Battery management device and method

Abstract

A battery management device that manages a battery includes a plurality of voltage detection circuits and a plurality of discharge circuits, each voltage detection circuit being connected to a corresponding one of a plurality of battery cells, each discharge circuit being connected to a corresponding one of the plurality of battery cells. The battery management device causes a discharge of a battery cell having a voltage difference from a reference voltage that is greater than or equal to a predetermined first threshold value and less than a second threshold value that is greater than the first threshold value when a system of a vehicle is stopped, and causes a discharge of a battery cell having a voltage difference from the reference voltage that is greater than or equal to the second threshold value at least when the system is stopped or when the system is in operation.

Description

Technical Field

[0001] This disclosure relates to a battery management apparatus and method for managing a battery comprising multiple battery cells and installed on a vehicle. Background Technology

[0002] Traditionally, management devices for managing energy storage modules (batteries) are known in the art. These energy storage modules (batteries) comprise multiple cells connected in series and utilize the traction motor of a vehicle to transmit power (see, for example, Japanese Unexamined Patent Application Publication No. 2020-156119A). The management device includes a voltage detection circuit, multiple discharge circuits, and a control unit. The voltage detection circuit is connected to each node of the multiple cells via multiple voltage detection lines and detects the voltage of each cell. Each discharge circuit is disposed between two adjacent voltage detection lines and connected in parallel with a corresponding cell among the multiple cells. The control unit performs equalization control based on the voltage detected by the voltage detection circuit, controlling the discharge circuits and balancing the states of charge (SOC) (voltage) of the multiple cells. The control unit performs equalization control in a first mode before or during charging of the energy storage module by an external charging device. In the first mode, the control unit equalizes the actual rechargeable capacity of the multiple cells based on the current full charge capacity and the detected voltage of each cell. The control unit performs equalization control in a second mode before the vehicle begins to travel on electricity from the traction motor, or while the vehicle is traveling on electricity from the traction motor (before or during the discharge of multiple cells). In the second mode, the control unit equalizes the actual discharge capacity of multiple cells based on the current full charge capacity and the detected voltage of each battery. Summary of the Invention

[0003] In the aforementioned conventional management device, when current from a single cell flows through the discharge circuit due to equalization control, a voltage drop occurs in the voltage detection line due to its resistance. For example, due to changes in the temperature characteristics of the voltage detection line and the resistance in the discharge circuit, the current flowing through the discharge circuit and the voltage drop in the voltage detection line also vary in the discharge circuit and the voltage detection line, respectively. Therefore, it is difficult to reduce the voltage detection error caused by the voltage drop in the voltage detection line through correction. In the aforementioned management device, the voltage detection accuracy of the single cell is reduced due to the voltage drop. When equalization control is performed in a vehicle including the aforementioned management device while the energy storage module is charging using power from an external charging device or while the energy storage module is discharging and the vehicle is traveling using power from the traction motor, the reduced voltage detection accuracy may prevent proper control of the energy storage module's charging and the traction motor's control (discharging control).

[0004] This disclosure provides a method for equalizing the voltage of multiple battery cells while reducing the impact of reduced voltage detection accuracy of individual battery cells.

[0005] One aspect of this disclosure is a battery management device for managing a battery comprising multiple battery cells installed in a vehicle. The battery management device includes: multiple voltage detection circuits, each voltage detection circuit connected to a corresponding battery cell among the multiple battery cells via a pair of voltage detection lines, and each voltage detection circuit configured to detect the voltage of the corresponding battery cell; multiple discharge circuits, each discharge circuit connected to a corresponding battery cell among the multiple battery cells via a pair of voltage detection lines, and each discharge circuit configured to discharge the corresponding battery cell; a voltage difference acquisition unit configured to, for each of the multiple battery cells, acquire the voltage difference between the voltage of the battery cell detected by the voltage detection circuit and a reference voltage; and a cell balance control unit configured to, when the vehicle system is stopped, cause battery cells having a voltage difference greater than or equal to a predetermined first threshold and less than a second threshold greater than the first threshold to be discharged by the corresponding discharge circuit, and configured to, at least when the vehicle system is stopped or when the vehicle system is running, cause battery cells having a voltage difference greater than or equal to the second threshold to be discharged by the corresponding discharge circuit.

[0006] The battery management device disclosed herein includes multiple voltage detection circuits and multiple discharge circuits. Each voltage detection circuit is connected to a corresponding battery cell among multiple battery cells, and each discharge circuit is connected to a corresponding battery cell among multiple battery cells. The voltage detection circuit and discharge circuit corresponding to a battery cell share a pair of voltage detection lines. Therefore, when a battery cell is discharged by the corresponding discharge circuit to reduce its voltage to a reference voltage, a voltage drop occurs in the corresponding pair of voltage detection lines due to the resistance of each voltage detection line, and the voltage detection accuracy of the battery cell is reduced due to the voltage drop. Based on this, when the vehicle system is stopped, the cell balance control unit causes battery cells whose voltage difference between the battery cell voltage obtained by the voltage difference acquisition unit and the reference voltage is greater than or equal to a predetermined first threshold and less than a second threshold greater than the first threshold to be discharged by the corresponding discharge circuit. Accordingly, the opportunity for the discharge circuit to discharge battery cells with a relatively small voltage difference from the reference voltage is limited to when the vehicle system is stopped, such as when the vehicle is not in use or when the battery is not being charged by an external charging device. This reduces the impact of the reduction in the voltage detection accuracy of the battery cell 2 when the vehicle system is running. The cell balancing control unit causes battery cells with voltage differences greater than or equal to a second threshold to be discharged by their respective discharge circuits, at least when the vehicle system is stopped or when the vehicle system is running. This configuration provides sufficient opportunity to discharge battery cells with voltage differences relatively large compared to a reference voltage, thereby enabling the equalization of the voltages of multiple battery cells. The battery management device of this disclosure is therefore able to equalize the voltages of multiple battery cells while minimizing the impact of reduced voltage detection accuracy of individual cells.

