Power battery spray valve and thermal runaway critical energy determination method
By recording temperature and pressure curves on the power battery, calculating the critical energy of the injection valve and thermal runaway using a fitting model, and constructing a safety boundary diagram, the problem of unified judgment of thermal runaway risk of lithium-ion power batteries under different heating conditions is solved, realizing quantitative analysis and safety assessment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANAN UNIV
- Filing Date
- 2026-02-09
- Publication Date
- 2026-06-12
AI Technical Summary
In the existing technology, the thermal runaway risk of lithium-ion power batteries under different heating power and heat dissipation conditions is difficult to describe in a unified manner, the energy state of the injection valve lacks quantitative characterization, and there is a lack of a unified calculation method across multiple power continuous heating conditions.
By deploying temperature and pressure sensors on the power battery, temperature-time and pressure-time curves are recorded. Fitting parameters are extracted using a nonlinear fitting model, and the equivalent total heat dissipation coefficient and cell equivalent heat capacity are calculated. Combined with the valve injection time and thermal runaway time, the net input energy is determined, a power-time-energy safety boundary diagram is constructed, and the safety zone is divided.
This method enables unified determination under different heating power and heat dissipation conditions, and provides a quantitative description of the critical energy of the injection valve and the critical energy of thermal runaway. This improves the operability and scalability of the method and provides a theoretical basis for battery safety design.
Smart Images
Figure CN122193971A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery thermal runaway determination technology, and more specifically, to a power battery injection valve and a method for determining the critical energy of thermal runaway. Background Technology
[0002] With the widespread application of new energy vehicles and energy storage power stations, the risk of thermal runaway of lithium-ion power batteries under external thermal abuse conditions (continuous heating, fire, etc.) has attracted widespread attention. Existing research generally triggers thermal runaway through continuous heating tests, recording data such as temperature, time, pressure, and gas to analyze the thermal stability and safety boundaries of the battery.
[0003] Currently, thermal runaway is often categorized using temperature thresholds (such as a temperature measurement point reaching 150–200℃) or triggering time under a fixed continuous heating power as criteria. However, under different heating powers and heat dissipation conditions, the heating rate and temperature distribution of the battery vary, making it difficult to uniformly describe the thermal runaway risk under different operating conditions with a single temperature threshold. While the spray valve is generally considered a safety protection measure, in existing technologies, the energy state inside the cell when the spray valve occurs lacks quantitative characterization, and the "energy buffering" effect of the spray valve in delaying thermal runaway lacks a unified characterization. Although the concept of "critical energy for thermal runaway" exists in existing literature, it is mostly an estimation of the total input energy under a single operating condition. There is a lack of a complete method based on lumped parameter thermal models that can uniformly calculate the net input energy across multiple continuous heating conditions and simultaneously provide the critical energy for the spray valve and the critical energy for thermal runaway.
[0004] Therefore, it is necessary to design a method for determining the critical energy of thermal runaway in a power battery injection valve to solve the problems existing in the current technology. Summary of the Invention
[0005] In view of this, the present invention proposes a method for determining the critical energy of the injection valve and thermal runaway of a power battery, aiming to solve the problem of lacking a unified calculation of net input energy based on a lumped parameter thermal model that can span multiple power continuous heating conditions and simultaneously give the critical energy of the injection valve and the critical energy of thermal runaway.
[0006] This invention proposes a method for determining the critical energy of thermal runaway in a power battery injection valve, including: The power battery to be tested is charged to a preset state of charge, temperature sensors are installed at the corresponding positions of the power battery, and it is placed in a sealed environment. Under a first preset power, the power battery is continuously heated, and a first temperature-time curve is recorded. Fitting parameters are extracted from the first temperature-time curve through a nonlinear fitting model, and the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell are calculated based on the fitting parameters. The power battery is continuously heated under a second preset power set, which includes several different preset powers; the second temperature-time curve and pressure-time curve of each preset power in the second preset power set are recorded, and the valve injection time is determined by detecting that the pressure change rate exceeds a preset threshold based on the pressure-time curve; the thermal runaway time is determined by detecting that the temperature change rate exceeds a preset threshold based on the second temperature-time curve. Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, the heat dissipation loss per unit time is calculated, and the net input energy of the power battery is calculated cumulatively. The critical energy of the injection valve is determined by combining the injection valve time with the net input energy; the critical energy of thermal runaway is determined by combining the thermal runaway time with the net input energy; based on the critical energy of the injection valve and the critical energy of thermal runaway, a power-time-energy safety boundary diagram is constructed to divide the safe region, the injection valve-non-runaway region and the thermal runaway region.
[0007] Furthermore, when extracting fitting parameters from the temperature-time curve through nonlinear fitting, the process includes: A nonlinear fitting template was established using Origin, and the temperature-time curve was fitted with parameters using a nonlinear fitting model to obtain the fitting parameters.
[0008] Furthermore, when calculating the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, the following are included: The equivalent total heat dissipation coefficient between the battery cell and the environment is determined based on the fitting parameters and the first preset power. The equivalent heat capacity of the battery cell is determined based on the fitting parameters and the equivalent total heat dissipation coefficient.
[0009] Furthermore, when recording the second temperature-time curve and pressure-time curve for each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, the following steps are taken: Record the pressure-time curves under each preset power condition within the second preset power set; Extract the instantaneous pressure change rate of the pressure-time curve. When the instantaneous pressure change rate of three consecutive sampling points exceeds the preset pressure change rate threshold, determine the start time of the three consecutive sampling points as the valve spraying time.
[0010] Furthermore, when recording the second temperature-time curve and pressure-time curve of each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, the process also includes: Record the second temperature-time curves under each preset power condition within the second preset power set; The instantaneous temperature change rate of the second temperature-time curve is extracted by calculating the temperature difference per unit time. When the instantaneous temperature change rate increases to three times the heating rate per unit time and the duration exceeds the preset duration threshold, the starting moment of the temperature change is determined as the thermal runaway time.
[0011] Furthermore, when determining the net input energy of the power battery based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, the following steps are included: Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, combined with the ambient temperature and real-time temperature data of the power battery, the heat dissipation loss per unit time is calculated; and the unit net input energy is calculated; the unit net input energy during the heating process is accumulated to obtain the final net input energy.
