Thermal runaway prediction detection device and thermal runaway prediction detection program

Abstract

To provide a thermal runaway sign detection device and a thermal runaway sign detection program that can suppress power consumption in sign detection of thermal runaway in the time of vehicle stop.SOLUTION: A battery measurement unit 50 and a battery control ECU 70 which constitute a thermal runaway sign detection device that detects the sign of thermal runaway in a battery cell 42 installed in a vehicle include: a voltage response measurement unit 52 which measures the voltage variation of the battery cell 42; a setting unit 71 which sets the first determination mode in the time of vehicle stop and sets the second determination mode in the time of vehicle start; a first calculation processing unit 54 which causes voltage variation measurement at a prescribed timing in the first determination mode, calculates a complex impedance on the basis of the voltage variation and detects the sign of thermal runaway; and a second calculation processing unit 72 which causes voltage variation measurement at multiple timings in the second determination mode, calculates each complex impedance on the basis of the voltage variation, and detects the sign of thermal runaway on the basis of the change speed thereof.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a device for detecting a sign of thermal runaway of a power storage unit.

Background Art

[0002] Conventionally, in rare cases, a secondary battery may experience thermal runaway and a fire may occur. As a countermeasure, it has been considered to acquire the state of the secondary battery, such as voltage, battery temperature, internal resistance, etc., and detect a sign of thermal runaway of the secondary battery from these values (for example, 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, it is known that thermal runaway of a secondary battery occurs not only during the operation (charging and 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 ECU is in the stop state (sleep state), it is desirable to configure it to be activated to detect a sign of thermal runaway.

[0005] However, in order to calculate the internal resistance, etc., generally, it is necessary to apply some disturbance to the secondary battery and measure the fluctuation of the output current or output voltage of the secondary battery caused thereby. That is, in order to calculate the internal resistance, etc., the power of the secondary battery is consumed.

[0006] Therefore, conventionally, if the sign detection of thermal runaway is frequently performed during the stop, depending on the length of the stop period, the power consumption increases, and there is a possibility that the secondary battery may enter an over-discharged state.

[0007] The present invention was made to solve the above problems, and its main objective is to provide a thermal runaway prediction detection device and a thermal runaway prediction detection program that can suppress power consumption in the detection of thermal runaway precursors when a vehicle is stopped. [Means for solving the problem]

[0008] A thermal runaway prediction detection device to solve the above problems is: A thermal runaway prediction device for detecting signs of thermal runaway in an energy storage unit mounted on a mobile vehicle, A measuring unit that measures a measurement value indicating the battery state of the aforementioned power storage unit, A determination unit for detecting signs of thermal runaway includes a first determination mode in which the measurement unit measures a value at a predetermined timing and detects signs of thermal runaway based on that value, and a second determination mode in which the measurement unit measures a value at multiple timings, identifies the pattern of change in the battery state from those values, and detects signs of thermal runaway based on the pattern of change, The system includes a setting unit that sets the first determination mode when the vehicle is stopped, and sets the second determination mode when the mobile vehicle is started.

[0009] This allows for the detection of early signs of thermal runaway while reducing power consumption when the vehicle is stationary.

[0010] The thermal runaway prediction detection program to solve the above problem is: A thermal runaway prediction detection program implemented by a thermal runaway prediction detection device that detects signs of thermal runaway in an energy storage unit mounted on a mobile vehicle, A measurement process for measuring a measurement value indicating the battery state of the aforementioned energy storage unit, A determination process for detecting signs of thermal runaway includes a first determination mode in which the measurement process measures values ​​at predetermined timings and detects signs of thermal runaway based on those values, and a second determination mode in which the measurement process measures values ​​at multiple timings, identifies the pattern of change in the battery state from those values, and detects signs of thermal runaway based on the pattern of change, The system performs a setting process that sets the first determination mode when the vehicle is stopped, and sets the second determination mode when the vehicle is started.

[0011] This allows for the detection of early signs of thermal runaway while reducing power consumption when the vehicle is stationary. [Brief explanation of the drawing]

[0012] [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 diagram showing each measurement mode. [Figure 4] A graph showing the complex impedance plane plot and zero-crossing points. [Figure 5] A graph showing the relationship between time and the real part of the zero-crossing point during thermal runaway. [Figure 6] 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 7] A flowchart illustrating the overall process of detecting signs of thermal runaway. [Figure 8] A flowchart showing the flow of the measurement process. [Figure 9] A graph showing the relationship between the time, the rate of change of the real part of the zero-crossing point, and temperature during thermal runaway of a 25Ah battery cell. [Figure 10] A graph showing the relationship between the time, the rate of change of the real part of the zero-crossing point, and temperature during thermal runaway of a 50Ah battery cell. [Figure 11] A graph showing the relationship between the time, the rate of change of the real part of the zero-crossing point, and temperature during thermal runaway of a 150[Ah] battery cell. [Figure 12] A flowchart showing the overall flow of thermal runaway prediction detection in the second embodiment. [Figure 13] Block diagram of an example of a modified battery measurement unit. [Figure 14] Block diagram of another example of modification to the battery measurement unit. [Figure 15] Block diagram of another modification example of the battery measurement unit. [Figure 16] Block diagram of another modification example of the battery measurement unit. [Figure 17] Time chart regarding the measurement time in the first determination mode of the modification example.

Best Mode for Carrying Out the Invention

[0013] Hereinafter, a plurality of embodiments and their modification examples will be described with reference to the drawings for an embodiment in which a "thermal runaway prediction detection device" and a "thermal runaway prediction detection program" are applied to a power supply system of a vehicle (e.g., a moving body such as a hybrid vehicle or an electric vehicle). In the plurality of embodiments and their modification examples, parts that are functionally and / or structurally corresponding and / or associated may be assigned the same reference numerals, or reference numerals with different hundreds or more digits. For corresponding parts and / or associated parts, the description of other embodiments can be referred to.

[0014] (First Embodiment) 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 (power storage unit), 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). The battery control ECU 70 is, for example, a BMU (Battery Management Unit).

[0015] 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.

[0016] 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.

[0017] 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. In this embodiment, both the battery cells 42 and the battery modules 41 correspond to energy storage units.

[0018] 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.

[0019] The battery measurement unit 50 is a device that measures the State of Charge (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.

[0020] The battery control ECU 70 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 setting unit 71, a second calculation processing unit 72, a storage unit 73, and the like. The battery measurement unit 50 and the battery control ECU 70 constitute a thermal runaway prediction detection device.

[0021] 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.

[0022] 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, a first 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 first arithmetic processing unit 54.

[0023] 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 measures the response signal (voltage fluctuation) reflecting the complex impedance information of the battery cell 42 at the terminals of the battery cell 42.

[0024] Voltage fluctuations can be calculated, for example, by subtracting the terminal voltage of the battery cell 42 measured during AC current input from the terminal voltage of the battery cell 42 measured before AC current input. In this embodiment, the response signal is included in the measured value, and the voltage response measurement unit 52 is included in the measurement unit.

[0025] 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 instructions from the first arithmetic processing unit 54.

[0026] 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).

[0027] 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.

[0028] The first arithmetic processing unit 54 is equipped with a microcontroller consisting of a CPU (arithmetic unit) and a memory device (various types of memory), and realizes various functions by executing programs stored in the memory device. These various functions may be realized by hardware electronic circuits, or by both hardware and software.

[0029] The first arithmetic processing unit 54 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 first 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 first 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 alternating current, and outputs the measured response signal to the first arithmetic processing unit 54.

[0030] The first arithmetic processing unit 54 calculates information regarding the complex impedance of the battery cell 42 based on the response signal. The first 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 first arithmetic processing unit 54 also notifies the battery control ECU 70 of the calculation results and measurement results. The first arithmetic processing unit 54 also stores the calculation results and measurement results in the memory 54a.

[0031] 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).

[0032] 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.

