Battery pack

Abstract

This technology provides a way to prevent the battery cells near the bottom surface of the casing from overheating. [Solution] The battery pack disclosed herein may be detachable by sliding it against a battery pack mounting portion. The battery pack may comprise a casing and a plurality of battery cells housed inside the casing. The casing may have a through hole that opens downward. With respect to the front-rear direction, the through hole may be positioned behind the front end of the foremost battery cell among the plurality of battery cells, and in front of the rear end of the rearmost battery cell among the plurality of battery cells. With respect to the up-down direction, the inner surface of the casing at the location where the through hole is formed may be positioned above the lower end of the lowest battery cell among the plurality of battery cells.

Description

Technical Field

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[0001] The technology disclosed in this specification relates to a battery pack.

Background Art

[0002] Patent Document 1 discloses a battery pack that can be attached and detached by sliding it with respect to a battery pack attachment portion. The battery pack includes a casing and a plurality of battery cells housed inside the casing. When removing the battery pack from the battery pack attachment portion, the direction in which the battery pack is slid is defined as the forward direction, and when attaching the battery pack to the battery pack attachment portion, the direction in which the battery pack is slid is defined as the backward direction. When the battery pack is attached to the battery pack attachment portion, the direction in which the battery pack attachment portion is located as viewed from the battery pack is defined as the upward direction, the opposite direction of the upward direction is defined as the downward direction, and when the direction orthogonal to the front-back direction and the up-down direction is defined as the left-right direction, a through-hole that opens backward is formed in the casing. In the front-back direction, the through-hole is disposed behind the rear end of the rearmost battery cell among the plurality of battery cells. In the up-down direction, the inner surface of the casing at the location where the through-hole is formed is disposed above the lower end of the lowermost battery cell among the plurality of battery cells.

Prior Art Documents

[0005] The battery pack disclosed herein may be detachable by sliding it against a battery pack mounting portion. The battery pack may comprise a casing and a plurality of battery cells housed inside the casing. When removing the battery pack from the battery pack mounting portion, the direction in which the battery pack is slid is defined as the forward direction; when attaching the battery pack to the battery pack mounting portion, the direction in which the battery pack mounting portion is located relative to the battery pack when the battery pack is attached to the battery pack mounting portion is defined as the upward direction; the opposite direction of the upward direction is defined as the downward direction; and the direction perpendicular to the front-rear and up-down directions is defined as the left-right direction. In this case, the casing may have a through hole that opens downward. With respect to the front-rear direction, the through hole may be positioned behind the front end of the foremost battery cell among the plurality of battery cells, and in front of the rear end of the rearmost battery cell among the plurality of battery cells. With respect to the up-down direction, the inner surface of the casing at the location where the through hole is formed may be positioned above the lower end of the lowest battery cell among the plurality of battery cells.

[0006] With the above configuration, when the fan built into the charger is driven to draw air from inside the casing toward the charger, the air flows in through a downward-opening through-hole located behind the front end of the foremost battery cell and in front of the rear end of the rearmost battery cell, thus suppressing heat buildup near the bottom surface of the casing. This configuration prevents the battery cells near the bottom surface of the casing from becoming overheated. Furthermore, with the above configuration, since the inner surface of the casing where the through-hole is formed is located above the bottom end of the lowest battery cell, when the battery pack is placed on the mounting surface so that the bottom surface of the casing is in contact with the mounting surface, it is possible to prevent water or mud from the mounting surface from adhering to the through-hole and blocking the through-hole. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of the battery pack 2 of Example 1, taken from the rear right and above. [Figure 2] This is a perspective view from the rear left and lower side of the battery pack 2 of Example 1, with the battery pack 2 attached to the charger 4. [Figure 3] This is a cross-sectional view of the battery pack 2 of Example 1, seen from the right. [Figure 4] This is a perspective view of the battery pack 2 of Example 1, seen from the front right and lower. [Figure 5] This is a bottom view of the battery pack 2 of Example 1. [Figure 6] This is an enlarged cross-sectional view of the vicinity of the first ventilation hole 48 of the battery pack 2 of Example 1, viewed from the right. [Figure 7] This is an enlarged cross-sectional view of the vicinity of the second ventilation hole 50 of the battery pack 2 of Example 1, viewed from the right. [Figure 8] This is a perspective view of the battery pack 102 of Example 2, taken from the rear right and above. [Figure 9] This is a perspective view of the battery pack 102 of Example 2 attached to the charger 4, taken from the rear left and lower. [Figure 10]This is a cross-sectional view of the battery pack 102 of Example 2, taken from the right. [Figure 11] This is a perspective view of the battery pack 102 of Example 2, taken from the front, right, and lower. [Figure 12] This is a bottom view of the battery pack 102 of Example 2. [Figure 13] This is an enlarged cross-sectional view of the vicinity of the first vent hole 148 and the second vent hole 150 of the battery pack 102 of Example 2, viewed from the right. [Modes for carrying out the invention]

[0008] Representative and non-limiting examples of the present invention are described below in detail with reference to the drawings. This detailed description is intended simply to show those skilled in the art details for carrying out preferred examples of the present invention and is not intended to limit the scope of the invention. Furthermore, the disclosed additional features and inventions may be used separately from or in conjunction with other features and inventions to provide a further improved battery pack.

[0009] Furthermore, the combinations of features and processes disclosed in the following detailed description are not essential for carrying out the present invention in the broadest sense, and are described solely to illustrate representative examples of the present invention. Moreover, the various features of the following representative examples, as well as the various features described in the claims, do not necessarily have to be combined in the same way as the examples described herein, or in the order listed, to provide additional and useful embodiments of the present invention.

[0010] All features described herein and / or in the claims are intended to be disclosed individually and independently of each other, as limitations to the specific matters described in the original disclosure and in the claims, separate from the features described in the examples and / or in the claims. Furthermore, all descriptions of numerical ranges and groups or clusters are intended to disclose intermediate configurations as limitations to the specific matters described in the original disclosure and in the claims.

[0011] In a first aspect disclosed herein, the battery pack may be detachable by sliding it against a battery pack mounting portion. The battery pack may comprise a casing and a plurality of battery cells housed inside the casing. When removing the battery pack from the battery pack mounting portion, the direction in which the battery pack is slid is defined as the forward direction; when attaching the battery pack to the battery pack mounting portion, the direction in which the battery pack mounting portion is located relative to the battery pack when the battery pack is attached to the battery pack mounting portion is defined as the upward direction; the opposite direction of the upward direction is defined as the downward direction; and the direction perpendicular to the front-rear and up-down directions is defined as the left-right direction. In this regard, the through hole may be positioned behind the front end of the foremost battery cell among the plurality of battery cells, and in front of the rear end of the rearmost battery cell among the plurality of battery cells. With respect to the vertical direction, the inner surface of the casing at the location where the through hole is formed may be positioned above the lower end of the lowest of the plurality of battery cells.

