SE2430297A1 - Cell voltage monitoring connector for a fuel cell stack - Google Patents

Abstract

:Cell voltage monitoring connector (100) for monitoring a cell voltage of a fuel cell stack (1) having a plurality of alternatingly stacked bipolar plates (2) and membrane electrode assemblies (4), wherein the cell voltage monitoring connector (100) comprises a housing (101) made from an electrically insulating material and at least one electrical contact element (160; 170), which is made from an electrically conducting material and adapted to contact the bipolar plate (2), characterized in that the connector housing (101) has at least one protruding rib (110; 120) which is adapted to be inserted between a bipolar plate (2) and a membrane electrode assembly (4) of the fuel cell stack (1), wherein the at least one protruding rib (110; 120) is equipped with the electrical contact element (160; 170).

Description

Cell voltage monitoring connector for a fuel cell stack Description: The present invention relates to a voltage monitoring connector for a fuel cell stack according to the preamble of claim 1, as well as a fuel cell stack with such a cell voltage monitoring connector.

A fuel cell stack is usually formed by stacking a large number of unit cells into numerous layers. Each of the unit cells comprises at least a membrane electrode assembly (MEA) having an ion exchange membrane sandwiched between an anode and a cathode, and a bipolar plate, comprising an anode plate and a cathode plate, which are facing the respective anode or cathode of the membrane electrode assembly. Through the bipolar plates hydrogen fuel and an oxidizing agent are supplied to the MEA, which generates electric power. For such a fuel cell stack, management of the power generation state of each unit cell is necessary in order to control the amounts of supplied hydrogen and oxygen and/or to find a broken or malfunctioning unit fuel cell. To enable such management, the generated voltage for each unit cell is monitored and the control is carried out based on the monitored voltage. For monitoring the voltage each bipolar plate is connected to an electrical connector, which usually comprises a housing supporting a plurality of contact elements, which are adapted to electrically contact the bipolar plates.

Previously, a connector for monitoring the cell voltage of a bipolar plate of a fuel cell stack comprises a plurality of pins which are introduced into slots provided between the anode plate and the cathode plate of the bipolar plate. lnserting the pins of the cell voltage monitoring connector into the openings is a cumbersome process and requires a high precision. Further, the attaching position for the cell voltage monitoring connector has been located in a corner of the fuel cell stack, where the bipolar plates have no or only very less support, which resulted in a slight overhang that can lead to drooping, which in turn results in an uneven cell pitch (distance from cell to cell), which impede the inserting of the pins even mOTG.

PC24005 2024-05-28 lt is therefore object of the present invention to provide a cell voltage monitoring connector which improves the above-mentioned situation.

This object is solved by a cell voltage monitoring connector according to claim 1 as well as a fuel cell stack according to claim 14. ln the following a cell voltage monitoring connector for monitoring a cell voltage of a fuel cell stack is proposed. The fuel cell stack usually comprises a plurality of alternatingly stacked bipolar plates and membrane electrode assemblies, wherein the generated voltage is monitored at the bipolar plate. For that, a cell voltage monitoring connector is provided which comprises a housing made from an electrically insulating material and which usually comprises one or more electrical contact elements which are adapted to electrically contact at least one of the bipolar plates.

For providing a cell voltage monitoring connector which provides a simplified connecting possibility to the fuel cell stack, the connector housing has at least one protruding rib which is adapted to be inserted between a bipolar plate and a membrane electrode assembly, wherein the at least one protruding rib is equipped with the electrical contact element. Since the protruding rib carries the electrical contact element, the electrical contact element is brought into contact with the bipolar plate when attaching the housing to the fuel cell stack. Additionally, as the protruding rib is arranged between the bipolar plate and the membrane electrode assembly, the protruding rib ensures that the membrane electrode assembly is not accidentally covering the bipolar plate. An accidentally covered bipolar plate would prevent the bipolar plate from being contacted by the electrical contact element.

For simplifying the insertion of the protruding rib between the bipolar plate and the membrane electrode assembly, it is preferred that the at least one protruding rib may have a guiding element which is adapted to guide the protruding rib between the bipolar plate and the membrane electrode assembly.

According to a further preferred embodiment, the protruding rib has a straight part which is, in the assembled state, arranged in parallel to the bipolar plate and the membrane electrode assembly, respectively, and an inclined part which, in the assembled state, is inclined towards the bipolar plate, wherein the inclined part forms the guiding element. This enables the membrane electrode assembly to slide along the inclined part of the protruding rib and 2 thereby bends the membrane electrode assembly away from the bipolar plate, so that the bipolar plate is exposed for being contacted by the electrical contact element.

