State of Charge and Health Estimation of Vanadium Redox Flow Battery via Extended Kalman Filter

Vanadium redox flow batteries represent a highly promising energy storage solution for the future. For their stable operation it is crucial to advance the development of fast and robust battery management system that should not only monitor state of charge but also state of health while the battery is in operational mode. In this paper we propose to monitor state of charge and state of health for Vanadium redox flow battery by means of an extended Kalman filter with the aids of an equivalent circuit model. Our approach does not require the open circuit voltage measurement from the stack, which requires an extra cell and increases the complexity of battery system design. The equivalent circuit model aids in state of charge measuring and provides valuable insights to the internal states of Vanadium redox flow battery such as variation in ohmic losses over time which enables monitoring of state of health efficiently and allows proactive maintenance strategies. The study demonstrates the functionality of state of charge monitoring, validated through real-world testing on a 5kW experimental Vanadium redox flow battery test bench. Furthermore, state of health is assessed by observing changes in ohmic losses, also confirmed through experimental validation.