Patent Publication Number: US-2010124693-A1

Title: Secondary battery pack

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-293804, filed Nov. 17, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a secondary battery pack with a plurality of cells and a board for battery management. 
     2. Description of the Related Art 
     In general, a secondary battery pack is constructed so that a plurality of secondary batteries, e.g., square secondary batteries, are contained side by side in a housing. In each secondary battery, positive and negative electrode terminals are arranged flush with and spaced apart from each other. In the secondary battery pack of this type, the respective charging voltages of the individual secondary batteries (cells) need to be detected and managed. 
     In a secondary battery pack disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2006-139919, for example, a positive electrode terminal of one of secondary batteries, e.g., two adjacent batteries, in a housing and a negative electrode terminal of the other battery are connected by a bus-bar. One end of a lead wire is connected to this bus-bar, and the other end is led around and connected to a detection circuit or the like located in a predetermined position on the housing. 
     According to the secondary battery pack constructed in this manner, however, led-around portions of a plurality of lead wires to be confined to a given space first need to be bundled and trued up. Secondly, the lead wires need to be connected to bus-bars and the detection circuit, so that the connection operation is complicated, and wrong connection may be caused. Thirdly, if the lead wires are increased in number with the increase of the number of secondary batteries to be accommodated, a sufficient space is expected to be secured for the positive and negative electrode terminals of the batteries to avoid wire breakage by bending, so that the housing is inevitably enlarged. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of these circumstances, and its object is to provide a secondary battery pack configured so that operations for connecting secondary batteries and detection and control systems are simplified to prevent wrong connection and improve safety. 
     According to an aspect of the invention, there is provided a secondary battery pack comprising a plurality of cells each comprising a positive electrode terminal and a negative electrode terminal and arranged side by side; a battery management circuit board configured to monitor a voltage of the cells; and a plurality of bus-bars electrically connecting the electrode terminals of the adjacent cells, each of the bus-bars including first connecting portions connected to the electrode terminals and a second connecting portion connected directly to the battery management circuit board. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a perspective view showing a secondary battery pack according to a first embodiment of the invention; 
         FIG. 2  is an enlarged perspective view showing a junction between a board and a connecting piece of the secondary battery pack; 
         FIG. 3  is an exploded perspective view of the secondary battery pack; 
         FIG. 4  is an exploded perspective view of the battery pack; 
         FIG. 5  is a sectional view of the battery pack taken along line V-V of  FIG. 1 ; 
         FIG. 6  is a perspective view showing a secondary battery pack according to a second embodiment of the invention; 
         FIG. 7  is an exploded perspective view of the secondary battery pack according to the second embodiment; 
         FIG. 8  is an enlarged exploded perspective view showing a junction between a board and a connecting piece of the battery pack of the second embodiment; 
         FIG. 9  is a plan view showing the junction; and 
         FIG. 10  is an enlarged exploded perspective view showing a junction between a board and a connecting piece of a secondary battery pack according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Secondary battery packs according to embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view showing an outline of a secondary battery pack according to a first embodiment,  FIG. 2  is an enlarged perspective view showing a junction between a board and a connecting piece of the battery pack, and  FIG. 3  is an exploded perspective view showing a body and the board of the battery pack.  FIG. 4  is an exploded perspective view of the battery pack body, and  FIG. 5  is a sectional view of the battery pack taken along line V-V of  FIG. 1 . 
     As shown in  FIGS. 1 and 3  to  5 , the secondary battery pack comprises a battery pack body  12  and a battery management circuit board  14 . The battery pack body  12  comprises a plurality of (e.g., six) secondary batteries (cells)  10 , a housing  16  in the form of a rectangular box for accommodating the six secondary batteries  10 , and bus-bars  18  that electrically connect electrode terminals of the adjacent batteries. The circuit board  14  is connected to the batteries  10  and monitors the voltage and temperature of each battery. 
     As shown in  FIGS. 4 and 5 , each secondary battery  10  is a non-aqueous electrolyte secondary battery, such as a lithium-ion battery. For example, each battery  10  comprises a flat rectangular box-shaped container  20  formed of aluminum or aluminum alloy, an electrode body and an electrolyte (not shown) contained in the container, and positive and negative electrode terminals  21  and  22  each having, for example, a stepped rectangular shape. The electrode terminals  21  and  22  are arranged on one end face of the container and spaced apart from each other. These terminals are formed of, for example, aluminum or aluminum alloy. 
