26650 Battery - Dimensions, Chargers, and Flashlights

Lithium ion 26650 batteries are common choice for high drain devices that also require large capacity batteries, low self-discharge rate and large number number of charging and discharging cycles. Lithium ion 26650 rechargeable batteries are very similar to 18650 batteries, but they have ~2x larger volume and hence larger capacity/larger drain currents.

Most important features of 26650 rechargeable batteries are their native capacity, maximum pulse current, continuous drain current, maximum allowed charging current, protective electronics available, exact chemistry and similar.

26650 battery 1

26650 Battery Dimensions

26650 batteries size is standardized and it is:

- 26.5 mm (1.04 inches) in diameter, or ~26 mm.

- 65.4 mm (2.57 inches) in length, or ~65 mm.

Note that actual length may vary from the manufacturer to the manufacturer due to the fact that some models also feature protective electronics, button-type positive side, if the battery is rewrapped etc.

Most important features of 26650 batteries are their capacity, voltage, charging/discharging performances, number of charging/discharging cycles and similar, and all of them depends mainly on the battery chemistry and internal design.

26650 Battery Chemistry

Like 18650 batteries, 26650 batteries can be found in most common lithium-ion versions:

- IMR 26650 batteries feature Lithium Manganese Oxide (LiMn204) chemistry with nominal voltage of 3.6 - 3.7 V per cell and the maximum recommended charging voltage of 4.2 V.

IMR batteries commonly have smaller capacity when compared with other chemistries, but are capable of delivering stronger currents without adverse effects on the battery longevity.

IMR 26650 batteries commonly feature 5000 mAh (5 Ah) capacity and they are able to easily deliver 20 Amps continuously, 30 Amps with additional cooling and 50-60 Amps pulse current. Of course, such features vary from model to model and must be checked for every different battery model.

- INR 26650 batteries feature Lithium Manganese Nickel (LiNiMnCoO2) chemistry. INR lithium ion batteries are very similar to IMR batteries, they also feature 3.6-3.7 volts nominal voltage per single cell, 4.2 volts maximum charging voltage, etc. Also, they can provide large discharging currents, have slightly lower capacity, but also feature larger number of charging/discharging cycles, lower self-discharging rate etc.

flat top 26650 battery

When INR battery is combined with protective electronics, one gets a 26650 lithium-ion battery that is very safe to use, has capacity up to 5000 mAh and is able to provide 20-30 Amps easily.

- IFR 26650 batteries feature Lithium Iron Phosphate (LiFePO4) chemistry and they feature a nominal voltage of 3.2 - 3.3 V per cell, with the maximum recommended charging voltage of 3.5 - 3.6 V. IFR 26650 batteries are not very common.

- ICR 26650 batteries feature Lithium Cobalt Oxide (LiCoO2) chemistry with nominal voltage of 3.6 - 3.7 V per cell, and with the maximum recommended charging voltage of 4.2 V. Their maximum allowed discharge currents are often limited to just few C, but their capacity is larger when compared with other lithium-ion 26650 batteries.

Note: there are other chemistries available, including hybrid technologies like: Lithium Nickel Cobalt Oxide (LiNiCoO2), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2), etc. Also, some manufacturers produce non-rechargeable Lithium Thionyl Chloride batteries in Size C (~26x50 mm) and advertise them as both Size C batteries and 26605 batteries (with or without special battery holder/plug when used as 26650 battery replacement). These batteries feature large capacity even up to 9-10 Ah, good shelf life, good tolerance to cold and hot weather, low self-discharge rate and are used mostly in security systems and EDC devices like flashlights and similar.

non rechargeable 26650 battery

Flat or Button Positive (Top) Side/Terminal

Just like 18650 batteries, 26650 batteries also come with two different top (positive) sides: flat or button.

When replacing old 26650 batteries, it is very important to use new batteries that can fit the battery compartment of the device that you have, that discharging and charging features are the same (or better) and that the positive terminals are the same.

18650 button flat positive top

If the positive terminals (positive side) of the new battery is not the same, there is a great chance that the new battery simply will not fit the battery compartment or that it will fit, but it will not be able to achieve proper electrical contact.

Protected or Not 26650 Batteries

Protected 26650 batteries feature small protective electronics system that monitors the parameters of the battery including battery temperature, charging and discharging currents and voltages.

Protected 26650 batteries feature slightly smaller capacity, but they are much safer to use in non-intelligent devices that don't monitor batteries' conditions during discharge.

protected 26650 battery

When the conditions of the battery reach certain threshold, protective electronics shut-off the battery - it disconnects the battery from the rest of the world, until the conditions are not returned to the acceptable range. For example, if the battery voltage reaches 4.2 volts (if the 4.2 volts is the maximum allowed voltage), protective electronics will stop the charging process. If the discharge temperature reaches certain threshold, protective electronics simply disconnect the battery until it cools down, etc.

Personally - regardless of the device you have, 26650 batteries with protective electronics are highly recommended. After all, it is IMHO better to sacrifice 200-400 mAh of capacity and have safe battery than to risk fire, explosion or similar accident due to the battery's thermal runaway ... Just my 2c :)

 Rewrapped 26650 Batteries

Unfortunately, there are no Panasonic, Samsung, or Sony 26650 batteries on the market.

Also, there are large number of rewrapped 26650 batteries with exaggerated capacity and other battery features, which are not as safe as they should.

So, when trying to find proper 26650 battery, go for the batteries that have excellent reviews from other users, are made by just a few recommended brands that actually make 26650 batteries, or go for high-quality 18650 battery with special battery holder, and use it as 26650 battery with somewhat lower capacity.

26650 Battery Chargers

smart battery chargerMost 26650 batteries can be and should be charged using intelligent battery chargers that are able to test the battery and determine its type, size, capacity, condition etc.

Such battery chargers are relatively cheap and safe for use and often can charge NiCd, NiMH, and lithium ion batteries, regardless of their chemistry and size.

Such battery chargers can be plugged-in the wall power socket, car cigarette light adapter, some even support the use of USB ports, but at the price of longer charging etc.

Note: some 26650 battery, just like similar 18650 batteries, feature micro-USB (or some similar, standard) port, allowing the battery to be connected and charged directly from the USB ports. Their capacity is usually lower than the capacity of standard 26650 batteries, but they don't require dedicated battery charger - recommended battery type for people requiring just a few 26650 batteries.

 The Best 26650 Battery Flashlights

26650 batteries are commonly used in high drain devices like toys, flashlights, for vaping etc.

26650 flashlights use 1 to 4, sometimes even more 26650 batteries and are able to produce 3000-4000 lumens of light per single 26650 battery.

26650 flashlight

Such LED flashlights generally come with protective electronics that monitors the condition of LED(s), battery (or batteries) and if required decrease the light output and if absolutely required, shut off the flashlight until it cools down.

26650 flashlights are used as tactical flashlights, as EDC (Every Day Carry) flashlights, in emergencies, for outdoors activities etc.


26650 battery mLong Story Short: 26650 batteries store plenty of energy, ready to be used at the moment notice. Most common battery types are IMR and INR, with most intelligent chargers being able to distinguish between them and being able to charge them properly.

Protected 26650 batteries are by far safer than unprotected 26650 batteries, but they also feature somewhat smaller capacity.

When going for the new 26650 battery/batteries, be sure to know what kind of new battery you actually need (voltages, currents, capacity, etc.).