EP1859290A4 - Procede, systeme et appareil pour test en diagnostic d'une pile a elements electrochimiques - Google Patents

Procede, systeme et appareil pour test en diagnostic d'une pile a elements electrochimiques

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Publication number
EP1859290A4
EP1859290A4 EP05714645A EP05714645A EP1859290A4 EP 1859290 A4 EP1859290 A4 EP 1859290A4 EP 05714645 A EP05714645 A EP 05714645A EP 05714645 A EP05714645 A EP 05714645A EP 1859290 A4 EP1859290 A4 EP 1859290A4
Authority
EP
European Patent Office
Prior art keywords
voltage
gas
anode
cells
electrochemical cell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05714645A
Other languages
German (de)
English (en)
Other versions
EP1859290A1 (fr
Inventor
Rami Aboutallah
Stephane Masse
Daren Pemberton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hydrogenics Corp
Original Assignee
Hydrogenics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hydrogenics Corp filed Critical Hydrogenics Corp
Publication of EP1859290A1 publication Critical patent/EP1859290A1/fr
Publication of EP1859290A4 publication Critical patent/EP1859290A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04664—Failure or abnormal function
    • H01M8/04679—Failure or abnormal function of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04246—Short circuiting means for defective fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H01M8/04388—Pressure; Ambient pressure; Flow of anode reactants at the inlet or inside the fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H01M8/04432—Pressure differences, e.g. between anode and cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04552—Voltage of the individual fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04559—Voltage of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04574—Current
    • H01M8/04582—Current of the individual fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04574—Current
    • H01M8/04589—Current of fuel cell stacks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04664—Failure or abnormal function
    • H01M8/04671—Failure or abnormal function of the individual fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04197—Preventing means for fuel crossover
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a method, system and apparatus for diagnostic testing of an electrochemical cell stack.
  • the invention relates to automatic diagnostic testing of an electrochemical cell stack involving leak testing, short circuit testing and electrochemical crossover testing.
  • Fuel cells and electrolyzer cells are usually collectively referred to as electrochemical cells. Fuel cell-based systems are seen as an increasingly promising alternative to traditional power generation technologies, at least in part due to their low emissions, high efficiency and ease of operation. Generally, fuel cells operate to convert chemical energy into electrical energy.
  • One form of fuel cell employs a proton exchange membrane (PEM), where the fuel cell comprises an anode, a cathode and a selective electrolytic membrane disposed between these two electrodes.
  • PEM proton exchange membrane
  • a fuel such as hydrogen is oxidized at the anode to form cations (protons) and electrons.
  • the proton exchange membrane facilitates the migration of protons from the anode to the cathode.
  • the electrons cannot pass through the membrane and are forced to flow through an external circuit, thus providing an electrical current.
  • oxygen reacts at the catalyst layer with electrons returned from the electrical circuit to form anions.
  • the anions formed at the cathode react with the protons that have crossed the PEM to form liquid water as the reaction product, known as product water.
  • An electrolyzer cell uses electricity to electrolyze water to generate oxygen from its anode and hydrogen from its cathode.
  • a typical solid polymer water electrolyzer (SPWE) or proton exchange membrane (PEM) electrolyzer is also comprised of an anode, a cathode and a proton exchange membrane disposed between the two electrodes.
  • Water is introduced to, for example, the anode of the electrolyzer which is connected to the positive pole of a suitable direct current voltage.
  • Fuel cell systems normally employ a series of fuel cells together in what is called a fuel cell stack. Prior to installing a fuel cell stack in a fuel cell-based power generation system, it is desirable to test the stack to ensure that it functions properly and will operate within the appropriate operating parameters. It may also be desirable to perform such testing as a part of a diagnostic process once the stack has been in used for some time, for example where the stack performance appears to be sub-standard. [0007] Other electrochemical cells, such as electrolyzer cells, may be similarly arranged in series to form an electrolyzer cell stack. Testing of such electrolyzer cell stacks is also desirable, for example for diagnostic or quality assurance purposes.
  • FCATS fuel cell automatic test station
  • Hydrogenics Corporation Hydrogenics Corporation
  • FCATS fuel cell automatic test station
  • the FCATS is a sophisticated testing system which allows a fuel cell or fuel cell stack to be tested in isolation.
