PROCESS ORDER AND METHOD FOR MANUFACTURING A BATTERY MODULE

Abstract

The invention relates to a process arrangement for manufacturing a battery module comprising a module housing (1) in which a cell stack (3), in particular of pouch cells, is arranged and which is subjected to a mechanical preload (Fv) in a stacking direction between module housing walls (5, 7), a pressing station in which the cell stack (3) is subjected to a mechanical preload (Fv) in a pressing process by means of a workpiece carrier (21), and an insertion station in which a pull rod (43) pulls the cell stack (3) out of the workpiece carrier (21) into the module housing (1) in an insertion process while maintaining the mechanical preload (Fv). According to the invention, pull plates (27) are provided as an assembly aid to maintain and / or uniformly distribute the mechanical preload (Fv) of the cell stack (3) during the insertion process.

Description

Technical area

[0001] The invention relates to a process arrangement for producing a battery module according to the preamble of claim 1 and to a method for producing such a battery module according to the preamble of claim 10.

[0002] A battery module for a high-voltage battery system may comprise a module housing in which a cell stack is arranged. The cell stack is constructed from a plurality of pouch cells arranged one behind the other in the stacking direction. In the installed position, the cell stack is subjected to a mechanical preload between the module housing walls to compensate for volume changes in the battery cells during charging / discharging processes.

[0003] In a generic method for manufacturing such a battery module, carried out by the applicant / patent holder, the cell stack produced in a stacking process is subjected to a pressing process in which the cell stack is mechanically prestressed using a workpiece carrier. This is followed by a machining process in which, among other things, the cell conductors of the battery cells are electrically interconnected using busbars. A drawing-in process is then carried out in which the cell stack is drawn from the workpiece carrier into the module housing. During this process flow, the workpiece carrier remains permanently attached to the cell stack to keep it mechanically prestressed.

[0004] One challenge during the insertion process is maintaining the tensioned state of the cell stack during the transition from the workpiece carrier to the module housing, ensuring that the cell stack is positioned securely and without damage in the module housing. Pouch cells may be subjected to surface pressure during the insertion process, but this pressure should be distributed as evenly as possible across the entire cell body. If the cell membrane is subjected to localized stress, pressure points form, which can cause immediate or long-term damage to the cell interior.

[0005] Processes in which battery cells are placed in a module housing are also known, for example, from US 2022 / 0320569 A1, from DE 10 2019 109 715 A1 or from AT 519967 A4. State of the art

[0006] In the current state of the art, a localized or uneven load builds up on the battery cells on the outside of the stack during the pulling-in process. Depending on the force applied, such uneven loading can lead to cell damage. As increasingly powerful cells are being used in modern electromobility, cell swelling also increases in many cases. This leads to higher compression forces, which are necessary to continue to install such pouch cells in the module housing. The increasing compression forces also increase the degree of stress or damage exerted on the cells during the pulling-in process in the current state of the art. Furthermore, the clamping forces with more powerful battery cells can sometimes become so great that the pulling-in processes known from the current state of the art are no longer sufficient to overcome frictional resistance to the module housing and to insert the cell stack into the module housing. Description of the invention

[0007] The object of the invention is to provide a process arrangement and a method for manufacturing a battery module in which the cell stack can be drawn into the module housing of the battery module in a simple manner and without damage during the drawing-in process, particularly even under high mechanical prestress, compared to the prior art.

[0008] The object is achieved by the features of claim 1 or 10. Preferred developments of the invention are disclosed in the subclaims.

[0009] The invention relates to a process arrangement for manufacturing a battery module with a module housing in which a cell stack, in particular made of pouch cells, is arranged. In the assembled position, the cell stack installed in the module housing is subjected to a mechanical prestress in the stacking direction between module housing walls. The process arrangement for manufacturing such a battery module comprises a pressing station in which the cell stack is subjected to mechanical prestress in a pressing process using a workpiece carrier. The process arrangement also comprises a drawing-in station. In the drawing-in station, a tension rod draws the cell stack from the workpiece carrier into the module housing while maintaining the mechanical prestress.According to the characterizing part of claim 1, the mechanical prestress of the cell stack at the transition from the workpiece carrier to the module housing is maintained and evenly distributed throughout the cell stack as follows: The process arrangement includes tension plates that serve as assembly aids during the insertion process. The tension plates are arranged at both ends of the cell stack and are clamped together with the cell stack in the workpiece carrier. Each of the tension plates projects beyond the cell stack in the insertion direction by a tension plate projection.

