Redox flow cell rebalancing

A rebalance cell comprising:

• at least one source of ultraviolet radiation;
• at least one aqueous anolyte solution comprising at least one acid and at least one metal salt;
• at least one aqueous catholyte solution comprising at least one acid and at least one metal salt;
• an anode compartment and a cathode compartment separated by a membrane;
• and
• an electrode disposed in each of said anode and cathode compartments.

A control system for a rebalance cell of a flow cell battery, comprising

• one or more processors operating the flow cell battery system in multiple states, the multiple states comprising:
• an initial drain mode within which electrolyte is drained from the rebalance cell;
• an initial fill mode transitioned to from either the initialization mode or the initial drain mode, within which the rebalance cell is filled with electrolyte;
• a delay state transitioned to from the initial fill mode, within which a delay is realized;
• and
• an on state transitioned to from the delay state, within which power is applied to the rebalance cell.

A redox flow cell battery system comprising:

• a pair of electrodes disposed in separate half-cell compartments;
• a porous or ion-selective membrane separating the half-cell compartments;
• an electrolyte that is flowed through the half-cell compartments, wherein the electrolyte comprises chromium ions and iron ions;
• and
• a sensor for detecting a ratio of hydrogen to chlorine in a compartment of a portion of the flow battery system, the sensor comprising:
• a heating element capable of generating heat, during use;
• a temperature sensing element positioned to detect a temperature proximate to the heating element;
• and
• an enclosure encapsulating the heating element and the temperature sensing element.

A method for detecting a ratio of a first substance to that of a second substance in a mixture of substances, the method comprising:

• placing a sensor in a portion of a redox flow cell battery system comprising a mixture of hydrogen and chlorine, the sensor comprising:
• a heating element capable of generating heat, during use;
• a temperature sensing element positioned to detect a temperature proximate to the heating element;
• and
• an enclosure encapsulating the heating element and the temperature sensing element;
• generating heat in the heating element;
• measuring a temperature proximate to the heating element with the temperature sensing element;
• and
• determining the ratio of hydrogen to chlorine from the measured temperature.

A sensor for detecting a ratio of a concentration of a first substance to a concentration of a second substance in a mixture of substances, the sensor comprising:

• a heating element capable of generating heat, during use;
• a temperature sensing element positioned to detect a temperature proximate to the heating element;
• and
• an enclosure encapsulating the heating element and the temperature sensing element, wherein the enclosure is positionable in an environment containing the mixture of substances.