Protected Lithium-Ion rechargeable battery, 3.6V, 4900mAh, with on-board safety control circuit; rechargeable at least 500 times USB-C input charges from Streamlight AC/USB adapters and most other USB sources; battery charge status indicators around the port - red for charging, green for charged; charges in 6-hours using USB-C input Integrated safety circuit protects batteries from overcharge/over-discharge; additional safety features: pressure vent and integrated safety fuse Use the SL-B50 battery pack to power the ProTac 2.0, ProTac 2.0 Headlamp, and the ProTac 2.0 Rail Mount 2-year limited warranty