[0033] 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 (i.e., multiple periods) 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 compared to when it is high. In other words, the required output period differs for each measurement frequency.

[0034] Furthermore, as shown in Figure 3, for example, the battery control ECU 70 measures the complex impedance in a first measurement mode with low measurement accuracy during normal operation (such as in the first judgment mode described later), and switches to a second measurement mode with higher measurement accuracy than the first measurement mode to measure the complex impedance when there is a high possibility of an abnormality occurring in the battery cell 42 (such as when the vehicle is started).

[0035] Specifically, the first 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 has been output a predetermined number of times, and is calculated based on the measurement frequency. The number of waves is predetermined according to the required measurement accuracy.

[0036] For example, as shown in Figure 3, the wavenumber is 3 (first count) in the first measurement mode, and the wavenumber is 9 (second count) in the second measurement mode. The wavenumber in the second measurement mode is greater than that 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 an 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.

[0037] The first 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.

[0038] The AC current generation unit 51 outputs an AC current (fluctuation current) from the battery cell 42 based on an instruction signal. 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 AC current, converts the analog value of the measured response signal into a digital value, and outputs it to the first arithmetic processing unit 54. In this embodiment, the AC current is output from the battery cell 42, but the AC current generation unit 51 may input an AC current to the battery cell 42 from another power source, or it may generate an AC current by varying the load on the battery cell 42.

[0039] The first 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 first arithmetic processing unit 54 obtains the value of the alternating current. That is, it measures the value of the alternating current flowing through the first electrical path 81, analyzes the measured value of the alternating current by the measurement frequency, and extracts and obtains the actual alternating signal (measured signal).

[0040] The first 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 the AC signal output, respectively.

[0041] Next, the first arithmetic processing unit 54 determines whether the output period of the AC signal corresponding to each measurement mode has ended. In the first measurement mode, the output period is the time until three AC signals are output (i.e., three cycles), and in the second measurement mode, the output period is the time until nine AC signals are output (i.e., nine cycles). If the result of this determination is negative, the first arithmetic processing unit 54 continues the measurement. On the other hand, if the result of the determination is positive, the first arithmetic processing unit 54 stops the measurement.

[0042] The first arithmetic processing unit 54 obtains values ​​proportional to the real and imaginary parts of the response signal corresponding to the AC signal, and calculates the complex impedance at the measurement frequency of the AC signal based on these values. Specifically, it calculates all or any of the real part, imaginary part, absolute value, and phase of the complex impedance. The first arithmetic processing unit 54 then transmits (notifies) the calculated complex impedance to the battery control ECU 70 via the communication unit 55.

[0043] The battery measurement unit 50 periodically calculates the complex impedance of the battery cells 42 while changing the measurement frequency as described above during the operation of the vehicle equipped with the power supply system 10 (while the battery pack 40 is in operation), and the battery control ECU 70 creates a complex impedance plane plot based on these complex impedances.

[0044] Next, we will explain the principle for detecting signs of thermal runaway in battery cell 42. Figure 4 is a graph showing a complex impedance plane plot and zero-crossing points. The horizontal axis represents the real part of the complex impedance, and the vertical axis represents the imaginary part of the complex impedance. Zero-crossing points are the points where the graph of complex impedance intersects the horizontal axis, that is, the points where the imaginary part of the complex impedance is zero.

[0045] The black dots in the figure indicate that the complex impedance has been measured and calculated 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 the 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 the real part at the zero-crossing point A to increase sharply.

[0046] Figure 5 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.

[0047] Figure 6 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).

[0048] 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 there is a sign of thermal runaway in the battery cell 42.

[0049] 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).

[0050] However, as mentioned above, in order to calculate complex impedance, etc., it is generally necessary to introduce some kind of disturbance to the secondary battery and measure the resulting fluctuation in the output current or output voltage of the secondary battery. In addition, the battery measurement unit 50 or the battery control ECU 70 consume power when performing measurement and calculation processing. In other words, calculating complex impedance, etc., consumes power from the secondary battery. On the other hand, when the vehicle is stopped and not connected to an external charger, etc., it is generally not possible to operate the generator, etc., and there is no way to charge the secondary battery.

[0051] Therefore, conventionally, if thermal runaway warnings were frequently detected while the vehicle was stopped, the power consumption would increase depending on the length of the stop, potentially leading to over-discharge of the secondary battery. In this embodiment, however, measures have been taken to minimize power consumption while enabling the detection of thermal runaway warnings. These measures will be explained in detail below.

[0052] First, the overall flow of thermal runaway prediction detection performed by the thermal runaway prediction detection device, which consists of the battery measurement unit 50 and the battery control ECU 70, will be explained with reference to Figure 7.

[0053] The setting unit 71 of the battery control ECU 70 sets the first determination mode as the determination mode (step S102) and enters sleep mode when the vehicle operating mode is the stopped mode (step S101: YES). This reduces power consumption. When the setting unit 71 sets the first determination mode, it also instructs the battery measurement unit 50 that the first determination mode has been set and to calculate the complex impedance in the first measurement mode.

[0054] The stationary mode is set, for example, during the period when the ignition switch is off. Alternatively, the stationary mode may be set when the vehicle is stopped and no external charger is connected. Furthermore, the stationary mode may be set when the relay switch SMR is off, or when the shift position is in the P or N range. It may also be set according to vehicle operation mode instructions transmitted from other ECUs, such as the higher-level ECU 60.

[0055] Furthermore, even when the vehicle is stopped, the battery measurement unit 50 receives power from the battery cell 42 and other sources, remaining constantly operational and 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 smaller than that of the battery control ECU 70. This is because their performance and processing capabilities differ.

[0056] On the other hand, if the vehicle operating mode is not the stationary mode (step S101: NO), the setting unit 71 of the battery control ECU 70 sets the second determination mode as the determination mode (step S103). Also, when the setting unit 71 sets the second determination mode, it instructs the battery measurement unit 50 that the second determination mode has been set and to calculate the complex impedance in the second measurement mode. Steps S101 to S103 correspond to the setting process. Note that when the vehicle operating mode is not the stationary mode, for example, it is the vehicle start mode. The vehicle start mode is set during the period when the ignition switch or relay switch SMR is ON, or during the period when the shift position is in the D range.

[0057] When the first determination mode is set (step S104: YES), the battery measurement unit 50 takes the lead in performing various processes. At this time, the battery measurement unit 50 restricts communication with the battery control ECU 70 until the first determination mode is deactivated (until it is indicated that the second determination mode has been set). This helps to reduce power consumption. When the first determination mode is set, the battery measurement unit 50 performs a measurement process to measure the complex impedance at predetermined intervals (step S105).

[0058] Now, with reference to Figure 8, the measurement process in step S105 by the battery measurement unit 50 will be explained. As shown in Figure 8, the battery measurement unit 50 first determines the set measurement mode (step S201). The measurement mode is determined by determining whether the measurement mode set by the instruction from the setting unit 71 of the battery control ECU 70 is either the first measurement mode or the second measurement mode.

[0059] The battery measurement unit 50 measures various measurement values ​​in a set measurement mode for a predetermined target among the multiple battery cells 42 (steps S202 to S204). The number of targets to be measured may differ between the first determination mode and the second determination mode. For example, the number of targets to be measured in the first determination mode may be less than the number of targets to be measured in the second determination mode. In the first determination mode of the first embodiment, one predetermined battery cell 42 is used as the target to be measured, while in the second determination mode, all battery cells 42 are used as targets to be measured. Therefore, power consumption can be reduced in the first determination mode compared to the second determination mode.

[0060] To explain the process in steps S202 to S204 in detail, the battery measurement unit 50 acquires the temperature T of the battery cell 42 to be measured and calculates (estimates) the state of charge (SOC) of the battery cell 42 (step S202). 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 SOC of the battery cell 42 can be calculated (estimated), for example, based on the SOC at a predetermined time and the integrated value of the current that flowed through the battery cell 42 thereafter. The temperature T and SOC of the battery cell 42 are also included in the measured values.

