The causes are usually exhausted batteries and how the burning time is measured.
How to measure the burning time:
For about 2 years, there is an ANSI standard for measuring the duration of combustion of a flashlight.This standard requires that the autonomy of a lamp is measured until only 10% of the original light output can be provided.
This obviously does not meet user expectations. The size of the gap between expectations and the actual value provided according to standard lamps varies widely. If the lamp provides progressively less light, there is a huge difference. If the lamp stops once, then it is perfectly possible to use the standard.
Flashlights running on AA or AAA batteries (mini pencils)
There are many powerful flashlights that run on AA batteries. These include the Fenix TK20 and TK45.
These flashlights operate on alkaline batteries ‘ordinary’ or NiMH, as desired.
The requirements that these flashlights submit the batteries are very high. So high, in fact, that the best alkaline battery is not enough.
Alkaline batteries can be used but, when the lamp is used in the highest position, the maximum current of the battery is insufficient and is prematurely empty.
NiMH rechargeable batteries are the best solution.They are very resistant to high amperage is asked of them. You will see that when using NiMH batteries the flashlight becomes much less hot and burning the specified time may be more or less reached, or in some cases completely.
The statement of the autonomy provided by manufacturers as Fenix is based on the use of NiMH batteries. Alkaline batteries is not a problem. But the burning time, when used at maximum power is halved.It also depends heavily on the quality of alkaline batteries. Using the lamp at maximum power for a long time continuous or break times is also important. In the latter case, the burning time is longer because the batteries have a chance to cool down from time to time.
Flashlights that run on CR123A or 18650 batteries
For lamps that operate on CR123A or 18650 batteries, there is less difference between the actual and specified life. Both types of batteries are capable of providing a large amount of current.
However, for lamps that operate on both types of batteries, you will notice that the burning time is longer with 18650 batteries (rechargeable) with the CR123A batteries (non-rechargeable).
We need a new standard
Duty explain afterwards why a lamp burns less time than what you expected, we find this very annoying. So we will soon introduce our own norm next to the manufacturer’s indication. That way you know what you can expect from a lamp before buying.