Power distribution equipment

Abstract

To provide a power distribution device which can switch between series connection and parallel connection of a battery and can more appropriately correspond to both an external short circuit and a battery short circuit.SOLUTION: A power distribution device includes: first to seventh lines L1 to L7; a first switch SW1 for controlling conduction and interruption in the third line L3; a second switch SW2 for controlling conduction and interruption in the fourth line L4; a third switch SW3 for controlling conduction and interruption in the fifth line L5; a control part 63 for controlling a conduction state and an interruption state of the first to third switches SW1 to SW3; a first fuse F1 provided in the third line L3; a second fuse F2 which is provided in the fourth line L4 and whose conduction capacity is lower than the first fuse F1; and a third fuse F3 which is provided in the fifth line L5 and whose conduction capacity is lower than the first fuse F1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power distribution device.

Background Art

[0002] In recent years, in consideration of the environment, electric vehicles equipped with high-voltage batteries such as EVs (Electric Vehicles) and PHEVs (Plug-in Hybrid Electric Vehicles) have emerged. The voltages of these electric vehicles have been increasing year by year, for example, from about 400V to about 800V. Along with the increase in the voltage of electric vehicles, the rated voltage of the chargers for electric vehicles has also increased, and it has become possible to support vehicles equipped with high-voltage batteries. However, since chargers with large specifications also consume a large amount of power, it is difficult to install them in areas with poor power conditions, and it is also difficult to replace all the currently installed chargers so that they can all support, for example, a voltage of 800V.

[0003] Therefore, a power distribution device has been proposed that enables series connection, parallel connection, or switching of secondary batteries mounted on electric vehicles (see, for example, Patent Document 1). According to this power distribution device, by switching to parallel connection during charging, the voltage during charging can be made lower than when in series connection. Therefore, it is possible to charge a high-voltage electric vehicle even with a low voltage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, the power distribution device described in Patent Document 1 can have a short circuit occur externally, such as on the load side and the charger side, and since it switches between series connection and parallel connection, it is necessary to handle external short circuits for both connection states. Further, the power distribution device described in Patent Document 1 also needs to protect against battery short circuits that may occur when a failure occurs in the switch for switching between series connection and parallel connection. In particular, the power distribution device described in Patent Document 1 is configured to provide fuses for individual switches to handle switch failures.

[0006] However, since the power distribution device described in Patent Document 1 forms a path so as to pass through all cases whether the secondary batteries are connected in series or in parallel, it is necessary to select fuses considering the maximum current. For example, when the current conduction is 300 A in series and 100 A in parallel, a fuse corresponding to 300 A is required. Therefore, when an abnormality occurs in parallel, the time to withstand the abnormal state becomes long, and it is difficult to say that it is appropriately handled.

[0007] Therefore, an object of the present disclosure is to provide a power distribution device that can switch between series connection and parallel connection of batteries and can more appropriately handle both external short circuits and battery short circuits.

Means for Solving the Problems

[0008] To solve the above problems, a power distribution device according to an embodiment of the present disclosure includes a first battery positive terminal and a first battery negative terminal respectively connected to the positive and negative electrodes of a first battery, a second battery positive terminal and a second battery negative terminal respectively connected to the positive and negative electrodes of a second battery, a charger positive terminal and a charger negative terminal respectively connected to the positive and negative electrodes of a charger, a load positive terminal and a load negative terminal respectively connected to the positive and negative electrodes of a load, a first line connecting the first battery positive terminal and the charger positive terminal, a second line connecting the second battery negative terminal and the charger negative terminal, a third line connecting the second battery positive terminal and the first battery negative terminal, a first switch for controlling conduction and interruption in the third line, a fourth line connecting the second battery positive terminal and the first line, a second switch for controlling conduction and interruption in the fourth line, a fifth line connecting the second line and the first battery negative terminal, a third switch for controlling conduction and interruption in the fifth line, a sixth line connecting the charger positive terminal side of the first line, which is closer to the charger positive terminal than the connection point between the first line and the fourth line, and the load positive terminal, a seventh line connecting the charger negative terminal side of the second line, which is closer to the charger negative terminal than the connection point between the second line and the fifth line, and the load negative terminal, a control means for controlling the conduction state and interruption state of the first switch, the second switch and the third switch, a first fuse provided in the third line, a second fuse provided in the fourth line and having a lower current-carrying capacity than the first fuse, and a third fuse provided in the fifth line and having a lower current-carrying capacity than the first fuse.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a power distribution device that can switch between series connection and parallel connection of batteries and can more appropriately respond to both external short circuits and battery short circuits.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and can be appropriately changed without departing from the gist of the present invention. Also, in the embodiments shown below, there are some places where the illustration and description of some configurations are omitted. However, it goes without saying that well - known or well - understood technologies are appropriately applied within the range where there is no contradiction with the content described below regarding the details of the omitted technologies.

