The F13 is a nice light, takes a 26650, is nice and beefy, could run some decent power and still stay relatively cool. The UI, though, was rather annoying. H/M/L plus blinkies… yecch. Dis-co-nnect!
So, rather than suffering in silence, I figure I’d share my modding misery. 
Anyway, I was doing this already, didn’t want to stop (inertia, and all that), so just grabbed some Truly Crappy cellphone pix while I was already in-progress.
Start with a standard F13 ( http://www.gearbest.com/led-flashlights/pp_5499.html ). The driver was a µC with parallelled surface-mount chip-resistors to provide the ballast. So expect the current to be hideously unregulated from a fully-charged cell to almost depleted.
I chose this driver
instead. I don’t intend to run it from multiple cells, but it’s a somewhat hard-to-find 22mm driver. I’ve got plenty of 17mm and 20mm drivers, but never needed a 22mm driver. Now, I did. I got the 1-mode (on/off) to not have blinkies, and because the F13 should handle that power pretty well for an extended time.
These are they, nicely delivered as a single “stick”, 2-wide, for the total of 5 drivers I got. I snapped off the oddball one and filed down the periphery to let it fit easily into the head.
Well, first off, I had very limited headroom inside the head, what with a big honkin’ toroid taking up lots of space, plus the wires being looped through and coming out the hole. So I had to snake the wires out of the hole to come off the board directly. That got me this
plus, you can see the old driver on the table, with those 8 parallelled resistors on-board. Oh yeah, I had to desolder the spring from the original driver and solder it to this bugger.
Also, I didn’t want the wires wrapped around the toroid to be pressed up against the shelf that the LED sits on, so I took a PTFE disc insulator ( https://www.fasttech.com/p/1138102 ) and placed it inside the head on the opposite side of the shelf, thus:
Next came the emitter. Had my choice of a U2-4C ( https://www.fasttech.com/p/1574600 ), or a T6-3B ( https://www.fasttech.com/p/1425002 ). Chose the latter, a little whiter but a lower brightness bin, vs slightly warmer but brighter. Maybe my next one will be the 4C…
Didn’t mangle anything, thankfully. Damned wires had a life and will of their own, and didn’t want to be soldered to the star, the way they wriggled out almost every time I attempted it.
(Hey, I did say these were crappy pix…)
Anyway, I can’t find my microscopic tube of Arctic Silver 5, so for now it’s the reflector pressing the nekkid star to bare metal in the head. When I find it, I’ll grease it up. Don’t want to use thermal epoxy, or just glop on some Fujik, so I’ll wait ’til the AS5 turns up.
Anyway, here’s the finished product, which looks from the outside exactly the same as it did before I started.
And yes, it says XM-L2! No more of the omnipresent “XML-T6” [sic] like on cheap craptastic lights.
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So, that’s pretty much it. Had some problems with the switch, the insulating spacer coming out from the retaining ring and keeping the switch-board from making contact, but I ironed that out. Lights up nice and bright, does seem like it could be almost in the 4-figures lumen-range, but haven’t taken any tailcap-current measurements or anything yet.
I’m not too thrilled with the beam, as the hotspot is a little fuzzy, and it’s a little ringy. Wondering if I should shave down the included spacer / centering-ring in the reflector to let the LED sit a hair deeper in the reflector. Any beam-gurus, feel free to chime in with advice!
They have more options for 22mm drivers.
