Patent Publication Number: US-2022214402-A1

Title: Voltage detection line and voltage detection line module

Description:
TECHNICAL FIELD 
     The present invention relates to a voltage detection line and a voltage detection line module. 
     BACKGROUND ART 
     For example, known examples of a power source that requires high output voltage, such as for a vehicle, include a battery module in which a plurality of batteries is electrically connected. In such a battery module, neighboring batteries are electrically connected with each other via a bus bar. Further, for example, as disclosed in Patent Literature 1, a voltage detection line is attached to each bus bar, and a voltage between the batteries is detected. 
     In a battery module provided with voltage detection lines, there is a risk that when the voltage detection lines are short-circuited, batteries connected to these voltage detection lines may be short-circuited. On the other hand, in Patent Literature 1, a current limiting element that fuses when an overcurrent flows through a voltage detection line is provided in a middle of the voltage detection line. When the current limiting element is fused when the overcurrent flows, current flow in the voltage detection line is cut off, so that a short circuit between the batteries via the voltage detection line can be suppressed. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: Unexamined Japanese Patent Publication No. 2017-27831 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     As a result of intensive studies on a voltage detection line having a current limiting element, the inventors of the present invention have recognized that the possibility that a disconnected voltage detection line may be conducted again due to vibration from the outside, deflection of the voltage detection line, release of deflection, or the like is not zero. In order to enhance safety of a battery module, it is desirable to reduce the possibility of reconduction of the disconnected voltage detection line as much as possible. 
     In view of these respects, an object of the present invention is to provide a technique for suppressing reconduction of a disconnected voltage detection line. 
     Solution to Problem 
     One aspect of the present invention is a voltage detection line. The voltage detection lines include conductive wires and insulating films covering the conductive wires, and are voltage detection lines for detecting voltage of each battery. Each of the conductive wires includes a low-resistance part having a predetermined electrical resistance value, and a high-resistance part having a higher electrical resistance value than an electrical resistance value of the low-resistance part and fusing when an overcurrent flows through the conductive wire. Each of the insulating films includes a high-strength part covering the low-resistance part and having a predetermined strength, and a low-strength part covering the high-resistance part and having a strength lower than a strength of the high-strength part. 
     Another aspect of the present invention is a voltage detection line module. The voltage detection line module includes voltage detection lines of the above aspect and a support plate that supports the voltage detection lines. 
     It should be noted that any combination of the above components and conversions of the expression of the present invention between methods, devices, systems and the like are also effective as aspects of the present invention. 
     Advantageous Effect of Invention 
     According to the present invention, it is possible to suppress reconduction of a disconnected voltage detection line. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view of a battery module on which voltage detection lines according to an exemplary embodiment are mounted. 
         FIG. 2  is a plan view of the battery module. 
         FIG. 3  is a cross-sectional view of a conductive wire in a second region. 
         FIG. 4(A)  is a cross-sectional view taken along line A-A in  FIG. 3 .  FIG. 4(B)  is a cross-sectional view taken along line B-B of  FIG. 3 . 
         FIGS. 5(A) and 5(B)  are cross-sectional views of a part of the voltage detection line module according to the exemplary embodiment. 
         FIG. 6  is a cross-sectional view of a part of a voltage detection line module according to Modified Example 1. 
         FIG. 7  is a cross-sectional view of a part of a voltage detection line module according to Modified Example 2. 
         FIG. 8  is a plan view of a part of a battery module according to Modified Example 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be described based on a preferred exemplary embodiment with reference to the drawings. The exemplary embodiments are not intended to limit the invention but are examples, and all features described in the exemplary embodiments and combinations thereof are not necessarily essential to the invention. The same or equivalent components, members, and processes illustrated in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the scales and shapes of the parts illustrated in the drawings are determined for convenience in order to facilitate the description, and should not be interpreted as limitation unless otherwise mentioned. In addition, terms such as “first” and “second”, used in the present specification or claims do not represent any order or importance unless otherwise specified, but are intended to distinguish one configuration from another configuration. Further, in each drawing, some members that are not important for describing the exemplary embodiments are omitted. 
       FIG. 1  is an exploded perspective view of a battery module on which voltage detection lines according to an exemplary embodiment is mounted. In  FIG. 1 , output terminals  22 , bus bars  42 , and voltage detection lines  46  are simplified. Battery module  1  includes battery stack  2 , a pair of end plates  4 , cooling plate  6 , heat conductive layer  8 , side separators  10 , constraining members  12 , support plate  28 , voltage detection lines  46 , and cover plate  60 . 
     Battery stack  2  includes a plurality of batteries  14  and inter-cell separators  16 . Each of batteries  14  is a chargeable secondary battery such as a lithium ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery, for example. Each of batteries  14  is a so-called prismatic battery, and has exterior can  18  having a flat rectangular parallelepiped shape. Exterior can  18  has a substantially rectangular opening not illustrated in the drawing on one surface of the exterior can. An electrode assembly, an electrolyte and the like are housed in exterior can  18  through the opening. Sealing plate  20  that closes the opening of exterior can  18  is disposed in the opening. 
     Output terminal  22  of a positive electrode is disposed on sealing plate  20  at a position close to one end of the sealing plate in a longitudinal direction, and output terminal  22  of a negative electrode is disposed on sealing plate  20  at a position close to the other end. The pair of output terminals  22  is electrically connected to the corresponding one of a positive electrode plate and a negative electrode plate, constituting the electrode assembly. Hereinafter, output terminal  22  of the positive electrode is referred to as positive-electrode terminal  22   a , and output terminal  22  of the negative electrode is referred to as negative-electrode terminal  22   b  as appropriate. When there is no need to distinguish polarities of output terminals  22  from each other, positive-electrode terminal  22   a  and negative-electrode terminal  22   b  are collectively referred to as output terminals  22 . 