According to a further preferred embodiment, the connector housing has at least a pair of protruding ribs each having a first protruding rib and a second protruding rib, wherein each pair of protruding ribs defines an accommodation groove for accommodate a single bipolar plate of the plurality of bipolar plates, wherein the first protruding rib has a straight part which is parallel to the second protruding rib and, in the assembled state, parallel to the accommodated bipolar plate, and an inclined part which is inclined towards the second protruding rib and, in the assembled state, inclined towards the accommodated bipolar plate, and wherein the second protruding rib has a straight part which is parallel to the first protruding rib and, in the assembled state, parallel to the accommodated bipolar plate, and an inclined part which is inclined towards the first protruding rib and, in the assembled state, inclined towards the accommodated bipolar plate. Thereby the protruding ribs form "arrowheads" which separate in the assembling process two adjacent membrane electrode assemblies for exposing the bipolar plate, which is sandwiched by the adjacent membrane electrode assemblies, for being contacted by the electrical contact element.

Thereby it is further preferred that the dimensions of the housing are adapted to the dimensions of the fuel cell stack, so that a minimal distance between the inclined parts of the pair of protruding ribs is adapted to be smaller than a distance between two adjacent membrane electrode assemblies sandwiching the accommodated bipolar plate and larger than a thickness of the accommodated bipolar plate. Thereby it can be ensured that adjacent membrane electrode assemblies are automatically bended outside, when the cell voltage monitoring connector is assembled to the fuel cell stack, and the bipolar plate which shall be contacted by the electrical contact element is reliably exposed.

According to a further preferred embodiment, at least one protruding rib has a bipolar plate facing surface and the electrical contact element is arranged at bipolar plate facing surface.

This allows for an easy contact of the electrical contact element to the exposed bipolar plate.

Thereby it is further preferred that the electrical contact element is a spring element, particularly a flexible tongue, which is biased towards the bipolar plate. This ensures that the electrical contact element stays in contact with the bipolar plate under all circumstances. lt is further preferred if the electrical contact element has a fixed end with which the electrical contact element is attached to the protruding rib and a free end, wherein at the free end a part of the contacting element is designed as inclined part, which is inclined towards the protruding rib at which the bipolar plate connecting element is attached to. Similarly to the inclined part of the protruding rib, ensures the inclined part of the electrical contact element, that, during assembling, the electrical contact element does not abut against the front of the bipolar plate but is guided to the surface, at which the electric contact is then established. ln the above-mentioned case of the at least one pair of protruding ribs, it is further preferred that the pair of protruding ribs is equipped with a pair of bipolar plate connecting elements, so that the bipolar plate is clamped between the electrical contact elements. This allows for voltage monitoring information on both the anode and the cathode plate. Additionally provides the clamping a certain fixation of the entire cell voltage monitoring connector to the fuel cell stack so that the cell voltage monitoring connector cannot get accidentally detached from the fuel cell stack. lt is further preferred that the cell voltage monitoring connector is adapted to accommodate a border area (edge/rim(randbereich)/margin/periphery) of the bipolar plate. As the protruding rib provide an elongated groove, a significant long border area of the bipolar plate can be arranged in the groove, which improves both the electrical contact possibility as well as the stability of the attachment of the cell voltage monitoring connector to the fuel cell stack.

According to a further preferred embodiment, a plurality of protruding ribs and electrical contact elements are provided and the protruding ribs and electrical contact elements are arranged alternatingly at two opposite sides of the housing so that the protruding ribs and electrical contact elements on one side of the housing are adapted to contact every second bipolar plate. This allows for sufficient space for exposing the bipolar plate arranged between two adjacent membrane electrode assemblies. ln the special case of a pair of protruding ribs, this design also means that between two adjacent pairs of the protruding ribs the two bend away membrane electrode assemblies and one - on the first side of the housing - not contacted bipolar plate is accommodated. This bipolar plate however, is electrically contacted at the second side of the housing, where the pair of protruding ribs of the second side of the housing are arranged in such a way that this on the first side of the housing not electrically contacted bipolar plate is exposed for being electrically contacted.

According to a further preferred embodiment, the housing has at least one attaching element which is adapted to secure the attachment of the housing at the fuel cell stack. Thereby it can be ensured that the cell voltage monitoring connector is not coming loose from the fuel cell stack.

