Plug connection for a system for cell voltage monitoring of a fuel cell

Abstract

A plug connection for a system for cell voltage monitoring of a fuel cell has at least one plug (3) and at least one socket (1), wherein the socket (1) is formed in an edge region of a bipolar plate (10) of a fuel cell and is configured to interact with the plug (3) in order to produce an electrical connection. The plug (3) has at least two plug elements (4) and the socket (1) has at least two slots (2) each for one of the plug elements (4), wherein the at least two plug elements (4) are fixedly arranged in the plug (3) relative to one another at a respective plug position.

Description

[0001] Connector for a fuel cell voltage monitoring system

[0002] The present invention relates to a plug connection for a system for cell voltage monitoring of a fuel cell, a corresponding fuel cell, a fuel cell stack with at least one such fuel cell and a system for cell voltage monitoring with a corresponding plug connection.

[0003] Various types of fuel cells are known, for example polymer electrolyte membrane (PEM) fuel cells, which use hydrogen as fuel and air as oxidant. A fuel cell consists of electrodes, an anode, and a cathode, between which is an electrolyte (MEA - membrane electrode assembly). In a PEM fuel cell, the electrolyte is in the form of a polymer electrolyte membrane (PEM), which separates the two electrodes materially and electrically from each other but allows a specific type of ion, particularly protons, to pass through. The protons migrate through the membrane from the anode to the cathode, while the electrons pass through an external current circuit to generate electrical energy. At the cathode, the protons, the electrons, and the oxygen from the supplied air react to form water.

[0004] Since the electrical voltage of a single fuel cell is limited, several fuel cells are connected in series in a fuel cell stack (also called a "stack" or simply a "stack") to achieve a correspondingly higher voltage. The individual MEAs are separated from each other by bipolar plates, with the bipolar plates connecting the anodes and cathodes of consecutive MEAs to form the series circuit. A bipolar plate is responsible for supplying hydrogen and oxygen, removing water, and cooling the fuel cell stack. In addition, the bipolar plate on the anode (hydrogen) side absorbs the electrons released from the hydrogen and then returns them to the cathode (oxygen) side.

[0005] A critical component of fuel cell system operation is cell voltage monitoring (CVM). This allows for real-time monitoring of the electrical performance of the fuel cell stack and can help detect potential problems or failures that may occur during operation. By continuously measuring the voltage at each individual fuel cell in the fuel cell stack, this process can provide valuable information about the overall health and performance of the fuel cell system. Because fuel cell stacks consist of a large number of fuel cells, it is important that each fuel cell operates efficiently to optimize the overall performance of the fuel cell. Cell voltage monitoring is typically performed by sensors that measure the voltage of individual fuel cells.Deviations in cell voltage can indicate various problems, such as uneven fuel or air distribution within the fuel cell, clogged or damaged gas flow channels, electrical short circuits or interruptions, or aging or degradation of the fuel cell. By detecting such problems early, cell voltage monitoring can help prevent failures, improve fuel cell efficiency, and extend its service life.

[0006] However, installing a cell voltage monitoring system can be complex if a large number of plug connections must be made individually. Errors can also occur here, for example, if plug connections are not connected properly. However, when measuring the voltage, it is difficult to determine whether there is a fault in the operation of a fuel cell or whether the plug connection itself is faulty. The reliability of the cell voltage monitoring system can therefore be compromised. Furthermore, individual plug connections can become loose during operation, particularly if the system is subjected to vibrations, for example, in a vehicle. This also means that reliable cell voltage measurement cannot always be guaranteed.

[0007] The present invention is based on the object of providing a plug connection for a system for cell voltage monitoring of a fuel cell, which allows a more reliable voltage measurement.

[0008] This object is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims.

[0009] A first aspect of the invention relates to a plug connection for a system for cell voltage monitoring of a fuel cell. The plug connection comprises at least one plug and at least one socket. The socket is formed in an edge region of a bipolar plate of a fuel cell and is configured to interact with the plug to establish an electrical connection. The plug has at least two plug elements, and the socket has at least two sockets for each of the plug elements, wherein the at least two plug elements are fixedly arranged in the plug relative to one another at a respective plug position.

