VRF Battery Characterization Using Microwave Planar Complementary Split Ring Resonators

Abstract

The oxidation states of vanadium redox flow battery electrolytes need to be rebalanced for sustainable long term energy storage and battery performance monitoring. To achieve this, a complementary split-ring resonator is designed at 5.26 GHz to monitor the state of the charge of each electrolyte continuously in situ during battery operation. Sensor performance was tested on a 40 cell, 2.5 kW stack utilizing 40 L of electrolyte. Battery cycling was performed between 62 V -30 V (terminal voltage) with a max charge/discharge current of 40 A/45 A respectively. The transmission notch of the resonator measures resonance amplitude variation of~ 1 dB during charging cycle with~ 0.04 dB incertitude.