Fuel Cell with Built-in Impedance Measurement

Abstract

The fuel cell (10) comprises a stack (11) of bipolar plates (12) in a stacking direction (L), with two consecutive bipolar plates (12) forming a cell (14) between them. The fuel cell (10) further comprises two end plates (16) on either side of the stack (11) and a number of measurement modules (20) connected to the bipolar plates (12). Each measurement module (20) comprises at least one printed circuit (22) with a computer capable of determining diagnostic and prognostic characteristics of the stack (11) of bipolar plates (12). The measurement modules (20) are at least configured to measure the impedance of the fuel cell (10) when the fuel cell (10) is operating.

Description

[Technical field]

[0001] The present invention relates to a fuel cell. [Background technology]

[0002] Fuel cells are used as energy sources in various applications, particularly in electric vehicles. In a polymer electrolyte membrane fuel cell (PEFC), hydrogen is supplied to the anode of the fuel cell and oxygen is supplied as the oxidant to the cathode. The polymer electrolyte membrane fuel cell (PEFC) comprises a membrane electrode assembly (MEA) that comprises a non-conductive, proton-exchange solid polymer electrolyte membrane with an anode catalyst on one side and a cathode catalyst on the other side. The membrane electrode assembly (MEA) is sandwiched between a pair of conductive elements called bipolar plates, with gas diffusion layers made from carbon fiber or the like. The bipolar plates are generally rigid and thermally conductive. The bipolar plates function primarily as current collectors for the anode and cathode, and contain passages with appropriate openings to distribute gas reactants from the fuel cell across the respective surfaces of the anode and cathode catalysts, and to remove water produced at the electrodes.

[0003] Fuel cells are powered by a fuel, which is hydrogen, supplied to the anode, and an oxidant, which is oxygen or air, supplied to the cathode.

[0004] For example, U.S. Patent No. 9,997,792 discloses a fuel cell comprising a stack of cells connected to a computer using a ribbon of cable connected to each of the cells by a connection tab, the cable being held by a harness to press the cable against the connection tabs.

[0005] However, measurements made with this type of configuration are unreliable, the cells occupy a large amount of space, and the cables are prone to damage due to mechanical stresses such as vibrations or expansion generated during operation of the cell, thus shortening their useful life. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 9,997,792 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need to improve the reliability of measurements, reduce the overall size of fuel cells, and improve the service life of fuel cells. [Means for solving the problem]

[0008] To this end, the present invention relates to a fuel cell comprising a stack of bipolar plates along a stacking direction, two consecutive bipolar plates forming a cell between them, the fuel cell further comprising two end plates arranged on either side of the stack and a number of measurement modules connected to the stack of bipolar plates for measuring the electrical characteristics of the cell, each measurement module comprising at least one printed circuit including a calculator suitable for determining the electrical characteristics of the stack of bipolar plates, the measurement modules being at least configured to measure the impedance of the fuel cell when the fuel cell is operating.

[0009] The fuel cell may include one or more of the following characteristics, taken individually or according to any technically possible combination: Each measurement module is connected to the stack of bipolar plates by means of a connector that can be connected to a mating connector of the bipolar plate, while each measurement module comprises a number of aligned connectors and an additional connector configured to perform four-wire impedance measurements on packets of the number of cells covered by the measurement module. - the aligned connectors are configured in pairs to measure the voltage across a set of two consecutive cells arranged between the two connectors, while the additional connector of each measurement module is configured to inject a sinusoidal current into the mating connector of the bipolar plate in which the additional connector is received. - a sinusoidal current has a frequency comprised between 100 Hz and 5 kHz, more specifically between 500 Hz and 2 kHz; Each measurement module is configured to inject a sinusoidal current whose frequency is set independently of the other modules. - each measurement module is configured to isolate a component of a response voltage induced in the stack of bipolar plates by the sinusoidal current, the component having the same frequency as the frequency of the injected sinusoidal current, and to calculate the impedance of the fuel cell as the ratio between the amplitude of the isolated voltage component and the amplitude of the injected sinusoidal current.

[0010] A further subject of the invention is a vehicle comprising at least a fuel cell as defined above.

[0011] A further subject of the invention is a method of using a fuel cell as described above, comprising the step of measuring the impedance of the cell during operation using a measurement module.

[0012] Advantageously, - each measurement module is connected to the stack of bipolar plates by means of a connector inserted into a mating connector formed in the bipolar plate, each measurement module comprising a plurality of aligned connectors and an additional connector configured to perform four-wire impedance measurements on packets of the number of cells covered by the measurement module, while the side-by-side connectors are configured in pairs to measure the voltage of two consecutive cells disposed between said two connectors; The add-on connector of each measurement module is configured to inject a sinusoidal current into the mating connector in which the add-on connector is received. - measuring the impedance of the fuel cell during operation by the measurement module comprises measuring an impedance between 5 mΩ and 20 mΩ for 20 cells.

[0013] The invention will be better understood on reading the following description, given purely by way of example, and on referring to the drawings in which: [Brief description of the drawings]

[0014] [Figure 1] 1A and 1B are schematic front and side perspective views of a fuel cell according to a first embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic rear perspective view of the fuel cell shown in FIG. [Diagram 3] FIG. 2 is a schematic diagram of a stack of bipolar plates of the fuel cell shown in FIG. 1. [Figure 4] 2 is a schematic diagram of a first cross-section of a shell for a measurement module of the fuel cell shown in FIG. 1; [Diagram 5] 2 is a schematic diagram of a second cross-sectional side of the shell for the measurement module of the fuel cell shown in FIG. 1. [Figure 6] 2 is a top schematic view of the fuel cell shown in FIG. 1 with the module shell removed. [Figure 7] 7 is a top schematic view of the fuel cell shown in FIG. 1 with the module shell removed according to a variation of FIG. 6. [Figure 8] FIG. 2 is a schematic perspective view of the connections between modules and cells of a stack of bipolar plates of the fuel cell shown in FIG. 1. [Figure 9] FIG. 2 is a schematic diagram of the pins of the measurement module of the fuel cell shown in FIG. 1. [Figure 10] 2 is a schematic diagram of a first cross-sectional side of the pivot support of the fuel cell shown in FIG. 1; [Figure 11]FIG. 2 is a perspective view of the fuel cell of FIG. 1 with some elements not shown. [Figure 12] FIG. 2 is a schematic diagram showing the electrical connections of the fuel cell shown in FIG. [Figure 13] FIG. 2 is a schematic diagram of the electrical connections between the two measurement modules shown in FIG. 1 and an auxiliary module of the fuel cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 and 2 show a fuel cell 10 formed by a stack 11 of bipolar plates 12 .

