Method for calculating electric heating film parameters, electric heating film, battery pack and vehicle

Abstract

The present application discloses a method for calculating the parameters of an electric heating film, an electric heating film, a battery pack, and a vehicle. The method for calculating the parameters of the electric heating film includes: obtaining the property parameters of the battery cell and the target parameters of the electric heating film, and calculating the design parameters of the electric heating film; preparing the electric heating film and generating a simulated electric heating film according to the design parameters; obtaining test data of the electric heating film and simulation data of the simulated electric heating film; judging whether the test data and the simulation data meet the target conditions; when the test data and the simulation data do not meet the target conditions, adjusting the design parameters according to the test data and the simulation data; looping the preparation and simulation steps, the result data acquisition step, the judgment step, and the adjustment step until the test data and the simulation data meet the target conditions, and then determining the final adjusted design parameters as the electric heating film parameters. The method can quickly and accurately determine the design parameters of the electric heating film, which is conducive to shortening the research and development cycle of the electric heating film and reducing research and development costs.

Description

Technical Field

[0001] The present application relates to the technical field of electric heating films, and in particular to a method for calculating electric heating film parameters, an electric heating film, a battery pack, and a vehicle. Background Art

[0002] In the field of new energy vehicles, power is provided by power battery packs. However, battery packs have stringent temperature requirements during operation, especially when charging in low-temperature conditions. For lithium-ion batteries, the negative electrode Li+ in the cell is easily precipitated as metallic lithium. The precipitated lithium dendrites continue to grow and can easily puncture the separator, causing a short circuit in the battery pack, posing a threat to the battery pack's lifespan and safety. Therefore, to ensure the battery pack's service life and safety, a corresponding battery pack heating system must be designed for lithium-ion batteries. Commonly used heating methods include PTC (Positive Temperature Coefficient) heating, liquid heating, and electric heating films.

[0003] In the related art, the design of electric heating films only relies on experience to repeatedly and qualitatively adjust the design parameters. A method for systematically and quantitatively adjusting the design parameters has not yet been formed, which can easily lead to problems such as a long R&D cycle and unreliable design parameters of the electric heating films. Summary of the Invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present application is to propose a method for calculating the parameters of an electric heating film. This method can be used to quickly and accurately determine the design parameters of the electric heating film, thereby shortening the research and development cycle of the electric heating film and reducing research and development costs.

[0005] A second purpose of this application is to provide an electric heating film.

[0006] The third objective of this application is to provide a battery pack.

[0007] A fourth object of this application is to provide a vehicle.

[0008] In order to solve the above problems, the first aspect of the present application provides a method for calculating the parameters of an electric heating film, including: an acquisition step of acquiring the property parameters of the battery cell and the target parameters of the electric heating film; a calculation step of calculating the design parameters of the electric heating film based on the property parameters and the target parameters; a preparation and simulation step of preparing the electric heating film according to the design parameters and generating a simulated electric heating film according to the design parameters; a result data acquisition step of acquiring the test data of the electric heating film and the simulation data of the simulated electric heating film; a judgment step of judging whether the test data and the simulation data meet the target conditions; an adjustment step of adjusting the design parameters according to the test data and the simulation data when the test data and the simulation data do not meet the target conditions; and looping the preparation and simulation steps, the result data acquisition step, the judgment step and the adjustment step until the test data and the simulation data meet the target conditions, and then determining that the final adjusted design parameters are the electric heating film parameters.

[0009] According to the method for calculating the parameters of the electric heating film according to the embodiment of the present application, when determining the parameters of the electric heating film, the design parameters of the electric heating film are adjusted through the acquisition step, calculation step, preparation and simulation step, result data acquisition step, judgment step and adjustment step, and the preparation and simulation step, result data acquisition step, judgment step and adjustment step are circulated until the test data and simulation data meet the target conditions, and the final adjusted design parameters are determined as the electric heating film parameters. Therefore, the above steps can realize the systematic determination of the electric heating film parameters without relying solely on experience to repeatedly adjust the design parameters qualitatively, which is easy to shorten the R&D cycle and reduce R&D costs. In addition, the present application adopts a method of adjusting the design parameters by combining test data under different working conditions and simulation data after simulation analysis. Compared with a single experiment or simulation method, it can effectively improve the accuracy of the final adjusted design parameters, which is beneficial to improving the safety and reliability of the electric heating film design.

[0010] In some embodiments, the property parameters of the battery cell include at least the battery cell specific heat capacity, the battery cell mass and the rated voltage, and the target parameters of the electric heating film include at least the target heating efficiency, the target temperature rise rate and the preset coverage area. The calculation step calculates the design parameters of the electric heating film based on the property parameters and the target parameters, including: obtaining the rated power of the electric heating film based on the battery cell specific heat capacity, the battery cell mass, the target temperature rise rate and the target heating efficiency; determining the effective heating area of ​​the electric heating film based on the preset coverage area; obtaining the power density of the electric heating film based on the rated power and the effective heating area; obtaining the total resistance value of the electric heating film based on the rated power and the rated voltage; and using the effective heating area, the rated power, the power density and the total resistance value as the design parameters.

[0011] In some embodiments, determining the effective heating area of ​​the electric heating film according to the preset covering area includes: taking a preset proportion of the preset covering area as the effective heating area of ​​the electric heating film, wherein the preset proportion is 50%-70%.

