Thermal runaway prediction detection device for secondary batteries, and thermal runaway prediction detection program for secondary batteries

Abstract

To properly detect a sign of thermal runway of a secondary battery, even when the operation of the secondary battery stops.SOLUTION: The thermal runaway sign detection device of a battery cell 42 comprises a battery measurement unit 50 that measures a measurement value that indicates the battery state of the battery cell 42, and a battery control ECU 70 that detects a sign of thermal runaway in the battery cell 42. The battery measurement unit 50 determines whether or not to output a start signal on the basis of the measured value when the battery control ECU 70 is in a sleep state, and causes a start signal to be outputted when the result of this determination is positive. The battery control ECU 70 is actuated upon input of a start signal from the battery measurement unit 50 while in a sleep state, arithmetically processes the measured value inputted from the battery measurement unit 50, and detects a sign of thermal runaway from the result of arithmetic operation.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a device for detecting a sign of thermal runaway of a secondary battery.

Background Art

[0002] Conventionally, there is a device that measures the complex impedance of a secondary battery for a plurality of frequencies within a measurement range, creates a complex impedance plane plot (such as a Cole-Cole plot or a Bode plot) based on the measurement results, and grasps the characteristics of the electrodes and electrolyte of the secondary battery (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in very rare cases, a secondary battery may experience thermal runaway and cause a fire. As a countermeasure, it is conceivable to detect a sign of thermal runaway of the secondary battery from the grasped characteristics of the electrodes and electrolyte of the secondary battery. It is known that thermal runaway of a secondary battery occurs not only during the operation (charging / discharging) of the secondary battery but also during the stop (non-operating, disconnected from the electrical load). Therefore, even when the arithmetic device such as the secondary battery or the ECU is in a stopped (sleep) state, it is desirable to configure it to be activated to detect a sign of thermal runaway.

[0005] However, the timing of activating the arithmetic device is usually after a certain period of time has elapsed since the start of the stop (sleep), and is independent of the state of the secondary battery. Therefore, depending on the timing of activation of the arithmetic device, it may not be possible to appropriately detect a sign of thermal runaway.

[0006] This invention was made to solve the above problems, and its main purpose is to appropriately detect signs of thermal runaway even when the secondary battery is shut down. [Means for solving the problem]

[0007] A secondary battery thermal runaway prediction device to solve the above problem is: A measuring unit that measures a measurement value indicating the battery state of the secondary battery, The secondary battery includes a battery control unit that detects signs of thermal runaway, The measurement unit is configured to determine whether or not to output a startup signal based on the measured value when the battery control unit is in sleep mode, and to output a startup signal if the result of this determination is positive. When the battery control unit is in sleep mode, it is activated upon receiving a start signal from the measurement unit, processes the measured values ​​input from the measurement unit, and detects signs of thermal runaway from the calculation results.

[0008] According to the above configuration, when the battery control unit is in sleep mode, the measurement unit outputs a start signal based on the measured value. The battery control unit starts up upon receiving this start signal, processes the measured value input from the measurement unit, and detects signs of thermal runaway from the calculation results. This allows for the appropriate detection of signs of thermal runaway when any abnormality occurs in the battery state. Furthermore, the battery control unit can be kept in sleep mode until any abnormality occurs in the battery state, thereby suppressing power consumption.

[0009] A secondary battery thermal runaway prediction detection program to solve the above problem is: A measuring unit that measures a value indicating the battery state of a secondary battery, A thermal runaway prediction detection program for a secondary battery is implemented by a secondary battery thermal runaway prediction detection device, which includes a battery control unit that detects signs of thermal runaway in the secondary battery, If the battery control unit is in a sleep state, the measurement unit determines whether or not to output a start signal to the battery control unit based on the measurement value measured by the measurement unit, and if the determination result is positive, a start signal is output. When the battery control unit is in a sleep state, upon receiving the startup signal output in the startup signal output step, the battery control unit is started up, and a detection step is performed in which the battery control unit is instructed to process the measured values ​​input from the measurement unit and to detect signs of thermal runaway from the calculation results.

[0010] According to the above program, when the battery control unit is in sleep mode, it outputs a start signal based on the measured value to activate the battery control unit and detect signs of thermal runaway. This allows for the proper detection of signs of thermal runaway when any abnormality occurs in the battery state. Furthermore, the battery control unit can be kept in sleep mode until any abnormality occurs in the battery state, thereby suppressing power consumption. [Brief explanation of the drawing]

[0011] [Figure 1] Electrical circuit diagram of a power supply system. [Figure 2] Block diagram of the battery measurement unit and battery control ECU. [Figure 3] A time chart showing an example of measurement mode switching. [Figure 4] A diagram showing each measurement mode. [Figure 5] A graph showing the complex impedance plane plot and zero-crossing points. [Figure 6] A graph showing the relationship between time and the real part of the zero-crossing point during thermal runaway. [Figure 7] A graph showing the relationship between time and the rate of change of the real part of the zero-crossing point during thermal runaway. [Figure 8] A flowchart illustrating the measurement process. [Figure 9] A flowchart illustrating the detection process for detecting signs of thermal runaway in battery cells. [Figure 10] Graph showing the relationship between the time during thermal runaway of a battery cell with a capacity of 25 [Ah], the rate of change of the real part of the zero-crossing point, and the temperature. [Figure 11] Graph showing the relationship between the time during thermal runaway of a battery cell with a capacity of 50 [Ah], the rate of change of the real part of the zero-crossing point, and the temperature. [Figure 12] Graph showing the relationship between the time during thermal runaway of a battery cell with a capacity of 150 [Ah], the rate of change of the real part of the zero-crossing point, and the temperature. [Figure 13] Block diagram of a modified example of the battery measurement unit. [Figure 14] Block diagram of another modified example of the battery measurement unit. [Figure 15] Block diagram of another modified example of the battery measurement unit.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an embodiment in which the "secondary battery thermal runaway prediction detection device" and the "secondary battery thermal runaway prediction detection program" are applied to the power supply system of a vehicle (for example, a hybrid vehicle or an electric vehicle) will be described while referring to the drawings.

[0013] As shown in FIG. 1, the power supply system 10 includes a motor 20 as a rotating electrical machine, an inverter 30 as a power converter that supplies a three-phase current to the motor 20, a battery pack 40 that can be charged and discharged, a battery measurement unit 50 that measures the state of the battery pack 40, a battery control ECU 70 that controls the battery pack 40, and a host ECU 60 that controls the motor 20 and the like. The battery measurement unit 50 is, for example, a battery monitoring board (CSC: Cell Supervision Circuit). Also, the battery control ECU 70 is, for example, a BMU (Battery Management Unit).

[0014] The motor 20 (motor generator) is the vehicle's main motor and is capable of transmitting power to drive wheels (not shown). In this embodiment, a three-phase permanent magnet synchronous motor is used as the motor 20. The inverter 30 is composed of a full-bridge circuit having the same number of upper and lower arms as the number of phases in the phase windings, and the current supplied to each phase winding is adjusted by turning on and off switches (semiconductor switching elements) provided on each arm. For example, IGBTs (Insulated Gate Bipolar Transistors) can be used as switches.

[0015] The inverter 30 is equipped with an inverter control device (not shown), which controls the power supply by turning switches on and off in the inverter 30 based on various detection information from the motor 20 and the demands for power driving and power generation. As a result, the inverter control device supplies power from the battery pack 40 to the motor 20 via the inverter 30, driving the motor 20. The inverter control device also causes the motor 20 to generate power based on the power from the drive wheels, converts the generated power via the inverter 30, and supplies it to the battery pack 40 to charge the battery pack 40.

[0016] The battery pack 40 is electrically connected to the motor 20 via the inverter 30. The battery pack 40 has a terminal voltage of, for example, 100 [V] or more, and is composed of multiple battery modules 41 connected in series. Each battery module 41 is composed of multiple battery cells 42 connected in series. As the battery cells 42 (secondary batteries), for example, lithium iron phosphate batteries (LFP batteries), lithium-ion batteries, and nickel-metal hydride batteries can be used. Each battery cell 42 is a battery having an electrolyte (a solution consisting of an electrolyte and a solvent) and multiple electrodes.

