A method for heat dissipation control of lithium-ion battery packs

Abstract

This invention discloses a heat dissipation control method for lithium-ion battery packs, comprising three parts: acquiring battery aging state, establishing a heat generation model, and a heat dissipation control method. The battery aging state is obtained by testing the battery's internal resistance, and the battery parameters are characterized by differences in internal resistance. Then, a thermal-electric coupling model of the battery pack is established to test the heat distribution of the battery pack. The temperature distribution of the battery pack under the influence of three factors—wind speed, discharge rate constraint, and degree of aging—is obtained. Finally, a heat dissipation control strategy considering inconsistent aging is proposed to suppress the highest temperature and maximum temperature difference of the battery pack. This invention is applicable to battery pack applications in electric vehicles, energy storage systems, and power tools.

Description

Technical Field

[0001] This invention relates to a method for heat dissipation control of lithium-ion battery packs, belonging to the field of battery aging status identification and battery thermal management technology. Background Technology

[0002] The internal working mechanism of lithium-ion battery packs originates from electrochemical reactions. During these reactions, electrochemical heat generation is inevitable, and the battery pack temperature fluctuates under the influence of its own heat generation and external heat dissipation conditions. Simultaneously, factors such as internal resistance, charge / discharge rate, and reaction rate further affect the heat generation of the battery pack. Therefore, a coupling phenomenon exists where electricity generates heat, and heat alters electricity during operation. Excessively high battery temperatures accelerate battery aging, and in extreme cases, may even lead to thermal runaway, fire, and explosion. Conversely, excessively low battery temperatures increase internal resistance and reduce the electrochemical reaction rate, resulting in a significant decrease in the battery's discharge capacity.

[0003] To ensure the safety of aged batteries during use and to fully guarantee their lifespan and performance, an efficient battery thermal management system and a reasonable cooling strategy are crucial. Research revealed that methods for establishing battery thermal models are relatively mature, and preliminary explorations have been made into the heat generation and temperature changes of aged batteries. However, studies considering the temperature field distribution for consistent aging are relatively limited. Summary of the Invention

[0004] This invention provides a method for heat dissipation control of lithium-ion battery packs, which solves the problems of overheating during use caused by increased internal resistance after battery aging, which accelerates battery aging and leads to safety accidents.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for heat dissipation control of lithium-ion battery packs:

[0007] The temperature of all individual cells at the end of the battery pack discharge is collected. The highest temperature of the individual cells is taken as the highest temperature of the battery pack at the end of the discharge, and the maximum temperature difference between the individual cells is taken as the maximum temperature difference of the battery pack at the end of the discharge.

[0008] If the highest temperature and maximum temperature difference at the end of battery discharge are not within the set ideal range, then the pre-built battery heat dissipation model is used to conduct simulation tests by gradually increasing the inlet wind speed of the battery heat dissipation cooling structure to obtain the inlet wind speed corresponding to the highest temperature and maximum temperature difference at the end of battery discharge within the set ideal range, and the inlet wind speed of the battery heat dissipation cooling structure is adjusted to the inlet wind speed obtained from the simulation test.

[0009] If increasing the inlet air velocity of the battery pack heat dissipation cooling structure to its maximum value still cannot bring the highest temperature and maximum temperature difference at the end of the battery pack discharge into the set ideal range, then the battery pack discharge rate will be gradually reduced for simulation testing to obtain the battery pack discharge rate that brings the highest temperature and maximum temperature difference at the end of the battery pack discharge into the set ideal range.

[0010] Adjust the battery pack's discharge rate to the discharge rate obtained from the simulation test.

[0011] Furthermore, the battery pack heat dissipation model includes a battery internal resistance test model, and the construction process of the battery internal resistance test model includes:

[0012] A battery pack of the same model as the lithium-ion battery pack was subjected to different number of aging cycle tests. Charging experiments were conducted on the brand-new battery pack of the same model and the battery pack under different number of aging cycle tests. The internal resistance of the battery pack was measured every 5% increase in SOC. The internal resistance-SOC curve of the battery pack under different aging states was obtained by fitting. The current aging state of the battery pack was characterized by the internal resistance of the battery pack.

