Originally Posted by
noglider
I don't think so. The dynamo makes A/C, and the lights expect that. A battery provides DC and expect it on input, too.
LEDs require DC input.
It is easy to convert from AC to DC with a bridge rectifier, and perhaps some capacitors.
Going from DC to AC can be done in a number of ways. I believe high frequency is also used to regulate power.
Many of the more advanced headlights should already have some provision for stopping, and low voltage, thus using either batteries or capacitors.