why can't the the wheels turning on a car be used to charge a hybrid battery?

Question

i know that braking is used to charge the battery in a hybrid car, but why can't the wheels spinning be used in a similar fashion? electricity is generated by turing turbines of various kinds, windmills, waterfalls, even in a coal buring electrical plant electricity is generated by spinning turbines. whould not a car using the same principle be able to run just about endlessly?

Answer 1

Generators are not perfect devices---they have both electrical and mechanical sources of power loss or rather some of the energy is converted to heat through friction and resistance. Additionally, it would increase the load on the motor which increases the current requirements of the motor which increases something called the "I squared R losses". The motor will convert more of the electric energy from the battery to heat energy than it would without the generator. Essentially you will be adding more resistance and heat to the environment with the generator than without---and heat equals power lost that you could have otherwise used to get you further down the road.

That's why regenerative braking works so well, when the generators at the wheels are returning power to the batteries, they are creating a load or resistance... and the cars own momentum is the source for that power. As that energy or momentum is absorbed and converted to electricity the car slows down, which is what you wanted it to do to begin with so it's no big deal. If those generators were running all the time and not just during braking it would be like driving your car around with the e-brake on all the time... it would put a lot more load on the engine and would actually be less efficient.

You can't create electricity with electricity and compensate for energy lost to ineffencies in the mechanical devices that generate it and the energy that is required to propel the vehicle. It has to be supplemented in some other way.

Answer 2

Well when the wheels are turning, you would want all the electric/ gas powering the wheel to get maximum efficency out of the work being produced. So you could have a generator turning when the wheels are moving, but you would need much more energy to produce energy, so it would work agaist itself. But when slowing down or stopped, it would be the most effective. The generator (alternator) on your engine is only big enough to provide enough charging and enough energy to keep the car running and all accesory but under high rpm conditions, it will cut out to provide maximum engine power.

Answer 3

They do. There is a motor connected to the wheel and it is driving the wheel. When you want to stop, the power is removed from the wheel and the motor turns into a generator and feeds energy back to the battery.

That's how it works.

Answer 4

If you take energy away from the spinning wheel, that means the wheel will spin slower, and thus, the car will slow down. And guess what? That what regenerative braking is.