[0017] As shown in Figure 1, the positive terminal power supply path L1, which is connected to the positive terminal power supply terminal of the battery pack 40, is connected to the positive terminal terminal of an electrical load such as the inverter 30. Similarly, the negative terminal power supply path L2, which is connected to the negative terminal power supply terminal of the battery pack 40, is connected to the negative terminal terminal of an electrical load such as the inverter 30. A relay switch SMR (system main relay switch) is provided in both the positive terminal power supply path L1 and the negative terminal power supply path L2, and the relay switch SMR is configured to switch between supplying and disconnecting power.

[0018] The battery measurement unit 50 (measurement unit) is a device that measures the charge state (SOC) and state of health (SOH) of each battery cell 42. The battery measurement unit 50 is connected to the battery control ECU 70 and measures and outputs the complex impedance (impedance) of each battery cell 42. The battery measurement unit 50 can measure the complex impedance (AC impedance) of each battery cell 42 using multiple measurement modes with different measurement conditions. The configuration of the battery measurement unit 50 will be described later.

[0019] The battery control ECU 70 (battery control unit) controls the battery measurement unit 50 to measure the complex impedance of each battery cell 42 according to the selected (switched) measurement mode. The battery control ECU 70 includes a mode switching unit 71 (switching unit) and a TR (Thermal Runaway) detection unit 72 (detection unit), etc. The mode switching unit 71 and the TR detection unit 72 will be described later. The battery measurement unit 50 and the battery control ECU 70 constitute a thermal runaway prediction device for secondary batteries.

[0020] The higher-level ECU 60 requests power driving and power generation from the inverter control device based on various information. This information includes, for example, accelerator and brake operation information, vehicle speed, and the status of the battery pack 40. The higher-level ECU 60 also receives input from the battery control ECU 70, such as the results of measurements of the status of each battery cell 42.

[0021] Next, the battery measurement unit 50 and the battery control ECU 70 will be described in detail. As shown in Figure 2, the battery measurement unit 50 is provided to measure the battery state of each battery cell 42. The battery measurement unit 50 includes an AC current generation unit 51 connected to each battery cell 42 via a first electrical path 81, and a voltage response measurement unit 52 connected to each battery cell 42 via a second electrical path 82. The battery measurement unit 50 also includes a modulation signal generator 53 connected to the AC current generation unit 51, an arithmetic processing unit 54 connected to the voltage response measurement unit 52 and the modulation signal generator 53, and a communication unit 55 connected to the arithmetic processing unit 54.

[0022] The AC current generation unit 51 (current generation unit) uses the battery cell 42, which is the object of measurement, as a power source to output an AC current (fluctuation current). Specifically, the AC current generation unit 51 outputs an AC current from the battery cell 42 based on an instruction signal input from the modulation signal generator 53. As the AC current flows from the battery cell 42, a response signal (voltage fluctuation) reflecting the complex impedance information is generated in the terminal voltage of the battery cell 42. The voltage response measurement unit 52 (voltage measurement unit) measures the response signal (voltage fluctuation) reflecting the complex impedance information of the battery cell 42 at the terminals of the battery cell 42.

[0023] The modulation signal generator 53 is equipped with an oscillator that generates AC signals of arbitrary waveforms. The modulation signal generator 53 generates AC signals in the oscillator according to commands from the arithmetic processing unit 54.

[0024] In this embodiment, the AC signal is a sine wave signal, but it can be changed to any AC signal, such as a square wave or a triangular wave. Furthermore, the AC signal is biased with DC to prevent the AC current (fluctuating current) flowing from the battery cell 42 from becoming a negative current (reverse current to the battery cell 42).

[0025] The modulation signal generator 53 then converts the AC signal into a digital signal to generate an instruction signal, and instructs (outputs) the AC current generation unit 51 to generate an AC current based on the instruction signal.

[0026] The arithmetic processing unit 54 is equipped with a microcontroller consisting of a CPU (arithmetic unit) and memory devices (various types of memory), and realizes various functions by executing programs stored in the memory devices. These various functions may be realized by hardware electronic circuits, or by both hardware and software.

[0027] The arithmetic processing unit 54 (calculation unit) has a function to calculate the complex impedance of the battery cell 42. Here, an overview of the method for calculating the complex impedance will be described. The arithmetic processing unit 54 instructs the modulation signal generator 53 to measure the measurement frequency of the complex impedance. The modulation signal generator 53 generates an alternating current (fluctuation current) from the battery cell 42 via the alternating current generation unit 51 based on the instruction of the arithmetic processing unit 54. The voltage response measurement unit 52 measures the terminal voltage of the battery cell 42, measures the response signal (voltage fluctuation) in response to the input signal (alternating current), and outputs the measured response signal to the arithmetic processing unit 54.

[0028] The arithmetic processing unit 54 calculates information regarding the complex impedance of the battery cell 42 based on the response signal. The arithmetic processing unit 54 repeats this series of processes until it calculates the complex impedance for a predetermined number of measurement frequencies within the measurement range. The arithmetic processing unit 54 also notifies the battery control ECU 70 of the calculation results. The arithmetic processing unit 54 also stores the calculation results in the memory 54a.

[0029] The battery control ECU70, based on the calculation results, creates, for example, a complex impedance plane plot (Call-Call plot) to understand the characteristics of electrodes and electrolytes. It also understands the state of charge (SOC) and state of degradation (SOH).

[0030] It is not necessary to create the entire CallCall plot; focusing on a part of it is also acceptable. For example, during operation, the complex impedance at a specific frequency can be measured at regular time intervals, and changes in SOC, SOH, and battery temperature during operation can be determined based on the time variation of the complex impedance at that specific frequency. Alternatively, the complex impedance at a specific frequency can be measured at time intervals such as daily, weekly, or yearly, and changes in SOH, etc., can be determined based on the time variation of the complex impedance at that specific frequency. Furthermore, the complex impedance planar plot is not limited to the CallCall plot; Bode plots and other types can also be used.

[0031] Incidentally, in order to ensure the measurement accuracy of complex impedance, it is necessary to suppress errors by averaging (integrating) the measured values ​​of voltage fluctuations. For each AC signal at each measurement frequency, it is necessary to output a certain number of waves and measure the voltage fluctuations during that period. In other words, if the required accuracy is predetermined, it is necessary to output an AC signal with a number of waves corresponding to that accuracy. Here, if the measurement frequency is different, the number of waves per unit time will also be different. Therefore, if the measurement frequency is low, it will be necessary to output the AC current for a longer period of time compared to when the measurement frequency is high. In other words, the required output period differs for each measurement frequency.

[0032] Furthermore, as shown in Figure 3, for example, the battery control ECU 70 normally measures the complex impedance in a first measurement mode with low measurement accuracy, and if it determines that the battery cell 42 is abnormal based on the measurement results, it switches to a second measurement mode with higher measurement accuracy than the first measurement mode to measure the complex impedance. In other words, normally the complex impedance (correlation parameter) is measured in the first measurement mode (second mode) with low measurement accuracy, and if it determines that the battery cell 42 is abnormal, the complex impedance is measured in detail in the second measurement mode (first mode) with higher measurement accuracy. The timing of measuring the complex impedance in the first measurement mode is arbitrary; for example, the complex impedance is measured periodically in the first measurement mode. Alternatively, the complex impedance may be measured in the second measurement mode immediately after it is determined that the battery cell 42 is abnormal in the first measurement mode, or it may be measured in the second measurement mode after a predetermined time has passed since it was determined that it is abnormal.

[0033] Specifically, the arithmetic processing unit 54 determines the output period of the AC signal based on the set measurement frequency. The output period is the period until the AC signal wavenumber is output a predetermined number of times, and is calculated based on the measurement frequency. The predetermined number of times the wavenumber is output is determined in advance according to the required measurement accuracy.

