A charging/discharging apparatus (1, 101) comprising: a power supply device to supply electric power; an electric load; a connection path to be selectively connected to one of the power supply device and the electric load; and a plurality of battery module groups (104A, 104B) to be connected to the connection path, wherein each battery module group includes: a plurality of battery modules to be connected, in parallel to each other, to the connection path; a plurality of first switches each disposed between the corresponding battery module and the connection path, each of the first switches switching between an ON state where the corresponding battery module and the connection path are interconnected, and an OFF state where these are disconnected from each other; and a communication control device connected to the connection path and configured to control the first switches, the battery modules respectively include a plurality of storage batteries, and the communication control device includes a storage unit for storing voltage values or SOCs of the storage batteries in association with the respective battery modules; and the communication control device is configured to place only one switch of all the first switches in the ON state based on the stored voltage values or SOCs in the storage unit, when the connection path is connected to the power supply device, characterized in that the battery modules further include, respectively, a plurality of BMUs communicatable with the communication control device using a common identification signal, each BMU managing a state of the corresponding storage battery, and if a supply voltage from the power supply device is less than respective operating voltages for the BMU (42A, 42B) and the communication control device (8A, 8B), the communication control device (8A, 8B) in one of the battery module groups (104A, 104B), to which the one switch (6A, 6B) in the ON state belongs, is configured to switch the one switch and another first switch therein to the OFF and ON state respectively after the communication control device (8B, 8A) in another battery module group (104B, 104A) switches one of the first switches (6B, 6A) therein to the ON state. a power supply device to supply electric power; an electric load; a connection path to be selectively connected to one of the power supply device and the electric load; and a plurality of battery module groups (104A, 104B) to be connected to the connection path, wherein each battery module group includes: a plurality of battery modules to be connected, in parallel to each other, to the connection path; a plurality of first switches each disposed between the corresponding battery module and the connection path, each of the first switches switching between an ON state where the corresponding battery module and the connection path are interconnected, and an OFF state where these are disconnected from each other; and a communication control device connected to the connection path and configured to control the first switches, a plurality of battery modules to be connected, in parallel to each other, to the connection path; a plurality of first switches each disposed between the corresponding battery module and the connection path, each of the first switches switching between an ON state where the corresponding battery module and the connection path are interconnected, and an OFF state where these are disconnected from each other; and a communication control device connected to the connection path and configured to control the first switches, the battery modules respectively include a plurality of storage batteries, and the communication control device includes a storage unit for storing voltage values or SOCs of the storage batteries in association with the respective battery modules; and the communication control device is configured to place only one switch of all the first switches in the ON state based on the stored voltage values or SOCs in the storage unit, when the connection path is connected to the power supply device, characterized in that the battery modules further include, respectively, a plurality of BMUs communicatable with the communication control device using a common identification signal, each BMU managing a state of the corresponding storage battery, and if a supply voltage from the power supply device is less than respective operating voltages for the BMU (42A, 42B) and the communication control device (8A, 8B), the communication control device (8A, 8B) in one of the battery module groups (104A, 104B), to which the one switch (6A, 6B) in the ON state belongs, is configured to switch the one switch and another first switch therein to the OFF and ON state respectively after the communication control device (8B, 8A) in another battery module group (104B, 104A) switches one of the first switches (6B, 6A) therein to the ON state.