JP2001135290A - Battery pack and motor-driven tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack that has a simple structure, preventing a plurality of unit batteries housed in a container from rising in temperature and temperature fluctuations, and that can fully exhibit performance of the battery. SOLUTION: This pack and tool consist of a conduit body with bottom sandwiched between inner wall 21 and outer wall 22, houses a plurality of unit batteries 1 like nickel-hydrogen secondary battery or the like arranged in a loop to form a set battery between the inner and outer walls, and together possesses a conduit type container 2 having a shape of a space enclosed with the inner wall as a cavity 29 with open ends at its top and bottom, and a closure body 4 provided by closing the upper opening of the conduit container, having an opening 44 that communicates with the cavity 29, and particularly provides the inner wall of the conduit container, in such a manner that it slants from its bottom to the upper opening toward the cavity 29, and makes the top side of the cavity 29 surrounded by the inner wall gradually thinner, to make its opening cross-sectional area smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack having a simple structure capable of fully exhibiting battery performance by suppressing a temperature rise and a variation in battery temperature of a plurality of cells contained in a container, and this battery. The present invention relates to a power tool equipped with a pack as a drive source.

[0002]

2. Description of the Related Art Recently, secondary batteries such as nickel-metal hydride batteries have been used as driving sources for electric vehicles, electric assist bicycles, and electric tools. A battery used as a driving source of this type is generally provided as a battery pack in which a plurality of unit cells connected in series are housed in a container made of, for example, polycarbonate or ABS resin.

Meanwhile, in a conventional battery pack, a plurality of cells are exclusively housed in a container in a close-packed state, thereby increasing the volumetric efficiency and achieving a compact overall shape. Incidentally, when a battery pack is formed by accommodating a plurality of unit cells having a columnar shape in a container, generally, for example, as shown in FIG. While the peripheral surfaces are in contact with each other, they are arranged in three rows in a bale-stacked shape, and are accommodated in a rectangular container 2.

[0004]

However, in the battery pack having such a structure, the temperature between the unit cells 1 arranged along the wall surface of the container 2 and the unit cells 1 arranged at the center thereof is high. However, there is a problem that the variation is easily generated. That is, the heat of the unit cells 1 arranged along the wall surface of the container 2 is easily released through the wall surface of the container 2, but the heat of the unit cells 1 arranged at the center tends to be stored inside. It is in. Such a variation in battery temperature causes a variation in battery characteristics (battery capacity) of the individual cells 1. Moreover, when the battery pack is used in such a state, the life of the cell 1 having a smaller battery capacity is expended in order, so that, for example, the cell 1 whose life has expired may be inverted or recharged. Invites situations such as becoming. As a result, there arises a problem that the performance of the battery pack is significantly reduced, and the cycle life characteristic thereof is deteriorated.

[0005] When the unit cell 1 is a secondary battery such as a nickel-metal hydride battery, a large amount of heat is generated at the time of charging. Particularly, when the battery is charged with a large current in a short time, the heat generation phenomenon is remarkable. In addition, the charging efficiency of the nickel-hydrogen secondary battery decreases as the battery temperature increases, and the battery capacity decreases. Further, as the temperature rises, the hydrogen storage alloy constituting the negative electrode becomes more likely to be corroded by the electrolytic solution, causing a problem that the hydrogen storage / release capability of the hydrogen storage alloy deteriorates. Therefore, it is important to prevent the temperature of the single battery (nickel-hydrogen secondary battery) 1 housed in the container 2 from increasing, especially during charging.

In addition, a battery pack used as a drive source of an electric tool is generally required to have a structure that is robust against external impacts such as dropping since the electric tool itself is generally rough. . The present invention has been made in view of such circumstances, and an object of the present invention is to prevent a temperature rise of a plurality of cells contained in a container and suppress a variation in the temperature of each cell to reduce the battery performance. It is an object of the present invention to provide a battery pack capable of fully exhibiting the above.

Another object of the present invention is to provide a battery pack which is easy to manufacture and has a robust structure. Another object of the present invention is to provide a power tool provided with a battery pack having a robust and simple structure.