[0012] In a second embodiment disclosed herein, the battery pack of the first embodiment may comprise a first battery cell having a longitudinal direction in the left-right direction and a second battery cell having a longitudinal direction in the left-right direction and positioned adjacent to the rear of the first battery cell. With respect to the front-rear direction, the through-hole may be positioned behind the center of the first battery cell and in front of the center of the second battery cell.

[0013] According to the above configuration, the first battery cell and the second battery cell adjacent to each other before and after can be cooled in a balanced manner.

[0014] In the third aspect disclosed in this specification, in the battery pack of the second aspect, the through hole may have an elongated hole shape having a longitudinal direction in the left - right direction.

[0015] According to the above configuration, the first battery cell and the second battery cell can be cooled more uniformly in the left - right direction.

[0016] In the fourth aspect disclosed in this specification, in the battery pack of the first or second aspect, a recess that is recessed upward and extends in the left - right direction may be formed on the lower surface of the casing. The through hole may be disposed within the recess.

[0017] According to the above configuration, by using the recess formed for purposes such as finger placement when the user grips the battery pack, a through hole can be provided in the casing.

[0018] In the fifth aspect disclosed in this specification, in the battery pack of the fourth aspect, the through hole may have an elongated hole shape having a longitudinal direction in the left - right direction.

[0019] According to the above configuration, when the recess is used as a finger placement when the user grips the battery pack, the through hole can function as an anti - slip for the finger.

[0020] In the sixth aspect disclosed in this specification, in the battery pack of any one of the first to fourth aspects, when the battery pack is placed on the placement surface such that the lower surface of the casing abuts the placement surface, the through hole may communicate with the space in front of, behind, to the left, or to the right of the battery pack.

[0021] With the above configuration, when the battery pack is placed on the mounting surface so that the bottom surface of the casing is in contact with the mounting surface while the multiple battery cells are at a high temperature, the chimney effect allows air to flow from the outside of the casing into the inside of the casing through the through holes, thereby cooling the multiple battery cells.

[0022] In a seventh aspect disclosed herein, in a battery pack of any one of the first to sixth aspects, the inner surface of the casing at the location where the through-hole is formed may be positioned above the center of the lowest of the plurality of battery cells, with respect to the vertical direction.

[0023] With the above configuration, when the battery pack is placed on the mounting surface such that the lower surface of the casing is in contact with the mounting surface, it is possible to more effectively prevent water or mud from the mounting surface from adhering to the through-holes and blocking them.

[0024] (Example 1) The battery pack 2 of this embodiment shown in Figure 1 can be detachably attached to an electrical device (not shown). The electrical device operates using power supplied from the battery pack 2. The electrical device may be, for example, a power tool powered by a motor, such as a screwdriver or drill, or an electric work machine powered by a motor, such as a brush cutter or blower. Alternatively, the electrical device may be an electrical device without a motor, such as a light, radio, or speaker. The rated voltage of the battery pack 2 is, for example, 18V. The maximum voltage of the battery pack 2 is, for example, 20V. The rated capacity of the battery pack 2 is, for example, 9.0Ah.

[0025] As shown in Figure 2, the battery pack 2 can be detachably attached to the charger 4. The battery pack 2 is charged by power supplied from the charger 4. The battery pack 2 has a device mounting section 6. The charger 4 has a battery pack mounting section 8. The battery pack 2 can be attached to the charger 4 by sliding the device mounting section 6 relative to the battery pack mounting section 8 in a predetermined sliding direction. Hereinafter, the direction in which the battery pack 2 is slid when attaching it to the battery pack mounting section 8 will be referred to as the rear direction, and the direction in which the battery pack 2 is slid when removing it from the battery pack mounting section 8 will be referred to as the front direction. Also, when the battery pack 2 is attached to the battery pack mounting section 8, the direction in which the battery pack mounting section 8 is located relative to the battery pack 2 will be referred to as the up direction, and the opposite direction of the up direction will be referred to as the down direction. Furthermore, the direction perpendicular to the front-back direction and the up-down direction will be referred to as the left-right direction.

[0026] As shown in Figure 3, the battery pack 2 comprises a casing 10 and a battery cell unit 12 housed inside the casing 10. The casing 10 comprises a lower casing 14 and an upper casing 16. The vertical dimension of the battery pack 2 is, for example, in the range of 60 mm to 100 mm, more specifically, for example, 79 mm. The front-to-back dimension of the battery pack 2 is, for example, in the range of 115 mm to 155 mm, more specifically, for example, 136 mm. The left-to-right dimension of the battery pack 2 is, for example, in the range of 55 mm to 95 mm, more specifically, for example, 76 mm. The weight of the battery pack 2 is, for example, in the range of 0.6 kg to 1.4 kg, more specifically, for example, 1 kg.

[0027] The battery cell unit 12 comprises a plurality of battery cells 18, a cell holder 20 that holds the plurality of battery cells 18, and a control circuit board 22 that is held by the cell holder 20 above the cell holder 20. Battery-side terminals 24 are provided on the upper surface of the control circuit board 22.

[0028] Multiple battery cells 18 are arranged in three rows vertically. Each battery cell 18 is, for example, a lithium-ion battery cell. Alternatively, each battery cell 18 may be another type of secondary battery cell. Each battery cell 18 has a substantially cylindrical shape and is arranged so that its longitudinal direction is aligned with the left-right direction. The shape of each battery cell 18 is, for example, of the 18650 type, with a diameter of 18 mm and a longitudinal dimension of 65 mm. Alternatively, the shape of each battery cell 18 may be, for example, of the 21700 type, with a diameter of 21 mm and a longitudinal dimension of 70 mm. In the first row from the bottom, four battery cells 18 are arranged in a front-to-back direction. The battery cells 18 in the first row from the bottom are arranged so that their vertical positions are substantially the same. Each battery cell 18 in the first row from the bottom is located at the lowest position among the multiple battery cells 18. In the second row from the bottom, five battery cells 18 are arranged in a front-to-back direction. Regarding the front-to-back direction, the center positions of each battery cell 18 in the second row from the bottom are positioned so as not to overlap with the center positions of each battery cell 18 in the first row from the bottom. Of the battery cells 18 in the second row from the bottom, the first battery cell 18a from the front and the first battery cell 18b from the rear are positioned slightly lower than the other battery cells 18. In the third row from the bottom, i.e., the first row from the top, six battery cells 18 are arranged in a front-to-back direction. Regarding the front-to-back direction, the center positions of each battery cell 18 in the third row from the bottom are positioned so as not to overlap with the center positions of each battery cell 18 in the second row from the bottom. The battery cells 18 in the third row from the bottom are positioned so that their positions in the vertical direction are approximately the same. Of the battery cells 18 in the third row from the bottom, the first battery cell 18c from the front is located furthest forward among the multiple battery cells 18, and the first battery cell 18d from the rear is located furthest back among the multiple battery cells 18.

