Battery control device and battery control method

Abstract

To ensure safety during welding of a relay switch on a battery pack.SOLUTION: A battery control device 50 controls a battery pack 10 having a battery module 13 consisting of a plurality of battery cells 13a and a relay switch 27 for switching connection and disconnection of a current path. The battery control device includes: a cell balancing processing unit 61 that executes cell balancing processing to equalize remaining capacities of the plurality of battery cells 13a by discharging some or all of the plurality of battery cells 13a when the remaining capacities of the plurality of battery cells 13a are uneven; and a diagnostic processing unit 63 that diagnoses whether or not the relay switch 27 is welded. When it is determined that the relay switch 27 is welded, the cell balancing processing is executed and the plurality of battery cells 13a are forcibly discharged until the remaining capacities become equal to or less than a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery control device and a battery control method. [Background technology]

[0002] For example, battery packs installed in electric vehicles and the like include a fuse and a relay switch that can interrupt a current path. The fuse automatically melts to interrupt the current path when an overcurrent flows, while the relay switch switches between connecting and disconnecting the current path using an electrical signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-149802 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the fuse does not include a pyroelectric fuse that can intentionally interrupt the current path using an electrical signal, if the relay switch melts and becomes unable to interrupt the current path, the current path connecting the battery pack and other electronically controlled components cannot be interrupted unless an overcurrent flows, which means that the vehicle will be repaired or stored with the battery pack and other electronically controlled components still electrically connected.

[0005] An object of the present invention is to provide a battery control device and a battery control method that ensure safety when a relay switch of a battery pack is welded. [Means for solving the problem]

[0006] In order to solve the above problem, according to one aspect of the present invention, there is provided a battery control device that controls a battery pack including a battery module consisting of a plurality of battery cells and a relay switch that switches between connecting and disconnecting a current path, the battery control device including: a cell balancing processing unit that performs a cell balancing process to equalize the remaining capacities of the plurality of battery cells by discharging some or all of the plurality of battery cells when the remaining capacities of the plurality of battery cells are uneven; and a diagnostic processing unit that diagnoses whether the relay switch is welded, and that performs the cell balancing process when it is determined that the relay switch is welded, and forcibly discharges the plurality of battery cells until the remaining capacities of the plurality of battery cells become equal to or less than a predetermined threshold.

[0007] In order to solve the above problem, according to another aspect of the present invention, there is provided a battery control method for controlling a battery pack including a battery module consisting of a plurality of battery cells and a relay switch that switches between connecting and disconnecting a current path, the battery control method comprising: diagnosing whether the relay switch is welded; and, when it is determined that the relay switch is welded, performing a cell balancing process to equalize the remaining capacities of the plurality of battery cells by discharging some or all of the plurality of battery cells if the remaining capacities of the plurality of battery cells are uneven; and forcibly discharging the plurality of battery cells until the remaining capacities of the plurality of battery cells become equal to or less than a predetermined threshold. [Effects of the Invention]

[0008] As described above, according to the present invention, safety can be ensured when the relay switch of the battery pack is welded. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram illustrating an example of the configuration of a battery pack to which a battery control device according to an embodiment of the present invention can be applied; [Figure 2] FIG. 1 is an explanatory diagram illustrating a cell balancing circuit. [Figure 3] FIG. 2 is an explanatory diagram illustrating a configuration example of a battery control device according to the embodiment. [Figure 4] 4 is a flowchart illustrating a battery control method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the battery pack of the present invention will be specifically described. However, this embodiment shows one aspect of the present invention, does not limit the present invention, and can be arbitrarily modified within the scope of the present invention. In each drawing, the same reference numerals denote the same components, and the description thereof will be omitted as appropriate.

[0011] First, an example of the overall configuration of a battery pack to which the battery control device according to this embodiment can be applied will be described.

