Patent Publication Number: US-10326116-B2

Title: Battery device, electronic apparatus, and battery system

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. application Ser. No. 14/515,240, filed Oct. 15, 2014, now U.S. Pat. No. 9,455,426, which is a continuation application of U.S. application Ser. No. 14/189,370, filed Feb. 25, 2014, now U.S. Pat. No. 8,945,745, which is a continuation application of and claims the benefit of priority under 35 U.S.C. § 120 from U.S. application Ser. No. 13/849,776, filed Mar. 25, 2013, now U.S. Pat. No. 8,790,807, which is a continuation application of U.S. application Ser. No. 13/458,601, filed Apr. 27, 2012, now U.S. Pat. No. 8,470,465, which is a continuation application of U.S. application Ser. No. 13/116,781, filed May 26, 2011, now U.S. Pat. No. 8,241,774, which is a continuation application of U.S. application Ser. No. 11/836,310, filed Aug. 9, 2007, now U.S. Pat. No. 7,989,101, which is based upon and claims the benefit of priority under 35 U.S.C. § 119 from prior Japanese Patent Application JP 2006-230797, filed in the Japanese Patent Office on Aug. 28, 2006. The entire contents of each of the above is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a battery device used as a portable power source, an electronic apparatus in which the battery device is detachably mounted and used, and a battery system including a combination of the electronic apparatus with the battery device. 
     Description of the Related Art 
     Japanese Unexamined Patent Application Publication No. 2000-243365 discloses an example of a battery device of the related art as a portable power source. Japanese Unexamined Patent Application Publication No. 2000-243365 discloses a battery pack in which a rechargeable battery cell used as a power source for an electronic apparatus is stored; a battery mounting device on which the battery pack is mounted; and an electronic apparatus including a battery mounting mechanism on which the battery pack is mounted. The battery pack disclosed in Japanese Unexamined Patent Application Publication No. 2000-243365 includes “a battery cell; a case in which the battery cell is stored; an output terminal which is provided in the case and outputs power of the battery cell; and a second surface of the case which is provided continuously with a first surface of the case having the output terminal and provided approximately perpendicular to the first surface, where a recess is formed with a plurality of steps in an approximate center of the second surface”. 
     It may be expected that the battery pack having such a configuration may be prevented from being inappropriately mounted on a battery mounting device which is supposed to be incompatible (paragraph [0161] of the specification), for example. 
     Japanese Unexamined Utility Model Application Publication No. 2005-190929 discloses another example of a battery device of the related art. Japanese Unexamined Utility Model Application Publication No. 2005-190929 discloses a battery device and an electronic apparatus operated using the battery device. The battery device disclosed in Japanese Unexamined Utility Model Application Publication No. 2005-190929 includes “a case having a width, a thickness, and a length; a rechargeable battery provided in the case; and a battery side terminal provided on a surface of the case and connected to the rechargeable battery, where the battery device is inserted in the length direction into a battery housing chamber of an electronic apparatus and the battery side terminal is connected to a housing chamber side terminal of the battery housing chamber. A guide groove is formed in each side of the case in the crosswise direction, where the guide groove extends in the length direction and is engaged with a protrusion provided in the battery housing chamber to position the case in the thickness direction in the battery housing chamber”. 
     According to the battery device having such a configuration, it may be expected that “since a guide groove is formed in each side of the case in the crosswise direction of the battery device, where the guide groove extends in the length direction and is engaged with a protrusion provided in the battery housing chamber to position the case in the thickness direction in the battery housing chamber, it is possible to store, in the battery housing chamber, multiple types of battery devices different in thickness of the case, that is, different in volume” (paragraph [0005] of the specification). 
     However, in the battery device disclosed in Japanese Unexamined Patent Application Publication No. 2000-243365, a recess formed with a plurality of steps is provided in an approximate center of a rear surface of the case in which the battery cell is stored, and a protrusion corresponding to a shape of the recess is provided in a mounting portion of the electronic apparatus in which the battery device is mounted, in order to discriminate a type of the battery device. As a result, when a new battery device is developed, it may be necessary to increase the number of the steps in the recess of the battery device and provide a protrusion corresponding to the recess in the mounting portion of the electronic apparatus, and thus the recess of the battery device and the protrusion of the mounting portion have complicated shapes. 
     Further, each of the battery devices disclosed in Japanese Unexamined Patent Application Publication No. 2000-243365 and Japanese Unexamined Patent Application Publication No. 2005-190929 is formed as an exclusive component that may be mounted only on a mounting portion having a specific configuration of an electronic apparatus. Accordingly, one battery device may be mounted on an electronic apparatus having a mounting portion corresponding to the battery device, and a battery device corresponding to the electronic apparatus may separately be prepared for another type of an electronic apparatus including a mounting portion having a different mounting structure. 
     SUMMARY OF THE INVENTION 
     The number of steps in a recess of the battery device may have to be increased and provided a protrusion corresponding to the recess in a mounting portion of an electronic apparatus when a new battery device of the related art is developed, and thus the recess of the battery device and the protrusion of the mounting portion have complicated shapes. 
     A battery device according to an embodiment of the present invention includes an approximately rectangular parallelepiped battery enclosure incorporating a battery cell; and an output terminal which is placed to expose an output portion in an approximate center of at least a first surface of the battery enclosure in a crosswise direction and outputs power of the battery cell. The battery enclosure has a second surface, a first step surface, a second step surface, a first engaging portion, a second engaging portion, a first groove, and a second groove. The second surface is approximately perpendicular to the first surface. The first step surface is provided continuously with and approximately parallel to the second surface with a predetermined step on one side of the second surface in the crosswise direction. The second step surface is provided continuously with and approximately parallel to the second surface with a predetermined step on the other side of the second surface in the crosswise direction. The first engaging portion protrudes with predetermined width and thickness from the second surface to one side in the crosswise direction. The second engaging portion protrudes with predetermined width and thickness from the second surface in the crosswise direction to the other side. The first groove is formed with the first step surface and the first engaging portion. The second groove is formed with the second step surface and the second engaging portion. The most important feature is that a recess is provided in at least one of the first step surface and the second step surface. 
     An electronic apparatus according to an embodiment of the present invention includes a mounting portion in which a battery device is detachably mounted having an approximately rectangular parallelepiped battery enclosure incorporating a battery cell; and a connection terminal which is placed to expose a connection portion in an approximate center of at least a first surface of the mounting portion in a crosswise direction and is detachably connected to an output terminal that outputs power of the battery cell of the battery device. The mounting portion of the electronic apparatus has a second surface approximately perpendicular to the first surface; a first hook provided at a predetermined interval from the second surface and detachably engaged with a first engaging portion provided in the battery enclosure; and a second hook provided at a predetermined interval from the second surface and detachably engaged with a second engaging portion provided in the battery enclosure. A projection protruding away from the second surface is provided on at least one of the first hook and the second hook. 
     According to an embodiment of the present invention, there is provided a battery system including a combination of a battery device having a battery cell with an electronic apparatus having a mounting portion in which the battery device is detachably mounted. 
     The battery device has an approximately rectangular parallelepiped battery enclosure incorporating a battery cell; and an output terminal which is placed to expose an output portion in an approximate center in a crosswise direction of at least a battery side first surface of the battery enclosure and outputs power of the battery cell. The battery enclosure of the battery device has a battery side second surface, a first step surface, a second step surface, a first engaging portion, a second engaging portion, a first groove, and a second groove. The battery side second surface is approximately perpendicular to the battery side first surface. The first step surface is provided continuously with and approximately parallel to the battery side second surface with a predetermined step on one side of the battery side second surface in the crosswise direction. The second step surface is provided continuously with and approximately parallel to the battery side second surface with a predetermined step on the other side of the battery side second surface in the crosswise direction. The first engaging portion protrudes with predetermined width and thickness to one side from the battery side second surface in the crosswise direction. The second engaging portion protrudes with predetermined width and thickness to the other side from the battery side second surface in the crosswise direction. The first groove is formed with the first step surface and the first engaging portion. The second groove is formed with the second step surface and the second engaging portion. A recess is provided in at least one of the first step surface and the second step surface. 
     The electronic apparatus has a connection terminal which is placed to expose a connection portion in an approximate center of at least an electronic apparatus side first surface of the mounting portion in a crosswise direction and is detachably connected to the output terminal that outputs power of the battery cell of the battery device. The mounting portion of the electronic apparatus has: an electronic apparatus side second surface approximately perpendicular to the electronic apparatus side first surface; a first hook provided at a predetermined interval from the electronic apparatus side second surface and detachably engaged with a first engaging portion provided in the battery enclosure; and a second hook provided at a predetermined interval from the electronic apparatus side second surface and detachably engaged with a second engaging portion provided in the battery enclosure. A projection detachably engaged with the recess is provided in at least one of the first hook and the second hook. 