[0012] Furthermore, when determining the critical energy of the injection valve by combining the injection valve time with the net input energy, the following steps are included: Based on the determined valve timing, determine the net input energy value of the valve for the corresponding valve timing; The net input energy value of the injection valve is taken as the critical energy of the injection valve; the critical energy of the injection valve is the minimum energy threshold required for the power battery to produce the injection valve phenomenon. Statistical analysis was performed on the critical energy of the injection valve under each preset power condition within the second preset power set to determine the critical energy range data of the injection valve.
[0013] Furthermore, when determining the critical energy for thermal runaway by combining the thermal runaway time with the net input energy, the following steps are included: Based on the determined thermal runaway time, determine the net thermal runaway energy input value corresponding to the thermal runaway time; The net input energy value of thermal runaway is taken as the critical energy of thermal runaway, which is the minimum energy threshold required for the power battery to experience thermal runaway. Statistical analysis was performed on the critical energy of thermal runaway under each preset power condition within the second preset power set to determine the range of critical energy of thermal runaway.
[0014] Furthermore, when constructing the power-time-energy safety boundary diagram based on the critical energy of the injection valve and the critical energy of thermal runaway, it includes: A three-dimensional power-time-energy safety boundary diagram is drawn based on the critical energy range data of the injection valve, the critical energy range data of thermal runaway, the equivalent total heat dissipation coefficient, the equivalent heat capacity of the battery cell, the injection valve time, and the thermal runaway time. The power-time-energy safety boundary diagram is used to divide the area into a safe zone, a valve-non-runaway zone, and a thermal runaway zone.
[0015] Furthermore, it also includes: Based on the net input energy, the time required to reach the critical energy of the injection valve or the critical energy of thermal runaway under other power conditions is calculated. Based on the power-time-energy safety boundary diagram, predict the valve behavior and thermal runaway behavior of the power battery under different external heat source conditions.
[0016] Compared with existing technologies, the advantages of this invention are as follows: It proposes a method for determining the injection valve and thermal runaway based on net input energy, introducing two critical energy criteria: the critical energy of the injection valve and the critical energy of thermal runaway. This allows for a unified description of thermal runaway risk across different heating powers and heat dissipation conditions, avoiding the limitations of traditional methods that rely solely on temperature thresholds. By utilizing continuous low-power heating and fitting a lumped-parameter thermal model, the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell are obtained. These parameters are then uniformly applied to energy calculations under medium-to-high power conditions, avoiding complex modeling for each power or operating condition, improving the operability and scalability of the method, and achieving standardization of parameter calibration. By providing the critical energy of the injection valve and the critical energy of thermal runaway under the same energy scale, the difference between the critical energy of thermal runaway and the critical energy of thermal runaway under high-power conditions quantitatively illustrates the energy buffering effect of the injection valve on thermal runaway. This helps to scientifically explain the phenomenon of injection valves not running out of control under low power conditions, providing a theoretical basis for battery safety design. Relying on common fitting software (such as Origin) and spreadsheet software (such as Excel), the data processing workflow described in this paper has been implemented using Origin and Excel. This workflow can also be programmed in environments such as Matlab / Python, and is easy to reproduce and deploy in different laboratory and enterprise environments, reducing the technical threshold and implementation cost. By constructing a power-time-energy safety boundary diagram, the safe zone, the non-runaway zone, and the thermal runaway zone are distinguished, providing an intuitive and quantifiable assessment basis for thermal management system design, thermal fault simulation, and safety strategy formulation, thus transforming battery safety assessment from qualitative judgment to quantitative analysis. Attached Figure Description
[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart of the power battery injection valve and thermal runaway critical energy determination method provided in the embodiments of the present invention. Detailed Implementation
[0018] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0019] For this, please refer to Figure 1 As shown, this application proposes a method for determining the critical energy of thermal runaway in a power battery injection valve, including: S100: Charge the power battery under test to a preset state of charge, install temperature sensors at the corresponding positions of the power battery, and place it in a sealed environment. S200: Under the first preset power, the power battery is continuously heated, the first temperature-time curve is recorded, the fitting parameters are extracted from the first temperature-time curve through a nonlinear fitting model, and the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell are calculated based on the fitting parameters. S300: The power battery is continuously heated under the second preset power set, which includes several different preset powers; the second temperature-time curve and pressure-time curve of each preset power in the second preset power set are recorded, and the valve injection time is determined by detecting that the pressure change rate exceeds the preset threshold based on the pressure-time curve; the thermal runaway time is determined by detecting that the temperature change rate exceeds the preset threshold based on the second temperature-time curve. S400: Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, calculate the heat loss per unit time and accumulate the net input energy of the power battery. S500: Combine the valve timing with net input energy to determine the valve critical energy; combine the thermal runaway time with net input energy to determine the thermal runaway critical energy; based on the valve critical energy and the thermal runaway critical energy, construct a power-time-energy safety boundary diagram to divide the safe region, the valve-non-runaway region, and the thermal runaway region.
[0020] Specifically, this application proposes a method for determining the injection valve and thermal runaway of a power battery based on net input energy, building upon conventional continuous heating. It provides the critical energy for the injection valve and the critical energy for thermal runaway, achieving a unified criterion under different continuous heating powers and heat dissipation conditions. The total heat dissipation coefficient and equivalent heat capacity of the battery in a specific arrangement are obtained by fitting data under low-power continuous heating conditions. Based on this, unified calculations are performed on data under medium- and high-power conditions, thereby reducing workload and improving the generalizability of the determination. A data processing module (algorithm flow) is proposed, which can utilize common software tools (such as Origin and Excel) to perform fitting and energy calculations, providing a directly applicable calculation method for battery thermal safety assessment and simulation.
