Saturday, May 3, 2014

Can the pedaling energy charge the battery of an electric bike?




Drowzzy


Can the mechanical energy of pedaling be stored as electrical energy to be utilized later to run the bicycle automatically? I'm not talking about pure electric bikes that need regular charging, and not even about those that you pedal for a while as the bike stands still and then run it on electric power. I mean can you ride a bike and store the mechanical energy simultaneously? Will it be efficient? If so, then are such e-bikes available in the market, and what are they called so that I may Google for them?

Here's the scenario: I need a bicycle for regular commute, may be even for covering long distances. It's not feasible for a layman to pedal continuously for more than 5 to 10 miles. So I'm looking for a bike that you pedal for sometime, and when you're exhausted, you simply flick a button to make it run on electrical power which has been converted and stored from the mechanical energy of pedaling the bike; and then pedal again and auto-ride again and so forth. Will something like that be technically efficient, since you're moving the bike while pedaling as well as storing your spare energy?

Hope I haven't confused you. Thanks :)



Answer
You will have to pedal extra hard to keep the bike going and to charge the battery. It could be done, but it would be easier and more efficient to pedal a regular (lighter) bike.

Maybe you could use a large solar panel to power the bike

a battery question? try to build a electric bike.?




GusB


ok i found a 36v 350 watt scooter motor which i intend to mount on the bike. my question is what sort of battery should look for and for those batteries that you chose, how long would they last. and you tell how did you get the answer on how long do they last.


Answer
You will need a 36v battery pack. In order to calculate how long a battery will last you will need to know the ampere-hours (Ah) of the 36v battery pack and how many amps the motor takes to run. To get the amps of the motor, divide the wattage by the voltage. Hence, your motor takes 350/36 amps=9.7A., To work out how long you can then run the motor, divide the Ah of the battery pack by the motor current to give you a run time in hours. e.g.a 10Ah battery pack would last 10/9.7 hours=1.03hours or 1hour 2mins.

However, the real run time could vary dramatically from the above, which is a theoretical maximum. I'd factor it in at 70% less if I was wanting top know or alternatively get a battery pack 50% more than the above calculation. If you use a good controller rather than just on-off you will get increased time proportional to how much less current you are using and how efficient the controller is. Plus, the rating of the motor could be out either way. You will also have to factor in how efficiently you can connect it to the bike wheel. Any chain, belt or friction drive will introduce losses. Bike motors are often made part of the bike wheel hub to cut down on these losses.

Finally, the range of your bike and run time can vary with the type of battery, which might not hold it's voltage well or may dip under certain conditions of e.g. cold temperature, high load.

Have a look on www.instructables.com for lots of hints and tips.

Have fun and feel free to contact me if you want any more help with the maths of this..




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