     A battery device according to an embodiment of the present invention having such a configuration may provide a type discrimination portion for a new battery device with a simple structure and may be commonly used for multiple types of an electronic apparatus having different mounting systems. An electronic apparatus according to an embodiment of the present invention may provide a type discrimination portion for a new battery device with a simple structure, and a battery device mounted on a mounting portion of the electronic apparatus to supply power may be commonly used for multiple types of the electronic apparatus having different mounting systems. Further, a battery system according to an embodiment of the present invention including a combination of the battery device and the electronic apparatus described above may provide a battery system having advantages of the battery device and the electronic apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a bottom oblique view showing a first example of a battery device according to an embodiment of the present invention. 
         FIGS. 2A-2B  show a first example of a battery device according to an embodiment of the present invention, where  FIG. 2A  is a bottom view and  FIG. 2B  is a left side view. 
         FIGS. 3A-3C  show a first example of a battery device according to an embodiment of the present invention, where  FIG. 3A  is a front view,  FIG. 3B  is a rear view, and  FIG. 3C  is a D-D line cross-sectional view of  FIG. 2B . 
         FIG. 4  is a front oblique view of a digital video camera as a specific example of an imaging device shown as an example of an electronic apparatus according to an embodiment of the present invention. 
         FIG. 5  is a rear oblique view of a digital video camera as a specific example of an imaging device shown as an example of an electronic apparatus according to an embodiment of the present invention. 
         FIG. 6  is a rear view of a digital video camera as a specific example of an imaging device shown as an example of an electronic apparatus according to an embodiment of the present invention. 
         FIG. 7  is an oblique view of a rear panel having a mounting portion of the digital video camera shown in  FIG. 4 . 
         FIG. 8  is an exploded oblique view of a rear panel having a mounting portion, a slide member, and a support plate member of the digital video camera shown in  FIG. 4 . 
         FIGS. 9A-9C  show the rear panel shown in  FIG. 7  and others, where  FIG. 9A  is a front view of the rear panel,  FIG. 9B  is a view describing an initial state during mounting a battery device, and  FIG. 9C  is view describing a state after mounting the battery device. 
         FIG. 10  is an oblique view showing a second example of a rear panel having a mounting portion of an imaging device shown as an example of an electronic apparatus according to an embodiment of the present invention. 
         FIGS. 11A-11C  show the rear panel shown in  FIG. 10  and others, where  FIG. 11A  is a front view of the rear panel,  FIG. 11B  is a view describing an initial state during mounting a battery device, and  FIG. 11C  is view describing a state after mounting the battery device. 
         FIG. 12  is a bottom oblique view showing a second example of a battery device according to an embodiment of the present invention. 
         FIG. 13  is a front view showing a second example of a battery device according to an embodiment of the present invention. 
         FIG. 14  is an oblique view showing a third example of a rear panel having a mounting portion of an imaging device shown as an example of an electronic apparatus according to an embodiment of the present invention. 
         FIG. 15  is an U-U line cross-sectional view showing the rear panel shown in  FIG. 14  and others in a state where a battery device is mounted. 
         FIG. 16  is a front oblique view showing a fourth example of a mounting portion of an electronic apparatus according to an embodiment of the present invention. 
         FIG. 17  is a cross-sectional view of a mounting portion of a fourth example in which a battery device is mounted, the mounting portion having a dimension in a height direction Z 2  sufficiently larger than that of the battery device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A battery device, suitable electronic apparatus using the battery device, and a battery system including a combination of the battery device with the electronic apparatus are realized based on a simple structure, where a type of the battery device may be discriminated based on the simple structure, and there is no need to prepare separate battery devices for multiple types of an electronic apparatus having mounting portions with different structures and thus one battery device may be commonly used for the multiple types. 
       FIGS. 1 to 17  show examples of embodiments of the present invention. Specifically,  FIGS. 1 to 3  show a first example of a battery device according to an embodiment of the present invention, where  FIG. 1  is an oblique view,  FIG. 2A  is a bottom view,  FIG. 2B  is a left side view,  FIG. 3A  is a front view,  FIG. 3B  is a rear view, and  FIG. 3C  is a D-D line cross-sectional view of  FIG. 2B .  FIGS. 4 to 7  show an imaging device as an example of an electronic apparatus according to an embodiment of the present invention, where  FIG. 4  is a front oblique view of the imaging device,  FIG. 5  is a rear oblique view of the imaging device,  FIG. 6  is a rear view of the imaging device, and  FIG. 7  is an oblique view showing a first example of a rear panel of an exterior case.  FIG. 8  is an exploded oblique view showing a mounting portion, a slide member, and a support plate member, and  FIGS. 9A to 9C  describe a state of mounting a battery device in a mounting portion of an imaging device, where  FIG. 9A  is a front view of a rear panel,  FIG. 9B  is a view describing an initial state during mounting the battery device, and  FIG. 9C  is a view describing a state after mounting the battery device.  FIG. 10  is an oblique view showing a second example of a rear panel, and  FIGS. 11A to 11C  describe a state of mounting a battery device in a mounting portion of an imaging device, where  FIG. 11A  is a front view of the rear panel,  FIG. 11B  is a view describing an initial state during mounting the battery device, and  FIG. 11C  is a view describing a state after mounting the battery device. 
       FIGS. 12 and 13  show a second example of a battery device according to an embodiment of the present invention, where  FIG. 12  is an oblique view and  FIG. 13  is a front view.  FIG. 14  is an oblique view showing a third example of a rear panel, and  FIG. 15  is an U-U line cross-sectional view of  FIG. 14  in a state where a battery device is mounted.  FIG. 16  is a front oblique view of a fourth example of a mounting portion of an electronic apparatus according to an embodiment of the present invention, and  FIG. 17  is a view describing a mounting portion in which a battery device is mounted, the mounting portion having a dimension in a height direction Z 2  sufficiently larger than that of the battery device. 
     Example 1 
     First, a first example of a battery device according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . The battery device  1  includes: a battery enclosure  2  formed with a hollow enclosure; a battery cell and a control circuit board (not shown) provided inside the battery enclosure  2 ; and a battery side output terminal  3  provided in the battery enclosure  2 . 
     As shown in  FIG. 1 , the battery enclosure  2  shown in this example is formed as an approximately rectangular parallelepiped block-shaped container having a dimension L in a longitudinal direction Y, a dimension W in a crosswise direction X at right angles to the longitudinal direction Y, and a dimension H in a height direction Z at right angles to the longitudinal direction Y and the crosswise direction X. In this example, the dimensions of the battery enclosure  2  (length L, width W, and height H) are set to have a relation of: length L&gt;width W&gt;height H. However, a shape of a battery device according to an embodiment of the present invention is not limited to a shape of the battery device of this example, and the height H (for example, width W&lt;height H) is sufficiently be increased, to allow the width W longer than the length L (length L&lt;width W), and to use other variations in the dimensions, for example. The battery enclosure  2  is formed with a container-shaped upper case  4  with one surface open and a cover-shaped lower case  5  mounted to close the opening of the upper case  4 . 
     The upper case  4  has a rectangular upper surface  4   a , a front surface  4   b , a rear surface  4   c , a left side surface  4   d , and a right side surface  4   e . The front surface  4   b  is continuous with the upper surface  4   a  to be approximately perpendicular to one side Y of the upper surface  4   a  in the longitudinal direction. The rear surface  4   c  is continuous with the upper surface  4   a  to be approximately perpendicular to the other side Y of the upper surface  4   a  in the longitudinal direction. The left side surface  4   d  is continuous with the upper surface  4   a  to be approximately perpendicular to one side of the upper surface  4   a  in the crosswise direction X. The right side surface  4   e  is continuous with the upper surface  4   a  to be approximately perpendicular to the other side of the upper surface  4   a  in the crosswise direction X. Circular chamfers  4   f ,  4   f  each having a large radius of curvature are provided in a corner at which the upper surface  4   a  intersects with the left side surface  4   d  and a corner at which the upper surface  4   a  intersects with the right side surface  4   e , respectively. 
     The lower case  5  is formed with a lower surface  5   a , a front surface  5   b , a rear surface  5   c , a left step portion  5   d , and a right step portion  5   e . The lower surface  5   a  is approximately rectangular and shows a specific example of a second surface of the battery enclosure  2 . The front surface  5   b  forms part of a first surface continuous with the lower surface  5   a  to be approximately perpendicular to one side of the lower surface  5   a  in the longitudinal direction Y. The rear surface  5   c  has a third step surface  6   c  continuous with the lower surface  5   a  with a predetermined step from the other side in the longitudinal direction Y of the lower surface  5   a . The left step portion  5   d  has a first step surface  6   a  continuous with the lower surface  5   a  with a predetermined step from one side of the lower surface  5   a  in the crosswise direction X. The right step portion  5   e  has a second step surface  6   b  continuous with the lower surface  5   a  with a predetermined step from the other side of the lower surface  5   a  in the crosswise direction X. The front surface  5   b  of the lower case  5  and the front surface  4   b  of the upper case  4  form a front surface that is the first surface of the battery enclosure  2 . 
     An application portion  5   f  for application of a label is formed to have an appropriate depth on the lower surface  5   a  of the lower case  5 . As shown in  FIG. 3A , the first step surface  6   a  and the second step surface  6   b  are set to have an approximately equal height S (length in the height direction Z) from the lower surface  5   a . Further, the first step surface  6   a  and the second step surface  6   b  are also set to have an approximately equal width M (length in the crosswise direction X). The first step surface  6   a  and the second step surface  6   b  are formed to be approximately parallel to the lower surface  5   a , respectively. 
