Battery pack, sub-battery module, and method for manufacturing battery pack

Abstract

The present invention is a battery pack characterized in that the battery pack includes: a plurality unit cells; a bus bar 302 that electrically links terminals of the plurality of unit cells; a voltage detection line terminal 401 that is joined to the bus bar 302; a joining section 340 that joins the bus bar 302 and the voltage detection line terminal 401; and a bus bar holder on which the bus bar 302 and the voltage detection line terminal 401 are mounted. The battery pack is also characterized in that: the thickness Tb of the voltage detection line terminal 401 is less than the thickness Ta of the bus bar 302; and the distance between the voltage detection line terminal 401 and the bus bar 302 is such that the distance at an end section 401t of the voltage detection line terminal 401 is greater than the distance at a site closer to the joining section 340 than the end section 401t. Due to this configuration, a battery pack and a sub-battery module are provided in which heterogeneous metals and water droplets are not prone to be retained in the joining section between the bus bar and the voltage detection line terminal. Moreover, a method for manufacturing a battery pack is provided that can ensure the reliability of joining when the voltage detection line terminal is joined to the bus bar.

Description

Battery assembly, sub-battery module, and method of manufacturing battery assembly

[0001] The present invention relates to a battery pack, a sub-battery module, and a method for manufacturing a battery pack.

[0002] 2. Description of the Related Art Conventionally, there has been known a battery pack in which terminals of a plurality of cells are electrically connected by bus bars and which has voltage detection line terminals for measuring the voltage of the cells.

[0003] JP 2019-8889 A

[0004] It is desirable that dissimilar metals and water droplets do not accumulate at the joint between the bus bar and the voltage detection line terminal. Furthermore, reliability of the joint is required when joining the bus bar and the voltage detection line terminal. The present invention aims to provide a battery assembly and a sub-battery module in which dissimilar metals and water droplets are less likely to accumulate at the joint between the bus bar and the voltage detection line terminal. Another aim is to provide a method for manufacturing a battery assembly that can ensure reliability of the joint when joining the voltage detection line terminal to the bus bar.

[0005] In order to solve the above problems, the battery assembly of the present invention includes a plurality of unit cells. The battery assembly of the present invention includes a bus bar that electrically connects terminals of the plurality of unit cells. The battery assembly of the present invention includes a voltage detection line terminal joined to the bus bar. The battery assembly of the present invention includes a bus bar holder on which the bus bar and the voltage detection line terminal are mounted. The thickness of the voltage detection line terminal is smaller than the thickness of the bus bar. The distance between the voltage detection line terminal and the bus bar is larger at the end of the voltage detection line terminal than at a location closer to the joint than the end. Alternatively, in order to solve the above problems, the battery assembly of the present invention includes a plurality of unit cells. The battery assembly of the present invention includes a bus bar that electrically connects terminals of the plurality of unit cells. The battery assembly of the present invention includes a voltage detection line terminal joined to the bus bar. The battery assembly of the present invention includes a bus bar and a bus bar holder on which the voltage detection line terminal is mounted. The thickness of the voltage detection line terminal is smaller than the thickness of the bus bar. The joint joins the end of the bus bar and the end of the voltage detection line terminal. The distance between the voltage detection line terminal and the bus bar is larger at a location farther from the joint than at a location closer to the joint.

[0006] Alternatively, to solve the above problem, the sub-battery module of the present invention includes a bus bar for electrically connecting the terminals of a plurality of cells. The sub-battery module of the present invention includes a voltage detection line terminal joined to the bus bar. The sub-battery module of the present invention includes a joint that joins the bus bar and the voltage detection line terminal. The sub-battery module of the present invention includes a bus bar holder on which the bus bar and the voltage detection line terminal are placed. The thickness of the voltage detection line terminal is smaller than the thickness of the bus bar. The distance between the voltage detection line terminal and the bus bar is larger at the end of the voltage detection line terminal than at a location closer to the joint than the end.

[0007] Alternatively, to solve the above problem, a method for manufacturing a battery pack of the present invention includes a mounting step of arranging a bus bar for electrically connecting terminals of a plurality of cells and a voltage detection line terminal joined to the bus bar in a predetermined mounting area of ​​a bus bar holder. The method also includes a joining step of joining the bus bar and the voltage detection line terminal. The voltage detection line terminal has a thickness smaller than that of the bus bar. In the mounting step, the bus bar and the voltage detection line terminal are both plate-shaped, and after the joining step, the distance between the voltage detection line terminal and the bus bar at the end of the voltage detection line terminal is changed to a shape that is larger than the distance at a location closer to the joint than the end.

[0008] The present invention can provide a battery assembly and a sub-battery module in which dissimilar metals and water droplets are less likely to accumulate at the joint between the bus bar and the voltage detection line terminal, or a method for manufacturing a battery assembly that can ensure the reliability of the joint when joining the voltage detection line terminal to the bus bar.