Thereby the attaching element can be designed as clamping element, wherein the clamping element comprises two flexible arms, and wherein the housing further comprise at least one an opening for inserting a pin-like element, wherein the opening is arranged in such a way that the pin-like element is adapted to spread the flexible arms, whereby the housing is secured to the fuel cell stack.

A further aspect of the present invention relates to a fuel cell stack comprising a plurality of bipolar plates which sandwich a plurality of membrane electrode assemblies and at least one cell voltage monitoring connector as mentioned above.

Thereby it is particularly preferred that each bipolar plate and each membrane electrode assembly has at least one voltage monitoring connecting area in which each bipolar plate and each membrane electrode assembly has a recess which is designed as receiving opening and form an elongated pocket along the length of the fuel cell stack into which the housing of the cell voltage monitoring connector is at least partly insertable.

This allows for inserting a cell voltage monitoring connector which has alternatingly arranged pairs of protruding ribs, which electrically connect alternatingly every second bipolar plate so that in sum all bipolar plates of the fuel cell stack are electrically contacted and can be monitored.

According to aa further embodiment at least one of the anode and cathode plates has at least one spacer element which is adapted to stabilize a distance between two adjacent bipolar plates. The spacer element is preferably arranged in the vicinity of the recess.

Preferably, both anode and cathode plate have at least one spacer element. Most preferred, both anode and cathode plate have two or more spacer elements, which are arranged surrounding the recess.

Further preferred embodiments are defined in the dependent claims as well as in the description and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection. ln the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

The figures show: Fig. 1: schematic illustrations of a fuel cell stack; Fig. 2: schematic illustration of a fuel cell stack and a cell voltage monitoring connector; Figs. 3a-e: various schematic views of a first embodiment of the cell voltage monitoring connector; Figs. 4a-e: various schematic views of a second embodiment of the cell voltage monitoring connector; Figs. 5a-d: schematic cross-sectional illustrations of various stages in an assembling process of the cell voltage monitoring connector to a fuel cell stack; Figs. 6a-b: schematic illustrations of further aspects in the assembling process; and Fig. 7a-b: schematic illustration of a fasting of the cell voltage monitoring connector to the fuel cell stack. ln the following same or similar functioning elements are indicated with the same reference numerals.

Fig. 1 schematically illustrates views a part of a fuel cell stack 1, namely in perspective view - Fig. 1a and in cross-sectional view - Fig. 1b. Usually, a fuel cell stack 1 comprises bipolar plates 2, and multi-layer membrane electrode assemblies 4, which are alternatingly stacked and which form the cell stack body, which is illustrated in Fig. 1. Additionally, the fuel cell stack 1 usually comprises a pair of terminal plates (not illustrated) collecting the electric current produced by the cell stack body, and a pair of endplates (not illustrated) sandwiching the terminal plates. Typically, an insulation plate (not illustrated) is provided between each of the terminal plate and the adjacent endplate to insulate each terminal plate from the adjacent endplate.

The bipolar plates 2 themselves are a combination of an anode plate 6 and a cathode plate 8 (see Fig. 1b), which are fixed to each other, wherein adjacent bipolar plates are then separated, or with other words sandwiched, by the membrane electrode assemblies 4. The cathode and anodes plate which form the bipolar plates are usually electrically transmitting metal or graphite plates, so called flow field plates, having a flow field for the reactants at one side and a flow field for a cooling fluid on the other side. ln the assembled state of the bipolar plates, the flow field plates are placed on top of each other in such a way that the cooling fluid flow fields are facing each other, and the reactant fluid flow fields face the sandwiching membrane electrode assemblies.

The electric current is produced by the membrane electrode assemblies 4 during operation of the fuel cell stack in the electricity generating subassemblies. The electricity generating subassembly of a membrane electrode assembly comprise an ion-conducting membrane, and two electro catalyst layers being arranged at either side of the membrane serving as anode and cathode. During operation of the fuel cell stack, fuel, particularly hydrogen is provided at the anode, while an oxidant, usually oxygen or air is provided at the cathode.

At the anode, the electro catalyst, usually a platinum catalyst, causes the hydrogen to split into positive hydrogen ions (protons) and negatively charged electrons. The ion conducting membrane, e.g. the polymer electrolyte membrane (PEM) allows only the positively charged ions to pass through it to the cathode. At the cathode, the electrons and positively charged hydrogen ions combine with oxygen to form water, which flows out of the cell.

Since the ion conducting membrane allows only the positively charged ions to pass to the cathode, a voltage potential difference is created on both sides of the membrane electrode assembly and therefore between the bipolar plate assemblies.

