Abstract:
A battery pack includes a battery cell including an electrode tab, a cell holder through which the electrode tab is inserted, a connection tab welded to the electrode tab and providing a welded portion above the cell holder, and a fume discharge groove located in a region of the cell holder under the welded portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Korean Patent Application No. 10-2015-0026745, filed on Feb. 25, 2015, in the Korean Intellectual Property Office, and entitled: “Battery Pack,” is incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments relate to a battery pack. 
         [0004]    2. Description of the Related Art 
         [0005]    Unlike primary batteries, secondary batteries are rechargeable. Secondary batteries are used as energy sources of devices such as mobile devices, electric vehicles, hybrid electric vehicles, electric bicycles, and uninterruptible power supplies. Single-cell secondary batteries or multi-cell secondary batteries (secondary battery packs) in which a plurality of battery cells are electrically connected are used according to the types of external devices using the secondary batteries. 
       SUMMARY 
       [0006]    Embodiments are directed to a battery pack including a battery cell including an electrode tab, a cell holder through which the electrode tab is inserted, a connection tab welded to the electrode tab and providing a welded portion above the cell holder, and a fume discharge groove located in a region of the cell holder under the welded portion. 
         [0007]    The fume discharge groove may extend across a bottom side of the connection tab. 
         [0008]    The fume discharge groove may be a channel that extends across a bottom side of the connection tab between first and second points of the cell holder. 
         [0009]    The fume discharge groove may extend to an outside of the cell holder. 
         [0010]    The cell holder may be rectangular shaped and may include a pair of parallel long sides and a pair of parallel short sides. The fume discharge groove may include a first fume discharge groove extending in a direction parallel to the long sides and a second fume discharge groove extending in a direction parallel to the short sides. 
         [0011]    The battery pack may include a plurality of battery cells. The first fume discharge groove may successively cross bottom sides of two or more connection tabs arranged in the direction parallel to the long sides. 
         [0012]    The battery cells may be arranged in the direction parallel to the short sides. 
         [0013]    The first and second fume discharge grooves may be connected to each other in a region of the connection tab or in a region close to the connection tab. 
         [0014]    The cell holder and the connection tab may include position aligning portions that provide alignment between the cell holder and the connection tab. 
         [0015]    The position aligning portions may include a protrusion extending upward from the cell holder toward the connection tab and a hole in the connection tab to receive the protrusion. 
         [0016]    A guide rib may be located on the cell holder to guide a sensing line. 
         [0017]    The sensing line may be a wire connected to the connection tab or the electrode tab to transmit information about a state of the battery cell. 
         [0018]    The battery pack may include a plurality of connection tabs. At least one of the connection tabs may include an output terminal extending to a lateral side of the cell holder. 
         [0019]    A threaded part may be coupleable to the output terminal to connect an output cable to the output terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
           [0021]      FIG. 1  illustrates a view depicting a battery pack according to an exemplary embodiment; 
           [0022]      FIG. 2  illustrates a perspective view of battery cells depicted in  FIG. 1 ; 
           [0023]      FIG. 3  illustrates an exploded perspective view of the battery pack depicted in  FIG. 1 ; 
           [0024]      FIG. 4  illustrates a perspective view depicting output terminals; 
           [0025]      FIGS. 5 and 6  illustrate a plan view and a perspective view of an upper side of a cell holder for explaining fume discharge grooves; 
           [0026]      FIG. 7  illustrates a view depicting a battery pack according to another exemplary embodiment; 
           [0027]      FIG. 8  illustrates an exploded perspective view depicting the battery pack depicted in  FIG. 7 ; and 
           [0028]      FIGS. 9 and 10  illustrate a plan view and a perspective view of upper sides of cell holders for explaining fume discharge grooves. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art. 
         [0030]    In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout. 
         [0031]      FIG. 1  illustrates a view depicting a battery pack according to an exemplary embodiment.  FIG. 2  illustrates a perspective view of battery cells depicted in  FIG. 1 .  FIG. 3  illustrates an exploded perspective view of the battery pack depicted in  FIG. 1 . 
