Battery system

Abstract

To improve the convenience of a battery.SOLUTION: A battery system 100 includes a battery 10, a first main relay 20, and a second main relay 30. The battery 10 has a positive electrode and a negative electrode. The first main relay 20 is serially connected to the positive electrode side of the battery 10. The second main relay 30 is serially connected to the negative electrode side of the battery 10. At least one of the first main relay 20 and the second main relay 30 includes a relay group in which a plurality of relays 21, 22, 31, and 32 is connected in parallel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2019-129568 discloses a battery system including a plurality of battery modules and a plurality of switches. The plurality of battery modules can be switched between a series state in which they are connected in series by the plurality of switches and a parallel state in which they are connected in parallel. In the battery system, the series state and the parallel state of the plurality of battery modules are switched according to the degree of deterioration of the battery modules. According to such a battery system, it is preferably avoided that the battery system becomes unusable due to the switches becoming unable to be controlled to open and close.

[0003] Japanese Unexamined Patent Application Publication No. 2013-081316 discloses a charge control device for a power supply device capable of switching the connection method of a plurality of power storage elements between series and parallel. The charge and discharge control device selects the connection method at the start of charging based on the temperature and SOC of the power supply device. The charge and discharge control device controls the parallel charging current using an upper limit value larger than the upper limit value of the series charging current input to the power supply device. According to such a charge and discharge control device, it is said that the power supply device can be charged and discharged in a short time while suppressing deterioration of battery performance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventor intends to improve the convenience of the battery system.

Means for Solving the Problems

[0006] The battery system disclosed herein includes a battery, a first main relay, and a second main relay. The battery has a positive electrode and a negative electrode. The first main relay is connected in series on the positive electrode side of the battery. The second main relay is connected in series on the negative electrode side of the battery. At least one of the first main relay and the second main relay includes a relay group in which a plurality of relays are connected in parallel. The plurality of relays are each individually controlled to switch between a closed state and an open state. In such a battery system, the convenience of the battery system is improved.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the technology disclosed herein will be described with reference to the drawings. The embodiments described here are not, of course, intended to particularly limit the present invention. Each drawing is schematically drawn and does not necessarily reflect the actual object. Also, members and parts having the same function are appropriately given the same reference numerals, and duplicate explanations are appropriately omitted. In this specification, notations such as "X~Y" indicating a numerical range mean "X or more and Y or less" unless otherwise specified.

[0009] <Battery System 100> FIG. 1 is a schematic diagram showing a battery system 100. As shown in FIG. 1, the battery system 100 includes a battery 10, a first main relay 20, and a second main relay 30. The battery system 100 includes a controller 40. The controller 40 individually controls the opening and closing of each relay included in the first main relay 20 and the second main relay 30. The battery system 100 is an aggregate including, in addition to the battery, a configuration for controlling the battery and the like, and is also referred to as a battery pack. Connection parts 101 to 103 are provided in the battery system 100. The connection parts 101 to 103 are parts configured to be connectable to an external charger 80 and a load 70.

[0010] In this embodiment, the battery system 100 is connected to the load 70 via the connection part 101. Electric power is supplied from the battery 10 of the battery system 100 to the load 70. In this embodiment, the load 70 is a load of an electric vehicle and can be configured by an electric motor of the vehicle, an inverter, and the like. The battery system 100 is not limited to such a form and is applicable to battery systems other than those mounted on electric vehicles.

[0011] <Battery 10> The battery 10 has a positive electrode and a negative electrode. The battery 10 is a power storage device capable of extracting electric energy. Electric power supplied from the charger 80 is stored in the battery 10. The battery 10 is connected to the load 70 via the connection part 101. The battery 10 supplies electric power to the load 70.

[0012] The battery 10 includes a secondary battery that can be repeatedly charged and discharged by the movement of charge carriers between a pair of electrodes (a positive electrode and a negative electrode) through an electrolyte. The battery 10 includes, for example, a lithium-ion secondary battery, a nickel-metal hydride battery, or the like. The battery 10 may be a single cell 10a, or may be a battery pack 10A in which a plurality of single cells 10a are electrically connected to each other via a bus bar. In this embodiment, the battery 10 includes two battery packs 10A. The two battery packs 10A are connected in series. The single cells constituting the battery pack may be connected in series, may be connected in parallel, or may be connected in a combination of series and parallel. In this embodiment, in the battery pack 10A, a plurality of single cells 10a are connected in series.

