Abstract:
Sneaking of a charging current to a load is avoided, a voltage of a battery is not output to terminals of a connector, and the number of installed switch elements that make conductive or interrupt a feeding path is minimized. A battery pack  100  including a battery  10  that supplies power to a load  20  and to which power is supplied from a charger  40  includes: a relay connector  36  including first, second, and third terminals; a first feeder  13  that connects the load to the first terminal of the relay connector; a second feeder  11  that connects one electrode terminal of the battery to the second terminal of the relay connector; a third feeder  16  for which one terminal is connected to the third terminal of the relay connector; and a switch element  16   a  that is connected between the other terminal of the third feeder, and the other electrode terminal of the battery. The first terminal and the second terminal of the relay connector are short-circuited by a jumper wire  37   a  of a jumper plug  37,  and the second terminal and the third terminal of the relay connector are respectively connected to one electrode feeder and the other electrode feeder of the charger by using a charging connector  38.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a relay connecter that is provided in a feeding path from a battery that is rechargeable to a load and a feeding path from a charger to the battery, and a battery pack including the relay connector. 
       RELATED ART 
       [0002]    In a device, such as a vehicle, that is operated by a battery that is rechargeable, when a remaining capacity of the battery decreases, the battery needs to be connected to an external charger so as to be charged. In charging the battery from the charger, a feeding path from the battery to a load on the side of a machine base of the vehicle or the like is temporarily interrupted, and a feeding path from the charger to the battery is formed. 
         [0003]      FIG. 7  illustrates a conventional exemplary configuration of respective feeding paths connected to a battery, a load, and a charger. In the exemplary configuration illustrated in  FIG. 7 , a battery pack  100  incorporates a battery  10  that is rechargeable. The battery  10  supplies an operation current to a load  20 . A charging connector  32  is connected to a bipolar connector  31  such that a charging current is supplied from a charger  40 . 
         [0004]    A switch element  13   a  is interposed within a load positive-electrode feeder  13  that connects a battery positive-electrode feeder  11  connected to a positive electrode terminal of the battery  10  to the load  20 , and a switch element  14   a  is interposed within a load negative-electrode feeder  14  that connects a battery negative-electrode feeder  12  connected to a negative electrode terminal of the battery  10  to the load  20 . 
         [0005]    In addition, a switch element  15   a  is interposed within a charger positive-electrode feeder  15  that connects the battery positive-electrode feeder  11  and a positive electrode terminal of the charger  40 , and a switch element  16   a  is interposed within a charger negative-electrode feeder  16  that connects the battery negative-electrode feeder  12  and a negative electrode terminal of the charger  40 . 
         [0006]    These four switch elements  13   a,    14   a,    15   a,  and  16   a  respectively make conductive or interrupt the load positive-electrode feeder  13 , the load negative-electrode feeder  14 , the charger positive-electrode feeder  15 , and the charger negative-electrode feeder  16 . A mechanical switch such as a relay or a semiconductor switch such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) can be used for the switch elements  13   a,    14   a,    15   a,  and  16   a.    
         [0007]    In supplying the operation current from the battery  10  to the load  20 , the switch element  13   a  interposed within the load positive-electrode feeder  13  and the switch element  14   a  interposed within the load negative-electrode feeder  14  are turned on. At this time, the switch element  15   a  interposed within the charger positive-electrode feeder  15  and the switch element  16   a  interposed within the charger negative-electrode feeder  16  are turned off. 
         [0008]    In supplying the charging current from the charger  40  to the battery  10 , the charging connector  32  is connected to the bipolar connector  31 , and the switch element  15   a  interposed within the charger positive-electrode feeder  15  and the switch element  16   a  interposed within the charger negative-electrode feeder  16  are turned on. At this time, the switch element  13   a  interposed within the load positive-electrode feeder  13  and the switch element  14   a  interposed within the load negative-electrode feeder  14  are turned off. 
         [0009]    As described above, when the operation current is supplied from the battery  10  to the load  20 , the switch elements  13   a  and  14   a  are turned on, and the switch elements  15   a  and  16   a  are turned off. Consequently, a voltage of the battery  10  can be prevented from being output to terminals of the bipolar connector  31  from which the charging connector  32  has been extracted, and even when a foreign object is in contact with the terminals of the bipolar connector  31 , short circuit failure of the battery  10  can be prevented from being caused by the contact. 
