Battery pack

Abstract

A battery pack is disclosed. A battery pack according to one embodiment of the present invention may include: a base plate; a battery module installed on the base plate and having a first venting hole on its upper surface; a venting cover coupled to the upper surface of the battery module; a pack cover covering the venting cover; and an elastic member located between the venting cover and the pack cover.

Description

Technology Field

[0001] The present invention relates to a battery pack. Background Technology

[0002] As the demand for portable electronic products such as smartphones, tablet PCs, and smartwatches increases significantly and electric vehicles become increasingly widespread, research on batteries installed in them, particularly secondary batteries capable of repeated charging and discharging, is actively underway.

[0003] Currently commercialized rechargeable batteries include nickel-cadmium, nickel-hydrogen, nickel-zinc, and lithium-ion batteries. Among these, lithium-ion batteries are gaining attention for their advantages, such as the ability to charge and discharge freely with almost no memory effect compared to nickel-based batteries, a very low self-discharge rate, and high energy density.

[0004] These lithium secondary batteries primarily use lithium-based oxides and carbon materials as the positive and negative active materials, respectively. The lithium secondary battery comprises an electrode assembly in which a positive plate and a negative plate, each coated with the positive and negative active materials, are arranged with a separator in between, and an outer casing, namely a battery case, that seals and houses the electrode assembly together with an electrolyte.

[0005] Generally, lithium secondary batteries can be classified according to the shape of the casing into can-type secondary batteries, in which the electrode assembly is embedded in a metal can, and pouch-type secondary batteries, in which the electrode assembly is embedded in a pouch of aluminum laminate sheet.

[0006] Recently, secondary batteries are widely used for driving or energy storage not only in small devices such as portable electronic devices but also in medium-to-large devices such as electric vehicles and Energy Storage Systems (ESS). A single battery module can be formed by housing multiple such secondary batteries together inside a module case while electrically connected. In this case, each secondary battery included in a single battery module can be referred to as a battery cell. Furthermore, multiple such battery modules can be connected to form a single battery pack.

[0007] However, when a battery pack contains multiple battery modules, and each module contains multiple battery cells, it may be vulnerable to thermal chain reactions between modules or cells. For example, if an event such as thermal runaway occurs within a single battery module, it is necessary to suppress the propagation of this runaway to other battery modules or cells. If the propagation of thermal runaway between modules or cells is not properly suppressed, an event originating in a specific module or cell may trigger a chain reaction of thermal reactions in other modules or cells, potentially causing explosions or fires, or significantly amplifying their scale.

[0008] In particular, if an event such as thermal runaway occurs in a single battery module, gases or flames may be randomly released to the outside. If the release of such gases or flames is not properly controlled, they may be released toward other battery modules, potentially causing a thermal chain reaction in those modules. Specifically, module terminals may be located on the front side of a battery module to provide electrical connections to other battery modules or battery packs, such as module busbars. Therefore, if flames are released toward the front of such a battery module, they can damage the module terminals within the battery pack and cause an electrical short circuit. Furthermore, since other battery modules may be located in front of a specific battery module, if flames are released toward the front of that module, the emitted flames may spread toward other modules, making it easy for fire to spread between battery modules.

[0009] If thermal propagation between battery modules or between battery cells is not properly controlled, a rapid voltage drop in the battery module or battery pack may occur. This can lead to a sudden shutdown of the device equipped with the battery module or battery pack, causing unexpected damage. For example, if a sudden voltage drop in the battery pack occurs while an electric vehicle is in operation, there may not be enough time to move the electric vehicle to a safe location.

[0010] Furthermore, if thermal propagation between battery modules or battery cells is not properly controlled and a fire or explosion occurs suddenly, there is a high possibility of causing casualties to users. For example, if thermal runaway occurs in an electric vehicle and a certain amount of time is not secured before it progresses into a full-scale fire, the occupants may not be able to escape safely. The problem to be solved

[0011] Accordingly, the present invention is devised to solve the above-mentioned problems and aims to provide a battery pack with an improved structure capable of appropriately controlling the discharge of flames, etc. generated inside the battery module, and a vehicle including the same.

