[WIP] Supfire M6 series 18650 conversion (2S2P for now -- 4S possible)

This is what I’ve been thinking about for a simple, cheap, safe, and reversible series mod to the M6.

I still haven’t put enough time into figuring out Eagle so I haven’t been able to make to contact board.

The nylon legs are available on amazon along with the proper sized screws that I’ll post later.


The first prototype is being made this morning. I managed to simplify the leg assembly by using self retaining pcb spacers. This eliminates the only ‘ugly’ part of the design which was the need for metal screws. Now there are zero conductive parts other than the contacts. I’ll post a picture of what I make later today.


The prototype is working beautifully, and now that I’ve identified most of the quirks with the format and resolved them to my standards, I’m ready to move on and get these boards produced. I still need to learn Eagle, so I don’t know when I’ll be finished if I draw it up, but I’ve PMed other experienced users and they’re willing to put it together with dimensions that I supply. As for the hard goods involved. The nylon legs are $12.33/100pcs at Future Electronics . And assuming $1.50 for the Oshpark board this unit could go for as little as $2 (not including springs and brass buttons, which most modders have in stock).

Pretty cool! Designing the contact plate in Eagle is probably easier than what you did creating those drawings.

Thanks Richard,

I know I’d be able to do it, I’ve just been lazy I suppose. Never put the time in to learn what is required to get them produced with all the layers and drill files and what not…

Just watch Mattaus' videos, they're pretty good. I do a few things differently now, but they gave me enough guidance (and courage) to get started.

Don’t forget that it should be keyed. That’s easy enough, eliminate one leg and replace it with a plug/key/etc.

This is good, I’m glad someone will tackle this!

I put thought into a keying mechanism back when I was designing this, but didn’t think of anything that didn’t require someone to grind or drill into the battery tube. The only way to make it ‘idiot-proof’ is to make one leg extra long and drill a hole into one of the ears inside the battery tube.

Or I suppose you could make it require button tops and put a mechanical reverse polarity setup on it. Find nylon washers/bushings/rings slightly taller than the positive brass buttons and super glue them onto the board.

Huh? Either I don’t understand exactly what this thing is or you are overlooking the obvious. Where and how do you intend for this thing to interface with the M6?

I assume that the user will be required to leave the body tube in place and remove the tailcap, at which point this item will fall out of the light… yes?

I see that I misunderstood what this was. Carry on.

This is intended to drop into the top end of the battery tube after the required modifications were made to the stock contact board at the bottom to essentially convert the battery tube into a series carrier. As drawn, it is 2P2S, but with a slight modification we could make it 4S also.

Make sense now? Sorry for lacking descriptions early on.

Eh, the misunderstanding was my own fault.

Anyway it does make sense. Your mockup is about as elegant as this type of solution is going to get, other than lacking a method of keying it.

I’m not really 100% happy with any method I’ve seen or thought of for doing a series conversion on the M6. If there was a clean, reversible way to lock the body tube in place then I’d advocate Mike C’s method, but I just haven’t seen a good way to handle that either.

OP updated

Very nice, me neeeeds! lol

I have one in the wind at the moment to Australia in an effort to sort this out. Switching tubes to a modified TK75 extension tube so the carrier can be used. Hope it works! :wink:

One (or two) of yours would be nice for the reversibility.


Excited to see the results

Contact board is done. I made it from a full faced copper pcb from radio shack. It’s going into my second M6 to run 3 XHP-50s (soon to be 6) from four 25Rs using an old fubared M6 driver with just the FETs remaining. I hooked up the gates in parallel and I’m going to use the switch to run it momentary direct drive only. I’ll do my best to get some beamshots too tonight… but I’m not making any promises :wink:

That is one good looking creation JM. Very clever.

Nice work… can’t wait for the beam shot :beer:

So now that I’ve got a day of use on the piece, with plenty unnecessary times opening and closing the light, I can say with confidence this is a reliable solution. The design is naturally keyed and at least in 2P2S, you can’t physically put it together the wrong way.

As you can see by the unused hole and leftover solder, I tried at first using a central spring for + plate to driver contact… this worked but added that much more effort to compress the springs and get thread engagement. Another side effect was the spring would sometimes bind the contact plate inside the head, where it would remain after you opened it up. Nothing terrible but didn’t prove to be an advantage over my second solution, which is better for current carrying anyway.

As for the beamshots, I’m charging up all my batteries today and am going to try and do a full shoot of my collection if the conditions are good. It was too foggy last night and everything is wet so not ideal conditions…

But I’m kind of mad I built this. Now my modded K40M and XML2 M6 look like they’re running on primaries, and any light that’ll outdo it will require a lot of $$$$$$$$. lol. Still cracks me up that we call it BLF :beer:

BLF is generally budget in the beginning for most of us, who then proceed to put $60 worth of parts into a $35 light.

Very cool and very simple solution. I like it. Do you think there is enough length for protected cells?

Yes. They should be no problem. EDIT I checked with four cells measuring ~69mm and I could only manage one thread before I gave up. With softer springs (I used some strong ones) and shorter/no positive contacts it could be done. I figure though if anybody is running this setup they are using IMRs anyway. End EDIT I only have two protected 18650s so I can’t prove it with pics but the way the unit works is there is no lockout. As long as there is one thread engaged I can operate the light. Of course this isn’t a recommended way of running something, I only intend to illustrate the concept at an extreme.

The O-ring on the body tube is still completely covered by the head when fully tightened, since added length is only 1.6mm. I’ll go do my best to simulate protected cells… might use some magnets or something.