Deterioration of a power storage unit included in a vehicle is prevented or the power storage unit that has deteriorated is repaired, and the charge and discharge performance of the power storage unit is maximized to be maintained for a long time. Attention has focused on a reaction product formed on an electrode surface which causes malfunction or deterioration of a power storage unit such as a lithium-ion secondary battery. In the power storage unit used for a vehicle that runs on the power of an electric motor, rapid discharge occurring in the acceleration of the vehicle or the like tends to promote the solidification of the reaction product. The reaction product is removed by application of an electrical stimulus, specifically, an inversion pulse voltage.