[0008]

In order to achieve the above-mentioned object, a battery pack according to the present invention has a plurality of cells constituting an assembled battery arranged and accommodated in a container, and particularly forms a pair of loops. It consists of a bottomed gutter-like body sandwiched between the inner wall and the outer wall, and accommodates a plurality of cells forming a battery pack between the inner wall and the outer wall in a loop and accommodates the cells.
A gutter-like container having a space surrounded by the inner wall and having a hollow portion whose upper and lower sides are opened, and an opening communicating with the cavity of the gutter-like container, and an upper end opening of the gutter-like container is closed. In particular, the inner wall portion of the gutter-shaped container is provided so as to be inclined toward the hollow portion side from the bottom toward the upper end opening, and is surrounded by the inner wall portion. It is characterized in that the upper end side of the cavity to be formed is tapered to reduce the cross-sectional area of the opening.

That is, in the battery pack according to the present invention, the cavity formed by being surrounded by the inner wall of the gutter-shaped container is directed toward the cavity so that the opening cross-sectional area decreases toward the upper end side. By inclining the air, the flow of the air flowing through the cavity is made faster at the upper end side, thereby increasing the cooling efficiency. In a preferred aspect of the present invention, the gutter-like container is arranged so that a plurality of cylindrical cells are arranged and arranged in a side-by-side loop with their peripheral surfaces in contact with each other, and the gutter-like body is provided. Are formed to have a height corresponding to the height of the unit cell (claim 3). Furthermore, the inner wall portion and the outer wall portion of the trough-shaped container are provided so as to be inclined by 0.5 to 5 degrees toward the outside thereof (claim 3). The present invention is characterized in that the gutter-shaped container can be easily removed at the time of molding, and the structure thereof is made more robust. Also, a nickel-hydrogen secondary battery is used as the unit cell (claim 4).

Further, the present invention provides an electric tool in which the battery pack having the above structure is mounted as a drive source thereof.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a battery pack according to an embodiment of the present invention will be described with reference to the drawings by connecting, for example, 12 cylindrical nickel-hydrogen secondary batteries (cells 1) in series. The battery pack housed in the container 2 will be described as an example. FIG. 1 is an exploded perspective view showing the overall structure of a battery pack according to this embodiment, where 1 is a 12 columnar nickel-hydrogen secondary battery as a unit cell, and 2 is a nickel-hydrogen secondary battery. This is a container that houses batteries (unit cells) 1 side by side. Reference numeral 3 denotes a terminal block provided on the upper part of the nickel-metal hydride battery 1. Reference numeral 4 denotes a lid that covers the terminal block 3 and closes an upper opening of the container 2.

FIGS. 2 (a), 2 (b) and 2 (c) show the top structure, the side structure, and the longitudinal sectional structure of the battery pack shown in FIG. 1, respectively. The sectional structure along the line AA is shown. The container 2 is formed by, for example, injection molding a polycarbonate resin or an ABS resin. The container 2 has a pair of parallel wall portions and a pair of inner wall portions 21 looped in a so-called oval shape. Outer wall 2
And a bottomed gutter-like body (gutter-like container) forming a corridor-shaped battery storage space by connecting the inner wall 21 and the outer wall 22 at the bottom 23. The inner part of the gutter-like body forming the looped corridor-shaped battery storage space, that is,
The central portion of the container 1 surrounded by the inner wall portion 21 forms a hollow portion 29 penetrating from the top to the bottom.

Further, an inner wall portion 2 forming the above-mentioned battery housing space.
1 and the height of the outer wall portion 22 (depth of the gutter forming the battery storage space) are set slightly higher than the height (length) of the columnar unit cell 1, and the width of the bottom portion 23 is It is set slightly wider than the diameter of the columnar unit cell 1. In addition, the inner wall portion 21 and the outer wall portion 22 are provided with their upper end portions inclined about 0.5 to 5 ° toward the outside thereof,
It is intended to facilitate the removal during injection molding (molding). At the same time, due to the inclination of the inner wall portion 21, the opening cross-sectional area of the hollow portion 29 formed by being surrounded by the inner wall portion 21 is set so as to gradually narrow toward the upper end side. Incidentally, the columnar unit cell 1 is, for example, 4 / 5A.
It is of a size and has an outer diameter of 17 mm in diameter and 43 mm in height.