[0016] Each bipolar plate 12 is formed by two superimposed monopolar plates 12', 12'', here comprising an anode plate 12' and a cathode plate 12'', visible in FIG. 3. A cooling circuit is advantageously arranged between the two monopolar plates which are assembled together in a sealed manner.

[0017] In the example shown, the two monopolar plates 12', 12'' associated with the same bipolar plate 12 are made from metal and are welded or joined together.

[0018] In a variant (not shown), the monopolar plates are assembled in another way, for example with directly mounted seals such as silicone seals, etc. According to another variant (not shown), the bipolar plates are in one piece and are made, for example, from graphite.

[0019] More specifically, the fuel cell 10 comprises a plurality of cells 14 made in the form of a stack 11 of bipolar plates 12, the cells 14 being formed between two successive bipolar plates 12. The stack 11 thereby consists of a plurality of individual cells 14 connected in series. For each individual cell 14, the fuel cell 10 further comprises a membrane electrode assembly 15, the membrane electrode assembly 15 being interposed between the two bipolar plates 12 associated with the cell 14. The membrane electrode assembly 15 is shown diagrammatically in FIG.

[0020] The fuel cell 10 is intended for use, for example, in motor vehicles, in particular vehicles with electric motors.

[0021] The bipolar plates 12 are stacked along a stacking direction, which is defined as the longitudinal direction L in the following description.

[0022] The fuel cell 10 also comprises two end plates 16 arranged on either side of the stack 11. The bipolar plate 12 is sandwiched between the two end plates 16. The end plates 16 are made, for example, from aluminium.

[0023] An external fluid circuit (not shown) is connected to the fuel cell 10 at the end plates 16, and reactive gases are distributed to the membrane electrode assemblies 15 on the surface of the bipolar plates 12 via passages etched into the bipolar plates 12.

[0024] A measurement module 20 is connected to the stack 11 of bipolar plates 12 for measuring electrical characteristics of the cells 14 , such as the voltage at one or more terminals of the cells 14 .

[0025] Each module 20 serves to monitor the condition of the stack 11 for purposes of controlling the fuel cell system 10 .

[0026] Each module 20 comprises at least one printed circuit 22, and more specifically three printed circuits 22, including a computer suitable for determining diagnostic and prognostic characteristics of the stack 11 of bipolar plates 12, as seen in Figures 6 and 7, which are discussed in detail below.

[0027] For example, the characteristics include the state of health of the stack 11 of bipolar plates 12 , the location of the cells 14 in the stack of bipolar plates 12 , the voltage, impedance, and supply of the cells 14 of the fuel cell 10 .

[0028] The modules 20 are each enclosed by an outer shell 26 intended to cover and protect the printed circuits 22 .

[0029] The outer shell 26 has multiple functionalities, which are discussed in more detail below.

[0030] The shells 26 of the modules 20 are specifically foolproof. Thus, the modules 20 are configured to be assembled together without the possibility of error. For example, as shown in FIG. 4, each shell 26 is provided on a first transverse side 28 with male fasteners 30 that mate with female fasteners 32 formed on a second transverse side 34 of the shell 26 opposite the first side 28, as seen in FIG. 5. The shells 26 may thereby be assembled together without the risk of error.

[0031] For example, the male fastener 30 is a stud and the female fastener 32 is an arc-shaped groove that allows the stud to pivot in the groove.

[0032] Additionally, the modules 20 are configured to be assembled to the bipolar plate 12 without the possibility of error.

[0033] The outer shell 26 protects the printed circuitry 22 of the module 20 .

[0034] Preferably, the shells 26 of all of the modules 20 are identical.

[0035] The modules 20 are assembled together into a stack 11 of bipolar plates 12, typically using a mechanical frame 40.

[0036] Returning to FIGS. 1 and 2, the mechanical frame 40 advantageously comprises a fastening rail 42, a pivot shaft 44 and two pivot supports 46,48.

[0037] Each pivot support 46, 48 is positioned so as to be in contact with the end plate 16 and the module 20 when installed.

[0038] The pivot supports 46, 48 extend primarily along a transverse direction T perpendicular to the longitudinal direction L.

[0039] Each pivot support 46, 48 has a major dimension D defined along the transverse direction T that is less than a maximum width W of the respective end plate 16 defined along the transverse direction T.

[0040] Preferably, each pivot support 46 , 48 has a major dimension D that is comprised between 70% and 80% of the maximum width W of the respective end plate 16 .

[0041] Each pivot support 46, 48 has a minor dimension d defined along the longitudinal direction L that is substantially equal to the thickness E of the respective end plate 16 defined along the longitudinal direction L.

[0042] Advantageously, each of the two end plates 16 is provided with at least one orifice for receiving means 52 for fastening the pivot supports 46 , 48 to the respective end plate 16 .

[0043] For example, the fastening means 52 is a screw.

[0044] According to such an example, at least one receiving orifice 50 is threaded.

[0045] Each pivot support 46, 48 has at least one orifice 54 through which passes means 52 for fastening to the respective end plate 16. The at least one through orifice 54 for the passage of the fastening means 52 is configured to be located opposite the at least one receiving orifice 50 provided in the respective end plate 16.

[0046] More specifically, each pivot support 46, 48 is fastened to one of the two end plates 16 by means of two screws 52. Each screw 52 is, for example, a dome-shaped screw with six internal projections, 6 mm in diameter and 16 mm in length, having strength class 8.8 and made from steel and zinc.

[0047] The fastening rail 42 extends in a longitudinal direction L from one pivot support 46, 48 to the other.

[0048] Advantageously, the fastening rail 42 is provided with an orifice 55 for the passage of means 56 for fastening each pivot support 46 , 48 to the fastening rail 42 .

[0049] Each pivot support 46, 48 has at least one through hole 54' for the passage of means 56 for fastening to the fastening rail 42.

[0050] For example, the fastening means 56 is a screw.

[0051] More specifically, each pivot support 46, 48 is fastened to the fastening rail 42 by means of a screw 56. The screw 56 is, for example, a dome-shaped screw with six internal projections of 6 mm diameter and 16 mm length, having strength class 8.8 and made from steel and zinc.

[0052] Advantageously, the holes 55 through which the means 56 for fastening the fastening rail 42 pass are oval in shape.

