Battery module

Abstract

To obtain a battery module with a new configuration, capable of detecting the expansion of battery cells.SOLUTION: A battery module according to an embodiment includes a plurality of battery cells and a bus bar. The plurality of battery cells each includes a cell housing having a first end and a second end opposite the first end, and an electrode terminal provided at the first end, the battery cells being aligned in a second direction perpendicular to a first direction from the first end to the second end. The bus bar includes a body, a voltage detection terminal and a connection. The body ranges over the electrode terminals of two of the battery cells. The voltage detection terminal connects the body and the voltage detection terminal. Two of the cell housings adjacent to each other in the second direction push against each other by the expansion of the cell housings, so that the gap between the second ends of the two of the cell housings is increased to cause bending deformation of the bus bar. As the result, the connection breaks and the body is separated from the voltage detection terminal.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE An embodiment of the present invention relates to a battery module. [Background technology]

[0002] A battery module including a plurality of battery cells, a bus bar electrically connecting the battery cells, and a monitoring device for detecting the voltage of the battery cells is known. Depending on the charging and discharging conditions, the internal pressure of the battery cell housing may increase, causing the cell housing to swell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-197661 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of battery module, it would be beneficial to have a novel configuration that allows detection of swelling of the battery cells. [Means for solving the problem]

[0005] The battery module of the embodiment includes a plurality of battery cells, a bus bar, and a monitoring device. The plurality of battery cells each have a cell housing having a first end and a second end opposite to the first end, and an electrode terminal provided at the first end, and are arranged in a second direction perpendicular to a first direction from the first end to the second end. The bus bar is fixed to the electrode terminals of each of the two battery cells adjacent to each other in the second direction, and electrically connects the electrode terminals of each of the two battery cells. The monitoring device is electrically connected to the battery cells via the bus bar and detects the voltage of the battery cells. The bus bar has a main body, a voltage detection terminal, and a connection. The main body spans the electrode terminals of each of the two battery cells adjacent to each other in the second direction. The voltage detection terminal connects the main body and the voltage detection terminal. As the cell casing expands, two adjacent cell casings in the second direction push against each other, widening the space between the second ends of the two cell casings and bending the bus bar, causing the connection portion to break and separating the main body portion and the voltage detection terminal portion. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an exploded perspective view of a battery module according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view for explaining the positional relationship between the battery cells and the bus bars in the battery module of the first embodiment. [Diagram 3] FIG. 3 is a perspective view for explaining the positional relationship between the battery cells and the monitoring device in the module of the first embodiment. [Figure 4] FIG. 4 is a perspective view of the bus bar according to the first embodiment as viewed from above. [Diagram 5] FIG. 5 is a perspective view of the bus bar according to the first embodiment as viewed from below. [Figure 6] FIG. 6 is a perspective view of a portion of the bus bar according to the first embodiment as viewed from below. [Figure 7] FIG. 7 is a perspective view of a portion of the bus bar according to the first embodiment as viewed from below. [Figure 8] FIG. 8 is a side view of the battery cell string and bus bar group of the first embodiment, showing a state in which the cell casing is not swollen. [Figure 9] FIG. 9 is a side view of the battery cell string and bus bar group of the first embodiment, showing a state in which the cell casing has swelled and the bus bar group has been deformed. [Figure 10] FIG. 10 is a side view of two battery cells and one bus bar according to the first embodiment, showing a state in which the cell casing has swelled and the bus bar has been deformed. [Figure 11] FIG. 11 is a side view of the bus bar according to the first embodiment, showing the bus bar in a deformed state. [Figure 12] FIG. 12 is a perspective view of a portion of a bus bar according to a modified example of the first embodiment. [Figure 13] FIG. 13 is a perspective view of a portion of the bus bar of the second embodiment. [Figure 14] FIG. 14 is a perspective view of a bus bar according to the third embodiment. [Figure 15] FIG. 15 is an exploded perspective view of the bus bar according to the third embodiment. [Figure 16] FIG. 16 is a perspective view of a bus bar according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, exemplary embodiments of the present invention will be described. The configurations of the embodiments described below and the actions and effects brought about by the configurations are merely examples.

