Just tested my SBT90 D1v2 and D1K. Used a UT383-BT lux meter at 410cm distance. The difference was pretty surprising.
Output measured at peak, using 2H momentary turbo.
D1v2 (P28A): 92.6kcd
D1K (P45B): 126.8kcd
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Get the D1K. Higher output, better battery life, and marginally better thermal performance.
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Incredible! So, while the D1v2 is a bit (~7%) under, the D1K is impressively over (~27% !) their stated 100Kcd specs. As they’re very close it not exactly the same re: optics, and probably ditto re: driver, I wonder whether the only explanation for that isn’t the P45B in the D1K being capable of supplying way more current (45A vs 35A) than the P28A. Arithmetic seems to support this as 126.8/96.8-1= 31% ~ 29% =45/35-1…
If that hypothesis is correct, then feeding a P28A to the D1K would make it produce about the same candelas as the D1v2, no?
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It is in fact entirely from the battery. The reflectors are identical, and the drivers are almost identical too (21700 driver has a wider contact ring on the outside), being a simple FET in turbo. Keep in mind though that brightness does not increase linearly.
Yes putting a P28A in the D1K would cut the performance to D1v2 levels, and putting a LR2170LH would improve it further (small gains in performance compared to P45B in all the lights I’ve tested it).
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Thanks for these pics; I love to see what’s inside stuff, flashlights included!
You mean human vision registering brightness in a log2(N) way, right? Yes, I’m aware of that regarding lumens; wasn’t aware it also applied to candelas, but OFC it does as AFAICS candelas is just concentrated lumens (lumens/cm2).
Thanks for the confirmation. I just went to Google and searched for the LR2170LH, and was led right back here to BLF and this post of yours: Solved: Solving the mystery of the Nealsgadgets "LR2170HP" 21700 ultra high current cells
Interesting to note that the LR2170LH is capable of supplying 50A vs 45A for the P45B (so only ~11%+) while storing only 3000mAh vs 4500mAh of power (therefore ~ 33% -); as human perception of battery duration 
is quite possibly linear, I wonder whether the added CDR is worth the lost capacity…
Thanks for the advice @wolfgirl42! In terms of small host options I’ve basically discarded the D1, and I think the D1K is indeed the best option for my use case.
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While I couldn’t tell you for sure how much the LR2170LH can actually supply, I know for sure it is more than the P45B.
The official rating is only 30A, but 3 of them and a good driver are able to push an SBT90 to it’s absolute limit, and that’s accounting for losses in the tailsprings and wires. It’s probably getting something along the lines of 30A to the emitter, which is where the SBT90.2 current/output curve starts to plateau.
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Identical driver to the D1v2, and the same optics as well. I have a few KR1s but none with the SBT90. They’re a nice host but the 18650 battery limits the potential output, and I wouldn’t trust myself not to overheat the emitter in momentary turbo, because of how much further the hand is from the heat.
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Of course, I forgot the KR1 is a 18650 light 
then it’s out just like the D1, and only the D1K stands in terms of really good small-host SBT90.2 Hank options.
The only two other options with a Hank brain are then the K1 (as Hank itself calls it, a “medium”) or a large one like the Frankenlight/Hankonvoy 3x21D/4x18C with a DM11 driver board like the one you made.
It’s interesting to note that going the Hankonvoy route would not only yield a (way) more capable light, but also be less expensive, as it would cost just $75 for the 4x18C plus the $12 you mentioned for the DM11 board… round it up to $100 and it’s still quite a bit less expensive than the $140 Hank asks for his K1 (which AFAIK is his best-performing SBT90.2 light).
Of course, a lot of elbow grease is required to assemble the Hankonvoy… which makes me wonder why some enterprising soul isn’t offering it yet for us less-capable dummies (hint, hint! )
If you are doing the mod to a 4x18 you would also need an additional “28A” FET driver, which adds a bit more costs. It wouldn’t throw as much as the K1 either, having a smaller reflector. Maybe just 300-400kcd compared to 500-600k in the K1 or 900k in the 3x21D.
If you get this mod I would definitely recommend the large 3x21D host, the beam is very useful as far as a searchlight goes, visibly being useful up to 600-700m in the city with the naked eye, and still being visible at over 1km with a bit of magnification.
In my case the answer is unfortunately high shipping costs and low time availability for doing heavy modding. Though I would be glad to teach someone how to do it, so that they can have a very unique light. I think if you can do an emitter swap, you can do this too. It just takes a bit more time, and maybe some swearing too.
If you really, really, wanted me to put one together, I might be able to do it but the price might give you some sticker shock, and that wouldn’t include shipping (never can be sure of prices with the peruvian postal service either)
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I have ended up with 4 of the “HP” cells from Hank. Capacity tests show about 2700 to 2800 mAh. The P45B around 4350 average.
The output, based on testing of lights like the Valkyrie and TS30S have shown ~500 or more lumens increase with those lights using the (Lishen?) HP cells. For a few seconds… But this from lights with 5000 to 17,000 lumens. Not something that I can see. So I use the P45B cells. In fact, in the N103S I have been using the Q26800 cells. They drop output even more, but as I use lower levels much more than the MAX output, the added run time is well worth it. FWIW.
IOW, the HP cells (mine are 4 different types, so one never knows what they will get when ordering), especially for the price of ~$15 per, is not worth it. For me anyway.
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Thanks for chiming in! 
Yeah, I wasn’t planning on buying any cells from Hank (basically because I haven’t seen any being offered ), but now I will actively avoid them…
Whaaat? $15 for an unknown, supposedly “High Performance” cell (supposing that’s what “HP” means, and not “Horse Prodder” or similar 
) definitely doesn’t sound like a good idea, better to buy known quantities like the P45B at the most tradicional stores like 18650batterystore for less than $10 each… even if the idea of a flashlight coming empty all the way from China makes me sad. 
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He hasn’t sold batteries for several years. Caused too many shipping problems.
The cells are actually the Lishen LR2170LH that I am referring to. You can special order them from Vapcell for around $2 per cell. The performance of them is unbeatable, but they do run out pretty quickly.
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To everyone watching this: I finally decided on getting the D1K, so now I’m trying to decide on its options.
If you can, please chime in on this other topic I just opened: Thinking *really* hard about buying a Hank D1K with SBT90.2, what are my options?
TIA!