[0009] 7 is a perspective view showing a battery pack 1 according to an embodiment; FIG. 8 is a perspective view showing components of a battery 100 and a holding unit 200 disassembled in the stacking direction X; FIG. 9 is a perspective view showing the configuration of a busbar unit 300 and a voltage detection unit 400 according to a first embodiment; FIG. 10 is a view of the busbar unit 300 and the voltage detection unit 400 as viewed from the direction IV in FIG. 3; FIG. 11 is a view of the busbar unit 300 and the voltage detection unit 400 as viewed from the direction V in FIG. 3; FIG. 12 is an enlarged view of a portion indicated by VI in FIG. 4; FIG. 13 is a view showing the configuration of a busbar 302 and a voltage detection line terminal 401; FIG. 14 is a cross-sectional view taken along the line VIII-VIII in FIG. 7; FIG. 15 is an enlarged view of busbars 302a and 302b; FIG. 16 is an enlarged view of a voltage detection line terminal 401; FIG. 17 is a view of the busbars 302a and 302b and the voltage detection line terminal 401 fitted into a busbar holder 311 as viewed from the direction IV in FIG. 3; 10(b) is a diagram showing the state in which the bus bars 302a, 302b and the voltage detection line terminal 401 are arranged in the bus bar holder 311, as viewed from the V direction in FIG. 3. It is a conceptual diagram of the bus bars and the voltage detection line terminal 401 as viewed from the XI direction in FIG. 10(a). (a) to (b) are diagrams showing other shapes of the voltage detection line terminal 401. (a) to (b) are diagrams showing the positional relationship between the bus bar 302, the voltage detection line terminal 401, and the battery 100.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0011] <Overall Description of Battery Assembly 1> The configuration of the battery assembly 1 according to the embodiment will be described with reference to FIGS. 1 and 2. Embodiments of the present invention will be described with reference to the drawings. To facilitate understanding of each embodiment, the size and proportions of components may be exaggerated in each drawing. The same reference numerals are used for the same components in each drawing. In each drawing, the stacking direction X, width direction Y, and height direction Z of the battery assembly 1 are indicated by arrows. However, in each drawing, the stacking direction X, width direction Y, and height direction Z of the battery assembly 1 indicate the relative positional relationship within the same drawing. That is, if the battery assembly 1 is rotated 180 degrees and the top and bottom surfaces are reversed, or if the battery assembly 1 is rotated 90 degrees and the top surface is placed as a side, the stacking direction X, width direction Y, and height direction Z of the battery assembly 1 will change. In each drawing, the threads on the outer surfaces of the fastening bolts and the grooves on the inner surfaces of the insert nuts are omitted.

[0012] The configuration of a battery pack 1 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the battery pack 1 according to an embodiment. Fig. 2 is a perspective view showing the components of a battery 100 and a holding unit 200 disassembled in the stacking direction X.

[0013] The battery pack 1 is configured as, for example, a power source for operating a motor for running a vehicle. The battery pack 1 may also be configured as, for example, a power source for operating electrical equipment mounted on the vehicle.

[0014] 1 , the battery pack 1 includes a plurality of batteries 100, a holding unit 200 that holds the plurality of batteries 100, and a bus bar unit 300 that electrically connects the plurality of batteries 100. The battery pack 1 also includes a voltage detection unit 400 that detects the voltage of the batteries 100, and a temperature measurement unit (not shown) that measures the temperature of the batteries 100.

[0015] (Configuration of Battery 100) The battery 100 is an example of a single cell, and is stacked in the stacking direction X via a holding unit 200. For example, 24 batteries 100 are stacked. The battery 100 is configured, for example, by a lithium ion secondary battery. The battery 100 includes a current collector and an electrolyte. As shown in FIG. 2 , the battery 100 includes a container 101, a lid 102, a positive electrode terminal 103, a negative electrode terminal 104, and a safety valve 105. The components included in the battery 100 will be described below.

[0016] As shown in FIG. 2 , the battery 100 is formed in a rectangular parallelepiped shape. A positive electrode terminal 103 and a negative electrode terminal 104 are provided on an upper surface 100a of the battery 100 along the stacking direction X. The upper surface 100a corresponds to the upper surface of the battery 100 in FIG. 2 . The upper surface 100a is formed in a rectangular shape. The length of the upper surface 100a along the width direction Y of the battery 100 is longer than the length of the upper surface 100a along the stacking direction X of the battery 100. The upper surface 100a faces the busbar unit 300 shown in FIG. 1 . Two side surfaces 100b along the stacking direction X of the battery 100 face each other perpendicularly to the upper surface 100a. The side surfaces 100b are formed in a rectangular shape. The length of the side surfaces 100b along the height direction Z of the battery 100 is longer than the length of the side surfaces 100b along the stacking direction X of the battery 100. Two main surfaces 100 c of the battery 100 that face each other in the stacking direction X are in contact with the cell spacers 202 and the like of the holding unit 200 .

