I had one of the supposedly dead cells on the charger for three hours today. I eventually got tired of waiting for the little indicator light to change from red to green and just went ahead, testing to see if it had actually accepted the charge. Not before stripping off the ugly purple plastic skins as you can see.
Haha! Success! It's about as charged as I would expect given how long it was charging. I initially got a reading of 5-6 which is when I realized I had the dial set to measure amps, not volts. Derp. Upon correcting this, I got an accurate reading. I then re-tested the other cells and found none were below 2 volts, most in the 2.4-2.5 range.
Just to be sure I wasn't fooling myself again I brought a brand new NCR18650B to act as the control. It tested as I expected it to, confirming the accuracy of the multimeter with the new settings. I'm embarrassed I made such a basic error last time. :/
I was visited by a friendly, curious spider dude! I named him Trevor. Don't worry Trevor, you are safe under my watchful eye. There is no enmity in this house towards the spider kingdom, may our truce forever bless our respective peoples with a peace of plenty.
I only have a two bay 18650 charger at the moment, so it'll take a while to charge the lot of 6 cells, two at a time. After that's done I'll re-test to see where the voltages are and decide what I might be able to use these for after that.
Incidentally the plastic wrap is a normally important insulator. The entire outer shell of each 18650 is the negative terminal, only the small nub at the top is the positive terminal. I stripped the plastic anyway because they're going into a power bank which connects all the negative terminals together anyways and does a good job of contacting only the positive terminal on the top end.
Plus they just look cooler that way, and cool factor is more important than safety. If problems arise though I'll glue the paper insulator rings back to the top, which should help a bit. Until then, if there's a fire it should be safely contained on the bare concrete floor of the garage, unable to spread. Worst case scenario is that I lose both cells and the charger.
Stay Tuned!