Abstract: A method for detecting a current density distribution in a fuel cell stack by detecting the magnetic field, which surrounds the fuel cell stack and which is caused by a current flow in the fuel cell stack, is provided. Sensors for an x-component, a y-component and a z-component of the magnetic flux density detect the magnetic flux density at several points outside the fuel cell stack. The position of the sensors for the magnetic flux density is detected in relation to the fuel cell stack. The thus detected values for the magnetic flux density and the allocated position are converted into current density values according to the position in the fuel cell stack by using a Maxwell equation which defines the magnetic field strength and the material equation which relates the magnetic field strength to the magnetic flux density.

Abstract: The present invention relates to an improved fuel cell stack comprising a plurality of fuel cells connected in series and method for operation so that portions of the stack can be switched to parallel operation in response to an actuating signal by means of supplemental gas-intake ports having closable valves and optionally supplemental gas-exhaust ports having closable valves.

Abstract: A method for detecting a current density distribution in a fuel cell stack by detecting the magnetic field, which surrounds the fuel cell stack and which is caused by a current flow in the fuel cell stack, is provided. Sensors for an x-component, a y-component and a z-component of the magnetic flux density detect the magnetic flux density at several points outside the fuel cell stack. The position of the sensors for the magnetic flux density is detected in relation to the fuel cell stack. The thus detected values for the magnetic flux density and the allocated position are converted into current density values according to the position in the fuel cell stack by using a Maxwell equation which defines the magnetic field strength and the material equation which relates the magnetic field strength to the magnetic flux density.

Abstract: In the fuel cell arrangement disclosed in the specification, a fuel cell stack having a methanol reformer is connected in parallel with an electrical energy storage device, a charge condition detector detects the charge condition of the electrical energy storage device, and a control unit controls the operation of the fuel cell in accordance with the charge condition of the electrical energy storage device.

Abstract: In a process and arrangement for monitoring and/or controlling charging of a battery, particularly in a battery-powered vehicle, test data relevant to the monitoring are detected at the battery and sent to an evaluation unit through a power cable connecting the battery to at least one power consuming component. The evaluation unit is connected to the power cable and the test data are transmitted to the evaluation unit through the power cable using a coded alternating voltage. This eliminates the need for additional insulated signaling lines connecting the battery sensors to the evaluation unit and reduces the need for complicated wiring, particularly in batteries with modular construction as used in battery driven automobiles.