BATTERY CAPACITY ESTIMATION DEVICE, BATTERY CAPACITY ESTIMATION METHOD, AND COMPUTER PROGRAM PRODUCT

A battery capacity estimation device in an embodiment includes one or more hardware processors configured to: acquire an alternating current power or an alternating current energy that is input to and output from a storage battery system via a direct current-alternating current converter, the storage battery system being capable of controlling charge and discharge; acquire a state of charge (SoC) of the storage battery system; and estimate a battery capacity of the storage battery system based on the acquired alternating current power or the acquired alternating current energy and the acquired SoC.