         [0010]    Further, when the charging current is supplied from the charger  40  to the battery  10 , the switch elements  15   a  and  16   a  are turned on, and the switch elements  13   a  and  14   a  are turned off. Consequently, a sneak current that causes the charging current from the charger  40  to flow to the load  20  via the load positive-electrode feeder  13  and the load negative-electrode feeder  14  can be avoided. 
         [0011]    As another exemplary configuration for switching an interconnection of a battery, a load, and a charger, an exemplary configuration in which a connection between the battery and the load and a connection between the battery and the charger are switched by inserting or extracting a connector and a jumper plug is known.  FIG. 8  illustrates an exemplary configuration in which connections of a battery, a load, and a charger are switched by inserting or extracting a connector and a jumper plug. This exemplary configuration is disclosed in Patent Document 1 listed below or the like. 
         [0012]    In the exemplary configuration of  FIG. 8 , an overcurrent breaking element  17  that interrupts an overcurrent, a thermistor  10   a  that monitors a temperature of a battery  10  at the time of charging, and a thermal breaker  10   b  that stops charging according to information of the thermistor  10   a  are provided. A relay connector  33  that both a jumper plug  34  and a charging connector  35  of a charger  40  can be compatibly inserted into or extracted from is also provided. 
         [0013]    The relay connector  33  has six electrode terminals. A battery positive-electrode feeder  11  is connected to a first terminal (in  FIG. 8 , the first terminal is simply indicated as “1”; the same applies hereinafter) as a positive electrode terminal via the overcurrent breaking element  17 . The charger negative-electrode feeder  16  is connected to a second terminal. The load positive-electrode feeder  13  to a load  20  is connected to a third terminal. 
         [0014]    One terminal of the thermal breaker  10   b  is connected to a fourth terminal of the relay connector  33 , one terminal of the thermistor  10   a  is connected to a fifth terminal, and the other terminal of the thermal breaker  10   b  and the other terminal of the thermistor  10   a  are connected to a sixth terminal. 
         [0015]    The jumper plug  34  includes a pair of a first pin and a third pin (in  FIG. 8 , the first pin and the third pin are simply indicated as “1” and “3”, respectively) that are electrically short-circuited by a jumper wire  34   a.  By inserting the jumper plug  34  into the relay connector  33 , the first terminal and the third terminal of the relay connector  33  are short-circuited. 
         [0016]    In supplying an operation current from the battery  10  to the load  20 , the jumper plug  34  is inserted into the relay connector  33  such that the operation current is supplied to the load  20  via a path of the battery  10 →the battery positive-electrode feeder  11 →the overcurrent breaking element  17 →the first terminal of the relay connector  33 →the first pin of the jumper plug  34 →the jumper wire  34   a →the third pin of the jumper plug  34 →the third terminal of the relay connector  33 →the load positive-electrode feeder  13 →the load  20 →the load negative-electrode feeder  14 →the battery negative-electrode feeder  12 →the battery  10 . 
         [0017]    The charger  40  includes the charging connector  35  connected to the relay connector  33 , and a power plug  41  connected to a commercial power supply. The charging connector  35  includes a first pin (in  FIG. 8 , the first pin is simply indicated as “1”; the same applies hereinafter), a second pin, a fourth pin, a fifth pin, and a sixth pin that are respectively connected to the first terminal, the second terminal, the fourth terminal, the fifth terminal, and the sixth terminal of the relay connector  33 . The charging connector  35  is a connector that is inserted into the relay connector  33  when the battery  10  is charged by the charger  40 . 
         [0018]    In supplying a charging current from the charger  40  to the battery  10 , the charging connector  35  is inserted into the relay connector  33  such that the charging current is supplied to the battery  10  via a path of the charger  40 →the first pin of the charging connector  35 →the first terminal of the relay connector  33 →the overcurrent breaking element  17 →the battery positive-electrode feeder  11 →the battery  10 →the battery negative-electrode feeder  12 →the charger negative-electrode feeder  16 →the second terminal of the relay connector  33 →the second pin of the charging connector  35 →the charger  40 . 