[0012] In some embodiments, the judgment step of judging whether the test data and the simulation data meet the target conditions includes: determining the temperature zones of the electric heating film according to the test data or the simulation data; and judging whether the test data and the simulation data of each temperature zone meet the target conditions.

[0013] In some embodiments, when the test data and the simulation data do not meet the target conditions, the design parameters are adjusted according to the test data and the simulation data, including: determining a first temperature zone in which the test data and the simulation data do not meet the target conditions; and adjusting the design parameters corresponding to the first temperature zone according to the test data and the simulation data of the first temperature zone.

[0014] In some embodiments, the test data and the simulation data include at least a test temperature rise rate; adjusting the design parameters corresponding to the first temperature zone according to the test data and simulation data of the first temperature zone includes: comparing the test temperature rise rate of each first temperature zone with the target temperature rise rate; if the test temperature rise rate of the first temperature zone is greater than the target temperature rise rate, reducing the rated power corresponding to the first temperature zone, or, if the test temperature rise rate of the first temperature zone is less than the target temperature rise rate, increasing the rated power corresponding to the first temperature zone; obtaining the power density corresponding to the first temperature zone according to the adjusted rated power.

[0015] In some embodiments, reducing the rated power corresponding to the first temperature zone includes: obtaining the absolute value of the temperature rise rate difference based on the test temperature rise rate of the first temperature zone and the target temperature rise rate; obtaining the descent rate based on the test temperature rise rate of the first temperature zone and the absolute value of the temperature rise rate difference; obtaining the reduced power based on the descent rate and the rated power of the first temperature zone; and using the difference between the rated power of the first temperature zone and the reduced power as the rated power corresponding to the first temperature zone after reduction.

[0016] In some embodiments, increasing the rated power corresponding to the first temperature zone includes: obtaining the absolute value of the temperature rise rate difference based on the test temperature rise rate of the first temperature zone and the target temperature rise rate; obtaining the growth rate based on the test temperature rise rate of the first temperature zone and the absolute value of the temperature rise rate difference; obtaining the increased power based on the growth rate and the rated power of the first temperature zone; and using the sum of the rated power of the first temperature zone and the increased power as the increased rated power corresponding to the first temperature zone.

[0017] In some embodiments, the test data and the simulation data include at least a test temperature rise rate, a test heating rate, a test dry-burning temperature and a test battery cell temperature difference, and the target conditions include at least: the test temperature rise rate of each temperature zone of the electric heating film is greater than or equal to the target temperature rise rate; the test heating efficiency of each temperature zone of the electric heating film is greater than or equal to the target heating efficiency; the test dry-burning temperature of each temperature zone of the electric heating film is less than or equal to the maximum allowable dry-burning temperature; and the test battery cell temperature difference is less than or equal to a preset temperature threshold.

[0018] A second aspect of the present application provides an electric heating film, which is prepared according to the electric heating film parameters obtained by the method for calculating electric heating film parameters as described in the above embodiment.

[0019] According to the electric heating film of the embodiment of the present application, the electric heating film parameters are obtained by adopting the method for calculating the electric heating film parameters provided by the above embodiment, which can not only shorten the research and development cycle of the electric heating film and reduce the research and development cost, but also ensure the safety and reliability of the designed electric heating film.

[0020] A third embodiment of the present application provides a battery pack, comprising: a battery module; and the electric heating film described in the above embodiment, wherein the electric heating film is arranged on the battery module and is used to heat the battery module.

[0021] According to the battery pack of the embodiment of the present application, by adopting the electric heating film provided by the above embodiment, the service life and safety of the battery pack are improved.

[0022] A fourth embodiment of the present application provides a vehicle comprising the battery pack described in the above embodiment.

[0023] According to the vehicle of the embodiment of the present application, the driving safety of the vehicle can be improved by adopting the battery pack provided by the above embodiment.

[0024] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0026] Figure 1 is a flow chart of a method for calculating parameters of an electric heating film according to one embodiment of the present application;

[0027] Figure 2 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0028] Figure 3 is a schematic diagram of an electric heating film according to an embodiment of the present application;

[0029] Figure 4 is a flow chart of a method for calculating parameters of an electric heating film according to another embodiment of the present application;

[0030] Figure 5 It is a structural schematic diagram of a vehicle according to an embodiment of the present application.

[0031] Reference numerals:

[0032] Vehicle 10;

[0033] Battery pack 1; battery module 2; electric heating film 3. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present application are described in detail below.

[0035] In order to solve the above problems, the first embodiment of the present application proposes a method for calculating the parameters of the electric heating film. This method can quickly and accurately determine the design parameters of the electric heating film, which is conducive to shortening the R&D cycle of the electric heating film and reducing R&D costs.

[0036] Reference below Figure 1 The method for calculating the parameters of the electric heating film according to the embodiment of the present application is described as follows: Figure 1 As shown, the method at least includes steps S1 to S7.

[0037] Step S1, an acquisition step, acquires the property parameters of the battery cell and the target parameters of the electric heating film.

[0038] The cell attribute parameters can be understood as the characteristic parameters of the cell after the design is completed, for example, they may include parameters such as the specific heat capacity, cell mass, and rated voltage of the cell. The target parameters of the electric heating film can be understood as the target parameters that the electric heating film can achieve during operation, which are pre-set according to actual needs, for example, they may include target heating efficiency or target temperature rise rate.

