Shirnask, if the copper washer doesn’t fit down over the cell then your light should work just as well without the copper washer. Rare to find a washer that has an ID that will slip over the 21700 cell, it has to be as thin as the battery tube itself almost. Please check your washer, see if it fits over the cell. If it doesn’t, the cell hits the washer and leaves the tail cap offset by the thickness of the washer and is actually adding to the length of the cell.
I know Fireflies asks us not to use the 30T in the Nichia version, not sure about the others. I had planned to use the 30T, but will be changing that plan until I know the emitters can handle it, or until I change the emitters. Since I had ordered the Luminus SST-20 emitters, which are totally new to me, I’ll have some testing to do. May end up using a 20650 cell, don’t know at this time. Have some, may as well use them if everything else is ruled out.
From my previous posts in this thread-
My champagne Tube is 21.4 mm.
Sofirn 4000mAh= 21.7mm.
Shockli 4000mAh=21.7mm.
Samsung INR21700-50E= 21.1mm.
Samsung IMR21700-30T=21.2mm.
Rofis RF21700=21.8mm.
Texas Toasted, can you tell if the Sofirn, Shockli, and Rofis cells are double wrapped? Might it be sufficient to pull the wrapper, or both, and rewrap?
Shirnask, please, look at it… if the cell is protruding from the tube then the washer will stack on the cell and make the entire assembly that much longer. Humor me. This is the first time I’ve done this….
Dale, the difference it makes is that you no longer have to compress the spring in the tail cap completely just to have the tube make contact - the difference between grinding the cap on as hard as you can just to make contact and a gentle 2 finger twist. I can make it work without them but I destroyed one o-ring getting the SST20 tight enough on a 30T without them. I agree that if you don’t already have batteries get ones that fit without this, but other wise this is much better than destroying o-rings and crushing springs
I never crank down on threads, it shows something is amiss. Remove the spring in the tail cap if necessary, put a small dab of solder in it’s place, but never crank down a threaded cap on a cell to gain contact that isn’t there. Dangerous on the cell, at the very least you cause damage that can’t be repaired.
So, Shirnask, from what you’re saying you’re using the copper washer to compress the driver spring and make contact to the tube, why not just ream the ID of the washer so it clears the cell then it’d be an easy fit, solder the washer to the tail PCB ground and be done with it.
MWS, I can’t tell from their pictures but I get the impression they just put their black wrap over the existing cell. At the corners it seems almost “padded” as though this is the case (a factory wrapper inside the Sofirn wrapper) If not, I would strip the wrapper and leave the bare metal can, then wrap that in the ultra thin Kapton tape to prevent it grounding inside the tube. I’d use the cell, wouldn’t be a waste of money. Ultimately I’d keep an eye on it of course and when a proven better cell came along I’d retire the Sofirn cell. But I’d get some use out of it first.
Me? If that still wouldn’t work I’d bore the tube.
Yeah Yeah Yeah, everybody doesn’t have a lathe. But you don’t have to have a lathe, a wooden dowel and sandpaper can get it done. Where there’s a will, there’s a way. (Old Lumens would be proud! )
actually I believe he means that the washer makes contact to the tube sooner and he doesn’t have to compress the spring near as much?
the washer just needs to clear the spring.
I suspect that the copper washer mod is only working because the washer is contacting the -Ve of the cell and the outer trace of the tail PCB, acting a bit like a retaining ring by providing a continuity path from end of the tube to the tail PCB, that isn’t there in the original design, and bypassing the tail spring.
Meanwhile the tailcap will be hanging on by a few threads less (depending on thickness of the washer), and the o-ring in a different position than designed.
You could also try something different such as a circle of solid copper wire at the head, to effectively lengthen the tube. Anneal it first to dead-soft (just get it red hot, and pickle off the scale in some acid, or polish it). If the o-ring ends up displaced from the sealing surface in the head (I didn’t see any such thing on the photos, just seemed like rough threading all the way), PTFE tape around the threads might solve that.
Tom Tom you are mistaken, the tube must make contact with the copper washer before there is continuity and can be disconnected by less than a quarter turn.
He’s only partially mistaken, the spring pushes the parts away from each other and breaks the contact. The better way to do it is to allow the cell to pass through the washer, or use a copper wire like that which is in the center of coaxial cable. This will effectively make the battery tube longer, like Tom Tom said, and not interfere with the cell or the o-ring placements.
Believe it or not, in the 500+ lights I’ve modded this HAS come up before…
Which ever end I add copper wire to to gain the 1.5 to 2 mm extra length will necessarily displace the o-ring on that end of the tube by the same amount. Also the head is quite deep and a pain to solder. Also it took less than 1 minute to pull a washer out of the drawer and drop it in the tail cap for an effective solution. I can shape and solder a piece of wire on the driver but that’s a lot of effort to gain very little
Dale, I know this is just small change for you but it is a no effort fix for those less capable
(Old Lumens would be proud! 
)