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Fri Dec 29, 2006 11:42 pm Post subject:
Electric Motor for Recharging |
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I was thinking about the problem with charging the batteries on an electric vehicle and came across something; couldn't you have two of the same motors and use one to drive the car, and the other to recharge it? The recharging motor would be driven by an axle so it would be just like the motor powering the car except it won't be powered by the battery. Lets say the driven motor requires X amount of energy to be driven, wouldn't the other motor generate X amount of energy since it would be spinning at the same rpm? Actually it probably wouldn't generate the exact same because of friction lost but I think it would be enough to make the battery last a lot longer. But anyways am I missing something because I don't read about people doing this so is there a reason why it won't work or will it and they just don't do it?
Kyle |
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Sat Dec 30, 2006 12:23 am Post subject:
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so you're saying that one electric motor is driving the car, and another electric motor to charge the battery?
not possible, because the charging motor is using the electricity from the battery as well. A motor cannot produce more energy than is being used.
same as if a generator was being run off an axle from the road. It would be working against the driving motor. There is major electromagnetic forces within a Generator that prevents movement.
Take a Petrol powered generator for instance. The engine spins a coil within a magnet, this causes electrons to flow. As soon as you start drawing power from the coil it causes a magnetic force within the generator that prevents movement.
I hope what I wrote made sense. I tried to explain what I learned in Electronics class  |
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Sat Dec 30, 2006 4:15 am Post subject:
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In order to also drive the 2nd charge motor the first would have to be larger and therefore would also drain more power, plus the whole package will be heavier and thus use more power.
Put simply it is more effective just to make the driving motor more efficient. |
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Sat Dec 30, 2006 5:21 pm Post subject:
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| heh pretty much useless, that's why we have hybrids, just get a bigger battery or something, or a solar panal on the roof and hood, and move to auz |
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Sun Dec 31, 2006 3:43 pm Post subject:
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Also you are forgetting the load caused by the charging electric motor, nevermind the weight, what your proposing is a propetual motion machine.
Let's say you have 2 10hp electric motors, the one pushing will be applying 10hp, the one charging will be taking AWAY 10hp because of the electromagnetic load. I'm on pain meds right this minute so I can't remember the name of that force, electro-motive force, or something hehe.
And this is disreguarding friction and heat losses as you mentioned  |
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Sun Dec 31, 2006 6:24 pm Post subject:
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yeah i couldn't remember the name (perpetual motion machine)
in fact the idea would technically produce more power than input, which is impossible |
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Sun Dec 31, 2006 9:41 pm Post subject:
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Ok, so basically they cancel each other out. Thanks for the help though.
Kyle |
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Mon Dec 03, 2007 10:57 am Post subject:
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Another option would be to use the same motor that drives the vehicle to also charge it.
This would make it more expensive, but induction braking has been around for a long time. Trains use it I believe.
Basically what you are doing is replacing the brakes. When you are coasting or braking you would be creating a charging current (a bit like engine braking with a gas engine). Obviously the greater the braking load, the greater the charging current.
This would never replace the power used, but could put back a good percentage. Enough to increase your range.
Terry |
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Mon Dec 03, 2007 7:17 pm Post subject:
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Regenerative breaking has been around for a long time, all the hybrid and fully electrical vehicles have been using it for atleast the last few generations.
But keeping that in mind, you can't use the engine to do all the braking you still have to use disk brakes for bringing the car to a complete stop |
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Tue Dec 04, 2007 4:10 am Post subject:
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| superdaver wrote: |
But keeping that in mind, you can't use the engine to do all the braking you still have to use disk brakes for bringing the car to a complete stop |
I wasn't trying to imply that it would be a complete replacement for brakes, just a better method of recharging the batteries on the go.
Maybe I should have made myself a little clearer! 
It would certainly reduce brake wear as well. An added bonus! 
Just being pedantic now, but reverse emf braking can be used to bring a vehicle to a complete halt. Especially with modern cars power to weight ratios. It is just that it would not be economical to do so as it would use power. It would be like trying to reverse whilst going forward. Pedantic mode off! |
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| Posted:
Thu Jan 24, 2008 10:19 am Post subject:
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http://pmlflightlink.co.uk/
Just go check it out.
_________________
Components, core kits, premium component kits and rollers now available |
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Fri Jan 25, 2008 3:36 pm Post subject:
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| Those are impressive specs. 750Nm of torque - thats over 550 lb-ft at 2k rpm! I'd love to see a light-weight all-electric sports car with those. Still I wonder if it would be feasible to mount them inboard |
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