Modding a 3AA NiMH Flashlight with a XM-L T6 Emitter, need your input


I am going to put a T6 Emitter into a Chinese made 3AA Flashlight, (which light? - not yet, it's part of the suspense).

I will be using 3 Eneloops (2000mah) for batteries. This is a mod because I will have to replace the reflector & lens, as well as making a heatsink for the emitter. I will probably use the stock battery holder, but I may mod it severely to help cut down on resistance. (or maybe not, since I might need the resistance).

My dilemma is whether I do it "DD" or use a current limiting board. I would like to do it DD as I have done with many P7 emitters, but since I have not used a T6, I suspect it may be more problematic doing DD.

Keeping within a "budget" I would immediately think of using a KD AMC7135*8+MCU circuit board, knowing that I can modify the modes with the "star grounding" technique. It's the cheapest board around short of a plain 2800mah AMC7135*8 board with no modes. Also I may piggyback 1 or 2 AMC7135 chips to up the current to the emitter. It's just not fun unless it's hotrodded!Tongue Out

The problem I have (or lack of knowledge I have) comes with the very small range of "efficiency" with these boards. I need to know if it will work well with 3AA NiMH. I know when they are fresh off the charger at 4.2v or higher it would be OK, but what happens when they fall to 3volts? The AMC7135 board (from what I read) looses efficiency severely on the low side of 4V and the high side of 4V, so is it worth using the board, or is it easier just to count on the "inherent resistance" of the cheap battery holder and do it with "DD"?

I just don't want to fry the emitter, but I'm not sure how much it will take long term. I have a P7 that has been running on DD 4AA NiMH for well over a year and it works fine, but are the T6 emitters as tough as the P7s are? I know I could just do a P7, but I want something new. The fun for me is in the doing, not the using.

...and No - I don't want a MagLite. I am just sick of doing MagLites. I know I could do one with 4AA and the board, but I am just tired of MagLites...

if you use a driver, you might want to look at this single mode driver from DX. it's pretty efficient and can handle lower input voltages. i used it to make this light and it runs well on a AA or a 14500. it drives only half as much current at 1.2 v input as it does at 4.2 v input, but efficiency is excellent at both levels.

Ok, but it only puts out about half of the current that a T6 can utilize? Part of this idea for a mod, is the old "stuff as much as you can into a small light" routine. (grunt, grunt)Wink I want to try to hit 3000mah if possible into the emitter.

Well I did a C88 (3xAA) with XM-L using the 7135-based 2.8amp board from Illumination Supply (or ShiningBeam). Programmed the three different modes myself, and the light is working great. As for efficiency I'm not exactly sure, but I always use the 7135-based boards for my 3xAA setups. Really couldn't be much simpler.

Start with DD with no resistance mods. Check current draw. After every resistance mod, check again. You may not need to add the driver (for current limiting anyway)

Any idea what the voltage or the amp draw is thru the emitter on a fresh set of batteries?

I just wondered if others had done this already and what they found with DD and 3AA on a T6. Every build is different, but it helps to know what others have already done. Nothing new here, except for people like me who haven't done it yet...

Nope, I don't even know how to measure that :( I just measure by the tailcap and see 2.8 amps. As I understand it, as long as there is little resistance, almost all of the current flowing through the tailcap will be going to the emitter.

@ jonnyC - well done on your mod, sounds good. But I would be concered about the resistance in the light using one of those 3AA batt holders. Those holders were not made for 3A! If they are anyting like other cheap 3AA holders I've used they will be holding back the current. The best bet is to try and solder the springs to the metal parts if you can, that would help.

Yup, that's what I did :) I was actually considering connecting all of the metal parts with wires (well, in series obviously), but I got the full amperage out of it by just soldering the springs to the metal.

From playing with those budget 3AA battery holders, I know they will take 3A, but not for long periods of time, the plastic can get warped. I would think that with a low Vf emitter, like the T6, that taking all the resistance out of the system with DD 3AA would overamp the emitter quickly, but that is only a guess, since I haven't done a T6. With the P7s (DSWOJ), I have done, they take 5.4 amps direct (4AA Eneloops) and don't turn blue or burn out. Just not sure if the T6 is that strong. Worst case would be what? 4.5A max maybe on 3 fresh batts? If the emitter can take that, then I wouldn't worry and do all the resistance mods including making a battery pack instead of using the stock holder.

Olny one way to find out I guess. Just buy 2 and have the spare if it blows.Surprised

Just keep in mind most of those 3AA holders can only flow about 2 amps. I had to convert my C-88 to an 18650 after putting an XML and a 3 amp driver in it because the 3AA couldn't flow enough amps for what I wanted.

I got about 2.5 amps by soldering heavy spring into the holder.

Great mind think alike, or in other words, looks like I was teaching you all to suck eggs!

Nice work guys.