[0008] The drawings are schematic, and the dimensional relationships and ratios of each element may differ from reality. Furthermore, the drawings may include parts whose dimensional relationships and ratios differ from one another. Furthermore, in this specification, ordinal numbers are used only to distinguish between parts, members, portions, positions, directions, etc., and do not indicate order or priority.

[0009] In the following description, an X-axis, Y-axis, Z-axis Cartesian coordinate system is used. The X-axis direction includes the +X direction and the -X direction. The Y-axis direction includes the +Y direction and the -Y direction. The Z-axis direction includes, for example, the +Z direction which is the upward direction and the -Z direction which is the downward direction. For example, the X-axis, Y-axis plane is a horizontal plane, and the Z-axis direction is a vertical direction. The -X direction is an example of a first direction, and the Y-axis direction is an example of a second direction.

[0010] <First embodiment> Fig. 1 is an exploded perspective view of a battery module according to a first embodiment. Fig. 2 is a perspective view for explaining the positional relationship between battery cells and bus bars in the battery module according to the first embodiment. Fig. 3 is a perspective view for explaining the positional relationship between battery cells and a monitoring device in the module according to the first embodiment.

[0011] 1 to 3, a battery module 1 of this embodiment includes multiple battery cells 2, an insulating module housing 5 that houses the multiple battery cells 2, multiple bus bars 3 that electrically connect two adjacent terminals of the multiple battery cells 2 housed in the module housing 5, and a monitoring device 4 that is electrically connected to the battery cells 2 via the bus bars 3 and detects (measures) the voltage of the battery cells 2. The battery module 1 is also referred to as an assembled battery.

[0012] For example, in the battery module 1, at least one of a series connection structure in which a plurality of battery cells 2 are electrically connected in series and a parallel connection structure in which a plurality of battery cells 2 are electrically connected in parallel is formed.

[0013] The battery cell 2 is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion battery, and includes a flat or substantially rectangular cell casing 20 made of aluminum or an aluminum alloy, and a power generating element 27 housed together with a non-aqueous electrolyte in the cell casing 20. That is, the battery cell 2 is, for example, a prismatic can cell.

[0014] The cell casing 20 has a bottomed rectangular cylindrical casing body 200 and a lid 201 integrally attached to an opening (not shown) of the casing body 200 by melting or the like. The upper surface of the lid 201 in the Z-axis direction is a terminal surface 203. Two types of terminals, a positive electrode terminal 23 and a negative electrode terminal 24, are provided at intervals in regions on both sides of the terminal surface 203 in the longitudinal direction (X-axis direction). Hereinafter, the positive electrode terminal 23 and the negative electrode terminal 24 are collectively referred to as electrode terminal 22. The cell casing 20 is also referred to as a container.

[0015] Furthermore, the battery cell 2 is provided with a rabbet 25 for discharging gas generated inside the cell casing 20, at the center of the terminal surface 203, and a liquid injection port 26 for injecting non-aqueous electrolyte into the cell casing 20. The rabbet 25 is, for example, an X-shaped groove provided in a thin-walled portion located between the positive electrode terminal 23 and the negative electrode terminal 24 of the lid 201.

[0016] The cell casing 20 has a bottom surface 204 on the opposite side of the terminal surface 203 in the Z-axis direction, a pair of short side surfaces 205 that are side surfaces continuing from the bottom surface 204, and a pair of long side surfaces 206 that are side surfaces continuing from the bottom surface 204. In FIG. 1, the pair of short side surfaces 205 are surfaces that face each other in the X-axis direction. The pair of long side surfaces 206 are surfaces that face each other in the Y-axis direction. The long side surfaces 206 of the battery cells 2 housed in the module casing 5 face each other in the Y-axis direction. The terminal surface 203, the bottom surface 204, the pair of short side surfaces 205, and the pair of long side surfaces 206 of the battery cell 2 in normal operation are flat surfaces. The terminal surface 203 is an example of a first end portion, and the bottom surface 204 is an example of a second end portion.

