A really simple method to prevent battery overcharge is to take the positive lead from the genny and put a capacitor across it to receive the charge. The larger the capacitor the better.
Connect the negative from the cap to battery negative. From the cap positive connect two heavy rectifiers, one going to battery positive and the other remaining free.
Connect the second rectifier in series with an SCR and a resistive load, like a few bulbs or heating elements in parallel.
Decide what the peak charge voltage on your battery should be, then get a zener diode for that voltage and put it between the cap positive and the gate on the SCR.
When the capacitor voltage rises beyond that zener voltage (meaning the battery is charged enough), the zener allows the SCR gate to turn on and stay on as long as the generator is providing enough current. All this excess will discharge through the load that's in series with the SCR.
If the wind dies down and power generation stops, the SCR shuts off. The next time the wind starts up, it will push the battery voltage back up and the SCR will turn on again to protect the battery.
That adds up to 1 big capacitor, 2 diodes, 1 zener, 1 SCR, and 1 resistive load.