A charge/discharge control system comprising: a power generating unit; an electrical load; a plurality of battery modules; a first connecting path with which the battery modules are connected in parallel to each other; a first switch which is disposed among the first connecting path, the power generating unit, and the electrical load and switchable between an on-state in which the first connecting path is connected with the power generating unit or the electrical load and an off-state in which the first connecting path is disconnected from the power generating unit and the electrical load; and a controller which is supplied with electrical power from the power generating unit or the battery modules, wherein each of the battery modules includes a battery, a second switch which is switchable between an on-state in which the battery is connected with the first connecting path and an off-state in which the battery is disconnected from the first connecting path, and a battery management device which controls a state of the battery and a switching operation of the second switch, a third switch is disposed between each of the battery management devices and the first connecting path, the third switch being switchable between an on-state in which the battery management device is connected with the first connecting path and an off-state in which the battery management device is disconnected from the first connecting path, the controller works to control switching operations of the first switch and the third switches, and in a case where the first switch is placed in the on-state in which the first connecting path is connected with the power generating unit in order to charge the battery modules, the controller turns on all the third switches of all the battery modules and the battery management devices obtain the level of voltage developed at each of the battery modules: if one of the battery modules, of which the battery develops a level of voltage lowest in the battery modules, is defined as the m th battery module, and another of the battery modules, of which the battery develops a level of voltage which is the second lowest in the battery modules, is defined as the ( m+ 1) th battery module; the controller turns off all the third switches except for the third switch corresponding to the battery module in which the level of voltage developed at the battery thereof is lower than or equal to the m th charge switching threshold; the controller turns on the second switch and the third switch of the ( m+ 1) th battery module when a condition where the level of voltage at the m th battery module during charging, of which the second switch and the third switch are each in the on-state, reaches the level of voltage at the ( m+ 1) th battery module is met. a power generating unit; an electrical load; a plurality of battery modules; a first connecting path with which the battery modules are connected in parallel to each other; a first switch which is disposed among the first connecting path, the power generating unit, and the electrical load and switchable between an on-state in which the first connecting path is connected with the power generating unit or the electrical load and an off-state in which the first connecting path is disconnected from the power generating unit and the electrical load; and a controller which is supplied with electrical power from the power generating unit or the battery modules, wherein each of the battery modules includes a battery, a second switch which is switchable between an on-state in which the battery is connected with the first connecting path and an off-state in which the battery is disconnected from the first connecting path, and a battery management device which controls a state of the battery and a switching operation of the second switch, a third switch is disposed between each of the battery management devices and the first connecting path, the third switch being switchable between an on-state in which the battery management device is connected with the first connecting path and an off-state in which the battery management device is disconnected from the first connecting path, the controller works to control switching operations of the first switch and the third switches, and in a case where the first switch is placed in the on-state in which the first connecting path is connected with the power generating unit in order to charge the battery modules, the controller turns on all the third switches of all the battery modules and the battery management devices obtain the level of voltage developed at each of the battery modules: if one of the battery modules, of which the battery develops a level of voltage lowest in the battery modules, is defined as the m th battery module, and another of the battery modules, of which the battery develops a level of voltage which is the second lowest in the battery modules, is defined as the ( m+ 1) th battery module; the controller turns off all the third switches except for the third switch corresponding to the battery module in which the level of voltage developed at the battery thereof is lower than or equal to the m th charge switching threshold; the controller turns on the second switch and the third switch of the ( m+ 1) th battery module when a condition where the level of voltage at the m th battery module during charging, of which the second switch and the third switch are each in the on-state, reaches the level of voltage at the ( m+ 1) th battery module is met.