What happens when the cells lose contact? Does the light shuts off or does it blink off and resume at the same brightness?
Shuts off. And you have to hit it pretty hard. Don’t see a problem here, at least with new springs.
Seems that you little mistaken with 7135 usage.
It is linear when you have 100% 7135 and 0% FET.
All other mods cant be called “linear”. I.E. in ramping you will never catch this situation, even if you stack extra 32x7135 board.
That’s slightly encouraging and maybe a reason not to lose the inner springs.
It is a big issue for me, have taken a tumble using SRK clone, bad enough but to have no light (and torch fallen from hand) in pitch black, I had a worrying moment. Fortunately backup torch in pocket, so found it.
Lanyard used ever since.
I understand that. I mostly will use the torch with only the 7135 in use. I would like to double this output, so I spend most time with 7135 only, highly efficient, and only move into the 7135+FET modes when I need to. I mostly use torches at low levels, trying to keep night vision, and only turn them up high when necessary (e.g. searching for something).
Other drivers are now being designed with two banks of 7135, to allow much more operation in linear region, and less FET, for this reason.
But intermediate levels are a combination of full 7135 use, and PWM from FET. This transition region is where doubling the 7135 current might make the ramping less smooth. TK went to a lot of trouble on the earlier FET+1 drivers to fine tune this transition for well balanced results.
And when the FET is in use, the LEDs are being zapped with the full maximum current allowed by spring bypasses etc. so even if the light ouput is relatively low, the LEDs are still being driven past their peak efficiency, I discussed this much earlier.
You could look at lexel’s FET+1+15 driver for the Q8 ? [Sold] 4. Batch "TA" Bistro/Bistro HD OTSM/Narsil drivers, 46mm for Q8 1S or 2S, Clicky or E-switch, SIR404
The SupFire M6 holds up well in the jolt test. I should re-test the lights, but I got a few with similar battery 1 spring mounts besides SRK clones, COURUI, Crelant 7G9, etc. I should re-check. The Q8 proto did the worse of the bunch I tested at the time, but I think the production Q8 is doing better.
> lanyard
Yep, been in the dark suddenly and it’s no fun. I use lanyards, belt clips, and the little glow-in-the-dark keyfobs that Andygold used to sell — on all my regularly used lights.
Living in an earthquake area, I want to know where they are when the power fails suddenly.
Yes, that is the way to go, but when Q8 driver was designed these ideas weren’t evolved. I guess it would be done differently starting today. I like to make the best of what I have before major mods like new drivers, and do so frugally. Easy to spend lots more $ satisfying desire, but I think the Q8 is a very good platform as-is. Just thinking about a simple 7135 stack at the moment, for my own peculiar preference, not suggesting it’s of interest to most.
On the soldering issue, some time back (a few years ago) I had trouble even soldering two wires together. When I first started modding flashlights it was aggravating. I broke down and bought a Hakko 888 (analog) and started using .031 Kester rosin core solder. Everything started going so smoothly after that! I got to where adding 7135’s was easy, would have 16 to 24 chips on all my Qlites! 
I don’t use flux, never bought a remover pen, never bought the braid (have always run a Tenergy silicone covered wire in the center of the spring). I did get a helping hands, it sits on a shelf all dusty.
If I’m building a driver and soldering by hand, the smaller bevel tip works wonders. I got away from it when I bought a hot air station from Justin, and since that one died I bought a heavier duty unit that’s a stand-alone hot air station. Now I pretty much always use the heavy 2 sided bevel that came on the iron. My pound spool of .031 is running low, about time to buy another I suppose. This spool has gotten me through literally hundreds of mods, well worth buying once and having the right stuff on hand.
I very truthfully believe that with the right tools, the right solder, virtually anyone can learn to be good at it. I grew up hauling lumber, shingles, sheetrock, mortar for the brick layers. I am not in any way an electrical engineer, totally sucked at soldering before getting the above kit. So really, if I can do it, virtually anyone can!
Edit: Proof is in the pudding? My SupFire M6 has a piggybacked FET driver of my own build, now fitted with 3 Luminus SST-40 emitters. Driven by TK’s ramping software. It makes 20 to 8866 lumens. Tail current is 28.74Amps. 
The TA SRK 1+15+FET drivers with Narsil existed before the Q8 project started
it was simple not considered, even after I asked if it is still possible months ago it was declined to add more 7135s to the driver design
I remember you asking for that Lexel, shame it wasn’t implemented for a more complete and more efficient package.
I thought that ramping covered all levels, from lowest (7135 only) to highest. Am I mistaken ?
Most places are sold out and have not restocked.
I think they have been discontinued.
Buy now.
Time to look for alternative ? I think a previous poster mentioned one. It’s actually something you can easily mix up for yourself if necessary.
Fasttech quote ingredients as Ingredients: ZnO (24), NH4cl (30), Hcl (6), C3H3COH (30), H2O (12) and Surfactant (3)
Its the HCl and NH4Cl that are the key ingredients (sal ammoniac and muriatic acid in old fashioned terms), silversmiths, model engineers etc. have been mixing up their own fluxes for ages. Otherwise you might find a good silver-soldering flux like Harris “Stay Clean” is good enough (but it doesn’t have the acid and sal-ammoniac I think). Just the zinc chloride.
Actually I was surprised that GOOT could be posted, maybe that’s why it has vanished. Hanging on to my bottle, and will keep it for special occasions.
http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Fluxes/Stay-Clean-Liquid-Flux.aspx
You are right. And as you said the point where the FET comes into play is critical.
Now that’s the perfect motivation/argument right there to have a lanyard/glow ring/keyring light. All it takes is one trip or slip and you are effectively blind and incapable of finding your light again, assuming it is still working. I have been in pitch darkness outside once where I was incapable of finding my car, just 20m away. A single match would have been invaluable to me.
Lowest is PWMed 7135 which is also not linear (close, but no).
How are you going to catch it? I like linear mod but if I want to use it I will set with 3-5 fixed mods that includes one 100% 7135. After you can add as many chips as you want. But in ramping you will just pass this border (between 100% 7135 and low % FET) and wont recognize this easily.
This was down a steep wooded hillside, eventually found the torch maybe 50 yards below me. Limped home with damaged knee, three butterfly plasters needed to fix. Meanwhile found what I was searching for, thank goodness.