Method, device and system for detecting thermal runaway of battery, vehicle and equipment

Abstract

The invention discloses a method, device and system for detecting thermal runaway of a battery, a vehicle and equipment, and relates to the technical field of batteries. A specific embodiment of the method comprises the following steps: acquiring a current state of charge of a battery pack; according to the current charge state, determining a target gain multiple for amplifying an output signal of a pressure sensor and a pressure threshold value and / or a pressure change rate threshold value for thermal runaway judgment; according to the target gain multiple, amplifying an output signal of a pressure sensor in the battery pack to obtain an amplified signal; according to whether the amplified signal meets the pressure threshold value and / or the pressure change rate threshold value, whether thermal runaway happens to the battery or not is determined. According to the embodiment, thermal runaway of the battery can be detected in time.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method, apparatus, system, vehicle, and equipment for detecting battery thermal runaway. Background Technology

[0002] Battery thermal runaway occurs when the rate of heat generation inside the battery is much higher than the rate of heat dissipation, leading to a large accumulation of heat. This triggers a series of exothermic chemical reactions inside the battery, causing the temperature to rise rapidly in a very short time, ultimately resulting in battery fire, explosion, and the release of toxic gases.

[0003] In the process of realizing this invention, the inventors discovered that the prior art has at least the following problems: the gas production rate and total amount are different under different states of charge (SOC) of the battery. If a uniform detection standard is used to detect battery thermal runaway, it will lead to a low accuracy rate in detecting thermal runaway. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a method, apparatus, battery management unit, system, vehicle, and equipment for detecting battery thermal runaway, which can detect battery thermal runaway in a timely manner.

[0005] A method for detecting battery thermal runaway includes: Obtain the current state of charge of the battery pack; Based on the current state of charge, determine the target gain factor for amplifying the output signal of the pressure sensor and the pressure threshold and / or pressure change rate threshold for thermal runaway detection; Amplify the output signal of the pressure sensor inside the battery pack according to the target gain factor to obtain the amplified signal; Whether the battery has experienced thermal runaway is determined based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

[0006] The step of obtaining the current state of charge of the battery pack includes: Receive the real-time state of charge (SOC) of the battery pack from the battery management system, or calculate the real-time SOC based on the battery parameters collected by the analog front-end chip in the battery management system. For cases where the real-time state of charge is less than or equal to the lowest state of charge, or greater than or equal to the highest state of charge, the real-time state of charge is calibrated using an open-circuit voltage. For cases where the real-time state of charge is greater than the minimum state of charge but less than the maximum state of charge, the real-time state of charge is calibrated using the cell surface expansion force. The calibrated real-time state of charge is determined as the current state of charge of the battery pack.

[0007] The method of calibrating the real-time state of charge using the cell surface expansion force includes: Determine the current battery health status of the battery pack; The current rate of change of the expansion force of the cell surface corresponding to the real-time state of charge of the battery pack is highly sensitive to the change of state of charge. Therefore, the real-time state of charge is calibrated by using the state of charge corresponding to the current rate of change of expansion force and the current state of battery health in the preset mapping relationship between expansion force change rate, battery health state and state of charge. If the rate of change of the current expansion force of the cell surface expansion force corresponding to the real-time state of charge of the battery pack is low in sensitivity to the change of state of charge, then the mapping relationship and open-circuit voltage are used to calibrate the real-time state of charge.

[0008] The step of calibrating the current state of charge using the mapping relationship and open-circuit voltage includes: Based on the mapping relationship, determine the first calibrated state of charge corresponding to the current rate of change of expansion force and the current state of battery health; The real-time state of charge is calibrated using open-circuit voltage to obtain a second calibrated state of charge; If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is less than or equal to the calibration threshold, then the current state of charge is calibrated using the first calibration state of charge. If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is greater than the calibration threshold, then the current state of charge is calibrated using the second calibration state of charge.

[0009] Determining the target gain factor for amplifying the pressure sensor output signal based on the current state of charge includes: The gain mapping relationship between different charge state ranges and gain factors is pre-stored, and the gain mapping relationship is configured such that the lower the charge state, the higher the target gain factor; Query the interval to which the current state of charge belongs, and determine the corresponding gain factor as the target gain factor.

[0010] The pressure threshold and / or pressure change rate threshold used for thermal runaway detection include: When the current state of charge is in the high state of charge range, the pressure threshold for thermal runaway detection is configured as the first pressure threshold. When the current state of charge is in the intermediate state of charge range, the pressure threshold for thermal runaway detection is configured as a second pressure threshold, which is less than the first pressure threshold. When the current state of charge is in the low state of charge range, the pressure threshold for thermal runaway detection is configured as a third pressure threshold and / or a pressure change rate threshold, wherein the third pressure threshold is less than the second pressure threshold.

[0011] Before the pressure threshold for determining thermal runaway is configured as the second pressure threshold, the method further includes: The current state of charge is in the intermediate state of charge range, and the initial gas production rate of thermal runaway is controlled by the electrochemical polarization process. The second pressure threshold is determined as a linear function of the current state of charge.

[0012] Before the pressure threshold for determining thermal runaway is configured as the third pressure threshold and / or the pressure change rate threshold, the method further includes: The current state of charge is in the low state of charge range, the concentration of lithium ions in the negative electrode is reduced, and the initial gas production pressure of thermal runaway is proportional to the square root of the current state of charge. The third pressure threshold is determined based on the square root function of the current state of charge.

[0013] The step of determining whether the battery has experienced thermal runaway based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold includes: When the current state of charge is in the low state of charge range If the pressure value corresponding to the amplified signal is greater than or equal to the third pressure threshold, then thermal runaway is determined to have occurred. or, If the instantaneous pressure change rate or average pressure change rate corresponding to the amplified signal is greater than the pressure change rate threshold, then thermal runaway is determined to have occurred.