[0007] In the battery management device described above, the cell balance control unit can be configured to cause battery cells with a voltage difference greater than or equal to a second threshold to be discharged by the discharge circuit in a manner that increases the discharge time of the battery cell with the larger the voltage difference. This reduces the chance of simultaneous (parallel) discharge of battery cells by the discharge circuit and voltage detection by the voltage detection circuit when the vehicle system is in operation, and satisfactorily reduces the impact of reduced voltage detection accuracy of battery cells.

[0008] In the battery management device described above, the voltage detection circuit can be configured to detect the voltage of the corresponding battery cells at predetermined intervals; and the cell balancing control unit can be configured to, when the voltage detection circuit is not detecting voltage while the vehicle system is running, cause battery cells with a voltage difference greater than or equal to a second threshold and less than a third threshold greater than the second threshold to be discharged by the discharge circuit, and is configured to, while the vehicle system is running, cause battery cells with a voltage difference greater than or equal to the third threshold to be discharged by the discharge circuit regardless of whether the voltage detection circuit is detecting voltage. This configuration minimizes the impact of reduced voltage detection accuracy of battery cells when battery cells with a voltage difference greater than or equal to the second threshold from the reference voltage are discharged by the discharge circuit while the vehicle system is running, and promotes cell balancing.

[0009] In the battery management device described above, the voltage detection circuit may include a resistor connected in series with a battery cell, a capacitor connected in parallel with the battery cell, and a voltage sensor for detecting the voltage between the terminals of the capacitor. The cell balance control unit may be configured such that battery cells having a voltage difference greater than or equal to a second threshold and less than a third threshold are discharged by the discharge circuit from the time the voltage detection circuit ends until the voltage detection circuit begins voltage detection again. Accordingly, the capacitor in the voltage detection circuit, discharged by the discharge circuit on the battery cell, can be charged before the voltage detection circuit begins (resumes) voltage detection. Therefore, this configuration provides satisfactory voltage detection accuracy for the voltage detection circuit.

[0010] In the battery management device described above, the detected value of the voltage detection circuit can be limited between an upper limit voltage and a lower limit voltage; and the cell balance control unit can be configured to change the range between the upper limit voltage and the lower limit voltage according to the voltage difference when a battery cell with a voltage difference greater than or equal to a second threshold is discharged by the discharge circuit. This configuration can satisfactorily reduce the impact of reduced voltage detection accuracy of the battery cell caused by the discharge of the battery cell by the discharge circuit.

[0011] In the battery management device described above, the reference voltage can be the minimum value among the voltages of multiple individual battery cells.

[0012] Another aspect of this disclosure is a battery management method for managing a battery comprising multiple battery cells installed in a vehicle by using multiple voltage detection circuits and multiple discharge circuits. Each voltage detection circuit is connected to a corresponding battery cell among the multiple battery cells via a pair of voltage detection lines, and each voltage detection circuit is configured to detect the voltage of the corresponding battery cell. Each discharge circuit is connected to a corresponding battery cell among the multiple battery cells via a pair of voltage detection lines, and each discharge circuit is configured to discharge the corresponding battery cell. The battery management method includes: for each of the multiple battery cells, acquiring the voltage difference between the voltage of the battery cell detected by the voltage detection circuit and a reference voltage; and, when the vehicle system is stopped, causing battery cells having a voltage difference greater than or equal to a predetermined first threshold and less than a second threshold greater than the first threshold to be discharged by the corresponding discharge circuit, and causing battery cells having a voltage difference greater than or equal to the second threshold to be discharged by the corresponding discharge circuit, at least when the vehicle system is stopped or when the vehicle system is running.

[0013] This method can therefore balance the voltage of multiple battery cells while reducing the impact of reduced voltage detection accuracy of individual battery cells. Attached Figure Description

[0014] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein similar reference numerals denote similar elements, and wherein:

[0015] Figure 1 This is a schematic configuration diagram of a vehicle equipped with the battery management device disclosed herein;

[0016] Figure 2 This is a schematic configuration diagram of the battery management device disclosed herein;

[0017] Figure 3 It is a timing diagram showing the change in the detected value of the voltage sensor when a battery cell is discharged by the discharge circuit of the battery management device of this disclosure;

[0018] Figure 4 This is a flowchart illustrating an example of a routine executed by the battery management device of this disclosure;

[0019] Figure 5 This is a timing diagram illustrating the process of discharging a single battery cell by the discharge circuit of the battery management device of this disclosure;

[0020] Figure 6 This is a timing diagram illustrating the process of discharging a single battery cell by the discharge circuit of the battery management device of this disclosure; and

[0021] Figure 7This is a timing diagram illustrating the process of discharging a single battery cell by the discharge circuit of the battery management device of the present invention. Detailed Implementation

[0022] The modes for carrying out the invention disclosed herein will be described with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic configuration diagram of a vehicle 100 equipped with the battery management device 10 disclosed herein. Figure 1 The vehicle 100 shown is a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV, PHEV) that includes a battery 1 and a motor generator (three-phase AC motor) MG. The battery 1 is managed by a battery management device 10, and the motor generator MG is connected to the battery 1 via a system main relay (not shown) and an electrical control device including an inverter (not shown), and is able to use the battery 1 to transmit power to output traction power and regenerative braking force.

