Abstract:
Provided are battery packs capable of preventing electrical shorts due to incorrect arrangement of polarities of the battery packs during assembly of an uninterruptible power supply (UPS) having the battery packs and a UPS having the battery packs. The battery pack includes: a casing housing a plurality of cells; first and second terminals arranged to protrude outwardly from a first surface of the casing and having opposite polarities; a first attachment unit formed on a second surface of the casing; and a second attachment unit formed on a third surface of the casing, disposed opposite the second surface of the casing, wherein the first attachment unit and the second attachment unit are not symmetrical to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0115917, filed Nov. 27, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Aspects of the present invention relate to a battery pack and an uninterruptible power supply (UPS) having the same. 
     2. Description of the Related Art 
     An uninterruptible power supply (UPS) is a device supplying power to a load even if a power failure occurs. A UPS is used as a buffer between a commercially supplied power and an electrical load requiring continuous power supply. Such a UPS stores power in a storage battery during commercial power supply, and stably supplies safe power of excellent quality stored in the storage battery to equipment in during a power failure or a failure of the power supply input terminal of the equipment. 
     Such a UPS includes a rectifier, an inverter, and a battery system. The capacity of a battery system in a UPS varies according to types of equipment to which power is to be supplied in during a power failure. Generally, a large capacity battery system is used for supporting large-scale manufacturing equipment and computer systems. 
     SUMMARY 
     Aspects of the present invention include battery packs capable of preventing electrical shorts due to incorrect arrangement of polarities of the battery packs during assembly of an uninterruptible power supply (UPS) having the battery packs and a UPS having the battery packs. 
     According to an aspect of the present invention, a battery pack includes a casing housing a plurality of cells; first and second terminals arranged to protrude outwardly from a first surface of the casing and having opposite polarities; a first attachment unit formed on a second surface of the casing; and a second attachment unit formed on a third surface of the casing, disposed opposite the second surface of the casing, wherein the first attachment unit and the second attachment unit are not symmetrical to each other. 
     According to another aspect of the present invention, the first attachment unit may protrude outwardly from the second surface of the casing, and the second attachment unit may protrude outwardly from the third surface of the casing. 
     According to another aspect of the present invention, the first attachment unit and the second attachment unit may have different shapes or different sizes. 
     According to another aspect of the present invention, a width of the first attachment unit may be different from a width of the second attachment unit. 
     According to another aspect of the present invention, the width of either of the first attachment unit or the second attachment unit may be greater than the width of the other of the first attachment unit or the second attachment unit. 
     According to another aspect of the present invention, a height of the first attachment unit may be different from a height of the second attachment unit. 
     According to another aspect of the present invention, the height of either of the first attachment unit or the second attachment unit may be greater than the height of the other of the first attachment unit or the second attachment unit. 
     According to another aspect of the present invention, the first attachment unit may be a groove in the second surface, and the second attachment unit may be a groove in the third surface. 
     According to another aspect of the present invention, the first attachment unit and the second attachment unit may have different shapes or different sizes. 
     According to another aspect of the present invention, a depth of either of the first attachment unit or the second attachment unit may be greater than a depth of the other of the first attachment unit or the second attachment unit. 
     According to another aspect of the present invention, a width of either of the first attachment unit or the second attachment unit may be greater than a width of the other of the first attachment unit or the second attachment unit. 
     According to another aspect of the present invention, the first attachment unit may protrude outwardly from the second surface, and the second attachment unit may be a groove in the third surface. 
     According to another aspect of the present invention, the first attachment unit may be a groove in the third surface, and the second attachment unit may protrude outwardly from the third surface. 
     According to an aspect of the present invention, an uninterruptible power supply (UPS) includes at least one battery pack, each of which includes a casing housing a plurality of cells; first and second terminals that are arranged to protrude outwardly from a first surface of the casing and having opposite polarities; a first attachment unit formed on a second surface of the casing; and a second attachment unit formed on a third surface of the casing, disposed opposite the second surface of the casing, wherein the first attachment unit and the second attachment unit are not symmetrical to each other; and a housing including at least one storage unit for housing the at least one battery pack, wherein the at least one storage unit includes third attachment units and fourth attachment units, wherein the third attachment units and the fourth attachment units are respectively attached to the first and second attachment units and hold the at least one battery pack. 
     According to another aspect of the present invention, adjacent ones the third attachment units of the storage units arranged adjacent to each other may face different directions. 
     According to another aspect of the present invention, one of the third attachment units of one of the storage unit and one of the fourth attachment units of another one of the storage unit, which is adjacent to the one of the storage units, may face the same direction. 
