This is just my initial impression and use, I'll update in a few months. This initial review is using a basic AA alkaline battery.EDIT - Update #1: With the Lithium Ion 14500 battery, on Turbo, this headlight throws some serious light. Seriously, I've never had/seen such a powerful headlamp before. I know of course there are even more powerful/brighter ones out there, but the limited research I've done on them is they start around $60. I can't see why I would need to travel with more than one baSee full review