Battery pack

Abstract

Provided is a battery pack configured so that a circuit board, which is connected to a battery block having a plurality of secondary battery cells, is fixed to a board holder, and output lead wires are connected. The output lead wires are routed such that a first lead wire and a second lead wire run along a peripheral wall on one side of the board holder. In the board holder, a first clamp piece, which protrudes from an upper section of the peripheral wall, and a second clamp piece, which protrudes from an intermediate section that is of the peripheral wall and that is below the first clamp piece, are integrally formed, with the first lead wire guided therebetween and routed to a prescribed location. The second clamp piece is integrally formed with a third clamp piece that protrudes downward from the intermediate section in the protruding direction. The second lead wire is guided to a holding gap between the third clamp piece and the peripheral wall, and the first lead wire and the second lead wire are located above and below the second clamp piece and routed in two rows.

Description

Battery pack

[0001] The present invention relates to a battery pack having output leads connected to a circuit board.

[0002] A battery pack including multiple secondary battery cells connects the output of a battery block, which is formed by connecting multiple secondary battery cells in parallel and series, to a circuit board, and controls the charging and discharging of the battery block using semiconductor devices mounted on the circuit board. Such a battery pack is secured to the battery block with the circuit board housed and secured in a board holder. The circuit board, to which the positive and negative outputs of the battery block are connected, is connected to output lead wires for charging and discharging the battery block. The output lead wires connected to the circuit board are extended from the board holder and connected to connectors for charging and discharging, leading to external connections (see Patent Document 1). It is desirable to wire the output lead wires extended from the board holder in a compact manner to ensure smooth assembly. It is also important to avoid applying load to the connection between the circuit board and the output lead wires.

[0003] Meanwhile, in recent years, as battery pack capacities have increased, battery packs have been adopted that have separate discharge connectors for discharging from the battery block to a load and charge connectors for charging the battery block. Battery packs with this structure use thick discharge leads to connect the circuit board to the discharge connector so that a large current can be carried during discharge, and thin charge leads to connect the circuit board to the charge connector so that a predetermined amount of power can be charged during charging. This structure requires two output lead wires to connect the circuit board to the discharge connector and the charge connector, which further poses the problem of complicated wiring of the output lead wires.

[0004] Japanese Patent Application Laid-Open No. 2008-166208

[0005] The present invention was developed with the aim of solving the above problems, and one of the objects of the present invention is to provide a battery pack that can be assembled efficiently while having a structure that allows multiple output lead wires connected to a circuit board to be wired compactly.

[0006] A battery pack according to one embodiment of the present invention includes a battery block having multiple secondary battery cells, a circuit board connected to the battery block, a board holder that secures the circuit board, and an output lead wire connected to the circuit board. The board holder is made of resin and has a peripheral wall around the bottom plate, with the circuit board positioned inside. The output lead wire includes a first lead wire and a second lead wire, and the first lead wire and the second lead wire are routed along the outer periphery of the peripheral wall on one side of the board holder. The board holder is integrally molded with a plurality of first clamp pieces that protrude outward from the upper part of the peripheral wall and a plurality of second clamp pieces that protrude outward from a middle portion of the peripheral wall below the first clamp pieces. The first lead wire is guided between the first clamp piece and the second clamp piece, and is held from both the top and bottom to route it in a predetermined position. The second clamp piece is integrally formed with a third clamp piece that protrudes downward from the middle in the protruding direction, and the second lead wire is guided into a retaining gap formed between the third clamp piece and the peripheral wall and wired to a predetermined position, with the first lead wire and the second lead wire being wired in two rows above and below the second clamp piece.

[0007] The above battery pack has the advantage that multiple output lead wires connected to the circuit board can be wired compactly. Furthermore, the above battery pack can be assembled efficiently by wiring multiple output lead wires compactly, which realizes the advantage of improving work efficiency.

[0008] 1. A schematic perspective view showing a battery pack according to one embodiment of the present invention. 2. A cross-sectional view of the battery pack of FIG. 1 taken along line II-II. 3. A block diagram of a battery pack according to one embodiment of the present invention. 4. A schematic perspective view of a core pack of a battery pack according to one embodiment of the present invention. 5. An exploded perspective view of the core pack shown in FIG. 4. 6. An enlarged perspective view showing a board holder to which a circuit board and an output lead wire are fixed. 7. A bottom perspective view of the board holder shown in FIG. 6. 8. An exploded perspective view of the circuit board and board holder shown in FIG. 6. 9. A cross-sectional view of the board holder shown in FIG. 6 taken along line IX-IX. 10. A cross-sectional view of the board holder shown in FIG. 6 taken along line XX. 11. An enlarged perspective view of the board holder shown in FIG. 11 from below.

[0009] One key feature of the present invention will now be described. In a battery pack including a battery block formed by connecting multiple secondary battery cells in parallel and series, the positive and negative output terminals of the battery block are located at both ends of the battery block, and are therefore connected to both ends of a circuit board that is placed on one side of the battery block. However, because a charge / discharge switch, such as a semiconductor device that controls charge / discharge, is connected to the output side of the battery block, the positive output connected to the end of the circuit board is connected to a semiconductor device, such as a semiconductor device, mounted on the end of the circuit board. As a result, the output from the semiconductor device is drawn from the center of the circuit board. Because there is a concern that the output lead wire drawn from the center of the circuit board may adversely affect other mounted components if it is placed above the circuit board, it is preferably routed outside the circuit board.

[0010] In battery packs that have separate discharge leads for discharging from the battery block to a load and charge leads for charging the battery block, both the charge and discharge leads must be pulled out from the circuit board, so a wiring structure is required to prevent the charge and discharge leads from interfering with each other. If the charge and discharge leads were wired on both sides of the circuit board holder that houses the circuit board, the width of the board holder would increase, making it impossible to wire the two leads compactly. The present invention was developed to solve this problem.

[0011] A battery pack according to one embodiment of the present invention comprises a battery block having a plurality of secondary battery cells, a circuit board connected to the battery block, a board holder for fixing the circuit board, and an output lead wire connected to the circuit board, wherein the board holder is made of resin and has a peripheral wall around the bottom plate, with the circuit board positioned inside, and the output lead wire comprises a first lead wire and a second lead wire, and the first lead wire and the second lead wire are wired along the outer surface of the peripheral wall on one side of the board holder. The substrate holder is integrally formed with a plurality of first clamp pieces that protrude outward from the upper part of the peripheral wall and a plurality of second clamp pieces that protrude outward from a middle part of the peripheral wall below the position of the first clamp pieces, and the first lead wire is guided between the first clamp piece and the second clamp piece and held from both the top and bottom sides and wired to a predetermined position, the second clamp piece is integrally formed with a third clamp piece that protrudes downward from a middle part in the protruding direction, the second lead wire is guided into a holding gap formed between the third clamp piece and the peripheral wall and wired to a predetermined position, and the first lead wire and second lead wire are wired in two rows above and below the second clamp piece.

