Cell contacting system in a battery module or pack

Abstract

The invention relates to a cell contacting system by means of which elementary storage cells are electrically connected to one another in series and / or parallel circuits in order to form a battery module and / or pack, and at least one electrical contact for a pole of an elementary storage cell is in the form of an electrical fuse element in the cell contacting system. The aim of the invention is to improve a cell contacting system comprising electrical fuse elements. This is achieved in that the cell contacting system (1) is provided with fuse elements (6, 8) for each elementary storage cell (3) as protection against a low-resistance short circuit and as protection against a medium-resistance short circuit.

Description

[0001] Cell contacting system in a battery module or pack

[0002] The present invention relates to a cell contacting system in which elementary storage cells are electrically interconnected in series and / or parallel circuits to form a battery module or pack, and in which at least one electrical contact to a pole of an elementary storage cell is designed as an electrical safety element.

[0003] It is known that a battery system comprises at least one battery module, with several battery modules potentially being combined to form a pack. All these units are constructed from a multitude of elementary storage cells interconnected by a cell contacting system to achieve predetermined electrical connection values ​​for current flow at a specific voltage and a predetermined electrical storage capacity. Such cell contacting systems comprise cell connectors made of aluminum or copper sheet, which are electrically contacted at the respective electrical poles of the relevant elementary storage cells in a suitable manner. The cell connectors are usually mounted on a plastic carrier, which, among other things, protects the metallic component of the cell contacting system from other current-carrying components and the cells themselves, both mechanically and electrically, including against short circuits.

[0004] The state of the art for battery modules and packs based on such elementary cells or storage cells for use in vehicles generally stipulates that they have application-specific formats with the densest possible packing of the aforementioned cells in a typically cylindrical format. Currently common cell formats are known, for example, under the designations 18650, 21700, and 46800, with increasing electrical power and physical mass in this series. It is known, among other things, from EP 2 008 354 Bl and EP 2 416 405 Bl, that electrical fuses are provided in the cell contacting system to safely disconnect even a single elementary storage cell from a current path in the event of an electrical fault and the associated excessive current flows. In order to prevent overheating from affecting a single cell to, in the event of a fault, i.d.R.To prevent damage to closely spaced memory cells, each cell is equipped with a safety element, such as a bond wire. This safety element is designed to irreversibly disconnect the affected memory cell from the overall system in the event of an overload. This approach can easily be applied to cuboid-shaped elementary memory cells.

[0005] For the fuse element to trip reliably, it must have a defined constriction in the current path connecting a basic memory cell to the cell contacting system. The fuse element is dimensioned to withstand a predetermined thermal overload caused by a specified short-circuit current.

[0006] The present invention aims to improve a cell contacting system comprising electrical safety elements.

[0007] This problem is solved according to the invention by a cell contacting system in which elementary storage cells are electrically interconnected in series and / or parallel circuits to form a battery module and / or pack, with the features of claim 1, in that the cell contacting system provides safety elements as protection against a low-resistance short circuit and as protection against a medium-resistance short circuit of each elementary storage cell.

[0008] For a fuse element, an electro-thermal trip is a normal occurrence. The melting or tripping of the fuse element occurs due to a low-resistance short circuit in the battery system, usually a short circuit between the positive and negative terminals of a battery cell with a very high current flow. One cause of such a fault can be a metallic part that, for example, becomes dislodged from the cell contact system due to a strong vibration and, over a short distance, causes this short circuit by connecting the positive terminal of the cell to the negative terminal of the battery cell.

[0009] In addition to the electrical short circuit described above, a cell-internal fault leading to a thermal event with strong heating of the affected elementary storage cell represents a second fault scenario that must also necessarily result in the shutdown of the affected elementary storage cell by triggering a fuse. The development of elementary storage cells shows a clear trend towards ever larger cells. Large storage cells are characterized not only by a large capacity for storing electrical energy, but also by a large thermal mass, which prevents reliable disconnection by a fuse designed solely for extremely high current flows in the event of a medium-resistance short circuit. A so-called...A fuse element designed to reliably interrupt a medium-resistance short circuit must be dimensioned so that melting and tripping of the fuse element is caused by the heat emanating directly from the relevant elementary storage cell during a thermal runaway or thermal event. In contrast to an electrical short circuit, this thermal fault condition is characterized by a still comparatively moderate current flow, which is generally significantly lower than the short-circuit current of a so-called low-resistance short circuit as described above.

