Selecting an LED Flashlight or Headlamp

Run time is a key trait to examine when selecting an LED flashlight or headlamp. Run time measures how long a flashlight or headlamp will work on one set of batteries. This measurement is important for many different reasons. For example, an enthusiastic fisherman might select an LED flashlight based on run time because he hates switching out batteries during out-back fishing expeditions. In a wilderness or home emergency, particularly if batteries are scarce, your flashlight's run time could become a critical factor in your survival. Every consumer can appreciate run time as an indication of a flashlight's efficiency; well made models will typically feature longer run times.

How It is Measured

The American National Standards Institute's (ANSI) flashlight ratings include a logo for the time a flashlight can run. The standard design, which manufacturers can display on their packaging, lists the hours or minutes an incandescent or LED headlamp or flashlight can run on one set of batteries. Usable power is defined as 10 percent of original light output; therefore, this time is calculated from the moment the flashlight is turned on at full power until it emits just 10 percent of its original beam.

However, some flashlight and headlamp manufacturers prefer measuring run time differently. That's because many LED headlamps and flashlights are still quite bright at 10 percent of their original power. For instance, a high-performance headlamp could shine 350 lumens at full power; 10 percent of that amount would be 35 lumens - still a usable amount of light. To accurately describe this time, some manufacturers instead measure the amount of time that a flashlight can run while providing the light of the full moon at two meters. This is considered the bare minimum amount of light required for emergency situations.

Driving Factors

There are many different factors that influence a flashlight's run time, including:

External temperature. Extreme cold or heat effects battery performance. LED flashlight or headlamp packaging doesn't typically include time information for extreme temperatures, but it's smart to keep this phenomenon in mind while using your flashlight.

Number of LED chips. More LED chips create more light that can reach farther into the dark. However, more LED chips also require more batteries to sustain the time the flashlight can run.

Brightness. You can conserve battery power by using flashlights on lower brightness settings. Typically, the time a flashlight can run is measured according to the brightest available setting, so you should be able to extend your LED flashlight's useful time by using a dimmer setting.

Number and size of batteries. Flashlight designers understand that they must add more batteries to extend run time. Similarly, larger batteries lift power levels. LED flashlight engineers must balance product weight, high battery costs on the consumer end, and run time. The size and number of batteries required is something to notice as you select an LED flashlight.

Do not mistake run or use time with LED life. Run time explains how long a flashlight can operate on one set of batteries. LED life measures how long the LED bulbs in each flashlight will function. For a fair comparison of run time, compare LED flashlights using the ANSI FL1 Standard. If the headlamp or LED flashlight you're considering doesn't display the ANSI standard, see if you can find a comparable measurement, such as the number of hours the product will run until its output is that of the full moon.