Abstract:
A battery pack that easily replaces a protective circuit module according to a capacitance of battery cells and an external environment and including a commonly usable protective circuit module irrespective of an outer appearance of the battery pack. The battery pack includes a plurality of battery cells, a battery case in which the plurality of battery cells are disposed, a protective circuit part electrically connected to the battery cells, and a protective circuit module in which the protective circuit part is disposed. The battery case and the protective circuit module are physically separable from and connectable to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0115963, filed Nov. 27, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Aspects of the present invention relate to a battery pack. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a battery pack used for portable external electrical devices, such as notebooks, personal digital assistants (PDAs), and camcorders, include a plurality of battery cells because of a limited capacitance of the respective battery cells. 
         [0006]    Recently, a chargeable and dischargeable secondary battery is used as the battery pack. The charging and discharging efficiency of the secondary battery differ according to respective battery cells included in the secondary battery. Thus, the battery pack is generally connected to a circuit, such as a protective circuit module (PCM), that controls charging and discharging of each of the battery cells to perform uniform charging and discharging operations or a circuit that prevents the battery cells from being overcharged and overdischarged. 
         [0007]    However, a typical commercial battery pack has a structure in which battery cells and the PCM are disposed in a case. Thus, due to this structure, it is difficult to replace the PCM according to a capacitance of the battery cells and external environment. Also, in the typical battery pack, since the PCM is changed in configuration according to the outer appearance and shape of the battery pack, it is difficult to commonly use the PCM. In other words, it is difficult to use a PCM designed for a specific battery pack in other different battery packs. Also, since a space in which the battery cells are disposed is not separated from a space in which the PCM is disposed, a short circuit of the PCM due to a contact between the PCM and a leaking electrolyte may occur when the electrolyte of the lithium ion battery leaks out. 
       SUMMARY 
       [0008]    Aspects of the present invention provide a battery pack that easily replaces a protective circuit module according to capacitance of battery cells and external environment and includes a commonly usable protective circuit module irrespective of an outer appearance of the battery pack. 
         [0009]    Aspects of the present invention provide a battery pack including: a plurality of battery cells; a battery case in which the battery cells are disposed; a protective circuit part electrically connected to the battery cells; and a protective circuit module in which the protective circuit part is disposed, wherein the battery case and the protective circuit module are physically separable from and connectable to each other. 
         [0010]    According to another aspect of the present invention, the battery case may include: a lower battery case in which the battery cells are disposed; and an upper battery case disposed on the lower battery case to cover the battery cells. 
         [0011]    According to another aspect of the present invention, the protective circuit module may include: a body part receiving the protective circuit part therein; a first coupling terminal disposed on a lateral surface of the body part and electrically connected to a portable electrical device; and a second coupling terminal disposed on another lateral surface of the body part and electrically connected to the battery cells. 
         [0012]    According to another aspect of the present invention, the battery case may include: a lower battery case in which the battery cells are disposed; and an upper battery case disposed on the lower battery case to cover the battery cells; a coupling slot defined in a lateral surface of the lower battery case and having an inwardly recessed groove shape to receive the second coupling terminal; and a conductive tab disposed on an exposed surface within the groove of the coupling slot and electrically connected to the battery cells. 
         [0013]    According to another aspect of the present invention, the battery case may include a module receiving part disposed on a lateral surface of the battery case to receive the protective circuit module. 
         [0014]    According to another aspect of the present invention, the battery case may include: a coupling slot formed on a lateral surface of the module receiving part and having an inwardly recessed groove shape to receive the second coupling terminal; and a conductive tab disposed on an exposed surface within the groove of the coupling slot and electrically connected to the battery cells. 
         [0015]    According to another aspect of the present invention, when the protective circuit module is coupled to the battery case, an exposed surface of lateral surfaces of the battery case may be parallel to a surface on which the first coupling terminal of the body part is disposed. 
         [0016]    According to another aspect of the present invention, the battery case may further include a coupling member disposed on another lateral surface of the module receiving part opposite to the lateral surface of the module receiving part in which the coupling slot is formed. 
         [0017]    According to another aspect of the present invention, in the module receiving part of the battery case, the other lateral surface opposite to the lateral surface in which the coupling slot may be formed is recessed in an arc shape, and, in the protective circuit module, the other lateral surface opposite to the lateral surface on which the second coupling terminal is disposed is formed in an arc shape corresponding to the recessed arc shape. 
         [0018]    According to another aspect of the present invention, the protective circuit module may further include a coupling groove formed in a shape corresponding to a shape of the coupling member of the battery case. 