         [0032]    Referring to  FIG. 1 , the battery pack may include at least two battery cells C and a cell holder  110  to which the battery cells C are coupleable. The battery cells C may include lithium-ion battery cells. Each of the battery cells C may include an electrode assembly having a stacked structure formed by first and second electrode plates having different polarities and a separator disposed between the first and second electrode plates. A plurality of first and second electrode plates and a plurality of separators may be stacked in the electrode assembly to increase the output power and capacity of the battery cell C. 
         [0033]    In addition, referring to  FIG. 2 , the each of the battery cells C may include a case  13  to seal the electrode assembly. The battery cells C may be pouch type battery cells, each including a relatively flexible case  13  instead of a metal can. The battery cells C may include electrode tabs  10  electrically connected to the electrode assemblies (not shown) and extending outward from the cases  13 . Each of the battery cells C may include first and second electrode tabs  11  and  12  respectively making electrical connection with the first and second electrode plates and thus having different polarities. In this specification, the term “electrode tab(s)  10 ” refers to one or both of the first and second electrode tabs  11  and  12 . The battery cells C may include terraces  15  from which the electrode tabs  10  outwardly extend. 
         [0034]    Referring to  FIG. 3 , the battery cells C may be coupleable to the cell holder  110 . For example, the battery cells C may be coupleable to the cell holder  110  in such a manner that the electrode tabs  10  of the battery cells C are exposed on an upper surface of the cell holder  110 . The cell holder  110  may support and hold the battery cells C. The battery cells C may be maintained at proper positions when inserted into the cell holder  110 . The cell holder  110  may structurally combine the battery cells C into a single module. 
         [0035]    The cell holder  110  may include a plurality of tab holes  110 ′ corresponding to the battery cells C. The electrode tabs  10  extending from the battery cells C may be inserted through the tab holes  110 ′ and exposed to the outside. The tab holes  110 ′ may be paired such that the first and second electrode tabs  11  and  12  extending from each of the battery cells C may be inserted through a pair of the tab holes  110 ′. For example, the first and second electrode tabs  11  and  12  extending from one of the battery cells C may be inserted through a pair of the tab holes  110 ′, and then the first and second electrode tabs  11  and  12  may be bent forward or backward in opposite directions to make electrical connection with neighboring battery cells C disposed in front and rear directions. 
         [0036]    Battery cells C neighboring each other in a front-to-rear direction may be electrically connected to each other through connection tabs  120  superposed on the first and second electrode tabs  11  and  12  of the battery cells. For example, battery cells C arranged in the front-to-rear direction may be structurally modularized by the cell holder  110  and then may be electrically modularized by the connection tabs  120 . 
         [0037]    The connection tabs  120  may be superposed on the electrode tabs  10  that extend from the cell holder  110  through the tab holes  110 ′. The connection tabs  120  may be coupleable to the electrode tabs  10  by, for example, welding. 
         [0038]    For example, the connection tabs  120  may include pairs of first and second connection tabs  121  and  122 . Each pair of first and second connection tabs  121  and  122  may be disposed on lower and upper sides of the electrode tabs  10  to place the electrode tabs  10  therebetween. As described above, when the electrode tabs  10  are sandwiched between the first and second connection tabs  121  and  122  of the connection tabs  120  disposed on the lower and upper sides of the electrode tabs  10 , electric connection between the electrode tabs  10  and the connection tabs  120  may be made more smoothly. For example, the electric contact area between the connection tabs  120  and the electrode tabs  10  may be increased. Moreover, the coupling strength between the connection tabs  120  and the electrode tabs  10  may be improved. 
         [0039]    For example, the electrode tabs  10  extending from the battery cells C may be inserted through the tab holes  110 ′ of the cell holder  110  and tab holes  121 ′ of the first connection tabs  121  and exposed on upper surfaces of the first connection tabs  121 . The second connection tabs  122  may be superposed on the upper surfaces of the first connection tabs  121  on which the electrode tabs  10  are exposed. 
