Patent Publication Number: US-2011064993-A1

Title: Battery array with reliable low-resistance connections

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery array having a plurality of battery cells connected by metal plates, and in particular to a battery array optimally suited for use as a power source for a motor that drives an electric-powered vehicle such as a hybrid car, fuel-cell vehicle, electric automobile (electric vehicle EV), or electric motor-bike. 
     2. Description of the Related Art 
     A battery array can connect many battery cells in series to increase output voltage, and in parallel to increase charging current. Accordingly, a high power, high output battery array used as a power source for a motor that drives a vehicle has a plurality of battery cells connected in series to increase output voltage. Since a battery array used in this type of application is charged and discharged with high currents, the plurality of battery cells are connected by low-resistance metal plates. (Refer to Japanese Laid-Open Patent Publication No. H05 343105 (1993).) 
     In the battery array of JP H05 343105A, both ends of the metal plates are attached to battery cell electrode terminals via nuts. Specifically, electrode terminals are passed through through-holes in the metal plates, and nuts are threaded onto the electrode terminal bolts to attach the metal plates to the electrode terminals. In a battery array with this structure and battery cells having positive and negative electrode terminals made of different type (dissimilar) metals, the contact surfaces of the metal plates and the positive and negative electrode terminals cannot be the same metal type. For example, for lithium ion batteries having dissimilar metal positive and negative electrode terminals that are aluminum and copper connected by copper metal plates, dissimilar metal contact surfaces are formed at the aluminum electrode terminals. A battery array having metal plate and electrode terminal dissimilar metal contact surfaces has the drawback that galvanic corrosion can occur at the dissimilar metal contact surfaces, and stable low contact resistance connections cannot be maintained over a long period. Galvanic corrosion results from current flow between the dissimilar metals, and that current causes metal to electrically dissociate and corrode. 
     The present invention was developed with the object of correcting the drawback described above. Thus, it is a primary object of the present invention to provide a battery array that can connect battery cell electrode terminals with metal plates in a manner that maintains stable low resistance connections over a long period while connecting different type metals at the positive and negative electrode terminals of the battery cells. 
     SUMMARY OF THE INVENTION 
     The battery array of the present invention is provided with a plurality of battery cells  1 ,  31  having positive and negative electrode terminals  2 ,  32  that are different metals, and the positive and negative electrode terminals  2 ,  32  of each battery cell  1 ,  31  are connected by metal plates  3 ,  23 ,  33 ,  43 ,  53 . Each metal plate  3 ,  23 ,  33 ,  43 ,  53  is clad material having a first metal plate  3 A,  23 A,  33 A,  43 A,  53 A that connects to one electrode terminal  2 ,  32  of a battery cell  1 ,  31  and a second metal plate  3 B,  23 B,  33 B,  43 B,  53 B that connects to a different electrode terminal  2 ,  32 . The clad material first metal plate  3 A,  23 A,  33 A,  43 A,  53 A and second metal plate  3 B,  23 B,  33 B,  43 B,  53 B are joined at a junction between positive and negative electrode terminal  2 ,  32  connecting regions. 
     The battery array described above has the characteristic that it can connect battery cell electrode terminals in series or parallel with metal plates in a manner that maintains stable low resistance connections over a long period while connecting different type metals at the positive and negative electrode terminals of the battery cells. This is because the first metal plate that connects to one of the electrode terminals of a battery cell and the second metal plate that connects to a different electrode terminal are clad material joined at a junction between the positive and negative electrode terminal connecting regions. Clad material is not simply a laminate of different type metals, but rather is strongly joined together at the junction interface where the different metals are in an alloyed state. Accordingly, in a metal plate made of clad material, there is no ingress of water or air to the junction between the different metals, and galvanic corrosion does not occur at the junction interface. Therefore, metal plates that are dissimilar metal clad material joined at a junction between positive and negative electrode terminals have the characteristic that each electrode terminal can be connected with the same metal type to prevent galvanic corrosion and enable stable electrical connection over a long period. 
