One of my favorite flashlighlights is the Underwater Kinetics UK 4AA eLED, 18 hours on a set of alkaline batteries.
Quote:
This light is designed for industrial applications and has the following hazardous location ratings listed on the packaging:

UL: CL I, DIV II, GP A, B, C, D, CL II, DIV 2 GP G, CL III, DIV 2 T4
I called the company and spoke to an engineer about whether or not the light could be used with lithium batteries, because the specs call for Alkaline batteries. The light is fully regulated, so lithium batteries will work and should give even longer runtime with a longer shelf-life. However, per the company, use of lithium batteries nullifies all of those hazardous area ratings. The light has a pressure vent in its tailcap in case I do decide to disregard the manufacturer's recommendation. It would probably work and I've considered trying lithium batteries, but if the issue is sporadic, it may test fine and then fail when you really need it.

As for the debrief at Doug's link, quality control rules. The lithium batteries I have on hand are Energizer AA and AAA and Surefire 123's.
_________________________
Better is the Enemy of Good Enough.
Okay, what’s your point??