     According to another aspect of the present invention, the first attachment unit may protrude outwardly from the second surface of the casing, the second attachment unit may protrude outwardly from the third surface of the casing, the third attachment units may be sunk into the housing in correspondence to the first attachment, such that the third attachment units are attachable to the first attachment unit, and the fourth attachment units may be sunk into the housing in correspondence to the second attachment, such that the fourth attachment units are attachable to the second attachment unit. 
     According to another aspect of the present invention, a width of the first attachment unit may be different from a width of the second attachment unit. 
     According to another aspect of the present invention, a height of the first attachment unit may be different from a height of the second attachment unit. 
     According to another aspect of the present invention, the first attachment unit may be a groove in the second surface, the second attachment unit may be a groove in the third surface, the third attachment unit may protrude outwardly from the housing in correspondence to the first attachment, such that the third attachment units are attachable to the first attachment unit, and the fourth attachment units may protrude outwardly from the housing in correspondence to the second attachment, such that the fourth attachment units are attachable to the second attachment unit. 
     According to another aspect of the present invention, a depth of the first attachment unit may be different from a depth of the second attachment unit. 
     According to another aspect of the present invention, a width of the first attachment unit may be different from a width of the second attachment unit. 
     According to another aspect of the present invention, the first attachment unit may protrude from the second surface, the second attachment unit may be a groove in the third surface, the third attachment units may be sunk into the housing in correspondence to the first attachment, such that the third attachment units are attachable to the first attachment unit, and the fourth attachment units may protrude outwardly from the housing in correspondence to the second attachment, such that the fourth attachment units are attachable to the second attachment unit. 
     According to another aspect of the present invention, the first attachment unit may be a groove in the second surface, the second attachment unit may protrude outwardly from the third surface, the third attachment units may protrude outwardly from the housing in correspondence to the first attachment, such that the third attachment units are attachable to the first attachment unit, and the fourth attachment units may be sunk into the housing in correspondence to the second attachment, such that the fourth attachment units are attachable to the second attachment unit. 
     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 
       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: 
         FIG. 1  is a perspective view of a battery pack according to an embodiment of the present invention; 
         FIG. 2  is a front view of the battery pack of  FIG. 1 ; 
         FIG. 3  is a front view of a battery pack according to another embodiment of the present invention; 
         FIG. 4  is a perspective view of a battery pack according to another embodiment of the present invention; 
         FIG. 5  is a front view of the battery pack of  FIG. 4 ; 
         FIG. 6  is a front view of a battery pack according to another embodiment of the present invention; 
         FIG. 7  is a perspective view of a battery pack according to another embodiment of the present invention; 
         FIG. 8  is a front view of the battery pack of  FIG. 7 ; 
         FIG. 9  is a perspective view of a UPS according to an embodiment of the present invention; 
         FIG. 10  is a perspective view of a UPS according to another embodiment of the present invention; and 
         FIG. 11  is a perspective view of a UPS according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIG. 1  is a perspective view of a battery pack  10  according to an embodiment of the present invention, and  FIG. 2  is a front view of the battery pack  10  of  FIG. 1 . Referring to  FIGS. 1 and 2 , the battery pack  10 , according to the present embodiment, includes a casing  11 , a first terminal  12 , a second terminal  13 , and a data communication terminal  14 . 
     The casing  11  houses cells (not shown). The casing  11  includes an attachment space of appropriate size according to a size and number of cells housed in the attachment space. The casing  11  has various shapes according to the size and number of cells housed in the casing  11 . For example, the casing  11  has a hexahedral shape, as shown in  FIG. 1 . However, aspects of the present invention are not limited thereto, and the casing  11  may have other suitable shapes. 
     The first terminal  12 , the second terminal  13 , and the data communication terminal  14  are arranged on a first surface  11   a  of the casing  11 . A first attachment unit  15  is arranged on a second surface  11   b  of the casing  11 . A second attachment unit  16  is arranged on a third surface  11   c , which faces the second surface  11   b  of the casing  11 . 
     The first terminal  12  and the second terminal  13  operate either to allow currents to flow from the cells to the outside or to allow a charging current to flow into the cells. The first terminal  12  and the second terminal  13  are arranged on the first surface  11   a  of the casing  11 . First ends of the first terminal  12  and the second terminal  13  are connected to tags electrically connecting cells within the casing  11 . Second ends of the first terminal  12  and the second terminal  13  extend outside the casing  11 . The first terminal  12  and the second terminal  13  have opposite polarities. If the first terminal  12  has a positive polarity, the second terminal  13  may have a negative polarity, and vice versa. 