[0017] The current collector of the battery 100 corresponds to a charge / discharge element between which electric power is input and output. The current collector of the battery 100 is configured by winding or stacking a positive electrode and a negative electrode with a separator interposed therebetween. The container 101 contains the current collector and an electrolyte. The lid 102, together with the container 101, seals the current collector and the electrolyte. The lid 102 is joined to the container 101. The positive electrode terminal 103 and the negative electrode terminal 104 relay the input and output of electric power between the current collector and the electrical device. The positive electrode terminal 103 and the negative electrode terminal 104 are attached to the lid 102. The positive electrode terminal 103 of one battery 100 and the negative electrode terminal 104 of the other battery 100, which are adjacent along the stacking direction X, face each other in the stacking direction X, as shown in FIG. 2 . The safety valve 105 ruptures toward the outside of the battery 100 when the internal pressure of the battery 100 exceeds a predetermined value. The safety valve 105 is also called a split valve. The safety valve 105 is provided in the lid 102, for example.

[0018] (Configuration of holding unit 200) The holding unit 200 holds multiple batteries 100. As shown in Fig. 2, the holding unit 200 includes a first end spacer 201, a cell spacer 202, and a second end spacer 203. The holding unit 200 also includes a first end block 211, a second end block 212, an insulating member 221, and an insert nut 222. As shown in Fig. 1, the holding unit 200 also includes a first side plate 231, a second side plate 232, and a fastening bolt 241. The configuration included in the holding unit 200 will be described below.

[0019] As shown in FIG. 2 , the first end spacer 201 is provided between the first end block 211 and the battery 100. The first end spacer 201 contacts the first battery 100 located at one end of the 24 stacked batteries 100. The first end spacer 201 insulates the first end block 211 from the battery 100. The first end spacer 201 covers each side surface of the first end block 211 and the battery 100 along the width direction Y. The first end spacer 201 covers a portion of the side surface 100b of the battery 100 along the stacking direction X. The thickness of the first end spacer 201 along the stacking direction X is sufficiently thinner than the thickness of the battery 100 along the stacking direction X. The first end spacer 201 is formed of an insulating material.

[0020] As shown in FIG. 2 , the cell spacers 202 are provided between adjacent batteries 100. The cell spacers 202 hold and insulate the adjacent batteries 100. The cell spacers 202 cover the main surfaces 100c of the adjacent batteries 100 along the width direction Y and a portion of the side surfaces 100b of the adjacent batteries 100 along the stacking direction X. The thickness of the cell spacers 202 along the stacking direction X is sufficiently thinner than the thickness of the batteries 100 along the stacking direction X. The cell spacers 202 are made of an insulating material.

[0021] As shown in FIG. 2 , the second end spacer 203 is provided between the battery 100 and the second end block 212. The second end spacer 203 contacts the 24th battery 100 located at the other end of the 24 stacked batteries 100. The second end spacer 203 insulates the battery 100 from the second end block 212. The second end spacer 203 covers each side surface of the first end block 211 and the battery 100 along the width direction Y. The second end spacer 203 covers a portion of the side surface 100b of the battery 100 along the stacking direction X. The thickness of the second end spacer 203 along the stacking direction X is sufficiently thinner than the thickness of the batteries 100 along the stacking direction X. The second end spacer 203 is formed of an insulating material.

[0022] As shown in FIG. 2 , the first end block 211 is stacked with the first battery 100 located at one end of the 24 stacked batteries 100 via a first end spacer 201. The first end block 211 extends along a width direction Y that intersects with the stacking direction X of the batteries 100. The first end block 211 is adjacent to the battery 100 located at the end along the stacking direction X and supports the battery 100. The first end block 211 is formed in a rectangular parallelepiped shape extending in the width direction Y. Fastening bolts 241 are screwed into a plurality of screw holes 211m formed on the side surface of the first end block 211 along the width direction Y. As shown in FIG. 1 , the first end block 211 is fixed to the first side plate 231 by the fastening bolts 241. Similarly, the first end block 211 is fixed to the second side plate 232 by the fastening bolts 241. The first end block 211 is formed with insertion holes 211n for inserting bolts or the like for fixing the battery pack 1. The first end block 211 is made of, for example, metal or resin.

