Pondering how much light I got for different battery types, I resorted to manufacturers published figures - for a given output, in lumens, how long would a light provide illumination, relative to its weight.

Bottom line - lithium ion batteries are considerably more efficient than AA, providing almost three times longer light.

I compared a Zebralight H53, with rechargeable batteries against a Zabralight H600, equipped with 18650 battery @3000mAh.

H53 provided 4.2 hours at 106 lumens, weighing 2.8 oz.

H600 provided 13.6 hours at 126 lumens weighing 3.3 oz.

I assume roughly comparable results at different lumen outputs.

I have both models and I like them equally - sturdy and dependable, but I can hike all night with the 600 - not the case with the 53.

Comments welcome...

Good analysis.

I like looking at a number of factors in a headlamp:

• Is this for regular use or going to be squirreled away in a kit? For regular use headlamps I really like either onboard USB-rechargeable or a commonly sized rechargeable LiIon cell. For kit headlamps, I prefer a common primary cell available in lithium (there's the now-discontinued Fenix HL50 that takes either 1xAA or 1xCR123A).
• Size and weight.
• Mode spacing and UI.
• Minimum output (very useful for not waking up Mrs. Magnet).
• Max output.
• Runtime, particularly at what is likely to be the most common output levels.

This is going to also depend on temperature.

Lithium ion performance drops off in colder temperatures, at around -20C (-4F) would expect 50% less performance.

Whereas the H53 could run on LiFeS2 (Energizer L91) primaries which are good to -40C (-40F)

These lamps are used regularly. Interestingly enough, my regularly packed bag contains AA lithium primaries as backup for the H53, I do also carry a backup LiOn for the H600, which I check periodically(every three months).

Good point about temps. My performance level is depressed, as well, at -40(F or C, makes little difference).

If it's for a kit, also a mechanical lockout. Though believe most aluminium bodied lights have it, just by unscrewing battery cap a half-twist to break the connection.

That first point was why like AA/14500 lights. 14500 with onboard USB for regular times, but can have AA lithium primaries on hand when that runs out and can't recharge.

Noticed Zebralight dropped 14500 support in the H53, pretty sure they had it in the H52.

Where this works, it's great. Where it doesn't, I use a label printer to create a "REMOVE BEFORE USE" tag that I put between the base of the battery and the battery cap, leaving enough of the tag out of the screw threads to be very noticeable. I haven't had any issues doing that so far, but I'd definitely suggest that one make sure to test that the label doesn't do something Bad to the threads.

look at the nu25.

Great suggestion. What is it and where do I find it?

I have to be the world's biggest stick in the mud when it comes to rechargeable batteries! I've got a couple of Fenix-branded 18650s that came with a light and I almost never use it or them. But I did get a Petzl with a CORE pack, charges via micro-USB, and I like it very much! Run time isn't as good as with 3 x lithium AAA batteries but it's good enough especially since it's supposed to be able to be charged a couple hundred times. It does charge very slowly though.

Today though I took a pretty huge plunge! I just ordered a Cloud Defensive OWL weapon light that only uses 18650s. In fact, they state flatly that use of CR123a will void the warranty! At $369 it's a bit of a leap for an old rechargeable-hater like me but as an old IT instructor told me, "you gotta go with the new." Hopefully it lives up to the [considerable] hype.

FWIW, I'm not sure the lumen rating really says much. The figure given is often "goosed" a bit by the marketing dept. And it doesn't really tell you a lot about the actual performance of the light. IMO the measured candela is a better real-world indicator of output. Candela is the intensity of light that actually radiates in a given direction vs the lumens which is the total light from the emitter. A somewhat sloppy analogy would be shaft horsepower and horsepower at the rear wheels. Some companies list the ANSI lumens and candela.

Coming back to WMLs for a moment, something like a Modlite will have a rating of maybe 1200 lumens but 60,000 candela. That will subjectively smoke most Chinese lights that claim 1,500 lumens (at perhaps 15,000 candela). Much of this comes down to reflector design, etc.

When the rubber hits the road I'm not super hung up on how bright a headlamp is; I'm much more concerned with run time. I avoid the highest level most of the time and go with MED to LOW, and certainly as low as I can go and still see what I'm trying to see. Sure, I'll take my "flamethrower" lights out to the woods to play with them a bit, but most actual tasks I use a headlamp for don't require so much power. Especially if there's a full moon out!

Of course, if you're a spelunker or do long night hikes perhaps there may be times more output would be helpful.