     In the battery array of the present invention, the battery cells  1  can be rectangular battery cells, and metal plates  3 ,  23 ,  43  can connect the positive and negative electrode terminals  2  of adjacent battery cells  1  to connect the battery cells  1  in series. Each metal plate  3 ,  23 ,  43  has through-holes  4  to insert battery cell  1  positive and negative electrode terminals  2 , electrode terminals  2  can be inserted in the through-holes  4 , and the electrode terminals  2  and metal plate  3 ,  23 ,  43  can be welded for connection. Further, at least one of the through-holes  4  can be an elongated hole  4 A to allow the inserted electrode terminals  2  to move in the direction of battery cell  1  stacking. Welding rings  5 , can be provided on the surface of the metal plates  3 ,  23 ,  43  to close-off open regions of the elongated holes  4 A, and the electrode terminals  2  can be welded to the metal plates  3 ,  23 ,  43  via the welding rings  5 ,  25 . 
     The battery array described above has the characteristic that the clad material metal plates can be stably and reliably weld-attached to the electrode terminals while absorbing dimensional error in the battery cells and metal plates via the elongated holes. This is because error in the dimensions of the battery cells and the metal plates can be absorbed by electrode terminal insertion in the elongated holes. In addition, gaps formed by insertion of the electrode terminals in the elongated holes can be closed-off by welding rings, and electrical connection can be made without gaps by welding the welding rings. 
     In the battery array of the present invention, a welding ring  5 ,  25  can be either a crimping ring  2 X formed by pressure-deformation to widen the upper end of an electrode terminal  2  inserted in an elongated hole  4 A, or a metal ring  6  that is a sheet-metal piece separate from the electrode terminal  2  and provided with a center hole  6 A for electrode terminal  2  insertion. In this battery array, welding rings formed as crimping rings by widening the ends of the electrode terminals can be weld-attached to the metal plates for reliable connection. Further, with welding rings that are metal rings separate from the electrode terminals, the metal rings can be weld-attached to the electrode terminals and metal plates for reliable electrical connection without putting a load on the electrode terminals. 
     In the battery array of the present invention, the positive and negative electrode terminals  2 ,  32  of the battery cells  1 ,  31  can be aluminum and copper, and the metal plates  3 ,  23 ,  33 ,  43 ,  53  can be clad material with a junction between first metal plates  3 A,  23 A,  33 A,  43 A,  53 A and second metal plates  3 B,  23 B,  33 B,  43 B,  53 B that are aluminum and copper. However, in this patent application, the term aluminum is used in the wider sense to include aluminum alloys, and the term copper is used in the wider sense to include copper alloys. 
     In the battery array described above, since the electrode terminals are aluminum and copper and the metal plates are also aluminum and copper, the metal plates can be electrically connected to electrode terminals that are the same metal type in a stable manner that does not generate galvanic corrosion. 
     In the battery array of the present invention, the metal plates  3 ,  23 ,  33 ,  43 ,  53  can be first metal plates  3 A,  23 A,  33 A,  43 A,  53 A and second metal plates  3 B,  23 B,  33 B,  43 B,  53 B joined at junctions with step-shaped interfaces. This battery array has the characteristic that since the junction interfaces are step-shaped, the first metal plates and second metal plates can be stably and reliably joined in a robust manner. 
     In the battery array of the present invention, the battery cells  1 ,  31  can be lithium ion batteries. This battery array has the characteristic that since the battery cells are lithium ion batteries, it can increase charging and discharging capacities while being light-weight. 
