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Golf cart generator/starter

Friday, August 1st, 2008

Jeff:

I have been researching DC motors to produce 12v @ 20+ amps at about 800 rpm. I see these golf cart generator/starter motors might work.

What do you know about these motors? Can they produce 20-25 amps 12v DC power and at what rpm’s. My application is to produce power from a turning engine 1-1/4″ shaft on a sailboat when sailing. I can produce about 800-900 rpm’s using a 6:1 pulley ratio shaft to motor at 6-7 knots.

Thanks,

J Regar

Sounds like you are trying to re-invent the wheel. Several companies make an off-the-shelf water turbine that is self-contained and you just drop in a fast moving stream or pull behind a boat to generate electricity.

Since the internal generator and propeller drive are designed to rotate at the correct RPM for the typical speed through the water you are talking about, you do not need pulleys, belts, or drives, and all battery charging controls are built-in. These units are light weight, small, and specifically designed for this application.

Check with any of the solar suppliers that advertise in the magazine.

Good Luck,

Jeff Yago

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Posted in Generator, Water turbine

Generator question

Monday, July 14th, 2008

Jeff,

I have a home with a year around stream running beside it. I am sure I would not be permitted to dam the channel, but I am wondering if I were to have a 3″ pipe with about 8′ of fall suspended in the flow, and a 1/2 hp deep well pump mounted on it and driven by the water flow, would it act as a generator? the lowest flow is probably about 10 gallons/sec.

Dave Mckee

Oregon

Dave:

You cannot make an AC well pump generate electrical power no matter how fast you run water through it. The reason would take me 4 pages to explain but its due to the basic theory of operation of any AC type motor. It is possible to cause a DC motor to generate electricity if you drive its shaft, but I really doubt you have a DC well pump since these are only used with battery and solar power systems. In addition, most modern pumps, regardless of AC or DC operation, use a magnetic shaft drive to allow sealing the pump section from the motor section, and I am not sure how well this magnetic drive will work in reverse.

Now for the good news – If I lived right next to any stream that flowed 10 gallons per second, you can bet I would have already purchased a water turbine generator. There are many manufacturers who make many different sizes and types of these generators. If your stream and land has lots of fall, most people extend the pipe upstream as far as possible to achieve any more flow, since a lower flow at a higher head pressure is usually more effective in generating power than a higher flow of a lower head pressure. Again, lots of technical reasons why this is so, but if your stream really is year round and you can extend a pipe to a higher upstream position you should do this.

Here are a few sources for more information:

www.backwoodssolar.com/

www.utilityfree.com/hydro/

Good luck!

Jeff Yago

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