18500 Li-ion Battery adapter to replace 3 x AAA cartridge

This is an adapter you can put an 18500 _rechargeable_ battery (or even an 18650 cell) into so that it's snug in the place of a 3 x AAA cartridge, like in a lot of LED flashlights. The lower battery voltage (3.7 for Li-ion vs. 4.5V for alkaline) is pretty much offset by the lower internal resistance of Lithium electrochemistry, so the flashlight appears just as bright.
Electrical safety is up to you; don't use this if you don't understand the risks.
That being said, I haven't had any issu