     The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an oblique view of a battery array for an embodiment of the present invention; 
         FIG. 2  is an exploded oblique view of the battery array shown in  FIG. 1 ; 
         FIG. 3  is an exploded oblique view showing the stacking structure of the battery cells and insulating spacers of the battery array shown in  FIG. 1 ; 
         FIG. 4  is a vertical cross-section of a battery cell; 
         FIG. 5  is an enlarged oblique view showing connection of the electrode terminals and metal plates of the battery array shown in  FIG. 1 ; 
         FIG. 6  is an enlarged oblique view showing an assembly step for connecting adjacent electrode terminals with metal plates; 
         FIG. 7  is an enlarged oblique view showing an assembly step for connecting adjacent electrode terminals with metal plates; 
         FIG. 8  is an enlarged oblique view of a metal plate; 
         FIG. 9  is an enlarged oblique view of another example of a metal plate; 
         FIG. 10  is an exploded oblique view of a battery array for another embodiment of the of the present invention; 
         FIG. 11  is an enlarged oblique view showing an assembly step for connecting electrode terminals and metal plates of the battery array shown in  FIG. 10 ; 
         FIG. 12  is an enlarged oblique view showing an assembly step for connecting electrode terminals and metal plates of the battery array shown in  FIG. 10 ; 
         FIG. 13  is an enlarged oblique view showing an assembly step for connecting electrode terminals and metal plates of the battery array shown in  FIG. 10 ; 
         FIG. 14  is an exploded oblique view of a battery array for another embodiment of the of the present invention; 
         FIG. 15  is an enlarged oblique view showing connection of the electrode terminals and metal plates of the battery array shown in  FIG. 14 ; 
         FIG. 16  is an enlarged oblique view showing another example of a metal plate; 
         FIG. 17  is an enlarged oblique view showing connection of the electrode terminals and metal plates of a battery array for another embodiment of the of the present invention; and 
         FIG. 18  is an oblique view of a metal plate shown in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The following describes embodiments of the present invention based on the figures. 
     The battery array of the present invention is primarily installed on-board an electric-powered vehicle such as a hybrid car or electric automobile (electric vehicle EV), and is used as a power source to supply power to a driving motor to drive the vehicle. 
     The battery array shown in  FIGS. 1-3  has a plurality of battery cells  1  stacked and held together in a manner insulating individual battery cells  1 . The battery cells  1  are rectangular battery cells. Further, the rectangular battery cells  1  are lithium ion rechargeable batteries. However, the battery array of the present invention is not limited to battery cells that are rectangular, and also is not limited to lithium ion rechargeable batteries. Any batteries that can be charged, such as nickel hydride batteries, can also be used as the battery cells. As shown in  FIG. 4 , a rectangular battery cell has an electrode unit  10 , which is a stack of positive and negative electrode plates, held in an external case  11  filled with electrolyte and the opening of the external case  11  closed-off in an air-tight manner by a sealing plate  12 . The external case  11  of the figure has a rectangular cylindrical-shape with a closed bottom and the opening at the top closed-off in an air-tight manner by the sealing plate  12 . 
     The external case  11  is deep drawn formed metal such as aluminum, and has a conducting surface. The stacked battery cells  1  are formed in thin rectangular-shapes. The sealing plates  12  are fabricated from the same metal as the external case  11  such as aluminum sheet-metal. Each sealing plate  12  has positive and negative electrode terminals  2  mounted on its end regions via insulating material  13 . The positive and negative electrode terminals  2  are connected to the internal positive and negative electrode plates. In a lithium ion rechargeable battery, the external case  11  is not connected to an electrode. Since the external case  11  is connected to the internal electrode plates via electrolyte, it attains an intermediate potential between that of the positive and negative electrode plates. However, one of the battery cell electrode terminals can be connected to the external case via a lead-wire as well. In this battery cell, the electrode terminal connected to the external case can be mounted on the sealing plate without insulation. 
     The battery array has a plurality of battery cells  1  stacked to form a rectangular solid block configuration. The battery cells  1  in the figures are stacked in a block configuration in a manner that aligns the electrode terminal  2  surfaces, which are the sealing plate  12  surfaces, in the same plane. The battery array of  FIGS. 1 and 2  has electrode terminals  2  disposed on the upper surface of the block. The battery cells  1 , which have positive and negative electrode terminals  2  at the end regions of the sealing plates  12 , are flipped left-to-right during stacking to reverse the polarity of adjacent electrode terminals  2 . As shown in the figures, this battery array has adjacent electrode terminals  2  on both sides of the block connected by metal plates  3  to connect the battery cells  1  in series. The end regions of each metal plate  3  are connected to a positive and negative electrode terminal  2  to connect the battery cells  1  in series. Although the battery array of the figures connects the battery cells  1  in series to increase output voltage, the battery array of the present invention can also connect battery cells in series and parallel to increase output voltage and output current. 
