A 21700 battery is a high capacity lithium ion rechargeable battery. Their proper name is a “21700 cell”. 7v and has between 3000 mAh and 5100 mAh (mili-amp-hours). This makes it larger than the popular 18650 battery, which measures 18mm x 65mm. In these codes, the first two digits show the diameter in millimeters, while the next three represent the height in tenths of a millimeter. From electric bikes to power tools and electric vehicles, this battery offers a perfect balance of capacity, power output, and. . The 21700 battery is a cylindrical lithium-ion battery with a diameter of 21mm and a length of 70mm. It offers a nominal voltage of 3. 7 volts and are used where constant voltage is needed and also provide a low self-discharge rate and larger charging and discharging cycles.
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