[0010] The operational reliability of a battery module or pack is therefore significantly increased by providing safety elements in a cell contacting system according to the invention as protection against a low-resistance short circuit and as protection against a medium-resistance short circuit in each elementary storage cell. This covers both fault scenarios, namely an electrical short circuit at the poles and a thermal event, in the respective elementary storage cell, each of which now leads to the shutdown of the respective elementary storage cell to protect the battery system.

[0011] Advantageous further developments are the subject of the respective dependent claims. Accordingly, the fuse element, designed for a medium-resistance short circuit, is arranged and connected to the metallic stamped-bent structure of the cell contacting system, facing a respective cell pole of the elementary storage cells. The medium-resistance short circuit, as an internal cell fault, heats a cell pole significantly more than a so-called cell terminal or a cell cup that is electrically insulated from the cell pole and has a comparatively large surface area. To optimize heat input and ensure rapid tripping of the respective fuse element, a cell pole is therefore electrically and thermally connected to the relevant fuse elements.In one embodiment of the invention, a separate fuse element designed for a low-resistance short circuit is provided at each elementary memory cell, wherein a fuse element designed for a low-resistance short circuit is connected in series with the fuse element designed for a medium-resistance short circuit at each of the elementary memory cells. For reasons of space, it is preferred that a fuse element designed for a low-resistance short circuit of an elementary memory cell is arranged at a cell terminal. This makes it possible to connect differently designed fuse elements of the cell contacting system to the oppositely polarized terminals of the elementary memory cell.

[0012] Preferably, a fuse element comprises a mechanical compensating section in the form of a section of sheet metal bent in a substantially S-shape, resembling a loop. This compensating section merges into the fuse element at one end and has a notch at the opposite end. This notch acts as a thermal barrier against the subsequent cell contacting system and prevents excessive heat dissipation from the fuse element. Thus, the compensating section forms a small thermal capacitance, ensuring that the fuse element is at essentially the same temperature level at both connection points. This design feature ensures compliance with a predetermined thermal tripping characteristic of the fuse element, which is designed for a medium-resistance short circuit.

[0013] In a preferred embodiment of the invention, the locking element is subjected to mechanical tensile or bending stress. This stationary mechanical stress acting on the locking element does not affect the tripping behavior of the locking element itself, but advantageously serves to pull apart the remaining ends of the fused locking element when the locking element is switched off, thereby preventing any further electrical connection between these ends by significantly increasing the air gap between them.

[0014] In a further development of the invention, the mechanical tensile or bending stress acting on the locking element contacted with an elementary memory cell is adjustable by means of a shear edge of a thermally stable insert or a section of a plastic carrier of the cell contacting system, or in another way, by designing a connection surface to be displaceable by a distance when connected to a pole of the elementary memory cell. In exemplary embodiments, an insert or a section of a plastic carrier is spring-elastically pre-tensioned after contact of the locking element with an elementary memory cell.

[0015] In a particularly preferred embodiment of the invention, a shear edge is dimensioned such that, when the locking element melts, the shear edge is designed to engage between or slide between the melted ends of the locking element, thereby releasing the spring-elastic preload. This increases the electrical insulation between the melted ends of the locking element and also prevents any possibility of unintentional electrically conductive reconnection in the area of ​​the separated locking element.

[0016] Preferably, a flux is provided on or attached to the thermally or medium-resistance short-circuit tripping fuse element. The flux prevents the fuse element from tripping in the event of a medium-resistance short circuit, thus preventing the formation of an oxide layer on the metal of the fuse element. This feature is particularly important when using aluminum and its alloys as the material for the fuse element. In one embodiment of the invention, the fuse element designed for a low-resistance short circuit is also equipped in an analogous manner.