[0021] In the initial stage, the battery under test is charged to a preset state of charge, and temperature sensors are placed on the heating surface, back, or other key locations of the battery to continuously collect temperature change data during the heating process. Simultaneously, the battery is placed in a sealed or semi-sealed environment, and pressure sensors or video acquisition devices are deployed as needed to record pressure changes in real time and assist in identifying valve-induced events during heating. Through this arrangement, basic data such as temperature-time curves, pressure-time curves, and ambient temperature can be acquired simultaneously. In the parameter calibration stage, a first preset power is selected as the low-power heating condition for continuous heating of the battery. Under this power condition, the battery temperature typically rises slowly without significant self-heating, valve-induced events, or thermal runaway. Based on the temperature-time curves obtained in this stage, an equivalent thermal model is used to describe the battery's thermal behavior, and fitting parameters are extracted from the temperature-time curves using nonlinear fitting. Furthermore, the equivalent total heat dissipation coefficient between the cell and the environment, as well as the equivalent heat capacity of the cell, are calculated based on the fitting parameters, thus completing the thermal parameter calibration under specific arrangement and environmental conditions. The obtained equivalent total heat dissipation coefficient and equivalent heat capacity can serve as a unified parameter basis for subsequent analysis of different power conditions under the same conditions. During the multi-power continuous heating stage, a second preset power set is selected to continuously heat the power battery. This power set includes several different medium-to-high power conditions (e.g., 300W, 400W, etc.). Under each power condition, the temperature-time curve and pressure-time curve of the power battery are fully recorded. During data processing, the time of the valve injection event is determined by analyzing the abrupt change characteristics or pressure change rate characteristics of the pressure-time curve; the time of the thermal runaway event is determined by analyzing the sudden increase characteristics of the temperature rise rate in the temperature-time curve. The aforementioned valve injection time and thermal runaway time are used as key time nodes for subsequent energy calculations and criticality determination. Based on this, combined with the equivalent total heat dissipation coefficient and equivalent heat capacity of the cell obtained from the aforementioned calibration, the net input energy of the power battery during continuous heating is calculated according to the energy conservation relationship. The net input energy is the continuous heating input energy minus the energy lost through heat dissipation, and can be obtained by integrating or analytically calculating the heating power and temperature data. By analyzing the change of net input energy over time, the effective energy input accumulated by the power battery at any given moment can be obtained. Then, by combining the valve injection time with the corresponding net input energy, the minimum energy threshold required for the power battery to experience valve injection, i.e., the valve injection critical energy, is determined. Similarly, by combining the thermal runaway time with the corresponding net input energy, the minimum energy threshold required for the power battery to experience thermal runaway, i.e., the thermal runaway critical energy, is determined. Statistical analysis of the valve injection critical energy and thermal runaway critical energy obtained under different continuous heating power conditions reveals their distribution range and variation patterns, thereby quantifying the role of valve injection behavior in delaying or influencing the thermal runaway process.Finally, based on the obtained critical energy for valve injection, critical energy for thermal runaway, and corresponding power and time information, a power-time-energy safety boundary diagram for the power battery is constructed. By dividing this safety boundary diagram into different regions, the safe operating region of the power battery under the influence of external heat sources, the transition region where valve injection occurs but thermal runaway has not yet occurred, and the dangerous region where thermal runaway occurs can be clearly distinguished. This safety boundary diagram can not only be used to evaluate the thermal safety performance of the power battery under certain conditions, but also to predict the time required for the power battery to reach valve injection or thermal runaway under different external heat source power conditions.
[0022] The working process and principle begin with the standardized sample preparation of the power battery under test. The power battery is charged to a specified state of charge according to a predetermined scheme, ensuring that the initial energy state of the battery is controllable and repeatable. Temperature sensors are placed at key locations on the power battery, including at least one side surface near the external heat source and the opposite back surface, to comprehensively reflect the temperature rise characteristics of the battery during heating. The power battery is placed in a sealed or semi-sealed environment to simulate the limited heat dissipation conditions the battery might encounter in actual applications, and to provide a stable test space for subsequent pressure change monitoring during valve-induced events. The power battery is continuously heated under a first preset power condition. This first preset power is typically selected as a low heating power to prevent significant self-heating, valve-induced events, or thermal runaway during heating. By collecting temperature-time curves under this condition, the typical thermal response behavior of the power battery under the current arrangement and environmental conditions can be obtained. Based on this temperature change process, a nonlinear fitting method is used to fit the temperature change trend over time, thereby extracting fitting parameters characterizing the battery's thermal response. Based on these parameters, the equivalent total heat dissipation coefficient between the battery cell and the environment, as well as the equivalent heat capacity of the battery cell, are calculated. The equivalent total heat dissipation coefficient reflects the battery's comprehensive ability to dissipate heat to the outside world under the current environmental and installation conditions, while the equivalent heat capacity of the battery cell reflects the battery's thermal inertia characteristics in response to externally input heat. These two parameters are stable under the same arrangement conditions and can serve as a unified thermal parameter basis for subsequent multi-power condition analysis. After completing the low-power thermal parameter calibration, the power battery is further continuously heated under a second preset power set. The second preset power set includes multiple levels of continuous heating power, typically covering a medium to high power range, to simulate the impact of external heat sources of varying intensities on the power battery. Under each preset power condition, the temperature-time curve and pressure-time curve of the power battery are recorded. By analyzing the pressure change process, the pressure surge caused by the rapid release of gas inside the battery can be identified, thus determining the timing of the battery's valve-like behavior. Similarly, by analyzing the temperature change rate, abnormally rapid temperature increases within a short period can be identified, thus determining the timing of thermal runaway. Therefore, key characteristic parameters such as valve-like behavior time and thermal runaway time are obtained under different continuous heating power conditions. Based on the equivalent total heat dissipation coefficient and cell equivalent heat capacity obtained from the aforementioned calibration, a unified analysis of the energy input process of the power battery under various continuous heating conditions is performed. By comprehensively considering the energy provided by external heating and the energy dissipated to the environment by the battery during heating, the net input energy of the power battery at any given time is determined. This net input energy characterizes the amount of energy truly absorbed by the battery and participating in the internal thermal evolution process after excluding the influence of heat dissipation, thus avoiding the inaccuracies caused by using heating power or heating time alone as criteria.The previously determined valve injection time and thermal runaway time are correlated with the net input energy at the corresponding times. At the time point of valve injection, the cumulative net input energy obtained by the power battery at that time is extracted and used as the valve injection critical energy, representing the minimum energy condition required for the power battery to experience valve injection. Similarly, at the time point of thermal runaway, the corresponding net input energy is extracted and used as the thermal runaway critical energy, representing the minimum energy condition required for the power battery to experience thermal runaway. By comprehensively analyzing the valve injection critical energy and thermal runaway critical energy obtained under different continuous heating power conditions, a three-dimensional power-time-energy safety boundary diagram can be further constructed. This power-time-energy safety boundary diagram uses continuous heating power, heating duration, and net input energy as coordinate axes to divide the power battery's behavior under external heat sources into different safety zones. The area below the critical energy for valve injection is considered a safe zone, indicating that the battery will not experience valve injection or thermal runaway under these conditions. The area between the critical energy for valve injection and the critical energy for thermal runaway is the area where valve injection may occur but has not yet entered a state of thermal runaway. The area exceeding the critical energy for thermal runaway is the thermal runaway zone, indicating a high risk of thermal runaway for the battery. This safety boundary diagram allows for the prediction of the battery's safety status over different heating durations under known external heat source power conditions, and also enables the reverse assessment of the permissible safe exposure time at a specific energy threshold.