     As shown in  FIGS. 1 and 3  to  5 , the housing  16  comprises a bottom wall  24  in the form of a rectangular plate, an open-bottomed cover body  26  in the form of a rectangular box, and a lid body  28  in the form of a rectangular plate. These members are formed of an insulating material such as a synthetic resin. The bottom wall  24  is formed with engagement grooves  25  as many as the secondary batteries  10 , six in number in this case. Each engagement groove  25  has an elongated rectangular shape corresponding to the cross-sectional shape of the container  20  of each secondary battery  10  and extends transversely relative to the bottom wall  24 . Further, the engagement grooves  25  are arranged at regular intervals along the length of the bottom wall  24 . 
     Six engagement holes  27  as many as the secondary batteries  10  are formed in a ceiling wall  26   a  of the cover body  26 . Each engagement hole  27  has an elongated rectangular shape corresponding to the cross-sectional shape of the container  20  of each secondary battery  10  and extends transversely relative to the ceiling wall  26   a . The engagement holes  27  are arranged at regular intervals along the length of the ceiling wall  26   a . When the cover body  26  is overlaid on the bottom wall  24 , the engagement holes  27  are opposed individually to the engagement grooves  25  of the bottom wall  24 . Partition ribs  30  are formed integrally on the inner surface of the ceiling wall  26   a  so as to be located individually in the adjacent engagement holes  27 . 
     Each secondary battery  10  is contained in the housing  16  with the lower end portion of its container  20  fitted in each corresponding engagement groove  25  and with the upper end portion passed through each corresponding engagement hole  27  of the ceiling wall  26   a . Thus, the six secondary batteries  10  are held in a row such that the respective principal surfaces of the containers  20  face one another with predetermined gaps between them. The one end face of each container  20  on which the positive and negative electrode terminals  21  and  22  are arranged is exposed into the engagement hole  27 . 
     In the present embodiment, each two adjacent secondary batteries  10  are arranged in such a manner that their respective positive and negative electrode terminals  21  and  22  are located reversely to one another. In other words, the six batteries  10  are located so that the electrode terminals  21  and  22  are arranged alternately in two rows along their array. 
     The lid body  28  of the housing  16  comprises apertures  32  corresponding individually to the electrode terminals  21  and  22 , and bosses  34  that support the battery management circuit board  14 . The apertures  32  are arranged in two rows at regular intervals. Each aperture  32  has a rectangular shape greater than that of each electrode terminal of each secondary battery  10 . The bosses  34  (e.g., three in number) protrude from the upper surface of the lid body  28  and are located individually on the longitudinally opposite end portions and central portion of the lid body  28 . 
     The lid body  28  is fixed to the cover body  26  so as to overlie the ceiling wall  26   a  of the cover body  26 , thereby covering one end face of each secondary battery  10 . The positive and negative electrode terminals  21  and  22  of each secondary battery  10  are located in their corresponding apertures  32  of the lid body  28  and exposed upward through the apertures. 
     As shown in  FIGS. 3 to 5 , the secondary batteries  10  are connected in series by the bus-bars  18 . Each bus-bar  18  is formed by, for example, bending a metal plate of aluminum or the like. Each bus-bar  18  comprises a pair of rectangular connecting portions  18   a  and a curved coupling portion  18   b  extending between the connecting portions  18   a . Each connecting portion  18   a  is formed with a terminal aperture  18   c  with which the electrode terminal  21  or  22  of each secondary battery  10  engages. The connecting portions  18   a  serves as first connecting portions. Further, each bus-bar  18  comprises a connection terminal  36 , which extends at right angles to a surface of each connecting portion  18   a  from the coupling portion  18   b . The connection terminal  36  is formed of the same conductive material (aluminum in this case) as the bus-bar  18  so as to be integral with the bus-bar  18 . The connection terminal  36  serves as a second connecting portion and its extended end portion is coated with a conductive film, such as copper that is easily wettable with solder. 
     One of the connecting portions  18   a  of each bus-bar  18  is connected to the electrode terminal  21  of each secondary battery  10 , while the other connecting portion  18   a  is connected to the negative electrode terminal  22  of the adjacent secondary battery  10 . Each connecting portion  18   a  is joined to its corresponding electrode terminal  21  or  22  by welding, e.g., laser welding, with the distal end portion of the electrode terminal fitted in the terminal aperture  18   c . The laser welding may be replaced with electron beam welding or resistance welding. The six secondary batteries  10  are connected in series with one another by the five bus-bars  18 . The respective connection terminals  36  of the bus-bars  18  extend upward in a direction substantially perpendicular to the lid body  28  of the housing  16 . 