[0023] As shown in FIG. 2 , the second end block 212 is stacked with the 24th battery 100 located at the other end of the 24 stacked batteries 100 via a second end spacer 203. The second end block 212 extends along the width direction Y of the batteries 100. The second end block 212 is adjacent to the battery 100 located at the end along the stacking direction X and supports the battery 100. The second end block 212 is formed in a rectangular parallelepiped shape extending in the width direction Y. Fastening bolts 241 are screwed into multiple screw holes formed on the side surface of the second end block 212 along the width direction Y. As shown in FIG. 1 , the second end block 212 is fixed to the first side plate 231 by the fastening bolts 241. Similarly, the second end block 212 is fixed to the second side plate 232 by the fastening bolts 241. The second end block 212 is formed with insertion holes 212n for inserting bolts or the like to secure the battery pack 1. The second end block 212 is formed of, for example, metal or resin.

[0024] 2, the insulating member 221 is inserted into the first end block 211. The insulating member 221 is also inserted into the second end block 212. The insulating member 221 is formed, for example, in a rectangular parallelepiped shape. The insulating member 221 is made of an insulating material.

[0025] The insulating member 221 may be configured as follows. That is, the insulating member 221 may be molded integrally with the first end spacer 201, or may be molded separately from the first end spacer 201 and then joined to the first end spacer 201. In such a case, the first end block 211 has a recess on its surface facing the first end spacer 201 that accommodates the insulating member 221 along the stacking direction X. Similarly, the insulating member 221 may be molded integrally with the second end spacer 203, or may be molded separately from the second end spacer 203 and then joined to the second end spacer 203. In such a case, the second end block 212 has a recess on its surface facing the second end spacer 203 that accommodates the insulating member 221 along the stacking direction X.

[0026] The insert nut 222 is embedded in a recess formed in the upper surface of the insulating member 221. A fastening bolt is anchored to the insert nut 222 via a bus bar that is electrically connected to an external control device, for example.

[0027] 1 , the first side plate 231 is arranged at one end of the stacked batteries 100 in the width direction Y, along the stacking direction X of the stacked batteries 100. The first side plate 231 holds the batteries 100 along the stacking direction X. The first side plate 231 is fixed to the first end block 211 and the second end block 212 by fastening bolts 241.

[0028] 1 , the second side plate 232 is arranged along the stacking direction X of the stacked plurality of batteries 100, at the other end of the plurality of batteries 100 in the width direction Y. The second side plate 232 holds the plurality of batteries 100 along the stacking direction X. The second side plate 232 is fixed to the first end block 211 and the second end block 212 by fastening bolts 241.

[0029] (Configuration of Busbar Unit 300 and Voltage Detection Unit 400) FIGS. 3 to 6 are diagrams showing the configuration of the busbar unit 300 and the voltage detection unit 400 according to an embodiment. Of these, FIG. 3 is a perspective view showing the configuration of the busbar unit 300 and the voltage detection unit 400 according to an embodiment. FIG. 4 is a diagram showing the busbar unit 300 and the voltage detection unit 400 as viewed from the direction IV in FIG. 3. It can also be said that FIG. 4 is a diagram showing the busbar unit 300 and the voltage detection unit 400 as viewed from the direction opposite to the Z direction. It can also be said that FIG. 4 is a diagram showing the front surface of the busbar unit 300. FIG. 5 is a diagram showing the busbar unit 300 and the voltage detection unit 400 as viewed from the direction V in FIG. 3. It can also be said that FIG. 5 is a diagram showing the busbar unit 300 and the voltage detection unit 400 as viewed from the Z direction. It can also be said that FIG. 5 is a diagram showing the back surface of the busbar unit 300. FIG. 6 is an enlarged view of the portion indicated by VI in FIG. 4.

[0030] As shown in Figures 3 to 6, the bus bar unit 300 includes a first end bus bar 301, a plurality of bus bars 302, a second end bus bar 303, and a bus bar holder 311. As shown in Figures 3 and 4, the voltage detection unit 400 includes a harness 450. The harness 450 is an assembly that brings together a voltage detection line terminal 401, a voltage detection line 402, a connector 403, and a temperature measurement unit.

[0031] The first end bus bar 301 is joined to the negative terminal 104 (see FIG. 2 ) of the battery 100 that is closest to the first end block 211 among the 24 stacked batteries 100. The bus bar 302 electrically connects the terminals of the plurality of batteries 100. As a result, as shown in FIG. 3 , the bus bar 302 electrically connects one battery 100 to another battery 100 that are adjacent to each other along the stacking direction X. The bus bar 302 joins the positive terminal 103 of one battery 100 that is adjacent to each other along the stacking direction X to the negative terminal 104 (see FIG. 2 ) of the other battery 100 that is adjacent to each other along the stacking direction X. The second end bus bar 303 is joined to the positive terminal 103 of the battery 100 that is closest to the second end block 212 among the 24 stacked batteries 100.

