You can definitely do it, just bear in mind that you'll need to drop the voltage down to the appropriate level. This will vary depending on how many batteries you intend to charge at once (you could just wire them all in parallel keeping a constant voltage but reduced current). You can probably pick up a dedicated voltage regulator for this, or just use an easily sourced LM317 and some resistors to get you what you need. Chuck in a 4001 diode to prevent back feeding and you should be good to go.
This is a perfect application for small scale wind turbines.