Battery pack having a film thermistor and a dip thermistor

A battery pack contains a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the battery cells; a second thermistor disposed closest to the second battery cell among the battery cells. A case of the battery pack holds the battery cells, the first thermistor, and the second thermistor. The first battery cell is disposed such that at least one of the other battery cells is interposed between the first battery cell and a wall surface of the case in a direction orthogonal to a longitudinal direction of the first battery cell. The second battery cell is disposed such that none of the other battery cells is interposed between the second battery cell and the wall surface of the case in a direction orthogonal to a longitudinal direction of the second battery cell.

This application is the US national stage of International Patent Application No. PCT/JP2019/043746 filed on Nov. 7, 2019, which claims priority to Japanese Patent Application 2018-225408 filed on Nov. 30, 2018.

TECHNICAL FIELD

Techniques disclosed by the present specification relate to battery packs.

BACKGROUND ART

A battery pack is disclosed in Japanese Patent Application Publication No. 2005-287091. The battery pack comprises a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor; a second thermistor; and a case accommodating the plurality of battery cells, the first thermistor, and the second thermistor. Because the first thermistor and the second thermistor are both disposed such that they are surrounded on all sides by the battery cells, the temperature of battery cells, which have a high temperature, can be obtained.

SUMMARY OF THE INVENTION

In a battery pack that comprises a plurality of battery cells, it is desirable that not only the temperature of a battery cell having a high temperature but also the temperature of a battery cell having a low temperature can be obtained. In the battery pack of Japanese Patent Application Publication No. 2005-287091, the first thermistor and the second thermistor are both disposed such that they are surrounded by a plurality of battery cells. Therefore, even if, for example, an attempt is made to obtain the temperature of a battery cell having a low temperature using the second thermistor, the temperature detected using the second thermistor will become higher than the temperature of the low-temperature battery cell since the second thermistor is disposed in a position surrounded by battery cells having a higher temperature than the low-temperature battery cell. In the present specification, techniques are provided that make it possible to obtain the temperature of a battery cell having a low temperature as well as the temperature of a battery cell having a high temperature in a battery pack comprising a plurality of battery cells.

The present specification discloses a battery pack. This battery pack may comprise: a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor, and the second thermistor. The first battery cell may be disposed at a position where (an)other battery cell(s) is (are) interposed between the first battery cell and a wall surface of the case with respect to a direction orthogonal to a longitudinal direction of the first battery cell. The second battery cell may be disposed at a position where no other battery cell is interposed between the second battery cell and the wall surface of the case with respect to a direction orthogonal to a longitudinal direction of the second battery cell. It is noted that “(an)other battery cell(s) is (are) interposed between a battery cell and the wall surface of the case” as recited herein means that it is not possible to project the entirety of the battery cell onto the wall surface of the case without interfering with the other battery cell(s), while “no other battery cell is interposed between a battery cell and the wall surface of the case” means that the entirety of the battery cell is able to be projected on the wall surface of the case without interfering with another battery cell.

The present specification also discloses another battery pack. The battery pack may comprise a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor, and the second thermistor. The plurality of battery cells may comprise: an upper battery cell group disposed in an upper row; a lower battery cell group disposed in a lower row; and a middle battery cell group disposed between the upper battery cell group and the lower battery cell group. The first battery cell may be included in the middle battery cell group. The second battery cell may be included in either the upper battery cell group or the lower battery cell group.

The present specification discloses yet another battery pack. This battery pack may comprise: a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor and the second thermistor. The plurality of battery cells may comprise: an upper battery cell group disposed at a position facing an upper surface of the case; a lower battery cell group disposed at a position facing a lower surface of the case; and a middle battery cell group disposed between the upper battery cell group and the lower battery cell group. The first battery cell may be included in the middle battery cell group. The second battery cell may be included in either the upper battery cell group or the lower battery cell group.

DETAILED DESCRIPTION

In one or more embodiments, a battery pack may comprise: a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor, and the second thermistor. The first battery cell may be disposed at a position where (an)other battery cell(s) is (are) interposed between the first battery cell and a wall surface of the case with respect to a direction orthogonal to a longitudinal direction of the first battery cell. The second battery cell may be disposed at a position where no other battery cell is interposed between the second battery cell and the wall surface of the case with respect to a direction orthogonal to a longitudinal direction of the second battery cell.

Generally, in a battery pack that accommodates a plurality of battery cells in a case, heat dissipation from an outer surface of the case to air outside of the case occurs. Since another battery cell is interposed between the first battery cell and the wall surface of the case in the above-described configuration, heat dissipation via the wall surface of the case is difficult, and thus the first battery cell tends to have a high temperature. Furthermore, since no other battery cell is interposed between the second battery cell and the wall surface of the case, heat dissipation tends to occur via the wall surface of the case, and thus the second battery cell tends to have a low temperature. In the above-described configuration, the temperature of the first battery cell, which tends to have a high temperature, can be obtained using the first thermistor, and the temperature of the second battery cell, which tends to have a low temperature, can be obtained using the second thermistor. According to the above-described configuration, the temperature of a battery cell having a high temperature as well as the temperature of a battery cell having a low temperature can be obtained in a battery pack comprising a plurality of battery cells.

In one or more embodiments, the case may comprise an air supply hole through which air is introduced and an air discharge hole through which air is discharged.

According to the above-described configuration, the temperature of a battery cell having a high temperature as well as the temperature of a battery cell having a low temperature can be obtained in a battery pack that cools a plurality of battery cells by using air that flows in the interior of the case from the air supply hole to the air discharge hole.

In one or more embodiments, the second thermistor may be disposed at a position where the distance from the position to the air supply hole is smaller than the distance from the position to the air discharge hole.

In a battery pack that cools a plurality of battery cells by using air that flows in the interior of the case from the air supply hole to the air discharge hole, air immediately after flowing into the air supply hole will have the lowest temperature and air immediately before flowing out from the air discharge hole will have the highest temperature. Therefore, a battery cell disposed close to the air supply hole will tend to have a low temperature, while a battery cell disposed close to the air discharge hole will tend to have a high temperature. According to the above-described configuration, the temperature of a battery cell having a lower temperature can be obtained using the second thermistor.

In one or more embodiments, the first thermistor may be disposed at a position where the distance from the position to the air discharge hole is smaller than the distance from the position to the air supply hole.

In a battery pack that cools a plurality of battery cells by using air that flows in the interior of the case from the air supply hole to the air discharge hole, a battery cell disposed close to the air supply hole will tend to have a low temperature, while a battery cell disposed close to the air discharge hole will tend to have a high temperature. According to the above-described configuration, the temperature of a battery cell having a higher temperature can be obtained using the first thermistor.

In one or more embodiments, the battery pack may further comprise a circuit board accommodated in the case and disposed between the air discharge hole and the plurality of battery cells. Each of the first thermistor and the second thermistor may be connected to the circuit board. The first thermistor may comprise a film thermistor. The second thermistor may comprise a dip thermistor.

Generally, although film thermistors have high detection accuracy for temperature, it is difficult to extend them to a position spaced apart from the circuit board. Conversely, although dip thermistors have low detection accuracy for temperature, they can be easily extended to a position spaced apart from the circuit board. According the above-described configuration, because the circuit board is disposed between the air discharge hole and the plurality of battery cells, it is possible to obtain the temperature of a high-temperature battery cell with high accuracy by obtaining the temperature of a battery cell disposed close to the air discharge hole, that is, the temperature of a battery cell that tends to have a high temperature, using the first thermistor that comprises a film thermistor. Further, according the above-described configuration, even with the circuit board disposed between the air discharge hole and the plurality of battery cells, the temperature of a battery cell disposed close to the air supply hole, that is, the temperature of a battery cell that tends to have a low temperature, can be obtained using the second thermistor that comprises a dip thermistor.

In one or more embodiments, a battery pack may comprise: a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor, and the second thermistor. The plurality of battery cells may comprise: an upper battery cell group disposed in an upper row; a lower battery cell group disposed in a lower row; and a middle battery cell group disposed between the upper battery cell group and the lower battery cell group. The first battery cell may be included in the middle battery cell group. The second battery cell may be included in either the upper battery cell group or the lower battery cell group.

Since other battery cells are interposed between the first battery cell and upper and lower surfaces of the case in the above-described configuration, heat dissipation via the upper and lower surfaces of the case is difficult, and thus the first battery cell tends to have a high temperature. Furthermore, since no other battery cell is interposed between the second battery cell and the upper or lower surface of the case, the heat dissipation tends to occur via the upper or lower surface of the case, and thus the second battery cell tends to have a low temperature. In the above-described configuration, the temperature of the first battery cell, which tends to have a high temperature, can be obtained using the first thermistor, and also the temperature of the second battery cell, which tends to have a low temperature, can be obtained using the second thermistor. According to the above-described configuration, the temperature of a battery cell having a high temperature as well as the temperature of a battery cell having a low temperature can be obtained in a battery pack comprising a plurality of battery cells.

In one or more embodiments, a battery pack may comprise: a plurality of battery cells that includes a first battery cell and a second battery cell; a first thermistor disposed closest to the first battery cell among the plurality of battery cells; a second thermistor disposed closest to the second battery cell among the plurality of battery cells; and a case accommodating the plurality of battery cells, the first thermistor and the second thermistor. The plurality of battery cells may comprise: an upper battery cell group disposed at a position facing an upper surface of the case; a lower battery cell group disposed at a position facing a lower surface of the case; and a middle battery cell group disposed between the upper battery cell group and the lower battery cell group. The first battery cell may be included in the middle battery cell group. The second battery cell may be included in either the upper battery cell group or the lower battery cell group.

Since other battery cells are interposed between the first battery cell and upper and lower surfaces of the case in the above-described configuration, the heat dissipation via the upper and lower surfaces of the case is difficult, and thus the first battery cell tends to have a high temperature. Furthermore, since no other battery cell is interposed between the second battery cell and the upper or lower surface of the case, heat dissipation tends to occur via the upper or lower surface of the case, and thus the second battery cell tends to have a low temperature. In the above-described configuration, the temperature of the first battery cell, which tends to have a high temperature, can be obtained using the first thermistor, and the temperature of the second battery cell, which tends to have a low temperature, can be obtained using the second thermistor. According to the above-described configuration, the temperature of a battery cell having a high temperature as well as the temperature of a battery cell having a low temperature can be obtained in a battery pack comprising a plurality of battery cells.