[0010] The invention is therefore based on creating a plug connection which establishes two (electrical) connections by means of a plug and a matching socket in a bipolar plate. For this purpose, the plug has at least two, in particular exactly two plug elements which are arranged fixedly relative to one another in the plug, i.e. are fixed or immobile. In the case of two plug elements, the plug can therefore also be referred to as a "double plug". The socket in the bipolar plate accordingly has at least two, in particular exactly two sockets and can thus provide a "double socket". The two plug elements (and thus the sockets) are in particular arranged in spatial proximity to one another, i.e. adjacent to one another, and can therefore be referred to as mechanically linked.In particular, the slots can be located in a common section of the bipolar plate's edge area, for example, on a common edge, and therefore point in the same direction. This eliminates the need to insert the connector elements into the slots individually; instead, the two connections can be established simultaneously.

[0011] The "double" plug connection offers increased mechanical stability compared to a plug connection with only one plug element and correspondingly one slot. This can also improve the stability and reliability of the electrical contact, particularly in applications subject to vibration, such as those that occur when a fuel cell system is used in a vehicle while driving. Furthermore, the redundant provision of the plug elements can improve the reliability of voltage measurements. For example, the plausibility of a voltage measurement can be checked. For this purpose, the voltage values ​​​​tapped at the plug elements can be compared, for example using appropriate logic. This makes it possible to quickly determine whether the plug connection was made correctly.For example, if there is a significant difference in the voltage values ​​of the two connector elements, there is a high probability that there is a fault in the connector. The two connections established by the connector can also be used differently, for example, one for supplying power to an evaluation electronics and the other for the actual voltage measurement.

[0012] The term "plug connection" used here refers in particular to a connection between a plug, the "male part," and a socket, the "female part." The plug connection is established in particular by mechanically inserting the plug into the socket, with the plug and socket each having electrically conductive components to establish an electrical connection, in particular for tapping a voltage or current. Insertion takes place in a "plug-in direction." The plug connection can be made without a lock or with a releasable or non-releasable lock. For example, the plug connection can mechanically snap or engage. The plug has plug elements, which can also be referred to as "pins," and which make up the part of the plug that establishes the electrical connection.The plug can accordingly have a housing that holds the plug elements and be connected to a line, such as a cable or wire. The socket has slots that are configured to accommodate the plug elements and can also be referred to as "pockets." In particular, the mechanical shape and arrangement of the slots in a socket are designed to match (complement) the design of the plug and its plug elements.

[0013] As used herein, the terms "comprises," "includes," "includes," "has," "has," "with," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.

[0014] Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present). The terms "a" or "an" as used herein are defined to mean "one or more." The terms "another" and "a further," and any other variations thereof, are to be construed to mean "at least one further."

[0015] The term “plurality” as used here shall mean “two or more”.

[0016] The term “configured” or “set up” to fulfil a specific function (and respective modifications thereof) is to be understood within the meaning of the invention that the corresponding device is already in a design or setting in which it can carry out the function or is at least adjustable - i.e. configurable - so that it can carry out the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or the like for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes.

[0017] Preferred embodiments of the plug connection are described below, which can be combined with each other as well as with the other aspects of the invention described, unless this is expressly excluded or is technically impossible.

[0018] In some embodiments, the slots of a socket have a distance along an edge of the bipolar plate that is less than or equal to the width of a slot. It is understood that the plug elements of a plug then also have a corresponding distance. This small distance puts the slots in close proximity, so that essentially the same cell voltage is tapped across the plug elements of a plug. In contrast, as will be described below, the cell voltage can vary across a bipolar plate, so that slots that are further apart from one another can potentially deliver different voltage values, for example if they are located on opposite edges of a bipolar plate. This spatial proximity also means that the plug elements of a plug can be easily plugged in simultaneously in one operation.In some embodiments, the plug elements are each formed by an electrically conductive wire which is bent in a plane and is thereby shaped and configured to fit into the respective slot to establish a respective electrical connection. The bend(s) of the wire can improve electrical contact or mechanical hold in the respective slots. Since the wire is bent in a plane, a plug element is nevertheless flat and thus suitable for contacting a fuel cell, which is a very flat component typically within a fuel cell stack. The wire can have any cross-section, for example round, square or flat. The connection to a circuit board (in particular also the plug) can be established, for example, by soldering or crimping.It goes without saying that any combination of connections and cross-sectional shapes of wires on printed circuit boards are conceivable.

