LED FLASHLIGHTS ARE NEAT AND FUNCTIONAL BUT...
Understanding the power source is critical!
When it comes to selecting an LED Flashlight, you would be wise to start by looking at the battery(ies) it takes to operate the light. There are many battery types on the market, with each having limits on its use. Did you know certain environments require certain batteries? That's just part of the consideration when selecting a light. BATTERY TYPES--BATTERY LIMITS--BATTERY SAFETY, all need to a part of your light selection.
Today's batteries are varied and POWERFUL! There is much to know about all your battery choices--18650 rechargeable batteries, 14500 rechargeable batteries, 26650 rechargeable batteries, alkaline throw-away batteries, etc. What does all this mean??
KNOW YOUR BATTERY TYPES
Selecting a flashlight is like buying a car: if you want the automobile to operate using a certain fuel type, you go to the dealership and ask to see all the autos that are powered by diesel, gasoline, electricity, etc. When selecting a flashlight, FIRST you may want to consider what kind of battery(ies) you want to use in the light...throw-away, rechargeable, Ni-MH, li-ion, lithium, etc. Factors such as the temperature of the environment where you are going to operate the flashlight must be considered. Not all batteries are designed for certain temperatures. You don't want to purchase a flashlight or headlamp for your next Arctic trip only to find out it won't operate when reaching your destination.
Rechargeable batteries fall into one of these chemistry categories: Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH) or Lithium Ion (Li-Ion) technologies. Then there are the non-rechargeable, throw-away batteries: alkaline and lithium.
A. Lithium Ion (Li-ion) Rechargeable Batteries
Rechargeable flashlight batteries found in lights made in the past several years are generally Lithium Ion. Lithium Ion (Li-ion)
batteries come in various sizes:
14500 Rechargeable Li-ion Battery: These are smaller and are similar in size to a regular AA battery. If your light operates on a regular throw-away AA alkaline battery, NEVER ASSUME that it will also take a 14500 rechargeable battery. Always check the flashlight specifications.
16340 Rechargeable Li-ion Battery: These are close in size to a CR123A/RCR123A battery BUT a 16340 battery is normally a little larger in length than the CR123A battery. MAJOR IMPORTANCE: voltages are normally different between these batteries. Again, always check the flashlight specs to understand which battery types and voltages the light will accept.
18650 Rechargeable Li-ion Battery: These are larger in diameter and in length than a standard AA battery size. The 18650 Li-ion battery is an extremely popular battery source for today's flashlights since the 18650 battery carries so much power. Presently, 18650 battery sizes and styles can vary from one manufacturer to another. However, the battery industry is striving to standardize 18650 battery size. 18650 batteries are generally 3.6/3.7 volts and have various mAh (milliamp) ratings. The mAh rating is solely for determining how often you will have to recharge your battery. The higher the mAh rating, the longer the run time between charges, generally speaking. 18650 batteries are not designed to operate optimally in temperatures below freezing.
21700 Rechargeable Li-ion Battery: These are a similar size to 18650 batteries, but are a little bit wider and longer. Just like 18650 batteries, 21700 batteries are usually 3.6//3.7 volts. They tend to have high mAh ratings, around 4000 - 5000 typically. With a 21700 battery, a flashlight can still be fairly compact while delivering a high output and long runtimes.
26650 Rechargeable Battery: This is a high performance/high capacity battery designed to provide excellent power for high-drain devices. The size of a 26650 battery is a larger diameter and longer length. Because of their size, they are able to deliver much power to a small flashlight. A 26650 battery normally has a high mAh rating, allowing a long run time between charges.
B. Nickel-Metal Hydride (NiMH) Rechargeable Batteries
These rechargeable batteries normally come in AAA, AA, C, D, 9-Volt, and 12-volt sizes. They are a great all-around battery. The downside is they have a shorter shelf life than a lithium-ion battery.
C. Lithium (NOT Lithium-Ion) Non-Rechargeable Batteries
These come in AAA, AA, 9-Volt, and small cylinder ( CR123A) sizes. Because they have a slow self-discharge rate, these batteries can have a shelf life up to 10 years, depending on the brand. Lithium batteries perform very well in below freezing temperatures. If you will be using your flashlight or headlamp in extremely cold temperatures, be sure the device will operate on a CR123A battery.
D. Alkaline Non-Rechargeable Batteries
These are the most commonly found battery types and aren't rechargeable. They are also very inexpensive. You will find them in these sizes: AAA, AA, C, D, 9-volt, and button cells. The downside of alkaline batteries is they have a tendency to leak, causing damage to any device they are in. It is recommended that you power up the device about once a week when using alkaline batteries. This will lessen the chance of a battery leak but there is still a possibility of a leak. If you don't plan to use the light often, it would be safer to store the batteries OUTSIDE of the device. Another downside is their low power output, which affects the run time and lumen output you can get from this battery chemistry.
KNOW WHAT TO EXPECT FROM DIFFERENT BATTERY TYPES
Once you determine which battery type is for you, then you can realistically select a flashlight. Here is a common request we get from customers:
"I would like a 2000-lumen flashlight that runs on the commonly found alkaline battery. I also want to carry the flashlight in my pocket."
Now that you understand batteries, you will see why this isn't possible. Alkaline batteries are very low power so achieving 2000 lumens in a pocket-size flashlight using an alkaline battery just isn't possible.
To get high lumens, you need high-powered batteries! To get high lumens in a small flashlight, you need high-powered batteries! When you add multiple high-powered batteries, you are able to reach extremely high lumens.
This chart should help in understanding the relationship between battery types/flashlight size/lumen output.
KNOW BATTERY QUALITY & SAFETY
Now that you understand batteries better, know that not all batteries are created equally. Batteries are a case of "you get what you pay for." Because the new lithium-ion batteries are so powerful (and potentially dangerous), you never want to cut corners on such batteries. If you need to save money, buy a less expensive flashlight rather than purchase a lower-quality battery.
With the exception of alkaline batteries, you always want to purchase PROTECTED batteries. Protected batteries have built-in safety measures to prevent over charge, over discharge, and over heating. Fenix protected batteries have three levels of protection built into the batteries. For a more extensive discussion on protected and non-protected batteries, READ HERE.
It is important to properly store batteries when not inside a device. You always want to store batteries in a clean, dry location. It is important that stored batteries don't make series contact, positive to negative ends. Inspect your batteries often for any bulges, wrapping tears, or degradation. Properly discard the battery immediately if you notice any battery failure.