Battery pack

Abstract

The present invention addresses the problem of realizing excellent impact resistance strength while efficiently dissipating the heat energy of battery cells. This battery pack is formed by housing, in a battery case 4, a battery assembly 1X obtained by electrically connecting a plurality of battery cells 1. The battery case 4 comprises: a lower case 6 provided with a peripheral wall 6b around a bottom plate 6a and having an upper surface opening; and an upper case 5 formed in a manner of closing the upper surface opening of the lower case 6. The lower case 6 is a metal case, and the inside of the metal case is filled with a potting resin 10. The potting resin 10 fills the gaps between the battery cells 1 and the metal case and thermally bonds the battery cells 1 and the metal case in a state of surface contact.

Description

Battery pack

[0001] The present disclosure relates to a battery pack that houses a plurality of rechargeable battery cells, and more particularly to a battery pack that can be used as a power source for supplying power to heavy construction machinery, construction equipment, etc. for civil engineering and construction.

[0002] Battery packs in which a large number of secondary batteries are connected in series and / or in parallel are used as power sources for heavy machinery or power supply devices for electric vehicles. The battery pack arranges secondary batteries in a fixed position with a resin battery holder and houses them in a battery case.

[0003] Such a battery pack can increase the output voltage by increasing the number of battery cells connected in series, and can increase the battery capacity by increasing the number of battery cells connected in parallel. Especially in view of the recent demand for higher output, the number of battery cells used in battery packs tends to increase. On the other hand, each battery cell generates heat by charging and discharging a large current. Therefore, in order to use the battery cells stably over a long period of time, it is required to cool the battery pack efficiently.

[0004] In order to efficiently dissipate the heat energy generated by the battery cells to the outside, a battery pack has been developed in which a metal plate with excellent heat conduction characteristics is insert-molded into a plastic case with poor heat conductivity (Patent Document 1).

[0005] The battery case in which the metal plate is embedded can improve the heat conduction characteristics by the metal plate. However, the battery case with insert molding of the metal plate not only increases the manufacturing cost of the case, but also has a problem that since the metal plate is embedded in the plastic with poor heat conduction state, the heat energy generated by the battery cells cannot be efficiently dissipated to the outside. Furthermore, the plastic battery case can be reinforced by embedding the metal plate, but the entire case, especially the corners where impact resistance is required, is not reinforced by the metal plate, and there is a problem that sufficient impact resistance cannot always be achieved in applications that receive strong impacts.

[0006] International Publication No. 2013 / 077205

[0007] This disclosure was developed with the aim of solving the above problems, and one of its objectives is to provide a battery pack that can efficiently dissipate the heat energy generated by the battery cells, as well as achieve excellent impact resistance. Means for solving the problem and the effects of the invention

[0008] To achieve the above objective, a battery pack according to one aspect of the present disclosure is a battery pack comprising a battery assembly in which a plurality of battery cells are electrically connected and housed in a battery case, wherein the battery case has a lower case with a peripheral wall around a bottom plate and an upper opening, and an upper case that closes the upper opening of the lower case, the lower case is a metal case, the metal case is filled with potting resin, the potting resin fills the gap between the battery cells and the metal case, and the battery cells and the metal case are thermally bonded in a surface contact state. The above battery pack has the advantage of efficiently dissipating the heat generated by the battery cells and also achieving excellent impact resistance.

[0009] Figure 1 is a schematic perspective view of a battery pack according to one embodiment of the present disclosure, viewed from above. Figure 1 is a schematic exploded perspective view of the battery pack. Figure 2 is a schematic exploded perspective view of the battery pack, viewed from below. Figure 1 is a further schematic exploded perspective view of the battery pack, viewed from below. Figure 4 is a schematic exploded perspective view of the battery pack, viewed from below. Figure 4 is a schematic plan view of the battery assembly and sub-battery holder, viewed from above. Figure 6 is a schematic perspective view of the battery holder, viewed from below. Figures 1 and 6 are schematic longitudinal cross-sectional views along line VIII-VIII of the battery pack. Figure 6 is a schematic longitudinal cross-sectional view and an enlarged cross-sectional perspective view of the main part, showing the battery pack without battery cells along line IX-IX. Figure 6 is a schematic longitudinal cross-sectional perspective view of the battery pack along line X-X. Figure 6 is an enlarged cross-sectional perspective view of the main part of the battery pack.

