Originally Posted by
Redhatter
Sounds like a plan for a back-up but what powers the light when you stop? Last bike I had (rim-mounted) dynamo lights on you had to get about 20km/hr to see anything with them and lacked any sort of battery to keep them lit when you stopped.
You get full power somewhere around 10-15 km/hr and most lights in the USD60 price bracket come with a standlight feature that uses a built in capacitator. The standlight will not provide as much light, and will only burn for a limited period of time (several minutes).
--J