+1. Always nice to have more options and having a 21700 tube would make the D4S a bit lighter and slightly more portable when required.
I would also prefer D4S with 21700.
I wonder if 21700 cell technology will be the one to keep growing with Tesla and vaping using it more and more. I’m glad that there are some solid 26650 choices out there but a quick and nonscientific look around leads me to believe that a bunch of new and high-performing 21700 cells have popped up recently.
You’ll get there, give it time 
Yeah never say never, i agree. 
For the 21700 tube that could be nice, but i do like the 26650 format, for my hand size it's almost perfect, the 18650 format feel a bit too tiny in comparison, and quad batteries like the BLF Q8 a bit too large.
But it would definitely be a nice option to have even if the D4S style would be less appealing in my opinion. 
Tesla’s interest is high-density cells ala the mythical Panasonic 3.6Ah 18650 - they need range first, performance second and have the volume/mass overhead to arrange huge numbers of cells in parallel. Commercially-available 5Ah 21700s are close to the energy density of 18650s (0.74 Wh/cc vs 0.79 Wh/cc); the little information I can find on Tesla’s 21700 states 877.5 Wh/L (0.88 Wh/cc) or 21.275Wh / cell - a simple calculation to arrive at a ~5.9Ah cell … performance characteristics aren’t known but I would expect perhaps 2C.
As volume industrial customers, the power tool manufacturers can drive R&D in the high-performance cell segment - they have to build packs with low cell counts with high-rate cells and merely acceptable density and they buy in considerable volumes. This is the land of >10C cells and markedly higher $/Wh metrics.
Based on the slightly greater girth of Ryobi’s new-ish ONE+ +HP batteries and the multiples of 3AH on capacity I suspect 21700s. 3AH high-rate 18650s are probably more costly and - based on the data I can find - deliver less current than comparable 21700s. My cursory research suggests that the Samsung 30T is a likely candidate - 3AH, 35A peak current, 126 nominal peak watts per cell; as such 3/6/9Ah packs should have 630/1260/1890 watts peak power potential, respectively. Real world maximum power is apt to be closer to the 3Ah peak 630W (35A@18V), more would likely exceed the pack/tool contact/conductors’ ratings - 1260W would demand 70A, 1890W 105A.
You would still have the two options, 21700 and 26650
I was going to buy the E07 because it works with 21700 and I try to keep my gear as simple as possible so I don't want to have 20 different battery sizes (only 18650 and 21700), but decided for the D4S because:
-it's throwier
-has less leds, (I don't need 7 leds in a light that barely sustains 800-900lm)
-has better build quality (emisar is a sure bet)
I'm sure there are a lot of people that choose the E07 instead of the D4S because of the battery size
A 21700 tube would also allow the use of a pocket clip
I would absolutely love a 21700 Emisar D4S with pure Anduril.
All this whining about cells when, in fact, the 21700 actually DOES work in the supplied D4S…
I didn't say easily
Since we all probably have 18650s around it’s worth noting that the D4’s magnetic tailcap makes using 18650s casually quite easy. Otherwise, a simple spacer (rolled up paper, convenient-sized PVC, something 3D printed) will allow an 18650 to snugly slot in. Personally, I don’t need the runtime that a 26650 offers over an 18650 nor does the better current that high-rate 26650s offer matter that much to me. Nonetheless I opted for the pack-in 26650 that intl-outdoor offers since it will work in my chargers without much difficulty.
All other things being equal, fewer LEDs is good for throw because more optic per LED can be used while more LEDs will be driven at lower currents thus be more efficient and generate more light within a given power envelope.
I recall a D4S pocket clip prototype, but I’ve slept since then and that’s a lot of girth to manage.
Possible to get some outdoor beam shots comparing the two?
CaptainBears, for you…
That’s not at all what it looks like.
Shadow is telling me to throw something, anything… a log or a rock or a ball or his bowl… anything! He wants to fetch something for a little while then fight me over it for a while more…
Big baby is what he is…
damn, can you guys advise if I bricked my MCU?
the flashlight doesn’t turn on at all anymore, no aux or any flashing.
I followed these instructions:
and it did the erase and rewrite. then it warned me that the byte 0x0000 didn’t match and that the fuse was set, something e0 and if i wanted to rewrite the fuse. I put Y and it never completed.
Now it doesn’t turn on 
do I have to order a new one and does anybody want to buy my brand new bricked d4s (sst20 3000k)
I am interested in buying it. But lets try and get it working first. Like Man-Shadow said. Try and flash it again. Several times.
Someone more flash savvy may be able to help.
Do you have the means to replace the MCU ?
thanks for the help!
I can’t seem to get it to connect again. I’m not sure if it is the usb or connector wires I have or if it is the unit itself not being recognized because it is fried.
I can’t turn on the flashlight nor does it show any signs of life otherwise
I don’t have the means to replace the MCU
It’s probably bricked, and won’t work until after being physically removed from the driver board, reflashed with a high-voltage programmer, and soldered back on.
If you had said “no” to the fuse change, it would probably be recoverable… but a bad fuse value can’t be fixed with any easy methods.
Damn. Does anybody offer this service on this forum
Thanks for getting back to me personally Toykeeper!
You have done the hard part, getting setup for flashing. Can’t you just pop a few bucks to mouser and get some backup attinys? then you just desolder and replace with a new one already flashed.
I just received another D4S and flashed it with the anduril.2018-08-22.EMISAR_D4S hex file. The flash was successful, but several of the functions no longer work (no access to the aux LEDs, can’t switch between step and smooth modes, etc.). I used this same flash procedure on another D4S several months ago and it worked perfectly. Is there another hex file that I should be using now or is there something else that I should be doing ?
Thanks,
Mike