To prevent the occurrence of a battery exchange request even during large-current operation provided that an air battery is usable by performing restoring operations on the battery by stopping large-current consuming operations by judging the operation mode and checking the battery for restored state through the battery restoring operations and, when the battery is exhausted, issuing a battery exchange request.

Whether the voltage value of an air battery is higher or lower than an LVA voltage is judged and, when the voltage is lower than the LVA voltage, the voltage detecting operations are terminated. When the voltage is lower than the LVA voltage, whether or not the battery is in a large-current operating mode is judged (S22). When the battery is not in the large-current operating mode, a battery exchange request is issued, because the battery is exhausted. When the battery is the large current operating mode, however, voltage restoring operations are executed. Then whether or not the voltage restoring operations are completed is judged by using restoration canceling time as an index (S24) and, when the voltage restoring operations are completed, the voltage restoring operations are canceled (S25) and whether or not the voltage of the air battery becomes higher than the LVA voltage is judged (S26). When the voltage is not higher than the LVA voltage, a battery exchange request is issued because the battery is exhausted (S30). When the voltage is higher than the LVA voltage, the battery is shifted to synchronous catching operations, namely, the standby mode of portable terminal equipment (S27). Finally, whether or not the equipment is in an operating zone is judged (S28) and the voltage returning processing is terminated.