[0012] According to the above configuration, the first lead wire and the second lead wire are wired in two rows, one above the other, along the outer circumferential surface of the peripheral wall on one side of the board holder, so that the first lead wire and the second lead wire can be wired in a space-saving manner without increasing the outer shape of the board holder to which the output lead wires are wired. In particular, according to the above configuration, the first lead wire is guided between the first clamp piece and the second clamp piece integrally molded on the peripheral wall of the board holder and held from both sides to be positioned in a fixed position, while the second lead wire is guided into a holding gap formed between the peripheral wall and the third clamp piece integrally molded on the second clamp piece to be positioned in a fixed position. Therefore, the second clamp piece serves both to fix the first lead wire and the second lead wire, so that the first lead wire and the second lead wire can be efficiently positioned in a fixed position, and by arranging the first lead wire and the second lead wire in two rows, above and below the second clamp piece, the first lead wire and the second lead wire can be insulated from each other and a neat and beautiful appearance can be achieved.

[0013] In a battery pack according to another embodiment of the present invention, the first clamp pieces and the second clamp pieces can be arranged alternately and offset from one another so as not to overlap one another in a plan view.

[0014] According to the above configuration, the first clamp pieces and the second clamp pieces that hold the top and bottom of the first lead wire are alternately arranged so as not to overlap each other in a plan view. Therefore, the first lead wire can be easily and quickly wired by alternately guiding it to the underside of the first clamp piece and the upper side of the second clamp piece. This structure allows for easy wiring even when the first lead wire is thick and difficult to bend. Furthermore, according to the above configuration, even when the first lead wire is held from both the top and bottom, the first clamp pieces and the second clamp pieces are alternately arranged, so that either the top or bottom is always open. This has the advantage of allowing for effective heat dissipation even when the first lead wire is energized and generates heat.

[0015] Furthermore, with the above configuration, the first clamp piece and the second clamp piece, which are arranged so as not to overlap each other in a plan view, have the advantage that they can be molded from resin using a mold with a simple structure. This is because the upper mold that forms the upper surface of the second clamp piece can be positioned without interfering with the first clamp piece, and the lower mold that forms the lower surface of the first clamp piece can be positioned without interfering with the second clamp piece. In other words, a board holder with the above configuration can be easily molded from resin using a pair of upper and lower molds.

[0016] In another embodiment of the battery pack of the present invention, the first clamp piece has a retaining protrusion at the tip that protrudes downward, and the first lead wire wired between the multiple first clamp pieces and the multiple second clamp pieces can be held in a fixed position via the retaining protrusion.

[0017] According to the above configuration, a retaining protrusion that protrudes downward is provided at the tip of the first clamp piece, so that the first lead wire guided between the first clamp piece and the second clamp piece can be positioned in a fixed position while being held in place by the retaining protrusion to prevent it from slipping out.

[0018] In another embodiment of the battery pack of the present invention, the second clamp piece has a support protrusion at the tip that protrudes upward, and the first lead wire wired between the first clamp piece and the second clamp piece can be supported in a fixed position via the support protrusion.

[0019] According to the above configuration, a support protrusion that protrudes upward is provided at the tip of the second clamp piece, so that the first lead wire guided between the first clamp piece and the second clamp piece can be positioned in a fixed position while being supported by the support protrusion to prevent it from shifting position.

[0020] In another embodiment of the battery pack of the present invention, the third clamp piece has a locking protrusion at the tip that protrudes toward the peripheral wall, and the second lead wire guided into the retaining gap can be held in a fixed position via the locking protrusion.

[0021] According to the above configuration, a locking protrusion that protrudes toward the peripheral wall is provided at the tip of the third clamp piece, so that the second lead wire guided between the third clamp piece and the peripheral wall can be positioned in a fixed position while being held in an engaged state by the locking protrusion.

[0022] In another embodiment of the battery pack of the present invention, the second clamp piece is formed as a wide plate extending in the direction of extension of the peripheral wall, a through hole is opened in the area excluding the outer periphery, a third clamp piece is formed along the opening edge of the through hole, which is the tip side opening edge located on the tip side of the second clamp piece, and the locking protrusion is formed to protrude toward the peripheral wall beyond the tip side opening edge.

[0023] According to the above configuration, the second clamp piece is made into a plate-like shape with a width in the extension direction of the peripheral wall, a through hole is opened in the area excluding the outer periphery, and the third clamp piece is formed along the tip side opening edge of this through hole.By utilizing this through hole, the locking protrusion of the third clamp piece can be molded using a mold with a simple structure.

[0024] In another embodiment of the battery pack of the present invention, the battery block connects multiple secondary battery cells in parallel to form a parallel unit, and the multiple parallel units are connected in series, the circuit board is provided with connection leads for detecting the voltage of the parallel unit, and the connection leads are extended to the outside of the board holder, and the connection leads can be positioned on the upper surface of the first clamp piece.

[0025] According to the above configuration, the voltage detection line drawn from the board holder to detect the voltage of the battery block is placed on the upper surface of the first clamp piece integrally molded with the peripheral wall, which has the advantage that the voltage detection line can be placed while being insulated from the first lead wire and the second lead wire.

[0026] In another embodiment of the battery pack of the present invention, the first lead wire has a connection terminal at the end on the circuit board side, and the board holder has a fixing base to which the connection terminal of the first lead wire is fixed, which is integrally molded on the outer peripheral surface of the peripheral wall to which the output lead wire is wired, and the circuit board has a connection plate to which the connection terminal of the first lead wire is connected fixed, and the connection plate is extended to the fixing base, and the connection terminal and connection plate can be fixed to the fixing base via connection screws to connect the first lead wire to the circuit board.

