Yes it will be at 'battery volts' when it reaches it's cut-in speed. Cut-In is the point at which your genny will start charging the battery, or the battery voltage. when your genny is producing less than battery voltage it will spin freely, but when it starts producing more voltage than the battery it will start being loaded since it will be charging the battery at that point. The voltage will not go up with an increase of RPMs after that, the voltage will be locked to the battery voltage after that, but the mechanical drag will increase and the Amps will start going up.
The battery will always try to keep the voltage going into it, at the voltage level of the battery itself. The battery will be sitting at 13 volts, and your Wind/Solar power will be 22 volts open circuit. As soon as you connect your open circuit Wind/Solar power to the battery, POOF ,everything is now running at 13 volts. It pretty much doesn't matter what voltage you want to charge the battery with, Your genny may be making 65 volts open, but connect it to the battery and then everything is at the battery voltage.
What happens to all that extra voltage? It's converted to amps and that is where you start to worry about your stator burning up. Once your wind genny reaches Cut-In (battery voltage) the measured volts will be the battery voltage which should be increasing slowly as it is charging. As your genny speeds up past cut-in the voltage doesn't increase, but the amps do. Under most circumstances you don't have to worry about the voltage of the device you are connecting to the battery, your worry will be with the ability of the charging device to deliver the Amps without burning up.
When Charging a battery try to keep the current going in to less then 10% of the capacity of the battery. For Example: a 100 amphour battery should be charging at 10 amps or less.