[0012] FIG. 1 is a configuration diagram showing a secondary battery system including a power distribution device according to the present embodiment. The secondary battery system 1 shown in FIG. 1 includes a high-voltage battery 10, a charging junction box (hereinafter referred to as J / B) 20, a rapid charger (charger) 30, a high-voltage J / B 40, a high-voltage load (load) 50, and a power distribution device 60.

[0013] The high-voltage battery 10 includes a first battery 11, a second battery 12, a first monitoring unit 13, a second monitoring unit 14, and a battery ECU (Electronic Control Unit) 15.

[0014] The first battery 11 and the second battery 12 are composed of secondary batteries such as rechargeable lithium-ion batteries. Such first battery 11 and second battery 12 are each capable of supplying a high voltage of 400 V or the like, for example, to drive the high-voltage load 50 in an electric vehicle. In the present embodiment, the first battery 11 and the second battery 12 are assumed to have the same voltage.

[0015] The first monitoring unit 13 monitors the voltage, current, and temperature of the first battery 11. The second monitoring unit 14 monitors the voltage, current, and temperature of the second battery 12. The battery ECU 15 calculates the state of charge of the first battery 11 and the second battery 12 based on information from the first monitoring unit 13 and the second monitoring unit 14. Further, the battery ECU 15 may calculate the degree of deterioration and detect abnormalities of the first battery 11 and the second battery 12.

[0016] The charging J / B20 is a relay device interposed between the power distribution device 60 and the rapid charger 30. The charging J / B20 includes a first charging relay 21 and a second charging relay 22. The first charging relay 21 controls the connection between the positive electrode side of the rapid charger 30 and the power distribution device 60. The second charging relay 22 controls the connection between the negative electrode side of the rapid charger 30 and the power distribution device 60. The first charging relay 21 and the second charging relay 22 may be either mechanical contact type or semiconductor type. The same applies to the first and second high-voltage relays 41 and 42, and the first to third switches SW1 to SW3 described later.

[0017] The rapid charger 30 supplies power for charging the first battery 11 and the second battery 12 through the charging J / B20 and the power distribution device 60. The rapid charger 30 may supply power with a voltage of, for example, 400V or 800V. The power distribution device 60 determines whether to connect the first battery 11 and the second battery 12 in series or in parallel according to such supplied power, and charges the first battery 11 and the second battery 12 in that connection state. Although the secondary battery system 1 according to the present embodiment is assumed to be charged by the rapid charger 30, it is not particularly limited thereto and may be charged by a general charger that is not rapid.

[0018] The high-voltage J / B40 is a relay device interposed between the power distribution device 60 and the high-voltage load 50. The high-voltage J / B40 includes a first high-voltage relay 41 and a second high-voltage relay 42. The first high-voltage relay 41 controls the connection between the positive electrode side of the high-voltage load 50 and the power distribution device 60. The second high-voltage relay 42 controls the connection between the negative electrode side of the high-voltage load 50 and the power distribution device 60. The high-voltage load 50 is a motor or the like that generates the driving force of the vehicle.