         [0040]    In the exemplary embodiment, the connection tabs  120  and the electrode tabs  10  may be coupled to each other by welding. In a comparative example, the connection tabs  120  and the electrode tabs  10  may be coupled to each other by soldering. However, soldering is a manual process using a large amount of solder. Accordingly, the quality of soldering may not be uniform, and the coupling between the connection tabs  120  and the electrode tabs  10  could be broken at a weak point. In addition, if solder were to scatter to another conductive part from a coupling portion, a short circuit could occur. In addition, depending on properties of a material used to form the electrode tabs  10 , the electrode tabs  10  could exhibit poor bonding characteristics. For example, if the electrode tabs  10  are formed of an aluminum material, bonding errors could arise due to galvanic corrosion. In the exemplary embodiment, however, welding is used. Thus, process automation may be possible, and coupling quality may be uniformly maintained without electrical connection errors or a short circuit. 
         [0041]    Referring to  FIG. 3 , the connection tabs  120  and the cell holder  110  may include position aligning portions  121   a ,  122   a , and  110   a  for position alignment therebetween. For example, the position aligning portions  110   a ,  121   a , and  122   a  may include protrusions  110   a   1  formed on the cell holder  110  and holes  121   a  and  122   a  formed in the connection tabs  120  for receiving the protrusions  110   a   1 . Owing to coupling between the protrusions  110   a   1  and the holes  121   a  and  122   a , the connection tabs  120  may be disposed at proper positions. In this state, the connection tabs  120  may be aligned with the electrode tabs  10  exposed on the upper surface of the cell holder  110  and may be connected to the electrode tabs  10 . 
         [0042]    For example, as described above, the connection tabs  120  may include the pairs of first and second connection tabs  121  and  122  disposed on the lower and upper sides of the electrode tabs  10 . The first and second connection tabs  121  and  122  to be superposed at the same position may be aligned with each other by coupling the first and second connection tabs  121  and  122  to the same protrusions  110   a   1  formed on the cell holder  110 . The position aligning portions  110   a ,  121   a , and  122   a  may have suitable shapes such that the position aligning portions  110   a ,  121   a , and  122   a  may regulate relative assembling positions of the connection tabs  120  and the cell holder  110 . 
         [0043]    The position aligning portions  110   a ,  121   a , and  122   a  may include ribs  110   a   2  formed on the cell holder  110 . The ribs  110   a   2  may extend on the cell holder  110  in one direction, and edges of the connection tabs  120  may be inserted between the ribs  110   a   2 . The ribs  110   a   2  may include ribs extending in different directions and aligned with sides of the connection tabs  120 . 
         [0044]    The cell holder  110  may include support ribs  115  protruding toward the battery cells C. The support ribs  115  may protrude downwardly toward the battery cells C. The support ribs  115  may support portions of the battery cells C, for example, the terraces  15  of the battery cells C. For example, when the battery cells C are coupled to the cell holder  110  through a lower side of the cell holder  110  the support ribs  115  may help to prevent the terraces  15  of the battery cells C from colliding with a lower surface of the cell holder  110  and may maintain a proper distance between the cell holder  110  and the terraces  15  of the battery cells C, thereby helping to prevent the electrode tabs  10  from being damaged during a welding process. The support ribs  115  may protrude from the cell holder  110  toward the terraces  15  of the battery cells C. Accordingly, the coupling height of the battery cells C may be regulated to maintain a proper distance between the cell holder  110  and the battery cells C. The cell holder  110  may be less likely to be damaged by collision, and the electrode tabs  10  may be less likely to be damaged during welding. 
         [0045]      FIG. 4  is a perspective view illustrating output terminals  130 . 
         [0046]    Referring to  FIG. 4 , the connection tabs  120  electrically connecting pairs of the electrode tabs  10  may include the output terminals  130 . For example, a connection tab  120  disposed at a forefront position and a connection tab  120  disposed at a rearmost position may include the output terminals  130 . The output terminals  130  and the connection tabs  120  may be formed as one-piece parts extending from the upper surface of the cell holder  110  to form a lateral side of the cell holder  110 . Output cables  155  (only one is shown in  FIG. 4 ) may be connected to the output terminals  130  to form a charging and discharging current path. 
         [0047]    The output cables  155  may be connected to the output terminals  130  using threaded parts  150 . When the output terminals  130  are connected to the output cables  155  using the threaded parts  150  instead of soldering or welding, a connection process may be simply performed within a short time. 
         [0048]      FIGS. 5 and 6  illustrate a plan view and a perspective view of an upper side of the cell holder  110  for explaining fume discharge grooves (g). For clarity of illustration, elements of the cell holder  110  other than the fume discharge grooves (g) are not shown in  FIG. 6 . 
