Battery pack

Abstract

To provide a technology capable of suppressing damage to a battery cell housed in a cell case even when impact is applied to a lower case.SOLUTION: A battery pack includes an upper case, an outer case having a lower case fixed to the upper case, a battery cell, and a cell case that houses the battery cell. A clearance is provided between the lower case and the entire lower surface of the cell case.SELECTED DRAWING: Figure 19

Description

[Technical Field]

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

[0002] A battery pack is disclosed in Patent Document 1. The battery pack in Patent Document 1 includes an outer case having an upper case and a lower case fixed to the upper case, battery cells, and a cell case that houses the battery cells. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-203703 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if a user drops the battery pack, an impact may be applied to the lower case of the outer case, causing the lower case to deform. In the case of the battery pack of Patent Document 1, if the lower case deforms, the lower case may come into contact with the cell case, causing the cell case to deform, which may damage the battery cells housed in the cell case.

[0005] The present specification provides a technique that can prevent damage to battery cells housed in a cell case even when an impact is applied to the lower case. [Means for solving the problem]

[0006] The battery pack disclosed in this specification comprises an outer case having an upper case and a lower case fixed to the upper case, battery cells, and a cell case that houses the battery cells, and a clearance is provided between the lower case and the entire lower surface of the cell case.

[0007] In the battery pack described above, even if the lower case of the outer case is subjected to an impact and deformed, the lower case can be prevented from coming into contact with the underside of the cell case, thereby preventing damage to the battery cells housed in the cell case when an impact is applied to the lower case. [Brief explanation of the drawings]

[0008] [Figure 1A] 1 is a perspective view of a battery pack 2 of a first embodiment as viewed from above on the front right. [Figure 1B] 1 is a perspective view of a battery pack 2 of a first embodiment as viewed from the front right below. [Figure 1C] 1 is a perspective view of a battery pack 2 of a first embodiment as viewed from above and rear right. [Figure 2] FIG. 2 is a bottom view of the battery pack 2 of the first embodiment as seen from below. [Figure 3] FIG. 2 is a right side view of the battery pack 2 of the first embodiment as viewed from the right. [Figure 4A] FIG. 2 is a bottom view of the upper case 14 of the first embodiment as seen from below. [Figure 4B] FIG. 2 is a perspective view of the upper case 14 of the first embodiment as viewed from the front lower left. [Figure 4C] 1 is a cross-sectional view of the slide rail 20 of the upper case 14 of the first embodiment as seen from the rear. [Figure 5] FIG. 4B is an enlarged view of the portion V surrounded by the dashed line in FIG. 4A. [Figure 6] FIG. 2 is a top view of the lower case 15 of the first embodiment as viewed from above. [Figure 7] 7 is an enlarged perspective view of the portion VII indicated by the broken line in FIG. 6, as viewed from above and rear right. [Figure 8] FIG. 2 is a perspective view of the lower case 15 of the first embodiment as seen from above, rear, and left. [Figure 9A] 1 is a perspective view of a battery module 10 of a first embodiment as viewed from above on the front right. [Figure 9B] 1 is a perspective view of a battery module 10 of a first embodiment as viewed from above, rear, and left. [Figure 10] FIG. 9B is a cross-sectional view taken along line XX in FIG. 9A. [Figure 11A] 1 is a perspective view of a cell case 80 of a first embodiment as viewed from above on the front right. [Figure 11B] FIG. 2 is a perspective view of the right cell case 85 of the first embodiment as viewed from above, rear left. [Figure 11C] FIG. 2 is a top view of the cell case 80 of the first embodiment, as viewed from above. [Figure 12A] FIG. 2 is a top view showing a state in which the battery module 10 and the lower case 15 are fixed together in the first embodiment. [Figure 12B] FIG. 2 is a top view of the battery pack 2 of the first embodiment. [Figure 13A] FIG. 12B is an enlarged view of the portion XIII enclosed by the dashed line in FIG. 12A. [Figure 13B] FIG. 13B is a cross-sectional view taken along line XIIIB-XIIIB in FIG. 13A. [Figure 14] 2 is a cross-sectional view of a battery pack 2 according to the present embodiment. FIG. [Figure 15] FIG. 15 is an enlarged view of the portion XV surrounded by the dashed line in FIG. [Figure 16] 2 is a cross-sectional view of a battery pack 2 according to the present embodiment. FIG. [Figure 17] FIG. 17 is an enlarged view of a portion XVII enclosed by a dashed line in FIG. 16. [Figure 18] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment, as viewed from the right. [Figure 19] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment, as viewed from the right. [Figure 20] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment, as seen from behind. [Figure 21] FIG. 11 is a cross-sectional view taken along line XXI-XXI in FIGS. 12A and 12B. [Figure 22] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment attached to a charger 300, as viewed from the left. [Figure 23] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment attached to a charger 300, as viewed from the left. [Figure 24A]1 is a perspective view of a battery pack 2 according to a first embodiment attached to a power tool 200, as viewed from the upper right front. [Figure 24B] 1 is a cross-sectional view of a battery pack 2 according to a first embodiment attached to a power tool 200, as viewed from behind. [Figure 25A] 1 is a perspective view of a battery pack 2 according to a first embodiment attached to a charger 300, as viewed from the lower left rear. FIG. [Figure 25B] FIG. 2 is a perspective view of the charger 300 as seen from the left rear bottom. [Figure 26] FIG. 10 is a perspective view of a battery pack 602 of a second embodiment as viewed from the front right below. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one or more embodiments, the cell casing may be threaded onto the outer casing.

[0010] With the above configuration, it is possible to prevent the outer case and the cell case from becoming misaligned, for example, if the user drops the battery pack, etc. Therefore, it is possible to further prevent damage to the battery cells housed in the cell case when an impact is applied to the lower case.

[0011] In one or more embodiments, the lower case may house three or more battery cells arranged parallel to the bottom surface of the lower case. The three or more battery cells may include outer battery cells closest to the corners of the lower case and inner battery cells disposed inside the outer battery cells. A clearance between the lower case and a first retaining portion that holds the outer battery cells on the underside of the cell case may be larger than a clearance between the lower case and a second retaining portion that holds the inner battery cells on the underside of the cell case.

[0012] When a user drops a battery pack, for example, impacts are likely to be applied to the four corners of the bottom surface of the lower case of the outer case. That is, the four corners of the bottom surface of the lower case are most likely to deform. The distance between the first retaining portion that holds the outer battery cell and the corner of the four corners of the bottom surface of the lower case that is closest to the outer battery cell is shorter than the distance between the second retaining portion that holds the inner battery cell and the corner of the four corners of the bottom surface of the lower case that is closest to the outer battery cell. Therefore, when the four corners of the bottom surface of the lower case are deformed, the bottom surface of the lower case is more likely to come into contact with the first retaining portion than with the second retaining portion. With the above configuration, even when the four corners of the bottom surface of the lower case are deformed, the lower case can be prevented from coming into contact with the underside of the cell case. Therefore, when an impact is applied to the lower case, damage to the battery cells housed in the cell case can be prevented.

[0013] In one or more embodiments, the first holding portion may be composed of an end holding portion that holds the longitudinal end side of the outer battery cell and a center holding portion that holds the longitudinal center side of the outer battery cell. The clearance between the end holding portion and the lower case may be larger than the clearance between the center holding portion and the lower case.

