The NITECORE NL1826R 18650 battery is a revolutionary battery designed with a built-in micro-USB charging port making charging easier than ever! No more need for an extra charger as this battery can be charged directly using a standard micro-USB charging cable (sold separately). Simply plug the battery into an available power source and a red indicator light under the + pole (positive) will turn green upon completion. Alternatively, these batteries can still be charged on an external charger if desired. The NL1826R batteries are designed for powering high drain devices such as high-output flashlights, lanterns, headlamps, and bike lights, as well as a variety of other appliances and devices. With built in smart charging circuitry and other integrated safety features through-out, this battery will safely work in the majority of button-top compatible devices.