LiFePO4 balancing question
 

Before my charger timed out at 120 minutes, I had two cells at 3.6v and the third at 3.35v. I was charging at 1amp and this is the first time I've ever charged it. Can I continue to charge the pack? What do I do about the unbalanced cell? The battery is a turnigy 4500mah 3s LiFePO4 and the charger is an iCharger 208b. Also, how do I check the capacity of the battery pack?

Thanks

Sounds like you have a bad cell - I'd leave the battery on balance mode only which should bring everything back into line and try recharging but it could be knackered...

Doesn't bode well for me as I just ordered a pair of these packs...

The other Turnigy 3s I ordered is perfect and the two 2s packs are good also. Thanks for your reply

That's what I hate about HC's warranty policy. They won't cover any packs that have been put through a charge cycle, yet often times like this situation you can't know the cell is bad until you charge it. Catch 22.

Yeah, it seems like the low price comes at a gamble. You generally come out ahead, but it's still a PITA. And their warranty policy is pretty crappy. It's basically like not having one. And even it is covered, it's almost cheaper/faster/easier to just get another pack rather than shipping it back and forth again due to their high shipping costs.

Re: capacity checking- difficult to do. If you can drain the packs down until they 'dump' ( easiest to do this just buy driving the truck until the power/ speed drops off to a crawl suddenly ), then do a full charge & see how many mah were pumped back in.

You should be able to do a 4.5amp charge if your charger is capable, but definately do it in balance mode with the little white connector plugged in, should take roughly an hour.

Set your charger on Nimh, 1.0A or less, and charge it for a bit to see if you can get it up. Once it gets up to nominal, set your charger back to LIFEP04 and charge it. Then balance it again. I've done it with several A123's I bought from HopmeUp (their warranty is just as crappy as HC's - 'cept they will ban you from buying from them if you complain!!!). Oh, and disconnect the balancer when you do the Nimh charging.

Are those packs 3S1P or 2P? Problem I had with the A123's is that I couldn't
"see" the bad cell since they were 2S2P. Had to completely take them apart and measure the cell voltages. But I learned a lot about putting packs together!

They are 2p

I had one of the 2S Turnigy LiFes that was out of balance on the first charge. I put it on balancer mode until it evened out and ran 4 half cycles on it (discharged about 2200 mAHr and recharge). By the 3rd or 4th cycle the pack stayed balanced very well (within .01 v).

BTW, I'm doing the half cycles because of some product description info I read on a LiFe pack sold by A-Main - said not to take them down more that 50% for the first 20 cycles. Is this is real issue?

New to me, though it is said of all lithium batts you should take it easy for the first few runs before they are broken in fully.

When should I use storage mode fo a LiFePO4? A week, few weeks or months?

I'd say that if its been a stable pack, you probably wont have to worry too much about them (based on my exp. with the A123's)

Well, I think the third cell puffed. The pack only registers about 6.6 volts on the charger and when I plug in the balancer it gives me an error. I'm not going to bother with any warranty stuff but what can I do with the pack or how do I salvage the other two cells? I don't even know where to begin on opening and separating the pack.

Cut off all the shrink and tape covering the connections, then take a few photos- we shoudl be able to ID what you need to do to make a 2s pack from the 3s.