Embodiments

A power supply system600, which is shown inFIG.1, comprises a battery pack2, an electrical device200, and a charger400. The battery pack2can be detachably attached to the electrical device200. The electrical device200may be, for example, an electric power tool such as an electric drill, an electric grinder, electric circular saw, an electric chain saw, an electric reciprocating saw or the like; it may be an electric work machine such as an electric mower, an electric trimmer, an electric blower or the like; or it may be another electrical device such as a light, a radio or the like. When attached to the electrical device200, the battery pack2supplies power to the electrical device200. The battery pack2also can be detachably attached to the charger400. When attached to the charger400, the battery pack2is supplied with power from the charger400.

As shown inFIGS.2to4, the battery pack2comprises a battery module10(seeFIGS.5to7) and a case12accommodating the battery module10. It is noted that, in the following description, when the battery pack2is attached to the electrical device200or the charger400, the direction in which the electrical device200or the charger400is located as viewed from the battery pack2will be referred to as upward, and the opposite direction will be referred to as downward. Further, the direction in which the battery pack2is slid when being attached to the electrical device200or the charger400will be referred to as rearward, and the direction in which the battery pack2is slid when being detached from the electrical device200or the charger400will be referred to as frontward. That is, in the following description, the front-rear direction corresponds to the sliding direction in which the battery pack2is slid with respect to the electrical device200or the charger400.

The nominal voltage of the battery pack2is, for example, 64 V. The nominal capacity of the battery pack2is, for example, 5 Ah. The dimension of the battery pack2in the front-rear direction is, for example, approximately 220 mm. The dimension of the battery pack2in the up-down direction is, for example, approximately 130 mm. The dimension of the battery pack2in the right-left direction is, for example, approximately 110 mm. The weight of the battery pack2is, for example, approximately 2 kg. The nominal voltage, dimensions, and weight of the battery pack2vary depending on the number of battery cells40(to be described later) or the like, and the aforementioned numerical values are merely examples.

With regard to the case12, overall it is formed in a substantially cuboid shape, and the case12is divided into an upper case14and a lower case16. The upper case14and the lower case16are each composed of an insulating material such as a resin. The upper case14and the lower case16are fixed to each other by metal screws18.

As shown inFIG.2, slide rails20, a terminal receiver portion22, and a hook mount portion24are formed on the upper case14. The slide rails20extend along the front-rear direction and are respectively disposed at right and left edges of an upper portion of the upper case14. The slide rails20slidably engage with slide rails210(seeFIG.19) of the electrical device200or slide rails414(seeFIG.23) of the charger400when the battery pack2is attached to and detached from the electrical device200or the charger400. The terminal receiver portion22is disposed between the left and right slide rails20and receives power terminals204and signal terminals206(seeFIG.19) of the electrical device200or power terminals410and signal terminals412(seeFIG.23) of the charger400when the battery pack2is attached to the electrical device200or the charger400. The hook mount portion24is disposed at an upper front portion of the upper case14. A hook26is provided on the hook mount portion24. The hook26is a resin member and comprises a manipulation portion26aand an engaging portion26b. The hook26is held by the upper case14and in a movable manner in the up-down direction. The hook26is biased upward by a not shown compression spring and moves downward when the manipulation portion26aand/or the engaging portion26bare pressed downward. The engaging portion26bengages with a housing (not shown) of the electrical device200or a housing402(seeFIG.22) of the charger400when the battery pack2is attached to the electrical device200or the charger400to fix the battery pack2to the electrical device200or the charger400. To detach the battery pack2from the electrical device200or the charger400, a user moves the engaging portion26bdownward by pressing the manipulation portion26adownward. By sliding the battery pack2in this state, the battery pack2can be detached from the electrical device200or the charger400. The manipulation portion26ahas a shape that is concaved downward from a front side toward a rear side. Therefore, when the user presses the manipulation portion26adownward with his/her finger placed on the manipulation portion26a, the user can press the manipulation portion26adownward without the finger slipping therefrom.

As shown inFIG.4, a gripping recess28is provided in the lower case16. The gripping recess28is disposed at a lower front portion of the lower case16. The gripping recess28opens downward. The user can lift and carry the battery pack2with his/her index, middle, ring and little fingers placed in the gripping recess28. Further, the user can detach the battery pack2from the electrical device200or the charger400with one hand by pressing down the manipulation portion26awith the thumb while placing the index, middle, ring and little fingers in the gripping recess28. A protective layer30is provided on a lower portion of the lower case16. The protective layer30is, for example, an elastomer. The protective layer30covers vicinities of corners of a lower surface of the lower case16. Therefore, if the battery pack2is dropped, damage to the corners of the lower case16can be mitigated. The protective layer30also covers the interior of the gripping recess28. Therefore, when the user lifts the battery pack2with fingers placed in the gripping recess28, the load applied to the user's fingers can be dispersed.

As shown inFIG.2, a display portion32is provided on a front surface of the lower case16. The display portion32comprises an indicator32athat shows the user the remaining amount of charge in the battery pack2and a button32bthat switches ON/OFF the display of the indicator32a. The display portion32is disposed on an outer surface of the case12between the manipulation portion26aof the hook26and the gripping recess28. Therefore, when the user attaches or detaches the battery pack2to or from the electrical device200or the charger400with the fingers placed on the manipulation portion26aand in the gripping recess28, the user can easily check the remaining amount of charge in the battery pack2via the display portion32.

As shown inFIGS.5to7, the battery module10comprises the plurality of battery cells40, the cell holder42holding the plurality of battery cells40, a control circuit board44fixed to the cell holder42, and a display circuit board46connected to the control circuit board44.

Each of the battery cells40is a secondary battery cell, such as a lithium ion battery cell, having a substantially cylindrical shape, in which a positive electrode is formed at one end, and a negative electrode is formed at the other end. As shown inFIG.8, the battery cells40are arranged such that their longitudinal direction is along the right-left direction. The battery cells40are arranged side by side in the up-down direction and in the front-rear direction. In the present embodiment, the battery cells40are arranged four abreast in the up-down direction and are arranged eight abreast in the front-rear direction. The nominal voltage of each battery cell40is, for example, 4 V. The nominal capacity of each battery cell40is, for example, 2.5 Ah. The cell holder42is a resin member and is divided into a right cell holder48and a left cell holder50. The right cell holder48holds vicinities of right ends of the plurality of battery cells40. The left cell holder50holds vicinities of left ends of the plurality of battery cells40. The right cell holder48and the left cell holder50are fixed to each other by metal screws52. The right cell holder48comprises a plurality of lead plates54that contact the electrodes (the positive or negative electrodes) disposed at the right ends of the battery cells40. The left cell holder50comprises a plurality of lead plates56that contact the electrodes (the positive or negative electrodes) disposed at the left ends of the battery cells40. As shown inFIG.5, each of the plurality of lead plates54,56is connected to the control circuit board44which is disposed on top of the cell holder42.

The control circuit board44is fixed to the cell holder42by metal screws58in the state in which it has been placed on an upper portion of the cell holder42. On the control circuit board44are provided a pair of power terminals60used for discharging or charging and a plurality of signal terminals62used for transmitting and receiving signals when the battery pack2is attached to the electrical device200or the charger400. The pair of power terminals60is disposed at positions that sandwich the plurality of signal terminals62on both the right and left sides.

As shown inFIGS.9to11, the power terminals60are fabricated by cutting and bending a metal plate. The power terminals60comprise a support portion60a, lower bent portions60b, holder portions60c, and upper bent portions60d. The support portion60ais formed into a substantially rectangular tube shape that extends in the up-down direction. A cross section of the support portion60ais a substantially rectangular shape whose longitudinal direction is along the front-rear direction. Downward-protruding support ribs60eare formed at a lower end of the support portion60a. The support ribs60efix the power terminal60to the control circuit board44and electrically connect the power terminal60to the control circuit board44.

The lower bent portions60bare formed on both the left and right sides of the support portion60a. The lower bent portions60bare formed into a shape that is bent inward from an upper end of the support portion60a. The holder portions60care formed into a flat plate shape that is bent and extends slightly outward from upper ends of the lower bent portions60b. When the power terminals204or the power terminals410are engaged in the power terminals60, an inclination angle of each holder portion60cis adjusted such that it becomes a parallel angle with a surface of the power terminal204of the electrical device200or with a surface of the power terminal410of the charger400; that is, it becomes an angle that achieves surface contact with a surface of the power terminal204or with a surface of the power terminal410. The upper bent portions60dare formed into a shape that is bent outward from upper ends of the holder portions60c.

A plurality of slits60fis formed in the power terminals60. Each of the slits60fis formed into a U-shape that extends from the upper ends of the upper bent portions60dto lower ends of the lower bent portions60b. Hereinbelow, in combination, the lower bent portions60b, the holder portions60c, and the upper bent portions60d, which have been divided by the slits60f, will be referred to as elastic holder piece pairs60gof the power terminal60. That is, the power terminals60comprise the support portion60aand the plurality of elastic holder piece pairs60gthat extend upward from the support portion60a.

Upon insertion of the power terminals204or the power terminals410into the power terminals60, front edges of the power terminals204or the power terminals410penetrate between the elastic holder piece pairs60gof the power terminals60; as a result, the elastic holder piece pairs60gopen outward and the power terminals204or the power terminals410are held by the elastic holder piece pairs60g. At this time, by pressing the holder portions60cof the power terminals60against the power terminals204or the power terminals410owing to the elastic restoring force of the elastic holder piece pairs60g, the power terminals60engage with the power terminals204or the power terminals410. That is, when the battery pack2has been attached to the electrical device200or the charger400, the elastic holder piece pairs60greceive the power terminals204or the power terminals410and hold the power terminals204or the power terminals410from both sides. On the other hand, when the power terminals204or the power terminals410are pulled out from the power terminals60, the engagement of the power terminals60with the power terminals204or the power terminals410is released. Then, the elastic holder piece pairs60greturn to their original shape owing to the elastic restoring force of the elastic holder piece pairs60g.

In each of the power terminals60, insertion guide ribs60hare formed at rear ends of the rearmost elastic holder piece pair60g, namely, the elastic holder piece pair60gthat is the first to receive the power terminal204or the power terminal410upon attachment of the battery pack2to the electrical device200or the charger400. The insertion guide ribs60hare formed into a shape that extends rearward from rear ends of the holder portions60cand is bent outward. By forming the insertion guide ribs60h, insertion of the power terminals204or the power terminals410can be performed smoothly.

In each of the power terminals60, insertion guide recesses60iare formed in rear ends of the elastic holder piece pairs60gother than the rearmost elastic holder piece pair60g. The insertion guide recesses60iare formed by cutting out, from the rear edges of the elastic holder piece pairs60g, the lower bent portion60b, the holder portion60c, the upper bent portion60dinto a substantially arc notch. By forming the insertion guide recesses60i, insertion of the power terminals204or the power terminals410can be performed smoothly.

