To give an alarm that the battery has run out in consideration of the use condition, not only the data on the remaining capacity of the battery in a portable instrument.

The necessary alarm is that the battery run out, for example, in a day, while such as alarm has little effect to inform the remaining capacity of the battery is 10%. Further, as for a primary battery, giving the alarm in the situation that no primary battery can be obtained, or as for a secondary battery, giving the alarm in the situation that the battery cannot be charged is meaningless; but instead, the timing for giving the alarm should be considered. Therefore, by storing a model of power consumption of the instrument in the instrument and always grasping the current capacity of the battery, the time when the battery runs out is estimated, and if necessary, the alarm is given when the instrument is used under the similar situation.