The Fenix ARB-L21-5000 Rechargeable Li-ion 3.6V 5000 mAh battery offers exceptional power and efficiency for your high-performance outdoor gear. This robust 21700 rechargeable battery delivers the voltage and power required for extended runtimes and higher lumen capacities, ensuring your devices are always ready for action. The ARB-L21-5000 is designed with safety and durability in mind. It features protective circuits inside the anode and supports up to 500 charging cycles, providing you with reliable power over time. Additionally, it includes three sets of overheat protection: pressure relief, microporous, and PTC cathodal block, ensuring safety during use. With a maximum current of 7.5A and recommended charging current at 1A (5A maximum), this battery is engineered for optimal performance. Note that it does not include an on-board USB port for direct charging, but this small concession is outweighed by its impressive energy output and longevity. Perfect for powering your outdoor equipment, the Fenix ARB-L21-5000 Li-ion battery is a dependable choice for enthusiasts and professionals alike.