[0012] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by those skilled in the art from the description of the invention below. means of solving the problem

[0013] A battery pack according to one embodiment of the present invention for achieving the above-mentioned purpose may include: a base plate; a battery module installed on the base plate and having a first venting hole on its upper surface; a venting cover coupled to the upper surface of the battery module; a pack cover covering the venting cover; and an elastic member located between the venting cover and the pack cover.

[0014] In addition, the elastic member can be fixed between the venting cover and the pack cover.

[0015] In addition, the elastic member can be compressed between the venting cover and the pack cover.

[0016] In addition, the elastic member may be attached to the upper surface of the venting cover.

[0017] In addition, the above elastic members may be provided in multiple numbers.

[0018] Additionally, the venting cover may include a first cover that is coupled to the upper surface of the battery module and covers the first venting hole.

[0019] In addition, the first cover may have a separating line facing the first venting hole.

[0020] In addition, the above separation line may be configured to be detachable when a thermal event occurs from the battery module.

[0021] In addition, the separation line may extend along the perimeter of the first venting hole.

[0022] In addition, the venting cover may further include a second cover coupled to the upper surface of the first cover.

[0023] In addition, the second cover may include a second venting hole that exposes the separation line.

[0024] In addition, when a thermal event occurs from the battery module, the first venting hole and the second venting hole may be configured to be in communication.

[0025] An automobile according to one aspect of the present invention includes a battery pack of the present invention. Effects of the invention

[0026] According to at least one of the embodiments of the present invention, when gas or flame is generated inside a battery module, the discharge of such gas or flame can be appropriately controlled.

[0027] According to at least one of the embodiments of the present invention, the electrical safety of the battery pack can be improved.

[0028] According to at least one of the embodiments of the present invention, heat propagation can be suppressed. Brief explanation of the drawing

[0029] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a drawing showing a battery pack according to one embodiment of the present invention. Figure 2 is a drawing showing the battery pack of Figure 1 with the pack cover separated. Figure 3 is a diagram showing a separated configuration of a battery pack of Figure 1. Figure 4 is a drawing showing the battery module of the battery pack of Figure 3. Figure 5 is a diagram showing a partial configuration of the battery module of Figure 4 separated. Figure 6 is a drawing showing the battery module, venting cover, and elastic member of Figure 3 separated. Figure 7 is a diagram showing the combination of the components of Figure 6. Figure 8 is a drawing showing the cross-sectional configuration along the cutting line B-B' of Figure 2. Figure 9 is a drawing showing the cross-sectional configuration along the cutting line A-A' of Figure 1. Figure 10 is a diagram showing the cross-sectional configuration of Figure 9 when a thermal event occurs. Specific details for implementing the invention

[0030] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, and should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0031] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all aspects of the technical concept of the present invention; thus, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0032] FIG. 1 is a drawing showing a battery pack according to an embodiment of the present invention. FIG. 2 is a drawing showing the pack cover (150) of the battery pack of FIG. 1 separated. FIG. 3 is a drawing showing a part of the battery pack of FIG. 1 separated.

[0033] Referring to FIGS. 1 to 3, a battery pack according to one embodiment of the present invention may include a base plate (110), a battery module (200), a venting cover (400), a pack cover (150), and an elastic member (500).

[0034] The base plate (110) may have a square shape. The base plate (110) may have a flat shape. The base plate (110) may form the exterior of the battery pack. The base plate (110) may provide an internal space for the battery pack.

[0035] A plurality of battery modules (200) may be provided. The battery modules (200) may be installed, fastened, coupled, fixed, or attached to the upper surface of the base plate (110). The battery modules (200) may have a first venting hole (211) on the upper surface. The first venting hole (211) may connect the inside and outside of the battery modules (200). A plurality of first venting holes (211) may be provided. When a thermal event occurs from the battery modules (200), the venting gas (g, see FIG. 10) may be discharged through the first venting hole (211).