[0029] As shown in Figure 1, the upper surface 16a of the upper casing 16 has terminal openings 26, battery-side rails 28, cooling openings 30, engagement openings 32, and operating openings 34. The terminal openings 26 are positioned to correspond to the battery-side terminals 24 of the control circuit board 22. When attaching the battery pack 2 to an electrical device or charger 4, the battery-side terminals 24 of the battery pack 2 and the device-side terminals (not shown) of the electrical device or charger 4 are mechanically engaged and electrically connected via the terminal openings 26. The battery-side rails 28 extend along the front-rear direction to the left and right of the terminal openings 26. When attaching the battery pack 2 to an electrical device or charger 4, the battery-side rails 28 of the battery pack 2 slidably engage with the device-side rails (not shown) of the electrical device or charger 4 in the front-rear direction. The cooling openings 30 are positioned in front of the terminal openings 26. When the battery pack 2 is attached to the charger 4 for charging, a fan (not shown) built into the charger 4 drives cooling air into the casing 10 through the cooling opening 30. Alternatively, when the battery pack 2 is attached to the charger 4 for charging, a fan built into the charger 4 drives cooling air out from the casing 10 through the cooling opening 30. The engagement opening 32 is located in front of the cooling opening 30. The operating opening 34 is located in front of the engagement opening 32. Hooks 36 are attached to the engagement opening 32 and the operating opening 34. The hook 36 has an engagement portion 36a that protrudes outward from the engagement opening 32 and an operating portion 36b that is exposed to the outside through the operating opening 34. As shown in Figure 3, the hook 36 is supported by the cell holder 20 via a compression spring 38. The compression spring 38 biases the hook 36 upward relative to the cell holder 20.

[0030] When the battery pack 2 is attached to the electrical device or charger 4, the engaging portion 36a engages with the engaging groove (not shown) of the electrical device or charger 4, preventing the battery pack 2 from sliding forward. This prevents the battery pack 2 from being removed from the electrical device or charger 4. To remove the battery pack 2 from the electrical device or charger 4, the user pushes the operating portion 36b. This operation causes the hook 36 to move downward, disengaging the engaging portion 36a from the engaging groove of the electrical device or charger 4, and allowing the battery pack 2 to slide forward relative to the battery device or charger 4. From this state, the user can remove the battery pack 2 from the electrical device or charger 4 by sliding it forward.

[0031] As shown in Figure 4, front guard portions 40 projecting forward and downward are formed at the front lower right and front lower left ends of the lower casing 14. A rear guard portion 42 projecting backward and downward is formed at the rear lower end of the lower casing 14. If the battery pack 2 is accidentally dropped, the front guard portion 40 or the rear guard portion 42 will collide with the ground or floor. As shown in Figure 3, each battery cell 18 is positioned away from the front guard portion 40 or the rear guard portion 42 inside the casing 10, so that even if the front guard portion 40 or the rear guard portion 42 collides with the ground or floor, damage to each battery cell 18 can be suppressed.

[0032] As shown in Figure 4, the lower casing 14 has a first finger rest recess 44 and a second finger rest recess 46. The first finger rest recess 44 is located inward in the left-right direction from the front guard portion 40 and spans the front surface 14a and the lower surface 14b of the lower casing 14. The front-rear dimension of the first finger rest recess 44 is, for example, in the range of 10 mm to 50 mm, more specifically, for example, 27 mm. The left-right dimension of the first finger rest recess 44 is, for example, in the range of 40 mm to 80 mm, more specifically, for example, 48 mm. The second finger rest recess 46 is located on the lower surface 14b of the lower casing 14 and is positioned behind the first finger rest recess 44. The front-rear dimension of the second finger rest recess 44 is, for example, in the range of 5 mm to 30 mm, more specifically, for example, 16 mm. The left-right dimension of the second finger rest recess 44 is, for example, within the range of 40mm-80mm, and more specifically, for example, 48mm. The left-right width of the first finger rest recess 44 and the left-right width of the second finger rest recess 46 are approximately the same.

[0033] As shown in Figure 3, the first finger rest recess 44 is positioned close to the first battery cell 18e from the front of the first row of battery cells 18 from the bottom, and the first battery cell 18a from the front of the second row of battery cells 18 from the bottom. The first finger rest recess 44 is positioned along the front-rear and left-right directions and includes a substantially planar finger rest surface 44a facing downward, a substantially cylindrical surface 44b positioned rearward and lower than the finger rest surface 44a and conforming to the outer shape of the front-downward shape of the battery cell 18e, and an anti-slip portion 44c that protrudes downward from the front end of the finger rest surface 44a and extends in the left-right direction. The vertical distance from the lower surface 14b of the lower casing 14 to the finger rest surface 44a is, for example, in the range of 5 mm to 25 mm, more specifically, for example, 14 mm. The front-rear dimension of the finger rest surface 44a is, for example, in the range of 2 mm to 15 mm, more specifically, for example, 10 mm. In the vertical direction, the finger rest surface 44a is located above the lower end of the battery cell 18e, above the center of the battery cell 18e, below the upper end of the battery cell 18e, and below the lower end of the battery cell 18a. In the front-to-back direction, the rear end of the finger rest surface 44a is located behind the front end of the battery cell 18a, behind the center of the battery cell 18a, in front of the rear end of the battery cell 18a, and in front of the front end of the battery cell 18e. That is, the first finger rest recess 44 is located in front of the battery cell 18e and in the space below the battery cell 18a. Furthermore, in the front-to-back direction, the front end of the finger rest surface 44a is located in front of the front end of the battery cell 18a, in front of the center of the first battery cell 18c from the front of the third row of battery cells 18 from the bottom, and behind the front end of the battery cell 18c.

[0034] The second finger rest recess 46 is positioned close to the first battery cell 18e from the front and the second battery cell 18f from the front in the first row of battery cells 18 from the bottom. The second finger rest recess 46 has a front cylindrical surface 46a that is substantially cylindrical in shape and follows the rear lower outer shape of the battery cell 18e, and a rear cylindrical surface 46b that is substantially cylindrical in shape and follows the front lower outer shape of the battery cell 18f.

