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Discussion Starter · #1 ·
could anybody tell me what rpm a vw dynamo needs to spin to provide sufficiant charge to charge a 12v battery?

Im asking as im considering using one in a home made wind generator to charge a lesiure battery but i have doubts if the turbine would spin at enough rpm to drive the dynamo directly or if im going to have to use a gearing system to spin the dynamo faster.
 

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Instead of the Dynamo, consider an alternator (VW or otherwise).
Higher ouput units available and they can produce rated output
at lower RPM.

Either way, you are probably going to need some kind of gearing.
Aim for 1000 RPM or more.

There are many people engaged in DIY wind power.
GOOGLE about for lots of resources.

http://www.windstuffnow.com/main/
 

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It's about 1300-1500 rpm before the dynamo cuts in.

As Speedy Jim says, I would use an Alternator not only for the lower cut in speed but the Bug dynamo regulator is really inefficient and loses a lot of power through the resistance of the contacts etc etc.

I once considered building an electronic regulator but for the current it's a damn sight easier just to buy an alternator.
 

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Discussion Starter · #4 ·
I dont want to use an alternator as the magnetic field is generated by the electic from the generator /battery thus incurring more losses than a dynamo.

The reason for using a dynamo is the fact it uses permenant magnets.

I could use an alternator if i installed permenant magnets in it and rewound it with smaller gauge wire so the cut in point is at a lower rpm but im trying to not have to go to all that trouble.

If i can find a permenat magnet dc motor that normally operates around or just below 1000rpm when supplied with 12 volts then that would be an ideal bit of kit for use as a dc generator but so far ive not managed to find a motor of that spec.
 

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The VW Dynamo does not have a PM field. The field
is wound and draws a few Amps from the charging circuit.

Only wound-field machines (Dynamo or alternator)
can be easily regulated with small amps.
A PM machine would have to be regulated on the output (high amps)
side unless mechanical means were used to vary the field strength.
 
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