An 18650 battery^[1] or 1865 cell^[2] is a cylindrical lithium-ion battery common in electronic devices. The batteries measure 18 mm (0.71 in) in diameter by 65 mm (2.56 in) in length, giving them the name 18650.^[3] The battery is 3.7 volts.

Panasonic first developed the 18650 battery in 1994 "when there was a growing need for ever smaller and lighter storage batteries that could be used for ever longer periods of time".^[4] They are now commonly used in power tools, electric bicycles, laptops, and electric vehicles.^[5]

This section needs expansion. You can help by adding to it. Find sources: "18650 battery chemistry" lithium-ion battery chemistry – news · newspapers · books · scholar · JSTOR (November 2023)

18650 batteries are most commonly lithium-based^{[citation needed]}.

By 2023, some sodium-ion variants were available in the 18mm x 65 mm cylindrical cell form factor as well.^{[6][better source needed]}

18650 batteries are commonly used in packs, where a battery management system (BMS) is required, especially once cells age and perform differently. BMS boards balance the voltage of cells in series and protect against over- and under-discharge.

18650 battery cells are used in a wide variety of products from the 1990s through the 2020s, and is widely regarded as the most produced lithium-ion cell size.^[7] 18650/1865 cells are used in many laptop computer batteries, cordless power tools, many electric cars, electric scooters,^[8] most e-bikes, older portable powerbanks, electronic cigarettes,^[9][10] portable fans, and LED flashlights. Nominal voltage is 3.6-3.7 V.^[11][5]

In the electric automobile sector, they are used in the first three vehicles manufactured by Tesla, the first-generation Roadster (late 2000s), Model S (2012+), and the Model X (2015+).^[12]

Wikimedia Commons has media related to 18650 batteries.

• List of battery sizes