[0039] In the embodiment, since the function of the electric heating film is to heat the battery cell, the property parameters of the battery cell play an important role in the design of the electric heating film. Therefore, the embodiment of the present application takes the target parameters of the electric heating film as the design target, and combines the property parameters of the battery cell to calculate the parameters of the electric heating film.

[0040] Specifically, for any battery pack, battery cells suitable for vehicle applications will be developed in the early stage based on the vehicle's range and cell capacity requirements. Therefore, after the development of the battery cells is completed, the property parameters of the battery cells will no longer change. Therefore, after the battery pack structure is determined, the property parameters of the battery cells can be determined, providing a basis for the subsequent calculation of the electric heating film parameters.

[0041] Step S2, a calculation step, calculates the design parameters of the electric heating film according to the attribute parameters and the target parameters.

[0042] The design parameters of the electric heating film may be understood as parameters that affect the working performance of the electric heating film when the electric heating film is designed, for example, the rated power and area of ​​the electric heating film.

[0043] In the embodiment, the design parameters of the electric heating film are calculated according to the property parameters and the target parameters through relevant theoretical formulas, that is, the design parameters calculated according to the property parameters and the target parameters are theoretical values ​​of the electric heating film.

[0044] Step S3, a preparation and simulation step, prepares the electric heating film according to the design parameters and generates a simulated electric heating film according to the design parameters.

[0045] Specifically, the structure of the electric heating film includes a PI film (polyimide film) and an electric heating core, so the design parameters are used as design indicators to determine the process parameters of the PI film and the electric heating core, such as the resistance, length, width of the electric heating core and the area of ​​the PI film, and other process parameters, and after relevant process operations, a preliminary version of the electric heating film sample is prepared; similarly, the design parameters are used as design indicators to determine the process parameters of the PI film and the electric heating core, such as the resistance, length, width of the electric heating core and the area of ​​the PI film, and other process parameters, and after relevant drawing operations, a preliminary version of the simulated electric heating film is generated, such as a 3D simulation model of the electric heating film.

[0046] It should be noted that the prepared initial version of the electric heating film sample and the simulated electric heating film were obtained by evenly arranging the electric heating core with the design parameters as the design input. That is to say, based on the design parameters, when designing the initial version of the electric heating film and the simulated electric heating film, the process parameters such as the resistance, length and width of the electric heating core were evenly distributed.

[0047] Step S4, a result data acquisition step, acquires the test data of the electric heating film and the simulation data of the simulated electric heating film.

[0048] The test data and simulation data are the property parameters of the electric heating film itself, such as heating efficiency, and working property parameters, such as temperature rise rate, obtained through actual measurement or simulation.

[0049] Specifically, the prepared preliminary electric heating film samples are subjected to working condition tests to measure the electric heating film under different working conditions. For example, the heating performance of the electric heating film is tested such as low-temperature charge and discharge heating test, the mechanical performance is tested such as vibration heating test, and the safety is tested such as thermal balance test, and the test data of the electric heating film is obtained so that the working performance of the electric heating film can be judged by the test data. At the same time, the generated simulated electric heating film is subjected to thermal simulation, and simulation data is obtained when the temperature field reaches a steady state so that the working performance of the electric heating film can be judged by the simulation data. Therefore, by combining experiments and simulations under different working conditions to simultaneously test the electric heating film, the problem of excessive difference between the simulation data and the actual measured data of the finished product after the electric heating film is finalized due to a single detection method can be avoided, which is beneficial to improving the accuracy of calculating the parameters of the electric heating film and improving the safety and reliability of the electric heating film design.

[0050] Step S5 is a judgment step, which judges whether the test data and the simulation data meet the target conditions.

[0051] The target conditions are pre-set working requirements that can be met by the electric heating film after it is finalized.

[0052] Specifically, the obtained test data and simulation data are judged respectively. If both the test data and the simulation data meet the target conditions, it means that the electric heating film prepared with the design parameters can achieve the expected working requirements for the electric heating film; if the test data and / or simulation data do not meet the target conditions, it means that the electric heating film prepared with the design parameters cannot meet the expected working requirements for the electric heating film, therefore, step S6 is executed to further adjust the design parameters of the electric heating film.

[0053] Step S6, an adjustment step, when the test data and the simulation data do not meet the target conditions, adjust the design parameters according to the test data and the simulation data.

[0054] In the embodiment, the design parameters of the electric heating film are the design indicators of the electric heating film, and the process parameters are the basic data during the process operation of the electric heating film. When the electric heating film is actually prepared, the electric heating film is prepared by the process parameters determined by the design parameters. That is, when preparing the electric heating film, the design parameters of the electric heating film are changed by designing different process parameters.

[0055] Specifically, when the test data and simulation data do not meet the target conditions, it means that the electric heating film prepared by the design parameters calculated by the theoretical formula cannot meet the expected requirements for battery cell heating in actual application. Therefore, based on the target conditions, the process parameters when preparing the electric heating film are adaptively adjusted according to the test data and simulation data to change the design parameters and achieve the purpose of adjusting the design parameters.

[0056] Step S7, looping the preparation and simulation steps, the result data acquisition step, the judgment step and the adjustment step until the test data and the simulation data meet the target conditions, and then determining the final adjusted design parameters as the electric heating film parameters.

