which I even sanded down old corrosion to ensure good contact.


12 amps should not make an appreciable drop on a bus bar.

You should post a picture of the setup and where you are charging and where you are measuring, something aint right.


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## GoElectric (Nov 15, 2015)

Interesting. Looking-forward to reading about your progress. Especially if you can kick-start them.


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## Jayls5 (Apr 1, 2012)

nucleus said:


> After you charged them what was the resting voltage?


It never really finishes charging. I keep hitting the 2 hour charge limit, which makes sense considering I'm charging a 500AH bank at a mere 12A. On the bright side, they are higher than what I started at... 

After about 12 hour or so of charging, one side of the bank is 3.34v and the other side is 3.32v open circuit... 

(The voltage difference used to be even worse until I decided to put the charge leads on opposite ends of the bus bars for the last 5 hours of charging I did.)



dcb said:


> 12 amps should not make an appreciable drop on a bus bar.
> 
> You should post a picture of the setup and where you are charging and where you are measuring, something aint right.



I know the wiring looks chaotic. Don't laugh:
https://i.sli.mg/daeKsr.jpg

















I tried a couple different charging wire sizes and clamp connectors to be sure my limits weren't coming from a crappy charger connection. I've tried 8 AWG wire with beefy clamps, and it didn't make a difference.


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## dcb (Dec 5, 2009)

please don't continue to try charging them, especially after an overdischarge, that can be a recipe for disaster. At a minimum, go one cell at a time and do it in the middle of the yard outside.

This isn't a good situation. Gonna suggest you just get some modules from a nissan leaf or volt, but you have to sort out the rest of the bike (charger/controller/etc). These aren't lead acid batteries that you can coax a little extra life out of, they are much more volatile.


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## Jayls5 (Apr 1, 2012)

dcb said:


> please don't continue to try charging them, especially after an overdischarge, that can be a recipe for disaster. At a minimum, go one cell at a time and do it in the middle of the yard outside.
> 
> This isn't a good situation. Gonna suggest you just get some modules from a nissan leaf or volt, but you have to sort out the rest of the bike (charger/controller/etc). These aren't lead acid batteries that you can coax a little extra life out of, they are much more volatile.


Just to clarify, only 2 cells were over discharged. I'm throwing those 2 away and not charging them. The rest were all sitting at 3.2v upon purchase of the bike. 

I don't intend on using these for EV purposes necessarily. I just want to be able to get some use out of a potentially 3.2 kWh of freebie batteries - perhaps for 500w trolling motor or UPS backup.

I don't see how what I'm doing is dangerous. The charger is properly going into CV mode to not exceed 3.6v to the batteries. I was just surprised how easily a low charge rate got it to hit CV mode on the huge bank.

On a max charged LiFePO4 battery, does it stay at the charger's terminating voltage, or do they drop down to a lower resting open circuit voltage?


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## dcb (Dec 5, 2009)

You have been warned.


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## Jayls5 (Apr 1, 2012)

dcb said:


> You have been warned.


I just don't understand your warning.

This battery chemistry is already inherently safe, and I am doing a proper CC/CV low current charge rate. There is no evidence of swelling, no heat buildup, etc.

I'm even going out of my way to do this in parallel to guarantee none of them get past an unsafe voltage during this painfully slower charging process. I could have done 6S in series, but I opted for a method that ensures no cell can possibly get out of the safe range as I charge.


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## dcb (Dec 5, 2009)

last time, test them individually, in a safe place. What you are saying doesn't make any sense.

good luck.


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## Jayls5 (Apr 1, 2012)

Ok, so I am trying a single cell now.

This one isn't from the 5 in parallel I had been working on charging.

This one was still sitting around 3.2v like when I purchased it. I set a 20A charge limit. The charger is able to feed 8A into it before it hits 3.6v and enters CV mode. This still seems saggy for a 0.08C charge rate.

Or... should I assume that the cells were just already pretty high on SOC upon purchase? I just thought 3.2v was at the lower end of the DOD curve.


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## GoElectric (Nov 15, 2015)

Notwithstanding the fact they are behaving as if high impedance, I'm guessing with cells in parallel (or otherwise) a damaged cell could short-out. If there are more cells in parallel, they would try to discharge through the shorted cell, an BOOM!?

You sound like you are being observant and diligent, but - yeah - be careful.

I don't know how much LiPO cells sag, but that sounds like a lot. Someone-else suggested discharging one, then you know where you are; this seems like a good idea. If those cells were not run dead, it seems worth the effort.


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## nucleus (May 18, 2012)

3.3 Volts or so is normal after letting them rest overnight. Now do a discharge cycle on each battery individually to see how much capacity they have.


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## Yabert (Feb 7, 2010)

Personally, two years ago my 154v nominal Headway 38120S pack was drop to 4v (less than 0,1v per cell).
After, I charged each cell who wasn't at 0v and I now use those cells on a ebike with success since one year.
http://www.diyelectriccar.com/forums/showpost.php?p=763538&postcount=329

Cells who don't take charge simply heat and became hot (to touch). Lifepo4 cells are pretty safe!
IMHO, Jay can parallel charge each cell who stay at 3,2v whitout load, but it's inevitably safer to charge each cell separatly.


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## Jayls5 (Apr 1, 2012)

Thanks Yabert. I've watched torture tests of LiFePO4 cells and could not believe the level of abuse they tolerated.

I even waited a month after purchasing the bike just to see if any cells dropped in voltage while I owned them. Nope, sat there around 3.2v just like the guy said they had been at for over a year.

People here telling me that these cells rest at 3.3v after a charge is very encouraging. I've pumped in about 45 AH into the single from when I posted last night, and the charge current continues to reduce in CV mode. I'm down to 3.5A feeding into the battery, so I'm pretty sure this one cell will be finished charging for a discharge test soon.


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