[0013] Furthermore, the battery pack heat dissipation model includes a battery pack thermal-electric coupling model. This thermal-electric coupling model uses a hybrid pulse power test experiment to identify the parameters of the battery's equivalent circuit model, including:

[0014] Discharge the battery pack and charge it fully using a constant current and constant voltage charging method with a 1C charging current and a 0.05C cutoff current.

[0015] Discharge the battery pack at 1C for 10 seconds, let it rest for 40 seconds, then charge it at 1C for 10 seconds. After that, let it rest for 1 hour. Repeat this step a predetermined number of times.

[0016] Collect battery pack charge and discharge data to obtain battery pack test current curves and response voltage curves;

[0017] The parameters of the battery equivalent circuit model are determined based on the battery pack test current curve and response voltage curve.

[0018] Furthermore, the process of calculating the battery pack temperature using the battery pack thermal-electric coupling model is as follows:

[0019] Given the initial temperature T of the battery pack init In this case, combined with the already determined equivalent circuit parameters R0 and R of the lithium-ion battery p and C p The heat generation power of the battery pack is calculated based on the heat generation formula, and the battery pack temperature T is obtained through the heat transfer equation of the battery pack. batt ,in:

[0020] The heat generation formula of the battery pack is:

[0021]

[0022] Where Q is the total heat generated by the battery pack, Q r T is the heat of reaction, in J; E is the electromotive force, in J; e The ambient temperature is expressed in Kelvin (K). denoted as , where is the temperature coefficient of the galvanic cell's electromotive force; n is the charge passing through the separator at the end of charging and discharging, in C; and F is the Faraday constant, F = 96485.4 C·mol⁻¹. -1 ·K -1 Q p Ir is the polarization heat, in J; I1 is the branch current across the polarization internal resistance during charging and discharging, in A; R0 p and C p Q is the polarization resistance, measured in Ω. j Q is the Joule heat, measured in J; I is the branch current across the internal resistance of a single cell during charging and discharging, measured in A; R0 is the internal resistance of a single cell, measured in Ω; s The heat of side reaction is expressed in J, where the heat of polarization is Q. p Joule heat Q j It is a scalar quantity, the heat of reaction Q r The size is determined by the battery's charge and discharge state; The temperature gradient is along the normal direction of the textured surface, in K / m; the heat transfer equation of the battery pack is:

[0023]

[0024] Where: ρ is the battery pack density, in kg / m³. 3 ;T batt Battery pack temperature, in Kelvin (K); k r k Φ and k θ Φ represents the thermal conductivity of the battery pack along the cylindrical coordinate axes r, Φ, and θ, respectively, in W / (m·K); u represents the internal heat generation rate of the battery pack, in m / s.

[0025] Furthermore, the battery pack heat dissipation model includes a three-dimensional thermal simulation model of the battery pack, and the construction process of the three-dimensional thermal simulation model of the battery pack is as follows:

[0026] A battery pack cooling structure model was built using COMSOL Multiphysics;

[0027] The physical field simulation conditions for the battery pack cooling structure model are set at three interfaces: laminar flow, fluid heat transfer, and lumped cell.

[0028] Ultra-fine free tetrahedral network elements are used on the outer shell of the battery pack cooling structure model, and quadrilateral meshes are automatically generated for the individual cells inside the cooling structure of the battery pack cooling structure model by sweeping.

[0029] Furthermore, the battery pack discharge rate is gradually reduced in 0.1C increments.