[0053] The oval holes 55 provide some clearance of the fastening rails 42 to the pivot supports 46, 48 along the longitudinal direction L, thereby improving the module's resistance to vibration and expansion induced during the life of the fuel cell 10.

[0054] Advantageously, as can be seen in Figure 10, each pivot support 46, 48 is provided on a transverse side 57 intended to be in contact with a module 20 by means of a male or female fastener 59 which mates with a female fastener 32 or male fastener 30, respectively, formed on the transverse sides 28, 34 of the shell 26 of each module 20, so that the shells 26 can be assembled to the pivot supports 46, 48 without risk of error.

[0055] For example, male fastener 59 is a stud and female fastener 61 is an arc-shaped groove that allows the stud to pivot in the groove.

[0056] The pivot shaft 44 extends between two longitudinal ends 60,62.

[0057] The pivot shaft 44 extends parallel to the fastening rail 42 .

[0058] Each longitudinal end 60,62 of the pivot shaft 44 is carried by a respective pivot support 46,48.

[0059] To that end, the pivot supports 46 , 48 have, for example, two aligned cylindrical through-holes 64 for receiving the pivot shaft 44 .

[0060] The pivot shaft 44 preferably has a groove configured to be positioned between two through holes 64 for receiving the pivot shaft 44 when the pivot shaft 44 is engaged in the respective pivot supports 46,48.

[0061] Each pivot support 46 , 48 also advantageously has a tab 66 located between the two through holes 64 for receiving the pivot shaft 44 .

[0062] The pivot shaft 44 is locked in place at tabs 66. When the stack 11 compresses or expands, the pivot support 46 moves in translation along the pivot shaft 44.

[0063] The pivot supports 46 , 48 mechanically hold the entire system formed by the pivot shaft 44 and the fastening rail 42 .

[0064] The shell 26 of the module 20 is fastened to the fastening rail 42 by means of a projection 70 provided with a locking tooth 71, for example.

[0065] The projections 70 advantageously extend along a height direction Z perpendicular to the longitudinal direction L and the transverse direction T.

[0066] The shell 26 of the module 20 is fastened to the pivot shaft 44, for example by means of a cylindrical groove 72 which fits over the pivot shaft 44. The groove 72 has, for example, a linear contour. In a variant, the groove 72 has, for example, a three-dimensional contour.

[0067] When the shell 26 of the module 20 is fastened to the pivot shaft 44 but not to the fastening rails 42 , the shell 26 is rotatable about an axis A defined by the pivot shaft 44 .

[0068] When the shell 26 of the module 20 is assembled together to the fastening rails 42 and pivot shafts 44 using the male and female fasteners 30, 32, the shell 26 of the module 20 is thereby locked against translation and rotation along the transverse direction T and the elevation direction Z.

[0069] Some clearance is allowed along the longitudinal direction L to limit wear due to vibration and expansion.

[0070] According to the example shown in Fig. 6, each module 20 comprises three printed circuits 22. The printed circuits 22 extend mainly along the transverse direction T and two printed circuits 22 extend mainly along the height direction Z.

[0071] The three printed circuits 22 are electrically connected to each other by ribbons 75 of the cable, e.g., two ribbons 75 between the printed circuits 22 extend mainly along the transverse direction T, one of the two printed circuits 22 extends mainly along the height direction Z, and the ribbon 75 between the two printed circuits 22 extends mainly along the height direction Z.

[0072] To electrically connect the modules 20 to each other and to ensure continuity of the measurements of the electrical properties of the cells 14, each module 20 is connected to strips 76 for connecting the modules 20 to each other.

[0073] 6, the strips 76 are in the form of two half-strips arranged on either side of a median transverse plane P of the module 20. The strips 76 extend mainly along a transverse direction T.

[0074] Preferably, the strip 76 is located adjacent the projection 70 for fastening the shell 26 to the fastening rail 42 .

[0075] The strip 76 includes a plurality of pins 78 for connecting the strip 76 to at least one printed circuit 22 of the module 20 .

[0076] The pins 78 are oriented along a height direction Z.

[0077] The pins 78 serve to mechanically and electrically connect the strip 76 to the module 20 .

[0078] The strip 76 further comprises leaf springs 80 disposed on either side of the strip 76 along the transverse direction T.

[0079] The strip 76 includes, for example, seven pairs of leaf springs 80 .

[0080] The leaf spring 80 is dome shaped.

[0081] The strip 76 is assembled to the module 20 such that the pins 78 of the strip 76 are positioned between the strip 76 and the printed circuit 22 .

[0082] Thus, when the strip 76 is assembled to the module 20 , the leaf springs 80 protrude from each of the transverse sides 28 , 34 of the shell 26 of the module 20 .

[0083] The leaf springs 80 of the shells 26 of two adjacent modules 20 counteract compression and expansion that may occur during the service life of the fuel cell 10, thus always ensuring mechanical and electrical contact between the strips 76 of the two shells 26 and, as a result, always ensuring mechanical and electrical contact between the two adjacent modules 20.

[0084] The leaf spring 80 is an example of a preferred embodiment of a contactor between two adjacent modules 20 .

[0085] The strips 76 ensure continuity in the measurement of the electrical properties of the cells and create connections for linking all the modules 20 together by a supply line and a communication bus, in particular a CAN bus, without the use of cables between the modules 20. Each module 20 is thereby supplied with energy for its own operation, in particular for the operation of the printed circuits 22, for carrying out the measurements of the electrical properties, for transmitting the results of the measurements, etc. Advantageously, when one of the modules 20 of the fuel cell 10 fails, this does not prevent the other modules 20 of the battery 10 from functioning.

[0086] In the variant, as can be seen in Fig. 7, the three printed circuits 22 are electrically connected to each other by contacts 75', such as, for example, a plurality of contacts 75' between the printed circuits 22 extending mainly along the transverse direction T and one of the two printed circuits 22 extending mainly along the height direction Z, and a plurality of contacts 75' between the printed circuits 22 extending mainly along the transverse direction T and the other of the two printed circuits 22 extending mainly along the height direction Z. According to such a variant, the strip 76 has the same shape as in the variant of Fig. 6.

[0087] Advantageously, the cells 14 are arranged in packets of 20 cells 14 .

[0088] Twenty cells 14 require twenty-one bipolar plates 12 .

[0089] To that end, 21 bipolar plates 12 are stacked, with two successive bipolar plates 12 defining a cell 14 between them.