[0012] FIG. 1 is a schematic diagram showing an example of the configuration of a battery pack 10, and shows a schematic diagram of the battery pack 10 as seen from above. The battery pack 10 is mounted on, for example, a hybrid electric vehicle or a pure electric vehicle. The battery pack 10 includes a case 11, a battery module 13 housed in the case 11, a positive electrode 17a, a negative electrode 17b, bus bars 21 and 23 connecting the battery module 13 to the positive electrode 17a and the negative electrode 17b, respectively, and a circuit board 30.

[0013] The battery module 13 is comprised of a plurality of battery cells 13a and is provided in the case 11. Each battery cell 13a has a positive terminal and a negative terminal on both longitudinal sides of its upper surface, and is stacked such that the positive and negative terminals are alternately arranged at the top and bottom in the figure. The positive and negative electrodes of adjacent battery cells 13a are electrically connected using cell connectors 15, and the plurality of battery cells 13a are connected in series as a whole. Both ends of the plurality of series-connected battery cells 13a are electrically connected to a positive electrode 17a and a negative electrode 17b protruding from the top surface of the case 11 by bus bars 21 and 23, respectively.

[0014] Of the bus bars 21 and 23, for example, a fuse 25 and a contactor 27 are provided midway on the bus bar 21 that connects the positive electrode 17a and the battery module 13. The fuse 25 melts and cuts off the current path when an overcurrent flows. The contactor 27 corresponds to a relay switch that switches between connecting and disconnecting the current path using an electric signal.

[0015] The circuit board 30 is mounted with a battery control device 50, a cell balancing circuit 31, and a contactor drive circuit 33. In addition, the circuit board 30 is mounted with a voltage sensor 35, a temperature sensor 37, and other electronic components and electrical circuits.

[0016] The battery control device 50 manages the charging / discharging and status of the battery module 13. The cell balancing circuit 31 is operated by an electrical signal from the battery control device 50, and is used to execute a cell balancing process in which, when the remaining capacities SOC of the plurality of battery cells 13a are uneven, some or all of the plurality of battery cells 13a are discharged to equalize the remaining capacities SOC of the plurality of battery cells 13a.

[0017] The contactor drive circuit 33 is operated by an electrical signal from the battery control device 50 and controls the supply of electricity to the contactor 27. When the contactor 27 is energized, the contactor 27 is in a connected state, and the positive electrode 17a and the negative electrode 17b are electrically connected. On the other hand, when the supply of electricity to the contactor 27 is stopped, the contactor 27 is in a cut-off state, and the positive electrode 17a and the negative electrode 17b are electrically disconnected.

[0018] The voltage sensor 35 measures the voltage of each battery cell 13a in the battery module 13. The temperature sensor 37 measures the temperature of any battery cell 13a. A plurality of temperature sensors 37 may be provided to measure the temperature of any of the plurality of battery cells 13a.

[0019] FIG. 2 shows a schematic diagram of an example of a cell balancing circuit 31. The illustrated cell balancing circuit 31 includes charge amount (remaining capacity) measurement terminals 41_n, 41_n-1... and cell balancing terminals 43_n, 43_n-1... connected to the positive terminals of the battery cells 13a_n, 13a_n-1.... The charge amount measurement terminals 41_n, 41_n-1... are used to measure the remaining capacity of each battery cell 13a. For example, a voltage sensor that measures the voltage of the battery cell 13a_n is connected to the charge amount measurement terminals 41_n, 41_n-1.

[0020] A discharge resistor 47 is provided in a current path connecting the cell balancing terminals 43_n, 43_n-1, etc., to the positive terminal of the battery cell 13a and the cell balancing terminal 43_n. A relay switch 49 is provided in a current circuit connecting the cell balancing terminals 43_n, 43_n-1 of the battery cells 13a_n and 13a_n-1 adjacent in series.

