For the current supply of the terminal the Lithium-Ion battery HA-G20BAT is used. A rechargeable, not exchangeable by the user, backup battery secures the main memory if the capacity of the main battery is low or during the change of the main battery. The backup battery is charged by the main battery.
Main Battery (7.4V)
8 - 13 Hours
Further information, especially about calculating the running time can be found in the Hardware Manual.