         [0019]    According to another aspect of the present invention, the protective circuit module may include: a body part receiving the protective circuit part; a first connector disposed on a lateral surface of the body part and electrically connected to a portable electrical device; and a second connector disposed on the other lateral surface of the body part and electrically connected to the plurality of battery cells. 
         [0020]    According to another aspect of the present invention, the battery case may include a module receiving part disposed on a lateral surface of the battery case to receive the protective circuit module. 
         [0021]    According to another aspect of the present invention, the battery case may include a connector receiving part disposed on a lateral surface of the module receiving part to receive the second connector, and the connector receiving part is electrically connected to the plurality of battery cells and the second connector. 
         [0022]    According to another aspect of the present invention, when the protective circuit module is coupled to the battery case, an exposed surface of lateral surfaces of the battery case may be parallel to a surface on the protective circuit module on which a first connector of the body part is disposed. 
         [0023]    According to another aspect of the present invention, the protective circuit module may further include coupling protrusions protruding outwardly from both lateral surfaces of the protective circuit module. 
         [0024]    According to another aspect of the present invention, the battery case may further include inwardly recessed coupling grooves on both lateral surface of the module receiving part and each having a shape corresponding to respective one of the coupling protrusions. 
         [0025]    According to another aspect of the present invention, the battery case may include at least one detachment member detaching the portable electrical device. 
         [0026]    Aspects of the present invention provide a battery pack including: a plurality of battery cells; a lower battery case in which the plurality of battery cells are disposed; an upper battery case covering a portion of the lower battery case; a protective circuit part electrically connected to the plurality of battery cells; and a protective circuit module receiving the protective circuit part, wherein the protective circuit module may be disposed on lateral surfaces of the lower battery case and the upper battery case covering another portion of the lower battery case not covered by the upper battery case, and wherein the upper battery case or the lower battery case and the protective circuit module are physically separable from and connectable to each other. 
         [0027]    According to another aspect of the present invention, the protective circuit module may include: a body part receiving the protective circuit part and surrounding a portion of the lower battery case and a lateral surface of the lower battery case; a connector disposed on an exposed surface of the body part and electrically connectable to a portable electrical device; and a coupling terminal electrically connecting the plurality of battery cells to the protective circuit part, wherein the coupling terminal couples the body part to the upper battery case or the lower battery case. 
         [0028]    According to another aspect of the present invention, the lower battery case may include an inwardly recessed coupling slot disposed on a lateral surface to which the protective circuit part is coupled to receive the coupling terminal. 
         [0029]    According to another aspect of the present invention, when the protective circuit module is coupled to the upper battery case and the lower battery case, a top surface of the upper battery case and a top surface of the protective circuit module may be parallel to each other. 
         [0030]    According to another aspect of the present invention, when the protective circuit module is coupled to the upper battery case and the lower battery case, a lateral surface of the upper battery case, a lateral surface of the lower battery case, and a lateral surface of the protective circuit module may be parallel to each other. 
         [0031]    According to another aspect of the present invention, when the protective circuit module is coupled to the upper battery case and the lower battery case, a bottom surface of the lower battery case and a bottom surface of the protective circuit module may be parallel to each other. 
         [0032]    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 
         [0033]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0034]      FIG. 1  illustrates an exploded perspective view of a battery pack according to an embodiment of the present invention; 
           [0035]      FIG. 2  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention; 
           [0036]      FIG. 3  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention; 
           [0037]      FIG. 4  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention; 
           [0038]      FIG. 5  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention; 
           [0039]      FIG. 6  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention; 
           [0040]      FIG. 7  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention; 
           [0041]      FIG. 8  illustrates a bottom perspective view of a protective circuit module of a battery pack according to another embodiment of the present invention; and 
           [0042]      FIG. 9  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    Reference will now be made in detail to the present embodiments of the present 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 present invention by referring to the figures. 
         [0044]      FIG. 1  illustrates an exploded perspective view of a battery pack according to an embodiment of the present invention, and  FIG. 2  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention. Referring to  FIGS. 1 and 2 , a battery pack  100 , includes battery cells  10 , a circuit part  110 , a battery case  120 , and a protective circuit module (PCM)  130 . 