[0019] In some associated embodiments, the wire has at least a first bend, which forms a part of the plug element that leads in a plugging direction, wherein the first bend has an angle in the range of approximately 90 to approximately 180 degrees, for example in the range of approximately 120 to approximately 150 degrees, such as approximately 135 degrees. This shape relates in particular to the unplugged state. The bend, in which, for example, an end region at a free end of the wire can be bent over, can improve handling during assembly, particularly compared to a simple (straight) wire. In particular, however, as will be explained below, the mechanical hold of a plug element in a slot as well as the electrical contact can be improved.

[0020] In some embodiments, a section of the wire extending from the first bend to a free end of the wire has at least one second bend, wherein the second bend forms a projection of the plug element transversely to the plug-in direction, which projection is designed to cooperate with a bulge in the corresponding slot when the plug connection is made, in order to thereby allow the plug connection to snap into place, wherein the wire is designed to be elastically deformed when snapping into place. While the first bend forms the leading end during plug-in, the lateral second bend, in interaction with a correspondingly shaped slot, which may have a bulge or nose, can provide a snap-in or latching plug connection. For this purpose, the sections of the plug element, i.e. the free end of the wire and the end of the wire connected to the plug, bend towards one another during plug-in.Due to the shape of the slot, when plugged in towards the end, the elastic deformation of the wire causes it to bend open again and thus snap into place.

[0021] In some associated embodiments, the free end of the wire is configured to protrude from the slot and beyond the edge of the bipolar plate after the plug connection has snapped into place, so that the snapped-in plug connection can be released by elastically deforming the wire when the free end is applied. In this way, a simple, detachable connection can be created. To release the snapped-in connection, the wire sections of the plug element can be pressed together by grasping the free end, so that the bulge in the slot can be passed when pulled in the opposite direction to the plugging direction.

[0022] In some embodiments, the plug element and the slot are designed such that, when the plug connection is established, electrical contact exists between the plug element and the slot at at least two contact areas spaced apart from one another. The contact areas can be arranged, in particular, along a contour of the slot. Two or more, for example three, contact areas can be provided, which are contacted when a plug element is fully received in a slot. The reliability of the plug connection can be improved by having several contact areas compared to just one contact area, since the electrical connection can still be established or maintained even if there is no contact in one of the contact areas.In particular, it can be provided that the shape of the plug elements, especially in a plan view of the plane in which the wire is bent, and the plug-in locations are adapted to each other but not completely identical. This allows for higher tolerances between the plug element and the plug-in location, particularly compared to embodiments in which identical shapes are intended.

[0023] In some embodiments, the plug-in locations are each formed by a lateral cutout in the edge region of the bipolar plate, wherein the cutout has at least one web extending across the cutout, wherein the plug elements are configured to electrically contact the at least one web when the plug-in connection is established. This can contribute to improving the electrical contact of the plug-in connection. In particular, in addition to the contact regions along the contour of the plug-in location, further contact regions or contact surfaces can be created. For example, a ramp can be provided as a "crossbar" at the end (the "lowest point") of a plug-in location, i.e. in the region in which the leading end of the plug element comes into contact.At least one crossbar can also be provided in a central area of ​​the socket, over which the plug element is pushed during insertion and against which it then rests upon complete insertion (particularly in the plane in which the wire is bent). The crossbars can also potentially improve the mechanical stability of the plug connection, as the plug element is additionally clamped.

[0024] A second aspect of the invention relates to a fuel cell with a bipolar plate which has at least one socket for a plug connection according to the first aspect.

