The Nitecore NL2150 21700 Li-ion battery features a long lifespan, high energy density and powerful performance. First introduced by the electric car industry, this 21700 cell has a 5000mAh capacity, 3.6V and 14.4Wh. As with all Nitecore batteries safety is paramount and the NL2150 cell has a range of safety features to keep you, your devices and chargers as safe as possible. The 21700 battery has an innovative anode design with high temperature resistance, built-in PTC to inhibit high current surges, pressure relief valve which activates in the event of a rapid temperature increase and a microporous barries that protects the delicate internal components. Externally, the cell is equipped with nickel-plated stainless steel protectors at both ends and is coated with a durable metallic film to guard against abrasion. The 21700 is recommended to use with the following Nitecore chargers: UI1, UI2, UMS2 and UMS4. - Capacity: 5000mAh - Voltage: 3.6V - Continuous Discharge Current: 5A max - Weight: 73 g / 2.57 oz. (approx) - Length: 75.2±0.3 mm / 2.96"±0.01" - Diameter: 21.6±0.3 mm / 0.85"±0.01" - Never expose the battery to water or fire - When charging or using batteries, ensure the positive and negative ends correspond with the positive (+) and negative (-) symbols - To extend battery life it is recommended that it is charged every three months when unused for long periods - Keep out of reach of children