         [0045]    A chargeable and dischargeable secondary battery is used as the battery cells  10 . Specifically, a cylindrical lithium secondary battery having a high operating voltage of about 3.6 volts and a high energy density per unit weight is used as the battery cells  10 . The battery cells  10  include six battery cells  10   a ,  10   b ,  10   c ,  10   d ,  10   e , and  10   f . However, aspects of the present invention are not limited thereto and a number of the battery cells  10  may vary. The battery cells  10  are designed so that a top surface and a bottom surface of each of the battery cells  10  have polarities different from each other. For example, the bottom surfaces of the battery cells  10  is electrically connected to a negative electrode of an electrode assembly (not shown) of the battery case  120 , and the top surfaces of the battery cells  10  is electrically connected to a positive electrode of the electrode assembly (not shown) within the battery cells  10  of the battery case  120 . However, aspects of the present invention are not limited thereto, and the battery cells  10  may be connected in other suitable configurations. 
         [0046]    The circuit part  110  includes first to fourth conductive plates  111 ,  112 ,  113 , and  114  and first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . In  FIG. 1 , reference symbols B+ and B− represent large current terminals and power source parts of both ends of corresponding ones of the battery cells  10  connected in series or in parallel. The reference symbol B− represents a low potential terminal as a negative power source part, and the reference symbol B+ represents a high potential terminal as a positive power source part. Reference symbols B 1  and B 2  represent sensing terminals that are portions at which the battery cells  10  having different polarities are connected to each other in series. The respective sensing terminals B 1  and B 2  correspond to an intermediate potential terminal between the high potential terminal and the low potential terminal. 
         [0047]    The first conductive plate  111  is electrically connected to negative electrodes of the two battery cells  10   a  and  10   b  disposed at a lower end of the battery cells  10 , or in other words, the lowest potential terminal B−. The second conductive plate  112  has a bent portion so that it bends back upon itself. The two battery cells  10   a  and  10   b  of the battery cells  10  are electrically connected to each other in parallel at a side of the bent portion of the second conductive plate  112 . Also, the two battery cells  10   c  and  10   d  of the battery cells  10  are electrically connected to each other in parallel at another side of the bent portion of the second conductive plate  112 . The two battery cells  10   a  and  10   b  disposed at one side of the bent portion and the two battery cells  10   c  and  10   d  disposed at the other side of the bent portion are connected in series by the second conductive plate  112 . The third conductive plate  113  has a bent portion so that it bends back upon itself. The two battery cells  10   c  and  10   d  of the battery cells  10  are electrically connected to each other in parallel at a side of the bent portion of the third conductive plate  113 . The two battery cells  10   e  and  10   f  of the battery cells  10  are electrically connected to each other in parallel at another side of the bent portion of the third conductive plate  113 . The two battery cells  10   c  and  10   d  disposed at a side of the bent portion and the two battery cells  10   e  and  10   f  disposed at another side of the bent portion are connected in series by the third conductive plate  112 . The fourth conductive plate  114  is electrically connected to positive electrodes of the two battery cells  10   e  and  10   f  disposed at an upper end of the battery cells  10 , i.e., the high potential terminal B+. The first to fourth conductive plates  111 ,  112 ,  113 , and  114  are formed of any one of nickel (Ni), copper (Cu), or aluminium (Al). However, aspects of the present invention are not limited thereto and the first to fourth conductive plates  111 ,  112 ,  113  and  114  may be formed of other suitable materials. Also, it would be understood by one of ordinary skill in the art that when the number of the battery cells  10  increases, the number of the conductive plates increases accordingly. 
         [0048]    The first conductive tab  115  has an end electrically connected to the first conductive plate  111  of the low potential terminal B− and another end facing a surface of the battery case  120 . The second conductive tab  116  and the third conductive tab  117  each have an end electrically connected to the second conductive plate  112  and the third conductive plate  113 , respectively, and other ends facing a surface of the battery case  120 . The fourth conductive tab  118  has an end electrically connected to the fourth conductive plate  114  of the high potential terminal B+ and another end facing a surface of the battery case  120 . A power of the battery cells  10  is supplied to a portable electrical device connected to the battery pack  100  through the first conductive tab  115  and the fourth conductive tab  118 . However, aspects of the present invention are not limited thereto and other conductive tabs  115  to  118  may be used to supply power to the portable electrical device. Also, the first to fourth conductive tabs  115 ,  116 ,  117 , and  118  are formed of Ni. Coated conductive wires may be used as the first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . However, aspects of the present invention are not limited thereto and other suitable materials may be used to form the first through fourth conductive tabs  115  to  118 . 
         [0049]    The first to fourth conductive plates  111 ,  112 ,  113 , and  114  and the first to fourth conductive tabs  115 ,  116 ,  117 , and  118  are connected to each other using various methods according to configurations and dispositions of the battery cells  10 . 