     As shown in  FIGS. 5-7 , the electrode terminals  2  are mounted on the sealing plates  12  via insulating material  13  and have cylindrical ends. Crimping rings  2 X can be established by pressure-deformation to widen the ends of cylindrical electrode terminals  2 . The electrode terminal  2  of  FIG. 7  has a circular cylindrical end and is pressure-deformed to establish a crimping ring  2 X. However, the battery array of the present invention does not necessarily require pressure-deformation of the electrode terminals to establish crimping rings. This is because metal plates can be weld-attached to the upper ends of the electrode terminals. These electrode terminals can be circular cylindrical-shaped, polygonal cylindrical-shaped, or they can have ring-shaped projections established around the outsides of the upper ends to weld-attach and connect metal plates to the upper ends. 
     The positive and negative electrode terminals  2  are not the same type of metal, but rather are different (dissimilar) metals. A lithium ion battery has an aluminum positive electrode  2 A and a copper negative electrode  2 B. The metal plates  3  have metals connected at either end that are the same as the dissimilar metal electrode terminals  2 . A metal plate  3  that connects battery cells  1  with aluminum and copper electrode terminals  2  is clad material with an aluminum first metal plate  3 A and a copper second metal plate  3 B. A metal plate  3  is clad material with a junction between the first metal plate  3 A and the second metal plate  3 B at the boundary between electrode terminal  2  connecting regions. This metal plate  3  is connected to battery cell  1  positive and negative electrode terminals  2  with the first metal plate  3 A in contact with an aluminum positive electrode  2 A and the second metal plate  3 B in contact with a copper negative electrode  2 B. The first metal plate  3 A aluminum does not contact the copper negative electrode  2 B, and the second metal plate  3 B copper does not contact the aluminum positive electrode  2 A. 
     As shown in  FIG. 8 , a clad material metal plate  3  has a junction at the boundary between the first metal plate  3 A and the second metal plate  3 B with a step-shape. Or, as shown in  FIG. 9 , the clad material metal plate  23  has a junction at the boundary between the first metal plate  23 A and the second metal plate  23 B that is an inclined surface tightly connecting the metal plates. The metal plates  3 ,  23  of  FIGS. 8 and 9  have first metal plate  3 A,  23 A aluminum that is thicker than second metal plate  3 B,  23 B copper, and a step is established on the upper surfaces of the clad material. 
     The metal plates  3  of the figures are provided with through-holes  4  at either end for electrode terminal  2  insertion. Electrode terminals  2  of adjacently disposed battery cells  1  are connected by inserting the electrode terminals  2  through the two through-holes  4  established at the ends of a metal plate  3 . Here, an electrode terminal  2  is inserted in a through-hole  4 . With the electrode terminal  2  inserted in the through-hole  4 , a laser is shined on the boundary between the outside surface of the electrode terminal  2  and the inside surface of the through-hole  4  to laser-weld and attach the electrode terminal  2  and the metal plate  3 . To stably and reliably laser-weld a metal plate  3  to an electrode terminal  2 , it is important to contact the outside surface of the electrode terminal  2  to the inside surface of the through-hole  4  without gaps. This is because gaps between a through-hole  4  and electrode terminal  2  impede stable connection via laser-welding. Accordingly, the through-holes  4  have an inside diameter that allows tight contact of the inside surface with inserted electrode terminals  2 , and specifically, the inside diameter of the through-holes  4  is essentially the same size as the outside diameter of the electrode terminals  2 . Therefore, it is necessary to make the inside diameter of the through-holes  4  a size that allows no play between the inserted electrode terminals  2 . 