[0035] As shown in Figure 5, the lower casing 14 has two first ventilation holes 48, two second ventilation holes 50, two third ventilation holes 52, and six drainage holes 54. The first ventilation holes 48 have an elongated shape with a longitudinal direction in the front-to-back direction and are arranged side by side in the left-to-right direction on the finger rest surface 44a of the first finger rest recess 44. The front-to-back dimension of the first ventilation holes 48 is, for example, in the range of 1 mm to 15 mm, more specifically, for example, 8 mm. The left-to-right dimension of the first ventilation holes 48 is, for example, in the range of 1 mm to 4 mm, more specifically, for example, 3 mm. The second ventilation holes 50 have an elongated shape with a longitudinal direction in the left-to-right direction and are arranged side by side in the left-to-right direction on the front cylindrical surface 46a of the second finger rest recess 46. The front-to-back dimension of the second ventilation holes 50 is, for example, in the range of 1 mm to 4 mm, more specifically, for example, 1.5 mm. The dimensions of the second ventilation hole 50 in the left-right direction are, for example, in the range of 1 mm to 10 mm, and more specifically, for example, 5.5 mm. The third ventilation hole 52 has an elongated shape with its longitudinal direction in the front-rear direction and is arranged side by side in the left-right direction near the rear end of the lower surface 14b of the lower casing 14. The dimensions of the third ventilation hole 52 in the front-rear direction are, for example, in the range of 1 mm to 10 mm, and more specifically, for example, 7 mm. The dimensions of the third ventilation hole 52 in the left-right direction are, for example, in the range of 1 mm to 4 mm, and more specifically, for example, 3.5 mm. The drainage holes 54 have a circular shape and are arranged side by side in the front-rear direction near the right end and left end of the lower surface 14b of the lower casing 14. The diameter of the drainage holes 54 is, for example, in the range of 1 mm to 4 mm, and more specifically, for example, 2.5 mm. In the left-right direction, the third ventilation hole 52 is located inside the drain hole 54, the first ventilation hole 48 is located inside the third ventilation hole 52, and the second ventilation hole 50 is located inside the first ventilation hole 48.

[0036] As shown in Figure 6, in the vertical direction, the inner surface of the lower casing 14 where the first ventilation hole 48 is located (i.e., the finger grip surface 44a) is located above the lower end of the battery cell 18e, above the center of the battery cell 18e, below the upper end of the battery cell 18e, and below the lower end of the battery cell 18a. In the front-rear direction, the front end of the first ventilation hole 48 is located behind the front end of the battery cell 18c, which is the furthest forward of the multiple battery cells 18, in front of the center of the battery cell 18c, and in front of the rear end of the battery cell 18c. In the front-rear direction, the rear end of the first ventilation hole 48 is located behind the front end of the battery cell 18c, which is the furthest forward of the multiple battery cells 18, behind the center of the battery cell 18c, and in front of the rear end of the battery cell 18c. When the battery pack 2 is placed on the mounting surface RS such that the lower surface 14b of the lower casing 14 is in contact with the mounting surface RS, the first ventilation hole 48 is in communication with the space in front of the battery pack 2.

[0037] As shown in Figure 7, in the vertical direction, the inner surface of the lower casing 14 at the location where the second ventilation hole 50 is located (i.e., the front cylindrical surface 46a) is positioned above the lower end of the battery cell 18e, above the lower end of the battery cell 18f, below the center of the battery cell 18e, and below the center of the battery cell 18f. In the front-rear direction, the front end of the second ventilation hole 50 is positioned behind the center of the battery cell 18e and in front of the rear end of the battery cell 18e. In the front-rear direction, the rear end of the second ventilation hole 50 is positioned behind the center of the battery cell 18e and in front of the rear end of the battery cell 18e. When the battery pack 2 is placed on the mounting surface RS such that the lower surface 14b of the lower casing 14 abuts against the mounting surface RS, the second ventilation hole 50 does not communicate with the space in front of, behind, to the left, or to the right of the battery pack 2.

[0038] As shown in Figure 5, the third vent hole 52 and the drain hole 54 are both formed on the lower surface 14b of the lower casing 14, and are therefore located below the first vent hole 48 and the second vent hole 50. For this reason, if water enters the inside of the casing 10, by positioning the battery pack 2 so that the lower surface 14b of the lower casing 14 faces vertically downward, the water inside the casing 10 is discharged to the outside of the casing 10 through the third vent hole 52 and the drain hole 54.

[0039] As shown in Figure 2, consider the case where, when the battery pack 2 is attached to the charger 4 for charging, air flows into the casing 10 through the cooling opening 30 due to the operation of a fan built into the charger 4. In this case, the air that flows into the casing 10 through the cooling opening 30 cools the multiple battery cells 18 and then flows out to the outside of the casing 10 through the first vent 48, second vent 50, third vent 52, and drain hole 54. In contrast, consider the case where, when the battery pack 2 is attached to the charger 4 for charging, air flows out from the inside of the casing 10 through the cooling opening 30 due to the operation of a fan built into the charger 4. In this case, air flows into the casing 10 through the first vent 48, second vent 50, third vent 52, and drain hole 54. The air that flows into the casing 10 cools the multiple battery cells 18 and then flows out to the outside of the casing 10 through the cooling opening 30.

[0040] In the battery pack 2 of this embodiment, the first ventilation holes 48 and the second ventilation holes 50 are formed on the finger grip surface 44a and the front cylindrical surface 46a, which are located above the lower surface 10b of the casing 10. This allows for more balanced cooling of the first-to-last battery cell 18 and the second-to-last battery cell 18 compared to when the first-to-last ventilation holes 48 and the second-to-last battery cell 50 are formed at a lower position.

[0041] In this embodiment, the battery pack 2 has a shape that separates the first vent hole 48, the second vent hole 50, the third vent hole 52, and the drain hole 54 from the multiple battery cells 18. Therefore, even if a long, thin foreign object such as a nail enters through the first vent hole 48, the second vent hole 50, the third vent hole 52, or the drain hole 54, it is possible to prevent the foreign object from coming into contact with the multiple battery cells 18.

[0042] (Example 2) The battery pack 102 of this embodiment, shown in Figure 8, has substantially the same configuration as the battery pack 2 of Embodiment 1. The battery pack 102 of this embodiment can be detachably attached to an electrical device (not shown). The electrical device operates using power supplied from the battery pack 102. The electrical device may be, for example, a power tool powered by a motor, such as a screwdriver or drill, or an electric work machine powered by a motor, such as a brush cutter or blower. Alternatively, the electrical device may be an electrical device without a motor, such as a light, radio, or speaker. The rated voltage of the battery pack 102 is, for example, 18V. The maximum voltage of the battery pack 102 is, for example, 20V. The rated capacity of the battery pack 102 is, for example, 12.0Ah.

[0043] As shown in Figure 9, the battery pack 102 can be detachably attached to the charger 4. The battery pack 102 is charged by power supplied from the charger 4. The battery pack 102 has a device mounting section 106. The charger 4 has a battery pack mounting section 8. The battery pack 102 can be attached to the charger 4 by sliding the device mounting section 106 relative to the battery pack mounting section 8 in a predetermined sliding direction. Hereinafter, the direction in which the battery pack 102 is slid when attaching it to the battery pack mounting section 8 will be referred to as the rear direction, and the direction in which the battery pack 102 is slid when removing it from the battery pack mounting section 8 will be referred to as the front direction. Also, when the battery pack 102 is attached to the battery pack mounting section 8, the direction in which the battery pack mounting section 8 is located relative to the battery pack 102 will be referred to as the up direction, and the opposite direction of the up direction will be referred to as the down direction. Furthermore, the direction perpendicular to the front-back direction and the up-down direction will be referred to as the left-right direction.