         [0050]    The battery case  120  includes a lower battery case  121  and the upper battery case  122 . The lower battery case  121  has a box shape with an opened upper portion. Also, the lower battery case  121  is configured to directly receive the battery cells  10  and the circuit part  110 . A coupling slot  121   c  is disposed at a lateral surface  121   a  of the lower battery case  121 . A portion of the lateral surface  121   a  of the lower battery case  121  is recessed to define the coupling slot  121   c  having a groove shape. The coupling slot  121   c  is electrically connected to the battery cells  10  through the first to fourth conductive plates  111 ,  112 ,  113 , and  114  and the first and fourth conductive tabs  115 ,  116 ,  117 , and  118 . A conductive tab (not shown) electrically connected to a protective circuit part  131  is disposed on an outer surface of the groove of the coupling slot  121   c . The lower battery case  121  is formed of an insulating resin. However, aspects of the present invention are not limited thereto and the lower battery case  121  may be formed of other suitable materials. 
         [0051]    The upper battery case  122  may have a box shape with an opened lower portion. The upper battery case  122  may have a size corresponding to that of the opened upper portion of the lower battery case  121 . The upper battery case  122  may be formed of an insulating resin. The upper battery case  122  and the lower battery case  121  are coupled to each other to protect the battery cells  10  and the circuit part  110  from external environment such as external impacts and dusts. 
         [0052]    The PCM  130  includes the protective circuit part  131 , a body part  132 , a first coupling terminal  133 , and a second coupling terminal  134 . The protective circuit part  131  is electrically connected to the coupling slot  121   c  through the second coupling terminal  134 . As a result, the protective circuit part  131  is electrically connected to the battery cells  10  through the first to fourth conductive plates  111 ,  112 ,  113 , and  114  and the first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The protective circuit part  131  controls charging and discharging of the battery cells  10  through a circuit (not shown) disposed therein to prevent the battery cells  10  from being overcharged and overdischarged. 
         [0053]    The body part  132  has a bar shape with an empty space therein. The body part  132  receives the protective circuit part  131  therein. An insulating resin is molded to form the body part  132 . However, aspects of the present invention are not limited thereto and other materials may be used to form the body part  132 . 
         [0054]    The first coupling terminal  133  is disposed on a lateral surface  132   a  of the body part  132 . The first coupling terminal  133  is inserted into a slot (not shown) disposed in the portable electrical device. The first coupling terminal  133  may have a plate shape. A conductive tab  133   a  is electrically connected to the protective circuit part  131  and is exposed from the first coupling terminal  133  so that it is electrically connected to the portable electrical device. 
         [0055]    The second coupling terminal  134  is disposed on another lateral surface  132   b  of the body part  132 . The second coupling terminal  134  has a shape corresponding to a shape of the coupling slot  121   c  of the battery case  120 . That is, the second coupling terminal  134  has a plate shape. The second coupling terminal  134  is inserted into the coupling slot  121   c  of the battery case  120 . A conductive tab  134   a  is electrically connected to the protective circuit part  131  and is exposed from the second coupling terminal  134  so that it is electrically connected to a conductive tab (not shown) of the coupling slot  121   c . Since the coupling slot  121   c  is electrically connected to the battery cells  10 , when the PCM  130  is coupled to the battery case  120 , the protective circuit part  131  is electrically connected to the battery cells  10 . 
         [0056]    As described above, the battery case  120  and the PCM  130  are electrically connected to each other and the PCM  120  and the portable electrical device are electrically connected to each other as well as firmly coupled to each other by the first coupling terminal  133  and the second coupling terminal  134 . Thus, in the battery pack  100  according to the present embodiment, a separate detachment member for coupling the battery case  120  or the PCM  130  to the portable electrical device is not required. 
         [0057]      FIG. 3  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention, and  FIG. 4  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention. Referring to  FIGS. 3 and 4 , a battery pack  200  is different from the battery pack  100  of  FIGS. 1 and 2  with respect to a battery case  220  and a protective circuit module (PCM)  230 . Thus, in descriptions of the battery pack  200  according to the present embodiment, the battery case  220  and the PCM  230  will be mainly described. Also, parts equal to or similar to those of the battery pack  100  of  FIGS. 1 and 2  have the same reference numerals, and the detailed descriptions will be omitted. 