[0013] The battery 10 of the battery system 100 is charged by a charger 80. The battery 10 is connected to the charger 80 via connection portions 102 and 103. The battery system 100 is configured to be connectable to either a normal charger (hereinafter also referred to as a "normal charger") 82 or a rapid charger (hereinafter also referred to as a "rapid charger") 83. The battery system 100 can be connected to the normal charger 82 via the connection portion 102. The battery system 100 can be connected to the rapid charger 83 via the connection portion 103. The normal charger 82 and the rapid charger 83 may be connected to a common connection portion.

[0014] For the normal charger 82 for in-vehicle batteries, the output of the normal charger 82 can be about 1 kW to 6 kW. The current flowing through the battery 10 during charging by the normal charger 82 can be about 5 A to 15 A. The rapid charger 83 is a charger for charging with a higher output than the normal charger 82. For the rapid charger 83 for in-vehicle batteries, the output of the rapid charger 83 can be about 50 kW to 350 kW. The current flowing through the battery 10 during charging by the rapid charger 83 can be about 100 A to 400 A. Note that the output and current during normal charging and rapid charging are not limited to the above-mentioned values. The output and current during normal charging and rapid charging can vary depending on the usage form of the battery system 100 and the like. For example, when the battery system 100 is used for mobile terminals such as notebook computers, smartphones, and tablet terminals, the output and current during normal charging and rapid charging are lower than the above-mentioned values.

[0015] The battery 10 and the connection part 101 are connected via connection lines 101a and 101b. The connection line 101a is connected to the positive electrode side of the battery 10. The connection line 101b is connected to the negative electrode side of the battery 10. The connection lines 102a and 102b extending from the connection part 102 are respectively connected to the connection lines 101a and 101b. The connection lines 103a and 103b extending from the connection part 103 are respectively connected to the connection lines 101a and 101b. At one end of the connection lines 101a and 101b extending from the connection part 101, a first main relay 20 and a second main relay 30 are respectively provided.

[0016] Between the battery 10 and the connection part 101, a first main relay 20 and a second main relay 30 are provided. The connection and disconnection with the load 70 and the charger 80 are switched by the first main relay 20 and the second main relay 30.

[0017] 〈The first main relay 20〉 The first main relay 20 is connected in series to the positive electrode side of the battery 10. The first main relay 20 switches the connection state between the battery 10, the load 70, and the charger 80 on the positive electrode side of the battery 10. The first main relay 20 includes relay groups 21, 22 (a plurality of relays 21, 22). In the relay groups 21, 22, a plurality of relays 21, 22 are connected in parallel. Each of the plurality of relays 21, 22 is configured to be individually switchable between an open state and a closed state.

[0018] 〈Second main relay 30〉 The second main relay 30 is connected in series to the negative electrode side of the battery 10. The second main relay 30 switches the connection state between the battery 10, the load 70, and the charger 80 on the negative electrode side of the battery 10. Similar to the first main relay 20, the second main relay 30 includes relay groups 31, 32 (a plurality of relays 31, 32). In the relay groups 31, 32, a plurality of relays 31, 32 are connected in parallel. Each of the plurality of relays 31, 32 is configured to be individually switchable between an open state and a closed state. The relays 21, 22, 31, 32 are not particularly limited as long as they can switch the connection and disconnection of the battery 10, the load 70, and the charger 80. As the relays 21, 22, 31, 32, electromechanical relays may be used, or semiconductor relays may be used.

[0019] In the battery system 100, both the first main relay 20 and the second main relay 30 include a relay group in which a plurality of relays (relays 21, 22 in the first main relay 20 and relays 31, 32 in the second main relay 30) are connected in parallel.

[0020] A precharge circuit 25 that prevents inrush current from flowing into the load 70 and the battery 10 is connected in parallel to the first main relay 20.

[0021] 〈Precharge circuit 25〉 The precharge circuit 25 is provided on the positive electrode side of the battery 10. The precharge circuit 25 is a circuit in which a precharge resistor 26 and a precharge relay 27 are connected in series. The precharge circuit 25 is a circuit that prevents an inrush current from flowing when power is supplied from the battery system 100 to the load 70, when power is supplied from the charger 80 to the battery system 100, etc.

[0022] Before the load 70 is activated, the first main relay 20, the second main relay 30, and the precharge relay 27 are in the open state. When the load 70 is activated, the second main relay 30 and the precharge relay 27 are switched to the closed state. The switching of the precharge relay 27 is controlled by the controller 40. The load 70 is connected to the battery system 100 via the precharge circuit 25. At this time, due to the provision of the precharge resistor 26 in the precharge circuit 25, power is supplied to the load 70 from the battery 10 with a low current. Thereafter, the first main relay 20 is closed in a state where the potential of the load 70 has risen, and then the precharge relay 27 is opened. This prevents a large current from flowing when the load 70 is activated.