[0061] Next, the battery measurement unit 50 outputs an alternating current (fluctuating current) of a predetermined frequency from the battery cell 42 to be measured, and measures the voltage fluctuation of the battery cell 42 in response to the alternating current (step S203). 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 4, 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 S201 switched on.

[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 S204). 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. The battery measurement unit 50 then stores the measurement results (various measured values) and calculation results (such as the real part of the zero-crossing point) in the memory 54a (step S205). In this embodiment, the battery measurement unit 50 stores the measured voltage value, complex impedance parameters (real part, imaginary part, etc.), current value, battery temperature, etc. in the memory 54a. Then, the measurement process is terminated (END). In the following, the measurement results and calculation results may be collectively referred to as the measurement results.

[0063] As shown in Figure 7, after the measurement process in step S105 is completed, the first arithmetic processing unit 54 of the battery measurement unit 50 determines whether there is a sign of thermal runaway based on the complex impedance calculated based on the measured value in step S105 (step S106). In step S106, for example, if the real part of the complex impedance is outside a predetermined allowable range, the first arithmetic processing unit 54 determines that there is a sign of thermal runaway, and if it is within the allowable range, it determines that there is no sign of thermal runaway. The allowable range is predetermined based on simulation or experimental results. If the determination result in step S106 is negative, the battery measurement unit 50 then terminates this series of processes (END).

[0064] On the other hand, if the determination result in step S106 is affirmative, the first arithmetic processing unit 54 notifies the battery control ECU 70 of this fact, starts the battery control ECU 70, and has it perform various countermeasures when it is determined that there are signs of thermal runaway (step S107). For example, the battery control ECU 70 stores that there are signs of thermal runaway in the battery cell 42 and also notifies the higher-level ECU 60 that there are signs of thermal runaway in the battery cell 42. That is, the battery control ECU 70 detects that there are signs of thermal runaway in the battery cell 42 and notifies the higher-level ECU 60 via communication that there are signs of thermal runaway (abnormality) in the battery cell 42. The battery control ECU 70 may also perform fail-safe processing, such as turning off the relay switch SMR to insulate the battery pack 40 from the load, or limiting the current. It may also shut down the power supply system 10 and put the vehicle into a dormant state. Upon receiving the notification, the higher-level ECU 60 alerts the vehicle driver to the abnormality, for example, through an alarm. The higher-level ECU 60 may also notify a monitoring center or other device capable of communicating with the vehicle of the abnormality. After this, the entire process is terminated (END).

[0065] Next, the processing of the battery control ECU 70 when the second determination mode is set (step S104: NO) will be described. The second arithmetic processing unit 72 of the battery control ECU 70 determines whether the first measurement has been completed by the battery measurement unit 50 and whether the result of the first measurement has been stored in the storage unit 73 (step S108).

[0066] If this determination result is negative, the second arithmetic processing unit 72 of the battery control ECU 70 instructs the battery measurement unit 50 to perform the first measurement (step S109). When the battery measurement unit 50 is instructed to perform the first measurement, it performs the measurement process in the same manner as in step S105 (step S110). In the second determination mode, all battery cells 42 are to be measured, so the measurement process is performed for all measurement targets. The battery measurement unit 50 then transmits the measurement result for each measurement target to the battery control ECU 70 (step S111).

[0067] The second arithmetic processing unit 72 of the battery control ECU 70 stores the received measurement result as the first result in the storage unit 73 (step S112). At this time, the measurement result is stored for each measurement target. In step S112, before storage, the second arithmetic processing unit 72 of the battery control ECU 70 standardizes the real part of the input zero-crossing point. 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 the process of 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. This map and formula can be calculated in advance based on tests using the battery cell 42. Then, this series of processes is terminated (END).

[0068] On the other hand, if the result of the first measurement is stored (step S108: YES), the second arithmetic processing unit 72 of the battery control ECU 70 instructs the battery measurement unit 50 to perform a second measurement (step S113). The instruction for the second measurement is given after a predetermined time Δt has elapsed since the completion of the voltage fluctuation measurement in the previous measurement (first measurement instruction). That is, information regarding the temperature T of the battery cell 42, the SOC of the battery cell 42, and the complex impedance (the real part of the zero-crossing point) is obtained after the predetermined time Δt. The predetermined time Δt is, for example, 1 to 5 [min]. It is preferable that it be longer than 1 [min], and even more preferable that it be longer than 2 [min]. On the other hand, it is preferable that it be 1 [hour] or less, and even more preferable that it be 20 [min] or less. The predetermined time Δt may also be the time since the temperature T of the battery cell 42 was obtained and the SOC of the battery cell 42 was calculated in the previous measurement.

[0069] When the battery measurement unit 50 is instructed to perform a second measurement, it performs the measurement process for all measurement targets in the same manner as in step S109, etc. (step S114). Then, the battery measurement unit 50 transmits the measurement results to the battery control ECU 70 (step S115).

[0070] The second arithmetic processing unit 72 of the battery control ECU 70 stores the received measurement result as the second result in the storage unit 73 for each measurement target (step S116). In step S116, similar to step S112, before storing, the second arithmetic processing unit 72 of the battery control ECU 70 standardizes the real part of the input zero-crossing point.

[0071] The battery control ECU 70 then identifies the pattern of change in the battery state from the results of the first and second measurements (step S117). Specifically, it calculates the rate of change of the real part of the zero-crossing point. 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 first measurement to the converted value Re_Zb of the real part of the zero-crossing point calculated after a predetermined time Δt by the predetermined time Δt (ΔVRe_Z = ΔRe_Z / Δt). Similarly, in step S177, the rate of change is calculated for each measurement target.

[0072] Next, the battery control ECU 70 determines whether there is a sign of thermal runaway by determining whether the rate of change of the real part of the zero-crossing point ΔVRe_Z is greater than the threshold C (step S118). 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 S118: NO), it is determined that there is no sign of thermal runaway and the process is terminated. Note that the determination that there is no sign of thermal runaway is made only if 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 for all measured objects.

[0073] On the other hand, in the determination in step S118, if it is determined that the rate of change of the real part of the zero-crossing point ΔVRe_Z is greater than the threshold C (step S118: YES), the battery control ECU 70 performs various countermeasures as in step S107 when it is determined that there is a sign of thermal runaway (step S119). After that, this series of processes is terminated (END). Note that in the process of step S118, a determination is made for each measurement target, and if it is determined that the rate of change of the real part of the zero-crossing point ΔVRe_Z is greater than the threshold C for any measurement target, it is determined that there is a sign of thermal runaway.

[0074] In the first embodiment, steps S105, S110, and S114 correspond to measurement processing. Steps S107, S117, and S118 correspond to determination processing. In particular, step S107 corresponds to determination processing in the first determination mode, and steps S117 and S118 correspond to determination processing in the second determination mode. The first arithmetic processing unit 54 and the second arithmetic processing unit 72 constitute the determination unit. The first arithmetic processing unit 54 corresponds to the determination unit that performs determination in the first determination mode, and the second arithmetic processing unit 72 corresponds to the determination unit that performs determination in the second determination mode.

[0075] The series of processes shown in Figure 7 are executed at predetermined execution cycles. The execution cycle may differ depending on whether the stopping mode (or first determination mode) is set or not. Furthermore, unless the vehicle operation mode is changed, the processes in steps S101 to S103 do not need to be executed.

[0076] Here, we will provide supplementary explanation regarding the detection of signs of thermal runaway. Referring to Figures 9 to 11 below, we will explain 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 in battery cells of different capacities.

