I've started building a wind generator. I've crafted myself 2 wooden blades for testing. Blades are 55cm long and at the base 10cm wide. Weighs about 300 grams including centre hub. I've found a source (windynation) stating that, with blades of that size, a 10mph wind could spin the blades at 400ish rpm under load (max 500watt).

Now I have this electric scooter engine, 24v DC, 150 watts, 2500rpm. It would be nice to get 80 watts into my 24v battery system. I have a 1/5 gearing ratio with the belt from the scooter to the wheel, so getting the rpm's shouldn't be that much of a problem.

My issue is : how to regulate the voltage for battery charging? I get the dump loads(preventing free spinning generator). But I often see just the generator connected to the batteries with a simple diode.The generators voltage will be pulled down to that of the battery, so that's ok as long as you have overcharge protection. My generator outputs 3-26v, and I need 28v to charge the batteries, I'll need a step up converter that's capable of efficiently converting a variable input voltage to 28v. I could use an arduino for pwm, use that to drive the boost converter to a stable 27,4v output voltage.
Or: don't mind the pwm modifcation, just boost the signal high enough (+27v) that it'll charge the batteries. My gut says it's not the best idea to feed higher charging voltages than necessary into a battery, but then they're lead acid, so they can take a beating.

 

Does the scooter motor have permanent magnets to create the field? Most simple motors do.
In that case it is not easy to regulate the output voltage. There are two ways:

• Dump the excess power - early motorbikes used to have a huge zener diode to do this.
• Have a switching voltage regulator between the generator and load.

Bear in mind that an unloaded (or lightly) generator may produce a much higher output voltage than you expect. The switching regulator must be able to cope with this.

Some simple systems just assume the battery will get overcharged!