In each of the power terminals60, removal guide ribs60jare formed at front ends of the elastic holder piece pairs60gother than the frontmost elastic holder piece pair60g. The removal guide ribs60jare formed into a shape that extends forward from the front ends of the holder portions60cand is bent outward. By forming the removal guide ribs60j, removal of the power terminals204or the power terminals410can be performed smoothly.

As shown inFIGS.12and13, the signal terminals62are fabricated by cutting and bending a metal plate. The signal terminals62comprise a support portion62a, lower bent portions62b, holder portions62c, and upper bent portions62d. The support portion62ais formed into a substantially rectangular tube shape extending in the up-down direction. A cross section of the support portion62ais a substantially rectangular shape whose longitudinal direction is along the front-rear direction. Downward-protruding support ribs62eare formed at a lower end of the support portion62a. The support ribs62efix the signal terminal62to the control circuit board44and electrically connect the signal terminal62to the control circuit board44.

The lower bent portions62bare formed on both left and right sides of the support portion62a. The lower bent portions62bare formed into a shape that is bent inward from an upper end of the support portion62a. The holder portions62care formed into a flat plate shape that extends and is bent slightly outward from upper ends of the corresponding lower bent portions62b. When the signal terminals206or the signal terminals412are engaged in the signal terminals62, an inclination angle of each holder portion62cis adjusted such that it becomes a parallel angle with a surface of the signal terminal206of the electrical device200or with a surface of the signal terminal412of the charger400; that is, it becomes an angle that achieves surface contact with a surface of the signal terminal206or a surface of the signal terminal412. The upper bent portions62dare formed into a shape that is bent outward from upper ends of the holder portions62c. Hereinbelow, in combination, the lower bent portions62b, the holder portions62c, and the upper bent portions62dwill be referred to as elastic holder piece pairs62gof the signal terminals62. That is, the signal terminals62comprise the support portion62aand the elastic holder piece pair62gthat extends upward from the support portion62a.

Upon insertion of the signal terminals206or the signal terminals412into the signal terminals62, front edges of the signal terminals206or the signal terminals412penetrate between the elastic holder piece pair62gof the signal terminals62; as a result, the elastic holder piece pairs62gopen outward and the signal terminals206or the signal terminals412are held by the elastic holder piece pairs62g. At this time, by pressing the holder portions62cof the signal terminals62against the signal terminals206or the signal terminals412owing to the elastic restoring force of the elastic holder piece pairs62g, the signal terminals62engage with the signal terminals206or the signal terminals412. That is, when the battery pack2is attached to the electrical device200or the charger400, the elastic holder piece pairs62greceive the signal terminals206or the signal terminals412and hold the signal terminals206or the signal terminals412from both sides. On the other hand, when the signal terminals206or the signal terminals412are pulled out from the signal terminals62, the engagement of the signal terminals62with the signal terminals206or the signal terminals412is released. Then, the elastic holder piece pairs62greturn to their original shape owing to the elastic restoring force of the elastic holder piece pairs62g.

In each of the signal terminal62, insertion guide ribs62hare formed at rear ends of the elastic holder piece pair62g. Each of the insertion guide ribs62hare formed into a shape that extends rearward from a rear end of its corresponding holder portion62cand is bent outward. By forming the insertion guide ribs62h, insertion of the signal terminals206or the signal terminals412can be performed smoothly.

In each of the signal terminals62, removal guide ribs62iare formed at front ends of the elastic holder piece pair62g. The removal guide ribs62iare formed into a shape that extends frontward from a front end of its corresponding holder portion62cand is bent outward. By forming the removal guide ribs62i, removal of the signal terminals206or the signal terminals412can be performed smoothly.

As shown inFIG.5, the display circuit board46is connected to the control circuit board44via signal lines64. The display circuit board46is disposed near a rear surface of the display portion32of the lower case16. The display circuit board46comprises LEDs46athat change the display contents of the indicator32aand a switch46bthat detects a manipulation on the button32b. It is noted that a guide66that holds the signal lines64is formed on the right cell holder48so that the signal lines64do not loosen.

A screw receiver48ais formed on a front portion of the right cell holder48. A screw receiver50ais formed on a front portion of the left cell holder50. The screw receivers48a,50aare disposed above a center of the cell holder42in the up-down direction. As shown inFIG.6, a screw receiver48bis formed on a rear portion of the right cell holder48. A screw receiver50bis formed on a rear portion of the left cell holder50. The screw receivers48b,50bare disposed above the center of the cell holder42in the up-down direction. The screw receivers48a,50aare disposed below the screw receivers48b,50b. As shown inFIG.14, in an inner front portion of the lower case16, screw bosses16a,16bare formed at positions corresponding to the screw receivers48a,50a. In an inner rear portion of the lower case16, screw bosses16c,16dare provided at positions corresponding to the screw receivers48b,50b. It is noted that, as shown inFIG.7, a cushion material68is attached to a lower portion of the cell holder42. The cushion material68is, for example, rubber.

As shown inFIG.15, the battery module10is attached to the lower case16in the state in which the upper case14has been removed. At this time, the battery module10is fixed to the lower case16by metal screws70in the state in which it has been placed on an inner bottom surface of the lower case16. As shown inFIG.16, the front screws70are screwed into the screw bosses16a,16bof the lower case16from above the screw receivers48a,50aof the cell holder42. As shown inFIG.17, the rear screws70are screwed into the screw bosses16c,16dof the lower case16from above the screw receivers48b,50bof the cell holder42. By doing so, the battery module10can be firmly fixed to the lower case16. It is noted that, since the cushion material68is interposed between the lower surface of the battery module10and the inner bottom surface of the lower case16, transmission of vibration and impact between the battery module10and the lower case16can be curtailed.

As shown inFIGS.2to4, in the state in which the upper case14is attached to the lower case16, the heads of the screws70are not exposed to outside of the battery pack2because they are completely covered by the upper case14. Therefore, the effect of static electricity or the like on the exterior of battery pack2can be curtailed from reaching into the battery module10within the battery pack2via the screws70.

As shown inFIG.18, the electrical device200comprises a housing (not shown) and battery pack mounts202provided on the housing to be capable of attaching and detaching the battery packs2. The battery packs2are attachable to/detachable from the battery pack mounts202by being slid in predetermined sliding directions with respect to the battery pack mounts202. In the example shown inFIG.18, the electrical device200comprises two battery pack mounts202, and thus two battery packs2are attachable thereto. It is noted that, unlike this example, the electrical device200may comprise only one battery pack mount202and only one battery pack2may be attachable thereto, or the electrical device200comprise include three or more battery pack mounts202and three or more battery packs2may be attachable thereto.

As shown inFIG.19, the battery pack mount202comprises the power terminals204, the signal terminals206, protective ribs208, and the slide rails210. In the state in which the battery pack2is attached to the battery pack mount202, the power terminals204of the electrical device200are engaged with, and electrically connected to, the power terminals60of the battery pack2, while the signal terminals206of the electrical device200are engaged with, and electrically connected to, the signal terminals62of the battery pack2. The protective ribs208comprise side plates208aand a rear plate208b. The side plates208ahave a plate shape along the front-rear direction and the up-down direction, and the side plates208aare disposed on both left and right sides of each of the power terminals204as well as on both the left and right sides of each of the signal terminals206s. The rear plate208bhas a plate shape along the right-left direction and the up-down direction, is disposed behind the power terminals204and the signal terminals206, and is coupled to each of the side plates208a. The slide rails210extend along the front-rear direction and are disposed respectively at the left and right ends of the battery pack mount202. When attaching/detaching the battery pack2to/from the electrical device200, the slide rails210slidably engage with the slide rails20of the battery pack2.

As shown inFIG.20, the lower ends of the side plates208aand the rear plate208bare located below the lower ends of the power terminals204and the signal terminals206. Further, as shown inFIG.21, the front ends of the side plates208aare located forward relative to the front ends of the power terminals204and the signal terminals206. Therefore, even in the state in which the battery pack2is not attached to the battery pack mount202and the battery pack mount202is exposed to the outside, the user can be prevented from accidentally touching the power terminals204and/or the signal terminals206. In particular, as shown inFIG.18, in case the electrical device200is attachable to a plurality of battery packs2, a battery pack2or battery packs2is/are attached to some of the battery pack mounts202, and no battery pack(s)2is/are attached to the rest of the battery pack mounts202, there is a risk that a high voltage will be output to the power terminals204and/or the signal terminals206of the battery pack mount(s)202to which no battery pack(s)2is/are attached. Even in such a case, according to the electrical device200of the present embodiment, the safety of the user can be ensured because the user will not accidentally come into contact with the power terminals204and/or the signal terminals206.

As shown inFIG.21, the front ends of the side plates208a, which are disposed on both sides of the power terminals204, are located forward of the front ends of the other side plates208a. Therefore, the user can be more reliably prevented from coming into contact with the power terminals204.

As shown inFIG.22, the charger400comprises the housing402; battery pack mounts404provided on the housing402and capable of attaching/detaching the battery pack2; a power cable406that extends from the housing402and is connectable to an alternating-current source; and a control circuit board408(seeFIG.24) accommodated in the housing402. The battery packs2are attachable/detachable to/from the battery pack mounts404by being slid in predetermined sliding directions with respect to the battery pack mounts404. In the example shown inFIG.22, the charger400comprises two battery pack mounts404, and thus two battery packs2are attachable thereto. It is noted that, unlike this example, the charger400may comprise only one battery pack mount404and only one battery pack2may be attached thereto, or the charger400may comprise three or more battery pack mounts404and three or more battery packs2may be attached thereto. The control circuit board408converts the alternating-current power supplied from the power cable406into direct-current power and charges the battery pack(s)2attached to the battery pack mount(s)404.

As shown inFIG.23, the battery pack mounts404comprise the power terminals410, the signal terminals412, the slide rails414, a terminal cover416, and a blower fan418(seeFIG.24). The power terminals410, the signal terminals412, and the blower fan418are connected to the control circuit board408. In the state in which the battery pack2is attached to the battery pack mount404, the power terminals410of the charger400are engaged with, and are electrically connected to, the power terminals60of the battery pack2, while the signal terminals412of the charger400are engaged with, and are electrically connected to, the signal terminals62of the battery pack2. The terminal cover416is slidable between a protecting position (seeFIG.22), where the power terminals410and the signal terminals412are covered by the terminal cover416, and a retracted position (seeFIG.23), where the power terminals410and the signal terminals412are exposed. The terminal cover416is biased toward the protecting position by a compression spring (not shown). When the battery pack2is attached to the charger400, the terminal cover416is pushed by the upper case14of the battery pack2such that it is moved from the protecting position to the retracted position. The blower fan418suctions air from the battery pack mount404when the battery pack2is being charged.

