Excellent review! Thanks for the data on lumen comparison.
I think if you mod it to take more current, it would drain batteries quickly.
Hey Relic,
This is a smashing review, very comprehensive.
Have you had a chance to play with the drive current on this yet? If so how much are you cutting the resistance by to see any good gains?
Dear god, how have I missed this. Have you tried playing baseball with this?
Nice pics by the way!
No chance to mess with it yet. My first step will be to try to push the driver further. I will probably add some heatsinking to the driver if I can.
I’d like to get up to 5000 lumens OTF, but I don’t think the driver has that in it.
I get the impression that everything on flashlight market is designed with Optimum Efficiency, emitter efficiency that is. Getting the most light with the least energy loss.
Driving an XML around 800mA has the highest efficiency verses anywhere above 1amp.
Very nice work with the custom heat sinks. Like you, I lap almost everything that conducts heat these days.
The aluminum body of the flashlight with its radiating fins would have faster heat absorption than going through the trapped air in the cavity.
I wonder if you’d get better heat conduction by pressing that thermally conductive “mud” into the fins leaving enough to touch flashlight body, all around. So you’d get the most direct heat conduction to the body.
Fwiw.
Nice looking light ! 
its almost like an enlarged UF T90 or TF X6 and with more emitters.
The anodized heatsink will radiate heat (as IR) into the chamber which will hit the anodized interior of the driver space cavern and be absorbed. Since the driver gets to a much higher temperature than the host (~80C vs 50C), the net radiation transfer will be away from the driver.
Adding physical contact would help for sure. If I can figure out a clean way to do that, this will be the host to try it on. There’s lots of driver space to work with; I can almost fit four 18650s in there! 
Relic, how did you trim the emitter centering spacers?
I just ordered a black AK90 and should have it in a couple weeks.
I trimmed them with very sharp side cutters.
If you take the reflector out, make sure to make a temporary alignment mark. There must be small machining variations in the emitter positions. The reflector would only go back on the way it came off.
Hi everyone! I finally registered. Vestureofblood as been a very kind person in helpinge with a few questions via emails. I have this particular light and want to do this mod. This will be my first resistor mod so I would need a little guidance as far as which r22 resistors I need.
Relic, would you mind giving me the part number from digikey for the r22 resistors? I already have some nice forged copper heatsinks.
Would you mind taking a picture of the resistors already in place?
Thank you so much in advance!
Ken
Nice mod relic. You guys amaze me with your soldering and little experiments with these little thingymebobswatchamecallits. Thanks for sharing.
Welcome to BLF Hyprmtr!
You can do the resistor mod two ways. Add two R22 in series, or one R47. Both will give about the same result, but the single resistor is easier to do.
Digikey R47: 73L4R47J CTS Resistor Products | Resistors | DigiKey (cheaper)
Digikey R22: RL73K2BR22JTD TE Connectivity Passive Product | Resistors | DigiKey (slightly more current, more expensive)
Fasttech alternative: https://www.fasttech.com/products/0/10003143/1234400-0805-022r-smd-precision-resistors-100-piece (slower delivery, lower cost for 100 pcs)
I’ll take a pic of the ‘tented’ resistors later on when I get the chance.
Ok great! Thank you so much! I will definitely be sharing more of my projects here.
Ken
Oh, one question. The picture would answer my question but, did you leave the original resistors in place or did you remove them?
Ken
Nice mod and nice results…
5.4A with four cells should make this light to the brightest budget light available.
Have you tried undervoltage protection? What is the current with decreasing voltage?
Nice mod Relic38!
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