     Exterior can  18 , sealing plate  20 , and output terminals  22  are electric conductors and are made of metal, for example. Sealing plate  20  and the opening of exterior can  18  are joined to each other by, for example, laser welding. Respective output terminals  22  are inserted into through-holes (not illustrated) formed in sealing plate  20 . A seal member (not illustrated) having an insulating property is interposed between respective output terminals  22  and respective through-holes. 
     In the description of the present exemplary embodiment, for convenience, sealing plate  20  forms an upper surface of battery  14 , and a bottom surface of exterior can  18  disposed on a side opposite to sealing plate  20  forms a lower surface of battery  14 . Battery  14  has two main surfaces that connect the upper surface and the lower surface of battery  14  to each other. The main surfaces are surfaces that have the largest area among six surfaces of battery  14 . The main surfaces are long side surfaces that are connected to long sides of the upper surface and long sides of the lower surface. Two remaining surfaces other than the upper surface, the lower surface, and two main surfaces form side surfaces of battery  14 . These side surfaces are a pair of short side surfaces that is connected to short sides of the upper surface and short sides of the lower surface. 
     For convenience, in battery stack  2 , surfaces of batteries  14  closer to an upper surface are referred to as an upper surface of battery stack  2 , surfaces of batteries  14  closer to a lower surface are referred to as a lower surface of battery stack  2 , and surfaces of batteries  14  closer to side surface are referred to as side surfaces of battery stack  2 . These directions and positions are defined for convenience unless otherwise specified. Therefore, for example, the portion defined as the upper surface in the present invention does not always mean that the portion defined as the upper surface is positioned above the portion defined as the lower surface. 
     Valve  24  is disposed on sealing plate  20  between the pair of output terminals  22 . Valve  24  is also referred to as a safety valve. Valve  24  is a mechanism for releasing a gas in each battery  14 . Valve  24  is configured to release an internal gas by opening valve  24  when an inner pressure of exterior can  18  is increased to a predetermined value or more. For example, valve  24  includes: a thin part that is formed on a part of sealing plate  20  and is thinner than other parts of valve  24 ; and a linear groove formed on a surface of the thin part. In this configuration, when an internal pressure of exterior can  18  increases, valve  24  is opened by tearing the thin wall part with the groove as a tearing starting point. Valve  24  of each battery  14  is connected to exhaust duct  38  described later, and the gas inside the batteries are discharged from valves  24  to exhaust duct  38 . 
     Each battery  14  has insulating film  26 . Insulating film  26  is, for example, a cylindrical shrink tube, and is heated after exterior can  18  is made to pass through the inside of insulating film  26 . Accordingly, insulating film  26  shrinks and covers two main surfaces, two side surfaces, and a bottom surface of exterior can  18 . Insulating film  26  can prevent a short circuit between batteries  14  disposed adjacently to each other or between battery  14  and end plate  4  or constraining member  12 . 
     The plurality of batteries  14  are stacked to each other at a predetermined interval such that the main surfaces of batteries  14  disposed adjacently to each other face each other. Note that, the term “stack” corresponds to arranging a plurality of members in any one direction. Therefore, stacking batteries  14  also includes arranging the plurality of batteries  14  in the horizontal direction. In the present exemplary embodiment, batteries  14  are horizontally stacked. Accordingly, stacking direction X of batteries  14  is a direction of extending in the horizontal direction. Hereinafter, when appropriate, a direction that is horizontal and is perpendicular to stacking direction X is referred to as horizontal direction Y, and a direction that is perpendicular to stacking direction X and horizontal direction Y is referred to as vertical direction Z. 
     Respective batteries  14  are disposed in a state where output terminals  22  are directed in a same direction. In the present exemplary embodiment, respective batteries  14  are disposed in a state where output terminals  22  are directed upward in the vertical direction. With respect to respective batteries  14 , when batteries  14  disposed adjacently to each other are connected in series, batteries  14  are stacked in a state where positive-electrode terminal  22   a  of one battery  14  and negative-electrode terminal  22   b  of another battery  14  are disposed adjacently to each other. When batteries  14  disposed adjacently to each other are connected in parallel, batteries  14  are stacked to each other in a state where positive-electrode terminal  22   a  of one battery  14  and positive-electrode terminal  22   a  of another battery  14  are disposed adjacently to each other. 
     Inter-cell separator  16  is also referred to as an insulating spacer, and is formed of a resin sheet having an insulating property, for example. Examples of the resin constituting inter-cell separator  16  include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified-PPE). Inter-cell separator  16  is disposed between two batteries  14  disposed adjacent to each other to electrically insulate two batteries  14  from each other. 
     Battery stack  2  is sandwiched between the pair of end plates  4  in stacking direction X of batteries  14 . The pair of end plates  4  is disposed at both ends of battery stack  2  in stacking direction X along which batteries  14  are stacked. The pair of end plates  4  is disposed adjacently to batteries  14  positioned at both ends in stacking direction X, via external end separator  5 . External end separator  5  can be made of the same resin material as inter-cell separator  16 . Each end plate  4  is a metal plate made of metal such as iron, stainless steel, or aluminum. By interposing external end separator  5  between end plate  4  and battery  14 , end plate  4  and battery  14  are electrically insulated from each other. Each end plate  4  has fastening holes  4   a  on two surfaces that are directed in horizontal direction Y. 
     Support plate  28  is placed on the upper surface of battery stack  2 . Support plate  28  is a plate-like member that supports voltage detection lines  46 . Voltage detection lines  46  are members for detecting voltage of each battery  14 . Voltage detection lines  46  of the present exemplary embodiment detect voltages of the plurality of stacked batteries  14 . 
