Can someone telll why electric cars when moving can generate power when moving so that it keeps the main batteries charged. I know some have this on the wheels and charge when braking.
I just think if the car is moving there must be a way of powering a generator to keep the car charged so that you have continuous power and no need to charge the car at home or at a garage!

I think you may need to look up "perpetual motion" on Wikipedia! Yes, you can top up batteries during braking or on downhill runs, but you will not capture anywhere near enough energy to accelerate or get it back up the hill.

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Andy Millar CEng MIET MCMI

http://www.linkedin.com/in/millarandy

Turning a generator isn't free; it takes mechanical energy.

In the case of regenerative braking, the generator is taking kinetic energy from the car and producing electricity. Removing kinetic energy slows the car down - which is what you wanted, and produces electricity to charge the battery - which is a handy side-effect.

Leaving the generator running all the time would produce a constant drag on the car (as if you were applying the brakes), and so you would have to send more power to the motors to make up for it.

The trouble is that the motors aren't 100% efficient, and neither is the generator. So the extra electricity you have to send to the motors is more than the generator is producing. The end result is a flat battery.

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S P Barker BSc PhD MIET

Thanks for the replies I see what you are saying maybe we need the 40:1 ratio gearbox that was presented on Dragons Den to help drive the generator!

Trucks have been using this technology for years but it only works when you are not accelerating. It's called a retarder in that application.

Thanks Jackhowe I will have to look that up I have never heard of retarder before.

I guess you're right. Because it will be no longer useful in some area that need speed.