Could this be an 18650? (Cordless screwdriver)

Black & Decker apparently no longer makes the Li3100 cordless screwdriver, and the only replacement part listed for it is the charger. (Which seems to be permanently on back order.) Luckily, I have two, one right at hand, the other one "somewhere."
The screwdriver is supposed to be around 3.2 volts. The battery has no markings on it except those polarity symbols. It shows 0.15V on my DMM right now. Even a day or more on the charger didn't seem to get it to where it could make the screwdriver do anything. (Motor or LED work light.)

Would it be possible to substitute a lithium rechargeable 18650 for that, and maybe even gain some mAh in the process? I don't have a clue what its original specs were, but the label on the "wall wart" charger says the charger's output is 9VDC, 100mA.

Your screwdriver is not running on a Li-Co cell, so it would not be incompatible with the LG Li-Co cell, which is a 3.7 volt battery. I would stop trying the charge the apparently depleted 3.2volt battery, and do not try to charge it up in a charger that would charge to 4.2 max. Other members, more knowledgeable re Li_Ion's will pipe in soon.

Bill

Thanks, Bill. I'm assuming you mean it would "not be compatible." And what LG LiCo cell are you referring to? The one I linked to says it's a Li-Ion.