[0027] The above configuration has the advantage that the first lead wire arranged along the peripheral wall can be reliably connected to the circuit board by screwing. In particular, with the above structure, the fixing base for screwing the connection terminal provided at the tip of the first lead wire is integrally formed on the outer peripheral surface of the peripheral wall, and the connection plate connected to the circuit board extends to the fixing base, so that the connection terminal provided at the tip of the first lead wire wired along the outer peripheral surface of the peripheral wall can be connected to the connection plate and fixed to the fixing base.

[0028] In another embodiment of the battery pack of the present invention, the fixing base has a columnar boss portion into which a connecting screw is screwed, and also has a flange portion that protrudes toward the outer periphery of the boss portion, and the flange portion is provided with a plurality of fourth clamp pieces that are integrally molded and protrude downward along the outer periphery of the boss portion, so that the second lead wire can be guided into the outer periphery gap formed between the fourth clamp piece and the boss portion and positioned in a predetermined position.

[0029] According to the above configuration, when the second lead wire wired along the peripheral wall is extended beyond the fixed base to which the first lead wire is fixed, it can be guided into the outer peripheral gap formed between the boss portion and the fourth clamp piece provided on the flange portion of the fixed base, thereby bypassing the boss portion of the fixed base and wiring without interfering with the first lead wire.

[0030] In another embodiment of the battery pack of the present invention, the flange portion has a plurality of through holes opening along the outer peripheral surface of the boss portion, and a fourth clamp piece is formed along the opening edge of these through holes, which is the outer peripheral opening edge that follows the outer peripheral edge of the flange portion, and the tip of the fourth clamp piece can be provided with a locking protrusion formed to protrude toward the boss portion beyond the outer peripheral opening edge.

[0031] According to the above configuration, the fourth clamp piece has a distal end provided with a locking projection that protrudes toward the boss, so that the second lead wire guided between the fourth clamp piece and the boss can be positioned in a fixed position while being locked by the locking projection. Furthermore, according to the above configuration, the flange has a plurality of through holes, and the fourth clamp piece is formed along the outer periphery of the through holes. By utilizing the through holes, the locking projection of the fourth clamp piece can be formed using a mold with a simple structure.

[0032] In another embodiment of the battery pack of the present invention, the first lead wire and the second lead wire are flexible lead wires formed by covering the periphery of a metal core wire with an insulating layer, and the outer diameter of the first lead wire can be larger than the outer diameter of the second lead wire.

[0033] According to the above configuration, the first lead wire, which is a thick lead wire, can be securely held from above and below by the first clamp piece and the second clamp piece, while the second lead wire, which is a thin lead wire, can be securely held while being guided into the narrow holding gap formed between the third clamp piece and the peripheral wall.

[0034] In a battery pack according to another embodiment of the present invention, the output lead can be a positive lead, the first lead can be a discharge lead, and the second lead can be a charge lead.

[0035] With this configuration, the thicker discharge lead wire allows for safe conduction even when the discharge current instantaneously increases under the specified conditions of the main device (load). Furthermore, even when a large discharge current flows and heat is generated by Joule heating, the discharge lead wire can be positioned above the second clamp piece, away from the battery block, reducing the adverse effects of heat generated by the discharge lead wire on the battery block.

[0036] The present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts that appear with the same reference numerals in multiple drawings indicate the same or equivalent parts or members.

[0037] Furthermore, the embodiments shown below are specific examples of the technical concept of the present invention and are not intended to limit the present invention thereto. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended as examples and are not intended to limit the scope of the present invention thereto. Furthermore, the content described in one embodiment or example can also be applied to other embodiments or examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity of explanation.

[0038] The battery pack of the present disclosure can be used as a driving power source for mobile objects such as electric carts, electric scooters, and assisted bicycles, as a power source for portable electrical devices such as radios, electric cleaners, and power tools, as a backup power source for servers in stationary power storage applications, as a power supply device for home, office, or factory use, and as a driving power source for vehicles such as hybrid cars and electric automobiles. Hereinafter, a battery pack used as a driving power source for an electric motorcycle will be described as one embodiment of the present invention.

[0039] [Embodiment 1] A battery pack according to Embodiment 1 of the present invention is shown in Figures 1 to 12. In these figures, Figure 1 is a perspective view showing the battery pack according to Embodiment 1, Figure 2 is a cross-sectional view of the battery pack of Figure 1 taken along line II-II, Figure 3 is a block diagram of the battery pack of Embodiment 1, Figure 4 is a schematic perspective view of a core pack of the battery pack of Embodiment 1, Figure 5 is an exploded perspective view of the core pack of Figure 4, Figure 6 is a perspective view of a circuit board and a board holder, Figure 7 is a bottom perspective view of the board holder of Figure 6, Figure 8 is an exploded perspective view of the circuit board and a board holder of Figure 6, Figure 9 is an enlarged cross-sectional view of the board holder of Figure 6 taken along line IX-IX, Figure 10 is an enlarged cross-sectional view of the board holder of Figure 6 taken along line X-X, Figure 11 is an enlarged perspective view of the board holder, and Figure 12 is an enlarged perspective view of the board holder of Figure 11 seen from below.

[0040] The battery pack 100 shown in these figures comprises a battery block 10 having multiple secondary battery cells 1, a circuit board 4 connected to the battery block 10, a board holder 2 to which the circuit board 4 is fixed, and output leads 5 connected to the circuit board 4. Furthermore, the battery pack 100 shown in Figures 1 and 2 has the board holder 2, to which the circuit board 4 is fixed, fixed in a fixed position on the top surface of the battery block 10 to form a core pack 9, and this core pack 9 is housed in an exterior case 8.

[0041] (Secondary Battery Cell 1) The secondary battery cell 1 is a rechargeable secondary battery, and a lithium-ion secondary battery can be used. However, the present invention does not limit the secondary battery cell 1 to a lithium-ion battery. All other rechargeable secondary batteries, including currently used secondary batteries such as nickel-metal hydride batteries, nickel-cadmium batteries, and lithium polymer secondary batteries, as well as all-solid-state batteries to be developed in the future, can be used. The secondary battery cell 1 in FIG. 5 is a cylindrical battery, each with positive and negative electrodes at both ends. Multiple cylindrical batteries are arranged parallel to each other in multiple rows and columns, like a straw-bale stack. However, the arrangement of the multiple secondary battery cells 1 is not limited to this example; any arrangement can be used as appropriate. For example, the multiple secondary battery cells 1 can be arranged in a matrix. Furthermore, although the battery pack 100 shown in the figure uses cylindrical secondary battery cells 1, the secondary battery cells 1 can also be batteries other than cylindrical batteries, such as prismatic batteries.