     Further, as shown in  FIG. 1A , a first engaging portion  7  and a second engaging portion  8  are provided in the lower case  5 , where the first engaging portion  7  is formed protruding from one side of the lower surface  5   a  with predetermined width N and thickness T in the crosswise direction X that is the second surface, and the second engaging portion  8  is formed protruding with predetermined width N and thickness T from the other side of the lower surface  5   a  in the crosswise direction X. The first engaging portion  7  and the second engaging portion  8  are symmetrical with each other, and the width (protrusion length) N of each of the first engaging portion  7  and the second engaging portion  8  is set to be about ½ the width M of each of the first step surface  6   a  and the second step surface  6   b . The thickness T of each of the first engaging portion  7  and the second engaging portion  8  is set to be ½ or less the height S of each of the first step surface  6   a  and the second step surface  6   b.    
     The first engaging portion  7  has a first engaging piece  7   a , a second engaging piece  7   b , and a third engaging piece  7   c  provided at appropriate intervals in the longitudinal direction Y. The first engaging portion  7   a  is placed on a front surface  5   b  side, the third engaging portion  7   c  is placed on a rear surface  5   c  side, and the second engaging portion  7   b  is placed in a middle between the first engaging portion  7   a  and the third engaging portion  7   c . A first opening  10   a  is provided between the first engaging piece  7   a  and the second engaging piece  7   b , and a second opening  10   b  is provided between the second engaging piece  7   b  and the third engaging piece  7   c . Similarly, the second engaging portion  8  has a first engaging piece  8   a , a second engaging piece  8   b , and a third engaging piece  8   c  provided at appropriate intervals in the longitudinal direction Y. The first engaging portion  8   a  is placed on a front surface  5   b  side, the third engaging portion  8   c  is placed on a rear surface  5   c  side, and the second engaging portion  8   b  is placed in a middle between the first engaging portion  8   a  and the third engaging portion  8   c . A third opening  10   c  is provided between the first engaging piece  8   a  and the second engaging piece  8   b , and a fourth opening  10   d  is provided between the second engaging piece  8   b  and the third engaging piece  8   c.    
     Further, as shown in  FIGS. 2 and 2A , a first rib  11   a  is provided on a rear surface  5   c  side of the first engaging piece  7   a  of the first engaging portion  7 ; a second rib  11   b  is provided on a rear surface  5   c  side of the second engaging piece  7   b ; and a third rib  11   c  is provided on a rear surface  5   c  side of the third engaging piece  7   c . Similarly, a first rib  12   a  is provided on a rear surface  5   c  side of the first engaging piece  8   a  of the second engaging portion  8 ; a second rib  12   b  is provided on a rear surface  5   c  side of the second engaging piece  8   b ; and a third rib  12   c  is provided on a rear surface  5   c  side of the third engaging piece  8   c . A protrusion length (width) P of each of the first ribs  11   a ,  12   a  and the second ribs  11   b ,  12   b  is set to be about ½ a protrusion length (width) N of each of the first engaging pieces  7   a ,  8   a  and the second engaging pieces  7   b ,  8   b . On the other hand, a protrusion length (width) of each of the third ribs  11   c ,  12   c  is set to be approximately equal to a protrusion length (width) N of each of the third engaging pieces  7   c ,  8   c.    
     An opening  14  for the output terminal  3  to expose part of the output terminal  3  is provided on a front surface  5   b  side of the lower case  5 . The opening  14  is formed as a continuous notch from the front surface  5   b  to the lower surface  5   a  and is provided to notch a whole approximate center of the front surface  5   b  in the crosswise direction X. Further, two first discrimination recesses  15   a ,  15   b  to discriminate a type of the battery device  1  are provided on both sides of the opening  14  of the lower case  5  in the crosswise direction X. The two first discrimination recesses  15   a ,  15   b  are each formed to have a specific shape according to a shape, a power capacity, or the like of the battery device  1 . 
     As shown in  FIGS. 1 and 2B , two second discrimination recesses  9   a ,  9   b  to discriminate a type of the battery device  1  are provided on the first step surface  6   a  at a predetermined interval in the longitudinal direction Y. Similarly, two third discrimination recesses  13   a ,  13   b  to discriminate a type of the battery device  1  are provided on the second step surface  6   b  at a predetermined interval in the longitudinal direction Y. The second discrimination recesses  9   a ,  9   b  are each formed to have a specific depth (height) K from the first step surface  6   a  and the third discrimination recesses  13   a ,  13   b  are each formed to have a specific depth (height) J from the second step surface  6   b  according to a shape, a power capacity, and others of the battery device  1 . In this example, the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  are approximately symmetrically formed so that the depth K is approximately equal to the depth J. However, the depth K of the second discrimination recesses  9   a ,  9   b  and the depth J of the third discrimination recesses  13   a ,  13   b  in an embodiment of the present invention are not limited to those in this example, and the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  may be asymmetrically formed to make the depth K differ from the depth J. 
     In this example, the number of the second discrimination recesses  9  or the third discrimination recesses  13  is set to be two. However, the number of the second discrimination recesses  9  or the third discrimination recesses  13  is not limited to the number in this example, and the number of the second discrimination recesses  9  may be one and the number of the third discrimination recesses  13  may be three, for example. Further, in this example, the second discrimination recesses  9  and the third discrimination recesses  13  are formed in each of the first step surface  6   a  and the second step surface  6   b ; however, it is also possible to form the second discrimination recesses  9  or the third discrimination recesses  13  on either one of the first step surface  6   a  and the second step surface  6   b . The second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  show a specific example of a recess in an embodiment of the present invention. 
     As shown in  FIGS. 1 and 3A , the output terminal  3  mounted on the opening  14  of the lower case  5  has a block-shaped terminal holder  16  having at least: a front surface  16  coplanar with the front surface  5   b  of the lower case  5 ; and a lower surface  16   b  approximately perpendicular to the front surface  16   a  and coplanar with the lower surface  5   a  of the lower case  5 . The terminal holder  16  has: multiple (four in this example) electrode slits  17   a ,  17   a  in which electrodes are placed; and two positioning slits  17   b ,  17   b  placed on both sides of the multiple electrode slits  17   a . The electrode slits  17   a  and the positioning slits  17   b  are formed in a corner of the terminal holder  16  as groove-shaped notches continuous from the front surface to the bottom surface. 
     Positioning protrusions of a connection terminal  56  provided in a mounting portion of an electronic apparatus described later are each engaged with the two positioning slits  17   b  of the terminal holder  16 . Similarly, electrodes of the connection terminal  56  are each engaged with the four electrode slits  17   a . Battery side electrodes of the output terminal  3  (not shown) are each placed in the four electrode slits  17   a . The battery cell incorporated in the battery enclosure  2  is electrically connected to each of the battery side electrodes of the output terminal  3 . 
     The lower case  5  having such a configuration is overlapped with the upper case  4  to close an opening of the upper case  5  and portions overlapped in this manner are joined together. Obviously, the portions may be joined together by use of an adhesive, by thermally welding, or by another joining method, for example. Accordingly, the battery enclosure  2  is formed having the upper case  4  and the lower case  5  integrated. A battery cell having one or more battery cells and a control circuit board having a microcomputer including a CPU, a RAM and ROM, and an interface are stored in the battery enclosure  2 . The battery cell and the control circuit board are electrically connected to each other and also connected to the output terminal  3 . The output terminal  3  is formed so that power of the battery cell may be output and data of information on a battery capacity, a property, and others may be communicated between the output terminal  3  and external electronic apparatus. The battery device  1  is formed in this manner. 
     Next, a first example of an imaging device included in suitable electronic apparatus using the battery device  1  as a portable power source will be described with reference to  FIGS. 4 to 6 . The device shown in  FIGS. 4 to 6  is a digital video camera used as a first example of an imaging device. The digital video camera  20  includes a tape cassette having a magnetic tape as an information storage medium and converts an optical image into electric signals using an imaging element (such as a CCD (charge coupled device) or a CMOS image sensor) showing a specific example of an imaging mechanism, so that the image information may be recorded in the magnetic tape and displayed in a display device  23  formed with a flat panel such as a liquid crystal display. 
     However, an information storage medium used in an imaging device showing a specific example of an electronic apparatus according to an embodiment of the present invention is not limited to the magnetic tape shown in this example. It is possible to use disc-shaped recording media such as recordable optical discs, magneto-optical discs, and magnetic discs including DVD-Rs, DVD-RWs, DVD-RAMs, MOs, and FDs as information storage media. An electronic apparatus using such a disc-shaped recording medium may be realized as an optical disc video camera when using an optical disc; or a magneto-optical disc still camera when using a magneto-optical disc, for example. Further, such an electronic apparatus may be realized as a magnetic disc electronic organizer when using a magnetic disc. 