[0017] In a further development of the invention, the flux is coated externally with a protective layer and, in particular, covered by a layer of lacquer. The lacquer layer provides mechanical and / or thermal protection for the flux on the locking element.

[0018] In summary, connecting an elementary storage cell via safety elements designed to trigger due to an electrical short circuit and a thermal event in the elementary storage cell in question significantly increases the operational reliability of a battery module or pack through appropriate design adaptation of the cell contacting system.

[0019] Further features and advantages of embodiments of the invention are explained in more detail below with reference to exemplary embodiments and the drawing. The drawing schematically shows:

[0020] Figure 1: a detail of a top view of an embodiment of a cell contacting system, indicating the contacting of some elementary memory cells with a fuse element at each cell pole and cell terminal; Figures 2a - 2c: a perspective view with a corresponding top view of an embodiment of a fuse element for protection against a medium-resistance short circuit, indicating a further development with a side view;

[0021] Figures 3a and 3b: a perspective view and a top view of an exemplary embodiment of a safety element for protection against a low-resistance short circuit;

[0022] Figures 4a - 4c: a side view of a further embodiment of a fuse element for protection against a medium-resistance short circuit before and after installation and after the fuse element has tripped and

[0023] Figures 5a - 5c : a top view of a section of a cell contacting system known from the prior art with locking elements at the cell poles of each elementary storage cell of a battery system with a section magnification and a side view thereof .

[0024] Across the various illustrations of the drawing, the same reference symbols are always used for identical elements. Without limiting the invention, the following discussion assumes a flat housing as a cuboid body for a module and / or pack of a high-voltage battery system built therefrom, in which, due to the high number and density of the electrical connections, elementary storage cells of a cylindrical design are considered. However, it is obvious to those skilled in the art that in the same 03860PWQ

[0025] Adaptations to other spatial shapes are also possible, moving away from flat housings, e.g., to a polygonal or even curved housing, to improve the utilization of available installation space. The battery module is designed for storing electrical energy from any source, such as an external charging station or a generator-driven electric motor, and for supplying stored electrical energy to power, among other things, the drive motor and auxiliary and assistance systems. Furthermore, adaptations to applications outside of terrestrial vehicles are easily possible, particularly for stationary storage devices. The described cell contacting systems according to the invention can also be transferred to a cell contacting system for prismatic or pouch storage cells without further drawings.

[0026] In high-voltage battery storage systems, many individual cells are connected in modules and / or packs to form a larger system via series and / or parallel connections. If a single cell fails, for example, due to an internal short circuit, this leads to very high fault currents, which can cause the affected cell to thermally break down and thus quickly and inevitably lead to the thermal destruction of the entire battery system. To prevent such destruction caused by a single cell in the event of a fault, a fuse is typically installed on each cell. This fuse irreversibly disconnects the affected cell from the overall system in the event of an overload caused by a low-resistance short circuit and correspondingly high currents.The fuse element represents a constriction in the current path, which melts due to overheating caused by a short-circuit current. 03860PWQ.