[0023] Understandably, by systematically testing and modeling power batteries under controlled continuous heating conditions, the behavior of the injection valve and thermal runaway is transformed from a "time or temperature criterion" to an "energy criterion." Compared to existing methods that rely solely on empirical judgments under temperature abrupt changes or single power conditions, this invention calibrates the equivalent total heat dissipation coefficient and cell equivalent heat capacity of the power battery in a specific arrangement under low-power conditions, enabling the thermal response characteristics of the battery during heating to be quantitatively described using unified thermal parameters. Based on this, by accurately identifying the injection valve time and thermal runaway time under different continuous heating power conditions, and combining this with energy balance relationships, the critical energy of the injection valve and the critical energy of thermal runaway are calculated, thereby normalizing complex and variable thermal events into comparable energy thresholds. This method eliminates the influence of different heating powers, different heating rates, and different time sequences on the judgment results, improving the stability, repeatability, and engineering consistency of injection valve and thermal runaway judgments. By constructing a three-dimensional safety boundary map of power-time-energy, it is possible to distinguish the safe zone of the power battery under the action of external heat source, the zone where the valve is injected but thermal runaway has not occurred, and the zone where thermal runaway has occurred. This not only enables retrospective analysis of the results that have occurred, but also allows for the deduction of the time of occurrence of the valve injection or thermal runaway when the intensity of the external heat source is known, thus realizing a predictive assessment of the thermal safety behavior of the power battery.
[0024] This application further proposes a method for extracting fitting parameters from temperature-time curves through nonlinear fitting, including: Use Origin to create a nonlinear fitting template, and then use the nonlinear fitting model to fit the parameters of the temperature-time curve to obtain the fitting parameters.
[0025] The nonlinear fitting model is a thermal model, and its formula is: ; Among them, mc p dT / dt is the equivalent heat capacity of the battery cell; dT / dt is the rate of change of temperature with respect to time; P in is the continuous heating power; h is the equivalent total heat dissipation coefficient between the cell and the environment; T is the current temperature of the cell; T0 is the ambient temperature.
[0026] Further solutions from the above thermal model: ; Where T(t) is the cell temperature at time t; T0 is the ambient temperature; a and b are fitting parameters; and t is time.
[0027] Using the temperature curve of the first preset power condition P, where the first preset power is low power (e.g., 200W, 300W), a nonlinear fitting model is used for fitting: a and b are fitting parameters. A nonlinear fitting template can be established using fitting software such as Origin to perform nonlinear fitting on the measured T(t) to obtain a and b.
[0028] Specifically, under the first preset power condition, a constant and relatively low continuous heating power is applied to the power battery, ensuring the cell is in a safe temperature rise stage without significant self-heating, valve ejection, or thermal runaway. During this stage, the cell's temperature change is primarily determined by the energy balance between the continuous heating input and heat dissipation to the environment, which can be approximated as satisfying the conditions of a lumped parameter thermal model. Based on this, the cell is considered an equivalent thermal unit with a uniform temperature distribution, and its thermal behavior can be described by the energy conservation principle: the change in heat per unit time is equal to the difference between the continuous heating power input and the heat dissipation loss, where the heat dissipation loss is proportional to the temperature difference between the cell temperature and the ambient temperature. Therefore, a nonlinear thermal model is established using the cell's equivalent heat capacity, equivalent total heat dissipation coefficient, continuous heating power, and ambient temperature as parameters to describe the cell temperature change over time. In actual data processing, complete temperature-time data under the first preset power condition is first collected, and the data undergoes necessary smoothing and noise reduction to reduce the impact of measurement noise on the fitting accuracy. Subsequently, the analytical form corresponding to the thermal model was used as the nonlinear fitting function. Ambient temperature was introduced as a known constant into the model, and parameters reflecting thermal characteristics were used as variables to be fitted. This analytical model can characterize the exponential temperature rise of the battery cell under constant continuous heating conditions, gradually approaching the steady-state temperature from the initial temperature. Its fitting parameters directly reflect the temperature rise amplitude and the time scale for reaching thermal equilibrium under the state of continuous heating and heat dissipation equilibrium. In the fitting process, a nonlinear fitting template was established using Origin software, with time as the independent variable, the measured battery cell temperature as the dependent variable, and the analytical temperature function selected as the fitting model. The data was iteratively fitted using the least squares method until the fitting residuals met the preset accuracy requirements. The fitting parameters obtained through this nonlinear fitting process correspond to the ratio of continuous heating power to heat dissipation capacity and the ratio of equivalent heat dissipation coefficient to the equivalent heat capacity of the battery cell, respectively. Furthermore, combined with the known first preset continuous heating power, the fitting parameters can be converted into equivalent total heat dissipation coefficient and equivalent heat capacity parameters of the battery cell with clear physical meaning. Since the cell did not experience valve ejection or thermal runaway under the first preset power condition, the fitted equivalent total heat dissipation coefficient and the cell's equivalent heat capacity can truly reflect the overall thermal characteristics of the cell under the current arrangement, environmental conditions, and installation method.