         [0049]    Referring to  FIGS. 5 and 6 , the fume discharge grooves (g) may be formed in the cell holder  110 . The fume discharge grooves (g) may be formed to discharge welding gas and contaminants when the connection tabs  120  and the electrode tabs  10  are welded. The term “fumes” may refer to welding gas and contaminants generated as byproducts during a welding process. 
         [0050]    The fume discharge grooves (g) may be formed under welded portions (coupling portions) between the connection tabs  120  and the electrode tabs  10 . For example, the fume discharge grooves (g) may be formed in regions overlapping the connection tabs  120  (regions under the connection tabs  120 ) or regions close to the connection tabs  120 . The fume discharge grooves (g) may be channels extending from first points to second points of the cell holder  110 . For example, the fume discharge grooves (g) may be channels crossing bottom sides of the connection tabs  120  and extending away from the bottom sides of the connection tabs  120 . In this case, fumes generated during welding of the connection tabs  120  may be easily discharged to the outside. The fume discharge grooves (g) may extend to the outside of the cell holder  110  such that fumes generated during welding may easily discharged to the outside of the cell holder  110 . 
         [0051]    Referring to  FIG. 6 , the fume discharge grooves (g) may extend on the cell holder  110  in two directions. For example, the cell holder  110  may include a pair of parallel long sides  110 L and a pair of parallel short sides  110 S, and the fume discharge grooves (g) may include first and second fume discharge grooves g 1  and g 2  extending in parallel with the long sides  110 L and the short sides  110 S. The first and second fume discharge grooves g 1  and g 2  may be formed at a plurality of positions corresponding to the connection tabs  120 . For example, a plurality of battery cells C may be arranged along the short sides  110 S of the cell holder  110  and coupled to the cell holder  110 . 
         [0052]    The first fume discharge grooves g 1  may extend across the connection tabs  120 . For example, the first fume discharge grooves g 1  may extend across the connection tabs  120  in a direction parallel to the long sides  110 L. As described below, the first fume discharge grooves g 1  and the second fume discharge grooves g 2  may extend in mutually crossing directions such that the first and second fume discharge grooves g 1  and g 2  may be connected to each other. 
         [0053]    At least one of both ends of each of the second fume discharge grooves g 2  may extend to the outside of the cell holder  110 . For example, the second fume discharge grooves g 2  may extend in parallel with the short sides  110 S, and ends of the second fume discharge grooves g 2  may reach the outside of the cell holder  110 . The first and second fume discharge grooves g 1  and g 2  may extend in different directions and may meet each other in regions of the connection tabs  120  or regions close to the connection tabs  120 . For example, the first and second fume discharge grooves g 1  and g 2  may be connected to each other in regions close the connection tabs  120 . In this case, when the connection tabs  120  are welded, fumes may be rapidly discharged in two directions. 
         [0054]    The fume discharge grooves (g) may extend across regions of the connection tabs  120  or regions close to the connection tabs  120 . The terms “regions of the connection tabs  120 ” or “regions close to the connection tabs  120 ” may refer to welded portions between the connection tabs  120  and the electrode tabs  10  or regions close to the welded portions. If the fume discharge grooves (g) extend across the connection tabs  120 , fumes may be efficiently discharged. In this case, however, if the connection tabs  120  and the electrode tabs  10  are suspended above the fume discharge grooves (g), a support area for a welding process could be reduced. Therefore, some of the fume discharge grooves (g) may be formed outside welding portions. For example, the second fume discharge grooves g 2  may be formed at positions slightly away from the connection tabs  120 . 
         [0055]    Fumes may be rapidly discharged through the fume discharge grooves (g) when the connection tabs  120  are welded. Accordingly, the connection tabs  120  may be properly welded. For example, if fumes were to accumulate in welded portions between the connection tabs  120  and the electrode tabs  10 , the quality the welded portions could be lowered, and the cell holder  110  could be damaged by the fumes having a high temperature. 
         [0056]    In the exemplary embodiment, the output power of the battery pack may be increased by increasing the number of battery cells C included in the battery pack. For example, the battery pack may be expanded by repeatedly arranging unit packs, each being a group of battery cells C. 