[0032] The busbar holder 311 mounts the busbar 302 and the voltage detection line terminal 401. The busbar holder 311 is provided with mounting areas for the busbar 302 and the voltage detection line terminal 401. The busbar 302 and the voltage detection line terminal 401 are then fitted in an overlapping manner into these mounting areas. The busbar holder 311 is, for example, a resin molded product.

[0033] The voltage detection line terminal 401 is disposed on top of the bus bar 302 and is joined to the bus bar 302. In this way, the voltage detection line terminal 401 detects the voltage of the battery 100. The voltage detection line 402 is joined to the voltage detection line terminal 401, and information on the voltage detected by the voltage detection line terminal 401 is sent to an external control device via a connector 403. The first end bus bar 301, the bus bar 302, the second end bus bar 303, and the voltage detection line terminal 401 are formed from, for example, a clad material in which copper and aluminum are joined together, copper, or aluminum.

[0034] (Configuration of Bus Bar 302 and Voltage Detection Line Terminal 401) FIG. 7 is a diagram showing the configuration of the bus bar 302 and the voltage detection line terminal 401. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. Note that in FIG. 7, the bus bar holder 311 and the bus bar 302 are depicted semi-transparently for ease of understanding. The bus bar 302 is composed of a pair of bus bars 302a and 302b. The bus bars 302a and 302b connect the terminals of the battery 100. In this case, as shown in FIG. 8, for example, the bus bar 302b is connected to the negative electrode terminal 104 as a terminal. In this case, the bus bar 302a is connected to the positive electrode terminal 103 as a terminal. Each bus bar 302a, 302b has three surfaces: a bottom M1 extending along the XY plane; a side M2 ​​extending along the YZ plane from the bottom M1 in the Z direction; and an upper portion M3 extending along the XY plane from the side M2 ​​in the X direction. The upper portions M3 of the bus bars 302a, 302b overlap and are electrically connected. The voltage detection line terminal 401 is connected to the first end bus bar 301, the multiple bus bars 302, and the second end bus bar 303 of the bus bar unit 300, respectively. The voltage detection line terminal 401 is connected to these terminals by, for example, laser welding. As shown in FIG. 8 , the voltage detection line terminal 401 is connected to the surface of the bottom M1 of the bus bar 302b facing opposite the Z direction. As shown in FIG. 7 , the voltage detection line 402 connected to the voltage detection line terminal 401 is arranged so as to extend from the voltage detection line terminal 401 in the direction opposite the Y direction.

[0035] FIG. 9( a) is an enlarged view of busbars 302a and 302b. FIG. 9( a) shows busbar 302b viewed in the direction opposite to the Z direction in FIG. 7. FIG. 9( b) is an enlarged view of voltage detection line terminal 401. FIG. 9( b) shows voltage detection line terminal 401 viewed in the direction opposite to the Z direction in FIG. 7. As shown in FIG. 9( a), busbar 302b has recesses 321a and 321b formed as displacement restriction portions. As shown in FIG. 9( b), voltage detection line terminal 401 has recesses 421a and 421b formed as displacement restriction portions. These displacement restriction portions are arranged so that the displacement restriction portions of busbar 302 and voltage detection line terminal 401 overlap each other when installed in busbar holder 311. In other words, when installed in busbar holder 311, recesses 321a and 421a are in the same position and overlap each other. Moreover, the recess 321b and the recess 421b are at the same position and overlap each other.

[0036] FIG. 10( a) is a diagram showing the busbars 302a and 302b and the voltage detection line terminal 401 fitted into the busbar holder 311. FIG. 10( a) shows the busbar holder 311, the busbars 302a and 302b, and the voltage detection line terminal 401 as viewed from the direction IV in FIG. 3. FIG. 10( b) is a diagram showing the voltage detection line terminal 401 placed in the busbar holder 311. FIG. 10( b) shows the busbar holder 311 and the voltage detection line terminal 401 as viewed from the direction V in FIG. 3. Note that in FIG. 10( b), the busbar holder 311 is depicted semi-transparently for ease of understanding. The busbar holder 311 has a displacement restriction receiving portion that engages with the displacement restriction portion and restricts the displacement of the busbar 302 and the voltage detection line terminal 401. 10(a) and 10(b), the displacement restriction receiving portions are convex portions 331a and 331b. That is, concave portions 321a and 421a, which are displacement restriction portions, engage with convex portion 331a, which is the displacement restriction receiving portion. On the other hand, concave portions 321b and 421b, which are displacement restriction portions, engage with convex portion 331b, which is the displacement restriction receiving portion. Note that when the displacement restriction portions are convex portions, the displacement restriction receiving portions become concave portions. This allows bus bar 302b and voltage detection line terminal 401 to be positioned in bus bar holder 311 with greater precision.