[0029] Understandably, by abstracting the temperature-time response process of a power battery under low-power continuous heating conditions into a simplified first-order equivalent thermal model, and using nonlinear fitting to directly invert the fitting parameters a and b from the measured temperature curve, quantitative calibration of the cell's equivalent total heat dissipation coefficient h and equivalent heat capacity mcp is achieved. This avoids the uncertainties caused by measuring or assuming complex structural dimensions and material thermal properties one by one in traditional methods. This method is based on a complete temperature rise curve for overall fitting, which can utilize global information on temperature changes over time. By selecting a low-power condition without self-heating reaction and valve behavior for fitting, the model assumptions can be guaranteed to hold, and the fitted thermal parameters can truly reflect the heat dissipation characteristics and thermal inertia of the cell under given arrangement and environmental conditions. By establishing a standardized nonlinear fitting template in general data analysis software such as Origin, the parameter extraction process can be automated and repeatable, reducing the influence of subjective human judgment on the results and improving the consistency of parameter comparison between different batches and models of cells.
[0030] This application further proposes the following methods for calculating the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell: The equivalent total heat dissipation coefficient between the battery cell and the environment is determined based on the fitted parameters and the first preset power. The equivalent heat capacity of the battery cell is determined by combining the fitted parameters with the equivalent total heat dissipation coefficient.
[0031] The formula for calculating the equivalent total heat dissipation coefficient is as follows: ; Where h is the equivalent total heat dissipation coefficient between the battery cell and the environment; P is the first preset power; and a is the fitting parameter.
[0032] The formula for calculating the equivalent heat capacity of a battery cell is as follows: ; Among them, mc p denoted as , where is the equivalent heat capacity of the battery cell; h is the equivalent total heat dissipation coefficient between the battery cell and the environment; and b is the fitting parameter.
[0033] That is, by fitting a temperature rise curve under low power conditions, the h and mc of the battery cell in this arrangement can be calibrated. p These parameters can be used for data processing under the same conditions for other power operating conditions.
[0034] Specifically, when calculating the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, this invention calibrates the thermal characteristics of the battery cell under current arrangement conditions by using thermal model parameter fitting and back-calculation based on the temperature rise behavior of the power battery under low-power continuous heating conditions. Specifically, under a first preset power condition (the first preset power is a low-power condition, such as 200W or 300W), the power battery is continuously and stably heated, ensuring the battery cell is in a safe temperature rise stage without valve ejection, spontaneous reaction, or significant self-heating. Within this stage, the temperature change of the battery cell is mainly determined by the balance between continuous heating input and heat dissipation to the environment, conforming to the basic assumptions of the equivalent lumped parameter thermal model.
[0035] By performing nonlinear fitting on the recorded first temperature-time curve, fitting parameters a and b, characterizing the temperature rise amplitude and rate, can be obtained. Fitting parameter a reflects the final stable temperature rise amplitude of the battery cell relative to the ambient temperature under the continuous heating power and heat dissipation conditions; fitting parameter b reflects the rate at which the battery cell temperature approaches a stable state over time, reflecting thermal inertia. Based on fitting parameter a and combined with the known first preset power P, the equivalent total heat dissipation coefficient h between the battery cell and the environment can be calculated. This equivalent total heat dissipation coefficient comprehensively characterizes the overall ability of the battery cell to dissipate heat to the surrounding environment through convection, radiation, and structural heat transfer under the current arrangement. Its value is related to factors such as the surface condition of the battery cell, the installation method, environmental conditions, and the structure of the test chamber. After obtaining the equivalent total heat dissipation coefficient h, the equivalent heat capacity mc of the battery cell can be calculated by further combining it with fitting parameter b. p Equivalent heat capacity is used to characterize the amount of heat that a battery cell needs to absorb or release during a unit temperature change, reflecting the comprehensive thermal inertial characteristics of the battery cell's material system, structural form, and internal thermal mass distribution.
[0036] Understandably, by performing nonlinear fitting on only one temperature rise curve under low-power conditions, the equivalent total heat dissipation coefficient h and the cell's equivalent heat capacity mcp can be simultaneously calibrated, thus avoiding the uncertainties and safety risks associated with directly calculating thermal parameters under high-power or critical conditions. Since the heat dissipation path and heat capacity characteristics of the cell remain consistent under the same arrangement and environmental conditions, the calibrated h and mcp can be used as fixed thermal parameters for thermal analysis and energy calculation of the same power battery under other continuous heating power conditions. This calculation method not only improves the stability and repeatability of thermal parameter acquisition but also enables quantitative modeling of the power battery's thermal behavior and consistent analysis across power conditions while ensuring safety.
[0037] This application further proposes recording the second temperature-time curve and pressure-time curve for each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, including: Record the complete pressure-time curves under each preset power condition within the second preset power set; Extract the instantaneous pressure change rate of the pressure-time curve. When the instantaneous pressure change rate of three consecutive sampling points exceeds the preset pressure change rate threshold, determine the start time of the three consecutive sampling points as the valve spraying time.
[0038] Specifically, in recording the second temperature-time curves and pressure-time curves for each preset power within the second preset power set, and determining the valve ejection time and thermal runaway time, complete data acquisition is required for each preset power condition. For pressure data, the pressure-time curve should be continuously recorded throughout the heating process. Pressure sensors need to be installed in the sealed environment or test chamber of the power battery to accurately capture instantaneous pressure changes caused by gas expansion inside the cell or valve ejection events. In the data processing stage, the instantaneous pressure change rate at each sampling point is extracted by analyzing the pressure-time curves. ΔP / Δt can typically be calculated using the central difference method or other numerical differentiation methods. A predetermined pressure change rate threshold is set, which can be obtained through preliminary testing or no-load noise analysis. When the instantaneous pressure change rate at three consecutive sampling points exceeds this threshold, the power battery is considered to have experienced a valve ejection phenomenon. At this time, the start time of these three sampling points is taken as the valve ejection time to accurately calibrate the time node of valve ejection.
[0039] Understandably, this method eliminates short-term pressure fluctuations or noise interference, ensuring the accuracy and repeatability of the valve determination and improving the accuracy of the valve timing determination.
[0040] This application further proposes recording the second temperature-time curve and pressure-time curve for each preset power within the second preset power set, and when determining the valve injection time and thermal runaway time, it also includes: Record the complete second temperature-time curves under each preset power condition within the second preset power set; The instantaneous temperature change rate of the second temperature-time curve is extracted by calculating the temperature difference per unit time. When the instantaneous temperature change rate increases to three times the heating rate per unit time and the duration exceeds the preset duration threshold, the starting moment of the temperature change is determined as the thermal runaway time.