[0090] Two consecutive monopolar plates 12', 12'' are arranged back-to-back and form between them at least one pocket 84 at one edge 85 of the bipolar plate 12 along the height direction Z.

[0091] Each pocket 84 is configured to receive a pin 90 of module 20 for measuring an electrical characteristic of a cell 14 .

[0092] Each pin 90 is a non-limiting example of a connector configured to connect to a pocket 84 , and each pocket is a non-limiting example of a connector that fits over a pin 90 .

[0093] In the illustrated example, each pin 90 forms a male connector while each pocket 84 forms a female connector that mates with the pin 90. Of course, other configurations between the male / female connectors are possible. In a variation (not shown), the male and female connectors are reversed, for example, the pins are formed on one edge of the bipolar plate 12 while the pockets are formed in the module 20, forming a mirror configuration of the arrangement shown in the figures. Of course, other configurations between the connectors and mating connectors are possible.

[0094] Preferably, two consecutive bipolar plates 12 are stacked head-to-tail such that only at least one pocket 84 of every other bipolar plate 12 is at the same height in the vicinity of the module 20, as seen in FIG.

[0095] According to the illustrated example, each bipolar plate 12 forms exactly two pockets 84 for receiving a pin 90 respectively.

[0096] The second pocket 84 makes it possible to measure four wires per group of twenty cells 14. The same is used to measure the impedance.

[0097] More specifically, each pocket 84 is shaped to cooperate with the pin 90 .

[0098] For each pocket 84 , two consecutive bipolar plates 12 define a peripheral wall 92 of the pocket 84 when in contact with each other.

[0099] Preferably, each pocket 84 has an open end 94 where the peripheral wall 92 has a conical shape.

[0100] Such a shape has the advantage of guiding the pins 90 of the module 20 into the interior of the pocket 84 .

[0101] Advantageously, the peripheral wall 92 of each pocket 84 has a stamping 93 to form a small area passage for the pin 90 .

[0102] The stamping 93 serves to strengthen the pocket 84 and makes it possible to ensure electrical contact between the pin 90 and the pocket 84 inside the pocket 84 .

[0103] The stamping 93 also has the function of locking the pin 90 at a certain depth when it is inserted into the pocket 84, making it possible to avoid drilling said pocket 84.

[0104] Each module 20 advantageously includes ten aligned pins 90 configured to connect ten pockets 84 of the bipolar plates 12 to the module 20, and an additional pin 95 configured to connect to a second pocket 84 of one of the ten bipolar plates 12, as seen in Figures 8 or 11. The additional pin 95 and a like one of the aligned pins 90 configured to connect to the same bipolar plate 12 as the additional pin 95 are referred to as "twinned."

[0105] Advantageously, each additional pin 95 has a similar, and preferably identical, structure to the aligned pin 90. The structure of the additional pins 95 and the structure of the second pocket 84 associated with the additional pins 95 are not limiting. Together, the additional pins 95 and the second pocket 84 form an additional connector / mating connector pair.

[0106] The ten aligned pins 90 serve to measure the voltage of two consecutive cells 14 between two consecutive pins 90. In other words, the aligned pins 90 are arranged in pairs to measure the voltage at the terminals of a set of two consecutive cells 14 that are located between the two pins 90.

[0107] Additional pins 95 are arranged substantially parallel to the array of pins 90, preferably at the longitudinal ends of the module 20. For each module, the additional pins 95 are configured to inject a current into the pocket 84 in which the current is received, thereby making it possible to measure the impedance in 20 cells 14. Thus, each module 20 measures one impedance for every 20 cells 14. The injected current is controlled, for example, by the printed circuit 22.

[0108] Each pin 90, 95 of the module is advantageously designed to promote effective and durable electrical contact over time between the module 20 and the bipolar plate 12, as seen in FIG.

[0109] To that end, each pin 90 , 95 of the module 20 is shaped such that when the pin 90 , 95 is inserted into a corresponding pocket 84 , the pin 90 , 95 exerts two opposing forces on the peripheral wall 92 of the pocket 84 .

[0110] Pins 90, 95 of module 20 are preferably identical.

[0111] This facilitates modular design.

[0112] Each pin 90, 95 extends primarily along a first direction, more specifically, a height direction Z, and has a notch 97 along said first direction over a portion 96, which separates said portion 96 into two sub-portions 98 on either side of the notch 97.

[0113] Each sub-portion 98 has a ridge 100 in a second direction, more specifically along the longitudinal direction L, which is substantially perpendicular to the first direction. The ridges 100 of the two sub-portions 98 extend in opposite directions.

[0114] Thereby, the pins 90, 95 are domed in the sub-part 98, which makes the sub-part 98 rigid but somewhat flexible. The connection of the pin 90 in the pocket 84 requires pressing in the pin. This ensures a strong and durable electrical contact between the pin 90 and the respective pocket 84, resulting in the two monopolar plates 12', 12" forming the pocket 84.

[0115] Electrical contact is ensured regardless of expansion or vibration that may occur during the life of the fuel cell 10 , specifically due to the spring effect induced by the particular shape of the pockets 84 and pins 90 .

[0116] According to a variant, the pins 90 , 95 of each module 20 have a different shape, and more particularly any shape that is technically feasible for connecting each module 20 to a cell 14 .

[0117] When a module 20 is connected to the cells 14, there remains at least one pocket 84 formed by a bipolar plate 12 at the longitudinal end 104 of the stack 11 of cells 14 that is not connected to a module 20. This bipolar plate 12 is called the last bipolar plate 12.

[0118] To that end, returning to FIG. 10, one of the pivot supports 46 has a location 106 for fastening an additional component 108 for contact with the final bipolar plate 12 .

[0119] The additional component 108 has at least one pin 110 that is intended to be received in a pocket 84 formed by a bipolar plate 12, hereafter referred to as the final bipolar plate 12. As with pins 90 or 95, the pin 110 is an example of a connector that is configured to connect to a mating connector, here pocket 84.

[0120] More specifically, the additional component 108 has two pins 110 .

[0121] In the same manner as module 20, the pins 110 of each of the additional components 108 are shaped such that when the pins 110 are inserted into the pockets 84, the pins 110 exert two opposing forces on the peripheral walls of the pockets 84.

[0122] The two pins 110 of the additional component 108 are preferably identical.

[0123] Each pin 110 extends primarily along a first direction, more specifically, a height direction Z, and has a notch 114 along said first direction over a portion 112, which separates said portion into two sub-portions 116 on either side of the notch 114.