[0036] The venting cover (400) can be installed, fastened, coupled, fixed, or attached to the upper surface of the battery module (200). The venting cover (400) can facilitate the discharge of venting gas (g). Additionally, the venting cover (400) can protect the battery module (200) from flames or venting gas (g) generated outside the battery module (200).

[0037] The pack cover (150) may have a square plate shape. The pack cover (150) may have a flat plate shape. The pack cover (150) may form the exterior of the battery pack. The pack cover (150) may cover the internal space of the battery pack.

[0038] The elastic member (500) may be positioned between the venting cover (400) and the pack cover (150). The elastic member (500) may provide a restoring force (RF, see FIG. 10) to the venting cover (400). Additionally, the elastic member (500) may provide a restoring force (RF) to the pack cover (150).

[0039] When a thermal event occurs from the battery module (200), the venting gas (g) can be discharged at a high pressure. As a result, the venting cover (400) can be separated from the battery module (200).

[0040] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. By the elastic member (500) providing a restoring force (RF) to the venting cover (400), the bonded state between the venting cover (400) and the battery module (200) can be stably maintained.

[0041] Referring to FIGS. 1 to 3, a battery pack according to one embodiment of the present invention may include a side wall (120) and a partition wall (300).

[0042] The side wall (120) can be installed, fastened, joined, fixed, or attached to the upper surface of the base plate (110). The side wall (120) can be composed of four. The side wall (120) can be arranged along the perimeter of the base plate (110). The side wall (120) can form the exterior of the battery pack. The side wall (120) can provide an internal space. The battery module (200) can be surrounded by the side wall (120).

[0043] The partition wall (300) may include a first partition wall (301) and a second partition wall (302). The partition wall (300) may be provided in multiple numbers. The partition wall (300) may be installed, fastened, fixed, coupled, or attached to the upper surface of the base plate (110). The partition wall (300) may partition the internal space of the battery pack. A battery module (200) may be located in each space partitioned by the partition wall (300). Additionally, the partition wall (300) may face at least one side of the battery module (200).

[0044] The pack cover (150) may have a square plate shape. The pack cover (150) may have a flat plate shape. The pack cover (150) may form the exterior of the battery pack. The pack cover (150) may cover the internal space of the battery pack. The pack cover (150) may be installed, fastened, coupled, fixed, or attached to the side wall (120). Additionally, the pack cover (150) may be installed, fastened, coupled, fixed, or attached to the partition wall (300). Additionally, the pack cover (150) may cover the upper surface of the battery module (200).

[0045] The fastening member (160) can fasten the base plate (110) and the side wall (120). Additionally, the fastening member (160) can fasten the base plate (110) and the partition wall (300).

[0046] FIG. 4 is a drawing showing the battery module (200) of the battery pack of FIG. 3. FIG. 5 is a drawing showing a partial configuration of the battery module (200) of FIG. 4 separated.

[0047] Referring to FIGS. 3 to 5, a battery module (200) of a battery pack according to one embodiment of the present invention may include a case (210), a plurality of battery cells (220), a pad (250), a busbar frame assembly (230), and an end cover (240).

[0048] The case (210) may have a rectangular shape. The case (210) may also be referred to as a frame (110). The case (210) may provide space inside. The case (210) may have a top surface, a bottom surface, and a pair of sides. Additionally, the case (210) may have a shape with an open front and rear. The case (210) may have a first venting hole (211) on the top surface. The first venting hole (211) may connect the inside and outside of the case (210).

[0049] A plurality of battery cells (220) may be stacked in the left-right direction or the Y-axis direction. In this case, the battery cell (220) may refer to a secondary battery. The battery cell (220) may include a storage portion (221) having an electrode assembly, a first sealing portion (222) protruding to the front and rear sides of the storage portion (221), and a second sealing portion (223) protruding to the upper side of the storage portion (221). Additionally, the battery cell (220) may include electrode leads (224) protruding to the front and rear sides of the first sealing portion (222), respectively. In particular, the battery cell (220) may be a pouch-type secondary battery. Each battery cell (220) may be extended along the front-rear direction or the X-axis direction. The electrode leads (121) may protrude to the front and rear of each battery cell (220).

