great build!
do you have beamshots?
Beamshots got put on hold… I got held up on fine tuning voltage monitoring values in the firmware, then yesterday a driver I had been waiting on showed and I had to give it a go: Mod: Small Sun ZY-T08 MT-G2 (without cells in series conversion)
But now that that is done I should be able to get some beamshots taken shortly.
Beamshots got put on hold again. I had to put together a new driver after an incident…
I took it to work to show a colleague and my boss heard about it asked to try it. I told him a little about it and he asked if he could take a look inside it. “Yes, but…” was all I had time to say before he tried to unscrew the battery tube like you normally would on a light like this, but not on mine as I’ve converted to 2S2P with springs. By doing this he crushed the springs and shorted the cells. I got it apart and took the cells out, but as I had to unscrew the battery contact plate on the back with four screws it took a bit of time. It was getting really hot and smoke was coming out. I can tell you, it’s kind of nerve-racking trying to disarm a potential bomb like this…
Two of the springs completely melted and some bits got stuck on the cells, one was still shorting even after I got them all out. The driver, springs and cells got fried. I don’t mind the driver (I got three driver PCBs from OSH Park) and who cares about the springs and components, but the cells where mighty fine new Samsung 25Rs :_( He offered to pay for them but I have to take most of the blame here for not telling him, I knew perfectly well what he is capable of.
Anyhow, I learned a few things. If I where to sell one of these I have to secure the battery tube so you can’t try to open it like that, and that the contact plate on the rear should have some sort of quick release so it’s not necessary to have a screwdriver nearby and unscrew four screws… and also to be weary of putting a light like this into the hands of someone who has their thumb in the middle of their hand (Swedish expression).
Two springs vanished, only a few traces of them left.
Anyhow, it’s back together with a final version of firmware and I’ve taken a few beamshots that I’ll be posting shortly.
Ohh man, what an incident. Have the boss make it up to you by having him purchase another like this one (but with upgraded safety maybe)
Ouch! Shame about the cells, but good thing nothing worse happened!
I’m always wary about letting other people use or borrow modified lights especially with unprotected cells.
Building an awesome modified light is one thing, making it completely idiot proof is a whole other story, haha 
Looking forward to seeing the beamshots!
That’s a bummer butt when you can have a mishap and learn something without injury it’s a good day—I always go to the rifle range with this old timer to site in before deer season— He put a .308 in a .270 rifle —It blew the side of the stock about 35’ to the left and stung his forehand really good—That’s all—He said look at my Browning .270—I said Podna you got by cheap today—could of blown his arm or his face off
You have some biiig nuts up there in Sweden! Taking that apart while it was frying the cells.... Where is the smiley that beats up Chuck Norris when you need it!
I am happy that you are safe and I am happy that you can rebuild it already. But holy heii what an incident. Respect for how you handled it!
i am not generally in this type of flashlights but this triple mtg2 looks very special. congrat on your good electronic skills too.
reading on this thread everything looks ok to me till the moment i see the photo of the spring and the soldered wire. i thought this setup is little bit risky with my mind. later on sadly i read about the incident. but i think you should he happy with the incident, bc after all no one was harmed . and what hapen should always remember to all us that, when u play with multi li ion setups, safty should take priority in designing.
still i can not do otherwise but joining Ledsmoke and the rest waiting impatiently for beamshots!
Thanks all. The spring issue was a bit of a concern but I aligned the driver with the battery tube perfectly. Not an issue if you know what you’re doing… but yeah, it certainly wasn’t idiot proof. A cheap lesson learned for sure.
I finished up the firmware for this light. Running it on a mechanical switch with an off time cap is the perfect UI for me. Some firmware details:
Three modes, PWM levels 20, 80, 255.
Turbo timeout 60 seconds.
Short press induces next mode.
Medium press induces previous mode.
Long press induces voltage display with blinks. The voltage values are read and written to memory every 5 seconds when the light is on and under load. When long press indicator is triggered the latest stored voltage value is read from memory and flashed out according to levels. I’ve been looking at HKJ’s Samsung charts to get an idea where I want the levels.
Voltage monitoring values are adjusted for low voltage step down at 6.6V and critical voltage shut off at 6.1V.
I programmed a limiter to prevent highest mode when low voltage is flagged but had no more space. I have one more PCB from OSH Park so I’m considering mounting a ATtiny25 or 85 on it as I have a few of both lying around. 25 will be enough for the above, but I want to dig into the 85 for more flexibility in a headlight project I’m working on.
Edit: Taken these beamshots off. I’ve taken new ones and added to OP.
A bit of red loctite [271] (the gotta have heat to get it apart) might be the best bet for securing the battery tube blue [242] would be good, but it still can be broken loose (unless you use ALOT of it)
Glad it didn’t go worse with the incident!
Still an awesome build
i.e run the light for a couple mins then twist? 
—
Turning on my IPD: (Idiot Prediction Device)
“Oh shit this light is getting hot, ouch! Can’t touch it. F*ck I better get the cells out before they cook!”. Grabs towel and twists head in a rush to get the cells out, SHORT, FIZZ, BANG etc” 
—
Red loctite is pretty potent stuff. But considering the operating temperature of the light and the real danger inherent in this design I’d suggest a grub nut or something along those lines to make sure it’s not going to turn unless you want it to. Plus easier to maintain than with loctite.
Not sure if there’s a good place to drill and tap for a grub on this light though.
I’ve taken new beamhots and added them to the OP. The indoor beamhots don’t really do the light justice, the difference is less noticeable in the photos. The outdoor shots are a little better though.
I do like the beam profile of this light. Floody with a rather large nice hotspot.
Do you have a way of measuring current accurately, or lux?
I’d be keen to see what you’re output curve looks like and how long it manages to stay in regulation especially since you have a comparable amount of 7135s as my BTU.
I’d be interested in that too, but I don’t have anything to measure lux. The DMM I use usually gives quite stable readings when PWM is on 255, but it’s rated for max 10A.
Dunno, but my e-switch firmware seems to be a similar solution - click to step up mode, long click to step down from high, longer hold for strobe (or any mode you'd like), 1 sec idle to lock-in the current mode, then when the light is ON, one click to turn it OFF. So you got quick access to lowest mode, quick access to highest mode, and one click turn OFF from any mode. Also when it's ON locked in, you can do a long press to go to lower mode, then you are back in to the state of changing modes.
Edit: btw, this is an awesome mod! Love it! I realize now this setup with the zener mod is much better with a full power switch rather than e-switch. The zener mod with an e-switch will have a huge parasitic drain. Wonder bout the lumens output of this. Dunno off-hand what a MT-G2 does at 6A, but I'm thinking on the 3500 to 4000 range each? So, maybe this light does 10K to 12K? Maybe higher?
Thanks Tom! don’t know how many lumens but it’s quite a lot. My light has the same amount of 7135 chips as LinusHofmann’s triple MT-G2 BTU, but he is running LiPo cells. The samsungs I have in this light are up to the job but there is a little voltage sag, between 0.4 to 0.8V on high.
The newer E-switch firmwares do seem good but they are rather recent additions that where not available when I had my M6 in stock condition. I was taking it apart so I could test and develop E-switch functions like the ones you mentioned but I somehow lost the driver. I’ve always preferred mechanical switches, so when I started designing my own driver I just had to try it. I really like it
The light has now been used for the purpose I built it for. Here are the first photos it helped produce:
nice pictures!
Very cool!