I don't have any 18650's nor a charger. Ditto for the 14500's except for a pair of the Safts. I have my eye on a JETBeam that runs on a single 14500. Eventually I'll probably have to delve into the rechargeables but I prefer regular CR123A lithium primaries for reliability, cold weather power and availability.

Still, those look like real flamethrowers!

Is there a reason you didn't get the PC10?

I specifically chose it over the PC series because I wanted one with just a HIGH and LOW. Generally I avoid lights with a zillion different modes; I don't want them or need them, and they drive up the price of the light and make it harder to use IMOHO. So far I've never once used SOS or strobe nor wished I had them. I guess I can imagine a scenario where they'd be useful but when it comes to light I like the KISS approach!

I currently use AA and AAA batteries exclusively. I'm considering making the plunge into flashlights that use CR123 batteries. Is the improvement in performance worth the trouble?

It is for me, but I have an addiction to lumens. I ask myself if the flashlight-intensive activities I'm involved with are influencing my flashaholism, or the other way 'round?

If you try it and find that the improved output and runtime isn't enough for you, then you can ebay your light.

Well, the performance is better. AA cells are nominally 1.5 volts vs. the 3 volts for a CR123A battery. A good alkaline AA is around 2700 mAh vs. around 1550 mAh for a single CR123A. So in the same size light you can generally have one x AA or 2 x CR123A. You definitely get more lumens from the higher voltage lights as a rule. The re-chargeable cells are even more powerful but lack the long shelf life/low-self-discharge rate of lithiums and aren't as good in the cold.

But to me switching to lithium batteries is what completely changed the equation for me. The best price I can find on lithium AAs is generally around $1.75 each (Energizer Advance Lithium- the Ultimates are even higher). I get CR123A batteries for $1 online. My two most used lights both run on 1 x CR123A.

To me CR123A makes the most sense. I have at least 8 flashlights that use them, plus one weapon light. I still have a few lights laying around that use AA or AAA, mostly very small lights like my Fenix EO1. But for the bulk of my uses CR123A suits me best.

Phaedrus, you're absolutely correct about the disparity between AAs and CR123As in terms of mAh, but Watt hours are more important for capacity. There we see that a 3V CR123A with 1550mAh has a measurable advantage over a 1.5V AA with 2700mAh.

The voltage difference means that the "pill" in the flashlight doesn't have to bring the voltage up as far to meet the needs of the emitter, so the effective output and runtime is tremendously better for CR123A flashlight versus one using AAs.

Very true. Takes me back to Basic Electronics and Electronics Lab!

The Energiser Lithiums Ultimate AAs are rated at 3200mA @1.5V though.

Personally I don't see an advantage going to CR123s from AAs if using Energiser Lithiums Ultimates as the AA flashlight can still be used with Alkalines, NiCd, NiMhs etc all with varying degrees of performance. The way the flashlight regulates the LED could be another matter though but this is highly dependent from one flashlight to another.

The Fandyfire UV-S5 that I recently purchased (makes for an excellent ceiling bouncer) will have a energy capacity total of around 40-45 Whrs and will give a similar output to a domestic 100+W incandescent bulb for about 2hrs.. or around 3-400 lumen for about 10+ hours.

Although 18650 Rechargeable Lithium Ion's are restricted to the cells that you already own in an emergency the higher rated cells such as the Panasonic NCR18650A cells will give 3100mA @3.6V = 11,160mWhrs

Panasonic NCR18650B is also available but much more expensive giving 3400mA

So a comparison;

CR123a - 1550 x 3 = 4,650mWhrs
AA lithium Primary 3200 x 1.5 = 4,800mWhrs
NCR18650 = 3100 x 3.6 = 11,160mWhrs

Another flashlight that might be of interest for area illumination tasking work, which looks to have a very good form factor size to Cell capacity ratio combined with fully adjustable output upto 200+ Lumen.

http://dx.com/p/uf-h3b-cree-xr-e-q5-230l...-x-18650-122182

...at the high end of the LED's output where it draws a lot of current. At more moderate settings wouldn't the AA's higher mAh give a light more run-time? It seems so judging by the run-times of similar FourSevens 2xAA and 2x123A lights.