[0024] As shown in the figure, battery 1 is a so-called high-voltage battery, comprising, for example, multiple battery cells 2 connected in series. The multiple battery cells 2 can be distributed and housed within module housings (not shown) of multiple battery modules, and the multiple battery modules can be connected in series, for example. The battery cells 2 in each battery module are, for example, ternary lithium-ion battery cells based on nickel-cobalt-aluminum oxide (NCA) or lithium iron phosphate.

[0025] like Figure 2 As shown, the battery management device 10 of vehicle 100 includes a microcomputer 11, one or more integrated circuits (ICs) 15, multiple filter resistors Rf, multiple discharge resistors Rb, and multiple filter capacitors Cf. The microcomputer 11 includes a central processing unit (CPU), read-only memory (ROM), and random access memory (RAM). Each management IC 15 includes multiple switching elements (e.g., transistors) Sw and multiple voltage sensors V, and is connected to the microcomputer 11. The number of switching elements Sw, the number of voltage sensors V, and the number of filter capacitors Cf in the battery management device 10 are the same as the total number of battery cells 2 in battery 1. Figure 2 As shown, the battery management device 10 is connected to the battery cell 2 via a plurality of voltage detection lines Lv. Each voltage detection line Lv is connected at one end to the positive terminal of the battery cell 2 and at the other end to the negative terminal of the battery cell 2, or to a node between adjacent battery cells 2.

[0026] Two (pair) voltage detection lines Lv connected to both ends of a battery cell 2 are connected to each other via a filter resistor Rf, a filter capacitor Cf, and another filter resistor Rf. That is, the filter capacitor Cf is connected in parallel to each battery cell 2 via the pair of voltage detection lines Lv and the two filter resistors Rf. Each voltage sensor V of the management IC 15 detects the voltage between the terminals of the corresponding filter capacitor Cf. Accordingly, the pair of voltage detection lines Lv, the two filter resistors Rf, the filter capacitor Cf, and the voltage sensor V form a voltage detection circuit 16 for detecting the voltage (voltage between terminals) of the corresponding battery cell 2. The battery management device 10 includes multiple voltage detection circuits 16 provided for multiple battery cells 2 (the number of voltage detection circuits 16 is the same as the number of battery cells 2).

[0027] A discharge resistor Rb and a filter resistor Rf are connected in parallel to each voltage detection line Lv, and a pair of voltage detection lines Lv connected to both ends of a battery cell 2 are connected to the corresponding switching element Sw of the management IC 15 via the discharge resistor Rb. With this configuration, by turning on the switching element Sw, current from the corresponding battery cell 2 flows through the two discharge resistors Rb to reduce the voltage of the battery cell 2. Therefore, the voltage of the battery cells 2 can be balanced. That is, a pair of voltage detection lines Lv, two discharge resistors Rb, and the switching element Sw form a discharge circuit 17 for discharging the corresponding battery cell 2. Therefore, the battery management device 10 includes multiple discharge circuits 17 provided for multiple battery cells 2 (the number of discharge circuits 17 is the same as the number of battery cells 2).

[0028] The management IC 15 causes each voltage sensor V to detect the voltage of the corresponding filter capacitor Cf (i.e., the corresponding battery cell 2) at a predetermined period (e.g., 150 ms), and completes the voltage detection of each battery cell 2 and the self-diagnostic processing of the management IC 15 within a time shorter than the predetermined period (e.g., 100 ms) from the start of voltage detection. The management IC 15 sends the detection value of each voltage sensor V to the microcomputer 11. The microcomputer 11 limits the detection value of each voltage sensor V of the management IC 15 between a predetermined upper limit voltage (positive value) and a predetermined lower limit voltage (negative value). The microcomputer 11 calculates the open circuit voltage (OCV) of each battery cell 2 based on the detection value of each voltage sensor V, and calculates the state of charge (SOC) of each battery cell 2 based on the open circuit voltage. In response to a command signal from the microcomputer 11, the management IC 15 controls the switching element Sw indicated by the command signal to be turned on and off.