[0010] The embodiments of this disclosure will be described below with reference to the drawings. However, the embodiments shown below are illustrative examples of battery packs for realizing the technical concept of the present invention, and this disclosure does not limit the battery pack to the following. Furthermore, the components shown in the claims are not limited to the components of the embodiments. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention to those components alone, unless otherwise specifically stated, but are merely illustrative examples. The size and positional relationships of the components shown in each drawing may be exaggerated to clarify the explanation. Furthermore, in the following description, the same name and reference numerals indicate the same or similar components, and detailed explanations are omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that multiple elements are made of the same component, with one component serving multiple elements, or conversely, the function of one component may be shared among multiple components. In addition, some of the contents described in some embodiments may be applicable to other embodiments.

[0011] A battery pack according to one embodiment of the present disclosure is a battery pack comprising a battery assembly in which a plurality of battery cells are electrically connected and housed in a battery case, wherein the battery case comprises a lower case having a peripheral wall around a bottom plate and an upper opening, and an upper case that closes the upper opening of the lower case, wherein the lower case is a metal case and the metal case is filled with potting resin, and the potting resin fills the gap between the battery cells and the metal case, thereby thermally bonding the battery cells and the metal case in a surface contact state.

[0012] The above battery pack has the advantage of efficiently dissipating heat by conducting the heat energy generated by each battery cell to the metal case, thereby preventing problems caused by the temperature rise of the battery cells. This is because each battery cell and the metal case, which has excellent thermal bonding properties, are thermally bonded in a surface contact state via the potting resin, allowing the heat energy generated by the battery cells to be efficiently conducted to the metal case via the potting resin. Furthermore, the above battery pack has the advantage of suppressing temperature variations among the battery cells, thereby suppressing the imbalance in degradation caused by temperature differences. This is because the potting resin, which is thermally bonded in a surface contact state, dissipates the heat energy generated by each battery cell evenly, suppressing temperature variations among the battery cells. This also prevents the problem of specific battery cells degrading in a short period of time, which would shorten the lifespan of the entire battery pack, and thus has the advantage of effectively extending the lifespan of the battery pack.

[0013] Furthermore, the above battery packs have improved strength and rigidity of the battery case, enhancing impact resistance and making them suitable for various applications requiring high impact resistance. In particular, they are ideal for use in harsh environments such as construction machinery and heavy equipment, preventing failures due to impacts such as drops, and ensuring safe operation over long periods. This is because the battery packs have a metal case at the bottom, and potting resin, which is filled into the metal case, fills the gaps between the battery cells, battery assemblies, and the metal case. This structure prevents the impact of the metal case from concentrating on a specific part of the battery assemblies. Instead, the impact of the metal case is dispersed by the potting resin and acts on the battery assemblies, preventing localized damage to the battery assemblies.

[0014] In other embodiments of the present disclosure, the battery pack can have a plastic case for the upper case.

[0015] In other embodiments of the present disclosure, a battery pack comprises a battery holder made of insulating material, in which a plurality of battery cells are arranged in fixed positions, and the battery holder may include a retaining plate with insertion holes into which each battery cell is inserted and positioned. The above battery pack has the advantage that the battery holder and retaining plate position each battery cell in a predetermined posture and position, thereby enhancing the thermal bonding effect between the battery cells and the potting resin of the metal case, efficiently dissipating the heat generated by the battery cells, and also achieving excellent impact resistance.

[0016] A battery pack according to another embodiment of the present disclosure includes a first potting resin filled on top of a battery holder and a second potting resin filled between the battery holder and a bottom plate, wherein the first potting resin is thermally bonded to the outer surface of the battery cell, and the second potting resin can thermally bond the bottom of the battery cell to the bottom plate. The above battery pack has the advantage that the first and second potting resins enhance the thermal bonding effect between the battery cell and the potting resin of the metal case, efficiently dissipating the heat generated by the battery cell, and also achieving excellent impact resistance.

[0017] In another embodiment of the present disclosure, the battery pack includes a battery holder with vertically penetrating injection holes for potting resin, and the through-potting resin filling the injection holes can thermally bond a first potting resin and a second potting resin.

[0018] The above battery pack has the advantage of being able to smoothly and seamlessly inject uncured, paste-like potting resin into the top and bottom of the battery holder, and in addition, the potting resin fills the top and bottom of the battery holder, creating a wide surface contact state with the battery cell surface, and thermally bonding the first potting resin and the second potting resin through a through-potting resin, thereby uniformly and efficiently dissipating the heat generated by the battery cell, suppressing the temperature rise of the battery cell, and preventing deterioration due to temperature rise. In particular, the above battery pack has the advantage of being able to quickly and stably inject uncured, paste-like potting resin into the bottom of the battery holder without gaps through the injection through-hole, thermally bonding the second potting resin and the battery cell over a wide contact area, efficiently conducting the heat generated by the battery cell to the bottom plate of the metal case, and suppressing the adverse effects caused by temperature rise.

