Closed loop control for fuel cell water management

A method of maintaining hydrate state by determining an electrochemical impedance (ECI) of a fuel cell, the method comprising:

• verifying stable operating conditions for the fuel cell;
• measuring a current output by the fuel cell and recording a first current value;
• measuring a voltage across the fuel cell and recording a first voltage value;
• perturbing the current output from the fuel cell;
• verifying the current output by the fuel cell and the voltage across the fuel cell have stabilized following the perturbing of the current output;
• measuring the current output by the fuel cell and recording a second current value;
• measuring the voltage across the fuel cell and recording a second voltage value;
• determining ECI of the fuel cell by dividing difference between the first voltage value and second voltage value by the difference between the first current value and the second current value;
• identifying a target ECI for the fuel cell, which corresponds to a target hydration state for the fuel cell;
• and
• adjusting a cathode flow to the fuel cell, by a controller commanding an oxidizer system, based on the determined ECI;
• wherein the ECI is an indicator for the hydration state of the fuel cell;
• wherein the current output and the voltage are considered stable when the measured results are not fluctuating by more than a predetermined amount;
• wherein the controller commanding the oxidizer system to decrease cathode flow rate when the determined ECI minus two standard deviations is larger than the target ECI;
• and
• wherein the controller commanding the oxidizer system to increase cathode flow rate when the determined ECI minus two standard deviations is smaller than the target ECI.