LED FlashLight Batteries- How Long they Last

How Long do LED flashlight batteries Last
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Do you want to know how long your LED flashlight and/or head lamp batteries are going to last? This can be difficult information to find online. Some companies list flashlights for sale and do not list how long batteries will last in their products.  Some other companies that do provide battery life information do not go into enough detail about the run times of their products. 

As a very general estimate, a low-lumen flashlight (under 50 lumens) will run for about 20-50 hours.  A flashlight with 50-150 lumens will run for about 6-12 hours on it’s highest setting, and high lumen flashlight or headlamp (over 150 lumens) will run about 2-8 hours on their highest settings.

  These estimates are very broad, and your flashlight batteries may get significantly higher or lower life depending on the product.  Below lists some of the factors impacting the battery life of LED flashlights and headlamps.

Flashlight Battery Life

There are multiple things that can impact how long a flashlight’s battery will last, including:

  • Type of battery (AAA, AA, C, CR123a, D, 18650, etc..)
  • Quality/Material of Battery (Alkaline, NiMH, NiZn, Lithium, Carbon Zinc, Zinc Chloride, etc…)
  • Number of batteries your flashlight holds
  • Brightness of the light (Lumens)
  • Number of light settings on your flashlight, and what setting you use
  • Power draw from the flashlight
  • Battery voltage regulation in the flashlight

Listed below are some things that you can look for to help you determine how long your batteries will last. 

Power Settings (High, Medium, Low, Strobe)

Some flashlights have multiple power settings, and may only display the run time of their flashlight on the highest setting.  Other flashlights may display the run times for multiple settings

For example, the Nitecore MT20A 360 Lumen tactical flashlight pictured to the right has the run times listed for multiple settings in the description.  The product description states that it has 5 brightness levels, and gives the run time for all 5 of those levels, which are:

  • Turbo: 360 lumens/1 hr 45 mins
  • High: 240 lumens/ 2 hr 15 min
  • Mid: 120 lumens/ 5 hr 45 min
  • Low: 17 lumens/ 24 hr
  • Ultralow: 1 lumen/180 hr

This is very helpful information that many flashlight companies don’t list on their packaging.

How Long will AAA or AA Batteries Last in a LED Flashlight?

Below is a table I created while looking up some different run times for  AA and AAA LED flashlights on Amazon.  As you can see, the run times vary greatly.

AA and AAA LED Flashlight Batteries will last approximately 1 1/2 hours -7 hours when a flashlight is on it’s highest setting, and may last for days if the flashlight is on it’s lowest setting. 

Flashlight- Run Time Standards

In 2009, there were a set of standards developed known as ANSI FL1, (American Nation Standards Institute) that companies selling flashlights can display on their package if they choose to use these standards.  Companies are not required to display these standards on their packaging if they choose not to. 

The items they can display are:

  • Run Time
  • Peak Beam Intensity,
  • Light OutPut,
  • Beam Distance,
  • Water Resistance
  • WaterProof  
  • The flashlight on the right displays the FL1 standards on the packaging, and shows a run time of 2 hr/30 m.

The run time is a good tool to get an idea of a flashlight’s run time, but it may not be very helpful tool when trying to compare flashlights (it does not always compare apples to apples). 

Run Time- Different Batteries

The flashlight package might show the run time of the batteries included with the flashlight.   Many flashlights come with “heavy duty” batteries, that do not last as long as an Alkaline or NiMH battery

Some run times displayed show the results of testing higher quality batteries.  This can make it difficult to compare run times for different flashlights because they may not use the same type battery during testing.

The 9-Lumen, Rayovac flashlight pictured to the right is an example of this;  It displays 52 hours of run time on the package with a heavy duty battery (the battery that is included), but states in the description that it will run for 160 hours on an alkaline battery.

How run time is tested

Run time is measured 30 seconds after the light is turned on, and then stopped when the light is at 10% of it’s original output value.  So just because a flashlight states a certain run time on its highest setting (3 hours on a 150 lumen flashlight, for example) does not mean you are going to get the 150 lumens for 3 hours (the flashlight dims over time). 

Run Time is better shown on a graph that shows what flashlight’s brightness level is at after a certain amount of time.

Type of Battery

The type of battery makes a big difference in how long your batteries will last in your flashlight or headlamp.  A lot of the flashlights for sale today come with “heavy duty” batteries, which is a Zinc Carbon or Zinc Chloride battery. 

These batteries do not last nearly as long as Alkaline, Nimh, or Lithium batteries.    

It is also important to know that different batteries have different capacities. For example, a AA (Double-A) battery has approximately 2-3 times the capacity of a AAA (triple-a) battery made of the same material (i.e. alkaline). 

C and D batteries have significantly higher capacities than AA or AAA batteries

Flashlights that hold multiple batteries have a higher energy capacity than lights that can only hold one battery.   The more batteries a flashlight can hold, the higher the capacity should be, and the light will have a higher run time on average.

There are some flashlights that can use rechargeable batteries.  NiMH, 18650, and CR123a batteries are also options for some flashlights, and may be able to be used for a higher number of lumens.

 

Batteries for an Emergency Kit

If you have an emergency kit at home, and you are purchasing a LED Flashlight, headlamp, or batteries for your flashlight, you need to consider what kind of batteries to purchase.

I recommend having a flashlight that can use disposable batteries because you may have a power outage, and may not be able to recharge your device.  Also, try to find a LED headlamp and flashlight with a long battery run-time.

Alkaline or Lithium Batteries

If you do purchase disposable batteries for your flashlight, I recommend either Alkaline or Lithium batteries.   

Alkaline batteries are cheaper than Lithium Batteries. Alkaline batteries have about a 5-10 year shelf life, and Lithium batteries have about a 15-20 year shelf life.  Lithium batteries can handle extreme temperatures better than Alkaline.

“Heavy Duty” Zinc Chloride batteries only have a shelf life of approximately 2-4 years, and have a much lower energy capacity than alkaline or lithium batteries.

AA or AAA Batteries

 If your flashlight is for an emergency kit, I recommend buying a flashlight and/or headlamp that uses either AA or AAA batteries because you can use these batteries for a lot of other devices during an emergency.   

If you are buying a flashlight or headlamp for your emergency survival kit, I recommend purchasing one with multiple power settings.  You may want to use a very low setting during an emergency to conserve light

For Example, I have a lot of AA and AAA batteries in my emergency supply, but I don’t have any extra CR123A or 18650 batteries stashed away.  Some flashlights that use 18650 batteries can also use AAA batteries.

The Streamlight Pro Tac 88033 pictured on the right (Amazon Link), uses 2AA batteries, and displays a run time of up to 36 hours on it’s lowest setting.

Tactical Flashlight

You also may need a high powered light at times (self defense, signaling someone during an emergency, etc…) I recommend having multiple flashlights/headlamps in your emergency kit, but if you’re only going to have one, it should be a tactical flashlight with multiple power settings.  

Headlamp

Headlamps are good to have in your emergency kit for hands-free lighting, and the ones that can hold multiple batteries usually have a decent “run time” 

The headlamp pictured on the right is a 90 Lumen headlamp, and states that it has a run time of 8 1/2 hours on the highest setting (there are 3 settings).  

Conclusion

Led flashlight and headlamp battery life varies due to all of the reasons listed above.  If run time is important to you, do as much research as you can about the specific product you would like to buy, but realize if their is a “run time” listed on the product, it may not be very helpful when trying to compare it to another product.   You may need to do additional research to find what battery was used during the test.