Slightly larger than the AA battery, an 18650 battery (classified by its 18mm x 65mm size) is an industrial standard rechargeable lithium-ion battery often used in all types of battery packs for all sorts of purposes such as energy storage devices, drones, robot vacuums, portable power tools, electric vehicles, and many other high-drain devices. Before using 18650 batteries, check with your device manufacturer for compatibility. With more than 100 available 18650 battery models at IMRbatteries.com, browse our most popular 18650 battery brands including: Samsung, LG and Sony Murata.