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electric motor/generator question

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Mikdsmi

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I have a small DC electric motor that I salvaged from a weedeater. I would like to use it for a generator/alternator on my riding lawnmower so I can run better lights. I can spin it in a drill and it will produce at least 50 volts but not enough current. Is there a way to regulate the 50 or so volts down to say 12 and get more current say 10 amps or so?
 
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You could use a switching regulator, but it still likely won't give that much power. What is the motor current at 50V?

15 to 20 amps is a lot of power. Are you trying to illuminate your whole yard?
 
I'm with crut, are you sure you know what you want to do here? That's four to eight times the power of the average car headlight illumination system. You would literally blind anyone within 10 feet.
 
Thanks. I guess your right. I changed my post to read 10 amps. I just want to be able to run 2 auto headlights. I dont know what the current is at 50 v because my meter doesnt measure current but the motor data plate read 2.8 amps.
 
I would think car headlights would run on AC current just fine, just connect a transformer from the alternator before the bridge rectifier,
 
Do you have 4 lights on the mower?

If so, put them in series and turn the motor in the drill. See how bright they shine.
 
Colins idea of putting four in series is a good one, but the brightness is going to be all over the place.
 
Just guessing but most likely the weed eater motor originally ran at around 4000 - 5000 RPM off of a rectified 120 VAC source. Being that most power drills are 2200 RPM or less and you are getting 50 volts at at that speed your best bet would be to spin it faster and just use standard 120 volt lights instead.

Just dont go past the motors rated working amps and you should be fine. A little experimenting with load and drive speed will be needed though. At full load it may need to spin considerably faster than it did as a motor to produce 120 volts DC with a 2.8 amp load.

Also a pair of 100 - 150 watt halogen flood lights would work very well as lawn mower headlights and would spread out the light much better than automotive type bulbs would.
 
What was the DC voltage and current the weed eater ran at?

The voltage output as a generator will depend on load and rotational speed. You can measure short circuit current and open circuit voltage. Limitation on current is wire sized used in motor. Pretty save to run generator up to current the original motor drew with weed eater mechanical load.
 
If you have 4 lamps of the same wattage, they can be put in series. But this is not a very practical answer.
120v lamps will not take the shock of a lawn mower.
I think the best idea is to get a $40.00 100watt inverter and charge the 12v battery in the mower
or buy a 12v alternator from the wreckers.
 
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Then why did you suggest it colin??
You'll lose 15% or so of the power using an inverter right off the line, and the alternator itself can't handle the load in the first place so you can't just tack on a battery, as it would have to be charged offline. The alternator has to be replaced or as the poster is trying to find a solution for right now a motor needs to be attached to a power take off to drive the lights.
 
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