Car alternators use spinning electromagnets in the armature to induce current into the coils of the stator and charge your car's battery and/or run your headlights, etc. Your car's voltage regulator is designed to change how much power it puts into the alternator's electromagnets and thus change how powerful the magnetic field is, and therefore how much power it generates. When your car is using lots of power, the voltage regulator increases the power to the magnjetic field and the alternator loads up and makes more power. When the battery is full, the voltage regulator reduces power to the electromagnets, letting the alternator spin more freely and make less power.
With any kind of wind turbine, when the batteries get full during a windstorm, you MUST keep the wind turbine loaded up--otherwise it will freewheel, overspeed and blow up. A car voltage regulator would perform the opposite function...it unloads the alternator when the batteries fill.
With a permanent magnet alternator, your battery bank is an integral part of the electrical circuit and regulates the voltage on it's own -- UNTIL the batteries get full. At that point you need to divert power to a Dump Load.
See these FAQs for "How do I regulate my windmill?" for more details on regulation, dump loads, shunt regulators, etc.
Good voltage regulator discussion here:
http://www.fieldlines.com/story/2003/7/18/8715/42490