[0019] In another embodiment of the present disclosure, the battery pack includes a battery holder with a retaining stopper at the lower end of a cell-holding cylinder into which the battery cells are inserted and positioned, the retaining stopper having an exposed opening that exposes the bottom surface of the battery cell, and a bottom potting resin filled in the exposed opening that can thermally bond the bottom surface of the battery cell to the metal case.

[0020] The above battery pack has the advantage of efficiently dissipating the heat generated by each battery cell by conducting heat transfer to the metal case. This is achieved by positioning each battery cell in a fixed location using a battery holder, and by closely bonding the bottom surface of each battery cell with a bottom potting resin. Furthermore, the bottom surface of each battery cell can be closely bonded to the metal case, which has excellent thermal conductivity, over a wide contact area via the bottom potting resin.

[0021] In another embodiment of the present disclosure, the retaining stopper has a communication gap that connects adjacent exposed openings, and the communication potting resin filled in the communication gap can thermally bond adjacent bottom potting resins. The above battery pack has the advantage that the communication potting resin is filled in the communication gap and thermally bonds adjacent bottom potting resins, thereby suppressing the temperature difference between adjacent battery cells, suppressing the imbalance in degradation due to temperature variations in each battery cell, and thus extending the effective life of the battery pack.

[0022] A battery pack according to another embodiment of the present disclosure includes a sub-battery holder made of molded insulating material, located inside the battery case and above the battery holder, with each battery cell positioned in a fixed position, and a first potting resin can be filled between the sub-battery holder and the battery holder. The above battery pack has the advantage that by filling the space between the sub-battery holder and the battery holder with the first potting resin, the heat generated by the battery cells can be efficiently dissipated, and excellent impact resistance can also be achieved.

[0023] A battery pack according to another embodiment of the present disclosure may include an insulating film disposed between the bottom surface of a battery cell and the surface of a bottom plate to insulate the battery cell from the bottom plate of a metal case.

[0024] Battery packs according to other embodiments of the present disclosure may include a Thermal Interface Material (TIM) disposed between the bottom surface of the battery cell and the bottom plate.

[0025] In another embodiment of the present disclosure, a battery pack is provided in which an insulating film and a TIM (Thermal Interface Material) are laminated and disposed between the bottom surface of the battery cell and the surface of the bottom plate.

[0026] In other embodiments of the present disclosure, the metal case of the lower case of the battery pack may be made of aluminum. The aluminum in the present disclosure refers to the inclusion of aluminum, and includes aluminum alloys.

[0027] In another embodiment of the present disclosure, the battery pack comprises a battery assembly with lead wires connected to the positive and negative electrodes on the upper end surface of each battery cell, and the upper case has an opening for a lead window through which the lead wires are brought out to the outside. (Embodiment 1)

[0028] Figures 1 to 11 illustrate an example of a battery pack 100 according to Embodiment 1 of the present disclosure. The battery pack 100 shown in these figures is a specific example used as a power source to supply power to construction machinery and heavy machinery. However, the battery pack 100 of the present disclosure is not limited to use in construction machinery and the like, but can be used in all applications where heat dissipation characteristics and impact resistance are required. The battery pack 100 includes terminals for supplying power to a load, output connectors, a circuit board for controlling the charging and discharging of the battery cell 1, etc. However, the terminals, connectors, circuit board, etc. can be made into an optimal shape and positioned in an optimal location according to the application. Therefore, the above figures disclose the battery cell 1, battery holder 2, battery case 4, potting resin 10, etc., which are essential to the battery pack 100, without disclosing connectors, circuit boards, etc.