[0034] For example, as shown in Figure 4, the predetermined number of measurements is 3 (second measurement) in the first measurement mode, and 9 (first measurement) in the second measurement mode. The predetermined number of measurements in the second measurement mode is greater than the predetermined number of measurements in the first measurement mode. Thus, the number of times the voltage fluctuation of the battery cell 42 is measured by the voltage response measurement unit 52 after the AC current is output by the AC current generation unit 51 differs between the first and second measurement modes. In other words, the method of measuring the complex impedance differs between the first and second measurement modes. For this reason, the measurement time in the second measurement mode is longer than that in the first measurement mode. The measurement accuracy in the second measurement mode is higher than that of the first measurement mode. The power consumption of the battery cell 42 in the first measurement mode is less than that of the battery cell 42 in the second measurement mode.

[0035] The arithmetic processing unit 54 then instructs the modulation signal generator 53 to set the measurement frequency. The modulation signal generator 53 sets the frequency of the AC signal to be output by the oscillator according to the instructed measurement frequency. The oscillator of the modulation signal generator 53 then generates an AC signal according to the set measurement frequency. The modulation signal generator 53 converts the analog signal of the generated AC signal into a digital signal and outputs an instruction signal to the AC current generation unit 51 to output the AC signal.

[0036] The AC current generation unit 51 inputs an AC current (input signal) to the battery cell 42 based on an instruction signal, causing the battery cell 42 to output an AC current (fluctuating current). The voltage response measurement unit 52 measures the terminal voltage of the battery cell 42, measures the response signal (voltage fluctuation) in response to the input signal (AC current), converts the analog value of the measured response signal into a digital value, and outputs it to the arithmetic processing unit 54. The AC current generation unit 51 may input an AC current (fluctuating current) to the battery cell 42, or it may vary the load on the battery cell 42.

[0037] The arithmetic processing unit 54 calculates information regarding the complex impedance of the battery cell 42 based on the alternating current and voltage fluctuations. Specifically, the arithmetic processing unit 54 acquires the measured value of the alternating current. That is, it measures the alternating current flowing through the first electrical path 81, analyzes the measured alternating current by the frequency of each alternating signal (measurement frequency), and extracts and acquires each alternating signal (measurement signal) that actually flowed.

[0038] The arithmetic processing unit 54 then analyzes the response signal based on the acquired AC signal and calculates a value proportional to the real part of the response signal and a value proportional to the imaginary part (information regarding complex impedance). The values ​​proportional to the real part and imaginary part of the response signal are the average values ​​(integral values) from the start of output for each AC signal.

[0039] Next, the arithmetic processing unit 54 determines whether the output period for the AC signal corresponding to each measurement mode has ended. In the first measurement mode, the output period is the period until three AC signals are output, and in the second measurement mode, the output period is the period until nine AC signals are output. If the result of this determination is negative, the arithmetic processing unit 54 continues measurement and calculation. On the other hand, if the result of the determination is positive, the arithmetic processing unit 54 stops the generation of the AC signal.

[0040] The arithmetic processing unit 54 obtains values ​​proportional to the real and imaginary parts of the response signal corresponding to the AC signal, and based on these, calculates all or any of the absolute value and phase of the complex impedance at the measurement frequency of the AC signal. The arithmetic processing unit 54 then transmits (notifies) the calculated complex impedance to the battery control ECU 70 via the communication unit 55.

[0041] Figure 5 shows a complex impedance plane plot and a graph indicating zero-crossing points. The battery measurement unit 50 periodically measures the complex impedance of the battery cells 42 while changing the measurement frequency during the operation of the vehicle equipped with the power supply system 10 (while the battery pack 40 is operating) and creates a complex impedance plane plot. The horizontal axis represents the real part of the complex impedance, and the vertical axis represents the imaginary part of the complex impedance. A zero-crossing point is the point where the graph of complex impedance intersects the horizontal axis, that is, the point where the imaginary part of the complex impedance is zero.

[0042] The black dots in the figure indicate that the complex impedance is measured over a wide range of frequencies, from low to high. The diameter of the real part of the arc mainly represents the reaction resistance, which is the resistance when molecules move from the electrodes into the solution (electrolyte) in the battery cell 42. The real part at zero-crossing point A, indicated by the white circle, mainly represents the solution resistance, which is the resistance when charges move through the solution in the battery cell 42. The inventors of this application have focused on the fact that when the battery cell 42 (battery module 41, battery pack 40) experiences thermal runaway, the solution vaporizes, causing a sharp increase in the real part at zero-crossing point A.

[0043] Figure 6 is a graph showing the relationship between time t and the real part Re_Z at the zero-crossing point during thermal runaway of the battery cell 42. Before thermal runaway of the battery cell 42, the real part Re_Z[mΩ] at the zero-crossing point is, for example, Re_Za[mΩ] or Re_Zb[mΩ] and hardly changes. Then, when thermal runaway occurs in the battery cell 42, the real part Re_Z at the zero-crossing point increases sharply. Note that the real parts Re_Za and Re_Zb at the zero-crossing point are converted values ​​obtained by converting the real part Re_Z at the zero-crossing point calculated using the current temperature and current SOC of the battery cell 42 to the real part at the zero-crossing point when the temperature T of the battery cell 42 is a predetermined temperature and the SOC of the battery cell 42 is a predetermined SOC (predetermined energy storage state). The reason for converting the real part Re_Z at the zero-crossing point to a converted value is that the complex impedance of the battery cell 42 is affected by the temperature T and state of charge (SOC) of the battery cell 42, and the real part Re_Z at the zero-crossing point is also affected by the temperature T and SOC of the battery cell 42.

[0044] Figure 7 is a graph showing the relationship between time t and the rate of change ΔVRe_Z of the real part Re_Z at the zero-crossing point during thermal runaway of the battery cell 42. The rate of change ΔVRe_Z of the real part Re_Z at the zero-crossing point can be calculated by dividing the amount of change ΔRe_Z of the real part Re_Z at the zero-crossing point by the time Δt required for that change (ΔVRe_Z = ΔRe_Z / Δt).

[0045] For example, if the real part Re_Z[mΩ] at the zero-crossing point changes from Re_Za[mΩ] to Re_Zb[mΩ] over time Δt[min], the rate of change of the real part Re_Z at the zero-crossing point ΔVRe_Z[mΩ / min] = (Re_Zb - Re_Za) / Δt. When the battery cell 42 experiences thermal runaway, the rate of change of the real part Re_Z at the zero-crossing point ΔVRe_Z increases sharply in the preceding stage. That is, the rate of change of the real part Re_Z at the zero-crossing point ΔVRe_Z increases sharply as a sign that the battery cell 42 (battery module 41, battery pack 40) is about to experience thermal runaway. Therefore, in this embodiment, when the rate of change of the real part Re_Z at the zero-crossing point ΔVRe_Z exceeds a threshold C (is greater than threshold C), it is detected that the battery cell 42 is showing signs of thermal runaway.

[0046] Incidentally, it is known that thermal runaway of secondary batteries such as battery cells 42 can occur not only while the secondary battery is operating (charging and discharging), but also when it is stopped (not running, disconnected from electrical load). For this reason, it is desirable to configure the system to detect signs of thermal runaway even when the vehicle is stopped (when battery cells 42 are stopped and the battery control ECU 70 etc. is in sleep mode).

[0047] Furthermore, if the timing for activating the battery control ECU 70 is set to a certain period of time after the start of sleep mode, depending on the activation timing, it may not be possible to properly detect signs of thermal runaway. In other words, if the sleep mode duration is extended, there is a risk of thermal runaway occurring during that time. On the other hand, if the sleep mode duration is shortened and the ECU is activated frequently, power consumption cannot be suppressed, which is a trade-off.

[0048] Therefore, in this embodiment, the device is activated after a certain period of time has elapsed since the start of the sleep state, and even before that period of time has elapsed, if there is a possibility that some kind of abnormality has occurred in the battery cell 42, even if it is not considered an abnormality, the device is activated.

[0049] The following provides a detailed explanation. The battery control ECU 70 has a sleep function that allows it to enter a sleep state at a predetermined timing. The predetermined timing is, for example, the timing when the ignition switch is turned off, or the timing when a certain amount of time has elapsed since the vehicle came to a stop. The battery control ECU 70 also has a start instruction circuit 75. The start instruction circuit 75 is a circuit that issues a start instruction to the battery control ECU 70 when the elapsed time since entering the sleep state exceeds a preset start time.