[0037] 10(b), a joint 340 that joins the bus bar 302b and the voltage detection line terminal 401 is provided between the recessed portions 421a and 421b, which are displacement restriction portions. The joint 340 is provided at a position where the bus bar 302b and the voltage detection line terminal 401 overlap. As described above, the joining is performed by, for example, laser welding, and in this case, the joint 340 is a laser weld mark. In this case, it can also be said that the joint 340 is provided between the recessed portions 321a and 321b, which are displacement restriction portions. Furthermore, in this case, it can also be said that the joint 340 is provided between the protruding portions 331a and 331b, which are displacement restriction receiving portions. In this case, the joining can be performed with greater precision.

[0038] 11 is a conceptual diagram of the bus bar 302 and the voltage detection line terminal 401 as viewed from the XI direction in FIG. 10( a). As shown in the figure, the thickness Tb of the voltage detection line terminal 401 is smaller than the thickness Ta of the bus bar 302 (Tb<Ta). Furthermore, the distance between the voltage detection line terminal 401 and the bus bar 302 at the end 401t of the voltage detection line terminal 401 is larger than the distance at a location closer to the joint 340 than the end 401t. Note that the distance between the voltage detection line terminal 401 and the bus bar 302 refers to the distance between the voltage detection line terminal 401 and a plane including the surface of the bus bar 302 facing the voltage detection line terminal 401. This also means that the voltage detection line terminal 401 becomes more distant from the bus bar 302 as it moves away from the joint 340. That is, the voltage detection line terminal 401 is joined to the bus bar 302 at the joint 340, but is bent at the joint 340. This can also be said to mean that the voltage detection line terminal 401 is roughly "L" shaped with the joint 340 as the apex. This is because tensile residual stress acts on the voltage detection line terminal 401 during laser welding, and because the voltage detection line terminal 401 is a thin plate, it is bent into this shape due to the tensile residual stress. On the other hand, the bus bar 302 is also plate-shaped, but because it is thicker than the voltage detection line terminal 401, the bus bar 302 is less affected by the tensile residual stress. Therefore, it is less likely to bend than the voltage detection line terminal 401 and maintains its plate-like state. This can also be said to mean that bus bar 302 has a flat plate shape, and the gap between voltage detection line terminal 401 and bus bar 302 is deformed by laser welding, so that the gap at end 401t of voltage detection line terminal 401 is larger than the gap at a location closer to joint 340 than end 401t. Alternatively, it can also be said that voltage detection line terminal 401 has end 401t that is spaced apart from bus bar 302. This makes it easier for dissimilar metals and water droplets (shown as G in the figure) that are generated at joint 340 between bus bar 302 and voltage detection line terminal 401 during laser welding to separate from joint 340 and less likely to remain between bus bar 302 and voltage detection line terminal 401.

[0039] 12(a) and 12(b) are diagrams showing other shapes of the voltage detection line terminal 401. Of these, FIG. 12(a) shows a case where the bus bar 302 and the voltage detection line terminal 401 are joined by fillet welding. In this case, the voltage detection line terminal 401 has an opening K, and the joint 340 is located at the edge of the opening K. In this case, due to the action of tensile residual stress, the distance between the voltage detection line terminal 401 and the bus bar 302 is larger at the end 401t of the voltage detection line terminal 401 than at a location closer to the joint 340 than the end 401t. This can also be said to mean that the voltage detection line terminal 401 is shaped so that it moves away from the bus bar 302 as it moves away from the joint 340.

[0040] 12(b) shows a case where the bus bar 302 and the voltage detection line terminal 401 are joined by butt welding. In this case, the joint 340 joins the end 302t of the bus bar 302 and the end 401t of the voltage detection line terminal 401. In this case as well, due to the action of tensile residual stress, the distance between the voltage detection line terminal 401 and the bus bar 302 is larger at locations farther from the joint 340 than at locations closer to the joint 340. This can also be said to mean that the voltage detection line terminal 401 is shaped to move away from the bus bar 302 as it moves away from the joint 340.

[0041] 13(a) and 13(b) are diagrams showing the positional relationship between the bus bar 302, the voltage detection line terminal 401, and the battery 100. Of these, FIG. 13(a) is a diagram showing the positional relationship between the bus bar 302, the voltage detection line terminal 401, and the battery 100 in the above-described embodiment. In this case, the voltage detection line terminal 401 is arranged on the side of the bus bar 302 where the battery 100 is arranged. In other words, the voltage detection line terminal 401 is arranged between the bus bar 302 and the battery 100 in the Z direction. It can also be said that the battery 100, the voltage detection line terminal 401, and the bus bar 302 are arranged in this order in the Z direction. This contributes to space saving when arranging the voltage detection line terminal 401.

