Charging control device, battery system, and charging control method

A charging control method of a charging control device which charges a battery device,

• the battery device including:
• a battery group with a plurality of storage battery systems in parallel in each of which a plurality of batteries are connected in series,
• a system switch which switches between connection and disconnection of the storage battery system, and
• a bypass switch which bypasses each of the plurality of batteries forming the plurality of storage battery systems,
• the charging control method comprising:
• a controlling step of controlling the system switch and the bypass switch to control charging of the battery device,
• wherein in the controlling step, a total voltage is estimated when each battery is not bypassed in each of the plurality of storage battery systems, the storage battery system having a low voltage among the estimated total voltages is selected, and selective charging of charging the selected storage battery system is repeatedly executed so that an estimated total voltage difference between the storage battery system having the low voltage in the estimated total voltage and the storage battery system having a high voltage in the estimated total voltage is less than a predetermined value.