     The digital video camera  20  has: an exterior case  21  showing a specific example of a case main body formed with an enclosure forming an appearance; a tape drive device that is stored in the exterior case  21  and drives a magnetic tape of a tape cassette detachably mounted on the tape drive device to record (write) and reproduce (read) information signals; a control circuit to control driving of the tape drive device; a lens device  22  to incorporate a subject image as light to guide the image to the imaging device; and a display device rotatably attached to the exterior case  21 . 
     As shown in  FIGS. 4 to 6 , the exterior case  21  is formed with a hollow enclosure and formed in an approximately rectangular parallelepiped shape by a driving device side panel  21 A and a display device side panel  21 B placed opposite to each other in a transverse direction; a front panel  21 C to close a front opening of an enclosure formed with combining both panels; and a rear panel  21 D to close a rear opening of the enclosure. The exterior case  21  has a longitudinal direction Y set to be a back-and-forth direction and is used as raised in a crosswise direction X. A lens device  22  is provided in an upper portion of the exterior case  21  in a state where a subjective lens  24  as an imaging lens of a lens system is exposed on a front surface. 
     The lens device  22  is attached to the exterior case  21  in a state where an optical axis of the lens system is in a horizontal direction. An imaging element (not shown) is attached to a rear portion of the lens device  22  in the exterior case  21 . A view finder device  25  is placed behind the lens device  22  to reflect a subject image input from the lens device  22 . An opening is provided in the upper portion of the external case  21  to expose an accessory shoe in which accessories such as a video light and an external microphone are detachably mounted. The accessory shoe is placed immediately in front of the view finder device  25  and usually detachably covered with a shoe cap  27  to open and close the opening. Further, a light emitting portion  28  of a flash device and an incorporated stereo-type microphone  29  are placed on the front panel  21 C. 
     As shown in  FIG. 4 , the display device  23  is attached to a display device side panel  21 B so that an attitude of the display device  23  may be modified. The display device  23  is formed with: a flat panel (not shown) formed with a flat liquid crystal display or the like; a panel case  31  in which the flat panel is stored; and a panel support  32  to support the panel case  31  so that an attitude of the panel case may be modified with respect to the display device side panel  21 B. The panel support  32  has: a horizontal rotation portion to make the panel case  31  rotatable at about 90° in a horizontal direction with a vertical axis as a rotation center; and a back-and-forth rotation portion to make the panel case  31  rotatable at about 180° in a back-and-forth direction with a horizontal axis as a rotation center. 
     Accordingly, the display device  23  may be freely in a state where the flat panel is stored in a side surface of the display device side panel  21 B; in a state where the flat panel faces backward by rotating the panel case  31  at 90° from that state; in a state where the flat panel faces forward by rotating the panel case  31  at 180° from that state; or in a state where the flat panel is in an intermediate position among these positions. A main body operation portion  33  formed with a plurality of operation buttons is provided on a side surface of the display device side panel  21 B above the display device  23 . 
     As shown in  FIG. 5 , a deck cover  34  to closably cover a tape deck in which the tape cassette is detachably mounted is closably provided on the driving device side panel  21 A. The tape deck is a device to transport the mounted tape cassette to a predetermined position and to draw the magnetic tape from the cassette and load the tape on a rotation drum or the like of the tape drive device, and then allow the magnetic tape to run at a predetermined speed to record (write) and/or reproduce (read) information signals. The deck cover  34  to cover the tape deck has: a power source switch also used as a mode selector switch; a shutter button  36  to photograph a static image; a zoom button  37  to continuously enlarge (tele) or reduce (wide) an image within a predetermined range; an opening/closing switch  38  to lock and unlock the deck cover  34 ; and a video recording button  39  to photograph a moving image. 
     The power source switch  35  has functions to switch the power source on and off by a rotation operation and to switch a plurality of function modes to each other to repeat them by performing a rotation operation with the power source switched on. Further, a hand belt  51  is attached to the deck cover  34  and a hand pad  42  is mounted on the hand belt  51 . The hand belt  51  and the hand pat  42  support a hand of a user holding the exterior case  21  to prevent dropping of the digital video camera  20 , for example. 
     As shown in  FIGS. 5 and 6 , a mounting portion  44  is provided on a rear surface of the exterior case  21  as a battery housing in which the battery device  1  as a portable power source is detachably mounted. The mounting portion  44  is placed lower than an approximate center of the rear surface of the exterior case  21 , and is provided to open backward in the rear panel  21 D forming the rear surface of the exterior case  21 . The driving device side panel  21 A is provided to the right of the rear panel  21 D. The video recording button  39  is placed in the driving device side panel  21 A. The display device side panel  21 B is provided to the left of the rear panel  21 D. A light emitting button  46  of the flash device and a night shot selector switch  47  are placed in the display device side panel  21 B. 
     As shown in  FIG. 7 , the rear panel  21 D is formed with a panel member formed longer in a vertical direction, and the mounting portion  44  formed with a recess is formed in one surface of the rear panel D. The mounting portion  44  has a rectangular opening  45  approximately as large as the battery device  1  (precisely, the mounting portion  44  has a length in a crosswise direction X 1  approximately equal to that of the opening  45 , but has a length in a longitudinal direction Y 1  which is a length of the battery device  1  plus a length of a clearance to allow the battery device  1  to be stored in the opening  45  by rotating the battery device  1  with one edge in the longitudinal direction of the battery device as a rotation center). 
     The opening  45  has a bottom surface  45   a , a lower surface  45   b , an upper surface  45   c , a left side surface  45   d , and a right side surface  45   e . The bottom surface  45   a  is rectangular and shows a specific example of a second surface of the mounting portion  44 . The lower surface  45   b  is continuous with one side of the bottom surface  45   a  in the longitudinal direction Y 1  and approximately perpendicular to the bottom surface  45   a  and shows a specific example of an electronic apparatus side first surface. The upper surface  45   c  is continuous with the other side in the longitudinal direction Y 1  of the bottom surface  45   a  and approximately perpendicular to the bottom surface  45   a . The left side surface  45   d  is continuous with one side in the crosswise direction X 1  at right angles with the longitudinal direction Y 1  of the bottom surface  45   a  and approximately perpendicular to the bottom surface  45   a . The right side surface  45   d  is continuous with the other side in the crosswise direction X 1  of the bottom surface  45   a  and approximately perpendicular to the bottom surface  45   a . The opening  45  is provided with the longitudinal direction Y 1  set to be a vertical direction. 
     Further, an upper facing  48  protruding upward is provided on the upper surface  45   c , and an insertion hole  48   a  into which an operation projection  66  is inserted is provided on the upper facing  48 . A lower facing  49  is provided to be continuously projected laterally and downward in a portion ranging from a lower portion of the right side surface  45   e  to the lower surface  45   b . A fitting hole  50  to which a connection terminal  56  described later is fitted is provided in an approximate center of the lower surface  45   b . The fitting hole  50  is formed as a notch continuously extending from the lower surface  45   b  to a middle of the bottom surface  45   a.    
     There are provided, on the bottom surface  45   a  of the opening  45 , two first penetration holes  51   a ,  51   b  into which a first hook  61  described later may penetrate and two second penetration holes  52   a ,  52   b  into which a second hook  62  may penetrate. The two first penetration holes  51   a ,  51   b  are provided along the left side surface  45   d  of the opening  45 , where the first lower penetration hole  51   a  is placed at a predetermined interval from the lower surface  45   b  and the first upper penetration hole  51   b  is placed at a predetermined interval from the first lower penetration hole  51   a . The two second penetration holes  52   a ,  52   b  are provided along the left side surface  45   d  of the opening  45 , where the second lower penetration hole  52   a  is placed at a predetermined interval from the lower surface  45   b  and the second upper penetration hole  52   b  is placed at a predetermined interval from the second lower penetration hole  52   a . The first penetration holes  51   a ,  51   b  and the second penetration holes  52   a ,  52   b  are provided symmetrically with each other. The first penetration holes  51   a ,  51   b  and the second penetration holes  52   a ,  52   b  are formed as rectangular holes extending in the longitudinal direction Y 1  of the opening  45  so that a first hook  61  and a second hook  62  may be moved in a vertical direction at a predetermined distance, respectively. 
     Further, as shown in  FIGS. 9A to 9C , the first lower penetration hole  51   a  is provided opposite to the first opening  10   a  placed between the first engaging piece  7   a  and the second engaging piece  7   b  of the first engaging portion  7  of the battery device  1  mounted on the mounting portion  44 . Similarly, the second lower penetration hole  52   a  is provided opposite to the third opening  10   c  placed between the first engaging piece  8   a  and the second engaging piece  8   b  of the second engaging portion  8  of the battery device  1 . The first upper penetration hole  51   b  is provided opposite to the second opening  10   b  placed between the second engaging piece  7   b  and the third engaging piece  7   c  of the first engaging portion  7  of the battery device  1 . Similarly, the second upper penetration hole  52   b  is provided opposite to the fourth opening  10   d  placed between the second engaging piece  8   b  and the third engaging piece  8   c  of the second engaging portion  8  of the battery device  1 . 