As shown inFIG.3, in the battery pack2, power terminal openings72and signal terminal openings74are formed in the terminal receiver portion22of the upper case14. The power terminal openings72are disposed corresponding to the power terminals60of the control circuit board44, and are formed at positions and in shapes such that the power terminals204of the electrical device200and the power terminals410of the charger400can pass therethrough. The signal terminal openings74are disposed corresponding to the signal terminals62of the control circuit board44, and are formed at positions and in shapes such that the signal terminals206of the electrical device200and the signal terminals412of the charger400can pass therethrough. When the battery pack2is attached to the electrical device200, the power terminals204enter the power terminal openings72and engage with the power terminals60, and the signal terminals206enter the signal terminal openings74and engage with the signal terminals62. When the battery pack2is attached to the charger400, the power terminals410enter the power terminal openings72and engage with the power terminals60, and the signal terminals412enter the signal terminal openings74and engage with the signal terminals62.

In the terminal receiver portion22of the battery pack2, recessed grooves76are formed in the upper case14on both the left and right sides of the power terminal openings72and on both the left and right sides of the signal terminal openings74. The recessed grooves76are formed at positions and in shapes such that the recessed grooves76can receive the side plates208aof the protective ribs208of the electrical device200. Therefore, lower ends of the recessed grooves76are located below lower ends of the power terminal openings72and the signal terminal openings74, and front ends of the recessed grooves76are located forward relative to front ends of the power terminal openings72and the signal terminal openings74. Further, the recessed grooves76open in two directions, namely, in the up direction and in the rear direction.

As shown inFIG.25, vent holes78are formed in lower surfaces of the recessed grooves76that are disposed between the power terminals60and the signal terminals62as well as in lower surfaces of the recessed grooves76that are disposed between two signal terminals62that are adjacent to each other in the right-left direction. The vent holes78comprise a plurality of holes78adisposed in the lower surface of one recessed groove76. Therefore, the size of individual holes78acan be made smaller compared to the example shown inFIG.40where one large vent hole78is provided in the lower surface of one recessed groove76, and thus the ingress of foreign matter from outside of the battery pack2through the vent holes78into the interior can be curtailed. Further, a vent hole79is formed in the upper surface of the upper case14at a position offset rearward from the terminal receiver portion22.

As shown inFIG.26, slits80are formed in the control circuit board44between the power terminals60and the signal terminals62as well as between two signal terminals62that are adjacent to each other in the right-left direction. The slits80are disposed at positions facing the vent holes78of the upper case14. By providing the slits80in the control circuit board44, the occurrence of short circuits between the power terminals60and the signal terminals62and/or between two signal terminals62that are adjacent to each other in the right-left direction can be curtailed, even if a conductive substance, such as water, enters into the interior of the battery pack2and adheres to the control circuit board44. Further, a slit81is formed in the control circuit board44at a position offset rearward from the signal terminals62. The slit81is disposed at a position facing the vent hole79of the upper case14. Notches44athat extend between the lead plates54, which are adjacent to one another, are formed in a right edge of the control circuit board44. By providing the notches44ain the control circuit board44, the occurrence of short circuits between the lead plates54, which are adjacent to one another in the front-rear direction, can be curtailed even if a conductive substance, such as water, enters into the interior of the battery pack2and adheres to the control circuit board44. Notches44bthat extend between the lead plates56, which are adjacent to one another, are formed in a left edge of the control circuit board44. By providing the notches44bin the control circuit board44, the occurrence of short circuits between the lead plates56, which are adjacent to one another in the front-rear direction, can be curtailed, even if a conductive substance, such as water, enters into the interior of the battery pack2and adheres to the control circuit board44.

As shown inFIG.27, openings82are formed in an upper surface of the cell holder42. The vent holes78of the upper case14and the slits80of the control circuit board44are disposed at a position facing an opening82of the cell holder42. Further, the vent hole79of the upper case14and the slit81of the control circuit board44are disposed at a position facing an opening82of the cell holder42.

As shown inFIG.24, air supply holes84are formed in the lower surface and rear surface of the lower case16. In addition, the hook mount portion24of the upper case14serves as an air supply hole84since air can flow through a clearance between the hook26and the upper case14.

When the blower fan418of the charger400is driven with the battery pack2attached to the charger400, the blower fan418suctions air from the battery pack mount404. When this happens, air flows from the outside through the air supply holes84into the interior of the battery pack2. The air, which has flowed into the interior of the battery pack2, passes through spaces between the battery cells40and flows toward the openings82of the cell holder42. At this time, the battery cells40are cooled by the air flowing around them. Most of the air that reached the openings82of the cell holder42flows through the slits80of the control circuit board44, flows through the vent holes78of the upper case14, and then flows into the recessed grooves76of the terminal receiver portion22. The air, which flowed to the recessed grooves76, flows through the battery pack mount404of the charger400and then reaches the blower fan418. In addition, a portion of the air that reached the openings82of the cell holder42flows through the slit81of the control circuit board44, flows through the vent hole79of the upper case14, and then reaches the blower fan418of the charger400. Further, another portion of the air that reached the openings82of the cell holder42flows through the notches44a,44bof the control circuit board44, further flows through the vent holes78,79of the upper case14, and then reaches the blower fan418of the charger400. As shown inFIG.23, an air discharge hole402ais formed in the housing402of the charger400. The air drawn into the interior of the housing402by the blower fan418flows through the interior of the housing402of the charger400and then is discharged to the outside through the air discharge hole402a.

In the battery pack2, the vent holes78,79of the upper case14are disposed to face the slits80,81of the control circuit board44. Owing to making such a configuration, air underneath the control circuit board44is suctioned through the slits80,81as air flows out from the vent holes78,79. Therefore, the portion of the plurality of battery cells40that is located right underneath the control circuit board44can be cooled sufficiently.

In addition, in the battery pack2, the openings82of the cell holder42are disposed to face the slits80,81of the control circuit board44. Owing to making such a configuration, air flows from the spaces between the battery cells40toward the openings82of the cell holder42as air is suctioned through the slits80,81. Therefore, the portion of the plurality of battery cells40that is located near the center can be cooled sufficiently.

The control circuit board44need not comprise the slit81, and may comprise only the slits80. Corresponding to this, the case14need not comprise the vent hole79, and may comprise only the vent holes78.

As shown inFIG.40, a single large vent hole78may be formed in the upper case14in the lower surface of each of the recessed grooves76. In this case, air can easily flow through these vent holes78and the cooling performance for the battery cells40can be improved, compared to the case shown inFIG.25in which a plurality of holes78awas formed in the lower surface of each of the recessed grooves76.

As shown inFIG.41, vent holes83may be formed in the upper case14in the lower surface of the recessed grooves76that are disposed between the power terminals60and the slide rails20. The vent holes83may comprise a plurality of holes83adisposed in the lower surface of one recessed groove76. As shown inFIG.42, slits85may be formed in the control circuit board44between the power terminals60and the lead plates54,56. By providing the slits85in the control circuit board44, the occurrence of short circuits between the power terminals60and the lead plates54,56can be curtailed, even if a conductive substance, such as water, enters into the interior of the battery pack2and adheres to the control circuit board44. The slits85may be disposed at positions facing the vent holes83of the upper case14. According to the configurations ofFIGS.41and42, the amount of air that flows through the spaces between the battery cells40by driving the blower fan418of the charger400can be increased, and thus the cooling performance for the battery cells40can be improved.

As shown inFIG.28, the battery pack2comprises a first thermistor90and a second thermistor92. The first thermistor90and the second thermistor92are both connected to the control circuit board44. The first thermistor90is, for example, a film thermistor. The second thermistor92is, for example, a dip thermistor. Generally, although film thermistors have high detection accuracy for temperature, it is difficult to extend them to a position spaced apart from the control circuit board44. Conversely, although dip thermistors have low detection accuracy for temperature, they can be easily extended to a position spaced apart from the control circuit board44. In the battery pack2, the first thermistor90detects the temperature of a battery cell40athat is located near the center among the battery cells40arranged in the up-down direction and in the front-rear direction, while the second thermistor92detects the temperature of a battery cell40bthat is located near the outer edge among the battery cells40arranged in the up-down direction and in the front-rear direction. In this case, the first thermistor90is disposed closest to the battery cell40aamong the plurality of battery cells40and detects the temperature at a position that is surrounded by other battery cells40. The second thermistor92is disposed closest to the battery cell40bamong the plurality of battery cells40and detects the temperature at a position that is not surrounded by other battery cells40. Further, the first thermistor90detects the temperature at a position where (a) battery cell(s)40is (are) interposed between the position and the upper case14and/or the lower case16, while the second thermistor92detects the temperature at a position where no battery cell40is interposed between the position and the lower case16. Further, the first thermistor90detects the temperature at a position where the distance from the position to the vent holes78, through which air flows out from the interior of the battery pack2to the outside, is shorter than the distance from the position to the air supply holes84through which air flows into the interior from the outside. The second thermistor92detects a temperature at a position where the distance from the position to the air supply holes84through which air flows into the interior from the outside is shorter than the distance from the position to the vent holes78through which air flows out from the interior of the battery pack2to the outside.

Generally, among the battery cells40arranged in the up-down direction and in the front-rear direction, the battery cells40that are located near the center tend to have a high temperature because heat dissipation is difficult, while the battery cells40located near an outer edge tend to have a low temperature because heat dissipation is easy. In addition, in a configuration in which the battery cells40are cooled by air that flows in through the air supply holes84and flows out through the vent holes78, air flowing in through the air supply holes84has a low temperature and the air flowing out through the vent holes78has a high temperature; thus the battery cells40located close to the air supply holes84tend to have a low temperature, and the battery cells40located close to the vent holes78tend to have a high temperature. Therefore, in case the first thermistor90and the second thermistor92are disposed as described above, the battery cell40a, which the first thermistor90detects the temperature, has the highest temperature among the battery cells40during charging, while the battery cell40b, which the second thermistor92detects the temperature, has the lowest temperature among the battery cells40during charging. As such, by using the first thermistor90and the second thermistor92, the temperature of the battery cell40a, which is the highest among the battery cells40of the battery pack2during charging, and the temperature of the battery cell40b, which is the lowest among the battery cells40during charging, can be obtained.