[0025] In some embodiments of the fuel cell, the bipolar plate has at least two sockets arranged along the circumference of the bipolar plate in spaced-apart edge regions of the bipolar plate. In particular, the bipolar plate can have four or even six sockets. It is understood that each of the sockets then has at least two, in particular exactly two, plug-in locations, corresponding to the plug connection described above according to the first aspect of the invention. The sockets can be distributed along the circumference of the bipolar plate, in particular substantially uniformly. The sockets can advantageously also be provided on opposite edges of the bipolar plate, for example one or two on each short edge of the bipolar plate. In principle, one socket (and thus one plug-in connection) is sufficient for tapping the cell voltage, especially if only one socket is present.If multiple sockets are present, not all of them necessarily need to be connected. For example, symmetrically positioned sockets can simplify assembly if only one of them is connected to a plug.

[0026] However, multiple sockets and thus plug connections per fuel cell can also be used to tap the cell voltage at different points on the bipolar plate, enabling "spatially resolved" voltage detection (or current measurement). Voltage differences or, if applicable, a voltage gradient across the plate can then be detected, which can indicate various malfunctions. Plug connections according to the first aspect allow so-called "multipoint cell voltage monitoring" to be implemented in a particularly simple and cost-effective manner. For example, it can then also be designed for field operation of series-produced (industrial mass production) fuel cell systems, rather than just for test bench operation.

[0027] A third aspect of the invention relates to a fuel cell stack with at least one fuel cell according to the second aspect. In particular, a selected plurality of fuel cells can be provided in the fuel cell stack, in which a cell voltage tap is provided by means of at least one plug connection according to the first aspect. These can be fuel cells at the edge of the fuel cell stack, for example, but also in the middle of the fuel cell stack. For example, fuel cells in the fuel cell stack can be monitored at specific intervals. In test operation, more fuel cells can be monitored than is possible or necessary in field operation. It is understood that, if necessary, all fuel cells of a fuel cell stack could also be monitored in this way.To facilitate assembly, one or more "collective connectors" may be provided, which may comprise multiple connectors and thus connector elements as described above, for example, ten connectors or 20 connector elements. The collective connector can thus provide a "holding geometry" so that all connectors in a fuel cell stack do not have to be installed individually.

[0028] A fourth aspect relates to a system for monitoring the cell voltage of a fuel cell having at least one plug connection according to the first aspect and / or at least one fuel cell according to the second aspect and / or a fuel cell stack according to the third aspect, wherein the system comprises a device for detecting the cell voltage, which is connected or connectable to the fuel cell or at least one of the fuel cells of the fuel cell stack by means of at least one plug connection according to the first aspect. Furthermore, a device for monitoring the detected cell voltage can be provided. By appropriately evaluating the detected cell voltage, conclusions can be drawn about possible malfunctions of a fuel cell.

[0029] The features and advantages explained with reference to the first aspect of the invention also apply accordingly to the other aspects of the invention. Further advantages, features, and possible applications of the present invention will become apparent from the following detailed description in conjunction with the drawings.

[0030] It shows:

[0031] Fig. 1 is a plan view of a bipolar plate according to a first embodiment and a detailed view thereof;

[0032] Fig. 2 is a plan view of a bipolar plate according to a second embodiment;

[0033] Fig. 3 is a perspective view of a plug connection according to a first embodiment;

[0034] Fig. 4 is a perspective view of a plug connection according to a second embodiment;

[0035] Fig. 5 to Fig. 7 steps for making the plug connection;

[0036] Fig. 8 shows various views of a socket according to another embodiment; and

[0037] Fig. 9 different views of a socket according to another embodiment.

[0038] Throughout the figures, the same reference numerals are used for the same or corresponding elements of the invention. The figures are schematic and therefore do not necessarily represent the actual objects to scale.

[0039] Fig. 1 shows a bipolar plate 10 according to a first embodiment in plan view, along with a detailed view of a corner thereof. The bipolar plate 10 has connections 11, 12, 13, 14, 15, 16. A cathode gas (oxidizing agent, in particular air) is supplied via the inlet 12 of the bipolar plate 10 and then flows over the cathode side of the bipolar plate 10. Corresponding reaction products (in particular water) leave the bipolar plate 10 via the outlet 15. An anode gas (fuel, in particular hydrogen) is supplied in a similar manner via the inlet 11 and flows over the anode side. Residues are discharged via the outlet 14. A coolant is supplied via the inlet 13, flows through hollow channels inside the bipolar plate 10 and finally leaves the bipolar plate 10 at the outlet 16. The detailed view indicates the beginning of a channel structure 19 through which the coolant flows.Corresponding channel structures are also provided for the cathode gas and the anode gas. The exact structures are not relevant to the present invention. Therefore, the central part of the bipolar plate 10 is hidden.

