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Small generator from motor

Tinker Unique

Dec 1, 2014
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Dec 1, 2014
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Have been looking for the "rework needed" to get a small 12v (or less) electric motor and turning it into a generator. In the past, the starter motor on "old-time cars", were ALSO the generator after the motor has been started and running. I would like to get a small motor and turn it into a 12v. trickle charger. I can build an ammeter-style turbine and connect it to a reduction gear-drive to a small motor, and wire it up to a battery. WHAT mods are needed, if any ??? Could be used to charge a 12v battery while fishing in a small boat and using the other battery for trolling. When the battery runs down, come back to the vehicle and change batteries, continue fishing.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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25,510
Explain again what you want to do...

Is it that you want to use one battery to power a motor, which turns a generator, which charges another battery?

If so, you are better off using the first battery to charge the second, or even better, just use the first battery.
 

Tinker Unique

Dec 1, 2014
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Dec 1, 2014
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What I want to build = A small generator powered by a small wind-driven turbine (annometer-style) 3 arms with "cups" on each arm rotating in the wind - gear driven to a small motor/generator. When fishing with a small boat and an electric trolling motor, the "generator" will charge a back-up battery to be changed out when the first battery is discharged. The batteries can be exchanged, and fishing / putting around the lake can continue. The "turbine/generator" will be mounted on my vehicle in the parking lot near the boat ramp. The original post was asking about a small motor to be used as a generator, like used to be on some of the older cars. IF NOT, what else is needed ?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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25,510
You have to consider the practicality of this. If you are going to recharge a lead acid battery in the same time it takes to discharge then you need to provide more charge current than the discharge current (about 50% more for a lead acid battery).

Will a small anemometer powered generator be able to do this? I doubt it.

First question is how much power does the trolling motor draw? Do you know how many amps? Alternatively do you know the capacity of the battery in Ah and how long it takes the trolling motor to discharge it? You may know these figures off the top of your head, but this web site explains it quite clearly.

Now we know this, we can estimate the power we need to generate from the wind. Let's say the motor draws 15A. That means we need about 22A from the generator, that's about 280W. How big is a wind turbine capable of 280W? Here is a 300W turbine. It has a 1.5m diameter and is recommended to be mounted 6m above the ground, and requires wind at 12m/s (that's 43km/h).

Does that sound reasonable?
 

Tinker Unique

Dec 1, 2014
22
Joined
Dec 1, 2014
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What I had in mind is using a small 12v motor, and use it as a generator if possible. I can use an electric window motor, windshield wiper motor or a heater fan motor. IF the motor can also be used as a generator. OR, does it need to be re-wound or modified in some way. Light "research" says that a small hobby motor can be used as a generator. I can make a "transmission/gear set" and the body to house the fan/turbine, gears, and the generator. I got the idea years ago from a bicycle generator that spun on the rear tire. A 4" fan threaded to the shaft, made a small light illuminate, for my sons "fort". Two of them put out enough light for his friends to read books inside after dark, and power a small battery (removed) powered TV.
 

Bluejets

Oct 5, 2014
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DC motors used as generators need to run rather fast to get any sort of usable power from them.

Not much chop trying to "gear-up" as you'll find you won't get enough torque to start it moving let alone generate.
 
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