  • the FCATS provides a range of tests and provides full reactant feeds, ensures an appropriate operating environment (e.g. appropriate humidity levels of the air supply to the cathode) and monitors various process parameters and conditions as the fuel cell or fuel cell stack is running.
  • the FCATS is not, however, designed for automatic diagnostic testing of electrochemical cell stacks that are not operating to consume reactants.
  • aspects of the invention are generally directed to apparatus, systems and methods for use in automated diagnostic testing of electrochemical cell stacks.
  • the invention relates to apparatus for diagnostic testing of an electrochemical cell stack, where each cell of the stack has an anode plate, a cathode plate and a membrane therebetween.
  • the apparatus comprises a multiplexer, a voltage monitor, a power supply module, a gas supply module and a control module.
  • the multiplexer switches current to one - A -
  • the voltage monitor monitors the voltage between the anode plate and the cathode plate of one ore more cells.
  • the power supply module supplies power to the multiplexer.
  • the gas supply module supplies fuel gas and non-fuel gas to the electrochemical cell stack.
  • the control module is electrically connected to each of the multiplexer, the voltage monitor, the power supply module and the gas supply module and is configured to control each of these in conducting automatic diagnostic testing of the electrochemical cell stack.
  • the control module is configured to determine, through the diagnostic testing, whether the electrochemical cell stack has one or more gas leaks and, if so, which of the one or more cells is affected by the one or more gas leaks.
  • the control module is further configured to determine a degree of crossover of electrochemical reactant of each cell and whether any of the cells appears to be short-circuited.
  • the control module preferably comprises a computer processor having computer program instructions stored in an associated memory or otherwise accessible to the computer processor.
  • the computer program instructions when executed by the computer processor, cause the control module to conduct the diagnostic testing.
  • Another aspect of the invention relates to a multiplexer for supplying current to one or more electrochemical cells in an electrochemical cell stack during diagnostic testing of the stack.
  • the multiplexer comprises a microcontroller, a power supply circuit and a plurality of switching circuits.
  • the power supply circuit is responsive to power control signals from the microcontroller to supply power to the plurality of switching circuits.
  • Each switching circuit switchably supplies current to respective electrochemical cells during the diagnostic testing, in response to the switching control signals from the microcontroller.
  • the switching circuits each comprise transistors for switching current to the electrochemical cells.
  • the transistors have a relatively high current tolerance and are therefore suitable for switching current to electrochemical cells.
  • Preferred transistors for such an application include MOSFETs.
  • certain embodiments of the invention provide a diagnostic testing system for an electrochemical cell stack.
  • the control module of the testing system executes program instructions for controlling the gas supply module to provide gas to the electrochemical cell stack, either as part of leak testing or short-circuit testing or hydrogen crossover testing.
  • the multiplexer acts as a current or voltage supply to one or more of the cells in the electrochemical cell stack.
  • the voltage monitor measures the potential difference across the anode and cathode plates of selected one or more cells of the electrochemical cell stack in order to determine the electrical characteristics of those cells under the test conditions.
  • the diagnostic testing system is configured to conduct several tests in sequence, using a single gas supply module, multiplexed current or voltage supply and voltage monitor, without having to perform the tests manually and without requiring the electrochemical cell stack to be connected and disconnected for the purpose of separate testing at several different test stations.
  • the diagnostic testing system provides greater efficiency and reliability of testing, while being of a reduced complexity, structure and manufacturing cost relative to the FCATS.
  • the multiplexer is designed to switch current to the electrochemical cells within the stack. This is done using a series of current switching circuits within the multiplexer, each current switching circuit corresponding to a particular cell in the stack. These current switching circuits are transistor- based circuits which receive a DC voltage and, depending on signals from the multiplexer microcontroller, apply the voltage to the corresponding cell.
  • the current switching circuits avoid the need for switching using relays, with their inherent mechanical limitations on reliability and bulky, low-density packing, while providing comparable current switching capability.
  • Existing switching element integrated circuits are relatively high- density but cannot handle the current levels required to be supplied to a fuel cell stack.
  • the current switching circuits employed in the multiplexer advantageously provide relatively high density on a printed circuit board and, at the same time, allow currents of a higher magnitude to be switched to the various cells in the stacks.