[0010] The pulling-in process is therefore structured as follows: At the beginning of the pulling-in process, the tension plate projections leading the cell stack are retracted into the module housing and, building up a uniform mechanical preload, slide against the inside of the respective module housing wall. As the pulling-in process continues, the tension rod pulls the cell stack trailing the tension plate projections into the module housing. By using the two tension plates according to the invention, it is possible to apply a high mechanical preload to the battery cells without subjecting them to specific points during the pulling-in process. The tension plates serve both as protection for the two stack ends and as force distributors, introducing point or linear forces across the entire surface of the respective cell stack end.Furthermore, the tension plates provide a stable point of application, for example, to transfer tensile force into the cell stack. The tensile force is absorbed by the battery cells on the outside of the stack across their entire surface.

[0011] The further the cell stack is pulled into the module housing during the insertion process, the larger the contact area between the two joining partners becomes. In a module requiring high mechanical preload, this frictional contact between the joining partners can lead to damage to the cell stack in the prior art. With the help of the tension plates according to the invention, the cell stack can be reliably pulled in even with high mechanical preload, since the entire mechanical preload is introduced into the module housing by the tension plates.

[0012] In a technical implementation, the module housing can comprise a base body formed as an extruded profile, which, viewed in the insertion direction, has two opposing open housing sides. These sides can be aligned with the cell stack during the insertion process. The tie rod can therefore be guided through the open sides of the module housing during the insertion process, resulting in a favorable introduction of the insertion force into the cell stack.

[0013] In a specific embodiment, the insertion process can be divided into a first insertion process step and a second insertion process step. In the first insertion process step, the tension rod pulls the tension plates with the intermediate cell stack, acting as a motion-coupled pre-assembly unit, from the workpiece carrier into the module housing until a cell stack end position is reached. In the second process step, the two tension plates are removed from the module housing so that no assembly aids remain in the module housing.

[0014] The cell stack's end position is preferably reached when the cell stack comes into contact with a retainer during the first pulling-in process step. This means that once the cell stack's end position is reached, further movement of the cell stack in the pulling-in direction is prevented by the retainer. In this case, the two tension plates can be pulled out of the module housing in the second pulling-in process step, preferably with the aid of the tension rod. In the second pulling-in process step, the tension rod is moved further in an extraction direction that coincides with the pulling-in direction. As a result, the tension plates - now decoupled from the cell stack - are pulled out of an open side of the module housing facing away from the workpiece carrier.

[0015] It is preferred if a clearance is formed between the tie rod and the cell stack, viewed in the pull-in direction. The retainer can be positioned in the clearance during the second pull-in process step. In this case, the retainer can exert a retaining force on the cell stack over a sufficiently large area and in alignment with the pull-in direction.

[0016] The cell conductors of the battery cells stacked in the cell stack protrude from the cell stack, perpendicular to the stacking direction, for example, on both sides. The cell conductors of the cell stack are electrically interconnected via busbars. These are integrated into a plastic carrier. In addition to the busbars, the plastic carrier can also contain other electrical components, such as temperature sensors. The electrical interconnection of the battery cells is carried out in a machining process that takes place after the pressing process. In the second drawing-in process step, the retainer is therefore not in direct contact with the easily deformable cell conductors, but rather in contact with the plastic carrier.

[0017] In a battery module that requires a high mechanical prestress of the cell stack, there is a risk that the sliding properties of the respective tension plate will no longer be sufficient to pull the tension plates out of the module housing without damage in the second pulling-in process step. Against this background, the sliding ability of the tension plates can be increased as follows: A sliding film can be used as a lubricant. The sliding film can preferably be positioned on a fold-over basis as a loop-shaped double layer between the respective tension plate and the cell stack end. The loop-shaped double layer can consist of an outer layer on the tension plate side and an inner layer on the cell stack side, viewed in the stacking direction. The outer layer and the inner layer are preferably each extended beyond the cell stack in the pulling-in direction with an outer layer film end and an inner layer film end.This allows the outer layer and / or the inner layer of the sliding film to be easily subjected to tensile forces to control the sliding properties of the respective tension plate. Such control of the sliding properties during the drawing-in process can preferably be designed as follows: In the first drawing-in process step, the two film ends of the inner layer and the outer layer, together with the respective tension plate, can be connected to the tension rod in a force-transmitting manner. This creates a sufficiently large friction force buildup between the cell stack, the (non-movable) double film layer, and the tension plate to maintain the movement coupling between the cell stack and the respective tension plate in the first drawing-in process step.

