Abstract: The invention relates to a method for operating a fuel cell system in a mode of reduced power output. The fuel cell system comprises a fuel cell stack (BS) having at least one fuel cell (BZ) with an anode (A), a cathode (K), and a proton exchange membrane, anode and cathode inlets, anode and cathode outlets, and a hydrogen and air supply. In order not to adversely affect the life span of the fuel cell system, the air supply to the cathode (K) is interrupted during the changeover to the mode of reduced power output, and an electric voltage (U) of the fuel cell stack (BS) is reduced by means of a current pulse.

Abstract: A method for shutting down a fuel cell system having at least one fuel cell, especially a fuel cell provided with a proton exchanging membrane, anode and cathode inlets, anode and cathode outlets, an anode recirculation circuit, a device which is operated according to the Venturi principle and is used to convey the gas in the anode recirculation circuit, and a hydrogen and air supply is disclosed. A method characterized by low emission values and high efficiency is provided. The hydrogen supply to the anode is interrupted during shutdown of the fuel cell system and the current generated from the residual hydrogen is supplied to an electric consumer.

Abstract: In a method and apparatus for wetting a fuel cell unit on the basis of a predetermined dew point nominal value as a function of the operating state of the fuel cell unit, a corrected dew point nominal value is determined using a predetermined dew point nominal value, a component-specific correction value, and a process correction value. The corrected dew point nominal value is used to set the required amount of water for optimum wetting of the fuel cell unit.

Abstract: The invention relates to a method for operating a fuel cell system in a mode of reduced power output. The fuel cell system comprises a fuel cell stack (BS) having at least one fuel cell (BZ) with an anode (A), a cathode (K), and a proton exchange membrane, anode and cathode inlets, anode and cathode outlets, and a hydrogen and air supply. In order not to adversely affect the life span of the fuel cell system, the air supply to the cathode (K) is interrupted during the changeover to the mode of reduced power output, and an electric voltage (U) of the fuel cell stack (BS) is reduced by means of a current pulse.

Abstract: A fuel cell system is provided having at least one switching means (16, 17, 18) for reversing the direction of a flow of at least one working medium in a fuel cell unit (10), with the fuel cell unit (10) having a cathode (11), an anode (12) and a cooling water device (13) in a housing (26). Advantageously more reliable operation with less component complexity is made possible by the switching means (16, 17, 18) being arranged outside the housing (26).

Abstract: The invention concerns a method for operation of a drive unit of a vehicle, including a drive machine and a transmission with at least two gears. A quantity that characterizes acceleration of the vehicle and a quantity that characterizes the power of the drive engine are continuously determined. A gear shift speed range and a second speed range bounded by a lowest and highest attainable speed in the target gear can be established for a gear shift process in the initial gear. The gear shift speed range is bounded at least by a lower gear shift speed and an upper gear shift speed and the second speed range is bounded by a lower target speed, as well as an additional speed. The gear shift process is initiated as a function of the determined acceleration. The lower target speed is achieved in a gear shift process in a first limiting stage (high acceleration at low input speeds or limited deceleration at low input speeds) during initiation of a gear shift at a number of gear shift speeds.