L1 vs L2 efficiency question

I am pretty new to electronics, so please forgive my basic understanding.

Why is a Surefire L1, with its 1 battery, rated at 2 hours at 15 lumens, while the L2 gets 9 times as much emitted energy (i.e., 15 lumens for 18 hours) from only twice the battery capacity?

If you can equate energies as lumen-hours, then the L2 should be (15*18/2=135)/(15*2/1=30) 4.5 times as efficient as the L1. I realize circuit function is much more complicated than that, but I don't get how this works.

I am really curious about all the gory details, but any explanation or pointers to sources of information would be great.

Scott

STrange -- I tried to post this in the LED section. Mods, feel free to move this.

Scott

Manufacturers' runtimes are completely inaccurate. Disregard them.

I think the 15 lumens spec for the L1 is not correct. Mine is putting out what I think is closer to 30 lumens, so on high it should be brighter than the L2 on low. The L2 on low will still get more lumens per battery cell than the L1 because it isn't pulling as much current out of its two cells as the L1 is on its single cell. With that higher current draw, the cell provides power less efficiently due to internal resistance and chemistry factors.

Even accounting for the above, there still seems to be a gap. The L2 buck circuit (voltage down-converter) is probably more efficient than the L1 boost circuit (voltage up-convertor).

the L2 on low runs for "only" 8-10 hours.
It makes me feel sad that now even premium brands like Surefire state wrong runtimes.

And the LuxV is more efficient at this low power level.

The L2 on low draws 160 mA at 6 Volt, puts out a bit less than 15 lumen on average.
The L2 on high draws 1.4 Amps at 6 Volt, puts out a bit more than 65 lumens on average.
The new L1 draws 900 mA on High at 3 Volts, and puts out 25 lumens on average.

If you make a lumen/watt comparison, as expected, the most efficient setup is the L2 on low.

Anthony

Ok, I get the battery thing, and have also read about LED efficiency changes. I don't know anything about "buck" and "boost" circuits though. Anyone know where I can see a circuit diagram?

Scott

I'm not a electronics wiz either but in layman's terms, a buck circuit "bucks" against a higher voltage, lowering down to the desired level, whereas a boost circuit "boosts" a lower voltage up to the desired level at a sacrifice of some efficiency.