[0014] The battery pack is a lithium iron phosphate battery pack or a ternary lithium battery pack.

[0015] According to a second aspect of the present invention, an apparatus for detecting battery thermal runaway is provided, comprising: The acquisition module is used to acquire the current state of charge of the battery pack; The parameter module is used to determine the target gain factor of the amplified pressure sensor output signal and the pressure threshold and / or pressure change rate threshold for thermal runaway judgment based on the current state of charge. An amplification module is used to amplify the output signal of the pressure sensor in the battery pack according to the target gain factor, so as to obtain an amplified signal. The judgment module is used to determine whether thermal runaway has occurred based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

[0016] According to a third aspect of the present invention, a battery management unit is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method described above.

[0017] According to a fourth aspect of the present invention, a system for detecting battery thermal runaway is provided, including a pressure sensor disposed in a battery pack and a battery management unit as described above.

[0018] According to a fifth aspect of the present invention, a vehicle is provided, including the apparatus for detecting battery thermal runaway as described above.

[0019] According to a sixth aspect of the present invention, an electronic device for detecting battery thermal runaway is provided, comprising: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors perform the methods described above.

[0020] One embodiment of the above invention has the following advantages or beneficial effects: It utilizes a target gain factor to amplify the output signal of the pressure sensor within the battery pack, thereby improving the resolution of the output signal. Then, it determines the occurrence of thermal runaway based on the pressure threshold and / or pressure change rate threshold for thermal runaway detection. This method is applicable to different states of charge, thus enabling timely detection of battery thermal runaway.

[0021] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0022] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the main process of a method for detecting battery thermal runaway according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the process for calibrating the real-time state of charge according to an embodiment of the present invention; Figure 3 This is the SOC-OCV curve of a battery according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the process for calibrating the real-time state of charge using the cell surface expansion force according to an embodiment of the present invention; Figure 5 This is a flowchart illustrating the process of determining the target gain factor according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the process for determining parameters for thermal runaway according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the main structure of a device for detecting battery thermal runaway according to an embodiment of the present invention; Figure 8 This is an exemplary system architecture diagram in which embodiments of the present invention can be applied; Figure 9 This is a schematic diagram of the structure of a computer system suitable for implementing terminal devices or servers of the present invention. Detailed Implementation

[0023] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0024] In order to detect battery thermal runaway in a timely manner, the following technical solutions in the embodiments of the present invention can be adopted.

[0025] See Figure 1 , Figure 1 This is a schematic diagram of the main process of a method for detecting battery thermal runaway according to an embodiment of the present invention, which specifically includes the following steps: S101. Obtain the current state of charge of the battery pack.

[0026] A battery pack consists of multiple battery cells connected in series and parallel. Multiple battery packs combined provide power to various devices such as vehicles. Battery packs are typically managed by components such as a Battery Management System (BMS) and a thermal management system.

[0027] Furthermore, the State of Charge (SOC) involved in this embodiment of the invention is the percentage of the battery pack's current remaining usable capacity relative to its current actual maximum usable capacity. As an example, the current SOC is received from the BMS, or calculated in real time based on battery parameters collected by the analog front-end (AFE) chip in the BMS. For instance, the SOC is updated every 5 minutes.

[0028] The technical solutions in the embodiments of the present invention are applicable to lithium iron phosphate (LFP) battery packs or ternary material (NCM) battery packs.

[0029] S102. Based on the current state of charge, determine the target gain factor for amplifying the output signal of the pressure sensor and the pressure threshold and / or pressure change rate threshold for thermal runaway detection.

[0030] In embodiments of the present invention, a pressure sensor is used to measure the air pressure inside the battery pack. For example, the pressure sensor is installed in the air duct of the battery pack. When multiple pressure sensors are installed in the battery pack, the maximum pressure value measured by multiple pressure sensors is used to detect battery thermal runaway, thereby improving detection sensitivity.

[0031] Under different states of charge, the output signal of the pressure sensor is relatively small, which seriously affects the accuracy of judging thermal runaway. A programmable gain amplifier (PGA) can be used to dynamically adjust the target gain factor of the pressure sensor output signal according to the state of charge (SOC).

[0032] Furthermore, pressure thresholds and / or pressure change rate thresholds are determined for thermal runaway detection based on the current state of charge. These pressure thresholds and / or pressure change rate thresholds change accordingly as the current state of charge changes.

[0033] S103. Amplify the output signal of the pressure sensor in the battery pack by the target gain factor to obtain the amplified signal.

[0034] The output signal of the pressure sensor inside the battery pack is amplified using a target gain factor to obtain the amplified signal. The amplified signal is significantly larger than the pressure sensor output signal, thereby improving the sensitivity of the output signal recognition.

[0035] S104. Determine whether the battery has experienced thermal runaway based on whether the amplified signal meets the pressure threshold and / or pressure change rate threshold.

[0036] If the amplified signal meets the pressure threshold and / or the pressure change rate threshold (i.e., the amplified signal is greater than the pressure threshold, and / or the pressure change rate of the amplified signal is greater than the pressure change rate threshold), thermal runaway of the battery is determined. As an example, the pressure change rate threshold is preferentially used as the criterion to improve the sensitivity of determining thermal runaway.

[0037] In the above embodiments, the pressure threshold and / or pressure change rate threshold used for thermal runaway detection are determined based on the current state of charge, improving the specificity of thermal runaway detection. The pressure sensor output signal is amplified using a target gain factor to enhance the sensitivity of thermal runaway detection, thus enabling timely detection of battery thermal runaway.