[0030] Accordingly, a computer-readable storage medium storing one or more programs: the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0031] Accordingly, a computing device includes:

[0032] One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0033] The beneficial effects achieved by the present invention are as follows: (1) The present invention provides a heat dissipation control method for lithium battery packs that takes into account aging during use. It can ensure that the highest temperature and maximum temperature difference of the battery pack during discharge can still be controlled within the ideal range under the condition of considering inconsistent aging. This method adjusts the inlet wind speed of the battery pack cooling structure and reasonably reduces the battery pack discharge rate under the premise of considering inconsistent aging of the battery pack, thereby achieving the purpose of suppressing the highest temperature and maximum temperature difference of the battery pack. This method is simple, practical and universally applicable; (2) The heat dissipation control method for lithium battery packs with inconsistent aging characteristics proposed in the present invention can ensure that the highest temperature and maximum temperature difference of the individual cells are suppressed within a safe range at the end of the battery pack discharge; reduce battery aging caused by excessive battery temperature and avoid the risk of thermal runaway during charging. Attached Figure Description

[0034] Figure 1 This is a graph showing the change in battery internal resistance with the number of cycles.

[0035] Figure 2 This is a test current diagram for HPPC.

[0036] Figure 3 The result is a voltage response diagram for the HPPC test.

[0037] Figure 4 This is a schematic diagram of the battery thermal-electric coupling model.

[0038] Figure 5 A flowchart illustrating a heat dissipation strategy for aging lithium battery packs.

[0039] Figure 6This is a cloud map showing the temperature distribution of a battery pack employing a heat dissipation strategy. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0041] This invention discloses a method for heat dissipation control of a lithium-ion battery pack, comprising the following steps:

[0042] Step 1: Conduct 500 cycle tests on the battery. Take a brand new battery and batteries that have undergone 50, 100, 150, 200, 250, 300, 350, 400 and 500 cycles of aging test respectively for charging experiments. Measure the battery’s internal resistance in ohms for every 5% increase in SOC and fit the internal resistance-SOC curve of the battery in different aging states.

[0043] Step 2: Establish a battery thermal-electric coupling model and use the Hybrid Pulse Power Characteristic (HPPC) test experiment to identify the battery equivalent circuit model parameters, and construct a finite element thermal simulation model of the battery pack;

[0044] Step 3: The temperature distribution of the battery pack was tested from three aspects: inlet wind speed, discharge rate, and aging degree. Simulation results showed a negative correlation between inlet wind speed and the maximum temperature difference and highest temperature of the battery pack; while the discharge rate of the battery pack was positively correlated with both the maximum temperature difference and highest temperature. For battery packs with synchronized aging, the maximum temperature and maximum temperature difference increased with increasing aging degree. However, for battery packs with inconsistent aging, the maximum temperature and maximum temperature difference showed a trend of first decreasing and then increasing with increasing dispersion in inconsistent aging.

[0045] Step 4: Based on the simulation results of Step 3, it is analyzed that the inlet air velocity and discharge rate of the battery module are the key factors for controlling the temperature consistency of the battery pack with inconsistent aging. Therefore, a heat dissipation strategy is proposed for the discharge process of the battery pack. The goal is to suppress the highest temperature and the maximum temperature difference at the end of the battery pack discharge within the ideal range. Battery pack temperature data is collected, and a temperature threshold is set. If the threshold is exceeded, the inlet air velocity of the battery pack air-cooling structure is increased until the maximum air velocity is reached, and then the battery pack discharge rate is reduced.

[0046] First, the battery underwent 500 cycle tests. Batteries with 0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 aging cycles were used for charging experiments. The battery's internal resistance was measured for every 5% increase in SOC, and internal resistance-SOC curves for different aging states were fitted. Combined with existing aging data of the same type of lithium battery in the laboratory, the battery aging state was identified. Next, a thermal-electric coupling model of the battery was established, and the parameters of the equivalent circuit model were identified using the Hybrid Pulse Power Characteristic (HPPC) test, establishing a battery pack thermal model. Third, based on the established battery pack thermal model, the temperature distribution of the battery pack was tested from three aspects: inlet air velocity, discharge rate, and degree of aging. Finally, with the goal of suppressing the highest temperature and maximum temperature difference of the battery pack within an ideal range, the inlet air velocity of the battery pack's air-cooling structure was increased, and the battery pack discharge rate was reasonably reduced, thereby optimizing the heat dissipation control of the battery pack.

