3xAAA vs. 4xAAA vs. 26650 Size Comparison

I thought I would take some measurements and share them comparing 3xAAA carriers, 4xAAA carriers, and 26650 cells.

Some 26650 lights also state they will run on 3xAAA's (example: SkyEye F13, Poppas W-878 or Ultrafire Version). Some 26650 lights state they will run on 4xAAA's (example: UltraOK HD2010-looking light on Ebay). It has been my inclination that many lights that are 26650 sized could run on 4xAAA's (at least NiMh, possibly alkalines for a short time). I believe 3xAAA's could be used at times, but 4xAAA's would help overcome some voltage sag. I'm unsure how the extra voltage comes into play. These lights run on medium or low wouldn't cause too much voltage sag and I suppose some drivers handle the additional voltage better than others. I'm not sure how much of a risk it is to try 4AAA's in a 26650 light, so proceed to do so at your own risk.

My measurements were taken with the only 4xAAA carrier I have (from the Ebay Ultra OK light listed above), a 3xAAA carrier that came with the Poppas W-878, a protected Trustfire Flame 26650 (from FastTech), and an unprotected King Kong INR raised-top from Int'l Outdoor Store. I measured at various spots looking for the largest measurements. Carriers were loaded with Rayovac NiMh pre-charged cells. If I remember correctly, the 3xAAA carrier has it's widest measurement with cells loaded, but the 4xAAA carrier is widest at the diameter of the carrier itself.

3xAAA Carrier: 22.2mm
4xAAA Carrier: 25.5mm
TF Flame 26650 Protected: 26.3mm
King Kong INR 26650 Unprotected: 26.35mm

I also took a couple measurements of inside battery tube diameters of two 26650 lights (smallest diameter measured on each):

Ultrafire HD2010: 26.9mm
Trustfire A8 (BLF Edition): 26.7mm

As you can see, 4xAAA carriers (assuming other carriers are not much wider than mine) should fit in 26650 sized lights with little rattle. The 3xAAA carriers rattle a lot inside 26650 lights (my Poppas W-878 for example as seen below).

Some photos:

3xAAA on the left, and 4xAAA on the right:

Again 3xAAA on the left, and 4xAAA on the right:

4xAAA alongside TF Flame & King Kong:

Showing the slop of a 3xAAA Carrier in a 26650 light:

I am not proposing we all run our high-powered 26650 lights on 4AAA NiMh's instead. I am simply saying that 4xAAA NiMH's are a viable alternative, especially for non-flashaholics or people that can't be trusted running Li-Ions. They also provide an alternative in a situation where you don't have access to 26650s, or are unable to recharge them (i.e. out camping where a camp store or local shop has AAA's available).

Any thoughts? Would anyone like to provide input about the voltage issue (i.e. voltage of 4xAAA alkalines being used in low or medium mode)? I know the Poppas W-878 uses a driver which is direct-drive on high and I don't know how it would do with 4xAAA alkalines or NiMh's (though I suspect they would sag enough to not be an issue).


Good info. Thank you for sharing.

Edit: I’m curious to hear what some of the knowledgeable ones thoughts are on your question.

And for anyone interested, here is a link to the 4xAAA carrier at FastTech (which is very similar to mine, but mine appears to have brass springs / contacts EDIT - I was wrong, just look at my photo - it's the 3xAAA that has the brass).


Thanks for the info. Say, that 3 AAA Copper Top and Bottom look better built, any source for the 4 AAA with Copper?

Meaning this Black Copper One at FT.


It's probably brass and not copper, but you could pull an Old-Lumens and use copper foil/springs to remake contacts for it.

I don't have a source for a better 4xAAA (FastTech finally got them and that is the only source I know of without a 1000 minimum order quantity).



Wouldn’t 4xAAA, in series, provide 4.8V - 6V? So if a driver was spec’ed for, say 3V - 4.7V, wouldn’t the 4xAAA voltage be too high?

Still learning…


Well that's my question. Voltage would be a bit higher with fresh cells, but then there is voltage sag (how much I don't know, though it's less of a sag in low or medium modes). Plus with many of these drivers we don't know their voltage specs. That Ultra OK I linked above is fine with 4xAAA's. I have a suspicion that direct-drive drivers are the best types for AAA use.


the m10 does work on 4aaa although I didn’t try it for long.

nanjg drivers are supposedly able to cope but will get hotter at 6v than at 4.2v as they just burn off the excess, the voltage sag may alleviate this though.

An m10 sized light with xp-g2 at a max of 2a would be a nice bug out bag light with a 4aaa carrier packed, hmmm….


I’ve only been really interested for a relatively short time, but early on, I had one experience, where I tried a 14500 in a new 1xAA light, because I was curious if it’d work.

The LED went dark blue for less than a second, and then the light stopped working.

Thank goodness it was an el-cheapo light, but I won’t be doing that again :(! Not on purpose anyway…

theres another thread where we were talking about this, apparently with the voltage sag it will do fine
i don’t have time to hunt it down now, but if you search for threads me or old lumens have posted in recently you should find it
i did a search on this last week for my cyclone c88, 4AA will not physically fit, though i think 4AAA will but i’m not interested in going down that route, the battery life would not be satisfactory

I've done 4AA with NANJG drivers and they are fine. The voltage sags when the light is turned on and then it stabilizes in about 30 seconds. On high mode with an XM-L, 3 amp NANJG, I get about 4.9-5.2v for fresh Eneloops after about 30 seconds and then it settles and slowly drops off from there. I would think that any driver made for one Li-ion would work fine with 4AA.

I get a little higher initial reading with 4AA holders modded with copper.


Maybe part of what you’re seeing is the voltage drop over the copper (wire, or whatever) in the carrier?

In other words, that wire, etc. in the carrier has some amount of resistance/impedance, so when you turn on the light, there’s probably a small amount of current surge (to fill up capitances, etc.). Current x resistance/impedance gives you a voltage drop (over the resistance/impedance, i.e., across the “wire”), then, as the current surge subsides, the voltage drop across the wire diminishes.

Copper would probably be a better conductor (i.e., less resistance/impedance), and the less resistance/impedance, the smaller the current-related voltage drop would be.

Just a theory :)…

not by a lot, i tried 3AA in the carrier and by themselves, the difference was negligible

hmmm, I wonder if the direct drive HD2010’s would be fine with the 4AAA’s. Maybe with the higher Vf of the XML2 combined with the voltage sag would prevent frying the emitter. Seems like it would work. I can’t picture AAA’s lasting very long at all though, but you have to compromise when trying to make safe lights for people that are not on lithium.

EDIT: I’m an idgit. I just wondered the same question you posed in the OP. Please disregard this post.

Excellent write-up, Garry.

Thanks for the info.

Can anyone tell me if a 26650 would fit in a an LED Lenser T7/P7?

I got a couple of those 4xAAA carriers from Fasttech, but they’re way shorter than a 26650 and won’t make contact by themselves. They don’t have that elongated contact on the top like the carrier from the Aleto light has.
With a quick and dirty fix using magnets and copper coins, my Poppas S7 (the same as a Poppas W-878 afaik) lights up fine, though.

Thanks for that feedback.


No not without some modifications anyway. The led lenser’s 4 aa carrier has both contacts pos/neg at the top of the carrier instead of the the regular negative on bottom and positive on top like the 26650 has. Plus there would be difference in voltage that might also make a difference in output, being less with the 26650.

Anyone run across any decent 4AAA holders since this thread started?

I'm giving away some 26650 light to non-flashaholics. Worst case I can use the FT 4AAA holder and modify it be longer.