[0042] (Battery Block 10) The battery block 10 has multiple rechargeable battery cells 1 housed in a battery holder 11 and arranged in fixed positions. The battery holder 11 holds each rechargeable battery cell 1 in a parallel orientation, with the end surface electrodes on both ends of the rechargeable battery cell 1 positioned on the same plane. The battery holder 11 has multiple cylindrical storage sections 12 that individually house the rechargeable battery cells 1. The battery holder 11 shown in FIG. 5 is divided into left and right holder units 11A, 11A, and is structured so that the two divided cylindrical storage sections 12 sandwich the rechargeable battery cells 1 from both ends. The battery holder 11 is made of a material with excellent insulating properties, for example, a resin such as polycarbonate.

[0043] Multiple rechargeable battery cells 1 housed in a battery holder 11 are connected in parallel and in series via lead plates 13 connected to the end electrodes on both ends. As shown in FIG. 3 , a battery block 10 is formed by connecting multiple rechargeable battery cells 1 in parallel to divide them into parallel units 10A, and connecting multiple parallel units 10A in series to increase output voltage. The battery block 10 shown in FIGS. 2 to 5 has 14 parallel units 10A, each of which has eight rechargeable battery cells 1 connected in parallel, connected in series. The battery block 10 shown in the figure uses 112 rechargeable battery cells 1 connected in 14 series x 8 parallel configurations, but this configuration is not limited to this. The number of series and parallel connections can be set as desired depending on the required specifications.

[0044] The battery block 10 is connected to the circuit board 4 via output lead plates 14 that are connected to lead plates 13 located on the positive and negative output sides of the parallel and series-connected secondary battery cells 1. In the battery block 10 shown in the figure, the positive output lead plate 14A is connected to one end of the circuit board 4 (upper left in FIG. 4 ) via a current interruption device 44. In addition, the negative output lead plate 14B of the battery block 10 is connected to the other end of the circuit board 4 (lower right in FIG. 4 ).

[0045] (Lead Plates 13) The lead plates 13 connect the end electrodes of the rechargeable battery cells 1 to each other, connecting multiple rechargeable battery cells 1 in parallel and in series. These lead plates 13 are made of highly conductive metal plates such as aluminum or nickel. Furthermore, in the illustrated battery block 10, each lead plate 13 is connected to a circuit board 4 located above the battery holder 11. The lead plate 13 shown in FIG. 4 has a connection portion 13A that protrudes from the upper end and connects to the circuit board 4. This lead plate 13 inputs the voltage of a parallel unit 10A, in which multiple rechargeable battery cells 1 are connected in parallel, to the circuit board 4 via the connection portion 13A. The connection portion 13A is connected to a connection lead 45 that is connected to the circuit board 4, so that the voltage of the parallel unit 10A is input to the circuit board 4.

[0046] (Circuit Board 4) The circuit board 4 mounts electronic components that implement a protection circuit 40 that controls the charging and discharging of the rechargeable battery cells 1. The circuit board 4 is a double-sided board with semiconductor elements 43 that control charging and discharging and other electronic components mounted on both the front and back sides, allowing each component to be optimally positioned. The semiconductor elements 43 include a discharge switch 41 that controls discharging of the battery block 10 and a charge switch 42 that controls charging. The protection circuit 40 detects the voltage, remaining capacity, temperature, current, etc. of the rechargeable battery cells 1 that make up the battery block 10 and controls the charge and discharge current to prevent overcharging and overdischarging of the rechargeable battery cells 1. The protection circuit 40 can also detect abnormal conditions in the rechargeable battery cells 1 and control the charge and discharge current to prevent deterioration of the rechargeable battery cells 1 and degradation of their electrical characteristics. The semiconductor elements 43 of the protection circuit 40 are FETs, transistors, etc.

[0047] (Output Lead Wire 5) The battery pack 100 has output lead wires 5 connected to the circuit board 4 for charging and discharging the battery block 10 or for detecting the voltage of the battery block 10 or the secondary battery cells 1 that make up the battery block 10. The output lead wires 5 connect the battery block 10 to an external load, such as a device main body or a charger, to charge and discharge the battery block 10. Alternatively, the output lead wires 5 output voltage detection signals to external devices. As shown in FIG. 3 , the output lead wires 5 shown in this embodiment include a positive lead wire 55 connected to the positive side of the battery block 10 and a negative lead wire 56 connected to the negative side of the battery block 10. The positive lead wire 55 is connected to a semiconductor element 43 on the circuit board 4 that is connected to the positive side of the battery block 10. As shown in FIGS. 6 to 10 , the positive electrode lead wire 55 is composed of a first lead wire 51 and a second lead wire 52 of different diameters, with the outer diameter of the first lead wire 51 being larger than the outer diameter of the second lead wire 52. In the battery pack 100 shown in the figures, the first lead wire 51 with the larger outer diameter serves as a discharge lead wire 57, and the second lead wire 52 with the smaller outer diameter serves as a charge lead wire 58. As shown in FIG. 3 , the discharge lead wire 57, which is the first lead wire 51, is connected to a discharge connector 61 and is connected to a main device (not shown), which is an external load, via the discharge connector 61. The charge lead wire 58, which is the second lead wire 52, is connected to a charge connector 62 and is connected to an external charger (not shown) via the charge connector 62.

[0048] 3 and 6, the negative lead wire 56 is made up of a third lead wire 53 and a fourth lead wire 54 of different diameters, with the third lead wire 53 having a larger outer diameter being connected to a discharge connector 61 as a negative line connected to a load, and the fourth lead wire 54 having a smaller outer diameter being connected to a charger as a negative line connected to a charger. The third lead wire 53 has a connection terminal 59 at its tip, which is connected via a connection screw 69 to a metal output terminal 49 fixed to one end of the circuit board 4. The fourth lead wire 54 is directly connected to the circuit board 4 by soldering or the like.

[0049] The first lead wire 51, the second lead wire 52, the third lead wire 53, and the fourth lead wire 54 are flexible lead wires that have a metal core wire coated with an insulating layer. The lead wires whose surfaces are coated with an insulating layer in this manner have excellent insulation properties and flexibility, which allows for simple and easy wiring.

