A second batch of used batteries arrived, I got nearly 1000 cells, about a third of them I have in a box, 2/3 are still in their laptop packs waiting for me to rip them open.
I'm contemplating buying another ~1000 cells, or first using what I have to build a pack and do some testing with that.
My chargers, cell holders etc.. arrived, and it took some messing about to get it all to work.
Firstly, the battery clips don't make contact with the flat-top batteries, so I added a solder blob in each one to make it so they do. further more, the crimp on the wires isn't really good, so a few of them had bad contact. (Some more solder fixed that too.)
The single cell chargers don't take kindly to reverse polarity, so 3 out of the 10 died when I accidentally put in cells backwards. Whoops.
Also, I was using my laptop and a bunch of USB cables to power them, not really the best way, now I hooked up some LM2596 boards in parallel and set to 5.00v output. I added a little stick-on heatsink on them, because at 3A each they get quite hot.
I ordered more battery clips, chargers and some of those adjustable DC-DC converter boards (I borrowed these from another project, and its nice to have spares)
Next up, building the battery discharging device. The idea is to use a 2.5A capable transistor, a 10W 1.8Ohm resistor, a beefed up battery clip, multiply that by 10, and add an Arduino and an lcd display to make a 10-cell-at-a-time discharger to figure out how good all the individual cells are. I might add some diodes so I don't blow stuff up in there too.