[0050] A pad (250) may be placed between multiple battery cells (220). The pad (250) may be placed between at least some of the battery cells (220) and / or on the outer edge of the stack. For example, the pad (250) may be configured to be placed between every four battery cells (220) stacked in the left-right direction.

[0051] These pads (250) may be provided with an elastic material to absorb swelling of the battery cell (220). For example, the pads (250) may be made of a foam material such as polyurethane. Alternatively, the pads (250) may be provided with a material capable of blocking heat or flames. For example, the pads (250) may be provided with an insulating or fireproof material such as silicone or mica.

[0052] A busbar frame assembly (230) may be provided at the front and rear of a plurality of battery cells (220), respectively. The busbar frame assembly (230) may be electrically connected to the electrode leads (121) of the plurality of battery cells (220).

[0053] A pair of end covers (240) can be attached to the front and rear of the case (210), respectively. A pair of end covers (240) can cover the front and rear of the case (210). The end covers (240) can have a rectangular shape.

[0054] FIG. 6 is a diagram showing the battery module (200), venting cover (400), and elastic member (500) of FIG. 3 separated. FIG. 7 is a diagram showing the combination of the components of FIG. 6.

[0055] Referring to FIGS. 3, 6 and 7, an elastic member (500) of a battery pack according to one embodiment of the present invention may be installed, fastened, coupled, fixed, or attached to the upper surface of a venting cover (400).

[0056] According to this configuration of the present invention, the elastic member (500) can stably provide a restoring force (RF) to the venting cover (400). As a result, the combined state of the venting cover (400) and the battery module (200) can be stably maintained.

[0057] Referring to FIGS. 3, 6, and 7, the elastic member (500) of a battery pack according to one embodiment of the present invention may be provided in a plurality.

[0058] According to this configuration of the present invention, a plurality of elastic members (500) can stably provide a restoring force (RF) to the venting cover (400). The combined state of the venting cover (400) and the battery module (200) can be stably maintained.

[0059] Referring to FIGS. 3, 6 and 7, a venting cover (400) of a battery pack according to one embodiment of the present invention may include a first cover (410).

[0060] The first cover (410) may be installed, fastened, coupled, fixed, or attached to the upper surface of the battery module (200). Additionally, the first cover (410) may be installed, fastened, coupled, fixed, or attached to at least one side of the battery module (200).

[0061] The first cover (410) may be configured to cover the first venting hole (211). The first cover (410) may cover a plurality of first venting holes (211) in their entirety. The first cover (410) may include a heat-resistant material.

[0062] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. The first cover (410) can prevent or block flames or venting gas (g) generated outside the battery module (200) from entering the interior of the battery module (200) through the first venting hole (211). As a result, the propagation of thermal events can be suppressed.

[0063] Referring to FIGS. 3, 6 and 7, a first cover (410) of a battery pack according to one embodiment of the present invention may have a separating line (411) facing a first venting hole (211).

[0064] The separation line (411, score line) may be used as a general term including and referring to a perforated line (411, perforated line), notching line (411, notching line), cutting line (411, cutting line), shredding line (411, shredding line), tear line (411, tear line), or separation line (411, separation line). The separation line (411) may be configured to be easily separated by pressure applied to the first cover (410).

[0065] According to this configuration of the present invention, the thermal safety of the battery module (200) can be improved. When a thermal event occurs inside the battery module (200), the venting gas (g) can push the separator line (411) through the first venting hole (211) to separate at least a part of the first cover (410) or form a hole. As a result, the inside and outside of the battery module (200) can be connected, and the venting gas (g) can be discharged to the outside of the battery module (200).

[0066] In addition, according to this configuration of the present invention, the first cover (410) can prevent or block high-temperature gas or flammable particles generated from the outside of the battery module (200) from entering the interior of the case (210). As a result, the propagation of thermal events to the battery cell (220) inside the case (210) can be blocked.

