this is my first time posting here also I'm very new to electrical engineering. i am building a pull cord (like a lawn mower) human powered generator and I'm looking for ways to increase the current output.

since i want the device to be as small and portable as possible i had originally bought a basic gimbal motor that is generally used for drone and thought i would turn it into a generator.

i bought the motor that had the lowest kv rating (31), since thats how many rpms it would makes per volt. i figured if i reverse that and treat it as a generator then i would be able to get a high power output at low rpms. i thought since p=iv then if i have a high voltage reading then the current wouldn't be an issue.

however although i was able to get a modest voltage reading (around 30 volts per pull) i didn't take into account that most of that would be lost to heat as i go and charge a pair of lipos. what i need is a way to increase the current so i can charge the batteries faster. I'm thinking maybe if i can increase the torque that would help. I'm trying to be able to charge the batteries as fast as possible, even if it requires more work.

is there a way to increase the current of a generator? or are there already of the shelf motors that have high current? what if i charge ultra capacitors from the generator instead? i know they can charge faster so will they increase the current?

i am very new to all of this. anything helps!!! :)

thanks, ita

  • 1
    \$\begingroup\$ What voltage and current are you actually looking for? Your question is a bit vague. And have you thought about using a car alternator? They are designed for charging batteries. \$\endgroup\$
    – F. Bloggs
    Jul 9 '15 at 15:27

Please realize that:

Power = Voltage x Current

So the actual value of the current does not matter !

Hmm, OK, but I still want more current !

Well then, do you have enough voltage ? You mention 30 V, what is the voltage of the battery you're trying to charge ? As long as it is lower than 30V we're OK. You can use an electronic device called a DCDC converter to convert that 30V and too low current into a lower voltage and a proportionally higher current ! This is such a device: DCDC Downconverter module

I would advise to also use some kind of charge control unit since Lithium based batteries are a bit picky concerning charging and especially overcharging.

Probably there are also modules that can do both (lower voltage and increase current, charge control) in one but these are a bit harder to find.

So: keep the motor as-is but use some electronics to connect the generator to the batteries

Hope this helps.

  • \$\begingroup\$ He needs to also use a 3-phase Shottky rectifier with smoothing capacitor before going to a buck module. \$\endgroup\$ Nov 13 '17 at 16:26

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