     Two protrusion pieces  55   a ,  55   b  to position and support engagement of the battery device  1  are provided on both corners on a lower edge of the opening  45 . The two protrusion pieces  55   a ,  55   b  are formed with a predetermined clearance from the lower surface  45   a  to protrude upward from the lower surface  45   b . When the battery device  1  is mounted, the first protrusion piece  55   a  is engaged with the first engaging piece  7   a  of the first engaging portion  7  of the battery device  1 , and the second protrusion piece  55   b  is engaged with the first engaging piece  8   a  of the second engaging portion  8  of the battery device  1 . A connection terminal  56  is provided in an approximate center between the first protrusion piece  55   a  and the second protrusion piece  55   b , where the connection terminal is detachably connected to the output terminal  3  of the battery device  1  when the battery device  1  is mounted. 
     The connection terminal  56  has a shape and a structure corresponding to those of an output portion of the output terminal  3  of the battery device  1 . Specifically, the connection terminal  56  has: four main body side electrodes  57  that are provided corresponding to the number of electrodes of the output terminal  3  and may be inserted into the four electrode slits  17   a , respectively; and two guide pieces  58  that may be inserted into the two positioning slits  17   b ,  17   b , respectively. The four main body side electrodes  57  are placed on the mounting portion  44  at equal predetermined intervals in the crosswise direction X 1 , and the two guide pieces  58  are provided outside the electrodes  57  at a predetermined interval. 
     As shown in  FIG. 8 , a slide member  60  is placed on a rear surface of the rear panel  21 D having the mounting portion  44 , and a support plate member  64  is placed on a rear surface of the slide member  60 . The slide member  60  is supported with respect to the rear panel  21 D slidably in a vertical direction that is the longitudinal direction Y 1  in the mounting portion  44 . The support plate member  64  is fixed to the rear panel  21 D to prevent dropping of the slide member  60 . A coil spring  65  showing a specific example of an energizing member to energize the slide member  60  away from the connection terminal  56  is present between the slide member  60  and the rear panel  21 D. 
     The slide member  60  has: a base  60   a  formed with an approximately rectangular plate smaller than the bottom surface  45   a  of the opening  45 ; and an operation portion  60   b  provided protruding upward and continuously with an upper edge of the base  60   a . The first hook  61  and the second hook  62  are provided at a predetermined interval between them on one surface of the base  60   a . The first hook  61  is placed on one side of the base  60   a  in a crosswise direction X 1 , and the second hook  62  is placed on the other side of the base  60   a  in the crosswise direction X 1 . The first hook  61  is formed with a first hook piece  61   a  on a side remote from the operation portion  60   b  and a second hook piece  61   b  on a side close to the operation portion  60   b . Similarly, the second hook  62  is formed with a first hook piece  62   a  on a side remote from the operation portion  60   b  and a second hook piece  62   b  on a side close to the operation portion  60   b.    
     The two hook pieces  61   a ,  61   b  of the first hook  61  are placed in series on the base  60   a  in a longitudinal direction Y 1 ; similarly, the two hook pieces  62   a ,  62   b  of the second hook  62  are placed in series on the base  60   a  in the longitudinal direction Y 1 . The four hook pieces  61   a ,  61   b ,  62   a ,  62   b  are symmetrically placed on the base  60   a  with respect to the longitudinal direction Y 1 . Further, nails protruding toward the operation portion  60   b  are provided on tops of the four hook pieces  61   a  to  62   b , respectively. Each nail having an appropriate length extends approximately parallel to the base  60   a . The four hook pieces  61   a  to  62   b  are slidably inserted from a rear surface side into the four penetration holes  51   a ,  51   b ,  52   a ,  52   a  of the rear panel  21 D, respectively. Internal and external surfaces of a top of each nail of the four hook pieces  61   a  to  62   b  each preferably have an inclined plane having an appropriate size in order to facilitate engagement with and detachment from the first engaging portion  7  and the second engaging portion  8  of the battery device  1 . 
     Further, first discrimination projections  53   a ,  53   b  and second discrimination projections  54   a ,  54   b  inserted into the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  of the battery device  1 , respectively, are provided in the nails of the four hook pieces  61   a  to  62   b , respectively. The four discrimination projections  53   a  to  54   b  are formed on one ends of the nails located away from the base  60   a , respectively. The four discrimination projections  53   a  to  54   b  have a function to discriminate the first battery device  1  mountable in the mounting portion  44  and a second battery device not mountable in the mounting portion  44 , the second battery device having an external shape approximately identical to that of the first battery device  1  but not having the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b.    
     In order to obtain such a function, as shown in  FIGS. 9A to 9C , the first hook piece  61   a  having the first discrimination projection  53   a  of the first hook  61  is provided in a position where the first hook piece  61   a  may be engaged with the second engaging piece  7   b  of the first engaging portion  7  of the battery device  1  mounted on the mounting portion  44  and may be inserted into the second discrimination recess  9   a . Similarly, the second hook piece  61   b  having the first discrimination projection  53   b  of the first hook  61  is provided in a position where the second hook piece  61   b  may be engaged with the third engaging piece  7   c  of the first engaging portion  7  of the battery device  1  and may be inserted into the second discrimination recess  9   b . The first hook piece  62   a  having the second discrimination projection  54   a  of the second hook  62  is provided in a position where the first hook piece  62   a  may be engaged with the second engaging piece  8   b  of the second engaging portion  8  of the battery device  1  and may be inserted into the third discrimination recess  13   a . Similarly, the second hook piece  62   b  having the second discrimination projection  54   b  of the second hook  62  is provided in a position where the second hook piece  62   b  may be engaged with the third engaging piece  8   c  of the second engaging portion  8  of the battery device  1  and may be inserted into the third discrimination recess  13   b . The first discrimination projections  53   a  to  54   b  show a specific example of a projection in an embodiment of the present invention. 
       FIG. 7  shows a state where the four hook pieces  61   a  to  62   b  are inserted into the four penetration holes  51   a ,  51   b ,  52   a ,  52   b . In this insertion state, an operation projection  66  provided in the operation portion  60   b  of the slide member  60  is slidably inserted into the insertion hole  48   a  provided on the upper facing  48  of the rear panel  21 D, and accordingly a top of the operation projection  66  protrudes toward a rear surface side. The operation projection  66  protrudes in a direction identical to those of the four hook pieces  61   a  to  62   b  with a height approximately equal to those of the four hook pieces  61   a  to  62   b . A long hole  67  to store the coil spring  65  and an opening window  68  to avoid interference with other components are also provided in the base  60   a  of the slide member  60 . 
     A slide side spring bearing piece  69  in which one edge of the coil string  65  sits is provided on one side of the long hole  67  in the base  60   a  in a longitudinal direction Y 1 . A rear panel  21 D side spring bearing portion  71  provided opposite to the spring bearing piece  69  is inserted into the other side of the long hole  67  in the longitudinal direction Y 1 . The spring bearing portion  71  is provided on a rear surface of the rear panel  21 D, and the coil string  65  in a compressed state is present between the spring bearing portion  71  and the spring bearing piece  69 . The slide member  60  is always energized away from the connection terminal  56  by an elastic force of the coil spring  65 . 
     The support plate member  64  slidably supports the slide member  60  between the support plate member  64  and the rear panel  21 D and functions to prevent dropping of the coil spring  65 . The support plate member  64  is formed smaller than the rear panel  21 D but larger than the slide member  60  and is clamped and fixed to the rear panel  21 D by a fixing screw. Multiple attachment brackets  64   a  and fixing portions  64   b  are provided in the support plate member  64 . 
     The mounting portion  44  having such a configuration may be assembled as follows, for example. First, as shown in  FIG. 8 , the slide member  60  is allowed to face a rear surface of the rear panel  21 D, and the support plate member  64  is placed on the rear surface of the slide member  60  to hold the slide member  60  between the rear panel  21 D and the support plate member  64 . Then, the four hook pieces  61   a ,  61   b ,  62   a ,  62   b  protruding on one surface of the base  60   a  of the slide member  60  are inserted and allowed to penetrate into the four penetration holes  51   a ,  51   b ,  52   a ,  52   b  provided in the opening  45  of the rear panel  21 D, respectively, from the rear surface of the rear panel  21 D. Accordingly, tops of the four hook pieces  61   a  to  62   b  are each allowed to protrude into the opening  45 , and a predetermined clearance is formed between an internal surface of each nail and the bottom surface  45   a  of the opening  45 . 
     At the same time, the operation projection  66  provided on a top of the operation portion  60   b  of the slide member  60  is inserted and allowed to penetrate into the insertion hole  48   a  provided in the upper facing  48  protruding from an upper side of the opening of the rear panel  21 D. Next, the coil spring  65  is allowed to be present between the spring bearing portion  71  of the rear panel  21 D and the spring bearing piece  69  of the slide member  60 . Thereafter, the support plate member  64  is overlapped with the slide member  60 , and the support plate member  64  is clamped and fixed to the rear panel  21 D by a fixing screw. Accordingly, the slide member  60  is slidably supported between the support plate member  64  and the rear panel  21 D. The slide member  60  is always energized away from the connection terminal  56  by an elastic force of the coil spring  65 . Assembly of the mounting portion  44  is completed in this manner, and the rear panel  21 D may be assembled. 
