Abstract:
Disclosed herein is a separation-type connecting member, which electrically connects electrode terminals of unit cells. The connecting member comprises two or more separated connecting bodies, which are connected to the corresponding electrode terminals during the assembly of a secondary battery module, and which are electrically connected with each other by additional conductive members to complete the battery module. The present invention also provides a method of improving the performance of a battery module that is capable of connecting unit cells in parallel with each other to level the voltage of the unit cells while the battery module is manufactured using the connecting member, specifically, before the unit cells are connected in series with each other, or while the battery module is used, thereby minimizing the voltage difference between the unit cells.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a connecting member used to electrically connect electrode terminals of unit cells in a high-output, large-capacity secondary battery module or pack and a method of improving the performance of a battery module by leveling voltage.  
         [0002]     More particularly, the present invention relates to a separation-type connecting member, which electrically connects electrode terminals of unit cells, comprising two or more separated connecting bodies, which are connected to the corresponding electrode terminals during the assembly of a secondary battery module, and which are electrically connected with each other by additional conductive members to complete the battery module, and a method of improving the performance of a battery module that is capable of connecting unit cells in parallel with each other to level the voltage of the unit cells while the battery module is manufactured using the connecting member, specifically, before the unit cells are connected in series with each other, or while the battery module is used, thereby minimizing the voltage difference between the unit cells.  
       BACKGROUND OF THE INVENTION  
       [0003]     Recently, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. Also, the secondary battery has attracted considerable attention as a power source for electric vehicles and hybrid electric vehicles, which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel. As a result, kinds of applications using the secondary battery are being increased owing to advantages of the secondary battery, and hereafter the secondary battery is expected to be applied to more applications and products than now.  
         [0004]     Secondary batteries have different structures depending upon outputs and capacities required by applications and products, to which the secondary batteries are applied. For example, small-sized mobile devices, such as mobile phones, personal digital assistants (PDAs), digital cameras, and laptop computers, use one or several small-sized, light cells for each device according to the reduction in size and weight of the corresponding products. On the other hand, medium- or large-sized devices, such as electric bicycles, electric motorcycles, electric vehicles, and hybrid electric vehicles, use a medium- or large-sized battery module (or medium- or large-sized battery pack) having a plurality of cells electrically connected with each other because high output and large capacity is necessary for the medium- or large-sized devices. The size and weight of the battery module is directly related to the receiving space and output of the corresponding medium- or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, light battery modules.  
         [0005]     Generally, a medium- or large-sized secondary battery module is manufactured by mounting a plurality of unit cells in a case (housing) having a predetermined size and electrically connecting the unit cells. A rectangular secondary cell or a pouch-shaped secondary cell, which can be stacked with high integration, is normally used as the unit cell. Preferably, the pouch-shaped cell is used as the unit cell, since the pouch-shaped cell is light and inexpensive.  
         [0006]     The secondary battery module is manufactured by electrically connecting the plurality of unit cells with each other. Especially, all or some of the unit cells are connected in series with each other to provide high output. As a result, an engineer may be exposed to high voltage during the manufacture of the battery module, and therefore, great notice must be taken of safety in manufacturing the battery module. Electrical short-circuits during the assembly of the battery module can cause injury to the engineer and reduction in performance of the unit cells. Consequently, more careful assembly of the battery module is required so as to solve the above-mentioned short-circuit problem, which greatly reduces the productivity of battery modules.  
         [0007]     Also, it is necessary to interrupt the operation of the battery module in the abnormal state, for example, overcurrent or overheating occurs, thereby securing the safety of the battery module. In addition, it is preferable that such interruption of the operation of the battery module be accomplished by module-type members that allow the unit cells, by which the abnormal operation of the battery module is caused, to be checked and replaced, since this construction is economically useful.  
         [0008]     Meanwhile, when the unit cells are cells having the same capacity and voltage, the medium- or large-sized secondary battery module is optimally operated. Although the unit cells have the same capacity and voltage, however, the unit cells normally have voltage difference due to the restrictions in manufacturing the unit cells, which are caused by various factors. Also, voltage difference between the unit cells may occur due to several factors during the use of the battery module as well as during the manufacture of the battery module.  
         [0009]     Consequently, there is a high need to minimize the voltage difference between the unit cells, and thus, to optimally maintain the operation of the battery module.  
       SUMMARY OF THE INVENTION  
       [0010]     Accordingly, it is an object of the present invention to substantially obviate the above-mentioned problems of the conventional arts as well as the technical problems requested from the past.  
         [0011]     A first object of the present invention is to provide a connecting member used to electrically connect electrode terminals of unit cells that is capable of greatly reducing a risk of an engineer receiving an electric shock due to short circuits and a possibility of damage to the unit cells during the assembly of a secondary battery module.  
         [0012]     A second object of the present invention is to provide a connecting member that allows safety elements to interrupt the operation of unit cells, which can cause the abnormal operation of a battery module, such as overcurrent and overheating, the safety elements being provided for each unit cell to be easily checked and replaced.  
         [0013]     A third object of the present invention is to provide a method of manufacturing a medium- or large-sized battery module using the connecting member.  
         [0014]     A fourth object of the present invention is to provide a method of improving the performance of a battery module, during the assembly or the use of the battery module, to optimally operate the battery module.  
         [0015]     A fifth object of the present invention is to provide an apparatus that is capable of performing the method of improving the performance of the battery module.  
         [0016]     In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a connecting member used to electrically connect electrode terminals of unit cells constituting a secondary battery module with each other, the connecting member comprising: a first terminal connecting body connected to the electrode terminal of one unit cell (a); and a second terminal connecting body connected to the electrode terminal of another unit cell (b), wherein the first terminal connecting body and the second terminal connecting body are separated from each other while the first terminal connecting body and the second terminal connecting body are connected to the corresponding electrode terminals, and the electrical connection between the unit cell (a) and the unit cell (b) is accomplished by coupling a conductive member to the first terminal connecting body and the second terminal connecting body.  
