Determining state of charge, molarity and oxidation state in a flow battery and controlling a flow battery

A flow battery comprising:

• at least one electrochemical battery cell in fluid communication with an anolyte electrolyte and a catholyte electrolyte;
• a reference cell in fluid communication with at least one of the anolyte electrolyte and the catholyte electrolyte and in fluid communication with a reference electrolyte having a known electric potential, the reference cell to measure at least one of i) an anolyte potential difference, across the reference cell, between the anolyte electrolyte and the reference electrolyte, and ii) a catholyte potential difference, across the reference cell, between the catholyte electrolyte and the reference electrolyte;
• and
• a computing device comprising circuitry configured to:
• process the at least one of the anolyte potential difference and the catholyte potential difference to determine a respective state of charge (SOC) of the anolyte electrolyte and catholyte electrolyte for controlling operation of the flow battery, the computing device determining the respective SOC without a measurement of the potential difference between the anolyte electrolyte and the catholyte electrolyte.