[0029] In the battery management device 10, the voltage detection circuit 16 and the discharge circuit 17 corresponding to a single battery cell 2 share a pair of voltage detection lines Lv, such as Figure 2 As shown in the diagram. Accordingly, when the switching element Sw is turned on and the corresponding battery cell 2 is discharged by the corresponding discharge circuit 17, due to the resistance of each voltage detection line Lv (see Figure 17), Figure 2 (The dashed line in the diagram) and a voltage drop (e.g., approximately tens of millivolts) occurs in the corresponding pair of voltage sensing lines Lv, and as Figure 3 The decrease in the detected value of the corresponding voltage sensor V shown corresponds to a voltage drop. For example, due to changes in the temperature characteristics in the voltage detection line Lv and the changes in the discharge resistor Rb in the discharge circuit 17, the current flowing through the discharge circuit 17 (equalization current) and the amount of voltage drop in the voltage detection line Lv also change in the discharge circuit 17 and the voltage detection line Lv, respectively. Therefore, it is not easy to reduce the voltage detection error of each voltage sensor V due to the voltage drop in the voltage detection line Lv by correction. When equalizing the voltage of the battery cell 2, it is necessary to consider the impact of the reduced voltage detection accuracy of the battery cell 2 due to the voltage drop in the voltage detection line Lv.

[0030] Based on this, in order to minimize the impact of reduced voltage detection accuracy of battery cell 2 due to voltage drop in voltage detection line Lv, while balancing the voltage of multiple battery cells 2, the battery management device 10 performs... Figure 4 The routine shown determines the conditions for discharging the battery cell 2 by the discharge circuit 17 for each battery cell 2. The microcomputer 11, acting as a cell balance control unit, executes at predetermined time intervals (very small time intervals) when the vehicle 100's start switch (ignition switch) (not shown) is turned on and the vehicle 100's system is running. Figure 4 The routine.

[0031] exist Figure 4 At the start of the routine, the microcomputer 11 (CPU) acquires the voltage V of each battery cell 2 detected by each voltage sensor V of the management IC 15. n (“n” represents the number of battery cell 2, and n = 1, 2, ..., N-1, N, where “N” is the total number of battery cells 2) (Step S100). The microcomputer 11 also obtains the minimum voltage V. min (Step S110) The minimum voltage V min The voltages V1, V2, ..., V obtained in step S100 are... N The minimum value among them is determined, and the variable n (the number of battery cell 2) is set to 1 (step S120).

[0032] Then, the microcomputer 11, which is the voltage difference acquisition unit, calculates (acquires) the voltage V of the nth battery cell 2 acquired in step S100. n With the minimum voltage V as the reference voltage min Voltage difference ΔV between n (=V n -V min (Step S130), and determine the voltage difference ΔV n Whether it is greater than or equal to a predetermined first threshold Vref1 (a relatively small positive value) (step S140). When the microcomputer 11 determines the voltage difference ΔV... n When the voltage is less than the first threshold Vref1 (step S140: No), the microcomputer 11 clears the first discharge flag and the second discharge flag for the nth battery cell 2 to indicate the voltage V of the nth battery cell 2. n Approaching minimum voltage V min Furthermore, it is not necessary to reduce the voltage V of the nth battery cell 2 by discharging. n (Step S145).

[0033] When the start switch is off and the vehicle 100 system is stopped, a first discharge flag is set for battery cell 2 to be discharged by discharge circuit 17. When the vehicle 100 system is running, a second discharge flag is set for battery cell 2 to be discharged by discharge circuit 17. After step S145, microcomputer 11 increments variable n (step S190) and determines whether variable n is greater than the total number N of battery cells 2 (step S200). When microcomputer 11 determines that variable n is less than or equal to the total number N of battery cells 2 (step S200: no), microcomputer 11 repeats step S130 and subsequent steps.

[0034] When the microcomputer 11 determines the voltage difference ΔV n When the voltage difference ΔV is greater than or equal to the first threshold Vref1 (step S140: yes), the microcomputer 11 determines the voltage difference ΔV. n Is the voltage difference ΔV greater than or equal to a second threshold Vref2, which is greater than the first threshold Vref1 (step S150)? When the microcomputer 11 determines the voltage difference ΔV... n When the voltage is less than the second threshold Vref2 (step S150: No), the microcomputer 11 determines that it is necessary to reduce the voltage V of the nth battery cell 2 by discharging. nHowever, it is unnecessary to discharge the nth battery cell 2 when the vehicle 100 system is in operation. Therefore, the microcomputer 11 sets a first discharge flag and clears a second discharge flag for the nth battery cell 2 (step S155). After step S155, the microcomputer 11 increments the variable n (step S190) and determines whether the variable n is greater than the total number N of battery cells 2 (step S200). When the microcomputer 11 determines that the variable n is less than or equal to the total number N of battery cells 2 (step S200: no), the microcomputer 11 repeats step S130 and subsequent steps.

[0035] When the microcomputer 11 determines the voltage difference ΔV n When the voltage difference ΔV is greater than or equal to the second threshold Vref2 (step S150: yes), the microcomputer 11 determines the voltage difference ΔV. n Is the voltage difference ΔV greater than or equal to a third threshold Vref3, which is greater than the second threshold Vref2 (step S160)? When the microcomputer 11 determines the voltage difference ΔV... n When the voltage Vref3 is less than the third threshold (step S160: No), the microcomputer 11 determines that it is necessary to reduce the voltage V of the nth battery cell 2 by discharging, both when the vehicle 100 system is stopped and when the vehicle 100 system is running. n Therefore, the microcomputer 11 sets a first discharge flag and a second discharge flag for the nth battery cell 2 (step S165).

