Abstract: A fuel cell reversal event is diagnosed by integrating current density via a controller in response to determine an accumulated charge density. The controller executes a control action when the accumulated charge density exceeds a threshold, including recording a diagnostic code indicative of event severity. The control action may include continuing stack operation at reduced power capability when the accumulated charge density exceeds a first threshold and shutting off the stack when the accumulated charge density exceeds a higher second threshold. The event may be detected by calculating a voltage difference between an average and a minimum cell voltage, and then determining if the difference exceeds a voltage difference threshold. The charge density thresholds may be adjusted based on age, state of health, and/or temperature of the fuel cell or stack. A fuel cell system includes the stack and controller.

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: A fuel cell system includes a fuel cell stack and a controller. The fuel cell stack includes a catalyst and a stack voltage. The controller increases efficiency of the fuel cell stack by minimizing or removing an accumulation of oxides on the catalyst during a low-power operating mode of the fuel cell system. The controller executes a method for dynamically controlling the stack voltage during a detected low-power operating mode. The method includes commanding low-voltage/high-power pulses to the fuel cell stack via the controller at a magnitude and frequency sufficient for minimizing or removing the oxides. The system may include a direct current-direct current (DC-DC) boost converter, with the controller programmed to command the power pulses from the DC-DC boost converter. Or, the controller may be configured to command the power pulses by controlling a feed rate of the oxygen and/or the hydrogen.

Abstract: A fuel cell reversal event is diagnosed by integrating current density via a controller in response to determine an accumulated charge density. The controller executes a control action when the accumulated charge density exceeds a threshold, including recording a diagnostic code indicative of event severity. The control action may include continuing stack operation at reduced power capability when the accumulated charge density exceeds a first threshold and shutting off the stack when the accumulated charge density exceeds a higher second threshold. The event may be detected by calculating a voltage difference between an average and a minimum cell voltage, and then determining if the difference exceeds a voltage difference threshold. The charge density thresholds may be adjusted based on age, state of health, and/or temperature of the fuel cell or stack. A fuel cell system includes the stack and controller.

Abstract: A fuel cell system for a vehicle or other system includes a fuel cell stack, a DC-DC boost converter, and a controller. The stack has a plurality of fuel cells and a stack voltage. The controller regulates the stack voltage during start-up of the fuel cell stack via the boost converter, and is programmed with a plurality of calibrated voltage profiles each having a corresponding magnitude and rate of change. The controller is configured to execute a method which includes detecting an air start of the fuel cell stack in response to a requested start-up of the fuel cell stack. The controller then enforces the stack voltage to the predetermined voltage profiles during an actual start-up of the fuel cell stack, doing so via regulation of the boost converter and using the plurality of calibrated voltage profiles.

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: A fuel cell system for a vehicle or other system includes a fuel cell stack, a DC-DC boost converter, and a controller. The stack has a plurality of fuel cells and a stack voltage. The controller regulates the stack voltage during start-up of the fuel cell stack via the boost converter, and is programmed with a plurality of calibrated voltage profiles each having a corresponding magnitude and rate of change. The controller is configured to execute a method which includes detecting an air start of the fuel cell stack in response to a requested start-up of the fuel cell stack. The controller then enforces the stack voltage to the predetermined voltage profiles during an actual start-up of the fuel cell stack, doing so via regulation of the boost converter and using the plurality of calibrated voltage profiles.

Abstract: A fuel cell temperature-measuring system includes a coolant source that provides coolant at a total coolant flow rate and an initial coolant temperature. A flow field plate defines peripheral flow channels and active area flow channels through which coolant flows. The flow field plate is adapted to be positioned in a fuel cell stack between individual fuel cells. A total coolant flow provided to the common input divides into a bypass flow that flows through the peripheral flow channels and an active area flow that flows through the active area flow channels. The bypass flow combines with the active area flow to emerge from the common output with an output coolant temperature. The fuel cell temperature-measuring system includes a temperature sensor that measures the output coolant temperature from the common output. Finally, a temperature estimator estimates an active area coolant temperature from the output coolant temperature.

Abstract: A fuel cell system includes a fuel cell stack and a controller. The fuel cell stack includes a catalyst and a stack voltage. The controller increases efficiency of the fuel cell stack by minimizing or removing an accumulation of oxides on the catalyst during a low-power operating mode of the fuel cell system. The controller executes a method for dynamically controlling the stack voltage during a detected low-power operating mode. The method includes commanding low-voltage/high-power pulses to the fuel cell stack via the controller at a magnitude and frequency sufficient for minimizing or removing the oxides. The system may include a direct current-direct current (DC-DC) boost converter, with the controller programmed to command the power pulses from the DC-DC boost converter. Or, the controller may be configured to command the power pulses by controlling a feed rate of the oxygen and/or the hydrogen.

Abstract: Systems and methods for initiating voltage recovery procedures in a fuel cell system based in part on an estimated specific activity over the life of a fuel cell catalyst are presented. In certain embodiments, SA loss of catalyst and electrochemical surface area loss of a FC system may be estimated. An output voltage of the FC system may be estimated based on the estimated SA loss and the electrochemical surface area loss. An amount of recoverable voltage loss may be determined based on a comparison between the estimated output voltage and a measured output voltage. Based on the determined amount of recordable voltage loss, a FC system control action (e.g., a voltage recovery procedure) may be initiated.

