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Generator or Alternator To Keep EV Charged?

by Kai Soukka
(Melbourne , Australia)

Can regular alternators be connected to the running gear to self charge the batteries, thereby eliminating the need to externally recharge?

What if an overpowerful motor is used? The extra power would run the recharge so as not to take from performance.

I'm no electrician, yet, I feel there will be some mathematical law that says this is impossible due to heat or other power losses, via friction, or consumption of energy. (Right?)

G'day, Kai -

You're right. There's a physics law getting in your way; the second law of thermodynamics, aka "no such thing as a free lunch".

What you're describing, an "alternator (generator, actually) connected to the running gear", is pretty much what happens with regenerative braking, and why we love it so much! It puts that hard-earned mechanical energy that would be wasted as brake-friction-heat back into the battery pack to be used later.

All electric motors can technically be used as generators, you're right about that, you don't need a separate device. (Though the 3-phase AC motors do it better than the series DC motors because of properties of the motor and control of the motor that make this so.)

The electric motor can't generate electricity with the excess from powering the wheels, though. These processes are in opposite directions. Complex control makes the AC motor capable of running forward to power the wheels, then backward to function as a brake and recapture that mechanical energy back into electrical energy.

But that energy originally came from somewhere.

The energy that got your EV's wheels rolling in the first place came right out of your battery pack. Any gizmo that converts that mechanical energy back into electrical energy, even if it's perfectly efficient, can't put back more than it received in the first place.

Thanks for writing in!

All the best,

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