@TheBreadmonkey@beige.party Sure. Have the battery drive a tiny electric motor that powers a dynamo that charges the battery. (This is a joke, of course. The reason it wouldn't work is that a dynamo pushes back against you if you draw current off it. That's how an EV's regenerative brakes work. You always get less power out of a dynamo than you put in, just as you do with a motor, and just as you do with a battery.)