A method for starting a fuel cell in a fuel cell system, at temperatures below the freezing point of water, includes, in a first step, that the hydrogen concentration in the anode is increased; after which, in a second step, an anode pressure is increased for a fixed period of time, and while air is supplied to the cathode, the maximum possible current is drawn from the fuel cell, and after which, in a third step, the fuel cell is switched in a load-free manner and the anode pressure is reduced. After the third step, the second step and the third step are repeated successively until a sufficient performance of the fuel cell for its normal operation is reached.

A fuel cell unit includes: a fuel cell stack including: a cell stack; a first terminal respectively disposed at a first end of the cell stack in the first direction; and a second terminal disposed at a second end of the cell stack in the first direction, an end plate disposed at a side opposite to the cell stack with respect to the first terminal; a power converter that converts output power of the fuel cell stack; a stack case that houses the fuel cell stack; a power converter case that houses the power converter and is fixed to the stack case; a first bus bar that electrically connects the first terminal and the power converter in the stack case and the power converter case; and a second bus bar that electrically connects the second terminal and the power converter in the stack case and the power converter case.

A fuel cell system includes a fuel cell stack configured to supply power to an electric motor for driving a vehicle as well as generating power by an electrochemical reaction between a fuel gas and an oxidant gas, a discharge circuit and the discharge control circuit. The discharge circuit may form a plurality of discharge paths through which power generated in the fuel cell stack is discharged switching elements switching the connection relationships between resistance elements. The discharge control circuit form a second discharge path whose resistance value is smaller than the resistance value of the first discharge path and to switch the discharge through a first discharge path to discharge through the second discharge path when the detected voltage that is detected by the voltage detection unit is lower than a predetermined threshold voltage during the discharge through the first discharge path.

A fuel cell system is configured to generate power by supplying anode gas and cathode gas to a fuel cell. The fuel cell system includes a load connected to the fuel cell and an IV estimation unit configured to change an output current of the fuel cell with a predetermined width by adjusting power supplied to the load during the warm-up of the fuel cell. The fuel cell system is configured to estimate an IV characteristic of the fuel cell on the basis of at least two sets of an output current value and an output voltage value detected while the output current is changed. The fuel cell system includes an IV estimation stop unit configured to stop the execution of the IV estimation on the basis of an output of the fuel cell during the execution of the IV estimation.

A method for accurately measuring the impedance of the fuel cell stack in the vehicle during operation of the vehicle includes determining whether measuring the impedance of the fuel cell stack is requested during driving of the vehicle driven by using a power of a fuel cell stack, switching a DC-DC converter connecting the fuel cell stack and a battery to each other to a buck mode when measuring the impedance is requested, thereby blocking output current of the fuel cell stack from flowing to the battery through the DC-DC converter, determining a first current value of the fuel cell stack for measuring the impedance, controlling a resistance value of a COD variable resistor consuming the output current of the fuel cell stack according to the first current value, and measuring the impedance of the fuel cell stack while the output current of the fuel cell stack is maintained at the first current value.

A system for operating a fuel cell includes a controller configured to derive an output limit value of the fuel cell through an interval average value corresponding to an average of output values of the fuel cell for a designated time and a cumulative average value corresponding to an average of the output values of the fuel cell until the current point in time after starting to operate the fuel cell, and to control operation of the fuel cell based on the derived output limit value.

A current limiting method of a fuel cell stack is capable of preventing current of the fuel cell stack from rapidly dropping to prevent jerking or shock from occurring while a vehicle travels. The method includes: determining whether performance deterioration of a unit cell of the fuel cell stack has occurred, employing a feed forward control type current limiting logic of the fuel cell stack before an output of the fuel cell vehicle is lowered, decreasing the current of the fuel cell stack to a predetermined level by the feed forward control type current limiting logic, and gradually restoring the current of the fuel cell stack to a maximum current usage value from a point in time when the current of a load is used.

The disclosed embodiments relate to the design of a portable and cost-effective fuel cell system for a portable computing device. This fuel cell system includes a fuel cell stack which converts fuel into electrical power. It also includes a fuel source for the fuel cell stack and a controller which controls operation of the fuel cell system. The fuel system also includes an interface to the portable computing device, wherein the interface comprises a power link that provides power to the portable computing device, and a bidirectional communication link that provides bidirectional communication between the portable computing device and the controller for the fuel cell system.

Described herein is a fuel cell system including a coolant control valve to switch a flowing path of a coolant through a first fluid passage passing through a fuel cell stack and a second fluid passage passing through a cathode oxygen depletion (COD) heater, and a controller to perform a shutdown sequence and control a valve opening amount of the coolant control valve connected to the first fluid passage and the second fluid passage, when shutdown is requested for the fuel cell stack. The coolant control valve is formed by integrating a first valve to switch a flowing path of the coolant flowing into a pump with a second valve to switch a flowing path of a coolant pumped by the pump.

Disclosed a fuel cell system including an air pump that injects air into a fuel cell stack, a purge valve that performs hydrogen purging based on an opening degree, and a controller that calculates a cumulative current of the fuel cell, and performs at least one of a first operation of controlling the number of rotations of the air pump based on the cumulative current, a second operation of controlling the opening degree of the purge valve, or a combination of the first operation and the second operation.