     Support plate  28  covers the upper surface of battery stack  2 , that is, surfaces on which each valve  24  of respective batteries  14  is disposed. Support plate  28  has a plurality of openings  32  through which a plurality of valves  24  are exposed at positions corresponding to valves  24  formed on respective batteries  14 . The plurality of openings  32  are formed in base plate  33  extending along the upper surface of battery stack  2 . Support plate  28  includes exhaust duct  38  that temporarily stores the gas ejected from respective batteries  14 . Accordingly, support plate  28  also functions as a so-called duct plate. Exhaust duct  38  extends in stacking direction X of batteries  14  and is connected to valves  24  of respective batteries  14 . Respective valves  24  communicate with exhaust duct  38  through openings  32 . 
     Exhaust duct  38  is defined by: first wall part  34  that covers the upper sides of the plurality of openings  32 ; and a pair of second wall parts  36  which surrounds the sides of respective openings  32 . The pair of second wall parts  36  is arranged in horizontal direction Y with the plurality of openings  32  interposed therebetween. First wall part  34  faces each valve  24 . The pair of second wall parts  36  protrudes from base plate  33  toward cover plate  60 , and forms both side surfaces of exhaust duct  38 . First wall part  34  is fixed to upper ends of the pair of second wall parts  36  to form a top surface of exhaust duct  38 . 
     Support plate  28  has openings  40  through which output terminals  22  are exposed at positions corresponding to output terminals  22  of respective batteries  14 . Bus bars  42  are placed on respective openings  40 . The plurality of bus bars  42  are supported by support plate  28 . Accordingly, support plate  28  also functions as a so-called bus bar plate. Bus bars  42  placed in respective openings  40  electrically connect output terminals  22  of batteries  14  disposed adjacently to each other. 
     Support plate  28  of the present exemplary embodiment is made of a resin such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE) except for first wall part  34 . First wall part  34  is made of metal such as iron or aluminum. The pair of second wall parts  36  is integrally formed with base plate  33  by molding. First wall part  34  is fixed to the pair of second wall parts  36  by fastening members (not illustrated) such as screws. 
     Each of bus bars  42  is a substantially strip-shaped member made of metal such as copper or aluminum. One end of bus bar  42  is connected to output terminal  22  of one battery  14 , and the other end of bus bar  42  is connected to output terminal  22  of another battery  14 . Bus bar  42  and output terminal  22  are bonded to each other by, for example, laser welding or ultrasonic bonding. With respect to bus bars  42 , output terminals  22  having the same polarity in a plurality of batteries  14  disposed adjacently to each other may be connected in parallel by bus bars  42  to form a battery block, and these battery blocks may be connected in series by bus bars  42 . Bus bars  42  connected to output terminals  22  of batteries  14  positioned at both ends in stacking direction X each have external connection terminal  44 . External connection terminal  44  is connected to an external load (not illustrated). 
     Voltage detection lines  46  placed on support plate  28  are electrically connected to the plurality of bus bars  42  to detect voltage of each battery  14 . Voltage detection lines  46  include a plurality of conductive wires  80  (refer to  FIG. 2 ). One end of each conductive wire  80  is connected to each bus bar  42 , and the other end is connected to connector  48 . Connector  48  is connected to an external battery ECU (not illustrated) or the like. Battery ECU controls detection of a voltage or the like of each battery  14 , charging and discharging of each battery  14 , and the like. 
     Cooling plate  6  has a flat plate shape extending in stacking direction X and in horizontal direction Y, and is made of a material having high thermal conductivity such as aluminum. Cooling plate  6  is connected to battery stack  2  in a heat-exchangeable manner to cool respective batteries  14 . Battery stack  2  is placed on cooling plate  6  such that the lower surface of battery stack  2  faces a cooling plate  6 . Cooling plate  6  may be connected to the outside of battery module  1  in a heat-exchangeable manner. A flow path through which a refrigerant such as water or ethylene glycol flows may be disposed in cooling plate  6 . 
     Heat conductive layer  8  is a member having an insulating property which is interposed between battery stack  2  and cooling plate  6 . Heat conductive layer  8  covers the entire bottom surface of battery stack  2 . Heat conductive layer  8  can be formed of, for example, a known resin sheet having good thermal conductivity, such as an acrylic rubber sheet or a silicone rubber sheet. In addition, heat conductive layer  8  may be made of a known adhesive agent, grease, or the like having a good thermal conductivity and an insulating property. When exterior can  18  is sufficiently insulated by insulating film  26  or the like, heat conductive layer  8  may not have the insulating property. 
     Side separators  10  are members that have an insulating property and insulate constraining members  12  and battery stack  2  from each other. In the present exemplary embodiment, the pair of side separators  10  is arranged in horizontal direction Y. Battery stack  2 , the pair of end plates  4 , cooling plate  6 , and heat conductive layer  8  are disposed between the pair of side separators  10 . Each of side separators  10  is made of, for example, a resin having an insulating property. Examples of the resin constituting side separators  10  include the same thermoplastic resin as the Inter-cell separator  16 . 
     Side separator  10  of the present exemplary embodiment has first part  50 , second part  52 , and third part  53 . First part  50  has a rectangular flat plate shape, and extends in stacking direction X of batteries  14  along a side surface of battery stack  2 . Second part  52  has a strip shape extending in stacking direction X, and protrudes from a lower side of first part  50  toward a battery stack  2 . Third part  53  has a strip shape extending in stacking direction X, and protrudes from an upper side of first part  50  toward the battery stack  2 . Battery stack  2 , cooling plate  6 , and heat conductive layer  8  are disposed between second part  52  and third part  53 . 
     Constraining members  12  are also referred to as bind bars, and are elongated members that are long in stacking direction X of batteries  14 . In the present exemplary embodiment, a pair of constraining members  12  is arranged in horizontal direction Y. Each of constraining members  12  is made of metal. Examples of metal constituting constraining members  12  include iron and stainless steel. Battery stack  2 , the pair of end plates  4 , cooling plate  6 , heat conductive layer  8 , and the pair of side separators  10  are disposed between the pair of constraining members  12 . 