         [0017]     According to the present invention, the unit cells are arranged in a predetermined form, for example, the unit cells are stacked, during the manufacture of the secondary battery module, the terminal connecting bodies of the connecting member are connected to the corresponding unit cells, and then other components of the battery module are assembled and coupled. Subsequently, the unit cells are electrically connected with each other by conductive members at the later or final step of the battery module manufacturing process. Consequently, a risk of electrical short circuits of the unit cells during the assembly of the battery module is greatly reduced. Also, when each of the conductive members is a fuse, a bimetal, or a positive temperature coefficient (PTC) element, the electrical connection between the terminal connecting bodies is accomplished by the above-specified safety elements. Consequently, it is possible to couple the safety elements to the corresponding unit cells and to easily check and replace the unit cells causing the abnormal operation of the battery module. In addition, as will be described hereinafter, the terminal connecting bodies of the connecting member are connected in parallel with each other, before the electric connection of the unit cells by the conductive members, to easily perform voltage leveling, whereby the operation of the battery module is optimized.  
         [0018]     The unit cells are not particularly restricted so long as the unit cells are secondary cells which can be charged and discharged. As the unit cells are preferably used lithium secondary cells using lithium transition metal oxide or composite oxide as cathode active material. Also, the shape of the unit cells is not particularly restricted. Preferably, the rectangular cells and the pouch-shaped cells, which can be stacked in high density, are used as the unit cells.  
         [0019]     The terminal connecting bodies of the connecting member are not particularly restricted so long as the terminal connecting bodies can be connected to the electrode terminals of the corresponding unit cells while the terminal connecting bodies are separated from each other.  
         [0020]     In a preferred embodiment of the present invention, the connecting member further comprises: an insulating member mounted between electrode terminals of the neighboring unit cells for accomplishing the electrical insulation between the electrode terminals, the insulating member being coupled to the electrode terminals, and the first and second terminal connecting bodies of the connecting member are electrically connected to the electrode terminals of the corresponding unit cells while the first and second terminal connecting bodies of the connecting member are coupled to the insulating member. The electrical insulation between the electrode terminals of the unit cells while the unit cells are stacked is guaranteed by the provision of the insulating member. Consequently, a possibility of short circuits is greatly reduced, and the connecting member is easily connected to the electrode terminals.  
         [0021]     The insulating member serves to electrically insulate the electrode terminals of the neighboring unit cells from each other. Consequently, the insulating member is made of an electrically insulating material. Preferably, the insulating member is made of various plastic resins, although the insulating member is not particularly restricted so long as the insulating member electrically insulates the electrode terminals of the neighboring unit cells from each other.  
         [0022]     The insulating member may be coupled with the electrode terminals of the unit cells in various manners. In a preferred embodiment of the present invention, the electrode terminals of the unit cells are provided with though-holes, and the insulating member is provided with coupling protrusions, which correspond to the through-holes. Consequently, the coupling protrusions of the insulating member are fitted in the though-holes of the electrode terminals, and therefore, the secure coupling between the insulating member and the electrode terminals is accomplished. Preferably, the coupling protrusions are also provided with through-holes, such that the electrode terminals stacked while the insulating member is disposed between the electrode terminals, are further securely coupled with each other by coupling members inserted through the through-holes of the coupling protrusions.  
         [0023]     In a preferred embodiment of the present invention, the insulating member is constructed in the shape of a rectangular block, which conforms to a gap between the electrode terminals of the stacked unit cells. The gap between the electrode terminals, while the unit cells are stacked, is provided in the shape of a rectangle. Consequently, the rectangular block conforming to the gap is more stable.  
         [0024]     More preferably, the block comprises two assembly unit bodies constructed such that the assembly unit bodies can be coupled with or separated from each other, a cathode terminal of the unit cell being coupled to one of the assembly unit bodies while an anode terminal of the unit cell is coupled to the other assembly unit body. Consequently, the present invention has an advantage in that the connection of the electrode terminals and the coupling of the connecting member are sequentially performed by the provision of the assembly-type insulating member.  
         [0025]     The connecting member, which serves to electrically connect the electrode terminals of the unit cells with each other, is made of a conductive material. Preferably, the connecting member is made of metal, although the connecting member is not particularly restricted so long as the connecting member electrically connects the electrode terminals with each other.  
         [0026]     The coupling between the connecting member and the insulating member may be accomplished in various manners when the connecting member is coupled to the insulating member and electrically connected to the corresponding electrode terminals. In a preferred embodiment of the present invention, the connecting member comprises: a first terminal connecting body connected to the electrode terminal of one unit cell (a); and a second terminal connecting body connected to the electrode terminal of another unit cell (b) adjacent to the unit cell (a). The first terminal connecting body and the second terminal connecting body of the connecting member is coupled to the insulating member in such a manner that the first terminal connecting body and the second terminal connecting body surround the insulating member, or the first terminal connecting body and the second terminal connecting body are inserted into engaging grooves formed at the insulating member.  
         [0027]     For example, the first terminal connecting body and the second terminal connecting body are coupled to the insulating member such that the first and second terminal connecting bodies are connected to the corresponding electrode terminals, and the first terminal connecting body and the second terminal connecting body are connected with each other by a conductive member for accomplishing the electrical connection between the first terminal connecting body and the second terminal connecting body after the first and second terminal connecting bodies are coupled to the insulating member. Preferably, the conductive member is a safety element, such as a fuse, a bimetal, or a positive temperature coefficient (PTC) element.  
         [0028]     In accordance with another aspect of the present invention, there is provided a method of manufacturing a secondary battery module using the above-described connecting members. Specifically, the secondary battery module manufacturing method according to the present invention comprises the steps of: (A) mounting unit cells, which can be charged and discharged, in a module case; (B) connecting the terminal connecting bodies of connecting members as set forth in claim  1  to electrode terminals of the unit cells; (C) assembling and coupling other components of the battery module; and (D) coupling conductive members to the terminal connecting bodies to perform the electrical connection between the electrode terminals.  