[0042] 13(b) is a diagram showing another example of the positional relationship between the bus bar 302, the voltage detection line terminal 401, and the battery 100, which is different from the embodiment described above. In this case, the voltage detection line terminal 401 is arranged on the opposite side of the bus bar 302 from the side on which the battery 100 is arranged. In other words, the battery 100, the bus bar 302, and the voltage detection line terminal 401 are arranged in this order in the Z direction. This makes it easy to ensure space between the bus bar 302 and the battery 100. Even if another member is arranged between the bus bar 302 and the battery 100, it is easy to ensure an insulation distance.

[0043] (Configuration of Temperature Measurement Unit) The temperature measurement unit measures the temperature of the battery 100 based on control by, for example, an external control device. The temperature measurement unit includes a temperature sensor and an electric wire.

[0044] (Effects of Battery Pack 1 of the Embodiment) The effects of the battery pack 1 of the embodiment will be described. The distance between the voltage detection line terminal 401 and the bus bar 302 at the end 401t of the voltage detection line terminal 401 is larger than the distance at a location closer to the joint 340 than the end 401t. This makes it possible to provide a battery pack in which dissimilar metals and water droplets are less likely to accumulate at the joint 340 between the bus bar 302 and the voltage detection line terminal 401. Laser welding the joint 340 makes it easier to join the bus bar and the voltage detection line terminal. The distance between the voltage detection line terminal 401 and the bus bar 302 at the end 401t of the voltage detection line terminal 401 is larger than the distance at a location closer to the joint 340 than the end 401t. This makes it easier for dissimilar metals and water droplets to escape from the joint 340. The spacing between the voltage detection line terminal 401 and the busbar 302 is larger at the end 401t of the voltage detection line terminal 401 than at a location closer to the joint 340 than the end 401t, making it easier for dissimilar metals and water droplets to escape from the joint when fillet welding is performed. The spacing between the voltage detection line terminal 401 and the busbar 302 is larger at the end 401t of the voltage detection line terminal 401 than at a location closer to the joint 340 than the end 401t, making it harder for dissimilar metals and water droplets to accumulate between the busbar 302 and the voltage detection line terminal 401. Arranging the battery 100, voltage detection line terminal 401, and busbar 302 in this order contributes to space savings. Arranging the battery 100, busbar 302, and voltage detection line terminal 401 in this order makes it easier to ensure space between the busbar 302 and the battery 100. An insulating distance can be easily ensured even if other components are disposed between the bus bar 302 and the battery 100. Laser welding the joint 340 improves the workability of joining. The distance between the voltage detection line terminal 401 and the bus bar 302 at the end 401t of the voltage detection line terminal 401 is larger than the distance at a location closer to the joint 340 than the end 401t, which makes it difficult for dissimilar metals and water droplets generated by laser welding to accumulate.

[0045] (Sub-Battery Module) In the above example, the battery pack 1 has been described, but the busbar unit 300 can also be considered an invention of a sub-battery module. This sub-battery module includes a busbar 302 that electrically connects the terminals of a plurality of batteries 100, a voltage detection line terminal 401 joined to the busbar 302, a joint 340 that joins the busbar 302 and the voltage detection line terminal 401, and a busbar holder 311 on which the busbar 302 and the voltage detection line terminal 401 are placed. The voltage detection line terminal 401 is characterized in that a thickness Tb of the voltage detection line terminal 401 is smaller than a thickness Ta of the busbar 302, and the voltage detection line terminal 401 is spaced further from the busbar 320 as it moves away from the joint 340.

[0046] (Effects of the Sub-Battery Module) A sub-battery module can be provided in which dissimilar metals and water droplets are less likely to accumulate at the joints between the bus bars and the voltage detection line terminals.

[0047] (Method for Manufacturing Battery Pack 1) The above-described embodiment can also be considered as an invention of a method for manufacturing the battery pack 1. In this case, the method for manufacturing the battery pack 1 includes the following two steps: (A) a mounting step of arranging bus bars 302 for electrically connecting the terminals of the plurality of batteries 100 and voltage detection line terminals 430 to be joined to the bus bars 302 in predetermined mounting areas of the bus bar holder 311. (B) a joining step of joining the bus bars 302 and the voltage detection line terminals 430.

[0048] In this case, the thickness Tb of the voltage detection line terminal 401 is smaller than the thickness Ta of the bus bar 302. In the placing step, both the bus bar 302 and the voltage detection line terminal 401 are plate-shaped. On the other hand, after the joining step, the voltage detection line terminal 401 changes shape so that it moves away from the bus bar 302 as it moves away from the joining portion 340.

[0049] (Effects of the manufacturing method of the battery pack 1) Before joining, the bus bar 302 and the voltage detection line terminal 401 are both plate-shaped, and are joined in an overlapping state. In the prior art, the bent bus bar 302 and the flat voltage detection line terminal 401 were joined in an overlapping joint state, but by making both of them plate-shaped, a flat overlapping joint can be achieved. In this case, the reliability of the joint 340 can be improved.

