The Fenix ARB-L18 3500U battery is a high quality Li-ion battery that is perfect for any 18650 powered torch. The battery has a built-in micro-USB port removing the need for an external charger (although can be charged in a mains charger if preferred.)
The battery is specifically designed for high intensity LED illumination.
To recharge, simply plug a micro USB cable (not included) into the battery. The built-in indicator will change from red to blue when fully charged.