[_ Old Earth _] Stellographic oxygenetic statophonic deloverbarator

[Barbarian]

Why can't electric cars have alternators?. Or do they?, It seems they have to keep charging the battery.

You can't make energy. You can't destroy it. You can only convert it from some other form of energy. So if you use the kinetic energy of a turning mechanism to make electricity, you will reduce the kinetic energy of the mechanism by the amount of electrical energy you produce, minus friction and other losses.

If this puzzles you, try this:
Get a reasonably thick-walled copper or aluminum pipe. A one-foot length should be fine. Get a large neodymium magnet as strong as you can, a bit smaller in diameter than the inside diameter of the pipe. Look down the pipe and drop the magnet into it. It will be a revelation for you. The magnet, as it moves past the conductive metal, will generate an electrical field. That energy will be produced by converting the kinetic energy of the falling magnet to electrical energy. And in doing so, guess what happens to the velocity of the falling magnet.