treadmill motors for DIY windmill

[darenmiller]

I am tinkering around with treadmill motors, and was told thati would have to get them to spin really fast to create enough power to charge a 24v battery bank. however, I was not told how fast!
So I have a few questions I hope I can get real answers to:
(1.)how fast is fast?, 8:1ratio?;
(2.)can I take two treadmill motors and put them in series to achieve 24v at the head without frying them?

[Flux]

I am not an expert on these motors, but typical figures from ebay seem to indicate that they run at 4200 rpm with 180v dc.

As a generator with losses acting backwards you will have to spin at 5000 + to get 180 .  So 500rpm for 18v gives a cut in speed of near 700 rpm. Assuming one motor will just about handle a 6ft prop we need about 3:1 speed increase for a sensible tsr.

If you drive 2 motors together and connect them in series you halve the cut in speed. You gain this at the cost of an extra motor with no gain in current output. Unless the things have shafts at both ends to cascade them you have a messy drive arrangement. With a fast prop you may get away with direct drive with 2 motors in series.

Don't try 2 independent windmills connected in series, that doesn't work.

Flux

[darenmiller]

I would need to pull 26-30v to charge my battery bank out out the treadmill motors. That's why I was thinking an 8:1 ratio. For I live in northern Idaho where 5-20mph wind is common through the night, and 50+ is easy to.
I would like them just to help top the batteries off during the night.
Would them 5  hyperspin blade 28" from windy nation work for this that I'm planning on doing?

[Flux]

Not familiar with the blades so can't comment, others may be familiar with them. You will need some form of protection if you get winds up to 50mph.

You will need furling or some other protection.

Flux

[darenmiller]

Thank you for your time...

[gww]

Would a voltage doubler give any useful power from a motor like this?
gww

[Flux]

Voltage doublers don't work on dc, a boost converter would work but basically these are high speed motors and the slower you run them the less you can get out.

Flux

[gww]

flux
Thank you
gww

[darenmiller]

I think you guys took this in the wrong direction!
 I've been using these treadmill motor's, and their not bad for the buck spent. I get approximately 40 amp hrs. out of 8 hrs. of good wind on my 24v battery bank system.
I may not have made myself clear in the beginning...
 I'm talking about using two treadmill motor's on one 5blade system ("the pulley design I have works great") however... I'm asking before I hook up the two motor's, can I wire the wires coming out like neg. to pos. In series to pump up the power at less wind speeds?

[darenmiller]

I said it wrong to began with!

[joestue]

if you have the torque to spin both motors at low wind speeds, it will work.

[darenmiller]

Without frying the motor windings?

[joestue]

can't promise you that.

But you might try building a current or voltage, or rpm triggered series parallel switch.

--or just build another turbine with the second motor.

[darenmiller]

Thank you!

[Flux]

As long as both motors are driven mechanically at the same speed from a common drive you can connect them in series, yes plus of one to neg of the second. It will halve the cut in speed but the current rating is the same as for one motor, the current is common to both. You will burn them out if you try to take too much current so whether or not they burn out depends on your ability to control the blade output in high winds.

Previously you implied that you get significant high wind, with proper matching of speed and prop you may well exceed the rating of the motors without some furling scheme. With only one motor your blades may not run fast enough to burn a motor out but if properly matched you will have the same problem with one motor.

I would never try running any reasonably matched wind turbine in gale force winds without some form of power limiting. As I said previously you can lower the cut in speed with 2 motors but you don't gain any extra maximum output.

Flux