     To insert two electrode terminals without play in the two through-holes, it is necessary to make the distance between the two electrode terminals precisely equal to the distance between the two through-holes. However, there is error in the dimensions of a battery cell  1 , and in a configuration that sandwiches insulating spacers  15  between battery cells  1 , there is also error in the dimensions of the insulating spacers  15 . Consequently, it is difficult to establish a uniform distance between two adjacent electrode terminals  2 . To enable reliable laser-welding of the electrode terminals  2  even when the distance between electrode terminals  2  varies due to dimensional errors, the metal plates  3  of the figures have one of the through-holes  4  made as an elongated hole  4 A. An elongated hole  4 A has a long narrow shape that extends in a direction allowing the distance between through-holes  4  to vary, which is in the lengthwise direction of the metal plate  3 . This allows two electrode terminals  2  with variable distance between the electrode terminals  2  to be inserted in the metal plate  3 . 
     As shown in  FIG. 6 , when an electrode terminal  2  is inserted in an elongated hole  4 A, gaps are established between the electrode terminal  2  and the inside surface of the elongated hole  4 A. A welding ring  5  is provided to close-off these gaps. As shown in  FIG. 7 , the welding ring  5 , which is on the upper surface of the metal plate  3 , closes-off gaps between the electrode terminal  2  and the elongated hole  4 A allowing reliable laser-welding of the metal plate  3  to the electrode terminals  2 . 
     In the battery array of the figures, the through-hole  4  for negative electrode terminal  2 B insertion is formed as an elongated hole  4 A. Specifically, a circular through-hole  4  is established in the aluminum first metal plate  3 A, and an elongated hole  4 A is established in the copper second metal plate  3 B. In the battery array of  FIG. 7 , the copper negative electrode  2 B is inserted through an elongated hole  4 A and the end of the electrode terminal  2  is widened to establish a welding ring  5  that is a crimping ring  2 X. The circular cylindrical end of this electrode terminal  2  is pressure-deformed to widen it in a ring-shape to establish the welding ring  5 . The welding ring  5 , which is a crimping ring  2 X, makes contact with the surface of the copper second metal plate  3 B. As shown in  FIG. 5 , the copper negative electrode terminal  2 B is reliably connected to the copper second metal plate  3 B by laser-welding the perimeter of the crimping ring  2 X. 
     The electrode terminals  2  and metal plates  3  of the battery array described above are connected by the following steps. 
     (1) As shown in  FIG. 6 , electrode terminals  2  of adjacent battery cells  1  are inserted in the through-holes  4  at either end of a metal plate  3 . A circular electrode terminal  2  is inserted through the circular through-hole  4  and no gaps are formed between the electrode terminal  2  and the through-hole  4 . A circular electrode terminal  2  is also inserted through the elongated hole  4 A and gaps are formed between the electrode terminal  2  and the elongated hole  4 A. 
     (2) As shown in  FIG. 7 , the electrode terminal  2  inserted in the elongated hole  4 A is pressure-deformed and widened to form a crimping ring  2 X on the upper surface of the electrode terminal  2 . The outline of the crimping ring  2 X is larger than the elongated hole  4 A and closes-off the gaps between the elongated hole  4 A and the electrode terminal  2 . 
     (3) As shown in  FIG. 5 , laser energy is focused along the circular perimeter of the circular through-hole  4  to laser-weld the electrode terminal  2  to the metal plate  3 . In addition, laser energy is focused along the perimeter edge of the crimping ring  2 X, which is the welding ring  5 , at the elongated hole  4 A to laser-weld the perimeter edge of the welding ring  5  to the metal plate  3 . 
     Although the metal plates  3  described above have one of the through-holes  4  formed as an elongated hole  4 A, the battery array of the present invention can also have both through-holes formed as elongated holes. In this battery array, crimping rings are formed by widening the ends of both electrode terminals and perimeter edges of the crimping rings are laser-welded to the metal plates for connection. 
     Further, the battery array of  FIGS. 10-13  is provided with welding rings  25  that are sheet-metal metal rings  6 , which are separate parts from the electrode terminals  2 . Since the battery array of the figures has a copper negative electrode  2 B inserted in the elongated hole  4 A, the metal ring  6  is made from copper the same as the negative electrode  2 B. Specifically, the metal ring  6  is made from sheet-metal that is the same material as the electrode terminal  2 . In addition, each metal ring  6  is provided with a circular center hole  6 A for electrode terminal  2  insertion. The inside diameter of the center hole  6 A is approximately equal to the outside diameter of the electrode terminal  2  to allow insertion of the electrode terminal  2  without forming gaps. The outside diameter of a metal ring  6  is a size that enables the elongated hole  4 A to be closed-off. 
