Raymond, that might be looming in the future... but as it is I am fairly happy with the amount of light and the beam pattern of the 6V/10W. So I am going to see this upgrade through first.

I taped my battery together enough to do a test burn yesterday. With 5 (nominally) 1,2V AA batteries wired in series I got close to 70 minutes of burn time, which would be ok. What surprised me was that fresh from the charger the five cells produced a tad over 7V. I had originally planned to run 6 AAs, but apparently that would take the voltage close to 8,5V. From what I've read, running a 6V bulb at 7,2V is ok. But over 8V - I dunno.

How much do y'all overvolt your halogens and have you actually checked the voltage you get from your power source?

--J