[0077] Figures 9-11 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 9 is a battery cell with a capacity of 25[Ah], a nickel-based material NCM (Ni, Co, Al, Mn) positive electrode, and a Gr (graphite) negative electrode. Figure 10 is a battery cell with a capacity of 50[Ah], a nickel-based material NCM positive electrode, and a Gr negative electrode. Figure 11 is a battery cell with a capacity of 150[Ah], an LFP (Li, Fe, P) positive electrode, and a Gr negative electrode.

[0078] 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 9, 250 Hz for the battery cell in Figure 10, and 120 Hz for the battery cell in Figure 11. Thus, the predetermined frequency tends to decrease as the capacity of the battery cell increases. Despite these differences, in all of Figures 9 to 11, 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.

[0079] 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 9 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.

[0080] As shown in Figures 9-11, the complex impedance changes before thermal runaway occurs, which clearly indicates that voltage fluctuations also occur. Therefore, a large change in voltage clearly suggests that some kind of malfunction may be occurring.

[0081] In the first embodiment described above, the following effects can be obtained.

[0082] The setting unit 71 sets a first judgment mode when the vehicle is stopped, and a second judgment mode when the vehicle is started. When the first judgment mode is set, the battery measurement unit 50 measures the battery at predetermined timings and detects signs of thermal runaway based on those measurements. When the second judgment mode is set, the battery control ECU 70 measures the battery at multiple timings, identifies the pattern of change in the battery state from those measurements, and detects signs of thermal runaway based on the pattern of change. Therefore, when the vehicle is stopped and the possibility of thermal runaway is low, the number of measurement cycles can be reduced to lower power consumption. On the other hand, when the vehicle is started and the possibility of thermal runaway is higher than when the vehicle is stopped, the second measurement mode is set, allowing for more accurate detection of signs of thermal runaway compared to the first judgment mode.

[0083] The voltage response measurement unit 52 measures the measurement value using either a first measurement mode, which measures the measurement value with normal accuracy, or a second measurement mode, which consumes more power than the first measurement mode to measure the measurement value with higher accuracy. Specifically, in the second measurement mode, which is set during vehicle startup mode, the number of waveforms of the AC current output from the battery cell 42 is increased compared to the first measurement mode, that is, the output period is extended and the measurement time is extended, thereby suppressing errors and improving measurement accuracy. As a result, when the vehicle is running and the possibility of thermal runaway is higher than when the vehicle is stopped, the second measurement mode is set, making it possible to detect signs of thermal runaway with high accuracy.

[0084] On the other hand, during the first judgment mode, which is set while the vehicle is stopped, the first measurement mode, which consumes less power than the second measurement mode, is set. Therefore, although the measurement accuracy decreases while the vehicle is stopped, the power consumption during measurement can be further reduced.

[0085] In this embodiment, during the first judgment mode, one predetermined battery cell 42 among the battery cells 42 constituting the battery pack 40 is selected as the measurement target, and the measurement value is taken only once. This allows for lower power consumption. On the other hand, during the second judgment mode, all battery cells 42 are selected as the measurement target, and the measurement value is taken. This increases power consumption, but makes it easier to detect signs of thermal runaway.

[0086] During the first judgment mode, the battery measurement unit 50 restricts communication with the battery control ECU 70 until signs of thermal runaway are detected. It then processes the measured values ​​to calculate the complex impedance and detects signs of thermal runaway from the calculated complex impedance. This prevents the power-hungry battery control ECU 70 from being activated, thus further reducing power consumption.

[0087] On the other hand, when the second judgment mode is set, the second arithmetic processing unit 72 of the battery control ECU 70 causes the first arithmetic processing unit 54 of the battery measurement unit 50 to calculate complex impedance at multiple timings, receives the calculated complex impedances, calculates the change patterns of the received impedances, and detects signs of thermal runaway from the change patterns. At that time, the second arithmetic processing unit 72 calculates a converted value based on the battery temperature and SOC from the real part of the zero-crossing point calculated by the battery measurement unit 50, calculates the rate of change of the converted value (real part), and determines signs of thermal runaway. Therefore, signs of thermal runaway can be detected with high accuracy while the vehicle is running, when the possibility of thermal runaway is higher than when the vehicle is stopped. In addition, in the second judgment mode, the rate of change is calculated, not just the difference in complex impedance, so signs of thermal runaway can be detected with even higher accuracy.

[0088] During stationary mode, the battery control ECU 70 enters sleep mode, and the battery measurement unit 50 restricts communication with the battery control ECU 70. This allows for further reduction of power consumption.

[0089] The system detects signs of thermal runaway by measuring the rate of change in the real part of the AC impedance. Therefore, it can detect signs of runaway earlier compared to detection based on the rate of change in voltage or battery temperature.

[0090] 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 two modes: a first measurement 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 measured is 3 (first count), and a second measurement mode in which the number of times is greater than 3 is 9 (second count). Therefore, 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.

[0091] The second arithmetic processing unit 72 calculates the rate of change ΔVRe_Z of the real part of the complex impedance Re_Z calculated by the first arithmetic processing unit 54 and a predetermined time Δt, and detects 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. 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 at multiple frequencies within the measurement range, and it is only necessary to measure the complex impedance of the battery cell 42 at 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 of [ms] × wavenumber (number of times).

[0092] The second arithmetic processing unit 72 calculates the rate of change ΔVRe_Z of the real part of the complex impedance Re_Z calculated by the first arithmetic 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 SOC), 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.

[0093] (Second Embodiment) In the second embodiment, some of the processes in the first embodiment are modified. These will be explained in detail below with reference to Figure 12. Figure 12 shows the overall flow of thermal runaway prediction detection in the second embodiment. The series of processes shown in Figure 12 are executed at predetermined execution cycles. As mentioned above, the execution cycle may be different depending on whether the stop mode is set or not.

[0094] The setting unit 71 of the battery control ECU 70 determines, when the vehicle operating mode is the stationary mode (step S301: YES), whether the pre-detection flag, which indicates that signs of thermal runaway have already been detected in the first determination mode, is set to "0" (step S302). The pre-detection flag will be described later. If this determination result is positive, that is, if signs of thermal runaway have not yet been detected in the first determination mode (pre-detection flag = 0), the setting unit 71 sets the first determination mode as the determination mode (step S303). The setting unit 71 also instructs the battery measurement unit 50 that the first determination mode has been set.

[0095] On the other hand, if the judgment result in step S302 is negative, that is, if signs of thermal runaway have already been detected in the first judgment mode (when the pre-detection flag = 1), the setting unit 71 sets the second judgment mode as the judgment mode (step S304). The setting unit 71 also instructs the battery measurement unit 50 that the second judgment mode has been set.

[0096] Furthermore, if the vehicle operation mode is not the stopped mode (step S301: NO), the setting unit 71 of the battery control ECU 70 similarly sets the second determination mode as the determination mode (step S304). The setting unit 71 also instructs the battery measurement unit 50 that the second determination mode has been set. In the second embodiment, steps S301 to S304 correspond to the setting process.

[0097] Next, the setting unit 71 of the battery control ECU 70 determines whether the system has been switched to the second determination mode because signs of thermal runaway have been detected in the first determination mode (step S305). That is, regardless of the stationary mode, the setting unit 71 determines whether the second determination mode has been set because the pre-detection flag has been set to "1".

[0098] If this determination result is positive, the setting unit 71 instructs the battery measurement unit 50 to calculate the complex impedance in the second measurement mode (step S306). In the second embodiment, unless the pre-detection flag is set to "1", the measurement is normally performed in the first measurement mode. Regardless of the stationary mode, if the pre-detection flag is set to "1", that is, if there is a high possibility of signs of thermal runaway, the second measurement mode is set.

[0099] If the result of step S305 is negative, or if the first determination mode is set after the processing in step S306 (step S307: YES), the battery measurement unit 50 will then take the lead in performing various processes. At this time, the battery measurement unit 50 will restrict communication to the battery control ECU 70 until the first determination mode is released (until it is indicated that the second determination mode has been set). Once the first determination mode is set, the battery measurement unit 50 will perform a measurement process to measure the complex impedance at predetermined intervals (step S308). The measurement process in step S309 is the same as the measurement process in step S105 of the first embodiment, so its explanation will be omitted.

