A vehicle includes first and second fuel-cell stacks, a first coolant circuit having conduit arranged to circulate coolant through the first fuel-cell stack, a second coolant circuit having conduit arranged to circulate coolant through the second fuel-cell stack, a heater in fluid communication with at least the first coolant circuit, and an isolation valve assembly configured to proportion a flow of coolant between the first and second coolant circuits. The isolation valve assembly includes valving. The valving has an isolation position in which the first and second circuits are isolated. The valving also has at least one mixing position in which the first and second circuits are in fluid communication.

A fuel cell system includes a first fuel cell having an electrode area made of first electrode material, and a second fuel cell having an electrode area made of second electrode material having low durability against output voltage variation in comparison with the first electrode material. The fuel cell system is configured to supply electrical power to a motor generator. The fuel cell system includes a required electrical power acquisition unit configured to obtain required electrical power of the motor generator, and a control unit configured to control the second fuel cell in a manner that a variation of output electrical power of the second fuel cell becomes not more than a predetermined limit variation, and control the first fuel cell in accordance with the required electrical power and output electrical power of the second fuel cell.

A fuel cell system mounted on a vehicle includes: a fuel cell stack; a refrigerant circulation passage connected to the fuel cell stack; a refrigerant circulation pump arranged in the refrigerant circulation passage and configured to circulate a refrigerant; and a controller configured to control a power generation amount of the fuel cell stack according to a request driving force of the vehicle and control the refrigerant circulation pump. The controller is configured to set a rotational speed of the refrigerant circulation pump within a range equal to or lower than a rotational speed upper limit based on a temperature of the fuel cell stack, and the controller sets the rotational speed upper limit lower at a time a vehicle speed is equal to or lower than a stop determination value as compared with a time the vehicle speed is higher than the stop determination value.

A method for starting a cold or frozen fuel cell stack as efficiently and quickly as possible in a vehicle application is based upon a state of charge of a first power source such as a high voltage battery. Power flow between the first power source and fuel cell system is coordinated in conjunction with a specific load schedule and parallel control algorithms to minimize the start time required and optimize system warm-up.

A fuel cell system includes a fuel cell stack having a membrane electrode assembly and an internal reactant gas passage, a unit that detects or estimates an actual retained water quantity (R.W.Q.), and a power generation control unit having a normal-time mode, a normal-time drying mode and a stop-time drying mode. In the normal-time drying mode, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time mode until the actual R.W.Q. is decreased to a target R.W.Q. In the stop-time drying mode, when the actual R.W.Q. is equal to or more than a flooding threshold at a time of detection of a system stop instruction, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time drying mode until the actual R.W.Q. is decreased to a target R.W.Q.

An electrical power control system includes a first fuel cell system and a second fuel cell system, and a waste electricity unit connected in series with a switch unit. The waste electricity unit and the switch unit are connected in parallel with each of the fuel cell systems. At a time when at least one power supply system is started, a control unit selectively executes a charging control and a waste electricity control, based on at least one of temperature information and electrical storage information. The charging control suppresses a rise in voltage by supplying the electrical power of the power supply system to the power storage device. The waste electricity control suppresses a rise in voltage by supplying the electrical power of the power supply system to the waste electricity unit.

A fuel cell system that can improve an operating efficiency while minimizing an increase in cost for a configuration is provided. A fuel cell system (10) includes a fuel cell stack (11), an air pump (13), and an electric power control unit (15). The air pump (13) is connected to an output terminal of the fuel cell stack (11). The air pump (13) is configured to supply air as an oxidizing agent gas to the fuel cell stack (11). The electric power control unit (15) includes a first circuit unit (31) and a second circuit unit (32). The first circuit unit (31) is connected to the output terminal of the fuel cell stack (11) and is configured to perform step-up electric power conversion on an input from the fuel cell stack (11). The second circuit unit (32) is configured to perform bidirectional electric power conversion for stepping-up an input from the fuel cell stack (11) and for stepping-down an output to the air pump (13).

The present disclosure makes it possible to store data on the cause of an output shortage in a memory while reducing the capacity of the memory for storing data on an output shortage. A fuel cell system of the present disclosure comprises: a drive motor for driving a vehicle; a plurality of power sources that include a fuel cell and a secondary battery; a memory that stores data on a failure of output of the drive motor; and a controller that controls writing of the data on the failure into the memory. When an actual output value of the drive motor is smaller than a reference value decided by an output request value, the controller stores in the memory data on operating state of one of power sources, with an actual output value smaller than a power source output request value.

A method of cleaning power cells in an array of power cells, comprising coupling at least one first power cell to second power cells in an array of power cells and causing the second power cells to drive the at least one first power cell with a voltage to clean catalyst on the at least one first power cell.

A method for performing one or more proactive remedial actions to prevent anode flow-field flooding in an anode side of a fuel cell stack at low stack current density. The method includes identifying one or more trigger conditions that could cause the anode flow-field to flood with water, and performing the one or more proactive remedial actions in response to the identified trigger conditions that removes water from the anode side flow-field prior to the anode flooding occurring.