[cherrypicker]

I've used a power inverter in my car to charge things in the past. It should work well on a bike, but you need to remember to add up everything that running on your bike. The generators are relatively small (usually less than 500W). Headlights, ingition, taillight and instruments will eat up at least 200-250W. I'd leave 10% in reserve, so you're only left with 200W. Plenty to charge a few batteries, but add heated grips and vest and you might find your engine mysteriouly shutting off while riding.

Be sure also to add a fuse on the pistive side between the inverter and the battery if you decide to modify the normal cigarette lighter plug which has a fuse inside it.