The electricity generating subassembly of the membrane electrode assembly it usually framed by a subgasket, which serves also the purpose to provide an electrical isolation between two adjacent bipolar plates 2-1 and 2-2 (See Fig. 1b). For that the membrane electrode assembly 4 and particularly the subgasket of the membrane electrode assembly 4 is extending over the bipolar plate as is illustrated in the Figs.

During the operation of the fuel cell stack, the voltage produced by the stacked cells needs to be monitored for determining whether the stack is operating within its intended operation 7 parameters. For that, it is known that the bipolar plates are equipped with cell voltage monitoring connectors, which are fixed to the bipolar plates and are provided with wires for connecting the voltage monitoring units to an external voltage monitoring controller, which monitors and controls the operation of the stack.

However, since the membrane electrode assembly 4 is extending over the bipolar plate 2, it might happen that the cell voltage monitoring connector are not electrically contacting the bipolar plate 2 but are in contact with the membrane electrode assembly 4 which hinders the voltage monitoring.

As can be further seen in the Fig. 1a and 2, the fuel cell stack 1 may further have a recess 10 (receiving opening) which is adapted to accommodate the cell voltage monitoring connector 100. ln the illustrated embodiment, the receiving opening/recess 10 may be designed as pocket having an entrance area 12 and an accommodation area 14, wherein the entrance area 12 widens into the accommodation area 14. Thereby an undercut 16 is formed which might be used for fastening and securely attaching the cell voltage monitoring connector 100 into the pocket 10 as will be explained with reference to Figs. 5 and 6 later on.

Further, each bipolar plate 2 has at least one, preferably two spacer elements 18, 19, which are adapted to stabilize a distance between the bipolar plates 2, so that the adjacent bipolar plate are distanced by a defined and predictable cell pitch CP (see Fig. 1b). The spacer elements are preferably arranged at both sides of the receiving opening 10. Additionally, the spacer elements may be arranged on both, the anode and the cathode plates. These spacer elements 18, 19 are not shown in Figs. 3 to 7 for the sake of providing distinguishable illustrations.

As can be seen in Fig. 2, the cell voltage monitoring connector 100 has housing 101 made from an electrically isolating material with a front side 102, two sides 104, 106 and a back side 108. With the front side 102, the cell voltage monitoring connector 100 is introduced and accommodated into the pocket 10, wherein the sides 104, 106 come into contact with the fuel cell stack and are adapted to provide the electrical contact for the voltage monitoring. At the back side 108, the cell voltage monitoring connector 100 may be equipped with electrical connections for connecting the cell voltage monitoring connector 100 to a control unit (not illustrated).

Fig. 3 and 4 illustrated two embodiments for the cell voltage monitoring connector 100.

Fig. 3 illustrates various schematic views of a first embodiment of a cell voltage monitoring connector 100. Thereby, Fig. 3a illustrates a perspective view of the cell voltage monitoring connector 100 from the front and illustrating the first side 104, Fig. 3b illustrates a perspective view of the cell voltage monitoring connector 100 from the back and illustrating the second side 106, Fig. 3c illustrates a plan view of the front of the cell voltage monitoring connector 100; Fig. 3d illustrates a plan view of the back of the cell voltage monitoring connector 100; and Fig. 3e illustrates a cross sectional view of the cell voltage monitoring connector 100.

Analogously, Fig. 4 illustrates various schematic views of a second embodiment of an cell voltage monitoring connector 100. Thereby, Fig. 4a illustrates a perspective view of the cell voltage monitoring connector 100 from the front and illustrating the first side 104, Fig. 4b illustrates a perspective view of the cell voltage monitoring connector 100 from the back and illustrating the second side 106, Fig. 4c illustrates a plan view of the front of the cell voltage monitoring connector 100; Fig. 4d illustrates a plan view of the back of the cell voltage monitoring connector 100; and Fig. 4e illustrates a cross sectional view of the cell voltage monitoring connector 100.

As illustrated in Fig. 2 as well as Figs. 3 and 4, the cell voltage monitoring connector 100 has a housing 101 having a first side 104 and a second side 106. Both sides 104 106 are equipped with a plurality of protruding ribs 110, 120(see Fig. 3a, 4a and 3b, 4b), which are formed as pair of protruding ribs 130. With other words, in the illustrated case, each side 104, 106 has eight protruding ribs, wherein always two ribs 1101, 1201; 1102, 1202; 1103, 1203; 1104, 1204; 1105, 1205; 1106, 1206; 1107, 1207; 1108, 1208; form the respective pair of protruding ribs 1301, 1302, 1303, 1304, 1305, 1306, 1307, 1308, see particularly Fig. 3d, 4d.