[0067] Referring to FIGS. 3, 6, and 7, a separation line (411) of a first cover (410) of a battery pack according to one embodiment of the present invention may be configured to be detachable when a thermal event occurs from a battery module (200). The separation line (411) may form a separation area (412). The separation area (412) may be an area surrounded by the separation line (411).

[0068] The separation area (412) may face the first venting hole (211). Additionally, the separation area (412) may face at least a portion of the plurality of battery cells (220). Alternatively, the first cover (410) or the separation area (412) may face at least a portion of the upper surface of the plurality of battery cells (220).

[0069] According to this configuration of the present invention, the thermal safety of the battery module (200) can be improved. When a thermal event occurs, the separation area (412) can be separated from the first cover (410). Venting gas (g) can be discharged to the outside through a hole formed by separating the first venting hole (211) and the separation area (412).

[0070] Referring to FIGS. 3, 6 and 7, the separation line (411) of a battery pack according to one embodiment of the present invention may extend along the perimeter of the first venting hole (211). Alternatively, the separation line (411) may be formed inside the area facing the first venting hole (211).

[0071] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. When a thermal event occurs inside the battery module (200), the separation of the separator line (411) can be facilitated. As a result, the venting gas (g) can be discharged smoothly.

[0072] Referring to FIGS. 3, 6 and 7, a venting cover (400) of a battery pack according to one embodiment of the present invention may include a second cover (420). The term venting cover (400) may be used as a collective term for the first cover (410) and the second cover (420).

[0073] The second cover (420) may be installed, fastened, coupled, fixed, or attached to the upper surface of the first cover (410). Additionally, the second cover (420) may be installed, fastened, coupled, fixed, or attached to at least one side of the first cover (410). The second cover (420) may include a heat-resistant material or a fire-resistant material. For example, the second cover (420) may include a mica material. Additionally, the second cover (420) may be composed of a material with higher hardness than the first cover (410).

[0074] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. The second cover (420) can protect the battery module (200) from flames generated from the outside. As a result, the propagation of thermal events can be suppressed.

[0075] In addition, according to this configuration of the present invention, by including a material with high hardness for the second cover (420), the separation of the first cover (410) from the battery module (200) can be prevented or suppressed. The combined state of the first cover (410) and the battery module (200) can be stably maintained.

[0076] Referring to FIGS. 3, 6 and 7, a second cover (420) of a battery pack according to one embodiment of the present invention may include a second venting hole (421). The second venting hole (421) may be positioned to expose a separator line (411).

[0077] According to this configuration of the present invention, the thermal safety of the battery module (200) can be improved. When a thermal event occurs, the separation area (412) can be separated from the first cover (410). Venting gas (g) can be discharged to the outside through the first venting hole (211), the hole formed by separating the separation area (412), and the second venting hole (421).

[0078] FIG. 8 is a drawing showing a cross-sectional configuration along the cutting line B-B' of FIG. 2. FIG. 9 is a drawing showing a cross-sectional configuration along the cutting line A-A' of FIG. 1. Referring to FIG. 8 and FIG. 9, an elastic member (500) of a battery pack according to one embodiment of the present invention can be compressed between a venting cover (400) and a pack cover (150). By fastening the pack cover (150) to a side wall (120) or a partition wall (300), the pack cover (150) can press the elastic member (500). For example, before the pack cover (150) is fastened to the side wall (120) or the partition wall (300), the height (h1) of the elastic member (500) may be 14 mm. And when the pack cover (150) is fastened to the side wall (120) or partition wall (300), the height (h2) of the elastic member (500) can be compressed to 8mm.

[0079] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. The compressed elastic member (500) can provide a restoring force (RF) to the venting cover (400). As a result, the bonded state between the venting cover (400) and the battery module (200) can be maintained stably.

[0080] Referring to FIGS. 8 and 9, an elastic member (500) of a battery pack according to one embodiment of the present invention may be fixed between a venting cover (400) and a pack cover (150). The elastic member (500) may be fixed by being compressed by the pack cover (150) and the venting cover (400). Additionally, the elastic member (500) may be installed, fastened, coupled, fixed, or attached to the upper surface of a second cover (420).