     The battery device  1  may be mounted on and detached from the mounting portion  44  formed as described above in the following manner, for example.  FIG. 9A  is a view describing the rear panel  21 D with a front view of the mounting portion  44 ,  FIG. 9B  is a view describing a state when insertion of the battery device  1  starts, and  FIG. 9C  is a view describing a locked state when insertion of the battery device  1  is completed. In  FIGS. 9B and 9C , the three engaging pieces  8   a ,  8   b ,  8   c  of the second engaging portion  8  are engaged with the two hook pieces  62   a ,  62   b  of the second hook  62  and the second protrusion piece  55   b  in the same manner in which the three engaging pieces  7   a ,  7   b ,  7   c  of the first engaging portion  7  formed symmetrically with the engaging pieces  8   a ,  8   b ,  8   c  are engaged with the two hook pieces  61   a ,  61   b  of the first hook  61  and the first protrusion piece  55   a . Therefore, an operation of one set formed with the first engaging portion  7  and others is described here, and description of an operation of the other set formed with the second engaging portion  8  and others is omitted. 
     First, a case of mounting the battery device  1  in the mounting portion  44  will be described. In this case, as shown in  FIG. 9B , a front surface on a output terminal  3  side of the battery device  1  is allowed to face a lower edge of the opening  45  of the mounting portion  44 . The first engaging piece  7   a  of the first engaging portion  7  and the first engaging piece  8   a  of the second engaging portion  8  provided on both sides of a first surface of the battery device  1  in the crosswise direction X are each and engaged by hooking with the first protrusion piece  55   a  and the second protrusion piece  55   b  provided on both corners of the lower edge of the opening  45 . In such an engaging state, the battery device  1  is rotated closer to the mounting portion  44  with contact areas with the two protrusion pieces  55   a ,  55   b  as rotation centers. 
     Accordingly, the second engaging piece  7   b  of the battery device  1  approaches the first hook piece  61   a , the third engaging piece  7   c  approaches the second hook piece  61   b , and the second engaging piece  7   b  is brought into contact with the first hook piece  61   a . The battery device  1  in this state is rotated and pushed into the opening  45 , so that the second engaging piece  7   b  presses and moves the first hook piece  61   a  toward the connection terminal  56  against an elastic force of the coil spring  65 . When the second engaging piece  7   b  hurdles the first hook piece  61   a , the third engaging piece  7   c  is then brought into contact with the second hook piece  61   b . When the third engaging piece  7   c  hurdles the second hook piece  61   b , the battery device  1  is completely inserted into the opening  45 , and the lower surface  5   a  as a second surface of the battery device  1  is brought into contact with the bottom surface  45   a  as a second surface of the mounting portion  44 . 
     As a result, the output terminal  3  of the battery device  1  is connected to the connection terminal  56  of the mounting portion  44 . Accordingly, the battery device  1  is electrically connected to the digital video camera  20 , and power of the battery device  1  is supplied to the digital video camera  20  from the output terminal  3  through the connection terminal  56 . Record the subject to operate the digital video camera  20  to photograph a subject and record the subject in a recording medium and to watch photographic information recorded in the recording medium in the display device  23 , for example. 
     In this case, the first discrimination projection  53   a  provided in the first hook piece  61   a  of the first hook  61  is inserted into the second discrimination recess  9   a  provided on the first step surface  6   a  of the battery device  1 . Similarly, the second discrimination projection  54   a  provided in the first hook piece  62   a  of the second hook  62  is inserted into the third discrimination recess  13   a  provided on the second step surface  6   b  of the battery device  1 . The first discrimination projection  53   b  provided in the second hook piece  61   b  of the first hook  61  is inserted into the second discrimination recess  9   b  provided on the first step surface  6   a  of the battery device  1 . Similarly, the second discrimination projection  54   b  provided in the second hook piece  62   b  of the second hook  62  is inserted into the third discrimination recess  13   b  provided on the second step surface  6   b  of the battery device  1 . 
     Since the first hook piece  61   a  and the second hook piece  61   b  are free in this manner, the slide member  60  slides away from the connection terminal  56  by an elastic force of the coil spring  65 . As a result, as shown in  FIG. 9C , the first hook piece  61   a  is engaged with the second engaging piece  7   b  and the second hook piece  61   b  is engaged with the third engaging piece  7   c . Similarly, in the second hook  62 , the first hook piece  62   a  is engaged with the second engaging piece  8   b  and the second hook piece  62   b  is engaged with the third engaging piece  8   c . Accordingly, the battery device  1  is locked by the four hook pieces  61   a ,  61   b ,  62   a ,  62   b  engaged with the four engaging pieces  7   b ,  7   c ,  8   b ,  8   c  and fixed to the mounting portion  44 . 
     On the other hand, it may be impossible to mount a battery device in the mounting portion  44  when the battery device does not have the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  corresponding to the first discrimination projections  53   a ,  53   b  and the second discrimination projections  54   a ,  54   b  on the first step surface  6   a  and the second step surface  6   b , respectively. 
     Accordingly, the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  are provided in the battery device  1 , and the first discrimination projections  53   a ,  53   b  and the second discrimination projections  54   a ,  54   b  corresponding to the discrimination recesses are provided in the mounting portion  44 . In this manner a type of the battery device may be discriminated based on a simple structure without further complicating a shape of the first discrimination recesses  15   a ,  15   b  of the battery device  1 , even if the number of types of the battery device is further increased. 
     When the battery device  1  mounted on the mounting portion  44  is removed, a user manually operates the operation projection  66  toward a disengaging side as shown in  FIG. 9C . Specifically, in this example, the user presses the operation projection  66  to allow the slide member  60  to slide toward the connection terminal  56  against an elastic force of the coil spring  65 . The slide member  60  is moved to a place where the four hook pieces  61   a ,  61   b ,  62   a ,  62   b  are detached from the four engaging pieces  7   b ,  7   c ,  8   b ,  8   c , so that the battery device  1  may be removed. Consequently, the battery device  1  may be removed from the mounting portion  44  by raising an edge opposite to the output terminal  3  of the battery device  1  and rotating the battery device  1  with the two first engaging pieces  7   a ,  8   a  engaged with the two protrusion pieces  55   a ,  55   b  as centers. 
       FIGS. 10 and 11A  show a second example of a mounting portion of an electronic apparatus according to an embodiment of the present invention. This mounting portion  74  differs from the mounting portion  44  of the first example in that a first hook  81  and a second hook  82  are securely fixed in an opening  75  of a rear panel  73  and a stopper member  77  is provided to limit movement of the battery device  1  mounted on a predetermined position of the mounting portion  74 . Since the mounting portion is formed in the same manner as in the first example except for that point, the same components as in the first example are indicated by the same symbols and their repeated description is omitted, and different components are selectively described. 
     The opening  75  of the rear panel  73  has: a bottom surface  75   a  as an approximately rectangular second surface of the mounting portion  74 ; a lower surface  75   b  as a first surface continuous with one side of the bottom surface  75   a  in a longitudinal direction Y 1  and approximately perpendicular to the bottom surface  75   a ; a left side surface  75   d  continuous with one side of the bottom surface  75   a  in a crosswise direction X 1  at right angles to the longitudinal direction Y 1  and approximately perpendicular to the bottom surface  75   a ; and a right side surface  75   e  continuous with the other side of the bottom surface  75   a  in the crosswise direction X 1  and approximately perpendicular to the bottom surface  75   a . The opening  75  for the mounting portion  74  is formed with the bottom surface  75   a , the lower surface  75   b , the left side surface  75   d , and the right side surface  75   e . The opening  75  is provided in the rear panel  73  with the longitudinal direction Y 1  set to be a vertical direction. 
     The first hook  81  has: a first hook piece  81   a  placed on a connection terminal  56  side; and a second hook piece  81   b  placed at a predetermined interval in the longitudinal direction Y 1  from the first hook piece  81   a . The first hook piece  81   a  is formed protruding inward from and integrally with the left side surface  75   d  of the rear panel  73 . A first protrusion piece  55   a  is provided on a connection terminal  56  side of the first hook piece  81   a . Similarly, the second hook  82  has: a first hook piece  82   a  placed on a connection terminal  56  side; and a second hook piece  82   b  placed at a predetermined interval in the longitudinal direction Y 1  from the first hook piece  82   a . The first hook piece  82   a  is formed protruding inward from and integrally with the right side surface  75   e  of the rear panel  73 . A second protrusion piece  55   b  is provided on a connection terminal  56  side of the first hook piece  82   a.    
     The second hook piece  81   b  of the first hook  81  is formed continuously and integrally with the bottom surface  75   a  and the left side surface  75   d  of the opening  75 . The second hook piece  82   b  of the first hook  82  is formed continuously and integrally with the bottom surface  75   a  and the right side surface  75   e  of the opening  75 . Cast holes  78  for injection molding using a die are formed in the bottom surface  75   a  for the four hook pieces  81   a ,  81   b ,  82   a ,  82   b  and the left and right protrusion pieces  55   a ,  55   b , respectively. A second discrimination projection  79  to discriminate a type of the battery device  1  is provided between the second protrusion piece  55   b  and a fitting hole  50  for a connection terminal  56 . 