     The data communication terminal  14  is arranged on the first surface  11   a  of the casing  11 . Data regarding temperatures or charging status of housed cells are transmitted to outside via the data communication terminal  14 . The first attachment unit  15  and the second attachment unit  16  guide the battery pack  10  when the battery pack  10  is inserted into a UPS and fix a position of the battery pack  10  after the battery pack  10  is inserted into the UPS. 
     The first attachment unit  15  protrudes outwardly from the second surface  11   b  of the casing  11 . The second attachment unit  16  protrudes outwardly from the third surface  11   c  of the casing  11  in a direction opposite from a direction in which the first attachment unit  15  protrudes. The first attachment unit  15  and the second attachment unit  16  shown in  FIGS. 1 and 2  have hexahedral shapes. However, aspects of the present invention are not limited thereto, and shapes of the first attachment unit  15  and the second attachment unit  16  may vary. 
     The shapes and sizes of the first attachment unit  15  and the second attachment unit  16  may be different from each other. Referring to  FIG. 2 , a height h 1  of the first attachment unit  15  is the same as the height h 2  of the second attachment unit  16 , but the width w 1  of the first attachment unit  15  is less than the width w 2  of the second attachment unit  16 . However, aspects of the present invention are not limited thereto, and the width w 1  of the first attachment unit  15  may be smaller than the width w 2  of the second attachment unit  16 . Since the shapes and sizes of the first attachment unit  15  and the second attachment unit  16  are different from each other, an electric short due to an incorrect connection of positive and negative polarities is prevented when a plurality of the battery packs  10  are inserted into a UPS. 
     Referring to  FIG. 9 , the battery packs  10  are arranged in a line in a housing  101  of a UPS  100 , such that the first and second terminals  12  and  13  of each of the battery packs  10  are exposed. Battery packs  10   a ,  10   b ,  10   c , and  10   d  are electrically and mechanically connected to each other via busbars (not shown) connecting the first and second terminals  12  and  13 . A busbar connects terminals of opposite polarities. For example, a busbar connects the first terminal  12  of the battery pack  10   a  and the second terminal  13  of the second battery pack  10   b . For such a busbar connection, it is necessary to arrange the battery packs  10   a  and  10   b  in the housing  101  such that the first terminals  12  and the second terminals  13 , which have opposite polarities, are alternately arranged along a one direction. If terminals of the same polarity are arranged in a line (e.g. both the first terminal  12  of the battery pack  10   a  and the first terminal  12  of the second battery pack  10   b  are arranged to face an upward direction t, terminals of the same polarity are connected via a busbar, and an electric short may occur. However, in the battery pack  10 , the width w 1  of the first attachment unit  15  and the width w 2  of the second attachment unit  16  are different from each other. Therefore, according to an embodiment of the present invention, the battery packs  10  are not inserted such that terminals of the same polarity are adjacent to each other, and the battery packs  10  are inserted into the housing  101  such that terminals of opposite polarities are adjacent to each other. 
       FIG. 3  is a front view of a battery pack  20  according to another embodiment of the present invention. Referring to  FIG. 3 , the first terminal  12 , the data communication terminal  14 , and the second terminal  13  are arranged on a first surface  21   a  of a casing  21 . Furthermore, a first attachment unit  25  is arranged on a second surface  21   b  of the casing  21 , and a second attachment unit  26  is arranged on a third surface  21   c  of the casing  21 . The battery pack  20 , according to the present embodiment, is identical to the battery pack  10  of the previous embodiment, wherein the first attachment unit  25  and the second attachment unit  26  protrude outwardly from the casing  21 . However, according to the present embodiment, the shapes of the first attachment unit  25  and the second attachment unit  26  are different from the shapes of the first attachment unit  15  and the second attachment unit  16  of the embodiment of  FIG. 1 . In other words, in the battery pack  20 , according to the present embodiment, a width w 1  of the first attachment unit  25  is the same as a width w 2  of the second attachment unit  26 , but the height h 1  of the first attachment unit  25  is different from the height h 2  of the second attachment unit  26 . As shown in  FIG. 3 , a height h 1  of the first attachment unit  25  is smaller than a height h 2  of the second attachment unit  26 , or vice versa. 
       FIG. 4  is a perspective view of a battery pack  30  according to another embodiment of the present invention, and  FIG. 5  is a front view of the battery pack  30  of  FIG. 4 . Referring to  FIGS. 4 and 5 , in the battery pack  30 , according to the present embodiment, the first terminal  12 , the data communication terminal  14 , and the second terminal  14  are arranged on a first surface  31   a  of a casing  31 . 