         [0058]    The battery case  220  includes a lower battery case  221  and an upper battery case  222 . The lower battery case  221  has a box shape with an opened upper portion. Also, the lower battery case  221  is configured to directly receive battery cells  10  and a circuit part  110 . A recessed module receiving part  221   b  is disposed in a lateral surface  221   a  of the lower battery case  221  to receive the PCM  230 . A coupling slot  221   c  having an inwardly recessed groove shape is disposed in a lateral surface of the module receiving part  221   b  to receive the PCM  230 . The coupling slot  221   c  is electrically connected to the battery cells  10  through first to fourth conductive tabs  115 ,  116 ,  117 , and  118  and first to fourth conductive plates  111 ,  112 ,  113 , and  114 . A conductive tab (not shown) is electrically connected to a protective circuit part  231  and is disposed on an exposed surface within the groove of the coupling slot  221   c . A recessed portion having an arc shape  221   d  is disposed on a lateral surface opposite to the lateral surface  221   a  in the module receiving part  221   b . The arc shape  221   d  allows the PCM  230  to be smoothly coupled to the battery case  220 . A protruding coupling member  221   e  is disposed on a portion of the arc shape  221   d  to firmly couple the PCM  230  to the battery case  220 . Also, the lower battery case  221  is formed of an insulating resin. However, aspects of the present invention are not limited thereto and the lower battery case  221  may be formed of other suitable materials. 
         [0059]    The upper battery case  222  has a box shape with an opened lower portion. The upper battery case  222  has a size and configuration corresponding to the size and configuration of the opened upper portion of the lower battery case  221 . Specifically, a module receiving part  222   b  receiving the PCM  230  is defined in a lateral surface  222   a  of the upper battery case  222 . An inwardly recessed arc shape (not shown) corresponding to the arc shape  221   d  is formed in a lateral surface of the module receiving part  222   b . Also, the upper battery case  222  is formed of an insulating resin. However, aspects of the present invention are not limited thereto and the upper battery case  222  may be formed of other suitable materials. 
         [0060]    The PCM  230  includes a protective circuit part  231 , a body part  232 , a first coupling terminal  233 , and a second coupling terminal  234 . The protective circuit part  231  is electrically connected to the coupling slot  221   c  of the lower battery case  221  through the second coupling terminal  234 . As a result, the protective circuit part  231  is electrically connected to the battery cells  10  through the first to fourth conductive plates  111 ,  112 ,  113 , and  114  and the first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The protective circuit part  231  controls charging and discharging of the battery cells  10  through a circuit (not shown) disposed therein to prevent the battery cells  10  from being overcharged and overdischarged. 
         [0061]    The body part  232  has a bar shape with an empty space therein. The body part  232  receives the protective circuit part  231  therein. A protruding arc shape  232   d  corresponding to the recessed shape of the arc shape  221   d  of the battery case  220  is formed on a lateral surface of the body part  232 . Also, a coupling groove  232   e  corresponding to the protruding coupling member  221   e  of the battery case  220  is formed in the lateral surface of the body part  232 . Here, a portion of the arc shape  232   d  of the body part  232  is recessed to define the coupling groove  232   e . Also, an insulating resin may be molded to form the body part  232 . However, aspects of the present invention are not limited thereto and the body part  232  may be formed of other suitable materials. 
         [0062]    The first coupling terminal  233  is disposed on a lateral surface  232   a  of the body part  232 . The first coupling terminal  233  is inserted into a slot (not shown) defined in a portable electrical device. The first coupling terminal  233  has a plate shape. A conductive tab  233   a  is electrically connected to the protective circuit part  231  and is exposed from the first coupling terminal  233  so that it is electrically connected to the portable electrical device. 
         [0063]    The second coupling terminal  234  is disposed on a lateral surface  232   b  of the body part  232 . The second coupling terminal  234  has a shape corresponding to a shape of the coupling slot  221   c  of the battery case  220 . That is, the second coupling terminal  234  has a plate shape. The second coupling terminal  234  is inserted into the coupling slot  221   c  of the battery case  220 . A conductive tab  234   a  is electrically connected to the protective circuit part  231  and is exposed from the second coupling terminal  234  so that it is electrically connected to the coupling slot  221   c . Since the coupling slot  221   c  is electrically connected to the battery cells  10 , when the PCM  230  is coupled to the battery case  220 , the protective circuit part  231  is electrically connected to the battery cells  10 . 
         [0064]    Referring to  FIG. 4 , according to a coupling state between the battery case  220  and the PCM  230 , the lateral surfaces  221   a  and  222   a  of the battery case  220  are parallel to the lateral surface  232   a  on which the first coupling terminal  233  of the body part  232  of the PCM  230  is disposed. Due to the above-described structure, an external structure of the battery pack  200  is simplified, and a portable electrical device suitable for the battery pack  200  is more simply designed. Also, since the PCM  230  is received into the battery case  220 , the PCM  230  is firmly coupled to the battery case  220 . In addition, the battery case  220  and the PCM  230  or the PCM  230  and the portable electrical device are electrically connected to each other as well as firmly physically coupled to each other by the first coupling terminal  233  and the second coupling terminal  234 . Thus, in the battery pack  200  according to another embodiment, a separate detachment member for coupling the battery case  220  or the PCM  230  to the portable electrical device is not required. 