[0124] Each sub-portion 116 has a ridge 118 along a second direction, the second direction being perpendicular to the first direction.

[0125] The ridges 118 of the two sub-portions 116 extend in opposite directions.

[0126] Thereby, the pin 110 is domed in the sub-portion 116, which balances the rigidity of the sub-portion 116 with some elasticity. The connection of the pin 110 in the pocket 84 requires pressing in the pin. This ensures a strong and durable electrical contact between the pin 110 and the respective pocket 84, resulting in the two monopolar plates 12', 12" forming the pocket 84.

[0127] Furthermore, the additional component 108 has at least one metal contact 120 , more specifically two metal contacts 120 , for connection with an adjacent module 20 .

[0128] Furthermore, the pivot support 46 supporting the additional component 108 has at least one metal contact 121 , more specifically five metal contacts 121 , for connection with an adjacent module 20 .

[0129] More specifically, the metal contacts 120 , 121 are intended to contact the leaf springs 80 of the strips 76 associated with said adjacent modules 20 .

[0130] As a result, the potential of the last bipolar plate 12 is transmitted to the computer of the adjacent module 20. Thereby, all the cells 14 of the fuel cell 10 are connected to the module 20 in order to enable the measurement of their electrical characteristics.

[0131] Advantageously, the pivot support 46 supporting the additional component 108 further comprises a connector 122 for connecting the stack 11 of bipolar plates 12 to a motherboard, shown diagrammatically in Figure 12, by means of an external computer 123. The connector 122 does not require a cable.

[0132] The mechanical frame 40 holds the entire system formed by the modules 20 , the pivot shafts 44 , the fastening rails 42 and the pivot supports 46 , 48 and allows for the expansion of the modules 20 .

[0133] The outer shell 26 of each module 20 allows the printed circuitry 22 to be located in close proximity to the stack 11 while protecting the stack 11 from external damage.

[0134] The quality of the measurements made by module 20 is improved, allowing the module to perform multi-frequency impedance measurements, specifically according to a four-wire method, as will be discussed in more detail below.

[0135] More generally, it should be understood that the electrical characteristics measured by each module 20 are available to all other elements connected to the module 20 through the communication bus and the contactors 80. More specifically, the additional component 108 has access to the measured electrical characteristics, such as, for example, the value of the voltage measured at the terminals of each cell 14 and transmitted via the communication bus. In the example, a voltage is measured at the terminals of each set of two consecutive cells 14 arranged between two consecutive pins 90. Similarly, an external computer 123 connected to the connector 122 also has access to the measurements made by each measurement module 20 and transmitted via the transmission bus, more specifically, to the electrical characteristics of each cell 14, or, in the example, the electrical characteristics of each set of two consecutive cells 14 arranged between two consecutive pins 90 at the terminals at which the voltage measurement is performed.

[0136] The contactors 80 and the metal contacts 120 are also configured to transmit electrical energy between adjacent modules 20 or between the additional component 108 and a module 20 adjacent to the additional component 108, so that the electrical energy is made available for the operation of the modules 20, in particular for the operation of the printed circuits 22 of each module 20, for obtaining the voltage of the bipolar plates 12, for voltage measurements, impedance measurements, for injecting current, etc.

[0137] In the illustrated example, the module 20 incorporates a calculator for determining diagnostic and prognostic characteristics of the stack 11 of bipolar plates 12. Alternatively, an external calculator 123 determines diagnostic and prognostic characteristics of the stack 11 of bipolar plates 12. Thereby, it is possible to build the module 20 with a relatively simple and robust structure to perform reliable measurements of electrical quantities related to the cells 14.

[0138] In the illustrated example, a group of twenty bipolar plates 12 corresponds to each module 20, or, in other words, a group of twenty cells 14. Ten aligned pins 90 of a module 20 are connected to each of the first, third, etc., up to a nineteenth bipolar plate 12. In other words, the twentieth bipolar plate 12 associated with a module 20 is not connected to the module 20.

[0139] 11-13, the module 20 positioned on the left of the figure will be referred to as module 201, and the module 20 positioned on the right of the figure will be referred to as module 202, with the understanding that the concepts of right and left are arbitrary herein. Thus, right hand side module 202 is positioned between left hand side module 201 and mating module 108.

[0140] The left hand side module 201 is connected to a first bipolar plate 12 associated with the right hand side module 202 via a contactor 80 and via one of the aligned pins 90 of the right hand side module 202. Stated differently, the left hand side module 201 is connected to an eleventh bipolar plate 12 via a contactor 80 and via the right hand side module 202, which in turn is connected to the left hand side module 201 defining ten consecutive cells 14.

[0141] Similarly, the right hand side module 202 is connected to the eleventh bipolar plate 12 via contactors 80 and 120 and via the additional module 108 and the first of the two connectors 110 of the additional module 108. The eleventh bipolar plate 12 to which the mating module 108 is connected is thus the last plate 12 in the stack 11.

[0142] More generally, each measurement module 20 is thereby connected to an eleventh bipolar plate 12 via an adjacent module 20 or via an adjacent mating module 108. The eleventh bipolar plate 12 defines between them ten sets of two consecutive cells 14. Each module 20 is thereby associated with the ten sets of two consecutive cells 14 via the aligned pins 90 associated with the module 20 and via an adjacent module 20 or via an adjacent mating module 108. Each module 20 is thereby configured to measure the voltage at the terminals of each set of two consecutive cells 14 associated with the measurement module 20, i.e. here the ten sets of two consecutive cells 14.

[0143] Similarly, the left hand side module 201 is connected to the first bipolar plate 12 by means of the additional pin 95 associated with the left hand side module 201. On the other hand, the same left hand side module 201 is also connected to the first bipolar plate 12 associated with the right hand side module 202 via the contactor 80 and via the additional pin 90 of the right hand side module 202. In other words, the left hand side module 201 is connected to the eleventh bipolar plate 12.

[0144] As a result, the left-hand side module 201 is, on the one hand, connected to the first bipolar plate 12 by both the first pin 90 and the first additional pin 95, and, on the other hand, connected to the eleventh bipolar plate 12 via the second pin 90 and the second additional pin 95 belonging to the right-hand side module 202.

[0145] As mentioned above, for each module 20, the additional pin 95 of the module is configured to inject current. The left hand side module 201 is thereby configured to inject current via a first additional pin 95 forming a first wire, and to "withdraw" current via a second additional pin 95 forming a second wire. At the same time, the left hand side module 201 is also configured to measure the voltage between the first and eleventh bipolar plates 12 via the first and second pins 90.