[0014] The end-side holding portions are closer to the four corners of the bottom surface of the lower case than the center-side holding portions. This configuration prevents the lower case from coming into contact with the underside of the cell case even if the four corners of the bottom surface of the lower case are deformed. Therefore, damage to the battery cells housed in the cell case can be prevented when the lower case receives an impact.

[0015] In one or more embodiments, a step may be provided on the bottom surface of the lower case between the side surface of the outer battery cell and the side surface of the inner battery cell that face each other, and the step may slope downward from the inner battery cell side toward the outer battery cell side.

[0016] According to the above configuration, the clearance between the first holding portion and the lower case can be made larger than the clearance between the second holding portion and the lower case. Therefore, even if the four corners of the bottom surface of the lower case are deformed, the lower case can be prevented from contacting the underside of the cell case. Therefore, when an impact is applied to the lower case, damage to the battery cells housed in the cell case can be further prevented.

[0017] In one or more embodiments, the thickness of the four corners of the lower portion of the cell casing may be greater than the thickness of the cell casing below the longitudinal axis of the battery cell.

[0018] If the lower case is deformed, it is highly likely that the lower case will come into contact with the four corners of the lower part of the cell case. With the above configuration, it is possible to increase the strength of the parts of the cell case that are highly likely to come into contact with the lower case. Therefore, even if the lower case comes into contact with the cell case, damage to the battery cells housed in the cell case can be suppressed.

[0019] (First Example) The battery pack 2 of the embodiment will be described below with reference to the drawings. As shown in FIG. 24A , the battery pack 2 can be detachably attached to a power tool 200. While FIG. 24A illustrates an example in which the power tool 200 is an electric screwdriver, the power tool 200 may be, for example, an electric drill, an electric grinder, an electric circular saw, an electric chainsaw, an electric reciprocating saw, an electric lawn mower, an electric brush cutter, or an electric blower. When attached to the power tool 200, the battery pack 2 supplies power to the power tool 200. As shown in FIG. 25 , the battery pack 2 can be detachably attached to a charger 300. When attached to the charger 300, the battery pack 2 receives power from the charger 300. In the following description, when the battery pack 2 is attached to the power tool 200 or the charger 300, the direction in which the power tool 200 or the charger 300 is located as viewed from the battery pack 2 is referred to as "upward," and the opposite direction is referred to as "downward." Furthermore, with regard to the battery pack 2, the direction in which the battery pack 2 is slid when attached to the power tool 200 or the charger 300 is referred to as the rearward direction, and the direction in which the battery pack 2 is slid when removed from the power tool 200 or the charger 300 is referred to as the forward direction. That is, in the following description, the forward and backward directions correspond to the sliding directions in which the battery pack 2 is slid relative to the power tool 200 or the charger 300.

[0020] As shown in FIGS. 1 to 13B, the battery pack 2 includes a battery module 10 (see FIG. 9) and an outer case 12 (see FIG. 1) that houses the battery module 10. The outer case 12 is formed in a generally rectangular parallelepiped shape overall, and is divided into an upper case 14 and a lower case 15. As shown in FIG. 2, the upper case 14 and the lower case 15 are fixed to each other with four screws 18.

[0021] (Configuration of upper case 14) As shown in FIG. 1A, the upper case 14 is formed with a slide rail 20, a terminal receiving portion 22, a hook 24, and a ventilation hole 26.

[0022] The slide rail 20 extends in the front-to-rear direction and is disposed at the left and right ends of the upper portion of the upper case 14. As shown in FIG. 1A, the slide rail 20 includes a base 20a, an upward extension 20b, a first right extension 20c, and a second right extension 20d. As shown in FIG. 4C, the upward extension 20b extends upward from the left end of the base 20a. The first right extension 20c extends right from the upward extension 20b. The lower end of the first right extension 20c is located above the upper end of the base 20a. The right end of the first right extension 20c is located leftward of the right end of the base 20a. The second right extension 20d extends rightward from the upward extension 20b. The right end of the second right extension 20d coincides with the right end of the first right extension 20c in the left-right direction. As shown in FIG. 1A, the second right extension 20d is connected to the base 20a. The first right extension 20c and the second right extension 20d are provided with a plurality of recesses 20e aligned in the front-to-rear direction. The slide rail 20 slidably engages with the slide rail (not shown) of the power tool 200 and the slide rail 302 of the charger 300 (see FIG. 25B) when the battery pack 2 is attached to or detached from the power tool 200 or the charger 300. Specifically, the slide rail (not shown) of the power tool 200 and the slide rail 302 of the charger 300 slide between the base 20a and the first right extension 20c.

[0023] The terminal receiving portion 22 has four terminal openings 22a to 22d provided on the front upper surface 14b1 of the upper case 14. The terminal openings 22a to 22d are disposed between the left and right slide rails 20 and receive terminals 208a, 208b, 210a, and 210c (see FIG. 24B) of the power tool 200 and terminals (not shown) of the charger 300 when the battery pack 2 is attached to the power tool 200 or the charger 300. The terminal openings 22a to 22d are provided in the following order from the right slide rail 20 to the left slide rail 20: terminal opening 22a, terminal opening 22b, terminal opening 22c, and terminal opening 22d. As shown in FIGS. 1C, 12B, and 24B, battery-side recesses 23a to 23d are provided to surround the terminal openings 22a to 22d. The terminal openings 22a to 22d and the battery-side recesses 23a to 23d have a U-shape when viewed from above the battery pack 2. The battery-side recesses 23a to 23d are provided slightly below the front upper surface 14b1 of the outer case 12. In other words, the front upper surface 14b1 and the battery-side recesses 23a to 23d have a stepped shape.

[0024] The hook 24 is disposed at the upper front portion of the upper case 14. The hook 24 is a resin member and includes an operating portion 24a and a protruding portion 24b. The operating portion 24a is provided on the front surface 14a of the upper case 14. The hook 24 is held by the upper case 14 so as to be movable up and down. The hook 24 is biased upward by a compression spring (not shown), and moves downward when the operating portion 24a or the protruding portion 24b is pressed downward. When the battery pack 2 is attached to the power tool 200 or the charger 300, the protruding portion 24b engages with the housing (not shown) of the power tool 200 or the housing 304 of the charger 300 (see FIG. 25B ), thereby securing the battery pack 2 to the power tool 200 or the charger 300. When the battery pack 2 is to be removed from the power tool 200 or the charger 300, the user presses the operating portion 24a downward, causing the protruding portion 24b to move downward. In this state, the battery pack 2 can be slid to remove it from the power tool 200 or the charger 300. The operation unit 24a has a recessed shape on the inside. Therefore, when a user places a finger on the operation unit 24a and presses it downward, the finger can be pressed down without slipping.

[0025] The ventilation hole 26 is located rearward of the slide rail 20. The ventilation hole 26 is located at the rear of the rear upper surface 14b2 of the outer case 12. The rear upper surface 14b2 is located lower than the front upper surface 14b1 and higher than the base 20a of the slide rail 20. A battery-side recess 27 is provided on a portion of the right side, a portion of the left side, and in front of the ventilation hole 26. The battery-side recess 27 is located slightly lower than the rear upper surface 14b2. That is, the rear upper surface 14b2 and the battery-side recess 27 have a stepped shape. The charger 300 is provided with a charger-side protrusion 306 (see FIG. 25B ) that has a shape corresponding to the battery-side recess 27. Therefore, when the battery pack 2 is attached to the charger 300, the charger-side protrusion 306 is inserted into the battery-side recess 27.

