I'm a high school physics student, so keep my limited knowledge in mind. Basically the other day I had the idea to create a charger for my iPod that's powered by a windmill, which I could attach to the outside of my car. I've never actually built a windmill before, but I'm pretty confident I can get one working. What I don't know, however, is whether I can charge my battery with the AC current the windmill will produce. Can you charge a battery with AC, or does it have to be DC? I'm sure there's also other potential problems that I haven't thought of, but I thought it was a cool idea so I decided to look into it. Is something like this even possible?