BTU — Beyond The Ultimate
It’s the original idea. 
Beyond The Ultimate, excellent!
I have 3 BTU Shockers, one with de-domed XM-L2 U4 1A’s and a massive copper heat sink (head filling copper, with a 17mm driver fitted in a driver pocket at the rear of the copper sink), one with 3x 9V MT-G2 that does 10,000 lumens, and one with 3 XHP-70’s with TIR’s fitted inside each reflector cup to tame the beam and it still makes 14,455 lumens. Beyond the Ultimate indeed! 
Dale - Those Shockers are amaz'n, specially the XHP70 version!
Always wondered what the BTU stood for... I recall those beamshots RIC posted in the intro thread on the Shocker - it's awesome, like having 3 C8's.
I’m going to have to carve that into one of my Shockers so I won’t forget what it means. I like it!
Yeah Tom, and you’ve made some serious Super Shockers in your time… WBTU (WAY Beyond the Ultimate) 
BTU Shocker II will be ready next month if thing goes ok.
That is fantastic! I look forward to seeing that beast’s Version 2.0
Ready and willing, want one of those for sure.
Already told Richard he better have my name on one of the mini’s…
1x26350 and 1x26300. So, two different cells in series. Does anyone have any concerns about safety?
Yeah, no, wouldn’t do it. Different capacities, like, not happening.
I think he was talking theoretical, because two 26350’s would be too long to fit the stock light. Whether it could be done remains to be seen.
If you read the retailer’s description, that cell combination is listed there.
All well and good, but I wouldn’t do it!
Edit: This description? “Battery: 1×26650 / 1×26350 / 1×18650 / 1×18350 / (26350+26300) ; Recommend High drain 15A or 20A battery for this light.”
Seems to me he’s saying in place of an 18350 that an 26350 or 26300 would work. All the other power options listed are 4.2V, not sure it’s safe to assume it’ll work on 2 cells at 8.4V. I don’t know, it’s confusing.
Nor would I, it’s just curious that such a thing would even be suggested.
Ric? Are you saying that the driver can handle 8.4V to run this XHP-35? Has it been tested with this 26350+26300 combination?
To my knowledge we’ve only just recently been able to get a 26350 cell, I’m not aware of any 26300’s. But there are a lot of things I forget or simply am not aware of.
Edit: Also, Ric, are there two versions or does the one version have the extension tube such that it can be configured either way, short or long? I was wanting the short version but unsure if I can get the 26350 cell, so it really interests me if the extension tube comes with the light by default that we could set it up according to our use or the available power supply.
best one yet! Good job Ric!
I’m pulling the numbers from the Cree LED spreadsheet tool. 1.5 amp driver is a bit over the 1.05 max it list for the XHP35. However with a 12 volt XHP50 and XHP70 it puts the lumen out put to 2545 and 2817 lumens respectively. This little light has so much easy modding potential written all over it.
Edited.
The battery supplier told us their 2000mAh 26300 has same capacity with 26350. But at last we are not able to get the 2000mAh 26300.
The light listed at mountain electronics says it comes with both battery tubes.
I don’t think so! Someone please clarify about this!
What’s Included:
PK26 Flashlight
1x 26350 and 1x 26650 Tubes
Lanyard
Spare O-Rings
Stainless Steel Clip
That is taken from mountain electronics website.