[0023] Also, before the battery 10 is charged, the first main relay 20, the second main relay 30, and the precharge relay 27 are in the open state. When the battery 10 is charged, the second main relay 30 and the precharge relay 27 are switched to the closed state. The load 70 is connected to the charger 80 via the precharge circuit 25. At this time, due to the provision of the precharge resistor 26 in the precharge circuit 25, power is supplied to the battery 10 from the charger 80 with a low current. Thereafter, the first main relay 20 is closed in a state where the potential of the battery 10 has risen, and then the precharge relay 27 is opened. This prevents a large current from flowing at the start of charging of the battery 10. The above opening and closing of the precharge relay 27 is also referred to as a precharge sequence.

[0024] Incidentally, when charging a battery, the battery may be rapidly charged in order to shorten the charging time. When rapidly charging the battery, it is necessary to charge the battery with a large output. Also, in order to achieve long-term operation with a single charge, a battery with a large capacity may be used. Even in this case, the battery may be rapidly charged in order to shorten the charging time. Furthermore, even when supplying (discharging) the electrical energy charged in the battery to an external load, depending on the usage mode of the battery system, a large current may flow to the external load. Thus, a large current may flow in the charge and discharge circuit of the battery. When a current flows, the charge and discharge circuit may generate heat due to the resistance of the components constituting the circuit. For example, in a relay that switches the connection between the battery and the load, heat may be generated according to the contact resistance in the closed state. Such heat generation increases as the current flowing through the circuit increases. Also, in order to reduce the contact resistance in the relay and reduce heat generation, a large relay designed according to the charge and discharge current may be used as the main relay.

[0025] In the above-described embodiment, the battery system 100 includes a battery 10, a first main relay 20, and a second main relay 30. The battery 10 has a positive electrode and a negative electrode. The first main relay 20 is connected in series to the positive electrode side of the battery 10. The second main relay 30 is connected in series to the negative electrode side of the battery 10. The first main relay 20 includes a relay group 21, 22 in which a plurality of relays 21, 22 are connected in parallel. With such a configuration, in the first main relay 20, the current flowing through the relays 21, 22 is divided. Therefore, the heat generation in each of the relays 21, 22 is reduced. As a result, in the relays 21, 22, problems (such as thermal welding) due to deterioration of the relays 21, 22 caused by heat are less likely to occur. Such a battery system 100 is also easily adaptable to rapid charge and discharge in which a large current flows through the battery 10, and the convenience of the battery system 100 is improved.

[0026] In addition, in the battery system 100, the weight of the relay can be reduced as compared with the case where a large relay is used as the main relay. As a result, the energy for driving the relay can be reduced. In the battery system 100, since a small relay can be used, there are more options for component selection, and the manufacturing cost can be reduced.

[0027] In the above-described embodiment, similar to the first main relay 20, the second main relay 30 includes relay groups 31 and 32 in which a plurality of relays 31 and 32 are connected in parallel. Both the first main relay 20 and the second main relay 30 include relay groups in which a plurality of relays are connected in parallel. With such a configuration, heat generation in each of the relays 21, 22, 31, and 32 can be reduced on both the positive electrode side and the negative electrode side of the battery 10. Further, since the relay groups are provided on both the positive electrode side and the negative electrode side of the battery 10, the reliability of the battery system 100 can be improved due to redundancy.

[0028] Note that the relay group does not necessarily have to be provided in both the first main relay 20 and the second main relay 30. The relay group may be provided only in the first main relay 20 or may be provided only in the second main relay 30. Further, in the above-described embodiment, the first main relay 20 and the second main relay 30 each include two relays. However, the present invention is not limited to such a form, and the first main relay 20 and the second main relay 30 may each include three or more relays. The number of relays may be determined based on the value of the current that can flow through the charge and discharge circuit.

[0029] In the battery system 100, switching between the open state and the closed state of the plurality of relays 21, 22, 31, and 32 is controlled by the controller 40.

[0030] 〈Controller 40〉 The controller 40 individually switches the closed state and the open state of each of the plurality of relays 21, 22, 31, 32 according to predetermined conditions. The controller 40 can be, for example, a computer such as an ECU (Electronic Control Unit) or a circuit board with a microcomputer. The computer performs required functions, for example, in accordance with a predetermined program. Each function of the computer is processed by the cooperation of an arithmetic unit (also referred to as a processor, CPU (Central Processing Unit), MPU (Micro-Processing Unit)) of the computer, a storage device (such as a memory or a hard disk), and software.

