Wow, must be the nimh pack's flatter discharge curve improving the runtime. The D cells should weigh around 5.5-6 ounces each, so 12 of them would be around 4.5 pounds, which should be a pound or so lighter than the SLA pack. I mentioned in the other thread that I still like the idea of using Sony NP-F970 compatible lithium ion camcorder/video light packs (7.2 volt 6600 mAH, about $30 on ebay, you'd use two of them). They are pretty lightweight, certainly less than a pound each, and a pair should run the light for 1.5 hours or so.[/QUOTE
That's a good price on the Sony compatible packs, but they have a circuit inside to limit there current draw and will not work unless you take them apart and remove this circuit. This leaves you with an unprotected pack that could be easily discharged to low.