     A first attachment unit  35  is arranged on a second surface  31   b  of the casing  31 , and a second attachment unit  36  is arranged on a third surface  31   c  of the casing  31 . The first attachment unit  35  is a groove in the second surface  31   b , and the second attachment unit  36  is a groove in the second surface  31   c . The first attachment unit  35  and the second attachment unit  36  are differently shaped grooves. In other words, a depth h 1  of the first attachment unit  35  and a depth h 2  of the second attachment unit  36  are different from each other. Referring to  FIG. 5 , the depth h 1  of the first attachment unit  35  is smaller than the depth h 2  of the second attachment unit  36 , or vice versa. A width w 1  of the first attachment unit  35  is the same as a width w 2  of the second attachment unit  36 . 
       FIG. 6  is a front view of a battery pack  40  according to another embodiment of the present invention. Referring to  FIG. 6 , in the battery pack  40  according to the present embodiment, the first terminal  12 , the data communication terminal  14 , and the second terminal  14  are arranged on a first surface  41   a  of a casing  41 . 
     A first attachment unit  45  is arranged on a second surface  41   b  of the casing  41 , and a second attachment unit  46  is arranged on a third surface  41   c  of the casing  41 . Although the battery pack  40 , according to the present embodiment, is identical to the battery pack  30  shown in  FIG. 5 , with the first attachment unit  45  and the second attachment unit  46  formed as grooves, the shapes of the first and second attachment units  45  and  46 , according to the present embodiment are different from those of the first and second attachment units  35  and  36  according to the previous embodiment. In other words, although a depth h 1  of the first attachment unit  45  and a depth h 2  of the second attachment unit  46  are the same, a width w 1  of the first attachment unit  45  is different from a width w 2  of the second attachment unit  46 . As shown in  FIG. 6 , the width w 1  of the first attachment unit  45  is greater than the width w 2  of the second attachment unit  46 , or vice versa. 
       FIG. 7  is a perspective view of a battery pack  50 , according to another embodiment of the present invention, and  FIG. 8  is a front view of the battery pack  50  of  FIG. 7 . Referring to  FIGS. 7 and 8 , in the battery pack  50 , according to the present embodiment, the first terminal  12 , the data communication terminal  14 , and the second terminal  13  are arranged on a first surface  51   a  of a casing  51 . Furthermore, a first attachment unit  55  is arranged on a second surface  51   b  of the casing  51 , and a second attachment unit  56  is arranged on a third surface  51   c  of the casing  51 . The first attachment unit  55  protrudes outwardly from the second surface  51   b  of the casing  51 , whereas the second attachment unit  56  is a groove in the third surface  51   c.    
       FIG. 9  is a perspective view of a UPS  100  according to an embodiment of the present invention. Referring to  FIG. 9 , the UPS  100 , according to the present embodiment, includes the housing  101  and the battery packs  10   a ,  10   b ,  10   c , and  10   d.    
     The housing  101  includes storage units  110   a ,  110   b ,  110   c , and  110   d  housing the battery packs  10   a ,  10   b ,  10   c , and  10   d , respectively. Each of the storage units  110   a ,  110   b ,  110   c , and  110   d  includes a third attachment unit  105  and a fourth attachment unit  106 . Each of the third attachment units  105  and the fourth attachment units  106  are respectively attached to the first attachment units  15  and the second attachment units  16 , so that the battery packs  10   a ,  10   b ,  10   c , and  10   d  slide into and are housed in the housing  101 . Furthermore, each of the third attachment units  105  and the fourth attachment units  106  hold the battery packs  10   a ,  10   b ,  10   c , and  10   d  when the battery packs  10   a ,  10   b ,  10   c , and  10   d  are housed in the housing  101 . 
     In detail, the third attachment units  105  of the storage units  110   a ,  110   b ,  110   c , and  110   d  are attached to the first attachment units  15  of the battery packs  10   a ,  10   b ,  10   c , and  10   d , respectively. The fourth attachment units  106  of the storage units  110   a ,  110   b ,  110   c , and  110   d  are attached to the second attachment units  16  of the battery packs  10   a ,  10   b ,  10   c , and  10   d , respectively. The third attachment units  105  and the fourth attachment units  106  are formed to have the shapes corresponding to the shapes of the first attachment units  15  and the second attachment units  16 . Thus, the third attachment units  105  and the fourth attachment units  106  are attached to the first attachment units  15  and the second attachment units  16 , respectively. 
     Referring to  FIG. 9 , the first attachment units  15  and the second attachment units  16  protrude outwardly from the second surface  11   b  and the third surface  11   c , respectively. Therefore, the third attachment units  105  and the fourth attachment units  106  are sunk into the housing  101  in correspondence to the shapes of the first attachment units  15  and the second attachment units  16 . In particular, although a height h 1  of the first attachment unit  15  is the same as a height h 2  of the second attachment unit  16 , a width w 1  of the first attachment unit  15  is smaller than a width w 2  of the second attachment unit  16 . Therefore, although depths y 1  and y 2  of the third attachment unit  105  and the fourth attachment unit  106  are the same, a width x 1  of the third attachment unit  105  may be smaller than a width x 2  of the fourth attachment unit  106 . 
