Abstract: A method for determining if there is a gas leak in an anode volume of a fuel cell stack in a fuel cell system. The method includes determining a total amount of gas loss in the anode volume of the fuel cell stack during a predetermined period of time, and monitoring losses of the gas from the anode volume during the predetermined period of time, such as reaction losses, crossover losses and overboard losses. The method also includes subtracting the losses of the gas from the total amount of gas loss to get an anode leak loss and comparing the anode leak loss to a predetermined threshold to identify a hydrogen gas leak.

Abstract: Systems, methods, and devices which optimize fuel-cell stack airflow control are described. According to aspects of the present disclosure, actuation of at least one cathode-flow actuator is initialized to an initial state based on a desired oxygen flowrate to operate the fuel-cell stack in a voltage-controlled mode, a stack current produced by the fuel-cell stack is determined that corresponds to operation at the actuation of the cathode-flow actuators, a flowrate of oxygen exiting the fuel-cell stack is calculated based on the stack current, the flowrate of oxygen exiting the fuel-cell stack is compared to the desired oxygen flowrate exiting the fuel-cell stack, and actuation of at least one of the cathode-flow actuators is modified in response to the flowrate of oxygen being different from the desired oxygen flowrate. The modified actuation reduces the difference between the desired oxygen flowrate and the flowrate of oxygen exiting the fuel-cell stack.

Abstract: A method of operating a fuel cell stack that powers a vehicle includes determining when the vehicle is in a non-moving state, calculating an O2 concentration over time of an assumed enclosed space while the vehicle is in the non-moving state, establishing a set of O2 concentration concern levels that includes a first O2 concentration concern level being less than a standard atmospheric O2 concentration and a second O2 concentration concern level being less than the first O2 concentration concern level, comparing the O2 concentration of the assumed enclosed space over time with the set of O2 concentration concern levels, and operating the fuel cell stack without restriction when the vehicle is in the non-moving state so long as the O2 concentration of the assumed enclosed space remains greater than the first O2 concentration concern level.

Abstract: A method for evaluating voltage sensor output using a diagnostic system includes: measuring an overall fuel cell stack voltage using a stack voltage sensor; identifying a fuel cell voltage of a first end cell using a first end cell voltage sensor and a second end cell using a second end cell voltage sensor; determining if a maximum value of the overall fuel cell stack voltage, the fuel cell voltage of the first end cell or the second end cell is less than a sensor limit, and if a minimum value of the fuel cell voltages is greater than the sensor limit; performing a test to identify if the maximum value is greater than an average sensor signal value and if the average sensor signal value is greater than the minimum value; and conducting a test to identify if the minimum value is less than a first predetermined threshold.

Abstract: Systems, methods, and devices which optimize fuel-cell stack airflow control are described. According to aspects of the present disclosure, actuation of at least one cathode-flow actuator is initialized to an initial state based on a desired oxygen flowrate to operate the fuel-cell stack in a voltage-controlled mode, a stack current produced by the fuel-cell stack is determined that corresponds to operation at the actuation of the cathode-flow actuators, a flowrate of oxygen exiting the fuel-cell stack is calculated based on the stack current, the flowrate of oxygen exiting the fuel-cell stack is compared to the desired oxygen flowrate exiting the fuel-cell stack, and actuation of at least one of the cathode-flow actuators is modified in response to the flowrate of oxygen being different from the desired oxygen flowrate. The modified actuation reduces the difference between the desired oxygen flowrate and the flowrate of oxygen exiting the fuel-cell stack.

Abstract: A system and method for determining the purity level of hydrogen gas fuel provided to an anode side of a fuel cell stack, and then modifying models and algorithms used by the system based on the purity level. The method includes determining whether predetermined criteria have been met that are necessary to obtain an accurate hydrogen gas fuel purity level, and if so, comparing a measured voltage or current of the fuel cell stack to a modeled voltage or current of the fuel cell stack. If the comparison between the measured voltage or current and the modeled voltage or current is greater than a predetermined threshold, then the method adapts a hydrogen gas concentration value to a lower purity level to be used by downstream models.

Abstract: A method for evaluating voltage sensor output using a diagnostic system includes: measuring an overall fuel cell stack voltage using a stack voltage sensor; identifying a fuel cell voltage of a first end cell using a first end cell voltage sensor and a second end cell using a second end cell voltage sensor; determining if a maximum value of the overall fuel cell stack voltage, the fuel cell voltage of the first end cell or the second end cell is less than a sensor limit, and if a minimum value of the fuel cell voltages is greater than the sensor limit; performing a test to identify if the maximum value is greater than an average sensor signal value and if the average sensor signal value is greater than the minimum value; and conducting a test to identify if the minimum value is less than a first predetermined threshold.

