Battery pack

Abstract

To provide a battery pack capable of suppressing secondary contraction of an exterior cover consisting of a heat-shrinkable tube.SOLUTION: A battery pack 1 has: a cell assembly 3 consisting of a plurality of battery cells 2 covered with a cell cover 8 consisting of a heat-shrinkable tube; and an exterior cover 4 covering the cell assembly and consisting of a heat-shrinkable tube. The battery cells are arranged in parallel in a direction crossing a longitudinal direction of the cells. The cell cover and the exterior cover have openings at end parts in the longitudinal direction. A contact part where an outer peripheral surface of one battery cell of two battery cells adjacent to each other and an outer peripheral surface of the other battery cell are in contact with each other is applied with an adhesive agent to form a fixing part 10 unifying both battery cells. The fixing part extends in a line in the longitudinal direction of the battery cells.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery pack formed by combining a plurality of battery cells. [Background technology]

[0002] One example of a power source is a battery pack, which is made by arranging multiple battery cells made of secondary batteries, encasing them inside heat-shrinkable tubing, and then packing them by heating and shrinking the heat-shrinkable pack. The heat-shrinkable tubing keeps the multiple battery cells together so that they do not come apart, and its insulating properties prevent short circuits between the battery pack and other components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-83804 Summary of the Invention [Problem to be solved by the invention]

[0004] Battery packs are subject to temperature changes depending on the charging and usage environment. Heat-shrinkable tubing shrunk during the battery pack manufacturing process can undergo secondary shrinkage if it is subsequently exposed to temperatures above its shrinkage initiation temperature. Even if the amount of shrinkage each time is small, if the tubing is subjected to multiple temperature fluctuations, the total amount of shrinkage can become large. As a result, conductive parts that should be covered by the tubing can become exposed, causing unexpected problems such as short circuits.

[0005] Therefore, in the past, secondary shrinkage of the heat-shrinkable tube was prevented by attaching a non-thermally shrinkable tape along the shrinkage direction of the heat-shrinkable tube of the battery pack to integrate it with the heat-shrinkable tube.

[0006] However, adding tape increases the number of manufacturing steps and increases manufacturing costs.

[0007] In view of the above problems, an object of the present invention is to provide a battery pack that can suppress secondary shrinkage of a heat-shrinkable tube while suppressing manufacturing costs. [Means for solving the problem]

[0008] In order to achieve the above object, the battery pack of the present invention includes a cell assembly having a plurality of battery cells whose outer peripheral surfaces extending in the longitudinal direction are covered with cell covers made of first heat-shrinkable tubing, the battery cells being arranged in parallel in a direction intersecting the longitudinal direction; and an outer cover that covers the cell assembly and is made of a second heat-shrinkable tube made of the same or a different material as the first heat-shrinkable tube, wherein the cell cover and the outer cover each have an opening at an end in the longitudinal direction, and have a fixing portion that fixes one battery cell and the other battery cell by applying an adhesive to a contact portion where the outer surface of one battery cell contacts the outer surface of the other battery cell, and the fixing portion extends linearly along the longitudinal direction. [Effects of the Invention]

[0009] According to the present invention, secondary shrinkage of an exterior cover made of a heat-shrinkable tube can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a battery pack according to an embodiment; [Figure 2] (a) is a top view of the cell assembly, and (b) is a front view of the cell assembly. DETAILED DESCRIPTION OF THE INVENTION

[0011] A battery pack according to an embodiment of the present invention will be described below with reference to the drawings.

[0012] The battery pack 1 shown in FIG. 1 includes a cell assembly 3 made up of four secondary battery cells 2 (hereinafter referred to as battery cells), an exterior cover 4 that covers the cell assembly 3, and lead wires 5.

[0013] Each battery cell 2 is a nickel-metal hydride battery of the same specifications. Each battery cell 2 has a cylindrical outer surface 6 with its longitudinal axis as its axis, and has electrode terminals 7 at both longitudinal ends. The outer surface 6 of each battery cell 2 is covered with a cell cover 8 made of a first heat-shrinkable tube. The cell cover 8 is brought into close contact with the outer surface 6 of each battery cell 2 by thermal shrinkage of the first heat-shrinkable tube, forming a cylindrical shape that extends continuously from one longitudinal end to the other along the outer surface 6. Both longitudinal ends of the cell cover 8 are open. The first heat-shrinkable tube is made of a resin that begins to shrink when the temperature exceeds a predetermined shrinkage initiation temperature.

[0014] The electrode terminals 7 of the battery cells 2 can be electrically connected to other battery cells, lead wires, and other electrical components through the openings in the cell cover 8.

