Provided are a method and an apparatus controlling a water flooding failure in a fuel cell dual-stack system. The method includes: acquiring a hydrogen pressure drop reference value of the stack system in each normal working condition to obtain a control value; collecting a current pressure drop at a hydrogen side, and determining whether the current pressure drop at the hydrogen side is higher than the control value corresponding to a current normal working condition; determining a faulted stack according to voltages or currents of the first stack and the second stack if the current pressure drop at the hydrogen side is higher than the control value corresponding to the current normal working condition; reducing an opening degree of a flow regulating valve of the faulted stack, and increasing an opening degree of a flow regulating valve of the other stack.

A fuel cell arrangement for carrying out a method for ascertaining the overvoltage of a working electrode in a fuel cell, in which the potential of a reference electrode compared to the grounded counter electrode is measured. For the measurement, a fuel cell comprising a polymer electrolyte membrane is used, in which the counter electrode comprises a lateral edge having at least one convexly curved region, and the electrolyte membrane surface, adjoining the counter electrode, comprises an electrode-free region in which the reference electrode is disposed on the electrolyte membrane surface. In contrast, the working electrode is continuous, which is to say has a large surface. The minimum distance L.sub.gap between the reference electrode and the edge of the counter electrode L.sub.gap=3×L.sub.l,r with (a) and (b), where m=ionic conductivity of the electrolyte membrane (Ω.sup.−1 cm.sup.−1), b.sub.ox=Tafel slope of the half cell for the electrochemical reaction of the working electrode, l.sub.m=membrane layer thickness (cm) and j.sub.ox.sup.0=exchange current density of the catalyst of the working electrode per unit of electrode surface in (A cm.sup.−2). This arrangement can advantageously be used to ensure that the potential measured at the hydrogen-fed reference electrode corresponds to the overvoltage of the working electrode with sufficient accuracy. The method can be applied to polymer electrolyte membrane fuel cells (PEMFC), to direct methanol fuel cells (DMFC) or to high-temperature fuel cells (SOFC).

This specification describes a system and method for controlling the voltage produced by a fuel cell. The system involves providing a bypass line between an air exhaust from the fuel cell and an air inlet of the fuel cell. At least one controllable device is configured to allow the flow rate through the bypass line to be altered. A controller is provided to control the controllable device. The method involves varying the rate of recirculation of air exhaust to air inlet so as to provide a desired change in fuel cell voltage.

A fuel cell power controller tracks load current and fuel cell output voltage, and alerts on excessive fuel cell ramp rate, so another power source can supplement the fuel cell and/or the load can be reduced. A power engineering process makes efficient use of available fuel cell power by ramping up power flow rapidly when power is available, while respecting the ramp rate and other power limitations of the fuel cell and safety limitations of the load. Power flow decreases after an alert indicating an electrical output limitation of the fuel cell. Permitted power flow increases in response to a power demand increase (actual or requested) from the load in the absence of the alert. Power flow may increase or decrease in a fixed amount, a proportional amount, or per a sequence. A power controller relay may trip open on a low fuel cell output voltage or high load current.

A state of charge indicator arrangement for a redox flow battery system having a reference cell arrangement for measuring potential difference between a positive electrolyte and a negative electrolyte of the flow battery and an auxiliary reference electrolyte arrangement is provided. The indicator includes a discrete auxiliary electrolyte reservoir for housing a redox electrode in association with a reference electrolyte of known composition comparable to the desired or initial composition of the flow battery electrolyte for which it provides a reference, a means of measuring the potential difference between the auxiliary reference electrolyte and the electrolyte of the reference cell arrangement and an ionic pathway conduit linking the auxiliary reference electrolyte reservoir with the electrolyte of the reference cell arrangement, which is configured for low fluid diffusion rate.

The invention relates to a supply circuit of the cathode (250) of at least one electrochemical cell (200) of the PEMFC type, which further comprises a membrane (290) separating an anode (210) and said cathode (250), with this circuit comprising: a supply channel (220) comprising an inlet (282) and making it possible to convey a fluid (90) in contact with the cathode (250); a discharge channel (280) that makes it possible to remove gases from the cell, a recirculation channel (100, 100), comprising: a first opening (102) connected to the outlet (284) of the discharge channel (280); a second opening (104) connected to the inlet (282) of the supply channel (280), by the intermediary of a connector (80); a third opening (106) and means for removing (140) that allow at least one portion of the fluid (90) to be removed from the recirculation channel by the third opening (106), the recirculation channel (100, 100) and/or the supply channel further comprising at least one compressor (C1, C2), which makes it possible to control the flow rates and/or the proportion of the fluids to be mixed in the connector.

During power reduction transitions of a fuel cell power plant, the excess electric energy generated by consumption of reactants is extracted, during one or more periods of time, by a voltage limiting device control (200) in response to a controller (185) as i) energy dissipated in a resistive auxiliary load or ii) as energy applied to an energy storage system (201) (a battery), in boost and buck embodiments. The controller operates the voltage limiting device control in response to the positive time derivative of the voltage of one or more of the fuel cells exceeding a predetermined limiting value.

A method of calibrating an offset of a pressure sensor, by which an offset of a sensing value of a pressure sensor, which detects a pressure of hydrogen in a fuel cell system, is accurately calibrated. The method includes receiving, by a controller, a sensing value of a pressure sensor which detects a hydrogen pressure in a state where a hydrogen supply starts after a start of a fuel cell system; counting, by the controller, a time for which the sensing value of the pressure sensor increases from a first pressure P.sub.1 to a second pressure P.sub.2; calculating, by the controller, an offset value corresponding to the counted time by use of stored setting data; and calibrating, by the controller, a subsequent sensing value of the pressure sensor by the calculated offset value in real time when the offset value is calculated.

A method for diagnosing a water-containing state of a fuel cell stack includes steps of: applying an alternating current (AC) signal having a predetermined frequency to the fuel cell stack to calculate each of an electrolyte membrane impedance, an anode impedance, and a cathode impedance from an output voltage and an output current of the fuel cell stack corresponding to the AC signal; and diagnosing the water-containing state of the fuel cell stack on the basis of the electrolyte membrane impedance, the anode impedance, and the cathode impedance.

A method for making contact with a plurality of separator plates of a fuel cell system includes the steps of: inserting at least one connecting element of a cell voltage monitoring system between two directly adjacent separator plates so that two connecting parts of the connecting element that are able to move with respect to one another are arranged at least in certain regions between the directly adjacent separator plates; and relatively moving the two connecting parts that are able to move with respect to one another so that at least one first connecting part of the connecting parts moves at least in sections toward a separator plate of the directly adjacent separator plates.