Method for restoring performance

A method for restoring performance of a vanadium redox flow battery module in a battery system,

• wherein the battery system comprises:
• at least two battery modules connected in series,
• a power conversion system;
• and
• a control device,
• wherein the at least two battery modules are connected to the power conversion system, and wherein each battery module comprises:
• a cell device;
• a tank device for storing an electrolyte;
• and
• two pumps for conveying the electrolyte through the cell device,
• wherein the control device is configured to detect an operating state of the power conversion system and to drive the two pumps in the at least two battery modules,
• wherein the method comprises the following steps in the indicated order:
• identifying at least one degraded battery module from the at least two battery modules;
• switching off pumps of the at least one degraded battery module at a time t1;
• and
• switching on the pumps of the at least one degraded battery module at a time t2,
• wherein a length of a time interval Δt=t2−t1 is selected such that, at time t2, a terminal voltage of the at least one degraded battery module is negative, but overcharging of the electrolyte present in the cell device of the at least one degraded battery module is avoided, and
• wherein switching off the pumps and switching on the pumps are carried out while the battery system is being discharged.