DCPM Motor for a Wind Generator

Volts/RPM for DCPM motors is fairly linear and your voltage calculation is ballpark correct.

thanks, I have ordered the motor

You'll need a little more than 12 VDC to charge battery, and you'll also need a method to control the RPM of the wind generator. Or, you'll need a wide-range voltage controller so that it doesn't blow up the battery should the generator get out of control and spin up to, say, 1000 RPM.

Now all you have to do is figure out a way to regulate the wind so that this motor doesn't spin faster than 150 RPM and boil the electrolytes out by applying more than 16V to a 12V battery.

I wonder how automotive alternators charge a battery?

You use what is called a charge controller which manages the batteries charge and dumping off the excess to another load once the batteries are fully charged. That load can be anything from another bank of batteries, to a dummy resistor load, or some kind of appliance.

Suggest you look at the forum:

http://www.fieldlines.com

It's run by a group of very experienced DIY'ers. VERY experienced. These guys have wind turbine design, construction and operation down. Read through their forum. They have lots of advice for newbs, lots of stories, examples and suggestions.

...AND it's almost as much fun as reading the CR4 forum!

A more satisfactory solution would be to use a motor from a Fisher & PayKal washing machine - ac so that speed does not need to be controlled, use a transformer to drop voltage then a bridge rectifier to give you 12 volts DC

The voltage out would be 12 Volts as you say.

The voltage required to charge the battery will be higher than 12V. eg you require about 14V input to charge at around 10A to 15A, depending on the state of the battery. More input volts, more amps charge.

Remember though that the current available from the motor remains the same. You are limited by the gauge of wire used in the motor.

If you ran the motor at 3500 rpm the current would be the same, but the voltage doubled, so the power out would be doubled.

Paddy, totally correct and GA from me.

The output voltage of the DC motor will be 12 or 14 volt depending on the windspeed, but the total output power of the DC motor will be far to small.

If one needs 10 Ampères to load a battery and the nominal motor voltage is 180 VDC, this means the motor has to have an output power from at least 180 x 10 /0.95 = 1895 Watt or +/- 2.5 Hp at the motorshaft. When spinning at 1750 RPM, this is not a very small motor (IEC size 100 or 112 ?)

If the motor shaft power is far much smaller, it will take a long time to load your batteries.

GA!

I do agree that a brushless motor would be best, but these motors are a lot harder to find. At least ones tat would fare well in this type of application. The motor that I have is a brushed DC motor though. Look at a car alternator. It is used as a form of generator, and it uses brushes that are fixed in regards to rotation.

The motor that I am getting is a totally enclosed non ventilated motor. There should be little to no way for water to get in if it were to get soaked in the rain.

The bearings in the motor are ball bearings which should be able to handle a small axial load and I am only guessing, but if I design the blades well enough that should only be a few pounds. The axial load should only be a noticeable factor in a higher wind. If I did find it to be a problem though, I could retrofit some sort of axial load bearing at the rear end of the shaft to help take some of the stress.

A car generator is really today an alternator. The brushes are ONLY there to supply DC to the rotor coil to allow output voltage control, via slip rings (not a commutator!). AC is taken off via diodes from the stator fields and is therefore rectified before being supplied to the vehicle as DC.

On a DC motor or generator, it is very very important that the brushes on the commutator are specifically aligned in a "null" position to take off the voltage developed (or supplied in the case of a motor!) with the least amount of sparking. Sparking heats up the commutator and slowly destroys the brushes at the same time....

Car Alternators are so built that cooling air (and rain!) can pass through to keep things cool......without damaging anything!!!

Generally speaking, ball bearings, unless SPECIFICALLY designed for axial loads, do not handle them well or for long. So it might be a great idea to identify the exact size of the bearings and see if you can replace them with same size, but with a good axial thrust quality.....at least you need to get the part number off the bearing and check whether its already got a "legal" axial load specification....but as these are generally several times more expensive than normal ball bearings, you will find that to be true very very seldom......

You are probably better off using a drive belt or gears to stop axial loads being transmitted to the ball bearings.....that way you can also "change gears" to get the rotation speed correct.....

Also, you will have to be careful with a PM motor used as a generator as the polarity changes with the direction of rotation....could cause some fireworks if you do not correctly cater for that!!!