[john61ct]

All in one string, no paralleling?

Have you balanced them, or verified they are balanced against each other? At what SoC point?

Have you cap tested each?

 

[ampitup_co]

All in one string, no paralleling?

Have you balanced them, or verified they are balanced against each other? At what SoC point?

Have you cap tested each?

I pull out the 3 turd batteries (and one good one) and connect them in series and use a 12V charger to charge them and an inverter to discharge. When I wire them in parallel I can balance them at 3.2 volts, and 3.3 volts with a power supply.

I've not done a proper capacity test on these since I can't seem to charge fully?

 

[john61ct]

You are very likely damaging them further charging them like that.

3S means do not go past 10.5V, if CC/ Bulk stage only, at maximum 80A.

10.35V would be better if you want precision, holding that (Absorb / CV cycle) until current drops below say 5A.

Then isolate each cell,

record voltage of each with a known accurate DMM

let sit a few hours, ideally 24 or more

then record them again and report back.

Also, meantime start cap testing on the ones you think are OK.

Best if you started getting better gear, really want an electronic dummy load that will do single cells,

or a good hobby charger that can do a decent discharge rate.

 

[ampitup_co]

3S means do not go past 10.5V, if CC/ Bulk stage only, at maximum 80A.

I've got 4 cells in series, not 3, when charging using a 12V LiFePO4 charger.