It is noted that, among the plurality of battery cells40arranged in the up-down and front-rear directions, the battery cells40that are arranged in the front-rear direction in the uppermost row are called upper battery cell group40c, the battery cells40that are arranged in the front-rear direction in the lowermost row are called lower battery cell group40d, and the battery cells40that are arranged in the up-down and front-rear directions between the upper battery cell group40cand the lower battery cell group40dare called middle battery cell group40e. The battery cell40a, which the first thermistor90detect the temperature, is included in the middle battery cell group40e, while the battery cell40b, which the second thermistor92detects the temperature, is included in the lower battery cell group40d.

When a charging start instruction is received from the battery pack2while the battery pack2is attached to a battery pack mount404, the charger400performs charging of the battery pack2. During charging of the battery pack2, the charger400receives as charging parameters from the battery pack2each of a permitted charging voltage, a permitted charging current, a charging-current-reduction start voltage, and a cut-off current. Then, the charger400charges the battery pack2at a charging voltage that is the permitted charging voltage or lower and at a charging current that is the permitted charging current or lower. When the charging voltage reaches the charging-current-reduction start voltage during the charging of the battery pack2, the charger400gradually reduces the charging current. Then, when the charging current is reduced to the cut-off current during the charging of the battery pack2, the charger400terminates the charging of the battery pack2. It is noted that, in case a charging termination instruction is received from the battery pack2during the charging of the battery pack2, the charger400terminates the charging of the battery pack2at that time.

Various processes executed by the control circuit board44in connection with the charging of the battery pack2will be described hereinbelow. The control circuit board44of the battery pack2executes a charging-start determination process shown inFIG.29while the battery pack2is attached to a battery pack mount404of the charger400.

In S2, the control circuit board44obtains the temperature detected using the first thermistor90as a first temperature as well as a temperature detected using the second thermistor92as a second temperature.

In S4, the control circuit board44determines a first charging-start voltage threshold. The control circuit board44stores in advance a correspondence relationship between battery cell temperatures and charging-start voltage thresholds, which is shown inFIG.30. In the correspondence relationship ofFIG.30, charging-start voltage thresholds for low battery cell temperatures are set lower than a charging-start voltage threshold for an ordinary battery cell temperature, while the charging-start voltage threshold for high battery cell temperatures is set equal to the charging-start voltage threshold for the ordinary battery cell temperature. The control circuit board44specifies the first charging-start voltage threshold by using the first temperature and the correspondence relationship ofFIG.30.

In S6, the control circuit board44specifies a second charging-start voltage threshold. The control circuit board44specifies the second charging-start voltage threshold by using the second temperature and the correspondence relationship ofFIG.30.

In S8, the control circuit board44specifies a charging-start voltage threshold. In the present embodiment, the control circuit board44specifies the lower one of the first and second charging-start voltage thresholds as the charging-start voltage threshold.

In S10, the control circuit board44determines whether voltages of all the battery cells40are lower than the charging-start voltage threshold. In case the voltage of any of the battery cells40is the charging-start voltage threshold or higher (in case of NO), the process returns to S2. In case the voltage of all the battery cells40is lower than the charging-start voltage threshold (in case of YES), the process proceeds to S12.

In S12, the control circuit board44obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S14, the control circuit board44determines whether both the first temperature and the second temperature are lower than a predetermined charging-start upper limit temperature (e.g., 55° C.). In case either of the first temperature and the second temperature is the charging-start upper limit temperature or higher (in case of NO), the process returns to S12. In case both the first temperature and the second temperature are lower than the charging-start upper limit temperature (in case of YES), the process proceeds to S16.

In S16, the control circuit board44determines whether both the first temperature and the second temperature are higher than a predetermined charging-start lower limit temperature (e.g., 2° C.). In case either of the first temperature and the second temperature is the charging-start lower limit temperature or lower (in case of NO), the process returns to S12. In case both the first temperature and the second temperature are higher than the charging-start lower limit temperature (in case of YES), the process proceeds to S18.

In S18, the control circuit board44outputs the charging start instruction to the charger400. By doing this, charging of the battery pack2by the charger400starts. After S18, the process ofFIG.29is terminated.

While the battery pack2is being charged by the charger400, the control circuit board44of the battery pack2simultaneously executes a charging parameter creation process shown inFIG.31and a charging abnormality determination process shown inFIG.32.

The charging parameter creation process shown inFIG.31will be described hereinbelow. In S22, the control circuit board44obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S24, the control circuit board44determines a first permitted charging voltage, a first permitted charging current, a first charging-current-reduction start voltage, and a first cut-off current. The control circuit board44stores in advance a correspondence relationship between battery cell temperatures and permitted charging voltages, which is shown inFIG.33; a correspondence relationship between battery cell temperatures and permitted charging currents, which is shown inFIG.34; a correspondence relationship between battery cell temperatures and charging-current-reduction start voltages, which is shown inFIG.35; and a correspondence relationship between battery cell temperatures and cut-off currents, which is shown inFIG.36. In the correspondence relationship ofFIG.33, permitted charging voltages for low battery cell temperatures are set lower than a permitted charging voltage for an ordinary battery cell temperature, while a permitted charging voltage for high battery cell temperatures is set equal to the permitted charging voltage for the ordinary battery cell temperature. In the correspondence relationship ofFIG.34, permitted charging currents for low battery cell temperatures are set lower than a permitted charging current for the ordinary battery cell temperature, while permitted charging currents for high battery cell temperatures are set lower than the permitted charging current for the ordinary battery cell temperature. In the correspondence relationship ofFIG.35, charging-current-reduction start voltages for low battery cell temperatures are set lower than a charging-current-reduction start voltage for the ordinary battery cell temperature, while a charging-current-reduction start voltage for high battery cell temperatures is set equal to the charging-current-reduction start voltage for the ordinary battery cell temperature. In the correspondence relationship ofFIG.36, cut-off currents for low battery cell temperatures are set lower than a cut-off current for the ordinary battery cell temperature, while cut-off currents for high battery cell temperatures are set higher than the cut-off current for the ordinary battery cell temperature. The control circuit board44specifies the first permitted charging voltage, the first permitted charging current, the first charging-current-reduction start voltage, and the first cut-off current by using the first temperature and the correspondence relationships ofFIGS.33to36.

In S26, the control circuit board44determines a second permitted charging voltage, a second permitted charging current, a second charging-current-reduction start voltage, and a second cut-off current. The control circuit board44specifies the second permitted charging voltage, the second permitted charging current, the second charging-current-reduction start voltage, and the second cut-off current by using the second temperature and the correspondence relationships ofFIGS.33to36.

In S28, the control circuit board44specifies a permitted charging voltage, a permitted charging current, a charging-current-reduction start voltage, and a cut-off current. In the present embodiment, the control circuit board44specifies the lower one of the first and second permitted charging voltages as the permitted charging voltage. Similarly, the control circuit board44specifies the lower one of the first and second permitted charging currents as the permitted charging current, specifies the lower one of the first and second charging-current-reduction start voltages as the charging-current-reduction start voltage, and specifies the lower one of the first and second cut-off currents as the cut-off current.

In S30, the control circuit board44outputs the permitted charging voltage, the permitted charging current, the charging-current-reduction start voltage, and the cut-off current to the charger400. The charger400performs the charging process of the battery pack2based on the permitted charging voltage, the permitted charging current, the charging-current-reduction start voltage, and the cut-off current that were outputted from the battery pack2.

In S32, the control circuit board44determines whether the charging by the charger400has been terminated. In case the charging has not been terminated yet (in case of NO), the process returns to S22. In case the charging has been terminated (in case of YES), the process ofFIG.31is terminated.

The charging abnormality determination process shown inFIG.32will be described hereinbelow. In S42, the control circuit board44obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S44, the control circuit board44determines whether both the first temperature and the second temperature are lower than a predetermined charging upper limit temperature (e.g., 60° C.). In case either of the first temperature and the second temperature is the charging upper limit temperature or higher (in case of NO), the process proceeds to S46. In S46, the control circuit board44sends a charging termination instruction to the charger400due to abnormally high temperature, and the process ofFIG.32is terminated. In case both the first temperature and the second temperature are lower than the charging upper limit temperature in S44(in case of YES), the process proceeds to S48.

In S48, the control circuit board44determines whether both the first temperature and the second temperature are higher than a predetermined charging lower limit temperature (e.g., 0° C.). In case either of the first temperature and the second temperature is lower than the charging lower limit temperature (in case of NO), the process proceeds to S50. In S50, the control circuit board44sends a charging termination instruction to the charger400due to abnormally low temperature, and the process ofFIG.32is terminated. In case both the first temperature and the second temperature are higher than the charging lower limit temperature in S48(in case of YES), the process proceeds to S52.

In S52, the control circuit board44determines a first abnormal voltage threshold. The control circuit board44stores in advance a correspondence relationship between battery cell temperatures and abnormal voltage thresholds, which is shown inFIG.37. In the correspondence relationship ofFIG.37, abnormal voltage thresholds for low battery cell temperatures are set lower than an abnormal voltage threshold for the ordinary battery cell temperature, while an abnormal voltage threshold for high battery cell temperatures is set lower than the abnormal voltage threshold for the ordinary battery cell temperature. The control circuit board44specifies the first abnormal voltage threshold by using the first temperature and the correspondence relationship ofFIG.37.

In S54, the control circuit board44specifies a second abnormal voltage threshold. The control circuit board44specifies the second abnormal voltage threshold by using the second temperature and the correspondence relationship ofFIG.37.

In S56, the control circuit board44specifies an abnormal voltage threshold. In the present embodiment, the control circuit board44specifies the lower one of the first and second abnormal voltage thresholds as the abnormal voltage threshold.

In S58, the control circuit board44determines whether voltages of all the battery cells40are lower than the abnormal voltage threshold. In case the voltage of any one of the battery cells40is the abnormal voltage threshold or higher (in case of NO), the process proceeds to S60. In S60, the control circuit board44sends a charging termination instruction to the charger400due to abnormally high voltage, and the process ofFIG.32is terminated. In case the voltages of all the battery cells40are lower than the abnormal voltage threshold in S58(in case of YES), the process proceeds to S62.

In S62, the control circuit board44determines whether the charging by the charger400has been terminated. In case the charging has not been terminated yet (in case of NO), the process returns to S42. In case the charging has been terminated (in case of YES), the process ofFIG.32is terminated.

It is noted that, while the charger400is performing the charging of the battery pack2, the control circuit board408of the charger400obtains the temperature detected using the first thermistor90and the temperature detected using the second thermistor92from the battery pack2, and controls the operation of the blower fan418. When the charger400starts a charging operation on the battery pack2, the control circuit board408executes a blower control process shown inFIG.38.