[0146] The four-wire technique or system (also called four-wire measurement or Kelvin measurement) serves to measure electrical impedance while nullifying disturbances due to the resistance of wiring and connections. In the four-wire technique, a known current is injected and flows in two of the four wires that run through the element in question, here a group of twenty cells 14. The injected current generates a response voltage at the terminals of the component in question, which response voltage is measured, for example with a voltmeter, by the calculator of the module 20 and / or by an external calculator 123. Thus, the ratio between the known injected current and the measured voltage allows the impedance of the element under consideration to be accurately calculated.

[0147] Similarly, the right-hand side module 202 is connected, on the one hand, to the first bipolar plate 12 via an additional pin 95 belonging to the right-hand side module 202, and, on the other hand, to the eleventh bipolar plate 12 via the switching section 80 and via one of the pins 110 of the auxiliary module 108.

[0148] More generally, each measurement module 20 comprises a number of aligned connectors 90 and an auxiliary connector 95. Each module 20 is also connected to an additional connector 90 and an additional auxiliary connector 95 via an adjacent measurement module 20 or via an adjacent auxiliary module 108. The auxiliary connector 95 forms a first wire, the additional auxiliary connector 95 forms a second wire, the two aligned connectors 90 of the auxiliary connector 95 form a third wire, and the two aligned connectors 90 of the additional auxiliary connector 95 form a fourth wire. The naming of the first to fourth wires is not limiting. By using four wires, each measurement module 20 is configured to perform a four-wire impedance measurement at the terminals of the set of cells 14 covered by the measurement module 20.

[0149] A method for installing the measurement module 20 in the fuel cell 10 according to the present invention will now be described.

[0150] The first module 20 is assembled to the mechanical frame 40 adjacent one of the pivot supports 46 .

[0151] More specifically, the shell 26 of the first module 20 is fastened to the pivot shaft 44 using, for example, a cylindrical groove 72 in the shell 26 that fits over the pivot shaft 44 .

[0152] The shell 26 of the first module 20 is rotatably moveable about an axis A defined by a pivot shaft 44 .

[0153] The first module shell 26 is advantageously fastened to the fastening rail 42 by means of the projections 70 , by wedging the fastening rail 42 into the projections 70 .

[0154] The first module 20 is mounted to one of the pivot supports 46 .

[0155] More specifically, the male fasteners 59 of the pivot support 46 are connected to the female fasteners 32 of the first module 20, or the male fasteners 30 of the first module 20 are connected to the female fasteners of the pivot support 46, according to the arrangement of the male and female members in each module 20 and the pivot support 46.

[0156] In the illustrated example, the male fastener 30 is a stud and the female fastener 32 is an arc-shaped groove in which the stud 30 pivots.

[0157] At least one of the leaf springs 80 of the strip 76 positioned on the transverse side 28 oriented towards the pivot support 46 advantageously contacts at least one metal contact 120 of the additional component 108 for contact with the last bipolar plate 12 and at least one metal contact 121 of the pivot support 46.

[0158] Contact of the shell 26 of the first module 20 with at least one metal contact 120 , 121 causes compression of the leaf spring 80 of the strip 76 .

[0159] Furthermore, each pin 90 of the first module 20 is received in a pocket 84 formed by two consecutive monopolar plates 12 ′, 12 ″ of the stack 11 of the fuel cell 10 .

[0160] More specifically, ten aligned pins 90 of a first module 20 are received in ten pockets 84 of ten bipolar plates 12, and an additional pin 95 is received in a second pocket 84 of one of the bipolar plates 12.

[0161] The ten aligned pins 90 of the first module 20 serve to measure the voltage of two consecutive cells 14 between two consecutive pins 90 .

[0162] Pre-fastening of the first module 20 to the pivot support 46 and the mechanical frame 40 ensures that the pins 90 of the first module 20 are received in the corresponding pockets 84 .

[0163] To this end, each pin 90 of the first module 20 is preferably pressed into a respective pocket 84 .

[0164] The shape of each pocket 84 advantageously guides each pin 90 of the first module 20 into the interior of said pocket 84 .

[0165] The shape of the pins 90 of each of the first modules 20 favors effective and durable electrical contact between the first modules 20 and each of the bipolar plates 12 over time.

[0166] Such an arrangement ensures a strong and durable electrical contact between the pins 90 and the respective pockets 84 resulting from the two monopolar plates 12 ′, 12 ″ forming the pockets 84 .

[0167] Electrical contact is ensured regardless of expansion or vibration that may occur during the life of the fuel cell 10 , specifically due to the spring effect induced by the particular shape of the pockets 84 and pins 90 .

[0168] When the first module 20 is connected to a respective cell 14, at least one pocket 84 formed by the two monopolar plates 12′, 12″ closest to the pivot support 46 adjacent the first module 20 does not receive a pin 90 of the first module 20.

[0169] For this purpose, at least one pin 110 of an additional component 108 for contact with the last bipolar plate 12 is received in said pocket 84 .

[0170] Thereby, it is possible to measure the voltage of the two consecutive cells 14 closest to the pivot support 46 next to the first module 20 .

[0171] More specifically, two pins 110 of the additional component 108 for contact with the last bipolar plate 12 are received in two pockets 84 formed by the bipolar plate 12 closest to the pivot support 46 adjacent the first module 20.

[0172] In the same manner as the first module 20 , the pins 110 of each of the additional components 108 for contact with the last bipolar plate 12 are preferably pressed into the respective pockets 84 .

[0173] The shape of each pocket 84 advantageously guides the respective pin 110 of the additional component 108 into the interior of said pocket 84 for contact with the final bipolar plate 12 .

[0174] The shape of the pins 110 of each of the additional components 108 for contact with the final bipolar plate 12 promotes effective and durable electrical contact between the additional components 108 and the bipolar plate 12 over time.

[0175] Such an arrangement ensures a strong and durable electrical contact between the pins 110 and the respective pockets 84 resulting from the two monopolar plates 12 ′, 12 ″ forming the pockets 84 .

[0176] Electrical contact is ensured regardless of expansion or vibration that may occur during the life of the fuel cell 10 , in particular due to the spring effect induced by the particular shape of the pockets 108 and pins 110 .

[0177] The method of installing the measurement module 20 includes assembling the second module 20 into the pocket 84 formed by the first module 20 and the bipolar plates 12 of the fuel cell 10 .

