Redox flow battery systems, and methods of operating a redox flow battery

Electrolyte overcharge or overdischarge inhibit redox flow battery system, and a method of operating a redox flow battery. A circulation supplying pump electrolyte into the battery cell, and a pump control unit for controlling the flow rate of the pump, the electrolyte on the inlet side state of charge supplied to the battery cell, the electrolyte discharged from said battery cell the outlet side charging state, and provided with a measuring unit for measuring at least two parameters selected from the charge-discharge current to be input to the battery cell, wherein the pump control unit, from the parameters measured by the measuring section to calculate the charging and discharging efficiency of the battery cell, the based on the charge and discharge efficiency, the pump flow rate calculation the electrolyte discharged from the battery cells to determine the flow rate of the pump so as not to be overcharged or overdischarged parts and a redox flow battery system with a pump flow rate instruction unit for setting a flow rate determined by the pump flow rate calculation unit to the pump.