         [0019]    As described above, the relay connector  33  is interposed within feeding of the operation current and feeding of the charging current, and the jumper plug  34  and the charging connector  35  that are inserted into the relay connector  33  are prepared. When the operation current is supplied to the load  20 , the jumper plug  34  is inserted into the relay connector  33  such that the battery  10  and the load  20  are connected. During the non-operation of the load  20 , the jumper plug  34  is extracted from the relay connector  33  such that the load positive-electrode feeder  13  is completely cut from the battery  10 . 
         [0020]    When the battery  10  is charged, the charging connector  35  is inserted into the relay connector  33  such that the charging current is supplied to the battery  10  via the first pin and the second pin of the charging connector  35  and the first terminal and the second terminal of the relay connector  33 . Because the load positive-electrode feeder  13  is disconnected during charging, the charging current from the charger  40  does not flow to the load  20  via the load positive-electrode feeder  13 , and the charging current is prevented from sneaking into the load  20 . 
         [0021]    In this exemplary configuration, the first terminal of the relay connector  33  connected to the battery positive-electrode feeder  11  is used to supply power from the charger  40  to the battery  10  and to supply power to the load  20  through the load positive-electrode feeder  13  via the jumper plug  34 . As a result, the number of terminals of the relay connector  33  can decrease, and a cost can also decrease. 
       CITATION LIST 
     Patent Documents 
       [0022]    Patent Document 1: Japanese Laid-Open Patent Publication No. 2003-70168 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0023]    In the exemplary connection configuration illustrated in  FIG. 7  of a battery, a load, and a charger, four switch elements  13   a,    14   a,    15   a,  and  16   a  that make conductive or interrupt a feeding path are provided, and therefore, a cost for the four switch elements is added. During the operation of the load  20 , a current that maintains the switch elements  13   a  and  14   a  interposed within the load positive-electrode feeder  13  and the load negative-electrode feeder  14  in an ON state needs to continue to flow, and this results in an increase in current consumption of the battery  10 . 
         [0024]    In the exemplary configuration illustrated in  FIG. 8  in which a connector and a jumper plug are inserted or extracted, when both the jumper plug  34  and the charging connector  35  are extracted from the relay connector  33 , a voltage of the battery  10  is output to the first terminal and the second terminal of the relay connector  33 . When a foreign object comes into contact with the first terminal and the second terminal of the relay connector  33 , the contact causes short circuit failure of the battery  10 . 
         [0025]    In view of the problems above, the present invention provides a relay connector and a battery pack in which, in a connection configuration of a battery, a load, and a charger, a sneak current that causes a charging current from the charger to flow to the load is not generated, a voltage of the battery is not output to terminals of a connector, and the number of installed switch elements that make conductive or interrupt a feeding path can be minimized. 
       MEANS FOR SOLVING THE PROBLEMS 
       [0026]    A relay connector according to the present invention includes first, second, and third terminals. The first terminal is connected to a feeder that supplies power to a load, the second terminal is connected to one electrode terminal of a battery, the third terminal is connected to one terminal of a switch element for which the other terminal is connected to the other electrode terminal of the battery and the load, the first terminal and the second terminal are short-circuited by a jumper wire of a jumper plug, and the second terminal and the third terminal are respectively connected to one electrode feeder and the other electrode feeder of a charger by using a charging connector. 
         [0027]    The second terminal may be connected to the one electrode terminal of the battery via an overcurrent breaking element. 
         [0028]    The overcurrent breaking element may be interposed within a middle of a feeder through which a feeding current to the load flows, the feeder being a portion of a feeder connecting the other electrode terminal of the battery and the switch element. 
         [0029]    A battery pack according to the present invention is a battery pack including a battery that supplies power to a load and to which power is supplied from a charger. The battery pack according to the present invention includes: a relay connector including first, second, and third terminals; a first feeder that connects the load to the first terminal of the relay connector; a second feeder that connects one electrode terminal of the battery to the second terminal of the relay connector; a third feeder for which one terminal is connected to the third terminal of the relay connector; and a switch element that is connected between the other terminal of the third feeder, and the other electrode terminal of the battery and the load. The first terminal and the second terminal of the relay connector are short-circuited by a jumper wire of a jumper plug, and the second terminal and the third terminal of the relay connector are respectively connected to one electrode feeder and the other electrode feeder of the charger by using a charging connector. 