[0178] More specifically, the second module 20 is fastened to the pivot shaft 44 and to the fastening rails 42 of the mechanical frame 40 in the same manner as the first module 20 .

[0179] Also, the male fasteners 30 of the first module 20 are connected to the female fasteners 32 of the second module 20, or the male fasteners 30 of the second module 20 are connected to the female fasteners 32 of the first module 20 according to the arrangement of the male and female members in each module 20.

[0180] In the illustrated example, the male fastener 30 is a stud and the female fastener 32 is an arc-shaped groove in which the stud 30 pivots.

[0181] When the shell 26 of the module 20 is assembled together to the fastening rails 42 and pivot shafts 44 using the male and female fasteners 30, 32, the shell 26 of the module 20 is thereby locked against translation and rotation along the transverse direction T and the elevation direction Z.

[0182] The integral assembly of the shell 26 of the module 20 allows not only the automation of the method but also a time saving for the insertion of the module 20 in the stack of bipolar plates 12 .

[0183] The first module 20 and the second module 20 are electrically connected to each other.

[0184] More specifically, the strips 76 of the second module 20 are assembled to the strips 76 of the first module 20 .

[0185] For this reason, at least one of the leaf springs 80 of the strip 76 of the second module 20 positioned on the transverse side 34 oriented toward the first module 20 advantageously comes into contact with at least one of the leaf springs 80 of the strip 76 of the first module 20.

[0186] Contact of the shell 26 of the first module 20 with the shell 26 of the second module 20 causes compression of the leaf springs 80 of each of the strips 76 .

[0187] Furthermore, each pin 90 of the second module 20 is received in a pocket formed by the two monopolar plates 12 ′, 12 ″ of the fuel cell 10 .

[0188] More specifically, ten aligned pins 90 of the second module 20 are received in ten pockets 84 of the ten bipolar plates 12, and an additional pin 95 is received in a second pocket 84 of one of the bipolar plates 12.

[0189] Thereby, it is possible to measure the voltage of two consecutive cells 14 defined between a first module 20 and a second module 20. More precisely, each pin 90 of the array of pins 90 makes it possible to obtain the potential of the bipolar plate 12 to which it is connected. For two given bipolar plates 12, the voltage between the two bipolar plates 12 is calculated by taking the difference between the potentials associated with each of the bipolar plates 12. The voltages of the two cells 14 are examples of the electrical characteristics of the two cells 14.

[0190] In the illustrated example, only one of the two bipolar plates 12 is connected to one of the modules 20 via a respective one of the aligned pins 90. In other words, two consecutive aligned pins 90 are configured to measure the voltage before and after a set of two consecutive cells 14 that are located between said two pins 90.

[0191] In a variant (not shown), each bipolar plate 12 is connected to the measurement module 20 via an aligned pin 90. It is thereby possible to obtain the potential of each bipolar plate 12 and to deduce from it the voltage between any two of the bipolar plates of the stack 11. According to other variants, only one bipolar plate 12 out of three, or even one out of four, etc., is connected to the aligned pin 90. However, the illustrated configuration is preferred, since the same allows a sufficiently fine monitoring of the operation of the cells 14.

[0192] Pre-fastening of the second module 20 to the first module 20 and the mechanical frame 40 ensures that the pins 90 of the second module 20 are received in the corresponding pockets 84 .

[0193] To this end, each pin 90 of the second module 20 is preferably pressed into a respective pocket 84 .

[0194] The shape of each pocket 84 advantageously guides each pin 90 of the second module 20 into the interior of said pocket 84 .

[0195] The shape of the pins 90 of each of the second modules 20 favors effective and durable electrical contact between the second modules 20 and each of the bipolar plates 12 over time.

[0196] Such an arrangement ensures strong and durable electrical contact between the pins 90 and the respective pockets 84 which the monopolar plates 12 ′, 12 ″ form as a result.

[0197] Electrical contact is ensured regardless of expansion or vibration that may occur during the life of the fuel cell 10 , specifically due to the spring effect induced by the particular shape of the pockets 84 and pins 90 .

[0198] Thereby, the computer contained in the module 20 is directly connected to the cell 14 without the need for cables.

[0199] Although the illustrated example includes two modules 20, the fuel cell 10 is not limited to two modules and may include more modules, such as, for example, ten modules 20 for connecting 200 cells 14.

[0200] Similarly, in the illustrated example, each module 20 comprises ten aligned pins 90 configured to connect ten pockets 84 of ten bipolar plates 12 to said module 20. The number of pins 90 provided on each module 20 is not limiting, and the principles of the invention, specifically the acquisition of the potential of the bipolar plates 12 connected to the module 20 and the measurement of the impedance of the four wires that can be transferred to the measurement module 20, may comprise more or less than ten pins 90.

[0201] To install the following modules, if appropriate, the method discussed in detail above for installing the second module 20 is repeated as many times as necessary.

[0202] Using the method according to the invention, assembly is simple and no cables are used to connect the modules 20 to the cells 14 and to each other. The mounting also advantageously does not allow the use of cables to connect the modules 20 to the motherboard.

[0203] Thereby, the quality of the measurement is improved and allows for subsequent more detailed analysis.

[0204] Once installed, the module 20 is suitable for determining diagnostic and prognostic characteristics of the stack 11 of bipolar plates 12 by means of a calculator included in the module 20 .

[0205] For example, the characteristics include the state of health of the stack 11 of bipolar plates 12 , the location of the cells 14 in the stack of bipolar plates 12 , the voltage, impedance, and supply of the cells 14 of the fuel cell 10 .

[0206] Not only the ten aligned pins 90 of each module 20, but also, where appropriate, pins 110 of an additional contact component 108 aligned with the pins 90 of a module 20 serve to measure the voltage of two consecutive cells 14 between two consecutive pins 90, 110.

[0207] The additional pins 95 of each module 20, as well as additional contact components 108, if appropriate, are configured to inject a sinusoidal current into the pockets 84 in which they are received, thereby making it possible to perform impedance measurements on the number of cells 14 covered by each module 20 when the fuel cell 10 is in operation, more specifically, on 20 cells 14 in the example shown.

[0208] In operation, the fuel cell 10 has an output current of up to 500 A (amps), depending on the stack technology.

[0209] The injected sinusoidal current has a frequency comprised between 100 Hz (Hertz) and 5 kHz (Kilohertz). More specifically, the injected sinusoidal current has a frequency comprised between 500 Hz and 2 kHz.

