Thanks to all who helped me with my previous question on halogen bulbs!

Here's the next one: What is the voltage-limiting or power-limiting requirement, based on how voltage that is greater than 6.0 volts degrades the life of the bulb? Clearly 12 volts is too much.

Has anyone looked at the voltage limiters on some existing halogen headlamps? I would, if I had one.

I'm thinking about using a halogen lamp with a bottle generator.