Abstract: Systems and methods for improving conditions for anion contaminant removal in a cathode of a PEMFC system are presented. A fuel cell system consistent with certain embodiments may include a cathode compartment having a compressor coupled thereto. The compressor may be configured to receive an input cathode gas via a compressor input and supply the input cathode gas to the cathode compartment via a compressor output. The fuel cell system may further include a cathode gas recirculation value coupled to the cathode compartment configured to receive a cathode exhaust gas output and to selectively provide at least a portion of the cathode exhaust gas output to the compressor input. Consistent with certain embodiments disclosed herein, the compressor may be further configured to supply at least a portion of the cathode exhaust gas output to the cathode compartment via the compressor output.

Abstract: Systems and methods for initiating voltage recovery procedures in a fuel cell system based in part on an estimated specific activity over the life of a fuel cell catalyst are presented. In certain embodiments, SA loss of catalyst and electrochemical surface area loss of a FC system may be estimated. An output voltage of the FC system may be estimated based on the estimated SA loss and the electrochemical surface area loss. An amount of recoverable voltage loss may be determined based on a comparison between the estimated output voltage and a measured output voltage. Based on the determined amount of recordable voltage loss, a FC system control action (e.g., a voltage recovery procedure) may be initiated.

Abstract: Systems and methods for improving conditions for anion contaminant removal in a cathode of a PEMFC system are presented. A fuel cell system consistent with certain embodiments may include a cathode compartment having a compressor coupled thereto. The compressor may be configured to receive an input cathode gas via a compressor input and supply the input cathode gas to the cathode compartment via a compressor output. The fuel cell system may further include a cathode gas recirculation value coupled to the cathode compartment configured to receive a cathode exhaust gas output and to selectively provide at least a portion of the cathode exhaust gas output to the compressor input. Consistent with certain embodiments disclosed herein, the compressor may be further configured to supply at least a portion of the cathode exhaust gas output to the cathode compartment via the compressor output.

Abstract: A method for determining when to operate a voltage recovery process for recovering a reversible voltage loss of a fuel cell stack in a fuel cell system. The method includes estimating an irreversible voltage loss of the fuel cell and an actual voltage of the fuel cell stack, and determining whether a difference between the estimated irreversible voltage loss and the estimated actual voltage exceed a threshold, and if so, the voltage recovery process is performed.

Abstract: A system and method for estimating an amount of carbon support loss in fuel cells of a fuel cell stack in a vehicle, for example, during vehicle off-times. The system and method include estimating an amount of time that a hydrogen concentration in the fuel cell stack is zero and calculating an amount of carbon loss based on the amount of time that the hydrogen concentration in the fuel cell stack is zero.

Abstract: System and methods for preventing battery depletion in a vehicle are disclosed. In certain embodiments, a method for preventing depletion of a battery included in a vehicle may include receiving a measurement of the SOC of the battery from an SOC sensor. A determination may be made as to whether the SOC of the battery has reached a threshold indicating that the battery is nearing depletion. Based on the determination, a notification may be transmitted to a remote device associated with a user of the vehicle. In certain embodiments, the user may use the notification to decide whether to remotely start a system of the vehicle to recharge the battery.

Abstract: A method for determining the health of the membranes in a fuel cell stack. The total parasitic current of the fuel cells in the stack is determined. From the total parasitic current, the shorting resistance and the cross-over parasitic current are determined. The health of the membranes is then determined from the cross-over parasitic current and the shorting resistance.

Abstract: A system and method for estimating an amount of carbon support loss in fuel cells of a fuel cell stack in a vehicle, for example, during vehicle off-times. The system and method include estimating an amount of time that a hydrogen concentration in the fuel cell stack is zero and calculating an amount of carbon loss based on the amount of time that the hydrogen concentration in the fuel cell stack is zero.

Abstract: System and methods for preventing battery depletion in a vehicle are disclosed. In certain embodiments, a method for preventing depletion of a battery included in a vehicle may include receiving a measurement of the SOC of the battery from an SOC sensor. A determination may be made as to whether the SOC of the battery has reached a threshold indicating that the battery is nearing depletion. Based on the determination, a notification may be transmitted to a remote device associated with a user of the vehicle. In certain embodiments, the user may use the notification to decide whether to remotely start a system of the vehicle to recharge the battery.

Abstract: A method for determining the health of fuel cells in a fuel cell stack. The method includes maintaining a constant flow of hydrogen to the anode side of the fuel cell stack, shutting off a flow of air to a cathode side of the fuel cell stack when a predetermined concentration of hydrogen in the anode side has been achieved, and identifying a catalyst surface area and a catalyst support surface area for catalyst layers in the fuel cell stack. The method also includes determining the total parasitic current of the fuel cell stack to determine a cross-over parasitic current and a shorting resistance of the fuel cell stack. The method further includes calculating the catalyst surface area and the catalyst support surface area of the catalyst layers and comparing the difference between the identified catalyst surface area and the calculated catalyst surface area to estimate the change in the catalyst surface area.