[0210] A sinusoidal current injected into the stack 11 induces a voltage response on the order of a few mV (millivolts). The voltage can be measured by an analog-to-digital converter equipped with an amplifier stage.

[0211] In the measured voltage signal, the measurement module 20 separates the voltage component having the same frequency as the injected sinusoidal current. The impedance is then calculated in the measurement module 20 as the ratio between the amplitude of the voltage component and the amplitude of the injected sinusoidal current.

[0212] The impedance value is typically calculated every second.

[0213] Each module 20 injects current independently of the other modules 20, so that the frequency of the injected current may differ from one module 20 to another module 20. This allows for simultaneous four-wire impedance measurements in multiple measurement modules 20.

[0214] The measured impedance is between 5 mΩ (milliohms) and 20 mΩ for 20 cells 14, and preferably is about 10 mΩ for 20 cells 14.

[0215] Such values ​​are advantageously small and such an arrangement serves to provide modular, multi-frequency impedance measurements instead of performing a single impedance measurement on the entire stack of bipolar plates 11. Thus, reliability is improved.

[0216] Using the method according to the invention, assembly is simple and no cables are used to connect the modules 20 to the cells 14 and to each other. The mounting also advantageously does not allow the use of cables to connect the modules 20 to the motherboard.

[0217] Thereby, the quality of the measurement is improved and allows for subsequent more detailed analysis.

[0218] The above-described embodiments and variations can be combined with each other to create additional embodiments of the present invention. [Explanation of symbols]

[0219] 10 fuel cell 11 Stack 12 Bipolar Plates 12' Anode plate, monopolar plate 12″ cathode plate, monopolar plate 14 Cells 16 End Plate 20 Measurement Module 22 Printed circuit 26 Outer shell 28 First Crossing 30 Male fasteners, studs 32 Female fastener, groove 34 Second Crossing 40 Mechanical Frame 42 Fastening rail 44 Pivot shaft 46, 48 Pivotal support 50 Receiving Orifice 52 Fastening means, screws 54, 54' through orifice, through hole 55 Orifice, hole 56 Fastening means, screws 57 Crossing Side 59 Male fastener 61 Female fastener 60, 62 Longitudinal ends 64 Through hole 66 Tabs 70 protrusions 71 Locking teeth 72 Cylindrical Groove 75 Ribbon 75′ Contact 76 Strip 78 pin 80 Leaf springs, contactors, switching parts 84 Pockets 85 edge 90 pin, connector 92 Perimeter Wall 93 Stamping 94 Open End 95 extra pins, auxiliary connector 96 part 97 Notch 98 Subpart 100 bumps 104 Longitudinal end 106 Fastening location 108 Additional components, auxiliary modules, mating modules 110 pin 112 part 114 Notch 116 Subpart 118 Prominence 120, 121 Metal contacts 122 Connector 123 External computer 201 Left hand module 202 Right hand module A-axis D Larger dimension of pivot supports 46, 48 d small dimension of pivot supports 46, 48 E Thickness of end plate 16 L Longitudinal P midline transverse section T transverse direction W Maximum width of end plate 16 Z height direction

Claims

1. 1. A fuel cell (10) comprising a stack (11) of bipolar plates (12) along a stacking direction (L), two consecutive bipolar plates (12) forming a cell (14) therebetween, said fuel cell (10) further comprising two end plates (16) arranged on either side of said stack (11) and a plurality of measurement modules (20) connected to said stack (11) of bipolar plates for measuring electrical characteristics of said cells (14), each measurement module (20) comprising at least one printed circuit (22) including a calculator suitable for determining electrical characteristics of said stack (11) of bipolar plates (12), said measurement modules (20) being at least configured to measure an impedance of said fuel cell (10) when said fuel cell (10) is in operation.

2. Each of the measurement modules (20) is connected to the stack (11) of bipolar plates (12) by means of pins (90) that are inserted into connectors (84) that fit into the bipolar plates (12); 2. The fuel cell (10) of claim 1, wherein each of the measurement modules (20) comprises a plurality of aligned connectors (90) and an auxiliary connector (95) configured to perform four-wire packet-by-packet impedance measurements of the number of cells (14) covered by the measurement module (20).

3. The aligned connectors (90) are arranged in pairs to measure the voltage across a set of two consecutive cells (14) placed between the two connectors (90); 3. The fuel cell (10) of claim 2, wherein the additional connector (95) of each of the measurement modules (20) is configured to inject a sinusoidal current into the mating connector of the bipolar plate in which the additional connector (95) is received.

4. 4. The fuel cell (10) according to claim 3, wherein the sinusoidal current has a frequency comprised between 100 Hz and 5 kHz, more particularly between 500 Hz and 2 kHz.

5. 5. The fuel cell (10) of claim 3 or 4, wherein each said measurement module (20) is configured to inject a sinusoidal current whose frequency is set independently of the other modules (20).

6. 6. A fuel cell (10) according to any one of claims 3 to 5, wherein each of the measurement modules (20) is configured to isolate a component of a response voltage induced in the stack (11) of bipolar plates (12) by the sinusoidal current, the component having the same frequency as the frequency of the injected sinusoidal current, and to calculate the impedance of the fuel cell (10) as the ratio between the amplitude of the isolated voltage component and the amplitude of the injected sinusoidal current.

7. A vehicle comprising at least one fuel cell (10) according to any one of claims 1 to 6.

8. A method of using a fuel cell (10) according to any one of claims 1 to 6, comprising the step of measuring the impedance of said fuel cell (10) during operation using said measurement module (20).

9. Each of the measurement modules (20) is connected to the stack (11) of bipolar plates (12) by means of connectors (90, 95) inserted into mating connectors (84) formed on the bipolar plates (12), each of the measurement modules (20) comprising a plurality of aligned connectors (90) and auxiliary connectors (95) configured to perform four-wire impedance measurements in packets of the number of cells (14) covered by the measurement module (20); The aligned connectors (90) are arranged in pairs to measure the voltage of two consecutive cells (14) disposed between the two connectors (90); 9. The method of claim 8, wherein the additional connector (95) of each of the measurement modules (20) is configured to inject a sinusoidal current into the mating connector (84) in which the additional connector (95) is received.

10. 10. The method of claim 8 or 9, wherein the step of measuring the impedance of the fuel cell (10) during operation by the measurement module (20) comprises measuring an impedance comprised between 5 mΩ and 20 mΩ for 20 cells (14).

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