[0036] When the microcomputer 11 determines the voltage difference ΔV n When the voltage is less than the third threshold Vref3 (step S160: No), the microcomputer 11 further sets a temporary discharge prohibition flag for the nth battery cell 2 in step S165 to provide sufficient voltage detection accuracy for each voltage sensor V of the management IC 15. When the temporary discharge prohibition flag is set, during the voltage detection of the battery cell 2 and the self-diagnostic processing of the management IC 15 when the system of the vehicle 100 is running, the discharge of the battery cell 2 by the discharge circuit 17 is prohibited to provide sufficient voltage detection accuracy for each voltage sensor V.

[0037] Subsequently, the microcomputer 11 sets the standby time tw and the upper and lower voltage limits for limiting the detection value of the voltage sensor V (step S167). The standby time tw is the amount of time that should be provided between the end of the discharge of the battery cell 2 by the discharge circuit 17 and the start (recovery) of the voltage detection of the battery cell 2 by the voltage sensor V when the system of the vehicle 100 is running. That is, when the switching element Sw of the management IC 15 is turned on and the corresponding battery cell 2 is discharged by the corresponding discharge circuit 17, a voltage drop occurs in the corresponding pair of voltage detection lines Lv. Therefore, the filter capacitor Cf of the corresponding voltage detection circuit 16 that shares the voltage detection line Lv with the discharge circuit 17 is discharged to a voltage determined by the time constant based on the capacitance of the filter capacitor Cf and the resistance value of the filter resistor Rf, and the conduction time of the switching element Sw.

[0038] Therefore, in order to provide sufficient voltage detection accuracy for the voltage sensor V, it is necessary to charge the filter capacitor Cf with an electrical force corresponding to the electrical force discharged from the filter capacitor Cf during the discharge of the battery cell 2 by the discharge circuit 17 before the voltage sensor V starts (resumes) voltage detection. Therefore, in step S167, the microcomputer 11 sets the standby time tw to the time for charging the filter capacitor Cf with an electrical force corresponding to the electrical force discharged from the filter capacitor Cf due to the discharge of the battery cell 2. In this embodiment, the standby time tw set in step S167 is a fixed value predetermined based on, for example, the capacitance of the filter capacitor Cf of the voltage detection circuit 16 and the resistance value of the filter resistor Rf, and the time from the end of the self-diagnostic processing of the voltage sensor V and the management IC 15 until the next start of voltage detection of the voltage sensor V.

[0039] In step S167, the microcomputer 11 sets the upper limit voltage to a positive value that is less than the value used when the battery cell 2 is not discharged by the discharge circuit 17, and sets the lower limit voltage to a negative value that is greater than the value used when the battery cell 2 is not discharged by the discharge circuit 17. Therefore, the microcomputer 11 narrows the range between the upper and lower limits. After step S167, the microcomputer 11 increments the variable n (step S190) and determines whether the variable n is greater than the total number N of battery cells 2 (step S200). When the microcomputer 11 determines that the variable n is less than or equal to the total number N of battery cells 2 (step S200: No), the microcomputer 11 repeats step S130 and subsequent steps.

[0040] When the microcomputer 11 determines the voltage difference ΔV nWhen the voltage Vref3 is greater than or equal to the third threshold (step S160: Yes), the microcomputer 11 determines that it is necessary to reduce the voltage V of the nth battery cell 2 by discharging both when the vehicle 100 system is stopped and when the vehicle 100 system is running. n Therefore, the microcomputer 11 sets both a first discharge flag and a second discharge flag for the nth battery cell 2 (step S170). When the voltage difference ΔV n When the voltage is greater than or equal to the third threshold Vref3, the microcomputer 11 also clears the temporary discharge prohibition flag for the nth battery cell 2 in step S170 so as to prioritize the discharge of the battery cell 2, that is, to prioritize equalizing the voltage of the battery cell 2 compared to providing sufficient voltage detection accuracy for each voltage sensor V of the management IC 15.

[0041] The microcomputer 11 also sets the upper limit voltage to a positive value that is less than the value set in step S167, and sets the lower limit voltage to a negative value that is greater than the value set in step S167 (step S180). As a result, when the voltage difference ΔV n When the voltage is greater than or equal to the third threshold Vref3, the range between the upper and lower voltage limits is greater than the range between the upper and lower voltage limits when the voltage difference ΔV is determined. n The threshold is further narrowed when the value is greater than or equal to the second threshold Vref2 and less than the third threshold Vref3. After step S180, the microcomputer 11 increments the variable n (step S190) and determines whether the variable n is greater than the total number N of battery cells 2 (step S200). When the microcomputer 11 determines that the variable n is less than or equal to the total number N of battery cells 2 (step S200: no), the microcomputer 11 repeats step S130 and subsequent steps.

[0042] When executing the above Figure 4 In the routine and when determining the conditions for discharging battery cells 2 by the discharge circuit 17 for all (N) battery cells 2, in step S200, it is determined that the variable n is greater than the total number N of battery cells 2. When the microcomputer 11, which is the cell balance control unit, determines that the variable n is greater than the total number N of battery cells 2 (step S200: Yes), the microcomputer 11 ends. Figure 4 The routine, together with the management IC 15, balances the voltage of multiple battery cells 2 to a minimum voltage V based on the conditions for discharging the battery cells 2 by the discharge circuit 17, determined for each battery cell 2. min .