[0050] On the other hand, the battery measurement unit 50 receives power from the battery cell 42 and other sources, and continues to operate at all times, continuously measuring the battery state (voltage, complex impedance, etc.). In other words, the battery measurement unit 50 does not enter a sleep state. The power consumption of the battery measurement unit 50 is small compared to the power consumption of the battery control ECU 70. This is because their performance and processing capabilities differ.

[0051] Furthermore, the arithmetic processing unit 54 of the battery measurement unit 50 is configured to determine whether or not the battery control ECU 70 is in a sleep state. For example, the arithmetic processing unit 54 determines whether or not the battery control ECU 70 is in a sleep state based on whether or not the clock circuit that operates when the battery control ECU 70 is in a sleep state is operating.

[0052] When the battery measurement unit 50 determines that the device is in sleep mode, if it has measured a value indicating the battery status, it stores the measurement result in the memory 54a. Alternatively, the measurement value may be stored in the memory 54a regardless of whether the device is in sleep mode or not. In this embodiment, the battery measurement unit 50 stores the measured voltage value, complex impedance, current value, battery temperature, etc. It may also store the internal gas pressure of the battery, the type of gas being generated, etc. In this case, each measurement value is stored over time. In other words, each measurement value is stored as historical data.

[0053] Furthermore, the battery measurement unit 50 has a startup signal output circuit 57, which is a startup signal output unit that outputs a startup signal. When the arithmetic processing unit 54 determines that the battery control ECU 70 is in a sleep state, it decides whether or not to output a startup signal based on the measured value, and if it decides to output a startup signal, it causes the startup signal output circuit 57 to output a startup signal.

[0054] In this embodiment, when the arithmetic processing unit 54 determines that the battery control ECU 70 is in a sleep state, it refers to the history data stored in the memory 54a and calculates the voltage change per unit time. If the voltage change is greater than or equal to a predetermined value, the arithmetic processing unit 54 determines that there may be some abnormality in the battery cell 42 and causes the start signal output circuit 57 to output a start signal.

[0055] While the possibility of an anomaly was determined based on the voltage change, the possibility of an anomaly may also be determined based on changes in other measured values. For example, an anomaly may be determined based on changes in complex impedance, battery temperature, or gas pressure. Furthermore, an anomaly may be determined if the measured value itself is above a predetermined value, rather than just the amount of change. For example, an anomaly may be determined if the battery temperature is above a predetermined temperature. Additionally, the possibility of an anomaly may be determined based on two or more measured values ​​or changes, or a measured value and a change.

[0056] It is desirable to set the predetermined value from a value within the boundary range between the normal range and the abnormal range. In other words, it is desirable to set the predetermined value to a value within a range that is difficult to distinguish between the normal range and the abnormal range, so that the possibility of an anomaly can be detected. Needless to say, if the value is within the abnormal range, an activation signal should be output.

[0057] The battery control ECU 70 starts up and performs various processes when it receives a start signal from the battery measurement unit 50 or when it is instructed to start up by the start instruction circuit 75. These processes include detection processes to detect signs of thermal runaway. Alternatively, the start signal may be input to the start instruction circuit 75, which then issues a start instruction to start the battery control ECU 70.

[0058] Next, the measurement process will be explained with reference to Figure 8. The measurement process is performed by the battery measurement unit 50 at predetermined intervals. This measurement process is executed continuously while the battery measurement unit 50 is running, regardless of whether the battery control ECU 70 is in sleep mode or not. This measurement process also includes a process to wake up the battery control ECU 70 if it is in sleep mode.

[0059] The battery measurement unit 50 determines the set measurement mode (step S101). The measurement mode is determined by determining whether the measurement mode set by the instruction from the mode switching unit 71 of the battery control ECU 70 is either the first measurement mode or the second measurement mode.

[0060] The battery measurement unit 50 measures various measurement values ​​in the set measurement mode (steps S102 to S104). More specifically, the battery measurement unit 50 acquires the temperature T of the battery cell 42 and calculates the state of charge (SOC) of the battery cell 42 (step S102). The temperature T of the battery cell 42 can be acquired, for example, based on the output of a thermistor or the like attached to the battery cell 42 (battery module 41, battery pack 40). The state of charge (SOC) of the battery cell 42 can be calculated, for example, based on the SOC at a predetermined time and the integrated value of the current that has flowed through the battery cell 42 thereafter.

[0061] Next, the battery measurement unit 50 outputs an alternating current (fluctuating current) of a predetermined frequency from the battery cell 42 and measures the voltage fluctuation of the battery cell 42 in response to the alternating current (step S103). The predetermined frequency is the measurement frequency at which the imaginary part of the complex impedance of the battery cell 42, calculated based on the voltage fluctuation of the battery cell 42, becomes zero, that is, the measurement frequency at which the graph of the complex impedance intersects the horizontal axis. For example, the predetermined frequency is the measurement frequency at zero-crossing point A in the Cole-Cole plot in Figure 5, and can be calculated in advance based on tests using the battery cell 42. Note that this voltage fluctuation measurement is performed with the measurement mode set in step S101 enabled.

[0062] Next, the battery measurement unit 50 calculates the real part of the zero-crossing point based on the AC current and voltage fluctuations (step S104). The method for calculating the real part of the zero-crossing point is the same as the method for calculating information on the complex impedance of the battery cell 42 based on the AC current and voltage fluctuations, as described above.

[0063] The battery measurement unit 50 then stores various measurement values ​​(measurement results) in the memory 54a (step S105). Next, the battery measurement unit 50 determines whether or not the battery control ECU 70 is in sleep mode (step S106). If this determination is negative, the battery measurement unit 50 outputs (transmits) the measurement values, such as information on complex impedance, to the battery control ECU 70 (step S107). Then, the measurement process ends (END).

[0064] On the other hand, if the result of the determination in step S106 is positive, the battery measurement unit 50 calculates the amount of change in voltage per unit time and determines whether the amount of change is greater than a predetermined value (step S108). The unit time is arbitrary, but for example, it is 1 to 5 [min]. The amount of change can be calculated from the history data of voltage values ​​stored in memory 54a. In this case, it is desirable to use the most recent amount of change. If the result of the determination in step S108 is positive, the battery measurement unit 50 causes the start signal output circuit 57 to output a start signal (step S109). Then, the measurement process ends (END). On the other hand, if the result of the determination in step S108 is negative, the battery measurement unit 50 ends the measurement process as is (END).

[0065] Next, we will explain the processes performed by the battery control ECU 70 while the ignition switch is on (when the system is not in sleep mode).

[0066] The battery control ECU 70 periodically determines the characteristics of the battery cell 42 based on the information regarding the complex impedance of the battery cell 42 measured by the battery measurement unit 50. For example, the battery control ECU 70 periodically has the battery measurement unit 50 measure the complex impedance in a first measurement mode, and if it determines that the battery cell 42 is abnormal based on the measurement result (measured value), it switches to a second measurement mode and has the battery measurement unit 50 measure the complex impedance again. The battery control ECU 70 then creates a complex impedance plane plot based on the measured complex impedance to determine the characteristics of the electrodes and electrolyte, as well as the state of charge (SOC) and state of degradation (SOH).

[0067] Next, the detection process for detecting signs of thermal runaway after startup will be explained with reference to Figure 9. The detection process is executed when the battery control ECU 70 starts up from sleep mode. Specifically, it is executed when the start instruction circuit 75 instructs the ECU to start up, or when a start signal is input and the ECU starts up while in sleep mode.

[0068] After the detection process begins, the battery control ECU 70 switches the measurement mode of the battery measurement unit 50 (step S201). In step S201, when the unit is started from sleep mode and measurement is performed for the first time, the measurement mode is switched to the first measurement mode regardless of the input of a start signal. In step S201, the battery control ECU 70 may switch the measurement mode to the first measurement mode (second mode) if it is started by being instructed to start by the start instruction circuit 75, and switch to the second measurement mode (first mode) if it is started by inputting a start signal.

