some info from the mod i've done to my Storm. I think it's a great headlamp, i just wanted it to be slightly more floody... so i swapped the XP-E with an XP-G2:
XP-E (1/100s f/2.8 ISO 200)
XP-G2 (1/100s f/2.8 ISO 200)
(you can also check the picture from Szemhazai in the first post, he got similar results swapping with an XP-G since the die size is the same)
but of course the more you get, the more you want
so I have modded the driver as well.
the sense resistors used by the driver are R240 and R620 at the bottom of the board, on the back size:
that's how they work: the left resistor is used for the main led, the side leds use BOTH the resistor in series (so that makes 0,86 ohm)
The stock currents are 400mA for the main LED and 110 mA for the side leds (they are in parallel, so 55mA each)
acoording to what i've measured the driver follows this relation: i = K / R
where K is around 95 (current in mA and R in ohm)
so here's my modded driver
i moved the 0,620 res to the left and sandwiched it together with a 0,330 res i took from another driver. That makes a 0,215 ohm resistor, which gave me 440mA output. I guess 10% more current should be in the safe range for all the components (it's my main headlamp and i need it to be reliable).
XP-G2 @ 440 mA (1/100s f/2.8 ISO 200)
comparison:
(the difference in the XP-G2 beamshot shape at 400 and 440 mA is due the position of the depth of the led in the optics: at 400 mA i was playing with it and trying to solder the MCPCB a bit more forward, but then when i had finished modding i realized that the position of the MCPCB is fixed by the small "plastic heatsink". I may try swapping the XP-G2 with an XT-E though
http://www.candlepowerforums.com/vb/showthread.php?377397-XP-G2-vs-XT-E )
I have then shorted the two pads on the right side instead of putting the spare 0,240 resistor there (which would have given me 210 mA output) cause i wanted the side leds to have the same output of the spot led [
IMPORTANT: i have done that cause i have swapped the two side leds with two xp-g, i haven't found the model of the stock leds but i doubt they can reach over 200mA each safely]
swapping the side leds with XP-Gs makes no sense unless you want to drive them at much higher current than the stock 110mA (55mA each): i couldn't see any difference in the output and i have measured basically the same voltage drop at 110mA so also the efficiency is the same at currents that low.
XP-Gs at 110mA
(1/100s f/2.8 ISO 800)
XP-Gs at 440mA
(1/100s f/2.8 ISO 800)
(the output seems much lower than the spot XP-G2 but that's just because the wall was 2-3 meters far... but the output is comparable, just one is spot and one is flood)
P.S.
the efficiency of the flood mode might be considerably lower than the spot mode because of the two resistors they have cause they are in parallel, i have to measure their voltage drop to see whether it is significant or not.