[0015] The arrangement of the battery cells 2 will be described below. Focusing on one battery cell 2-1, as shown in Figure 2(a), the other battery cells 2-2 are arranged in parallel such that their longitudinal directions are parallel to the one battery cell 2-1 and the outer circumferential surface 6 of the one battery cell 2-1 is in contact with the outer circumferential surface 6 of the other battery cell 2-2. Furthermore, the longitudinal ends of each battery cell 2, 2 are arranged flush with each other.

[0016] Furthermore, the number of battery cells 2 is determined by the ratings, usage conditions, charging specifications, etc. of the device that uses the battery pack 1, and is arranged in, for example, an S array, a W array, or an E array. In this embodiment, four battery cells 2 are arranged in an E array. That is, two battery cells 2 are arranged side by side, and two battery cells 2 are connected in series in the longitudinal direction.

[0017] In the above arrangement, the outer peripheral surface 6 of one battery cell 2 is in contact with the outer peripheral surface 6 of another battery cell 2, so that a linear contact portion 9 is formed between the two battery cells 2,2.

[0018] By applying or pouring a liquid adhesive onto this contact portion 9 and allowing it to solidify, this portion becomes a fixing portion 10 that fixes one battery cell 2 to another battery cell 2, as shown in FIG. 2(b). This fixing portion 10 integrates the one battery cell 2 with the other battery cell 2. A material that is resistant to thermal contraction due to heating when solidified is selected for the adhesive.

[0019] In this embodiment, the fixing portion 10 is formed continuously from one end to the other end in the longitudinal direction of the outer peripheral surface 6 of the battery cell 2, as shown in FIG. 2(a).

[0020] In the manner described above, the cell assembly 3 is formed.

[0021] A pair of lead wires 5 for extracting power from the battery cells 2 to the outside are electrically connected to the cell assembly 3. Furthermore, the longitudinal ends of the cell assembly 3 are each covered with an insulating cover 11.

[0022] The cell assembly 3 is then covered with a second heat-shrinkable tube, which is then heat-shrunk to form the exterior cover 4. The second heat-shrinkable tube may be made of the same resin as the first heat-shrinkable tube or a different resin. If the second heat-shrinkable tube is made of a different resin from the first heat-shrinkable tube, it will begin to shrink when the temperature exceeds the specific shrinkage initiation temperature of the second heat-shrinkable tube.

[0023] The exterior cover 4 has a cylindrical shape with an opening 4a at the longitudinal end of the cell assembly 3. The exterior cover 4 fits tightly against the cell assembly 3. The edge of the opening 4a is located inward from the periphery of the longitudinal end 3A of the cell assembly 3, and also covers the periphery of the longitudinal end 3A of the cell assembly 3. This periphery corresponds to the slight gap between the longitudinal end of the battery cell 2 and the lid 11. Covering this gap with the exterior cover 4 prevents short-circuiting with the electrode terminals 7 of the battery cell 2. The exterior cover 4 also exposes the center of the longitudinal end of the cell assembly 3 through the opening 4a.

[0024] The battery pack 1 configured as described above is used as a power source or backup power source for electrical equipment, and can be used for the electrical equipment once the battery cells 2 are charged. Furthermore, because the battery cells 2 are secondary battery cells, the battery pack 1 can be charged and discharged multiple times.

[0025] The battery pack 1 may be exposed to heat generated when the battery cells 2 are charged or when the attached electrical equipment is in operation. If this heat generation causes the temperature of the battery pack 1 to exceed the shrinkage start temperature of the second heat-shrinkable tube, the exterior cover 4 will attempt to undergo secondary shrinkage. However, the exterior cover 4 comes into contact with the cell covers 8 of the battery cells 2 that form the outer shell of the cell assembly 3, and the fixing parts 10 of the battery cells 2 do not shrink even when the shrinkage start temperature is exceeded. This suppresses shrinkage of the cell covers 8 near the fixing parts 10, and therefore suppresses shrinkage of the exterior cover 4 that overlaps the cell covers 8.

[0026] Furthermore, because the fixing portion 10 extends continuously and uninterrupted from one end to the other in the longitudinal direction of the battery cell 2, the area in which shrinkage of the exterior cover 4 near the fixing portion 10 is suppressed is wider than the area of ​​the exterior cover where shrinkage is suppressed by conventional point-like fixing portions, and secondary shrinkage of the entire exterior cover 4 is also suppressed.

[0027] As a result, even if the environmental temperature repeatedly fluctuates above the shrinkage start temperature, the portion of the exterior cover 4 covering the peripheral portion of the longitudinal end of the cell assembly 3 does not shrink, and the connection point between the lid 11 and the electrode terminal 7 is not exposed.