Abstract: Disclosed are fuel cell architectures, fuel cell stack monitoring systems, and control logic for detecting fluid property changes in a fuel cell stack. A method is disclosed for detecting a flow property change of a fluid in a fuel cell system. This method includes determining, e.g., through system analysis or accessing a look-up table, a correlation between voltage change of the fuel cell system and flow property of the fluid, and determining, from the voltage-property correlation, a calibrated voltage drop corresponding to the property change of the fluid. The method monitors system voltage (e.g., moving average voltage of the fuel cell stack operating at steady state), and detecting a voltage magnitude change in the system voltage, e.g., when an anode exhaust valve is opened. Responsive to the voltage magnitude change being greater than the calibrated voltage drop, a signal is generated indicating detection of the flow property change.

Abstract: A method of operating a fuel cell stack that powers a vehicle includes determining when the vehicle is in a non-moving state, calculating an O2 concentration over time of an assumed enclosed space while the vehicle is in the non-moving state, establishing a set of O2 concentration concern levels that includes a first O2 concentration concern level being less than a standard atmospheric O2 concentration and a second O2 concentration concern level being less than the first O2 concentration concern level, comparing the O2 concentration of the assumed enclosed space over time with the set of O2 concentration concern levels, and operating the fuel cell stack without restriction when the vehicle is in the non-moving state so long as the O2 concentration of the assumed enclosed space remains greater than the first O2 concentration concern level.

Abstract: A method for controlling a pressure drop across the anode side or the cathode side of a fuel cell stack by controlling the intrusion of a cell separator into the flow channels in a feeder region of the stack so as to create a larger pressure volume on a pressure bias side of the stack. The method controls the flow rates of one or both of the cathode and anode reactant gases so as to cause the cell separators in an inlet feeder region and/or an outlet feeder region to move relative to the anode side and the cathode side so as to change a flow volume in the inlet feeder region and/or the outlet feeder region to control the pressure drop.

Abstract: A system and method for determining the purity level of hydrogen gas fuel provided to an anode side of a fuel cell stack, and then modifying models and algorithms used by the system based on the purity level. The method includes determining whether predetermined criteria have been met that are necessary to obtain an accurate hydrogen gas fuel purity level, and if so, comparing a measured voltage or current of the fuel cell stack to a modeled voltage or current of the fuel cell stack. If the comparison between the measured voltage or current and the modeled voltage or current is greater than a predetermined threshold, then the method adapts a hydrogen gas concentration value to a lower purity level to be used by downstream models.

Abstract: Disclosed are fuel cell architectures, fuel cell stack monitoring systems, and control logic for detecting fluid property changes in a fuel cell stack. A method is disclosed for detecting a flow property change of a fluid in a fuel cell system. This method includes determining, e.g., through system analysis or accessing a look-up table, a correlation between voltage change of the fuel cell system and flow property of the fluid, and determining, from the voltage-property correlation, a calibrated voltage drop corresponding to the property change of the fluid. The method monitors system voltage (e.g., moving average voltage of the fuel cell stack operating at steady state), and detecting a voltage magnitude change in the system voltage, e.g., when an anode exhaust valve is opened. Responsive to the voltage magnitude change being greater than the calibrated voltage drop, a signal is generated indicating detection of the flow property change.

Abstract: A method for controlling a pressure drop across the anode side or the cathode side of a fuel cell stack by controlling the intrusion of a cell separator into the flow channels in a feeder region of the stack so as to create a larger pressure volume on a pressure bias side of the stack. The method controls the flow rates of one or both of the cathode and anode reactant gases so as to cause the cell separators in an inlet feeder region and/or an outlet feeder region to move relative to the anode side and the cathode side so as to change a flow volume in the inlet feeder region and/or the outlet feeder region to control the pressure drop.

Abstract: A method for determining if there is a gas leak in an anode volume of a fuel cell stack in a fuel cell system. The method includes determining a total amount of gas loss in the anode volume of the fuel cell stack during a predetermined period of time, and monitoring losses of the gas from the anode volume during the predetermined period of time, such as reaction losses, crossover losses and overboard losses. The method also includes subtracting the losses of the gas from the total amount of gas loss to get an anode leak loss and comparing the anode leak loss to a predetermined threshold to identify a hydrogen gas leak.

Abstract: A fuel cell plate for a fuel cell assembly is provided that includes a pair of unipolar plates including a flow field, an inlet flow distributor, and an outlet flow distributor, wherein the flow distributors are produced from a porous material to control liquid water throughout the reactant flow path.