[0038] exist Figure 2 In this process, the current state of charge (SOC) of the battery pack is obtained and then calibrated. Specifically, this includes the following steps: S201. Receive the real-time state of charge (SOC) of the battery pack sent by the battery management system, or calculate the real-time SOC based on the battery parameters collected by the analog front-end chip in the battery management system.

[0039] Real-time state of charge (SOC) can be obtained from the battery management system (BMS) or calculated directly from the current collected by the AFE chip using the ampere-hour integration method. Considering that real-time SOC is the basis for determining the target gain, pressure threshold, and / or pressure change rate threshold, it is necessary to verify the real-time SOC to improve its accuracy.

[0040] S202. For cases where the real-time state of charge is less than or equal to the minimum state of charge, or greater than or equal to the maximum state of charge, the real-time state of charge is calibrated using open-circuit voltage; for cases where the real-time state of charge is greater than the minimum state of charge but less than the maximum state of charge, the real-time state of charge is calibrated using cell surface expansion force.

[0041] The method for verifying the real-time state of charge can be determined based on the relationship between the real-time state of charge and the minimum and maximum states of charge. As an example, Figure 3 The horizontal axis represents the State of Charge (SOC), and the vertical axis represents the Open Circuit Voltage (OCV). The minimum state of charge is 10%, and the maximum state of charge is 90%. When the real-time state of charge is less than or equal to 10%, or greater than or equal to 90%, the slope of the open circuit voltage (OCV) is significant, the voltage change sensitivity is high, and the calibration error is controllable.

[0042] If the real-time state of charge is less than or equal to the minimum state of charge, or greater than or equal to the maximum state of charge, and the voltage change sensitivity is high while the calibration error is controllable, then OCV calibration of the real-time state of charge is used.

[0043] A thin-film pressure sensor is installed on the surface of the battery cell to monitor changes in the surface expansion force. The thin-film pressure sensor collects the surface expansion force of the battery cell. When the real-time state of charge is greater than the minimum state of charge but less than the maximum state of charge, the surface expansion force of the battery cell is used to calibrate the real-time state of charge.

[0044] S203. Determine the calibrated real-time state of charge as the current state of charge of the battery pack.

[0045] Real-time estimates of the state of charge inevitably contain errors, and these errors accumulate over time. Without calibration, both the sensitivity and accuracy of detecting battery thermal runaway will decrease.

[0046] exist Figure 2 In the embodiments, the accuracy of the current state of charge is a prerequisite for thermal runaway detection. The real-time state of charge is calibrated by comparing the real-time state of charge with the lowest and highest states of charge.

[0047] Figure 4 This is a schematic diagram of the process for calibrating the real-time state of charge using the surface expansion force of the battery cell according to an embodiment of the present invention.

[0048] S401. Determine the current battery health status of the battery pack.

[0049] The battery management system updates the current state of battery health (SOH) using the most accurate charging data after each full charge. The current battery health of the battery pack can be determined from the battery management system.

[0050] S402. If the current rate of change of the expansion force of the cell surface corresponding to the real-time state of charge of the battery pack is highly sensitive to the change of state of charge, then the real-time state of charge is calibrated according to the state of charge corresponding to the current rate of change of expansion force and the current state of battery health in the preset mapping relationship between the rate of change of expansion force, the battery health state and the state of charge.

[0051] A mapping relationship between the rate of change of expansion force, battery health status, and state of charge (SOC) is established beforehand. The rate of change of cell surface expansion force is calculated by comparing the change in cell surface expansion force per unit time with the change in the current SOC. If the current rate of change of cell surface expansion force is >0.1N / %SOC, it is determined that the current rate of change of cell surface expansion force is highly sensitive to changes in SOC; if the current rate of change of cell surface expansion force is ≤0.1N / %SOC, it is determined that the current rate of change of cell surface expansion force is low in sensitivity to changes in SOC.

[0052] The current rate of change of the expansion force on the cell surface is highly sensitive to changes in the state of charge. The mapping relationship between the rate of change of expansion force and the state of health (SOH) of the battery is queried to calibrate the real-time state of charge.

[0053] In one embodiment of the present invention, the above mapping relationship needs to be updated accordingly as SOH changes. For example, if the change in SOH is greater than or equal to a change threshold, the mapping relationship is updated based on SOH, where the change threshold is 5%.

[0054] S402. If the rate of change of the current expansion force of the cell surface expansion force corresponding to the real-time state of charge of the battery pack is low in sensitivity to the change of state of charge, then the mapping relationship and open circuit voltage are used to calibrate the real-time state of charge.

[0055] The current rate of change of the expansion force on the cell surface is not very sensitive to changes in the state of charge. The real-time state of charge can be calibrated according to either the mapping relationship or the open-circuit voltage.

[0056] Method 1: The first calibrated state of charge is obtained by querying the mapping relationship between the cell surface expansion force change rate and SOH.

[0057] Method 2: The current state of charge is calibrated using the open-circuit voltage to obtain the second calibrated state of charge.

[0058] The real-time state of charge is calibrated by selecting either the first or second calibration state of charge using the absolute value of the difference between the first and second calibration states of charge.

[0059] If the absolute value of the difference between the first calibrated state of charge and the second calibrated state of charge is less than or equal to the calibration threshold, it indicates that the accuracy of the first calibrated state of charge is higher, and the real-time state of charge is calibrated using the first calibrated state of charge.

[0060] If the absolute value of the difference between the first and second calibrated states of charge is greater than the calibration threshold, it indicates that the second calibrated state of charge is more accurate, and the real-time state of charge is calibrated using the second calibrated state of charge. For example, if the calibration threshold is 5%.