         [0030]    The overcurrent breaking element may be provided between the one electrode terminal of the battery and the second terminal of the relay connector in the second feeder. 
         [0031]    The overcurrent breaking element may be interposed within a middle of a fourth feeder through which a feeding current to the load flows, the fourth feeder being a portion of a feeder connecting the other electrode terminal of the battery and the switch element. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0032]    According to the present invention, in a connection configuration of a battery, a load, and a charger, the battery and the load or the battery and the charger are connected using a relay connector by inserting or extracting a jumper plug or a charging connector into or from the relay connector, and a switch element is arranged in a feeder that is connected only to the charger. Consequently, a sneak current that causes a charging current from the charger to flow to the load is not generated, and a voltage of the battery is not output to terminals of a connector, the number of installed switch elements that make conductive or interrupt a feeding path can be minimized, and current consumption during the operation can be minimized. 
         [0033]    Further, an overcurrent breaking element is provided in a feeding path through which both a charging current and an operation current flow, and consequently, elements including a battery, parts, or the like can be protected from either overcurrent, of the operation current or the charging current, by using one overcurrent breaking element. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0034]      FIG. 1  illustrates an exemplary connection configuration of a battery, a load, and a charger, using a relay connector. 
           [0035]      FIG. 2  illustrates an exemplary configuration in which a relay connector is arranged in a machine base or the like on a load side. 
           [0036]      FIG. 3  illustrates a first exemplary configuration in which an overcurrent breaking element is further provided. 
           [0037]      FIG. 4  illustrates a second exemplary configuration in which an overcurrent breaking element is further provided. 
           [0038]      FIG. 5  illustrates an exemplary connection configuration of an overcurrent breaking element using a terminal block in the first exemplary configuration. 
           [0039]      FIG. 6  illustrates an exemplary connection configuration of an overcurrent breaking element using a terminal block in the second exemplary configuration. 
           [0040]      FIG. 7  illustrates a conventional exemplary configuration of respective feeding paths connected to a battery, a load, and a charger. 
           [0041]      FIG. 8  illustrates a conventional exemplary configuration in which connections of a battery, a load, and a charger are switched. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0042]    Embodiments of the present invention are described with reference to the drawings.  FIG. 1  illustrates an exemplary connection configuration of a battery, a load, and a charger, using a relay connector of the present invention. In the exemplary connection configuration of  FIG. 1 , a battery pack  100  incorporates a battery  10  that is rechargeable. When a jumper plug  37  is connected to a relay connector  36 , the battery  10  supplies an operation current to a load  20 , and when a charging connector  38  is connected to the relay connector  36 , a charging current is supplied from a charger  40 . 
         [0043]    A first terminal (in  FIG. 1 , the first terminal is simply indicated as “1”; the same applies hereinafter) of the relay connector  36  is connected to a load positive-electrode feeder  13  of the load  20 , a second terminal is connected to a battery positive-electrode feeder  11  of the battery  10 , and a third terminal is connected to one terminal of a charger negative-electrode feeder  16  that is connected only to the charger  40 . 
         [0044]    The other terminal of the charger negative-electrode feeder  16  is connected to one terminal of a switch element  16   a,  and the other terminal of the switch element  16   a  is connected to a negative electrode terminal of the battery  10 . Alternatively, the other terminal of the switch element  16   a  is connected to a battery negative-electrode feeder  12  that is connected to the negative electrode terminal of the battery  10 . 
         [0045]    In the description of the embodiments, like the load positive-electrode feeder  13 , the battery positive-electrode feeder  11 , the charger negative-electrode feeder  16 , the battery negative-electrode feeder  12 , and the like, the terms “positive electrode” and “negative electrode” are added to respective feeders according to the exemplary configuration of  FIG. 1  in order to simply distinguish and describe the respective feeders. However, a configuration having the same function and action can even be implemented by employing a circuit configuration having a polarity opposite to the polarity of the exemplary configuration of  FIG. 1 , and the feeders according to the present invention are not limited by the terms “positive electrode” and “negative electrode”. 