     Furthermore, the depths y 1  and y 2  of the third attachment unit  105  and the fourth attachment unit  106  are the same as respective heights h 1  and h 2  of the first attachment unit  15  and the second attachment unit  16 . Also, the width x 1  of the third attachment unit  105  is the same as the width w 1  of the first attachment unit  15 , and the width x 2  of the fourth attachment unit  106  is the same as the width w 2  of the second attachment unit  16 . However, aspects of the present invention are not limited thereto, and the width x 1  and the depth y 1  of the third attachment unit  105  may be respectively greater than the width w 1  and the height h 1  of the first attachment unit  15 , and the width x 2  and the depth y 2  of the fourth attachment unit  106  may be respectively greater than the width w 2  and the height h 2  of the second attachment unit  16 . Thus, the first attachment unit  15  and the second attachment unit  16  are respectively attached to the third attachment unit  105  and the fourth attachment unit  106 . 
     The third attachment units  105  and the fourth attachment units  106  of the storage units  110   a ,  110   b ,  110   c , and  110   d  are arranged to face different directions. In detail, the third attachment unit  105  of the storage unit  110   a  faces an upward direction t of the housing  101 . The fourth attachment unit  106  of the storage unit  110   a  faces a downward direction b of the housing  101 . On the other hand, the third attachment unit  105  of the storage unit  110   b , which is adjacent to the storage unit  110   a , faces the downward direction b of the housing  101 , whereas the fourth attachment unit  106  of the storage unit  110   b  faces the upward direction t of the housing  101 . Furthermore, the third attachment unit  105  and the fourth attachment unit  106  of the storage unit  110   c  face the upward direction t and the downward direction b of the housing  101 , respectively. 
     In other words, the third attachment unit  105  of the storage unit  110   a , the fourth attachment unit  106  of the storage unit  110   b , the third attachment unit  105  of the storage unit  110   c , and the fourth attachment unit  106  of the storage unit  110   d  face the upward direction t. On the other hand, the fourth attachment unit  106  of the storage unit  110   a , the third attachment unit  105  of the storage unit  110   b , the fourth attachment unit  106  of the storage unit  110   c , and the third attachment unit  105  of the storage unit  110   d  face the downward direction b. The third attachment units  105  and the fourth attachment units  106  are alternately arranged to face the upward direction t, whereas the fourth attachment units  106  and the third attachment units  105  are alternately arranged to face the downward direction b. 
     As described above, in the UPS  100 , according to the present embodiment, the third attachment units  105  and the fourth attachment units  106  have different shapes and are alternately arranged. Thus upper ends and lower ends of the battery packs  10   a ,  10   b ,  10   c , and  10   d  are alternately arranged with respect to adjacent battery packs  10   a ,  10   b ,  10   c , and  10   d . Therefore, the first and second terminals  12  and  13  of opposite polarities are alternately arranged. In other words, the first attachment unit  15  and the second attachment unit  16  of the battery pack  10   a  are respectively attached to the third attachment unit  105  and the fourth attachment unit  106 . The battery pack  10   a  is disposed in the storage unit  110   a , in which the third attachment unit  105  faces the upward direction t and the fourth attachment unit  106  faces the downward direction b. Thus the battery pack  10   a  is arranged such that the first terminal  12  is disposed above a data communication terminal  14  in the upward direction t and the second terminal  13  is disposed below the data communication terminal  14  in the downward direction b. 
     Furthermore, the first attachment unit  15  and the second attachment unit  16  of the battery pack  10   b  are respectively attached to the third attachment unit  105  and the fourth attachment unit  106 . The battery pack  10   b  is disposed in the storage unit  110   b , in which the third attachment unit  105  protrudes in the downward direction b and the fourth attachment unit  106  protrudes in the upward direction t. Thus the battery pack  10   b  is arranged such that the first terminal  12  is disposed below a data communication terminal  14  in the downward direction b and the second terminal  13  is disposed above the data communication terminal  14  in the upward direction t. In the same regard, the battery pack  10   c  is arranged such that the first terminal  12  and the second terminal  13  of the battery pack  10   c  are disposed so as to be opposite in direction as that of the first and second terminals  12  and  13  of the battery pack  10   b . Also, the battery pack  10   d  is arranged such that the first terminal  12  and the second terminal  13  are disposed so as to be opposite in direction as that of the first and second terminals  12  and  13  of the battery pack  10   c.    