[0061] If the absolute value is less than or equal to the calibration threshold, it indicates that the first calibration state of charge and the second calibration state of charge are sufficiently close. Since the first calibration state of charge can fully reflect the change in the expansion force on the cell surface, the first calibration state of charge is preferred. If the absolute value is greater than the calibration threshold, it indicates that the first calibration state of charge and the second calibration state of charge are different, and the more reliable second calibration state of charge can be used.

[0062] exist Figure 4 In the embodiments, the real-time charge state is calibrated by using the expansion force on the surface of the battery cell in a corresponding manner. The use of the above-mentioned corresponding manner can improve the accuracy of the charge state.

[0063] Figure 5 This is a schematic flowchart illustrating the determination of the target gain factor according to an embodiment of the present invention.

[0064] S501. Pre-store the gain mapping relationship between different charge state ranges and gain multiples. The gain mapping relationship is configured such that the lower the charge state, the higher the target gain multiple.

[0065] In the initial stages of battery thermal runaway, the gas production is small and slow, resulting in a very weak initial electrical signal from the pressure sensor. This initial signal is typically in the millivolt range. Such a weak signal is easily masked by inherent electronic noise in the circuit, environmental electromagnetic interference, and vehicle vibration noise. By using a gain factor, the weak pressure sensor output signal can be amplified, making its amplitude much higher than the noise level.

[0066] The following example illustrates the gain mapping relationship between setting the state of charge range and the gain factor. This gain mapping relationship reflects that the lower the state of charge, the higher the target gain factor.

[0067] Pressure sensor sensitivity: 10V / 250 kPa = 0.04 V / kPa. That is, for every 1 kPa pressure change, the output voltage changes by 0.04V (40mV).

[0068] Without using the target gain factor, the minimum pressure change that can be resolved is: (1 LSB) / (pressure sensor sensitivity) = 0.0008V / (0.04 V / kPa) = 0.02 kPa. This means that, theoretically, a change of 0.02 kPa can be sensed, but this is only an ideal situation that does not consider noise.

[0069] As an example, when SOC < 10%, a pressure change of 0.1 kPa needs to be detected. The original pressure sensor signal change corresponding to a pressure change of 0.1 kPa is: 0.1 kPa. 0.04 V / kPa = 0.004 V (4mV). A 4mV signal change is very close to, and may even be drowned out by circuit noise, making direct measurement unreliable. A programmable gain amplifier (PGA) is needed to amplify the pressure sensor output signal.

[0070] Specifically, the 0.1 kPa pressure change is amplified to a level that the analog-to-digital converter (ADC) can clearly and stably recognize. This signal change typically needs to be greater than 5-10 LSB. The original signal change from the pressure sensor is set to 0.8 mV.

[0071] Set the target to 10 LSB: 10 0.8mV = 8mV.

[0072] The required gain G = target voltage change / original voltage change = 0.008V / 0.004V = 2. However, this is only the minimum requirement. To allow sufficient margin and suppress noise, choose a higher gain, such as 4x or 8x.

[0073] See Table 1, which shows the gain mapping relationship between the state of charge interval and the gain factor.

[0074] Table 1

[0075] S502. Query the interval to which the current state of charge belongs, and determine the corresponding gain multiple as the target gain multiple.

[0076] In the above gain mapping relationship, the corresponding gain factor is determined based on the interval to which the current state of charge belongs. This is to amplify the pressure sensor output signal according to the gain factor.

[0077] exist Figure 5 In one embodiment, a pre-stored gain mapping relationship between the state of charge interval and the gain factor is used to determine the corresponding gain factor for amplifying the pressure sensor output signal, thereby dynamically improving the resolution of the pressure sensor output signal based on the current state of charge.

[0078] Figure 6 This is a schematic flowchart illustrating the process of determining parameters for thermal runaway according to an embodiment of the present invention. Based on the correspondence between the current state of charge and the state of charge region, corresponding thresholds are determined. For example, according to a first threshold and a second threshold for the state of charge, the area is divided into three intervals: a high state of charge region, a medium state of charge region, and a low state of charge region, where the first threshold is greater than the second threshold. For example, the first threshold for the state of charge is 30%, and the second threshold is 10%.

[0079] S601. When the current state of charge is in the high state of charge range, the pressure threshold for judging thermal runaway is configured as the first pressure threshold.

[0080] When the current state of charge (SOC) is in the high SOC range, it indicates that the active materials of the battery's positive and negative electrodes are in a highly usable state, and the stored chemical energy of the battery has reached or is close to its peak. Gas generation reactions in the battery pack are dominated by electrochemical polarization, and thermal runaway is assessed by setting a first pressure threshold. For example, the first pressure threshold is 5.0 kPa.

[0081] S602. When the current state of charge is in the intermediate state of charge range, the pressure threshold for judging thermal runaway is configured as a second pressure threshold, which is less than the first pressure threshold.

[0082] When the current state of charge (SOC) is in the intermediate range, the amount of gas produced in the battery pack decreases compared to the high SOC range. The amount of gas produced decreases with SOC, and the second pressure threshold decreases accordingly. Experimental data shows that when SOC = 10%, the pressure is approximately 1.2 kPa. The presence of thermal runaway can be determined using the corresponding second pressure threshold.

[0083] In one embodiment of the present invention, the current state of charge is in the intermediate state of charge range, with sufficient reactants on the electrode surface. The initial gas generation rate of thermal runaway is mainly dominated by electrochemical polarization, and the current state of charge reflects the reaction rate of electrochemical polarization. Considering that the battery voltage change is relatively gradual in the intermediate state of charge range, the relationship between the thermal runaway critical pressure threshold and the state of charge (SOC) is simplified to a linear function within this range. That is, the second pressure threshold P2 is determined as a linear function of the current state of charge.