[0019] The power distribution device 60 changes the connection state of the first battery 11 and the second battery 12 between series state and parallel state during charging from the rapid charger 30 through the charging J / B20 or discharging to the high-voltage load 50 through the high-voltage J / B40.

[0020] The power distribution device 60 has a plurality of terminals 60a to 60h. The first battery positive terminal 60a and the first battery negative terminal 60b are terminals respectively connected to the positive and negative electrodes of the first battery 11. The second battery positive terminal 60c and the second battery negative terminal 60d are terminals respectively connected to the positive and negative electrodes of the second battery 12. The charger positive terminal 60e and the charger negative terminal 60f are terminals respectively connected to the positive and negative electrodes of the rapid charger 30. The load positive terminal 60g and the load negative terminal 60h are terminals respectively connected to the positive and negative electrodes of the high-voltage load 50.

[0021] Furthermore, the power distribution device 60 includes a plurality of lines L1 to L7, a plurality of switches SW1 to SW3, a plurality of fuses F1 to F3, a plurality of current sensors 61, a voltage sensor 62, and a control unit (control means) 63.

[0022] The first line L1 connects the first battery positive terminal 60a and the charger positive terminal 60e. The second line L2 connects the second battery negative terminal 60d and the charger negative terminal 60f. The third line L3 connects the second battery positive terminal 60c and the first battery negative terminal 60b. Note that, as will be described later, one end side (from the terminal 60c to the connection point P1 in FIG. 1) of the third line L3 is shared with the fourth line L4, and the other end side (from the terminal 60b to the connection point P2 in FIG. 1) is shared with the fifth line L5. The third line L3 connects the first battery negative terminal 60b and the second battery positive terminal 60c via these shared portions L34 and L35. The first switch SW1 controls conduction and interruption in the third line L3 and is provided at a position in the third line L3 excluding the shared portions L34 and L35.

[0023] The fourth line L4 connects the second battery positive terminal 60c and the first line L1. One end side of the fourth line L4 forms a common part L34 with the third line L3. The second switch SW2 controls conduction and interruption in the fourth line L4 and is provided at a position excluding the common part L34 with the third line L3 in the fourth line L4.

[0024] The fifth line L5 connects the second line L2 and the first battery negative terminal 60b. The other end side of the fifth line L5 forms a common part L35 with the third line L3. The third switch SW3 controls conduction and interruption in the fifth line L5 and is provided at a position excluding the common part L35 with the third line L3 in the fifth line L5.

[0025] The sixth line L6 connects a connection point P4 located on the charger positive terminal 60e side of the connection point P3 between the first line L1 and the fourth line L4 and the load positive terminal 60g. The seventh line L7 connects a connection point P6 located on the charger negative terminal 60f side of the connection point P5 between the second line L2 and the fifth line L5 and the load negative terminal 60h.

[0026] The first to third fuses F1 to F3 are mechanical fuses that blow when an overcurrent flows. Among these fuses F1 to F3, the second and third fuses F2 and F3 are designed to have a lower current-carrying capacity than the first fuse F1. Here, the first fuse F1 is provided on the third line L3, particularly at a position excluding the common parts L34 and L35 of the third line L3. Also, the second fuse F2 is provided on the fourth line L4, particularly at a position excluding the common part L34 of the fourth line L4. Further, the third fuse F3 is provided on the fifth line L5, particularly at a position excluding the common part L35 of the fifth line L5. Specifically, in this embodiment, the first fuse F1 is provided on the side of the first battery negative terminal 60b from the first switch SW1. The second fuse F2 is provided on the side of the connection point P3 from the second switch SW2. The third fuse F3 is provided on the side of the connection point P5 from the third switch SW3.

[0027] The current sensors 61 are provided respectively on the fourth line L4 and the fifth line L5, and output signals corresponding to the currents in the fourth line L4 and the currents in the fifth line L5. In this embodiment, the current sensors 61 are provided respectively at the common part L34 between the third line L3 and the fourth line L4, and at the common part L35 between the third line L3 and the fifth line L5.

