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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What about regenerative and alternator combined?
by: Anonymous

What if you use your regenerative braking as well as a belt drive going to a larger gear so as not to overturn a alternator so that it can produce its power to return to the battery as well

pma to charge motor
by: Anonymous

Hello. I have had the same thought as others that using an alternater would work to charge a battery. But I believe that using a pma would do the trick because there is almost no added load. Plus I have seen many homemade pma's that will charge batteries to run a house all day and night. So they should be able to charge your car batteries if you build it right. I understand the ideas of thermal dynamics but I wonder if they are actually correct if the energy output can never exceed the energy input then how do people exist? How can a whale one of the largest animals on the planet live off of plankton. We see this law overturned everyday just don't recognize it. And I may have all my ideas wrong but I have not found anyone who can give me an answer to these questions. Thanks for the site and your help in this area. Take care.

Still thinking....
by: Kai Soukka

Hey Lynne ,
Thanx for your reply. I'm of the frame of mind this is still solveable. Energies converted from potential ( battery ) to kinetic (motion) then dissipated as losses ( heat , light , sonic , drag )
are all calculable ; and can be shown mathematically. What goes in , goes out , and return energy loss is factually an energy drain. Accepted. This drain eventually diminishes stored energy to depletion. Accepted.
Energy is all around us. Nicolai Tesla theorised this first ? Future harnessing of , say radio waves , into electricity ;will minimise heavy batteries and drain loads from weight/gravity drag.
Laugh , scoff , neigh say me now. Just wait another 100 years. Unless we want to have a crack at it now ?

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