[0084] As an example, the relationship between SOC and pressure is first determined through thermal runaway experiments, and then the parameters of the linear function are determined using function continuity and smoothness constraints. P2 = 8.0 SOC+2.6. The 8.0 slope comes from the thermal runaway experiment, while 2.6 is the solution to the continuity constraint at the first pressure threshold, ensuring the continuity of the pressure threshold in the intermediate and high charge states.

[0085] S603. When the current state of charge is in the low state of charge range, the pressure threshold for judging thermal runaway is configured as a third pressure threshold and / or a pressure change rate threshold, wherein the third pressure threshold is less than the second pressure threshold.

[0086] When the current state of charge is in the low state of charge range, to improve the accuracy of thermal runaway detection, a third pressure threshold and / or a pressure change rate threshold are used to determine whether thermal runaway has occurred. For example, if the pressure value corresponding to the amplified signal is greater than or equal to the third pressure threshold, thermal runaway is determined to have occurred. Alternatively, if the pressure change rate corresponding to the amplified signal is greater than the pressure change rate threshold, thermal runaway is determined to have occurred.

[0087] In one embodiment of the present invention, the current state of charge (SOC) is in a low SOC range, and the rate of gas generation reaction in the initial stage of battery thermal runaway is mainly controlled by the diffusion process of lithium ions in the negative electrode active material. According to Fick's diffusion law and diffusion-controlled electrochemical reaction kinetics, the reaction rate of gas generation reaction is inversely proportional to the square root of time. Since the current SOC is directly related to the concentration of remaining reactive lithium ions in the negative electrode, the third pressure threshold for accumulated thermal runaway gas generation pressure exhibits an approximate square root function relationship with SOC. That is, the initial thermal runaway gas generation pressure is proportional to the square root of the current SOC, and the third pressure threshold P3 is determined based on the square root function of the current SOC.

[0088] As an example, the square root function is more suitable for nonlinear gas production characteristics at low SOC compared to a linear function. The initial decrease in the third pressure threshold is smaller as the SOC decreases, while the decrease in the third pressure threshold increases later. The coefficients of the square root function are determined using the solution to the continuity constraint at the second pressure threshold to ensure the continuity of the pressure threshold in the medium and low state-of-charge (SOC) regions. P3 = 1.075 The square root function is used to further compress the threshold, solving the detection problem of low pressure caused by minimal gas production in the current low charge state range.

[0089] In one embodiment of the present invention, when the current state of charge (SOC) is in the low SOC range, a pressure threshold and / or a pressure change rate threshold can be used to determine whether thermal runaway has occurred. If the pressure value corresponding to the amplified signal meets the pressure threshold or the pressure change rate threshold, then thermal runaway is determined to have occurred. Using the above technical solution, at the current SOC = 5%, a pressure change rate of 0.5 kPa / s is sufficient to determine if thermal runaway has occurred. The sensitivity is 10 times higher than that of the prior art.

[0090] As an example, if the pressure value corresponding to the amplified signal is greater than or equal to the third pressure threshold, then thermal runaway is determined to have occurred. Alternatively, if the instantaneous pressure change rate or average pressure change rate corresponding to the amplified signal is greater than the pressure change rate threshold, then thermal runaway is determined to have occurred.

[0091] The instantaneous rate of change of pressure is the derivative of pressure with respect to time. It corresponds to the sampling interval of the pressure sensor. The instantaneous rate of change of pressure is used to quickly determine whether thermal runaway has occurred. When the instantaneous rate of change of pressure exceeds a pressure change rate threshold, it indicates a rapid pressure change, and thermal runaway has occurred or is about to occur violently.

[0092] The average pressure change rate is the average rate of change over a relatively long time window. A consistently positive average pressure change rate that increases slowly indicates the beginning of gas production within the battery pack. When the average pressure change rate exceeds a pressure change rate threshold, it indicates a pressure change and predicts that thermal runaway is imminent.

[0093] The pressure change rate threshold was obtained based on experimental data analysis. Specifically, thermal abuse tests were conducted on cells with different SOCs (especially low SOCs), and high-frequency data on pressure changes over time were collected. The pressure change rate range of the effective thermal runaway signal was analyzed, while pressure change rate data from a large number of interference sources were also collected. A value that could maximize the separation of thermal runaway and non-thermal runaway data was sought. For safety, a margin was added to the above value to obtain the pressure change rate threshold.

[0094] The following example uses a lithium iron phosphate battery pack as an example.

[0095] Receive the current state of charge from the BMS. The minimum state of charge is 10% and the maximum state of charge is 30%.

[0096] Referring to Table 2, the current states of charge are 40%, 20%, and 8%.

[0097] Table 2

[0098] For example, if the current state of charge is 40%, and the current state of charge is greater than the maximum state of charge, then the open-circuit voltage is used to calibrate the current state of charge.

[0099] The current state of charge (SOC) is 20%, which is greater than the minimum SOC and less than the maximum SOC. Based on the current SOC, the rate of change of surface expansion force of the battery cell is determined to be low-sensitive to changes in SOC. If the absolute value of the difference between the first and second calibrated SOCs is greater than a calibration threshold, the current SOC is calibrated using the second calibrated SOC.

[0100] If the current state of charge is 8%, or if the current state of charge is less than the minimum state of charge, then the open-circuit voltage is used to calibrate the current state of charge.

[0101] For the current state of charge, query the interval to which the current state of charge belongs, and determine the target gain multiple in Table 2.

[0102] Based on the current state of charge, query the interval to which the current state of charge belongs, and determine the pressure threshold in Table 2.