[0100] After the measurement process in step S308 is completed, the first calculation processing unit 54 of the battery measurement unit 50 determines whether there is a sign of thermal runaway based on the complex impedance calculated from the measured values ​​in step S308 (step S309). The process in step S309 is the same as in step S106, so the explanation is omitted. If the determination result in step S309 is negative, the battery measurement unit 50 then terminates this series of processes (END).

[0101] On the other hand, if the result of the determination in step S309 is positive, the first arithmetic processing unit 54 notifies the battery control ECU 70 of this fact and instructs it to set the pre-detection flag to "1" (step S310). Then, this series of processes is terminated (END). Note that if the pre-detection flag is set to "1", the execution cycle of the series of processes shown in Figure 12 may be accelerated.

[0102] Next, the processing of the battery control ECU 70 when the second determination mode is set (step S307: NO) will be described. In this case, the battery control ECU 70 performs the processing in steps S311 to S321. The processing in steps S311 to S321 is the same as the processing in steps S108 to S118 of the first embodiment, so the explanation will be omitted.

[0103] In the determination in step S321, 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 S321: YES), the battery control ECU 70 confirms that there are no malfunctions in the battery measurement unit 50 or other measuring components that measure the measured value (step S322). The measuring components include the battery measurement unit 50, the battery control ECU 70, the voltage sensor, the current sensor, the thermosensor, etc. The malfunction check is performed by a well-known method. If this determination result is negative, that is, if there is a malfunction in the measuring component, the battery control ECU 70 terminates this series of processes (END). In this case, processing to notify that a malfunction has occurred, or other processing to be performed when a malfunction occurs, may be executed.

[0104] On the other hand, if the result of the determination in step S323 is positive, that is, if there is no malfunction, the battery control ECU 70 confirms that there is a sign of thermal runaway and performs various countermeasures to deal with the sign of thermal runaway in the same manner as in step S119 (step S323). After that, this series of processes is terminated (END).

[0105] Furthermore, if the judgment result in step S321 is negative, that is, if no signs of thermal runaway were detected during the second judgment mode, the battery control ECU 70 may set the pre-detection flag to "0".

[0106] In the second embodiment described above, the following effects can be obtained.

[0107] If the setting unit 71 detects signs of thermal runaway while the first judgment mode is being set, it sets the second judgment mode and detects signs of thermal runaway in the second judgment mode. In other words, if the pre-detection flag is set to "1", it does not immediately confirm that there are signs of thermal runaway and perform various countermeasures, but rather it determines again whether there are signs of thermal runaway in the second judgment mode. This ensures that even if the less accurate first judgment mode is set while the vehicle is stopped, the detection accuracy can be ultimately guaranteed. In other words, false detections can be prevented while suppressing power consumption.

[0108] In the second embodiment, unlike the first embodiment, even if signs of thermal runaway are detected while the first judgment mode is being set, the signs of thermal runaway are not confirmed. Instead, the second judgment mode is set, measurements are taken again, and the presence or absence of signs of thermal runaway is re-determined in the second judgment mode. This allows for reduced power consumption by decreasing the number of measurements under normal circumstances, while increasing the number of measurements to accurately detect signs of thermal runaway when there is a high probability of such signs occurring. Furthermore, since signs of thermal runaway are re-determined in the second judgment mode when signs of thermal runaway are detected while the first judgment mode is being set, it is possible to suppress misjudgments even if the tolerance range is narrowed in the first judgment mode. Therefore, when determining signs of thermal runaway in step S308, narrowing the tolerance range of the complex impedance makes it easier to detect signs of thermal runaway in the first judgment mode, thereby suppressing the oversight of signs of thermal runaway in the first judgment mode.

[0109] The battery measurement unit 50 measures the measured value in the first measurement mode while the first judgment mode is set. However, if signs of thermal runaway are detected while the first judgment mode is set, i.e., the pre-detection flag is set to "1" and the second judgment mode is set, the unit measures the measured value in the second measurement mode. This allows for suppression of power consumption during measurement under normal circumstances, while enabling accurate measurement of the measured value and calculation of highly accurate complex impedance when there is a high probability of signs of thermal runaway occurring.

[0110] (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.

[0111] 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.

[0112] In step S118 of Figure 8 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 S118: 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 S119). 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.

[0113] The second arithmetic processing unit 72 in the above embodiment may calculate the rate of change ΔVRe_Z of the real part of the complex impedance Re_Z based on the real part of the complex impedance Re_Z and a predetermined time Δt, without converting the real part of the complex impedance Re_Z calculated by the first arithmetic processing unit 54 to the real part of the complex impedance at a predetermined temperature and a predetermined SOC. The second arithmetic processing 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 a threshold C.

[0114] In the first measurement 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. Specifically, the first 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.

[0115] In the above embodiment, the first arithmetic processing unit 54 can shorten the predetermined time Δt in the processing of step S113 in Figure 8 and step S316 in Figure 12, 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 to measure the voltage fluctuation of the battery cell 42 in the previous step until the execution of the second measurement instruction 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 at an earlier stage.

[0116] The battery measurement unit 50 in the above embodiment may have a third measurement 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 and the second measurement mode.

[0117] In the above embodiment, 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.

[0118] In the above embodiment, as shown in Figure 14, the battery measurement unit 50 may be provided with one AC current generation unit 51 for a plurality of battery cells 42, and a voltage response measurement unit 52 for each battery cell 42. Then, with the plurality of battery cells 42 as the measurement target (target for detecting signs of thermal runaway), an AC current may be passed through the plurality of battery cells 42 together, and the voltage fluctuation of each battery cell 42 may be measured by each voltage response measurement unit 52.

[0119] In the above embodiment, 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 a plurality of battery cells 42. Then, with the plurality of battery cells 42 as the measurement target (target for detection of thermal runaway signs), an AC current may be passed through the plurality of battery cells 42 together, and the voltage fluctuations of the plurality of battery cells 42 may be measured together by the voltage response measurement unit 52.

[0120] In the above embodiment, as shown in Figure 16, the AC current generation unit 51 may be placed outside the battery measurement unit 50, and AC current may be supplied from the AC current generation unit 51 to a plurality of battery cells 42. Alternatively, a current sensor A100 may be provided on the current path of the AC current, and a current detection unit 100 may be provided that receives the current value from the current sensor A100 and calculates it. The current detection unit 100 may include a current calculation unit 101 that calculates the current value (digital value) from the measured value (analog value) input from the current sensor A100, a third calculation processing unit 102 that acquires the current value from the current calculation unit 101 and performs various calculation processing, a communication unit 104 that communicates with the battery control ECU 70, etc., and a fault determination unit 105 that determines a fault in the current detection unit 100.

[0121] Furthermore, as shown in Figure 16, one battery measurement unit 50 may be provided for multiple battery cells 42, and each of the multiple battery cells 42 may be provided with a voltage response measurement unit 52 within the single battery measurement unit 50. Alternatively, one first calculation processing unit 54 may be provided for each battery measurement unit 50, and the complex impedance of each battery cell 42 (measurement target) may be calculated based on the measured values ​​input from the multiple voltage response measurement units 52. Also, as shown in Figure 16, each battery measurement unit 50 may be equipped with a fault determination unit 56 for determining a failure of the battery measurement unit 50, or the battery control ECU 70 may be equipped with a fault determination unit 75 for determining a failure of the battery control ECU 70. Note that in step S322 of Figure 12 of the second embodiment described above, if any of the fault determination units 56, 75, or 105 determine that there is a fault, the battery control ECU 70 may make a negative determination (determine that there is a component failure). Furthermore, in the first determination mode, the third arithmetic processing unit 102 may be provided with functions for calculating complex impedance and detecting signs of thermal runaway (functions of the first arithmetic processing unit 54).

