Degradation of a secondary battery or the like is prevented. A reduction in the capacity of a secondary battery or the like due to charging or discharging is prevented. A secondary battery module in which a secondary battery can be charged in a charging period into which short discharging periods are inserted is provided. A secondary battery module in which a plurality of secondary batteries are connected in parallel, and in a charging period of the secondary batteries, current due to short-time discharging of one secondary battery can be used for charging another secondary battery is provided. To carry out such operation, a secondary battery module includes a plurality of secondary batteries, a DC/DC converter, a switch, and a control circuit.