[0026] As shown in FIG. 4A, the upper case 14 has four screw holes 28 and five first protrusions 30a-30e. Screws 18 (see FIG. 2) are threaded into the four screw holes 28. As shown in FIG. 4B, the first protrusions 30a-30e protrude downward (i.e., toward the cell case 80) from the top surface of the upper case 14. As shown in FIG. 4C, the first protrusion 30d is provided below the slide rail 20 (specifically, the base 20a), i.e., on the inside of the upper case 14. The first protrusions 30a-30c and 30e are also provided below the slide rail 20. As shown in FIG. 5, the first protrusion 30 is composed of a thick portion 32a and a thin portion 32b. The thickness of the thick portion 32a in the left-right direction is greater than the thickness of the thin portion 32b in the left-right direction. In the first protrusion 30, thick portions 32a and thin portions 32b are formed alternately. As shown in Fig. 4A, each of the first protrusions 30a to 30d is composed of four thick portions 32a and three thin portions 32b. The first protrusion 30e is composed of three thick portions 32a and two thin portions 32b. As shown in Fig. 5, the length L1 in the front-rear direction of each of the first protrusions 30a to 30d is longer than the length L2 in the front-rear direction of the first protrusion 30e.

[0027] As shown in FIG. 4A, upper case 14 is provided with six second protrusions 34a to 34f for aligning upper case 14 and lower case 15. As shown in FIG.

[0028] (Configuration of the lower case 15) As shown in FIGS. 1B and 8, the lower case 15 is composed of a front surface 15a, a right side surface 15b, a rear surface 15c, a left side surface 15d, and a bottom surface 15e. The front surface 15a is composed of a first upwardly extending surface 17a extending perpendicularly to the bottom surface 15e, an inclined surface 17b inclined relative to the bottom surface 15e, and a second upwardly extending surface 17c extending perpendicularly to the bottom surface 15e. As shown in FIG. 13B, the inclined surface 17b is inclined downward toward the rear. As shown in FIG. 1A, the lower case 15 is provided with an air vent 40 and a display unit 42. The display unit 42 is provided on the front surface 15a of the lower case 15. The display unit 42 includes a remaining charge display unit 42a that displays the remaining charge of the battery pack 2 to the user and a button 42b that switches the remaining charge display on and off. 1B, sloping surface 17b of lower case 15 is provided with ventilation holes 58a to 58d. Furthermore, bottom surface 15e of lower case 15 is provided with a hook 19. Hook 19 is used when removing battery pack 2 from power tool 200 or charger 300. Specifically, the user hooks hook 19 with the index finger or middle finger and presses operating unit 24a (see FIG. 1A) downward with the thumb.

[0029] As shown in FIG. 3, the ventilation hole 40 is provided in the lower part of the right side surface 15b of the lower case 15. The ventilation hole 40 is composed of ten holes 40a to 40j. The ten holes 40a to 40j are arranged in two rows, one above the other. Of the five holes 40a to 40e provided in the lower row, the rearmost hole 40a and the frontmost hole 40e have shorter front-to-rear lengths than the holes 40b to 44d. Furthermore, of the five holes 40f to 44j provided in the upper row, the rearmost hole 40f and the frontmost hole 40j have shorter front-to-rear lengths than the holes 40g to 44i. Furthermore, as shown in FIG. 8, a ventilation hole 41 similar to the ventilation hole 40 is also provided in the lower part of the left side surface 15d of the lower case 15. The ventilation hole 41 is composed of ten holes 41a to 41j.

[0030] As shown in FIG. 6, the lower case 15 has four screw holes 46, five front ribs 48, 50, 52, 54, and 56, four vent holes 58a-58d, eight side ribs 60a-60h, four screw holes 62, and six second recesses 64a-64f. The four screw holes 46 are provided at positions corresponding to the four screw holes 28 (see FIG. 4A) of the upper case 14. The four screw holes 62 are used to fasten the lower case 15 to the battery module 10. The second recesses 64a-64f are provided at positions corresponding to the second protrusions 34a-34f (see FIG. 4A) of the upper case 14. The bottom surface 15e of the lower case 15 is composed of a flat portion 16a, a protrusion 16b, a recess 16c, and a step 16d. The protruding portion 16b protrudes upward from the flat portion 16a. As shown in FIG. 18, the protruding portion 16b has a shape that conforms to the underside of the cell case 80, which will be described later. As shown in FIG. 6, the recessed portions 16c are provided at the four corners 15f of the bottom surface 15e of the lower case 15. As shown in FIG. 19, the step portion 16d connects the flat portion 16a and the recessed portion 16c. The step portion 16d slopes downward from the inside to the outside of the lower case 15. The thickness t1 of the lower case 15 at the flat portion 16a is the same as the thickness t1 of the lower case 15 at the recessed portion 16c.

[0031] As shown in FIG. 7, the front ribs 48, 50, 52, 54, and 56 are provided on the inclined surface 17b. The front ribs 48, 50, 52, 54, and 56 extend upward from the inclined surface 17b and rearward from the front surface 15a of the lower case 15. The rear end of the front rib 48 is approximately aligned with the rear end of the inclined surface 17b, and the upper end of the front rib 48 is approximately aligned with the uppermost end of the inclined surface 17b. The upper surface of the front rib 48 is flat. The rear end of the front rib 50 is approximately aligned with the rear end of the inclined surface 17b, and the upper end of the front rib 50 is located higher than the upper end of the remaining battery indicator 42a. The front rib 50 also has a groove 50a. An LED board 84 (see FIG. 13A), which will be described later, passes through the groove 50a. The rear ends of the front ribs 52 and 54 are located forward of the rear end of the inclined surface 17b. The upper ends of the front ribs 52, 54 are located higher than the upper end of the remaining amount indicator 42a. The front rib 56 is composed of a light-shielding wall portion 56a and a flat portion 56b. The light-shielding wall portion 56a has the same structure as the front ribs 52, 54. The flat portion 56b has the same structure as the front rib 48.

[0032] The space above the inclined surface 17b is divided into four spaces S1 to S4 by the front ribs 48, 50, and 56. Specifically, the first space S1 is defined by the front rib 48, the second space S2 is defined by the front ribs 48 and 50, the third space S3 is defined by the front ribs 50 and 56, and the fourth space S4 is defined by the front rib 56. Air vents 58a to 58d are provided in each of the spaces S1 to S4, respectively. The air vents 58a to 58d penetrate the lower case 15 in the vertical direction. Therefore, water that has entered the outer case 12 and flows into the spaces S1 to S4 is drained through the air vents 58a to 58d.

[0033] As shown in FIG. 6, the side ribs 60a to 60d extend leftward from the right side surface 15b of the lower case 15. As shown in FIG. 8, the lower ends of the side ribs 60a to 60d extend upward from the bottom surface 15e of the lower case 15. The upper ends of the side ribs 60a to 60d are located slightly lower than the upper end of the lower case 15. The side ribs 60a to 60d are provided between adjacent holes 40 in the front-to-rear direction. Specifically, the side rib 60a is provided between the holes 40a, 40f and the holes 40b, 40g, the side rib 60b is provided between the holes 40b, 40g and the holes 40c, 40h, the side rib 60c is provided between the holes 40c, 40h and the holes 40d, 40i, and the side rib 60d is provided between the holes 40d, 40i and the holes 40e, 40j. The side ribs 60e to 60h have the same structure as the side ribs 60e to 60h, except that they extend rightward from the left side surface 15d of the lower case 15.