[0122] In the above embodiment, an alternating current may be passed through the entire battery module 41 and the voltage fluctuations of each battery cell 42 may be measured (detecting signs of thermal runaway), or the voltage fluctuations of the entire battery module 41 may be measured (detecting 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 (detecting signs of thermal runaway), or the voltage fluctuations of the entire battery pack 40 may be measured (detecting signs of thermal runaway).

[0123] In the above embodiment, the functions of the setting unit 71 and the second calculation processing unit 72 may be provided in the battery measurement unit 50. In that case, the battery measurement unit 50 constitutes a secondary battery thermal runaway prediction detection device. Alternatively, the functions of the first calculation processing unit 54 may be provided in the battery control ECU 70.

[0124] In the above embodiment, 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 for detecting signs of thermal runaway in the battery measurement unit 50 and the battery control ECU 70 may also be installed in an in-vehicle charger (AC charger, DC charger, V2H (Vehicle To Home) charger), the battery measurement unit and battery control ECU of a replaceable battery pack, the charging EMS (Energy Management System) of a charging station, etc.

[0125] In the above embodiment, if the higher-level ECU 60 is in sleep mode, such as when the ignition is off, it may be activated to issue an alarm or the like if it ultimately detects an abnormality in conjunction with a diagnostic result other than the thermal runaway warning. Alternatively, 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 of detecting the thermal runaway warning may be performed multiple times, and it may be determined that an abnormality has been detected only if the thermal runaway warning has been detected multiple times. This can suppress false detections of abnormalities and malfunctions of alarms, etc.

[0126] 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.

[0127] In the above embodiment, the battery cell 42 was used as the measurement target, but the battery module 41 or the battery pack 40 may also be used as the measurement target.

[0128] In the first determination mode of the above embodiment, the possibility of an anomaly may be determined by parameters other than complex impedance. For example, the possibility of an anomaly may be determined based on the voltage value. Alternatively, for example, the possibility of an anomaly may be determined based on battery temperature or gas pressure. Furthermore, it is not necessary to make a determination based on a single measurement value; the possibility of an anomaly may be determined based on the difference or quotient of measurement values ​​of multiple measurement targets measured at predetermined timings. For example, if the voltage difference or temperature difference is above a threshold, the possibility of an anomaly may be determined. Note that if the possibility of an anomaly is determined by parameters other than complex impedance, it is desirable to determine the signs of thermal runaway again in the second determination mode to prevent misjudgment.

[0129] In step S106 of the above embodiment, it is desirable that the boundary value of the acceptable range be set from a value within the boundary range between the normal range and the abnormal range. That is, it is desirable to set the boundary value of the acceptable range as 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.

[0130] In the second embodiment described above, if the second determination mode is set while the vehicle is stopped, the battery control ECU 70 may enter a sleep state between the time the first measurement process is executed and the time the second measurement process is executed.

[0131] In the above embodiment, the battery cell 42 or battery module 41 to be measured does not need to remain the same throughout, but may be changed periodically. This makes it possible to suppress large changes in the charge storage state of a particular battery cell 42.

[0132] In the second determination mode of the above embodiment, the measurement target was all battery cells 42, but this may be changed to any number.

[0133] In the first determination mode of the above embodiment, the battery measurement unit 50 determined whether or not the real part of the complex impedance was within an acceptable range. However, the determination method in the first determination mode can be arbitrarily changed as long as the measurement is performed at a predetermined timing. For example, the determination of whether or not the thermal runaway is based on whether or not one or more parameters of the complex impedance—the real part, imaginary part, absolute value, and phase—are within predetermined acceptable ranges. Also, when acquiring the response signal (voltage fluctuation) to calculate the complex impedance, an AC current at the measurement frequency that becomes zero-crossing point A in the Cole-Cole plot of Figure 4 was input and output. However, it is not necessary to limit the measurement frequency to zero-crossing point A, and the measurement frequency can be arbitrarily changed.

[0134] In the first determination mode of the above embodiment, only one measurement target was used. However, as long as the measurement is performed at a predetermined timing, two or more battery cells 42 or battery modules 41 may be used as measurement targets. In this case, the first calculation processing unit 54 of the battery measurement unit 50 may use the complex impedance of one of the multiple measurement targets as a reference to determine the difference or quotient of the complex impedances of each measurement target, and detect signs of thermal runaway based on whether the difference or quotient falls within a predetermined allowable range. Alternatively, the average value of the complex impedance of the measurement targets may be calculated, and signs of thermal runaway may be detected based on whether the average value falls within an allowable range. When determining the difference, quotient, or average value, the difference or quotient may be of the real part, imaginary part, absolute value, or phase of the complex impedance. This is expected to allow for more accurate detection of signs of thermal runaway compared to the case where only one measurement target is used.

[0135] In this case, it is desirable that the battery cell 42 to be measured as a reference and the battery cell 42 to be measured for comparison are physically separated by a certain distance so that if one of them overheats, the heat generated by that cell does not affect the other. This makes it easier for differences in measurement values ​​to occur when multiple measurement targets are used, and allows for more accurate detection of signs of thermal runaway.

[0136] Furthermore, it is desirable that the battery temperature of the reference battery cell 42 be monitored by a thermistor or the like to confirm that it is normal. This allows for more accurate detection of signs of thermal runaway when multiple measurement targets are used.

[0137] Furthermore, in the first determination mode, if there are multiple measurement targets, it is desirable for the battery measurement unit 50 to measure each target once. This shortens the time spent inputting and outputting AC current, and suppresses large changes in the charge state of a particular battery cell 42.

[0138] Furthermore, in the first determination mode, when measuring multiple measurement targets at predetermined timings, it is not necessary for the AC current output period and the voltage fluctuation measurement period to be set within exactly the same period; they may be slightly offset within a predetermined limit. For example, as shown in Figure 17(a), if there are four measurement targets 42a to 42d, they may be measured at predetermined timings as long as they are set sequentially and continuously without interruption in the measurement period. Specifically, in Figure 17(a), the measurement period end time T12 for measurement target 42a is set to begin at T13 for the measurement period of the next measurement target 42b. From there, until the measurement period of the last measurement target 42d ends, the measurement end time of the previous measurement target becomes the measurement start time of the next measurement target.

[0139] Furthermore, as shown in Figure 17(b), some overlap is permitted as long as the measurement periods are not interrupted. Specifically, in Figure 17(b), the start time T22 of the measurement period for the next measurement target 42b is set before the end time T23 of the measurement period for the measurement target 42a is reached. Thereafter, until the end of the measurement period for the last measurement target 42d, the start time of the measurement for the next measurement target is set before the end time of the measurement for the previous measurement target is reached.

[0140] Furthermore, for example, if the time from the start of measurement of the first measurement target to the completion of measurement of the last measurement target is within a predetermined time (e.g., 1 min), the measurement may be considered to have taken place at a predetermined timing.

[0141] Each measurement period is set for each measurement mode. Specifically, it corresponds to the period during which an AC current of the wavenumber set for each measurement mode is output, as described in the above embodiment.

[0142] In the second determination mode of the above embodiment, the measurement frequency may differ between the first and second measurements.

[0143] In the second determination mode of the above embodiment, the complex impedance of different measurement targets (battery cell 42 or battery module 41) may be measured in the first measurement and the second measurement, and signs of thermal runaway may be detected based on whether the difference or quotient between them is within an acceptable range.

[0144] In the above embodiment, the number of wavenumbers was changed between the first measurement mode and the second measurement mode, but the output period or measurement period may also be changed. Furthermore, the amplitude of the input AC signal may be changed between the first measurement mode and the second measurement mode. Also, the measurement period may be changed between the first measurement mode and the second measurement mode.

