To clarify the lumen/turbo jargon:
Turbo is like sprinting, and the "high" is like running, medium like jogging, and so forth.
Turbo is to get a peak at MAX brightness/range...a way to sprint when you need to.
To avoid overheating (Just like the runner), it steps down from turbo after a few minutes.
The brightness on the XT11 is controlled by the VOLTS from the cells. The RUN TIME is related to the mAh of the cells themselves...higher mAh = more run time.
So, the 18650 has ~ 4.2 v, and there's one of them, so the light's brightness is from the ~ 4.2v
The 18650 also has up to 3100 mAh to use for run time.
The CR123's are also ~ 3.0 v (Primaries), but there's TWO of them, so a total of 6 v for added brightness.
The CR123's are also ~ 1,500 mAh, less than half of the 18650's 3,100 mAh for ~ 1/2 the run time.
The RCR123's (Rechargables) are ~ 4.2 v like the 18650's...but - again, there's TWO of them...so that's 8.4 volts for even MORE brightness.
The RCR123's only have ~ 750 mAh though, about half of the Primaries' 1,500 mAh, for ~ 1/2 of THEIR run time (~ 1/4 of the 18650's run time)
For the circuit on the XT11, you add volts and mAh stay the same in this case. Some other lights are wired the opposite way, so brightness is the same, but run time is additive, and so forth. (Series vs parallel, etc...)
So, when you boil down the options, you can have your fire burn longer, or, use up your wood faster but have it be brighter.
:D
At Photon Fest 18, we measured some lights, and the XT11 put out a bit over 600 lumens on turbo with an 18650, stepping down to ~ 500 L when it got hot. When its cool, you have the ~ 600+ L again.
The same light with RCR123's was pumping out 850 L though, AFTER running long enough to step down....a LOT brighter...but instead of ~ 2.5 hours of run time with 3,100 mAh of cell endurance, we are down to 750 mAh, more like a half hr of total run time.
Almost all lights now a days step down to avoid over heating. Some advertise it, some don't. In the olden days, the lights would either just not HAVE the ability to "sprint" when you wanted a kick...or, would have it, but, the light would just dim as the cells drained...and only be at full brightness on a fresh cell....or, would be regulated to not go over a certain current to have the light just be able to jog...but never run, etc.
:D
The XT11 for example is regulated to maintain brightness even as the cells drain...the circuits suck all the juice they can from the cells to maintain regulation at the required flow rate.
This is one reason better cells work better, as its not just the mAh...its the discharge rate they can support. Cells that can take a higher discharge rate can support more powerful (higher amp draw) lights.
If patrolling/covering an area that takes more than ~ 1/2 hr to cover, and you can see what you need to with ~ 500-600 L, etc...then the use of the single 3100 mAh 18650 works best, and that's how I personally edc the light.
If your use is more like only short bursts of bright max power light, as I use for weapon mounted functions, etc...as in on/acquire the target, and then off and move, etc, or, I am MOSTLY just using low or medium brightness, reading maps, not bumping into stuff, etc...a short run time might not be a problem....as the lower intensities extend run time like crazy.
So, I find it great with a single 18650...that's what works most of the time for me.
I like Callies Kustoms, AW, and Redilast the most, and that's what I mostly have. Xtar and Eagletac, etc, are also good. I look at HJK's reviews mostly to see what the discharge rates, and actual performance are for cells...as I trust our in house resources more than an advertisement for info.
Try to order from a CONUS site rather than waiting on a slow boat from China...I find I don't have the patience for that.
:D
