21700 batteries are high-capacity lithium-ion cells that measure 21mm in diameter and 70mm in length. They are commonly used in high-drain devices like flashlights, vape mods, and power tools. These measurements make it larger than the widely used 18650 cell, which measures 18mm by 65mm. This increase in size allows the 21700 to deliver higher energy storage and improved performance. As a high-performance cylindrical lithium-ion. . Lithium battery sizes refer to the standardized physical measurements of rechargeable cells, usually coded as five-digit numbers like 18650 or 21700. In these codes, the first two digits show the diameter in millimeters, while the next three represent the height in tenths of a millimeter.
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