The container 2 has an inner wall 21 and an outer wall 2
2 and a gutter-shaped battery storage space comprising a bottom 23
The two unit cells 1 are stored in a line in a side-by-side manner in a loop with their peripheral surfaces in contact with each other. Specifically, a circle is formed by arranging one unit cell 1 with a slight eccentricity between the ends of two unit cell arrays in which five unit cells 1 are arranged side by side in the longitudinal direction. 1 arc length
The gutter-shaped battery storage space is set such that two unit cells 1 are arranged in a loop in an oval shape. A space between the peripheral surface of each cell 1 housed in the container 2 and the inner wall portion 21 and the outer wall portion 22 is appropriately filled with a heat conductive material such as silicone. The thermal coupling of is increased.

A notch 24 for fitting a stopper 5 to be described later is formed in a portion of the outer wall 22 which forms a wall surface in the longitudinal direction.
Is provided. Four screw bosses 25 are provided upright along the outer wall 22 inside the gutter-shaped battery storage space. These screwing bosses 25 are provided by utilizing the space formed on the side of the columnar unit cell 1 which is housed with the peripheral surfaces thereof in contact with each other. The storage is not obstructed. Rather, these bosses 25 define the storage position of the unit cell 1 so that rattling is prevented.

A flange 26 is provided at the upper end of the inner wall 21 so as to protrude outward from the gutter-shaped battery storage space, that is, toward the cavity 29 formed in the center of the container 2. . The flange 26 has a role of supporting the terminal block 3 at an upper portion thereof, and also has a role of fitting with a central portion of the lid 4 to support the central portion of the lid 4 from below as described later. Carry.

On the other hand, the plurality of cells 1 housed in the gutter-shaped battery housing space of the above-described container 2 are arranged in an oval loop along the housing space as described above, and a lead (not shown) is provided. They are connected in series by the body. The upper ends of the unit cells arranged in an oval loop are covered with a cover body 11 made of, for example, an insulating material, so that the arrangement shape is stably maintained.

Further, a terminal block 3 provided on the upper part of the unit cell row
Has a generally U-shaped block body shape made of an insulating material, and has a pair of positive and negative electrode lead terminals 31 and 32 on outer sides of both sides along the longitudinal direction of the unit cell array arranged in an oval shape.
, And three auxiliary terminals 33, 34, 35 are provided on the outer side of the curved side along the short side direction connecting these both side parts. The pair of positive and negative electrode lead terminals 31, 32
Are connected to electrode leads of a battery pack composed of a plurality of unit cells 1 connected in series. The three auxiliary terminals 33, 34, 35 are used for charging one unit cell, and these auxiliary terminals 33, 34, 35 include:
It is connected to the electrode lead of the assembled battery via a resistor incorporated inside the terminal block 3 or a thermistor or a thermostat arranged on the peripheral surface of the unit cells 1 arranged in a loop. The function of these auxiliary terminals 33, 34, 35 will be described later with reference to FIG.

The lid 4 for covering the unit cell row accommodated in the container 2 and the terminal block 3 provided thereon and closing the upper opening of the container 2 is composed of an inner wall 21 and an outer wall of the container 2. A substantially flat main body 41 fitted to the upper end of the base 22, and a portion of the main body 41 facing the terminal block 3 is partially raised to form a housing space for the terminal block 3 on the back side. And a portion 42. Five rectangular openings 43 (43a) that expose the electrode lead terminals 31, 32 and the three auxiliary terminals 33, 34, 35 so that they can be connected to the outside are formed on the outer wall of the protrusion 42. , 43b,
To 43e). In the central portion of the main body portion 41, the hollow portion 29 of the container 2 is located on the side of the protrusion 42.
Is provided with an opening 44 communicating with the opening.

Further, a substantially rectangular opening for fitting the stopper 5 is formed on the longitudinal side of the main body 41 in cooperation with the notch 24 provided on the outer wall 22 of the container 2 described above. A falling wall 45 to be formed is provided. When the lid 4 covers the upper end opening of the container 2, the falling wall 45 fits into the upper part of the notch 24 to form the opening with the notch 24.

The lid 4 is fixed to the container 2 containing the unit cell 1 by screwing a screw 49 inserted from above the lid 4 through a through hole 47 provided in the main body 41 to the top of the boss 25. This is done by screwing into. In addition, a packing member (not shown) is appropriately interposed between the upper end portions of the inner wall portion 21 and the outer wall portion 22 of the container 2 and the lid 4 to close the battery storage space in a sealed state.