[0040] For tapping the cell voltage in a cell voltage monitoring system, the bipolar plate 10 has four sockets 1 for plug connections, two each on the longitudinal edges 17, 18. The sockets 1 each have two slots 2. These are each designed to accommodate a corresponding plug 3, which is described below. It can be provided to set up a plug connection for only one of the sockets 1 in order to tap the cell voltage. However, it can also be provided to establish multiple plug connections for several or all sockets 1. In this way, a spatially resolved voltage measurement can be carried out. By evaluating the voltages recorded at various points on the bipolar plate 10, conclusions can be drawn about possible malfunctions. For monitoring the cell voltage, however, it is generally sufficient to establish only one plug connection via one of the sockets 1.The symmetrical arrangement of the sockets also allows the bipolar plate to be mounted rotated by 180 degrees.

[0041] The bipolar plate 10 is, in particular, part of a fuel cell (not shown), which in turn may be part of a fuel cell stack comprising a plurality of fuel cells (also not shown). In a fuel cell stack, it may be provided to monitor the cell voltage of several fuel cells, which may be distributed throughout the fuel cell stack. This allows the function of the entire fuel cell stack to be monitored.

[0042] Fig. 2 shows a bipolar plate 10 according to a second embodiment. This differs from the bipolar plate 10 in Fig. 1 only in that only two sockets 1 are provided instead of four. In this respect, reference is made to the above description of Fig. 1. According to the embodiment in Fig. 2, only one socket 1 is arranged on each longitudinal edge 17, 18 of the bipolar plate 10. These are offset diagonally such that the bipolar plate 10 (comparable to the bipolar plate 10 in Fig. 1) has a rotationally symmetrical design, so that the bipolar plate 10 can also be mounted rotated 180 degrees around the center point. Fig. 3 shows a first embodiment of a plug connection with a plug 3 and a socket 1. The plug 3 is designed as a double plug and has two plug elements 4 ("pins"), which are received in corresponding slots 2 ("pockets") of the socket 1 in the bipolar plate 10.The plug elements 4 are mechanically in the plug.

[0043] 3, wherein a connector housing or part of a printed circuit board is indicated in Fig. 3. The plug connection is designed redundantly by providing two plug elements 4 and correspondingly two slots 2. This can, on the one hand, improve the mechanical stability of the plug connection compared to a plug connection with only one pin. On the other hand, the plug connection can be checked for plausibility by comparing the two voltage measurements on the two plug elements 4. Since both voltage values ​​should be approximately the same when functioning correctly, a difference in the voltages can indicate that the plug connection is not functioning or has not been established correctly, for example that the plug 3 is not firmly seated. As will be explained below with reference to Fig.As will be explained in more detail in Figures 5, 6, and 7, the plug connection is "snapped" (or engaged) because the plug elements 4 are formed by elastically deformable wires. The bent shape of the wire and the corresponding shape of the sockets 2 ensure that the plug connection is secure.

[0044] Fig. 4 shows another embodiment of the plug connection, which is essentially similar to the embodiment shown in Fig. 3. Only the shape of the plug elements

[0045] 4 and correspondingly the slots 2 differ slightly. In particular, however, in the embodiment of Fig. 4, the wire is provided with an additional bend shortly before the free end 8. This allows the free end 8 to be grasped in order to thereby compress the plug element 4. This allows the plug connection to be unlocked and the plug 3 to be easily pulled out of the socket 1. The mirror-inverted arrangement of the two plug elements 4 and the slots 2 facilitates this, since both plug elements 4 can be unlocked simultaneously by pressing them together from the sides.