[0034] (Configuration of battery module 10) As shown in FIG. 9A, the battery module 10 includes a cell case 80, a control board 82, and an LED board 84. The cell case 80 is made of an insulating material, such as a resin material. As shown in FIG. 11A, the cell case 80 is divided into a right cell case 85 and a left cell case 86. A vent hole 81a is provided in the front portion 80a of the cell case 80, and a vent hole 81b is provided in the rear portion 80b of the cell case 80. Thickened portions 80c are provided at the four corners of the lower portion of the cell case 80. As shown in FIG. 19, the thickness t11 of the thickened portions 80c is greater than the thickness t12 of a cell holding portion 87, which will be described later. As shown in FIG. 11A, the top surface 80d of the cell case 80 has a shape corresponding to the longitudinal side surface of a battery cell 90 (see FIG. 10), which will be described later. A recessed portion 80g is provided between two adjacent battery cells 90 on the top surface 80d of the cell case 80. The top surface 80d of the cell case 80 is provided with four screw bosses 83 used to connect the control board 82 and the cell case 80. As shown in FIG. 9B, protrusions 116a to 116c that protrude upward from the top surface 80d of the cell case 80 are provided at the top of the left side surface 80f of the cell case 80. As shown in FIG. 11C, the protrusions 116a to 116c are arranged so as to straddle two adjacent battery cells 90. First recesses 110a to 110c are provided in the protrusions 116a to 116c. The first recesses 110a to 110c are provided at positions corresponding to the first protrusions 30a to 30c (see FIG. 4A) of the upper case 14. As shown in FIG. 9A, protrusions 116d and 116e that protrude upward from the top surface 80d of the cell case 80 are provided at the top of the right side surface 80e of the cell case 80. 11C, protrusions 116d, 116e are arranged so as to straddle two adjacent battery cells 90. First recesses 110d, 110e are provided in protrusions 116d, 116e. The first recesses 110d, 110e are provided at positions corresponding to first protrusions 30d, 30e (see FIG. 4A) of the upper case 14, respectively. As shown in FIG. 11C, protrusions 116a-116e and first recesses 110a-110e are provided outside of the control board 82 when the battery module 10 is viewed from above.The first recesses 110a to 110e are provided between two lead plates 92, which will be described later. As shown in Fig. 9A, the protrusion 116d and the first recess 110d are provided between the lead plates 92c and 92d, and the protrusion 116e and the first recess 110e are provided between the lead plates 92d and 92e. As shown in Fig. 9B, the protrusion 116a and the first recess 110a are provided between the lead plates 92j and 92k, the protrusion 116b and the first recess 110b are provided between the lead plates 92i and 92j, and the protrusion 116c and the first recess 110c are provided between the lead plates 92h and 92i.

[0035] As shown in FIG. 11B, the right cell case 85 is provided with ten cell holding portions 87a to 87j. The ten cell holding portions 87a to 87j are arranged in two rows, one above the other. As shown in FIG. 18, which is a cross-sectional view of the battery pack 2 at the center position in the left-right direction, the cell holding portions 87a to 87c have a central holding portion 89a that holds the center of a battery cell 90, which will be described later. Also, as shown in FIG. 19, which is a cross-sectional view of the battery pack 2 at a position where a recessed portion 16c is provided on the right rear side of the lower case 15, the cell holding portions 87a to 87c have an end face holding portion 89b that holds the right end face of the battery cell 90 in the longitudinal direction. Although not shown, the cell holding portions 87d and 87e also have a central holding portion and an end face holding portion. 11B, connecting portions 88 for connecting the right cell case 85 and the left cell case 86 are provided between the cell holding portions 87a, 87b, 87f, and 87g and between the cell holding portions 87d, 87e, 87i, and 87j. Although not shown, the left cell case 86 is provided with ten cell holding portions corresponding to the ten cell holding portions 87a to 87j of the right cell case 85 and two connecting portions corresponding to the two connecting portions 88 of the right cell case 85.

[0036] As shown in FIG. 10 , ten battery cells 90a to 90j are arranged in two upper and lower rows in the cell case 80. The battery cells 90 are cylindrical secondary battery cells, such as lithium-ion battery cells, with a positive electrode formed on one end and a negative electrode formed on the other end. In this embodiment, the battery cells 90 are 18650-type lithium-ion battery cells with a rated voltage of 3.6 V. The battery cells 90 are arranged so that the positive and negative electrodes of adjacent battery cells 90 in the vertical direction are opposite to each other. Of the battery cells 90a to 90e in the lower row, the rearmost battery cell 90a is arranged so that its right end surface is the negative electrode and its left end surface is the positive electrode. Similarly, the battery cells 90b to 90e are arranged so that their right end surface is the positive electrode and their left end surface is the negative electrode. Among the upper-row battery cells 90f-90j, the rearmost battery cell 90f is arranged so that its right end surface is the positive electrode and its left end surface is the negative electrode. Similarly, the battery cells 90g-90j are arranged so that their right end surface is the negative electrode and their left end surface is the positive electrode. A metal portion 91 (see, for example, FIG. 20) constituting the positive electrode of each battery cell 90 and a metal portion constituting the negative electrode are connected to the end surfaces of the battery cell 90. One end of each battery cell 90 is connected via a metal portion to metal lead plates 92a-92f provided on the right side surface 80e of the cell case 80 (see FIG. 9A), and the other end of each battery cell 90 is connected via a metal portion to metal lead plates 92g-92k provided on the left side surface 80f of the cell case 80 (see FIG. 9B). As shown in FIG. 20, a waterproof ring 95 is provided on the metal portion 91 constituting the positive electrode of each battery cell 90. 9A and 9B, the thick circle on the surface of the lead-plate 92 indicates the area inside which the waterproof ring 95 is located. Therefore, the positive electrode of the battery cell 90 is connected to the thick circle on the surface of the lead-plate 92.

[0037] As shown in FIG. 9A, the lead plates 92a-92f are arranged at intervals from one another. Therefore, the lead plates 92a-92f are insulated from one another. The lead plate 92a is connected only to the positive electrode of battery cell 90f. The lead plate 92f is connected only to the negative electrode of battery cell 90j. The lead plate 92b connects two adjacent battery cells 90a and 90b in the front-to-rear direction. The lead plates 92c-92e connect two adjacent battery cells 90a and 90b in the diagonal direction. Specifically, the lead plate 92c is connected to the negative electrode of battery cell 90g and the positive electrode of battery cell 90c. The lead plate 92d is connected to the negative electrode of battery cell 90h and the positive electrode of battery cell 90d. The lead plate 92e is connected to the negative electrode of battery cell 90i and the positive electrode of battery cell 90e.