         [0046]    Note that the first feeder described in the above Means for Solving the Problems corresponds to the load positive-electrode feeder  13 , the second feeder corresponds to the battery positive-electrode feeder  11 , the third feeder corresponds to the charger negative-electrode feeder  16 , and the fourth feeder corresponds to the battery negative-electrode feeder  12 . The one electrode terminal of the battery described in the above Means for Solving the Problems corresponds to the positive electrode terminal of the battery  10 , and the other electrode terminal of the battery corresponds to the negative electrode terminal of the battery  10 . 
         [0047]    Accordingly, a first terminal of the relay connector  36  is connected to the feeder  13  that supplies power to the load  20 , a second terminal is connected to one electrode terminal of the battery  10 , and a third terminal is connected to one terminal of the switch element  16   a  for which the other terminal is connected to the other electrode terminal of the battery  10  and the load  20 . 
         [0048]    In the embodiments, the relay connecter  36  having the first, second, and third terminals has been described. However, in the present invention, a connector having at least three terminals, first, second, and third terminals, may be provided, and a relay connector having only three terminals does not always need to be provided. It goes without saying that a function and action similar to those of the present invention can be achieved by using a four-or-more-electrode connector having four or more terminals and applying a connection form similar to that of the embodiments to three terminals of the four or more terminals. 
         [0049]    A jumper wire  37   a  is provided in the jumper plug  37 , and the jumper wire  37   a  electrically short-circuits a first pin (in  FIG. 1 , the first pin is simply indicated as “1”; the same applies hereinafter) that is connected to the first terminal of the relay connecter  36  and a second pin connected to the second terminal of the relay connecter  36 . The jumper plug  37  shields, in a connectionless state, a third pin connected to the third terminal of the relay connecter  36 . 
         [0050]    In the battery pack  100 , the load negative-electrode feeder  14  connected to the load  20  is always connected to the negative terminal of the battery  10 , or to the battery negative-electrode feeder  12  of the battery  10 . When an operation current is supplied from the battery  10  to the load  20 , the jumper plug  37  is inserted into the relay connecter  36  such that the battery positive-electrode feeder  11  is connected to the load positive-electrode feeder  13  of the load  20  via the jumper wire  37   a  in the jumper plug  37 , and the operation current can be supplied to the load  20 . 
         [0051]    Namely, the operation current is supplied from the battery  10  to the load  20  via a path of the battery  10 →the battery positive-electrode feeder  11 →the second terminal of the relay connecter  36 →the second pin of the jumper plug  37 →the jumper wire  37   a →the first pin of the jumper plug  37 →the first terminal of the relay connecter  36 →the load positive-electrode feeder  13 →the load  20 →the load negative-electrode feeder  14 →the battery negative-electrode feeder  12 →the battery  10 . 
         [0052]    The charging connector  38  used to charge the battery  10  from the charger  40  shields, in a connectionless state, a first pin (in  FIG. 1 , the first pin is simply indicated as “1”; the same applies hereinafter) that is connected to the first terminal of the relay connecter  36 , the charging connector  38  connects a second pin connected to the second terminal of the relay connecter  36  to a positive electrode feeder of the charger  40 , and the charging connector  38  connects a third pin connected to the third terminal of the relay connecter  36  to a negative electrode feeder of the charger  40 . 
         [0053]    When a charging current is supplied from the charger  40  to the battery  10 , the charging connector  38  is inserted into the relay connecter  36  and the switch element  16   a  is turned on such that the charging current is supplied from the charger  40  to the battery  10  via the second and third pins of the charging connector  38 , the second and third terminals of the relay connecter  36 , and the switch element  16   a.    
         [0054]    Namely, the charging current is supplied from the charger  40  to the battery  10  via a path of the positive electrode feeder of the charger  40 →the second pin of the charging connector  38 →the second terminal of the relay connecter  36 →the battery positive-electrode feeder  11 →the battery  10 →the battery negative-electrode feeder  12 →the switch element  16   a →the charger negative-electrode feeder  16 →the third terminal of the relay connecter  36 →the third pin of the charging connector  38 →the negative electrode feeder of the charger  40 . 