[0031] The controller 40 includes a communication unit 41, a mode determination unit 42, a mode setting unit 43, a permissible current determination unit 44, an instruction unit 45, a voltage determination unit 46, a current determination unit 47, a completion determination unit 48, and a storage unit 49. Each of the units 41 to 49 of the controller 40 may be realized by one or more processors or may be incorporated into a circuit. The communication unit 41 of the controller 40 is configured to be communicable with a current sensor 50, a voltage sensor 60, and a host controller 75.

[0032] The battery system 100 includes a current sensor 50. The current sensor 50 measures the charge and discharge current flowing through the battery 10. In this embodiment, the current sensor 50 is provided between the battery 10 and the first main relay 20. The position of the current sensor 50 is not particularly limited. The charge and discharge current measured by the current sensor 50 is transmitted to the controller 40.

[0033] The battery system 100 includes a voltage sensor 60. The voltage sensor 60 measures the voltage of the battery 10. In this embodiment, the voltage sensor 60 is provided for each of the series-connected battery packs 10A. The voltage sensor 60 may measure the voltage of each corresponding battery pack 10A, or may measure the voltage of each single battery 10a that constitutes the battery pack 10A. The voltage of the battery pack 10A measured by each voltage sensor 60 is transmitted to the controller 40.

[0034] The controller 40 is configured to be communicable with a host controller 75. In this embodiment, the host controller 75 is a controller of an electric vehicle on which the battery system 100 and the load 70 are mounted, and is also referred to as an in-vehicle ECU.

[0035] Hereinafter, the control of switching the open and closed states of the plurality of relays 21, 22, 31, 32 by the controller 40 will be described. FIG. 2 is a flowchart showing the processing executed in the controller 40. When the battery system 100 is activated, charge / discharge and control of the relays 21, 22, 31, 32 are started. When the battery system 100 is activated, the relays 21, 22, 31, 32 and the precharge relay 27 are in the open state.

[0036] In step S1 of FIG. 2, the mode determination unit 42 of the controller 40 determines the charge / discharge mode. Here, as the charge / discharge mode, a rapid charge mode, a normal charge mode, and a load charge / discharge mode are set. The rapid charge mode is a mode when a rapid charger 83 is connected to the connection part 103. The normal charge mode is a mode when a normal charger 82 is connected to the connection part 102. The load charge / discharge mode is a mode when no charger 80 is connected to the connection parts 102 and 103, and power is supplied from the battery 10 to the load 70 via the connection part 101. In this embodiment, when the vehicle is not connected to the charger 80 and is running or stopped, the load charge / discharge mode is set. In the load charge / discharge mode, power may be supplied from the load 70 to the battery system 100 side.

[0037] The upper controller 75 recognizes the connection states of the connection parts 101 to 103 and transmits a signal corresponding to the mode to be set to the controller 40. The controller 40 receives the signal transmitted from the upper controller 75. In step S1, the mode determination unit 42 determines the charge and discharge mode according to the signal from the upper controller 75. In step S1, if the mode determination unit 42 determines that it is the rapid charge mode, the process proceeds to step S21.

[0038] 〈Rapid Charge Mode〉 In step S21 of FIG. 2, the mode setting unit 43 sets the control of the controller 40 to the rapid charge mode. Next, in step S22 of FIG. 2, the allowable current determination unit 44 determines the allowable current during charging of the battery 10. The allowable current can be determined by the remaining amount (SOC) of the battery, the deterioration state (SOH) of the battery, the temperature of the battery, etc. The allowable current may be determined in consideration of the thermal limit characteristics of the components (in this embodiment, the relays 21, 22, 31, 32) in the charge and discharge circuit. The allowable current may be determined according to the resistance of the component, the current flowing through the component, and the time for which the current is expected to flow.

[0039] FIG. 3 is a graph showing the fluctuations of the current and voltage during charging and the states of the relays 21, 22, 31, 32. In this embodiment, the battery 10 is charged by so-called CCCV (Constant Current, Constant Voltage) charging. As shown in FIG. 3, until the voltage of the battery 10 reaches a predetermined threshold value Vth1, the battery 10 is charged at a constant current. When the voltage of the battery 10 becomes equal to or higher than the predetermined threshold value Vth1, the battery 10 is charged at a constant voltage. Note that the charging of the battery 10 is not limited to CCCV charging, and it may be charged by other known charging methods.