In S72, the control circuit board408drives the blower fan418.

In S74, the control circuit board408determines whether the charging of the battery pack2has been terminated. In case the charging has been terminated (in case of YES), the process proceeds to S76. In S76, the control circuit board408stops the blower fan418, and the process ofFIG.38is terminated. In case the charging has not been terminated yet in S74(in case of NO), the process proceeds to S78.

In S78, the control circuit board408obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S80, the control circuit board408determines whether both the first temperature and the second temperature are lower than a predetermined blower stop temperature (e.g., 15° C.). In case either of the first temperature and the second temperature is the blower stop temperature or higher (in case of NO), the process returns to S74. In case both the first temperature and the second temperature are lower than the blower stop temperature (in case of YES), the process proceeds to S82.

In S82, the control circuit board408stops the blower fan418.

In S84, the control circuit board408determines whether the charging with regard to the battery pack2has been terminated. In case the charging has been terminated (in case of YES), the process ofFIG.38is terminated. In case the charging has not been terminated yet (in case of NO), the process proceeds to S86.

In S86, the control circuit board408obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S88, the control circuit board408determines whether both the first temperature and the second temperature are higher than a predetermined blower start temperature (e.g., 17° C.). In case either of the first temperature and the second temperature is the blower start temperature or lower (in case of NO), the process returns to S84. In case both the first temperature and the second temperature are higher than the blower start temperature (in case of YES), the process returns to S72.

A process executed by the control circuit board44in connection with discharging of the battery pack2will be described hereinbelow. The control circuit board44of the battery pack2executes a discharge-abnormality determination process shown inFIG.39while the battery pack2is attached to the battery pack mount202of the electrical device200and is discharging to the electrical device200.

In S92, the control circuit board44obtains the temperature detected using the first thermistor90as the first temperature as well as the temperature detected using the second thermistor92as the second temperature.

In S94, the control circuit board44determines whether both the first temperature and the second temperature are lower than a predetermined discharging upper limit temperature (e.g., 85° C.). In case either of the first temperature and the second temperature is the discharging upper limit temperature or higher (in case of NO), the process proceeds to S96. In S96, the control circuit board44sends a discharging termination instruction to the electrical device200due to abnormally high temperature, and the process ofFIG.39is terminated. In case both the first temperature and the second temperature are lower than the discharging upper limit temperature in S94(in case of YES), the process proceeds to S98.

In S98, the control circuit board44determines whether the discharging to the electrical device200has been terminated. In case the discharging has not been terminated yet (in case of NO), the process returns to S92. In case the discharging has been terminated (in case of YES), the process ofFIG.39is terminated.

In the above-described embodiment, the side plates208aof the protective ribs208of the electrical device200may be disposed only on both sides of the power terminals204and need not be disposed on both sides of the signal terminals206. Corresponding to this, the recessed grooves76of the battery pack2may be provided only on both sides of the power terminals60and need not be provided on both sides of the signal terminals62.

In the above-described embodiment, although the power terminals60of the battery pack2are disposed such that the signal terminals62are sandwiched from both sides in the right-left direction, the arrangement of the power terminals60and the signal terminals62may be another arrangement. Corresponding to this, the arrangement of the power terminals204and the signal terminals206of the electrical device200and the arrangement of the power terminals410and the signal terminals412of the charger400may be an arrangement that differs from the above-described embodiment, as long as it corresponds to the arrangement for the power terminals60and the signal terminals62of the battery pack2.

In the above-described embodiment, although the power terminals60and the signal terminals62of the battery pack2are installed on the control circuit board44, the power terminals60and the signal terminals62may be installed on another terminal circuit board (not shown) that is separate from the control circuit board44and is electrically connected to the control circuit board44.

In the above-described embodiment, the blower fans418of the charger400are configured to suction air from the battery pack mounts404. Unlike this, the blower fans418may be configured to discharge air toward the battery pack mounts404. In this case, as shown inFIG.43, the vent holes78of the battery pack2function as air supply holes through which air is introduced from the outside into the battery pack2, and the air supply holes84of the battery pack2function as air discharge holes through which air is discharged from the interior of the battery pack2to the outside. In the example shown inFIG.43, the hook mount portion24of the upper case14does not function as an air supply hole84because the clearance between the hook26and the upper case14is closed such that air cannot flow therethrough. In this case, air that has entered the battery pack2through the vent holes78flows through the slits80of the control circuit board44, then flows through the openings82of the cell holder42, and flows into the spaces between the battery cells40. The air, which entered the spaces between the battery cells40, cools the battery cells40and then flows out to the outside of the battery pack2through the air supply holes84. In the example shown inFIG.43, the first thermistor90is disposed at a position where the distance from the position to the air supply holes84through which air flows out to the outside from the inside of the battery pack2is shorter than the distance from the position to the vent holes78through which air flows into the battery pack2from the outside, while the second thermistor92is disposed at a position where the distance from the position to the vent holes78through which air flows into the battery pack2from the outside is shorter than the distance from the position to the air supply holes84through which air flows out to the outside from the interior of the battery pack2. In the example ofFIG.43as well, the battery cell40a, which the first thermistor90detects the temperature, has the highest temperature among the battery cells40during charging, and the battery cell40b, which the first thermistor90detects the temperature, has the lowest temperature among the battery cells40during charging. As such, by using the first thermistor90and the second thermistor92, the temperature of the battery cell40a, which is the highest among the battery cells40during charging of the battery pack2, and the temperature of the battery cell40b, which is the lowest among the battery cells40during the charging, can be obtained.

In the above-described embodiment, a case was described in which the battery pack2comprises thirty-two battery cells40, the nominal voltage of the battery pack2is 64 V, and the nominal capacity of the battery pack2is 5 Ah. Unlike this, the battery pack2may comprise sixteen battery cells40, the nominal voltage of the battery pack2may be 64 V, and the nominal capacity of the battery pack2may be 2.5 Ah. In this case, as shown inFIG.44, the battery cells40are arranged in four abreast in the up-down direction and also are arranged four abreast in the front-rear direction. In case the first thermistor90and the second thermistor92have been disposed as shown inFIG.44, the battery cell40a, which the first thermistor90detects the temperature, has the highest temperature among the battery cells40during charging, and the battery cell40b, which the second thermistor92detects the temperature, has the lowest temperature among the battery cells40during charging. As such, by using the first thermistor90and the second thermistor92, the temperature of the battery cell40a, which is the highest among the battery cells40during charging to the battery pack2, and the temperature of the battery cell40b, which is the lowest among the battery cells40during the charging, can be obtained.

The battery pack2may be configured as shown inFIGS.45and46. In the battery pack2according to the present modified example, the air supply holes84are formed in lower portions of right and left surfaces of the lower case16and the lower surface of the lower case16, and are not formed in any other places. In addition, in the battery pack2according to the present modified example, the vent holes78,79are not formed in the upper case14, but instead a vent hole77is formed in a rear portion of the upper surface of the upper case14. As shown inFIG.46, in the battery pack2according to the present modified example, a notch86is formed in a rear end of the control circuit board44. The notch86is disposed at a position facing the vent hole77of the upper case14. In addition, although not shown, an air supply passage that communicates with the blower fan418is provided in the charger400corresponding to the battery pack2according to the present modified example. The air supply passage is disposed at a position facing the vent hole77when the battery pack2is attached. When the blower fan418of the charger400is driven with the battery pack2attached to the charger400, air is suctioned from the interior of the case12of the battery pack2, through the vent hole77, to the air supply passage of the charger400. In this way, air flows in the battery pack2from the outside through the air supply holes84, the power terminal openings72, and the signal terminal openings74into the interior. The air, which flowed into the interior of the battery pack2, flows through spaces between the battery cells40, the notch86of the control circuit board44, and the vent hole77of the upper case14, and then flows out to the outside of the battery pack2. During this, the plurality of battery calls40is cooled by the air flowing therearound.

As shown inFIG.46, in the battery pack2according to the present modified example, the first thermistor90and the second thermistor92are both film thermistors. The first thermistor90is disposed in a middle row of the plurality of battery calls40and detects the temperature of the battery cell40adisposed at a position that is spaced apart from the vent hole77. The second thermistor92is disposed in the upper row of the plurality of battery cells40and detects the temperature of the battery cell40bdisposed near the center in the front-rear direction. That is, in the present modified example, the battery cell40ais included in the middle battery cell group40e, and the battery cell40bis included in the upper battery cell group40c. The first thermistor90is disposed near the central portion of the battery cell40awith respect to the right-left direction. The second thermistor92is disposed near an end portion of the battery cell40bwith respect to the right-left direction.

In the battery pack2according to the present modified example, with regard to the battery cell40a, heat dissipation is difficult since it is surrounded by other battery cells40. Further, the battery cell40ais difficult to cool since the air does not flow much around the battery cell40awhen the blower fan418of the charger400is driven. Therefore, the battery cell40atends to have a high temperature during charging. To the contrary, with regard the battery cell40b, heat dissipation is easy since it is not surrounded by other battery cells40. Further, the battery cell40bcools easily since the air that flowed in from the power terminal openings72and the signal terminal openings74of the upper case14and passed through the slits80of the control circuit board44flows near the battery cell40bwhen the blower fan418of the charger400is driven. Therefore, the battery cell40btends to have a low temperature during charging. Owing to the configuration of the present modified example as well, the temperature of the battery cell40ahaving a high temperature during charging can be obtained using the first thermistor90and the temperature of the battery cell40bhaving a low temperature during charging can be obtained using the second thermistor92.

As described above, in one or more embodiments, the battery pack2comprises the plurality of battery cells40, the cell holder42holding the plurality of battery cells40, and the case12accommodating the cell holder42therein. The case12comprises the lower case16(an example of a first case) and the upper case14(an example of a second case) fixed to the lower case16. The cell holder42is fixed to the lower case16by the screws70(an example of a fastener). The screws70are shielded from the outside of the case12when the lower case16has been fixed to the upper case14.

According to the above configuration, because the screws70that fix the cell holder42to the lower case16are shielded from the outside of the case12, the effect of static electricity or the like on the exterior of the case12does not reach into the interior of the case12via the screws70. In a battery pack2that comprises the case12accommodating the cell holder42holding the plurality of battery cells40, the effect of static electricity or the like on the exterior of the case12can be curtailed from reaching into the interior of the case12.

In one or more embodiments, the battery pack2further comprises the cushion material68interposed between the lower case16and the cell holder42.

