“Then after 2 or 3 hours it dimmed and went out…”

I have the Gerber Triode (another single AAA headlamp) and a Gerber Infinity Ultra (single AA flashlight with clip). I noticed in Gerber lights, they have a step up converter. It has to so the 1.5V can be at 3.4V to power the white LED. However, it’s not current regulated. It’s hard to notice with the eye but a photodiode meter can pick it up: As the battery voltage falls, so does the step up converter and thus falls the light output.

If you used a NiMh, then plan on a couple of hours and it won’t be as bright as an alkaline or lithium—the latter 2 giving you longer and brighter runtimes because of their higher voltages.

The Tempo should way outlast the e+lite in brightness. However, the e+lite will stay dim for much much longer. Coin Cell flashlights will dim greatly in the 1st 15 minutes and then go forever (weakly of course). However, I don’t like how dim they are. Plus, in the end, AAA batteries are cheaper and easier to find. Plus you just need to buy a 2 or 4 pack of AAA’s. I don’t like lights that use 3 AAA or 3AA because you can’t by batteries in three’s! Plus the 3 cell lights also fade immediately after you put the batteries in.

My fenix L1D on the other hand, steps up the voltage and holds it constant as the battery dies so you get bright light for most of the life of the battery. However, when it goes out, it goes out! I have about a 5 minute warning because I notice the light is much dimmer than usual (it’s in its downward spiral slope). With the fenix-- plan on longer runtimes with lithium or NiMH but not alkaline. For the fenix circuitry, low internal battery resistance is best (where alkaline fails).

Like backpacking gear, LEDs can also suck you into the abyss…

-Barry