The D40A is a fine light indeed. Wish the buttons were easier to find in the dark though.
This Ozark and Coleman look interesting.
Ok, I confirmed it has mode memory, you have to wait 3 seconds before turning the light back on or it'll advance modes. Reverse clicky. Quick non-scientific test doesn't show a visible thermal stepdown and after about 10 minutes or so in 60F ambient temperature it's reasonably hot. Thermal appears to be good enough to not damage the LED before the batteries run down in my opinion. I'd recommend the more cautious to monitor flashlight temperatures themselves. Keep in mind this IS a budget light.
What are the theoretical advantages/disadvantages of 2*AA vs. 3*AA vs. 4*AA when driving an XML? I’ve got a 2*AA Klaurus on order and am interested in getting another AA based light.
Wish granted: Here’s a hint, with eyes closed and by feel, buttons are on opposite side of whatever you attach to lanyard hole 
. Many have commented D40A’s lanyard hole to be worse placement ever. Without said placement, I would be feeling up my light every time I use it.
Personally use an extra leftover sturdy plain nylon zipper pull. Ends together in a single knot and pulled through hole with dental floss. Took apart supplied lanyard to remove lightweight metal clip (metal on metal would also drive me nuts) and reassembled using zipper pull as connector. So with light in jacket pocket, once I feel knot that is looped and snug to hole, I know where buttons are at all times. 
My noob guess at this question would be this:
Pros:
- better runtimes
- more light output depending on what form factor would give you the closest to the max output wattage that the LED can handle.
Cons:
- size
- limited types of shapes for the flashlight. ie- 4*AA = soda can (EA4) vs. long tube (PA40, Starry Light)
I was more interested in a comparison between efficiency. Which lends itself most to driving an XML led. I would think 3*AAA since 4.5v is close to 18650, but I’m not sure if 4v is ideal either.
Thanks for the tip Kst. I have been using the lanyard as a guide, but it's so thin (not the stock lanyard) I can barely feel it either. You got me thinking I should change to a different lanyard.
Some info on 2S, 3S, 4S:
2S - Need a boost type driver which is inefficient and has limited current potential
3S - Very close to the Vf of the emitter. So no driver needed if desired. Limited current potential due to not having much voltage overhead, but better than 2S.
4S - Need buck or linear driver to bring down voltage. Higher levels of current can be delivered to the emitter.
I feel like I left something out above, but can't put a finger on it.
You can count 1S, very close and worse in efficiency than 2S. (1S is not multiple AA)
3S won’t fully drive an emitter and brightness will start falling as soon as the light is turned on
Congrats on Sunwayman :D!
For how much and where did you get those lights?
Im thinking of getting couple of them from Ebay for less than 6$ shipped per one unit, hows the heatsinking and battery runtime, output :D?
Ive started to ask lots of questions here recently, looks like I want to buy yet another light, even tho after I got SD10, D40A and EA8 I thought Im done with new lights for a while :D!
A bit late to the party, but in 4xAA, the D40A is top dog, IMO. Can be found in the mid-$50’s still.
I’m interested in that Starry-Night thing, and the price puts it in budget category for sure…
The only thing i would not like about that D40A is the 3 min turbo, if it had an override for continuous turbo then it would be ideal.
Also got the dive lights from ebay around 6usd, not really tested the runtime or if i did i cant remember. Its really a nice light but being made of plastic, the heat management is pretty poor as it only transfer to the aluminum pill. I believe its only on the 100 lumen range so it could manage.Its great as around the house light or for lending as it runs on AA batts and have decent runtime that will get you through the night.
Thanks, Ian, thats what I wanted to know!
I will probably buy these to replace SD10 on duty right now at the country side :D!
Where the heck did you find them for 6 bucks? Google search shows 80 dollars for a D40. You meant 60 bucks I presume, which is what Im seeing of fleabay
Is it worth the premium over the Starry Light?
Now, that is a real budget light! Dorcy makes good stuff. We tend to ignore the pedestrian, everyday lights, like this one, or the Indestructibles, Not enough Coolth , maybe?
But if you want a reasonably priced light that just keeps working, doesn’t break the bank, and will last till something brighter and shinier comes sky-hooting over the horizon… :bigsmile:
O.K., really dumb question…what is PWM?
Next, where is the useful information for those of us who just want to know is it waterproof, and how long the light will last when we are sinking in up to mud to our chins, and a wild animal has run away with our shoes, and we can’t hear the girlfriend screaming any more :bigsmile: …how long does it really run in the modes we will mostly use, and how warm does it get, if at all, in the common modes ? Will it provide constant, unflickering light till the batteries die?
The circuit usually regulates the output by making it blink really fast. The faster (more Hertz, or times per second), the better. Otherwise it will looks like an annoyying strobo effect. Specially in low modes (where the width of the pulse is shorter), or when you move the light fast
How is anyone supposed to know which modes you mostly use? I have some lights that are used in moonlight mode 90% of the time, others are on high 95+% of the time they're on.
BTW, in the right circumstance, girlfriends that can't run fast are worth their weight in gold.