BLF Community Battery Pulls Overview Thread (Laptop packs and Tool Packs)

I tore into some DELL XX326 11.1V 60WH packs.

I started by trying to read data out of them with PackProbe. Only a few yielded any data, and what they gave was patchy. I pulled open the rest to see if I could figure out why they weren’t working. I could tell that all of them had one or more bad bank of cells. I could also tell that some of the spot welds had broken at some point, perhaps while I was twisting the packs to get the case open.

When I checked cell voltages in situ, I found that all of the packs I opened had bad banks. Some worse than others.

Hmm, that ain’t good, how does each bank look…

Huh, I guess those aren’t bad, the rest though…

Umm, weird…

–2.69v?!? That can’t be right, but the polarity on the multimeter is right.

I looked at a few more packs. Found some more reverse polarity cells, but not with as much potential. A bunch of flat cells, and when I tore out individual cells, I found 0v cells paired with ~3.5v cells in the same bank and more broken spot welds. Not quite sure what is going on, other than these being lousy packs.

Out of 18 cells from three packs, I only have 3 (Samsung ICR18650-28As) that are anywhere worth charging.

Update: The three cells I charged are pretty hammered. When charged to 4.2v and tested on my Opus, they all put up about 1,720 mAh discharge capacity at 500mA drain. These cells are designed for 4.3 discharge voltage, and according to HJKs tests, when charged to 4.2 they give up about 8% of their capacity, which would put them at ~2,600 mAh from 4.2v when new. Internal resistance as measured by my Zh-yu battery analyzer from Fastech is ~75mOhm (for comparison, on the same rig, some pink samsungs pulled from one of those $12 Acer packs with a dozen or so cycles on them now come in at ~60mOhm, and some Sanyo blue top from a 110-cycle Lenovo pack I got from Hagg911 measure 55mOhm).