Why doesn't my flashlight burn as long as the manufacturer claims?
Perhaps you noticed it before: your flashlight doesn't burn as long as the manufacturer claims. Did the manufacturer lie? Is the light broken? Not at all. It is often the result of how the manufacturer measures the burn time and which batteries you use.
How does the manufacturer measure the burn time?
The manufacturer measures the burn time of a flashlight or head torch according to the so-called ANSI norm. According to these rules they measure the burn time until the light produces only 10% of the output you started with. Let's say a light starts with 200 lumens and ends with 20 lumens after 2 hours. Those two hours are listed by the manufacturer.
The good thing of this standard is that all brands use it. As such you can easily compare them. But there is, of course, a difference between your expectations and what the light actually produces. Some flashlights or head torches gradually produce less light. At that point the ANSI standard is useless, because it won't correspond with your expectations. However, if the output becomes less all at once, the standard can definitely come in handy.
Which influence does the battery type have?
Another factor for the burn time of your flashlight or head torch is the battery type. The battery you use is key. As such you should carefully check the battery the manufacturer recommends for your light.
Flashlights and head torches with AA or AAA batteries
For lights that work AA or AAA batteries you can choose from 'regular' alkaline batteries or rechargeable NiMH batteries. You can easily use the regular alkaline batteries, but you will notice that in the highest mode the batteries will be drained faster. All because powerful lights ask a lot from these batteries. This does, however, depend on the quality of the alkaline batteries. Better batteries last longer than batteries of a lesser quality.
NiMH batteries do come into their own. These can handle what the light asks them to do. And you will notice that the light won't heat up as much. Also! Very importantly, that the light reaches the listed burn time. The burn time Fenix manufacturers list is based on the use of NiMH batteries.
Flashlights and head torches on CR123A, 21700 or 18650 batteries
For these battery types variations in the burn time are not as frequent. These batteries are very good at producing a lot of power. Sometimes a light allows you to use two types of batteries. 2x CR123A or 1x21700, for instance. When compared you see that 18650 batteries and 21700 batteries reach a longer burn time than CR123A batteries. The burn time the manufacturer lists is then always based on the use of 18650 or 21700 batteries.