[0028] The voltage sensor 62 outputs a signal corresponding to the potential difference between the first line L1 and the second line L2. More specifically, the voltage sensor 62 outputs a signal corresponding to the potential difference between the connection point P7 located between the connection point P3 and the connection point P4 on the first line L1, and the connection point P8 located between the connection point P5 and the connection point P6 on the second line L2.

[0029] Figure 2 is a block diagram showing the details of the control unit 63 shown in Figure 1. The control unit 63 controls the entire power distribution device 60, and includes an SW control unit 63a, a voltage measurement unit 63b, a current measurement unit (current measurement means) 63c, and a failure determination unit 63d.

[0030] The SW control unit 63a controls the conduction state (on) and cutoff state (off) of the first switch SW1, the second switch SW2, and the third switch SW3. FIGS. 3 and 4 are state diagrams showing the control states by the SW control unit 63a shown in FIG. 2. First, as shown in FIG. 3, when the SW control unit 63a wants to connect the first battery 11 and the second battery 12 in series, it turns on the first switch SW1 and turns off the second switch SW2 and the third switch SW3. Thereby, for example, during charging, a route (see thick line) of the first line L1, the first battery 11, the third line L3, the second battery 12, and the second line L2 is formed. Therefore, the first battery 11 and the second battery 12 are in a series state. On the other hand, as shown in FIG. 4, when the SW control unit 63a wants to connect the first battery 11 and the second battery 12 in parallel, it turns off the first switch SW1 and turns on the second switch SW2 and the third switch SW3. Thereby, during charging, a route (see thick line) of the first line L1, the first battery 11, the fifth line L5, and the second line L2 and a route (see thick line) of the first line L1, the fourth line L4, the second battery 12, and the second line L2 are formed. Therefore, the first battery 11 and the second battery 12 are in a parallel state.

[0031] The voltage measurement unit 63b measures a voltage corresponding to the potential difference between the first line L1 and the second line L2 according to the signal from the voltage sensor 62. The current measurement unit 63c measures the current in the fourth line L4 (particularly the common part L34) and the current in the fifth (particularly the common part L35) according to the signal from the current sensor 61.

[0032] The failure determination unit 63d determines failures such as an external short circuit or a battery short circuit. This failure determination unit 63d determines an external short circuit on the rapid charger 30 side or the high-voltage load 50 side and a battery short circuit in the event of a failure of the first switch SW1, the second switch SW2, and the third switch SW3 based on the voltage measured by the voltage measurement unit 63b and the current measured by the current measurement unit 63c.

[0033] For example, when an external short circuit occurs during the series connection of the first and second batteries 11 and 12, an overcurrent flows on the third line L3. Also, when an external short circuit occurs during the parallel connection of the first and second batteries 11 and 12, an overcurrent flows on the fourth line L4 and the fifth line L5. Further, when a battery short circuit occurs in the first battery 11 or the second battery 12, an overcurrent flows in some locations. The fault determination unit 63d determines whether there is such a current trend based on the measurement result of the current measurement unit 63c, and determines an external short circuit or a battery short circuit.

[0034] Note that the fault determination unit 63d according to the present embodiment can also determine faults in the first switch SW1, the second switch SW2, and the third switch SW3 based on the measurement result of the current measurement unit 63c and the measurement result of the voltage measurement unit 63b. The first switch SW1, the second switch SW2, and the third switch SW3 can have an ON fault that is always on and an OFF fault that is always off. The fault determination unit 63d can determine such faults. For example, assume that the voltage measurement unit 63b detects a voltage of 400V even though the SW control unit 63a turns off all the switches SW1 to SW3. In this case, it can be said that one of the second switch SW2 and the third switch SW3 has an ON fault. The fault determination unit 63d determines the fault based on such voltage measurement. Further, in this case, for example, when the current measurement unit 63c measures a predetermined current in the common part L34 and detects a current of zero in the common part L35, the fault determination unit 63d specifies an ON fault in the second switch SW2.

