I prefer 2XAA with primary Lithimum for my car over the rest.
I don't care much for the long appearance of the usual 2xAA light, I will prefer a 1x18650 light (like the Olight S20) any time, but in the side-by-side format I find 2xAA lights very attractive and handy, like the SWM D20A. I hope one day a moddable budgetversion in this format appears on the market.
The Fenix E21 and LD22 are 2x AA. The TK20 was a decent 2x AA light. Personally I don’t see the point in 2x AA lights anymore. A 1x 18650 light is shorter, more powerful, and more choices.
The battery, and its associated complications.
Inexperience and too many rules to follow for muggles as opposed to just use the damn thing
Convenience of leaving lithium primaries or nimh in the car for long periods without recharging.
Convenience of replacement options at every service station or supermarket
Theres quite a few reasons for non li ion whether they matter to you or not.
I have many lights, all with different sized batteries. Although I really like my 18650 sized lights, I use a bored Surefire 9P with a sleeve, an M31 variant and 2-AA Duraloop cells daily. I like the fact that I have many different battery options with many different light engine options. I can use 2-18500 cells with an M61 variant. I can also use 3-CR-123A cells if need be. And I can use 2-AA or 2-14500 cells. Many different options is what I like. The larger host fits my hands better, and feels comfortable and much sturdier to hold. Keep an open mind with these 2-AA sized hosts. Could come in handy someday, you never know. Just be mindful of voltage use and light engines.
You misunderstood what I was saying. I’m not knocking AA or AAA lights. They have a place and purpose. Every vehicle we have has a single AA light or the occasional triple AAA light. There is one in every bedroom and a couple in the drawer in the kitchen. Small, compact, generally cheap, and I have loads of Eneloop and other rechargeable batteries. The advantage of these is that they can just be stored around. That being said, I personally have no need for a linear 2S AA flashlight. For the size, I’d rather have a 18650 light. I have a Fenix TK20, and I used it briefly but always went back to an 18650 light. I used carried it as a backup light for hunting until it fell out and was lost in the woods for about a year. I unfortunately had to replace the batteries for that trip with some alkalines as my eneloops were drained. They leaked while it was lost and damaged the light. I’ve thought about trying to fix it a couple of times but never do as I really wouldn’t use it anyway. It just sits in a box in my office. I like single AA lights, but back to the original post, yes I do feel that 2x AA lights are obsolete. That’s just my $0.02
Too bad there’s no 2xAA lights that have cells sitting side by side. It would take up a little more pocket space but be more comfortable than a single AA light because of the flat surface.
When using Li-Ion, it’s easier on the cell if you avoid a slow drain. Here’s one of several articles I read that best explains why:
That is interesting. Nice that particle accelerator soft X-ray sources are helping to improve our flashlights! But my keychain light has, none the less, dropped to not much over an amp., while my 18650 cells show little loss.
It's a shame that high quality plastic hosts are practically forgotten and unavailable. Plastic is not worse than aluminum by itself, it's just underrated and manufacturers and consumers alike fail to see its appeal. Better plastic is most likely at least no more expensive than decent aluminum, but cheap bad aluminum is really cheap and the worst plastic is by far the cheapest.
Heatsinking is a potential problem with plastic flashlight bodies, but that's something we might begin to half seriously discuss at the point where el cheapo aluminum lights no longer have alkaleak form factor or hollow pills(that is never). As BLF members have proved, flashlight bodies can be (ply)wood just as well as shiny all copper tubing. 
I don't generally appreciate additive plastic manufacturing a lot. Then again, it might become popular in the near future in the flashlight building hobby. And that in turn affects the industry.
All my small lights 1x AA and AAA are thermal limited with a Lion, so are even some 1x AA Eneloops, so plastic I think is a thing of the past and low output only.
2AA potentially offers a MASSIVE performance hike over a 1AA.
Don’t let the headline figures of some 1AA lights fool you. Sure they can have a high output ‘burst’ mode. But they will be unable to sustain such outputs.
The Olight S15 Baton is a great example of this. Take a look at these plots:
On 1AA the output is pathetic and the runtime poor. On 2AA the output is much much better, as is the runtime. And importantly the regulation.
On a 14500 the output and regulation are ok, but runtime is pathetic.
I know there are other 1AA lights with really high output like the Zebralights. But take a look, the output plummets and total runtime is tiny.
1AA simply isn’t good for output, runtime and regulation. And while 2AA is nowhere near as good as an 18650, it generally beats 14500 power or 16340 when sustained output and runtime are important.
Would the difference between my LD12 and my LD22 look like that?
One of my favorites is the SureFire Outdoorsman. They are a great light. Perfect camping light. I pack 8 eneloops and my solar charger. It works out great.
Maglite has likely made good money on two AA lights. The new Pro series are pretty decent lights too.
