A newfangled trend is popping up on certain flashlights: Power level indicators. On the one hand, an added LED screen is one more thing that can break over time. On the other hand, certain flashlight users would greatly value knowing precisely how much light time is left. (In NYC, I was friendly with a cop who talked about the stress of conducting potentially dangerous tasks—clearing the stairwell and basement of a housing project during a blackout, for instance—without knowing if your flashlight was going to run out of juice.)

Designers (or more likely, the bean counters) have decisions to make when it comes to depicting battery life. This can be done well, or poorly.

Lame

This XP11R, by Oregon-based Coast Products, does the bare minimum. It shows you just three things: 1) When you've got some unspecified amount of battery power, 2) when the battery is low, and 3) when the battery is depleted. Only the second indication is somewhat useful, and the third one makes no sense at all. When you try to turn the flashlight on and it doesn't illuminate, that tells you the battery's depleted.

Bad

This LD45R flashlight, by Chinese manufacturer Fenix, indicates the battery life with bars, which isn't particularly helpful--how long does a bar last? Furthermore, that part of the display is dwarfed by the lumen value, which is not helpful at all; your eyes can tell you whether you've set the flashlight bright enough to see.

Also Bad

This Luxor LX735 flashlight is by California-based PLX Devices. You can practically tell the company is based in Silicon Valley; the screen shows you a graphic representation of battery levels, like the Fenix does—then redundantly adds a numerical percentage. That probably sounds great to tech nerds, but doesn't provide truly useful information. No one sets out to do a task in the dark and thinks "This should take about 60% of my battery to execute."

Great

This Jeep Power Indicator Flashlight was created in collaboration between Jeep and Energizer. The power level indicator on it is much better than the others; it shows you, in minutes and hours, how much battery life you've got left.

Even better, it updates the time remaining as you adjust the brightness level:

That's information you can truly use. For instance, if you estimate it's going to take you another ten minutes to change the tire and the flashlight's running low, you can actually take some action and lower the light level in order to improve your situation. Hats off to the designers.