[0050] (Board holder 2) The board holder 2 holds the circuit board 4 in a fixed position. As shown in Figures 2 and 4, the battery pack 100 has the board holder 2, to which the circuit board 4 is fixed, fixed to the battery holder 11 of the battery block 10. The present invention does not specify the location of the board holder 2, but the board holder 2 can be placed and fixed on the top surface of the battery holder 11, as shown in Figures 2 and 4.

[0051] The board holder 2 includes a bottom plate 21 and a peripheral wall 22 connected to the outer edge of the bottom plate 21. The board holder 2 shown in FIG. 3 has a shallow box-like shape with the peripheral wall 22 surrounding the bottom plate 21, and the interior of the peripheral wall 22 serves as a storage section 20 for storing a circuit board 4. The board holder 2 shown in FIGS. 6 to 10 includes a pair of opposing peripheral walls 22A extending longitudinally along both sides of the circuit board 4, and a pair of end peripheral walls 22B formed by connecting the ends of the pair of opposing peripheral walls 22A. The board holder 2 is formed by integrally molding the bottom plate 21 and the peripheral wall 22 from resin. Examples of resins that can be used to mold the board holder 2 include polycarbonate, which has excellent heat resistance and impact resistance. The illustrated board holder 2 has a gap above the bottom plate 21 to allow electronic components to be mounted on the backside of the circuit board 4. The board holder 2 has a support base 23 that protrudes from a bottom plate 21 , and the circuit board 4 is placed on the support base 23 and fixed in place with fixing screws 68 .

[0052] Furthermore, two positive electrode lead wires 55 connected to the circuit board 4 are wired along the outer peripheral surface of one of the opposing peripheral walls 22A of the peripheral wall 22 on one side of the board holder 2. The two positive electrode lead wires 55 wired along the peripheral wall 22 have their tips connected to the center of the circuit board 4 and extend from the middle of the longitudinal direction of the peripheral wall 22 toward one end. As described above, the positive electrode lead wire 55 is made up of the first lead wire 51 and the second lead wire 52 of different diameters, and the discharge lead wire 57, which is the first lead wire 51 having a larger outer diameter, and the charge lead wire 58, which is the second lead wire 52 having a smaller outer diameter, are wired along the peripheral wall and fixed in place.

[0053] (First clamp pieces 31, second clamp pieces 32) In order to position the two positive lead wires 55 in fixed positions, the board holder 2 is provided with a plurality of first clamp pieces 31 that protrude outward from the upper part of the peripheral wall 22 and a plurality of second clamp pieces 32 that protrude outward from an intermediate portion of the peripheral wall 22 below the position of the first clamp pieces 31, which are integrally molded. The board holder 2 shown in the figures has the first clamp pieces 31 provided at the upper end of the peripheral wall 22 and the second clamp pieces 32 provided at intermediate portions between the top and bottom of the peripheral wall 22. The plurality of first clamp pieces 31 molded at the upper end of the peripheral wall 22 are arranged at predetermined intervals along the extension direction of the peripheral wall 22. The plurality of second clamp pieces 32 molded at intermediate portions between the top and bottom of the peripheral wall 22 are also arranged at predetermined intervals along the extension direction of the peripheral wall 22. The first clamp pieces 31 and the second clamp pieces 32 are arranged parallel to one another and alternately arranged along the extension direction of the peripheral wall 22, so that the first lead wire 51 guided between the first clamp pieces 31 and the second clamp pieces 32 is sandwiched and held from both the top and bottom. The structure in which the first clamp pieces 31 and the second clamp pieces 32 are alternately arranged vertically as described above allows for the provision of open areas 35 between adjacent first clamp pieces 31 and adjacent second clamp pieces 32, which has the advantage of allowing for effective heat dissipation even when the first lead wire 51 is energized and generates heat. The vertical spacing between the first clamp pieces 31 and the second clamp pieces 32 arranged vertically and spaced apart is approximately equal to or slightly larger than the outer diameter of the first lead wire 51, so that the first lead wire 51 guided between the first clamp pieces 31 and the second clamp pieces 32 can be reliably held.

[0054] The illustrated substrate holder 2 includes three first clamp pieces 31 extending from the left-right middle of the opposing peripheral wall 22A toward the right end in the figure. Of the three first clamp pieces 31, the first clamp piece 31A located on the left side in the figure and the first clamp piece 31B located in the middle are plate-shaped and extend in the extension direction of the peripheral wall 22, making them wider in width, while the first clamp piece 31C located on the right side has a narrower width. The illustrated first clamp pieces 31A and 31B have widths that are greater than the amount of protrusion from the peripheral wall 22, and the first clamp piece 31C protrudes from the peripheral wall 22 by a greater amount than its width.

[0055] The first clamp pieces 31A, 31B having this shape are configured so that the connection lead 45, which is drawn out from the circuit board 4 and connected to the connection portion 13A of the lead plate 13, is located on the upper surface, thereby insulating the connection lead 45 from the discharge lead 57 and charge lead 58, which are the positive lead wire 55. In this way, the configuration in which the first clamp pieces 31A, 31B are located above the discharge lead 57, which is the first lead wire 51, allows the first clamp pieces 31A, 31B to double as insulating walls that insulate the connection lead 45 from the positive lead wire 55, thereby reliably insulating the connection lead 45. The first clamp pieces 31A, 31B shown in the figures also have upstanding walls 31b on their widthwise edges, which prevent the connection lead 45 from shifting position.

[0056] The first clamp piece 31 has a holding protrusion 31a that protrudes downward from the underside of its tip. This shape of the first clamp piece 31 allows the first lead wire 51, which is wired between the alternating first clamp pieces 31 and the alternating second clamp pieces 32, to be held in place by the holding protrusion 31a. The holding protrusion 31a shown in the figure has a central convex shape that is mountain-shaped in side view. This holding protrusion 31a gradually tapers from the apex of the mountain shape toward the tip of the first clamp piece 31 and gradually tapers from the apex of the mountain shape toward the rear end of the first clamp piece 31. This shape of the holding protrusion 31a smoothly guides the first lead wire 51 along the slope of the mountain shape and stably holds the outer periphery of the first lead wire 51 guided between the first clamp piece 31 and the second clamp piece 32, keeping the outer periphery of the first lead wire 51 along the slope of the mountain shape.

[0057] The second clamp pieces 32 are plate-shaped with a width that extends in the extension direction of the peripheral wall 22, and three second clamp pieces 32A, 32B, 32C are provided at positions that do not face the multiple first clamp pieces 31A, 31B, 31C provided at the upper end of the opposing peripheral wall 22A. The second clamp piece 32A shown in the figure has a width that is greater than the amount by which it protrudes from the peripheral wall 22, while the second clamp pieces 32B, 32C have a width that is approximately equal to the amount by which they protrude from the peripheral wall 22.

