I've picked up some discarded laptop battery packs from my local campus.
One battery was 3S2P 18650 cells, two of the pairs are OK ( they had ~4.0v and I get from them approx 2050 mah per cell (tested with Imax B8),
But the last pair had reversed -0.27v !!!
First question is: how could this happen in the first place? There's big PCB in the laptop battery to prevent this kind of situation
I've tried to charge these - 0.27v cells, but my charger won't accept them (it says reverse polarity).
Maybe I just charge them manually, with 4.2v and some resistor in series to limit the current?
Or connect to healthy full battery in parallel, through a 10ohm resistor ?
Is it safe to use them?