To acquire an exact life of a battery by calculating the consumed power of the battery on the basis of an operation result.

The channel terminal 24 measures an operating time during which a certain operation is carried out and discriminates an operation class to count number of operation times. The terminal 24 calculates the entire power consumption of the battery from the power consumption of the battery by one preset operation and the number of operation times. The terminal 24 discriminates the residual capacity from the effective capacity of the battery and the power consumption of the battery to able to predict the service life of the battery. The terminal 24 informs the center side system 20 of this information through a telephone line 28.