Abstract: A fuel cell system includes a fuel cell in which cells are stacked, a voltage sensor that detects a voltage in unit of one or more of the cells, a control unit that determines an operating point of the fuel cell and causes the fuel cell to operate. The control unit causes the fuel cell to operate at a low efficiency operating point having a lower efficiency than an efficiency of a reference operating point in a warm-up operation. In the warm-up operation, the control unit calculates a total number of the cells in which the voltage detected by the voltage sensor is equal to or less than a predetermined first reference voltage and calculates an exhaust hydrogen concentration based on the total number or the cells.

Abstract: A fuel cell system includes a fuel cell in which cells are stacked, a voltage sensor that detects a voltage in unit of one or more of the cells, a control unit that determines an operating point of the fuel cell and causes the fuel cell to operate. The control unit causes the fuel cell to operate at a low efficiency operating point having a lower efficiency than an efficiency of a reference operating point in a warm-up operation. In the warm-up operation, the control unit calculates a total number of the cells in which the voltage detected by the voltage sensor is equal to or less than a predetermined first reference voltage and calculates an exhaust hydrogen concentration based on the total number or the cells.

Abstract: A fuel cell system includes a fuel cell, an impedance measuring instrument, and a control device. The control device is connected to the impedance measuring instrument. The impedance measuring instrument measures the impedance of the fuel cell according to the AC impedance method. The control device stores in advance a reference value corresponding to a reference hydrogen concentration. The control device compares the real part Z? of impedance acquired via the impedance measuring instrument against the reference value. When Z? is equal to or greater than the reference value, the control device estimates the hydrogen concentration of the fuel cell to be equal to or less than the reference hydrogen concentration.

Abstract: A fuel cell system includes a fuel cell, an impedance measuring instrument, and a control device. The control device is connected to the impedance measuring instrument. The impedance measuring instrument measures the impedance of the fuel cell according to the AC impedance method. The control device stores in advance a reference value corresponding to a reference hydrogen concentration. The control device compares the real part Z? of impedance acquired via the impedance measuring instrument against the reference value. When Z? is equal to or greater than the reference value, the control device estimates the hydrogen concentration of the fuel cell to be equal to or less than the reference hydrogen concentration.