[0058] The second clamp piece 32 has a support protrusion 32a that protrudes upward from the upper surface of its tip. This shape of the second clamp piece 32 allows the first lead wire 51, which is wired between the alternating first clamp pieces 31 and the alternating second clamp pieces 32, to be supported by the support protrusion 32a to prevent misalignment and to be positioned in a fixed position. The support protrusion 32a shown in the figure has a mountain-like shape in a side view. This support protrusion 32a is shaped so that it tapers from the apex of the mountain toward the tip of the second clamp piece 32 and from the apex of the mountain toward the rear end of the second clamp piece 32. This shape of the support protrusion 32a smoothly guides the first lead wire 51 along the slope of the mountain shape and supports the outer periphery of the first lead wire 51 guided between the first clamp piece 31 and the second clamp piece 32 while keeping the slope of the mountain shape. The second clamp pieces 32A and 32B shown in the figure have support protrusions 32a on both sides of their tip, and the second clamp piece 32C has a support protrusion 32a on one side of its tip, on the left side in the figure.

[0059] Furthermore, as shown in the figure, the multiple first clamp pieces 31 and the multiple second clamp pieces 32 are arranged alternately and offset from one another so as not to overlap one another in a plan view. This structure has the advantage of allowing for easy and quick wiring by alternately guiding the first lead wire 51 to the underside of the first clamp piece 31 and the upper side of the second clamp piece 32. For example, if a first clamp piece having a holding protrusion and a second clamp piece having a support protrusion are arranged opposite each other, the first lead wire must be inserted through the gap between the support protrusions of the opposing first clamp piece and second clamp piece, which requires elastic deformation of the first clamp piece or the second clamp piece, or elastic deformation of the insulating coating of the first lead wire. In contrast, a structure in which a plurality of first clamp pieces 31 and a plurality of second clamp pieces 32 are arranged one above the other so as not to overlap each other has the advantage that wiring can be performed while alternately guiding the holding protrusions 31 a of the first clamp pieces 31 and the support protrusions 32 a of the second clamp pieces 32, making it possible to simply and easily wire even thick lead wires that are difficult to bend. This is advantageous in a structure in which a thick discharge lead wire 57 is arranged between the first clamp piece 31 and the second clamp piece 32.

[0060] Furthermore, the structure in which the multiple first clamp pieces 31 and the multiple second clamp pieces 32 are arranged so that they do not overlap one another in a plan view has the advantage that the first clamp pieces 31 and the second clamp pieces 32 can be resin-molded using a mold with a simple structure. This is because the upper mold that forms the upper surface of the second clamp piece 32 can be positioned without interfering with the first clamp piece 31, and the lower mold that forms the lower surface of the first clamp piece 31 can be positioned without interfering with the second clamp piece 32. In other words, the substrate holder 2 with the above structure can be easily resin-molded using a pair of upper and lower molds.

[0061] (Third Clamp Piece 33) The second clamp piece 32 further includes a third clamp piece 33 integrally formed therewith and protruding downward from a middle portion in the protruding direction. As shown in FIG. 9 , the second clamp piece 32 of this shape defines a retention gap 36 between the third clamp piece 33 and the peripheral wall 22, and the second lead wire 52 is guided into this retention gap 36 and wired to a predetermined position. The third clamp piece 33 shown in FIG. 9 includes a locking protrusion 33a at its tip end that protrudes toward the peripheral wall 22. The third clamp piece 33 holds the second lead wire 52 guided into the retention gap 36 in a predetermined position via the locking protrusion 33a. The second clamp piece 32 of the above structure guides and holds the second lead wire 52 in the retention gap 36 formed between the third clamp piece 33 located at its middle portion and the peripheral wall 22, making it suitable for wiring a charging lead wire 58 having a smaller outer diameter than the discharging lead wire 57.

[0062] Furthermore, the second clamp piece 32 shown in the figures has an overall plate-like shape with a certain width and a through-hole 32b formed in the entire area except for the outer periphery. The second clamp piece 32 has a third clamp piece 33 formed along a leading edge 32x of the through-hole 32b, which is the edge of the opening and located at the leading end of the second clamp piece 32. Furthermore, a locking protrusion 33a is formed at the leading end of the third clamp piece 33, protruding further toward the peripheral wall 22 than the leading edge 32x in a plan view. Because the second clamp piece 32 with this structure is formed using a through-hole, the locking protrusion 33a of the third clamp piece 33 can be formed using a mold with a simple structure. This is because the locking protrusion 33a of the third clamp piece 33 can be formed while forming the through-hole using a molding rod protruding from the molding surface of the upper mold that molds the top surface of the second clamp piece 32.

[0063] As described above, the first lead wire 51 is guided and held between the first clamp piece 31 and the second clamp piece 32 that are integrally molded with the peripheral wall 22, and the second lead wire 52 is guided and held in the holding gap 36 that is provided between the second clamp piece 32 and the peripheral wall 22, so that the two positive lead wires 55, i.e., the discharge lead wire 57 and the charge lead wire 58, that are wired along the outer circumferential surface of one side of the peripheral wall 22 are wired in two rows above and below the second clamp piece 32. This structure in which the first lead wire 51 and the second lead wire 52 are wired in two rows above and below along the outer circumferential surface of one side of the peripheral wall 22 of the substrate holder 2 does not increase the external shape of the substrate holder 2 to which the two positive lead wires 55 are wired, and allows the first lead wire 51 and the second lead wire 52 to be wired in a space-saving manner while remaining compact. Furthermore, by wiring the first lead wire 51 and the second lead wire 52 in two rows above and below the second clamp piece 32, insulation can be achieved by the second clamp piece 32 while providing a neat and beautiful appearance.

[0064] (Fixing Base 24) As described above, the first lead wire 51, which is wired along the outer peripheral surface of the peripheral wall 22, is connected to the circuit board 4 at the center of the board holder 2. The board holder 2 shown in FIGS. 10 to 12 has a fixing base 24 integrally molded on the outer peripheral surface of the peripheral wall 22, to which the output lead wire 5 is wired, for fixing the tip of the first lead wire 51. The fixing base 24 shown in the figures has a thickness approximately half the height of the peripheral wall 22, and is tall enough to comfortably accommodate the connection terminal 59 provided at the tip of the first lead wire 51, which is disposed between the first clamp piece 31 and the second clamp piece 32. A crimp terminal with a screw hole is fixed to the first lead wire 51 as the connection terminal 59. A connection plate 46, to which the connection terminal 59 of the first lead wire 51 is connected, is fixed to the circuit board 4, and this connection plate 46 extends beyond the peripheral wall 22 from the circuit board 4 to the fixing base 24.