[0046] In both embodiments, provisions can be made to take measures to prevent or reduce the ingress of moisture or water into the socket 1 or the plug-in locations 2. This is particularly important because, at low temperatures below freezing, the expanding ice can cause damage to the socket 1 and thus ultimately to the fuel cell. For protection, the plug-in locations can, for example, be subjected to a hydrophobic treatment, i.e., they can be given a hydrophobic coating or treatment. The hydrophobic (water-repellent) property thus created protects the plug-in locations 2 from the ingress of water without changing their shape or other functionality. Equally conceivable, however, is a filling or covering of the plug-in locations 2, which keeps out moisture or water but allows the insertion of the plug elements 4 and thus the establishment of the plug-in connection.

[0047] Fig. 5, Fig. 6 and Fig. 7 show different phases during the establishment of the plug connection (for reasons of clarity, only one plug element 4 and one slot 2 are shown in each case; it is understood that this also applies to the second half of the plug connection).

[0048] Fig. 5 shows the plug element 4 before it is inserted into the socket 2 along the insertion direction 20. As already mentioned, the plug element 4 is formed from an elastically deformable and electrically conductive wire. This wire is bent in one plane to achieve a shape that matches the socket 2 and is simultaneously flat. A first bend 5 of approximately 135 degrees forms the end of the plug element 4 leading in the insertion direction 20, which, due to its rounded yet pointed shape, can be easily inserted into the socket 2. For automated assembly, it can be provided to use the socket 2 (or its entrance at the edge of the bipolar plate 10) as an optical marker, which is detected by a detection device (not shown), such as a camera, in order to correctly align the plug 3 with the socket 1.A further bend 6 (here approximately 90 degrees) is provided, which, in conjunction with a bulge 9 in the slot 2, enables the plug connection to snap into place. A further bend 7 (here also approximately 90 degrees) in front of the free end 8 facilitates the above-described gripping of the free end 8 to release the snapped-in (locked) plug connection.

[0049] Fig. 6 shows a phase during insertion. The elastic deformation of the plug element 4 is clearly visible (see arrow). The compression is caused in particular by the bulge 9 in the slot 2. Since pushing the plug element 4 forward in the insertion direction 20 requires some force, this can be used to monitor the assembly. In particular, a force-displacement curve can be measured and compared with a force-displacement curve associated with correct assembly. If, for example, excessive forces occur, this may be an indication that insertion is blocked or impeded. Insufficient force may also indicate an error, for example that the wire has broken off and therefore does not offer the expected resistance during insertion.

[0050] Fig. 7 now shows the fully assembled state of the plug connection (see also Fig. 4). In particular, it can be seen that the plug element 4, after the bend 6 has passed the bulge 9, has bent back up due to elastic deformation (see arrow). Here, however, not quite into its original unloaded shape (Fig. 5), so that the plug element 4 sits in the slot 2 with a certain clamping force. The bend 6 engages behind the bulge 9 in the slot 2 so that the plug connection snaps into place and the risk of accidental release, for example in the event of vibrations, is reduced. The plug element 4 is now in electrical contact with the slot 2, so that a cell voltage of the fuel cell can be tapped via the plug connection.The electrical contact is established at three spaced-apart contact areas 21, 22, 23, since the plug element 4 has a shape that matches, but is not identical to, the connector 2. This allows for greater tolerances during assembly. It is understood that the contact areas can also be referred to as contact points, even if they do not necessarily have to be point-shaped in the true sense of the word.

[0051] Fig. 8 and Fig. 9 show two ways in which the contact between plug element 4 and slot 2 can be improved if necessary. Fig. 8 shows a slot 2 with two transverse webs 24, which contact the plug element 2 in addition to the contact areas 21, 22, 23. On the one hand, this can improve the electrical contact. On the other hand, the webs 24 can also create an additional clamping effect. Fig. 9 shows a slot with a ramp 25 at the end. Due to the increased resistance thus generated, particularly towards the end of the plugging process, both the electrical contact and the mechanical hold of a plug element 4 in the slot 2 can also be improved if necessary.

[0052] While at least one exemplary embodiment has been described above, it should be appreciated that a wide variety of variations exist. It should also be understood that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide a guide to implementing at least one exemplary embodiment; it being understood that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the subject matter as defined in the appended claims, as well as their legal equivalents.

