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Old 01-07-2017, 07:01 PM
Jayls5 Jayls5 is offline
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Default Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

I purchased an EV motorcycle that had 10 of these:
http://www.evsource.com/datasheets/B...B_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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  #2  
Old 01-07-2017, 07:27 PM
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onegreenev onegreenev is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

Quote:
Originally Posted by Jayls5 View Post
I purchased an EV motorcycle that had 10 of these:
http://www.evsource.com/datasheets/B...B_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?
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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Old 01-07-2017, 07:32 PM
dcb dcb is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

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.

Last edited by dcb; 01-07-2017 at 07:36 PM.
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Old 01-07-2017, 08:52 PM
Jayls5 Jayls5 is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

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Originally Posted by onegreenev View Post
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-...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?

Last edited by Jayls5; 01-07-2017 at 08:57 PM.
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Old 01-07-2017, 09:19 PM
dcb dcb is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

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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Old 01-08-2017, 04:40 AM
Jayls5 Jayls5 is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

Quote:
Originally Posted by dcb View Post
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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Old 01-08-2017, 12:04 PM
nucleus nucleus is offline
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Question Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

After you charged them what was the resting voltage?
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Old 01-08-2017, 01:06 PM
dcb dcb is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

Quote:
Originally Posted by Jayls5 View Post
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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Old 01-08-2017, 04:27 PM
GoElectric GoElectric is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

Interesting. Looking-forward to reading about your progress. Especially if you can kick-start them.
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Old 01-08-2017, 06:33 PM
Jayls5 Jayls5 is offline
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Default Re: Inherited ten 100 AH LiFePO4 prismatic batteries... need tips.

Quote:
Originally Posted by nucleus View Post
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.)

Quote:
Originally Posted by dcb View Post
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.

Last edited by Jayls5; 01-08-2017 at 08:30 PM.
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