I did some ceiling bounce lumen estimates on my (NW) DQG18650. There were measurents before from _the_ and relic38, and those were undoubtly better performed than mine, but here are the numbers anyway, actually consistent with their numbers and somewhere in between:
low: 12.5 lumens
med: 157 lumens
high: initially 470 lumen, within a second already 420 lumen, settling after two minutes at 335 lumens and from there a very slow decline.
What I believe is happening on high setting is the following: the very rapid decrease within the second is actually pointing at a unusual high thermal resistance very close the led, directly where it sits on the board, then the still fast decline points at a lot of thermal resistance anywhere through the board to the body. The very slow decline leftover after two minutes is the limited surface area from body to air, so that the body is still warming up slowly.
Design-wise just the limited surface area of the body is not avoidable (it is already made of aluminium and we want this light small) and it is not a big problem anyway. The other thermal issues can be avoided largely by a different design (such as using a small pill anyway with separate led board and driver, it will cost a few mm extra). It made me wonder wether the board the driver is made on and where the led sits on is a metal core one? I noticed from the DQGAAA that that is not the case, and my guess is that it is the same here so that the heat path directly near the led is only through the electrical traces and not through the board at all, which may also be the reason to choose for fujiking the board behind the alu divider in the head.
Going from 470 to 335 lumens means a decline to 71% of initial output. If you look at Cree's xml data sheet about junction temp/luminous flux that would mean a junction temperature of about 155 deg. C ! Awfully close to the melting point of solder, bad for the led anyway. I hope my measurements were lousy and this is not true .
I don't think it is voltage sag, I used a Efest 18650 IMR battery fully loaded, at 2.0A in the first minutes (not seconds) the voltage drop is 0.3V the most, the voltage stays very near to 4V. It will affect output but nothing near to 30%. And I could repeat the same drastic output decline after cooling down for half an hour without recharging the battery.
Actually, it has nothing to do with the small size of the flashlight, what happens very near to the led is what causes the lumendrop. I suppose there is not much you can do afterwards, but the design can certainly be improved. The fact is however that a 30% increase of output is nothing impressive enough for the majority of people (apart from us freaks), and the fact that the led does not even get close to its 100000 hours lifetime is also not a concern for most users (same discussion was happening on the bad heatsinking of the Nitecore EA8).
Comparing the DQG Tiny18650 to a ZL SC52 could not be much more apples vs oranges. The DQG is a budget light in every sense of the word. It is simple and gets the job done. ZL SC52 is a top end light. Fit & finish, build quality, modes, thermal management, performance and price are on a whole other level.
Comparing the SC52 and SC600 would make more sense. Obviously, the sc600 costs considerably more than the DQG. For good reason. But the SC600 is the 18650 version of the SC52 if that is what you want.
If you want to compare the DQG tiny18650 to a AA powered light the best parallel would be the DQG AA. Same FnF, same build, 1 less mode on the AA, similar thermal management [weaknesses], lower performance, and lower price - in keeping with it being a AA powered light.
For what it is, the DQG tiny18650 is a cool little light. But I don’t think zebralight is losing any sleep over it stealing their customers… Just as I doubt Porsche worries about VW customers.
True, the price and quality are in a different league. But this and the SC52 are the two ‘very small but very bright’ options right now, so it’s inevitable that they’ll be compared as they fill a similar niche in that respect.
The main differences other than general build are in UI, heatsinking/longevity, and runtime. Of course this will have longer runtime despite less efficient circuitry, but it’s heatsinking is nowehere near as good as the zebra and that may adversely affect the long term performance of the light (though it also may not).
Crucially, the UIs are completely different. The zebra is a side clicky with easy and fast access to the three programmed ‘primary’ modes and with many more ‘secondary’ options, especially at the low end of the output spectrum. That is where it really excels in my opinion. In comparison the three mode twisty scroll through of the DQG will seem very slow, awkward and inconvenient, even though it works ok when considered alone.
That is an interesting point. They are indeed both very small and very bright. Yet quite different.
In a way, the sc52 is a bigger performance accomplishment b/c it is so bright on NiMH instead of higher current li-ions. On the other hand, the DQG is most compact relative to the size of the cell it uses.
DQG is much simpler in design. You could even say “crude” in comparison to ZL, but that all comes down to the price. Conversely, QC will be much better with ZL as a brand, that also comes with their much higher price. This sort of relationship is always inescapable with all goods and services… It is why there are ‘budget’ and ‘premium’ markets.
For what each light is, they are both good buys. But… again… you can’t realistically compare a VW GTI to a Porsche 911.
[Full disclosure: I don’t have an sc52, but I have an sc80]