[0065] The fixing base 24 has a cylindrical boss portion 25 in the center, into which a connection screw 67 is screwed, and with the connection terminal 59 of the first lead wire 51 placed on the connection plate 46 stacked on the upper surface of the boss portion 25, the connection screw 67 passing through the connection terminal 59 and the connection plate 46 is screwed into the boss portion 25, connecting the first lead wire 51 to the circuit board 4. The above fixing structure has the advantage that even a thick discharge lead wire 57 that is difficult to bend can be connected to the circuit board 4 without difficulty and reliably. In particular, connecting via the connection plate 46 and the connection terminal 59 allows for an ideal connection with low resistance.

[0066] (Fourth clamp piece 34) Furthermore, as shown in Fig. 11 , the fixed base 24 has a flange 26 that protrudes in the outer circumferential direction of the cylindrical boss portion 25. This flange 26 is disk-shaped and follows the outer shape of the boss portion 25, and is provided with a plurality of fourth clamp pieces 34 that are integrally molded and protrude downward along the outer circumferential surface of the boss portion 25. As shown in Fig. 12 , the fixed base 24 having this structure has an outer circumferential gap 27 formed between the fourth clamp piece 34 and the boss portion 25, and the second lead wire 52 is guided into this outer circumferential gap 27 to be wired to a predetermined position. In this structure, when the second lead wire 52 wired along the peripheral wall 22 is extended beyond the fixed base 24 to which the first lead wire 51 is fixed, the second lead wire 52 is guided into the outer peripheral gap 27 formed between the boss portion 25 and the fourth clamp piece 34 provided on the flange portion 26 of the fixed base 24, thereby allowing the second lead wire 52 to bypass the boss portion 25 of the fixed base 24 and be wired without interfering with the first lead wire 51.

[0067] 12 has a locking projection 34a at its tip that protrudes toward the boss 25. This fourth clamp piece 34 is configured to hold the second lead wire 52, which is guided into the outer circumferential gap 27, in place via the locking projection 34a. The second clamp piece 32 configured as described above causes the second lead wire 52, which is guided into the outer circumferential gap 27 formed between the boss 25 and the fourth clamp piece 34 provided on the outer periphery of the flange 26, to detour along the outer circumferential surface of the boss, making it suitable for wiring a charging lead wire 58, which has a smaller outer diameter than the discharging lead wire 57.

[0068] Furthermore, the flange 26 shown in FIGS. 10 to 12 has multiple through holes 28 formed along the outer peripheral surface of the boss 25, and the fourth clamp piece 34 is formed along the opening edges of these through holes 28, which are outer peripheral opening edges 28x that run along the outer peripheral edge of the flange 26. Furthermore, a locking protrusion 34a is formed at the tip of the fourth clamp piece 34, protruding toward the boss 25 beyond the outer peripheral opening edge 28x in a plan view. With the fixed base 24 having this structure, the fourth clamp piece 34 is formed using the through holes 28 of the flange 26, so the locking protrusion 34a of the fourth clamp piece 34 can be formed using a mold with a simple structure. This is because the locking protrusion 34a of the fourth clamp piece 34 can be formed while forming the through holes using a molding rod that protrudes from the molding surface of the upper mold that forms the top surface of the fixed base 24.

[0069] As described above, the structure in which the fixing base 24 is provided on the outer peripheral surface of the peripheral wall 22 has the advantage that the discharge lead 57, which is the first lead 51 routed along the outer peripheral surface of the peripheral wall 22, can be reliably connected to the circuit board 4 via the connection terminal 59. Furthermore, with the fixing base 24 configured as described above, the charging lead 58, which is the second lead 52 routed along the first lead 51 and beyond the fixing base 24, can be fixed in place while bypassing the boss 25 and connected to the circuit board 4. The second lead 52 routed along the boss 25 on the underside of the flange 26 further passes through the gap between the peripheral wall 22 and the fourth clamp piece 34 provided on the extension 26A of the flange 26, and then is drawn upward along the vertical wall 29 formed on the outer peripheral surface of the peripheral wall 22. The second lead 52 is further extended to the center of the circuit board 4 and fixed to the circuit board 4 by soldering or the like. In this way, the structure in which the second lead wire 52 is fixed in a fixed position by the fourth clamp piece 34 provided on the fixed base 24 has the advantage of effectively preventing poor contact from occurring over time at the connection between the second lead wire 52 and the circuit board 4.

[0070] (Potting Resin 6) As described above, the board holder 2 in which the circuit board 4 to which the output lead wires 5 are connected is fixed in the storage section 20 can be filled with potting resin 6 to embed the circuit board 4, as shown in FIG. 2. The potting resin 6 is a resin that is fluid in its uncured state, and after being injected and filled into the board holder 2, it hardens to embed the circuit board 4. A suitable example of the potting resin 6 is a transparent urethane resin. Urethane resin is a resin that hardens through a chemical reaction between polyol and an isocyanate curing agent. However, any resin that is fluid in its uncured state and can harden to embed the circuit board 4 in the board holder 2, such as epoxy resin or silicone resin, can also be used as the potting resin.

[0071] Although not shown, the above-described battery pack 100 can be housed in an outer case 8 with the core pack 9 housed in a waterproof inner bag. The inner bag is made of a resin with excellent waterproof properties and is molded into a box or bag shape that can house the core pack, with the core pack housed inside and the output lead wires 5 extending to the outside. For such an inner bag, for example, a resin with excellent heat resistance, flame retardancy, flexibility, abrasion resistance, etc. can be used, such as a polyolefin resin or a polyethylene resin, such as a PET resin. Alternatively, a heat-shrinkable tube that shrinks when heated may be used.

[0072] The battery pack according to the present invention can be suitably used as a driving power source for mobile objects such as electric carts and electric scooters in addition to power-assisted bicycles; as a power source for radios, and as a power source for portable electrical equipment such as electric cleaners and power tools; as a backup power source for servers and the like; and as a stationary power storage device for home, office, and factory use.

