How much energy loss would be if I used generator and motor to propel a bicycle instead of pedaling directly?

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I'm thinking of making a lightweight scooter that can be propelled by electric motor, but can be pedaled if the battery is gone. Instead of making the pedaling component main function, i want to pedal to store/generate electricity. Does this physically/electronically make sense, or would there be too much energy loss? What if I can find very efficient motor and generator?

Answer
About the best efficiency you can get with electric machines (motors/generators) is 90%, and this might be tough to find. Smaller motors are more likely to be about 80%. If you do get 90% on both, you can multiply 0.9*0.9=0.81 or about 80% total efficiency (ignoring friction loss etc. which you would have some of anyways). If your willing to pedal about 20% harder than a direct connection ... your good to go.

I have a couple of pretty big (about the size of car starter) 50V DC motors. When I hook them together and turn the shaft of one with my hand, the other turns almost as fast. They are pretty efficient ... so I think you have a chance.

Consider charging the battery with the motor as well. You could recover some of the power with regenerative breaking or when going down hill etc. and reuse it.

I'd do some efficiency tests with the generator/motor before you decide to build this thing ...

What are the best electric bicycles/brands on the market?

Q. I've heard about I-Zip so far but they are the only ones I know of. Are there any other good brands?

Answer
"Best" ? As an industry adviser, I hear this question all the time.

what is really important is what is best for your needs; some folks need mammoth hill climbing, others need great range, others want light weight.

The Ezee brand ebikes, and Bionx are pretty darn good.

I zip/schwinn is having warranty problems.

Giant if you need great range and nationwide service.

Be careful with crystalyte in the rain unless you get the go hub.

Make SURE that diagrams, skilled repair people, parts and a warranty are available.

many folks are disappointed that there is no service and their $1200 investment is useless after the first minor problems.


Below are very good dealers. say dick sent you

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Title Post: How much energy loss would be if I used generator and motor to propel a bicycle instead of pedaling directly?
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