According to the above configuration, vibration and/or impact can be curtailed from being transmitted from the case12to the cell holder42.

In one or more embodiments, the lower case16has a box shape in which the upper surface (an example of one side) is opened. The cell holder42is fixed to the lower case16by the screws70in the state in which the cell holder42has been placed on the inner bottom surface of the lower case16. The screws70are fastened at positions spaced apart from the inner bottom surface of the lower case16compared the center of the cell holder42with respect to a direction orthogonal to the inner bottom surface of the lower case16, namely with respect to the up-down direction.

According to the above configuration, the cell holder42which holds the plurality of battery cells40can be restrained from swaying with respect to the case12.

In one or more embodiments, each of the plurality of battery cells40has the substantially cylindrical shape having the longitudinal direction in the right-left direction (an example of a first direction). The plurality of battery cells40is held in the cell holder42in the state in which the battery cells40are arranged side by side in the front-rear direction (an example of a second direction orthogonal to the first direction). The screws70are fastened at positions that are on an inner side relative to both ends of the plurality of battery cells40with respect to the right-left direction and are on an outer side relative to the outermost battery cell40among the plurality of battery cells40with respect to the front-rear direction.

In case each of the plurality of battery cells40has the substantially cylindrical shape having its longitudinal direction in the right-left direction and the plurality of battery cells40is held in the cell holder42in the state in which the battery cells40are arranged side by side in the front-rear direction, components, such as the lead plates54,56, which are connected to the electrodes of the battery cells40, are provided at both ends of the plurality of battery cells40in the right-left direction. Therefore, if it is configured such that the screws70are fastened at positions that are on an outer side relative to both ends of the plurality of battery cells40with respect to the right-left direction and are on an inner side relative to the outermost battery cell40among the plurality of battery cells40with respect to the front-rear direction, it becomes necessary to avoid interference with the components near both ends of the battery cells40in the right-left direction, which results in an increase in size of the battery pack2. As described above, by configuring it such that the screws70are fastened at positions that are on the inner side relative to both ends of the plurality of battery cells40with respect to the right-left direction and are on the outer sides relative to the outermost battery cells40among the plurality of battery cells40with respect to the front-rear direction, the cell holder42can be fixed to the lower case16by the screws70without increasing the size of the battery pack2.

In one or more embodiments, the battery pack2further comprises the control circuit board44accommodated in the case12and electrically connected to the plurality of battery cells40. The control circuit board44is fixed to the cell holder42.

According to the above configuration, when manufacturing the battery pack2, the control circuit board44and the cell holder42can be attached to the lower case16in an integrated manner with the control circuit board44fixed to the cell holder42. Labor involved in manufacturing of the battery pack2can be reduced.

In one or more embodiments, in a plan view in a direction orthogonal to the control circuit board44, namely from above, the screws70are fastened at positions on an outer side relative to the control circuit board44.

According to the above configuration, when the cell holder42with the control circuit board44is fixed thereto is attached to the lower case16, fastening work for the screws70can be performed without interference with the control circuit board44. Labor involved in manufacturing of the battery pack2can be reduced.

In one or more embodiments, the battery pack2comprises the battery cells40, the control circuit board44(an example of a circuit board) on which the power terminals60and the signal terminals62(an example of a plurality of terminals) have been provided, and the case12accommodating the battery cells40and the control circuit board44therein. The control circuit board44comprises the slits80(an example of a through hole) disposed between the power terminals60and the signal terminals62. The case12comprises the vent holes78disposed at positions facing the slits80of the control circuit board44.

According to the above configuration, because the vent holes78provided in the case12are disposed at positions facing the slits80provided in the control circuit board44, air flowing in or flowing out through the vent holes78of the case12passes through the slits80of the control circuit board44. As such, even if the battery cells40and the control circuit board44are disposed close to each other within the case12, sufficient air can flow through between the battery cells40and the control circuit board44and thus the battery cells40located close to the control circuit board44can be sufficiently cooled. Further, according to the above configuration, the slits80provided in the control circuit board44are disposed between the power terminals60and the signal terminals62. Therefore, even if a conductive substance, such as water, enters the interior of the case12and adheres to the control circuit board44, the occurrence of short circuits between the power terminals60and the signal terminals62can be curtailed.

In one or more embodiments, the power terminals60and the signal terminals62include a first terminal (e.g., the power terminals60) and a second terminal (e.g., the signal terminals62adjacent to the power terminals60). The vent holes78comprise a plurality of holes78adisposed between a region of the upper case14facing the first terminal (e.g., the power terminal60) and a region of the upper case14facing the second terminal (e.g., the signal terminal62adjacent to the power terminal60).

If the size of the vent holes78provided in the case12is large, although the amount of air passing through the vent holes78is increased, foreign matter tends to enter into the interior of the battery pack2through the vent holes78. According to the above configuration, because the vent holes78comprise a plurality of holes78a, the size of individual holes78acan be reduced without reducing the amount of air passing through the vent holes78, and foreign matter can be curtailed from entering into the interior of the battery pack2through the vent holes78.

In one or more embodiments, the battery pack2further comprises the cell holder42accommodated in the case12and holding the battery cells40. The cell holder42comprises an opening82disposed at a position facing the slits80of the control circuit board44.

If the cell holder42shields a space between the slits80of the control circuit board44and the battery cells40in a configuration in which the battery cells40are held by the cell holder42, air passing through the slits80flows in the space between the control circuit board44and the cell holder42, which means that the battery cells40close to the slits80can not be sufficiently cooled. In the above configuration, because the cell holder42includes the opening82disposed at a position facing the slits80of the control circuit board44, air passing through the slits80flows through the opening82of the cell holder42. As such, the battery cells40close to the slits80can be sufficiently cooled.

In one or more embodiment, the case12comprises the recessed grooves76disposed between the power terminals60and the signal terminals62and opening in two directions. The vent holes78are disposed in bottom surfaces of the recessed grooves76.

According to the above configuration, an inner space of the recessed grooves76of the case12functions as a flow passage for air passing through the vent holes78. Further, according to the above configuration, either of the two directions in which the recessed grooves76open can be used as a direction in which air passing through the vent holes78flows into the case12or as a direction the air flows out from the case12, as desired. According to the above configuration, the degrees of freedom in designing a mechanism through which cooling air flows into the battery pack2or flows out therefrom can be increased.

In one or more embodiments, the battery pack2further comprises the lead plates54,56connecting the battery cells40to the control circuit board44. The control circuit board44further includes the slits85(an example of a second through hole) disposed between the power terminals60and the lead plates54,56. The case12further comprises the vent holes83(an example of a second vent hole) disposed at positions facing the slits85of the control circuit board44.

According to the above configuration, because the vent holes83provided in the case12are disposed at positions facing the slits85of the control circuit board44, air flowing into the case12or flowing out therefrom through the vent holes83passes through the slits85of the control circuit board44. As such, even if the battery cells40and the control circuit board44are disposed close to each other within the case12, sufficient air can flow between the battery cells40and the control circuit board44, and the battery cells40close to the control circuit board44can be sufficiently cooled. In addition, according to the above configuration, the slits85provided in the control circuit board44are disposed between the power terminals60and the lead plates54,56. Therefore, even if a conductive substance, such as water, enters the interior of the case12and adheres to the control circuit board44, the occurrence of short circuits between the power terminals60and the lead plates54,56can be curtailed.

In one or more embodiments, the control circuit board44comprises notches44a(or notches44b) formed between lead plates54(or lead plates56) that are adjacent to each other.

According to the above configuration, because air can also flow through the notches44a(or the notches44b) of the control circuit board44, sufficient air can flow through between the battery cells40and the control circuit board44, and thus the battery cells40close to the control circuit board44can be sufficiently cooled. In addition, according to the above configuration, the notches44a(or the notches44b) formed in the control circuit board44are disposed between the lead plates54(or lead plates56) that are adjacent to each other. Therefore, even if a conductive substance, such as water, enters the interior of the case12and adheres to the control circuit board44, the occurrence of short circuits between the lead plates54(or lead plates56) that are adjacent to each other can be curtailed.

In one or more embodiments, the battery pack2is attachable to/detachable from the charger400by sliding the battery pack2in the front-rear direction (an example of a predetermined sliding direction). The control circuit board44further comprises the slit81(an example of a third through hole) disposed at a position offset from the signal terminals62in the rear direction. The case12further comprises the vent hole79(an example of a third vent hole) disposed at a position facing the slit81of the control circuit board44.

According to the above configuration, because the vent hole79provided in the case12is disposed at a position facing the slit81provided in the control circuit board44, air flowing in or flowing out through the vent hole79of the case12passes through the slit81of the control circuit board44. As such, even if the battery cells40and the control circuit board44are disposed close to each other within the case12, sufficient air can flow through between the battery cells40and the control circuit board44, and the battery cells40close to the control circuit board44can be sufficiently cooled.

In one or more embodiments, the battery pack2comprises: the plurality of battery cells40that includes the battery cell40a(an example of the first battery cell) and the battery cell40b(an example of the second battery cell); the first thermistor90disposed closest to the battery cell40aamong the plurality of battery cells40; the second thermistor92disposed closest to the battery cell40bamong the plurality of battery cells40; and the case12accommodating the plurality of battery cells40, the first thermistor90, and the second thermistor92. The battery cell40ais disposed at a position where (an)other battery cell(s)40is (are) interposed between the battery cell40aand the wall surface of the case12with respect to the direction orthogonal to the longitudinal direction of the battery cell40a. The battery cell40bis disposed at a position where no other battery cell40is interposed between the battery cell40band the wall surface of the case12with respect to the direction orthogonal to the longitudinal direction of the battery cell40b.

Generally, in a battery pack2in which a case12accommodates a plurality of battery cells40therein, heat dissipation occurs from the outer surface of the case12to air outside of the case12. Since (an)other battery cell(s)40is (are) interposed between the battery cell40aand the wall surface of the case12in the above-described configuration, heat dissipation via the wall surface of the case12is difficult, and thus the battery cell40atends to have a high temperature. In addition, since no other battery cell40is interposed between the battery cell40band the wall surface of the case12, heat dissipation easily occurs via the wall surface of the case12, and thus the battery cell40btends to have a low temperature. In the above-described configuration, the temperature of the battery cell40athat tends to have a high temperature can be obtained using the first thermistor90and the temperature of the battery cell40bthat tends to have a low temperature can be obtained using the second thermistor92. In the above-described configuration, the temperature of the battery cell40ahaving a high temperature as well as the temperature of the battery cell40bhaving a low temperature can be obtained in a battery pack2comprising a plurality of battery cells40.