[0145] In the second embodiment described above, if signs of thermal runaway were detected in the first determination mode, that is, if the pre-detection flag was set to "1", the second determination mode was set, measurements were taken at different timings in the second determination mode, and the signs of thermal runaway were determined again based on those measurements. As a variation of this, if signs of thermal runaway were detected in the first determination mode, the measurement results taken during the first determination mode may be stored and used as the first measurement results to be used in the second determination mode. This eliminates the need to take measurements again at different timings after the second determination mode has been set. In other words, it eliminates the need to take the first measurement results again after the second determination mode has been set. This is expected to reduce processing time and power consumption.

[0146] In the first determination mode of the above embodiment, if there are multiple measurement targets, for example, signs of thermal runaway may be detected based on the difference or quotient between the average value of the complex impedance of a battery cell 42 constituting one battery module 41 and the average value of the complex impedance of a battery cell 42 constituting another battery module 41. The battery cell 42 to be measured may be changed as needed.

[0147] In the first determination mode of the above embodiment, the measurement target used as a reference may be the impedance of a component other than the battery cell 42. For example, a busbar or other component with a specified impedance is preferred.

[0148] In the above embodiment, the measurement period and measurement frequency of the complex impedance may be changed according to the environment, such as the voltage of the object to be measured, such as the battery cell 42, and the battery temperature.

[0149] In the second determination mode of the above embodiment, the impedance difference between the first and second measurement targets (first impedance difference) may be calculated based on the first measurement result, and the impedance difference between the first and second measurement targets (second impedance difference) may be calculated based on the second measurement result. The presence or absence of signs of thermal runaway may be detected based on whether the value obtained by subtracting the first impedance difference from the second impedance difference falls within an acceptable range. Alternatively, the presence or absence of thermal runaway may be detected by dividing the value obtained by subtracting the first impedance difference from the second impedance difference by the elapsed time as the rate of change and comparing it with a threshold value.

[0150] In the above embodiments or modifications, the mobile body on which the "thermal runaway prediction device" and "thermal runaway prediction program" are installed is not limited to a vehicle, but may also be, for example, an aircraft or a ship. Furthermore, the above modifications can be implemented in combination.

[0151] 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.

[0152] The following describes characteristic configurations extracted from the embodiments and modified examples described above. [Configuration 1] A thermal runaway prediction device (50, 70) that detects signs of thermal runaway in the energy storage unit (40, 41, 42) mounted on a mobile body, A measuring unit (52) that measures a measurement value indicating the battery state of the power storage unit, A determination unit (54, 72) detects signs of thermal runaway by having the measurement unit measure a value at a predetermined timing and detecting signs of thermal runaway based on that value, and by having the measurement unit measure a value at multiple timings, identifying the pattern of change in the battery state from those values ​​and detecting signs of thermal runaway based on the pattern of change. A thermal runaway prediction detection device comprising a setting unit (71) that sets the first determination mode when the vehicle is stopped and sets the second determination mode when the moving body is started. [Configuration 2] The thermal runaway warning detection device according to Configuration 1, wherein the setting unit sets a second determination mode when the determination unit detects signs of thermal runaway while the first determination mode is being set, and causes the determination unit to detect signs of thermal runaway in the second determination mode. [Configuration 3] The aforementioned measuring unit is It has a first measurement mode for measuring measurements with normal accuracy, and a second measurement mode for measuring measurements with higher accuracy, consuming more power than the first measurement mode. A thermal runaway prediction detection device according to configuration 1 or 2, wherein while the first determination mode is set, a measurement value is measured in the first measurement mode, and if a sign of thermal runaway is detected while the first determination mode is set and the setting unit sets the second determination mode, the measurement value is measured in the second measurement mode. [Structure 4] The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. A thermal runaway prediction device according to any one of configurations 1 to 3, wherein at least one of the input / output period of the fluctuating current, the amplitude of the fluctuating current, and the measurement period differs between the first measurement mode and the second measurement mode. [Composition 5] The energy storage unit is a battery pack (40) consisting of a plurality of battery cells (42) or battery modules (41), During the first determination mode, the measurement unit selects any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets and performs one measurement on each measurement target. The measurement unit inputs or outputs a fluctuating current to the object to be measured for a predetermined period of time and measures the voltage fluctuation of the object to be measured in response to the fluctuating current as a measured value. The determination unit, Based on the voltage fluctuation which is the measured value, the impedance of the object to be measured is calculated. A thermal runaway prediction device according to any one of configurations 1 to 4, which, during the first determination mode, detects signs of thermal runaway based on whether the difference, quotient, or average value of multiple measured impedances is within their respective allowable ranges. [Composition 6] The thermal runaway prediction detection device according to configuration 5, wherein the measurement unit, in the first determination mode, sets the time from the start of measurement of the first measurement target to the completion of measurement of the last measurement target to a predetermined time. [Composition 7] The measurement unit measures the voltage fluctuation of the object to be measured in response to the fluctuating current for a predetermined measurement time for each object to be measured. The thermal runaway prediction detection device according to configuration 5 or 6, wherein, during the first determination mode, at least a portion of the measurement time for each measurement target overlaps with the measurement time for other measurement targets. [Structure 8] The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The measurement unit is configured to, during the first determination mode, select any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets, and to perform a measurement once for each measurement target. Each measurement target is arranged at least at a certain distance apart in the thermal runaway prediction device according to any of configurations 1 to 7. [Composition 9] The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The measurement unit is configured to, during the first determination mode, select any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets, and to perform a measurement once for each measurement target. The thermal runaway prediction device according to any of configurations 1 to 8, wherein at least one of the measurement targets is monitored by a temperature sensor. [Configuration 10] The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The thermal runaway prediction detection device according to any of configurations 1 to 9, wherein the measurement unit measures any battery cell or battery module from among a plurality of battery cells or battery modules in the first determination mode, and measures all battery cells or battery modules in the second determination mode. [Composition 11] The determination unit consists of a first arithmetic processing unit (54) and a second arithmetic processing unit (72) that can communicate with the first arithmetic processing unit. The first arithmetic processing unit, while restricting communication with the second arithmetic processing unit during the first determination mode until signs of thermal runaway are detected, calculates impedance by processing the measured values ​​measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The thermal runaway prediction device according to any of configurations 1 to 10, wherein the second calculation processing unit, when the second determination mode is set, causes the first calculation processing unit to calculate impedance, receives the calculated multiple impedances, calculates the change patterns of the received multiple impedances, and detects signs of thermal runaway from the calculation results. [Composition 12] The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The thermal runaway prediction device according to any one of configurations 1 to 11, wherein the determination unit detects that there is a sign of thermal runaway in the second determination mode if the rate of change of the real part of the 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 impedance of the energy storage unit becomes 0, is greater than a threshold. [Composition 13] The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The measurement unit is capable of measuring the voltage fluctuation by a first measurement mode in which the wavenumber of the fluctuating current input and output to the energy storage unit during measurement is a first number, and a second measurement mode in which the wavenumber is a second number greater than the first number. The measurement unit measures the measurement value in the first measurement mode while the first determination mode is being set. If a sign of thermal runaway is detected while the first determination mode is being set and the setting unit sets the second determination mode, the measurement unit measures the measurement value in the second measurement mode. The thermal runaway prediction device according to any one of configurations 1 to 11, wherein the determination unit detects that there is a sign of thermal runaway when, in the second determination mode, the rate of change of the real part of the 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 impedance calculated based on the voltage fluctuation becomes 0 is greater than a threshold. [Composition 14] If the setting unit detects signs of thermal runaway while the first determination mode is being set, it sets the second determination mode. The thermal runaway prediction detection device according to any of configurations 1 to 13, wherein the determination unit detects signs of thermal runaway while the first determination mode is being set and the setting unit sets the second determination mode, and determines the signs of thermal runaway from the measured values ​​measured while the first determination mode is being set and one or more measured values ​​measured after the start of the second determination mode. [Composition 15] A thermal runaway prediction detection program implemented by a thermal runaway prediction detection device (50, 70) that detects signs of thermal runaway in the energy storage units (40, 41, 42) mounted on a mobile body, A measurement process for measuring a measurement value indicating the battery state of the aforementioned energy storage unit, A determination process for detecting signs of thermal runaway includes a first determination mode in which the measurement process measures values ​​at predetermined timings and detects signs of thermal runaway based on those values, and a second determination mode in which the measurement process measures values ​​at multiple timings, identifies the pattern of change in the battery state from those values, and detects signs of thermal runaway based on the pattern of change, A thermal runaway prediction detection program that performs a setting process to set the first determination mode when the vehicle is stopped, and to set the second determination mode when the vehicle is started. [Explanation of symbols]

[0153] 10...Power supply system, 40...Battery pack, 41...Battery module, 42...Battery cell, 50...Battery measurement unit, 51...AC current generation unit, 52...Voltage response measurement unit, 53...Modulation signal generator, 54...First arithmetic processing unit, 70...Battery control ECU, 71...Setting unit, 72...Second arithmetic processing unit.