[0029] The battery pack 100 shown in Figure 2 houses a battery assembly 1X, in which multiple rechargeable battery cells 1 are arranged in fixed positions, within a battery case 4. The battery case 4 closes the upper opening of the lower case 6 with the upper case 5, and places the battery assembly 1X inside. The battery assembly 1X holds the multiple battery cells 1 in fixed positions using battery holders 2. The battery case 4 uses a metal case for the lower case 6, and fills the metal case with potting resin 10. The potting resin 10 is thermally bonded to the battery cells 1 and the metal case, and the heat energy generated by the battery cells 1 is dissipated from the metal case. (Battery assembly 1X)

[0030] The battery assembly 1X in Figures 4 and 5 has multiple battery cells 1 positioned in fixed locations using a battery holder 2 and a sub-battery holder 3, with adjacent battery cells 1 electrically connected (not shown). The exploded perspective view of the battery assembly 1X in Figures 4 and 5 includes a sub-battery holder 3 in addition to the battery holder 2, with both the battery holder 2 and the sub-battery holder 3 positioned in fixed locations. The battery holder 2 holds the bottom of the battery cell 1 in place. The sub-battery holder 3 is stacked on top of the battery holder 2, holding and inserting the top of the battery cell 1 in place. The battery holder 2 and the sub-battery holder 3 hold multiple battery cells 1 in a stacked state in a parallel orientation (vertical orientation in the figures). Each battery cell 1 is positioned in fixed locations using the battery holder 2 and the sub-battery holder 3, with positive and negative electrodes on its upper surface and its bottom surface on the same plane. In a structure where a sub-battery holder 3 is placed on top of a battery holder 2, a filling space 24 for potting resin 10 is provided on top of the battery holder 2, and the potting resin 10 can be injected and filled into this space. In this structure, with the sub-battery holder 3 stacked on top of the battery cell 1, the uncured, paste-like potting resin 10 can be injected between the battery holder 2 and the sub-battery holder 3. Alternatively, with a fixed amount of uncured, paste-like potting resin 10 injected onto the battery holder 2 in which the battery cell 1 is positioned, the sub-battery holder 3 can be stacked on top of the battery holder 2, and the sub-battery holder 3 being stacked can be pressed against the potting resin 10 injected onto the upper surface of the battery holder 2, thereby bringing the bottom surface of the battery cell 1 into favorable surface contact with the potting resin 10. However, since the battery assembly 1X can position the battery cells 1 in place without providing a sub-battery holder 3, and a filling space 24 for the potting resin 10 can be provided between the battery holder 2 and the upper case 5, the sub-battery holder 3 is not an essential component of the battery pack 100 of this disclosure.

[0031] The battery holder 2 and sub-battery holder 3 are molded from insulating plastic to insulate adjacent battery cells 1 and arrange them in a parallel position. The battery holder 2 and sub-battery holder 3 are arranged in a horizontal position perpendicular to the longitudinal direction of the battery cells 1 and are provided with a cell holding cylinder 2a and a sub-cell holding cylinder 3a, which are cylindrical bodies into which each battery cell 1 is inserted and held in a fixed position in the vertical direction. As shown in Figures 4 to 6, the battery holder 2 and sub-battery holder 3 can arrange multiple battery cells 1 in a stacked state, allowing for space-efficient arrangement. The battery assembly 1X connects each battery cell 1 in series or parallel via connecting leads (not shown). However, the battery pack 100 of this disclosure does not specify the number or arrangement of battery cells 1 in this state. The battery assembly 1X can increase the output current of the battery pack 100 by connecting multiple battery cells 1 in parallel, and can increase the output voltage of the battery pack 100 by connecting battery cells 1 that are connected in parallel to each other in series. However, the battery pack 100 of this disclosure does not specify the number of battery cells 1 connected in parallel and the number of battery cells 1 connected in series. (Battery cell 1)

[0032] The battery cell 1 is a rechargeable secondary battery. In the battery pack 100 shown in Figures 4 to 6, the battery cell 1 is a cylindrical battery 1a. In this embodiment, a cylindrical lithium-ion secondary battery is used as the battery cell 1. Lithium-ion secondary batteries are suitable for high-capacity, high-output battery systems. This is because lithium-ion secondary batteries can achieve a large capacity relative to their volume and weight. However, the battery pack 100 of this disclosure is not limited to a lithium-ion secondary battery for the battery cell 1; other rechargeable secondary batteries such as lithium polymer batteries, nickel-metal hydride batteries, and nickel-cadmium batteries can also be used. Furthermore, the external shape is not limited to cylindrical; a prismatic battery can also be used. (Battery holder 2)

[0033] The battery holder 2 shown in the exploded perspective views of Figures 4 and 5 is formed as an integral structure, comprising an outer peripheral wall 21 positioned inside the peripheral wall 6b of the lower case 6, which is a metal case, and a battery cell 1 holding plate 22 located inside the outer peripheral wall 21, which has insertion holes 23 for each battery cell 1. The outer peripheral wall 21 has an outer shape that fits into the inner surface of the peripheral wall 6b of the metal case, and in the examples of Figures 4 and 5, it is formed in a rectangular shape. The holding plate 22 has insertion holes 23 in a stacked arrangement. The battery cells 1 are inserted into the insertion holes 23 and positioned in their designated locations within the battery holder 2.

