Would a metal paper clip suffice?
a scrap of copper wiring would probably be best. like the stuff you find as a “ground wire” in a light fixture or scraps trimmed from household electrical wires
Or a copper coin. 
Silver dollar!
Might be difficult to angle the larger coin into the battery tube to bridge the cell to the edge of the tube.
@contactr, never use a paperclip.
Trust me. You do not want molten steel on your hands.
Woohoo! My 21700 C8 host made it to the US! It’s in customs at LA, maybe another week or less…
Hi everyone,
Just an update…
My 2 x 21700 Sofirn branded cells have arrived and I have duly tried those in my C8F-21700 and I am still getting the same range of figures as I was previously (235-240 for 21700 version light, and 275-280 for 18650 version of the light). This is the really disappointing bit for me as the 21700 version is supposed to be around 3500 lumens and the 18650 around 2500.
Now, whether I would be able to “see” the extra 1000 lumens or not, I didn’t expect it to come in at less than the 2500 lumen version 
Especially with the added expense of buying the Sofirn 21700 cells too.
Tracy from Sofirn has been good enough to get in touch with me so hopefully I/we may be able to get some further info.
All the best,
Moley
Sofirn told me that in their tests they were getting around 3500 lumen. So they are stumped.
I still don’t think anybody has tried to simply bypass the entire tail cap with a piece of copper wire and measure the lumen output (like a ceiling bounce) to see if it jumps up or not. This is really easy to do and it eliminates the rear spring, rear switch, threaded contacts, etc… It can really help us to diagnose the problem.
Ps, mine is still being shipped so I can’t do anything to help, but make suggestions.
Hi everyone,
OK, so I bypassed the tail switch with some copper wire and took a Turbo reading again using a Sofirn 21700 cell and got around 245ish which I guess would be in the margin of error to be an equal result of a max of 240ish with the tail switch in place.
It was as an experience trying to hold the wire in place on the cell and the battery tube whilst pushing the battery in firmly AND operate the side switch whilst trying to bounce the light off of the ceiling
Hope this helps,
Moley.
Thanks. That does help. It means there’s nothing wrong with anything in the tail cap area. We can look elsewhere.
There must be something in the head/driver area. I think now we would need to inspect the driver. Maybe Sofirn switched to a different FET that is not so efficient? Maybe there is bad contact between the driver and body? We will have to see.
I got my 21700 host today, waiting for some specific emitters to get here…
My build is already in state of repair: one Luxeon V led decided to quit lighting for half of the die. I’m sure it is the one that I re-positioned too much during reflow, the solder already began to look brittle and I should have replaced the solder or add extra flux. But I’m out of Luxeon V’s (and money 
) unfortunately.
I thought about waiting for the Oslon Blacks but decided against it with the way this MCPCB is screwed to the reflector and such. So I sliced domes off Samsung LH351D 80 CRI 5000K emitters and built an Anduril driver for it. The Anduril firmware, to my experience, can be finicky about the switch in use and that’s the case here, actual working conditions are intermittent with a quick blink of the emitters the norm about 80% of the clicks. When it engages it ramps and works fine, but it’s not at all reliable. So these switches must have some peculiarities to em.
Beam profile looks really neat from these sliced Samsungs, works nicely. I’m using an iJoy 21700 3750mAh cell with one of Blue’s large springs cut off about 3 coils from the top. No bypass in it as yet. 20ga leads to the board with an SIR404DP FET. Left the spring bypassed tail switch section stock, again, for the moment.
Charging it up, will see if I can get it to work on the light box and get a read on it…
Oh yeah, the two white wires are the switch leads, the black illuminates a green emitter on the switch board and the red illuminates a red emitter, I didn’t try hooking either up as I really don’t care that much for an illuminated switch. (didn’t know where to put them on the Anduril driver anyway. lol [I used the D4S Anduril variant] )
I wonder if it uses a common ground or common positive? Did you happen to take a picture of the switch?
Could this be related to the other intermittent problem reported earlier in thread?
The LED’s on the switch seem to use a common ground, there are 4 wires… white, black, white, red. The 2 white at 1 and 3 position are the switch wires. I have tried a new switch, a second new switch, I tried a new switch directly on the wires with no board and that seemed to work so I removed the LED’s and resistors from the switch board and put the original switch back on (it has a longer post than mine) Seemed to work fine until I reassembled it and now the same issue.
I even moved the ground lead from the switch to the 7135 ground pad to ensure it’s solidly grounded. I don’t get it. I had Anduril act like this on my Meteor M43 and eventually replaced the rubber boot with a stiffer boot for a MagLight and it works fine, so I don’t know if this one is also because of the softer semi-transparent boot or what. Will check it again tomorrow and see where I can go with it.
It’s the boot with this switch. I tried several more things and ultimately, with the board installed and the retaining ring in place it works perfectly WITHOUT the boot. No glitches at all. Put the boot in and glitch city. So it would appear that the long post is being compressed by the shallow boot and not allowed to properly function. At least, in this particular light and with Anduril.
So maybe trimming the post with a razor blade 0.5mm-1mm would fix it?
It sounds like the software is not able to detect a switch click very well, is very finicky what the signal should be.
(my C8F 21700 host with mini-GT driver switches fine)