         [0065]      FIG. 5  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention, and  FIG. 6  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention. Referring to  FIGS. 5 and 6 , a battery pack  300  is different from the battery pack  100  of  FIGS. 1 and 2  with respect to a battery case  320  and a protective circuit module (PCM)  330 . Thus, in descriptions of the battery pack  300  according to the present embodiment, the battery case  320  and the PCM  330  will be mainly described. Also, parts equal to or similar to those of the battery pack  100  of  FIGS. 1 and 2  have the same reference numerals, and the detailed descriptions will be omitted. 
         [0066]    The battery case  320  includes a lower battery case  321  and an upper battery case  322 . The lower battery case  321  has a box shape with an opened upper portion. The lower battery case  321  is configured to directly receive battery cells  10  and a circuit part  110 . A recessed module receiving part  321   b  is formed in a lateral surface  321   a  of the lower battery case  321  to receive the PCM  330 . A connector receiving part  321   c  is formed in a lateral surface of the module receiving part  321   b . The connector receiving part  321   c  is electrically connected to first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The first to fourth conductive tabs  115 ,  116 ,  117 , and  118  are electrically connected to the battery cells  10  through first to fourth conductive plates  111 ,  112 ,  113 , and  114 . As a result, the connector receiving part  321   c  is electrically connected to the battery cells  10 . The connector receiving part  321   c  includes a plurality of cylindrical conductive tabs disposed perpendicular to a lateral surface of the lower battery case  321  in which the connector receiving part  321   c  is defined. Thus, the connector receiving part  321   c  is electrically connected to a protective circuit part  331 . Inwardly recessed coupling grooves  321   e  are formed in both lateral surfaces of the module receiving part  321   b . Also, a detachment member  321   f  coupling at least one portable electrical device is disposed on the lateral surface  321   a  of the lower battery case  321 . The lower battery case  321  is formed of an insulating resin. However, aspects of the present invention are not limited thereto, and the lower battery case  321  may be formed of other suitable materials. 
         [0067]    The upper battery case  322  has a box shape with an opened lower portion. The upper battery case  322  has a size and configuration corresponding to those of the opened upper portion of the lower battery case  321 . Specifically, a module receiving part  322   b  for receiving the PCM  330  is formed in a lateral surface  322   a  of the upper battery case  322 . The upper battery case  322  is formed of an insulating resin. However, aspects of the present invention are not limited thereto, and the upper battery case  322  may be formed of other suitable materials. 
         [0068]    The PCM  330  includes a protective circuit part  331 , a body part  332 , a first connector  333 , and a second connector  334 . The protective circuit part  331  is electrically connected to the connector receiving part  321   c  of the lower battery case  321  through a second connector  334 . As a result, the protective circuit part  331  is electrically connected to the battery cells  10  through the first through fourth conductive plates  111 ,  112 ,  113 , and  114  and the first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The protective circuit part  331  controls charging and discharging of the battery cells  10  through a circuit (not shown) disposed therein to prevent the battery cells  10  from being overcharged and overdischarged. 
         [0069]    The body part  332  has a bar shape with an empty space therein. The body part  332  receives the protective circuit part  331  therein. Outwardly protruding coupling protrusions  332   e , each having a shape corresponding to that of the respectively coupling grooves  321   e  of the battery case  320 , are disposed on both lateral surfaces of the body part  332 . When the PCM  330  is coupled to the battery case  320 , the coupling grooves  321   e  of the battery case  320  is coupled to the coupling protrusions  322   e  to further firmly couple the battery case  320  to the PCM  330 . 
         [0070]    The first connector  333  is disposed on a lateral surface  332   a  of the body part  332 . In the first connector  333 , a plurality of conductive tabs  333   a  having a plate shape and electrically connected to the protective circuit part  331  is disposed perpendicular to the lateral surface  332   a . The first connector  333  is electrically connected to a connector receiving part (not shown) to be disposed in a portable electrical device. 