     The electrode terminals  2  and metal plates  3  of the battery array described above are connected by the following steps. 
     (1) As shown in  FIG. 11 , electrode terminals  2  of adjacent battery cells  1  are inserted in the through-holes  4  at either end of a metal plate  3 . A circular electrode terminal  2  is inserted through the circular through-hole  4  and no gaps are formed between the electrode terminal  2  and the through-hole  4 . A circular electrode terminal  2  is also inserted through the elongated hole  4 A and gaps are formed between the electrode terminal  2  and the elongated hole  4 A. 
     (2) As shown in  FIG. 12 , a metal ring  6 , which is the welding ring  25 , is placed on top of the metal plate  3 , and the electrode terminal  2  inserted through the elongated hole  4 A is inserted through the charge  6 A of the metal ring  6 . Since the outline of the metal ring  6  is larger than the elongated hole  4 A, gaps between the elongated hole  4 A and the electrode terminal  2  are closed-off. 
     (3) As shown in  FIG. 13 , laser energy is focused along the circular perimeter of the circular through-hole  4  to laser-weld the electrode terminal  2  to the metal plate  3 . In addition, at the elongated hole  4 A, laser energy is focused along the inside edge of the center hole  6 A and along the outside perimeter edge of the metal ring  6 , which is the welding ring  25 , to laser-weld the inside edge of the center hole  6 A to the electrode terminal  2  and laser-weld the outside perimeter edge to the metal plate  3 . 
     Although the metal plates  3  described above have one of the through-holes  4  formed as an elongated hole  4 A, the battery array of the present invention can also have both through-holes formed as elongated holes. In this battery array, both electrode terminals can be inserted through the center holes of metal rings, and the inside and outside perimeter edges of the metal rings can be laser-welded to connect the metal rings to both the electrode terminals and the metal plate. 
     Further, the battery array of  FIGS. 14 and 15  has battery cells  31  provided with threaded stud electrode terminals  32  that are inserted through metal plate  33  through-holes  34 , and nuts  7  are threaded on those studs to connect the electrode terminals  32  to the metal plate  33 . In this battery array, the nuts  7  are made of the same metal as the electrode terminals  32 . In a battery array with battery cells  31  having aluminum positive electrodes  32 A and copper negative electrodes  32 B, the metal plates  33  are clad material with aluminum first metal plates  33 A and copper second metal plates  33 B. In addition, by making the nuts  7 A that screw onto the positive electrodes  32 A aluminum and making the nuts  7 B that screw onto negative electrodes  32 B copper, galvanic corrosion can be prevented. The metal plate  33  shown in the figures has both through-holes  34  made as elongated holes  34 A. 
     Further, the metal plate  43  of  FIG. 16  has both ends, which connect to electrode terminals  2 , formed in the shape of terminal connectors. This metal plate  43  has a first metal plate  43 A and a second metal plate  43 B formed in ring-shapes with through-holes  43 A at the center regions. The metal plate  43  is clad material with a junction formed between projections  43   a ,  43   b  from the ring-shaped first metal plate  43 A and second metal plate  43 B. In the same manner as the previously described embodiments, this metal plate  43  is clad material with an aluminum first metal plate  43 A and a copper second metal plate  43 B. The metal plate  43  of the figure has a junction interface between the first metal plate  43 A and the second metal plate  43 B that has a step-shape. In addition, this metal plate  43  has one through-hole  4  that is an elongated hole  4 A and another through-hole  4  that has a circular-shape. Similar to the previously described metal plates, this metal plate  43  is connected to electrode terminals by laser-welding the electrode terminals inserted through the through-holes, or by screwing nuts onto threaded stud electrode terminals inserted through the through-holes. 
