Electric Vehicles Rotating Header Image

How to turn a motor into a generator and use it to charge a car battery?

I am planning to build an electric vehicle and I would like to have regenerative brakes to increase its travel range.

Some people say that a motor and a generator are basically the same thing.

But how come a car alternator doesn’t turn on its own even when it’s connected to a car battery?

I plan to power the electric motor with four 12volt batteries connected in series to make a total of 48volts.

What should I do to be able to instantly convert the motor into a generator (to convert kinetic into electrical energy and charge
the batteries) as the vehicle is in motion?

is there a need for some complicated circuit boards to do this?

if I were able to switch the positive and negative connections to the motor as the vehicle is moving then would it charge the batteries?

Asked by:lethaldriver


  1. Pobept K says:

    A generator produces DC current
    a alternator produces AC current that is converted to DC current that is usable in automotive applications

  2. Steve W says:

    The simple answer is “Yes”, you need some complicated circuitry to make the power flow in the desired direction upon command.

    Both ac machines and dc machines can be used as motors or generators under the right conditions.

    An alternator is basically a permanent magnet AC generator with a diode bridge at the output, so power only flows OUT of its terminals. That’s why it won’t motor.

    A regular squirrel cage induction motor can be used as a generator, if there is an external ac source to provide the necessary excitation, and the external prime mover rotates faster than synchronous speed. Big wind turbines commonly use this approach.

    To do what you want for automotive applications, you need a power electronic converter that can adjust the voltages on the fly to direct power either into the machine (as a motor), or out of the machine (as a generator). Note that this is very different from just changing the polarity between battery and motor.
    If you only switch the applied polarity, the motor just tries to quickly change to spinning in the opposite direction. This works for braking, but puts a LOT of heat into the motor. Power is still flowing from battery to motor, and no re-generation occurs.

  3. muslem says:

    yes any generator can operates as motor and vis versa
    but u can’t acheive this idea
    as in order to make the motor operates as a generator to supply the batteries

Leave a Reply