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 Topic Title: Electric Cars Topic Summary: Created On: 25 July 2012 10:22 AM Status: Read Only Linear : Threading : Single : Branch
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 25 July 2012 10:22 AM malcan2004 Posts: 3 Joined: 25 July 2012 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! 25 July 2012 01:23 PM amillar Posts: 1918 Joined: 28 May 2002 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. ------------------------- Andy Millar CEng MIET CMgr MCMIhttp://www.linkedin.com/in/millarandy"The aim of argument, or of discussion, should not be victory, but progress." Joseph Joubert 25 July 2012 02:49 PM ectophile Posts: 596 Joined: 17 September 2001 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. ------------------------- S P Barker BSc PhD MIET 25 July 2012 03:55 PM malcan2004 Posts: 3 Joined: 25 July 2012 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! 12 August 2012 10:34 AM jackhowe Posts: 1 Joined: 18 July 2012 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. 12 August 2012 12:44 PM malcan2004 Posts: 3 Joined: 25 July 2012 Thanks Jackhowe I will have to look that up I have never heard of retarder before. 20 August 2012 07:10 AM electricaltestinguk1 Posts: 11 Joined: 12 July 2012 Originally posted by: jackhowe 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. I guess you're right. Because it will be no longer useful in some area that need speed.
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