[0041] Specifically, the process of recording the second temperature-time curves and pressure-time curves for each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, also includes a detailed analysis of the cell temperature data. For each preset power condition, the second temperature-time curve should be recorded completely, that is, the temperature change data of each measuring point on the surface or inside the cell over time should be continuously collected throughout the heating process. After the data acquisition is completed, the temperature signal needs to be preprocessed as necessary, such as removing high-frequency noise, smoothing filtering, or correcting the sampling time base, to ensure the accuracy of the temperature change rate calculation. Subsequently, by calculating the temperature difference per unit time, i.e., ΔT / Δt, the instantaneous temperature change rate dT / dt is extracted to identify the characteristics of temperature abrupt changes. A heating rate baseline is set, which can usually be obtained from the initial temperature rise slope of the low-power heating stage. When the instantaneous temperature change rate is detected to increase to more than three times the heating rate baseline per unit time, and the duration of this increase exceeds a preset duration threshold (e.g., 2–5 seconds, which can be determined according to the sampling frequency and temperature noise level), it is considered that a temperature abrupt change has occurred in the cell. At this point, the time when the temperature mutation begins is defined as the thermal runaway time.
[0042] Understandably, when the instantaneous temperature change rate increases to three times the heating rate per unit time and the duration exceeds the preset duration threshold, the start time of the temperature change is determined as the thermal runaway time. This identifies the start time of thermal runaway of the power battery and eliminates misjudgments caused by short-term temperature fluctuations or sensor noise.
[0043] This application further proposes methods for determining the net input energy of a power battery based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, including: Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, combined with the ambient temperature and real-time temperature data of the power battery, the heat dissipation loss per unit time is calculated; and the unit net input energy is calculated; the unit net input energy during the heating process is accumulated to obtain the final net input energy.
[0044] Wherein, under any heating power Pin, the net input energy of the battery cell during the time interval 0-t is defined by the formula: ; Among them, E net (t) represents the net input energy from time 0 to t; Pin represents the continuous heating power within the second preset power set; h represents the equivalent total heat dissipation coefficient between the battery cell and the environment; T represents the battery cell temperature; T0 represents the ambient temperature; and dt represents the integral with a small increment over time.
[0045] Among them, E net (t) is the energy of continuous heating minus the energy lost through heat dissipation, and the analytical formula is: ; Among them, E net (t) represents the net input energy from time 0 to t; mc p denoted as the equivalent heat capacity of the battery cell; T(t) is the temperature of the power battery at time t; T0 is the ambient temperature; h is the equivalent total heat dissipation coefficient between the battery cell and the environment; t is time; e is a mathematical constant.
[0046] Specifically, in determining the net input energy of a battery cell based on the calibrated equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, it is necessary to combine the recorded ambient temperature and the real-time temperature sequence of the battery cell, and calculate the heat dissipated by the battery cell to the outside world point by point in each time interval. For each sampling moment, the temperature difference between the battery cell and the environment is first calculated, and then this temperature difference is multiplied by the equivalent total heat dissipation coefficient to obtain the instantaneous heat dissipation power at that moment. Subsequently, the heat dissipation power is compared with the external heating power, and the difference between the two is the instantaneous net input power in that time interval. The cumulative net input power from the beginning to the current moment is obtained by summing the instantaneous net input power of all time intervals over time. When discrete sampling is used, the summation process is equivalent to multiplying the net input power of each sampling segment by the length of that segment and summing them to obtain the final net input energy. In the implementation process, it is recommended to preprocess the temperature and power data, including synchronizing the time base, smoothing high-frequency noise, removing abnormal sampling points, and supplementing a small number of missing data, to improve the stability of the instantaneous heat dissipation power and net input power calculation. If the applied heating power remains constant, the net input energy will initially rise rapidly over time and then tend towards a stable value. If the applied power varies over time, numerical integration should be used to accumulate the data based on the actual input power curve. To improve computational reliability, it is recommended to use both analytical and numerical methods simultaneously and cross-validate them: the analytical method is used to quickly estimate the trend while satisfying model assumptions, while the numerical method is used to handle real-world data with time-varying power, non-ideal boundaries, or more complex sampling noise. Selection criteria for sampling frequency and time resolution should be provided (e.g., to ensure the capture of instantaneous characteristics of valve and temperature abrupt changes), and the uncertainty introduced by equivalent parameters should be evaluated. If necessary, multiple repeated experiments should be conducted and averaged, or confidence intervals should be provided; finally, the cumulative net input energy is obtained.
[0047] Understandably, the final cumulative net input energy can be used to directly compare the differences in energy absorption at the same time under different power conditions, or, after knowing the time of the event, to directly read the critical energy of the injection valve and the critical energy of thermal runaway by substituting the data at the corresponding time. Similarly, this energy threshold can be used in reverse to estimate the time required to reach the same threshold under any applied power.
[0048] This application further proposes determining the critical energy of the injection valve by combining the injection valve time with the net input energy, including: Based on the determined valve timing, determine the net input energy value of the valve for the corresponding valve timing; The net input energy value of the injection valve is taken as the critical energy of the injection valve; the critical energy of the injection valve is the minimum energy threshold required for the power battery to produce the injection valve phenomenon. Statistical analysis was performed on the critical energy of the injection valve under each preset power condition within the second preset power set to determine the critical energy range data of the injection valve.
[0049] Specifically, determining the critical energy of the power battery's injection valve requires combining the net input energy calculated in the previous step. By analyzing the heating data of the power battery under various preset power conditions, the specific time of valve occurrence is determined, i.e., the moment when a pressure change occurs or the injection valve event is identified. The net input energy value corresponding to this injection valve time is extracted; this value represents the actual energy absorbed by the battery from its initial state to the point of injection valve occurrence under the given heating conditions. In this method, this energy value is defined as the injection valve critical energy, meaning it is the minimum energy threshold required for the power battery to experience injection valve phenomena under current conditions. To obtain more reliable and comprehensive data, statistical analysis of the injection valve critical energy under various power conditions within the second preset power set is necessary. By comparing and statistically analyzing the injection valve critical energy under different power levels, the range of injection valve critical energy data can be obtained. This data reflects the energy distribution required for the power battery to experience injection valve phenomena under different heating intensities.