[0073] DESCRIPTION OF SYMBOLS 100...Battery pack 1...Secondary battery cell 2...Board holder 4...Circuit board 5...Output lead wire 6...Potting resin 8...Outer case 9...Core pack 10...Battery block 10A...Parallel unit 11...Battery holder 11A...Holder unit 12...Storage cylinder portion 13...Lead plate 13A...Connection portion 14...Output lead plate 14A...Positive electrode side output lead plate 14B...Negative electrode side output lead plate 20...Storage portion 21...Bottom plate 22...Peripheral wall 22A...Opposite peripheral wall 22B...End surface peripheral wall 23...Support base 24...Fixing base 25...Boss portion 26...Flange portion 26A...Extension portion 27...Peripheral gap 28...Through hole 28x...Peripheral opening edge 29...Vertical wall portion 31, 31A, 31B, 31C...First clamp piece 31a...Retaining protrusion 31b...Upright wall 32, 32A, 32B, 32C...Second clamp piece 32a...Support protrusion 32b...Through hole 32x...Tip-side opening edge 33...Third clamp piece 33a...Latching protrusion 34...Fourth clamp piece 34a...Latching protrusion 35...Open area 36...Retention gap 40...Protection circuit 41...Discharge switch 42...Charge switch 43...Semiconductor element 44...Current interruption element 45...Connection lead 46...Connection plate 49...Output terminal 51...First lead wire 52...Second lead wire 53...Third lead wire 54...Fourth lead wire 55...Positive electrode side lead wire 56...Negative electrode side lead wire 57...Discharge lead wire 58...Charge lead wire 59...Connection terminal 61...Discharge connector 62...Charge connector 67...Connection screw 68...Fixing screw 69...Connection screw

Claims

1. A battery pack comprising: a battery block having a plurality of secondary battery cells; a circuit board connected to the battery block; a board holder fixing the circuit board; and an output lead wire connected to the circuit board, wherein the board holder is made of resin and has a peripheral wall around a bottom plate with the circuit board arranged inside, the output lead wire comprising a first lead wire and a second lead wire, the first lead wire and the second lead wire being wired along the outer periphery of the peripheral wall on one side of the board holder, the board holder being integrally formed with: a plurality of first clamp pieces protruding outward from an upper part of the peripheral wall, and a plurality of second clamp pieces protruding outward from a middle part of the peripheral wall below the positions of the plurality of first clamp pieces, the first lead wire being held between at least one of the plurality of first clamp pieces and at least one of the plurality of second clamp pieces and wired in a predetermined position, Each of the plurality of second clamp pieces is integrally formed with a third clamp piece that protrudes downward from a middle portion in the protruding direction, the second lead wire is guided into a retaining gap formed between the third clamp piece and the peripheral wall and wired to a predetermined position, and the first lead wire and the second lead wire are each positioned above and below the plurality of second clamp pieces and wired in two rows.

2. A battery pack as described in claim 1, wherein the plurality of first clamp pieces and the plurality of second clamp pieces are arranged alternately and offset from one another so as not to overlap each other in a plan view.

3. A battery pack as described in claim 2, wherein each of the plurality of first clamp pieces has a holding protrusion that protrudes downward from its tip, and the first lead wire that is wired between the plurality of first clamp pieces and the plurality of second clamp pieces is held in a fixed position via the holding protrusion.

4. A battery pack as described in claim 2, wherein the plurality of second clamp pieces have support protrusions at their tips that protrude upward, and the first lead wires that are wired between the plurality of first clamp pieces and the plurality of second clamp pieces are supported in a fixed position via the support protrusions.

5. A battery pack as described in claim 2, wherein the third clamp piece has a first locking projection at its tip that protrudes toward the peripheral wall, and the second lead wire guided into the retaining gap is held in place via the first locking projection.

6. A battery pack as described in claim 5, wherein each of the second clamp pieces is a wide plate extending in the extension direction of the peripheral wall, and has a through hole in an area excluding the outer periphery, the third clamp piece is formed along the opening edge of the through hole, which is the tip-side opening edge located at the tip of each of the second clamp pieces, and the first engaging protrusion is formed to protrude toward the peripheral wall beyond the tip-side opening edge.

7. A battery pack as claimed in any one of claims 1 to 6, wherein the battery block connects the plurality of secondary battery cells in parallel to form a parallel unit and connects the plurality of parallel units in series, the circuit board is provided with connection leads for detecting the voltage of the parallel unit and the connection leads are drawn out to the outside of the board holder, and the connection leads are arranged on the upper surface of the first clamp piece.

8. A battery pack as claimed in any one of claims 1 to 6, wherein the first lead wire has a connection terminal at its tip on the circuit board side, the board holder has a fixing base to which the connection terminal of the first lead wire is fixed, which is integrally formed on the outer peripheral surface of the peripheral wall to which the output lead wire is wired, the circuit board has a connection plate to which the connection terminal of the first lead wire is connected fixed, and the connection plate is arranged to extend up to the fixing base, and the connection terminal and the connection plate are fixed to the fixing base via connection screws, thereby connecting the first lead wire to the circuit board.

9. A battery pack as described in claim 8, wherein the fixing base has a columnar boss portion into which the connecting screw is screwed, and a flange portion protruding in the outer circumferential direction of the boss portion, and the flange portion is provided with a plurality of fourth clamp pieces that are integrally formed and protrude downward along the outer circumferential surface of the boss portion, and the second lead wire is guided into outer circumferential gaps formed between the plurality of fourth clamp pieces and the boss portion, and is positioned in a predetermined position.

10. A battery pack as described in claim 9, wherein the flange portion has a plurality of through holes opened along the outer peripheral surface of the boss portion, the plurality of fourth clamp pieces are formed along the opening edges of the plurality of through holes, which are outer peripheral opening edges that follow the outer peripheral edge of the flange portion, and the tip ends of the plurality of fourth clamp pieces are provided with second engaging protrusions that protrude toward the boss portion beyond the outer peripheral opening edge.

11. A battery pack as claimed in any one of claims 1 to 10, wherein the first lead wire and the second lead wire are flexible lead wires having a metal core wire covered with an insulating layer, and the outer diameter of the first lead wire is larger than the outer diameter of the second lead wire.

12. A battery pack according to claim 11, wherein the output lead wire is a positive lead wire, the first lead wire is a discharge lead wire, and the second lead wire is a charge lead wire.

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