[0028] For example, the state of the battery pack 1 after it has been subjected to the temperature cycle test of ISO 16750-4 150 times and 300 times is described.

[0029] In the temperature cycle test (ISO 16750-4), the environmental temperature of the battery pack 1 is changed from 95°C to -40°C in 0.5 minutes, then the battery pack 1 is left at the environmental temperature of -40°C for 30 minutes, then the environmental temperature is changed from -40°C to 95°C in 0.5 minutes, and the battery pack 1 is left at the environmental temperature of 90°C for another 30 minutes. This process is considered one cycle.

[0030] In a conventional battery pack, at least two battery cells are arranged in parallel in a direction transverse to the longitudinal direction, i.e., when the outer peripheral surfaces of one battery cell and the other battery cell are arranged so that they are in contact with each other, adjacent battery cells are fixed by applying an adhesive to a single point on the outer peripheral surfaces where the cells are in contact. After 150 temperature cycle tests were performed on a conventional battery pack, the shrinkage of the exterior cover in the longitudinal direction of the battery cells progressed, and the peripheral edges of the longitudinal ends of the cell assembly began to be partially exposed. Furthermore, after 300 cycles, the shrinkage of the exterior cover was more advanced than after 150 cycles, and the longitudinal length of the battery cells became shorter than the longitudinal length of the cell assembly. As a result, the longitudinal ends of the cell assembly were completely exposed from the exterior cover, and the outer peripheral surface near the ends was also exposed. The longitudinal ends of the cell assembly are covered with lids, but if the lid moves relative to the longitudinal ends of the cell assembly, creating a small gap between the lid and the ends, the electrode terminals will become exposed through the gap, which may cause a short circuit with other electrical components.

[0031] In contrast, in the battery pack 1 of the present embodiment, even after 300 temperature cycle tests, the amount of shrinkage of the exterior cover 4 is less than that of exterior covers of conventional configurations, and therefore the exterior cover 4 maintains a state in which it covers the peripheral edges of the longitudinal ends of the cell assembly 3. Therefore, the peripheral edges of the lids 11 that close the longitudinal ends of the cell assembly 3 are not exposed and remain covered by the exterior cover 4, preventing short circuits with other electrical components.

[0032] In this way, by covering each battery cell 2 with a cell cover 8 and providing the fixing portion 10 that fixes the battery cells 2 together continuously from one longitudinal end to the other longitudinal end of the outer surface 6 of the battery cell 2 to a predetermined length, secondary shrinkage of the outer cover 4 can be suppressed.

[0033] Furthermore, simply by making the fixing parts 10 that unite adjacent battery cells 2 longer than in conventional battery packs, secondary shrinkage of the exterior cover 4 is suppressed, eliminating the need for additional materials such as thermally non-expandable tape, thereby reducing manufacturing costs. As a result, a battery pack 1 that can withstand high temperatures can be provided at low cost.

[0034] In the above embodiment, the fixing portions 10 made of adhesive that fix the juxtaposed battery cells 2 to each other are provided continuously from one longitudinal end to the other longitudinal end of the outer peripheral surface of the battery cell 2, but secondary shrinkage of the exterior cover can also be suppressed even if the fixing portions are formed discontinuously from one end to the other end.

[0035] Furthermore, the battery cells 2 are not limited to nickel-metal hydride batteries, and any suitable type of secondary battery cell can be used. [Explanation of symbols]

[0036] 1 battery pack 6 Outer surface 8 Cell Cover 2 battery cells 3. Cell Assembly 4. Exterior cover 10 Fixed part

Claims

1. a cell assembly including a plurality of battery cells whose outer peripheral surfaces extending in a longitudinal direction are covered with cell covers made of first heat-shrinkable tubing, the battery cells being arranged in parallel in a direction intersecting the longitudinal direction; an exterior cover that covers the cell assembly and is made of a second heat-shrinkable tube made of the same material as or a different material from the first heat-shrinkable tube; A battery pack comprising: the cell cover and the exterior cover each have an opening at an end in the longitudinal direction, a fixing portion for fixing one battery cell and the other battery cell by applying a non-heat-shrinkable adhesive to a contact portion where the outer circumferential surface of one battery cell contacts the outer circumferential surface of the other battery cell, The battery pack, wherein the fixing portion extends linearly along the longitudinal direction.

2. The battery pack according to claim 1 , wherein the fixing portion is continuous from one end to the other end in the longitudinal direction of the battery cell.

3. The battery pack according to claim 1 , wherein the fixing portion is present partially between one end and the other end of the battery cell in the longitudinal direction.

4. 4. The battery pack according to claim 1, wherein the exterior cover covers a peripheral edge of an end of the cell assembly in the longitudinal direction while partially exposing the end of the cell assembly through the opening.

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