[0040] In step S23 of FIG. 2, the instruction unit 45 controls the main relay group (relays 21, 22 of the first main relay 20 and relays 31, 32 of the second main relay 30) to the closed state. In this way, during rapid charging, a plurality of relays (relays 21, 22 of the first main relay 20 and relays 31, 32 of the second main relay 30) are switched to the closed state. Note that relays 21, 22 can be brought to the closed state after the pre-charge sequence.

[0041] In step S24 of FIG. 2, charging of the battery 10 is started. During charging, the current Ibat1 of the battery 10 measured by the current sensor 50 and the voltage Vbat1 of the battery 10 measured by the voltage sensor 60 are appropriately transmitted to the controller 40. The battery 10 is charged according to the allowable current determined in step S22.

[0042] In step S25 of FIG. 2, the voltage determination unit 46 determines whether the voltage Vbat1 of the battery 10 is equal to or higher than the threshold value Vth1. If the voltage Vbat1 of the battery 10 is smaller than the threshold value Vth1 (No), the process returns to step S24 and charging continues. At this time, the battery 10 is continuously charged at a constant current, and the voltage Vbat1 rises (see FIG. 3). When the voltage Vbat1 of the battery 10 becomes equal to or higher than the threshold value Vth1 (Yes), the process proceeds to step S26. After the voltage Vbat1 becomes equal to or higher than the threshold value Vth1 for a while, the charging method of the battery 10 switches from constant current charging to constant voltage charging.

[0043] In step S26 of FIG. 2, the current determination unit 47 determines whether the current Ibat1 of the battery 10 is equal to or less than the threshold value Ith1. If the current Ibat1 of the battery 10 is larger than the threshold value Ith1 (No), the process returns to step S24 and charging continues. When the battery 10 is charged at a constant voltage, the current Ibat1 decreases (see FIG. 3). When the current Ibat1 of the battery 10 becomes equal to or less than the threshold value Ith1 (Yes), the process proceeds to step S27.

[0044] In step S27 of FIG. 2, the instruction unit 45 controls some of the relays among the relays 21 and 22 of the first main relay 20 and the relays 31 and 32 of the second main relay 30 to the open state. In this embodiment, the instruction unit 45 controls the relay 22 of the first main relay 20 and the relay 32 of the second main relay 30 to the open state. In this way, when the voltage Vbat1 is equal to or higher than a predetermined value and the current Ibat1 is equal to or lower than a predetermined value during rapid charge and discharge, the controller 40 switches at least one of the plurality of relays 21, 22, 31, 32, namely the relays 22 and 32, to the open state. Thereby, when the current Ibat1 is low, it is possible to reduce the power consumption of driving the relays 22 and 32 while suppressing relay failures due to heat.

[0045] In step S28 of FIG. 2, the completion determination unit 48 determines whether the charging of the battery 10 is completed. The determination condition for completion of charging is not particularly limited. The determination condition for completion of charging can be set according to whether the target power has been charged. The determination condition for completion of charging can be set according to, for example, the remaining battery level, voltage, current, charging time, etc. If it is determined that the charging is not completed (No), the charging continues. If it is determined that the charging is completed (Yes), the charging of the battery 10 is completed, and the power supply from the rapid charger 83 is stopped. The instruction unit 45 can control the relays 21, 22, 31, 32 to the open state.

[0046] In the above-described embodiment, the controller 40 switches the plurality of relays 21, 22, 31, 32 to the closed state during rapid charge and discharge. Thereby, it becomes less likely that problems due to deterioration of the relays 21, 22, 31, 32 caused by heat generated during rapid charge and discharge occur.

[0047] 〈Normal charging mode〉 In step S1 of FIG. 2, when the mode determination unit 42 determines that it is the normal charging mode, the process proceeds to step S31. In step S31 of FIG. 2, the mode setting unit 43 sets the control of the controller 40 to the normal charging mode. Next, in step S32 of FIG. 2, the allowable current determination unit 44 determines the allowable current during charging of the battery 10.

[0048] In step S33 of FIG. 2, the instruction unit 45 controls the first main relay 20 and the second main relay 30 to be in the closed state. In the normal charging mode, relay 21 of relays 21 and 22 of the first main relay 20 and relay 31 of relays 31 and 32 of the second main relay 30 are brought into the closed state. Note that relay 21 can be brought into the closed state after the pre-charge sequence. Relays 22 and 32 remain in the open state.

[0049] In step S34 of FIG. 2, charging of the battery 10 is started. During charging, the current of the battery 10 measured by the current sensor 50 and the voltage of the battery 10 measured by the voltage sensor 60 are transmitted to the controller 40. The battery 10 may be charged by the CCCV charging described above. In step S34, the battery 10 is charged according to the allowable current determined in step S32. In step S35 of FIG. 2, the completion determination unit 48 determines whether or not the charging of the battery 10 is completed. During charging, the charging method may be appropriately set by comparing the voltage and / or current of the battery 10 with a preset threshold value.

