# Harnessing wind energy w/ DC motor?

Before I begin, FYI, my skill level is I can make a few LED's blink. (So please... Simple is helpful)

I am trying to work on a project that when a DC motor is turned by hand or wind, it sends the power to charge a 9V rechargeable battery, is this even possible? if so, how would I do it besides directly hooking up the charger to the DC motor leads. Any Questions? -Thanks-

Totally depends on the DC motor. Some specs would help.

Yes, need more info on the motor type.

But in theory yes, you can certainly generate power this way.

The eventual complexity of the circuit will likely correlate to the efficiency of the power generation. I don't see an Arduino involved until you're at the very 'academic exercise in complexity' end of the spectrum.

You need RPM. Speed is what makes voltage. All DC motors will have a parameter called RPM per volt, which in your case is volts per RPM. If the motor shaft is not turning fast enough then it won't make enough voltage to exceed the battery voltage and push power back into the battery. Voltage boosters can be used to play with this and control the charge but your usual small 6,000RPM motor needs 6,000RPM to be a generator.

Hi, If you look at the hand powered torches that are around now, they use a gearbox to get the motor/generator to get the speed required to produce the energy required to do any charging.

http://en.wikipedia.org/wiki/Mechanically_powered_flashlight

Tom.... :)

the process is rather simple. you spin the device, it makes voltage. you have to produce more voltage than the thing you want to charge.

your choices are also pretty basic. spin faster make electronic circuit that boosts the voltage, be careful that a higher speed does not produce voltage that will damaged things.

make a gearbox to use the slower speed of the propeller to spin the motor faster.

spin a the right speed and all is good. too slow and no charging. too-too fast and it could damage things.

as for using the arduino, you could add that with a voltage monitor and show the voltage, rpm, all sorts of neat things.

Maybe I have my terms wrong but wouldn't the battery provide a back EMF that the current from the motor/applied would also have to overcome ?

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1:1: Maybe I have my terms wrong but wouldn't the battery provide a back EMF that the current from the motor/applied would also have to overcome ?

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Correct. All battery chargers have to produce a voltage greater than the battery, so current will flow into the battery, charging it.

That is why you need a control circuit of some kind to not allow the battery to discharge into the charger(your motor). It may be a single diode with proper voltage and current ratings will work for you.

A charge controller will also allow the charging current from your motor to switch from charging to warming a resistor when the battery is completely charged.

Paul

Unless you are conscious of how inefficient a small propeller and small motor are you will be very disappointed.

If you actually want to charge a battery solar panels would be better.

"Real" wind generators have propellers that are 10m or more in diameter and are rated in 10s and 100s of kW to get to a scale where the economics make sense.

...R