So people throw out disposable vapes all the time. I cracked one open to take a look and it turns out they have a 18500 battery in it. So I was thinking of 3D printing a spacer to make it the same size as a 18650 and putting some shrink wrap on them. I just wanted to see what people who know more than me think. Is this a bad idea that is going to burn my house down? a waste of time perhaps?
I did a trial run in my wurkkos fc11 and they seem to work, it charges and looks just as bright.
There is usually basic over discharge protection in the flashlight circuitry and over charge protection for lights with on light charging.
This usually works in conjunction with the protection circuit on the batteries.
18650 batteries (and other sizes) have become more wide spread because of the increased safety of protected batteries.
The batteries OP wants to use are unprotected cells who’s manufacturer is unknown, actual capacity is questionable and how they have been handled is unknown.