[0035] Next, the operation according to the present embodiment will be described. FIGS. 5 to 9 are state diagrams showing the flow of current in each short-circuit state.

[0036] First, as shown in FIG. 5, assume that an external short circuit occurs on the fast charger 30 side during series connection. In this case, an overcurrent flows through the route of the first line L1, the first battery 11, the third line L3, the second battery 12, and the second line L2. In this case, since the first fuse F1 is provided in the third line L3, the first fuse F1 can be blown to appropriately respond to the external short circuit on the fast charger 30 side during series connection.

[0037] Also, as shown in FIG. 6, assume that an external short circuit occurs on the high-voltage load 50 side during series connection. In this case, an overcurrent flows through the route of the sixth line L6, the first line L1 (however, from the positive terminal 60a of the first battery to the connection point P4), the first battery 11, the third line L3, the second battery 12, the second line L2 (however, from the negative terminal 60d of the second battery to the connection point P6), and the seventh line L7. Also in this case, since the first fuse F1 is provided in the third line L3, the first fuse F1 can be blown to appropriately respond to the external short circuit on the high-voltage load 50 side during series connection.

[0038] Furthermore, as shown in FIG. 7, assume that an external short circuit occurs on the fast charger 30 side during parallel connection. In this case, an overcurrent flows through both the route of the first line L1, the first battery 11, the fifth line L5, and the second line L2 (however, from the connection point P5 to the charger negative terminal 60f) and the route of the first line L1 (however, from the connection point P3 to the charger positive terminal 60e), the fourth line L4, the second battery 12, and the second line L2. In this case, since the second fuse F2 is provided in the fourth line L4 and the third fuse F3 is provided in the fifth line L5, both fuses F2 and F3 can be blown to appropriately respond to the external short circuit on the fast charger 30 side during parallel connection.

[0039] Note that although it is assumed in this embodiment that parallel connection is performed only during charging, it is not particularly limited to this. In the case where parallel connection is performed when operating the high-voltage load 50, the external short circuit on the high-voltage load 50 side can be similarly handled.

[0040] Also, as shown in FIG. 8, for example, assume that the SW control unit 63a attempts to connect in series when the second switch SW2 has an ON failure. In this case, a route of the first line L1 (from the positive terminal 60a of the first battery to the connection point P3), the first battery 11, the third line L3 (from the negative terminal 60b of the first battery to the connection point P1), and the fourth line L4 (from the connection point P1 to the connection point P3) is formed, resulting in a battery short circuit. Therefore, an overcurrent flows on this route. Here, since the first fuse F1 and the second fuse F2 are provided on the route, the second fuse F2 with a lower current-carrying capacity melts relatively early. Thus, it is possible to appropriately respond to the battery short circuit of the first battery 11.

[0041] Furthermore, as shown in FIG. 9, for example, assume that the SW control unit 63a attempts to connect in series when the third switch SW3 has an ON failure. In this case, a route of the third line L3 (from the connection point P2 to the positive terminal 60c of the second battery), the second battery 12, the second line L2 (from the negative terminal 60d of the second battery to the connection point P5), and the fifth line L5 (from the connection point P5 to the connection point P2) is formed, resulting in a battery short circuit. Therefore, an overcurrent flows on this route. Here, since the first fuse F1 and the third fuse F3 are provided on the route, the third fuse F3 with a lower current-carrying capacity melts relatively early. Thus, it is possible to appropriately respond to the battery short circuit of the second battery 12.

[0042] In this way, according to the power distribution device 60 according to the present embodiment, since the above circuit is constructed, when attempting to connect in series, the first switch SW1 is turned on and the second and third switches SW2 and SW3 are turned off. In this case, during an external short circuit, it will be cut off by the first fuse F1, and it is possible to appropriately respond to the external short circuit during series connection.