[0027] Figure 5a shows a top view of a section of a known cell contacting system 1, which is designed as a grid-like stamped and bent structure 2 made of a copper or aluminum sheet for providing desired electrical output parameters at terminals (not shown) of a battery module or pack by means of a predetermined electrical interconnection of elementary storage cells 3 in series and / or parallel circuits. In this cell contacting system 1, each electrical contact from the grid-like stamped and bent structure 2 to one of the poles P, N of an elementary storage cell 3 of cylindrical format is formed integrally by metallic webs 4. The metallic webs 4 have contact surfaces 5 at their free end regions.To connect each elementary memory cell 3, a contact surface 5p is pressed onto a positive pole P and a contact surface 5n onto a cell terminal N of a sleeve of the cylindrical memory cell 3, which is electrically insulated from the cell pole P, and permanently fixed by laser welding. Each web 4 to a contact surface 5p is designed as an electrical safety element 6 by virtue of its dimensions and, in particular, a free cross-section. The grid-like stamped-bent structure 2 made of sheet metal is connected to a carrier 7 for mechanical reinforcement, but also for electrical insulation from certain areas, especially of the elementary memory cells 3 and other current-carrying components not shown here. The carrier 7 consists of a very high temperature-resistant and permanently electrically insulating material, in this case a plastic.A connection between the stamped-bent structure 2 and the carrier 7 can be established by gluing, laminating, or snapping; in the present embodiment, hot stamping is provided as a permanent connection point. In the event of thermal runaway of an elementary storage cell 3 within a battery system (only indicated in Figure 5a), an internal short circuit can occur, for example, due to electrically conductive particles or damage to the cell contacting system 1. In general, the short circuit can be low-resistance at extremely high current flows, or medium-resistance at moderate currents within the range of normal operating currents, whereby in the latter case a large amount of heat is generated by an internal fault within a storage cell.In general, however, both types of short circuits can heat an elementary storage cell 3 in the battery system to such an extent, at least partially, that the affected elementary storage cell 3 can overheat and, in the worst case, thermally fail. The cell contacting system 1 described above with reference to Figure 5a shows a known approach to avoid the harmful effects of a low-resistance short circuit by means of individual cell protection. Here, parts of bridges 4 are structurally designed as segments of the cell contacting system 1 such that they act as electrical fuse elements 6 at very high currents and permanently disconnect an affected elementary storage cell 3 by melting.

[0028] Medium-resistance short circuits are not protected by a cell contacting system 1 according to Figure 5a, since in this case only currents in the range of a normal operating current flow, meaning that an individual cell protection system designed for high short-circuit currents by fuse elements 6 on a relevant elementary storage cell 3 does not trip. However, medium-resistance short circuits occur frequently in battery systems, for example in the scenarios given below:

[0029] 1. Due to the high heat generation during the thermal runaway of an elementary storage cell, the electrical insulation between the positive and negative terminals melts. This results in an electrical short circuit between the two terminals at the elementary storage cell itself, without the involvement of the cell contacting system. Since the electrical insulation does not completely decompose due to the heat, a certain residual insulating effect remains between the terminals, limiting the current flow below a tripping threshold of the thermal fuse 6, also shown in Figure 5a. This creates a medium-resistance short circuit with a continuously increasing release of heat.

[0030] 2. In encapsulated and / or foamed battery systems, parts of the metallic cell contacting system melt due to the extreme heat generated by a thermally leaking cell and the resulting hot gases. This leads to short circuits between the cells and / or the cell contacting system. However, because the encapsulation material also decomposes due to the heat, only medium-resistance short circuits typically occur within the battery system. Consequently, the thermally leaking cell, and usually the other affected cells as well, fails to shut down safely. This results in the accelerated and irreversible destruction of the entire battery system.

[0031] Medium-resistance short circuits cause significant heating of the affected cell and the adjacent cell contacting system. Temperatures well over 800°C are sometimes reached. This leads, among other things, to extensive melting of the cell contacting system, resulting in a metallic melt that creates a large-area short circuit in the battery system and / or melts the cell casings of other cells. This can cause thermal runaway in a cell to directly trigger widespread thermal propagation. Similarly, the plastic carrier of the cell contacting system can melt, which can also result in extensive electrical short circuits between cell connectors and cells within the battery system.The heat generated by these short circuits also leads to very large-scale and catastrophic thermal propagation, which inevitably leads to the complete destruction of the battery system.

