Plug In America |

Can electric vehicles self-charge?

Simply: No. Many people have proposed adding generators to EVs to allow the vehicles to partially recharge themselves. Some suggest generators on the wheels or drive shaft while others suggest small wind turbines behind the grille or on the roof. In each case, more energy would be consumed to turn the generators than could ever be recaptured. Attempting to generate while driving would result in a net loss of range.

There is no free lunch. Energy conversions are never 100% efficient, so every time we convert one form of energy to another, we lose some of that energy. We lose energy when we charge an EV's battery from the wall outlet. We lose energy when we take charge out of the EV's battery to push the car down the road. If we tried to convert the energy from the moving car back into battery charge, we would again lose energy.

Installing a generator on an EV would be akin to driving with the brakes on. For this reason, modern hybrids and EVs only recapture electrical charge when slowing down. The kinetic energy of the vehicle in motion is partially converted -- by the electric motor working in reverse -- into electricity that can be added back to the battery. This advantageous process slows the vehicle by capturing the vehicle's kinetic energy that is normally wasted to heat with traditional brakes. The problem comes when we do NOT want to slow down while simultaneously converting the kinetic energy of the car into battery charge. Spinning a generator will always require energy input. And that energy input will always slow the vehicle. To overcome this "slowing force" caused by the generator, additional energy must be consumed from the vehicle's battery to maintain speed. Because of the conversion losses mentioned earlier, more energy will be consumed than will be replaced. The ironic result of "self charging" would be a net loss of charge (resulting in shorter range).