[0044] As shown in Figure 10, the battery pack 102 comprises a casing 110 and a battery cell unit 112 housed inside the casing 110. The casing 110 comprises a lower casing 114 and an upper casing 116. The vertical dimension of the battery pack 102 is, for example, in the range of 70 mm to 110 mm, more specifically, for example, 92 mm. The front-to-back dimension of the battery pack 102 is, for example, in the range of 135 mm to 175 mm, more specifically, for example, 155 mm. The left-to-right dimension of the battery pack 102 is, for example, in the range of 55 mm to 95 mm, more specifically, for example, 76 mm. The weight of the battery pack 102 is, for example, in the range of 0.9 kg to 1.7 kg, more specifically, for example, 1.3 kg.

[0045] The battery cell unit 112 comprises a plurality of battery cells 118, a cell holder 120 that holds the plurality of battery cells 118, and a control circuit board 122 that is held by the cell holder 120 above the cell holder 120. Battery-side terminals 124 are provided on the upper surface of the control circuit board 122.

[0046] Multiple battery cells 118 are arranged in four rows vertically. Each battery cell 118 is, for example, a lithium-ion battery cell. Alternatively, each battery cell 118 may be another type of secondary battery cell. Each battery cell 118 has a roughly cylindrical shape and is arranged so that its longitudinal direction aligns with the left-right direction. The shape of each battery cell 118 is, for example, of the 18650 type, with a diameter of 18 mm and a longitudinal dimension of 65 mm. Alternatively, the shape of each battery cell 118 may be, for example, of the 21700 type, with a diameter of 21 mm and a longitudinal dimension of 70 mm. In the first row from the bottom, four battery cells 118 are arranged in a front-to-back direction. Of the battery cells 118 in the first row from the bottom, the first battery cell 118e from the front and the first battery cell 118g from the rear are positioned slightly higher than the other battery cells 118. Of the battery cells 118 in the first row from the bottom, three battery cells 118, excluding the first battery cell 118e from the front and the first battery cell 118g from the rear, are all located at the lowest position among the multiple battery cells 118. In the second row from the bottom, five battery cells 118 are arranged in a front-to-back direction. In the front-to-back direction, the center positions of each battery cell 118 in the second row from the bottom are positioned so as not to overlap with the center positions of each battery cell 118 in the first row from the bottom. Of the battery cells 118 in the second row from the bottom, the first battery cell 118a from the front and the first battery cell 118b from the rear are positioned slightly lower than the other battery cells 118. In the third row from the bottom, six battery cells 118 are arranged in a front-to-back direction. In the front-to-back direction, the center positions of each battery cell 118 in the third row from the bottom are positioned so as not to overlap with the center positions of each battery cell 118 in the second row from the bottom. Of the battery cells 118 in the third row from the bottom, the second battery cell 118h from the front and the second battery cell 118i from the rear are positioned slightly lower than the other battery cells 118. Of the battery cells 118 in the third row from the bottom, the first battery cell 118c from the front is located furthest forward among the multiple battery cells 118, and the first battery cell 118d from the rear is located furthest back among the multiple battery cells 118.In the fourth row from the bottom, which is the first row from the top, five battery cells 118 are arranged in a front-to-back direction. In the front-to-back direction, the center positions of each battery cell 118 in the fourth row from the bottom are not aligned with the center positions of each battery cell 118 in the third row from the bottom. The battery cells 118 in the fourth row from the bottom are arranged so that their positions in the vertical direction are approximately the same.

[0047] As shown in Figure 8, the upper surface 116a of the upper casing 116 has terminal openings 126, battery-side rails 128, cooling openings 130, engagement openings 132, and operating openings 134. The terminal openings 126 are positioned to correspond to the battery-side terminals 124 of the control circuit board 122. When the battery pack 102 is attached to an electrical device or charger 4, the battery-side terminals 124 of the battery pack 102 and the device-side terminals (not shown) of the electrical device or charger 4 are mechanically engaged and electrically connected via the terminal openings 126. The battery-side rails 128 extend along the front-rear direction to the left and right of the terminal openings 126. When the battery pack 102 is attached to an electrical device or charger 4, the battery-side rails 128 of the battery pack 102 are slidably engaged with the device-side rails (not shown) of the electrical device or charger 4 in the front-rear direction. The cooling openings 130 are positioned in front of the terminal openings 126. When the battery pack 102 is attached to the charger 4 for charging, a fan (not shown) built into the charger 4 drives cooling air into the casing 110 through the cooling opening 130. Alternatively, when the battery pack 102 is attached to the charger 4 for charging, a fan built into the charger 4 drives cooling air out from the casing 110 through the cooling opening 130. The engagement opening 132 is located in front of the cooling opening 130. An engagement member 133 is attached to the engagement opening 132, protruding to the outside from the engagement opening 132. The operating opening 134 is located in front of the engagement opening 132. An operating member 136 is attached to the operating opening 134, exposed to the outside through the operating opening 134. As shown in Figure 10, the engagement member 133 is supported by the cell holder 120 via a compression spring 138. The compression spring 138 biases the engaging member 133 upward relative to the cell holder 120. The operating member 136 is supported by the upper casing 116 so as to be rotatable around the pivot axis 134a. The rear end (not shown) of the operating member 136 is inserted into a through hole (not shown) formed in the engaging member 133. When the user performs a push operation on the operating member 136, the operating member 136 rotates from its initial position to the pushed-in position.As a result, the rear end of the operating member 136 moves downward, and the engaging member 133 is pushed downward against the biasing force of the compression spring 138. When the user releases the pushing operation of the operating member 136, the engaging member 133 moves upward due to the biasing force of the compression spring 138. As a result, the rear end of the operating member 136 moves upward, and the operating member 136 rotates from the pushed-in position to the initial position.

[0048] When the battery pack 102 is attached to the electrical device or charger 4, the engaging member 133 engages with the engaging groove (not shown) of the electrical device or charger 4, preventing the battery pack 102 from sliding forward. This prevents the battery pack 102 from being removed from the electrical device or charger 4. To remove the battery pack 102 from the electrical device or charger 4, the user pushes the operating member 136. This operation causes the engaging member 133 to disengage from the engaging groove of the electrical device or charger 4, allowing the battery pack 102 to slide forward relative to the battery device or charger 4. From this state, the user can remove the battery pack 102 from the electrical device or charger 4 by sliding it forward.

[0049] As shown in Figure 11, front guard portions 140 projecting forward and downward are formed at the front lower right and front lower left ends of the lower casing 114. A rear guard portion 142 projecting backward and downward is formed at the rear lower end of the lower casing 114. If the battery pack 102 is accidentally dropped, the front guard portion 140 or the rear guard portion 142 will collide with the ground or floor. As shown in Figure 10, each battery cell 118 is positioned away from the front guard portion 140 or the rear guard portion 142 inside the casing 110, so that even if the front guard portion 140 or the rear guard portion 142 collides with the ground or floor, damage to each battery cell 118 can be suppressed.