[0057] Specifically, based on the design parameters adjusted each time, electric heating film samples are re-prepared and simulated electric heating films are generated, and the electric heating film samples and simulated electric heating films are tested again. If the test data and simulation data obtained from the test do not meet the target conditions, the design parameters are adjusted again, and this cycle is repeated until the test data and simulation data meet the target conditions. It can be determined that the electric heating film prepared with the final adjusted design parameters can meet the expected requirements for battery cell heating in actual applications. Therefore, the final adjusted design parameters can be determined as the electric heating film parameters, and the electric heating film is prepared using the final adjusted design parameters as design indicators.

[0058] Thus, through the above steps S1 to S7, a systematic and accurate method for calculating the parameters of the electric heating film is formed, so that there is no need to repeatedly adjust the design parameters qualitatively based on experience alone, which can easily shorten the R&D cycle, reduce R&D costs, and effectively improve the accuracy of the final adjusted design parameters.

[0059] According to the method for calculating the parameters of the electric heating film according to the embodiment of the present application, when determining the parameters of the electric heating film, the design parameters of the electric heating film are adjusted through the acquisition step, calculation step, preparation and simulation step, result data acquisition step, judgment step and adjustment step, and the preparation and simulation step, result data acquisition step, judgment step and adjustment step are circulated until the test data and simulation data meet the target conditions, and the final adjusted design parameters are determined as the electric heating film parameters. Therefore, the above steps can realize the systematic determination of the electric heating film parameters without relying solely on experience to repeatedly adjust the design parameters qualitatively, which is easy to shorten the R&D cycle and reduce R&D costs. In addition, the present application adopts a method of adjusting the design parameters by combining test data under different working conditions and simulation data after simulation analysis. Compared with a single experiment or simulation method, it can effectively improve the accuracy of the final adjusted design parameters, which is beneficial to improving the safety and reliability of the electric heating film design.

[0060] In some embodiments, the property parameters of the battery cell include at least the battery cell specific heat capacity, the battery cell mass and the rated voltage. For the battery cell specific heat capacity, after the battery cell is determined, the specific heat capacity of the battery cell can be tested by an adiabatic calorimeter; for the battery cell mass, it can be tested by weighing. The target parameters of the electric heating film include at least a target heating efficiency, a target temperature rise rate, and a preset coverage area. The target temperature rise rate is the temperature rise of the battery cell per unit time when the electric heating film heats the battery cell. The preset coverage area can be understood as the area of ​​the battery cell that can be covered by the electric heating film, which is preset based on the structure of the battery pack. The target heating efficiency can be preset based on the expected requirements for the electric heating film to heat the battery cell. For example, to a certain extent, the heating efficiency of the electric heating film when heating the battery cell is related to the insulation effect of the battery pack. If the heat generated by the electric heating film during operation is completely absorbed by the battery cell, the heating efficiency of the electric heating film is 100%, that is, the target heating efficiency can be set to 100%. Alternatively, because the heat generated by the electric heating film during actual operation may be absorbed by other components in the battery pack, such as the tray, distribution box, or plastic parts, or dissipated to the external environment through the exposed parts of the battery pack body, and cannot be completely absorbed by the battery cell, the target heating power can be set below 100% based on the premise of meeting the heating requirements of the battery cell.

[0061] Specifically, for the calculation step, the rated power of the electric heating film can be obtained according to the specific heat capacity of the battery cell, the mass of the battery cell, the target temperature rise rate and the target heating efficiency. The calculation formula of the rated power of the electric heating film is as follows:

[0062]

[0063]

[0064] Where η is the target heating efficiency, C is the specific heat capacity of the battery cell, m c is the cell mass, ΔT / t is the target temperature rise rate, P is the rated power, T c (0) is the average temperature of the battery cell when the electric heating film does not heat the battery cell, T c (t) is the average temperature of the battery cell after the electric heating film heats the battery cell, and t is the time the electric heating film heats the battery cell.

[0065] And, the effective heating area of ​​the electric heating film is determined according to the preset covering area, wherein the effective heating area is the range of the actual arrangement of the electric heating core in the electric heating film. Specifically, since a cooler is provided in the battery pack, for example, Figure 2The battery pack structure shown in the figure will start cooling when the ambient temperature is too high. However, since the electric heating film is installed on the heat transfer path between the battery membrane group, that is, the battery cell and the cooler, the electric heating film has a certain impact on the cooling of the pack. In addition, when designing the electric heating film, while meeting the heating performance, the cost of the electric heating film must also be taken into account. In addition, when subsequently designing the wiring of the electric heating core of the electric heating film, the thickness and width specifications of the electric heating core and the spacing between adjacent wirings must also be considered, that is, the effective heating area should include the gaps between adjacent wirings. Therefore, taking the above into comprehensive consideration, the effective heating area of ​​the electric heating film is determined according to the preset covering area, so that the electric heating film can reduce costs while meeting the heating performance.

[0066] Among them, during the performance test of the electric heating film and the simulated electric heating film, two working conditions can be set for the battery pack with / without the electric heating film to determine the impact of the electric heating film on the cooling of the package.

[0067] In addition, the power density of the electric heating film is obtained based on the rated power and the effective heating area, wherein the power density is the power value per unit area of ​​the electric heating film. Specifically, the ratio of the rated power to the effective heating area is taken as the power density of the electric heating film. Since the power density determines the heating performance of the electric heating film and the dry-burning temperature when no load occurs, the power density can be used to determine the position where the highest temperature occurs during the use of the electric heating film, so as to facilitate the subsequent detection of the dry-burning temperature of the electric heating film and avoid the problem of affecting the service life of the electric heating film due to the excessively high dry-burning temperature of the electric heating film.