Here, the notch 24 and the falling wall 45 are provided.
The stopper 5 provided in the opening formed between the pressing portion 51 and the pressing portion 51 is formed by forming a substantially rectangular projecting portion, and an arm extending from a side portion of the pressing portion 51. The arm 52 has a shape with a hook 53 formed at the tip of the arm 52. As shown in FIG. 3, the stopper 5 projects the hook 53 from a hook hole 46 provided in the lid 4 and is fitted into the opening from the back side. Then, the hook 53 is biased toward the outside of the container 2 and supported by a leaf spring 55 provided on the back surface thereof, and is depressed inward by being pressed with a finger or the like so that the hook 53 is buried in the hook hole 46. It is provided as possible.

The hook 53 engages with an engaging projection provided on the housing 70 of the power tool on which the battery pack is mounted, thereby realizing mounting of the battery pack on the power tool. That is, in this battery pack, the lid body 4 side, which is the upper part, is used as a mounting portion for the power tool to the lower part of the housing 70, and the hook 53 is elastically biased inward while being in contact with the engaging projection. The power tool is configured to be mounted with a so-called one-touch operation. At the time of removal, the hook 53 is forcibly biased by pushing the pressing portion 51 inward, and the engagement between the hook 53 and the engaging projection provided on the housing 70 of the power tool is released. The battery pack can be removed toward the lower side of the housing 70.

Here, a description will be given of the thermistor, the resistor, and the thermostat incorporated in the terminal block 3 described above. These functional elements are provided to ensure safety during charging of the battery pack. That is, as shown in the electrical configuration of the battery pack in FIG. 4, a plurality of cells 1 are connected in series, and a pair of positive and negative electrode leads at both ends thereof are connected to electrode lead terminals 31 and 32, respectively. Then, it is connected to a load such as a motor of a power tool via these electrode lead terminals (+,-) 31, 32. Then container 2
Is a temperature-sensitive element for measuring the surface temperature of the unit cell 1, and is interposed between the auxiliary terminal (Th) 33 and the electrode lead terminal 32. During charging of the battery pack, the temperature of the cell 1 is monitored by monitoring the resistance value of the thermistor 81. The thermistor 81 is affixed to the peripheral surface of the unit cell 1 specified in advance.

The resistor 82 interposed between the auxiliary terminal (ID) 34 and the electrode lead terminal 32 has a resistance value according to the specifications of the battery pack. By measuring the resistance value of 81, for example, the number of unit cells 1 connected in series, the
It is required as information. By controlling charging of the battery pack according to the ID information, overcharging or the like is prevented beforehand. That is, even if the battery pack has the same external shape or the internal configuration such as the number of the stored single cells 1 and the battery voltage is different, the above-described I
The battery specification is determined from the D information, and the battery can be charged in an optimal state.

The auxiliary terminal 35 is used in place of the electrode lead terminal 32 when charging the battery pack.
By supplying a charging current between the electrode lead terminal 31 and the auxiliary terminal 35, the charging is performed. Thus, between the auxiliary terminal 35 and the electrode lead terminal 31, a temperature protection element for shutting off the charging path for the battery pack in response to the battery temperature at the battery pack itself, specifically, two thermostats 83, 84. Are interposed in series via the unit cells 1. These thermostats 83 and 84 are attached to, for example, the peripheral surfaces of the unit cells 1 forming the above-described two arc-shaped short sides along the arrangement direction of the plurality of unit cells 1 arranged in a loop. Provided. Since the single cells 1 are provided in a loop, even if a difference occurs in the battery temperature, the thermostats 83 and 84 are operated with an increase in the temperature of one of the single cells 1. And has the function of shutting off the charging path by itself.

The charging device connected to the terminal block 3 for charging the battery pack monitors the state of charge of the cell 1 (battery pack) from such auxiliary terminals 33, 34, 35, By controlling the time and the like, the battery pack is stably and efficiently charged. When the temperature of the battery pack rises despite the fact that the battery pack is charged under such charge control, the thermostats 83 and 84 described above cut off the charging path by themselves, thereby making the cells ( Battery pack).