     Output terminals  40  are connected individually to the negative electrode terminal  22  of that one of the secondary batteries  10  which is located at one end of the array and the positive electrode terminal  21  of the battery  10  at the other end. Each output terminal  40  comprises a rectangular connecting portion  40   a , a terminal aperture  40   b  in the connecting portion  40   a , an output end portion  40   c , and a connection terminal  42  extending perpendicularly upward from the connecting portion  40   a . The output terminal  40  is integrally formed of a metal plate of aluminum or the like. Each connecting portion  40   a  is joined to its corresponding electrode terminal  21  or  22  by laser welding, with the distal end portion of the electrode terminal fitted in the terminal aperture  40   b . The output end portion  40   c  extends onto the outside of the housing  26 . The respective connection terminals  42  of the output terminals  40  extend upward in a direction substantially perpendicular to the lid body  28  of the housing  16 . 
     The respective connection terminals  36  of the bus-bars  18  and the connection terminals  42  of the output terminals  40  are formed to be substantially flush with one another and arranged in two rows. 
     As shown in  FIGS. 1 ,  3  and  5 , the battery management circuit board  14  is formed having a rectangular shape substantially equal in size to the lid body  28  of the housing  16 . A wiring pattern of copper foil or the like is formed on the circuit board  14 , and control elements  44  are mounted on a substantially central part of the circuit board. These control elements  44  constitute a battery management unit  47 , which measures and monitors the voltage, temperature, etc., of the secondary batteries  10 . 
     The battery management circuit board  14  is formed with slit-shaped engagement holes  46  along its opposite side edges. These engagement holes  46  are arranged in two rows corresponding to the connection terminals  36  and  42  on the side of the battery pack body  12 . Conductive layers  50  of copper foil or metal deposit are formed on the respective inner surfaces and peripheries of the engagement holes  46 . The conductive layers  50  electrically conduct to the wiring pattern on the circuit board  14 . 
     Resistors  52  are mounted on the battery management circuit board  14 . The resistors  52  are formed to have resistance values of several to several hundreds of ohms and are connected between the battery management unit  47  and conductive layers  50 . The resistors  52  serve to suppress overdischarge from the secondary batteries  10 , thereby protecting the circuit board  14 . 
     The battery management circuit board  14  is located above the battery pack body  12  and attached to the bosses  34  of the lid body  28  by screws  62 . Thus, the circuit board  14  is supported on the bosses  34  and opposed to the lid body  28  with a gap therebetween. The respective connection terminals  36  and  42  of each bus-bar  18  and each output terminal  40  are passed through their corresponding engagement holes  46  of the circuit board  14  and attached to the conductive layers  50  of the circuit board  14  by solder beads  54 . Thus, the connection terminals  36  and  42  are connected mechanically and electrically to the circuit board  14  in a direct manner and further electrically connected to the battery management unit  47  through the resistors  52 . The battery management circuit board  14  is supported by the bus-bars  18  and output terminals  40 , as well as the bosses  34 , and firmly supported on and connected to the battery pack body  12 . Further, the circuit board  14  is electrically connected to the secondary batteries  10  through the bus-bars  18  including the connection terminals  36 . 
     The battery management unit  47  of the battery management circuit board  14  measures and monitors the voltage and temperature of the secondary batteries  10 , thereby preventing overcharge, overdischarge, etc., of the batteries. 
     According to the battery pack constructed in this manner, the bus-bars  18  that electrically connect the electrode terminals of the adjacent secondary batteries comprise the connection terminals  36  for detection, which are formed of the same material as the bus-bars and soldered directly to the battery management circuit board  14 . Thus, the secondary batteries  10  are electrically connected to the circuit board  14  by the bus-bars  18 . As compared with a conventional case where a plurality of lead wires are led around between secondary batteries and a circuit board, therefore, the battery pack body  12  and circuit board  14  can be connected more easily, and wrong connection can be prevented. Further, shorting of lead wires can be prevented to improve safety. Furthermore, the supporting structure for the circuit board  14  can be strengthened to improve the reliability of the secondary battery pack. 
     According to the arrangement described above, there may be obtained a secondary battery pack configured so that operations for connecting the secondary batteries and detection and control systems are simplified to prevent wrong connection and improve safety. 
     The following is a description of a secondary battery pack according to a second embodiment. 
       FIG. 6  is a perspective view showing the secondary battery pack according to the second embodiment,  FIG. 7  is an exploded perspective view showing a body and circuit board of the battery pack,  FIG. 8  is an enlarged perspective view showing a junction between the body and circuit board of the battery pack, and  FIG. 9  is an enlarged plan view showing the circuit board and a connecting piece of the battery pack. 