[0038] 9B, the lead plates 92g-92k are spaced apart from one another. Therefore, the lead plates 92g-92k are insulated from one another. The lead plates 92g-92k connect adjacent battery cells 90 in the vertical direction. Specifically, lead plate 92g connects the negative electrode of battery cell 90e to the positive electrode of battery cell 90j. Lead plate 92h connects the negative electrode of battery cell 90d to the positive electrode of battery cell 90i. Lead plate 92i connects the negative electrode of battery cell 90c to the positive electrode of battery cell 90h. Lead plate 92j connects the negative electrode of battery cell 90b to the positive electrode of battery cell 90g. Lead plate 92k connects the positive electrode of battery cell 90a to the negative electrode of battery cell 90f. With the above configuration, the ten battery cells 90 are electrically connected in series. Therefore, the rated voltage of the battery pack 2 is 36 V. Although not shown, insulating sheets are attached to the right side surface 80e and the left side surface 80f of the cell case 80.

[0039] According to the above configuration, the lead plates 92a, 92f connected to the control board 82 can be connected to the upper battery cells 90f, 90j via a power supply line (not shown). A larger current flows through the lead plates 92a, 92f connected to the control board 82 than through the other lead plates. For this reason, it is desirable that the lead plates 92a, 92f have a large width. According to the above configuration, it is possible to ensure a sufficient width for the lead plates 92a, 92f. Furthermore, if at least one of the lead plates 92a, 92f connected to the control board 82 is connected to a lower battery cell, it is necessary to wire a power supply line from the bottom of the cell case 60. Wiring a power supply line at the bottom of the cell case 60 is difficult because the clearance between the cell case 60 and the right side surface of the outer case 12 is small. According to the above configuration, because both lead plates 92a, 92f connected to the control board 82 are connected to the upper battery cells 90f, 90j, it is possible to easily wire the power supply lines connecting the lead plates 92a, 92f to the control board 82. Furthermore, compared to when at least one of the lead plates 92a, 92f is connected to the lower battery cell 90, the length of the current lines connecting the lead plates 92a, 92f to the control board 82 can be shortened, and therefore the resistance of the power supply lines connecting the lead plates 92a, 92f to the control board 82 can be reduced.

[0040] 10 , when the cell case 80 holds ten battery cells 90a-90j, the upper battery cells 90f-90j and the lower battery cells 90a-90e are spaced apart in the vertical direction. Furthermore, clearances are provided between the battery cells 90a, 90b, 90f, and 90g and the rear-side connecting portions 88, and between the battery cells 90d, 90e, 90i, and 90j and the front-side connecting portions 88. Therefore, air that flows into the cell case 80 through the air vent 81a or 81b in the cell case 80 can pass between the upper battery cells 90f-90j and the lower battery cells 90a-90e, between the battery cells 90a, 90b, 90f, and 90g and the rear-side connecting portions 88, and between the battery cells 90d, 90e, 90i, and 90j and the front-side connecting portions 88.

[0041] 9A, the control board 82 is disposed above the cell case 80. The control board 82 is disposed along a plane perpendicular to the up-down direction. The control board 82 is fixed to the cell case 80 via fasteners 100.

[0042] A plurality of terminals 102 are provided on the upper surface of the control board 82. The plurality of terminals 102 include a battery-side negative terminal 104a used for discharging or charging when the battery pack 2 is attached to the power tool 200 or the charger 300, a battery-side positive terminal 104b used for discharging or charging, and a plurality of battery-side signal terminals 106a to 106d used for transmitting and receiving signals. The battery-side negative terminal 104a and the battery-side positive terminal 104b are provided outside the battery-side signal terminals 106a to 106d in the left-right direction. The battery-side negative terminal 104a is provided on the right side of the control board 82, and the battery-side positive terminal 104b is provided on the left side of the control board 82. The battery-side signal terminals 106a and 106b are provided side by side in the front and rear. The battery-side signal terminals 106c and 106d are provided side by side in the front and rear. As shown in FIG. 12B, the battery-side negative terminal 104a is positioned at a position corresponding to the terminal opening 22a of the upper case 14, the battery-side signal terminals 106a and 106b are positioned at a position corresponding to the terminal opening 22b, the battery-side signal terminals 106c and 106d are positioned at a position corresponding to the terminal opening 22c, and the battery-side positive terminal 104b is positioned at a position corresponding to the terminal opening 22d.

[0043] 9A and 9B, the cell case 80 is provided with four fixing portions 112. Each fixing portion 112 is provided at a position corresponding to a screw hole 62 of the lower case 15. As shown in FIG. 12A, the lower case 15 and the battery module 10 are fixed to each other with four screws 114.

[0044] As shown in FIG. 9A, the LED board 84 is connected to the control board 82 via a signal line 120. The LED board 84 includes four LEDs 84a and a switch 84b. As shown in FIG. 13A, when the battery module 10 and the lower case 15 are fixed together, the LED board 84 is disposed near the rear surface of the display unit 42 of the lower case 15. Specifically, the LEDs 84a are disposed on the rear surface of the remaining battery level display unit 42a, and the switch 84b is disposed on the rear surface of the button 42b. That is, the LED board 84 faces the front surface 14a inside the lower case 15. The LED board 84 is inserted into the groove 50a of the front rib 50 of the lower case 15 and rests on the front ribs 48 and 56. Therefore, the LED board 84 is held by the lower case 15. The front surface of the LED board 84 contacts the rear ends of the front ribs 52 and 54 and the light-shielding wall portion 56a of the front rib 56. Moreover, the LED substrate 84 has ventilation holes 58a to 58d formed on the surface opposite to the lower surface 84c.

[0045] Below, with reference to Figures 14 to 17, we will explain the engagement clearance C1 between the first protrusion portion 30 of the upper case 14 and the first recess portion 110 of the battery module 10, and the engagement clearance C2 between the second protrusion portion 34 of the upper case 14 and the second recess portion 64 of the lower case 15.

[0046] As shown in Fig. 14, the first protrusions 30a to 30e of the upper case 14 are respectively received in the first recesses 110a to 110e of the battery module 10. As shown in Fig. 15, an engagement clearance C1 is provided between the first protrusion 30d and the first recess 110d.

[0047] As shown in FIG. 16, the second protrusions 34a to 34f of the upper case 14 are received in the second recesses 64a to 64f of the lower case 15, respectively. As shown in FIG. 17, an engagement clearance C2 is provided between the second protrusion 34e and the second recess 64e. The engagement clearance C2 is used to position the upper case 14 and the lower case 15. The engagement clearance C1 in FIG. 14 is used to prevent misalignment between the upper case 14 and the cell case 80. The engagement clearance C1 may be set to prevent misalignment between the upper case 14 and the cell case 80 and to prevent contact between the upper case 14 and the control board 82. Therefore, the engagement clearance C1 is larger than the engagement clearance C2. As shown in FIG. 16, the second protrusions 34a to 34f and the second recesses 64a to 64f form a labyrinth structure. This prevents water from entering the outer case 12.

[0048] Next, the case clearances C11 to C13 between the lower surface of the cell case 80 of the battery module 10 and the lower case 15 will be described with reference to Figures 18 and 19. As described above, Figure 18 shows a cross-sectional view of the battery pack 2 at the center position in the left-right direction, and Figure 19 shows a cross-sectional view of the battery pack 2 at the position where the recessed portion 16c is provided on the rear right side of the lower case 15.

[0049] 18, the lower surface of the cell case 80 does not contact the bottom surface 15e of the lower case 15. Specifically, a case clearance C11 is provided between the central holding portion 89a of the cell holding portions 87a to 87c and the protruding portion 16b that protrudes upward (i.e., inward) from the bottom surface 15e of the lower case 15. In addition, a case clearance C12 is provided between the central holding portion 89a and the flat portion 16a. The case clearance C12 is larger than the case clearance C11.