         [0057]      FIG. 7  illustrates a view depicting a battery pack according to another exemplary embodiment.  FIG. 8  illustrates an exploded perspective view of the battery pack depicted in  FIG. 7 . 
         [0058]    Referring to  FIG. 7 , the battery pack may include a first unit pack N 1  and a second unit pack N 2  coupleable to each other. As described below, the battery pack may be made up of only one of the first and second unit packs N 1  and N 2  or may be made up of the first and second unit packs N 1  and N 2  according to a desired output power or capacity level. As described below, the first and second unit packs N 1  and N 2  may have substantially the same structure. 
         [0059]    In the exemplary embodiment, the first and second unit packs N 1  and N 2  having substantially the same structure may be connected together to double the output power or capacity of the battery pack. The first and second unit packs N 1  and N 2  may have substantially the same structure. Accordingly, various performance requirements may be flexibly handled. For example, the battery pack may be constituted by a single unit pack such as the first unit pack N 1  or the second unit pack N 2  for applications requiring relatively low power levels or may be constituted by connecting the first and second unit packs N 1  and N 2  for applications requiring relatively high power levels. The battery pack may be constituted according to power requirements with one or more unit packs having substantially the same structure. Accordingly, the efficiency of processes for manufacturing the battery pack may be increased. Investments with respect to designs and production equipment for producing battery packs having different structures and output power levels may be avoided. 
         [0060]    In the exemplary embodiment, the first and second unit packs N 1  and N 2  may have substantially the same structure. The expression “substantially the same structure” indicates that although the first and second unit packs N 1  and N 2  do not have completely the same structure, the first and second unit packs N 1  and N 2  have almost identical structures. For example, the designs of the first and second unit packs N 1  and N 2  may be identical except for some parts such as expansion connection parts NC (described below). 
         [0061]    Referring to  FIG. 8 , cell holders  210  may include expansion connection parts NC. The expansion connection parts NC may be used to connect the first and second unit packs N 1  and N 2 . In more detail, the expansion connection parts NC may be formed on edge portions or outer portions of the cell holders  210 . The expansion connection parts NC of the first and second unit packs N 1  and N 2  may be coupleable to each other. For example, the cell holder  210  of the first unit pack N 1  may include expansion connection parts N 1   a  and N 1   b  to couple with the cell holder  210  of the second unit pack N 2 , and the cell holder  210  of the second unit pack N 2  may include expansion connection parts N 2   a  and N 2   b  to couple with the cell holder  210  of the first unit pack N 1 . 
         [0062]    Referring to  FIG. 8 , the cell holders  210  may include support ribs  215  protruding downwardly from the cell holders  210  for supporting terraces  15  of battery cells C. The support ribs  215  may be brought into direct contact with the terraces  15  of the battery cells C. Connection tabs  220  for electrically connecting the battery cells C may include first and second connection tabs  221  and  222 . The first and second connection tabs  221  and  222  may be disposed on lower and upper sides of electrode tabs  10  of the battery cells C such that the electrode tabs  10  may be sandwiched between the first and second connection tabs  221  and  222 . 
         [0063]      FIGS. 9 and 10  illustrate a plan view and a perspective view of upper sides of the cell holders  210  for explaining fume discharge grooves (g). For clarity of illustration, elements of the cell holders  210  other than the fume discharge grooves (g) are not shown in  FIG. 10 . 
         [0064]    Referring to  FIGS. 9 and 10 , the fume discharge grooves (g) may be formed in the cell holders  210 . The fume discharge grooves (g) may be formed under welded portions (coupling portions) between the connection tabs  220  and the electrode tabs  10 . For example, the fume discharge grooves (g) may be formed in regions overlapping the connection tabs  220  (regions under the connection tabs  220 ) or regions close to the connection tabs  220 . The fume discharge grooves (g) may be channels extending from first points to second points of the cell holders  210 . For example, the fume discharge grooves (g) may be channels crossing bottom sides of the connection tabs  220  and extending away from the bottom sides of the connection tabs  220 . Accordingly, fumes generated during welding of the connection tabs  220  may be easily discharged to the outside. The fume discharge grooves (g) may extend to the outside of the cell holders  210  such that fumes generated during welding may easily discharged to the outside of the cell holders  210 . 
