Making a wind turbine to charge a 12v battery

Tell us more about it. Type of motor, permanent magnet or field coils, how much friction

NT

Try

Hugh Piggott is one of the few people in the UK who talk sense about wind turbines.

Isn't any car alternator the obvious choice, since it already includes the regulator for a car battery?

Newshound wrote in news: snipped-for-privacy@mid.individual.net:

I vaguely recal reading that I'd neet to do some gearing to get the alternator to turn at a useful speed.

However, I already have an electric bike hub, so I hope it will suit, with no gearing.

Al

Peter Parry wrote in news: snipped-for-privacy@4ax.com:

Thanks for the lead. I've signed up for his site's forum, but it takes a while to get (manually) accepted and authorised.

Al

NT wrote in news:0e8a3cb1-d51b-433f-b97f- snipped-for-privacy@n12g2000yqh.googlegroups.com:

I wish I knew. The hub is off a Eurobike and was made in China. It is probably more than 5 years old, as the bike used gel-cell batteries, unlike the new generation of bikes which uses li-ion I think.

I guess I should get hold of a volt meter and connect it to the hub, and give it a manual spin...?

Al

that and the power wasted by the field coils

NT

Neither of these are ideal, but they're worth a go at it. The recommendation for Hugh Piggott is a good one, although there are a few websites out there that offer most of the same content.

A microlight propeller is intended for a rather higher airspeed than most winds. This will give a wind turbine that doesn't start in light winds. An effective turbine (for houses in the UK) is one that turns on the most days in the year, not the one that can extract the most power from a rare hurricane. Still, it's hard to make propellers otherwise, so this is a good start.

The electric bike motor might work, depending on how it's made. Quite a good start (for small sizes) is a brushless (BLDC) motor for radio control model aircraft. These use rare earth magnets and a polyphase stator: effectively a simple 3-phase AC motor, which is why they need a complex controller that is mostly a DC-AC inverter. The electric bike suitability depends on what type of motor it is - a DC motor (usually mounted on the bottom bracket) is not so good. A brushless motor, usually a hub, is a better deal. These are designed to run at slower shaft speeds (150-200 rpm) so they use multi-pole rotors (ring magnets). This encourages easier coupling to a wind turbine.

Electrically, the easiest way is to run them as an AC permanent magnet alternator, strictly a magneto. With a 6 diode bridge rectifier you can convert this to DC (car alternator is one source, but 3 diode pairs is usually cheapest). A wide input DC-DC converter (a module from China, via eBay) is then probably your easiest way to use this for battery charging.

I wouldn't use a car alternator on a wind turbine. They're too powerful by design, so you're working them in an under-power low- efficiency region. The design needs a battery power source to drive the field and they're just far too inefficient for wind generation - it's not important for a car, but a wind turbine might use all of its potential output just energizing the field. They also need a higher shaft speed (300 - 2000 rpm) so they're going to need a mechanical gearing from your turbine.

How much friction? !!!

innews: snipped-for-privacy@mid.individual.net:

yeah - throw them out and stick in some neodymium magnets! Piece of cake.

yes, some motors have a lot of it

ividual.net:

And youre going to get magnets of exactly the right geometry how?

Pretty easy on a car alternator. These use claw pole rotors, so you only need one big magnet stuck in the middle (probably a ring of little ones) and you preserve the original pole pieces. Matching the geometry is just a matter of a close-fitting iron shim, from scrap alternator pole laminations (it needs to take the rotation speed too), you don't have to make anything complicated.

Not so. They're horribly inefficient at converting the sort of energy you can get from an average wind. They are designed to work at perhaps twice crankshaft speed, and to produce maximum output (and efficiency) at around

harry wrote in news:91845333-7683-4b9a-8613- snipped-for-privacy@z7g2000vbp.googlegroups.com:

Thanks. I am right next to the sea in a very exposed location, so we do get a lot of wind. Yes, the direction thing is, for me, the easy bit. It's the electrical side of it that I find mind-boggling. I'm more mechanical than electrical!

Al

Andy Dingley wrote in news:7010afc3-97c8-4b99- snipped-for-privacy@hr10g2000vbb.googlegroups.com:

Yes - that was my conclusion too. I expect this will be my "Mark I"; at least it'll give me a starting point from which to build a better "Mark II" at some point, if "Mark I" proves problematic.

Thank you for the input. I assume it is a DC motor, and I think it has brushes. I was hoping that I could simply wire the hub directly to a 12v battery. However, come to think of it, it couldn't be that simple, because if I did that, the battery would want to turn the hub, thereby draining its own power...

I will find a volt meter and see if I get a reading when I spin the hub. Al

Andy Dingley wrote in news:7010afc3-97c8-4b99- snipped-for-privacy@hr10g2000vbb.googlegroups.com:

I put a volt meter accross the hub and gave it a spin. I get no reading at all. I was surprised to find that the hub only turns one way. I can hear something like a ratchet inside, which sounds like it is designed to prevent it from turning in a reverse direction...

Does this mean I'm flogging a dead horse with this hub?

Al

Go to hobby city and get the lowest KV RC flight motor you can.

You wont get more than a few hundred RPM out of it, so it is probably not OK to use a car alternator setup.