         [0029]     In step (A), the module case may have various structures. As will be described hereinafter, the module case may include upper and lower cases, which can be separated from each other, between which the unit cells are stacked one on another. The electrode terminals may have various orientations. Preferably, the unit cells are stacked such that the electrode terminals of the unit cells are arranged in the same orientation.  
         [0030]     When the terminal connecting bodies of connecting members are connected to the electrode terminals in step (B), the insulating member may be mounted as described above, and then the terminal connecting bodies of connecting members are coupled to the insulating member.  
         [0031]     Step (C), i.e., the step of assembling and coupling other components of the battery module includes manufacturing the battery module using all or some of the remaining components of the battery module excluding the connecting members. For example, the step of assembling and coupling other components of the battery module may include mounting circuit units for controlling the operation of the battery module. Consequently, the assembly and coupling of some components may be performed after step (D).  
         [0032]     Preferably, the secondary battery module manufacturing method further comprises the step of: connecting the terminal connecting bodies of connecting members in parallel with each other, between step (B) and step (C) or between step (C) and step (D), to level the voltage of the unit cells.  
         [0033]     The conductive members used in step (D) may be the above-described safety elements. At step (D), the unit cells are electrically connected with each other by the conductive members. In this way, the electrical connection between the unit cells is accomplished at the later or final step of the battery module manufacturing process, and therefore, a possibility of short circuits during the assembly of the battery module is greatly reduced.  
         [0034]     In accordance with another aspect of the present invention, there is provided a secondary battery module including the above-described connecting members. An exemplary embodiment of the secondary battery module will be described hereinafter with reference to  FIG. 1 .  
         [0035]     Meanwhile, the inventors have performed various experiments and research, and have found that, when a plurality of unit cells are connected in parallel with each other for a predetermined period of time during the manufacture or the use of a battery module, in which the unit cells are mounted, the voltage difference between the unit cells is minimized, and therefore, the battery module operates optimally.  
         [0036]     In accordance with another aspect of the present invention, there is provided a method of improving the performance of a battery module having a plurality of unit cells, comprising the steps of: connecting two or more of the unit cells, which are connected in series with each other, in parallel with each other, for a predetermined period of time during the manufacture or the use of the battery module, to level the voltage of the unit cells, thereby minimizing the voltage difference between the unit cells.  
         [0037]     The performance improving method is applied to a medium- or large-sized battery module having two or more unit cells, some or all of which are connected in series with each other to provide high output and large capacity.  
         [0038]     The number of the unit cells constituting the battery module may be changed depending upon desired capacity and output of the battery module. The unit cells may be connected in series with each other. Alternatively, the unit cells may be connected in series and parallel with each other.  
         [0039]     According to the present invention, at least two of the unit cells, which are connected in series with each other, are contemporarily connected in parallel with each other to level the voltage of the unit cells. Preferably, the voltage of all the unit cells, which are connected in series with each other, is leveled, or the voltage of all the unit cells, which are connected in series and in parallel with each other, is leveled.  
         [0040]     The time necessary to perform the parallel connection may be changed depending upon the number, the voltage, the capacity, and the desired leveling value of the voltage. In a preferred embodiment of the present invention, the parallel connection time is set such that the voltages of the respective unit cells, which are leveled by the voltage leveling, are equal to each other within 0.001V.  
         [0041]     The voltage leveling according to the present invention may be randomly performed during the manufacture or the use of the battery module. During the manufacture of the battery module, it is preferable that the voltage leveling be performed before the unit cells are connected in series with each other.  
         [0042]     In accordance with yet another aspect of the present invention, there is provided a parallel connection apparatus for performing the above-described voltage leveling.  
         [0043]     The parallel connection apparatus according to the present invention comprises a cathode terminal connection unit and an anode terminal connection unit, and each of the connection units has a plurality of connection members connected to cathode terminals and anode terminals of unit cells, the connection members being electrically connected with each other.  
         [0044]     In a preferred embodiment of the present invention, the connection members are conductive members having a plate-shaped strip structure, the connection members are arranged in line while the connection members are electrically connected with each other, the connection members are attached to an insulating unit body of each of the connection units, and a wire, which serves as another connection member, is coupled to the insulating unit body of each of the connection units while the wire is electrically connected to the connection members.  
         [0045]     The parallel connection apparatus is effectively used to level the voltage of a battery module having a plurality of unit cells sequentially stacked one on another. Electrode terminals of the stacked unit cells are arranged at regular intervals, and therefore, it is possible to connect connecting members having the same arrangement as the electrode terminals to the electrode terminals of the unit cells in one action. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0046]     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0047]      FIG. 1  is a perspective view illustrating a secondary battery module according to a preferred embodiment of the present invention, to which a separation-type connecting member according to the present invention is applied;  
         [0048]      FIG. 2  is a typical view illustrating stacking of unit cells on a lower case of the battery module shown in  FIG. 1 ;  
         [0049]      FIG. 3  is a typical view illustrating an assembly-type insulating member according to a preferred embodiment of the present invention, to which the separation-type connecting member according to the present invention is coupled, before assembly of the insulating member;  
         [0050]      FIG. 4  is a typical view illustrating a separation-type connecting member according to a preferred embodiment of the present invention;  
         [0051]      FIG. 5  is a typical view partially illustrating the connection of electrode terminals using the assembly-type insulating member shown in  FIG. 3  and the separation-type connecting member shown in  FIG. 4 ;  
         [0052]      FIG. 6  is a view illustrating a structure for leveling the voltage of unit cells of a battery module according to the present invention;  
         [0053]      FIG. 7  is a perspective view illustrating a voltage leveling-purpose parallel connection apparatus according to a preferred embodiment of the present invention;  
         [0054]      FIG. 8  is a graph illustrating the results of voltage leveling tests of seven unit cells according to the present invention; and  
         [0055]      FIG. 9  is a perspective view illustrating the connection of a fuse to each separation-type connecting member of  FIG. 4 , which is coupled to a sensing board assembly of the battery module. 
     