[0053] LIST OF REFERENCE SYMBOLS

[0054] 1 socket

[0055] 2 slots

[0056] 3 Plug 4 Plug element

[0057] 5 Bend

[0058] 6 Bend

[0059] 7 Bend

[0060] 8 free end 9 bulge

[0061] 10 bipolar plate

[0062] 11 Connection

[0063] 12 connection

[0064] 13 Connection 14 Connection

[0065] 15 Connection

[0066] 16 connection

[0067] 17 Longitudinal edge

[0068] 18 Longitudinal edge 19 Channels

[0069] 20 Plug-in direction

[0070] 21 Contact area

[0071] 22 Contact area

[0072] 23 Contact area 24 Cross bars

[0073] 25 Ramp

Claims

CLAIMS 1. Plug connection for a system for cell voltage monitoring of a fuel cell, comprising at least one plug (3) and at least one socket (1), wherein the socket (1) is formed in an edge region of a bipolar plate (10) of a fuel cell and is designed to interact with the plug (3) to establish an electrical connection, wherein the plug (3) has at least two plug elements (4) and the socket (1) has at least two plug locations (2) for each of the plug elements (4), wherein the at least two plug elements (4) are fixedly arranged in the plug (3) relative to one another at a respective plug position.

2. Plug connection according to claim 1, wherein the slots (2) of a socket (1) have a distance along an edge (17, 18) of the bipolar plate (10) which is less than or equal to a width of a slot (2).

3. Plug connection according to claim 1 or 2, wherein the plug elements (4) are each formed by an electrically conductive wire which is bent in a plane and thereby shaped and configured to fit into the respective plug-in location (2) to establish a respective electrical connection.

4. Plug connection according to claim 3, wherein the wire has at least a first bend (5) which forms a part of the plug element (4) leading in a plugging direction (20), wherein the first bend (5) has an angle in the range of 90 to 180 degrees.

5. Plug connection according to claim 4, wherein a section of the wire extending from the first bend (5) to a free end (8) of the wire has at least one second bend (6), wherein the second bend (6) forms a projection of the plug element (4) transversely to the plugging direction (20), which projection is designed to cooperate with a bulge (9) in the corresponding plug-in location (2) when the plug connection is made, in order to thereby snap the plug connection into place, wherein the wire is designed to be elastically deformed when snapping into place.

6. Plug connection according to claim 5, wherein the free end (8) of the wire is arranged, after the plug connection has been snapped in, to be pulled out of the socket (2) and to protrude beyond the edge (17, 18) of the bipolar plate (10) so that the snapped-in plug connection can be released by elastic deformation of the wire when acting on the free end (8).

7. Plug connection according to one of the preceding claims, wherein the plug element (4) and the socket (2) are designed such that, when the plug connection is established, there is electrical contact between the plug element (4) and the socket (2) at at least two contact areas (21, 22, 23) spaced apart from one another.

8. Plug connection according to claim 7, wherein the contact areas (21, 22, 23) are arranged along a contour of the plug-in location (2).

9. Plug connection according to one of the preceding claims, wherein the plug-in locations (2) are each formed by a lateral cutout in the edge region of the bipolar plate (10), wherein the cutout has at least one web (24, 25) extending across the cutout, wherein the plug elements (4) are designed to electrically contact the at least one web (24, 25) when establishing the plug connection.

10. Fuel cell with a bipolar plate (10) which has at least one socket (1) for a plug connection according to one of the preceding claims.

11. Fuel cell according to claim 10, wherein the bipolar plate (10) has at least two bushings (1) which are arranged along the circumference of the bipolar plate (10) in spaced-apart edge regions of the bipolar plate (10).

12. Fuel cell stack with at least one fuel cell according to claim 11.

13. A system for cell voltage monitoring of a fuel cell, comprising at least one fuel cell according to claim 10 or 11 or a fuel cell stack according to claim 12, wherein the system has a device for cell voltage detection which is connected or connectable to the fuel cell or at least one of the fuel cells of the fuel cell stack by means of at least one plug connection according to one of claims 1 to 9.

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