[0032] As a solution to the problem described above, Figure 1 shows an exemplary embodiment of a cell contacting system 1, indicating the contacting of several elementary memory cells 3 with a fuse element 6 designed for a low-resistance short circuit at each cell terminal N of the elementary memory cells 3, and a fuse element 8 designed for a medium-resistance short circuit at each cell pole P. The fuse element 8, which reliably trips in the event of a medium-resistance short circuit, is dimensioned such that melting and tripping of the fuse element 8 is caused by the heat that escapes from the respective elementary memory cell 3 directly into the fuse element 8 via the cell pole P during a thermal runaway or thermal event. The increasingly powerful elementary memory cells 3 currently exhibit a continuously increasing size and thus a steadily growing thermal mass.Heat generated in storage cell 3 due to thermal runaway dissipates via conduction through the terminals. The cell terminal P, which is significantly smaller than the cell terminal N, heats up much more. A close and effective thermal coupling of the fuse element 8, designed for medium-resistance short circuits, by connecting it to the cell terminal P, ensures the earliest possible response of the fuse element 8, resulting in a permanent shutdown of the affected elementary storage cell 3, even though the current flow up to this shutdown is typically significantly lower than the short-circuit current in a low-resistance short circuit.A direct comparison with the illustration in Figure 5a shows that a fuse element 6 designed for a short-circuit current is provided at each cell pole Pj, whereas in the embodiment shown in Figure 1, a fuse element 8 designed for a medium-resistance short circuit is provided. To clarify the differences, which are barely discernible in a direct comparison of the top views of Figures 1 and 5a, enlarged sections II and III are marked in Figure 1 and are subsequently shown and described in greatly enlarged form as Figures 2b and 3b, respectively.

[0033] In Figure 1, a partial top view of the cell contacting system 1 shows, for clarity, only a few elementary memory cells 3 to illustrate the two different contact configurations of the cell contacting system 1 at the cell terminals N and the cell poles P. Figure 2a shows a perspective view of an embodiment of a fuse element for protection against a medium-resistance short circuit. Figure 2b shows a supplementary top view of the partial view in Figure 2a, which shows part of a metallic bridge 4 with a transition into a compensating section 9 and connection to a terminal surface 5p by a fuse element 8 designed for a medium-resistance short circuit. The compensating section 9 has the form of a section of sheet metal bent in a substantially S-shape, similar to a loop, as is also used for mechanical tolerance compensation.Furthermore, the compensating section 9, opposite the securing element 8 and adjoining the web 4, is characterized by incisions 10, which are opposite each other and of the same size and depth, in order to give the compensating section 9 not only the functionality of a mechanical tolerance compensation but also the effect of a defined thermal mass. Since the incisions 10 allow heat to dissipate, heat that is generated internally in large quantities in the event of thermal runaway in an elementary storage cell 3, which is electrically and thermally connected to a cell pole P via the connection surface 5p. The cell pole P is heated much more strongly by internal processes in the elementary storage cell 3 than the significantly larger cell terminal N.The design of the equalizing section 9 described above creates an operating situation in which the fuse element 8, with significantly reduced heat dissipation, is at approximately the same temperature level on both sides and is thus essentially heated to the temperature level of the cell pole P. These measures enable the fuse element 8 to reliably trip in the event of a medium-resistance short circuit or a thermal event within the connected elementary storage cell 3 upon reaching a predetermined temperature threshold, which is significantly above the permissible operating temperature range of the elementary storage cell 3 during normal operation. The tripping of the fuse element 8 prevents any further current flow through the affected elementary storage cell 3.This prevents a further accelerated progression of thermal runaway in the relevant elementary storage cell 3 caused by current flow.

[0034] As another embodiment, as indicated in Figures 2b and 2c (side view), the fuse element 8, designed for a medium-resistance short circuit, is additionally coated with a flux 11 in one embodiment. However, the purpose of this flux 11 is not only to increase the flowability of the thermally melted metal of the fuse element 8 with the aim of ensuring reliable electrical isolation. In particular, when using aluminum and its alloys as the metallic material of the stamped-bent structure 2 of the cell contacting system 1, a surface oxide layer forms which can hinder the tripping of the fuse element 8 and the reliable interruption of any further current flow.A further purpose of coating the locking element 8 with such a flux 11 is therefore to prevent negative influences, in particular an oxide layer, on the release behavior of the locking element 8. Due to the importance of this function of the flux 11, an additional embodiment shown in Figures 2b and 2c indicates that the flux 11 is also covered by a protective layer 12, which in one embodiment is designed as a lacquer layer. This covering of the locking element 8 by the aforementioned coatings 11, 12 can also be used as additional thermal insulation against an immediate and, as a rule, less heated environment. This reduces heat loss from the locking element 8 through heat radiation.