[0068] And, the total resistance value of the electric heating film is obtained according to the rated power and the rated voltage, and the total resistance value can be calculated by the following formula.

[0069]

[0070] Among them, R is the total resistance value, U is the rated voltage, and P is the rated power.

[0071] Furthermore, the effective heating area, rated power, power density and total resistance value are used as design parameters to prepare a preliminary version of the electric heating film and generate a simulated electric heating film.

[0072] In some embodiments, a preset proportion of the battery cell surface area is used as the effective heating area of ​​the electric heating film, wherein the preset proportion is 50%-70%. Under this effective heating area, the negative impact of the electric heating film on the cooling of the package can be reduced, so that the electric heating film meets the heating performance, and the cost can be effectively reduced.

[0073] In some embodiments, the temperature zones of the electric heating film are determined according to the test data or the simulation data; and it is determined whether the test data and the simulation data of each temperature zone meet the target conditions.

[0074] Specifically, due to the different distribution of battery cells in the battery pack, such as the position of the battery cells, the battery cells in different areas will have different heating values ​​during actual operation, which will result in different heating requirements for the battery cells in different areas. Therefore, when the electric heating film heats the battery cells, when the temperature field reaches a steady state, the temperatures of the battery cells in different areas will also be different. For example, Figure 3 As shown, the heat dissipation of the battery cells at the edge is better than that of the battery cells in the middle, and the heat generated by the battery cells in the middle is higher than that of the battery cells at the edge. Therefore, at the same time, after the electric heating film heats all the battery cells, the temperatures of the battery cells at different positions will also be different. The battery cells working at different temperatures will affect the performance of the battery cells and reduce the service life of the battery pack. Therefore, considering the above situation, the embodiment of the present application performs temperature zoning on the electric heating film. Specifically, after all the battery cells in the battery pack are heated by the electric heating film, all the adjacent battery cells at the same temperature in the battery pack are divided into the same area according to the obtained test data or simulation data, and the local area on the corresponding electric heating film that heats the same area is used as a temperature zone of the electric heating film. Therefore, the electric heating film can be divided into multiple temperature zones according to the test data or simulation data, for example Figure 3 The figure shows a schematic diagram of different temperature zones of the electric heating film. Then, the test data and simulation data of each temperature zone are used to determine whether the target conditions are met. Thus, when adjusting the design parameters, only the design parameters of the temperature zones that do not meet the target conditions need to be adjusted, without adjusting the design parameters of the temperature zones that meet the target conditions. In this way, the electric heating film is locally judged to achieve the purpose of quantitatively adjusting the local design parameters of the electric heating film.

[0075] In some embodiments, a first temperature zone is determined in which the test data and simulation data do not meet the target conditions; the design parameters corresponding to the first temperature zone are adjusted according to the test data and simulation data of the first temperature zone, that is, the temperature zone in which the corresponding test data and simulation data do not meet the target conditions among all temperature zones of the electric heating film is taken as the first temperature zone, and the design parameters of the first temperature zone are adjusted so that the first temperature zone meets the expected requirements of the electric heating film.

[0076] In some embodiments, the test data and simulation data include at least a test temperature rise rate. Referring to the calculation formula of the rated power, it can be seen that the temperature rise rate is proportional to the product of the heating efficiency of the electric heating film and the rated power. Once the body structure and insulation method of the battery pack are determined, it can be considered that the heating efficiency of the electric heating film on the body battery cell is constant. Therefore, the temperature rise rate is proportional to the rated power of the electric heating film. Therefore, the embodiment of the present application adjusts the design parameters of the electric heating film based on the test temperature rise rate detected in each temperature zone to ensure the consistency of the electric heating film when heating the battery cell. Specifically, the test temperature rise rate of each first temperature zone is compared with the target temperature rise rate. If the test temperature rise rate of the first temperature zone is greater than the target temperature rise rate, it means that when the electric heating film heats the battery cell, the heat generated by the battery cell corresponding to the first temperature zone is higher. Therefore, in order to avoid the actual operating temperature of the battery cell at the first temperature zone being higher than that at other temperature zones, Therefore, if the temperature of the battery cell in the first temperature zone is lower than the target temperature rise rate, the rated power of the corresponding first temperature zone is increased to improve the heating effect of the battery cell in the first temperature zone, thereby ensuring the consistency of the working temperature of all the battery cells after heating at the same time. Alternatively, if the test temperature rise rate of the first temperature zone is lower than the target temperature rise rate, it means that when the electric heating film heats the battery cell, the heating value of the battery cell corresponding to the first temperature zone is relatively low. Therefore, in order to avoid the actual working temperature of the battery cell in the first temperature zone being lower than the corresponding battery cell temperature in other temperature zones, the rated power of the corresponding first temperature zone is increased to improve the heating effect of the battery cell in the first temperature zone, thereby ensuring the consistency of the working temperature of all the battery cells after heating at the same time, and then obtaining the power density of the corresponding first temperature zone according to the adjusted rated power. Therefore, by quantitatively adjusting the power zone distribution of the electric heating film, the consistency of the working temperature of the battery cell after the electric heating film is turned on for heating can be effectively guaranteed.

