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Flashlight Technology

Halogen, xenon, LEDs, and supercapacitors: there's more to it than you might think.

June 13, 2011  |  by Tim Dees - Also by this author

5.11 Tactical's Light for Life flashlights are powered by supercapacitors and feature multiple LEDs. Photo: 5.11 Tactical.

Power Supply

Most flashlights are powered by disposable or rechargeable batteries. Your best choice between these should consider how you plan to use the light. If the light is your primary, use-it-every-day tool, rechargeable batteries are probably your best option.

Nickel-metal hydride (NiMH) batteries, like the Eneloop from Sanyo, look and work just like disposable batteries and will hold a charge for up to a year. They're cheap enough that you can rotate through three sets (one in use, one spare, one in the charger) and probably never run out of light. NiMH cells are generally good for about 500 charge-discharge cycles. It's better to charge them when they're only partially run down, rather than flat. They are not prone to battery "memory," where charging the battery before it's completely flat will reduce its capacity. This is a problem with nickel-cadmium (NiCad) cells.

If the light is a spare, or one that won't be used much, replaceable/disposable lithium or alkaline batteries are a better bet. These batteries will hold a charge for up to 10 years. Battery capacity is measured in watt-hours (1 watt-hour is one watt of power delivered for one hour). Use this to compare different brands. Lithium cells are more costly, but deliver more watt-hours.

One drawback of both disposable and rechargeable batteries is temperature sensitivity. In my patrol days, I started each winter night shift by starting the patrol car, turning the defroster to full blast, and placing my rechargeable halogen light on the dashboard next to the defroster vents so it would warm. If I didn't do that, I had an aluminum paperweight. Once the light was warmed up, it would usually stay warm enough next to my body to keep it alive for the entire shift.

Whichever you choose, make sure you dispose of used batteries properly. Most hardware and electronics stores will accept batteries for recycling at no charge.


One unique flashlight that doesn't use batteries at all is the Light for Life from 5.11 Tactical. Instead of a battery, the Light for Life contains a supercapacitor that stores enough power to keep its LEDs on their 90-lumen medium-bright setting for half an hour, and at 20 lumens for almost an hour more. Holding the switch down produces a high beam of 270 lumens, either steady-burning or strobe.

No matter how much or how little juice remains in the supercapacitor, placing it in the supplied AC or DC car charger brings it to full power in less than 90 seconds. A flashing blue LED on the charger starts blinking when the light is inserted. The blinking becomes more rapid until it stays lit, indicating a full charge. The supercapacitor is rated for 50,000 charge-discharge cycles.

I received one of these lights as a product sample almost two years ago, and I was skeptical of the technology. The light has been traveling in my car, plugged into its charger, for all that time. It has never failed to work, and it still takes and holds a charge as well as it did on Day One. Had I tried this with a conventional rechargeable light, the battery would be fried by now.

Supercapacitors actually work better as the temperature drops, so that's not a problem. The light might not burn as long at the brightest setting as a conventionally powered light, but then again, it can be recharged to full capacity by the time you turn the corner from your last traffic stop. This innovation could become the next new standard in law enforcement lighting.

Tim Dees is a retired police officer and the former editor of two major law enforcement Web sites. He can be reached via [email protected]

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Comments (2)

Displaying 1 - 2 of 2

Josh B. @ 6/13/2011 5:44 PM

Excellent article. I wish the manufacturers would use a little more imagination, sense, and user-oriented attitude. For example, why not have flashlights like the "light for life" available in bright yellow? More useful for everyone from firefighters to campers to homeowners. For that matter, why not have a luminous band or a tiny flashing led so you could find the darned thing in the dark? Unless you're using a light for tactical purposes, bright yellow is better in every way than black or dark gray or green.

But then, since when do engineers listen to common sense or even my own wisdom?

Rick @ 6/14/2011 9:45 AM

We purchased the 5.11 flashlights. They are great and work as advertised, with one exception. The switch burns out when they are stored/used near our 400mhz radios. 5.11's customer service has been fantastic; I email them that a light has malfunctioned and they send a replacement out right away. 5.11 said that we're the only company that has had this issue. The problem will be solved when we switch radio freqs this year or early 2012.

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