The next generation 21700 customized rechargeable battery from NITECORE, the NL2150HPi has an amazing 5000mAh capacity. This powerful battery has improved performance, and superior energy density compared to previous 18650 batteries. Specifically designed for the i4000R, the “i” series batteries can work with any other NITECORE flashlight that accepts 21700 batteries. An extra 21700 is a great backup battery to have on hand, as more electronic products and NITECORE flashlights will utilize this battery. The NL2150HPi can be charged using a traditional charger like a NITECORE UI1 or through the i4000R’s built in charging port.