[0069] Subsequently, as explained in the measurement process described above, the battery measurement unit 50 acquires various measurement values ​​and outputs them to the battery control ECU 70. Specifically, the battery measurement unit 50 acquires the temperature T of the battery cell 42 and calculates the state of charge (SOC) of the battery cell 42. The battery measurement unit 50 also calculates the real part of the zero-crossing point based on the AC current and voltage fluctuations. The battery measurement unit 50 then outputs (transmits) the acquired or calculated various measurement values ​​to the battery control ECU 70. The battery control ECU 70 then receives the measurement values ​​(measurement results) from the battery measurement unit 50 (step S202).

[0070] Next, the battery control ECU 70 standardizes the real part of the input zero-crossing point (step S203). Specifically, the battery control ECU 70 calculates a converted value by converting the real part of the zero-crossing point calculated by the battery measurement unit 50 into the real part of the zero-crossing point when the temperature T of the battery cell 42 is at a predetermined temperature and the SOC of the battery cell 42 is at a predetermined SOC (predetermined energy storage state). This converted value can be calculated, for example, by applying the temperature T of the battery cell 42 and the SOC of the battery cell 42 obtained in step S202 to a map or formula that defines the relationship between the temperature T of the battery cell 42, the SOC of the battery cell 42, and the real part of the zero-crossing point. For example, 25 [°C] can be used as the predetermined temperature and 90 [%] as the predetermined SOC. Note that this map and formula can be calculated in advance based on tests using the battery cell 42.

[0071] Next, after a predetermined time Δt has elapsed since the previous step, in which an AC current of a predetermined frequency was output from the battery cell 42 and the voltage fluctuation of the battery cell 42 was measured, the battery control ECU 70 receives the measured values ​​from the battery measurement unit 50 (step S204). That is, it obtains information regarding the temperature T of the battery cell 42, the state of clock (SOC) of the battery cell 42, and the complex impedance (the real part of the zero-crossing point) after the predetermined time Δt. The predetermined time Δt is, for example, 1 to 5 [min]. Note that the predetermined time Δt may also be the time elapsed since the previous step, in which the temperature T of the battery cell 42 was obtained and the SOC of the battery cell 42 was calculated.

[0072] Next, the battery control ECU 70, similar to step S203, standardizes the real part of the zero-crossing point after a predetermined time Δt (step S205). Then, the battery control ECU 70 calculates the rate of change of the real part of the zero-crossing point (step S206). For example, the rate of change of the real part of the zero-crossing point ΔVRe_Z is calculated by dividing the amount of change ΔRe_Z (difference in conversion values) from the converted value Re_Za of the real part of the zero-crossing point calculated in the previous step to the converted value Re_Zb of the real part of the zero-crossing point calculated after the predetermined time Δt by the predetermined time Δt (ΔVRe_Z = ΔRe_Z / Δt).

[0073] Next, the battery control ECU 70 determines whether the rate of change of the real part of the zero-crossing point ΔVRe_Z is greater than the threshold C (step S207). If, in this determination, it is determined that the rate of change of the real part of the zero-crossing point ΔVRe_Z is not greater than the threshold C (step S207: NO), the battery control ECU 70 sets the startup time until the next startup in the startup instruction circuit 75 (step S208). In step S208, the battery control ECU 70 may set the startup time to be shorter when it is started by inputting a startup signal compared to when it is started by startup instruction from the startup instruction circuit 75. That is, if it is started because there is a possibility of some abnormality in the battery cell 42 but it is not possible to detect signs of thermal runaway, the startup time may be shortened so that it can be detected again immediately. For example, the startup time may be set to 1 hour when it is started by instruction from the startup instruction circuit 75, while the startup time may be set to 30 minutes when it is started by inputting a startup signal.

[0074] On the other hand, if, in the determination in step S207, it is determined that the rate of change ΔVRe_Z of the real part of the zero-crossing point is greater than the threshold C (step S207: YES), the battery control ECU 70 notifies the higher-level ECU 60 that there is a sign of thermal runaway in the battery cell 42 (step S210). That is, the battery control ECU 70 detects that there is a sign of thermal runaway in the battery cell 42 and notifies the higher-level ECU 60 via communication that there is a sign of thermal runaway (an abnormality) in the battery cell 42. Upon receiving the notification, the higher-level ECU 60 informs the vehicle driver of the abnormality, for example, by an alarm (warning). The higher-level ECU 60 may also notify a monitoring center or other device that can communicate with the vehicle of the abnormality upon receiving the notification. After that, this series of processes is terminated (END).

[0075] Steps S108 and S109 correspond to the startup signal output step, and the detection process corresponds to the detection step. Step S201 causes the battery control ECU 70 to function as a mode switching unit 71. Furthermore, steps S202 to S207 cause the battery control ECU 70 to function as a TR detection unit 72.

[0076] Figures 10-12 are graphs showing the relationship between time t, the rate of change of the real part of the zero-crossing point ΔVRe_Z (left axis), and temperature T (right axis) during thermal runaway of battery cells with different capacities. Here, the SOC of each battery cell is adjusted to 90%, and the temperature of each battery cell is simulated to rise at a constant rate. Figure 10 is a battery cell with a capacity of 25[Ah], a nickel-based material NCM (Ni, Co, Al, Mn) as the positive electrode, and Gr (graphite) as the negative electrode. Figure 11 is a battery cell with a capacity of 50[Ah], a nickel-based material NCM as the positive electrode, and Gr as the negative electrode. Figure 12 is a battery cell with a capacity of 150[Ah], an LFP (Li, Fe, P) as the positive electrode, and Gr as the negative electrode.

[0077] Depending on the capacity of each battery cell, the predetermined frequency at which the imaginary part of the complex impedance of the battery cell 42 becomes zero, i.e., the measurement frequency at which the graph of the complex impedance intersects the horizontal axis, differs. For example, the predetermined frequency is 400 Hz for the battery cell in Figure 10, 250 Hz for the battery cell in Figure 11, and 120 Hz for the battery cell in Figure 12. Thus, the predetermined frequency tends to decrease as the capacity of the battery cell increases. Despite these differences, in all of Figures 10 to 12, the rate of change of the real part of the zero-crossing point ΔVRe_Z rises sharply earlier than the time when the battery cell experiences thermal runaway and the temperature T rises sharply.

[0078] Therefore, by monitoring the rate of change of the real part of the zero-crossing point ΔVRe_Z, it is possible to detect signs of thermal runaway in the battery cell 42 before it actually occurs. Note that the battery cell in Figure 10 is equipped with a vent valve that releases internal gas when the internal pressure becomes abnormally high. When gas is released from the vent valve, the rate of change of the real part of the zero-crossing point ΔVRe_Z decreases temporarily, but the rate of change ΔVRe_Z rises sharply before the battery cell experiences thermal runaway.

[0079] Furthermore, as shown in Figures 10-12, it can be seen that the complex impedance changes before thermal runaway occurs, which clearly indicates that the voltage value also fluctuates. Therefore, if the voltage value changes significantly, it is clear that some kind of abnormality may be occurring.

[0080] The embodiment described in detail above has the following advantages.

[0081] (1) When the battery control ECU 70 is in sleep mode, the battery measurement unit 50 determines whether or not to output a start signal based on the measured value, and outputs a start signal if the determination result is positive. When the battery control ECU 70 is in sleep mode, it starts up when it receives a start signal from the battery measurement unit 50, processes the measured value input from the battery measurement unit 50, and detects signs of thermal runaway from the calculation result. As a result, even when the battery control ECU 70 is in sleep mode, if there is a possibility that some abnormality has occurred in the battery cell 42, it can detect that possibility and allow the battery control ECU 70 to appropriately detect signs of thermal runaway. In addition, the battery control unit can be kept in sleep mode until some abnormality occurs in the battery state, thereby suppressing power consumption.

[0082] (2) The calculation processing unit 54 of the battery measurement unit 50 outputs a start signal when the amount of voltage change per unit time is greater than a predetermined value while the battery control ECU 70 is in sleep mode. This makes it possible to determine the possibility of an abnormality in the battery cell 42 with a simple process that does not require much computational load.