According to the battery pack thus configured, the inner wall portion 2 of the container 2 having a loop-like corridor shape is provided.
Since the plurality of cells 1 are housed side by side in a loop between the first cell 1 and the outer wall 22, heat generated in each cell 1 is efficiently transmitted through the inner wall 21 and the outer wall 22. Will be released. Moreover, since the outside of the inner wall portion 21 at the center of the container 2 is a hollow portion 29 penetrating the container 2 vertically, a large heat radiation effect of the unit cell 1 through the hollow portion 29 can be expected. . In particular, since the opening cross-sectional area of the hollow portion 29 is set so as to be gradually narrowed toward the upper end side, the velocity of the air flow introduced from the lower portion of the hollow portion 29 and rising increases toward the upper end side. Cooling efficiency can be increased.

Further, since the structure is such that a plurality of cells 1 are arranged in a line in a loop, the heat radiation effect for each cell 1 is lower than that of the conventional general cell arrangement shown in FIG. It can be made almost constant. Therefore, a plurality of cells 1
The temperature variation of each cell 1 can be suppressed while effectively preventing the temperature rise of each of the cells 1. Therefore, the battery performance of each cell 1 can be sufficiently exhibited, and the battery performance as a battery pack can be sufficiently exhibited. Can be increased.

Further, a terminal block 3 is provided on the upper part of the unit cells 1 housed in a loop in the container 2 and the electrode leads thereof are led out, so that a plurality of unit cells 1 are arranged in a loop. Together with this, the lengths of the pair of electrode leads can be made uniform. Moreover, by providing the terminal blocks 3 at positions above both ends of the unit cells 1 connected in series as an assembled battery, the length of the electrode lead itself can be shortened. Therefore, effects such as minimizing the resistance loss via the electrode lead can be obtained. Further, if the electrode leads are arranged along the inner wall portion 21, the electrode leads can be effectively protected from external impact applied to the container 2, and therefore, the mechanical and structural stability can be improved. It will be possible to increase it sufficiently.

Further, according to this battery pack, the auxiliary terminals 33, 34, 35 connected via the thermistor 81, the resistor 82, and the thermostats 83, 84 as described above.
The auxiliary terminals 33, 34, and 35 allow the user to recognize the specifications of the battery pack and control the charging while monitoring the battery temperature, thereby preventing the battery temperature from rising. It can be charged safely. Furthermore, even when the charge control is not in time when the battery temperature rises, one of the thermostats 83, 84 provided at a plurality of locations along the unit cells 1 arranged in a loop shape responds to the battery temperature. Since the charging path is cut off, double safety measures can be taken.

According to the battery pack having the above structure,
In this structure, the lid 4 is mounted on a housing 70 such as a power tool. The container 2 is mounted on the housing 70 with the lid 4 interposed therebetween. Therefore, as long as the battery pack is not removed from the housing 70,
Of the cover 4 cannot be removed. Therefore, there is no problem that the lid 4 is unintentionally detached during use of the power tool. Further, the projecting portion 42 of the lid 4 which forms a housing space for the terminal block 3 on the back side thereof is covered with the housing 70 in a state of being mounted on the housing 70, so that in the use state, The battery pack has a so-called external shape without protrusion. Therefore, if the outer peripheral surface of the container 2, particularly the boundary portion between the outer wall portion 22 and the corner portion and the bottom portion 23, is formed into a curved surface, the overall shape is smooth regardless of the presence of the protrusion 42 in the lid portion 4. It is possible to improve the handleability.

Further, as the protruding portion 42, the terminal block 3 is housed on the back side, and the electrode lead terminals 31,
32 and the auxiliary terminals 33, 34, 35 need only be exposed so that they can be connected to the outside, so that their heights do not need to be very high. Therefore, the protrusion 42 on the lid 4
It is also easy to keep the height of the protrusion low, and the overall shape can be made compact. Further, it is possible to make the structure strong against external impact.

In a power tool equipped with a battery pack having such a structure, a built-in fan is driven by using, for example, the rotational force of the motor to allow air to flow into the motor through the cavity 29 of the container. With this configuration, it is possible to cool the electric motor of the power tool while cooling the battery pack itself by the airflow, and it is possible to further improve the cooling effect.
Further, since the container 1 itself has a rounded appearance as a whole, its corners and the like are less likely to be caught by clothes and the like when working with the power tool, and the handleability is good. Moreover, since there are no corners, local stress concentration can be reduced even when an impact due to a drop or the like is applied, and a robust structure can be obtained.