Claims

1. A thermal runaway prediction device (50, 70) that detects signs of thermal runaway in the energy storage units (40, 41, 42) mounted on a mobile vehicle, A measuring unit (52) that measures a measurement value indicating the battery state of the power storage unit, A determination unit (54, 72) for detecting signs of thermal runaway includes a first determination mode in which the measurement unit measures a value at a predetermined timing and detects signs of thermal runaway based on the value, and a second determination mode in which the measurement unit measures a value at multiple timings, identifies the pattern of change in the battery state from the value, and detects signs of thermal runaway based on the pattern of change. A thermal runaway prediction detection device comprising a setting unit (71) that sets the first determination mode when the vehicle is stopped and sets the second determination mode when the moving body is started.

2. The thermal runaway warning detection device according to claim 1, wherein the setting unit, when the determination unit detects signs of thermal runaway while the first determination mode is being set, sets a second determination mode and causes the determination unit to detect signs of thermal runaway in the second determination mode.

3. The aforementioned measuring unit is It has a first measurement mode for measuring measurements with normal accuracy, and a second measurement mode for measuring measurements with higher accuracy, which consumes more power than the first measurement mode. The thermal runaway prediction detection device according to claim 1, wherein while the first determination mode is being set, a measurement value is measured in the first measurement mode, and if a sign of thermal runaway is detected while the first determination mode is being set and the setting unit sets the second determination mode, the measurement value is measured in the second measurement mode.

4. The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The thermal runaway prediction device according to claim 3, wherein at least one of the input / output period of the fluctuating current, the amplitude of the fluctuating current, and the measurement period differs between the first measurement mode and the second measurement mode.

5. The energy storage unit is a battery pack (40) consisting of a plurality of battery cells (42) or battery modules (41), During the first determination mode, the measurement unit selects any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets and performs one measurement on each measurement target. The measurement unit inputs or outputs a fluctuating current to the object to be measured for a predetermined period of time and measures the voltage fluctuation of the object to be measured in response to the fluctuating current as a measured value. The determination unit, Based on the voltage fluctuation which is the measured value, the impedance of the object to be measured is calculated. A thermal runaway prediction device according to any one of claims 1 to 4, wherein, in the first determination mode, a thermal runaway precursor is detected based on whether the difference, quotient, or average value of multiple measured impedances is within their respective allowable ranges.

6. The thermal runaway prediction device according to claim 5, wherein the measurement unit, in the first determination mode, sets the time from the start of measurement of the first measurement target to the completion of measurement of the last measurement target to within a predetermined time.

7. The measurement unit measures the voltage fluctuation of the object to be measured in response to the fluctuating current for a predetermined measurement time for each object to be measured. The thermal runaway prediction device according to claim 5, wherein, during the first determination mode, at least a portion of the measurement time for each measurement target overlaps with the measurement time for other measurement targets.

8. The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The measurement unit is configured to, during the first determination mode, select any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets, and to perform one measurement for each measurement target. A thermal runaway prediction device according to any one of claims 1 to 4, wherein each measurement target is arranged at a distance of at least a certain interval.

9. The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The measurement unit is configured to, during the first determination mode, select any two or more battery cells or battery modules from among a plurality of battery cells or battery modules as measurement targets, and to perform one measurement for each measurement target. The thermal runaway prediction device according to any one of claims 1 to 4, wherein at least one of the measurement targets has its temperature monitored by a temperature sensor.

10. The energy storage unit is a battery pack consisting of multiple battery cells or battery modules. The thermal runaway prediction device according to any one of claims 1 to 4, wherein the measurement unit measures any battery cell or battery module from among a plurality of battery cells or battery modules during the first determination mode, and measures all battery cells or battery modules during the second determination mode.

11. The determination unit consists of a first arithmetic processing unit (54) and a second arithmetic processing unit (72) that can communicate with the first arithmetic processing unit. The first arithmetic processing unit, while restricting communication with the second arithmetic processing unit during the first determination mode until signs of thermal runaway are detected, calculates impedance by processing the measured values ​​measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The thermal runaway prediction device according to any one of claims 1 to 4, wherein the second calculation processing unit, when the second determination mode is set, causes the first calculation processing unit to calculate impedance, receives the calculated plurality of impedances, calculates the change pattern of the received plurality of impedances, and detects signs of thermal runaway from the calculation results.

12. The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The thermal runaway prediction device according to any one of claims 1 to 4, wherein the determination unit detects that there is a sign of thermal runaway in the second determination mode if the rate of change of the real part of the 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 impedance of the energy storage unit becomes 0 is greater than a threshold.

13. The measuring unit inputs or outputs a fluctuating current to the energy storage unit and measures the voltage fluctuation of the energy storage unit in response to the fluctuating current. The determination unit calculates impedance by processing the voltage fluctuation measured by the measurement unit, and detects signs of thermal runaway from the calculated impedance. The measurement unit is capable of measuring the voltage fluctuation by a first measurement mode in which the wavenumber of the fluctuating current input and output to the energy storage unit during measurement is a first number, and a second measurement mode in which the wavenumber is a second number greater than the first number. The measurement unit measures the measurement value in the first measurement mode while the first determination mode is being set. If a sign of thermal runaway is detected while the first determination mode is being set and the setting unit sets the second determination mode, the measurement unit measures the measurement value in the second measurement mode. The thermal runaway prediction device according to any one of claims 1 to 4, wherein the determination unit detects that there is a sign of thermal runaway when, in the second determination mode, the rate of change of the real part of the 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 impedance calculated based on the voltage fluctuation becomes 0 is greater than a threshold.

14. If the setting unit detects signs of thermal runaway while the first determination mode is being set, it sets the second determination mode. The thermal runaway prediction detection device according to any one of claims 1 to 4, wherein the determination unit detects signs of thermal runaway while the first determination mode is being set and the setting unit sets the second determination mode, and determines signs of thermal runaway from the measured values ​​measured while the first determination mode is being set and one or more measured values ​​measured after the start of the second determination mode.

15. A thermal runaway prediction detection program implemented by a thermal runaway prediction detection device (50, 70) that detects signs of thermal runaway in the energy storage units (40, 41, 42) mounted on a mobile body, A measurement process for measuring a measurement value indicating the battery state of the aforementioned energy storage unit, A determination process for detecting signs of thermal runaway includes a first determination mode in which the measurement process measures values ​​at predetermined timings and detects signs of thermal runaway based on those values, and a second determination mode in which the measurement process measures values ​​at multiple timings, identifies the pattern of change in the battery state from those values, and detects signs of thermal runaway based on the pattern of change, A thermal runaway prediction detection program that performs a setting process to set the first determination mode when the vehicle is stopped, and to set the second determination mode when the vehicle is started.

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