         [0055]    As described above, during the operation of the load  20 , the jumper plug  37  is inserted into the relay connecter  36 , and the switch element  16   a  is turned off. Consequently, the operation current can be supplied from the battery  10  to the load  20  without continuing to apply a current to the switch element  16   a  during the operation of the load  20 . 
         [0056]    Further, when the battery  10  is charged, the jumper plug  37  is extracted from the relay connecter  36 , the charging connector  38  is inserted into the relay connecter  36 , and the switch element  16   a  is turned on. Consequently, a charging current from the charger  40  is supplied only to the battery  10 , and the load positive-electrode feeder  13  of the load  20  is cut from the battery positive-electrode feeder  11 . Accordingly, a sneak current to the load  20  is not generated. 
         [0057]    Furthermore, when the jumper plug  37  and the charging connector  38  are extracted from the relay connecter  36 , the switch element  16   a  is turned off . As a result, a voltage of the battery  10  can be prevented from being output to terminals of the relay connecter  36 , and a short circuit failure of the battery  10  can be prevented from being caused by a contact of a foreign object with the terminals of the relay connecter  36 . 
         [0058]    The switch element  16   a  that prevents the voltage of the battery  10  from being output to the terminals of the relay connecter  36  does not always need to have a configuration in which the switch element  16   a  is provided so as to be interposed within the charger negative-electrode feeder  16  connected only to the charger  40 , as illustrated in  FIG. 1 , and the switch element  16   a  can have a configuration (1) in which the switch element  16   a  is provided so as to be interposed within the battery negative-electrode feeder  12  of the battery  10  that is a feeding path of both the operation current to the load  20  and the charging current from the charger  40 , or a configuration (2) in which the switch element  16   a  is provided so as to be interposed within the battery positive-electrode feeder  11  that is a feeding path of both the operation current to the load  20  and the charging current from the charger  40 . 
         [0059]    However, in both of the configurations (1) and (2), a holding current that maintains a switch element that is interposed within the battery negative-electrode feeder  12 , the battery positive-electrode feeder  11 , or the load positive-electrode feeder  13  in an ON state during the operation of the load  20  needs to continue to flow, and this results in an increase in current consumption of the battery  10 . 
         [0060]    On the other hand, in the configuration in which the switch element  16   a  is provided in the middle of the charger negative-electrode feeder  16  connected only to the charger  40 , as illustrated in  FIG. 1 , the switch element  16   a  can be in an ON state only during the charging, and the switch element  16   a  can be in an OFF state during the operation. This allows current consumption during the operation to decrease, compared with the configurations (1) and (2) described above. 
         [0061]      FIG. 1  illustrates an exemplary configuration in which the relay connecter  36  is arranged in the battery pack  100 ; however, the relay connecter  36  may be configured so as to be arranged in a machine base or the like on the side of the load  20 .  FIG. 2  illustrates an exemplary configuration in which the relay connector  36  is arranged in a machine base or the like on the side of the load  20 . A connection configuration illustrated in  FIG. 2  of the relay connector  36 , the battery  10 , the load  20 , and the switch element  16   a  is the same as the connection configuration illustrated in  FIG. 1 , and therefore an overlapping description is omitted. 
         [0062]      FIG. 3  illustrates a first exemplary configuration in which an overcurrent breaking element  17  such as a fuse is further provided. The first exemplary configuration illustrated in  FIG. 3  represents an exemplary configuration in which the overcurrent breaking element  17  is interposed within a middle of a battery positive-electrode feeder  11 . The battery positive-electrode feeder  11  is a feeding path of an operation current from a battery  10  to a load  20  and a feeding path of a charging current from a charger  40  to the battery  10 . Therefore, by arranging the overcurrent breaking element  17  in the battery positive-electrode feeder  11 , elements including the battery  10 , parts, or the like can be protected from either overcurrent, of the operation current or the charging current, by using one overcurrent breaking element  17 . 
