A system includes a first circuit in which storage battery units are connected in series, second circuits, adjusters that adjust the amounts of the currents flowing through the second circuits, and a controller that performs at least one of first control and second control. The first control is control in which the controller causes the adjusters to make the voltage of a first storage battery unit higher than the voltage of a second storage battery unit having a higher degree of degradation than the first storage battery unit by adjusting the amounts of the currents flowing through the second circuits and then stops a charge. The second control is control in which the controller causes the adjusters to make the voltage of the first storage battery unit lower than the voltage of the second storage battery unit by adjusting the amounts of the currents flowing through the second circuits and then stops a discharge.