MikeyMK

The wattage is fine (unless your headlight is mental), the volts are more likely the problem. If it kicks out 6v then that'll satisfy most pairs of lights.

You may want to wire it up via a rechargeable battery pack, so that the lights stay on when the wheel stops. If one of the lights takes a battery (often 3x AAA front or 2x AAA rear) then simply use rechargeable ones and include them on the circuit. The hub will keep them charged.

fietsbob

Remember Modern hub dynamos put out AC, the headlights for them have rectifiers and over power protection..

so the additional parts made to trickle charge your phones do a similar conversion , to put out USB regulated standard DC.

Tourist in MSN

That would be really complicated. Dynohub powered lights are available with a "stand light" option for a couple bucks more that have a big capacitor to keep lights lit while stopped at stop lights, etc. Headlamp stand light usually is not lit bright enough to see any great distance but is more than bright enough to be seen by other drivers and bright enough so that you can start out from a standing stop to see where you are going.

MikeyMK

There are two types of lights really, aren't there - see and be seen. Tail lamps only need to be the latter, and as you say, a capacitor is occasionally supplied in a non-battery version for such events.

For a proper headlight you really want a Cree diode, this can use a couple of watts, and such a light is often specified with a battery tray. As long as the voltage is close, it's absolutely fine to include this if wiring to a hub and use rechargeable batteries. I'd agree you're better off buying one that already has suitable reserve on board, though.

I have one that runs happily on 6v, 7.4v, 8.4v and 12v battery packs. It's a pretty blinding Cree L2 the supplier comically claims to be 30w... and yet runs on 2x18650s...
I should add i don't run a dyno. I'm working on a 48v headlight that'll benefit from the e-bike's regeneration, though.