[0103] Using the gain factor and pressure threshold in Table 2, the minimum detectable gas production corresponding to the current state of charge can be determined. It is evident that as the current state of charge (SOC) decreases, the minimum detectable gas production decreases accordingly, thereby improving the sensitivity of gas detection.

[0104] See Table 3 for a comparison between the traditional and proposed solutions. As the State of Charge (SOC) decreases, the gas production of the battery pack decreases significantly. The traditional solution is only suitable for high SOC applications. This solution is applicable to various SOC scenarios. Regardless of the SOC range, it can achieve wake-up, i.e., determine if thermal runaway has occurred in the battery pack.

[0105] Table 3

[0106] By adopting the technical solution in the embodiments of the present invention, the minimum detectable production pressure value can be reduced from 5 kPa to 0.5 kPa, and the detection rate of low SOC thermal runaway can be increased by more than 92%.

[0107] See Figure 7 , Figure 7 This is a schematic diagram of the main structure of a device for detecting battery thermal runaway according to an embodiment of the present invention. The device for detecting battery thermal runaway can implement a method for detecting battery thermal runaway. The device for detecting battery thermal runaway specifically includes: The acquisition module 701 is used to acquire the current state of charge of the battery pack; Parameter module 702 is used to determine the target gain factor of the amplified pressure sensor output signal and the pressure threshold and / or pressure change rate threshold for thermal runaway judgment based on the current state of charge. Amplification module 703 is used to amplify the output signal of the pressure sensor in the battery pack according to the target gain factor to obtain the amplified signal; The judgment module 704 is used to determine whether the battery has experienced thermal runaway based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

[0108] In one embodiment of the present invention, the acquisition module 701 is used to receive the real-time state of charge of the battery pack sent by the battery management system, or to calculate the real-time state of charge in real time based on the battery parameters collected by the analog front-end chip in the battery management system. For cases where the real-time state of charge is less than or equal to the lowest state of charge, or greater than or equal to the highest state of charge, the current state of charge is calibrated using open-circuit voltage. For cases where the real-time state of charge is greater than the minimum state of charge but less than the maximum state of charge, the real-time state of charge is calibrated using the cell surface expansion force. The real-time state of charge obtained after calibration is determined as the current state of charge of the battery pack.

[0109] In one embodiment of the present invention, the acquisition module 701 is used to determine the current battery health status of the battery pack; The current rate of change of the expansion force of the cell surface corresponding to the real-time state of charge of the battery pack is highly sensitive to the change of state of charge. Therefore, the real-time state of charge is calibrated by using the state of charge corresponding to the current rate of change of expansion force and the current state of battery health in the preset mapping relationship between expansion force change rate, battery health state and state of charge. If the rate of change of the current expansion force of the cell surface expansion force corresponding to the real-time state of charge of the battery pack is low in sensitivity to the change of state of charge, then the mapping relationship and open-circuit voltage are used to calibrate the real-time state of charge.

[0110] In one embodiment of the present invention, the acquisition module 701 is used to determine a first calibrated state of charge corresponding to the current rate of change of expansion force and the current state of battery health according to the mapping relationship. The real-time state of charge is calibrated using open-circuit voltage to obtain a second calibrated state of charge; If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is less than or equal to the calibration threshold, then the current state of charge is calibrated using the first calibration state of charge. If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is greater than the calibration threshold, then the current state of charge is calibrated using the second calibration state of charge.

[0111] In one embodiment of the present invention, parameter module 702 is used to pre-store the gain mapping relationship between different charge state intervals and gain factors, wherein the gain mapping relationship is configured such that: the lower the charge state, the higher the target gain factor; Query the interval to which the current state of charge belongs, and determine the corresponding gain factor as the target gain factor.

[0112] In one embodiment of the present invention, parameter module 702 is configured to set the pressure threshold for thermal runaway judgment as a first pressure threshold when the current state of charge is in the high state of charge range. When the current state of charge is in the intermediate state of charge range, the pressure threshold for thermal runaway detection is configured as a second pressure threshold, which is less than the first pressure threshold. When the current state of charge is in the low state of charge range, the pressure threshold for thermal runaway detection is configured as a third pressure threshold and / or a pressure change rate threshold, wherein the third pressure threshold is less than the second pressure threshold.

[0113] In one embodiment of the present invention, parameter module 702 is used to determine the second pressure threshold as a linear function of the current state of charge, wherein the current state of charge is in the intermediate state of charge range and the initial gas production rate of thermal runaway is controlled by the electrochemical polarization process.

[0114] In one embodiment of the present invention, parameter module 702 is used to determine the third pressure threshold based on the square root function of the current state of charge, where the current state of charge is in a low state of charge range, the negative electrode lithium ion concentration is reduced, and the initial gas generation pressure of thermal runaway is proportional to the square root of the current state of charge.

[0115] In one embodiment of the present invention, when the current state of charge is in the low state of charge range, the parameter module 702 is used to determine that thermal runaway has occurred if the pressure value corresponding to the amplified signal is greater than or equal to the third pressure threshold. or, If the instantaneous pressure change rate or average pressure change rate corresponding to the amplified signal is greater than the pressure change rate threshold, then thermal runaway is determined to have occurred.

[0116] In one embodiment of the present invention, the battery pack is a lithium iron phosphate battery pack or a ternary material battery pack.

[0117] The battery management unit in this embodiment of the invention can execute the methods described in the above embodiments. This embodiment of the invention also discloses a system for detecting battery thermal runaway, including a pressure sensor disposed in the battery pack and the aforementioned battery management unit. The device for detecting battery thermal runaway in this embodiment of the invention can be applied to vehicles.

[0118] Figure 8 An exemplary system architecture 800 is shown, which can be applied to a method or apparatus for detecting battery thermal runaway according to embodiments of the present invention.