[0021] The relay switch 49 switches between opening and closing the current circuit in response to an electric signal transmitted from the battery control device 50. Closing the relay switch 49 forms a discharge circuit 45 connected in parallel to the battery cell 13a_n. As a result, the charging power of the battery cell 13a_n flows through the discharge circuit 45, and the discharge resistor 47 releases the electric energy as heat energy, thereby discharging the battery cell 13a_n.

[0022] However, the configuration of the cell balancing circuit 31 is not limited to the above example, and any circuit may be used as long as it can discharge each battery cell 13a by an electrical signal.

[0023] FIG. 3 is a block diagram showing components of the battery control device 50 that are involved in determining whether the contactor 27 is welded and in discharging processing. The battery control device 50 includes a control unit 51 and a storage unit 53. The control unit 51 includes an arithmetic processing device such as a CPU (Central Processing Unit) and executes various arithmetic processing. The storage unit 53 includes storage elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory) and stores information such as programs executed by the control unit 51, various parameters used in the arithmetic processing, calculation results, and measurement results. The type and number of storage units 53 are not particularly limited. A portion of the storage unit 53 is used as a work area for the arithmetic processing device.

[0024] The control unit 51 includes a cell balancing processing unit 61, a diagnostic processing unit 63, and a discharge processing unit 65. Each of these units is implemented by a program executed by an arithmetic processing unit. However, part of the cell balancing processing unit 61, the diagnostic processing unit 63, and the discharge processing unit 65 may be implemented by hardware such as an analog circuit.

[0025] When the charge levels of the plurality of battery cells 13a are uneven, the cell balancing processing unit 61 performs cell balancing to equalize the charge levels of the plurality of battery cells 13a by driving the cell balancing circuit 31 to discharge some or all of the plurality of battery cells 13a. In this embodiment, the cell balancing processing unit 61 is configured to perform cell balancing even when the contactor 27 is welded.

[0026] The diagnostic processing unit 63 executes a process for diagnosing whether or not the contactor 27 is welded. The process for determining whether or not the contactor 27 is welded is not particularly limited, and may be a known method. For example, the diagnostic processing unit 63 measures the voltage across the contactor 27 when the contactor 27 is in a non-energized state using the contactor drive circuit 33, and determines that the contactor 27 is welded if the measured voltage exceeds zero.

[0027] When the diagnostic processing unit 63 determines that the contactor 27 is welded, the discharge processing unit 65 uses the cell balancing processing unit 61 to execute a process of forcibly discharging the plurality of battery cells 13a until the charge amount of the battery cells 13a becomes equal to or less than a predetermined threshold. For example, the discharge processing unit 65 causes the cell balancing processing unit 61 to start executing the cell balancing process when a system (hereinafter also referred to as a "power system") that includes the battery pack 10 and executes charge / discharge control using power output from the battery modules 13 is stopped. Furthermore, the discharge processing unit 65 ends the execution of the cell balancing process when the total voltage of the battery modules 13 becomes equal to or less than a predetermined threshold. The total voltage of the battery modules 13 is calculated as the sum of the voltages of the individual battery cells 13a measured by the voltage sensors 35.

[0028] The power system may be, for example, a drive system that controls a drive motor mounted on a hybrid electric vehicle or a pure electric vehicle, but the power system is not limited to a vehicle drive system.

[0029] Next, a flowchart of the determination of whether the contactor 27 is welded and the discharge process executed by the battery control device 50 will be described.

[0030] Fig. 4 shows a flowchart of the processing executed by the battery control device 50. The flowchart shown in Fig. 4 can be executed at any timing, for example, during startup of the power system in which the battery pack 10 is mounted.

[0031] First, when the battery control device 50 is activated, the diagnostic processing unit 63 diagnoses whether the contactor 27 is welded (step S11). Next, the diagnostic processing unit 63 determines whether the contactor 27 is welded based on the diagnosis result (step S13). If the contactor 27 is not welded (S13 / No), the diagnostic processing unit 63 ends the process as it is because forced discharge of the battery cell 13a is not necessary.