[0017] A positive electrode terminal 23 and a negative electrode terminal 24 for inputting and outputting current are attached to the lid 201 by being fixed to the lid 201 by crimping or by being cast in when the lid 201 is molded. The positive electrode terminal 23 and the negative electrode terminal 24 are electrically insulated from the lid 201. The positive electrode terminal 23 and the negative electrode terminal 24 are formed, for example, in a substantially flat plate shape.

[0018] A power generating element 27, which is housed in the cell casing 20 and is shown simplified by a dashed line, has its positive electrode electrically connected to a positive electrode terminal 23. The negative electrode of the power generating element 27 is electrically connected to a negative electrode terminal 24. The power generating element 27 includes, for example, a wound electrode group.

[0019] The module housing 5 is made of a material having electrical insulation properties. Examples of materials for forming the module housing 5 include resins such as polyphenylene ether, polycarbonate, and polybutylene terephthalate. The module housing 5 houses, for example, nine battery cells 2. In the module housing 5, one battery cell 2 and another battery cell 2 located next to the one battery cell 2 have their positive terminal 23 and negative terminal 24 located opposite to each other in the X-axis direction. Here, the multiple battery cells 2 housed in the module housing 5 are referred to as one battery cell string 2A. The module housing 5 is also referred to as a case.

[0020] The module housing 5 includes a box section 51. The box section 51 includes a pair of side walls 512 facing each other in the longitudinal direction (Y-axis direction) of the module housing 5, a pair of side walls 513 facing each other in the lateral direction (X-axis direction) of the module housing 5, and a bottom plate 515. The pair of side walls 512, the pair of side walls 513, and the bottom plate 515 are integrally formed.

[0021] The box portion 51 has multiple partition walls 516. Each partition wall 516 is disposed between a pair of side walls 512 in the Y-axis direction. The interior of the box portion 51 is divided in the Y-axis direction into nine storage chambers 517, the same number as the number of battery cells 2, by, for example, eight partition walls 516 disposed at equal intervals from each other. At least the outer surfaces of the partition walls 516 are formed from an electrically insulating material, and they also function as separators.

[0022] Each storage chamber 517 of the box portion 51 stores one battery cell 2, with the long sides 206 of the battery cells 2 facing each other in the Y-axis direction. For example, an adhesive is provided on the upper surface of the bottom plate 515 (the bottom surface of the storage chamber 517), and the bottom surface 204 of the battery cell 2 is adhered and fixed to the bottom plate 515 by the adhesive. In addition, each partition wall 516 ensures that the multiple battery cells 2 are appropriately positioned in the Y-axis direction. The adhesive (not shown) is, for example, a two-component curing epoxy resin adhesive, but is not limited to this and may be an extremely thin double-sided tape, etc.

[0023] In the battery cell row 2A, the short side direction of each battery cell 2 is parallel or approximately parallel to the longitudinal direction (Y-axis direction) of the module housing 5, and the long side direction of each battery cell 2 is parallel or approximately parallel to the short side direction (X-axis direction) of the module housing 5. In the battery cell row 2A, the height direction of each battery cell 2 is parallel or approximately parallel to the height direction (Z-axis direction) of the module housing 5.

[0024] 1, module housing 5 includes resin cover 52 serving as a top plate for box portion 51. Resin cover 52 includes flat plate portion 520 formed in a rectangular shape in a plan view, a lower frame portion (not shown) hanging down from an outer circumferential region of the lower surface of flat plate portion 520, wall portion 521 erected in an outer circumferential region of the upper surface of flat plate portion 520, and a plurality of terminal exposure holes 523 penetrating flat plate portion 520 in the thickness direction (Z-axis direction).

[0025] The upper portion of the battery cell string 2A housed in the box portion 51 fits into the space surrounded by the lower surface of the flat plate portion 520 and a lower frame portion (not shown). In addition, the positive electrode terminal 23 and the negative electrode terminal 24 of each battery cell 2 are exposed on the upper surface of the flat plate portion 520 through terminal exposure holes 523 of the flat plate portion 520.

[0026] As shown in FIG. 1, the upper surface side of the resin cover 52 is surrounded on all four sides by a wall portion 521, and an accommodating portion 528 for accommodating the bus bar 3 and the monitoring device 4 is formed.