     Further, as in the first example, discrimination projections  53   a ,  53   b ,  54   a ,  54   b  inserted into the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  of the battery device  1 , respectively, are provided in nails of the four hook pieces  81   a  to  82   b , respectively. The four first discrimination projections  53   a  to  54   b  are formed protruding away from the bottom surface  75   a  on external surfaces of the nails, respectively. 
     The stopper member  77  is placed to be brought into contact with the right side surface  75   e  on a side opposite to the lower surface  75   b  of the mounting portion  74 . The stopper member  77  is formed with: a stopper  77   a  protruding toward an upper portion of the battery device  1  mounted on the mounting portion  74  to regulate upward movement in the longitudinal direction Y 1  of the battery device  1 ; and an operation portion  77   b  continuous with the stopper  77   a  and protruding forward from the opening  75 . The stopper member  77  is energized by an elastic member (not shown) to always protrude forward. At this time, the stopper  77   a  protrudes toward an upper portion of the battery device  1 , so that the battery device  1  is prevented from being moved and dropped from the mounting portion  74 . When the operation portion  77   b  is pressed against an elastic force of the elastic member to move the stopper  77   a  backward, a surface of the stopper  77   a  is pressed down to a place coplanar with the bottom surface  75   a . Accordingly, the battery device  1  may be moved in the longitudinal direction Y 1 . 
     The battery device  1  of the first example of an embodiment of the present invention may be mounted on and detached from the mounting portion  74  having such a configuration as follows, for example.  FIG. 11A  is a view describing the rear panel  73  with a front view of the mounting portion  44 ,  FIG. 11B  is a view describing a state when insertion of the battery device  1  starts, and  FIG. 11C  is a view describing a locked state when insertion of the battery device  1  is completed. In  FIGS. 11B and 11C , the three engaging pieces  8   a ,  8   b ,  8   c  of the second engaging portion  8  are engaged with the two hook pieces  82   a ,  82   b  of the second hook  82  and the second protrusion piece  55   b  in the same manner in which the three engaging pieces  7   a ,  7   b ,  7   c  of the first engaging portion  7  formed symmetrically with the engaging pieces  8   a ,  8   b ,  8   c  are engaged with the two hook pieces  81   a ,  81   b  of the first hook  81  and the first protrusion piece  55   a . Therefore, an operation of one set formed with the first engaging portion  7  and others is described here, and description of an operation of the other set formed with the second engaging portion  8  and others is omitted. 
     First, a case of mounting the battery device  1  in the mounting portion  74  will be described. In this case, as shown in  FIG. 11B , the lower surface  5   a  of the battery device  1  is allowed to face the bottom surface  75   a  to make the lower surface  5   a  approximately parallel to the bottom surface  75   a  on an upper side (side opposite to the connection terminal  56 ) of the opening  75  of the mounting portion  74 . The battery device  1  is pressed against an energizing force of the stopper member  77 , and the first hook piece  81   a  of the first hook  81  is inserted into the first opening  10   a  between the first engaging piece  7   a  and the second engaging piece  7   b  of the first engaging portion  7 . At the same time, the second hook piece  81   b  of the first hook  81  is inserted into the second opening  10   b  between the second engaging piece  7   b  and the third engaging piece  7   c  of the first engaging portion  7 . Accordingly, the lower surface  5   a  as a second surface of the battery device  1  is brought into contact with the bottom surface  75   a  as a second surface of the mounting portion  74 . 
     In this case, as in the aforementioned example, the first discrimination projection  53   a  provided in the first hook piece  81   a  of the first hook  81  is inserted into the second discrimination recess  9   a  provided on the first step surface  6   a  of the battery device  1 . Similarly, the second discrimination projection  54   a  provided in the first hook piece  82   a  of the second hook  82  is inserted into the third discrimination recess  13   a  provided on the second step surface  6   b  of the battery device  1 . The first discrimination projection  53   b  provided in the second hook piece  81   b  of the first hook  81  is inserted into the second discrimination recess  9   b  provided on the first step surface  6   a  of the battery device  1 . Similarly, the second discrimination projection  54   b  provided in the second hook piece  82   b  of the second hook  82  is inserted into the third discrimination recess  13   b  provided on the second step surface  6   b  of the battery device  1 . 
     Next, the battery device  1  is allowed to slide toward the connection terminal  56 . Accordingly, as shown in  FIG. 11C , in the first hook  81 , the second engaging piece  7   b  is engaged with the first hook piece  81   a  and the third engaging piece  7   c  is engaged with the second hook piece  81   b . Similarly, in the second hook  82 , the second engaging piece  8   b  is engaged with the first hook piece  82   a  and the third engaging piece  8   c  is engaged with the second hook piece  82   b . Accordingly, the battery device  1  is locked by the four hook pieces  81   a ,  81   b ,  82   a ,  82   b  engaged with the four engaging pieces  7   b ,  7   c ,  8   b ,  8   c . At the same time, the stopper member  77  is energized to outside, so that the stopper  77   a  protrudes toward an upper portion of the battery device  1  and the stopper  77  is brought into contact with the third step surface  6   c  of the battery device  1 . This prevents the battery device  1  from being moved in the longitudinal direction Y 1  and dropped from the mounting portion  74 . 
     At this time, the output terminal  3  of the battery device  1  is connected to the connection terminal  56  of the mounting portion  74 . Accordingly, the battery device  1  is electrically connected to the digital video camera  20 , and power of the battery device  1  is supplied to the digital video camera  20  from the output terminal  3  through the connection terminal  56 . Accordingly, the digital video camera  20  may be operate to photograph a subject and record the subject in a recording medium and to watch photographic information recorded in the recording medium in the display device  23 , for example. 
     Further, it may be impossible to mount a battery device in the mounting portion  74  when the battery device does not have the second discrimination recesses  9   a ,  9   b  and the third discrimination recesses  13   a ,  13   b  corresponding to the first discrimination projections  53   a ,  53   b  and the second discrimination projections  54   a ,  54   b  on the first step surface  6   a  and the second step surface  6   b , respectively. 
     Accordingly, the mounting portion  74  of this example has the first discrimination projections  53   a ,  53   b  and the second discrimination projections  54   a ,  54   b  in addition to the discrimination projection  79  used heretofore. Accordingly, it is possible to discriminate a type of the battery device based on a simple structure without complicating a shape of the discrimination projection  79 , even if the number of types of the battery device is further increased. The battery device  1  may be mounted not only in the mounting portion  44  of the first example but also the mounting portion  74  of the second example having a different mounting structure. 
     Next, when the battery device  1  mounted on the mounting portion  74  is removed, a user manually operates the operation portion  77   b  toward a disengaging side as shown in  FIG. 11C . Specifically, in this example, the user presses the operation portion  77   b  to press a surface of the stopper  77   a  of the stopper member  77  down to a plane coplanar with the bottom surface  75   a  against an energizing force of the elastic body. The battery device  1  is allowed to slide to a place where the four engaging pieces  7   b ,  7   c ,  8   b ,  8   c  are detached from the four hook pieces  81   a ,  81   b ,  82   a ,  82   b . Accordingly, the four engaging pieces  7   b ,  7   c ,  8   b ,  8   c  are disengaged from the four hook pieces  81   a ,  81   b ,  82   a ,  82   b , and the battery device  1  may be removed. At this time, the output terminal  3  of the battery device  1  is pulled from the connection terminal  56 , and the battery device  1  is electrically disconnected from the digital video camera  20 . Consequently, the battery device  1  may be removed by pulling the battery device  1  away from the opening  75 . 
       FIGS. 12 and 13  show a second example of a battery device according to an embodiment of the present invention. The battery device  1 A of the second example differs from the battery device  1  of the first example in that a second discrimination recess  9 A is provided by chamfering a corner of a first step surface  6   a A over a predetermined length R in a longitudinal direction Y from one edge on an output terminal  3  side, and similarly a third discrimination recess  13 A is provided by chamfering a corner of a second step surface  6   b A over the predetermined length R in the longitudinal direction Y from one edge on an output terminal  3  side. The battery device  1 A is formed in the same manner as in the battery device  1  of the first example except for that point. 
     In this example, the length R of each of the second discrimination recess  9 A and the third discrimination recess  13 A in the longitudinal direction Y is set to be approximately equal to or less than a length between one edge on the output terminal  3  side and each of the third ribs  11   c ,  12   c . However, the length R of each of the second discrimination recess  9 A and the third discrimination recess  13 A in an embodiment of the present invention is not limited to the length in this example, and may be variously modified according to a type of the battery device. For example, the second discrimination recess  9 A and the third discrimination recess  13 A may be asymmetrically formed to have different lengths R in the longitudinal direction Y. It is also possible to form the second discrimination recess  9 A or the third discrimination recess  13 A on either one of the first step surface  6   a A and the second step surface  6   b A. Further, it is also possible to variously modify a chamfering depth of a corner of each of the first step surface  6   a A and the second step surface  6   b A. 