[0050] In step S35 of FIG. 2, the completion determination unit 48 determines whether or not the charging of the battery 10 is completed. Since the determination conditions and relays for charging completion can be the same as those in step S28, detailed description thereof is omitted. If it is determined that the charging is not completed (No), the charging continues. If it is determined that the charging is completed (Yes), the charging of the battery 10 is completed and the supply of power from the normal charger 82 is stopped. The instruction unit 45 can control relays 21 and 31 to be in the open state.

[0051] Here, although the case where the battery 10 of the battery system 100 is rapidly charged or normally charged has been described, it is not limited to such a form. The processing of the controller 40 described above is also applicable when power is supplied (discharged) from the battery 10 of the battery system 100 to the load 70 or the like. For example, as a usage pattern of the battery system 100, when rapid discharge and normal discharge are set, the above-described "rapid charge" and "normal charge" are appropriately read as "rapid discharge" and "normal discharge".

[0052] 〈Load charge / discharge mode〉 In step S1 of FIG. 2, when the mode determination unit 42 determines that it is the load charge / discharge mode, the process proceeds to step S41. In step S41 of FIG. 2, the mode setting unit 43 sets the control of the controller 40 to the load charge / discharge mode. Next, in step S42 of FIG. 2, the allowable current determination unit 44 determines the allowable current during charge and discharge of the battery 10.

[0053] In step S43 of FIG. 2, the current determination unit 47 determines whether or not the allowable current is equal to or less than the threshold Ith2. If the allowable current is equal to or less than the threshold Ith2 (Yes), the process proceeds to step S44. In step S44, relay 21 among relays 21 and 22 of the first main relay 20 and relay 31 among relays 31 and 32 of the second main relay 30 are closed, and the process proceeds to step S46. Relay 21 can be closed after the precharge sequence. Note that relays 22 and 32 remain open. In this way, the controller 40 switches the closed state and the open state of the plurality of relays 22 and 32 included in the relay groups 21, 22, 31, and 32 according to the allowable current. Thereby, while suppressing the malfunction of the relays 21 and 31 due to heat, the power consumption of driving the relays 22 and 32 can be reduced.

[0054] In step S43, when the allowable current is greater than the threshold Ith2 (No), the process proceeds to step S45. In step S45, the main relay group (relays 21 and 22 of the first main relay 20 and relays 31 and 32 of the second main relay 30) is closed, and the process proceeds to step S46. Relays 21 and 22 can be closed after the precharge sequence.

[0055] In step S46 of FIG. 2, the charging and discharging of the battery 10 is started. During charging and discharging, the current determination unit 47 may execute a determination as to whether or not the above-described allowable current is equal to or less than the threshold Ith2. For example, the determination of the allowable current and the determination as to whether or not the allowable current is equal to or less than the threshold Ith2 may be executed at a predetermined time interval. The closed states and open states of 21, 22, 31, and 32 may be appropriately switched according to the relationship between the allowable current and the threshold Ith2. For example, the processes of steps S42 to S46 described above may be repeated.

[0056] In the load charge / discharge mode, the allowable current can vary greatly according to the driving conditions of the vehicle and the like. Therefore, the magnitude relationship between the threshold Ith2 and the allowable current may change over time. The allowable current may be equal to or less than the threshold Ith2 or may be greater than the threshold Ith2. When the allowable current changes from a state greater than the threshold Ith2 to a state equal to or less than the threshold Ith2, the instruction unit 45 can switch the relays 22 and 32 among the plurality of relays 21, 22, 31, and 32 to the open state. The storage unit 49 stores that the relays 22 and 32 have been switched to the open state. Thereafter, when the allowable current changes from a state equal to or less than the threshold Ith2 to a state greater than the threshold Ith2, the instruction unit 45 can switch the relays 22 and 32, which were in the open state, to the closed state. Thereafter, when the allowable current again changes from a state greater than the threshold Ith2 to a state equal to or less than the threshold Ith2, the instruction unit 45 can switch at least one of the plurality of relays 21, 22, 31, and 32 to the open state. The storage unit 49 stores that the relays 22 and 32 were switched from the closed state to the open state last time. The instruction unit 45 switches the relays 21 and 31 other than the relays 22 and 32, which were switched from the closed state to the open state last time, to the open state.

