Mod 1: Driver Resistor Mod for 9-11 Amps
Disclaimer: Every light will have minor variations the could result in big changes in the drive current. I recommend you measure your emitter current before and after making mods. Do not rely on my test results alone; they may differ significantly from yours.
OK, time for some fun. I was pleased to see the stock power and efficiency numbers from this driver. Those results told me that this driver can be pushed quite a bit further. I went a little too far before settling on a number I’m comfortable with. It begins with the driver.
On a stock driver we find three resistors on two pads. You can see one R200, under it is one R082 and to the right is another R082. These are all in parallel, giving a resistance of 0.034 Ohms. This supplies the emitter with a respectable seven Amps. However, we have a nine Amp emitter, so…… yeah we need to get to nine Amps (at least 
). That 22AWG wire will have to go too.
First attempt: R082, R082, R100, R100 (0.0225 Ohms). I did this by removing the R200 and adding two R100 resistors. In hindsight, I should have known this was going to go too far. Running from a bench supply set to 12.6V, 4.3A, and it was hitting the limit. I cranked up the current and it went to around 4.8A in. The emitter current was 11.3A!!! Time to turn it off. I will note that the driver was handling it for at least a few seconds, for anyone who plans to mount the emitter directly on copper. This was too much for me…
Second Attempt: R082, R082, R100, R200. (0.0254 Ohms) From stock, add one R100 resistor. This was closer; 10.4A to the emitter, however still a little too high for my comfort.
Third Attempt: R082, R082, R200, R150. (0.0277 Ohms) From sock, add one R150 resistor (since I didn’t have one, I used two R330 resistors, equal to R165). Using this combo gives 9.7A of emitter current. This is where I wanted it. If you have the R150, I’d expect something around 10.0A.
Power In: 12.6V * 3.67A = 46.2W (up from 31.9W)
Power Out: 4.07V * 9.69A = 39.4W (up from 27.4W)
Efficiency: 85% (down from 86%)
Nice! The emitter power jumped by 13W and the efficiency is virtually the same as at stock.
But what about the real numbers; lumens and throw:
Light Output: ~1464 lm (up from 1200 lm)
Beam Intensity: ~73kcd (up from 50kcd) Updated, I found that measuring at 1 meter was creating an error, maybe due to my lux meter (max 50k lux). I don’t trust the original 50kcd number either, most likely closer to 57kcd. To verify, I measured at 5 feet and 12 feet, both came within a few percent of 73kcd. Not bad.
Now, what about the added heat in the driver. The LED is fine, there’s lots of heat sinking for it. The driver MOSFET and diode were getting quite hot at stock output levels (likely why they limited it to 7A). I needed to come up with something to get the heat away from the critical components. There’s lots of space in the driver chamber (you could bury a Pharoah in there). What about adding a heat sink?
That pesky toroid is in the way. Gonna have to move it. Off it comes.
There, now there is room to add a heat sink. I just glued it on with Fujik which should hold it fine. The two large black components on the right were not flush with each other, so one heat sink would not sit good. I solved this by sanding them down until they were flush (they already had the part number scraped off).
Here is the result, with the coil added back on, standing up this time.
And from the other side:
Depending on your heat sink the resistors may be covered. You may want to mod them first. This heat sink was just something I had lying around and fit quite well. If I get a chance to, I will measure it as well as the driver and its chamber.
One other change was getting rid of the 22AWG wire and using 20AWG instead.
Thermal management (in progress):
table(table#posts).
|Time (m)|0|1|2|3|5|10|15|
|Temperature (°C)|18.6|25.0|31.0|34.6|40.0|51.2|59.0|
After 15 minutes, the head is uncomfortable to hold. I would limit use on high at this duration for the preservation of the driver. The light output dropped to 1300 lm at the 15 minute mark.
Cell temperatures, 39, 31, 27. The addition of a neck heat sink really helps keep heat away from the cells.
Outdoor beamshots: (Added Feb 5, 2013)
My comparison unit was the trusty HD2010, driven around 4A, ~45kcd. It was rather cold and the air was somewhat clear. The target is a stand of spruce trees.
First up: 150m (title above picture)
Control - 150m
UF T90 - 150m
HD2010 - 150m
Next: 210m (title above picture)
Control - 210m
UF T90 - 210m
HD2010 - 210m
Finally: 260m (title above picture)
Control - 260m
UF T90 - 260m
HD2010 - 260m
Considering that before the mod these two lights were fairly close, this was a decent improvement in output. Those trees are a rather dark green, only the dead one out in front is a lighter target.
Note: on my photo editing machine these shots look close to what I seen live. On my other machine they look a little darker. They may only be good enough to compare to one another, not to other shots taken at other times. All shots taken at f5.6, 4s, ISO 400.
This was a successful mod for me on this light. I like the results and will probably leave it like that for a little while anyway.
Mod 2: Emitter Swap: MT-G2
This mod has its own thread, here