[0050] As shown in Figure 11, the lower casing 114 has a first finger rest recess 144 and a second finger rest recess 146. The first finger rest recess 144 is located inward in the left-right direction from the front guard portion 140, and spans the front surface 114a and the lower surface 114b of the lower casing 114. The front-rear dimension of the first finger rest recess 144 is, for example, in the range of 10 mm to 50 mm, more specifically, for example, 30 mm. The left-right dimension of the first finger rest recess 144 is, for example, in the range of 40 mm to 80 mm, more specifically, for example, 48 mm. The second finger rest recess 146 is located on the lower surface 114b of the lower casing 114, behind the first finger rest recess 144. The front-rear dimension of the second finger rest recess 144 is, for example, in the range of 5 mm to 30 mm, more specifically, for example, 17 mm. The left-right dimension of the second finger rest recess 144 is, for example, within the range of 40mm-80mm, and more specifically, for example, 48mm. The left-right width of the first finger rest recess 144 and the left-right width of the second finger rest recess 146 are approximately the same.

[0051] As shown in Figure 10, the first finger rest recess 144 is positioned close to the first battery cell 118e from the front of the first row of battery cells 118 from the bottom, and the first battery cell 118a from the front of the second row of battery cells 118 from the bottom. The first finger rest recess 144 is positioned along the front-rear and left-right directions and includes a substantially planar finger rest surface 144a facing downward, a substantially cylindrical surface 144b positioned rearward and lower than the finger rest surface 144a and conforming to the outer shape of the front lower part of the battery cell 118e, and an anti-slip portion 144c that protrudes downward from the front end of the finger rest surface 144a and extends in the left-right direction. The vertical distance from the lower surface 114b of the lower casing 114 to the finger rest surface 144a is, for example, in the range of 5 mm to 25 mm, and more specifically, for example, 12 mm. The front-to-back dimension of the finger rest surface 144a is, for example, within the range of 2mm-15mm, more specifically, for example, 9mm. In the vertical direction, the finger rest surface 144a is located above the lower end of the battery cell 118e, below the center of the battery cell 118e, below the upper end of the battery cell 118e, and below the lower end of the battery cell 118a. In the front-to-back direction, the rear end of the finger rest surface 144a is located behind the front end of the battery cell 118a, behind the center of the battery cell 118a, in front of the rear end of the battery cell 118a, and in front of the front end of the battery cell 118e. That is, the first finger rest recess 144 is located in front of the battery cell 118e and in the space below the battery cell 118a. Regarding the vertical direction, the finger rest surface 144a is located above the lower end of the second battery cell 118f from the front in the first row of battery cells 118 from the bottom, below the center of battery cell 118f, and below the upper end of battery cell 118f. Regarding the front-to-back direction, the front end of the finger rest surface 44a is located behind the front end of the first battery cell 118c from the front in the third row of battery cells 118 from the bottom, and in front of the center of battery cell 118c. Regarding the front-to-back direction, the rear end of the finger rest surface 44a is located behind the center of battery cell 118c and in front of the rear end of battery cell 118c.

[0052] The second finger rest recess 146 is positioned close to the first battery cell 118e and the second battery cell 118f from the front in the first row of battery cells 118 from the bottom. The second finger rest recess 146 has a front cylindrical surface 146a that follows the rear lower outer shape of battery cell 118e, a rear cylindrical surface 146b that follows the front lower outer shape of battery cell 118f, and a connecting surface 146c that connects the rear end of the front cylindrical surface 146a and the front end of the rear cylindrical surface 146b, is positioned along the front-rear and left-right directions, and is a substantially planar surface facing downwards. The vertical distance from the lower surface 114b of the lower casing 114 to the connecting surface 146c is, for example, in the range of 5 mm to 25 mm, more specifically, for example, 6 mm. The front-rear dimension of the connecting surface 146c is, for example, in the range of 2 mm to 15 mm, more specifically, for example, 4 mm. In the vertical direction, the connection surface 146c is located above the lower end of battery cell 118f, above the lower end of battery cell 118e, below the center of battery cell 118f, and below the center of battery cell 118e. In the front-rear direction, the front end of the connection surface 146c is located behind the rear end of battery cell 118e and in front of the front end of battery cell 118f. In the front-rear direction, the rear end of the connection surface 146c is located behind the rear end of battery cell 118e and in front of the front end of battery cell 118f.

[0053] As shown in Figure 12, the lower casing 114 has four first ventilation holes 148, four second ventilation holes 150, two third ventilation holes 152, and six drainage holes 154. The first ventilation holes 148 have an elongated shape with a longitudinal direction in the front-to-back direction and are arranged side by side in the left-to-right direction on the finger rest surface 144a of the first finger rest recess 144. The front-to-back dimension of the first ventilation holes 148 is, for example, in the range of 1 mm to 15 mm, more specifically, for example, 8 mm. The left-to-right dimension of the first ventilation holes 148 is, for example, in the range of 1 mm to 4 mm, more specifically, for example, 3 mm. The second ventilation holes 150 have an elongated shape with a longitudinal direction in the left-to-right direction and are arranged side by side in the left-to-right direction on the connecting surface 146c of the second finger rest recess 146. The dimensions of the second ventilation hole 150 in the front-to-back direction are, for example, in the range of 1 mm to 4 mm, and more specifically, for example, 3 mm. The dimensions of the second ventilation hole 150 in the left-to-right direction are, for example, in the range of 1 mm to 10 mm, and more specifically, for example, 5.5 mm. The third ventilation hole 152 has an elongated shape with its longitudinal direction in the left-to-right direction and is arranged side by side in the left-to-right direction near the rear end of the lower surface 114b of the lower casing 114. The dimensions of the third ventilation hole 152 in the front-to-back direction are, for example, in the range of 1 mm to 4 mm, and more specifically, for example, 3.5 mm. The dimensions of the third ventilation hole 152 in the left-to-right direction are, for example, in the range of 1 mm to 10 mm, and more specifically, for example, 7 mm. The drainage hole 154 has a circular shape and is arranged side by side in the front-to-back direction near the right end and left end of the lower surface 114b of the lower casing 114. The diameter of the drain hole 154 is, for example, in the range of 1 mm to 4 mm, more specifically, for example, 3 mm. With respect to the left-right direction, the first ventilation hole 148, the second ventilation hole 150, and the third ventilation hole 152 are located inward from the drain hole 154.

[0054] As shown in Figure 13, in the vertical direction, the inner surface of the lower casing 114 where the first ventilation hole 148 is located (i.e., the finger grip surface 144a) is located above the lower end of the lowest battery cell 118f among the multiple battery cells 118, above the center of the battery cell 18f, and below the upper end of the battery cell 118f. In the front-rear direction, the front end of the first ventilation hole 148 is located behind the front end of the furthest forward battery cell 118c among the multiple battery cells 118, in front of the center of the battery cell 118c, and in front of the rear end of the battery cell 118c. In the front-rear direction, the rear end of the first ventilation hole 148 is located behind the front end of the furthest forward battery cell 118c among the multiple battery cells 118, behind the center of the battery cell 118c, and in front of the rear end of the battery cell 118c. When the battery pack 102 is placed on the mounting surface RS such that the lower surface 114b of the lower casing 114 abuts against the mounting surface RS, the first ventilation hole 148 communicates with the space in front of the battery pack 102.