[0027] The busbar 3 is, for example, made of aluminum or an aluminum alloy formed into a substantially rectangular flat plate shape, and has through holes 3f arranged in the longitudinal direction (Y-axis direction) and penetrating therethrough in the thickness direction. The through holes 3f are countersunk holes for laser welding using a brazing material, and molten brazing material is poured in. The busbar 3 and the electrode terminals 22 are connected by the brazing material. Note that the busbar 3 is shown diagrammatically in Figs. 1 to 3. The configuration of the busbar 3 will be described in detail later.

[0028] The bus bar 3 is laser-welded, using a brazing material, to the positive terminal 23 and the negative terminal 24 of the battery cell 2 exposed from the terminal exposure hole 523 of the resin cover 52 shown in Fig. 1. Specifically, as shown in Fig. 2, one end of the bus bar 3 in the Y-axis direction is welded to the positive terminal 23 of one battery cell 2, and the other end of the bus bar 3 in the Y-axis direction is welded to the negative terminal 24 of the adjacent battery cell 2 in the Y-axis direction. In addition, the negative terminal 24 of one battery cell 2 is welded to the positive terminal 23 of the adjacent battery cell 2 on the opposite side to the adjacent battery cell 2 by the bus bar 3. Note that in Fig. 2, the module housing 5 accommodating the multiple battery cells 2 is shown simplified by a two-dot chain line.

[0029] For example, among the multiple battery cells 2 housed in the module housing 5 shown in Fig. 2, the positive electrode terminal 23 of the battery cell 2 located at the end position in the -Y direction in the module housing 5 and not connected by the bus bar 3 is connected to a positive power input / output terminal (not shown) via the bus bar 3. For example, among the multiple battery cells 2 housed in the module housing 5, the negative electrode terminal 24 of the battery cell 2 located at the end position in the +Y direction in the module housing 5 and not connected by the bus bar 3 is connected to a negative power input / output terminal (not shown) via the bus bar 3. The battery module 1 is charged and used by connecting the positive power input / output terminal (not shown) and the negative power input / output terminal (not shown) to a charging power source or a load.

[0030] In this manner, the multiple battery cells 2 are connected, for example, in series by the multiple bus bars 3 to form a battery module 1. In a battery module 1 including multiple battery cells 2 electrically connected in parallel, the multiple battery cells 2 can be electrically connected by, for example, connecting the negative electrode terminals 24 to each other by the bus bars 3 and connecting the positive electrode terminals 23 to each other by the bus bars 3. The multiple bus bars 3 form a bus bar group 11.

[0031] The monitoring device 4 shown in FIG. 1 is, for example, a circuit board device, and is also called a CMU (Cell Monitoring Unit) board. The monitoring device 4 has a cell monitoring IC and the like mounted on a rectangular plate-shaped circuit board 4a, detects (measures) the voltage and temperature of the battery cells 2, and is configured to be able to exchange data with, for example, a higher-level control device (not shown). As an example, the monitoring device 4 detects the voltage of the battery cells 2 based on voltage data (current) from a detection terminal portion 3b (described later) of the bus bar 3. An example of a higher-level control device is a BMU (Battery Management Unit). The monitoring device 4 has a function of controlling each of the multiple battery cells 2 of the battery module 1. The monitoring device 4 may also measure the charge / discharge amount of the battery cells 2, etc.

[0032] For example, the resin cover 52 is provided with an external communication connector (not shown), and the monitoring device 4 transmits and receives data to and from a higher-level control device through this external communication connector.

[0033] The monitoring device 4 is housed in a housing portion 528 of the resin cover 52. For example, as shown in Fig. 3, the lower surface, that is, the mounting surface 40, is connected to the upper surfaces of the multiple bus bars 3 welded to the multiple battery cells 2. Note that in Fig. 3, the module housing 5 shown in Fig. 1 is simplified and shown by a two-dot chain line to show the connection relationship between the monitoring device 4, the bus bars 3, and the battery cells 2.

[0034] 1, the battery module 1 includes a protective cover 19 to protect the monitoring device 4 electrically connected to the bus bars 3 and the battery cells 2. The protective cover 19 is made of an electrically insulating material and has a rectangular plate shape with upper and lower flat surfaces, and is placed in the accommodation portion 528 of the resin cover 52 so as to cover the monitoring device 4 from above.