[0081] According to this configuration of the present invention, the thermal safety of the battery pack can be improved. The compressed elastic member (500) can provide a restoring force (RF) to the venting cover (400). As a result, the bonded state between the venting cover (400) and the battery module (200) can be maintained stably.

[0082] FIG. 10 is a diagram showing the cross-sectional configuration of FIG. 9 when a thermal event occurs. Referring to FIG. 9 and FIG. 10, the first venting hole (211) and the second venting hole (421) of a battery pack according to one embodiment of the present invention may be configured to communicate when a thermal event occurs.

[0083] When a thermal event occurs from the battery cell (220), a venting gas (g) may be generated. The venting gas (g) can pressurize the separation area (412) in the upward direction or the +Z-axis direction through the first venting hole (211) of the case (210). As a result, the separation area (412) may be separated from the first cover (410). Additionally, as the separation area (412) is separated, a hole may be formed in the first cover (410). As a result, the first venting hole (211) and the second venting hole (421) may be connected. The venting gas (g) may be discharged to the outside of the battery module (200) through the first venting hole (211), the hole formed in the first cover (410), and the second venting hole (421). At this time, the elastic member (500) may provide a restoring force (RF) to the venting cover (400).

[0084] According to this configuration of the present invention, the thermal safety of the battery module (200) can be improved. When a thermal event occurs, the venting gas (g) can be easily discharged. In addition, the connection between the venting cover (400) and the battery module (200) can be stably maintained.

[0085] In addition, the battery pack according to the present invention may further include various other components in addition to the battery module, such as various battery pack components known at the time of filing the present invention, such as a BMS, busbar, relay, current sensor, etc.

[0086] The battery pack according to the present invention can be applied to vehicles such as electric vehicles or hybrid vehicles. That is, the vehicle according to the present invention may include the battery pack according to the present invention. In addition, the vehicle according to the present invention may further include various other components included in the vehicle in addition to such a battery pack. For example, the vehicle according to the present invention may further include a vehicle body, a motor, a control device such as an ECU (electronic control unit), etc.

[0087] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0088] 110: Base Plate 120: Sidewall 150: Pack Cover 160: Fastening member 200: Battery module 210: Case 211: First Venting Hall 220: Battery cell 221: Storage compartment 222: 1st sealing section 223: Second sealing section 224: Electrode Lead 230: Busbar frame assembly 240: End cover 250: Pad 300: Partition Wall 301: First Partition Wall 302: Second Partition Wall 400: Venting cover 410: First Cover 411: Separator line 412: Separation area 420: Second Cover 421: Second Venting Hall 500: Elastic member

Claims

Claim 1 A battery pack comprising: a base plate; a battery module installed on the base plate and having a first venting hole on its upper surface; a venting cover coupled to the upper surface of the battery module; a pack cover covering the venting cover; and an elastic member positioned between the venting cover and the pack cover. Claim 2 In claim 1, the elastic member is a battery pack fixed between the venting cover and the pack cover. Claim 3 In claim 1, the elastic member is a battery pack that is compressed between the venting cover and the pack cover. Claim 4 In claim 1, the elastic member is a battery pack attached to the upper surface of the venting cover. Claim 5 In claim 1, the elastic member is a battery pack provided in multiple quantities. Claim 6 In claim 1, the battery pack comprises a first cover that covers the first venting hole and is coupled to the upper surface of the battery module. Claim 7 In claim 6, the first cover is a battery pack having a separating line facing the first venting hole. Claim 8 In claim 7, the separator is configured to be detachable from the battery module when a thermal event occurs. Claim 9 In claim 7, the separation line is a battery pack extending along the perimeter of the first venting hole. Claim 10 In claim 7, the venting cover further comprises a second cover coupled to the upper surface of the first cover. Claim 11 In claim 10, the battery pack, wherein the second cover includes a second venting hole that exposes the separator line. Claim 12 A battery pack according to claim 11, wherein the first venting hole and the second venting hole are configured to communicate when a thermal event occurs from the battery module. Claim 13 An automobile comprising a battery pack according to any one of claims 1 to 12.

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