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dc generator

majorkuso

I want to use a dc motor to charge a cellphone, how would I choose an off the shelf dc motor to use as the generator? I am looking at something like this  https://www.amazon.com/2-5KG-Micro-Speed-Reducing-Motor/dp/B009AQLDSS/ref=pd_day0_469_2?ie=UTF8&psc=1&refRID=K49X1E2DXFR58MMTJ742. I am assuming if I can match the rpm it should be close to the running specs? I would like a similar current but higher voltage to step down to 5 volts, however I am think a buck/boost converter would be adequate?

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  • in reply to majorkuso

    Hi James,

    It is a matter of conservation of energy. You can not get more power out than is put into the system. In most cases like this one you will get a lot less out than is put in due to heat losses. If you multiply the voltage by the current (in Amps) you will have a number for the power in Watts. Any process that would increase the current will correspondingly lower the voltage. For example the power of 7 volts at 2 amps is equivalent to the power of 2 volts at 7 amps. In a system where you are wanting to charge a battery however it is necessary to have a voltage level that is above the voltage of the battery so that current can be made to flow back into the battery. The only way to get more current in your situation will be to put more power into the system by spinning your generator faster.

    John