[0035] Figures 3a and 3b show a perspective view and a top view of an embodiment of a fuse element 6 for protection against a low-resistance short circuit. Here, too, a web 4 of the metallic stamped-bent structure 2 extends into a compensating section 9, which is again approximately S-shaped. On a sloping flank of the compensating section 9, the fuse element 6 is formed by symmetrically arranged incisions 10 in a transition to the connection surface 5n as a very narrow constriction of a free conductor cross-section. Thus, the fuse element 6 also has a mechanical compensating section 9 opposite a connection surface 5n in the form of a section of sheet metal bent in an essentially S-shape, resembling a loop, with these functional parts being integrally formed as structural elements of a metallic stamped-bent part.The very high currents of an electrical short circuit melt the narrow fuse element 6 essentially independently of the temperature of the connection surface 5n, the compensation section 9 or other elements in the immediate vicinity, thus causing a permanent electrical separation that is necessary for safety reasons.

[0036] Figures 4a to 4c, analogous to the illustration in Figure 2c, show side views of a further embodiment of a fuse element 8 for protection against a medium-resistance short circuit before and after installation with an electrically permanent welded connection 13 between the connection surface 5p and a cell terminal P of an elementary memory cell 3, as well as after activation or melting of the fuse element 8 due to impermissible heating of the elementary memory cell 3, as caused by a thermal event. As can already be seen from the illustrations in Figures 1 and 5a, a cell contacting system 1, in addition to a stamped-bent structure 2 for realizing a predetermined electrical connection of the elementary memory cells 3, also has the carrier 7, which is fixed to the stamped-bent structure 2 by localized hot stamping as mechanical support for the stamped-bent structure 2.Looking at the assembly situation according to Figure 4a, it becomes clear that the electrically insulating support 7, arranged below the web 4 with adjoining elements as part of the stamped-bent structure 2, also very effectively protects against a short circuit between cell terminal N and the cell pole P, which is separated at the elementary storage cell 3 by a thin insulation I, even in a very confined space. The requirements for the thermal stability of the support 7, which is made of a plastic material here, can be reduced by using an additional insert (not shown here). In one embodiment, the insert, made of mica paper, is electrically insulating even at very high temperatures and mechanically stable in order to effectively prevent an electrical short circuit between cell terminal N and the cell pole P, which is separated at the elementary storage cell 3 by the very narrow insulation I.

[0037] In the transition to Figure 4b, the connection surface 5p is pressed over a distance h onto the cell pole P of the elementary storage cell 3 under spring-elastic deformation of the locking element 8 with the compensating section 9 and a lower part of the support 7. A permanent and electrically conductive connection 13 between the connection surface 5p and the cell pole P is created by laser welding. The locking element 8 is thus arranged in an installation position under permanent mechanical tensile or bending stress.

[0038] Figure 4c shows a situation in which the fuse element 8 has melted in response to a medium-resistance short circuit. Spherical remnants 14 of the fuse element 8, consisting of hot metal, the compensating section 9, and the contact surface 5p with the cell terminal P, are clearly visible at a distinct distance from one another. This distance between the spherical remnants 14 has increased due to the compensating section 9 no longer being spring-loaded. Furthermore, the restoration of an electrically conductive connection between the spherical remnants 14 is prevented by a shear edge 15 on the carrier 7, which, upon melting of the fuse element 8, is designed to engage between the melted ends of the fuse element 8, releasing the spring-loaded preload. This also enables an arc-quenching effect for the rapid interruption of current flow.For this purpose, the shear edge 15 is arranged approximately in the middle or in a central area under the locking element 8 before the locking element 8 is melted.

[0039] Analogous to the procedure described above, such a spring-elastic preload can also be adjusted on the fuse elements 6 designed for low-resistance short circuits with high current flows.

