What you want to look for is a surplus permanent magnet DC motor and pay attention to the RPM, shaft size, amps and voltage.
You need to look for a DC motor with a LOW RPM rating. The reason for this is because when we use a DC
motor as a generator it must spin much faster then the rated RPM to produce the rated voltage. Your goal is to obtain a DC motor with HIGH voltage (over 12v), HIGH current and LOW RPM rating.
An ideal motor would be one rated under 400 RPM at 30 volts. When this is used as a wind generator you could expect 12v at a low RPM.
If you do not have strong winds then you need a motor with a very low RPM rating. Obviously though, strong winds are the key to high generator output.
Below is a picture of a DC motor that we found on ebay for just $35!
A good DC motor that you can find quite easily from ebay is the 1150 RPM 38 VDC Ametek motor. These motors will produce about 13 volts at about 390 RPM. Perfect for a homemade wind generator. These motors cost about $50 and you can see a picture of it in the below ebay ad.
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