         [0063]      FIG. 4  illustrates a second exemplary configuration in which an overcurrent breaking element  17  such as a fuse is further provided. The second exemplary configuration illustrated in  FIG. 4  represents an exemplary configuration in which the overcurrent breaking element  17  is interposed within a middle of a battery negative-electrode feeder  12  of the battery  10 . The battery negative-electrode feeder  12  of the battery  10  is a portion of a feeding path of an operation current from the battery  10  to a load  20  and a portion of a feeding path of a charging current from a charger  40  to the battery  10 . Accordingly, by arranging the overcurrent breaking element  17  in the battery negative-electrode feeder  12 , elements including the battery  10 , parts, or the like can be protected from either overcurrent, of the operation current or the charging current, by using one overcurrent breaking element  17 . 
         [0064]      FIG. 5  illustrates an exemplary connection configuration of an overcurrent breaking element  17  using a terminal block in the first exemplary configuration illustrated in  FIG. 3 , and  FIG. 6  illustrates an exemplary connection configuration of an overcurrent breaking element  17  using a terminal block in the second exemplary configuration illustrated in  FIG. 4 . 
         [0065]    As an example, when three batteries  10  are connected in parallel, in the first exemplary configuration, a terminal block for four terminals  18   a  can be used to connect positive electrode terminals of the three batteries  10  to one battery positive-electrode feeder  11 , and a terminal block for five terminals  18   b  can be used to connect negative electrode terminals of the three batteries  10  to a load negative-electrode feeder  14  and a charger negative-electrode feeder  16 , as illustrated in  FIG. 5 . In the terminal block for four terminals  18   a  and the terminal block for five terminals  18   b,  respective terminals are connected via a common connection wire. 
         [0066]    The positive electrode terminals of the three batteries  10  are connected to three terminals of the terminal block for four terminals  18   a,  and the overcurrent breaking element  17  is connected between the other one terminal of the terminal block for four terminals  18   a  and a second terminal of a relay connector. The negative electrode terminals of the three batteries  10  are connected to three terminals of the terminal block for five terminals  18   b,  and the load negative-electrode feeder  14  and the charger negative-electrode feeder  16  are connected to the other two terminals of the terminal block for five terminals  18   b.  As illustrated in  FIG. 5 , in the first exemplary configuration, the overcurrent breaking element  17  can be connected by using one terminal block for four terminals  18   a  and one terminal block for five terminals  18   b.    
         [0067]    On the other hand, in the second exemplary configuration, a terminal block for four terminals  18   a  used to connect positive electrode terminals of three batteries  10  to a battery positive-electrode feeder  11 , a terminal block for four terminals  18   c  used to connect negative electrode terminals of the three batteries  10  to one terminal of the overcurrent breaking element  17 , and a terminal block for three terminals  18   d  used to connect the other terminal of the overcurrent breaking element  17  to a load negative-electrode feeder  14  and a charger negative-electrode feeder  16  are prepared, as illustrated in  FIG. 6 . 
         [0068]    As illustrated in  FIG. 6 , in the second exemplary configuration, three terminal blocks, two terminal blocks for four terminals  18   a  and  18   c  and one terminal block for three terminals  18   d,  need to be used to connect the overcurrent breaking element  17 . Therefore, one more terminal block needs to be provided, compared with the first exemplary configuration. 
         [0069]    In addition, the battery  10  and the load  20  are often configured so as to have a common ground potential by connecting a feeder on a negative electrode side of the battery  10  to a grounding wire of the load  20 . In this case, in an exemplary configuration in which the overcurrent breaking element  17  is provided in the battery negative-electrode feeder  12 , as in the second exemplary configuration, when the battery negative-electrode feeder  12  is interrupted by the overcurrent breaking element  17 , the feeder on the negative electrode side of the battery  10  is cut from the grounding wire or the like of the load  20 , and the battery  10  and the load  20  do not have a common ground potential. Therefore, in the configuration above, the first exemplary configuration is preferable to the second exemplary configuration. 
         [0070]    The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above, and various configurations or embodiments can be implemented without departing from the gist of the present invention. 
       Reference Signs List 
       [0000]    
       
           10  Battery 
           11  Battery positive-electrode feeder 
           12  Battery negative-electrode feeder 
           13  Load positive-electrode feeder 
           14  Load negative-electrode feeder 
           16  Charger negative-electrode feeder 
           16   a  Switch element 
           100  Battery pack 
           20  Load 
           36  Relay connector 
           37  Jumper plug 
           37   a  Jumper wire 
           38  Charging connector 
           40  Charger