[0050] 19, a case clearance C13 is provided between the recess 16c and the end-surface-side holding portion 89b corresponding to the battery cell 90a located closest to the corner 15f of the lower case 15. A step 16d is provided between the surface of the bottom surface 15e of the lower case 15 that faces the side surface 93a of the battery cell 90a and the surface that faces the side surface 93b of the battery cell 90b. Note that no step 16d is provided between the surface of the bottom surface 15e of the lower case 15 that faces the side surface 93b of the battery cell 90b and the surface that faces the side surface 93c of the battery cell 90c. Therefore, the case clearance C13 is larger than the case clearance C12.

[0051] Next, the positional relationship between the battery cell 90c located in the center of the lower row of the multiple battery cells 90 and the holes 40c and 40h provided to the right of the battery cell 90c will be described with reference to Figure 20. Note that the lead plate 92i has been omitted from Figure 20 for ease of understanding.

[0052] As shown in Figure 20, holes 40c and 40h are provided on the right side surface 15b at positions facing the longitudinal end face of the battery cell 90c. However, no holes are provided on the right side surface 15b at positions facing the longitudinal end face of the battery cell 90h located above the battery cell 90c. Portions of the holes 40c and 40h face the longitudinal end face of the battery cell 90h.

[0053] The metal portion 91 constituting the positive electrode of the battery cell 90c is provided on the right end face of the battery cell 90c. The lower ends 43h of the upper-stage holes 40h and the lower ends 43c of the lower-stage holes 40c are provided below the upper ends 94a of the battery cell 90c and the longitudinal axis A1 of the battery cell 90c. The lower ends 43c of the lower-stage holes 40c are also provided below the lower ends 91a of the metal portion 91 and the lower ends 94b of the battery cell 90c.

[0054] Next, referring to FIG. 21, the air flow inside the battery pack 2 will be described. For example, assume that the battery pack 2 is attached to the power tool 200, the power tool 200 is used by a user, and then the battery pack 2 is removed from the power tool 200. In this case, the battery pack 2 is hot. In such a situation, the vents 40 and 41 provided in the lower part of the lower case 15 shown in FIGS. 1A, 3, and 8 function as air intakes that introduce air from the outside to the inside of the battery pack 2. Specifically, the air around the battery pack 2 is heated, and flows into the battery pack 2 through the vents 40 and 41. The air introduced into the battery pack 2 through the vent 40 flows into the space between the multiple battery cells 90 and the lower case 15. As described above, the side ribs 60a to 60d are provided between the holes 40a to 40j. 20 , the air introduced through holes 40c and 40h flows into the space between the battery cells 90c and 90h and the right side surface 15b of the lower case 15. Similarly, the air introduced through holes 40a and 40f flows into the space between the battery cells 90b and 90g and the right side surface 15b of the lower case 15, the air introduced through holes 40b and 40g flows into the space between the battery cells 90b and 90g and the right side surface 15b of the lower case 15, the air introduced through holes 40d and 40i flows into the space between the battery cells 90d and 90i and the right side surface 15b of the lower case 15, and the air introduced through holes 40e and 40j flows into the space between the battery cells 90e and 90j and the right side surface 15b of the lower case 15. Therefore, the multiple battery cells 90 are reliably cooled. The air that flows into the space between the multiple battery cells 90 and the right side surface 15b of the lower case 15 cools the multiple battery cells 90, and then flows out of the battery pack 2 through the terminal openings 22a of the terminal receiving portion 22 of the upper case 14, etc. In this way, natural convection occurs when the battery pack 2 is at a high temperature. Note that the air introduced into the battery pack 2 through the ventilation holes 41 also flows into the space between each battery cell 90 and the left side surface 15d of the lower case 15, and is used to cool the battery cells 90.

[0055] 22 and 23, the air flow inside the battery pack 2 when the battery pack 2 is attached to the charger 300 will be described. The charger 300 is equipped with a blower fan (not shown) that is configured to draw air from the battery pack 2. In this state, the air vents 40 (see FIG. 1), 58a to 58d (see FIG. 6) of the battery pack 2 function as intake holes that introduce air from the outside to the inside of the battery pack 2, and the air vent 26 (see FIG. 1) of the battery pack 2 functions as an exhaust hole that exhausts air from the inside of the battery pack 2 to the charger 300.

[0056] 22, when the blower fan of the charger 300 is driven, air introduced into the battery pack 2 through the vent hole 58 (see FIG. 1B) flows into the space between the front part 80a of the cell case 80 and the front surface 15a of the lower case 15. An LED board 84 is provided between the front part 80a of the cell case 80 and the front surface 15a of the lower case 15. The air that has flowed into the space between the front part 80a of the cell case 80 and the front surface 15a of the lower case 15 flows into the cell case 80 between the front part 80a of the cell case 80 and the LED board 84, and through the vent hole 81a of the cell case 80. The air introduced into the cell case 80 passes between the upper-row battery cells 90f-90j and the lower-row battery cells 90a-90e, between the battery cells 90a, 90b, 90f, and 90g and the rear-side connecting portion 88, and between the battery cells 90d, 90e, 90i, and 90j and the front-side connecting portion 88. The air passing through the cell case 80 cools the multiple battery cells 90. The air that has cooled the multiple battery cells 90 is then introduced into the charger 300 via the ventilation holes 81b in the rear portion 80b of the cell case 80, the ventilation holes 26 in the upper case 14, and the ventilation holes 308 of the charger 300 that correspond to the ventilation holes 26 (see FIG. 25B ). As described above, when the battery pack 2 is attached to the charger 300, the charger-side protrusions 306 of the charger 300 are inserted into the battery-side recesses 27 around the ventilation holes 26. Therefore, compared to when the battery-side recess 27 is not provided around the ventilation hole 26, it is possible to reduce the amount of air drawn into the charger 300 through the gap between the battery pack 2 and the charger 300. This increases the amount of air flowing through the battery pack 2. As a result, the battery cells 90 and lead plates 92 inside the battery pack 2 can be cooled efficiently.

[0057] As shown in FIG. 23 , air introduced into the battery pack 2 through the vent 40 flows into the space between the multiple battery cells 90 (specifically, the lead plate 92) and the right side surface 15b of the lower case 15. The air that flows into the space between the battery cells 90 and the right side surface 15b of the lower case 15 flows forward above the multiple side ribs 60a-60d and into the space between the front portion 80a of the cell case 80 and the front surface 15a of the lower case 15. The air then flows in the same manner as in FIG. 22 . In this manner, the air introduced through the vents 58 and 40 is used to cool the multiple battery cells 90. In this embodiment, the vent 40 is provided in the lower part of the lower case 15, and therefore, when the battery pack 2 is attached to the charger 300, the vent 40 is located at a higher position than the charger 300. Dust and the like tend to accumulate at low heights, so that when the battery pack 2 is attached to the charger 300, dust and the like are less likely to be sucked in.