[0077] For example, reference Figure 3 As shown, a schematic diagram of electric heating films in different temperature zones is obtained by the above-mentioned method of quantitatively adjusting the power zone distribution of the electric heating film, wherein P1, P2, P3, P4, P5 and P6 respectively represent the rated power values ​​corresponding to different temperature zones.

[0078] In some embodiments, when reducing the rated power corresponding to the first temperature zone, the absolute value of the temperature rise rate difference can be obtained, for example, as Δv, based on the test temperature rise rate of the first temperature zone, for example, as V1, and the target temperature rise rate, for example, as V2 = ΔT / t, i.e., Δv = |V1-V2|; the descent rate can be obtained, for example, as h1, based on the test temperature rise rate V1 of the first temperature zone and the absolute value of the temperature rise rate difference Δv, i.e. The reduced power is obtained according to the drop rate h and the rated power P of the first temperature zone, for example, denoted as P low ,Right now The rated power P of the first temperature zone and the reduced power P low The difference between the two values ​​is taken as the rated power after the first temperature partition is reduced, for example, it is recorded as P 调1 , that is, P 调1 =PP low .

[0079] In some embodiments, when the rated power corresponding to the first temperature zone is increased, the absolute value of the temperature rise rate difference Δv can be obtained according to the test temperature rise rate V1 of the first temperature zone and the target temperature rise rate V2, that is, Δv = |V1-V2|; the growth rate is obtained according to the test temperature rise rate V1 of the first temperature zone and the absolute value of the temperature rise rate difference Δv, for example, recorded as h2, that is According to the growth rate h2 and the rated power P of the first temperature zone, the increased power is obtained, for example, denoted as P high ,Right now The rated power P of the first temperature zone and the increased power P high The sum of the values ​​is recorded as the rated power after the first temperature zone is increased, for example, as P 调2 , that is, P 调2 =P+P high .

[0080] It should be noted that after adjusting the rated power of the first temperature zone, the power density corresponding to the first temperature zone will also be adjusted accordingly based on the power density calculation formula. The adjusted power density is the ratio of the adjusted rated power to the heating area of ​​the first temperature zone.

[0081] In the embodiment, when the electric heating film is attached to the battery cell, the long-term high temperature resistance value of the adhesive on the electric heating film is lower than that of metal foil and PI film, only 110℃-120℃. Therefore, when dry burning occurs, it is easy to reach the temperature point where the adhesive fails at high temperature. In addition, since the structure of the battery pack determines that the rated power of the electric heating film is distributed according to different areas of the battery cell, that is, the rated power corresponding to different temperature zones is related to different areas of the battery cell. Therefore, the power density at different temperature zones can also be used to more accurately determine the highest temperature of the battery cell, so as to facilitate the adjustment of the power density at different temperature zones of the electric heating film, and ensure that the electric heating film and the battery cell operate within the appropriate temperature range. Taking the electric heating film diaphragm made of nickel-chromium alloy as an example, Table 1 shows the dry burning temperature table of the electric heating film under different power densities.

[0082] Table 1

[0083] <![CDATA[Power density (W / cm 2 )]]> 0.01 0.03 0.06 0.09 0.12 0.15 0.18 0.21 Dry burning temperature (℃) 26 39.2 52.8 66.1 75.9 85.2 96.2 114 <![CDATA[Power density (W / cm 2 )]]> 0.27 0.3 0.33 0.36 0.39 0.42 0.45 Dry burning temperature (℃) 120 125 133 142 150 154 160

[0084] As shown in Table 1, the dry-burning temperature of the electric heating film is linearly related to the power density to a certain extent. When the electric heating film is applied to the battery cell, the long-term high temperature resistance of the adhesive on the electric heating film is lower than that of metal foil and PI film, only 110℃-120℃. Therefore, when dry-burning occurs, it is easy to reach the temperature point where the adhesive fails at high temperature. Therefore, if the power density of a temperature zone in the electric heating film is designed too high, once dry-burning occurs in that temperature zone, the adhesive corresponding to that temperature zone will fail. Adjacent temperature zones will also be affected, causing large-scale adhesive failure or debonding problems, thereby shortening the service life of the electric heating film. Therefore, when calculating the parameters of the electric heating film, it is necessary to reasonably adjust the power density of the electric heating film in different temperature zones while meeting the temperature rise rate of the battery cell during operation of the electric heating film and avoiding the dry-burning temperature exceeding the long-term high temperature resistance of the adhesive. By controlling the peak power density, that is, the highest power density among all temperature zones, the maximum dry-burning temperature of the electric heating film is determined. This can effectively ensure that the electric heating film and the battery cell always operate within the appropriate temperature range.

[0085] In some embodiments, since the heating performance of the electric heating film is mainly reflected in the temperature rise rate of the battery cell, the temperature difference between the battery cells, the heating efficiency and the dry-burning temperature of the electric heating film during the process of starting and ending the heating of the battery cell, the above parameters are used as evaluation criteria when evaluating the electric heating film in the embodiments of the present application to determine whether the heating film meets the expected requirements.

[0086] The dry-heating temperature is the maximum temperature of the membrane when the electric heating film is turned on for heating and reaches thermal equilibrium without any load being applied.