[0035] Fig. 4 is a perspective view of the busbar of the first embodiment as viewed from above. Fig. 5 is a perspective view of the busbar of the first embodiment as viewed from below. Fig. 6 is a perspective view of a portion of the busbar of the first embodiment as viewed from below. Fig. 7 is a perspective view of a portion of the busbar of the first embodiment as viewed from below.

[0036] 4 to 7, the busbar 3 has a main body 3a, a voltage detection terminal 3b, and a plurality of (for example, two) connection portions 3c. Note that the voltage detection terminal 3b and the connection portions 3c are omitted from illustration in FIGS. 1 to 3.

[0037] The main body portion 3a spans the electrode terminals 22 of two battery cells 2 adjacent in the Y-axis direction. In detail, the main body portion 3a has a base portion 3d and two extension portions 3e. Line L1 in Figs. 4 to 7 indicates an example of the boundary between the base portion 3d and the two extension portions 3e. Note that the boundary between the base portion 3d and the two extension portions 3e is not limited to the above. The main body portion 3a is also referred to as a main circuit portion.

[0038] The base portion 3d is formed in a rectangular plate shape and extends over the electrode terminals 22 of two battery cells 2 adjacent in the Y-axis direction. The two through holes 3f described above are formed in the base portion 3d. The two extension portions 3e extend in the +X direction from the base portion 3d with a gap between them in the Y-axis direction. In other words, the two extension portions 3e protrude (project) in the +X direction from the base portion 3d with a gap between them in the Y-axis direction.

[0039] The voltage detection terminal portion 3b and the two extension portions 3e are provided between the two extension portions 3e. The bus bar 3 is provided with a through hole 3m surrounded by the base portion 3d, the two extension portions 3e, the voltage detection terminal portion 3b, and the two extension portions 3e.

[0040] The voltage detection terminal portion 3b is electrically connected to the monitoring device 4. For example, the voltage detection terminal portion 3b is fixed to a circuit board 4a of the monitoring device 4 by a brazing material or the like. The voltage detection terminal portion 3b may be directly fixed to the circuit board 4a, or may be fixed to the circuit board 4a via a conductive member.

[0041] The voltage detection terminal portion 3b is connected to two extension portions 3e of the main body portion 3a via two connection portions 3c. The voltage detection terminal portion 3b extends (protrudes) in the +X direction from between the two extension portions 3e. In detail, the voltage detection terminal portion 3b has a bent shape. As an example, the voltage detection terminal portion 3b has three plate portions 3g to 3i. The plate portion 3g extends in the +X direction from between the two extension portions 3e. The plate portion 3h extends in the +Z direction from the end portion of the plate portion 3g on the +X direction side. The plate portion 3i extends in the +X direction from the end portion of the plate portion 3h on the +Z direction side. The plate portion 3i is provided with a through hole 3j. A molten brazing material is poured into the through hole 33j. The brazing material connects the voltage detection terminal portion 3b and the circuit board 4a.

[0042] The two connection parts 3c connect the main body 3a and the voltage detection terminal 3b. In detail, the two connection parts 3c are arranged at an interval between the two extension parts 3e in the Y-axis direction and are interposed between the two connection parts 3c and the plate part 3g of the voltage detection terminal 3b. Each connection part 3c is provided with a V-shaped cutout 3k. As a result, at least a part of the connection part 3c is thinner than the main body 3a and the voltage detection terminal 3b. The connection part 3c has a lower strength than the main body 3a and the voltage detection terminal 3b around the connection part 3c. The connection part 3c is also called a fragile part, a thin part, an easily deformable part, or the like.

[0043] The battery module 1 configured as described above is charged by supplying power from a power source (not shown). Also, the battery module 1 is discharged by supplying power from the battery module 1 to a load. Hereinafter, the operation of the battery module 1 in the case where each battery cell 2 of the battery module 1 of this embodiment swells due to repeated charging and discharging will be described with reference to Figs. 8 to 11.