[0018] In the second drawing-in process step, however, only the outer layer film end and the respective tension plate are connected to the tension rod in a force-transmitting manner. The inner layer film end, on the other hand, is detached from the tension rod, meaning it is not subjected to the drawing-in force during the second drawing-in process step. This initiates a peeling process between the outer and inner layers, in which the outer and inner layers peel off each other with minimal friction. During the peeling process, the inner layer (not subjected to the drawing-in force) remains at the end of the cell stack, while the outer layer moves along with the tension plate.

[0019] The outer layer film end can be permanently connected to the respective tension plate in a force-transmitting manner, for example via a screw or clamp connection. It is preferred if the screw or clamp connection is implemented using clamping jaws. These can be clamped against each other with the outer layer film end interposed. The tension rod can be releasably supported in the threading direction on the clamping jaws of the two tension plates, in particular with the inner layer film end clamped between them. In this case, the following process can be implemented: After completion of the first threading process step, the tension rod is briefly released from the clamping jaws of the tension plates in order to release the intermediate clamping of the inner layer film end. This ensures that the inner layer film end is no longer connected to the tension rod in a force-transmitting manner during the second threading process step.In the second insertion process step, the peeling process already described takes place between the inner and outer layers of the sliding film.

[0020] The battery cells are preferably not stacked directly next to each other, but rather with compression pads of varying thicknesses, such as foam material, interposed. It is preferred if the cell stack is terminated at each of its two stack ends with such a compression pad. In this case, the compression pad arranged at the stack end is in contact with the respective tension plate. The tension plate therefore has no direct contact surface with the battery cell arranged at the stack end, thus protecting it from mechanical damage caused by the tension plates.

[0021] An embodiment of the invention is described below with reference to the attached figures: They show: Fig. 1 to 12 different views illustrating a method for manufacturing a battery module using a process arrangement according to the invention.

[0022] In the Fig. Figure 1 illustrates a finished battery module to the extent necessary for understanding the invention. Accordingly, the battery module comprises a cuboid module housing 1 in which a cell stack 3 is arranged. A base body of the module housing 1 is an extruded aluminum profile comprising a top wall 5, a bottom wall 7, a Fig. 1 front side wall 9 and a rear side wall (not shown). The base body has Fig. 1 has two open housing sides 11, which can be closed by means of end plates 13 via laser welding. The cell stack 3 is in the Fig. 1 is constructed from pouch cells which are subjected to a mechanical prestress Fv in a stacking direction between the top wall 5 and the bottom wall 7. The cell stack 3 also has lateral plastic supports 15 with busbars (not shown) integrated therein to support the lateral cell conductors 17 ( Fig. 2 or Fig. 3) of the cell stack 3 to be electrically interconnected.

[0023] The following is based on the Fig. 2 to 12 a process for the manufacture of the Fig. 1 described: Accordingly, in a stacking station not shown, a still unstressed cell stack 19 ( Fig. 2) and is then placed in a pressing station ( Fig. 4) is clamped in the stacking direction by a workpiece carrier 21 under the mechanical preload Fv. The workpiece carrier 21 has in the Fig. 4 has two pressure plates 23 which are clamped against each other by means of a clamping unit (not shown) with the cell stack 3 interposed.

[0024] This is followed by a processing process ( Fig. 5), in which the busbars located in the lateral plastic supports 15 are electrically connected to the cell conductors 17 of the cell stack 3 by laser welding. The assembly thus formed becomes a pulling station ( Fig. 6 and Fig. 7). In the drawing-in station, a drawing-in process is carried out in which the cell stack 3 is drawn while maintaining the mechanical prestress F V is pulled from the workpiece carrier 21 into the base body of the module housing 1.

[0025] The core of the invention lies in the design of the insertion process. This is designed to ensure the most uniform possible loading of the cell stack 3 during its transition from the workpiece carrier 21 into the module housing base body.

[0026] For this purpose, the process arrangement has two tension plates 27, for example made of metal, as assembly aids. The tension plates 27 are already in the stacking process ( Fig. 2) are arranged at the two stack ends of the cell stack 3. In the subsequent pressing process ( Fig. 4) the tension plates 27 are clamped together with the cell stack 3 in the workpiece carrier 21. As can be seen from the figures, each of the two tension plates 27 projects beyond the cell stack 3 in a pulling-in direction E with a tension plate projection 32. The tension plate projections 32 of both tension plates 27 can be brought into engagement with a tension rod 43 during the pulling-in process.

