Theoretical and Experimental Investigation of Voltage Current Characteristic, Losses and Self-discharge of a Vanadium Redox Flow Battery System

Abstract

The paper describes results of the theoretical and experimental investigation and the modeling of a 5 kW and 15 kWh vanadium redox flow battery system (VRFBS). The first part of the paper presents the dependence of the voltage-current characteristics on state of charge (SOC), temperature, and electrolyte flow rate, as well as models for the stack overvoltages based on current literature. Furthermore, losses due to shunt currents, vanadium diffusion and power consumption of peripheral equipment are discussed. The second part of the paper presents new results of experimental investigations and the modeling of the self-discharge behavior of the VRFBS during the standby phase (open circuit operation, when no electric and electrolyte currents present) and the phase directly after restart of the VRFBS.