[0050] Understandably, this not only quantifies the energy threshold of the power battery injection valve, but also provides a reliable basis for safety analysis, thermal management design, and the construction of power-time-energy boundaries, enabling accurate assessment of the safety status of the power battery under different external heat source interference conditions.
[0051] This application further proposes that when determining the critical energy for thermal runaway by combining the thermal runaway time with the net input energy, the following should be included: Based on the determined thermal runaway time, determine the net thermal runaway energy input value corresponding to the thermal runaway time; The net input energy value of thermal runaway is taken as the critical energy of thermal runaway, which is the minimum energy threshold required for the power battery to experience thermal runaway. Statistical analysis was performed on the critical energy of thermal runaway under each preset power condition within the second preset power set to determine the range of critical energy of thermal runaway.
[0052] Specifically, determining the critical energy for thermal runaway of a power battery requires relying on the recorded thermal runaway time, which is the moment when the temperature curve abruptly changes. By analyzing the heating data of the power battery under various preset power conditions, the thermal runaway time is determined, and the net input energy value corresponding to that time point is extracted. This value represents the actual energy absorbed from the battery's initial state until thermal runaway occurs. This energy value is defined as the critical energy for thermal runaway, i.e., the minimum energy threshold required for the power battery to experience thermal runaway under current conditions. To obtain comprehensive and reliable data, statistical analysis of the critical energy for thermal runaway under all different power conditions within the second preset power set is necessary. By comparing the distribution of the critical energy for thermal runaway under different power conditions, the range of the critical energy for thermal runaway is determined.
[0053] Understandably, this method quantifies the energy threshold required for thermal runaway of a power battery under different continuous heating power conditions, providing key parameters for the thermal safety assessment of power batteries.
[0054] This application further proposes a method for constructing a power-time-energy safety boundary diagram based on the critical energy of the injection valve and the critical energy of thermal runaway, including: A three-dimensional power-time-energy safety boundary diagram is drawn based on the critical energy range data of the injection valve, the critical energy range data of thermal runaway, the equivalent total heat dissipation coefficient, the equivalent heat capacity of the battery cell, the injection valve time, and the thermal runaway time. The power-time-energy safety boundary diagram is used to divide the safe zone, the valve-non-runaway zone, and the thermal runaway zone.
[0055] Specifically, in constructing the power-time-energy safety boundary diagram based on the critical energy of the injection valve and the critical energy of thermal runaway, it is necessary to summarize the previously obtained data, including the range data of the critical energy of the injection valve, the range data of the critical energy of thermal runaway, the equivalent total heat dissipation coefficient of the cell, the equivalent heat capacity of the cell, and the corresponding injection valve time and thermal runaway time. Using this data, a power-time-energy safety boundary diagram can be drawn in a three-dimensional coordinate system, where the horizontal axis typically represents continuous heating power, the vertical axis represents time, and the depth axis represents net input energy. This three-dimensional graph visually presents the energy and time required for the battery to go from its initial state to the occurrence of injection valve or thermal runaway under different power conditions, forming the thermal safety boundary of the power battery under different heating conditions. In the diagram, different regions can be divided according to the critical energy of the injection valve and the critical energy of thermal runaway. The safe region refers to the area where, under given power and time conditions, the net input energy of the battery does not reach the critical energy of the injection valve, and the changes in battery temperature and pressure are within the safe range, preventing injection valve or thermal runaway. The "non-runaway zone" refers to the area where the net input energy exceeds the valve's critical energy but has not reached the thermal runaway critical energy. During this zone, the battery may release valve pressure, but has not yet entered a thermal runaway state, demonstrating the valve's buffering effect in delaying thermal runaway. The thermal runaway zone, on the other hand, refers to the area where the net input energy reaches or exceeds the thermal runaway critical energy. Within this zone, the battery has entered a thermal runaway state, posing a safety risk.
[0056] Understandably, the power-time-energy safety boundary diagram not only shows the safety status of the battery under different power and time conditions, but also realizes the prediction and protection planning of the safe operation of the power battery under external heat source interference.
[0057] This application further includes: Based on the net input energy, the time required to reach the critical energy of the injection valve or the critical energy of thermal runaway under other power conditions is calculated. Predicting the valve behavior and thermal runaway behavior of power batteries under different external heat source conditions based on the power-time-energy safety boundary diagram.
[0058] Specifically, in the process of back-calculating and predicting the injection valve and thermal runaway behavior of a power battery based on net input energy, the critical energy for injection valve and thermal runaway calculated in the previous steps, along with the net input energy variation law under the corresponding power conditions, can be used to estimate the time required for the battery to reach the same energy threshold under other continuous heating power conditions. For any given continuous heating power, using the known equivalent total heat dissipation coefficient and the cell's equivalent heat capacity, combined with the power-time-energy relationship, the time required for the battery to absorb energy from its initial state to reach the critical energy for injection valve or thermal runaway under that power condition can be calculated. This back-calculation process can help predict the time points when the battery may experience injection valve or thermal runaway under different heating intensities, providing a basis for taking safety precautions in advance. Based on the already constructed power-time-energy safety boundary diagram, the heating power and time under different external heat source conditions can be mapped to the diagram, thereby intuitively predicting the battery's thermal response behavior under actual operating conditions. Within the safe zone, the net energy input to the battery does not reach the valve release or thermal runaway threshold, and the battery temperature and pressure changes are within the safe range. In the valve-non-runaway zone, the battery may exhibit valve release pressure behavior, but still maintains thermal stability, demonstrating the buffering effect of the valve in delaying thermal runaway. In the thermal runaway zone, the net energy absorbed by the battery has exceeded the thermal runaway threshold, and there is a sharp increase in temperature and potential safety risks.
[0059] Understandably, this predictive method can be used to quantitatively assess the valve behavior and thermal runaway behavior of power batteries under different external heat source conditions, thereby enabling proactive monitoring and management of the thermal safety status of power batteries.
