I've pretty much concluded that AA is the perfect EDC size, it's just a pity there aren't many really small lights that make full use of it, other than twisties which I find to be a pain. So far I have 3, which I believe are the only small AA clickies that exist:
- Eagletac D25A (I have the Ti version)
- Thrunite 10S
- Solarforce Z2
Every other AA light with a proper on/off switch is so big it might as well be a 2xCR123. In fact, the next smallest torch I have after these is the ITP A4 EOS, which is not much bigger and runs on 2xCR123. Of course, it's a twisty.
So, what's so great about them? Two things: Size and flexibility.
The Eagletac is available in two versions that nicely highlight the difference as they are basically identical apart from the battery. The D25A runs on AA, the D25C runs on CR123A.
- Both can run on lithium primaries. The CR123 has a higher voltage, which typically means double the output for half the time.
- Both can run on lithium ion rechargeables, in which case the capacity of the RCR123 and the 14500 is identical, so if you do this there is literally no difference between the two apart from the dimensions.
Whereas
- Only the A version can run on Eneloops (or standard NiMH rechargeables) because these don't exist in the CR123A size.
- Only the A version can run on cheap, readily available alkalines, because again these don't exist in the CR123A size.
The difference in size is that the A version is a bit longer, but is thinner. The C version is shorter, but fatter. Note that the proportions of the light are not as skewed as the proportions of the cells, because while the AA is about twice as long as the CR123A, both lights have the same amount of extra length dedicated to the emitter, reflector, lens, bezel, tailcap and switch. The effect on diameter is directly proportional. It's also worth remembering that volume increases with the
square of the diameter, so 10% more diameter means 21% greater volume. This matters for EDC.
Personally, for throwing in a pocket I find the thinner form factor to be much more useful. For evidence that most people would agree, look at smartphones: they keep getting bigger, but also thinner. They could run for longer if they were thicker, but thickness is at a premium in a pocket. Length is not, up to a point.
As I see it, there's only one scenario where a 1xCR123A light wins out over a 1xAA light and that is if you need to run on primaries and you also need high output, but runtime maybe isn't so much of a concern (and you certainly don't care about finding cheap replacement cells in an emergency).
In the real world however, many CR123A lights are sized appropriately whereas 1xAA lights are simply the same as the CR123A equivalent, only longer. Sunwayman are a great example of this. Just look at the V11R, which has an AA extender (many others do this too). There is no dedicated AA version of this light that benefits from being thinner. Even the older VxxA variations which are AA only use exactly the same size head. Presumably this is just to save the cost of designing a thinner version - just bore the body to a different diameter and hey presto, different light!
Of course it's also possible that by adding a couple of mm diameter that the light will have better throw, but I'm not sure it makes enough of a difference to matter at this size. To get any serious throw you need a much bigger reflector, or different optics altogether (e.g., aspheric).
There is a huge difference between AA and AAA lights, largely because of the massive difference in capacity between these cells. One AAA is about 1,000 mAh whereas one AA is about 2,500 mAh - about 2.5x the runtime at the same brightness. Single AAA lights tend to be basically keyring lights, which are fine as a backup, but won't come close to matching the capabilities of something like the D25A or indeed most other single AA lights.
Multi-cell lights are a different story, but they are of course all much bigger than a single AA, often bigger than 18650 lights which are likely better, except for the availability of emergency replacement cells. Of course, by having a single AA EDC in your pocket at all times, you can avoid that problem.
