Generating Power with your Electric Cars Wheels
Rotating shaft being the axle
Could you put a magnetic electrical generator on the axles of the unpowered wheels of your car to feed the battery/ could you use the wheels as a turbine?
Because they're turning anyway...
I've tried doing calculations for the size of generator you'd need to power the car independently (only plug-in for back up/resting power etc) but got over confused with kW and KWhr etc.
Is it pointless due to friction or something?
It's called "regenerative braking", actually. Somebody already thought of it, which happens to all my really good ideas, too.
If you've got an AC electric car motor and controller, the motor does exactly as you say - acts as a generator feeding back the energy from the motion energy of your car into your battery pack.
Trouble is, you can't get back more than you put in. So whatever you expended to get your car to - say, 50 mph - you can only put back some amount less than that through recapturing the energy from the car's motion.
Physics equations: well, a kilowatt (kW) is a unit of power. A kwh is a kilowatt hour, a unit of energy, and is just kilowatts multiplied by hours. See how easy that was?
For more Joy of EV Physics, see page 98 of Build Your Own Electric Vehicle.
All the best,