[0060] In summary, this paper proposes a method for determining the injection valve and thermal runaway based on net input energy. It introduces two critical energy criteria: the critical energy of the injection valve and the critical energy of thermal runaway. This allows for a unified description of thermal runaway risk across different heating powers and heat dissipation conditions, avoiding the limitations of traditional methods that rely solely on temperature thresholds. By utilizing continuous low-power heating and fitting a lumped-parameter thermal model, the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell are obtained. These parameters are then uniformly applied to energy calculations under medium-to-high power conditions, avoiding complex modeling for each power or operating condition, improving the method's operability and scalability, and achieving standardized parameter calibration. The critical energy of the injection valve and the critical energy of thermal runaway are given under the same energy scale. The difference between the critical energy of thermal runaway and that under high-power conditions is used to quantitatively explain the energy buffering effect of the injection valve on thermal runaway. This helps to scientifically explain the phenomenon of injection valves not running out of control under low power conditions, providing a theoretical basis for battery safety design. Relying on common fitting software (such as Origin) and spreadsheet software (such as Excel), the data processing workflow described in this paper has been implemented using Origin and Excel. This workflow can also be programmed in environments such as Matlab / Python, and is easy to reproduce and deploy in different laboratory and enterprise environments, reducing the technical threshold and implementation cost. By constructing a power-time-energy safety boundary diagram, the safe zone, the non-runaway zone, and the thermal runaway zone are distinguished, providing an intuitive and quantifiable assessment basis for thermal management system design, thermal fault simulation, and safety strategy formulation, thus transforming battery safety assessment from qualitative judgment to quantitative analysis.
[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A power battery injection valve and a method for determining the critical energy of thermal runaway, characterized in that, include: The power battery to be tested is charged to a preset state of charge, temperature sensors are installed at the corresponding positions of the power battery, and it is placed in a sealed environment. Under a first preset power, the power battery is continuously heated, and a first temperature-time curve is recorded. Fitting parameters are extracted from the first temperature-time curve through a nonlinear fitting model, and the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell are calculated based on the fitting parameters. The power battery is continuously heated under a second preset power set, which includes several different preset powers; the second temperature-time curve and pressure-time curve of each preset power in the second preset power set are recorded, and the valve injection time is determined by detecting that the pressure change rate exceeds a preset threshold based on the pressure-time curve; the thermal runaway time is determined by detecting that the temperature change rate exceeds a preset threshold based on the second temperature-time curve. Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, the heat dissipation loss per unit time is calculated, and the net input energy of the power battery is calculated cumulatively. The critical energy of the injection valve is determined by combining the injection valve time with the net input energy; the critical energy of thermal runaway is determined by combining the thermal runaway time with the net input energy; based on the critical energy of the injection valve and the critical energy of thermal runaway, a power-time-energy safety boundary diagram is constructed to divide the safe region, the injection valve-non-runaway region and the thermal runaway region.
2. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 1, characterized in that, Extracting fitting parameters from the temperature-time curve through nonlinear fitting includes: A nonlinear fitting template was established using Origin, and the temperature-time curve was fitted with parameters using a nonlinear fitting model to obtain the fitting parameters.
3. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 2, characterized in that, When calculating the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, the following should be included: The equivalent total heat dissipation coefficient between the battery cell and the environment is determined based on the fitting parameters and the first preset power. The equivalent heat capacity of the battery cell is determined based on the fitting parameters and the equivalent total heat dissipation coefficient.
4. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 3, characterized in that, When recording the second temperature-time curve and pressure-time curve for each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, the following steps are included: Record the pressure-time curves under each preset power condition within the second preset power set; Extract the instantaneous pressure change rate of the pressure-time curve. When the instantaneous pressure change rate of three consecutive sampling points exceeds the preset pressure change rate threshold, determine the start time of the three consecutive sampling points as the valve spraying time.
5. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 4, characterized in that, When recording the second temperature-time curve and pressure-time curve of each preset power within the second preset power set, and determining the valve injection time and thermal runaway time, the process also includes: Record the second temperature-time curves under each preset power condition within the second preset power set; The instantaneous temperature change rate of the second temperature-time curve is extracted by calculating the temperature difference per unit time. When the instantaneous temperature change rate increases to three times the heating rate per unit time and the duration exceeds the preset duration threshold, the starting moment of the temperature change is determined as the thermal runaway time.
6. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 5, characterized in that, When determining the net input energy of the power battery based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the cell, the following steps are included: Based on the equivalent total heat dissipation coefficient and the equivalent heat capacity of the battery cell, combined with the ambient temperature and real-time temperature data of the power battery, the heat dissipation loss per unit time is calculated; and the unit net input energy is calculated; the unit net input energy during the heating process is accumulated to obtain the final net input energy.
7. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 6, characterized in that, When determining the critical energy of the injection valve by combining the injection valve time with the net input energy, the following steps are included: Based on the determined valve timing, determine the net input energy value of the valve for the corresponding valve timing; The net input energy value of the injection valve is taken as the critical energy of the injection valve; the critical energy of the injection valve is the minimum energy threshold required for the power battery to produce the injection valve phenomenon. Statistical analysis was performed on the critical energy of the injection valve under each preset power condition within the second preset power set to determine the critical energy range data of the injection valve.
8. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 7, characterized in that, When determining the critical energy for thermal runaway by combining the thermal runaway time with the net input energy, the following steps are included: Based on the determined thermal runaway time, determine the net thermal runaway energy input value corresponding to the thermal runaway time; The net input energy value of thermal runaway is taken as the critical energy of thermal runaway, which is the minimum energy threshold required for the power battery to experience thermal runaway. Statistical analysis was performed on the critical energy of thermal runaway under each preset power condition within the second preset power set to determine the range of critical energy of thermal runaway.
9. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 8, characterized in that, When constructing the power-time-energy safety boundary diagram based on the critical energy of the injection valve and the critical energy of thermal runaway, the following steps are included: A three-dimensional power-time-energy safety boundary diagram is drawn based on the critical energy range data of the injection valve, the critical energy range data of thermal runaway, the equivalent total heat dissipation coefficient, the equivalent heat capacity of the battery cell, the injection valve time, and the thermal runaway time. The power-time-energy safety boundary diagram is used to divide the area into a safe zone, a valve-non-runaway zone, and a thermal runaway zone.
10. The method for determining the critical energy of thermal runaway in a power battery injection valve according to claim 9, characterized in that, Also includes: Based on the net input energy, the time required to reach the critical energy of the injection valve or the critical energy of thermal runaway under other power conditions is calculated. Based on the power-time-energy safety boundary diagram, predict the valve behavior and thermal runaway behavior of the power battery under different external heat source conditions.