Here's a note that some people are not aware of. An automotive alternator cannot charge a totally dead battery. Why? The term alternator means exactly what it suggests. It produces alternating current, which is converted to DC current through a half wave rectifier mounted inside the casing. It is in essence an induction alternator and requires the field to be energized before it can produce usable current. For this reason when used in a storage type application you must maintain one battery that will not be drained. This is paramount when wind conditions are so slack that no current is produced for a period long enough to drain all of your storage reserves. It's the same principal as saving water to prime the pump.
Offered by Jay.
Jay made a good point about a auto alternator not being able to charge a dead battery
because of no energy being available to power the field coil of the alternator. I had
considered this fact years ago and then it occurred to me you could use a secondary
generator (i.e., a P.M. motor ) attached to the drive shaft to energize the field only. You
would only use a size of motor capable of generating enough power to energize the field
and not much more.
Another idea I had to deal with this is to take the spool of wire in the ( rotor ) field and remove it, have a machinist turn a copy of the spool out ferrous metal ( I think it is aluminum ) and magnetize it with a large number of coils of magnet wire wrapped around it connected to a battery of 1.5 to 3 volts. Leave it connected long enough to make it magnetic when you remove the battery. Then you would of course remove the coiled wire and install in the center of the field rotor of the alternator. Now you would have a permanent magnet alternator.
Another solution I thought of that seems to be worth mentioning for comments is this: one of the early versions of electrical lights on a model T Ford was an arrangement of "V" shaped bar magnets all around the perimeter of the engines flywheel. They were attached to the flywheel with one bolt and a couple of washers so the ends of the magnets were at the edge of the flywheel. I know because I removed some of the magnets when I was a child and I wanted a magnet for science class at school. My Dad gave me a couple of wrenches and pointed me to the flywheel. "take them off and you can have all of them". Well they had one coil of magnet wire wrapped on a bolt that served as a "pickup coil". This is also similiar to the flywheel and pickup coil used as ignition of the Briggs engines. So it would be a simple matter in my mind to attach about 8 magnets to the perimeter of the wood disk of our cobbled up windgenerator and wrap some magnet wire around a couple of bolts through a slice of angle iron as a support mounted to the base board and arranged so the magnets pass very close to the pickup coils at 180 degrees to each other and wired in series and then to our controller. Oh, yes, the main drawback on the alternator lights was no one had come up with a regulator to control it and invariably the driver would over rev the engine with the lights on and burn out every light bulb in the car. Had to keep lots of spare bulbs around in the car.
Offered by Darrell.
I have been thinking about using a brake drum off a old large car or truck. I have collected some of the new thin really strong type niobium magnet. One could epoxy these to the inside of the break drum. The magnetic field and centrifugal force of the rotating drum will almost hold them in place without the epoxy. Reverse the north-south direction for adjacent magnets and space them apart. Next one would mount coils near the magnets but fixed on the drum backing plate so as to not turn with the drum or touch the magnets. The coils could be wound special or use two old transformers cut in half. Both half's with it's coil still around the iron core would be used and the 4 half's spaced around the inside of the perimeter of the break drum. If two step up transformers were cut in half then one would have two pare of similar windings that could be connected in parallel or series depending on the final voltage needed. One would end up with 2 different voltages and current ratings. One for each pair of transformer sides.
Offered by Mike.
I think the brake drum design has a lot of possibilities, and is worth testing. I would wind the pickup coils on bolts and make them as large as possible ( size of wire diameter and the number of windings too ) and the same as each other, wire them in series and at 180 degrees from each other. About the spool that holds the field coil in the auto alternators - I think it is aluminum so when the regulator cuts current to the field coils there would be no residual magnetism in the spool as that would interfere with control of the circuit. I may be wrong, but I believe that is the way it was explained years ago. Also there is a transformer that is variable called an autotransformer. It has a large knob in the center and you can adjust the output up and down manually. Something to keep in mind. Radio Shack used to sell them but I haven't noticed lately if they still do.
Offered by Darrell.