Abstract: The invention relates to a method for restoring the performance of a vanadium redox flow battery module in a battery system, the method comprising the following steps in the order indicated: identifying at least one degraded battery module; switching off the pumps of the at least one degraded battery module at a time t1; switching on the pumps of the at least one degraded battery module at a time t2; wherein the length of the time interval ?t=t2?t1 is selected such that, at the time t2, a terminal voltage of the degraded battery module is negative, but overcharging of the electrolyte located in the cell assembly of the degraded battery module is avoided, and wherein these steps, with the exception of the first step, take place while the battery system is being discharged.