Patent attributes
A state estimator estimates, based on at least one of a voltage, a current, and a temperature of a secondary battery, a state of the secondary battery including a state of charge (SOC) of the secondary battery. A discharge controller discharges, when a state of non-use of the secondary battery lasts for a predetermined period of time, the secondary battery such that an indicator indicating easiness of storage deterioration of the secondary battery to progress decreases in stages. The indicator includes a parameter that depends on an SOC of the secondary battery. A value of the indicator and a duration of stay in each stage are set such that a predetermined relationship holds between products in a plurality of stages, each of the products being derived from multiplying the value of the indicator and the duration of stay in each stage.