My “rule” is that even if they’ve got lousy capacity, as long as they don’t heat up in the charger, I’ll keep them.

I got “free” cells with a so-so light, and they’re pitiful, but they don’t heat up, so I use them in mum’s lights where she has this habit of just leaving flashlights on overnight (and claiming she doesn’t).

This way, if draining them to zero kills them (more), at least I’m not sacrificing a good cell, but one I’d be tossing anyway if it so much as looked at me funny.

If they heat up, charging or discharging, they’re gone.