Patent ID: 7773148

Claim:
A power system comprising: a battery unit that includes a battery; and an apparatus main body that operates on power supplied from the battery in the battery unit mounted thereat, the battery unit and the apparatus main body being engaged in information exchange, wherein: a work volume value, defined by an amount of an operation having been executed in the apparatus main body, is transmitted from the apparatus main body to the battery unit over a predetermined cycle; the battery unit calculates a cumulative work volume value of the work volume value at the apparatus main body and stores the cumulative work volume value therein, and the battery unit also detects a consumed battery capacity value indicating an extent to which a battery power has been consumed at the apparatus main body; the cumulative work volume value, the consumed battery capacity value and a charged battery capacity value are transmitted from the battery unit to the apparatus main body over the predetermined cycle; and the apparatus main body displays a battery use rate indicating an extent to which the battery has been used based upon the consumed battery capacity value and the charged battery capacity value, and also displays the cumulative work volume value at the apparatus main body.