[0083] (3) The startup time set in the startup instruction circuit 75 may be set shorter when the system is started based on the input of a startup signal compared to when the system is started based on a startup instruction from the startup instruction circuit 75. In this case, if there is a possibility of an abnormality in the battery cell 42 during the sleep state and the system is started based on the input of a startup signal but the signs of thermal runaway cannot be detected, the system can be started again in a short time and the signs can be detected again. In other words, even if the signs of thermal runaway could not be detected due to measurement errors or the like, they can be detected again.

[0084] (4) The rate of change of the real part of the AC impedance is used to detect signs of thermal runaway. Therefore, compared to detection based on the rate of change of voltage or battery temperature, signs of runaway can be detected earlier.

[0085] (5) The modulation signal generator 53, the AC current generation unit 51, and the voltage response measurement unit 52 (battery measurement unit 50) can measure voltage fluctuations in a second measurement mode (first mode) in which the number of times the voltage fluctuation of the battery cell 42 in response to the AC current output from the battery cell 42 is 9 (first count), and in a first measurement mode (second mode) in which the number of times is less than 9, 3 (second count). When measuring the voltage fluctuation of the battery cell 42 in response to the AC current output from the battery cell 42, the power consumption of the battery cell 42 can be suppressed in the first measurement mode compared to the second measurement mode. The mode switching unit 71 switches the modulation signal generator 53, the AC current generation unit 51, and the voltage response measurement unit 52 to the first measurement mode when the battery control ECU 70 is in sleep mode, that is, when the battery cell 42 is stopped (not started, disconnected from electrical load). Therefore, even if the voltage of the battery cell 42 is measured while the battery cell 42 is stopped, the power consumption of the battery cell 42 can be suppressed.

[0086] (6) The TR detection unit 72 calculates the rate of change ΔVRe_Z of the real part of the complex impedance Re_Z calculated by the calculation processing unit 54 and a predetermined time Δt, and detects that there is a sign of thermal runaway in the battery cell 42 when the calculated rate of change ΔVRe_Z is greater than the threshold C. In this way, the rapid increase in the real part of Re_Z at the zero-crossing point due to the vaporization of the solution can be detected as a sign of thermal runaway in the battery cell 42. Moreover, it is not necessary to measure the complex impedance of the battery cell 42 for multiple frequencies within the measurement range, and it is only necessary to measure the complex impedance of the battery cell 42 for a predetermined frequency where the imaginary part of the complex impedance is 0, so the power consumption of the battery cell 42 can be further suppressed. The voltage fluctuation of the battery cell 42 can also be measured in a short time of several to tens [ms] × wavenumber (number of times).

[0087] (7) The TR detection unit 72 calculates the rate of change ΔVRe_Z of the real part of the complex impedance Re_Z calculated by the calculation processing unit 54, based on the converted values ​​Re_Za and Re_Zb obtained by converting the real part of the complex impedance Re_Z when the temperature T of the battery cell 42 is a predetermined temperature and the state of charge (SOC) of the battery cell 42 is a predetermined SOC (predetermined state of charge), and a predetermined time Δt. With this configuration, the influence of the temperature T and SOC on the real part Re_Z at the zero-crossing point can be taken into account, and signs of thermal runaway of the battery cell 42 can be accurately detected.

[0088] (modified version) Furthermore, the configuration of the above embodiment can also be modified as follows. The following describes the modified examples. Parts identical to those in the above embodiment are denoted by the same reference numerals, and their description is omitted.

[0089] In the above embodiment, the higher-level ECU 60 may instruct the vehicle to take evasive action if it receives notification that there is a sign of thermal runaway (an abnormality) in the battery cell 42. The higher-level ECU 60 may also unlock the vehicle doors if it receives notification that there is a sign of thermal runaway in the battery cell 42. This can prevent a situation where the driver is unable to open the vehicle doors in a panic. The battery control ECU 70 may also shut down the battery pack 40 (power system 10) if it detects that there is a sign of thermal runaway in the battery cell 42. The power system 10 can also be installed in electric aircraft or electric ships, in which case it is important to shut down the battery pack 40 because it is difficult for the driver to escape from the electric aircraft or electric ship in the event of an abnormality.

[0090] In step S207 of Figure 9 of the above embodiment, in addition to determining that the rate of change ΔVRe_Z of the real part of the zero-crossing point is greater than the threshold C (step S207: YES), the battery control ECU 70 may notify the higher-level ECU 60 that there are signs of thermal runaway in the battery cell 42, provided that the temperature T of the battery cell 42 is higher than the determination temperature (e.g., 60 [°C]) (step S209). With this configuration, it is possible to suppress false detection of signs of thermal runaway in the battery cell 42 when the possibility of thermal runaway in the battery cell 42 is low.

[0091] The TR detection unit 72 in the above embodiment may calculate the rate of change ΔVRe_Z of the complex impedance based on the real part Re_Z of the complex impedance and a predetermined time Δt, without converting the real part Re_Z of the complex impedance calculated by the calculation processing unit 54 to the real part of the complex impedance at a predetermined temperature and a predetermined SOC. The TR detection unit 72 may then detect that there is a sign of thermal runaway in the battery cell 42 if the calculated rate of change ΔVRe_Z is greater than the threshold C.

[0092] In the first measurement mode (second mode) of the above embodiment, the magnitude (amplitude) of the alternating current (fluctuation current) output from the battery cell 42 may be made smaller than the magnitude of the alternating current output from the battery cell 42 in the second measurement mode (first mode). Specifically, the arithmetic processing unit 54 generates an alternating current signal in the oscillator of the modulation signal generator 53 so that the alternating current output from the battery cell 42 in the first measurement mode is smaller than the alternating current output from the battery cell 42 in the second measurement mode. The modulation signal generator 53 then converts the alternating current signal into a digital signal to generate an instruction signal and instructs (outputs) the alternating current generation unit 51 to generate an alternating current based on the instruction signal. With this configuration, when measuring the voltage fluctuation of the battery cell 42 in response to the alternating current output from the battery cell 42, the power consumption of the battery cell 42 can be further suppressed in the first measurement mode than in the second measurement mode.

[0093] In the above embodiment, the arithmetic processing unit 54 can shorten the predetermined time Δt in step S204 of Figure 9, as the temperature T of the battery cell 42 increases. That is, the waiting time (predetermined time Δt) from the time the battery cell 42 outputs an AC current of a predetermined frequency in the previous step to measure the voltage fluctuation of the battery cell 42, to the time the temperature T of the battery cell 42 is obtained, to the time the SOC of the battery cell 42 is calculated, and to the time the processing from step S204 onwards is executed can be shortened as the temperature T of the battery cell 42 increases. With this configuration, the higher the temperature T of the battery cell 42, the shorter the time interval at which the complex impedance is measured by the battery measurement unit 50. Therefore, when there is a high possibility that the battery cell 42 will experience thermal runaway, signs of thermal runaway can be detected earlier.

[0094] The battery measurement unit 50 (measurement unit) of the above embodiment may have a third measurement mode (third mode) in which the number of times the voltage fluctuation of the battery cell 42 is measured by the voltage response measurement unit 52 after the AC current generation unit 51 outputs an AC current is different from the number of times in the first measurement mode (second mode) and the second measurement mode (first mode).

[0095] As shown in Figure 13, the battery measurement unit 50 may be equipped with an AC current generation unit 51 and a voltage response measurement unit 52 for each battery cell 42. Then, with multiple battery cells 42 as the measurement target (target for detecting signs of thermal runaway), an AC current may be passed through each battery cell 42 individually, or an AC current may be passed through multiple battery cells 42 simultaneously, and the voltage fluctuation of each battery cell 42 may be measured by each voltage response measurement unit 52.

[0096] As shown in Figure 14, the battery measurement unit 50 may have one AC current generation unit 51 for multiple battery cells 42, and each battery cell 42 may have a voltage response measurement unit 52. Then, with multiple battery cells 42 as the measurement target (target for detecting signs of thermal runaway), an AC current may be passed through multiple battery cells 42 together, and the voltage fluctuation of each battery cell 42 may be measured by each voltage response measurement unit 52.