[0034] The upper surface of the retaining plate 22 is lower than the upper edge of the outer peripheral wall 21; in other words, the outer peripheral wall 21 protrudes from the upper surface of the retaining plate 22, and the battery holder 2 has a filling space 24 for the potting resin 10 inside the outer peripheral wall 21. The filling space 24 is filled with the first potting resin 11. As shown in the cross-sectional views of Figures 8 to 10, the first potting resin 11 is in close contact with the outer peripheral surface of the battery cell 1, and is thermally bonded to the surface of the battery cell 1 in a favorable state, efficiently dissipating the heat generated by the battery cell 1.

[0035] The battery holder 2 shown in Figures 4 and 5 has the lower part of the cell holding cylinder 2a protruding downward from the lower edge of the outer peripheral wall 21. The holding plate 22 shown in Figures 4 and 5 is shaped to arrange the cell holding cylinders 2a, which have insertion holes 23 on their inner surface, in a stacked manner, and a valley is formed between the outer surfaces of adjacent cell holding cylinders 2a in the region that protrudes downward from the outer peripheral wall 21. Potting resin 10 is filled into the valley formed between adjacent cell holding cylinders 2a. The valley potting resin filled into the valley fills the region along the lower part of the peripheral wall 6b of the metal case without any gaps, reinforcing the corner region of the lower edge of the metal case. The valley potting resin fills the gap between the outer peripheral surface of the holding plate 22 that protrudes downward from the outer peripheral wall 21 and the lower inner surface of the peripheral wall 6b, dispersing localized impacts such as drops received by the lower corner of the metal case, and further improving the impact resistance strength of the lower edge of the metal case through the cushioning effect caused by the deformation of the potting resin 10. Furthermore, the valley potting resin is in close surface contact with the outer surface and peripheral wall 6b of the cell holding cylinder 2a, and conducts the thermal energy of the cell holding cylinder 2a, which rises in temperature due to the heat generated by the battery cell 1, to the peripheral wall 6b of the metal case, thereby suppressing the temperature rise of the battery cell 1 via the cell holding cylinder 2a.

[0036] Furthermore, the battery holder 2 has injection through-holes 25 that penetrate the retaining plate 22 vertically and into which the potting resin 10 is injected into the lower surface of the retaining plate 22. The injection through-holes 25 are provided in an appropriate number and position to smoothly supply the uncured, paste-like potting resin 10 to the entire lower surface of the retaining plate 22. In the retaining plate 22 of the battery holder 2 shown in Figures 6, 7, and 9, specific insertion holes 23 arranged in a stacked state are designated as injection through-holes 25 into which the battery cells 1 are not inserted. The retaining plate 22 shown in the plan view of Figure 6 has injection through-holes 25 at both ends and in the center. The retaining plate 22 in Figure 6 has one injection through-hole 25 at each end and two injection through-holes 25 in the center. The injection through-hole 25 is shaped such that the retaining stopper 26 does not protrude from the inner surface of the insertion hole 23, as shown in Figures 7 and 9, to facilitate the smooth supply of the uncured, paste-like potting resin 10 supplied to the upper surface to the lower surface of the retaining plate 22 and to ensure even distribution across the entire surface. The injection through-hole 25 injects the uncured, paste-like potting resin 10, which is injected into the filling space 24 on the upper surface of the retaining plate 22, into the lower surface of the retaining plate 22. Furthermore, the through-potting resin 14 injected and curing through the injection through-hole 25 thermally bonds the first potting resin 11 curing on the upper surface of the battery holder 2 and the second potting resin 12 curing on the lower surface of the battery holder 2, thereby reducing the temperature difference between the first potting resin 11 and the second potting resin 12 and dissipating the heat generated by the battery cell 1 evenly.