     Therefore, in the UPS  100 , according to the present embodiment, the first terminals  12  and the second terminals  13  of the battery packs  10   a ,  10   b ,  10   c , and  10   d  are alternately arranged to be disposed in opposite directions with respect to the first and second terminals  12  and  13  of adjacent ones of the battery packs  10   a ,  10   b ,  10   c , and  10   d.    
     The first and second terminals  12  and  13  of opposite polarities of the battery packs  10   a ,  10   b ,  10   c , and  10   d , which are respectively housed in the storage units  110   a ,  110   b ,  110   c , and  110   d , are connected to each other via busbars (not shown), which are formed of a conductive metal. In other words, the first terminal  12  of the battery pack  10   a  is connected to the second terminal  13  of the adjacent battery pack  10   b , via a busbar, and the first terminal  12  of the battery pack  10   b  is connected to the second terminal  13  of the adjacent battery pack  10   c , via a busbar. Thus, adjacent battery packs  10   a ,  10   b ,  10   c , and  10   d  are connected in series. In the UPS  100 , according to the present embodiment, due to the differences in the shapes and arrangements of the first through fourth attachment units  15 ,  16 ,  105 , and  106 , the battery packs  10   a ,  10   b ,  10   c , and  10   d  are housed in the housing  101  such that the polarities of the terminals  12  and  13  of each of the battery packs  10   a ,  10   b ,  10   c , and  10   d  are alternately arranged. Therefore, the battery packs  10   a ,  10   b ,  10   c , and  10   d  are easily housed in the housing  101  without confirming polarities of each of the battery packs  10   a ,  10   b ,  10   c , and  10   d . Furthermore, the battery packs  10   a ,  10   b ,  10   c , and  10   d  are prevented from being housed in the housing  101  such that the terminals  12  and  13  having the same polarity are arranged adjacent to each other. Thus electric shorts due to incorrect connection of terminals having the same polarity may be prevented. 
       FIG. 10  is a perspective view of a UPS  200  according to another embodiment of the present invention. Referring to  FIG. 10 , the UPS  200 , according to the present embodiment, includes a housing  201  and battery packs  20   a ,  20   b ,  20   c , and  20   d.    
     The housing  201  includes storage units  210   a ,  210   b ,  210   c , and  210   d  housing the battery packs  20   a ,  20   b ,  20   c , and  20   d , respectively. Each of the storage units  210   a ,  210   b ,  210   c , and  210   d  includes a third attachment unit  205  and a fourth attachment unit  206 . The third attachment units  205  and the fourth attachment units  206  are respectively attached to the first attachment units  25  and the second attachment units  26  of the battery packs  20   a ,  20   b ,  20   c , and  20   d . The third attachment units  205  are formed to be attached to the first attachment units  25 , whereas the fourth attachment units  206  are formed to be attached to the second attachment units  26 . 
     Referring to  FIG. 10 , the first attachment units  25  and the second attachment units  26  protrude outwardly from second surfaces  21   b  and third surfaces  21   c , respectively. Therefore, the third attachment units  205  and the fourth attachment units  206  are sunk into the housing  201  in correspondence to shapes of the first attachment units  25  and the second attachment units  26 . A height h 1  of each of the first attachment units  25  is smaller than a height h 2  of each of the second attachment units  26 , whereas a width w 1  of each of the first attachment units  25  is the same as a width w 2  of each of the second attachment units  26 . Therefore, widths x 1  and x 2  of the third attachment units  205  and the fourth attachment unit  206 , respectively, are the same, whereas a depth y 1  of each of the third attachment units  205  is smaller than a depth y 2  of each of the fourth attachment unit  206 . However, aspects of the present invention are not limited thereto. For example, the width x 1  and the depth y 1  of each of the third attachment units  205  may be respectively greater than the width w 1  and the height h 1  of each of the first attachment units  25 , and the width x 2  and the depth y 2  of each of the fourth attachment units  206  may be respectively greater than the width w 2  and the height h 2  of each of the second attachment units  26 . Thus, the first attachment units  25  and the second attachment units  26  are respectively attached to the third attachment units  205  and the fourth attachment units  206 . 
     The third attachment units  205  and the fourth attachment units  206  of the storage units  210   a ,  210   b ,  210   c , and  210   d  are arranged to face different directions. In detail, the third attachment unit  205  of the storage unit  210   a  faces an upward direction t of the housing  201 , whereas the fourth attachment unit  206  of the storage unit  210   a  faces the downward direction b of the housing  201 . On the other hand, the third attachment unit  205  of the storage unit  210   b , which is adjacent to the storage unit  210   a , faces the downward direction b, whereas the fourth attachment unit  206  of the storage unit  210   b  faces the upward direction t. Furthermore, the third attachment unit  205  and the fourth attachment unit  206  of the storage unit  210   c  face the upward direction t and the downward direction b of the housing  201 , respectively. 
