Hi, I was just learning about Electric Vehicles, and how they are powered. Let us consider a BEV (Battery Electric Vehicle), and not a hybrid. So we just have the battery powering the drive train and the wheels. The other day a friend of mine asked why the each wheel of the car can't in turn be connected to an axle (going into the car parts, not outward), with fan-like blades at the end. As the wheels moved, the fan-blades would move too and if these blades were placed within the magnetic field of a strong permanent magnet, by Faraday's law this should generate electric current. This current could e used to charge the battery again. The idea seems great, but probably reveals a lack of basic understanding of a certain law. I am aware of the energy conservation principle and all, but I can't figure what would actually happen in such a set-up. I have had similar idease earlier (of using motion between a magnetic field to get electric enegry "again"), but I understand there is a flaw in it, which is why it hasn't been used till date. Can anyone explain?