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# Electric bike self powered no battery Answered

I have a hub motor 1000 watt for bicycle, I would like a hub generator that would power the motor hub with out a battery, can anyone tell me how I can get or make something like this, or ,,it takes a 48 volt battery, can I use a 12 volt battery and step up transformer , or 12 volt car generator and step up transformer, or dynamo hub and step up transformer , or would it only raise the voltage and not amps

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You did not mention what you want this motor to move.

I mean, do you want it to actually push a bicycle forward? Doing that will require a significant amount of power. I mean some significant fraction (e.g. 1/4, 1/2, 3/4) of that 1000 watt rating for the motor, and that power has to come from somewhere.

On the other hand, if all you want to do is watch the shaft of the motor spin, with no mechanical load... I think you could accomplish that just by connecting this motor directly to your 12 volt battery. Obviously, the motor will not spin as fast as it would connected to its full rated voltage, of 48 volts. Also obviously, the power draw, in amperes, multiplied by roughly 12 volts, should not be too bad, much much less than 1000 watts, if the motor is just spinning, but not connected to anything; i.e. only losing power to friction in the motor, and ohmic losses (i.e. I^2*R heating the windings by pushing current through them.)

But like I said at the beginning, you did not mention what thing you wanted to put in motion, or how fast you want it to move.

In the event you actually want to throughput something close to the motor's rated power, of 1000 watts, you know, that would be close to 20 A, at 48 V. Or 80 A at 12 V.

Power converters exist, in all shapes and sizes... but the cost, and mass, of these tends to scale with the amount of power throughput. By that I mean it is not unreasonable to expect a 1000 watt rated power converter to cost 10 times as much as a 100 watt rated one, and also to mass (or weigh) 10 times as much.

In fact, it might be the case that a power converter capable of boosting 12 V to 48 V, with 1000 watts of power throughput, will cost more than the cost of 4 of your 12 V battery. I mean putting 4, 12 V batteries in series, to make a 48 V battery, presumably one that can comfortably supply approximately 20 A of current, in the case when that motor is really loaded at its maximum, of approximately (20 A)*(48 V) = 960 W ~= 1000 watts.