Cathode inlet humidity sensing with oxygen sensor

A vehicle comprising:

• a stack of proton exchange membrane (PEM) fuel cells arranged to provide power to the vehicle and defining a body, the body including a coolant inlet and coolant outlet, a cathode inlet and cathode outlet corresponding to a cathode, an anode inlet and an anode outlet corresponding to an anode;
• a cathode humidifier fluidly connected to the cathode inlet to provide a humidified inlet stream to the cathode via the cathode inlet;
• an oxygen sensor downstream of the cathode humidifier and upstream of the cathode inlet to measure an oxygen content of the humidified inlet stream;
• and
• a controller connected to the cathode humidifier and the oxygen sensor and configured to
• determine a relative humidity of the humidified inlet stream based on the oxygen content provided from the oxygen sensor, and,
• upon the relative humidity being less than a predefined threshold humidity, operate the cathode humidifier to increase the relative humidity.

A fuel cell system comprising:

• a stack of proton exchange membrane (PEM) fuel cells defining a body, the body including a coolant inlet and coolant outlet, a cathode inlet and cathodic outlet corresponding to a cathode, an anode inlet and an anode outlet corresponding to an anode;
• a cathode humidifier fluidly connected to the cathode inlet to provide a humidified inlet stream to the cathode inlet;
• an oxygen sensor positioned upstream of the cathode inlet and downstream of the cathode humidifier, and configured to measure oxygen content of the humidified inlet stream;
• and
• a controller connected to the cathode humidifier and the oxygen sensor and configured to operate the cathode humidifier based on the oxygen content of the humidified inlet stream such that
• upon a relative humidity being less than a predefined threshold humidity, the cathode humidifier increases the relative humidity, and
• upon the relative humidity being more than or equal to the predefined threshold humidity and less than a maximum humidity, die cathode humidifier maintains the relative humidity.