I really want to like a dynamo solution, but for me it doesn't quite add up. The modded Philips light draws 7W, whereas I think dynamos are typically 3-5W. When I turn on my "main beam" light, the two together are drawing 22W, which is certainly out of reach of dynamos - and even if it wasn't, it's more than you'd want to pedal with. Obviously you don't *need* that much light, but it's fun Compared to my Li-Ion bottle battery, which isn't particularly heavy, recharges in a few hours, and will power the Philips light for 9 hours or so (or 13 if you ran it at 0.7A), the battery is much more practical.