I have been building 100p packs and not putting them in to production. After about 6 months or so one of my packs lost entire voltage and tested at 0 volts.
Apparently one or more of the cells is self discharging and took entire pack with it, but the discharge rate was so slow that it did not blow the fuse.
I was able to bump the pack and charge it to 4.2 with 6 amps imax and then run a discharge test at25 Amps hoping that my thermal camera will detect the bad cell but did not. 25A translates to .25 A per cell so I guess the load was not big enough to do so.
The good news is that the load test reviled expected capacity of 172 Ah from 4.15v to 3.2v what was expected. I do use 1800 - 2600 mAh in my packs of opus tested cells. Total opus, that discharges down to 2.8V, capacity of the pack should be 225 Ah.
I do not believe that I need to retest each cell individually for capacity, but only for self discharge.
My next test will be to charge the pack back up to 4.2v and take one site from the pack to disconnect all cell from each other and let them sit for 30 days to detect leaking cell/cells.
I guess my question is:
Whythe good cells did not lost the capacity even when the voltage drop to 0 ?
Apparently one or more of the cells is self discharging and took entire pack with it, but the discharge rate was so slow that it did not blow the fuse.
I was able to bump the pack and charge it to 4.2 with 6 amps imax and then run a discharge test at25 Amps hoping that my thermal camera will detect the bad cell but did not. 25A translates to .25 A per cell so I guess the load was not big enough to do so.
The good news is that the load test reviled expected capacity of 172 Ah from 4.15v to 3.2v what was expected. I do use 1800 - 2600 mAh in my packs of opus tested cells. Total opus, that discharges down to 2.8V, capacity of the pack should be 225 Ah.
I do not believe that I need to retest each cell individually for capacity, but only for self discharge.
My next test will be to charge the pack back up to 4.2v and take one site from the pack to disconnect all cell from each other and let them sit for 30 days to detect leaking cell/cells.
I guess my question is:
Whythe good cells did not lost the capacity even when the voltage drop to 0 ?