catalog:: staying-power::

Staying Power

Class 104

Staying Power

Watch out for words “Up To” and expect moonlight modes when you see very long battery lives listed

To best describe this point, let’s use a car example. Suppose you see a sweet looking, shiny convertible. It’s really nice looking car so you move in closer to learn more about it. There’s a sign on the dash saying it reaches top speeds of 120 mph...pretty impressive so far. You check out the side window to learn about gas mileage. The sheet in the window says MPG 50 city; 70 highway.

Is this realistic? Of course not. The gas mileage listed in the car above is simply not realistic. Driving cars beyond their optimal speed (55-60 mph for most cars) decreases fuel efficiency. Drive that car on the freeway at speeds over 70 mph (let alone speeds of 90 mph or more) and you'll realize that they've overpromised and under-delivered on their gas mileage. Most people would read those gas mileage specs and correctly conclude that it's simply not possible and that there must be something wrong with either the car or company. Unfortunately, most people would read battery life info for flashlights and not have any idea that they are being misled.

If a flashlight company is bold enough to misrepresent lumens, then they'll probably have no problem misrepresenting battery life. There are plenty of ads that we see for flashlights that advertise high lumens with extremely long battery lives. Here's an example:

FauxFurry (our fictional evil alterego) runs an ad for their newest FauxFuego800 flashlight that runs on 4 CR123 batteries and puts out 800 lumens for 80 hours. The font sizes in the ad are as follows:
800 lumens (36 pt); 80 hours (24 pt) font; the words "up to" (6 pt).

"I'd buy that for a dollar!"

The above is simply not possible.

There is a simple fact in lighting: increasing lumens decreases battery life.

Today's technology has limits and there simply is no way to get 800 lumens of light for 80 hours unless you have a humongous battery system to power it...sorry but 4 CR123s (or 2 18650s) will not cut it. Fauxfurry has advertised maximum lumens together with "moonlight mode" battery life. It's not a lie but it can mislead customers.

If you're unfamiliar with a moonlight mode, it is a low intensity mode (typically between 10 and 20 lumen) that allows the light to run for a very long time (sometimes in the 50 to 100 hour range). It is designed for the end user to use in survival situations or when they need just a little bit of light to get around or see.


You'll realize something is wrong when the batteries "unexpectedly" die after 30 minutes. The first suspicion is bad batteries, but they are not the problem. There is simply not enough energy in four CR123 batteries to run 800 Lumen worth of LEDs for more than three hours (with the LED state of technology in 2012).

The truth is that if you bought it, you would get one of three scenarios:

a) 800 lumen for 3 hours and it would shut off,
b) the choice of a lower intensity mode (around 40 lumen) which would allow the flashlight to function for 80 hours, or
c) 800 lumen for one hour or so, and the intensity would continue to drop to ever lower levels, until the flashlight finally shuts off 80 hours later.

So, the truth would be: 800 Lumen for 2-3 hours and 40 lumen for 80 hours.


If you are counting on a specific amount of high intensity light for an extended amount of time and you do not get it, you could find yourself in trouble. If the unit shuts off, and you did not have enough spare batteries, you could be in trouble.


Here is a As a Quick Sanity Check to help you identify frauds:

As of September 2012: One CR123A will give you up to 250 Lumen for one hour. Four of them will give you 1,000 Lumen for one hour, or 250 lumen for four hours.

If you find that what is being reported is close to this, then you are probably ok.

If it is off by a factor of 3 or 4, you are probably looking at incorrectly written specifications...