[0044] Fig. 8 is a side view of a battery cell row and a busbar group of the first embodiment, showing a state in which the cell casing is not swollen. Fig. 9 is a side view of a battery cell row and a busbar group of the first embodiment, showing a state in which the cell casing is swollen and the busbar group is deformed. Fig. 10 is a side view of two battery cells and one busbar of the first embodiment, showing a state in which the cell casing is swollen and the busbar is deformed. Fig. 11 is a side view of a busbar of the first embodiment, showing a state in which the busbar is deformed.

[0045] As shown in FIG. 8, before swelling occurs in the battery cell 2 due to repeated charging and discharging, the terminal surface 203, the bottom surface 204, a pair of short side surfaces 205, and a pair of long side surfaces 206 of the battery cell 2 are flat surfaces.

[0046] The battery cells 2 generate heat as the charging and discharging of each battery cell 2 is repeated. That is, the battery cells 2 generate heat that is approximated by the product of their internal resistance and the square of the charging and discharging currents as a result of charging and discharging. In addition, the power generating element 27 inside the battery cell 2 is a coil wound and stored together with an electrolyte, so that the thermal conductivity differs depending on the winding direction, stacking direction, and in-plane direction, and the ease of heat dissipation differs depending on each surface of the rectangular battery cell 2. The amount of heat generated is the largest at the center of the battery cell 2, and the amount of heat generated decreases from the center of the battery cell 2 toward the outer surface of the battery cell 2. That is, in the battery cell 2 shown in FIG. 1, a pair of long side surfaces 206, which have the largest area, generate the most heat, while the amount of heat generated decreases toward a pair of short side surfaces 205, a bottom surface 204, and a terminal surface 203 of the battery cell 2.

[0047] When the internal pressure of the prismatic (rectangular) battery cell 2 increases due to heat generation, the cell casing 20 swells from the state shown in FIG. 8 to the state shown in FIG. 9. As a result, as shown in FIG. 9, two cell casings 20 adjacent in the Y-axis direction come into contact with each other and push against each other, widening the gap between the bottom surfaces 204 of the two cell casings 20, and displacing the multiple battery cells 2 into a fan shape. This is because the terminal surfaces 203 of the two cell casings 20 are connected to each other by the bus bar 3, and the adjacent long side surfaces 206 push against each other with the bus bar 3 as a fulcrum. At this time, for example, the cell casing 20 breaks through the module casing 5. At this time, as shown in FIG. 10 and FIG. 11, the bus bar 3 is bent and deformed into a convex shape toward the two battery cells 2. As a result, stress concentration occurs at the connection portion 3c of the bus bar 3, and the connection portion 3c breaks. The breakage of the connection portion 3c separates the main body portion 3a from the voltage detection terminal portion 3b. At this time, the multiple bus bars 3 are bent and deformed with approximately the same curvature regardless of the installation location. Therefore, the connection portions 3c of the multiple bus bars 3 break at approximately the same time regardless of the installation location of the multiple bus bars 3. At this time, the main body portions 3a of the bus bars 3 do not break, so charging and discharging of the battery cells 2 can continue.

[0048] Thus, in this embodiment, the expansion of the cell casing 20 causes two adjacent cell casings 20 in the Y-axis direction to press against each other, widening the gap between the bottom surfaces 204 of the two cell casings 20 and bending the busbar 3, causing the connection portion 3c to break and separate the main body portion 3a from the voltage detection terminal portion 3b. That is, when a bending force is applied to the busbar 3, the largest stress is generated in the connection portion 3c, and the connection portion 3c of the busbar 3 breaks first.