[0055] In the vertical direction, the inner surface of the lower casing 114 where the second ventilation hole 150 is located (i.e., the connection surface 146c) is positioned above the lower end of the battery cell 118f, above the lower end of the battery cell 118e, below the center of the battery cell 118f, and below the center of the battery cell 118e. In the front-rear direction, the front end of the second ventilation hole 150 is positioned behind the rear end of the battery cell 118e and in front of the front end of the battery cell 118f. In the front-rear direction, the rear end of the second ventilation hole 150 is positioned behind the rear end of the battery cell 118e and in front of the front end of the battery cell 118f. When the battery pack 102 is placed on the mounting surface RS such that the lower surface 114b of the lower casing 114 abuts against the mounting surface RS, the second ventilation hole 150 does not communicate with the space in front of, behind, to the left, or to the right of the battery pack 102.

[0056] As shown in Figure 12, the third vent hole 152 and the drain hole 154 are both formed on the lower surface 114b of the lower casing 114, and are therefore located below the first vent hole 148 and the second vent hole 150. For this reason, if water enters the inside of the casing 110, by positioning the battery pack 102 so that the lower surface 114b of the lower casing 114 faces vertically downward, the water inside the casing 110 is discharged to the outside of the casing 110 through the third vent hole 152 and the drain hole 154.

[0057] As shown in Figure 9, consider the case where, when the battery pack 102 is attached to the charger 4 for charging, air flows into the casing 110 through the cooling opening 130 due to the operation of a fan built into the charger 4. In this case, the air that flows into the casing 110 through the cooling opening 130 cools the multiple battery cells 118 and then flows out to the outside of the casing 110 through the first vent 148, second vent 150, third vent 152 and drain hole 154. In contrast, consider the case where, when the battery pack 102 is attached to the charger 4 for charging, air flows out from the inside of the casing 110 through the cooling opening 130 due to the operation of a fan built into the charger 4. In this case, air flows into the casing 110 through the first vent 148, second vent 150, third vent 152 and drain hole 154. The air that flows into the casing 110 cools the multiple battery cells 118, and then flows out to the outside of the casing 110 through the cooling opening 130.

[0058] In the battery pack 102 of this embodiment, the first ventilation holes 148 and the second ventilation holes 150 are formed on the finger grip surface 144a and the connection surface 146c, which are located above the lower surface 110b of the casing 110. This allows for more balanced cooling of the first-to-last battery cell 118 and the second-to-last battery cell 118 compared to when the first ventilation holes 148 and the second-to-last battery cell 150 are formed at a lower position.

[0059] In this embodiment, the battery pack 102 has a shape that separates the first vent hole 148, the second vent hole 150, the third vent hole 152, and the drain hole 154 from the multiple battery cells 118. Therefore, even if a long, thin foreign object such as a nail enters through the first vent hole 148, the second vent hole 150, the third vent hole 152, or the drain hole 154, it is possible to prevent the foreign object from coming into contact with the multiple battery cells 118.

[0060] (modified version) In each of the above embodiments, the multiple battery cells 18, 118 do not have to be cylindrical in shape, but may be rectangular or pouch-shaped, for example.

[0061] In each of the above embodiments, the multiple battery cells 18, 118 may be arranged so that their longitudinal direction aligns with the front-to-back direction.

[0062] In each of the above embodiments, the multiple battery cells 18, 118 may be arranged in one or two rows in the vertical direction.

[0063] In each of the above embodiments, the first ventilation holes 48, 148 may have an elongated shape with a longitudinal direction in the left-right direction, or they may have a circular shape. The second ventilation holes 50, 150 may have an elongated shape with a longitudinal direction in the front-back direction, or they may have a circular shape.

[0064] (Features of the example) As described above, the battery pack 2,102 of one or more embodiments is detachable by sliding it against the battery pack mounting portion 8. The battery pack 2,102 comprises a casing 10,110 and a plurality of battery cells 18,118 housed inside the casing 10,110. When removing the battery pack 2,102 from the battery pack mounting section 8, the direction in which the battery pack 2,102 is slid is defined as the forward direction. When attaching the battery pack 2,102 to the battery pack mounting section 8, the direction in which the battery pack 2,102 is slid is defined as the rear direction. When the battery pack 2,102 is attached to the battery pack mounting section 8, the direction in which the battery pack mounting section 8 is located relative to the battery pack 2,102 is defined as the upward direction. The opposite direction of the upward direction is defined as the downward direction. The direction perpendicular to the front-rear and up-down directions is defined as the left-right direction. In this configuration, the casings 10,110 have first ventilation holes 48,148 and second ventilation holes 50,150 (examples of through holes) that open downwards. In the front-to-back direction, the first ventilation holes 48, 148 and the second ventilation holes 50, 150 are positioned behind the front end of the furthest forward battery cell 18c, 118c among the multiple battery cells 18, 118, and in front of the rear end of the furthest rear battery cell 18d, 118d among the multiple battery cells 18, 118. In the up-and-down direction, the inner surfaces of the casings 10, 110 where the first ventilation holes 48, 148 and the second ventilation holes 50, 150 are formed are positioned above the lower end of the lowest battery cell 18f, 118f among the multiple battery cells 18, 118.

[0065] With the above configuration, when the fan built into the charger 4 is driven to draw air from inside the casings 10 and 110 toward the charger 4, the air flows in through the first ventilation holes 48 and 148 and the second ventilation holes 50 and 150, which open downwards and are located behind the front ends of the foremost battery cells 18c and 118c, and in front of the rear ends of the rearmost battery cells 18d and 118d. This suppresses heat buildup near the lower surfaces 14b and 114b of the casings 10 and 110. By adopting this configuration, it is possible to suppress the high temperature of the battery cells 18 and 118 near the lower surfaces 14b and 114b of the casings 10 and 110. Furthermore, with the above configuration, the inner surfaces of the casings 10 and 110 where the first ventilation holes 48 and 148 and the second ventilation holes 50 and 150 are formed are positioned above the lower ends of the lowest battery cells 18f and 118f. Therefore, when the battery pack 2 and 102 are placed on the mounting surface RS such that the lower surfaces 14b and 114b of the casings 10 and 110 are in contact with the mounting surface RS, it is possible to prevent water and mud from adhering to the first ventilation holes 48 and 148 and the second ventilation holes 50 and 150 and blocking them.

[0066] In one or more embodiments of the battery pack 2,102, the plurality of battery cells 18,118 include battery cells 18e,118e (example of a first battery cell) having a longitudinal direction in the left-right direction, and battery cells 18f,118f (example of a second battery cell) having a longitudinal direction in the left-right direction and arranged adjacent to the rear of the battery cells 18e,118e. With respect to the front-rear direction, the second ventilation holes 50,150 are located behind the centers of the battery cells 18e,118e and in front of the centers of the battery cells 18f,118f.

