liviu.gelea
New Member
Hello. After founding a very detailed response to a question i was interested in about the "settling" voltage on lifepo4 batteries I thought this was a good place to ask for some help.
I bought 9 32700 cells I'm plannign to turn into a battery bank (4s2p). I bought 9 since I didn't trust them much and they were pretty cheap. In fact I bought 1 first and tested its capacity to above its rated 6000mAh ( it held above 6150mAh) and only then ordererd 8 more thinking I would exclude the worst one from the pack.
Now... since I bought them I didn't get the chance to test them all and kept them in storage for a year.
Recently I found that one of them had dropped to a mere 0.7v or started this way, who knows. I tried to "recover it" and charged it for a few hours at 2mAh until 2.8V, then using around 1A until full. Then tested it and it was 6139mAh. I so far tested a second one to 6245mAh and I'm in the process f charging all of them.
My question is what kind of tests I can do besides capacity to determine if it's safe to pair them inside a 4s2p bank and is it likey for a cell to be bad if it's the right capacity and has reasonable internal resistance?
For testing resistence I'm thinking I should do an AC test since I have a function generator and an oscilloscope besides a pretty good multimeter. Should I store them at full charge and worry if some drop more than others with time? should I just pair highest with lowest capacity in paralel to equalize the capacity of each 2p ?
Thanks.
I bought 9 32700 cells I'm plannign to turn into a battery bank (4s2p). I bought 9 since I didn't trust them much and they were pretty cheap. In fact I bought 1 first and tested its capacity to above its rated 6000mAh ( it held above 6150mAh) and only then ordererd 8 more thinking I would exclude the worst one from the pack.
Now... since I bought them I didn't get the chance to test them all and kept them in storage for a year.
Recently I found that one of them had dropped to a mere 0.7v or started this way, who knows. I tried to "recover it" and charged it for a few hours at 2mAh until 2.8V, then using around 1A until full. Then tested it and it was 6139mAh. I so far tested a second one to 6245mAh and I'm in the process f charging all of them.
My question is what kind of tests I can do besides capacity to determine if it's safe to pair them inside a 4s2p bank and is it likey for a cell to be bad if it's the right capacity and has reasonable internal resistance?
For testing resistence I'm thinking I should do an AC test since I have a function generator and an oscilloscope besides a pretty good multimeter. Should I store them at full charge and worry if some drop more than others with time? should I just pair highest with lowest capacity in paralel to equalize the capacity of each 2p ?
Thanks.