Ahh, that was 5 months ago. Seen a lot of posts after that talking bout it, but nothing that said he was actually planning on it - thanx!
He works with outside contractors for the drivers, so might even be a BLFer, dunno. 2A is a little under powered but it's the common level for XHP35 boost drivers. Certainly nothing new - a lot of lights on the market have single cell boosts for the XHP35 and HI, specially popular in the tactical market. The drain on a single cell is very high. It's what we, and DEL, found out the hard way with the original BLF GT. At 2 amps, the draw is significant, very difficult to achieve 2.5 amps. The XHP35's draw about 13.8 volts at 2 amps.
With loss's, I'm guessing it would have to draw 9 to 10 amps on a single cell to maintain 2 amps. 9 amps is like 20 minutes on a 30T if it can hold the draw til it empties, 27 minutes on a 40T, and that's optimistic. The XHP35 and HI have been around a long time now, doesn't make it obsolete, but it's not the most efficient. Granted though, if you can get one in a good tint, that's where the advantage may be. It also doesn't have the tint shifts of the 2nd generation of CREE's.
I like the XHP35 HI for its tint and beam profile. I’d expect it to have similar, or maybe even a little better throw than the XP-L HI in the K1 but with a larger hotspot.
A single XHP35 will draw more current from a single cell than something like an XP-L but it also makes a lot more lumens OTF. The boost driver will actually end up being more efficient (at similar currents) because you aren’t wasting any of that power as heat like with a MOSFET regulated driver. 2A on a single-cell 12v boost driver is perfect for using a 50E for a little extra runtime.
Of course if you just want maximum candela, the Osram is still the best choice.
I love my d1s 3a, this is so tempting. Is there a specific purpose for the green model? I’ve reread this whole thread and didn’t see anything. I’m back and forth on a w1 or w2.
I GOT TO GET ME ONE OF THESE!!!
Has anyone tried the sst-20 version? I’m partial to that emitter. You thoughts, please.
Just buy the green osram to become a jedi :sunglasses:
The K1 doesn’t come with a cell, does it? So would a high-drain 18650 (in a size adapter) produce equivalent light output in the K1? Like, say, a 30Q? I already have a bunch of those, and shorter runtime wouldn’t bother me.
As far as 21700 cells go, I think I saw some posts saying the 50E is about the best, but since the 30T and 40T have higher continuous-amp ratings wouldn’t they be better still for output? 
(again, sacrificing runtime)
No, the driver in the K1 is regulated so no matter which cell you use, it won’t draw more than a specified amount of current. I think the maximum current depends on which emitter you choose, but they are all within what any standard 18650 cell can supply.
Thanks for the info.
The XHP35 Hi version is now available to order.
top tier light with a low tier emitter
Thanks for the heads up!
Hank, do you have lumen or CRI numbers for the XHP35 you added?
The lumen and Cd numbers are listed on his webpage.
Therapist: and what do we do when we’re quarantined?
Me: add to cart
Therapist: no
Hank Wang: I just put a boost driver in the K1
I don’t see the lumens listed on Hank’s site for this particular Osram LED in the K1. Does anyone know?
lawallac, have you received this light yet?
Based on the drive current of 2A and tests of the XHP35 HI, that’s likely about 2300 emitter lumens for the 5000 and 6500K versions, so around 2000 out the front, which works out to about 145 cd/lm (it’s the least throwy emitter). A bit less for the warmer ones.
Which one will you get Zak? Coldy throwy or warmy yummy?
I bought 4000K. I don’t know the tint and CRI bin yet, and there’s a good chance I’ll be replacing the emitter with my own, also in 4000K. The ones I have where I am are 80 CRI, but I own a few in 90 CRI that I probably won’t see until travel is a reasonable thing to do again.