Thereby each pair of protruding ribs 130 form an inner groove 140 which is adapted to accommodate a bipolar plate 2 which is intended to be electrically contacted, and an outer groove 150 for accommodating other parts of the fuel cell stack 1, which are not intended to be electrically contacted.

Further, each protruding rib 110, 120 has an inner groove facing surface 111; 121, a front end 112; 122 and an outer surface 113, 123 facing/forming the outer groove 150.

For electrically contacting the bipolar plate 2 at least one of the protruding ribs 110, 120 carries on its groove facing surface 111, 121 an electrical contact element 160; 170. Preferably each rib 110, 120 is equipped with such an electrical contact element 160; 170, so that the bipolar plate 2 may be contacted on both sides as will be explained further below with respect to Figs. 5 and 6.

The electrical contact element 160; 170 (see also Fig. 5a) is in the illustrated embodiments a flexible spring tongue, having a fixed end 161; 171 and a free end 162; 172, wherein the fixed end 161; 171 is attached to the protruding rib 110; 120 and is adapted to be electrically contacted by contact pins 180. The contact pins 180 in turn can be accessed from the outside for connecting the cell voltage monitoring connector 1 to a control unit (not illustrated).

As is further illustrated in Fig. 3 and 4, particularly in Fig. 3e, 4e, the electrical contact element 160; 170 is arranged in such a way at the protruding rib 110, 120 that, the electrical contact element 160; 170 has a first inclined part 163; 173, which raised from its fixed end 161, 171 at the protruding rib 110, 120 into the space of the inner groove 140, thereby forming the free end 162; 172. At its free end 162, 172 in turn the electrical contact element 160, 170 has a second inclined part 164; 174 which is inclined in the opposite direction of the first inclined part 163; 173, so that the electrical contact element 160; 170 forms in cross- section a contact tip 165; 175, where in the assemble state, the electrical contact with the bipolar plate 2 is established. The second inclined parts 164; 174 form a receiving mouth 142 for the bipolar plate 2 and allow for a facilitated accommodation of the bipolar plate 2 as the bipolar plate cannot abut against the electrical contact element 160; 170, but is guided between the electrical contact elements 160, 170 contact tips 165; 175. lt should be further noted that, since the electrical contact element 160; 170 is a flexible tongue having a certain width, the contact tip 165; 175 contacts the bipolar plate 2 along its entire width in a line contact.

As can be further seen in the Figs. 3 and 4, each protruding rib 110, 120 has a straight part 114; 124 and an inclined part 115; 125, wherein the inclined parts 115; 125 of the protruding ribs 110, 120 forming the pair of protruding ribs are inclined towards each other. With other words, the inclined part 115 of protruding rib 110 is inclined towards the inclined part 125 of the other protruding rib 120 (see particularly Figs. 3e and 4e), so that the pair of protruding ribs 130 forms an "arrowhead" 132, which has an "open tip 134". The opening 134 between the two inclined parts 115, 125 is dimensioned such that a minimal distance D between two inclined parts 115, 125 is larger than a thickness of a bipolar plate 2 and smaller than a cell pitch, which will be explained in detail further below.

Besides the inclined parts 115, 125 forming the arrowhead, the protruding ribs 110, 120 of the cell voltage monitoring connector 100 may have further inclined surfaces as is illustrated in Figs. 3 and 4. As can be seen in Figs. 3 and 4, the front ends 112, 122 of the protruding ribs 110, 120 are also inclined in direction towards each other, so that the end faces 112, 122 also form arrowheads (see particularly Figs. 3c and 4c). This helps guiding the membrane electrode assembly 4 around the pair of protruding ribs 130 and exposing the bipolar plate 2 which shall be contacted, as will be explained further below with respect to Figs. 5, 6 and 7.

As is further illustrated in Figs. 3 and 4, the pairs of protruding ribs 130 on both sides 104, 106 are offset to each other. This in turn means that at one side, e.g. 104, the cell voltage monitoring connector 100 can only establish a contact with every second bipolar plate. The "left out" bipolar plates in turn are connected at the other side of the cell voltage monitoring connector 100.