     In the present exemplary embodiment, each of constraining members  12  includes flat surface part  54  and a pair of arm parts  56 . Flat surface part  54  has a rectangular shape, and extends in stacking direction X along the side surface of battery stack  2 . The pair of arm parts  56  protrudes toward a battery stack  2  from ends of flat surface part  54  on both sides in vertical direction Z. Battery stack  2 , cooling plate  6 , heat conductive layer  8 , and side separators  10  are disposed between the pair of arm parts  56 . 
     Contact plate  68  is fixed to regions of flat surface part  54  that face respective end plates  4  by welding or the like. Contact plate  68  is provided with through-holes  70  at positions corresponding to fastening holes  4   a  of end plate  4 . Flat surface part  54  has through-holes  58  at positions corresponding to through-holes  70  of contact plate  68 . 
     By making the pair of end plates  4  engage with flat surface parts  54  of respective constraining members  12 , the plurality of batteries  14  are sandwiched between end plates  4  in stacking direction X. Specifically, battery stack  2  is formed by alternately arranging the plurality of batteries  14  and the plurality of inter-cell separators  16 , and such battery stack  2  is sandwiched between the pair of end plates  4  with external end separators  5  interposed between battery stack  2  and end plates  4  in stacking direction X. Heat conductive layer  8  and cooling plate  6  are disposed on the lower surface of battery stack  2 . In such a state, battery stack  2 , the pair of end plates  4 , cooling plate  6 , and heat conductive layer  8  are sandwiched between the pair of side separators  10  in horizontal direction Y. Further, the pair of constraining members  12  sandwiches the whole body in horizontal direction Y from the outside of the pair of side separators  10 . 
     The pair of end plates  4  and the pair of constraining members  12  are aligned with each other such that fastening holes  4   a , through-holes  70 , and through-holes  58  overlap with each other. Fastening members  59  such as screws are made to pass through through-holes  58  and through-holes  70  and are made to threadedly engage with fastening holes  4   a . With such a configuration, the pair of end plates  4  and the pair of constraining members  12  are fixed to each other. By making the pair of end plates  4  and the pair of constraining members  12  engage with each other, the plurality of batteries  14  are fastened to each other and are constrained in stacking direction X. 
     Constraining members  12  sandwich the plurality of batteries  14  in stacking direction X. Constraining members  12  also sandwich battery stack  2 , heat conductive layer  8 , and cooling plate  6  in the arrangement direction of battery stack  2 , heat conductive layer  8 , and cooling plate  6 . Battery stack  2 , heat conductive layer  8 , and cooling plate  6  are sandwiched between the pair of arm parts  56  of each constraining member  12  in vertical direction Z. That is, constraining members  12  have both a function of fastening the plurality of batteries  14  and a function of fastening battery stack  2  and cooling plate  6 . 
     In a state where the pair of constraining members  12  is fixed to the pair of end plates  4 , first part  50  of side separator  10  is interposed between the side surface of battery stack  2  and flat surface part  54  of constraining member  12 . With such a configuration, the side surfaces of respective batteries  14  and flat surface part  54  are electrically insulated from each other. Second part  52  of side separator  10  is interposed between cooling plate  6  and arm part  56  of constraining member  12  on a lower side. With such a configuration, cooling plate  6  and arm part  56  of constraining member  12  on the lower side are electrically insulated from each other. Third part  53  of side separator  10  is interposed between the upper surface of battery stack  2  and arm part  56  of constraining member  12  on an upper side. With such a configuration, the upper surfaces of respective batteries  14  and arm part  56  of constraining member  12  on the upper side are electrically insulated from each other. 
     As an example, after assembling of these constituent elements is completed, support plate  28  is placed on battery stack  2 . Support plate  28  is fixed to battery stack  2  by making third parts  53  of the pair of side separators  10  engage with support plate  28 . Bus bar  42  is placed on output terminal  22  of each battery  14 . Voltage detection lines  46  are placed on support plate  28 . Subsequently, conductive wires  80  of voltage detection lines  46  are electrically connected to each bus bar  42 . In addition, each bus bar  42  is electrically connected to output terminals  22 . 
     Cover plate  60  is placed on an upper surface of support plate  28 . The cover plate  60  is a plate-shaped member that is placed on support plate  28  and covers voltage detection lines  46 . Cover plate  60  according to the present exemplary embodiment is a so-called top cover that forms a portion of an outer shell of battery module  1 , specifically, an upper surface of battery module  1 . Cover plate  60  prevents dew condensation water, dust, or the like from being brought into contact with output terminals  22 , valves  24  of batteries  14 , bus bars  42 , voltage detection lines  46 , and the like. 
     Cover plate  60  is made of a resin having an insulating property such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE). Cover plate  60  has insulating cover parts  62  at positions overlapping with external connection terminals  44  in vertical direction Z. In a state where cover plate  60  is placed on support plate  28 , external connection terminals  44  are covered by insulating cover parts  62 . 
     Both ends of cover plate  60  in horizontal direction Y are fixed to support plate  28 . Specifically, support plate  28  of the present exemplary embodiment has a plurality of engaging claws  72  at both ends of support plate  28  in horizontal direction Y in a state where the plurality of engaging claws  72  are disposed at an interval in stacking direction X. Further, cover plate  60  has engagement holes  74  at positions overlapping respective engaging claws  72  as viewed in vertical direction Z in base plate  61  extending along the upper surface of battery stack  2 . When cover plate  60  is placed on support plate  28 , each engaging claw  72  is inserted into each engagement hole  74 . As a result, both ends of cover plate  60  in horizontal direction Y are fixed to support plate  28  by snap-fitting. Support plate  28 , voltage detection lines  46 , and cover plate  60  constitute voltage detection line module  47 . 