[0043] That is, according to Figure 4 The setting of the first discharge flag and the second discharge flag in step S155, such as... Figure 4 As shown, when the system of vehicle 100 is running, the microcomputer 11 does not cause the voltage V, which serves as the reference voltage, to deviate from the minimum voltage V. minvoltage difference ΔV n Any battery cell 2 that is greater than or equal to a predetermined first threshold Vref1 and less than a second threshold Vref2 is discharged by the corresponding discharge circuit 17, and when the start switch is turned off and the vehicle 100 system stops, such battery cell 2 is discharged by the corresponding discharge circuit 17. Accordingly, the discharge circuit 17 discharges the battery cell 2 having a minimum voltage Vref1. min Relatively small voltage difference ΔV n The opportunity for battery cell 2 to discharge is limited to when the vehicle 100 system is stopped, such as when the vehicle 100 is not in use or when the battery 1 is not being charged by an external charging device (when the system main relay is off). When the battery cell 2 is discharged while the system is stopped, the system main relay is off, and power is supplied only to those devices necessary for the discharge process (such as the battery management device 10).

[0044] according to Figure 4 In step S165 or S170, the setting of the first discharge flag and the second discharge flag causes the microcomputer 11 to, at least when the system of the vehicle 100 is stopped or when the system of the vehicle 100 is running, to be related to the minimum voltage V. min voltage difference ΔV n Any battery cell 2 that is greater than or equal to the second threshold Vref2 is discharged by the corresponding discharge circuit 17. For example, when the system of vehicle 100 is in Figure 4 When the routine is still running after it has ended, the microcomputer 11 causes the minimum voltage V to be applied. min voltage difference ΔV n Any battery cell 2 with a voltage greater than or equal to the second threshold Vref2 is discharged by the corresponding discharge circuit 17. After the start switch is turned off, the microcomputer 11 causes the voltage difference ΔV to be applied when the vehicle 100 system stops. n Any battery cell 2 that is still equal to or higher than the second threshold Vref2 is discharged by the corresponding discharge circuit 17.

[0045] According to Figure 4 The setting of the temporary discharge prohibition flag in step S165, such as Figure 6 As shown, when the system of vehicle 100 is in operation, the microcomputer 11 causes the corresponding voltage sensor V (voltage detection circuit 16) to not be detecting voltage, resulting in a minimum voltage V. min voltage difference ΔV n Any battery cell 2 that is greater than or equal to the second threshold Vref2 and less than the third threshold Vref3 is discharged by the corresponding discharge circuit 17. Figure 4 The setting of the discharge temporary prohibition flag in step S170, such as Figure 7As shown in [Fig. ], the microcomputer 11 causes any battery cell 2 having a voltage difference ΔV min with respect to the minimum voltage V n greater than or equal to the third threshold value Vref3 to be discharged by the corresponding discharge circuit 17 regardless of whether the corresponding voltage sensor V (voltage detection circuit 16) is detecting the voltage when the system of the vehicle 100 is in operation. As a result, as can be seen from Figure 6 and 7 , when a battery cell 2 having a voltage difference ΔV min with respect to the minimum voltage V n greater than or equal to the second threshold value Vref2 is discharged by the discharge circuit 17 when the system of the vehicle 100 is in operation, the discharge time of the battery cell 2 having a large voltage difference ΔV n (ΔV n ≥Vref3) is longer than the discharge time of the battery cell 2 having a small voltage difference ΔV n (ΔV n <Vref3) (the same applies to the case where a battery cell 2 having a voltage difference ΔV min with respect to the minimum voltage V n greater than or equal to the second threshold value Vref2 is discharged by the discharge circuit 17 when the system of the vehicle 100 is stopped).

[0046] As Figure 6 shown, the microcomputer 11 causes any battery cell 2 having a voltage difference ΔV n greater than or equal to the second threshold value Vref2 and less than the third threshold value Vref3 to be discharged by the corresponding discharge circuit 17 from the end of the voltage detection (and self-diagnosis process) of the corresponding voltage sensor V (voltage detection circuit 16) until the standby time tw set in step S167 before the next voltage sensor V (voltage detection circuit 16) starts (resumes) voltage detection. Accordingly, after the battery cell 2 is discharged by the discharge circuit 17, the corresponding filter capacitor Cf can be charged with an electric power corresponding to the electric power discharged from the filter capacitor Cf due to the discharge of the battery cell 2 when the voltage sensor V resumes voltage detection.

[0047] As described above, the battery management device 10 of the vehicle 100 includes a plurality of voltage detection circuits 16 and a plurality of discharge circuits 17. Each voltage detection circuit 16 is connected to a corresponding one of the plurality of battery cells 2, and each discharge circuit 17 is connected to a corresponding one of the plurality of battery cells 2. The voltage detection circuit 16 and the discharge circuit 17 corresponding to one battery cell 2 share a pair of voltage detection lines Lv. Therefore, when the battery cell 2 is discharged by the corresponding discharge circuit 17 to reduce the voltage of the battery cell 2 to the minimum voltage V as a reference voltage minAt that time, due to the resistance of each voltage detection line Lv, a voltage drop occurs in the corresponding pair of voltage detection lines Lv, and the voltage detection accuracy of the battery cell 2 is reduced due to the voltage drop.