The illustrated cell voltage monitoring connector 1 has further a fastening mechanism 190, which function will be explained in detail with reference to Fig. 7, for fastening the cell voltage monitoring connector 100 to a fuel cell stack 1. The illustrated fastening mechanism of Fig. 3 and 4 comprises two arms 191, 192, which are adapted to extend into a receiving opening 10 in the fuel cell stack and a expansion pin 193, which is intended to act on the arms 191, 192 and bend the arms 191, 192 to the outsides for securing the cell voltage monitoring connector 100 in the accommodation area 14 of the receiving opening 10. The expansion pin 193 can be already arranged at the front side 102 as is illustrated in Fig. 3, but the cell voltage monitoring connector 1 can also be provided just with the arms 191, 192 as illustrated in Fig. 4 and a expansion pin (not illustrated) can be inserted into a through hole 194 from the backside 108 and act on the arms 191, 192 after the cell voltage monitoring 11 PC24005 2024-05-28 connector 100 has been arranged in the receiving opening 10. The expansion pin 193 can be accessed by the hole 194 arranged in the housing 101, which extends through the housing body from the front side 102 to the back side 108.

Figs. 5, 6 and 7 illustrate the assembling procedure of the cell voltage monitoring connector 100 to the fuel cell stack 1.

As can be seen in Fig. 5a, the cell voltage monitoring connector 100 is arranged at the fuel cell stack 1 in such a way that the arrowheads 132-1 is aligned with the bipolar plate 2-1, whereas the next bipolar plate 2-2 is aligned with arrowhead 132-5 arranged at the other side of the cell voltage monitoring connector 100. Thus, in the illustrated cross-sectional view, the pair of protruding ribs 130-1, 130-2, 130-3 and 130-4 which are illustrated in detail are designed to accommodate only every second bipolar plate 2, namely 2-1, 2-3, 2-5, and 2-7 respectively. The intermediate bipolar plates 2-2, 2-4, 2-6, and 2-8 are adapted to be accommodated and electrically contacted by means of the pair of protruding ribs 130-5, 130- 6, 130-7 and 130-8 arranged at the other side of the cell voltage monitoring connector 100.

The arrowheads 132 have now the following function. As the cell voltage monitoring connector 100 is approaching the fuel cell stack as is illustrated in Fig. 5b, the membrane electrode assemblies 4-1, 4-2; 4-3, 4-4; 4-5, 4-6 and 4-7, 4-8 sandwiching the bipolar plates 2-1; 2-3; 2-5 and 2-7 and respectively also the intermediate bipolar plates on the other side, abut against the inclined part 115, 125 of the protruding ribs 110, 120. Since the membrane electrode assembly 4 and particularly the subgasket is flexible, the membrane electrode assembly 4-1, 4-2; 4-3, 4-4; 4-5, 4-6; 4-7, 4-8 bends along the inclined surface 115, 125, and in direction of the adjacent bipolar plate 2-2; 2-4, 2-6, 2-8, so that the bipolar plate 2-1, 2-3, 2- , 2-7, which shall be electrically contacted is exposed.

When the cell voltage monitoring connector 100 is further inserted into the fuel cell stack, the bipolar plate 2-1 enters the inner groove 140 by means of the opening 134 defined between the inclined surface 115 and 125 and is directed to the electrical contact elements 160, 170 (see Fig. 5c). The membrane electrode assembly 4 is now bended around the protruding ribs 110, 120 and enters together with the bipolar plates 2-2, 2-4, 2-6, 2-8, which are not to be electrically contacted at this side of the cell voltage monitoring connector 100 the outer groove 150 of the cell voltage monitoring connector 100. 12 PC24005 2024-05-28 As can be further seen in Fig. 5c, the bipolar plates 2-1, 2-3, 2-5, 2-7 which shall be electrically contacted on the illustrated side of the cell voltage monitoring connector 100 are inserted now into the receiving mouth 142 defined by the oppositely inclined parts 164, 174 of the electrical contact elements.

By further pressing the cell voltage monitoring connector 100 into the fuel cell stack 1, the bipolar plate 2 slips between the contact tips 165, 175, so that an electrical contact is established and the bipolar plate 2 is clamped between the contact elements 160, 170 (see Fig. 5d).

Since the cell voltage monitoring connector 100 can only contact a subgroup of bipolar plates, in the illustrated case 8 bipolar plates, but a fuel cell stack may comprise up to 450 or even more bipolar plates, a plurality of cell voltage monitoring connectors 100-1, 100-2, ..., can be arranged at the fuel cell stack as is illustrated in Figs. 6a, 6b. Due to the offset arrangement of the pairs of protruding ribs 130, the overall shape of the cell voltage monitoring connector 100 is stepped, as is seen in Fig. 6b. This allows for stacking the cell voltage monitoring connectors 100-1, 100-2, on top of each other, without leaving a bipolar plate unconnected.