[0119] like Figure 8As shown, the vehicle system architecture 800 may include various systems, such as a driving control system 801, a power system 802, a sensor system 803, a control system 804, a lane change assist system 805, one or more peripheral devices 806, a power supply 807, a computer system 808, and a user interface 809. The method for detecting battery thermal runaway provided in this embodiment can be implemented through interaction with the aforementioned systems, or by controlling the systems through external devices, or by a robot driving the vehicle operating the systems. Optionally, the vehicle system architecture 800 may include more or fewer systems, and each system may include multiple components. Furthermore, each system and component of the vehicle system architecture 800 may be interconnected via wired or wireless means.

[0120] The powertrain 802 may include components that provide power to the vehicle. For example, the powertrain 802 may include an engine, an energy source, a transmission, wheels, tires, etc. The engine may be an internal combustion engine, an electric motor, an air-compressed engine, or other combinations of engines, such as a hybrid engine consisting of a gasoline engine and an electric motor, or a hybrid engine consisting of an internal combustion engine and an air-compressed engine. The engine converts the energy source into mechanical energy to supply the transmission. Examples of energy sources may include gasoline, diesel, other petroleum-based fuels, propane, other compressed gas-based fuels, ethanol, solar panels, batteries, and other electrical sources. The energy source may also provide energy to other systems in the vehicle. Furthermore, the transmission may include a gearbox, a differential, a drive shaft, and a clutch, etc.

[0121] The control system 804 may include software systems for implementing vehicle driving control, such as systems for analyzing the vehicle's surrounding environment, systems for pretensioning seat belts, systems for route planning, systems for avoiding obstacles, and vision systems for image analysis.

[0122] The power source 807 can provide power to various components of the vehicle. The power source 807 can be a rechargeable lithium-ion battery or a lead-acid battery.

[0123] The processor can be any conventional processor, such as a commercially available central processing unit (CPU). Alternatively, the processor can be a special-purpose device such as an application-specific integrated circuit (ASIC) or other hardware-based processor. Those skilled in the art will understand that the processor, computer, or memory can actually include multiple processors, computers, or memories that may or may not be stored in the same physical housing. For example, memory can be a hard disk drive or other storage media located in a housing different from that of a computer. Therefore, references to processors or computers will be understood to include references to a collection of processors or computers or memories that may or may not operate in parallel. Unlike using a single processor to perform the steps described herein, some components, such as steering and deceleration components, may each have their own processor that performs only determinations related to the component's specific function.

[0124] It should be understood that the components described above are merely an example. In actual applications, components in the various modules or systems mentioned above may be added or removed as needed. Figure 8 This should not be construed as a limitation on the embodiments of this application.

[0125] The following is for reference. Figure 9 It shows a schematic diagram of the structure of a computer system 900 suitable for implementing a terminal device of the present invention. Figure 9 The terminal device shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0126] like Figure 9 As shown, the computer system 900 includes a central processing unit (CPU) 901, which can perform various appropriate actions and processes based on programs stored in read-only memory (ROM) 902 or programs loaded from storage section 908 into random access memory (RAM) 903. The RAM 903 also stores various programs and data required for the operation of the system 900. The CPU 901, ROM 902, and RAM 903 are interconnected via a bus 904. An input / output (I / O) interface 905 is also connected to the bus 904.

[0127] The following components are connected to I / O interface 905: an input section 906 including a keyboard, mouse, etc.; an output section 907 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 908 including a hard disk, etc.; and a communication section 909 including a network interface card such as a LAN card, modem, etc. The communication section 909 performs communication processing via a network such as the Internet. A drive 910 is also connected to I / O interface 905 as needed. A removable medium 911, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed on drive 910 as needed so that computer programs read from it can be installed into storage section 908 as needed.

[0128] In particular, according to the embodiments disclosed in this invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 909, and / or installed from removable medium 911. When the computer program is executed by central processing unit (CPU) 901, it performs the functions defined above in the system of this invention.

[0129] It should be noted that the computer-readable medium shown in this invention can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this invention, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0130] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0131] The modules described in the embodiments of the present invention can be implemented in software or hardware. The described modules can also be housed in a processor; for example, a processor can be described as including an acquisition module, a parameter module, an amplification module, and a judgment module. The names of these modules do not necessarily limit the module itself; for example, the acquisition module can also be described as "for acquiring the current state of charge of the battery pack".

[0132] In another aspect, the present invention also provides a computer-readable medium, which may be included in the device described in the above embodiments; or it may exist independently and not assembled into the device. The computer-readable medium carries one or more programs, which, when executed by the device, cause the device to include: Obtain the current state of charge of the battery pack; Based on the current state of charge, determine the target gain factor for amplifying the output signal of the pressure sensor and the pressure threshold and / or pressure change rate threshold for thermal runaway detection; Amplify the output signal of the pressure sensor inside the battery pack according to the target gain factor to obtain the amplified signal; Whether the battery has experienced thermal runaway is determined based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

[0133] According to the technical solution of this invention, the output signal of the pressure sensor inside the battery pack is amplified by a target gain factor to improve the resolution of the output signal. Then, thermal runaway is determined based on the pressure threshold and / or pressure change rate threshold for thermal runaway detection. This method is applicable to different states of charge, thus enabling timely detection of battery thermal runaway.

[0134] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. It should be noted that the acquisition, storage, and application of user personal information involved in the technical solutions of this disclosure comply with relevant laws and regulations and do not violate public order and good morals.