  • Another aspect of the invention relates to a method of automated diagnostic testing of an electrochemical cell stack, preferably using the diagnostic testing system described above.
  • This aspect provides a method of automated diagnostic testing of an electrochemical cell stack having a plurality of cells, each cell in the electrochemical cell stack having an anode plate, a cathode plate and a membrane therebetween and the electrochemical cell stack defining, for each cell, an anode chamber, a cathode chamber and a coolant chamber, the method comprising the steps of:
  • step b) if it is determined in step b) that there is at least one gas leak, determining which cells are affected by the at least one gas leak by performing the steps of:
  • power supply module 160 supplies power to multiplexer 140 via a multiplexer power supply cable 142 and the multiplexer 140 uses this power to provide current or voltage to various of the cells in the fuel cell stack 170 via stack power supply conductors 144.
  • Multiplexer 140 is shown and described in further detail in relation to Figure 4.
  • Voltage monitor 150 is used to measure the electrical potential at various of the anode or cathode plates within the cells of the fuel cell stack 170 in order to assist in determining the electrical or electrochemical performance of such cells. Voltage monitor 150 is shown and described in further detail in relation to Figure 6.
  • Gas supply 210 comprises a hydrogen supply 212, an inert gas supply 214 and an air supply 216.
  • Hydrogen supply 212 and inert gas supply 214 preferably comprise tanks holding hydrogen and inert gases, respectively.
  • Example inert gases include, for example, nitrogen or helium, or other noble gases.
  • Air supply 216 may comprise a tank of compressed air or may be derived from the air in the local environment. In either case, air from air supply 216 is preferably filtered to remove any impurities.
  • control valve 263 When control valve 263 is opened and control valve 261 is closed, flow controller 252 permits inert gas delivery and controls inert gas flow to the anode conduit through control valve 266, to the cathode conduit through control valve 264, or to the coolant conduit through control valve 265.
  • the required flow rate is set by user input 122 or via a programmed test sequence run by control module 120.
  • control module 120 proceeds to conduct cell-specific leak checking. If the overall leak check does not indicate the existence of any leaks in the stack 170, control module 120 proceeds to perform the other diagnostic tests, as described later.
  • Control module 120 comprises a computer processor 320, a data acquisition module 330 and a memory 340 accessible to the computer processor 320.
  • Data acquisition module 330 may regularly sample or interrogate the flow and pressure instrumentation within gas supply module 130, storing such sample data within a dedicated memory (not shown) thereof for access by the computer processor 320 when the information is required. Alternatively, data acquisition module 330 may only temporarily buffer the digitized data from gas supply module 130 before passing it on to computer processor 320.
  • Computer processor 320 acts as the overall controller for the diagnostic testing system 100, communicating with other parts of the system, including data acquisition module 330, multiplexer 140, voltage monitor 150 and power supply module 160. Further, signals from user input means 122 are transmitted to the computer processor 320 for processing in a known fashion and computer processor 320 transmits display signals to display 124 for displaying graphics or other visual information to personnel operating the diagnostic testing system 100.
  • Computer processor 320 may also be in communication with one or more peripheral devices, such as a printer, or may be in communication with a network via a suitable network connection (not shown).
  • computer processor 320 may be in communication with a network via the network connection in order to provide diagnostic test reports to remote systems over the network or to receive controller instructions from a remote source.
  • Multiplexer 140 comprises a microcontroller 410, a switching circuit block 420 comprising a plurality of current switching circuits 500 (shown in Figure 5) and a power switching circuit 430.
  • Microcontroller 410 is configured to provide switching control signals on switching control lines 416 to each of the switching circuits 500 in switching circuit block 420 for selectively providing current to, or sinking current from, any of cells 0 to N in the stack via stack supply conductors 144.
  • Switching circuit block 420 receives a supply voltage from power supply module 160 via power supply circuit 430.
  • mulitplexer power supply cable 142 is electrically connected between the power supply module 160 and the power supply circuit 430 of multiplexer 140.
  • Power supply circuit 430 comprises a power supply enable switch (first switch) SW1 , which, when closed, completes a circuit between power supply module 160 and switching circuit block 420 via an active conductor 422 and a neutral conductor 424.