    
     DESCRIPTION OF MAIN REFERENCE NUMERALS OF THE DRAWINGS  
       [0056]    
       
         
               
               
               
             
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                   
               
             
             
               
                   
                 100: battery module 
                 200: unit cells 
               
               
                   
                 300: insulating member 
                 400: connecting member 
               
               
                   
                 500: fastener 
                 600: double-sided adhesive tapes 
               
             
          
           
               
                   
                 700: voltage leveling-purpose parallel connection apparatus 
               
             
          
           
               
                   
                 800: fuse 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0057]     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiments.  
         [0058]      FIG. 1  is a perspective view illustrating a secondary battery module  100  according to a preferred embodiment of the present invention, to which a separation-type connecting member according to the present invention is applied.  
         [0059]     Referring to  FIG. 1 , the battery module  100  includes an upper case  110 , a lower case  120 , a plurality of unit cells  200 , a first circuit unit  130 , a second circuit unit  140 , and a third circuit unit  150 . The unit cells  200  are stacked between the upper case  110  and the lower case  120 , which are separated from each other. The first circuit unit  130  is mounted at the front surface of the battery module  100 , the second circuit unit  140  is mounted at the lower surface of the battery module  100 , and the third circuit unit  150  is mounted at the rear surface of the battery module  100 .  
         [0060]     Since the upper case  110  and the lower case  120  are separated from each other, the number of the unit cells  200 , which are stackable one on another, is not limited by the upper case  110  and the lower case  120 . Consequently, it is possible to easily design the battery module  100 , such that the battery module  100  has desired electrical capacity and output, by modifying the first circuit unit  130  and the third circuit unit  150  depending upon the number of the stacked unit cells  200 . Also, the unit cells  200  are exposed, and therefore, heat dissipation is efficiently accomplished while the unit cells  200  are charged or discharged. According to circumstances, the upper case  110  may be omitted.  
         [0061]     The first circuit unit  130  is mounted at one side surface of the battery module  100  adjacent to electrode terminals of the unit cells  200 . The first circuit unit  130  includes a connecting member according to the present invention for connecting the unit cells  200  in parallel or in series with each other and a sensing board assembly for sensing voltage and/or current signals of the respective unit cells  200 .  
         [0062]     The second circuit unit  140  is electrically connected to the first circuit unit  130 . The second circuit unit  140  includes a main board assembly for controlling the battery module  100 . The main board assembly is mounted in a lower receiving part of the lower case  120 . The temperature of the battery may be sensed by the main board assembly.  
         [0063]     The third circuit unit  150  is electrically connected to the second circuit unit  140 . Also, the third circuit unit  150  is connected to an external input/output terminal while preventing overcurrent during charging and discharging electricity. The third circuit unit  150  is mounted at the other side surface of the battery module  100  such that the third circuit unit  150  is opposite to the first circuit unit  130 .  
         [0064]     According to circumstances, the first circuit unit  130 , the second circuit unit  140 , and the third circuit unit  150  may be partially or wholly constructed in a combined structure. Also, these circuit units  130 ,  140 , and  150  may be partially or wholly mounted at the same position of the battery module, i.e., one or two surfaces of the battery module. These constructions of the circuit units must be interpreted to be within the scope of the present invention.  
         [0065]      FIG. 2  is a typical view illustrating stacking of the unit cells on the lower case of the battery module shown in  FIG. 1 .  
         [0066]     Referring to  FIG. 2 , the lower case  120  is a rectangular structure almost corresponding to the outer appearance of the unit cell  200 . The lower case  120  includes an upper receiving part  121 , in which the unit cell  200  is received. According to circumstances, the lower case  120  may be a simple plate structure. Preferably, the lower case  120  is made of a plastic resin, such as acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC), or polybutylene terephthalate (PBT), which has high strength and electrical insulation.  
         [0067]     The unit cell  200  stacked on the lower case  120  is a pouch-shaped secondary cell, which has a cathode terminal  220  and an anode terminal  230  protruding from the upper end of a cell body  210 . At the electrode terminals  220  and  230  are formed though-holes  240 , respectively. Additional fixing members, for example, fasteners  500 , are inserted through the through-holes  240  and fixing holes  122  formed in the lower case  120 , while the unit cells  200  and  201  are stacked, and then nuts (not shown) are fitted on the fasteners  500  at the lower surface of the lower case  120 . Consequently, the unit cells  200  and  201  are fixed to each other.  
         [0068]     Between the electrode terminals  220  and  230  of the unit cells  200  and the electrode terminals  220  and  230  of the unit cells  201  are mounted an insulating member  300  for accomplishing the electrical insulation between the unit cells  200  and  201 . At the insulating member  300  are formed protrusions  310 , which are fitted in the though-holes  240  of the electrode terminals  220  and  230 . At the protrusions  310  are also formed through-holes  320 , and therefore, the electrical insulation between the fasteners  500  inserted through the through holes  320  of the protrusions  310  and the electrode terminals  220  and  230  is maintained.  
         [0069]     Also, two double-sided adhesive tapes  600  are attached to the cell body  210  of the unit cell  200 , whereby more stable coupling between the stacked unit cells  200  and  201  is guaranteed. Furthermore, the stacked unit cells  200  and  201  are spaced apart from each other by the thickness of the double-sided adhesive tapes  600 . The gap between the stacked unit cells  200  and  201  serves to absorb the change in volume of the unit cells  200  and  201  while the unit cells  200  and  201  are charged or discharged and to effectively dissipate heat generated from the unit cells  200  and  201  while the unit cells  200  and  201  are charged or discharged.  
         [0070]      FIG. 3  is a typical view illustrating an assembly-type insulating member according to a preferred embodiment of the present invention, to which the separation-type connecting member according to the present invention is coupled, before assembly of the insulating member.  
         [0071]     Referring to  FIG. 3 , the insulating member  300  comprises: a first assembly unit body  330  having a female coupling part  331  formed at one side thereof; and a second assembly unit body  340  having a male coupling part  341  formed at one side thereof such that the male coupling part  341  corresponds to the female coupling part  331 . The first assembly unit body  330  and the second assembly unit body  340  are coupled with or separated from each other. The insulating member  300  is constructed in the shape of a rectangular block when the first assembly unit body  330  and the second assembly unit body  340  are coupled with each other.  
         [0072]     At the outside parts of the upper ends of the respective assembly unit bodies  330  and  340  are formed coupling protrusions  350 , by which the assembly unit bodies  330  and  340  are coupled with another insulating member (not shown) stacked on the assembly unit bodies  330  and  340 . At the lower end surfaces of the assembly unit bodies  330  and  340  are formed coupling grooves  352 , which correspond to the coupling protrusions  350 . Also, the protrusions  310  are formed at the middle parts of the upper ends of the respective assembly unit bodies  330  and  340  such that the protrusions  310  are fitted in the though-holes (not shown) of the electrode terminals of the unit cell, as shown in  FIG. 2 .  
         [0073]     At the side of the second assembly unit body  340  is formed a hollow part  343 , by which a connecting member (not shown) is coupled with the insulating member  300  constructed by coupling the first assembly unit body  330  and the second assembly unit body  340 .  
         [0074]      FIG. 4  is a typical view illustrating a separation-type connecting member according to a preferred embodiment of the present invention.  
         [0075]     Referring to  FIG. 4 , the separation-type connecting member  400  comprises: a first terminal connecting body  410 , which is connected to one of the electrode terminals of the unit cell (for example, the cathode terminal); and a second terminal connecting body  420 , which is connected to the other electrode terminal of the unit cell (for example, the anode terminal). The terminal connecting bodies  410  and  420  are made of a conductive material and formed in the shape of a plate. At the respective terminal connecting bodies  410  and  420  are formed engaging grooves  412  and  422 , in which the protrusions  310  of the insulating member (see  FIG. 3 ) are fitted. The engaging groove  412  formed at the first terminal connecting body  410  is constructed in a closed type such that the corresponding protrusion of the insulating member is fitted into the engaging groove  412  of the first terminal connecting body  410  only from above. On the other hand, the engaging groove  422  formed at the second terminal connecting body  420  is constructed in an open type such that the corresponding protrusion of the insulating member is fitted into the engaging groove  422  of the second terminal connecting body  410  from both above and side. A process of assembling the insulating member and the connecting member will be described hereinafter with reference to  FIG. 5 .  
         [0076]     At the first terminal connecting body  410  is formed a connecting extension part  415 , which protrudes from the side thereof such that the connecting extension part  415  can be connected to the sensing board assembly in the assembled state.  
         [0077]     At the respective terminal connecting bodies  410  and  420  are formed engaging parts  430  and  440 , respectively, which are securely inserted into the hollow part  343  of the insulating member (see  FIG. 3 ). Each of the engaging parts  430  and  440  includes a first bent section  431  formed by bending inwardly a main body, which is made of a plate-shaped material, at a predetermined height and a second bent section  432  formed by vertically bending the first bent section  431 . Consequently, the engaging parts  430  and  440  can be elastically engaged in the hollow part of the insulating member.  
         [0078]      FIG. 5  is a typical view partially illustrating the connection of the electrode terminals of the unit cells using the assembly-type insulating member shown in  FIG. 3  and the separation-type connecting member according to the preferred embodiment of the present invention shown in  FIG. 4 . Specifically, the connection of the unit cells  200  and  201  in series using the insulating member  300  and the connecting member  400  is illustrated in  FIG. 5 .  
         [0079]     Referring to  FIG. 5 , the engaging parts  430  and  440  of the first and second terminal connecting bodies  410  and  420  of the connecting member are securely inserted into the hollow part  343  of the second assembly unit body  340  of the insulating member. Specifically, the engaging part  430  of the first terminal connecting body  410  is inserted into the hollow part  343  with the engaging part  430  upward, and the plate-shaped main body  414  covers the lower end surfaces of the first assembly unit body  330  and the second assembly unit body  340 . When the first terminal connecting body  410  is coupled to the insulating member as described above, the side bent section  431  of the engaging part  430  is moved inward along a lower guide groove  345  formed a predetermined length at the lower end of the hollow part  343 . When the engaging part  430  of the first terminal connecting body  410  is inserted into the hollow part  343  of the insulating member  300 , the first terminal connecting body  410  is mounted at the lower end surface of another insulating member (not shown) having no projections. For this reason, the engaging groove  412  is formed in the closed type.  
         [0080]     On the other hand, the engaging part  440  of the second terminal connecting body  420  is inserted into the hollow part  343  with the engaging part  440  downward, and the plate-shaped main body  424  covers the upper end surface of the second assembly unit body  340 . When the second terminal connecting body  420  is coupled to the insulating member as described above, the side bent section  441  of the engaging part  440  is moved inward along an upper guide groove  344  formed a predetermined length at the upper end of the hollow part  343 . When the engaging part  440  of the second terminal connecting body  420  is inserted into the hollow part  343  of the insulating member  300 , the second terminal connecting body  420  is mounted at the upper end surface of the insulating member  300  having the protrusions  312 . For this reason, the engaging groove  422  is formed in the open type.  
         [0081]     The two terminal connecting bodies  410  and  420  remain separated from each other as shown in the drawing (showing the state before the coupling) even after the terminal connecting bodies  410  and  420  are coupled to the insulating member  300 . The first terminal connecting body  410  is connected to a cathode terminal  221  of the unit cell  201  coupled to the lower end surface of the first assembly unit body  330 , and the second terminal connecting body  420  is connected to an anode terminal  230  of the unit cell  200  coupled to the protrusion  312  of the second assembly unit body  340 .  
         [0082]     Now, the process of assembling the insulating member and the connecting member will be described.  
         [0083]     First, the second terminal connecting body  420  is coupled to the second assembly unit body  340  (S 1 ). Next, the first terminal connecting body  410  is coupled to the insulating member  300  (S 2 ). Subsequently, the engaging groove  422  of the second terminal connecting body  420  coupled to the second assembly unit body  340  as described above is aligned with the through-hole  240  of the anode terminal  230  of the unit cell  200  (S 3 ). After that, the first assembly unit body  330  is coupled to the second assembly unit body  340  (S 4 ). Finally, the unit cell  200  is mounted at the insulating member  300  such that the protrusion  310  is fitted in the though-hole  240  of the cathode terminal  220 , and the protrusion  312  is fitted in the through-hole  240  of the anode terminal  230  (S 5 ). At this time, the cathode terminal  220  is brought into contact with another first terminal connecting body (not shown) to be coupled from above while the cathode terminal  220  is coupled to the protrusion  310 . On the other hand, the anode terminal  230  is brought into contact with the second terminal connecting body  420 , which is coupled to the protrusion  312 .  
         [0084]     The above-described assembly process is merely an example of a possible assembly process, and the sequence of the assembly process may be partially changed. For example, the step of coupling the first assembly unit body  330  and the second assembly unit body  340  (S 4 ) may be carried out first.  
         [0085]     As described above, the electrode terminals  220  and  230  are not electrically connected with each other while the terminal connecting bodies  410  and  420  of the connecting member  400  are connected to the electrode terminals  220  and  230 , respectively. Consequently, a risk of short-circuits is greatly reduced while the battery module is assembled.  
         [0086]     The battery module assembled as shown in  FIG. 5  has a circuit structure as shown in  FIG. 6 .  
         [0087]     Referring to  FIG. 6 , the battery module  100  includes a plurality of unit cells  200 ,  201 ,  202  . . .  209 , which can be charged and discharged. The unit cells  200 ,  201 ,  202  . . .  209  are connected in series with each other to provide high output. As shown in  FIG. 6 , the electrical connection between the unit cells  200 ,  201 ,  202  . . .  209  is released to perform voltage leveling. While the electrical connection between the unit cells is released, cathode terminals  210 ,  211 ,  212  . . .  219  of the unit cells  200 ,  201 ,  202  . . .  209  are connected in parallel with each other, and anode terminals  220 ,  221 ,  222  . . .  229  of the unit cells  200 ,  201 ,  202  . . .  209  are also connected in parallel with each other, using a parallel connection apparatus  700 , to perform the voltage leveling.  
         [0088]      FIG. 7  is a perspective view illustrating a voltage leveling-purpose parallel connection apparatus  700  according to a preferred embodiment of the present invention.  
         [0089]     Referring to  FIG. 7 , the voltage leveling-purpose parallel connection apparatus  700  comprises a cathode terminal connection unit  701  and an anode terminal connection unit  702 . The two connection units  701  and  702  are constructed approximately in the same shape. Each connection unit has a plurality of connection members  720  attached to a unit body  710  thereof. To each unit body  710  is connected a wire  730 . The connection members  720  have a plate-shaped strip structure. The connection members  720  are arranged at regular intervals. The connection members  720  are electrically connected with each other. Each wire  730  is provided at one end thereof with a connection cord  732 . The other end of the wire  730  is connected to the corresponding unit body  710 . The wire  730  is also electrically connected to the connection members  720 . The cathode terminal connection unit  701  and the anode terminal connection unit  702  may be separately manufactured as shown in  FIG. 3 . According to circumstances, however, the cathode terminal connection unit  701  and the anode terminal connection unit  702  may be manufactured such that cathode terminal connection unit  701  and the anode terminal connection unit  702  can be separated from or assembled with each other. Alternatively, the cathode terminal connection unit  701  and the anode terminal connection unit  702  may be manufactured in a single body. In any cases, cathode terminal connection parts and anode terminal connection parts of the voltage leveling-purpose parallel connection apparatus remain electrically insulated.  
         [0090]      FIG. 8  is a graph illustrating the results of voltage leveling tests of the unit cells, which are carried out as described above.  
         [0091]     Seven unit cells were connected in parallel with each other for approximately 7000 seconds to perform the voltage leveling. The unit cells to be tested were randomly selected from a plurality of lithium secondary cells (LG Chem, Ltd: E1™). It can be seen from the graph of  FIG. 8  that most of the unit cells had initial voltages, which were from 4.150V to 4.160V while some of the unit cells had initial voltages, which were from 4.130V to 4.140V, and therefore, the maximum voltage difference between the unit cells was approximately 0.030V. When the parallel-type voltage leveling according to the present invention was performed, after some time, the voltages of the respective unit cells reached approximately 4.147 to 4.148V, which was the leveled voltage. Consequently, when all of the unit cells are adjusted to the leveled voltage over some period of time, and then the unit cells are connected in series with each other, the unit cells are electrically connected with each other in the optimal battery module operation state.  
         [0092]      FIG. 9  is a perspective view illustrating the connection of a fuse to each separation-type connecting member, after the above-described voltage leveling process is completed, such that the terminal connecting bodies of the connecting member are electrically connected with each other. For the convenience of understanding, only the connecting members, by which the electrode terminals of the unit cells are connected with each other, are partially indicated with an imaginary line. A printed circuit board of  FIG. 9  is one of the components constituting the first circuit unit shown in  FIG. 1 . For the convenience of description, the printed circuit board will be indicated hereinafter by reference numeral  130 .  
         [0093]     The printed circuit board  130  is a rectangular plate-shaped member. A wide opening  131  is formed at the center of the printed circuit board  130 , and a plurality of drilled-holes  132  are formed through the printed circuit board  130  at one side of the wide opening  131 . To the respective drilled-holes  132  are connected circuits (not shown), which are printed on a board body  133  of the printed circuit board  130 . The circuits are connected to sockets  135 , which are formed at one end of the board body  133 . The number of the sockets  135  may be appropriately decided depending upon the number of the circuits connected to the sockets  135 . At the left upper end and the right lower end of the board body  133  are formed relatively large drilled-holes  136  and  137 , respectively, to which final cathode and anode terminals are connected when unit cells (not shown) are connected in series with each other. Specifically, final cathode and anode wires, which are used for the electrical connection between the unit cells connected in series with each other, are connected to the drilled-holes  136  and  137 .  
         [0094]     The opening  131  is provided to expose the connected regions of the electrode terminals of the unit cells, which are located opposite to the board body  133 . While the printed circuit board  130  is mounted, a safety element, such as a fuse, a bimetal, or a positive temperature coefficient (PTC) element, may be mounted at the electrode terminals through the opening  131 .  
