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0v pack
#1
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 at 25 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:
Why the good cells did not lost the capacity even when the voltage drop to 0 ?
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#2
Dropping the cells to 0v once for a short period of time isn't going to kill them. A good way to find the rogue cell is to charge the entire pack to 4.2V then snip all the fuses on one side so the cells aren't paralleled anymore. After a few weeks, go through and check the voltage of all cells. The bad cell should become obvious.
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#3
Like Mike said, snip snip. You could even do the snip and only charge a small row at high amps. But you would still need to get to about 2A per cell to make the hot one show itself.
Better to go Mikes way and take a little longer to find it
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#4
(12-01-2018, 03:15 PM)mike Wrote: Dropping the cells to 0v once for a short period of time isn't going to kill them. A good way to find the rogue cell is to charge the entire pack to 4.2V then snip all the fuses on one side so the cells aren't paralleled anymore. After a few weeks, go through and check the voltage of all cells. The bad cell should become obvious.

This^^^^ I have done this to a bad pack and found up to 3 cells that went to 0v immediately. Just pulled those cells replaced them with similar capacity and presto back in service. But before I put it back in service I let it site with one side disconnected totally for a month to see if any other cells were slow discharges and I found 2 more cells that after a month dropped to 3.9V so those went in the bin as well.
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