The Kanger Evod 650mAh battery has a regulated 3.7V output for consistency and an inbuilt 5 click on/off function.

They can be charged using a standard Ego USB charger.
Battery Size: Diametter 14mm; Length:80mm
Battery Output Voltage: Constant 3.7v
Battery Capacity: 650mAh
Battery button led: White
Threading: 510/eGo