[0032] On the other hand, if the diagnostic processing unit 63 determines that the contactor 27 is welded (S13 / Yes), the discharge processing unit 65 determines whether or not the power system in which charge / discharge control using the power output from the battery module 13 is performed has stopped (step S15). For example, the discharge processing unit 65 communicates with a control unit that controls the power system, acquires information on the operating state of the power system, and determines whether or not the power system has stopped.

[0033] If the discharge processing unit 65 determines that the power system is not stopped (S15 / No), it repeats the determination of step S15 until it determines that the power system is stopped. On the other hand, if the discharge processing unit 65 determines that the power system is stopped (S15 / Yes), the discharge processing unit 65 generates a command to cause the cell balancing processing unit 61 to start executing cell balancing processing (step S17). The cell balancing processing unit 61 connects some or all of the multiple battery cells 13a to the discharge circuit 45, and causes the discharge resistors 47 to generate heat, thereby forcibly discharging the battery cells 13a.

[0034] If the contactor 27 is welded, the battery pack 10 will need to be removed from the power system for repair or disposal, and so the discharge processing unit 65 may forcibly discharge all of the battery cells 13a. However, if all of the battery cells 13a are forcibly discharged, the amount of heat generated by the discharge resistor 47 will increase, and there is a risk that the battery module 13 or the battery pack 10 will overheat.

[0035] For this reason, the discharge processing unit 65 may execute forced discharge of the plurality of battery cells 13a while changing the battery cell 13a to be forcibly discharged. Alternatively, the discharge processing unit 65 may acquire the temperature detected by the temperature sensor 37, stop the forced discharge while the detected temperature is equal to or higher than a predetermined threshold, and resume the forced discharge when the detected temperature falls below the predetermined threshold. The predetermined threshold for the detected temperature may be set to any value equal to or lower than the heat resistance temperature of the battery module 13, for example.

[0036] Next, the discharge processing unit 65 determines whether the charge amount (remaining capacity) of the battery module 13 estimated based on the total voltage of the battery module 13 measured by the voltage sensor 35 is less than a predetermined threshold (step S19). The predetermined threshold for the charge amount may be set to any value so that the total voltage of the battery modules 13 is equal to or less than a voltage that is safe for an operator, for example.

[0037] If the discharge processing unit 65 determines that the charge amount (remaining capacity) of the battery module 13 is equal to or greater than the predetermined threshold (S19 / No), it continues the forced discharge of the battery cells 13a using the cell balancing process. On the other hand, if the discharge processing unit 65 determines that the charge amount (remaining capacity) of the battery module 13 is less than the predetermined threshold (S19 / Yes), it generates a command to stop the execution of the cell balancing process by the cell balancing processing unit 61 (step S21), and ends the series of processes.

[0038] As described above, the battery control device 50 according to an embodiment of the present disclosure includes a cell balancing processing unit 61 that performs cell balancing processing, a diagnostic processing unit 63 that diagnoses whether the contactor (relay switch) 27 is welded, and a discharge processing unit 65 that causes the cell balancing processing unit 61 to perform the cell balancing processing when it is determined that the contactor 27 is welded, and forcibly discharges the battery cells 13a until the remaining capacity of the battery cells 13a becomes equal to or less than a predetermined threshold.

[0039] Therefore, even if the contactor 27 is welded and the current path of the battery pack 10 cannot be interrupted by an electrical signal, the remaining capacity of the battery module 13 can be reduced so that the total voltage of the battery module 13 is below a safe voltage by utilizing the function of the cell balancing circuit 31 provided in the battery pack 10. This prevents the risk of discharge when removing the battery pack 10 or storing the battery pack 10 or a power system equipped with the battery pack 10.

[0040] Furthermore, the battery control device 50 according to this embodiment may acquire information on the temperature of the battery pack 10 and stop forced discharge while the temperature of the battery pack 10 is equal to or higher than a predetermined temperature threshold. This makes it possible to prevent overheating caused by forced discharge of power from the battery cells 13a.