[0047] Furthermore, step two can be performed by using the Hybrid Pulse Power Characteristic (HPPC) test experiment to identify the parameters of the battery's equivalent circuit model, as detailed below:

[0048] Step 1: After the battery has been stored for a long time, first discharge it completely at 1C.

[0049] Step 2: Charge the battery to 4.2V using a constant current and constant voltage charging method with a 1C charging current and a 0.05C cutoff current. At this point, the battery is considered fully charged.

[0050] Step 3: Discharge the battery at 1C for 10 seconds, let it rest for 40 seconds, and then charge it at 1C for 10 seconds.

[0051] Let it sit for 1 hour after completion;

[0052] Step 4: Repeat step 3 8 times. Collect battery charge and discharge data to obtain the battery test current curve and response voltage curve.

[0053] It should be noted that 1C refers to the current of the battery's nominal capacity. For example, a lithium battery with a nominal capacity of 1000mAh charged and discharged for 10 seconds at 1C means it is charged and discharged at a current of 1A for 10 seconds, and charging and discharging at 2C means it is charged and discharged at a current of 2A.

[0054] Furthermore, step two can be performed by calculating the battery temperature using a battery thermo-electric coupling model, as follows:

[0055] Given the initial temperature T of the battery pack initIn this case, combined with the already determined equivalent circuit parameters R0 and R of the lithium-ion battery p and C p The heat generation power of the battery pack is calculated based on the battery's heat generation formula, and the battery pack temperature T is obtained through the battery pack's heat transfer equation. batt .in:

[0056] The heat generated by a lithium-ion battery pack during operation mainly consists of four parts: the heat of reaction during electrochemical reactions, the Joule heat generated by overcoming the battery's internal resistance, the polarization heat generated by the imbalance of positive and negative electrode potentials, and the heat of side reactions generated in addition to the chemical reactions. The heat of side reactions is negligible compared to the heat generated by the three battery heat generation methods mentioned above, and therefore can be ignored in the modeling process. In summary, the total heat generation power Q of the battery pack and its detailed formula are shown in Equation (1):

[0057]

[0058] Q r T is the heat of reaction, in J; E is the electromotive force, in J; e The ambient temperature is expressed in Kelvin (K). denoted as , where is the temperature coefficient of the galvanic cell's electromotive force; n is the charge passing through the separator at the end of charging and discharging, in C; and F is the Faraday constant, F = 96485.4 C·mol⁻¹. -1 ·K -1 Q p Ir is the polarization heat, in J; I1 is the branch current across the polarization internal resistance during charging and discharging, in A; R0 p and C p Q is the polarization resistance, measured in Ω. When the battery is subjected to current excitation, this impedance characterizes the process of a slow change in terminal voltage. j Q represents Joule heating, measured in J; I represents the branch current across the battery's internal resistance during charging and discharging, measured in A; R0 represents the battery's internal resistance, measured in Ω. When a sudden current is applied to a lithium-ion battery, this resistance can cause an instantaneous change in the terminal voltage at the moment the current flows. s This is the heat of side reaction, measured in J. Among them, the polarization heat Q... p Joule heat Q j It is a scalar quantity, the heat of reaction Q r The size is determined by the battery's charge / discharge state. Lithium-ion battery packs have three heat transfer modes: heat conduction, heat convection, and heat radiation. Heat radiation accounts for a small proportion of the cooling process and can be ignored. Heat conduction can be represented by Fourier's law:

[0059]

[0060] q is the heat flux density, in W / m³. 2 k is the thermal conductivity, in W / m·K; This represents the temperature gradient along the normal direction of the textured surface, in K / m.