     In other words, the third attachment unit  205  of the storage unit  210   a , the fourth attachment unit  206  of the storage unit  210   b , the third attachment unit  205  of the storage unit  210   c , and the fourth attachment unit  206  of the storage unit  210   d  face the upward direction t, whereas the fourth attachment unit  206  of the storage unit  210   a , the third attachment unit  205  of the storage unit  210   b , the fourth attachment unit  206  of the storage unit  210   c , and the third attachment unit  205  of the storage unit  210   d  face the downward direction b. In other words, the third attachment units  205  and the fourth attachment units  206  are alternately arranged to face the upward direction t, whereas the fourth attachment units  206  and the third attachment units  205  are alternately arranged to face the downward direction b. 
     As described above, in the UPS  200 , according to the present embodiment, the third attachment units  205  and the fourth attachment units  206  have different shapes and are alternately arranged. Thus upper ends and lower ends of the battery packs  20   a ,  20   b ,  20   c , and  20   d  are alternately arranged. Therefore, the first and second terminals  12  and  13  having opposite polarities are alternately arranged. In other words, the first attachment unit  25  and the second attachment unit  26  of the battery pack  20   a  are respectively attached to the third attachment unit  205  and the fourth attachment unit  206 . Thus the battery pack  20   a  is arranged such that the first terminal  12  is disposed above a data communication terminal  14  in an upward direction t and the second terminal  13  is disposed below the data communication terminal  14  in the downward direction b. 
     Furthermore, the first attachment unit  25  and the second attachment unit  26  of the battery pack  20   b  are respectively attached to the third attachment unit  205  and the fourth attachment unit  206 . Thus the battery pack  20   b  is arranged such that the first terminal  12  is disposed above a data communication terminal  14  in an upward direction t and the second terminal  13  is disposed below the data communication terminal  14  in the downward direction b. In the same regard, the battery pack  20   c  is arranged such that the first terminal  12  and the second terminal  13  of the battery pack  20   c  are disposed in an opposite orientation as that of the first terminal  12  and the second terminal  13  of the battery pack  20   b . Additionally, the battery pack  20   d  is arranged such that the first terminal  12  and the second terminal  13  of the battery pack  20   d  are oriented similarly to the first terminal  12  and the second terminal  13  of the battery pack  20   b.    
     Therefore, in the UPS  200 , according to the present embodiment, the first terminals  12  and the second terminals  13  of the battery packs  20   a ,  20   b ,  20   c , and  20   d  are alternately arranged with respect to the first terminals  12  and the second terminals  13  of adjacent ones of the battery packs  20   a ,  20   b ,  20   c , and  20   d.    
     Accordingly, in the UPS  200 , according to the present embodiment, due to the differences in the shapes and arrangements of the first through fourth attachment units  25 ,  26 ,  205 , and  206 , the battery packs  20   a ,  20   b ,  20   c , and  20   d  are housed in the housing  201  such that the polarities of the terminals  12  and  13  of the respective battery packs  20   a ,  20   b ,  20   c , and  20   d  are alternately arranged. Therefore, the battery packs  20   a ,  20   b ,  20   c , and  20   d  are easily housed in the housing  201  without confirming polarities of each of the battery packs  20   a ,  20   b ,  20   c , and  20   d . Furthermore, the battery packs  20   a ,  20   b ,  20   c , and  20   d  are prevented from being housed in the housing  201  such that the terminals  12  and  13  having the same polarity are arranged adjacent to each other. Thus electric shorts due to incorrect connection of terminals having the same polarity is prevented. 
       FIG. 11  is a perspective view of a UPS  300  according to another embodiment of the present invention. Referring to  FIG. 11 , the UPS  300  according to the present embodiment includes a housing  301  and battery packs  50   a ,  50   b ,  50   c , and  50   d.    
     The housing  301  includes storage units  310   a ,  310   b ,  310   c , and  310   d  housing the battery packs  50   a ,  50   b ,  50   c , and  50   d , respectively. Each of the storage units  310   a ,  310   b ,  310   c , and  310   d  includes a third attachment unit  305  and a fourth attachment unit  306 . The third attachment units  305  and the fourth attachment units  306  are attached to first attachment units  55  and second attachment units  56  of the battery packs  50   a ,  50   b ,  50   c , and  50   d , respectively. The third attachment units  305  are formed to be attached to the first attachment units  55 , whereas the fourth attachment units  306  are formed to be attached to the second attachment units  56 . Referring to  FIG. 11 , the first attachment units  55  protrude outwardly from the second surfaces  51   b  of the casings  51 , respectively, whereas the second attachment units  56  are sunken inwardly from the third surfaces  51   c  of the casings  51 , respectively. 