[0048] Based on this, when the system of vehicle 100 stops, the microcomputer 11 causes... Figure 4 The voltage of battery cell 2 and the minimum voltage V obtained in step S130 min Voltage difference ΔV between n Any battery cell 2 that is greater than or equal to a predetermined first threshold Vref1 and less than a second threshold Vref2 that is greater than the first threshold Vref1 is discharged by the corresponding discharge circuit 17 (step S155). The microcomputer 11 causes the voltage difference ΔV to be present at least when the vehicle 100 system is stopped or when the vehicle 100 system is running. n Any battery cell 2 that is greater than or equal to the second threshold Vref2 is discharged by the corresponding discharge circuit 17 (steps S165, S170).

[0049] Accordingly, the discharge circuit 17 discharges the material having a voltage equal to the minimum voltage V. min Relatively small voltage difference ΔV n The opportunity for battery cell 2 to discharge is limited to when the vehicle 100 system is stopped, such as when the vehicle 100 is not in use or when the battery 1 is not being charged by an external charging device. This reduces the impact of reduced voltage detection accuracy of battery cell 2 when the vehicle 100 system is in operation. Furthermore, the above configuration provides sufficient opportunity to discharge the battery cell 2 with a voltage of V. min Relatively large voltage difference ΔV n The battery cell 2 is discharged, thereby balancing the voltage of multiple battery cells 2. As a result, the battery management device 10 is able to balance the voltage of multiple battery cells 2 while reducing the impact of reduced voltage detection accuracy of battery cells 2.

[0050] When the microcomputer 11 causes the minimum voltage V min voltage difference ΔV n When any battery cell 2 with a voltage greater than or equal to the second threshold Vref2 is discharged by the corresponding discharge circuit 17, it has a voltage difference ΔV greater than or equal to a third threshold Vref3, which is greater than the second threshold Vref2. n The discharge time of battery cell 2 is longer than that of battery cell 2 with a small voltage difference ΔVn less than the third threshold Vref3. That is, the microcomputer 11 causes a voltage difference ΔVn greater than or equal to the second threshold to be generated. n The battery cell 2 is discharged by the discharge circuit 17 so that the voltage difference ΔV nThe larger the battery cell 2, the longer the discharge time. This reduces the chance that the discharge of the battery cell 2 by the discharge circuit 17 and the voltage detection circuit 16 (voltage sensor V) will occur simultaneously (in parallel) when the system of the vehicle 100 is in operation, and can satisfactorily reduce the impact of reduced voltage detection accuracy of the battery cell 2.

[0051] That is, in the battery management device 10, each voltage detection circuit 16 (voltage sensor V) detects the voltage of the corresponding battery cell 2 at a predetermined period, and the microcomputer 11 causes the voltage difference ΔV to be adjusted when the corresponding voltage detection circuit 16 is not detecting voltage while the system of the vehicle 100 is running. n Any battery cell 2 that is greater than or equal to the second threshold Vref2 and less than the third threshold Vref3 is discharged by the corresponding discharge circuit 17. The microcomputer 11 also causes the voltage difference ΔV to be present while the vehicle 100 system is running, regardless of whether the corresponding voltage detection circuit 16 is detecting voltage. n Any battery cell 2 with a voltage greater than or equal to the third threshold Vref3 is discharged by the corresponding discharge circuit 17. This configuration enables the system in vehicle 100 to discharge at the minimum voltage V when the system is in operation. min voltage difference ΔV n When a battery cell 2 with a voltage greater than or equal to the second threshold Vref2 is discharged by the discharge circuit 17, the effect of reducing the voltage detection accuracy of the battery cell 2 is minimized, and the equalization of the battery cell 2 is promoted.

[0052] Each voltage detection circuit 16 of the battery management device 10 includes a filter resistor Rf connected in series with the corresponding battery cell 2, a filter capacitor Cf connected in parallel with the battery cell 2, and a voltage sensor V for detecting the voltage between the terminals of the filter capacitor Cf. The microcomputer 11 causes the voltage difference ΔV to... n Any battery cell 2 that is greater than or equal to the second threshold Vref2 and less than the third threshold Vref3 is discharged by the corresponding discharge circuit 17 from the end of voltage detection by the corresponding voltage sensor V (voltage detection circuit 16) until the standby time tw set in step S167 before the next voltage sensor V starts (resumes) voltage detection. Accordingly, the filter capacitor Cf of the voltage detection circuit 16, which is discharged by the discharge circuit 17 on the battery cell 2, can be charged before the voltage sensor V starts voltage detection. Therefore, this configuration provides satisfactory voltage detection accuracy of the voltage sensor V.

[0053] The battery management device 10 also calculates the SOC of each battery cell 2 based on the detection values ​​of the corresponding voltage sensor V (voltage detection circuit 16) limited between the upper and lower voltage limits. When the microcomputer 11 causes the minimum voltage V...min voltage difference ΔV n When a battery cell 2 with a voltage greater than or equal to the second threshold Vref2 is discharged by the discharge circuit 17, the microcomputer 11 determines the voltage difference ΔV based on the discharge circuit 17. n The range between the upper and lower voltage limits is changed (steps S167 and S180). This configuration satisfactorily reduces the impact of reduced voltage detection accuracy of battery cell 2 caused by the discharge circuit 17 discharging the battery cell 2.