[0041] The battery control device and the battery control method according to the above embodiment can be modified in various ways.

[0042] For example, when it is determined that the contactor (relay switch) 27 is welded, the battery control device 50 may cut off the supply of power from outside the battery pack 10 and perform cell balancing. For example, the battery control device 50 may communicate with a control unit that manages the power system, stop the supply of power to the battery pack 10, and operate modules such as the battery control device 50 and the cell balancing circuit 31 using the internal power of the battery module 13. For example, if the power system is a vehicle drive system, the power supply from a motor having a power generation function or an auxiliary battery to the battery control device 50 is stopped. This makes it possible to prevent a large current from being supplied to the battery pack 10 when the contactor (relay switch) 27 is welded.

[0043] Furthermore, when it is determined that the contactor (relay switch) 27 is welded, the battery control device 50 may start executing the cell balancing process in response to a command to start forced discharge from an external diagnostic device communicably connected to the battery control device 50. For example, after it is determined that the contactor 27 is welded, the battery control device 50 starts executing the cell balancing process when it receives a forced discharge command output by an operator operating the external diagnostic device at a repair shop or the like. This prevents, for example, a situation in which the remaining capacity of the battery module 13 decreases and the vehicle cannot be transported to a repair shop.

[0044] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0045] 10: Battery pack 13: Battery module 13a: Battery cell 17a: Positive electrode 17b: Negative electrode 21: Busbar 23: Busbar 25: Fuse 27: Contactor 31: Cell balancing circuit 33: Contactor drive circuit 35: Voltage sensor 37: Temperature sensor 45:Discharge circuit 47: Discharge resistor 49: Contactor (relay switch) 50: Battery control device 51: Control unit 53: Storage section 61: Cell balancing processing unit 63: Diagnostic processing unit 65: Discharge processing section

Claims

1. A battery control device (50) for controlling a battery pack (10) including a battery module (13) consisting of a plurality of battery cells (13a) and a relay switch (27) for switching between connection and disconnection of a current path, a cell balancing processing unit (61) that performs cell balancing processing to equalize the remaining capacities of the plurality of battery cells (13 a) by discharging some or all of the plurality of battery cells (13 a) when the remaining capacities of the plurality of battery cells (13 a) are uneven; a diagnostic processing unit (63) for diagnosing whether the relay switch (27) is welded; When it is determined that the relay switch (27) is welded, the cell balancing process is executed, and the plurality of battery cells (13 a) are forcibly discharged until the remaining capacity becomes equal to or less than a predetermined threshold. A battery control device characterized by:

2. Acquire information about the temperature of the battery pack (10); The forced discharge is stopped while the temperature of the battery pack (10) is equal to or higher than a predetermined temperature threshold.

2. The battery control device according to claim 1.

3. When it is determined that the relay switch (27) is welded, the supply of power from outside the battery pack (10) is cut off, and the cell balancing process is performed.

2. The battery control device according to claim 1.

4. receiving a command to start the forced discharge from an external diagnostic device communicably connected to the battery control device (50), and starting the execution of the cell balancing process; 2. The battery control device according to claim 1.

5. A battery control method for controlling a battery pack (10) including a battery module (13) consisting of a plurality of battery cells (13a) and a relay switch (27) that switches between connection and interruption of a current path, comprising: Diagnosing whether the relay switch (27) is welded; When it is determined that the relay switch (27) is welded, if the remaining capacities of the plurality of battery cells (13 a) are uneven, a cell balancing process is executed to equalize the remaining capacities of the plurality of battery cells (13 a) by discharging some or all of the plurality of battery cells (13 a), and forcibly discharging the plurality of battery cells (13 a) until the remaining capacities of the plurality of battery cells (13 a) become equal to or less than a predetermined threshold value. A battery control method comprising:

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