[0050] Furthermore, the busbar 302 may have a plating layer on the main surface facing the voltage detection line terminal 401. In this case, even if the surface of the plating layer is somewhat uneven, the high bonding strength of the joint 340 makes it less likely for bonding defects to occur. This reduces the burden of managing the plating layer. Furthermore, the bonding strength of the joint 340 can be easily ensured even in various operating environments where vibrations and the like occur.

[0051] (Battery Assembly of Other Embodiments) The battery assembly of the present invention is not limited to the configuration of the battery assembly described in the embodiments, and can be configured appropriately based on the content described in the claims.

[0052] The embodiments are described in detail or simply to make the present invention easier to understand, and do not necessarily include all of the components described, or may include components not shown. Also, some of the components of the embodiments may be deleted, replaced with components of other embodiments, or combined with components of other embodiments.

[0053] The number of batteries 100 included in the battery pack 1 is not limited to 24. The batteries 100 are not limited to lithium ion batteries. For example, nickel-metal hydride batteries and lead batteries can be used as the batteries 100. The batteries 100 are not limited to secondary batteries. For example, primary batteries can be used as the batteries 100.

[0054] 1 battery pack (single cell), 200 holding unit, 300 bus bar unit (sub-battery module), 302, 302a, 302b bus bar, 302t, 401t end, 311 bus bar holder, 340 joint, 400 voltage detection unit, 401 voltage detection line terminal, 402 voltage detection line

Claims

1. A battery pack comprising: a plurality of electric cells; a bus bar electrically connecting the terminals of the plurality of electric cells; a voltage detection line terminal joined to the bus bar; a joint joining the bus bar and the voltage detection line terminal; and a bus bar holder on which the bus bar and the voltage detection line terminal are placed, wherein the thickness of the voltage detection line terminal is smaller than the thickness of the bus bar, and the distance between the voltage detection line terminal and the bus bar at an end of the voltage detection line terminal is larger than the distance at a location closer to the joint than the end.

2. The battery pack according to claim 1, wherein the bus bar and the voltage detection line terminal are arranged to overlap, and the joint is provided at a position where the bus bar and the voltage detection line terminal overlap.

3. The battery pack according to claim 2, wherein the voltage detection line terminal is bent at the joint.

4. The battery pack according to claim 2, wherein the voltage detection line terminal has an opening, and the joint is located on the edge of the opening.

5. The battery pack according to claim 2, wherein the voltage detection line terminal has an end separated from the bus bar.

6. The battery pack according to claim 2, wherein the voltage detection line terminal is disposed on the side of the bus bar where the battery pack is disposed.

7. The battery pack according to claim 2, wherein the voltage detection line terminal is arranged on the opposite side of the bus bar from the side on which the battery pack is arranged.

8. The battery pack according to claim 1, wherein the joints are laser welded.

9. The battery pack described in claim 8, wherein the bus bar has a flat plate shape, and the gap between the voltage detection line terminal and the bus bar is deformed by the laser welding so that the gap at the end of the voltage detection line terminal is larger than the gap at a location closer to the joint than the end.

10. A battery pack comprising: a plurality of electric cells; a bus bar electrically connecting the terminals of the plurality of electric cells; a voltage detection line terminal joined to the bus bar; a joint joining the bus bar and the voltage detection line terminal; and a bus bar holder on which the bus bar and the voltage detection line terminal are placed, wherein the thickness of the voltage detection line terminal is smaller than the thickness of the bus bar, the joint joins an end of the bus bar and an end of the voltage detection line terminal, and the distance between the voltage detection line terminal and the bus bar is greater at a location farther from the joint than at a location closer to the joint.

11. A sub-battery module comprising: a bus bar that electrically connects the terminals of a plurality of single cells; a voltage detection line terminal joined to the bus bar; a joint that joins the bus bar and the voltage detection line terminal; and a bus bar holder that places the bus bar and the voltage detection line terminal thereon, wherein the thickness of the voltage detection line terminal is smaller than the thickness of the bus bar, and the distance between the voltage detection line terminal and the bus bar at the end of the voltage detection line terminal is larger than the distance at a location closer to the joint than the end.

12. A method for manufacturing a battery pack, comprising: a mounting step of arranging a bus bar for electrically connecting the terminals of a plurality of cells and a voltage detection line terminal to be joined to the bus bar in a predetermined mounting area of ​​a bus bar holder; and a joining step of joining the bus bar and the voltage detection line terminal, wherein the thickness of the voltage detection line terminal is smaller than the thickness of the bus bar, and in the mounting step, the bus bar and the voltage detection line terminal are both plate-shaped, and after the joining step, the gap between the voltage detection line terminal and the bus bar at the end of the voltage detection line terminal is changed to a shape that is larger than the gap at a location closer to the joint than the end.

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