Post last updated on July 13. 2021 by Wayne Wilson. Check also out the homepage for the latest posts

Most common flashlight batteries

This guide will navigate you through the jungle of various types of flashlight batteries, with pictures and explanations of what they are most commonly used for. When you buy a flashlight, you might see that it runs on for example 18650 3100mAh IMR batteries, which probably makes no sense unless you are already familiar with those terms. The 18650 part is the physical size of the battery, 18 mm in diameter and 65 mm in length, so a 21700 battery would be 21 mm in diameter and 70 mm in length. The 3100 mAh part means Milliamps Hour and measures power over time, the higher the mAh the more power the battery holds. The IMR is a product code that refers to Lithium-ion Manganese Rechargeable. If the battery says INR, it means Lithium Manganese Nickel, ICR means Lithium Cobalt Rechargeable. This sounds quite confusing, but it actually just tells what the main component of the battery is made of. When you are looking to buy spare batteries for your flashlight or other light sources, just make sure to buy the type listed in the requirements in the product info. A 18650 battery would not fit in anything using 21700 batteries, as it would be too small

26650: Mostly used in larger tube-shaped LED flashlights

26650 Battery

This battery type is mostly used in radio-controlled electronics, as well as some large high powered LED flashlights and electronic cigarettes. When used in flashlights it’s mostly on torches that use just one battery, or two after each other in a tube. The dimensions of the 26650 are 26 mm in diameter and 65 mm in height

21700: Common battery used in high lumen flashlights

21700 Batery

21700 batteries are slightly larger than the 18650 batteries and hold more power. Commonly used for the same products too. The most bright flashlights, like the Imalent MS18 usually run on 21700 batteries since it packs more power. The physical size of this battery is 21 mm in diameter and 70 mm in height

18650: The most used rechargeable flashlight battery

18650 Battery

The 18650 is the most commonly used battery type for everything that runs on rechargeable batteries, like flashlights, bike lights, vapes, laptops, cordless power tools, and so on. 18650 means that it is 18 mm in diameter and 65 mm in height. Tesla uses 18650 in its battery packs, thousands of them cramped together

16340 or RC123A: Rechargeable version of the CR123A

RC123A Battery

16340 and RC123A batteries are rechargeable versions of the disposable CR123A, all 3 having a diameter of 16 mm and a length of 34 mm. Mostly used in cameras, small flashlights, bike lights, and headlights. RC123A has a voltage level of 3.0 – 3.2, while the 16340 usually has 3.6V – 3.7V. RC123A is very little used and is mostly used as a reference to 16340. If you are gonna replace a CR123A with a 16340, make sure your gear is compatible with higher voltage first. Products usually states if it can run on rechargeable batteries

CR123A: Common disposable batteries for flashlights

CR123A Battery

The CR123A are disposable batteries commonly used as backups to replace 18650, as two CR123A batteries can replace one 18650. Smoke detectors, cameras, and various other equipment also use this battery size. The advantage of CR123A batteries over Alkaline batteries is that it holds a steady voltage over its lifespan, while Alkalines may experience drops in their voltage, which can cause annoying erratic performance

AA: Available as disposable and rechargeable batteries

AA Battery

AA batteries are very commonly used in various household electronics, and lots of low-lumen flashlights, headlamps, and bike lamps use disposable AA batteries. The size of AA’s are 14 mm in diameter and 51 mm in length. This battery size is also available as rechargeable batteries, but make sure they are before you stick them in a charger. The batteries will have text on the labels that says if they are rechargeable

AAA: Common battery for small household electronics

AAA Battery

The AAA sized batteries are also commonly used in household electronics, like keyboards, mouses, remote controls, various toys, etc. Small low-lumen everyday carry flashlights also tend to use this battery type. The size of these batteries is 10.5 mm in diameter and 48 mm in length, making them somewhat smaller than AA. Mostly used is the disposable Alkaline type, but they are also available as rechargeable batteries 

AAAA: Mostly used in keychain flashlights and penlights

AAAA Battery

These thin small batteries with a diameter of 8.3 mm and a length of 42.5 mm are mostly used in keychain flashlights, penlights, and laser pointers. The most used type is the disposable Alkaline batteries, but you can get them as rechargeable ones too, which can save you money in the long run if you use anything powered by AAAA batteries that runs out of juice extremely often. Not sure what kind of device that would be thou

D: Big thick batteries mostly used in large flashlights

D Battery

The D-type batteries are large in size and hold much power and last a long time, commonly used to power large cylindrical flashlights like the well-known Maglite brand, where multiple batteries are stacked after each other in a long tube. These batteries are 33.2 mm in diameter and have a length of 61.5 mm. D batteries are also available as rechargeable batteries, using the same name but are clearly marked as rechargeable