[0043] Also, since the above circuit is constructed, when parallel connection is desired, the first switch SW1 is turned off and the second and third switches SW2 and SW3 are turned on. In this case, in the event of an external short circuit, both the second fuse F2 and the third fuse F3 will blow. In particular, for the second fuse F2 and the third fuse F3, since their rated current capacities are lower than that of the first fuse F1, it is difficult for the time until interruption to become long in the case of an external short circuit during parallel connection, and an appropriate response to the external short circuit during parallel connection can be achieved.

[0044] Furthermore, when a failure occurs in which both the first switch SW1 and the second switch SW2 are turned on due to a switch failure, a route is formed that connects from the positive electrode of the first battery 11, through the second fuse F2 and the first fuse F1 in that order, to the negative electrode of the first battery 11. In this case, the second fuse F2, which has a lower rated current capacity than the first fuse F1, will blow, and an appropriate response to a battery short circuit on the first battery 11 side can be achieved.

[0045] In addition, when a failure occurs in which both the first switch SW1 and the third switch SW3 are turned on due to a switch failure, a route is formed that connects from the positive electrode of the second battery 12, through the first fuse F1 and the third fuse F3 in that order, to the negative electrode of the second battery 12. In this case, the third fuse F3, which has a lower rated current capacity than the first fuse F1, will blow, and an appropriate response to a battery short circuit on the second battery 12 side can be achieved.

[0046] From the above, a power distribution device 60 can be provided that can switch between series connection and parallel connection of the batteries 11 and 12 and can more appropriately respond to both external short circuits and battery short circuits.

[0047] Also, since the common parts L34 and L35 are provided, a part of the third line L3 and the fourth line L4, and a part of the third line L3 and the fifth line L5 can be made common, contributing to the simplification of the circuit. Further, the first to third fuses F1 to F3 can be provided at positions excluding the common parts L34 and L35, so that the fuses F1 to F3 can be provided at appropriate positions.

[0048] As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and modifications may be made without departing from the spirit of the present invention, or known or well-known technologies may be combined if possible.

[0049] FIG. 10 is a configuration diagram showing a secondary battery system 1 showing a modification according to the present embodiment. In the modification shown in FIG. 10, the power distribution device 60 is composed of electronic fuses such as pyro fuses and semiconductor fuses, rather than mechanical fuses in which the first fuse F1, the second fuse F2, and the third fuse F3 are blown by overcurrent. In particular, in the present embodiment, the first fuse F1, the second fuse F2, and the third fuse F3 are configured to be cut off by receiving a signal from the outside.

[0050] FIG. 11 is a block diagram showing details of the control unit 63 according to the modification shown in FIG. 10. As shown in FIG. 11, the control unit 63 includes a cutoff control unit (cutoff control means) 63e. The cutoff control unit 63e is capable of selectively cutting off the first to third fuses F1 to F3, which are electronic, and is configured to transmit a signal to the fuse among the first to third fuses F1 to F3 to be cut off. Here, when an external short circuit occurs during the series connection shown in FIGS. 5 and 6, overcurrents flow through both of the common portions L34 and L35. For this reason, when a current greater than the normal current (but lower than the overcurrent) flows through both of the common portions L34 and L35 by the current measurement unit 63c, the failure determination unit 63d can determine an external short circuit. And in such a case, the cutoff control unit 63e determines that an overcurrent will flow in the future and cuts off the first fuse F1. Similarly for the external short circuit shown in FIG. 7, the cutoff control unit 63e cuts off the second fuse F2 and the third fuse F3. In addition, the cutoff control unit 63e similarly cuts off the second fuse F2 or the third fuse F3 for a battery short circuit.

[0051] As described above, in the modification, the currents in each of the common portion L34 and the common portion L35 are measured, and the cutoff control unit 63e selectively cuts off the first fuse F1, the second fuse F2, and the third fuse F3, which are electronic fuses. For this reason, it is not required that an overcurrent flows during cutoff as in the case of a mechanical fuse, abnormal detection can be performed prior to the flow of an overcurrent, and cutoff at an appropriate location can be enabled.

