The Modification & The Materials
You probably know the Fenix E12 V2.0 flashlight, right? I believe some of you were more familiar with the old version of this flashlight, but I never had one, so I used the most recent version.
This flashlight was sent to me for review (upcoming on BLF, but with video published on YT here: https://youtu.be/k1WD04fZJr8 ), and I always wanted one to try to mod it.
The Fenix E12 V2.0 is one of the smallest AA flashlights in the market, it is perfect to gift one to someone not used to flashlights, but…I needed something more. :sunglasses:
Originally it has a Cool White emitter (MATCH CA18), a driver that only takes AA batteries (1.2V or 1.5V), no memory, and puts out 160 lumens. Some of the things I liked, but I felt that this little host could handle some more :smiling_imp:
When I started thinking about the mod there was a major issue I had: the driver. The Fenix E12 V2.0 takes 15mm driver, so using a 17mm driver (that would give me with much more UI options) was a no go. As currently there are no producers of 15mm drivers with UIs I like, I had to pick one from another flashlight I modded 2 years ago.
So I picked a 15mm driver with Bistro HD OTSM, made by Lexel, that I was using in the Lumintop Tool AA V2.0. It was already “shaved” on the sides to fit the Tool AA pill, but it could be used in the Fenix E12.
And given that I will use Bistro , and given that I always give names to my OL Contest projects, this one will be called The Bistrix Mule, a mix of Bistro and Fenix 
:partying_face: You’ll see the “mule” part right away 
By now you already know the driver I used, but you don’t know the LEDs. When I bought my Wurkkos TS10, I ordered some triple MCPCBs with CSP 4000K LEDs (Lumileds Chip Scale Package LatticePower CSP2323). And it was one of those MCPCBs that I used for this mod. Without the Aux leds, of course 
Well, but there are always issues when we want to use fancy things in simple lights, right? That’s the case here… To use those MCPCBs, we need special triple TIR optics, that I don’t have! Also, these MCPCBs are larger than the original of the Fenix (16,66mm vs 15,81mm) and cannot be trimmed down adequately to fit the head.
So…I needed to figure out another option. And that option would be to make a “mule” flashlight.
How? By elevating the MCPCB to near the lens and not using TIR, or reflector.
And this is how it was done!
PART 1
- first of all, I dismantled the light:
- by using a lighter, a leather belt and some pressure pliers I forced the rotation of the tailcap
- by using a work knife, I managed to get the bezel out (press-fit)
- by using the soldering iron, I unsoldered the MCPCB from the driver’s wires
- by using a toothpick I press the driver (glued) out of the head
[all these processes were previous to the modding process, and were done some weeks ago!!!]
These are the original parts of the flashlight and some of its internals. In the final mod I didn’t use some of them: the thin transparent ring, the black o-ring, the MCPCB & LED, the driver, the optic!
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PART 2
- secondly, I studied what I could use to make my “The Bistrix Mule” project become reality, and for that I picked:
- the 15mm driver w/ Bistro HD OTSM w/ 20AWG wires
- the triple MCPCB w/ 4000K 90 CRI CSP LEDs
- a sanded/filed copper DTP MCPCB
- a copper spacer I ordered kiriba-ru some time ago for another project
Also, for the final version, I kept the some of the original pieces:
screws
glass lens
head
tube
tailcap w/ reverse clicky switch
Both the thin copper DTP MCPCB and the copper spacer were already filed before but I needed to file then down a bit more. Also I needed to drill a hole in both of them. For that I used my Parkside rotary tool with different drills, and also some files to enlarge the holes and to flatten these two pieces.
I also needed to drill a hole in the centre of the shelf of the Fenix head , so that the wires could pass through the middle (since the MCPCB has a hole in the middle as well). Same process, same tools as above.
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PART 3
- third, with the holes drilled, it was time to start “mounting the cake”! Or the mule, in this case
1) check if the driver fits and works! YES, all good! :+1:
2) screws get back into the head, start making the ”copper sandwish” and put it on the shelf! YES, all good! :+1:
I needed to be sure that the copper pieces were as flat as possible so that:
a) they could sit together between them (and the shelf)
b) they could make the proper space to – as I said above – “elevate” the MCPCB enough so that it could fit in the upper space of the head, where it had a larger sitting diameter
3) it is time to sit the MCPCB over the copper sandwish and check it everything is OK, if the driver wires pass well through the holes, if the spaces are OK to fit the bezel and lens, and it there is no oscilation! YES, all good! :+1:
4) time to solder the wires to reach the final stages of the modification, and try to lit it up! WELL, almost all good… 
:cry:
This was the step when I started having some trouble. Using the 20AWG wires has a problem in this case, because they are thick and the silicone was protruding, which would cause me some issues fitting the bezel, lens and o-rings.
With the nail clippers, I trimmed a little bit the silicone to make it as flat as possible, but always being careful to avoid removing parts that could cause a short circuit. It worked well.
Still, it was still too tall to allow everything to fit well. This is when I needed to choose not to use the transparent o-ring between the lens and the bezel, nor the black o-ring that I would use as a spacer between the MPCPC and the lens.
I ended up using only the bezel and the lens which sits right on the wires, making it press fit (which is a liability in case the light falls, as it won’t have a cushion :zipper_mouth_face: )
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PART 4
- fourth, with all the things in place, I put a battery and it was time to let it shine
I didn’t mess with the driver configuration, so it is configured in the group 12:
I also think that this is what you can expect from a mule flashlight, a wide beam, without artifacts (well, maybe on the edges, eventually :p) 
A small comparison with the Wurkkos TS10 (right):
And a line-up comparison with other AA/14500 Flashlights
Lumintop FW1AA > Lumintop FWAA > The Bistrix Mule > Wurkkos TS10 > DQG Slim Ti AA
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PART 5
- fifth, I would like to make some reflection about this process:
1) it was not a complicated mod, nor a complicated build for this OL Contest, but I guess it keeps the modding spirit alive
2) It took me almost 3h30 making it since I needed to charge the rotary tool between drills since the batteries are not as good as they used to be :person_facepalming:
3) the most challenging part for me was to find the adequate spacers for the head, since I didn’t have any piece of copper, aluminium or brass that would fit the head exactly as I wanted or as it was needed, to keep the MCPCB in place. This was the part that put me to some major struggle but it ended up working well
4) I forgot to use thermal paste between the copper spacers and below the MCPCB :person_facepalming:
5) although the initial settings and specs of the Fenix were not the worst for an AA flashlight, I believe that it was improved, specially due to the possibility to configure the User Interface, and also because the tint and CRI improved
6) I wish I had a spare TIR optic for the triple CSP MCPCB because it would have been even funnier, although it would be also more complicated to fit it into the head.
7) from a modding and usability perspective, I know I could try to mod the tailswitch and make it a forward clicky switch, but I actually like the reverse option in this light (also, it keeps it smaller than lights with FC Switch)
8) the lens sitting over the wires is a liability in case the flashlight falls, as it won’t have a cushion and may break very easily :zipper_mouth_face:
9) I wish the H17F driver was made in 15mm single sided shape, since it would be perfect for this flashlight :heart_eyes:
10) although I could only make a single led flashlight, using the stock textured optic, it was more challenging to make this project
11) I like the imperfect final result of “The Bistrix Mule” :laughing:
:student: 
8)
:innocent:
