Abstract:
A battery pack includes a plurality of unit batteries disposed in a spacer and connected via electrode tabs in a case so as to facilitate assembly of the battery pack and to prevent movement of the unit batteries when the battery pack is used, thereby increasing performance and efficiency of manufacture of the battery pack.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0059908, filed on Jul. 1, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the invention relate to a battery pack, and more particularly, to a high power and high capacity battery pack including a plurality of unit batteries. 
         [0004]    2. Description of the Related Art 
         [0005]    Secondary batteries, unlike primary batteries, are rechargeable. Low capacity secondary batteries are used in small portable electronic devices, such as phones, notebook computers, and camcorders. High capacity secondary batteries are widely used as motor-driving power sources for hybrid vehicles. Such secondary batteries include cylinder type batteries and prismatic type batteries. A plurality of high power secondary batteries are connected in series to constitute a high capacity secondary battery, which is necessary to drive a motor of a device requiring high capacity, for example, a motor of an electric vehicle. 
         [0006]    As such, a single high capacity secondary battery, i.e., a battery module, includes a plurality of unit batteries connected in series and/or in parallel. Each of the unit batteries includes an electrode assembly including a positive electrode plate and a negative electrode plate with a separator therebetween; a case in which the electrode assembly is disposed; a cap assembly coupled to the case to close the case; and positive and negative terminals that protrude from the cap assembly and are connected electrically to collectors of the positive and negative electrode plates of the electrode assembly. Thus, the unit batteries of the battery module are spaced apart from each other and connected in series and/or in parallel through electrode tabs. The battery module is inserted into a spacer to space the unit batteries apart from each other. Finally, the battery module is electrically connected to a protection circuit board and disposed in an outer case to provide a completed battery pack. 
         [0007]    After being disposed in the outer case, the battery module of the battery pack may move in the outer case due to an external shock, so that the unit batteries may disconnect from each other or the protection circuit board. In an attempt to prevent such disconnection, a discrete gap prevention member is generally provided between the battery module and inner sidewalls of the outer case to prevent the battery module from moving in the outer case. However, since the discrete gap prevention member is added to the battery pack, manufacturing costs are increased. In addition, since it is difficult to assemble the discrete gap prevention member and the battery pack, productivity is decreased. 
         [0008]    Alternatively, a discrete inner case may envelop the battery module and then be disposed in the outer case. However, since the battery pack still has a gap between the added inner case and the inner sidewalls of the outer case, it is difficult to prevent movement of the battery module. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the invention provide a battery pack including a plurality of unit batteries; a spacer in which the unit batteries are disposed; an electrode tab that electrically connects at least two of the unit batteries to each other; a case in which the unit batteries and the spacer are disposed; and a gap prevention rib disposed on an inner wall of the case to correspond to the spacer. 
         [0010]    According to aspects of the invention, the unit batteries may be cylinder type batteries arranged in a multi-layer structure, and adjacent unit batteries in each of the layers may have opposite polarities. 
         [0011]    According to aspects of the invention, the spacer may include a body having a plate shape having seat surfaces that correspond to outer surfaces of the unit batteries; and partition walls disposed between the seat surfaces, the partition walls including heat diffusion recesses. 
         [0012]    According to aspects of the invention, the spacer may include a lead wire hole that extends in a longitudinal direction of the spacer, the longitudinal direction being parallel to a length of the unit batteries. 
         [0013]    According to aspects of the invention, the spacer may include stop ribs alternately disposed at both sides of the spacer to prevent movement of the unit batteries disposed on the spacer. 
         [0014]    According to aspects of the invention, the spacer may be formed of a soft plastic. 
         [0015]    According to aspects of the invention, the soft plastic may include at least one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (CPS), polyethylene terephthalate (PETE), and/or equivalents thereof. 
         [0016]    According to aspects of the invention, the case may include a bottom case in which the unit batteries and the spacer are disposed, and a top case that closes the bottom case, and the gap prevention rib may be disposed on an inner surface of a sidewall of the bottom case. 
         [0017]    According to aspects of the invention, the bottom case may include a bottom plate; and sidewalls inclined outward in an upward direction from the bottom plate, wherein an upper part of the gap prevention rib disposed away from the bottom plate may protrude from one of the sidewalls more than a lower part of the gap prevention rib disposed adjacent to the bottom plate. 
         [0018]    According to aspects of the invention, an upper part of the gap prevention rib may protrude about 1.656 mm from the one of the sidewalls, and the lower part of the gap prevention rib may protrude about 0.992 mm from the one of the sidewalls. 
         [0019]    According to aspects of the invention, the bottom case may include a bottom plate having seat recess parts, the seat recess parts may have a semicircular cross-section, and the unit batteries may be disposed on the seat recess parts. 
         [0020]    Aspects of the invention provide a battery pack including a plurality of unit batteries; a spacer in which the unit batteries are disposed; an electrode tab that electrically connects at least two of the unit batteries to each other; a case in which the unit batteries and the spacer are disposed; and a gap prevention rib disposed on an inner wall of the case to correspond to the electrode tab. 
         [0021]    According to aspects of the invention, the spacer may include a body having a plate shape with seat surfaces to correspond to outer surfaces of the unit batteries; and partition walls disposed between the seat surfaces, the partition walls including heat diffusion recesses. 
         [0022]    According to aspects of the invention, the spacer may include a lead wire hole that is disposed in a longitudinal direction of the spacer, the longitudinal direction being parallel to a length of the unit batteries. 
         [0023]    According to aspects of the invention, the spacer may include stop ribs alternately disposed at both sides of the spacer to prevent movement of the unit batteries disposed on seat surfaces of the spacer. 
         [0024]    According to aspects of the invention, the spacer may be formed of a soft plastic. 
         [0025]    According to aspects of the invention, the electrode tab may include a contact welded to at least one of the unit batteries, and a lead wire connection connected to a lead wire. 
         [0026]    According to aspects of the invention, the case may include a bottom case in which the unit battery and the spacer are disposed, and a top case that closes the bottom case, and the gap prevention rib may be disposed at an inner surface of a sidewall of the bottom case. 
         [0027]    According to aspects of the invention, the bottom case may include a bottom plate; and sidewalls inclined outward in an upward direction from the bottom plate, wherein an upper part of the gap prevention rib disposed away from the bottom plate may protrude from the sidewall more than a lower part of the gap prevention rib disposed adjacent to the bottom plate. 
         [0028]    According to aspects of the invention, the battery pack may further include an insulation tape disposed between the electrode tab and the case to protect the electrode tab. 
         [0029]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of embodiments of the invention, taken in conjunction with the accompanying drawings of which: 
           [0031]      FIG. 1  illustrates a perspective view of a battery pack according to an aspect of the invention; 
           [0032]      FIG. 2  illustrates a schematic view of the battery pack of  FIG. 1  in which a top case has been removed; 
           [0033]      FIG. 3  illustrates an exploded perspective view of the battery pack of  FIG. 1 ; 
           [0034]      FIG. 4  illustrates a perspective view of the spacer of  FIG. 3 ; 
           [0035]      FIG. 5  illustrates a schematic view of the spacer of  FIG. 4  in which unit batteries are disposed; 
           [0036]      FIG. 6  illustrates a schematic view of electrode tabs coupled to the unit batteries of  FIG. 5 ; 
           [0037]      FIG. 7  illustrates a perspective view of the bottom case of  FIG. 2 ; 
           [0038]      FIG. 8  illustrates a cross-sectional view of the bottom case of  FIG. 7 ; 
           [0039]      FIG. 9  illustrates a plan view of a bottom portion of the battery pack of  FIG. 1 ; 
           [0040]      FIG. 10  illustrates a perspective view of a bottom portion of a battery pack according to aspects of the invention; and 
           [0041]      FIG. 11  illustrates a plan view of the bottom portion of the battery pack of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0042]    Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the invention by referring to the figures. 
         [0043]      FIG. 1  illustrates a perspective view of a battery pack according to aspects of the invention.  FIG. 2  illustrates a schematic view of the battery pack of  FIG. 1  in which a top case has been removed.  FIG. 3  illustrates an exploded perspective view of the battery pack of  FIG. 1 .  FIG. 4  illustrates a perspective view of the spacer of  FIG. 3 .  FIG. 5  illustrates a schematic view of the spacer of  FIG. 4  in which unit batteries are disposed.  FIG. 6  illustrates a schematic view of electrode tabs coupled to the unit batteries of  FIG. 5 .  FIG. 7  illustrates a perspective view of the bottom case of  FIG. 2 .  FIG. 8  illustrates a cross-sectional view of the bottom case of  FIG. 7 .  FIG. 9  illustrates a plan view of a bottom portion of the battery pack of  FIG. 1 . 
         [0044]    As illustrated in  FIGS. 1 to 9 , a battery pack  100  according to aspects of the invention includes a plurality of unit batteries  110 , a spacer  120  that separates the unit batteries  110  from each other, electrode tabs  130  to connect the unit batteries  110  in series and/or in parallel, and a case in which the unit batteries  110 , the spacer  120 , and the electrode tabs  130  are disposed. The case houses the unit batteries  110 , the spacer  120 , and the electrode tabs  130 . An inner wall of the case is provided with gap prevention ribs  154  that correspond to the spacer  120 . 
         [0045]    The battery pack  100  further includes a protection circuit board  140  to protect the unit batteries  110  from being over-discharged or over-charged, and lead wires  141  to electrically connect the unit batteries  110  to the protection circuit board  140 . 
         [0046]    The battery pack  100  further includes an insulation tape  170  disposed on the outer surfaces of the electrode tabs  130 , a cushion tape  180  disposed on a lower surface of the case, and a holder  190  coupled to the upper portions of the unit batteries  110 . The protection circuit board  140  is disposed on the holder  190 . 
         [0047]    The unit batteries  110  are cylinder type batteries; however, aspects of the invention are not limited thereto, such that the unit batteries  110  may be prismatic type batteries or batteries of other shapes. Five unit batteries  110  are arranged in series and/or in parallel, and two groups of the five unit batteries  110  are arranged in two layers. However, aspects of the invention are not limited thereto, such that more or fewer unit batteries  110  may be arranged in more or fewer layers; for example, seven unit batteries  110  may be arranged in each of four layers. The adjacent unit batteries  110  in each of the layers have different polarities. That is, when an end of one of the adjacent unit batteries  110  has the positive pole (+), an adjacent unit battery  110  in the same layer is disposed such that an end of the adjacent battery  110  has the negative pole (−). 
         [0048]    As shown in  FIG. 4 , the spacer  120  includes a spacer body  121  having a plate shape that is provided with semicircular seat surfaces  122  corresponding to the outer surfaces of the cylinder type unit batteries  110 . However, aspects of the invention are not limited thereto, such that the seat surfaces  122  may be of other shapes so as to accommodate unit batteries  110  having different shapes, for example, prismatic type unit batteries. Five seat surfaces  122  are provided to each of the upper and lower surfaces of the spacer body  121  so that two layers of unit batteries  110  may be disposed in the spacer  120 . However, aspects of the invention are not limited thereto, such that the spacer  120  may include more or fewer seat surfaces  122  to respectively accommodate more or fewer unit batteries  110 . Partition walls  123  are disposed between the seat surfaces  122 . The partition walls  123  are provided with heat diffusion recesses  124 . For purposes of reference and not to be limiting, the poles of the unit batteries  110  are disposed at “sides” of the spacer  120 , while the surfaces of the spacer  120  parallel to the longitudinal direction of the unit batteries  110  and the partition walls  123  are the “ends” of the spacer  120 . 
         [0049]    Lead wire holes  125  pass through the spacer  120  in the longitudinal direction of the spacer body  121 , i.e., in a direction parallel to a longitudinal direction of the unit batteries  110 . Each of lead wire holes  125  is disposed between the two seat surfaces  122  disposed in the upper layer and the two seat surfaces  122  disposed in the lower layer. For example, four lead wire holes  125  are shown in  FIG. 4 . However, when the spacer  120  includes more or fewer seat surfaces  122 , the number of lead wire holes  125  may be increased or decreased accordingly. 
         [0050]    Both sides of the spacer body  121  are provided with stop ribs  126  that prevent movement of the unit batteries  110 , i.e., the stop ribs  126  are disposed adjacent to the poles of the unit batteries  110 . The stop ribs  126  are provided to at least one end of the seat surface  122 . Thus, the stop ribs  126  prevent the unit batteries  110  from being removed from the seat surfaces  122  in a longitudinal direction with respect to the spacer  120 , i.e., in a same direction as the direction of the lead wire holes  125 . The stop ribs  126  are disposed on the upper and lower sides of the lead wire holes  125 . The stop ribs  126  may be alternately provided to a first side and a second side of the seat surface  122  such that, although the stop ribs  126  are not provided at the end of each seat surface  122  along both the first and second sides of the spacer  120 , movement and removal of the unit batteries  110  can be prevented. Accordingly, since the stop ribs  126  may be disposed alternately to both sides of the spacer  120 , the stop ribs  126  do not interfere with the electrode tabs  130  when the electrode tabs  130  are welded to the unit batteries  110 . 
         [0051]    The spacer  120  may be formed of soft plastic that includes at least one of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (CPS), polyethylene terephthalate (PETE), and/or equivalents thereof. The soft plastic absorbs shock and supports and protects the unit batteries  110 . 
         [0052]    The electrode tab  130  connects two or four adjacent unit batteries  110  in series and/or in parallel. The electrode tab  130  is disposed on the sides of the spacer  120  to connect unit batteries  110  on both the upper and lower layers of the spacer  120 . When connecting four adjacent unit batteries  110 , four corners of the electrode tab  130  include contacts  131  that are welded to the positive poles (+) or the negative poles (−) of the unit batteries  110 . When connecting only two adjacent unit batteries  110 , each end of the electrode tab  130  includes contacts  131  that are welded to the positive poles (+) or the negative poles (−) of the unit batteries  110 . Further, the electrode tab  130  may be plurally provided to connect unit batteries  110  disposed in the spacer  120  in plural layers so that adjacent unit batteries  110  of different layers are connected in parallel and adjacent unit batteries  110  of a same layer are connected in series; however, aspects of the invention are not limited thereto, such that the plural electrode tabs  130  may connect the unit batteries  110  in series and/or in parallel in any arrangement. The center of the electrode tab  130  is provided with a lead wire connection  132  that supports the lead wire  141  passing there-through. The electrode tabs  130  may be formed of metal having a high conductivity, which includes at least one of nickel, aluminum, copper, and silver, but aspects are not limited thereto, such that the electrode tabs  130  may be formed of other materials and may include multiple layers, at least one of which has a high conductivity. 
         [0053]    The protection circuit board  140  may include a protection circuit (not shown) or an electric device (not shown) that protects the unit batteries  110  from over-discharging or over-charging. 
         [0054]    The lead wires  141  extend from the protection circuit board  140  to connect the protection circuit board  140  to the unit batteries  110 , i.e., the lead wires  141  may connect the protection circuit or the electric device of the protection circuit board  140  to the unit batteries  110 . The lead wires  141  pass through the lead wire holes  125  of the spacer  120  and are fixed to the lead wire connections  132  of the electrode tabs  130 . 
         [0055]    The case includes a bottom case  150  in which the unit batteries  110 , the spacer  120 , the electrode tabs  130 , and the protection circuit board  140  are disposed; and a top case  160  that closes an open upper part of the bottom case  150 . The bottom case  150  includes a bottom plate  151  and four sidewalls  152  that extend upward from edges of the bottom plate  151 . 
         [0056]    The upper surface of the bottom plate  151  includes a plurality of seat recess parts  153  on which the unit batteries  110  are placed. As shown in  FIG. 7 , the seat recess parts  153  have a semicircular cross-section which corresponds to the shape of the unit batteries  110 ; however, aspects of the invention are not limited thereto, such that the seat recess parts  153  may have other shapes, for example, to correspond to prismatic type unit batteries. The seat recess parts  153  may be arrayed in a lattice at the bottom plate  151  which corresponds to the unit batteries  110  disposed in the spacer  120 . 
         [0057]    As shown in  FIG. 9 , gap prevention ribs  154  are disposed on the inner surfaces of the sidewalls  152 . The gap prevention ribs  154  correspond to the spacer  120 . Thus, the gap prevention ribs  154  are vertically disposed on the inner wall of the case. A pair of the gap prevention ribs  154  that are parallel to each other is disposed in a region that corresponds to the spacer  120 , and the gap prevention ribs  154  may be disposed to correspond to the spacer  120  so that the gap prevention ribs  154  are arranged to align with the stop ribs  126  of the spacer  120 . 
         [0058]    As shown in  FIG. 8 , the sidewalls  152  are inclined from the bottom plate  151 . That is, the sidewalls  152  are inclined outward in the upward direction from the bottom plate  151 . Thus, the upper part of the gap prevention ribs  154  may protrude more than the lower part thereof. For example, a bottom end  154   b  of the gap prevention rib  154  may have a protruding length d 2  of about 0.992 mm, and a top end  154   a  of the gap prevention rib  154  may have a protruding length d 1  of about 1.656 mm. In other words, a protruding ratio of the top end  154   a  to the bottom end  154   b  may be about 3:2. However, the protruding ratio is not limited thereto, and the upper and lower protruding lengths of the gap prevention ribs  154  may be varied according to an inclined amount of the sidewalls  152  from the bottom plate  151 . As such, the upper part of the gap prevention ribs  154  protrudes more than the lower part thereof to support the spacer  120  without a gap. 
         [0059]    As shown in  FIGS. 1-3 , the top case  160  has a shape and a size for closing the open upper part of the bottom case  150 . Thus, the top case  160  has a plate shape to cover the bottom case  150  that has an approximate box shape. 
         [0060]    The insulation tape  170  is attached between the electrode tabs  130  and the bottom case  150  to protect the electrode tabs  130 . The cushion tape  180  is disposed in the bottom case  150 . The cushion tape  180  absorbs shock from the bottom plate  151  to protect the unit batteries  110 , and the cushion tape  180  is disposed on the upper surface of the bottom plate  151 . 
         [0061]    The holder  190  envelops the upper and side surfaces of the unit batteries  110  disposed in the spacer  120  to protect the unit batteries  110  from external shock, i.e., the holder  190  is disposed about top surfaces of the battery units  110  disposed in the spacer  120  and end surfaces of the spacer  120  parallel to the partition walls  123 . 
         [0062]    A method of assembling a battery pack configured as described above will now be described according to aspects of the invention. First, the unit batteries  110  are placed on the seat surfaces  122  of the spacer  120  such that the adjacent unit batteries  110  have reverse polarities. However, aspects of the invention are not limited thereto, such that the adjacent unit batteries  110  may have the same polarities and may be arranged in series and/or in parallel. The heat diffusion recesses  124  are provided to the partition walls  123  between the seat surfaces  122  to diffuse heat generated from the unit batteries  110  to the outside. The stop ribs  126 , alternately disposed along the sides of the spacer body  121 , prevent the unit batteries  110  from being removed from the spacer  120 . The stop ribs  126  support both ends of the unit batteries  110  to prevent the unit batteries  110  from being moved by external shock. 
         [0063]    The electrode tabs  130  are welded to both ends of at least two (or four) of the unit batteries  110 , respectively. Thus, the unit batteries  110  to which the electrode tabs  130  are welded are connected to each other in series and/or in parallel. 
         [0064]    The insulation tape  170  is attached to the outer surfaces of the electrode tabs  130 . The insulation tape  170  has a shape corresponding to the electrode tabs  130  to protect the electrode tabs  130 . 
         [0065]    The upper parts of the unit batteries  110  are coupled to the holder  190  that envelops the upper and side surfaces of the unit batteries  110 . 
         [0066]    The upper surface of the holder  190  is provided with the protection circuit board  140  out of which the lead wires  141  extend. The lead wires  141  are connected to the unit batteries  110 . The lead wires  141  pass through the lead wire holes  125  of the spacer  120  and are fixed to the lead wire connections  132  provided to the electrode tabs  130 . Thus, the lead wires  141  extend out from the protection circuit board  140  and are connected to the electrode tabs  130  welded to the unit batteries  110 . 
         [0067]    The unit batteries  110  placed on the spacer  120  and connected to the electrode tabs  130  and the protection circuit board  140  disposed on the holder  190 , i.e., a battery module, is then disposed in the bottom case  150 . Since the battery module is disposed on the cushion tape  180  above the bottom plate  151  of the bottom case  150 , the battery module is protected from colliding with the bottom plate  151 . 
         [0068]    The lower surfaces of the unit batteries  110  of the battery module are not enveloped by the holder  190  and are placed respectively on the seat recess parts  153  disposed on the upper surface of the bottom plate  151  of the bottom case  150 . The spacer  120  is in close contact with the gap prevention ribs  154  provided to the sidewalls  152  of the bottom case  150 . The gap prevention ribs  154 , in contact with the stop ribs  126  of the spacer body  121  of the spacer  120 , correspond to both sides of the spacer  120 . That is, the gap prevention ribs  154  support the spacer  120 , and the stop ribs  126  prevent movement of the unit batteries  110  placed on the spacer  120 . Thus, the gap prevention ribs  154  prevent movement of the unit batteries  110  placed on the spacer  120 . Particularly, since the top end  154   a  protrudes more than the bottom end  154   b , even when the sidewalls  152  of the bottom case  150  are inclined outward, the gap prevention ribs  154  are in close contact with the spacer  120 . Finally, the top case  160  is coupled to the upper part of the bottom case  150  via screws  195  to complete the assembling of the battery pack  100 . However, aspects of the invention are not limited thereto, such that the top case  160  and bottom case  150  may be coupled by other arrangements, such as pins, adhesives, tapes, latches, or other connectors. 
         [0069]    Hereinafter, a battery pack according to aspects of the invention will now be described with reference to  FIGS. 10 and 11 .  FIG. 10  illustrates a perspective view of a battery pack according to aspects of the invention.  FIG. 11  illustrates a plan view of a bottom portion of the battery pack of  FIG. 10 . 
         [0070]    As illustrated in  FIGS. 10 and 11 , a battery pack  200  includes the unit batteries  110 , the spacer  120  that separates the unit batteries  110  from each other, the electrode tabs  130  that connect the unit batteries  110  in series and/or in parallel, and a bottom case in which the unit batteries  110 , the spacer  120 , and the electrode tabs  130  are disposed. The inner wall of the case is provided with gap prevention ribs  254  corresponding to the electrode tabs  130 . 
         [0071]    The battery pack  200  further includes a protection circuit board (not shown) that protects the unit batteries  110  from over-discharging or over-charging, an insulation tape (not shown) attached to the outer surfaces of the electrode tabs  130 , a cushion tape (not shown) provided to the lower surface of the case, a holder (not shown) coupled to the upper parts of the unit batteries  110  and provided with the protection circuit board (not shown), and a top case (not shown) that closes the bottom case  250 . Since the battery pack  200  is the generally same as the battery pack  100  except for the bottom case  250  that includes the gap prevention ribs  254  that support the electrode tabs  130 , like reference numerals denote like elements, and a detailed description thereof will be omitted. 
         [0072]    The battery pack  200  includes the bottom case  250  in which the unit batteries  110 , the spacer  120 , and the electrode tabs  130  are disposed. 
         [0073]    The bottom case  250  includes a bottom plate  251  and four sidewalls  252  that extend upward from edges of the bottom plate  251 . The inner surfaces of the sidewalls  252  are provided with the gap prevention ribs  254 . 
         [0074]    As shown in  FIG. 11 , the gap prevention ribs  254  are disposed at positions that correspond to the electrode tabs  130  on the sidewalls  252 . Thus, the gap prevention ribs  254  are vertically disposed on the inner surfaces of the sidewalls  252 , and pairs of the gap prevention ribs  254  that are parallel to each other are disposed in regions that correspond to the electrode tabs  130 , i.e., the gap prevention ribs  254  are disposed to align with the electrode tabs  130 . 
         [0075]    A method of assembling the battery pack  200  is the same as that of the battery pack  100 . In the battery pack  200 , when the unit batteries  110  are disposed in the bottom case  250 , the gap prevention ribs  254  support the electrode tabs  130  welded to the unit batteries  110 . Thus, the state where the electrode tabs  130  are welded to the unit batteries  110  is maintained. Furthermore, the gap prevention ribs  254  prevent movement of the unit batteries  110 . 
         [0076]    According to the aspects of the invention as described above, the gap prevention ribs disposed on sidewalls of the bottom case support only the spacer, or only the electrode tabs. However, it will be appreciated that the spacer and the electrode tabs may be simultaneously supported by the gap prevention ribs. 
         [0077]    According to the aspects of the invention, a high capacity and high power battery pack includes a case in which a plurality of unit batteries are disposed and gap prevention ribs are brought in close contact with a spacer and/or electrode tabs to minimize movement of the unit batteries due to external shock, thereby preventing malfunction of the unit batteries to improve reliability of a product including the battery pack. 
         [0078]    Although several embodiments of the invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.