I love the whole concept of generating your own power. I’ve recently taken possession of a Schmidt and a Shimano Nexus dynamo hub, both of which I got cheap and both of which work, which is a bonus.
I’m not going to profess any real knowledge of these devices, but I wanted to mention them, purely because they’re interesting and they mean you don’t need batteries, which are pretty nasty – this includes rechargeables. Have a look here, if you fancy reading all about the toxic terror that the battery is.
The only real drawback to the dynamo hub is a bit of wheel resistance, principally when the light is on. Having used the Nexus for a while, I’ve got to say the benefits far outweigh the drawbacks. The hub is silent, unlike the bottle dynamo and there’s no issue with slippage in the wet. Additionally, you can now also attach a Busch and Muller E-Werk to your hub dynamo and power far more than just your lights.
Anyway, for those of you who want to read about the resistance in the various dynamo hubs currently on the market, have a look here. Quite an interesting pdf, I think. And for those of you whose hearts already belong to Schmidt, have a look here, just to qualify what you already instinctively suspected…