     Like reference numbers refer to like portions of the first and second embodiments, and a detailed description of those portions is omitted. The following description is focused on difference portions. 
     According to the second embodiment, as shown in  FIGS. 6 to 9 , a battery management circuit board  14  comprises a plurality of notches (engagement recesses)  60  in its two opposite side edges. These notches  60  are arranged in two rows corresponding to connection terminals  36  and  42  on the side of a battery pack body  12 . Each notch  60  is formed having a rectangular shape corresponding to the connection terminal  36  or  42  and a width and depth a little greater than the width and thickness, respectively, of the connection terminal. Conductive layers  50  of copper foil or metal deposit are formed on the respective inner surfaces and peripheries of the notches  60 . The conductive layers  50  electrically conduct to a wiring pattern on the circuit board  14 . 
     Resistors  52  are mounted on the battery management circuit board  14 . The resistors  52  are formed to have resistance values of several to several hundreds of ohms and are connected between a battery management unit  47  and the conductive layers  50 . The resistors  52  serve to suppress overdischarge from secondary batteries  10 , thereby protecting the circuit board  14 . 
     The battery management circuit board  14  is located above the battery pack body  12  and attached to bosses  34  of a lid body  28  by screws  62 . Thus, the circuit board  14  is supported on the bosses  34  and opposed to the lid body  28  with a gap therebetween. The respective connection terminals  36  and  42  of each bus-bar  18  and each output terminal  40  are caused to engage with their corresponding notches  60  of the circuit board  14  and attached to the conductive layers  50  of the circuit board  14  by solder beads  54 . Thus, the connection terminals  36  and  42  are connected mechanically and electrically to the circuit board  14  in a direct manner and further electrically connected to the battery management unit  47  through the resistors  52 . The battery management circuit board  14  is supported by the bus-bars  18  and output terminals  40 , as well as the bosses  34 , and firmly supported on and connected to the battery pack body  12 . Further, the circuit board  14  is electrically connected to the secondary batteries  10  through the bus-bars  18  including the connection terminals  36 . 
     Other configurations of the battery pack body  12  and battery management circuit board  14  are the same as those of the first embodiment. 
     According to the battery pack of the second embodiment constructed in this manner, the bus-bars  18  that electrically connect the electrode terminals of the adjacent secondary batteries comprise the connection terminals  36  for detection, which are formed of the same material as the bus-bars and soldered directly to the battery management circuit board  14 . Thus, the secondary batteries  10  are electrically connected to the circuit board  14  by the bus-bars  18 . As compared with the conventional case where the lead wires are led around between the secondary batteries and circuit board, therefore, the battery pack body  12  and circuit board  14  can be connected more easily, and wrong connection can be prevented. Further, shorting of lead wires can be prevented to improve safety. The supporting structure for the circuit board  14  can be strengthened to improve the reliability of the secondary battery pack. 
     According to the second embodiment, moreover, the notches  60  are used as connecting portions of the battery management circuit board  14 , so that the connection terminals of the bus-bars and output terminals can easily be aligned with the notches  60 , and connecting operations can be further facilitated. In removing any of the secondary batteries  10  from the battery pack for the purpose of replacement or repair, furthermore, the connection terminals  36  and  42  and circuit board  14  can easily be disconnected, so that the maintenance performance is improved. 
     While certain embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 
     As shown in  FIG. 10 , for example, connecting portions for the connection terminals of the battery management circuit board  14  may be disposed on side edges of the circuit board  14 . Specifically, the conductive layers  50  are formed on a plurality of parts of the side edges of the circuit board  14  and the surrounding parts, while the connection terminals  36  of the bus-bars  18  are connected directly to the side edges of the circuit board  14  through the conductive layers  50 . 
     Even with this arrangement, the same function and effect as in the foregoing embodiments can be obtained, and the connection terminals can be connected more easily. 
     The number of secondary batteries used in the secondary battery pack is not limited to six and may be varied as required. The positive and negative electrode terminals of each secondary battery are not limited to the shape of a prism and may be of another shape, such as the shape of a circular column. The bus-bars need not always be provided with the terminal apertures. The connection terminal of each bus-bar  18  may be configured to extend from the connecting portion  18   a  in place of the coupling portion  18   b . The shape and material of the bus-bars and the shape, material, and structure of the housing are not limited to the embodiments described herein and may be changed as required. 
     The bus-bar may have three or more first connecting portions configured to electrode terminals of three or more cells. The connecting terminal of the bus-bar may be formed of a material different from the material forming other part of the bus-bar.