ENERGY STORAGE APPARATUS, CAPACITY ESTIMATION METHOD FOR ENERGY STORAGE DEVICE, AND CAPACITY ESTIMATION PROGRAM FOR ENERGY STORAGE DEVICE

An energy storage apparatus includes external terminals, an energy storage device, a switch located in a current path from the energy storage device to the external terminal, a measurement unit that measures a current and a voltage of the energy storage device, and a management unit. The management unit cuts off discharge to an outside through the external terminal by controlling the switch when the voltage of the energy storage device falls below a threshold voltage equal to or higher than a minimum operating voltage of the measurement unit, and the management unit estimates a capacity of the energy storage device after an arbitrary time point t in a first period in which the voltage of the energy storage device decreases from the threshold voltage to the minimum operating voltage of the measurement unit based on an elapsed time from the arbitrary time point.