I looked up the Cree data sheets to get some approximate numbers. I used a current of 800 mA because that's what the 5x XR-E module drop-in for the WF-500 produces:
XR-E Q5 (couldn't find R2 info):
- Vf @ 800 mA = 3.6 V
- flux @ 800 mA = 210 lm
- total power dissipation for 5 LEDs = 14.4 W
XM-L T6:
- Vf @ 800 mA = 2.93 V
- flux @ 800 mA = 315 lm
- total power dissipation for 5 LEDs = 11.7 W
So in the WF-500, doing a straight swap to XM-Ls should give me 50% more output (not considering beam shape). And power dissipation will be almost 20% less. But the driver used in that 5x XR-E module can be modified to push out more current. So at the very least, I could modify the driver to produce 20% more current, so that power dissipation is the same as now. Otoh, I've used my WF-500+ ("+" means the stock xenon light with the 5x XR-E module) for several minutes at a time on high, and the light doesn't get uncomfortably hot. Therefore, I'm willing to drive it a bit harder than that, so let's say 40% more than the stock 800 mA, which is 1.12 A. Ignoring driver heating issues for now, the higher current should produce:
- Vf @ 1120 mA = 3 V
- flux @ 1120 mA = 420 lm
- total power dissipation for 5 LEDs = 16.8 W
16.8 W isn't that much more than 14.4 W, so I'm sure the WF-500 body can handle that for a few minutes.
Now the total output becomes 2100 lm though, not OTF of course. With the stock XR-Es, the total output was 1050.
What if I bumped the current up to 1.3A?
- Vf @ 1300 mA = 3.05 V
- flux @ 1300 mA = 490 lm
- total power dissipation for 5 LEDs = 19.8 W
- Total output = 2450 lm.
For the WF-500, maybe those few hundred lumens aren't worth the extra 3 W power dissipation. But the point of all these calculations was to show that we should be able to get a light like the one I'm wishing for:
- 5x XM-L
- 2x 26650 or 32xxx cells in series
- body & head with good heatsinking (the WF-500 has not much heatsinking)
- 2500 - 3000 lm at the LED; 2000 lm OTF or more
Edit: what about 3x XM-L at 2 A?...
- Vf @ 2 A = 3.18 V
- flux @ 2 A = 685 lm
- total power dissipation for 5 LEDs = 19.1 W
- Total output = 2055 lm.
So yeah, I'd prefer a 5x XM-L module, driving them at lower current.