[0057] As described above, when the controller 40 switches at least one of the plurality of relays 21, 22, 31, 32 from the closed state to the open state, it may preferentially switch from the closed state to the open state the relay that could not be switched from the previous closed state to the open state. By preferentially switching from the closed state to the open state the relay that could not be switched from the previous closed state to the open state, the bias in the time during which the plurality of relays 21, 22, 31, 32 are closed can be suppressed. As a result, problems such as the relays 21, 22, 31, 32 being welded due to heat generation associated with the charge and discharge current (in the case of semiconductor relays, a short circuit failure between the energized lines) are less likely to occur.

[0058] When the use of the vehicle ends, the battery system 100 is shut down. When the battery system 100 is shut down, the instruction unit 45 can control the relays 21, 22, 31, 32 to the open state.

[0059] Incidentally, the battery system may be provided with a mechanism for ensuring safety even when a relay is welded.

[0060] 〈Battery system 100A〉 FIG. 4 is a schematic diagram showing the battery system 100A. In FIG. 4, members and parts having the same functions as those in FIG. 1 are appropriately assigned the same reference numerals, and duplicate descriptions are appropriately omitted. As shown in FIG. 4, the battery system 100A includes a battery 10, a first main relay 20, a second main relay 30, and a pyro fuse 90. The pyro fuse 90 is provided in the conductive path through which the battery 10 flows. The pyro fuse 90 is an explosive type current breaker. The pyro fuse 90 contains gunpowder, and when the gunpowder is ignited, the conductive path is interrupted. The pyro fuse 90 is configured to be able to receive a signal from the controller 40. In this embodiment, the pyro fuse 90 is provided on the connection line 11 connecting the two battery packs 10A1, 10A2.

[0061] The controller 40 is provided with a welding detector 40a. The welding detector 40a diagnoses whether at least one of the first main relay 20 and the second main relay 30 is welded. The welding detector 40a can diagnose by detecting the current flowing through each relay 21, 22, 31, 32 or the voltage applied to each relay 21, 22, 31, 32. For example, when the relays 21, 22, 31, 32 are controlled to be in the open state, if the detected current or voltage is equal to or greater than the threshold value, it can be detected that the relay with the current or voltage equal to or greater than the threshold value is welded. When the welding detector 40a detects that at least one of the first main relay 20 and the second main relay 30 is welded, it transmits a cutoff signal to the pyro fuse 90. The pyro fuse 90 that receives the cutoff signal breaks the conductive path (in this embodiment, the connection wire 11).

[0062] The first main relay 20 and the second main relay 30 may be thermally welded due to rapid charge and discharge, long-term use, etc. If any of the relays 21, 22 connected in parallel or the relays 31, 32 is thermally welded, the resistance of the relay that is not thermally welded is low, and there is a possibility that the charge and discharge current may be biased. If the charge and discharge current is biased to one relay, there is a concern that unintended heat generation may occur in the relay through which a large current flows.

[0063] In the above-described embodiment, when the welding detector 40a detects that at least one of the first main relay 20 and the second main relay 30 is welded, the pyro fuse 90 breaks the conductive path. When the relay is welded, the unintended heat generation in the first main relay 20 and the second main relay 30 can be prevented by breaking the conductive path by the pyro fuse 90. Even when one relay is provided for each of the first main relay 20 and the second main relay 30, unintended heat generation can be prevented.

[0064] In the above-described embodiment, the pyro fuse 90 is provided between the assembled batteries 10A1 and 10A2. As a result, when welding of the relay occurs, the connection between the assembled batteries 10A1 and 10A2 is physically interrupted. Thereby, the safety of the work at the time of inspection of the battery system 100A after the breakage of the interruption path can be improved. Note that it is not essential to provide the pyro fuse 90 between the assembled batteries 10A1 and 10A2, and the pyro fuse 90 is provided in the conduction path of the battery 10, the load 70, and the charger 80.

[0065] As described above, the technologies disclosed herein have been variously described. Unless otherwise particularly specified, the embodiments etc. cited herein do not limit the present invention. Further, the technologies disclosed herein can be variously modified, and unless there are particular problems, each component and each process mentioned herein can be appropriately omitted or appropriately combined. Further, this specification includes the disclosures described in the following respective items.

[0066] Item 1: A battery having a positive electrode and a negative electrode, A first main relay connected in series on the positive electrode side of the battery, A second main relay connected in series on the negative electrode side of the battery and comprising At least one of the first main relay and the second main relay includes a relay group in which a plurality of relays are connected in parallel, The plurality of relays are each individually controlled to switch between a closed state and an open state, A battery system.