  • a first fuse F1 is connected in series with switch SW1 to guard against excessive current flow through active conductor 422 when switch SW1 is closed.
  • switch SW1 When switch SW1 is open, active conductor 422 is not connected to power supply module 160.
  • Switch SW1 is opened or closed, depending on a power supply switching signal on power switching line 414 from microcontroller 410.
  • Power supply circuit 430 further comprises a second switch
  • Switch SW2 which, when closed (and SW1 is open) completes a discharge circuit with switching circuit block 420 via active conductor 422 and neutral conductor 424 through discharge resistor Rd (of about 150 Ohms).
  • Switch SW2 is opened or closed in response to a discharge control signal on discharge control line 412 from microcontroller 410.
  • Microcontroller 410 controls switches SW1 and SW2 so that they are not both closed at the same time.
  • a second fuse F2 is connected in series with switch SW2 in order to prevent excessive current flow through the discharge circuit.
  • Microcontroller 410 transmits control signals on lines 412, 414 and 416 in response to corresponding instructions transmitted from control module 120 during operation of the diagnostic testing system 100. For example, when, as part of the short-circuit testing, a voltage is to be applied across the cells of the stack, control module 120 issues an appropriate command, for example via an RS-232 connection, to microcontroller 410, which closes switch SW1 , opens switch SW2 (if not already open) and provides switching control signals on lines 416 to the switching circuits in switching circuit block 420 to provide a voltage across the cells of the stack via a stack power supply conductors 144. Individual cell voltages are then measured by the voltage monitor 150, as described later.
  • Power supplied to power supply circuit 430 from power supply module 160 via multiplexer power supply cable 142 is controlled by computer processor 320 to supply voltages or currents of greater or lesser magnitudes, depending on the testing requirements.
  • the computer processor 320 of control module 120 communicates, preferably via a general purpose interface bus (GPIB), with power supply module 160 to set the output current and/or voltage level of power supply circuit 430.
  • GPIB general purpose interface bus
  • switching circuits 500 are configured to provide small voltages to the cells, as well as higher voltages in response to corresponding current or voltage levels at power supply circuit 430.
  • each switching circuit 500 effectively select the operating mode for that circuit. If the high signal line is active, the switching circuit 500 acts as a current source. However, if the low signal line is active, the switching circuit 500 acts as a current sink. The high and low signal lines cannot be both active at the same time. However, if neither of the high or low signal lines is active, the switching circuit 500 is effectively inoperative or "switched off'.
  • the low signal line is connected to the gate of a transistor Q3, such that, when the low signal line is active, transistor Q3, which is an N- channel MOSFET (metal-oxide semiconductor field-effect transistor), is enabled, effectively drawing current from the corresponding cell to ground (although this is actually to neutral conductor 424).
  • transistor Q3 which is an N- channel MOSFET (metal-oxide semiconductor field-effect transistor)
  • the load switch configuration formed by transistors Q1 and Q2 also comprises a resistor R1 connected between the high potential side of transistor Q2 and the high potential side of transistor Ql
  • the gate of transistor Q2 is connected to the high potential side (drain) of transistor Q1.
  • Resistor R1 is a biasing resistor that pulls up the gate of transistor Q2 to the level of the supply voltage 422. This effectively maintains transistor Q2 in a disabled state, unless transistor Q1 pulls the gate of transistor Q2 to ground.
  • the voltage of supply voltage 422 is large enough (for example, above about 2.7 volts) to polarize transistor Q2, it will let current flow, as long as transistor Q1 is enabled by the high signal line. However, if supply voltage 422 is relatively small (for example, below about 2.7 volts), then transistor Q4, which is an N-channel MOSFET, will be enabled by the high signal line instead and will supply current to stack supply conductor 144.
  • switching circuit 500 can source current from a range of supply voltages on active supply conductor 422, limited only by the breakdown voltages of the various transistors. Being able to source current from a range of voltages on active supply conductor 422 is important as various voltage or current levels will be required to be supplied to stack supply conductors 144 during the diagnostic testing. For example, for a single cell test, the voltage can be as low as 0.3 volts, whereas for a group of cells or even for an entire stack, the voltage requirement may exceed 50 volts. [0087] It will be understood that switching circuit 500 can be implemented in forms other than those shown in Figure 5 and described in relation thereto.
