Eraser, your battery bank is the "regulator". Any voltage over the battery voltage becomes amps into your battery bank. In a perfect situation, all voltage would become amps, but in the real world losses (heating in the stator) burn off drastic ammounts of potential power.
If you buy one of these units, then build Dan B's 10 footer (for a 12 volt system), or Hugh's 8 or 9 footer, you will see that the real power is in increasing blade diameter (more avalible watts per mph). Most people see low average windspeeds, and harvesting the most power between 7 to 15 mph seems the most usefull way to charge a system throughout the year. Both Dan's, and Hugh's systems furl, or turn partly out of the wind to survive high storm winds while charging. Ed at windstuff now has a kit for do it yourselfers to build. Many options are available, just don't expect to see 800 watts into your batteries often from the genset you posted or you may be very disapointed. Not worth 2 cents, hopefully someone with one of these units will chime in with what actual preformance they get... Gary D.