Besides the clamping force applied by the contact tips 165, 175, the cell voltage monitoring connector 100 can be additionally attached to the fuel cell stack 1 by means of the fastening mechanism 190. Fig. 7 a, b illustrated the fastening of the cell voltage monitoring connector 100 by means of the fastening mechanism 190.

After the cell voltage connector 100 is fully inserted into the fuel cell stack 1, the cell voltage connector is located according to Fig. 7a. As can be seen the cell voltage connector 100 can be still be detached as there is only the clamping force of the electrical contact tips 165, 175 acting on the bipolar plate 2 for holding the cell voltage monitoring connector 100 in place.

For securing the cell voltage connector 100 the expansion pin 193 of the fastening mechanism 190 can be screwed back, which results in an expanding of the arms 191, 192 until the arms 191, 192 come into contact with the undercut 16, which results in a form fitting arrangement of the cell voltage connector 100 in the receiving opening 10 of the fuel cell stack 1 - see Fig. 7b. This can lock the cell voltage monitoring connector 100 in place geometrically without exerting any force. Thereby the cell voltage monitoring connector 100 13 PC24005 2024-05-28 is securely fastened to the fuel cell stack 1 and can be removed similarly easily by simply re- screwing the expansion pin 193.

Alternatively, the expansion pin, e.g. pins, rivets or rod like elements (not illustrated) can be introduced from the backside 108 of the cell voltage monitoring connector after the cell voltage monitoring connector 100 is arranged in the receiving opening 10. For that the expansion pin 193 may be introduced into the through hole 194, which in turn act then on the arms 191, 192. For detaching, the expansion pin 193 are removed from the through hole 194.

The arms 191, 192 may have additional hooks, which facilitate inserting the cell voltage monitoring connector 100 into the receiving opening 10, and also increase the holding force of the arms at the undercut 16.

Besides expanding the arms 191, 192 by means of the expansion pin 193 it is also possible that the arms 191, 192 are biased, e.g. spring loaded, and are adapted to automatically expand as soon as the cell voltage monitoring connector 100 is arranged in the receiving opening 10. ln summary the main advantageous features of this new cell voltage connector concept is providing a cell voltage connector which is easily attached to the fuel cell stack by using an expanding feature to lock it in place without exerting force of the cells. Additionally, providing protruding ribs which separate bipolar plate and membrane electrode assembly allows for a simplified arrangement of the cell voltage monitoring connector at the fuel cell stack and guarantees that the bipolar plate is not accidentally covered by the membrane electrode assembly in the area of the electric contact.

Claims (16)

CLaims

1. Cell voltage monitoring connector for fuel cell stack Claims: 1. Cell voltage monitoring connector (100) for monitoring a cell voltage of a fuel cell stack (1) having a plurality of alternatingly stacked bipolar plates (2) and membrane electrode assemblies (4), wherein the cell voltage monitoring connector (100) comprises a housing (101) made from an electrically insulating material and at least one electrical contact element (160; 170), which is made from an electrically conducting material and adapted to contact the bipolar plate (2), characterized in that the connector housing (101) has at least one protruding rib (110; 120) which is adapted to be inserted between a bipolar plate (2) and a membrane electrode assembly (4) of the fuel cell stack (1), wherein the at least one protruding rib (110; 120) is equipped with the electrical contact element (160; 170).

2. Cell voltage monitoring connector (100) according to claim 1, wherein the at least one protruding rib (110; 120) has guiding element which is adapted to guide the protruding rib (110; 120) between the bipolar plate (2) and the membrane electrode assembly (4).

3. Cell voltage monitoring connector (100) according to claim 2, wherein the protruding rib (110; 120) has a straight part (114; 124) which is, in the assembled state, arranged in parallel to the bipolar plate (2) and the membrane electrode assembly (4), respectively, and an inclined part (115; 125) which, in the assembled state, is inclined towards the bipolar plate (2), wherein the inclined part (115; 125) forms the guiding element.