[0049] The monitoring device 4 judges (detects) whether or not swelling has occurred in the cell casing 20 based on the voltage data (current) from the voltage detection terminal 3b. Here, when the connection portion 3c breaks and the main body portion 3a and the voltage detection terminal 3b are separated, the voltage data from the voltage detection terminal 3b to the monitoring device 4 stops. That is, the current value drops. As an example, when voltage data is input from the voltage detection terminal 3b, the monitoring device 4 judges that swelling has not occurred in the cell casing 20, and when the voltage data from the voltage detection terminal 3b is no longer input (when the voltage data drops), the monitoring device 4 judges that swelling has occurred in the cell casing 20. In other words, when the voltage of the battery cell 2 can be detected, the monitoring device 4 judges that swelling has not occurred in the cell casing 20, and when the voltage of the battery cell 2 cannot be detected, the monitoring device 4 judges that swelling has occurred in the cell casing 20. Also, as an example, when voltage data is input from the multiple voltage detection terminal units 3b, the monitoring device 4 determines that no swelling has occurred in the cell casing 20, and when voltage data is no longer input (the voltage drops) from the multiple voltage detection terminal units 3b, the monitoring device 4 determines that swelling has occurred in the cell casing 20. In other words, when it is possible to simultaneously detect the voltages of multiple battery cells 2, the monitoring device 4 determines that no swelling has occurred in the cell casing 20, and when it is not possible to simultaneously detect the voltages of multiple battery cells 2, the monitoring device 4 determines that swelling has occurred in the cell casing 20. In this way, by determining the presence or absence of swelling in the cell casing 20 based on whether or not the voltages of the multiple battery cells 2 can be detected, the frequency of erroneous detection of swelling in the cell casing 20 can be reduced.

[0050] When the monitoring device 4 detects swelling in the cell casing 20, it transmits the detection result to a higher-level control device. When the higher-level control device receives the detection result indicating that swelling has occurred in the cell casing 20, it determines that an abnormality has occurred in the battery module 1. The control device then stops charging and discharging the battery module 1. This makes it possible to minimize the swelling and deformation of the cell casing 20 and damage to the battery module 1.

[0051] When a tensile force in the Y-axis direction acts on the busbar 3, the greatest stress occurs at the edge of the through hole 3f between the two through holes 3f in the main body 3a. Therefore, when a tensile force in the Y-axis direction acts on the busbar 3, the parts of the busbar 3 other than the connection parts 3c break first.

[0052] As described above, the battery module of the embodiment includes a plurality of battery cells 2, a bus bar 3, and a monitoring device 4. Each of the plurality of battery cells 2 includes a cell housing 20 having a terminal surface 203 (first end) and a bottom surface 204 (second end) opposite to the terminal surface 203, and an electrode terminal 22 provided on the terminal surface 203. The battery cells 2 are arranged in a Y-axis direction (second direction) perpendicular to a -Z direction (first direction) from the terminal surface 203 to the bottom surface 204. The bus bar 3 is fixed to each of the electrode terminals 22 of two battery cells 2 adjacent to each other in the Y-axis direction, and electrically connects the electrode terminals 22 of the two battery cells 2. The monitoring device 4 is electrically connected to the battery cells 2 via the bus bar 3 and detects the voltage of the battery cells 2. The bus bar 3 includes a main body portion 3a, a voltage detection terminal portion 3b, and a connection portion 3c. The main body 3a spans the electrode terminals 22 of the two battery cells 2 adjacent in the Y-axis direction. The voltage detection terminal 3b connects the main body 3a and the voltage detection terminal 3b. Due to the expansion of the cell casing 20, the two cell casings 20 adjacent in the Y-axis direction press against each other, widening the gap between the bottom surfaces 204 of the two cell casings 20 and bending the busbar 3, causing the connection portion 3c to break and separate the main body 3a and the voltage detection terminal 3b.

[0053] According to this configuration, for example, when the internal pressure of the cell housing 20 increases and the cell housing 20 swells, the connection portion 3c breaks and separates the main body portion 3a and the voltage detection terminal portion 3b. Therefore, the swelling of the cell housing 20 can be detected by the monitoring device 4.

[0054] In this embodiment, the connection portion 3c is provided with a notch 3k.

[0055] According to this configuration, the connecting portion 3c can be broken starting from the portion where the notch 3k is provided.

[0056] Next, a modified example of the first embodiment will be described. Fig. 12 is a perspective view of a portion of a busbar according to the modified example of the first embodiment. In this modified example, the busbar 3 has one connection portion 3c. With this configuration, breakage of the connection portion 3c occurs more easily. Furthermore, the shape of the busbar 3 can be simplified.

[0057] <Second embodiment> FIG. 13 is a perspective view of a portion of the bus bar of the second embodiment.