       FIGS. 14 and 15  show a third example of a mounting portion of an electronic apparatus according to an embodiment of the present invention which corresponds to the battery device  1 A of the second example. The mounting portion  74 A differs from the mounting portion  74  of the second example in that first discrimination projections  53   a A,  53   b A and second discrimination projections  54   a A,  54   ba  provided in nails of a first hook  81 A and a second hook  82 A, respectively, are each formed to have a shape corresponding to a shape of each of the second discrimination recess  9 A and the third discrimination recess  13 A of the battery device  1 A. The mounting portion  74 A is formed in the same manner as in the mounting portion  74  of the second example except for that point. 
     In this example, as shown in  FIGS. 14 and 15 , inclined planes corresponding to an inclination angle of the second discrimination recess  9 A of the battery device  1 A are provided on side surfaces of a first hook piece  81   a A and a second hook piece  81   b A of the first hook  81 A. Inclined planes formed continuously and integrally with an inclined plane on a side surface of the first hook  81 A are provided on side surfaces of the first discrimination projections  53   a A,  53   b A. Similarly, inclined planes corresponding to an inclination angle of the third discrimination recess  13 A of the battery device  1 A are provided on side surfaces of a first hook piece  82   a A and a second hook piece  82   b A of the second hook  82 A. Inclined planes formed continuously and integrally with an inclined plane on a side surface of the second hook  82 A are provided on side surfaces of the second discrimination projections  54   a A,  54   b A. 
       FIG. 16  shows a fourth example of a mounting portion of an electronic apparatus according to an embodiment of the present invention which corresponds to the battery device  1 A of the second example. The mounting portion  104  of this example is formed with a hollow battery holder  103 . 
     The mounting portion  104  has a bottom surface  105   a , a lower surface  105   b , an opening surface  105   c , a left side surface  105   d , a right side surface  105   e , and a front surface  105   f . The bottom surface  105   a  is an approximately rectangular second surface of the mounting portion  104 . The lower surface  105   b  has a first surface continuous with one side of the bottom surface  105   a  in a longitudinal direction Y 2  and approximately perpendicular to the bottom surface  105   a . The opening surface  105   c  is opposite to the lower surface  105   b  and opened in a shape identical to that of the lower surface  105   b . The left side surface  105   d  has a left step surface  107   a  continuous with the bottom surface  105   a  with a predetermined step on one side of the bottom surface  105   a  in a crosswise direction X 2  at right angles to the longitudinal direction Y 2  and is approximately perpendicular to the bottom surface  105   a . The right side surface  105   e  has a right step surface  107   b  continuous with the bottom surface  105   a  with a predetermined step on the other side of the bottom surface  105   a  in the crosswise direction X 2  and is approximately perpendicular to the bottom surface  105   a . The front surface  105   f  is opposite to the bottom surface  105   a  and continuous with and approximately perpendicular to the lower surface  105   b . A corner at which the front surface  105   f  intersects with the left side surface  105   d  and a corner at which the front surface  105   f  intersects with the right side surface  105   e  are each formed in a circular shape having a large radius of curvature. Further, the mounting portion  104  is formed with the bottom surface  105   a , the lower surface  105   b , the opening surface  105   c , the left side surface  105   d , the right side surface  105   e , and the front surface  105   f . The mounting portion  104  is provided in the battery holder  103  with the longitudinal direction Y 2  set to be a vertical direction. 
     The left step surface  107   a  and the right step surface  107   b  are each set to have a length in a height direction Z 2  (height) from the bottom surface  105   a  which is approximately equal to a height of each of the first step surface  6   a A and the second step surface  6   b A of the battery device  1 A. Further, the left step surface  107   a  and the right step surface  107   b  are formed to be approximately parallel to the bottom surface  105   a , respectively. In addition, as shown in  FIG. 16 , the mounting portion  104  has: a left connection surface  106   a  that connects one side of the bottom surface  105   a  in the crosswise direction X 2  to one side of the left step surface  107   a  in the crosswise direction X 2  and is approximately perpendicular to the bottom surface  105   a  and the left step surface  107   a ; and a right connection surface  106   b  that connects the other side of the bottom surface  105   a  in the crosswise direction X 2  to one side of the right step surface  107   b  in the crosswise direction X 2  and is approximately perpendicular to the bottom surface  105   a  and the right step surface  107   b.    
     The left connection surface  106   a  has a first hook  111  provided continuously with the left connection surface  106   a  and having a predetermined length from one edge on a lower surface  105   b  side in the longitudinal direction Y 2 . The first hook  111  is formed integrally with the left connection surface  106   a  to protrude inward from the left connection surface  106   a  with predetermined width and thickness. Similarly, the right connection surface  106   b  has a second hook  112  provided continuously with the right connection surface  106   b  and having a predetermined length from one edge on a lower surface  105   b  side in the longitudinal direction Y 2 . The second hook  112  is formed integrally with the right connection surface  106   b  to protrude inward from the right connection surface  106   b  with predetermined width and thickness. 
     A corner at which the left step surface  107   a  intersects with the left side surface  105   d  has a first discrimination projection  113  provided continuously and integrally with the corner and having a predetermined length from one edge on a lower surface  105   b  side in the longitudinal direction Y 2 . The first discrimination projection  113  is formed to connect the left step surface  107   a  to the left side surface  105   d  at a predetermined inclination angle. Similarly, a corner at which the right step surface  107   b  intersects with the right side surface  105   e  has a second discrimination projection  114  provided continuously and integrally with the corner and having a predetermined length from one edge on a lower surface  105   b  side in the longitudinal direction Y 2 . The second discrimination projection  114  is formed to connect the right step surface  107   b  to the right side surface  105   e  at a predetermined inclination angle. 
     The battery device  1 A may be mounted on and detached from the mounting portion  104  having such a configuration as follows, for example. First, a case of mounting the battery device  1 A in the mounting portion  104  will be described. In this case, the front surface  5   b  as a first surface of the battery device  1 A is allowed to face the opening surface of the mounting portion  104  on an upper side of the mounting portion  104 . Then, the first engaging portion  7  of the battery device  1 A is engaged with the first hook  111 , and similarly the second engaging portion  8  of the battery device  1 A is engaged with the second hook  112 . Next, the battery device  1 A is inserted into the mounting portion  104  along the first hook  111  and the second hook  112  until the output terminal  3  is engaged with the connection terminal  56 . 
     Accordingly, the first hook  111  is engaged with the first engaging piece  7   a , the second engaging piece  7   b , and the third engaging piece  7   c  of the first engaging portion  7  of the battery device  1 A. Similarly, the second hook  112  is engaged with the first engaging piece  8   a , the second engaging piece  8   b , and the third engaging piece  8   c  of the second engaging portion  8  of the battery device  1 A. This may prevent movement of the battery device  1 A in the height direction Z 2 . As shown in  FIG. 17 , according to this example, the battery device  1 A may be stored in the mounting portion  104 A having a dimension in the height direction Z 2  larger than that of the battery device  1 A. 
     A protrusion length (width) of each of the third ribs  11   c ,  12   c  most distant from the output terminal  3  of the battery device  1 A is set to be approximately equal to a protrusion length (width) N of each of the third engaging pieces  7   c ,  8   c . Accordingly, the third ribs  11   c ,  12   c  are brought into contact with the first hook  111  and the second hook  112  when the battery device  1 A is inserted into the mounting portion  104  from the rear surface. Therefore, a user may immediately understand that the battery device  1 A is inserted in a wrong direction. 
     Next, a user may remove the battery device  1 A mounted on the mounting portion  104  by holding portion of the battery device  1 A exposed from the mounting portion  104  and pulling out the battery device upward. It is also possible to remove the battery device  1 A by pushing the battery device  1 A out of the mounting portion  104  using a battery device removing portion (not shown). 
     The battery device  1 A having such a configuration may also exhibit the same effect as in the battery device  1  of the first example. That is, it is possible to discriminate a type of the battery device based on a simple structure without further complicating a shape of the first discrimination recesses  15   a ,  15   b  of the battery device  1 , even if the number of types of the battery device is further increased. Further, the battery device  1 A may be mounted on mounting portions having different mounting structures and thus may be effectively used. 
     As described above, according to a battery device, an electronic apparatus, and a battery system according to embodiments of the present invention, it is possible to discriminate a type of the battery device even when the battery device and the electronic apparatus have different attachment structures, one battery device may be used for multiple types of an electronic apparatus, and, on the contrary, one battery device may be used as an exclusive component for one type of an electronic apparatus. Accordingly, undesired use of a battery device may be prevented, and a predetermined battery device may be used for a predetermined type of an electronic apparatus to improve safety. A type of the battery device may be discriminated in multiple stages by changing a length, width, or position of a projection. 
     The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications may be effected without departing from the gist of the present invention. For example, in the aforementioned example, a battery device according to an embodiment of the present invention is used for a digital video camera as a specific example of an imaging device; however, the battery device may be used not only for a digital video camera, obviously, but also for various other types of an electronic apparatus such as an electronic still camera, a personal computer, an electronic dictionary, a DVD player, and a car navigation system. In the aforementioned example, an example is described where six engaging pieces are provided in a battery device and four hook pieces or two hooks are provided in a mounting portion; however, it is obvious that the number of the engaging pieces is not limited to six, the number of the hook pieces is not limited to four, and the number of the hooks is not limited to two. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.