[0058] The effect of the battery-side recesses 23a-23d of the upper case 14 of the battery pack 2 will be described with reference to Fig. 24B. Fig. 24B is a cross-sectional view of the battery-side signal terminal 106a (see Fig. 12A) of the battery pack 2 at the center in the front-rear direction when the battery pack 2 is attached to the power tool 200. As shown in Fig. 24B, the power tool 200 includes a terminal holder 202, which is provided with tool-side protrusions 206a-206d that protrude downward (i.e., toward the battery pack 2). The tool-side protrusion 206a is provided with a tool-side negative terminal 208a corresponding to the battery-side negative terminal 104a, and the tool-side protrusion 206d is provided with a tool-side positive terminal 208b corresponding to the battery-side positive terminal 104b. The tool-side protrusion 206b is provided with a tool-side signal terminal 210a corresponding to the battery-side signal terminal 106a. A tool-side signal terminal (not shown) corresponding to the battery-side signal terminal 106b is provided on the tool-side protrusion 206b in front of the tool-side signal terminal 210a. The tool-side protrusion 206c is provided with a tool-side signal terminal 210c corresponding to the battery-side signal terminal 106c. The battery-side signal terminal 106d is a terminal that is used only when the battery pack 2 is attached to the charger 300, so no tool-side signal terminal corresponding to the battery-side signal terminal 106d is provided on the tool-side protrusion 206c in front of the tool-side signal terminal 208c. When the battery pack 2 is attached to the power tool 200, the tool-side protrusions 206a to 206d are inserted into the battery-side recesses 23a to 23d, respectively. With this configuration, the creepage distance between two adjacent terminals in the left-right direction among the multiple terminals of the power tool 200 can be increased compared to when the tool-side protrusions 206a-206d are not provided on the terminal holder 202 of the power tool 200. Specifically, the creepage distance can be increased by the height of the tool-side protrusions 206a-206d. Therefore, it is possible to prevent a short circuit between two adjacent terminals in the left-right direction among the multiple terminals of the power tool 200.

[0059] In one or more embodiments, as shown in FIGS. 1 to 13 , a battery pack 2 includes an upper case 14, an outer case 12 including a lower case 16 fixed to the upper case 14, battery cells 90, and a cell case 80 that houses the battery cells 90. Also, as shown in FIGS. 18 and 19 , case clearances C11 to C13 are provided between the entire lower surface of the lower case 16 and the cell case 80. With this configuration, even if an impact is applied to the lower case 16 of the outer case 12 and the lower case 16 is deformed, the lower case 16 can be prevented from coming into contact with the underside of the cell case 80. Therefore, when an impact is applied to the lower case 16, deformation of the battery cells 90 housed in the cell case 80 can be prevented.

[0060] 12A, the cell case 80 is screwed to the lower case 16. With the above configuration, it is possible to prevent misalignment between the lower case 15 and the cell case 80, for example, when a user drops the battery pack 2. Therefore, it is possible to further prevent damage to the battery cells 90 housed in the cell case 80 when an impact is applied to the lower case 15.

[0061] In one or more embodiments, as shown in FIG. 10 , the lower case 15 accommodates five battery cells 90a-90e arranged parallel to the bottom surface 15e of the lower case 15. The five battery cells 90a-90e include battery cells 90a and 90e closest to corners 15f of the lower case 15 and battery cells 90b-90d located inside the battery cells 90a and 90e. As shown in FIG. 19 , a case clearance C13 between the cell holder 87a that holds the battery cell 90a and the lower case 16 is larger than a case clearance C12 between the cell holder 87b that holds the battery cell 90b and the lower case 15. This configuration can prevent the lower case 15 from coming into contact with the underside of the cell case 80 even if the four corners 15f of the bottom surface 15e of the lower case 15 are deformed. Therefore, when an impact is applied to the lower case 16, damage to the battery cells 90 housed in the cell case 80 can be further reduced.

[0062] In one or more embodiments, as shown in FIGS. 18 and 19 , the cell holder 87a for holding the battery cell 90a is composed of an end-side holder 89b for holding the longitudinal end of the battery cell 90a and a center-side holder 89a for holding the longitudinal center of the battery cell 90a. The case clearance C13 between the end-side holder 89b and the lower case 15 is larger than the case clearance C12 between the center-side holder 89a and the lower case 15. The end-side holder 89b is closer to the four corners 15f of the bottom surface 15e of the lower case 15 than the center-side holder 89a. This configuration prevents the lower case 15 from contacting the underside of the cell case 80 even if the four corners 15f of the bottom surface 15e of the lower case 15 are deformed. Therefore, damage to the battery cells 90 housed in the cell case 80 can be further reduced when an impact is applied to the lower case 16.

[0063] In one or more embodiments, as shown in FIGS. 6 and 19 , a step 16d is provided on the bottom surface 15e of the lower case 15 between the side surface 93a of the battery cell 90a and the side surface 93b of the battery cell 90b. The step 16d slopes downward from the battery cell 90b side toward the battery cell 90a side. According to the above configuration, the case clearance C13 between the cell holding portion 87a that holds the battery cell 90a and the lower case 16 can be made larger than the case clearance C12 between the cell holding portion 87b that holds the battery cell 90b and the lower case 16. Therefore, even if the four corners 15f of the bottom surface 15e of the lower case 15 are deformed, the lower case 15 can be prevented from contacting the underside of the cell case 80. Therefore, damage to the battery cells 90 housed in the cell case 80 can be further reduced when the lower case 15 is subjected to an impact.

[0064] 19 , the thickness t11 of the thick-walled portions 80c at the four corners of the lower part of the cell casing 80 is greater than the thickness t12 of the cell casing 80 below the longitudinal axis A1 of the battery cell 90. This configuration increases the strength of the portion of the cell casing 80 that is likely to come into contact with the lower case 16. Therefore, even if the lower case 16 comes into contact with the cell casing 80, damage to the battery cell 90 housed in the cell casing 80 can be suppressed.

[0065] (Correspondence) Battery cells 90a and 90e are examples of “outer battery cells.” Battery cells 90b to 90d are examples of “inner battery cells.” Cell holder 87a that holds battery cell 90a and cell holder 87b that holds battery cell 90b are examples of “first holder” and “second holder,” respectively.

[0066] (Second Example) A battery pack 602 of the second embodiment will be described with reference to FIG. 26 . In the battery pack 602 of the second embodiment, the structure of the lower case 615 of the outer case 612 differs from the structure of the lower case 15 of the outer case 12 of the battery pack 2 of the first embodiment. Furthermore, the size of the battery cells (not shown) housed in the outer case 612 of the battery pack 602 of the second embodiment differs from the battery cells 90 housed in the outer case 12 of the first embodiment. Specifically, the battery cells of the second embodiment are 21700-type lithium-ion battery cells with a rated voltage of 3.6 V. Therefore, the outer case 612 is larger in size than the outer case 12 of the first embodiment. The outer case 612 houses ten battery cells, and the method of connecting the battery cells is the same as the battery pack of the first embodiment. Therefore, the rated voltage of the battery pack 602 of the second embodiment is also 36 V.

[0067] 26 , two hooks 619a, 619b are provided on the bottom surface 615e of the lower case 615, aligned in the front-to-rear direction. With this configuration, when removing the battery pack 2 from the power tool 200 or the charger 300, the user can use one of the two hooks 619a, 619b, whichever is most suitable for the length of the user's fingers. This makes it easier to remove the battery pack 2 from the power tool 200 or the charger 300.