[0097] As shown in Figure 15, the battery measurement unit 50 may be equipped with one AC current generation unit 51 and one voltage response measurement unit 52 for multiple battery cells 42. Then, with multiple battery cells 42 as the measurement target (target for detecting signs of thermal runaway), an AC current may be passed through multiple battery cells 42 together, and the voltage fluctuations of multiple battery cells 42 may be measured together by the voltage response measurement unit 52.

[0098] Alternatively, an alternating current may be passed through the entire battery module 41 and the voltage fluctuations of each battery cell 42 may be measured (to detect signs of thermal runaway), or the voltage fluctuations of the entire battery module 41 may be measured (to detect signs of thermal runaway). Alternatively, an alternating current may be passed through the entire battery pack 40 and the voltage fluctuations of each battery cell 42 may be measured (to detect signs of thermal runaway), or the voltage fluctuations of the entire battery pack 40 may be measured (to detect signs of thermal runaway).

[0099] - When the vehicle is stopped for longer than the judgment time ts (e.g., when the ignition is off), if the battery control ECU 70 is in sleep mode, the battery measurement unit 50 may activate the battery control ECU 70. Alternatively, the mode switching unit 71 and the TR detection unit 72 can be located inside the battery measurement unit 50 (for example, in the calculation processing unit 54). In this case, the battery measurement unit 50 constitutes a secondary battery thermal runaway prediction detection device.

[0100] The power supply for the battery control ECU 70 and the battery measurement unit 50 may be a high-voltage battery pack 40 (battery module 41) or a low-voltage lead-acid battery, etc. The AC current generation unit 51 may also be provided in an external charger, etc. Furthermore, the function to detect signs of thermal runaway in the battery measurement unit 50 and the battery control ECU 70 may be installed in on-board chargers (AC chargers, DC chargers, V2H (Vehicle To Home) chargers), the battery measurement unit and battery control ECU of replaceable battery packs, the charging EMS (Energy Management System) of charging stations, etc. Similarly, the function to output a start signal based on the measured value may be installed in on-board chargers (AC chargers, DC chargers, V2H (Vehicle To Home) chargers), the battery measurement unit and battery control ECU of replaceable battery packs, the charging EMS (Energy Management System) of charging stations, etc.

[0101] - When the ignition is off, if the higher-level ECU 60 is in sleep mode, it may be activated to issue an alarm, etc., if it ultimately detects an abnormality in conjunction with a diagnostic result other than the thermal runaway warning. Also, if it ultimately detects an abnormality in conjunction with a diagnostic result other than the thermal runaway warning, it may be possible to secure power to the device to which the signal notifying of the abnormality is sent. Furthermore, if an abnormality is detected, the process for detecting the thermal runaway warning may be performed multiple times, and the detection of an abnormality may be confirmed only if the thermal runaway warning is detected multiple times. This can suppress false detections of abnormalities and malfunctions of alarms, etc.

[0102] In the detection process of the above embodiment, the battery control ECU 70 performed calculations on the measured values ​​(such as AC impedance) measured after startup to detect signs of thermal runaway. As a modification, the battery control ECU 70 may acquire the measured values ​​stored in the memory 54a of the battery measurement unit 50 after startup, perform calculations on the measured values, and detect signs of thermal runaway from the calculation results. For example, the battery measurement unit 50 may acquire the latest measured value and a measured value taken a predetermined time Δt before the measurement of the latest measured value from the measured values ​​stored in the memory 54a, and perform the process of step S207 based on these values.

[0103] • In step S208 above, when setting the startup time until the next startup, the startup time may be changed based on the measured value. For example, if the latest measured value input from the battery measurement unit 50 is within the boundary range between a predetermined normal range and an abnormal range, the startup time may be set shorter compared to when it is within the normal range. This allows for early detection of signs of thermal runaway if there is a possibility of an abnormality in the battery cell 42.

[0104] In the above embodiment, the calculation of AC impedance may be performed by the battery control ECU 70. In this case, the battery control ECU 70 simply requests and inputs the measured values ​​necessary for calculating AC impedance, such as AC current and voltage, from the battery measurement unit 50.

[0105] In step S207 of the above embodiment, if it is determined that the rate of change ΔVRe_Z of the real part of the zero-crossing point is greater than the threshold C (step S207: YES), the battery control ECU 70 determines that there is a sign of thermal runaway. As an alternative example, if, based on the measurement results measured in the first measurement mode, it is determined in step S207 that the rate of change ΔVRe_Z of the real part of the zero-crossing point is greater than the threshold C, it may measure again in the second measurement mode and finally determine whether or not there is a sign of thermal runaway based on the measurement results. If it is determined that there is a sign of thermal runaway based on the measurement results in the second measurement mode, the process in step S210, i.e., notification to the higher-level ECU 60, may be carried out.

[0106] Furthermore, it is also possible to implement a combination of the above variations. The control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control unit and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0107] The following describes characteristic configurations extracted from the embodiments and modified examples described above. [Configuration 1] A device for detecting signs of thermal runaway in secondary batteries, A measuring unit (50) that measures a measurement value indicating the battery state of the secondary battery, The secondary battery includes a battery control unit (70) that detects signs of thermal runaway, The measurement unit is configured to determine whether or not to output a startup signal based on the measured value when the battery control unit is in sleep mode, and to output a startup signal if the result of this determination is positive. The battery control unit, when in sleep mode, is activated upon receiving a start signal from the measurement unit, processes the measured values ​​input from the measurement unit, and detects signs of thermal runaway from the calculation results, thereby providing a thermal runaway prediction device for a secondary battery. [Configuration 2] The measuring unit has a memory (54a) for storing the measured values, The secondary battery thermal runaway prediction device according to Configuration 1, wherein when the battery control unit is activated in response to the input of the activation signal, it inputs the measured value stored in the memory of the measurement unit, processes the measured value, and detects signs of thermal runaway from the calculation result. [Configuration 3] The thermal runaway prediction device for a secondary battery according to configuration 1 or 2, wherein the measurement unit outputs the activation signal when the amount of change in the measured value per unit time is greater than a predetermined value when the battery control unit is in a sleep state. [Structure 4] The battery control unit is equipped with a startup instruction circuit (75) that instructs the unit to start up at predetermined startup intervals while in sleep mode. When the startup instruction circuit instructs the unit to start up, it starts up, receives a measurement value from the measurement unit, processes the measurement value, and is configured to detect signs of thermal runaway from the calculation result. The aforementioned startup time until the next startup is set when the system enters sleep mode. A thermal runaway prediction device for a secondary battery, as described in any of configurations 1 to 3, wherein when the device is started based on the input of the start signal, the start time until the next start is set to be shorter compared to when the device is started based on a start instruction by the start instruction circuit. [Composition 5] The measuring unit inputs or outputs a fluctuating current to the secondary battery and measures the voltage fluctuation of the secondary battery in response to the fluctuating current, and calculates the AC impedance of the secondary battery based on the voltage fluctuation. A secondary battery thermal runaway prediction device according to any one of configurations 1 to 4, wherein the battery control unit detects that there is a sign of thermal runaway in the secondary battery when the rate of change of the real part of the AC impedance, obtained based on the voltage fluctuation measured by the measurement unit with the fluctuating current at a predetermined frequency in which the imaginary part of the calculated AC impedance of the secondary battery becomes 0, is greater than a threshold. [Composition 6] The measurement unit is capable of measuring the voltage fluctuation by a first mode in which a fluctuating current is output from the secondary battery and the voltage fluctuation of the secondary battery in response to the fluctuating current is measured a first time, and a second mode in which the number of measurements is less than the first time. The aforementioned battery control unit, A switching unit (71) that switches the measurement unit to the second mode when the secondary battery is stopped, A thermal runaway warning device for a secondary battery according to any one of configurations 1 to 4, comprising: a detection unit (72) that, when the measurement unit is switched to the second mode by the switching unit, detects that there is a sign of thermal runaway in the secondary battery when the rate of change of the real part of the AC impedance obtained based on the voltage fluctuation measured by the measurement unit with the fluctuating current of a predetermined frequency in which the imaginary part of the AC impedance of the secondary battery calculated based on the voltage fluctuation becomes 0, is greater than a threshold; [Composition 7] The detection unit calculates the rate of change of the real part of the AC impedance based on a converted value obtained by converting the real part of the AC impedance to the real part of the AC impedance when the temperature of the secondary battery is at a predetermined temperature and the charge storage state of the secondary battery is at a predetermined charge storage state, as described in claim 6, for a secondary battery thermal runaway prediction device. [Structure 8] A thermal runaway prediction device for a secondary battery according to configuration 6 or 7, wherein the magnitude of the fluctuating current output from the secondary battery in the second mode is smaller than the magnitude of the fluctuating current output from the secondary battery in the first mode. [Composition 9] With the measurement unit switched to the second mode by the switching unit, the measurement unit measures the voltage fluctuation at predetermined time intervals using the fluctuating current of a predetermined frequency, and the calculation unit (54) calculates the real part of the AC impedance based on the measured voltage fluctuation. The detection unit calculates the rate of change of the real part of the AC impedance based on the real part of the AC impedance calculated by the calculation unit and the predetermined time. The calculation unit shortens the predetermined time as the temperature of the secondary battery increases, as described in any of configurations 6 to 8 for the secondary battery thermal runaway prediction device. [Configuration 10] The battery control unit is equipped with a startup instruction circuit (75) that instructs the unit to start up at predetermined startup intervals while in sleep mode. When the startup instruction circuit instructs the unit to start up, it starts up, receives a measurement value from the measurement unit, processes the measurement value, and is configured to detect signs of thermal runaway from the calculation result. The startup time until the next startup is set when the device enters sleep mode, and if the measured value input from the measuring unit at startup is within a predetermined boundary range between a normal range and an abnormal range, the startup time until the next startup is set to be shorter than when it is within the normal range, according to any of configurations 1 to 9 of the secondary battery thermal runaway prediction device. [Composition 11] A measuring unit (50) that measures a value indicating the battery state of a secondary battery, A secondary battery thermal runaway prediction detection device, which includes a battery control unit (70) that detects signs of thermal runaway in the secondary battery, implements a secondary battery thermal runaway prediction detection program, the program being implemented by the device, If the battery control unit is in a sleep state, the measurement unit determines whether or not to output a start signal to the battery control unit based on the measurement value measured by the measurement unit, and if the determination result is positive, a start signal is output. A secondary battery thermal runaway prediction program that, when the battery control unit is in a sleep state, triggers the activation of the battery control unit when the activation signal output in the activation signal output step is input to the battery control unit, causes the battery control unit to perform calculation processing on the measured values ​​input from the measurement unit, and detects signs of thermal runaway from the calculation results. [Explanation of Symbols]

