Fenix TK11 Q5 with 18650 has virtually no regulation. Meaning constant degrading light output.
Fenix TK11 R2 with 18650 has about an hour and half of 100% regulation due to the R2s VF. I think it's the VF frequency. Don't remember.
So if you go TK11 and want 18650 you have to use the R2, period. It only makes sense. After that hour and a half you still have an hour or degrading output.
If you want to use cr123 it just really doesn't matter. Same regulation.
It's near impossible for a flashlights circuitry to regulate multi-battery types at 100% output for X amount of time. The way the R2 is designed is why this happens, the hour and a half of 100% output, not the circuitry.
That's something people don't ever mention.
TK11 + 18650 means GET THE R2!!
I prefer the TK10 because I only use cr123 and I prefer the beam for tactical use. The TK11 is a nice thrower, but for general purposes it's not worth it.
I will mention this. BOTH TK11 and TK10 have an ENORMOUS amount of spill. IMO they both have throwy hotspots, with the TK11 being tighter and brighter, but they both have an enormous amount of spill. It's crazy how far the TK11 throws and puts so much light to the sides. Another thing people rarely note.
The TK12 I cannot speak of and will never. I won't but another Fenix but if I did it would't be that one. It's too complicated.
The UI gave me a headache.
Basically, what he said.
I have had my TK11 (Cree Q5) for about a year now, and like yourself a year ago when I asked on here what high performance light I should buy I was totally new to all of this. Almost a year later and I am
mostly glad that I bought the TK11 but also still have that one major niggle with it - NO regulation whatsoever therefore constantly degrading light output.
This is a REAL shame as far as the "TK" series is concerned, because I can and will personally vouch for the build quality and design of the TK11. It has a very throwy beam but as Search said it's almost got too much spill for my liking. My Dereelight DBS has (obviously) more throw but has less spill and I don't miss it. If I could change anything on the TK11 I would give it a regulation circuit and a different reflector. I say different reflector because the beam on mine is very uneven and full of artefacts. It doesn't bother me much but you can see where some of the extra money goes on more expensive throwers because (again referring to the DBS) my Dereelight has a near perfect beam with no artefacts whatsoever.
As far as durability, I recently put my TK11 through it's paces just to see if it could stand up to a beating (I bought this light to USE, not to baby like some of my collectable lights!). I tool a selection of my lights to one of Irelands nicest beaches one night a few weeks ago and decided that I would "test" the Fenix. I turned it to turbo mode and threw it several times as FAR and as HARD as I could. The sand it was landing on was wet and hard, not dry and soft. It survived that test so I started throwing it as HIGH up in the air as I could and letting it hit the ground. I did that well over 10 times and the light never flinched. Not satisfied that I had tested it well enough, I threw it into the sea a few times, retreiving it and shaking the water off it each time. The final test was to bury it in the wet sand and leave it there for a few minutes, dig it up again and toss it in the sea once more to wash it off. After all that abuse my light had barely a scratch on it. Obviously the HA coating can stand up to impact with abrasive surfaces like sand very well, and the orings and switch seal are clearly capable of serving their purpose too.
Overall I am very glad that I bought a TK11 as my first light. The lack of regulation never seems like a problem until you actually own a light that has full regulation and see how important and handy a feature it is for a flashlight to have. In that respect, after having carried some of my other regulated flashlights for a while I do miss it when using the Fenix - if I am out for a long period of time I will notice the beam deteriorating gradually and immediately wish that I had lifted the DBS or even my RA85-Tr.
I'd consider buying another TK11 - an R2, just for those 90 minutes or so of regulation on an 18650 cell (which is, incidentally what I run in my current TK11 Q5).
Sorry if I rambled a bit there but good luck in finding a suitable flashlight as your first high performance one.