[0054] For example, in Figure 4 In step S130, the minimum voltage V, which is replaced by the multiple battery cells 2, is... min The average voltage of multiple battery cells 2 can be used as a reference voltage. Figure 4 In step S130, instead of calculating the difference between the voltage of each battery cell 2 and the reference voltage, the SOC difference between the estimated SOC of each battery cell 2 and the reference SOC (e.g., the minimum of the estimated SOCs of multiple battery cells 2) can be calculated. Figure 4 In steps S140 to S160, the SOC difference can be compared with a first threshold to a third threshold. This form is particularly suitable for battery 1 where the battery cell 2 is a lithium-ion battery cell based on lithium iron phosphate (lithium iron phosphate battery cell). Figure 4 In step S167, instead of setting the standby time tw to a fixed value, it can be adjusted according to the voltage difference ΔV. n The standby time will be changed accordingly.

[0055] It should be understood that the invention disclosed herein is not limited to the embodiments described above, and various modifications can be made within the scope of this disclosure. The embodiments described above are merely specific forms of the invention as described in the "Summary of the Invention" section and are not intended to limit the elements of the invention described in the "Summary of the Invention" section.

[0056] The invention disclosed herein can be applied, for example, to the manufacture of battery management devices that manage batteries comprising multiple battery cells and are installed in vehicles.

Claims

1. A battery management device that manages a battery comprising multiple individual battery cells installed in a vehicle, characterized in that, The battery management device includes: Multiple voltage detection circuits, each of which is connected to a corresponding battery cell in the plurality of battery cells via a pair of voltage detection lines, and each of which is configured to detect the voltage of the corresponding battery cell at a predetermined period; A plurality of discharge circuits, each of the discharge circuits being connected to a corresponding battery cell among the plurality of battery cells via the pair of voltage detection lines, and each of the discharge circuits being configured to discharge the corresponding battery cell; A voltage difference acquisition unit is configured to acquire, for each of the plurality of battery cells, the voltage difference between the voltage of the battery cell detected by the voltage detection circuit and a reference voltage; and The individual balance control unit is configured as follows: This causes battery cells with a voltage difference greater than or equal to a predetermined first threshold and less than a second threshold greater than the first threshold to be discharged by the corresponding discharge circuit only when the vehicle's system is stopped. This causes battery cells with a voltage difference greater than or equal to the second threshold to be discharged by the corresponding discharge circuit when the vehicle system is stopped and when the vehicle system is running. A battery cell having a voltage difference greater than or equal to the second threshold and less than a third threshold greater than the second threshold is discharged by the discharge circuit when the voltage detection circuit is not detecting the voltage while the vehicle's system is in operation. When the system in the vehicle is in operation, the battery cell with a voltage difference greater than or equal to the third threshold is discharged by the discharge circuit, regardless of whether the voltage detection circuit is detecting voltage.

2. The battery management device according to claim 1, characterized in that, The cell balance control unit is configured to cause a cell with a voltage difference greater than or equal to the second threshold to be discharged by a discharge circuit in such a way that the larger the voltage difference, the longer the discharge time of the cell.

3. The battery management device according to claim 1, characterized in that: The voltage detection circuit includes a resistor connected in series with the battery cell, a capacitor connected in parallel with the battery cell, and a voltage sensor for detecting the voltage between the terminals of the capacitor; and The cell balance control unit is configured to cause a cell having a voltage difference greater than or equal to the second threshold and less than the third threshold to be discharged by the discharge circuit from when the voltage detection circuit ends until the voltage detection circuit begins to discharge.

4. The battery management device according to any one of claims 1 to 3, characterized in that: The voltage detection value of the voltage detection circuit is limited to between the upper limit voltage and the lower limit voltage; and The cell balance control unit is configured to change the range between the upper limit voltage and the lower limit voltage according to the voltage difference when a cell with a voltage difference greater than or equal to the second threshold is discharged by the discharge circuit.

5. The battery management device according to any one of claims 1 to 3, characterized in that, The reference voltage is the minimum value among the voltages of the plurality of individual battery cells.

6. A battery management method for managing a battery comprising a plurality of battery cells and installed in a vehicle by using a plurality of voltage detection circuits and a plurality of discharge circuits, each of the voltage detection circuits being connected to a corresponding battery cell among the plurality of battery cells via a pair of voltage detection lines, and each of the voltage detection circuits being configured to detect the voltage of the corresponding battery cell at a predetermined period, each of the discharge circuits being connected to a corresponding battery cell among the plurality of battery cells via the pair of voltage detection lines, and each of the discharge circuits being configured to discharge the corresponding battery cell, characterized in that... The battery management method includes: For each of the plurality of battery cells, the voltage difference between the voltage of the battery cell detected by the voltage detection circuit and the reference voltage is obtained; This causes battery cells with a voltage difference greater than or equal to a predetermined first threshold and less than a second threshold greater than the first threshold to be discharged by the corresponding discharge circuit only when the vehicle's system is stopped; This causes battery cells with a voltage difference greater than or equal to the second threshold to be discharged by the corresponding discharge circuit when the vehicle system is stopped and when the vehicle system is running. A battery cell having a voltage difference greater than or equal to the second threshold and less than a third threshold greater than the second threshold is discharged by the discharge circuit when the voltage detection circuit is not detecting the voltage while the vehicle's system is in operation. When the system in the vehicle is in operation, the battery cell with a voltage difference greater than or equal to the third threshold is discharged by the discharge circuit, regardless of whether the voltage detection circuit is detecting voltage.

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