         [0071]    The second connector  334  is disposed on another lateral surface  332   b  of the body part  332 . The second connector  334  has a shape corresponding to that of the connector receiving part  321   c  of the battery case  320 . In the second connector  334 , a plurality of conductive tabs  333   a  having a plate shape and perpendicular to the other lateral surface  332   b  of the body part  332  is disposed so that the conductive tabs  333   a  contact between the cylindrical conductive tabs of the connector receiving part  321   c . The conductive tabs  333   a  are electrically coupled to the cylindrical conductive tabs of the connector receiving part  321   c . Also, the conductive tabs  333   a  are electrically connected to the protective circuit part  331 . Since the connector receiving part  321   c  is electrically connected to the battery cells  10 , when the PCM  330  is coupled to the battery case  320 , the protective circuit part  331  is electrically connected to the battery cells  10 . 
         [0072]    Referring to  FIG. 6 , according to a coupling state between the battery case  320  and the PCM  330 , the exposed surfaces  321   a  and  322   a  of the lateral surfaces of the battery case  320  are parallel to the lateral surface  332   a  on which the first connector  333  of the body part  332  of the PCM  330  is disposed. A top surface  322   c  of the upper battery case  322  is parallel to a top surface  332   c  of the PCM  330 . Due to the above-described structure, an external structure of the battery pack  300  is simplified, and a portable electrical device suitable for the battery pack  300  is simply designed. Also, since the PCM  330  is received into the battery case  320 , the PCM  330  is firmly coupled to the battery case  320 . 
         [0073]    Unlike the battery pack  100  of  FIGS. 1 and 2 , since the battery case  320 , the PCM  330 , and the portable electrical device are coupled to each other using a connector instead of using a slot, an outwardly protruding coupling terminal does not exist. Thus, the battery pack  300  having a clean shape and small size is designed. However, when the battery case  320 , the PCM  330 , and the portable electrical device are coupled using the connectors, the coupling force therebetween may be reduced when compared a coupling force using coupling terminals. Thus, to reinforce the coupling force between the battery case  320 , the PCM  330 , and the portable electrical device, the coupling grooves  321   e  of the battery case  320 , the coupling protrusions of the PCM  330 , and the detachment member  321   f  of the battery case  320  are further provided. 
         [0074]      FIG. 7  illustrates an exploded perspective view of a battery pack according to another embodiment of the present invention.  FIG. 8  illustrates a bottom perspective view of a PCM of a battery pack according to another embodiment of the present invention.  FIG. 9  illustrates a perspective view of a coupling state of a battery pack according to another embodiment of the present invention. 
         [0075]    Referring to  FIGS. 7 to 9 , a battery pack  400  is different from the battery pack  100  of  FIGS. 1 and 2  in terms of structures of a battery case  420  and a protective circuit module (PCM)  430 . Thus, in descriptions of the battery pack  400  according to another embodiment, the battery case  420  and the PCM  430  will be mainly described. Also, parts equal to or similar to those of the battery pack  100  of  FIGS. 1 and 2  have the same reference numerals, and the detailed descriptions will be omitted. 
         [0076]    The battery case  420  includes a lower battery case  421  and an upper battery case  422 . The lower battery case  421  has a box shape with an opened upper portion. Also, the lower battery case  421  is configured to directly receive battery cells  10  and a circuit part  110 . A coupling slot  421   c  is formed in a lateral surface  421   a  of the lower battery case  421  to couple the PCM  430  to the battery case  420 . 
         [0077]    The coupling slot  421   c  is electrically connected to first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The first to fourth conductive tabs  115 ,  116 ,  117 , and  118  are electrically connected to the battery cells  10  through first to fourth conductive plates  111 ,  112 ,  113 , and  114 . As a result, the coupling slot  421   c  is electrically connected to the battery cells  10 . A conductive tab (not shown) is electrically connected to a protective circuit part  431  and is disposed on an exposed surface within a groove of the coupling slot  421   c.    
         [0078]    The upper battery case  422  has a box shape with an opened lower portion. The upper battery case  422  covers a portion of an upper portion of the battery cells  10 . That is, a lower end of the upper battery case  422  has an area less than an area of an upper end of the lower battery case  421 . 
         [0079]    The PCM  430  includes the protective circuit part  431 , a body part  432 , a connector  433 , and a coupling terminal  434 . The protective circuit part  431  is electrically connected to the coupling slot  421   c  of the lower battery case  421  through the coupling terminal  434 . As a result, the protective circuit part  431  is electrically connected to the battery cells  10  through the first to fourth conductive plates  111 ,  112 ,  113 , and  114  and the first to fourth conductive tabs  115 ,  116 ,  117 , and  118 . The protective circuit part  431  has an “L” shape over a portion of an upper portion of the lower battery case  421  and a lateral surface of the lower battery case  421  to optimize space utilization. Also, the protective circuit part  431  controls charging and discharging of the battery cells  10  through a circuit (not shown) disposed therein to prevent the battery cells  10  from being overcharged and overdischarged. 
