Well, the battery for my lighting system arrived today. It turns out, it's actually a 9V 5400mAh lithium ion battery, so it's even more powerful than I planned! This is excellent. I've calculated that it will draw 6.3W for a dual light system outputting 120 lumens (but no tail light), which should last for over 7.5 hours! If one of these battery packs is supposed to last for 3 hours, that means a current of 1.8 A is being drawn... more than enough overhead for this application. I may even be able to add a THIRD luxeon for a blinding 180 lumens. Now I'm just waiting for the luxeons flashlights to arrive...