Further, as shown in FIGS. 2 (c) and 3, for example, the container 2 has its inner wall portion 21 and outer wall portion 22 directed toward the upper end opening so as to have a wide frontage. Since the tapered shape is used, it is easy to remove the mold at the time of injection molding, and it is possible to easily realize the trough-shaped container 2 having a depth corresponding to the height of the unit cell 1. In addition, since the positions of the cells 1 housed in the gutter-shaped body are regulated by the bosses 25 and the like, the rattling of the cells 1 can be effectively suppressed, and the housing state of the cells 1 can be stabilized with a simple structure. , And excellent in strength.

The present invention is not limited to the above embodiment. For example, here, a battery pack configured to house twelve unit cells 1 has been described, but the number may be determined according to specifications. Further, it is of course possible to realize a battery pack having an increased current capacity by connecting a plurality of cells 1 in parallel as appropriate. Further, more temperature protection elements (thermostats) may be provided along the unit cells 1 arranged in a loop.

Further, the inner surfaces of the inner wall portion 21 and the outer wall portion 22 may be realized as a corrugated surface along the peripheral surface of the cell 1 so as to enhance the adhesion to the peripheral surface of the cell 1. is there. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0038]

As described above, according to the present invention, while a plurality of cells are stably accommodated structurally, the temperature rise of each cell and variation in temperature are suppressed, and the cell performance is sufficiently improved. It is possible to provide a battery pack that exhibits its performance. Moreover, since the opening cross-sectional area of the hollow portion surrounded by the inner wall portion of the container is gradually narrowed toward the upper end, the flow of air flowing through the hollow portion can be accelerated, and the cooling It is possible to increase efficiency. In addition, since the inner and outer peripheral walls are formed as containers having a slanted structure, it is possible to facilitate the removal of the shape during molding. Further, since a plurality of cells can be stably held, a battery pack having a structure excellent in strength against external impacts or the like can be realized, and an easy-to-use power tool can be provided. Can be played.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the overall structure of a battery pack according to one embodiment of the present invention.

FIG. 2 is a top view, a side view, and a top view of the battery pack shown in FIG.
FIG.

FIG. 3 is a sectional view of the battery pack shown in FIG.
The figure which shows the cross-section structure which follows.

FIG. 4 is a diagram showing an electrical configuration of the battery pack shown in FIG.

FIG. 5 is a diagram showing an arrangement structure of cells in a conventional general battery pack.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single cell 2 Container (gutter-shaped container) 3 Terminal block 4 Lid 5 Stopper body 21 Inner wall part 22 Outer wall part 23 Bottom part 29 Cavity part 31, 32 Electrode lead terminal 33, 34, 35 Auxiliary terminal 41 Main part 42 Projecting part 43 Opening 44 Opening 70 Power tool housing 81 Thermistor (temperature sensing element) 82 Resistance (ID information) 83,84 Thermostat (Temperature protection element)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Haruhiko Tanaka, Inventor Haruhiko 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Corporation (72) Inventor Yukinori Akamoto 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No. Toshiba Battery Corporation F-term (reference) 5H020 AA01 AS06 AS16 CC06 CC13 CC18 HH00

Claims (5)

[Claims] 1. A unit cell comprising a plurality of cells forming an assembled battery, a bottomed trough-like body sandwiched between a pair of inner wall portions and an outer wall portion forming a loop, wherein said trough-like body is provided between said inner wall portion and said outer wall portion. A plurality of cells are arranged in a loop and accommodated therein, and a gutter-shaped container having a space surrounded by the inner wall part and a hollow part opened up and down is provided. A lid having an opening communicating with the cavity, wherein the inner wall of the gutter-shaped container is provided to be inclined outward from the bottom toward the upper end opening, and is surrounded by the inner wall. A battery pack characterized in that the opening cross-sectional area on the upper end side of the formed cavity is narrowed. 2. The gutter-shaped container is for accommodating a plurality of columnar unit cells arranged in a side-by-side loop with their peripheral surfaces in contact with each other. The battery pack according to claim 1, wherein the inner wall and the outer wall have a height corresponding to a height of the unit cell. 3. An inner wall portion and an outer wall portion of the gutter-like container,
The battery pack according to claim 1, wherein each of the battery packs is provided at an angle of 0.5 to 5 ° toward the outside thereof. 4. The battery pack according to claim 1, wherein the unit cell is a nickel-metal hydride secondary battery. 5. An electric tool having the battery pack according to claim 1 mounted thereon as a drive source.