         [0080]    The body part  432  may have an “L” shape over a portion of an upper portion of the lower battery case  421  and a lateral surface of the lower battery case  421 . A space is defined within the body part  432  to receive the protective circuit part  431 . 
         [0081]    The connector  433  is disposed on a surface  432   a  and is exposed when the body part  432  is coupled to the battery case  420 . The connector  433  includes a plurality of plate-shaped conductive tabs  433   a  (not shown) that is electrically connected to the protective circuit part  431  and perpendicular to the surface  432   a  of the body part  432 . The connector  433  is electrically connected to a connector receiving part (not shown) to be defined in a portable electrical device. 
         [0082]    The coupling terminal  434  is disposed on a surface  432   c , which contacts the lower battery case  421  when the coupling terminal  434  is coupled to the battery case  420  of the body part  432 . The coupling terminal  434  has a shape corresponding to a shape of the coupling slot  421   c  of the battery case  420 . That is, the coupling terminal  434  has a plate shape and is coupled to the coupling slot  421   c  of the battery case  420  by being inserted into the coupling slot  421   c . Also, a conductive tab  434   a  electrically connected to the protective circuit part  431  is disposed on the coupling terminal  434  so that it is electrically connected to a conductive tab (not shown) of the coupling slot  421   c . Since the coupling slot  421   c  is electrically connected to the battery cells  10 , the protective circuit part  431  is electrically connected to the battery cells  10  when the PCM  430  is coupled to the battery case  420 . 
         [0083]    Referring to  FIG. 9 , according to a coupling state between the battery case  420  and the PCM  430 , a lateral surface  422   d  of the upper battery case  422  is coupled to a lateral surface  432   d  (see  FIG. 8 ) of the PCM  430 . Also, a top surface  422   b  of the upper battery case  422  is parallel to a top surface  432   b  of the PCM  430 . In addition, a lateral surface  421   f  of the lower battery case  421 , a lateral surface  422   f  of the upper battery case  422 , and a lateral surface  432   f  of the PCM  430  are parallel to each other. A lateral surface  421   g  of the lower battery case  421 , a lateral surface  422   g  of the upper battery case  422 , and a lateral surface  432   g  of the PCM  430  are parallel to each other. A bottom surface  421   e  of the lower battery case  421  and a bottom surface  432   e  of the PCM  430  may be parallel to each other. As a result, the PCM  430  is coupled to the battery case  420  to form a rectangular parallelepiped shape. Due to the above-described structure, a structure of the battery pack  400  is simplified, and a portable electrical device in which the battery pack  400  is disposed is simply designed. Also, in the battery pack  400 , according to the present embodiment, the battery case  420  and the PCM  430  are electrically connected to each other as well as physically firmly coupled to each other by the coupling terminal  434 . The protective circuit part  431  and the body part  432  each have corresponding “L” shapes. Thus, the protective circuit part  431  and the body part  432  are coupled to the lateral surface of the battery case  420  to optimize space utilization. 
         [0084]    As described above, in the battery packs according to the above-described embodiments, the PCM in which the protective circuit part is disposed is easily decoupled from and coupled to the battery case receiving the battery cells. Thus, a design of the battery pack as a whole and a design of a space within the battery pack of a portable electrical device receiving the battery pack is simplified. Also, the battery case is separable from the PCM. As a result, in case where the battery cell is a lithium ion battery, when an electrolyte of the lithium ion battery leaks out, a short circuit of the PCM due to a contact between the PCM and the leaking electrolyte is preventable. 
         [0085]    As described above, in the battery packs according to the above-described embodiments, since the PCM receiving the protective circuit part is easily separated and coupled, the PCM can be easily replaced according to a capacitance of the battery cell, an external environment, and user request. Also, according to a number of and dispositions of the battery cells, it is possible to independently design and modify the protective circuit part and the PCM of the battery pack. Thus, a design of the battery pack, as a whole, is simplified, and miniaturization of the battery pack is realizable. 
         [0086]    Also, in the battery packs according to the above-described embodiments, since the PCM in which the protective circuit part is disposed is easily decoupled from and coupled to the battery case having the battery cells, in case where the battery cell is the lithium ion battery, a short circuit of the PCM due to a contact between the PCM and the leaking electrolyte is preventable when the electrolyte of the lithium ion battery leaks out. 
         [0087]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.