LED flashlights are still evolving, but the best model powered by a single AA battery is currently the 4Sevens’ Quark. Its nearest competitor, the Fenix LD10, is a fine flashlight, but it’s not that much of an improvement over the L1D-CE that I reviewed a couple of years ago on Cool Tools. The original Fenix L1D-CE used a then-revolutionary LED emitter, the Cree XR-E, but since then several flashlights use even newer and more efficient LED emitters from Cree — including the 4Sevens Quark.
The Quark, as with Fenix, has the ability to use the same interchangeable head for three different battery configurations: a single AA battery body, or two AAs, or a single CR123 lithium body. And though the Fenix LD10 has a higher max output from a single AA than the 4Sevens Quark, the Quarks show better efficiency-brightness when used in the 2x AA or 1x CR123 configurations.
The Quarks also have a self-centering design for their emitters, so their beams are really close to flawless. Compared side-by-side with the Fenix beams (which are still pretty good) the difference is pretty obvious.
The maximum output of the Quark with a single regular alkaline AA battery is now an astounding 109 lumens. This is brighter than the once-monster Xeon SureFire 9P rated at 105 lumens with three CR123 Lithium batteries!
Although the Quark’s max output with a single AA is indeed very bright it is sometimes too bright — imagine trying to read with 109 lumens a few inches away. That’s why almost all of the better flashlights have lower light levels; and most users tend to use these lower levels far more than the maximum. The Quark AA goes one step better by providing a very low Moon mode level of 0.2 lumens (compared with the LD10’s 9 lumens low setting), which helps preserve one’s dark vision adaption for those close hand-held tasks.