  • the polarity of the circuit may be reversed, if desired, and P-channel MOSFETs can be used in place of N-channel MOSFETs and vice-versa, providing that the switching circuit 500 thus modified can switchably supply or sink current and/or voltage to the cells of an electrochemical cell stack.
  • any modified versions of switching circuit 500 should still allow current to be supplied to the cell from a relatively wide range of supply voltages on the supply conductor.
  • a voltage monitor analogous to voltage monitor 150 is described in commonly owned co-pending US Patent Application Serial No. 09/865,562, filed May 29, 2001 , the entire disclosure of which is hereby incorporated by reference. US Patent Application Serial No. 09/865,562 is published under US Publication No. 2002-0180447-A1. Another voltage monitor analogous to voltage monitor 150 is described in commonly owned co-pending US patent application serial no. 10/845,191 , filed May 13, 2004, the entire disclosure of which is hereby incorporated by reference. Other forms of voltage monitor 150 may be employed, providing that they have the described features and perform the described functions.
  • voltage-sensing conductors 650 connect to the fuel cell stack 170 at a voltage measuring assembly 660.
  • Voltage measuring assembly 660 is described in commonly owned co-pending US patent application serial no. 10/778,322, filed February 17, 2004, the entire disclosure of which is hereby incorporated by reference.
  • the voltage measuring assembly 660 extends parallel to the longitudinal direction of the fuel cell stack 170 and is mounted, at two ends thereof, on the side faces of two end plates of the fuel cell stack 170.
  • the voltage measuring assembly 660 generally comprises a printed circuit board (PCB) (not shown) and a plurality of probes (not shown) detachably secured, for example, by soldering, in a plurality of pinholes (not shown) in the PCB.
  • PCB printed circuit board
  • the pinholes are formed in a plurality of groups.
  • each pinhole group may consist of three pinholes.
  • the pinholes in each group are electrically connected with one another but each group of pinholes is not in electrical connection with any other group of pinholes.
  • Each group of pinholes is electrically connected to a multi-pin connector (not shown) secured, for example, by soldering, on the PCB via printed circuits (not shown).
  • One or more such multi-pin connectors may be provided on the
  • voltage sensing conductors 650 are coupled to the multi-pin connectors of voltage measuring assembly 660, for example using one or more corresponding wiring harness connectors.
  • Voltage monitor 150 comprises a controller 610, an analog to digital converter 620, a multiplexer 630 and a series of differential amplifiers
  • Differential amplifiers 640 are connected to voltage sensing conductors
  • Each of the differential amplifiers reads the voltages at two terminals
  • 640 provide an output indicative of the potential difference between the two terminals and this output is provided to the analog to digital converter 620 via multiplexer 630.
  • the digital output of the analog to digital converter 620 (in the form of quantized voltage measurements) is provided to controller 610 for processing.
  • the controller 610 controls the operation of the analog to digital converter 620 and the multiplexer 630, processes the digital output it receives and executes software instructions for communicating the received voltage measurements to control module 120.
  • Controller 610 requires relatively little processing capability as much of the processing of the voltage measurement information is performed by computer processor 320 within control module 120.
  • controller 610 preferably includes a memory (not shown) for storing any program code necessary for performing its voltage information gathering function.
  • Diagnostic testing method 700 uses diagnostic testing system 100 and the components thereof to perform diagnostic testing of fuel cell stack 170. Accordingly, method 700 will be described with reference to the steps shown in Figure 7 and the components of diagnostic testing system 100 shown in Figures 1 to 6.
  • Method 700 begins at step 710, in which leak testing of the whole stack is performed, as previously described in relation to Figure 2. If it is determined that there is a gas leak within the stack, the stack is tested, at step 720, to determine the specific cells which are affected by the leakage. If the leak testing performed at step 710 did not indicate any gas leakage within the stack, step 720 is not performed.
  • Leak testing of specific cells at step 720 is performed as a coolant-to-anode crossover leak test, a coolant-to-cathode crossover leak test or, at step 730, as part of an electrochemical (hydrogen) crossover test between the anode and cathode chambers of the cells.