     Therefore, the third attachment units  305  are sunk into the housing  301  in correspondence to the shapes of the first attachment units  55 , whereas the fourth attachment units  306  protrude outwardly from the housing  301  in correspondence to the shapes of the second attachment units  56 . A width x 1  and a height y 1  of each of the third attachment units  305  is the same as a width w 1  and a height h 1  of each of the first attachment units  55 , and a width x 2  and a depth y 2  of each of the fourth attachment units  306  is the same as a width w 2  and a height h 2  of each of the second attachment units  56 . However, aspects of the present invention are not limited thereto. For example, the width x 1  and the depth y 1  of each of the third attachment units  305  may be respectively greater than the width w 1  and the height h 1  of each of the first attachment units  55 , and the width x 2  and the depth y 2  of each of the fourth attachment units  306  may be respectively greater than the width w 2  and the height h 2  of each of the second attachment units  56 . Thus, the first attachment units  55  and the second attachment units  56  are easily attached to the third attachment units  305  and the fourth attachment units  306 , respectively. 
     The third attachment units  305  and the fourth attachment units  306  of the storage units  310   a ,  310   b ,  310   c , and  310   d  are arranged to face different directions. In detail, the third attachment unit  305  of the storage unit  310   a  faces the upward direction t of the housing  301 , whereas the fourth attachment unit  306  of the storage unit  310   a  faces the downward direction b of the housing  301 . On the other hand, the third attachment unit  305  of the storage unit  310   b , which is adjacent to the storage unit  310   a , faces the downward direction b of the housing  301 , whereas the fourth attachment unit  306  of the storage unit  310   b  faces the upward direction t of the housing  301 . As such, third and fourth attachment units  305  and  306  of adjacent storage units  310   a ,  310   b ,  310   c  and  310   d  are disposed so as to face opposite directions. In other words, the third attachment units  305  and the fourth attachment units  306  are alternately arranged to face the upward direction t, whereas the fourth attachment units  306  and the third attachment units  305  may be alternately arranged to face the downward direction b. 
     As described above, in the UPS  300 , according to the present embodiment, the third attachment units  305  and the fourth attachment units  306  have different shapes and are alternately arranged. Thus the upper ends and the lower ends of the battery packs  50   a ,  50   b ,  50   c , and  50   d  are alternately arranged. Therefore, the first and second terminals  12  and  13  having opposite polarities are alternately arranged. In other words, the first attachment unit  55  and the second attachment unit  56  of the battery pack  50   a  are respectively attached to the third attachment unit  305  and the fourth attachment unit  306 . Thus the battery pack  50   a  is arranged such that the first terminal  12  is disposed above a data communication terminal  14  in the upward direction t and the second terminal  13  is disposed below the data communication terminal  14  in the downward direction b. As such, first and second attachment units  55  and  56  of adjacent battery packs  50   a ,  50   b ,  50   c  and  50   d  are disposed so as to face opposite directions. 
     Therefore, in the UPS  300  according to the present embodiment, the first terminals  12  and the second terminals  13  of each of the battery packs  50   a ,  50   b ,  50   c , and  50   d  respectively housed in the storage units  310   a ,  310   b ,  310   c , and  310   d  are alternately arranged so that the second terminals  13  and the first terminals  12  of adjacent ones of the battery packs  50   a ,  50   b ,  50   c , and  50   d  are disposed on alternating sides of respective data communication terminals  14 . 
     Accordingly, in the UPS  300 , according to the present embodiment, due to the differences in the shapes and arrangements of the first through fourth attachment units  55 ,  56 ,  305 , and  306  as described above, the battery packs  50   a ,  50   b ,  50   c , and  50   d  are housed in the housing  301  such that the polarities of the terminals  12  and  13  of the battery packs  50   a ,  50   b ,  50   c , and  50   d  are alternately arranged. Therefore, the battery packs  50   a ,  50   b ,  50   c , and  50   d  are easily housed in the housing  301  without confirming polarities of each of the battery packs  50   a ,  50   b ,  50   c , and  50   d . Furthermore, the battery packs  50   a ,  50   b ,  50   c , and  50   d  are prevented from being housed in the housing  301  such that the terminals  12  and  13  having the same polarity are arranged adjacent to each other. Thus, electric shorts due to incorrect connection of terminals having the same polarity is prevented. 
     As described above, according to the one or more of the above embodiments of the present invention, electrical shorts due to incorrect arrangement of polarities during attachment of a plurality of battery packs is prevented. 
     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.