Convoluted, that’s what it is.
There is no 4V equation here. The XP-L’s in the Q8 pull 3.3-3.6V, even though the cells are 4.2V when charged. Similarly, there is no 6V equation in the L6 with XHP-70 or 70.2, since that emitters forward voltage is over 6V, especially when pushed, so if you’re figuring wattage of each light then a more accurate reading of voltage and amperage needs to be taken at the emitters. The Cree datasheet on the 70.2 shows that at 4.8A max current the Vf is between 5.6V and 6.1V, so figuring in 4V just to play easy with the math doesn’t actually equate to what’s going on. In the same way, Giorgo was exactly right in that 2 26650’s in the L6 are an 8.4V 5000mAh battery. Pushing the 70.2 hard with an FET driver has it’s Vf up around 6.8V or more, so there is a 6.8Vf on a falling 8.4V power supply. You can’t divide up the amperage being drawn just to satisfy easy math. 12A at 6.8V (2 parallel 2 series emitters) is 81.6 watts of power being consumed, in the same way that 21A at ~3.6V (4 parallel emitters) is 75.6 watts in an over- driven Q8. Since the 4 cells of the Q8 (all 4 cells together, a battery) are being drawn on in parallel, using 3000mAh cells will indeed give 12,000mAh of power supply, so the battery is running at a 1.75C draw, while in the L6 (at 12A) the 5000mAh battery is seeing a 2.4C draw, obviously falling faster due to the extra hit they’re taking.
Dealing with actual numbers, real time at-the-emitter voltages and amperages, makes it easier to understand where the heat is coming from and why the cells drain so fast. For me, anyway.
And for the record, merely swapping XP-L2’s into a Q8 only nets around 7300 lumens, even with spring bypasses. More needs to be done to get more output. And my Q8 with SST-40’s is making over 11,200 lumens on rested VTC5A cells.