[0027] The stack ends of the cell stack 3 are according to the Fig. 3 is formed by compression pads 29, for example, made of foam, so that direct contact of the tension plates 27 with the outer battery cells of the cell stack 3 is avoided. Additional compression pads 29 are arranged in the cell stack 3 between adjacent battery cells.

[0028] To increase the sliding properties, each of the tension plates 27 has a sliding film 31 ( Fig. 8 to 12). The sliding film 31 is positioned on the turn-over as a loop-shaped double layer between the respective tension plate 27 and the cell stack end, with an outer layer 33 on the tension plate side, viewed in the stacking direction, and an inner layer 35 on the cell stack side, which is fastened to a film fold 36 ( Fig. 11 and Fig. 12) merge into one another. The outer layer 33 and the inner layer 35 are according to the Fig. 8 are each extended in a pull-in direction E beyond the cell stack 3 with an outer layer film end 37 and an inner layer film end 39. The outer layer film end 37 is connected to the respective tension plate 27 via a clamping connection in a force-transmitting manner.

[0029] The clamp connection is in accordance with Fig. 8 to 10 are realized using clamping jaws 41. These are clamped to the tension plate projection 32 by means of a screw connection (not shown), with the outer layer film end 37 interposed. Furthermore, the pull-in station has the tie rod 43, which is releasably supported in the pull-in direction E on the clamping jaws 41 of the two tension plates 27, specifically with the inner layer film end 39 clamped between them.

[0030] The insertion process is divided into a first insertion process step and a second insertion process step. To prepare for the first insertion process step, the module housing base body, viewed in the insertion direction E, is aligned with its opposite open housing sides 11 in alignment with the cell stack 3, as shown in the Fig. 6 is indicated. The tie rod 43 is guided through the open housing sides 11 of the module housing base body during the insertion process. In the first insertion process step, the two film ends 37, 39 together with the respective tension plate 27 are connected to the tie rod 43 in a force-transmitting manner. This results in a sufficiently large friction force build-up between the cell stack 3, the sliding film double layer 31 and the tension plate 27. The tension plates 27 together with the intermediate cell stack 3 can thus be drawn into the module housing base body as a motion-coupled pre-assembly unit from the workpiece carrier 21 in the first insertion process step. At the beginning of the first insertion process step, according to the Fig. 6 first inserts the tension plate projections 32, which precede the cell stack 3, into the module housing base body and, while building up a mechanical prestress Fv, slides them against the bottom and top walls 5, 7. Subsequently, the tension rod 43 pulls the cell stack 3, which trails the tension plate projections 32, into the module housing base body.

[0031] The first insertion process step ends when the cell stack reaches its final position ( Fig. 7). This is defined by a retainer 45, which projects into a clearance 47 between the tie rod 43 and the cell stack 3. The retainer 45 acts as a movement stop, preventing further movement of the cell stack 3 in the retraction direction E.

[0032] In preparation for the second pulling-in process step, the tension rod movement in the pulling direction E is interrupted. The tension rod 43 is briefly released from the two clamping jaws 41 ( Fig. 8) so that the inner layer film end 39 is no longer in force-transmitting connection with the tension rod 43.

[0033] In the second drawing-in process step ( Fig. 7 and Fig. 10), the tension rod 43 pulls the two tension plates 27 - now decoupled from the cell stack 3 - out of the module housing side 11 facing away from the workpiece carrier 21 in a pull-out direction A that coincides with the pull-in direction E.

[0034] In the second drawing-in process step, only the outer layer film end 37 and the respective tension plate 27 are subjected to the drawing-in force of the tension rod 43, while the inner layer film end 39 is not connected to the tension rod 43. In this way, a peeling process ( Fig. 11 and Fig. 12) between the outer layer 33 and the inner layer 35. During the peeling process, the outer and inner layers 33, 35 peel off each other with low friction. During the peeling process, the inner layer 35 remains at the end of the cell stack, while the outer layer 33 moves in conjunction with the tension plate 27.