  • inert gas is supplied from the gas supply module 130 to the coolant conduit inlet of the stack while blocking the coolant outlet. Air is then supplied from gas supply module 130 to the cathode conduit at a rate of about 2mL/min/cm 2 /cell with no back pressure, heating or humidification.
  • hydrogen is supplied to the anode conduit of fuel cell stack 170 from gas supply module 130, at a rate of about 0.5mL/min/cm 2 /cell with no back pressure, heating or humidification.
  • the inert gas pressure at the coolant inlet is increased to about 20 psig.
  • the voltage monitor 150 is used to measure the cell voltages. Those cells indicating a substantially lower open circuit voltage than the other cells are determined to have a coolant to anode crossover leak. This is because any inert gas leaking from the coolant chamber of a cell to the anode chamber will dilute the hydrogen at the anode and cause the cell voltage to drop. [00102] It is known from the overall leak testing (step 710) whether the leak is a coolant-to-anode or a coolant-to-cathode crossover leak and the cell- specific testing at step 720 is performed accordingly.
  • the coolant-to-anode and coolant-to-cathode crossover tests are preferably checked by another testing method, as follows.
  • the gas supply module 130 provides hydrogen to the coolant conduit at a rate of about 2ml_/min/cm 2 /cell, while providing inert gas to the anode conduit of the stack at about 0.5ml_/min/cm 2 /cell and air is provided to the cathode conduit of the stack at about 2ml_/min/cm2/cell.
  • voltage monitor 150 measures the potential differences between the cells. In such conditions, the potential differences should be low in the absence of a leak.
  • Control module 120 receives the voltage measurements from voltage monitor 150 and determines whether any of the cells has a large or increasing open circuit voltage relative to the other cells, thus indicating that the hydrogen fuel gas is crossing over from the coolant chamber of such cells to the anode chamber.
  • the secondary coolant-to-cathode leak test is similar to that described above for the secondary coolant-to-anode leak test, except that voltage monitor 150 measures the cell voltages while air is supplied to the coolant conduit, inert gas is supplied to the cathode conduit and hydrogen is supplied to the anode conduit. Thus, if air crosses over from the coolant chamber to the cathode chamber of a cell, the cell will generate a larger or increasing open circuit voltage relative to the other cells.
  • control module 120 performs a comparison of the relative values of the cell voltages and, if the difference is large enough (i.e. above a pre-determined threshold) or if the difference in rate of change of cell voltages is large enough, the control module 120 determines that the cell is affected by a leak from its coolant chamber into its anode chamber or cathode chamber, as appropriate.
  • control module 120 determines the electrochemical crossover (i.e. leakage) rate between the anode and cathode chambers of these cells. This is performed in a roughly similar manner to the coolant-to- anode or coolant-to-cathode crossover leak testing of step 720. However, for step 730, hydrogen is supplied to the anode conduit and nitrogen or another inert gas is supplied to the cathode conduit. Also, for the cells undergoing the electrochemical (hydrogen) crossover test, multiplexer 140 supplies a voltage to those cells.
  • control module 120 controls power supply module 160 so as to incrementally increase the voltage supplied to power supply circuit 430 of multiplexer 140, which in turn increases the current through switching circuits 500, while voltage monitor 150 measures the voltages across each of the cells.
  • the cell current through the cells is measured by the multimeter within the power supply module 160.
  • a separate multimeter may be used in-line with the power supply module 160. Such a separate multimeter would communicate with control module 120 via a GPIB (bus).
  • GPIB bus
  • the level of the constant current corresponds to the hydrogen crossover rate and, accordingly, the crossover rate (in slpm) may be determined by multiplying the constant current value by a constant conversion factor.
  • Example test data are shown in Figure 8, plotted according to measured current on the vertical axis and applied voltage on the hotizontal axis. As illustrated in Figure 8 by the lower curve (shown by solid data points), the data points of a plotted voltage-current characteristic may indicate a constant current region. The level of the constant current region is then used to calculate the Hydrogen crossover rate. If the cell being tested is also subject to electrical short-circuiting, the voltage-current characteristic will not remain constant. Instead, it will show a strong linear dependence of measured current on the applied voltage in a region in which it would otherwise remain constant.
