Abstract: A fuel cell system that includes a cell voltage monitoring sub-system that measures the cell voltage of each cell in a fuel cell stack and provides an indication of a low performing or failed cell. The fuel cell system uses the cell voltage monitoring sub-system to determine if one of the wires connected to a bipolar plate in the stack is broken or has otherwise failed. The cell voltage monitoring sub-system uses differential amplifiers to compare the positive side voltage and the negative side voltage of a cell to determine if the cell voltage is low or the cell is failing. By looking at the outputs of two differential amplifiers in the cell voltage monitoring sub-system, it can be determined whether adjacent cells provide an indication of both cells failing, which would indicate that a connection wire has failed.

Abstract: A system and method for controlling the bleed valve in an anode recirculation loop of a fuel cell system. The system uses a model to determine the concentration of hydrogen in the recirculated gas by calculating the volume flow of the recirculated gas through a fuel cell stack, a pressure drop across the anode inlet and outlet of the stack, and the density of the recirculated gas, and using a measured temperature of the recirculated gas and a measured pressure drop across a recirculation pump.

Abstract: A system and method for controlling the speed of a recirculation pump in an anode recirculation loop of a fuel cell system based on a predetermined ratio of fresh hydrogen to recirculated anode gas. The system uses a model to determine the volume flow of the recirculated gas through a fuel cell stack to determine the recirculation rate based on a measured temperature of the recirculated gas, a measured pressure drop across a recirculation pump, a pressure drop across the anode inlet and outlet of the stack, a percentage of hydrogen in the recirculated gas, and the density of the recirculated gas.

Abstract: A system and method for controlling the speed of a recirculation pump in an anode recirculation loop of a fuel cell system based on a predetermined ratio of fresh hydrogen to recirculated anode gas. The system uses a model to determine the volume flow of the recirculated gas through a fuel cell stack to determine the recirculation rate based on a measured temperature of the recirculated gas, a measured pressure drop across a recirculation pump, a pressure drop across the anode inlet and outlet of the stack, a percentage of hydrogen in the recirculated gas, and the density of the recirculated gas.

Abstract: A system and method for controlling the bleed valve in an anode recirculation loop of a fuel cell system. The system uses a model to determine the concentration of hydrogen in the recirculated gas by calculating the volume flow of the recirculated gas through a fuel cell stack, a pressure drop across the anode inlet and outlet of the stack, and the density of the recirculated gas, and using a measured temperature of the recirculated gas and a measured pressure drop across a recirculation pump.

Abstract: A fuel cell system that includes a cell voltage monitoring sub-system that measures the cell voltage of each cell in a fuel cell stack and provides an indication of a low performing or failed cell. The fuel cell system uses the cell voltage monitoring sub-system to determine if one of the wires connected to a bipolar plate in the stack is broken or has otherwise failed. The cell voltage monitoring sub-system uses differential amplifiers to compare the positive side voltage and the negative side voltage of a cell to determine if the cell voltage is low or the cell is failing. By looking at the outputs of two differential amplifiers in the cell voltage monitoring sub-system, it can be determined whether adjacent cells provide an indication of both cells failing, which would indicate that a connection wire has failed.

Abstract: A fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, which are assembled into a stack, the system having a cathode side with a cathode inlet and a cathode outlet, with oxygen or an oxygen containing gas, such as for example air, being capable of being supplied to the cathode inlet and also having an anode side which has an anode inlet and an anode outlet, with hydrogen or a hydrogen rich gas being capable of being supplied to the anode inlet and with a feedback loop being provided in order to return at least a part of the hydrogen containing exhaust gases which arise at the anode outlet back to the anode inlet, characterized by a line which leads from the anode side to the cathode side and is designed to supply anode exhaust gases to the cathode inlet which, after reaction of the hydrogen component with oxygen at the cathode side to form water, leave the fuel cell system with the cathode exhaust gases via the cathode outlet.

Abstract: A fuel cell system comprising a plurality of fuel cells, in particular in the form of low temperature fuel cells, which are assembled into a stack, the system having a cathode side with a cathode inlet and a cathode outlet, with oxygen or an oxygen containing gas, such as for example air, being capable of being supplied to the cathode inlet and also having an anode side which has an anode inlet and an anode outlet, with hydrogen or a hydrogen rich gas being capable of being supplied to the anode inlet and with a feedback loop being provided in order to return at least a part of the hydrogen containing exhaust gases which arise at the anode outlet back to the anode inlet, characterized by a line which leads from the anode side to the cathode side and is designed to supply anode exhaust gases to the cathode inlet which, after reaction of the hydrogen component with oxygen at the cathode side to form water, leave the fuel cell system with the cathode exhaust gases via the cathode outlet.