To provide a fuel cell system configured to appropriately measure the AC impedance of a fuel cell. A fuel cell system wherein the controller controls ON and OFF of the switches of n phases; wherein the controller operates the switches of the n phases at different phases, and the controller operates the switches of the n phases at the same duty ratio; wherein the controller operates the switches of the n phases at the same phase, when the controller determines that a specific condition is met; and wherein the controller measures the AC impedance of the fuel cell from the current waveform and voltage waveform of the fuel cell.

A unit cell for a fuel cell stack including an anode catalyst layer separated by a polymer electrolyte membrane from a cathode catalyst layer, a first cell end plate separated by a first gas diffusion layer from the anode catalyst layer, and a second cell end plate separated by a second gas diffusion layer from the cathode catalyst layer, wherein the first cell end plate, the second cell end plate, or both include a matrix of electrically-conducting protrusions thereof.

To provide a fuel cell system configured to appropriately measure the AC impedance of a fuel cell. A fuel cell system wherein the controller controls ON and OFF of the switches of n phases; wherein the controller operates the switches of the n phases at different phases, and the controller operates the switches of the n phases at the same duty ratio; wherein the controller operates the switches of the n phases at different duty ratios, when the controller determines that a specific condition is met; and wherein the controller measures the AC impedance of the fuel cell from the current waveform and voltage waveform of the fuel cell.

A system and method of controlling water imbalance in an electrochemical cell is provided. The method includes determining a present water imbalance in the electrochemical cell by summing a water.sub.in and a water.sub.created less a water.sub.out. Water.sub.in represents an amount of water introduced into the electrochemical cell by an oxidant feed gas; water.sub.created represents an amount of water created by the electrochemical cell from the electrochemical reaction; and water.sub.out represents an amount of water discharged from the electrochemical cell by an oxidant exhaust gas. The method includes tracking a cumulative water imbalance during operation of the electrochemical cell by repeatedly determining the present water imbalance and continuing to sum the results during operation. And, the method also includes adjusting a flow rate of the oxidant feed gas entering the electrochemical cell based on the cumulative water imbalance.

A method of predicting a life of a membrane electrode assembly (MEA) of a fuel cell for electric power generation includes: deriving an operating condition for accelerated degradation, which is applicable to the fuel cell; operating the fuel cell for a specific time under the derived operating condition for accelerated degradation and under a normal operating condition, and identifying the degree of degradation of the fuel cell under each of the operating conditions; calculating an acceleration multiple based on the degree of degradation identified under the operating condition for accelerated degradation and under the normal operating condition; and predicting the life of the membrane electrode assembly based on the acceleration multiple.

A fuel cell including a plurality of elementary modules stacked on each other, at least one of the elementary modules including an oxidation unit generating electrons by oxidation of a fuel with an oxidant, an anode block including a fuel transporter support, for transporting an anode feed flow containing the fuel to an anode chamber, onto which is attached an anode electron collector, a cathode block including an oxidant transporter support, for transporting a cathode feed flow containing the oxidant to a cathode chamber, onto which is attached a cathode electron collector, the elementary module defining the anode chamber, respectively, the cathode chamber between the oxidation unit and the fuel transporter support, respectively, the oxidant transporter support, and being such that, prior to the assembly of the elementary module in said plurality, the anode block, respectively, the cathode block and the oxidation unit are attached to each other.

A fuel cell system includes: a fuel cell unit; first and second supply systems; a switching device; a switching control unit; an open circuit voltage obtaining unit; and a supply system control unit.

A power supply device for the electrical power supply of at least one consumer has a primary power grid, in which a fuel cell device is present, having a secondary power grid, in which a battery is present, having an operating voltage range bounded at the top by a maximum voltage and at the bottom by a minimum voltage, and having an operating current strength range for powering the at least one consumer. An open circuit voltage of the fuel cell device corresponds at most to the maximum voltage of the battery, while there is present in the primary power grid an impedance spectroscopy device, which is designed to perform an impedance spectroscopy measurement on the fuel cell device or on individual fuel cells of the fuel cell device. A fuel cell vehicle has such a power supply device and a method for starting a power supply device.

A fuel cell system includes: a fuel cell including an MEA including an electrolyte membrane and anode and cathode catalyst layers sandwiching the electrolyte membrane; an impedance measuring device measuring AC impedance of the fuel cell when AC voltage is applied to the fuel cell; an impedance acquisition unit configured to obtain a first imaginary part value of the AC impedance measured when AC voltage with a fixed frequency satisfying Fixed frequency [Hz]×(Thickness of the electrolyte membrane [μm]).sup.2≤500 [Hz×μm.sup.2] is applied in a state where a relative humidity of the MEA is 20% or greater, and a fuel gas is present and an oxidant gas is absent in the anode and cathode catalyst layers; and a metal ion estimation unit configured to estimate a content of metal ions in the electrolyte membrane based on the first imaginary part value of the AC impedance.

A system and method of controlling water imbalance in an electrochemical cell is provided. The method includes determining a present water imbalance in the electrochemical cell by summing a water.sub.in and a water.sub.created less a water.sub.out. Water.sub.in represents an amount of water introduced into the electrochemical cell by an oxidant feed gas; water.sub.created represents an amount of water created by the electrochemical cell from the electrochemical reaction; and water.sub.out represents an amount of water discharged from the electrochemical cell by an oxidant exhaust gas. The method includes tracking a cumulative water imbalance during operation of the electrochemical cell by repeatedly determining the present water imbalance and continuing to sum the results during operation. And, the method also includes adjusting a flow rate of the oxidant feed gas entering the electrochemical cell based on the cumulative water imbalance.