Redox flow battery system and method for operating redox flow battery system

A redox flow battery system includes a plurality of branch circuits electrically connecting a plurality of battery cell parts in parallel; a switching unit configured to switch conduction states of a closed loop in which the branch circuits are connected together; a circulation mechanism; a detection unit; a determination unit configured to determine whether or not a voltage difference between the open circuit voltages of the battery cell parts is more than a predetermined value; and a control unit configured to control a switching operation of the switching unit such that, when the determination unit determines the voltage difference to be more than the predetermined value, the closed loop is brought into a non-conducting state and, when the determination unit determines the voltage difference to be equal to or less than the predetermined value, the closed loop is brought into a conducting state.