Some flashlights powered by a single AAA battery, such as the MagLite Solitaire (*Est. $10) mentioned above, can also be considered key-ring flashlights. However, they're so much bigger than the Photon Micro-Light flashlights that it makes more sense to think of them as pocket-size or travel flashlights.
The waterproof Arc AAA Premium (*est. $45), often recommended in reviews, can get much more light out of a single AAA battery than the MagLite, because it boosts the voltage with a regulator. The voltage regulator keeps the light consistently bright for five hours, then automatically dims for at least another two hours before the battery needs replacement. This gives the Arc AAA Premium a big advantage over the MagLite flashlights and the Photon Micro-Light models as well -- all of which dim as the battery fades.
In addition, the Arc AAA Premium flashlight is waterproof, not just water-resistant, and it uses lithium, alkaline or rechargeable NiMH batteries. Like the Micro-Lights, it uses a 5mm Nichia LED, but the flashlight itself is bigger -- about 2.75 inches long -- and at 0.8 ounces, a bit heavier. The light output is about 9 lumens. For only about $5 more, the newer Arc AAA Premium w/GS LED (*est. $50) is slightly brighter at 10.5 lumens.
Those light levels are high enough for closeup work or to light a footpath, but for brighter, adjustable light, reviews recommend the single-AAA Fenix L0D (*est. $40) or L0D-CE (*Est. $45). The Fenix L0D uses a Luxeon LED while the L0D-CE uses a CREE XR-E bulb; both are twice as efficient as the 5mm Nichia bulb. This makes the Fenix L0D-CE bright enough to serve as a general-purpose flashlight -- amazing from an AAA battery. The Luxeon-LED version is similar, but it uses a textured reflector that spreads the light a bit more.
The brightness from these flashlights adjusts to 7.5, 20 or 50 lumens -- plus there's a strobe and an SOS light for emergencies. The expert review at FlashlightReviews.com says that at maximum brightness, the Fenix L0D-CE puts out as much light as a large 3D MagLite flashlight -- and at medium brightness, as much as a 2D MagLite. Owners say it can easily light up a yard. For many situations, therefore, the lowest light setting -- which runs 6 to 9 hours per battery -- will be bright enough. Unlike the Arc AAA, the Fenix flashlights have flat tails (even with a key ring inserted) so they can stand upright for general illumination.
One minor disadvantage of the Fenix L0D-CE is that instead of using a voltage regulator to adjust light levels, it uses pulse modulation -- the same method used by the Photon Micro-Light Freedom. This can result in some slight flickering at the low light level. Stepping up to the single-AA Fenix L1D-CE (*Est. $55) flashlight brings you a voltage regulator for consistent light, plus even brighter levels: 9, 40 and 80 lumens (plus a 90-lumen turbo/strobe mode) and longer runtime (two to 25 hours, depending on the light level). It's less than four inches long -- about the size of a typical Swiss Army knife -- and weighs 1.73 ounces. In a Cool Tools review at Kevin Kelly.org, Vincent Tseng, a flashlight enthusiast, says that of all the flashlights he's tried, the Fenix L1D-CE is the one he uses most.
For an even better combination of size, brightness and runtime, FlashlightReviews.com calls the 2-ounce Fenix P2D-CE (*Est. $55) the "perfect every day carry light," because it's "smaller than the 1D, with the output of the [bigger] 2D." It uses a high-quality Cree LED and a single CR123A cylindrical lithium-ion battery, so it's only about 3.25 inches long.
The Fenix P2D-CE also earns top ratings from owners reviewing it at Amazon.com, where one says it's "as bright as my 6D cell MagLite and fits in my pocket." Light levels adjust to 9, 40 and 80 lumens, plus a 135-lumen turbo/strobe mode. It runs about three hours on the high setting, 8 hours on medium and 30 hours on low. The sole disadvantage is that it uses only lithium-ion batteries.
As a budget pocket LED flashlight, staff at OpticsPlanet.com recommend the 3-LED, 3AAA Streamlight Clipmate (*Est. $18). It produces just one level of light (27 lumens), but runs up to 40 hours per set of 3 AAA batteries. Despite the number of batteries, it's pocket-sized at 3.5 inches long, but comes with a lanyard and removable clip. For use with the clip, the head rotates 360 degrees. The Clipmate is only water-resistant, not waterproof like the Fenix flashlights, and at this price, it lacks a voltage regulator or pulse modulation -- so the light gradually dims as the batteries fade.
Most 2AA flashlights are about six inches long -- too big for a pocket, but fine for a glove compartment. In this size range, reviews give top marks to the waterproof Fenix L2D-CE (*Est. $55), which uses two AA batteries and weighs just under two ounces. A voltage regulator boosts light levels and keeps the light consistent at any of three levels: 9, 40 or 80 lumens -- plus a 135-lumen strobe for emergencies.
Since it uses two CR123A lithium-ion batteries, the Fenix P3D-CE Premium Q5 (*Est. $70) is even shorter at about 4.5 inches. It's ranked third at CPFReviews.com, but among the top four flashlights, the Fenix P3D-CE gets the highest rating for "biggest bang for the buck." It provides both very bright light (at 9, 40 and 90 lumens) and nearly twice the runtime (5, 13 and 65 hours). For emergencies, the 215-lumen turbo mode could definitely signal rescuers.
If you only want a flashlight to help you stay on a path or read a map, a less expensive 2AA flashlight may be all you need. Like other MagLite flashlights, the Mini MagLite (*Est. $10) is water- and shock-resistant, adjusts from spot to flood beam, holds a spare bulb inside and carries a lifetime warranty. It provides about 5.5 hours of runtime, with brightness averaging about 15 lumens. Since it lacks a voltage regulator, the light will gradually dim.
The LED version of the MagLite 2AA flashlight (*Est. $20) produces nearly five times as much light as the incandescent model, and you shouldn't need to replace the Luxeon LED for about 100,000 hours. The main drawback is shorter runtime per set of batteries. Tests at FlashlightReviews.com show the light dimming to 50 percent in a little over three hours, and shortly thereafter, the batteries need replacing. This flashlight gets mixed reviews from owners at Amazon.com, partly because the light goes out so suddenly.
The MagLite 2AA LED produces a single light level that, with fresh batteries, is similar to the middle levels on the Fenix flashlights discussed above. However, the MagLite starts dimming right away, and total runtime is much shorter. It's a good budget choice, but the cost of battery replacements will eventually make the Fenix L2D-CE a more cost-effective flashlight -- with better features to boot. In addition, the Fenix P3D-CE offers even longer runtime -- ideal for a glove-compartment emergency flashlight.