       FIG. 2  is a plan view of battery module  1 . In  FIG. 2 , only some of batteries  14  and only some of conductive wires  80  are indicated by broken lines. Illustration of side separators  10 , constraining members  12 , and cover plate  60  are omitted. 
     Voltage detection lines  46  include detection line main body  76  and a plurality of tab terminals  78 . Detection line main body  76  includes stems  76   a  that macroscopically extend in stacking direction X of batteries  14 , and a plurality of branches  76   b  that branch from stems  76   a  toward bus bars  42 . An end of stem  76   a  is connected to connector  48 , and an end of each branch  76   b  extends to a vicinity of each bus bar  42 . 
     Detection line main body  76  includes a plurality of conductive wires  80  associated with each bus bar  42  and insulating films  82  covering the plurality of conductive wires  80 . That is, a set of voltage detection lines  46  of the present exemplary embodiment is a flexible printed circuit (FPC) board. Voltage detection lines  46  constituted by the FPC are placed in an orientation such that the thickness direction is parallel to vertical direction Z and the width direction and the length direction are parallel to an XY plane including stacking direction X and horizontal direction Y, and is placed on support plate  28 . The plurality of conductive wires  80  are made of a conductive material such as copper. Insulating films  82  are made of a resin such as polyimide (PI) or polyethylene naphthalate (PEN). One end of each conductive wire  80  is connected to connector  48 , and the other end extends to the vicinity of corresponding bus bar  42 . Therefore, each conductive wire  80  extends from stem  76   a  to branch  76   b.    
     For example, detection line main body  76  is obtained by bonding a metal foil to a surface of insulating film  82 , etching the metal foil to form a wiring pattern, that is, forming conductive wires  80 , and covering conductive wires  80  with insulating film  82 . Conductive wires  80  can also be formed on insulating film  82  by applying a material constituting conductive wires  80  to insulating film  82  by inkjet or the like. 
     Each tab terminal  78  is a belt-shaped metal member and electrically connects an end of each conductive wire  80  and each bus bar  42 . One end of each tab terminal  78  is placed on bus bar  42 , and is joined to bus bar  42  by, for example, laser welding or ultrasonic joining. The other end of each tab terminal  78  is joined to conductive wire  80  by, for example, soldering. As a result, each bus bar  42  and connector  48  are electrically connected. In addition, some of conductive wires  80  electrically connect external connection terminal  44  and connector  48 . 
     Tab terminal  78  is joined to a substantially central part of bus bar  42  in stacking direction X. Alternatively, tab terminal  78  is joined to a region of bus bar  42  that straddles two batteries  14 . As a result, a displacement amount of the joint between tab terminal  78  and bus bar  42  due to expansion and contraction of each battery  14  can be reduced. Therefore, the connection state between tab terminal  78  and bus bar  42  can be more stably maintained. 
     Detection line main body  76  has first regions  84  extending in stacking direction X of batteries  14  and second regions  86  extending in a direction intersecting stacking direction X. In the present exemplary embodiment, each second region  86  is provided in stem  76   a . Stem  76   a  has a structure in which a plurality of first regions  84  and a plurality of second regions  86  are alternately connected. In stacking direction X, each second region  86  is disposed between two adjacent branches  76   b.    
     Each battery  14  may expand and contract with use. When each battery  14  expands and contracts, bus bar  42  fixed to output terminal  22  of each battery  14  may be displaced in stacking direction X. In this case, the plurality of branches  76   b  fixed to each bus bar  42  can be relatively displaced in stacking direction X. Second region  86  extending in the direction intersecting stacking direction X can be more flexibly deformed following a displacement of branch  76   b  as compared with first region  84  extending in stacking direction X. Specifically, second region  86  is configured to extend in the direction intersecting stacking direction X. Thus, when a load in stacking direction X is applied to detection line main body  76 , second region  86  is subject to bending deformation or shear deformation, thereby allowing a displacement of branch  76   b  in stacking direction X. In order to more effectively follow the displacement of branch  76   b , as illustrated in  FIG. 2 , a structure having a curved outer shape, in other words, an arch-shaped structure is preferably included in second region  86 . In this configuration, when a load in stacking direction X is applied to detection line main body  76 , second region  86  is deformed such that both ends of second region  86  are separated from each other. Therefore, each second region  86  can function as a displacement absorbing part that absorbs a relative displacement of two branches  76   b  adjacently arranged across second region  86  in stacking direction X. Accordingly, the stability of electrical connection between each bus bar  42  and voltage detection lines  46  can be enhanced. 
       FIG. 3  is a cross-sectional view of conductive wire  80  in second region  86 .  FIG. 4(A)  is a cross-sectional view taken along line A-A of  FIG. 3 .  FIG. 4(B)  is a cross-sectional view taken along line B-B of  FIG. 3 .  FIG. 3  illustrates a cross section parallel to the XY plane. Each of conductive wires  80  includes low-resistance parts  88  and high-resistance part  90 . Each of low-resistance parts  88  is a part having a lower electrical resistance value than an electrical resistance value of high-resistance part  90 . High-resistance part  90  is a part having a higher electrical resistance value than an electrical resistance value of low-resistance part  88 . That is, low-resistance part  88  has a relatively low electrical resistance value, and high-resistance part  90  has a relatively high electrical resistance value. 