[0108] 10...Power supply system, 42...Battery cell, 50...Battery measurement unit, 51...AC current generation unit, 52...Voltage response measurement unit, 53...Modulation signal generator, 54...Calculation processing unit, 57...Startup signal output circuit, 60...Higher-level ECU, 70...Battery control ECU, 71...Mode switching unit, 72...TR detection unit, 75...Startup instruction circuit.

Claims

1. A device for detecting signs of thermal runaway in secondary batteries, A measuring unit (50) measures one of the following values ​​as a measurement indicating the battery state of the secondary battery: voltage, AC impedance, current, battery temperature, and internal gas pressure of the battery. It also inputs or outputs a fluctuating current of a predetermined frequency to the secondary battery, which makes the imaginary part of the AC impedance of the secondary battery zero, and measures the voltage fluctuation of the secondary battery in response to the fluctuating current. Based on the voltage fluctuation, it calculates the real part of the AC impedance of the secondary battery. The secondary battery includes a battery control unit (70) that detects signs of thermal runaway, The measurement unit is configured to determine whether the measured value is greater than or equal to a predetermined value, or whether the rate of change of the measured value per unit time is greater than or equal to a predetermined value, when the battery control unit is in sleep mode, and to output a start signal if the result of this determination is positive. A secondary battery thermal runaway prediction device that, when the battery control unit is in a sleep state, is activated upon receiving a start signal from the measurement unit, and detects signs of thermal runaway when the rate of change of the real part of the AC impedance calculated by the measurement unit is greater than a threshold.

2. The measurement unit has a memory (54a) that stores the real part of the AC impedance, The secondary battery thermal runaway prediction device according to claim 1, wherein when the battery control unit is activated in response to the input of the activation signal, it inputs the real part of the AC impedance stored in the memory of the measurement unit, processes the real part of the AC impedance to calculate its rate of change, and detects signs of thermal runaway from the rate of change.

3. The battery control unit is equipped with a startup instruction circuit (75) that instructs the unit to start up at predetermined startup intervals while in sleep mode. When the startup instruction circuit instructs the unit to start up, it receives the real part of the AC impedance from the measurement unit, processes the real part of the AC impedance to calculate its rate of change, and is configured to detect signs of thermal runaway from the rate of change. The aforementioned startup time until the next startup is set when the system enters sleep mode. The thermal runaway prediction device for a secondary battery according to claim 1, wherein when the device is started based on the input of the start signal, the start time until the next start is set to be shorter compared to when the device is started based on a start instruction by the start instruction circuit.

4. The measurement unit is capable of measuring the voltage fluctuation by a first mode in which, during a first period until the wavenumber of the fluctuating current output from the secondary battery reaches a predetermined first number of waves, the voltage fluctuation of the secondary battery in response to the fluctuating current output during the first period is continuously measured from the start to the end of the first period, and a second mode in which, during a second period until the wavenumber of the fluctuating current output from the secondary battery reaches a second number of waves which is less than the first number, the voltage fluctuation of the secondary battery in response to the fluctuating current output during the second period is continuously measured from the start to the end of the second period. The aforementioned battery control unit, A switching unit that switches to either the first mode or the second mode to cause the measuring unit to measure the voltage fluctuation, the switching unit (71) that switches the measuring unit to the second mode when the secondary battery is stopped, With the measurement unit switched to the second mode by the switching unit, the detection unit (72) detects that there is a sign of thermal runaway in the secondary battery if the rate of change of the real part of the AC impedance obtained based on the voltage fluctuation, measured by the measurement unit with the fluctuating current at a predetermined frequency where the imaginary part of the AC impedance of the secondary battery calculated based on the voltage fluctuation becomes 0, is greater than a threshold. The secondary battery thermal runaway prediction device according to any one of claims 1 to 3, wherein the switching unit switches to the first mode when the detection unit detects an abnormality in the secondary battery in the second mode, causes the measurement unit to measure the voltage fluctuation, and measures the AC impedance of the secondary battery calculated based on the voltage fluctuation.

5. A measuring unit (50) measures one of the following values ​​as a measurement of the battery state of a secondary battery: voltage, AC impedance, current, battery temperature, and internal gas pressure of the battery. It also inputs or outputs a fluctuating current of a predetermined frequency to the secondary battery, which makes the imaginary part of the AC impedance of the secondary battery zero, and measures the voltage fluctuation of the secondary battery in response to the fluctuating current. Based on the voltage fluctuation, it calculates the real part of the AC impedance of the secondary battery. A thermal runaway prediction detection program for a secondary battery is implemented by a secondary battery thermal runaway prediction detection device, which includes a battery control unit (70) that detects signs of thermal runaway in the secondary battery, When the battery control unit is in sleep mode, the measurement unit determines whether the measured value is greater than or equal to a predetermined value, or whether the rate of change of the measured value per unit time is greater than or equal to a predetermined value, and if the result of this determination is positive, it outputs a start signal. A secondary battery thermal runaway prediction program that, when the battery control unit is in a sleep state, triggers the battery control unit to be activated when the activation signal output in the activation signal output step is input to the battery control unit, and causes the battery control unit to compare the rate of change of the real part of the AC impedance calculated by the measurement unit with a threshold, and detects that there is a sign of thermal runaway if the rate of change is greater than the threshold.

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