         [0065]    Referring to  FIG. 10 , the fume discharge grooves (g) may extend on the cell holders  210  in two directions. For example, each of the cell holders  210  (that is, each of the cell holder  210  of the first unit pack N 1  and the cell holder  210  of the second unit pack N 2 ) may include a pair of parallel long sides  210 L and a pair of parallel short sides  210 S, and the fume discharge grooves (g) may include first and second fume discharge grooves g 1  and g 2  extending in parallel with the long sides  210 L and the short sides  210 S. The first and second fume discharge grooves g 1  and g 2  may be formed at a plurality of positions corresponding to the connection tabs  120 . 
         [0066]    In the exemplary embodiment, a plurality of battery cells C may be arranged along the short sides  110 S of each of the cell holders  210  and coupled to each of the cell holders  210 . In the exemplary embodiment, a plurality of unit packs such as the first and second unit packs N 1  and N 2  may be coupled together according to a desired number of battery cells C of the battery pack. Thus, although the number of battery cells arranged along short sides  210 S of each of the cell holders  210  is limited, the battery pack may be configured to have a high degree of output power. If a large number of battery cells were to be coupled to one cell holder  210 , it could be difficult to align the battery cells and the cell holder  210 . On the other hand, if unit packs each including a relatively small number of battery cells such as the first and second unit packs N 1  and N 2  according to embodiments are used, the battery pack may be easily assembled. 
         [0067]    Referring to  FIGS. 9 and 10 , the first fume discharge grooves g 1  may extend across one or more of the connection tabs  220 . At least one of both ends of each of the first fume discharge grooves g 1  may extend to the outside of the cell holders  210 . For example, the first fume discharge grooves g 1  may extend across two or more of the connection tabs  220  in a direction parallel to the long sides  210 L, and ends of the first fume discharge grooves g 1  may reach the outside of the cell holders  210 . 
         [0068]    The second fume discharge grooves g 2  may extend across the connection tabs  220 . At least one of both ends of each of the second fume discharge grooves g 2  may extend to the outside of the cell holders  210 . For example, the second fume discharge grooves g 2  may extend in parallel with the short sides  210 S, and ends of the second fume discharge grooves g 2  may reach the outside of the cell holders  210 . The first and second fume discharge grooves g 1  and g 2  may extend in different directions and may meet each other in regions of the connection tabs  220  or in regions close the connection tabs  220 . Accordingly, when the connection tabs  220  are welded, fumes may be rapidly discharged in two directions. 
         [0069]    The battery pack may include a protective circuit module to control charging and discharging operations of the battery cells C. The protective circuit module may monitor the states of the battery cells C. For example, the protective circuit module may measure status variables such as temperature, voltage, and current of the battery cells C and may control charging and discharging operations of the battery cells C based on results of the measurement. To this end, a plurality of sensing lines may be arranged on the cell holders  210 . For example, the sensing lines may transmit information regarding the states of the battery cells C to the protective circuit module. 
         [0070]    Guide ribs R may be formed on the cell holders  210 . The guide ribs R may guide the sensing lines. In more detail, owing to the guide ribs R, the sensing lines used to obtain status information of the battery cells C may be easily arranged without tangles. In addition, the guide ribs R may guide the assembling positions of the sensing lines. Accordingly, interference between components or a short circuit may be prevented. For example, the guide ribs R may guide the sensing lines to bypass paths to prevent overlapping between the connection tabs  220  and the sensing lines. 
         [0071]    As described above, according to the one or more of the above exemplary embodiments, the battery cells of the battery pack may be electrically coupled to each other using the connection tabs having an improved degree of coupling strength. For example, owing to the fume discharge grooves formed to rapidly discharge gas and contaminants when the connection tabs are welded, gas or contaminants may not accumulate in welded portions between the connection tabs and the electrode tabs of the battery cells, and damage to the cell holders during a welding process may be avoided. 
         [0072]    By way of summation and review, embodiments provide a battery pack in which a plurality of battery cells are electrically combined using a connection tab having improved coupling characteristics without damaging a cell holder. 
         [0073]    Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope thereof the present invention as set forth in the following claims.