     Low-resistance part  88  includes a large cross-sectional area having a relatively large cross-sectional area orthogonal to the extending direction of conductive wire  80 , that is, a current flowing direction. On the other hand, high-resistance part  90  includes a small cross-sectional area having a relatively small cross-sectional area orthogonal to the extending direction of conductive wire  80 . In the present exemplary embodiment, low-resistance part  88  has relatively large width A 1  (dimension in XY plane direction), and high-resistance part  90  has relatively small width A 2 . In addition, thickness B 1  (dimension in vertical direction Z) of low-resistance part  88  and thickness B 2  of high-resistance part  90  have a same size. Note that the cross-sectional area of low-resistance part  88  may be made larger than the cross-sectional area of high-resistance part  90  by making thickness B 1  of low-resistance part  88  relatively large and making thickness B 2  of high-resistance part  90  relatively small. High-resistance part  90  is preferentially fused when an overcurrent flows through conductive wire  80 . Accordingly, the overcurrent flowing through conductive wire  80  can be immediately cut off. 
     Insulating film  82  includes high-strength part  92  and low-strength part  94 . High-strength part  92  covers low-resistance part  88 . Low-strength part  94  covers high-resistance part  90 . High-strength part  92  has a relatively high-strength, and low-strength part  94  has a relatively low-strength. The “strength” denotes mechanical strength or heat resistance (heat resistance strength). In the present exemplary embodiment, coating thickness C 1  of high-strength part  92  in the width (XY plane direction) of low-resistance part  88  is larger than coating thickness C 2  of low-strength part  94  in the width of high-resistance part  90 . Since coating thickness C 2  is smaller than coating thickness C 1 , the strength of low-strength part  94  is weaker than the strength of high-strength part  92 . Coating thickness D 1  of high-strength part  92  in the thickness (vertical direction Z) of low-resistance part  88  is equal to coating thickness D 2  of low-strength part  94  in the thickness (vertical direction Z) of high-resistance part  90 . 
     Note that the strength of low-strength part  94  may be made weaker than the strength of high-strength part  92  by making coating thickness D 2  of low-strength part  94  smaller than coating thickness D 1  of high-strength part  92 . The “coating thickness” means a distance from an inner surface of insulating film  82  in contact with conductive wire  80  to an outer surface on the opposite side, and it does not matter whether “coating thickness” is in the thickness, width, or length of each voltage detection line  46 . In addition, when coating thickness D 2  of low-strength part  94  is made smaller than coating thickness D 1  of high-strength part  92 , the rigidity of low-strength part  94  can be made lower than the rigidity of high-strength part  92 . Since low-strength part  94  of the present exemplary embodiment is provided in second region  86  of detection line main body  76 , bending deformation and shearing deformation of second region  86  can be effectively allowed by setting the rigidity of low-strength part  94  to be lower than the rigidity of high-strength part  92 . 
     By covering high-resistance part  90  with low-strength part  94  having a relatively low-strength, when high-resistance part  90  is fused, insulating film  82  can be more reliably cut at the fused portion. As a result, since one end side and the other end side of disconnected conductive wire  80  can be physically separated from each other, the possibility that fused conductive wire  80  conducts again can be reduced. Hereinafter, in detection line main body  76 , a portion constituting high-resistance part  90  and low-strength part  94  is appropriately referred to as fusible portion  96 , and a portion constituting low-resistance part  88  and high-strength part  92  is appropriately referred to as non-fusible portion  98 . 
     High-resistance part  90  of the present exemplary embodiment is disposed in second region  86  of detection line main body  76 . Since high-resistance part  90  has a smaller cross-sectional area than a cross-sectional area of low-resistance part  88 , high-resistance part  90  is more easily deformed than low-resistance part  88 . Therefore, by disposing high-resistance part  90  in second region  86 , second region  86  can be more easily deformed. As a result, the stability of electrical connection between each bus bar  42  and voltage detection lines  46  can be further improved. 
       FIGS. 5(A) and 5(B)  are cross-sectional views of a part of voltage detection line module  47  according to the exemplary embodiment.  FIG. 5  (A) illustrates a state in which fusible portion  96  is connected.  FIG. 5(B)  illustrates a state in which fusible portion  96  is fused. Support plate  28  according to the present exemplary embodiment includes first protrusion  100 . First protrusion  100  protrudes upward in a vertical direction from base plate  33  of support plate  28 , and fusible portion  96  is placed on a tip thereof. Therefore, high-resistance part  90  of conductive wire  80  is supported from below by first protrusion  100 . 
     Since fusible portion  96  is supported by first protrusion  100 , when fusible portion  96  is fused, one end side and the other end side of the disconnected detection line main body  76  fall down by their own weight. At this time, the one end side and the other end side of detection line main body  76  are separated by first protrusion  100 . That is, first protrusion  100  functions as a screen. This makes it possible to more reliably prevent fused conductive wire  80  from being conducted again. 
     Further, support plate  28  has second protrusions  102 . Second protrusions  102  each are arranged to be shifted from first protrusion  100  in the plane direction where support plate  28  extends, that is, in the XY plane direction, and protrude upward in the vertical direction from base plate  33 . Non-fusible portions  98  adjacent to fusible portion  96  are placed on a tip of each second protrusion  102 . Therefore, each low-resistance part  88  adjacent to high-resistance part  90  in conductive wire  80  is supported from below by second protrusion  102 . Support plate  28  of the present exemplary embodiment has a pair of second protrusions  102 , and non-fusible portions  98  on both outer sides of fusible portion  96  are supported from below. 
     By supporting non-fusible portions  98  adjacent to fusible portion  96  by each second protrusion  102 , when fusible portion  96  is fused, it is possible to more reliably cause falling by their own weight of one end side and the other end side of the disconnected detection line main body  76 . As a result, the one end side and the other end side can be more reliably moved away from each other, so that fused conductive wire  80  can be more reliably suppressed from being conducted again. Second protrusion  102  of the present exemplary embodiment has a protrusion height lower than a protrusion height of first protrusion  100 . As a result, it is possible to more reliably cause falling by their own weight of the one end side and the other end side of the separated detection line main body  76 . 
