gary, i found out that a 12v 35watt halogen actually last quite a while with a small (racing) car battery (check some recent pics on FB). I probably had it on for at least 2 hours last night.
I need to do some measurements of my light, but I'll likely be ordering a 5 wat, 460 lumen LED for a replacement. Then hopefully get a smaller, maybe 4ah 12v battery
Drew that sounds like a good idea. If you buy a 5w led not set up for cars you can run them on 3 0r 4 Nmh 2500ma cells with a resistor or a small buck boost regulator my dual 3w runs about 2hrs on the 4 AA cells . in Nebraska now will be in Denver later today.
Gary Ross
c 630-797-6330