[0037] The battery holder 2 exposes the bottom surfaces of multiple battery cells 1 and arranges them on the same plane. By exposing and arranging the battery cells 1 on the same plane, the distance between the bottom surface and the metal case of the lower case 6 is kept constant, allowing the heat energy generated by each battery cell 1 to be evenly conducted through the potting resin 10. As shown in the perspective views of Figures 4 and 5, the battery holder 2 is provided with a cell holding cylinder 2a into which the battery cells 1 are inserted and positioned. The cell holding cylinder 2a has an opening at the top end to allow the battery cells 1 to be inserted, and a retaining stopper 26 is provided at the bottom end to hold the bottom surface of the battery cell 1 in place. The retaining stopper 26 is sandwiched between the bottom surface of the battery cell 1 and the surface of the metal plate when the battery holder 2 is placed in the metal case, thereby holding the battery cell 1 in place.

[0038] The retaining stopper 26 shown in Figures 7, 9 to 11 has an exposed opening 27 that partially exposes the bottom surface of the battery cell 1. Potting resin 10 is filled into the exposed opening 27 to form bottom potting resin 15. The bottom potting resin 15 makes surface contact with the bottom surface of the battery cell 1 and the surface of the metal case of the lower case 6, thermally bonding the battery cell 1 and the metal case. The cell holding cylinder 2a has communication gaps 28 for the potting resin 10 between the multiple retaining stoppers 26 provided at its lower end. The potting resin 10 filled into the communication gaps 28 becomes communication potting resin 16, which thermally bonds the bottom potting resin 15 that is thermally bonded to adjacent battery cells 1. In Figures 7 and 9, the multiple (6 in the enlarged view of Figure 7) communication gaps 28 radiate outwards from the center of a certain exposed opening 27, connecting multiple adjacent exposed openings 27. The structure in which the communicating potting resin 16 is thermally bonded to the bottom potting resin 15 allows the communicating potting resin 16 to conduct heat between adjacent bottom potting resins 15, thereby reducing the temperature difference between adjacent battery cells 1. This structure suppresses the degradation imbalance caused by temperature variations in each battery cell 1, thereby achieving the advantage of extending the effective lifespan of the battery pack 100. (Sub-battery holder 3)

[0039] The sub-battery holder 3, shown in the exploded perspective views of Figures 4 and 5, is stacked, connected, and positioned on top of the battery holder 2 to position the battery cell 1 in place. The sub-battery holder 3 is a rectangle approximately equal in shape to the inner shape of the outer peripheral wall 21 of the battery holder 2, and is stacked inside the outer peripheral wall 21 without misalignment by a fitting structure. The sub-battery holder 3 is stacked on top of the battery holder 2, and a filling space 24 for potting resin 10 is provided between it and the battery holder 2. The battery holder 2 shown in the exploded perspective view of Figure 4 has connecting bosses 29 protruding from its upper surface, which are used to stack the sub-battery holder 3 with the filling space 24 provided. In the battery holder 2 of Figure 4, the connecting bosses 29 are located on the upper surface of the retaining plate 22 and inside the outer peripheral wall 21, and are provided at the four corners and both ends of the longitudinal center. As shown in the cross-sectional perspective view of Figure 9, the sub-battery holder 3 is stacked on top of the connecting bosses 29 and fixed between it and the battery holder 2 with the filling space 24 provided. The sub-battery holder 3 can be fixed on top of the battery holder 2 via an upper case 5 stacked on top of it. The upper case 5 can be fixed to the battery holder 2 via set screws that pass through the upper case 5 and the sub-battery holder 3. The sub-battery holder 3 can also be integrated with the upper case 5.

[0040] The sub-battery holder 3 is provided with a sub-cell holding cylinder 3a having a sub-insertion hole 33 that partially inserts and positions the upper part of the battery cell 1, which is positioned in a fixed position in the battery holder 2. The sub-cell holding cylinder 3a is positioned directly above the cell holding cylinder 2a and at the same position in a plan view so as to hold the upper part of the battery cell 1, which is positioned in a fixed position in the cell holding cylinder 2a of the battery holder 2.

[0041] The sub-battery holder 3, shown in the cross-sectional perspective view of Figure 9, has a nozzle hole 30 for inserting the potting resin 10 injection nozzle directly above the injection through-hole 25 provided in the holding plate 22 of the battery holder 2. As shown in the figure, the injection nozzle is inserted into the nozzle hole 30, and the uncured, paste-like potting resin 10 is filled into the upper surface of the battery holder 2. (Battery case 4)