     In addition, cover plate  60  of the present exemplary embodiment has third protrusions  104 . Each of third protrusions  104  protrudes downward in the vertical direction from base plate  61 . A tip of third protrusion  104  pushes non-fusible portion  98  adjacent to fusible portion  96  toward support plate  28 . Therefore, low-resistance part  88  adjacent to high-resistance part  90  of conductive wire  80  is pressed toward support plate  28  by third protrusion  104 . Cover plate  60  of the present exemplary embodiment has a pair of third protrusions  104 , and non-fusible portions  98  on both outer sides of fusible portion  96  are pressed toward support plate  28 . 
     By pushing non-fusible portions  98  adjacent to fusible portion  96  downward in the vertical direction by each third protrusion  104 , when fusible portion  96  is fused, it is possible to more reliably cause falling by their own weight of one end side and the other end side of the disconnected detection line main body  76 . As a result, the one end side and the other end side can be more reliably moved away from each other, so that fused conductive wire  80  can be more reliably suppressed from being conducted again. 
     In addition, second protrusion  102  and third protrusion  104  are arranged to be shifted from each other in the plane direction where support plate  28  extends. A tip of second protrusion  102  protrudes toward cover plate  60  from a tip of third protrusion  104 . Therefore, the tip of third protrusion  104  protrudes toward support plate  28  from the tip of second protrusion  102 . Therefore, second protrusion  102  and third protrusion  104  overlap each other when viewed from a direction intersecting vertical direction Z in which support plate  28  and cover plate  60  are arranged. This makes it possible to suppress scattering of fragments of conductive wire  80  or insulating film  82  when fusible portion  96  is fused. 
     As described above, voltage detection lines  46  according to the present exemplary embodiment include conductive wires  80  and insulating films  82  covering the conductive wires  80 . Conductive wires  80  include low-resistance parts  88  having a predetermined electrical resistance value, and high-resistance parts  90  having a higher electrical resistance value than an electrical resistance value of low-resistance parts  88  and fusing when an overcurrent flows through any of conductive wires  80 . Insulating film  82  includes high-strength part  92  that covers low-resistance part  88  and has a predetermined strength, and low-strength part  94  that covers high-resistance part  90  and has a strength lower than a strength of high-strength part  92 . As a result, when high-resistance part  90  is fused, insulating film  82  can be more reliably cut at the fused portion. As a result, it is possible to keep the one end side and the other end side of the disconnected conductive wire  80  away from each other to suppress reconduction of the fused conductive wire  80  and generation of arc discharge. Therefore, reconduction of the disconnected voltage detection line  46  can be suppressed, and safety of battery module  1  can be enhanced. 
     Voltage detection line  46  has first regions  84  extending in stacking direction X of batteries  14  and second regions  86  extending in a direction intersecting stacking direction X. High-resistance part  90  is disposed in each second region  86 . As a result, when each bus bar  42  is displaced due to expansion or the like of each battery  14 , second region  86  can be more easily displaced. As a result, the stability of the electrical connection between each bus bar  42  and voltage detection lines  46  can be enhanced, and the safety of battery module  1  can be further enhanced. 
     Voltage detection line module  47  of the present exemplary embodiment includes voltage detection lines  46  and support plate  28  that supports voltage detection lines  46 . Support plate  28  includes first protrusions  100  that each support high-resistance part  90  from below. By supporting high-resistance part  90  by first protrusion  100 , when high-resistance part  90  is fused, the one end side and the other end side of the disconnected conductive wire  80  can fall down by their own weight, and the one end side and the other end side of conductive wire  80  can be isolated by first protrusion  100 . This makes it possible to more reliably suppress reconduction of the fused conductive wire  80  and generation of arc discharge. 
     In addition, support plate  28  of the present exemplary embodiment has second protrusions  102  that each supports low-resistance part  88  adjacent to high-resistance part  90  from below. As a result, when high-resistance part  90  is fused, the one end side and the other end side of the disconnected conductive wire  80  can be more reliably separated from each other. Therefore, the reconduction of the fused conductive wire  80  and the generation of the arc discharge can be more reliably suppressed. In addition, second protrusions  102  can suppress scattering of fragments of conductive wire  80  and insulating film  82  over a wide range when fusible portion  96  is fused. 
     Voltage detection line module  47  of the present exemplary embodiment includes cover plate  60  that is placed on support plate  28  and covers voltage detection lines  46 . Cover plate  60  has third protrusions  104  that each push low-resistance part  88  adjacent to high-resistance part  90  toward support plate  28 . As a result, when high-resistance part  90  is fused, the one end side and the other end side of the disconnected conductive wire  80  can be more reliably separated from each other. Therefore, the reconduction of the fused conductive wire  80  and the generation of the arc discharge can be more reliably suppressed. In addition, third protrusions  104  can suppress scattering of fragments of conductive wire  80  and insulating film  82  over a wide range when fusible portion  96  is fused. 
     In addition, in the present exemplary embodiment, second protrusions  102  and third protrusions  104  are arranged to be shifted from each other in the plane direction where support plate  28  extends, and a tip of each second protrusion  102  protrudes toward cover plate  60  from the tip of each third protrusion  104 . As a result, a passage having a labyrinth structure can be formed in a space sandwiched between support plate  28  and cover plate  60 . As a result, it is possible to more reliably suppress scattering of fragments of conductive wire  80  or insulating film  82  generated when fusible portion  96  is fused in a wide range. In the present exemplary embodiment, a pair of second protrusions  102  and a pair of third protrusions  104  are disposed respectively on each side of high-resistance part  90 . Therefore, fragments of conductive wire  80  or insulating film  82  can be more reliably kept in a vicinity of fusible portion  96 . 