[0087] Specifically, the test data and simulation data include at least a test temperature rise rate, a test heating rate, a test dry-burning temperature, and a test cell temperature difference, wherein the test cell temperature difference is the temperature difference between the cells being tested. The target conditions include at least: the test temperature rise rate of each temperature zone of the electric heating film is greater than or equal to the target temperature rise rate; the test heating efficiency of each temperature zone of the electric heating film is greater than or equal to the target heating efficiency; the test dry-burning temperature of each temperature zone of the electric heating film is less than or equal to the maximum allowable dry-burning temperature; and the test cell temperature difference is less than or equal to a preset temperature threshold. Thus, after cyclic preparation and simulation steps, result data acquisition steps, judgment steps, and adjustment steps, until the test data and simulation data meet the above target conditions, the final adjusted design parameters are determined as the electric heating film parameters.

[0088] In summary, according to the method for calculating the parameters of the electric heating film according to the embodiment of the present application, by taking the target parameters of the electric heating film as the design target and combining the property parameters of the battery cell, such as the core specific heat capacity, battery cell mass and rated voltage, the electric heating film for different temperature zones can be systematically and scientifically designed. There is no need to rely solely on experience to repeatedly adjust the design parameters qualitatively, which is easy to reduce the R&D cycle and reduce R&D costs. It can also quantitatively adjust the design parameters of different temperature zones, effectively improving the accuracy of the final adjusted design parameters. It can also ensure that the operating temperature of the battery cell remains consistent when heating the battery cell, and ensure that the electric heating film and the battery cell operate within an appropriate temperature range, which is beneficial to improving the safety and reliability of the electric heating film design.

[0089] The second embodiment of the present application provides an electric heating film. The electric heating film 3 is prepared according to the electric heating film parameters obtained by the method for calculating the electric heating film parameters provided in the above embodiment. For example Figure 3 Shown is a schematic diagram of electric heating films with different power zones. The electric heating film 1 is suitable for battery pack structures of different new energy vehicles and has wider applicability.

[0090] The following Figure 4 As shown, the method for calculating the parameters of the electric heating film provided by the above embodiment is used to illustrate the preparation process of the electric heating film. The specific steps are as follows.

[0091] Step S8, development process of electric heating film.

[0092] Step S9: determining the property parameters of the battery cell, specifically the battery cell specific heat capacity, battery cell mass and rated voltage.

[0093] Step S10: determining the rated power of the electric heating film.

[0094] Step S11, determining the effective heating area of ​​the electric heating film.

[0095] Step S12: determining the power density of the electric heating film.

[0096] Step S13: determining the total resistance of the electric heating film.

[0097] Step S14: making an electric heating film sample and generating a simulated electric heating film.

[0098] Step S15 , numerical simulation is used to determine simulation data such as the battery cell temperature field, the test temperature rise rate, and the test heating rate.

[0099] Step S16: experimentally verify and determine test data such as the battery cell temperature field, the test temperature rise rate, and the test heating rate.

[0100] Step S17 determines whether both the test data and the simulation data meet the target conditions, which are: the test cell temperature rise rate ≥ 0.3°C / min, the test cell temperature difference ≤ 5°C, the test heating efficiency ≥ 65%, and the test dry-boil temperature ≤ 60°C. If the target conditions are met, step S18 is executed; if not, step S10 is executed.

[0101] Step S18 , finalizing the design parameters of the electric heating film, and preparing the electric heating film with the design parameters corresponding to the target conditions finally being satisfied as the design target.

[0102] According to the electric heating film of the embodiment of the present application, the electric heating film parameters are obtained by adopting the method for calculating the electric heating film parameters provided by the above embodiment, which can not only shorten the research and development cycle of the electric heating film and reduce the research and development cost, but also ensure the safety and reliability of the designed electric heating film.

[0103] The third embodiment of the present application provides a battery pack, such as Figure 2 As shown, the battery pack 1 includes a battery module 2 and the electric heating film 3 provided in the above embodiment.

[0104] The electric heating film 3 is provided on the battery module 2 for heating the battery module 2 to avoid the problem of threatening the service life and safety of the battery module 2 when operating under low temperature conditions.

[0105] In some embodiments, the battery pack 1 controls the opening and closing of the electric heating film 2. For example, when the temperature of the battery cells in all battery modules collected by the temperature sensor reaches above 0°C, the relay that controls the switch of the electric heating film 2 is disconnected, so that the electric heating film stops working. In addition, when developing the battery pack 1, a higher temperature-resistant adhesive can be used, or the electric heating film 2 can be hot-pressed onto the cooler of the battery pack 1, so that one side of the cooler acts as a temperature plate, effectively solving the problem of dry burning of the electric heating film.

[0106] According to the battery pack 1 of the embodiment of the present application, by adopting the electric heating film 2 provided in the above embodiment, the service life and safety of the battery pack 1 are improved.

[0107] A fourth aspect of the present application provides a vehicle, such as Figure 5 As shown, the vehicle 10 includes the battery pack 1 provided in the above embodiment.

[0108] According to the vehicle 10 of the embodiment of the present application, the driving safety of the vehicle can be improved by adopting the battery pack 1 provided by the above embodiment.

[0109] In the description of this specification, any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes additional implementations in which functions may be performed in a different order than shown or discussed, including performing functions in a substantially simultaneous manner or in a reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0110] The logic and / or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and a portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in another suitable manner if necessary, and then storing it in a computer memory.