In one or more embodiments, the case12comprises the air supply holes84(an example of an air supply hole) through which air is introduced and the vent holes78(an example of an air discharge hole) through which air is discharged.

According to the above configuration, in a battery pack2in which the plurality of battery cells40is cooled by air flowing inside the case12from the air supply holes84to the vent holes78, the temperature of the battery cell40ahaving a high temperature as well as the temperature of the battery cell40bhaving a low temperature can be obtained.

In one or more embodiments, the second thermistor92is disposed at a position where the distance from the position to the air supply holes84is smaller than the distance from the position to the vent holes78.

In a battery pack2in which the plurality of battery cells40is cooled by air flowing inside the case12from the air supply holes84to the vent holes78, the air has the lowest temperature immediately after having flowed in through the air supply holes84and has the highest temperature immediately before flowing out through the vent holes78. Therefore, the battery cell(s)40disposed near the air supply holes84tend(s) to have a low temperature, while the battery cell(s)40disposed near the vent holes78tend(s) to have a high temperature. According to the above configuration, the temperature of the battery cell40bhaving a lower temperature can be obtained using the second thermistor92.

In one or more embodiments, the first thermistor90is disposed at a position where the distance from the position to the vent holes78is smaller than the distance from the position to the air supply holes84.

In a battery pack2in which the plurality of battery cells40is cooled by air flowing inside the case12from the air supply holes84to the vent holes78, the battery cell(s)40disposed near the air supply holes84tend(s) to have a low temperature, while the battery cell(s)40disposed near the vent holes78tend(s) to have a high temperature. According to the above configuration, the temperature of the battery cell40ahaving a higher temperature can be obtained using the first thermistor90.

In one or more embodiments, the battery pack2further comprises the control circuit board44(an example of circuit board) accommodated in the case12and disposed between the vent holes78and the plurality of battery cells40. Each of the first thermistor90and the second thermistor92is connected to the control circuit board44. The first thermistor90comprises a film thermistor. The second thermistor92comprises a dip thermistor.

According to the above configuration, because the control circuit board44is disposed between the vent holes78and the plurality of battery cells40, the temperature of the battery cell40ahaving a high temperature can be obtained with high accuracy by obtaining the temperature of the battery cell40adisposed near the vent holes78, namely the temperature of the battery cell40athat tends to have a high temperature, using the first thermistor90that comprises the film thermistor. In addition, according to the above configuration, even if the control circuit board44is disposed between the vent holes78and the plurality of battery cells40, the temperature of the battery cell40bdisposed near the air supply holes84, namely the temperature of the battery cell40bthat tends to have a low temperature, can be obtained using the second thermistor92that comprises the dip thermistor.

In one or more embodiments, the battery pack2comprises: the plurality of battery cells40including the battery cell40a(an example of the first battery cell) and the battery cell40b(an example of the second battery cell); the first thermistor90disposed closest to the battery cell40aamong the plurality of battery cells40; the second thermistor92disposed closest to the battery cell40bamong the plurality of battery cells40; and the case12accommodating the plurality of battery cells40, the first thermistor90, and the second thermistor92. The plurality of battery cells40comprises: the upper battery cell group40cdisposed in the upper row; the lower battery cell group40ddisposed in the lower row; and the middle battery cell group40edisposed between the upper battery cell group40cand the lower battery cell group40d. The battery cell40ais included in the middle battery cell group40e. The battery cell40bis included in either the upper battery cell group40cor the lower battery cell group40d.

Since other battery cells40are interposed between the battery cell40aand the upper and lower surfaces of the case12in the above-described configuration, heat dissipation via the upper and lower surfaces of the case12is difficult, and thus the battery cell40atends to have a high temperature. Further, since no other battery cell40is interposed between the battery cell40band the upper or lower surface of the case12, heat dissipation easily takes place via the upper or lower surface of the case12, and thus the battery cell40btends to have a low temperature. In the above-described configuration, the temperature of the battery cell40ahaving a high temperature can be obtained using the first thermistor90and the temperature of the battery cell40bhaving a low temperature can be obtained using the second thermistor92. In the above-described configuration, the temperature of the battery cell40ahaving a high temperature as well as the temperature of the battery cell40bhaving a low temperature can be obtained in a battery pack2comprising a plurality of battery cells40.

In one or more embodiments, the battery pack2comprises: the plurality of battery cells40including the battery cell40a(an example of the first battery cell) and the battery cell40b(an example of the second battery cell); the first thermistor90disposed closest to the battery cell40aamong the plurality of battery cells40; the second thermistor92disposed closest to the battery cell40bamong the plurality of battery cells40; and the case12accommodating the plurality of battery cells40, the first thermistor90and the second thermistor92. The plurality of battery cells40comprises: the upper battery cell group40cdisposed at a position facing the upper surface of the case12; the lower battery cell group40ddisposed at a position facing the lower surface of the case12; and the middle battery cell group40edisposed between the upper battery cell group40cand the lower battery cell group40d. The battery cell40ais included in the middle battery cell group40e. The battery cell40bis included in either the upper battery cell group40cor the lower battery cell group40d.

Since other battery cells40are interposed between the battery cell40aand the upper and lower surfaces of the case12in the above-described configuration, heat dissipation via the upper and lower surfaces of the case12is difficult, and thus the battery cell40atends to have a high temperature. Further, since no other battery cell40is interposed between the battery cell40band the upper or lower surface of the case12, heat dissipation easily takes place via the upper or lower surface of the case12, and thus the battery cell40btends to have a low temperature. In the above-described configuration, the temperature of the battery cell40ahaving a high temperature can be obtained using the first thermistor90and the temperature of the battery cell40bhaving a low temperature can be obtained using the second thermistor92. In the above-described configuration, the temperature of the battery cell40ahaving a high temperature as well as the temperature of the battery cell40bhaving a low temperature can be obtained in a battery pack2comprising a plurality of battery cells40.

In one or more embodiments, the power supply system600comprises the electrical device200and the battery pack2configured to be detachably attached to the electrical device200by being slid in the front-rear direction (an example of a sliding direction) with respect to the electrical device200. The electrical device200comprises the power terminals204(an example of a device-side power terminal) and the protective ribs208disposed on both sides of the power terminals204and extending to a position higher than the power terminals204. The battery pack2comprises the power terminals60(an example of a battery-side power terminal) that mechanically engage with and electrically connect to the power terminals204, and the case12accommodating the power terminals60. The case12comprises the power terminal openings72disposed at positions facing the power terminals60in the front-rear direction, and the recessed grooves76disposed on both sides of the power terminals60and extending along the front-rear direction.

In one or more embodiments, with regard to the electrical device200, the battery pack2is attachable/detachable by sliding the battery pack2in the front-rear direction (an example of a sliding direction). The electrical device200comprises the power terminals204(an example of a device-side power terminal) and the protective ribs208disposed on both sides of the power terminals204and extending higher than the power terminals204.

In one or more embodiments, the battery pack2is attachable to/detachable from the electrical device200by being slid with respect to the electrical device200in the front-rear direction (an example of a sliding direction). The battery pack2comprises the power terminals60(an example of a battery-side power terminal) and the case12accommodating the power terminals60. The case12comprises the power terminal openings72disposed at positions facing the power terminals60in the front-rear direction, and the recessed grooves76disposed on both sides of the power terminals60and extending along the front-rear direction.

According to the above configuration, because the protective ribs208, which extend higher than the power terminals204, are provided on both sides of the power terminals204of the electrical device200, the user will not accidentally come into contact with the power terminals204even in the state in which the battery pack2is detached from the electrical device200. According to the above configuration, because the recessed grooves76of the case12of the battery pack2receive the protective ribs208of the electrical device200when the battery pack2is attached to the electrical device200, the battery pack2can be attached to the electrical device200without interference between the protective ribs208and the case12.

In one or more embodiments, the electrical device200further comprises the signal terminals206(an example of a device-side signal terminal). The protective ribs208are also disposed on both sides of the signal terminals206and extend higher than the signal terminals206. The battery pack2further comprises the signal terminals62(an example of a battery-side signal terminal) which are accommodated in the case12and mechanically engage with and electrically connected to the signal terminals206. The case12further comprises the signal terminal openings74disposed at positions facing the signal terminals62in the front-rear direction. The recessed grooves76are also disposed on both sides of each signal terminal62.

In one or more embodiments, the electrical device200further comprises the signal terminals206(an example of device-side signal terminal). The protective ribs208are also disposed on both sides of the signal terminals206and extend higher than the signal terminals206.

In one or more embodiments, the battery pack2further comprises the signal terminals62(an example of a battery-side signal terminal) accommodated in the case12. The case12further comprises the signal terminal openings74disposed at positions facing the signal terminals62in the front-rear direction. The recessed grooves76are also disposed on both sides of the signal terminals62.

According to the above configuration, because the protective ribs208, which extend higher than the signal terminals206, are provided on both sides of the signal terminals206of the electrical device200, the user will not accidentally come into contact with the signal terminals206even in the state in which the battery pack2is detached from the electrical device200. It is noted that, according to the above configuration, because the recessed grooves76of the case12of the battery pack2receive the protective ribs208of the electrical device200when the battery pack2is attached to the electrical device200, the battery pack2can be attached to the electrical device200without interference between the protective ribs208and the case12.

In one or more embodiments, the electrical device200further comprises the slide rails210(an example of a device-side slide rail). At least one of the protective ribs208is disposed between a slide rail210and a power terminal204. The battery pack2further comprises the slide rails20(an example of a battery-side slide rail) that slidably engage with the slide rails210in the front-rear direction. At least one of the recessed grooves76is disposed between a slide rail20and a power terminal60.

In one or more embodiments, the electrical device200further comprises the slide rails210(an example of a device-side slide rail). At least one of the protective ribs208is disposed between a slide rail210and a power terminal204.

In one or more embodiments, the battery pack2further comprises the slide rails20(an example of a battery-side slide rail). At least one of the recessed grooves76is disposed between a slide rail20and a power terminal60.

Spaces for receiving the slide rails20of the battery pack2are often provided between the slide rails210and the power terminals204of the electrical device200, which allows for easy insertion of a user's finger. According to the above-described configuration, the user will not accidentally come into contact with the power terminals204through the spaces between the slide rails210and the power terminals204, even in the state in which the battery pack2is detached from the electrical device200. It is noted that, because the recessed grooves76of the case12of the battery pack2according to the above-described configuration receive the protective ribs208of the electrical device200when the battery pack2is attached to the electrical device200, the battery pack2can be attached to the electrical device200without interference between the protective ribs208and the case12.