Building a wind generator from a fan blade and car alternator is a great way to reuse household discards while using renewable resources to create electricity. Building a wind generator -- outside of the electrical wiring, for which you should consult an experienced electrician -- is a fairly simple process. Using a car alternator as the motor, however, complicates the process since car alternators generally produce power in response to a very high RPM, and wind generators, in general, do not produce a high RPM, but you can modify your alternator to make it suitable as a generator motor.
Unwind the heavy metal coils from the alternator and replace them with thin electrical wiring. The electrical wiring makes it possible for your alternator to produce power at a relatively low RPM.
Put on your safety glasses and remove the mounting screws from the regulator with 1/4-inch ratchet and socket. Remove the voltage regulator from the alternator and replace the screws. This will prevent the alternator from completely stopping the flow of charge down to your battery bank should the alternator produce too much current.
Drill holes in your fan blades, and use bolts to attach the fan blades to the rotor. Use bolts to attach your rotor to your alternator. Mount the blades, rotor and alternator on a wooden platform large enough to house all three.
Wire your alternator to a blocking diode using 12-gauge AWG cable. The blocking diode prevents charge from flowing out of the battery bank and back to your alternator if the alternator is not producing current.
Wire the blocking diode to the charge controller using 12-gauge AWG cable. The charge controller should be configured, according to manufacturer's specifications, for the amount of voltage current that you anticipate that your alternator will produce.
Wire the charge controller to a dump load. The dump load gets rid of any excess current that the alternator may produce by releasing it in the form of heat, thus preventing damage to the battery bank.
Wire the charge controller to the junction box of the battery bank, with 12-gauge AWG cable. Connect the positive and negative terminals of the charge controller to the positive and negative terminals that you will see on the junction box.
Wire the batteries in the battery bank together, using 8-gauge AWG cable. Connect the positive terminal of each battery to the negative terminal of the battery next to it, until all but two terminals (on two different batteries) are wired together in a series.
Connect the remaining two terminals of batteries in the battery bank to the AC inverter with 12-gauge AWG cable.
Consult an experienced electrician before wiring this circuit. Faulty electrical circuits can cause electrical shock and even death. Always wear safety goggles while removing the alternator. The screws located adjacent to the regulator can bounce off, causing damage to your eyes.