[0067] With the above configuration, the battery cells 18e, 118e and 18f, 118f, which are adjacent to each other, can be cooled in a balanced manner.

[0068] In one or more embodiments of the battery pack 2,102, the second ventilation holes 50,150 have an elongated shape with a longitudinal direction in the left-right direction.

[0069] With the above configuration, battery cells 18e, 118e and battery cells 18f, 118f can be cooled more uniformly in the left-right direction.

[0070] In one or more embodiments of the battery pack 2,102, first finger rest recesses 44,144 and second finger rest recesses 46,146 (examples of recesses) are formed on the lower surfaces 14b,114b of the casings 10,110, recessed upward and extending in the left-right direction. First ventilation holes 48,148 and second ventilation holes 50,150 are located within the first finger rest recesses 44,144 and second finger rest recesses 46,146.

[0071] According to the above configuration, the first finger rest recesses 44, 144 and the second finger rest recesses 46, 146, which are formed for purposes such as providing a finger rest when the user grips the battery pack 2,102, can be used to provide the first ventilation holes 48, 148 and the second ventilation holes 50, 150 in the casings 10, 110.

[0072] In one or more embodiments of the battery pack 2,102, the second ventilation holes 50,150 have an elongated shape with a longitudinal direction in the left-right direction.

[0073] With the above configuration, when the user uses the second finger rest recesses 46, 146 as finger rests when gripping the battery pack 2,102, the second ventilation holes 50, 150 can function as anti-slip surfaces for the fingers.

[0074] In one or more embodiments of the battery pack 2,102, when the battery pack 2,102 is placed on the mounting surface RS such that the lower surfaces 14b,114b of the casings 10,110 are in contact with the mounting surface RS, the first ventilation holes 48,148 are in communication with the space in front of, behind, to the left of, or to the right of the battery pack 2,102.

[0075] According to the above configuration, when the battery pack 2,102 is placed on the mounting surface RS such that the lower surfaces 14b,114b of the casings 10,110 are in contact with the mounting surface RS while the multiple battery cells 18,118 are at a high temperature, the chimney effect allows air to flow from the outside of the casings 10,110 into the inside of the casings 10,110 through the first ventilation holes 48,148, thereby cooling the multiple battery cells 18,118.

[0076] In one or more embodiments of the battery pack 2,102, the inner surface of the casing 10,110 where the first ventilation holes 48,148 are formed is positioned above the center of the lowest battery cell 18f,118f among the plurality of battery cells 18,118, with respect to the vertical direction.

[0077] With the above configuration, when the battery pack 2,102 is placed on the mounting surface RS such that the lower surfaces 14b,114b of the casings 10,110 are in contact with the mounting surface RS, it is possible to more effectively suppress the adhesion of water and mud to the first ventilation holes 48,148 and the blockage of the first ventilation holes 48,148 by water and mud on the mounting surface RS. [Explanation of Symbols]

[0078] 2: Battery pack 4: Charger 6: Equipment mounting section 8: Battery pack mounting section 10: Casing 12: Battery cell unit 14: Lower casing 14a:Front 14b: Bottom surface 16: Upper casing 16a:Top surface 18, 18a, 18b, 18c, 18d, 18e, 18f: Battery cells 20: Cell holder 22: Control circuit board 24: Battery side terminal 26: Opening for terminal 28: Battery side rail 30: Cooling opening 32: Engagement opening 34:Operation opening 36: Hook 36a: Engagement part 36b: Operation section 38: Compression spring 40: Front guard section 42: Rear guard section 44: First finger rest recess 44a: Finger rest surface 44b: Cylindrical surface 44c: Anti-slip part 46: Second finger rest recess 46a: Front cylindrical surface 46b: Rear cylindrical surface 48: First ventilation hole 50: Second ventilation hole 52: Third vent 54: Drainage hole 102: Battery pack 106: Equipment mounting section 110: Casing 112: Battery cell unit 114: Lower casing 114a: Front 114b: Bottom surface 116: Upper casing 116a:Top surface 118, 118a, 118b, 118c, 118d, 118e, 118f, 118g, 118h, 118i: Battery cells 120: Cell holder 122: Control circuit board 124: Battery side terminal 126: Terminal opening 128: Battery side rail 130: Cooling opening 132: Engagement opening 133: Engaging member 134:Operation opening 134a: Rotary shaft 136: Operating component 138: Compression spring 140: Front guard section 142: Rear guard section 144: First finger rest recess 144a: Finger rest surface 144b: Cylindrical surface 144c: Anti-slip part 146: Second finger rest recess 146a: Front cylindrical surface 146b: Rear cylindrical surface 146c: Connection surface 148: First ventilation hole 150: Second ventilation hole 152: Third vent 154: Drainage hole

Claims

1. A battery pack that can be attached and detached by sliding it against the battery pack mounting section, The aforementioned battery pack is Casing and, The casing comprises a plurality of battery cells housed inside the casing, When removing the battery pack from the battery pack mounting section, the direction in which the battery pack is slid is defined as the forward direction; when attaching the battery pack to the battery pack mounting section, the direction in which the battery pack is slid is defined as the backward direction; when the battery pack is attached to the battery pack mounting section, the direction in which the battery pack mounting section is located relative to the battery pack is defined as the upward direction; the opposite direction of the upward direction is defined as the downward direction; and the direction perpendicular to the front-back and up-down directions is defined as the left-right direction. The casing has a through hole that opens downwards. With respect to the front-to-back direction, the through-hole is positioned behind the front end of the foremost battery cell among the plurality of battery cells, and in front of the rear end of the rearmost battery cell among the plurality of battery cells. In the vertical direction, the inner surface of the casing at the location where the through hole is formed is positioned above the lower end of the lowest of the plurality of battery cells in the battery pack.

2. The aforementioned plurality of battery cells, A first battery cell having a longitudinal direction in the left-right direction, It has a longitudinal direction in the left-right direction and includes a second battery cell positioned adjacent to the rear of the first battery cell. The battery pack according to claim 1, wherein, with respect to the front-to-back direction, the through hole is positioned behind the center of the first battery cell and in front of the center of the second battery cell.

3. The battery pack according to claim 2, wherein the through hole has an elongated shape with a longitudinal direction in the left-right direction.

4. The lower surface of the casing has a recess that is indented upward and extends in the left-right direction. The battery pack according to claim 1 or 2, wherein the through hole is located within the recess.

5. The battery pack according to claim 4, wherein the through hole has an elongated shape with a longitudinal direction in the left-right direction.

6. A battery pack according to any one of claims 1 to 5, wherein when the battery pack is placed on the aforementioned mounting surface such that the lower surface of the casing abuts against the mounting surface, the through hole communicates with the space in front of, behind, to the left of, or to the right of the battery pack.

7. The battery pack according to any one of claims 1 to 6, wherein, with respect to the vertical direction, the inner surface of the casing at the location where the through hole is formed is positioned above the center of the lowest of the plurality of battery cells.

Images