[0068] Further features of the battery pack disclosed herein are set forth below. (Feature 1) A battery pack that can be slidably attached to a power tool, A first terminal; A second terminal; an outer case that houses the first terminal and the second terminal, a first terminal opening provided on a top surface of the outer case at a position corresponding to the first terminal and a second terminal opening provided at a position corresponding to the second terminal; The battery pack has battery-side recesses between the first terminal opening and the top surface, and between the second terminal opening and the top surface. (Feature 2) 2. The battery pack according to claim 1, wherein the battery-side recess has a shape corresponding to a tool-side protrusion of the power tool. (Feature 3) the first terminal is a discharge terminal, 3. The battery pack according to claim 1, wherein the second terminal is a signal terminal. (Feature 4) A first terminal; A second terminal; A third terminal; The fourth terminal, an outer case that houses the first terminal, the second terminal, the third terminal, and the fourth terminal, The outer case includes a pair of slide rails for slidingly receiving the power tool. a first terminal opening provided at a position corresponding to a first terminal, a second terminal opening provided at a position corresponding to a second terminal, a third terminal opening provided at a position corresponding to a third terminal, and a fourth terminal opening provided at a position corresponding to a fourth terminal on an upper surface of the outer case between the pair of slide rails; the first terminal opening, the second terminal opening, the third terminal opening, and the fourth terminal opening are arranged in this order from one slide rail of the pair of slide rails to the other slide rail; a battery-side recess provided between the first terminal opening and the top surface, between the second terminal opening and the top surface, between the third terminal opening and the top surface, and between the fourth terminal opening and the top surface. (Feature 5) 5. The battery pack according to claim 4, wherein the battery-side recess has a shape corresponding to a tool-side protrusion of the power tool. (Feature 6) the first terminal and the fourth terminal are discharge terminals, 6. The battery pack according to claim 4, wherein the second terminal and the third terminal are signal terminals. (Feature 7) A battery pack that can be attached to an external device by sliding from the front to the rear, Equipped with an outer case, The outer case is a pair of slide rails for slidingly receiving the external device; a terminal opening provided between the pair of slide rails; a surface between the pair of slide rails and rearward of the terminal opening; Ventilation holes and a battery-side recess provided between the pair of slide rails and between the surface rearward of the terminal opening and the air vent. (Feature 8) 8. The battery pack according to claim 7, wherein the battery-side recess has a shape corresponding to a device-side protrusion of the external device.

[0069] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0070] (First Modification) The cell case 80 may be fixed to the upper case 14 with screws.

[0071] (Second Modification) The case clearances C11 to C13 may be the same. Also, the case clearances C11 and C12 may be larger than the case clearance C13.

[0072] (Third Modification) The bottom surface 15e of the lower case 15 does not necessarily have to be provided with the step portion 16d.

[0073] (Fourth Modification) The thick portions 80c do not have to be provided at the four corners of the lower part of the cell case 80. In other words, when the cell case 80 is viewed from the right, the four corners of the lower part of the cell case 80 may have a shape that corresponds to the outer shape of the battery cell 90.

[0074] The technical elements described in this specification or drawings may exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives alone is technically useful. [Explanation of symbols]

[0075] 2: battery pack, 10: battery module, 12: outer case, 14: upper case, 14a: front surface, 14b1: front upper surface, 14b2: rear upper surface, 15: lower case, 15a: front surface, 15b: right side surface, 15c: rear surface, 15d: left side surface, 15e: bottom surface, 15f: corner, 16a: flat portion, 16b: protrusion, 16c: recess, 16d: step portion, 17a: first upward extension surface, 17b: inclined surface, 17c: second upward extension surface, 18: screw, 19: hook portion, 20: slide rail, 20a: base, 20b: upward extension portion, 20c: first right extension portion, 20d: second right extension portion lateral extension, 20e: recess, 22: terminal receiving portion, 22a to 22d: terminal opening, 23a to 23d: battery side recess, 24: hook, 24a: operating portion, 24b: protrusion, 26: vent, 27: battery side recess, 28: screw hole, 30a to 30e: first ridge, 32a: thick portion, 32b: thin portion, 34a to 34f: second ridge, 40: vent, 40a to 40j: hole, 41: vent, 41a to 41j: hole, 42: display, 42a: remaining amount display, 42b: button, 43c: bottom end, 43h: bottom end, 46: screw hole, 48: front rib, 50: front rib, 50a: groove, 5 2: front rib, 54: front rib, 56: front rib, 56a: light-shielding wall portion, 56b: flat portion, 58a to 58d: ventilation hole, 60a to 60h: side rib, 62: screw hole, 64a to 64f: second recessed portion, 80: cell case, 80a: front portion, 80b: rear portion, 80c: thick portion, 80d: top surface, 80e: right side surface, 80f: left side surface, 80g: recessed portion, 81a: ventilation hole, 81b: ventilation hole, 82: control board, 83: screw boss, 84: LED board, 84a: LED, 84b: switch, 84c: bottom surface, 85: right cell case, 86: left cell case, 87a to 87j: cell holding portion, 88: connecting portion, 89a: central holding portion, 89b: end surface holding portion, 90a to 90j: battery cell, 91: metal portion, 91a: lower end, 92a to 92k: lead plate, 93a to 93c: side surface, 93b: side surface, 93c: side surface, 94: waterproof ring, 94a: upper end, 94b: lower end, 100: fastener, 102: terminal, 104a: battery side negative terminal, 104b: battery side positive terminal, 106a to 106d: battery side signal terminal, 110a to 110e: first recess, 112: fixing portion, 114: screw, 116a to 116e: protrusion, 120: signal wire, 200: power tool, 202: terminal holding portion,206a to 206d: tool side protrusions, 208a: tool side negative terminal, 208b: tool side positive terminal, 210a, 210c: tool side signal terminal, 300: charger, 302: slide rail, 304: housing, 306: charger side protrusions, 308: ventilation hole, 602: battery pack, 612: outer case, 615: lower case, 615e: bottom surface, 619a, 619b: hooks,

Claims

1. an outer case including an upper case and a lower case fixed to the upper case; A battery cell; a cell case that houses the battery cell; A clearance is provided between the entire lower surface of the cell case and the lower case.

2. The battery pack according to claim 1 , wherein the cell case is screwed to the outer case.

3. The lower case has three or more battery cells arranged parallel to a bottom surface of the lower case, the three or more battery cells include an outer battery cell closest to a corner of the lower case and an inner battery cell provided inside the outer battery cell; 3. The battery pack according to claim 1, wherein a clearance between the lower case and a first holding portion that holds the outer battery cell on the underside of the cell case is larger than a clearance between the lower case and a second holding portion that holds the inner battery cell on the underside of the cell case.

4. the first holding portion is composed of an end face side holding portion that holds an end face side of the outer battery cell in the longitudinal direction, and a center side holding portion that holds a center side of the outer battery cell in the longitudinal direction, The battery pack according to claim 3 , wherein a clearance between the end surface side holding portion and the lower case is larger than a clearance between the center side holding portion and the lower case.

5. a step portion is provided between the bottom surface of the lower case and a side surface of the outer battery cell and a side surface of the inner battery cell that face each other; The battery pack according to claim 3 or 4, wherein the step portion slopes downward from the inner battery cell side toward the outer battery cell side.

6. The battery pack according to any one of claims 1 to 5, wherein the thickness of the four corners of the lower part of the cell case is thicker than the thickness of the cell case below the longitudinal axis of the battery cell.

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