[0067] Item 2: Further comprising a controller that controls switching between the closed state and the open state of the plurality of relays, The controller switches the plurality of relays to the closed state during rapid charge and discharge, the battery system according to Item 1.

[0068] Item 3: A controller that controls switching between the closed state and the open state of the plurality of relays, and A voltage sensor that measures the voltage of the battery, and a current sensor that measures the charge and discharge current flowing through the battery and further includes, When rapid charge and discharge is performed, the controller switches at least one of the plurality of relays to an open state when the voltage is equal to or higher than a predetermined value and the charge and discharge current is equal to or lower than a predetermined value. The battery system according to claim 2.

[0069] Item 4: A controller that controls switching between the closed state and the open state of the plurality of relays, and a current sensor that measures the charge and discharge current flowing through the battery and further includes, The controller switches between the closed state and the open state of the plurality of relays included in the relay group according to the allowable current. The battery system according to any one of claims 1 to 3.

[0070] Item 5: Further includes a controller that controls switching between the closed state and the open state of the plurality of relays, When the controller switches at least one of the plurality of relays from the closed state to the open state, the controller preferentially switches the relay that could not be switched from the closed state to the open state last time from the closed state to the open state. The battery system according to any one of claims 1 to 4.

[0071] Item 6: Both the first main relay and the second main relay include a relay group in which a plurality of relays are connected in parallel. The battery system according to any one of claims 1 to 5.

[0072] Item 7: Further includes a pyro fuse provided in the conduction path of the charge and discharge current flowing through the battery, The controller includes a welding diagnostic device that detects that at least one of the first main relay and the second main relay is welded. The battery system according to any one of items 1 to 6, wherein when the welding detector detects that at least one of the first main relay and the second main relay is welded, the conductive path is broken by the pyro fuse.

Explanation of Signs

[0073] 10 Battery 10a Single battery 10A, 10A1, 10A2 Battery pack 11 Connecting wire 20 First main relay 21, 22, 31, 32 Relay 25 Precharge circuit 26 Precharge resistor 27 Precharge relay 30 Second main relay 40 Controller 40a Welding detector 41 Communication unit 42 Mode determination unit 43 Mode setting unit 44 Allowable current determination unit 45 Indicator unit 46 Voltage determination unit 47 Current determination unit 48 Completion determination unit 49 Memory unit 50 Current sensor 60 Voltage sensor 70 Load 75 Host controller 80 Charger 82 Normal charger 83 Quick charger 90 Pyro fuse 100, 100A Battery system 101~103 Connection part 101a, 101b, 102a, 102b, 103a, 103b Connecting wire

Claims

1. A battery having a positive electrode and a negative electrode, A first main relay connected in series on the positive electrode side of the battery, A second main relay connected in series on the negative electrode side of the battery and comprising, At least one of the first main relay and the second main relay includes a relay group in which a plurality of relays are connected in parallel, The plurality of relays are each individually controlled to switch between a closed state and an open state, A battery system.

2. Further comprising a controller for controlling switching between the closed state and the open state of the plurality of relays, The controller switches the plurality of relays to a closed state during rapid charge and discharge. The battery system according to claim 1.

3. A controller for controlling switching between the closed state and the open state of the plurality of relays, A voltage sensor for measuring the voltage of the battery, A current sensor for measuring the charge and discharge current flowing through the battery and further comprising, The controller switches at least one of the plurality of relays to an open state when the voltage is equal to or higher than a predetermined value and the charge and discharge current is equal to or lower than a predetermined value during rapid charge and discharge. The battery system according to claim 2.

4. A controller for controlling switching between the closed state and the open state of the plurality of relays, A current sensor for measuring the charge and discharge current flowing through the battery and further comprising, The controller switches between the closed state and the open state of the plurality of relays included in the relay group according to the allowable current. The battery system according to any one of claims 1 to 3.

5. The battery system further includes a controller configured to control switching between the closed state and the open state of the plurality of relays. When the controller switches at least one of the plurality of relays from the closed state to the open state, the controller preferentially switches from the closed state to the open state the relay that could not be switched from the closed state to the open state the last time. The battery system according to any one of claims 1 to 3. **Claim 6** Both the first main relay and the second main relay include a relay group in which a plurality of relays are connected in parallel. The battery system according to any one of claims 1 to 3. **Claim 7** The battery system further includes a pyro fuse provided in a conduction path of a charge / discharge current flowing through the battery. The controller includes a welding detector configured to detect that at least one of the first main relay and the second main relay is welded. When the welding detector detects that at least one of the first main relay and the second main relay is welded, the conduction path is broken by the pyro fuse. The battery system according to any one of claims 1 to 3.

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