[0035] By connecting or disconnecting the inner layer film end 39 to / from the tie rod 43, the sliding properties between the respective tension plate 27 and the adjacent cell stack end can be controlled as follows during the drawing-in process: In the first drawing-in process step, the two film ends 37, 39 and the respective tension plate 27 are connected to the tie rod 43 in a force-transmitting manner. This reduces the sliding properties between the tie plate 27 and the adjacent cell stack end in order to ensure the movement coupling between the cell stack 3 and the tie plate 27. In the second drawing-in process step, the outer layer film end 37 and the respective tie plate 27 are connected to the tie rod 43, while the inner layer film end 39 is not connected to the tie rod 43. This initiates the peeling process ( Fig. 10 and Fig. 11) is initiated. Compared to the first insertion process step, the peeling process increases the sliding properties between the tension plate 27 and the adjacent cell stack end.

[0036] During the peeling process, the tension plate 27 and the foil edge 36 travel different distances. The distance travelled by the tension plate 27 (in the Fig. 12 indicated by the arrow I) is twice as large as the distance travelled by the foil fold 36 (in the Fig. 12 indicated by arrow II).

[0037] After the tension rod 43 has completely pulled the two tension plates 27 out of the module housing base body, it is moved further in the pull-out direction A until the foil fold 36 is also completely pulled out of the module. After completion of the second pulling-in process step, the battery module consists of the cell stack 3 and the module housing base body, ie, there is no assembly aid in the battery module.

[0038] Following the insertion process, the films 31 can be folded back into the center. The films 31 remain attached to the two tension plates 27. This allows them to be reused for the next insertion process until they show signs of wear. In this case, the sliding films 31 can be removed from the tension plates 27 and replaced with new ones. To minimize friction and possible abrasion between the tension plate 27 and the adjacent bottom or top wall 5, 7, the tension plate 27 can be coated on its outer side, for example, with Teflon. LIST OF REFERENCE SYMBOLS 1 module housing 3 cell stacks 5 Ceiling wall 7 Floor wall 9 Side wall 11 open housing side 13 Front plate 15 plastic carriers 17 cell arresters 19 cell stacks 21 workpiece carriers 23 Tension plate 24 clamping unit 25 pulling station 27 Tension plate 29 compression pad 31 sliding film 33 tension plate side outer layer 32 Tension plate overhang 35 cell stack side inner layer 36 foil folding 37 Outer layer film end 39 Inner layer film end 41 clamping jaws 43 tie rods 45 retainers 47 Release E retraction direction A Pull-out direction Fv mechanical preload I distance travelled by the tension plate 27 during the peeling process II Distance travelled by the film fold 36 during the peeling process