     Further, the battery array of  FIG. 17  directly connects a first metal plate  53 A to one electrode terminal  32 , and connects a second metal plate  53 B to another electrode terminal  32  through a lead-wire  55  and terminal connector  56 . As shown in  FIG. 18 , this metal plate  53  has a first metal plate  53 A formed in a ring-shape with a through-hole  54  at its center region, and is clad material with a junction formed between a projection  53   a  from the ring-shaped first metal plate  53 A and a second metal plate  53 B. The second metal plate  53 B does not connect directly to an electrode terminal  32 , but rather connects to an electrode terminal  32  through a lead-wire  55  and a terminal connector  56 . The end of the second metal plate  53 B is provided with a crimped region  53   x  that joins to one end of the lead-wire  55 . The second metal plate  53 B shown in the figures is provided with projecting pieces  53   c  that protrude from both sides, and has a crimped region  53   x  established by curling the pair of projecting pieces  53   c  in cylindrical-shapes to crimp onto the lead-wire  55  core  55 A. With the lead-wire  55  core  55 A inserted in the cylindrical-shaped crimped region  53   x  on the second metal plate  53 B, the crimped region  53   x  is compressed and deformed (crimped) to join the wire core  55 A to the crimped region  53   x . In addition, a terminal connector  56  is connected to the other end of the lead-wire  55 . The terminal connector  56  has a ring section  56 A with a through-hole  56   a  at its center region, and a crimped region  56 C is provided on a projection  56 B from the ring section  56 A to connect the core  55 A of the lead-wire  55  by crimping. 
     The metal plate  53  shown in  FIGS. 17 and 18  is also clad material with an aluminum first metal plate  53 A and a copper second metal plate  53 B. Further, the core  55 A of the lead-wire  55  connected to the second metal plate  53 B and the terminal connector  56  are the same type metal as the second metal plate  53 B. Specifically, the core  55 A of the lead-wire  55  is copper wire and the terminal connector  56  is copper plate. The battery array of  FIG. 17  has battery cells  31  provided with threaded stud electrode terminals  32 , the positive electrode  32 A and negative electrode  32 B, which are the electrode terminals  32  of adjacent battery cells  31 , are inserted through the through-hole  54  in the metal plate  53  and the through-hole  56   a  in the terminal connector  56 , and nuts  7  are screwed onto the electrode terminals  32  to connect the metal plate  53  and the terminal connector  56  to the electrode terminals  32 . In this battery array, since the battery cell  1  positive electrodes  32 A are aluminum and the negative electrodes  32 B are copper, the metal plates  53  are clad material with aluminum first metal plates  53 A and copper second metal plates  53 B, the cores  55 A of the lead-wires  55  are copper wire, and the terminal connectors  56  are copper plates. In addition, the nuts  7 A screwed onto positive electrodes  32 A are aluminum and the nuts  7 B screwed onto negative electrodes  32 B are copper to prevent galvanic corrosion. 
     As shown in  FIG. 3 , battery cells  1  that have metal external cases  11  have insulating spacers  15  sandwiched between adjacent battery cells  1  to electrically insulate the battery cells  1 . In addition to insulating adjacent battery cell  1  external cases  11 , the insulating spacers  15  establish cooling gaps  16  between the battery cells  1 . Accordingly, the insulating spacers  15  are fabricated by molding insulating material such as plastic. An insulating spacer  15  has ventilating grooves  15 A formed on both sides that establish the cooling gaps  16  between the insulating spacer  15  and the battery cells  1 . An insulating spacer  15  is provided with ventilating grooves  15 A extending in the horizontal direction, which is in a direction that joins the two ends of a battery cell  1 . Air is passed in a horizontal direction through the cooling gaps  16  established by the insulating spacers  15  to cool the battery cells  1 . 
     The battery cells  1  stacked with intervening insulating spacers  15  are held in fixed positions by fastening components  17  (see  FIGS. 1 and 2 ). The fastening components  17  are made up of a pair of endplates  18  disposed at both end planes of the battery cell  1  stack, and metal bands  19  with ends connected to the endplates  18  to hold the stacked battery cells  1  in a compressed state. 
     It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the spirit and scope of the invention as defined in the appended claims. The present application is based on Application No. 2009-210045 filed in Japan on Sep. 11, 2009, the content of which is incorporated herein by reference.