Claims

1. A method for detecting battery thermal runaway, characterized in that, include: Obtain the current state of charge of the battery pack; Based on the current state of charge, determine the target gain factor for amplifying the output signal of the pressure sensor and the pressure threshold and / or pressure change rate threshold for thermal runaway detection; Amplify the output signal of the pressure sensor inside the battery pack according to the target gain factor to obtain the amplified signal; Whether the battery has experienced thermal runaway is determined based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

2. The method for detecting battery thermal runaway according to claim 1, characterized in that, The step of obtaining the current state of charge of the battery pack includes: Receive the real-time state of charge (SOC) of the battery pack from the battery management system, or calculate the real-time SOC based on the battery parameters collected by the analog front-end chip in the battery management system. For cases where the real-time state of charge is less than or equal to the lowest state of charge, or greater than or equal to the highest state of charge, the real-time state of charge is calibrated using an open-circuit voltage. For cases where the real-time state of charge is greater than the minimum state of charge but less than the maximum state of charge, the real-time state of charge is calibrated using the cell surface expansion force. The calibrated real-time state of charge is determined as the current state of charge of the battery pack.

3. The method for detecting battery thermal runaway according to claim 2, characterized in that, The method of calibrating the real-time state of charge using the cell surface expansion force includes: Determine the current battery health status of the battery pack; The current rate of change of the expansion force of the cell surface corresponding to the real-time state of charge of the battery pack is highly sensitive to the change of state of charge. Therefore, the real-time state of charge is calibrated by using the state of charge corresponding to the current rate of change of expansion force and the current state of battery health in the preset mapping relationship between expansion force change rate, battery health state and state of charge. If the rate of change of the current expansion force of the cell surface expansion force corresponding to the real-time state of charge of the battery pack is low in sensitivity to the change of state of charge, then the mapping relationship and open-circuit voltage are used to calibrate the real-time state of charge.

4. The method for detecting battery thermal runaway according to claim 3, characterized in that, The step of calibrating the current state of charge using the mapping relationship and open-circuit voltage includes: Based on the mapping relationship, a first calibrated state of charge corresponding to the current rate of change of expansion force and the current battery health state is determined; The real-time state of charge is calibrated using open-circuit voltage to obtain a second calibrated state of charge; If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is less than or equal to the calibration threshold, then the current state of charge is calibrated using the first calibration state of charge. If the absolute value of the difference between the first calibration state of charge and the second calibration state of charge is greater than the calibration threshold, then the current state of charge is calibrated using the second calibration state of charge.

5. The method for detecting battery thermal runaway according to claim 1, characterized in that, Determining the target gain factor for amplifying the pressure sensor output signal based on the current state of charge includes: The gain mapping relationship between different charge state ranges and gain factors is pre-stored, and the gain mapping relationship is configured such that the lower the charge state, the higher the target gain factor; Query the interval to which the current state of charge belongs, and determine the corresponding gain factor as the target gain factor.

6. The method for detecting battery thermal runaway according to claim 1, characterized in that, The pressure threshold and / or pressure change rate threshold used for thermal runaway detection include: When the current state of charge is in the high state of charge range, the pressure threshold for thermal runaway detection is configured as the first pressure threshold. When the current state of charge is in the intermediate state of charge range, the pressure threshold for thermal runaway detection is configured as a second pressure threshold, which is less than the first pressure threshold. When the current state of charge is in the low state of charge range, the pressure threshold for thermal runaway detection is configured as a third pressure threshold and / or a pressure change rate threshold, wherein the third pressure threshold is less than the second pressure threshold.

7. The method for detecting battery thermal runaway according to claim 6, characterized in that, Before the pressure threshold for determining thermal runaway is configured as the second pressure threshold, the method further includes: The current state of charge is in the intermediate state of charge range, and the initial gas production rate of thermal runaway is controlled by the electrochemical polarization process. The second pressure threshold is determined as a linear function of the current state of charge.

8. The method for detecting battery thermal runaway according to claim 6, characterized in that, Before the pressure threshold for determining thermal runaway is configured as the third pressure threshold and / or the pressure change rate threshold, the method further includes: The current state of charge is in the low state of charge range, the concentration of lithium ions in the negative electrode is reduced, and the initial gas production pressure of thermal runaway is proportional to the square root of the current state of charge. The third pressure threshold is determined based on the square root function of the current state of charge.

9. The method for detecting battery thermal runaway according to claim 6, characterized in that, The step of determining whether the battery has experienced thermal runaway based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold includes: When the current state of charge is in the low state of charge range If the pressure value corresponding to the amplified signal is greater than or equal to the third pressure threshold, then thermal runaway is determined to have occurred. or, If the instantaneous pressure change rate or average pressure change rate corresponding to the amplified signal is greater than the pressure change rate threshold, then thermal runaway is determined to have occurred.

10. The method for detecting battery thermal runaway according to claim 1, characterized in that, The battery pack is a lithium iron phosphate battery pack or a ternary lithium battery pack.

11. A device for detecting battery thermal runaway, characterized in that, include: The acquisition module is used to acquire the current state of charge of the battery pack; The parameter module is used to determine the target gain factor of the amplified pressure sensor output signal and the pressure threshold and / or pressure change rate threshold for thermal runaway judgment based on the current state of charge. An amplification module is used to amplify the output signal of the pressure sensor in the battery pack according to the target gain factor, so as to obtain an amplified signal. The judgment module is used to determine whether thermal runaway has occurred based on whether the amplified signal meets the pressure threshold and / or the pressure change rate threshold.

12. A battery management unit, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method as described in any one of claims 1-10.

13. A system for detecting battery thermal runaway, characterized in that, It includes a pressure sensor disposed in the battery pack and a battery management unit as described in claim 12.

14. A vehicle, characterized in that, Includes the device for detecting battery thermal runaway as described in claim 11.

15. An electronic device for detecting battery thermal runaway, characterized in that, include: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-10.

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