         [0095]     As described with reference to  FIG. 5 , the connecting extension part  415  of each first terminal connecting body  410  is oriented toward the printed circuit board  130  while each connecting member is coupled to the corresponding insulating member. Since each first terminal connecting body  410  is stably fixed at the position corresponding to the electrode terminals of the unit cell, the connecting extension parts  415  are also located at their predetermined positions. Consequently, the printed circuit board  130  is placed on the connecting members  400  such that the connecting extension parts  415  can be inserted through the drilled-holes  132  of the printed circuit board  130 , which is the first step of the assembly process. After the first step of the assembly process is completed, the tips of the connecting extension parts  415  protrude from the board body  134  through the drilled-holes  132 . The protruding tips of the connecting extension parts  415  are soldered to accomplish the electrical connection and the physical coupling between the connecting members  400  and the printed circuit board  130 .  
         [0096]     Even after the coupling between the connecting members  400  and the printed circuit board  130  is accomplished, the first and second terminal connecting bodies  410  and  420  of the connecting members  400  remain separated from each other, and therefore, the first and second terminal connecting bodies  410  and  420  are not electrically connected with each other. Consequently, after the assembly of the relevant members is completed, it is necessary to connect the terminal connecting bodies  410  and  420  with a safety element or an additional conductive element such that the electrical conduction between the terminal connecting bodies  410  and  420  is accomplished.  FIG. 9  illustrates the electrical connection using a fuse  800 , which is a kind of safety element, and  FIG. 1  illustrates the whole structure of the battery module  100 , the electrical connection of which is accomplished by the fuse.  
         [0097]     Specifically, elastic connecting grooves  433  and  443  are formed at the engaging parts  430  and  440  of the first and second terminal connecting bodies  410  and  420  while the first terminal connecting body  410  and the second terminal connecting body  420  are coupled to the insulating member. The connecting terminals  820  and  830  of the fuse  800  are inserted into the connecting grooves  433  and  443  of the engaging parts  430  and  440 , whereby the electrical connection between the first terminal connecting body  410  and the second terminal connecting body  420  is accomplished.  
         [0098]     Consequently, the cathode terminal connection unit  701  and the anode terminal connection unit  702  of  FIG. 7  are connected to the engaging parts  430  and  440  of the first and second terminal connecting bodies  410  and  420 , respectively, while the fuses  800  are removed, to perform the voltage leveling. Specifically, the connection members  720  (see  FIG. 7 ) having the plate-shaped strip structure, which are arranged in line, are inserted into the connecting grooves  433  and  443 , and the connection cords  732  of the wires  730  are connected to the final electrode terminal connection parts  230  and  240  (see  FIG. 1 ) of the battery module, whereby the cathode terminals are connected in parallel with each other while the anode terminals are also connected in parallel with each other. The connection members  720  (see  FIG. 7 ) having the plate-shaped strip structure are arranged at the same intervals as the first and second terminal connecting bodies  410  and  420  electrically connected to the cathode and anode terminals of the unit cells (not shown), respectively. Consequently, the connection is accomplished by the one-step mounting process. Subsequently, the wires  730  are connected to the final electrode terminal connection parts  230  and  240 , whereby the parallel connection is accomplished.  
         [0099]     In the battery module  100  of  FIG. 1 , the electrode terminals of the unit cells  200  are electrically connected with each other by the fuses  800 . When the voltage leveling is required during the use of the battery module  100 , the fuses  800  are removed to release the electrical connection between the unit cells  200 , and then the parallel connection apparatus  700  of  FIG. 7  is connected to the battery module  100 . Consequently, it is possible to performing the voltage leveling of the battery module  100  during the use of the battery module  100 .  
         [0100]     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.  
       INDUSTRIAL APPLICABILITY  
       [0101]     As apparent from the above description, the first and second terminal connecting bodies constituting the separation-type connecting member for secondary battery modules according to the present invention are separated from each other even after the terminal connecting bodies are connected to the electrode terminals of the unit cells. Consequently, a risk of an engineer receiving an electric shock due to short circuits and a possibility of damage to the unit cells are greatly reduced during the assembly of the secondary battery module. In addition, the operation of the unit cells, which causes the abnormal operation of the battery module, such as overcurrent and overheating, is interrupted by the safety elements provided for each unit cell. Also, the safety elements are easily checked and replaced.  
         [0102]     Furthermore, the unit cells of the battery module including the above-described connecting members are connected in parallel with each other to perform the voltage leveling. Consequently, the voltage difference between the unit cells is minimized, and therefore, the battery module operates optimally. The voltage leveling can be randomly performed during the manufacture of the battery module, specifically, before the electrode terminals are connected in series with each other, or during the use of the battery module.  
         [0103]     The battery module according to the present invention can be variously utilized as a battery module for medium- or large-sized devices, such as electric bicycles, electric vehicles, and hybrid electric vehicles.