[0042] The battery case 4 has a lower case 6 and an upper case 5. The lower case 6 is a metal case. As shown in the perspective views of Figures 2 and 4, the lower case 6 is formed from metal into a rectangular box shape with an open top, and the top opening is closed by the upper case 5. The metal case of the lower case 6 is formed from aluminum (in this disclosure, aluminum is used to mean including aluminum alloys) into a box shape in which a peripheral wall 6b is integrally connected around a bottom plate 6a. An aluminum metal case can be manufactured by die-casting aluminum. A metal case with an integral structure of the bottom plate 6a and peripheral wall 6b can be made lighter while maintaining high impact strength. The top and bottom surfaces of the bottom plate 6a are flat, and the inner shape of the peripheral wall 6b is made approximately equal to the outer shape of the battery assembly 1X, so that the outer peripheral wall 21 of the battery assembly 1X and the battery holder 2 are arranged without gaps on the inner surface of the peripheral wall 6b, and a space is provided for filling the valleys between the battery cells 1 with potting resin 10.

[0043] The upper case 5 is a plastic case, preferably made by molding a thermoplastic plastic such as polycarbonate. The upper case 5 has an opening for lead wires to be brought out to the outside. The lead window 5a is located opposite the upper end of the battery cell 1, allowing the lead plates laminated on the positive and negative electrodes of each battery cell 1 to be brought out to the outside and connected to a circuit board (not shown) or the like, located outside the battery pack 100. (Insulating film, TIM)

[0044] The battery pack 100 shown in the exploded perspective view of FIG. 4 has an insulating film 7 and a TIM 8 laminated between the bottom surface of the battery cell 1 and the surface of the bottom plate 6a to insulate the bottom surface of the battery cell 1 from the metal case. A TIM (Thermal Interface Material) is a molded sheet in which a heat conductive material such as aluminum is embedded in an insulating plastic to improve heat conduction characteristics. The structure of arranging the insulating film 7 and the TIM 8 between the battery cell 1 and the metal case can reliably and stably hold the metal case of the lower case 6 and the battery cell 1 in an insulated state, realizing high safety. Either the insulating film 7 or the TIM 8 can be arranged between the bottom surface of the battery cell 1 and the bottom plate 6a of the metal case to insulate the battery cell 1 from the metal case. Further, the battery pack 100 using an insulating resin for the potting resin 10 can insulate the battery cell 1 from the metal case without using the insulating film 7 and the TIM 8. However, by using the insulating potting resin 10 and arranging either or both of the insulating film 7 and the TIM 8 between the battery pack 100 and the metal case, the battery cell 1 and the metal case can be reliably and stably insulated.

[0045] The above battery pack 100 can be assembled in the following steps. (1) Set the battery assembly 1X in which the battery cell 1 is arranged in a fixed position by the battery holder 2 and the sub-battery holder 3 on the metal case on the surface of the bottom plate 6a on which the insulating sheet 7 and the TIM 8 are laminated. The battery assembly 1X can be inserted inside the outer peripheral wall 21 of the lower case 6 and set in a fixed position.

[0046] (2) As shown in the cross-sectional perspective view of FIG. 9, an injection nozzle of the potting resin 10 is inserted into the nozzle hole 30 and the injection through-hole 25 of the sub-battery holder 3, and the uncured paste-like potting resin 10 is injected into the filling space 24 between the battery holder 2 and the sub-battery holder 3 to fill the space between the battery holder 2 and the sub-battery holder 3 with the potting resin 10. The potting resin 10 injected between the bottom potting resin 15 and the sub-battery holder 3 cures to become the first potting resin 11. The filled uncured paste-like potting resin 10 passes through the injection through-hole 25 provided in the holding plate 22 and is injected between the bottom surface of the battery cell 1 and the bottom plate 6a of the metal case. The uncured paste-like potting resin 10 injected here cures to become the second potting resin 12. The uncured paste-like potting resin 10 injected between the battery cell 1 and the side plate is injected into the exposed opening 27 and the communication opening 28 of the anti-leak stopper 26, cures to become the second potting resin 12 composed of the bottom potting resin 15 and the communication potting resin 16, and thermally bonds the bottom of the battery cell 1 to the bottom plate 6a of the metal case in a surface-contact state.

[0047] (3) After connecting the upper case 5 to the battery assembly 1X or without connecting it to the battery assembly 1X, the battery pack 100 is connected to the fixing plate 9 indicated by the chain line with a set screw passing through the upper case 5 and the lower case 6. The fixing plate 9 is provided with a female screw hole for screwing in and fixing the set screw and a recess for guiding an insulating collar into which the set screw is inserted.