4. Cell voltage monitoring connector (100) according to any one of the preceding claims, wherein the connector housing (101) has at least a pair of protruding ribs (130) each having a first protruding rib (110; 120) and a second protruding rib (110; 120), wherein each pair of protruding ribs (130) defines an accommodation groove for accommodate a single bipolar plate (2) of the plurality of bipolar plates, wherein the first protruding rib (110; 120) has a straight part (114; 124) which is parallel to the second protruding rib (110; 120) and, in the assembled state, parallel to the accommodated bipolar plate (2), and an inclined part (115; 125) which is inclined towards the second protruding rib (110; 120) and, in the assembled state, inclined towards the accommodated bipolar plate (2), and wherein the second protruding rib (110; 120) has a straight part (114; 124) which is parallel to the first protrudingPC24005 2024-05-rib (110; 120) and, in the assembled state, parallel to the accommodated bipolar plate (2), and an inclined part (115; 125) which is inclined towards the first protruding rib (110; 120) and, in the assembled state, inclined towards the accommodated bipolar plate (2).

5. Cell voltage monitoring connector (100) according to claim 4, wherein the dimensions of the housing (101) are adapted to the dimensions of the fuel cell stack (1) , so that a minimal distance (D) between the inclined parts (115; 125) of the pair of protruding ribs (130) is adapted to be smaller than a distance between two adjacent membrane electrode assemblies (4) sandwiching the accommodated bipolar plate (2) and larger than a thickness of the accommodated bipolar plate (2).

6. Cell voltage monitoring connector (100) according to any one of the preceding claims, wherein at least one protruding rib (110; 120) has a bipolar plate facing surface and the electrical contact element (160; 170) is arranged at bipolar plate facing surface.

7. Cell voltage monitoring connector (100) according to claim 6, wherein the electrical contact element (160; 170) is a spring element, particularly a flexible tongue, which is biased towards the bipolar plate (2).

8. Cell voltage monitoring connector (100) according to claim 6 or 7, wherein the electrical contact element (160; 170) has a fixed end (161; 171) with which the electrical contact element (160; 170) is attached to the protruding rib (110; 120) and a free end (162; 172), wherein at the free end (162; 172) a part of the contacting element is designed as inclined part (115; 125), which is inclined towards the protruding rib (110; 120) to which the electrical contact element (160; 170) is attached.

9. Cell voltage monitoring connector (100) according to any one of claims 4 to 8, wherein the pair of protruding ribs (130) is equipped with a pair of electrical contact elements (160; 170), so that in the assembled state an accommodated bipolar plate (2) is clamped between the electrical contact elements (160; 170).

10. Cell voltage monitoring connector (100) according to any one of the preceding claims, wherein the cell voltage monitoring connector (100) is adapted to accommodate a border area of the bipolar plate (2).PC24005 2024-05-

11. Cell voltage monitoring connector (100) according to any one of the preceding claims, wherein a plurality of protruding ribs (110; 120) and electrical contact elements (160; 170) are provided and the protruding ribs (110; 120) and electrical contact elements (160; 170) are arranged alternatingly at two opposite sides of the housing (101) so that the protruding ribs (110; 120) and electrical contact elements (160; 170) on one side of the housing (101) are adapted to contact every second bipolar plate (2).

12. Cell voltage monitoring connector (100) according to any one of the preceding claims, wherein the housing (101) has at least one attaching element which is adapted to secure the housing (101) at the fuel cell stack (1).

13. Cell voltage monitoring connector (100) according to claim 12, wherein the attaching element (190) is a clamping element, which comprises two flexible arms (191; 192), and wherein the housing (101) further comprise at least one an opening (194) for inserting a pin- like element (193), wherein the opening (194) is arranged in such a way that the pin-like element (193) is adapted to spread the flexible arms (191; 192), whereby the housing (101) is secured to the bipolar plate (2).

14. Fuel cell stack (1) comprising a plurality of bipolar plates (2) having an anode plate (6) and a cathode plate (8), which sandwich a plurality of membrane electrode assemblies (4) and at least one cell voltage monitoring connector (100) according to any one of the preceding claims.

15. Fuel cell stack (1) according to claim 14, wherein each bipolar plate (2) and each membrane electrode assembly (4) has at least one voltage monitoring connecting area in which each bipolar plate (2) and each membrane electrode assembly (4) has a recess (10) which form an elongated pocket along the length of the fuel cell stack (1) into which the housing (101) of the cell voltage monitoring connector (100) is at least partly insertable.

16. Fuel cell stack (1) according to claim 14 or 15, wherein at least one of anode plate (6) or cathode plate (8) has at least one spacer element (18; 19) for providing a predetermined distance (CP) between two adjacent bipolar plates (2), wherein the spacer element (18, 19) is preferably arranged in the vicinity of the recess (10).