[0052] Also, in the above, the first fuse F1 is provided on the first battery negative terminal 60b side of the first switch SW1 on the third line L3, but is not particularly limited thereto, and may be provided on the second battery positive terminal 60c side. Similarly, the second fuse F2 may be provided on the connection point P1 side of the second switch SW2. Further, the third fuse F3 may be provided on the connection point P2 side of the third switch SW3.

Description of Reference Numerals

[0053] 1: Secondary battery system 11: First battery 12: Second battery 30: Quick charger (charger) 50: High-voltage load (load) 60: Power distribution device 60a: First battery positive terminal 60b: First battery negative terminal 60c: Second battery positive terminal 60d: Second battery negative terminal 60e: Charger positive terminal 60f: Charger negative terminal 60g: Load positive terminal 60h: Load negative terminal 61: Current sensor 62: Voltage sensor 63: Control unit (control means) 63a: SW control unit 63b: Voltage measurement unit 63c: Current measurement unit (current measurement means) 63d: Fault judgment unit 63e: Shutdown control unit (shutdown control means) F1: First fuse F2: Second fuse F3: Third fuse L1: First line L2: Second line L3: Third line L4: Fourth line L5: Fifth line L6: Sixth line L7: Seventh line L34: Common part L35: Common part P3: Connection point P5: Connection point SW1: First switch SW2: Second switch SW3: Third switch

Claims

1. A first battery positive terminal and a first battery negative terminal respectively connected to the positive electrode and the negative electrode of the first battery, A second battery positive terminal and a second battery negative terminal respectively connected to the positive electrode and the negative electrode of the second battery, A charger positive terminal and a charger negative terminal respectively connected to the positive electrode and the negative electrode of the charger, A load positive terminal and a load negative terminal respectively connected to the positive electrode and the negative electrode of the load, A first line connecting the first battery positive terminal and the charger positive terminal, A second line connecting the second battery negative terminal and the charger negative terminal, A third line connecting the second battery positive terminal and the first battery negative terminal, A first switch for controlling conduction and interruption in the third line, A fourth line connecting the second battery positive terminal and the first line, A second switch for controlling conduction and interruption in the fourth line, A fifth line connecting the second line and the first battery negative terminal, A third switch for controlling conduction and interruption in the fifth line, A sixth line connecting the charger positive terminal side of the first line, which is closer to the charger positive terminal than the connection point between the first line and the fourth line, and the load positive terminal, A seventh line connecting the charger negative terminal side of the second line, which is closer to the charger negative terminal than the connection point between the second line and the fifth line, and the load negative terminal, Control means for controlling the conduction state and the interruption state of the first switch, the second switch, and the third switch, A first fuse provided in the third line, A second fuse provided in the fourth line and having a lower current-carrying capacity than the first fuse, A third fuse provided in the fifth line and having a lower current-carrying capacity than the first fuse, A power distribution device, characterized by comprising the above.

2. When one end side of the fourth line is shared with the third line and connected to the second battery positive terminal, and one end side of the fifth line is shared with the third line and connected to the first battery negative terminal, the first fuse is provided at a position in the third line excluding the shared portion between the fourth line and the fifth line, the second fuse is provided at a position in the fourth line excluding the shared portion with the third line, and the third fuse is provided at a position in the fifth line excluding the shared portion with the third line. The power distribution device according to claim 1, characterized by the above.

3. The first fuse, the second fuse, and the third fuse are electronic fuses that can be interrupted in response to an external signal, The control means, a current measurement means for measuring currents in each of a common portion between the third line and the fourth line and a common portion between the third line and the fifth line; a cutoff control means for selectively cutting off the first fuse, the second fuse, and the third fuse based on the current measured by the current measurement means; and The power distribution device according to claim 2, characterized by the above.

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