[0058] As shown in FIG. 13, this embodiment is different from the first embodiment mainly in the connection portion 3c of the busbar 3. The connection portion 3c of this embodiment is thinner and weaker than the main body portion 3a and the voltage detection terminal portion 3b. In addition, the connection portion 3c has flexibility (elasticity). The connection portion 3c can be made of a flexible material such as aluminum. The connection portion 3c may be a plate-shaped portion extending between the main body portion 3a and the voltage detection terminal portion 3b, or may be an assembly of multiple linear members extending between the main body portion 3a and the voltage detection terminal portion 3b.

[0059] According to this configuration, similarly to the first embodiment, when the busbar 3 is bent and deformed, the connection portion 3c breaks. At this time, in this embodiment, since the connection portion 3c has flexibility, the connection portion 3c breaks gradually, so that the swelling of the cell casing 20 can be detected in stages.

[0060] <Third embodiment> Fig. 14 is a perspective view of the bus bar according to the third embodiment. Fig. 15 is an exploded perspective view of the bus bar according to the third embodiment.

[0061] The present embodiment differs from the first embodiment mainly in the busbar 3. In the busbar 3 of the present embodiment, a main body portion 3a and a voltage detection terminal portion 3b are formed from separate members and are joined to each other by a connection portion 3c.

[0062] The voltage detection terminal portion 3b has two protruding portions 3n in addition to the three plate portions 3g to 3i. The two protruding portions 3n protrude in opposite directions from the plate portion 3g along the Y-axis direction. The two protruding portions 3n are superimposed on the upper surfaces of the two extending portions 3e of the main body portion 3a via the two connecting portions 3c. That is, the two connecting portions 3c bond the two protruding portions 3n to the main body portion 3a. The region R1 in FIG. 15 is the region where the connecting portions 3c are provided. The connecting portions 3c bond the entire overlapping region between the protruding portions 3n and the plate portion 3h.

[0063] The connecting portion 3c is, for example, a double-sided adhesive tape, or may be an adhesive.

[0064] According to this configuration, similarly to the first embodiment, when the busbar 3 is bent and deformed, the connection portion 3c breaks.

[0065] <Fourth embodiment> FIG. 16 is a perspective view of a bus bar according to the fourth embodiment.

[0066] This embodiment is different from the third embodiment mainly in the busbar 3. The two connection portions 3c of the busbar 3 in this embodiment are welded portions formed by joining the main body portion 3a and the voltage detection terminal portion 3b by welding. The two connection portions 3c are formed by welding the ends (short sides) in the Y-axis direction of the two protruding portions 3n to the main body portion 3a.

[0067] According to this configuration, similarly to the first embodiment, when the busbar 3 is bent and deformed, the connection portion 3c breaks.

[0068] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0069] 1...battery module, 2...battery cell, 3...bus bar, 3a...main body, 3b...voltage detection terminal, 3c...connection, 3k...notch, 4...monitoring device, 20...cell casing, 22...electrode terminal, 203...terminal surface (first end), 204...bottom surface (second end).

Claims

1. a cell housing having a first end and a second end opposite to the first end, and an electrode terminal provided at the first end; and a plurality of battery cells arranged in a second direction perpendicular to a first direction from the first end to the second end; a bus bar that is fixed to each of the electrode terminals of two of the battery cells adjacent to each other in the second direction and electrically connects the electrode terminals of the two battery cells; a monitoring device electrically connected to the battery cell via the bus bar and detecting a voltage of the battery cell; Equipped with The bus bar is a main body portion extending across the electrode terminals of each of the two battery cells adjacent to each other in the second direction; a voltage detection terminal portion electrically connected to the monitoring device; a connection portion that connects the main body portion and the voltage detection terminal portion; having the expansion of the cell casing causes the two cell casings adjacent to each other in the second direction to press against each other, widening the gap between the second ends of the two cell casings and bending the bus bar, thereby breaking the connection portion and separating the main body portion and the voltage detection terminal portion; Battery module.

2. The connection portion is provided with a notch. The battery module according to claim 1 .

3. The connection portion is flexible. The battery module according to claim 1 .

4. The connection portion joins the main body portion and the voltage detection terminal portion. The battery module according to claim 1 .

5. The bus bar has a plurality of the connection portions. The battery module according to claim 1 .

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