Claims

[1] Process arrangement for the production of a battery module with a module housing (1) in which a cell stack (3), in particular of pouch cells, is arranged, which is subjected to a mechanical prestress (Fv) in a stacking direction between module housing walls (5, 7), with - a pressing station in which the cell stack (3) can be placed under mechanical prestress (Fv) in a pressing process by means of a workpiece carrier (21), and - a drawing-in station in which a tie rod (43) draws the cell stack (3) from the workpiece carrier (21) into the module housing (1) in a drawing-in process while maintaining the mechanical prestress (Fv), characterized bythat, in order to maintain and / or evenly distribute the mechanical prestress (Fv) of the cell stack (3) during the drawing-in process, tension plates (27) are provided as assembly aids, that in particular the tension plates (27) are arranged at both stack ends of the cell stack (3) and are clamped together with the cell stack (3) in the workpiece carrier (21), that in particular each of the tension plates (27) projects beyond the cell stack (3) in the drawing-in direction (E) with a tension plate projection (32), so that in particular at the beginning of the drawing-in process the tension plate projections (32) leading the cell stack (3) move into the module housing (1) and are supported slidingly on the respective module housing wall (5, 7) while building up the mechanical prestress (Fv), and that in particular during the further course of the drawing-in process the tension rod (43) pulls the cell stack (3) trailing the tension plate projections (32) into the module housing (1) moves in. [2] Process arrangement according to claim 1, characterized by that the module housing (1) has, viewed in the drawing-in direction (E), two opposite open housing sides (11) which are aligned in alignment with the cell stack (3) in the drawing-in direction (E) during the drawing-in process, so that in particular the tie rod (43) can be guided through the open housing sides (11) of the module housing (1) during the drawing-in process. [3] Process arrangement according to claim 1 or 2, characterized by that the pulling-in process is divided into a first pulling-in process step, in which the tension rod (43) pulls the cell stack (3) and the tension plates (27) as a movement-coupled pre-assembly unit from the workpiece carrier (21) into the module housing (1), specifically until a cell stack end position is reached, and into a second pulling-in process step, in which the two tension plates (27) can be removed from the module housing (1). [4] Process arrangement according to claim 3, characterized byin that a retainer (45) is provided as a movement stop for carrying out the second pulling-in process step, and in that the retainer (45) prevents further movement of the cell stack (3) in the pulling-in direction (E) once the cell stack end position has been reached, and / or in that in the second pulling-in process step the tie rod (43) pulls the tie plates (27) out of an open housing side (11) of the module housing (1) facing away from the workpiece carrier (21) in a pulling-out direction (A) that coincides with the pulling-in direction (E), in a manner that is decoupled from movement by the cell stack (3), and / or in that, viewed in the pulling-in direction (E), a clearance (47) is formed between the tie rod (43) and the cell stack (3), in which clearance the retainer (45) can be positioned during the second pulling-in process step. [5] Process arrangement according to one of the preceding claims, characterized byin that, in order to increase the sliding properties, the respective tension plate (27) is supported at the end of the stack and / or at the adjacent module housing wall (5, 7) with the interposition of a lubricant. [6] Process arrangement according to claim 5, characterized by that the lubricant is a sliding film (31), and that in particular the sliding film (31) is positioned on the turn-up as a loop-shaped double layer between the tension plate (27) and the cell stack end, in particular with an outer layer (33) on the tension plate side, viewed in the stacking direction, and an inner layer (35) on the cell stack side, and that the outer layer (33) and the inner layer (35) each have an outer layer film end (37) and an inner layer film end (39) extended beyond the cell stack (3) in the pull-in direction (E). [7] Process arrangement according to claim 6, characterized bythat in the first drawing-in process step, the two film ends (37, 39) and the respective tension plate (27) are subjected to the drawing-in force of the tension rod (43), so that in particular a sufficiently large friction force builds up between the cell stack (3), the sliding film double layer (31) and the tension plate (27) in order to ensure the movement coupling between the cell stack (3) and the tension plate (27), and / or that in the second drawing-in process step, the outer layer film end (37) and the respective tension plate (27) are subjected to the drawing-in force of the tension rod (43), while the inner layer film end (39) is not in a force-transmitting connection with the tension rod (43), so that in particular in the second drawing-in process step, a peeling process takes place between the outer layer (33) and the inner layer (35), in which the outer and inner layers (33, 35) adhere to one another with peel off with low friction, leaving the inner layer (35) at the end of the cell stack,while the outer layer (33) moves along with the tension plate (27). [8] Process arrangement according to claim 6 or 7, characterized by that the outer layer film end (37) is connected to the respective tension plate projection (32) in a force-transmitting manner, in particular via a screw or clamp connection, and that in particular the screw or clamp connection is realized by means of clamping jaws (41) which are clamped together with the outer layer film end (39) interposed, and that in particular the tension rod (43) is releasably supported in the pulling-in direction (E) on the clamping jaws (41) of the two tension plates (27), in particular with the inner layer film end (39) being clamped intermediately, and that in particular after completion of the first pulling-in process step the intermediate clamping of the inner layer film end (39) can be released, in particular by briefly releasing the tension rod (43) from the clamping jaws (41) of the tension plates (27). [9] Process arrangement according to one of the preceding claims, characterized by that the cell stack (3) is terminated at each of its two stack ends with a compression pad (29). [10] Method for manufacturing a battery module with a module housing (1) in which a cell stack (3) is arranged, which is subjected to a mechanical prestress (Fv) in a stacking direction between module housing walls (5, 7), in particular by means of a process arrangement according to one of the preceding claims with - a pressing process in which the cell stack (3) is placed under mechanical prestress (Fv) by means of a workpiece carrier (21), and - a drawing-in process in which a tension rod (43) draws the cell stack (3) from the workpiece carrier (21) into the module housing (1) while maintaining the mechanical prestress (Fv), characterized byin that, in order to maintain the mechanical prestress (Fv) of the cell stack (3) during the drawing-in process, tension plates (27) are provided as an assembly aid, in particular in that the tension plates (27) are arranged at both stack ends of the cell stack (3) and are clamped together with the cell stack (3) in the workpiece carrier (21), in particular in that each of the tension plates (27) projects beyond the cell stack (3) in the drawing-in direction (E) with a tension plate projection (32), so that, in particular at the start of the drawing-in process, the tension plate projections (32) leading the cell stack (3) move into the module housing (1) and are supported in a sliding manner on the respective module housing wall (5, 7) while building up the mechanical prestress (Fv), and in particular in the further course of the drawing-in process, the tension rod (43) draws the cell stack (3) trailing the tension plate projections (32) into the module housing (1).

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