RCR123 battery. 3.7 volts
This 3.7V, 650mAh from has been specifically designed for use in high-drain devices and features integrated overcharge and over discharge protection circuitry which reduces the risk of damage to the battery. A pressure relief valve allows excess pressure, which can build up due to extreme or rapid changes of temperature or altitude, to be safely dissipated. With a life-cycle of around 500 charges, using this rechargeable battery can replace dozens of disposable ones - which helps the environment.