[0111] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used to implement: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0112] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0113] In addition, the functional units in the various embodiments of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into a module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0114] The storage medium mentioned above may be a read-only memory, a magnetic disk, or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application. Persons skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

[0115] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0116] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for calculating parameters of an electric heating film, characterized in that: include: An acquisition step of acquiring property parameters of the battery cell and target parameters of the electric heating film; a calculation step of calculating design parameters of the electric heating film according to the attribute parameters and the target parameters; Preparation and simulation steps, preparing the electric heating film according to the design parameters and generating a simulated electric heating film according to the design parameters; a result data acquisition step of acquiring test data of the electric heating film and simulation data of the simulated electric heating film; A judging step, judging whether the test data and the simulation data meet target conditions; an adjusting step, adjusting the design parameters according to the test data and the simulation data when the test data and the simulation data do not meet the target condition; The preparation and simulation steps, the result data acquisition step, the judgment step and the adjustment step are looped until the test data and the simulation data meet the target conditions, and the final adjusted design parameters are determined to be the electric heating film parameters.

2. The method for calculating electric heating film parameters according to claim 1, characterized in that: The property parameters of the battery cell include at least the battery cell specific heat capacity, the battery cell mass and the rated voltage; the target parameters of the electric heating film include at least the target heating efficiency, the target temperature rise rate and the preset coverage area; the calculation step of calculating the design parameters of the electric heating film based on the property parameters and the target parameters includes: Obtaining a rated power of the electric heating film according to the specific heat capacity of the battery core, the mass of the battery core, the target temperature rise rate, and the target heating efficiency; Determining the effective heating area of ​​the electric heating film according to the preset covering area; Obtaining the power density of the electric heating film according to the rated power and the effective heating area; Obtaining a total resistance value of the electric heating film according to the rated power and the rated voltage; The effective heating area, the rated power, the power density and the total resistance value are used as the design parameters.

3. The method for calculating electric heating film parameters according to claim 2, characterized in that: Determining the effective heating area of ​​the electric heating film according to the preset covering area includes: A preset proportion of the preset application area is used as the effective heating area of ​​the electric heating film, wherein the preset proportion is 50%-70%.

4. The method for calculating electric heating film parameters according to claim 2 or 3, characterized in that: The step of judging whether the test data and the simulation data meet the target conditions includes: Determining the temperature zones of the electric heating film according to the test data or the simulation data; It is determined whether the test data and the simulation data of each temperature partition meet the target condition.

5. The method for calculating parameters of an electric heating film according to claim 4, wherein the adjusting step, when the test data and the simulation data do not meet the target conditions, adjusts the design parameters according to the test data and the simulation data, comprising: Determining a first temperature zone where the test data and the simulation data do not satisfy the target condition; The design parameters corresponding to the first temperature partition are adjusted according to the test data and simulation data of the first temperature partition.

6. The method for calculating electric heating film parameters according to claim 5, characterized in that: The test data and the simulation data at least include a test temperature rise rate; Adjusting design parameters corresponding to the first temperature zone according to the test data and simulation data of the first temperature zone includes: comparing the test temperature rise rate of each of the first temperature zones with the target temperature rise rate; If the test temperature rise rate of the first temperature zone is greater than the target temperature rise rate, the rated power corresponding to the first temperature zone is reduced; or if the test temperature rise rate of the first temperature zone is less than the target temperature rise rate, the rated power corresponding to the first temperature zone is increased; The power density corresponding to the first temperature zone is obtained according to the adjusted rated power.

7. The method for calculating electric heating film parameters according to claim 6, characterized in that: Reducing the rated power corresponding to the first temperature zone includes: Obtaining an absolute value of a temperature rise rate difference based on a test temperature rise rate of the first temperature zone and the target temperature rise rate; Obtaining a descent rate according to the test temperature rise rate of the first temperature zone and the absolute value of the difference between the temperature rise rates; Obtaining a reduced power according to the reduction rate and the rated power of the first temperature zone; The difference between the rated power of the first temperature zone and the reduced power is used as the reduced rated power corresponding to the first temperature zone.

8. The method for calculating electric heating film parameters according to claim 6, characterized in that: Increasing the rated power corresponding to the first temperature zone, including: Obtaining an absolute value of a temperature rise rate difference based on a test temperature rise rate of the first temperature zone and the target temperature rise rate; Obtaining a growth rate according to the test temperature rise rate of the first temperature zone and the absolute value of the difference between the temperature rise rates; obtaining an increased power according to the growth rate and the rated power of the first temperature zone; The sum of the rated power of the first temperature zone and the increased power is used as the increased rated power corresponding to the first temperature zone.

9. The method for calculating parameters of an electric heating film according to any one of claims 5 to 8, characterized in that: The test data and the simulation data include at least a test temperature rise rate, a test heating rate, a test dry-burn temperature, and a test core temperature difference, and the target conditions include at least: The test temperature rise rate of each temperature zone of the electric heating film is greater than or equal to the target temperature rise rate; The test heating efficiency of each temperature zone of the electric heating film is greater than or equal to the target heating efficiency; The test dry-burning temperature of each temperature zone of the electric heating film is less than or equal to the maximum allowable dry-burning temperature; The temperature difference of the test cell is less than or equal to a preset temperature threshold.

10. An electric heating film, characterized in that: The electric heating film is prepared according to the electric heating film parameters obtained by the method for calculating electric heating film parameters according to any one of claims 1 to 9.

11. A battery pack, characterized in that: include: Battery modules; The electric heating film according to claim 10 is arranged on the battery module to heat the battery module.

12. A vehicle, characterized in that: Including the battery pack according to claim 11.

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