FYI:
One AA SF lego I like is that Ebay $20 head. I can put it on and run two 14500’s. It puts out a pretty healthy spot. It is a great little head for the money. I have taken the head apart, but have not had time to swap the led. I plan to do something with it soon. I kinda dislike the angry blue tint it has.
Most probably, although with some differences.
First up the LD12 is an XP-G2 and is only making 125 lumens. The Olight is an XM-L2 and makes 240 lumens on 1xAA (NiMh). The higher performance of the Olight on one AA means it suffers with regulation on that power source.
This chart (thanks to Selfbuilt), shows the LD12 has very good regulation on 1xAA (NiMh).
But it is important to note that it likely isn’t driving the LED as hard, hence why it is stable in it’s output.
Interestingly Selfbuilt claims 1h 30m as he does runtime tests down to 50% output. But as you can see on the plot, it’s output is stable until it steps down.
Fenix claim 2h 20m in Turbo, which is a massive difference.
But Fenix rate to ANSI FL1 standard, which means runtime is when output drops to 10% of the initial output at 30 seconds, i.e. when it reaches 12.5 lumens. To get this figure I suspect when the light steps down, it will continue working at a much reduced output until the battery is flat.
I say this, so as to help understand how the figures line up.
Selfbuilt hasn’t reviewed the LD22, so I don’t have a plot for it. However Fenix claim 215 lumens for 2h 30min.
So a lot more output than the LD12. And I suspect just as regulated. Without a plot we don’t know what it does however. But my hunch is, it will likely output 215 lumens for almost all of the rated runtime and when it steps down it will be to 10% and end the test. I say this as having double the voltage will allow for a longer regulated output.
Working on this theory, I suspect a more real word way of looking at it is:
LD12 = 125 lumens for 1h 30min (stable output)
Ld22 = 215 lumens for 2h 20min (stable output)
Basically a lot more output for a lot longer.
There is a market for a high output 2 hr runtime flashlight, but it is TINY in comparison to users well served with 30 min a charge on medium. Sure I have some big flashlights right up to the monster with the lead acid battery, but they will never live in my pocket for EDC and almost never get used.
There are many market segments in the flashlight industry. Most likely anyone who is aware of these concepts already uses lithium ion batteries, knows how to, and knows the huge benefits of doing so. The alkaleak commoners likely won't be able to tell the difference between a minimag, cigarette lighter or a proper modern light. It's enough to just see something. Does not matter how much or for how long. These cheap batteries are useless, ran out again. Gotta buy these same Duracells for more from somewhere else, maybe they will be better. Modes? You mean it's on or off?
My EDC flashlight is either a compact single 18650 light (jacket pocket or similar practical clothes) or way smaller like a 10440 size one(when wearing minimal summertime clothing, a suit etc).
A single (or double) AA alkaleak on average is less compact than a single 18650 because they're not designed to be practical. They're just supposed to be cheap and catch enough attention in their plastic package that someone who has "one flashlight" on their shopping list picks up that particular abomination on their supermarket trip.
Having said that, a well designed double AA side-by-side design makes sense as long as it is as flat as possible. If it's usable with li-ion, alkaleak(and thus NiMH and primary Li), it's a good idea.
Every once in a while threads like this come out from someone who just has no use for something, like moonlight mode, warm tint, all-flood optics, blinkies and the like, calling items he has no use for “obsolete” or “unuseful”.
I disagree with those saying 1x18650 lights are absolutely easier to carry than 2xAA lights. I have many of both categories, and for many common ways of carrying item’s diameter accounts for at least as much importance than its length. As far as tube shaped lights are concerned (since pocket carry usually rules out big heads) the beefiness of 18650 lights is usually as much, if not more, problematic than the added lenght of 2xAA ones.
Also, try carrying a li-ion powered light on a longer trip in the boonies without access to grid to recharge your cells, or lend your help in natural disasters scenarios (or get out of one yourself) with out of order infrastructures (we had quakes in the last years, so I know first hand), and good luck finding lithium CR123A primaries on your way.
Just store both, for the different purposes they satisfy.
Actually, I find the opposite to be true about li-ion in the wilderness. Li-Ion batteries are higher voltage/lower current than NiMH. Also, termination is simple and not affected by charge rate. Because of these things, Li-Ion is actually EASIER to charge in the wilderness or during natural disasters from solar panels (and other non-grid power sources) than NiMH.
LD22 is a nice flashlight but i still use the old LD25’s really love them for reliability and durability, only new 2 x AA light i have bought in several years is the ThruNite Archer 2A V2 NW for $29.95 which i find very reasonable for a outstanding EDC light.
I do love my 18650 lights especially the Fenix Pd35 and Thrunite TN12 2014, but for pure utility they will never replace the AA powered lights, simply because you can get AA cells anywhere on the planet.
Simply put a light that puts out 245 lumens for 1.5 hours on 2AA cannot be considered obsolete. You may prefer 18650 but AA light will be relevant for ever.
Marc.