ELECTRIC POWER DEVICE, DISPLAY DEVICE, CHARGING RATE CALCULATION METHOD, AND MEMORY MEDIUM

In an electric power device and a charging rate calculation method according to the present invention, a control unit: calculates a sum total (FCC) of respective full charging capacities of a plurality of detachable/attachable batteries; calculates a sum total (RC) of respective present charging capacities of the plurality of detachable/attachable batteries; and calculates an RSOC, which is an overall state of charge (SOC) of the plurality of detachable/attachable batteries, on the basis of the calculated sum total (FCC) of full charging capacities and the calculated sum total (RC) of present charging capacities.