     The exemplary embodiments of the present invention have been described in detail above. The above-described exemplary embodiment is merely a specific example for implementing the present invention. The contents of the exemplary embodiment do not limit the technical scope of the present invention, and many design changes such as changes, additions, and deletions of components can be made without departing from the spirit of the invention defined in the claims. Any new exemplary embodiment to which design change is made has an effect of each of the combined exemplary embodiment and modifications. In the above-described exemplary embodiment, with respect to the contents where such design changes are allowable, the contents are emphasized with expressions such as “of the present exemplary embodiment” and “in the present exemplary embodiment”. However, design changes are allowed even with respect to the contents without such expressions. Any combination of constituent elements included in the exemplary embodiments is also effective as an aspect of the present invention. Hatching applied to the cross sections in the drawings does not limit materials of objects to which the hatching is applied. 
     Modified Example 1 
       FIG. 6  is a cross-sectional view of a part of voltage detection line module  47  according to Modification Example 1. Note that illustration of cover plate  60  is omitted in  FIG. 6 . In voltage detection line module  47  according to Modified Example 1, first protrusion  100  has recess  100   a  at a tip of the first protrusion. That is, a part of the tip of first protrusion  100  is recessed in a direction away from fusible portion  96  supported by first protrusion  100 . In a state where fusible portion  96  is supported by first protrusion  100 , a part of the tip of first protrusion  100  and fusible portion  96  are in a non-contact state in recess  100   a . As a result, heat generated in fusible portion  96  is suppressed from being dissipated via first protrusion  100 , and fusible portion  96  can be more reliably fused. 
     Modified Example 2 
       FIG. 7  is a cross-sectional view of a part of voltage detection line module  47  according to Modified Example 2. Note that illustration of cover plate  60  is omitted in  FIG. 7 . In the exemplary embodiment, fusible portion  96  is supported from below by first protrusion  100 , but the present invention is not particularly limited to this configuration. For example, in Modified Example 2, detection line main body  76  is supported only by the pair of second protrusions  102 . Even with such a configuration, the one end side and the other end side of the separated detection line main body  76  can fall down by its own weight to move the one end side and the other end side away from each other. In Modified Example 2, detection line main body  76  has two fusible portions  96 , and non-fusible portion  98  adjacent to each fusible portion  96  is supported by second protrusion  102 . 
     Modified Example 3 
       FIG. 8  is a plan view of a part of battery module  1  according to Modified Example 3. In the exemplary embodiment, second region  86  is provided in stem  76   a  of detection line main body  76 , but the present invention is not particularly limited to this configuration. For example, in Modified Example 3, second region  86  is provided in branch  76   b . Branch  76   b  of Modification  3  has first region  84  extending in the stacking direction X of batteries  14  and second region  86  extending in a direction intersecting the stacking direction X. Even in such a configuration, second region  86  can be displaced following a displacement of bus bar  42  in stacking direction X. Therefore, the stability of electrical connection between each bus bar  42  and voltage detection line  46  can be enhanced. When second region  86  is provided in branch  76   b , first region  84  is not necessarily provided in branch  76   b . For example, branch  76   b  may have only a portion protruding linearly from stem  76   a  toward opening  40 , and this portion may constitute second region  86 . 
     However, in order to displace second region  86  following the displacement of bus bar  42  in stacking direction X, it is desirable that second region  86  provided in branch  76   b  be smoothly displaced in stacking direction X with respect to stem  76   a  of detection line main body  76 . On the other hand, as illustrated in  FIG. 8 , by adopting a structure in which first region  84  is provided in branch  76   b  and second region  86  having a curved outer shape is provided in the middle of first region  84 , second region  86  provided in branch  76   b  can be smoothly displaced with respect to stem  76   a . Therefore, second region  86  can effectively follow the displacement of bus bar  42  in stacking direction X. In addition, second region  86  may be provided in both stem  76   a  and branch  76   b.    
     OTHER EXAMPLES 
     In the exemplary embodiment, second protrusion  102  and third protrusion  104  are arranged to be shifted from each other, but the tip of second protrusion  102  and the tip of third protrusion  104  may be opposed to each other, and detection line main body  76  may be interposed between the two tips. 
     When an orientation of battery module  1  is determined such that cover plate  60  is positioned downward in a vertical direction and support plate  28  is positioned upward in the vertical direction, cover plate  60  can function as a support plate for voltage detection line  46 , and support plate  28  can function as a cover plate. In this case, by providing first protrusion  100  on cover plate  60 , fusible portion  96  can be supported from below by first protrusion  100 . In addition, third protrusion  104  provided on cover plate  60  can function as second protrusion  102 , and second protrusion  102  provided on support plate  28  can function as third protrusion  104 . 
     The number of batteries  14  that battery module  1  includes is not particularly limited. A structure of each part of battery module  1  including a fastening structure of end plates  4  and constraining members  12  is not limited. Batteries  14  may have a cylindrical shape or the like. 
     The exemplary embodiments may be specified by the items described below. 
     [Item 1] 
     A battery module including: batteries  14 ; and voltage detection lines  46  having conductive wires  80  and insulating films  82 , and configured to detect voltage of each of batteries  14 . Each of conductive wires  80  includes low-resistance part  88  having a predetermined electrical resistance value, and high-resistance part  90  having a higher electrical resistance value than an electrical resistance value of low-resistance part  88  and fusing when an overcurrent flows through conductive wire  80 . Each of insulating films  82  includes high-strength part  92  covering low-resistance part  88  and having a predetermined strength, and low-strength part  94  covering high-resistance part  90  and having a strength lower than a strength of high-strength part  92 . 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               28  support plate 
               46  voltage detection line 
               47  voltage detection line module 
               60  cover plate 
               80  conductive wire 
               82  insulating film 
               84  first region 
               86  second region 
               88  low-resistance part 
               90  high-resistance part 
               92  high-strength part 
               94  low-strength part 
               100  first protrusion 
               102  second protrusion 
               104  third protrusion