[0048] In the above steps, with the sub-battery holder 3 laminated on the battery holder 2, the uncured paste-like potting resin 10 is injected onto the battery holder 2. However, the uncured paste-like potting resin 10 can be filled onto the battery holder 2 without connecting the sub-battery holder 3 to the battery holder 2, and then the sub-battery holder 3 can be set on the battery holder 2. The sub-battery holder 3 presses and pressurizes the upper surface of the uncured paste-like potting resin 10, and is forcibly press-fitted from the injection through-hole 25 to the lower surface of the battery holder 2. The sub-battery holder 3 can also be set on the battery holder 2 and assembled.

[0049] The battery pack described herein incorporates a large number of battery cells and is suitable for use as a drive battery pack for construction machinery, heavy machinery, electric motorcycles, electric wheelchairs, electric tricycles, electric assist bicycles, electric carts, etc., where impact resistance and heat dissipation characteristics are required.

[0050] 100...Battery pack 1...Battery cell 1X...Battery assembly 1a...Cylindrical battery 2...Battery holder 2a...Cell retaining cylinder 3...Sub-battery holder 3a...Sub-cell retaining cylinder 4...Battery case 5...Upper case 5a...Lead window 6...Lower case 6a...Bottom plate 6b...Peripheral wall 7...Insulating film 8...TIM 9...Fixing plate 10...Potting resin 11...First potting resin 12...Second potting resin 14...Through-hole potting resin 15...Bottom potting resin 16...Communicating potting resin 21...Outer wall 22...Retaining plate 23...Insertion hole 24...Filling space 25...Injection through-hole 26...Retaining stopper 27...Exposed opening 28...Communicating gap 29...Connecting boss 30...Nozzle hole 33...Sub-insertion hole

Claims

1. A battery pack comprising a battery assembly in which multiple battery cells are electrically connected and housed in a battery case, wherein the battery case comprises a lower case having a peripheral wall around a bottom plate and an upper opening, and an upper case that closes the upper opening of the lower case, the lower case being a metal case, the metal case being filled with potting resin, the potting resin filling the gap between the battery cells and the metal case, and the battery pack being thermally bonded to the metal case in a surface contact state.

2. A battery pack according to claim 1, wherein the upper case is a plastic case.

3. A battery pack according to claim 1, wherein the battery assembly comprises a battery holder made of insulating material in which a plurality of the battery cells are arranged in fixed positions, and the battery holder comprises a retaining plate having insertion holes in which each of the battery cells is inserted and arranged in fixed positions.

4. A battery pack according to claim 3, wherein the potting resin comprises a first potting resin filled on the battery holder and a second potting resin filled between the battery holder and the bottom plate, the first potting resin being thermally bonded to the outer circumferential surface of the battery cell and the second potting resin being thermally bonded to the bottom of the battery cell and the bottom plate.

5. A battery pack according to claim 4, wherein the battery holder has an injection through-hole for the potting resin that penetrates vertically, and the through-potting resin filling the injection through-hole is a battery pack in which the first potting resin and the second potting resin are thermally bonded.

6. A battery pack according to claim 3, wherein the battery holder is provided with a retaining stopper at the lower end of a cell holding cylinder into which the battery cell is inserted and positioned, the retaining stopper having an exposed opening that exposes the bottom surface of the battery cell, and the bottom potting resin filled in the exposed opening thermally bonds the bottom surface of the battery cell to the metal case.

7. A battery pack according to claim 6, wherein the retaining stopper has a communication gap that connects adjacent exposed openings, and the communication potting resin filled in the communication gap is thermally bonded to adjacent bottom potting resins.

8. A battery pack according to claim 4, comprising a sub-battery holder formed from an insulating material which is located inside the battery case and above the battery holder, and which arranges each of the battery cells in a fixed position, wherein the first potting resin is filled between the sub-battery holder and the battery holder.

9. A battery pack according to claim 1, comprising an insulating film disposed between the bottom surface of the battery cell and the surface of the bottom plate, which insulates the battery cell from the bottom plate of the metal case.

10. A battery pack according to claim 1, comprising a TIM (Thermal Interface Material) disposed between the bottom surface of the battery cell and the bottom plate.

11. A battery pack according to claim 1, wherein an insulating film and a TIM (Thermal Interface Material) are laminated and disposed between the bottom surface of the battery cell and the surface of the bottom plate.

12. A battery pack according to claim 1, wherein the metal case of the lower case is made of aluminum.

13. A battery pack according to claim 1, wherein the battery assembly comprises lead wires connected to the positive and negative electrodes on the upper end surface of each of the battery cells, and the upper case has an opening in the lead window through which the lead wires are brought out to the outside.

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