  • the control module 120 determines that there is likely to be a short-circuit of the cell in addition to a degree of Hydrogen crossover.
  • the Hydroen crossover rate of such a cell is then determined following the short-circuit testing (described below in relation to step 742) by subtracting from the voltage-current characteristic the component thereof due to the short-circuit affecting that cell.
  • step 740 short-circuit testing of (preferably all of) the cells of fuel cell stack 170 is performed.
  • Step 740 is performed by supplying inert gas or air to the anode and cathode conduits of the stack, while supplying a voltage across the cells to be tested by multiplexer 140.
  • voltage monitor 150 monitors the open-circuit potential across the anode and cathode plates of each cell. Initially, the voltage applied across these cells by multiplexer 140 is relatively small, but increases incrementally to a normal cell operating voltage level between about 0.5 to 1.0 volts.
  • each such cell may be subjected, at step 742, to further testing to determine the degree of short-circuit affecting that cell. This is preferably done by supplying voltage to the affected cells using power supply module 160 through multiplexer 140 and measuring the current characteristics of the cells in the absence of any reactant gases.
  • the stack Before supplying the inert gas or air to the fuel cell stack 170 for the short-circuit testing, the stack is preferably flushed with a nitrogen (or other inert gas) purge. Similarly, with the other testing steps 710, 720 and 730, the stack conduits and cells are preferably purged or flushed so that none of the testing procedures are contaminated by gases or reaction byproducts resulting from earlier tests or operations. Additionally, after each test procedure in which multiplexer 140 provides current or voltage to fuel cell stack 170, microcontroller 410 closes switch SW2 and opens switch SW1 and thereby discharges any residual current in the cells through discharge resistor Rd. Such discharge is also required in the case where the stack is electronically charged by flow of reactants during coolant-to-anode/cathode open-circuit voltage testing, which does not use multiplexer 140.
  • the results of the testing are stored within memory 340, at step 750 and, at step 760, the stored tested results are used to generate a diagnostic test report for review on display 124 or via a peripheral device such as a printer.
  • the diagnostic test report may include the measured test results and determinations made by control module 120, based on the test results.
  • steps 710, 720 and 730 may be performed before or after steps 740 and 742.
  • steps 740 and 742 are preferably performed after steps 710 to 730.
  • steps 720 and 730 are preferably performed independently of each other.
  • Step 730 may be performed before or after step 720.

Abstract

La présente invention concerne un procédé, un système et un appareil de tests et diagnostics d'une pile à éléments électrochimiques, notamment à combustible ou électrolytique. Selon un mode de réalisation, l'appareil comporte un multiplexeur assurant les commutations de courant entre éléments de la pile, un régulateur de tension entre anode et cathode d'au moins un élément, une alimentation électrique pour le multiplexeur, et une alimentation en gaz, combustible ou non, de la pile. L'appareil comprend également un module de commande branché sur le multiplexeur et configuré pour le réguler ainsi que le régulateur de tension, l'alimentation électrique et l'alimentation en gaz en vue des tests et diagnostics de la pile. Le régulateur est également configuré pour rechercher par ces tests et diagnostics les éventuelles fuites de gaz de la pile, avec indication de l'élément en cause. Le module de commande est également configuré pour évaluer le niveau de transgression du réactif électrochimique par la membrane de chaque élément, et la probabilité de leur mise en court-circuit.
EP05714645A 2005-03-17 2005-03-17 Procede, systeme et appareil pour test en diagnostic d'une pile a elements electrochimiques Withdrawn EP1859290A4 (fr)

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JP5818227B2 (ja) 2010-10-25 2015-11-18 日産自動車株式会社 燃料電池システム
FR2991506B1 (fr) * 2012-05-29 2015-03-20 Commissariat Energie Atomique Procede de la mesure de la reproductibilite de n assemblages unitaires membrane echangeuse d'ions/electrodes par introduction d'agent polluant
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KR102256488B1 (ko) * 2017-09-14 2021-05-27 주식회사 엘지에너지솔루션 이차전지용 가스측정장치
CN107831359A (zh) * 2017-11-20 2018-03-23 浙江钰烯腐蚀控制股份有限公司 测试桩
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