[0040] A comparison of the known fuse 6 of Figures 5b and 5c with the two designs of fuse elements 8, 6 of Figures 2b, 2c, and 3b clearly illustrates the respective modifications to the design, with particular emphasis on adapting the novel fuse element 8 to a medium-resistance short circuit. Possible adaptations of the respective designs in response to the available installation space in each practical application are readily apparent to a person skilled in the art.

[0041] Reference numeral list Cell contacting system Stamping-bending structure Elementary storage cell of a cylindrical format Metallic bridge Connection surface

[0042] 5-pin connection surface on one cell pole / positive pole

[0043] 5n Connection surface on a cell terminal / negative pole electrical fuse element for a low-resistance short circuit with high current flow Carrier made of a thermally resistant and electrically insulating plastic Fuse element designed for a medium-resistance short circuit in case of strong internal cell heating Compensation section 0 Cut 1 Flux 2 Protective layer e.g. of lacquer over the flux 3 Permanent and electrically conductive welded joint 4 Spherical remnants of the fuse element 8 Made of metal 5 Shear edge on the carrier 7 h Distance between cell pole P and connection surface 5p before welding

[0044] I so I isolation between N and P at an elementary memory cell 3

[0045] N negative pole / cell terminal of the elementary memory cell 2

[0046] P Plus pole / cell pole of the elementary memory cell 2

Claims

Claims 1. Cell contacting system, by which elementary storage cells are electrically interconnected in series and / or parallel circuits to form a battery module and / or pack, and in which at least one electrical contact to a pole of an elementary storage cell is designed as an electrical safety element, characterized in that in a metallic stamped-bent structure (2) of the cell contacting system (1) safety elements (6, 8) are provided for each elementary storage cell (3) as protection against a low-resistance short circuit and as protection against a medium-resistance short circuit.

2. Cell contacting system according to the preceding claim, characterized in that the safety element (8) designed for a medium-resistance short circuit is arranged and connected to the metallic stamped-bent structure (2) of the cell contacting system (1) towards a respective cell pole (P) of the elementary memory cells (3).

3. Cell contacting system according to one of the preceding claims, characterized in that a fuse element (6) designed for a low-resistance short circuit is connected in series with the fuse element (8) designed for a medium-resistance short circuit at each of the elementary memory cells (3).

4. Cell contacting system according to one of the preceding claims, characterized in that a fuse element (6) designed for a low-resistance short circuit of an elementary memory cell (3) is attached to a cell terminal nal (N) of the relevant elementary memory cell (3) is arranged.

5. Cell contacting system according to one of the preceding claims, characterized in that a locking element (6, 8) has a mechanical compensation section (9) opposite a connection surface (5, 5p, 5n) in the form of a section of sheet metal bent in a substantially S-shape in the manner of a loop.

6. Cell contacting system according to the preceding claim, characterized in that the compensating section (9) has a notch (10) opposite the locking element (6, 8).

7. Cell contacting system according to one of the preceding claims, characterized in that the locking element (6, 8) is arranged in an installation position such that it is under mechanical tensile or bending stress.

8. Cell contacting system according to the preceding claim, characterized in that the locking element contacted with an elementary memory cell (3) (6, 8) acting mechanical tensile and / or bending stress through a shear edge (15) of a thermally stable insert or a section of a carrier (7) as part of the cell contacting system (1) or in any other way by displacing a contact surface (5, 5p, 5n) by a distance (h) when connecting to a pole (N, P) of the elementary storage cell (3) is adjustable.

9. Cell contacting system according to the preceding claim, characterized in that the shear edge (15) is dimensioned such that the shear edge (15) in a Melting of the locking element (6, 8) is designed to engage between the melted ends of the locking element (6, 8) by releasing the spring-elastic preload.

10. Cell contacting system according to one of the preceding claims, characterized in that the locking element (6, 8) is covered with a flux (11).

11. Cell contacting system according to the preceding claim, characterized in that the flux (11) is coated externally with a protective layer (12).

12. Cell contacting system according to the preceding claim, characterized in that the flux (11) is coated with a lacquer layer.

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