[0061] Thermal convection can be expressed by Newton's law of cooling:

[0062] q=h(T b -T f (3)

[0063] q is the heat flux density, in W / m³. 2 h is the convective heat transfer coefficient, in W / m³. 2 ·K;T b Temperature of the battery's outer surface, in Kelvin (K); T f is the temperature of the medium, in K; T is the temperature, in K.

[0064] The heat transfer equation for the battery pack can be expressed as:

[0065]

[0066] Where: ρ is the lithium-ion battery density, in kg / m³. 3 ;T batt Battery pack temperature, in Kelvin (K); k r k Φ and k θ Φ represents the thermal conductivity of the lithium-ion battery pack along the cylindrical coordinate axes r, Φ, and θ, respectively, in W / (m·K); u represents the internal heat generation rate of the battery pack, in m / s.

[0067] Furthermore, step two can be performed by building a three-dimensional thermal simulation model of the battery pack according to the following steps:

[0068] Step 1: Use COMSOL Multiphysics to build a Z-shaped groove air-cooled model of the battery pack;

[0069] Step 2: Set the physical field simulation conditions for the battery pack model at the three interfaces of laminar flow, fluid heat transfer, and lumped cell;

[0070] Step 3: Use ultra-fine free tetrahedral network units on the outer shell of the battery pack cooling model, and use a sweeping method to automatically generate quadrilateral meshes for the individual cells inside the cooling structure of the battery pack model.

[0071] Furthermore, the heat dissipation strategy described in step four is as follows:

[0072] Based on the battery pack temperature distribution under the influence of wind speed, discharge rate, and aging degree obtained in step 3, it can be seen that increasing wind speed and decreasing the battery pack discharge rate are both effective in suppressing the highest temperature and maximum temperature difference at the end of battery pack discharge. Based on this, a heat dissipation control strategy for the battery pack is proposed:

[0073] 1) First, conduct a discharge test on the battery pack under specified room temperature conditions, and measure the highest temperature and maximum temperature difference of the battery pack at the end of the discharge.

[0074] 2) If the highest temperature and maximum temperature difference at the end of the battery pack discharge exceed the ideal range, increase the inlet air velocity of the battery pack cooling structure. Measure the highest temperature and maximum temperature difference at the end of the battery pack discharge using simulation with the increased air velocity, and determine whether the sampling results meet the requirements. If they still do not meet the requirements, continue to increase the air velocity for simulation.

[0075] 3) If the simulated battery pack temperature still does not meet the requirements after increasing the inlet air velocity of the battery pack cooling structure until the air velocity reaches the upper limit, the battery pack discharge rate is gradually reduced at intervals of 0.1C, and the battery pack temperature data is measured by simulation until the highest temperature and the maximum temperature difference at the end of the battery pack discharge are suppressed within the ideal range.

[0076] The present invention will be specifically described below using a ternary lithium battery as an example.

[0077] Example

[0078] ISR18650-2.5Ah single-cell batteries were selected for testing. Charging experiments were conducted on batteries subjected to 0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 aging cycles. The battery's internal resistance (in ohms) was measured for every 5% increase in SOC. A two-dimensional graph was obtained, showing the battery under different aging conditions, with internal resistance R as the y-axis and SOC as the x-axis. Figure 1 As shown.

[0079] The equivalent circuit of the battery was constructed using the Thevenin model, and the parameters of the equivalent circuit of the lithium-ion battery were measured and identified through HPPC testing experiments, as detailed below:

[0080] Step 1: After the battery has been stored for a long time, first discharge it completely at 1C.

[0081] Step 2: Charge the battery to 4.2V using a constant current and constant voltage charging method with a 1C charging current and a 0.05C cutoff current. At this point, the battery is considered fully charged.

[0082] Step 3: Discharge the battery at 1C for 10 seconds, let it rest for 40 seconds, and then charge it at 1C for 10 seconds.

[0083] Let it sit for 1 hour after completion;

[0084] Step 4: Repeat step 3 8 times. Collect battery charge and discharge data to obtain the battery test current curve and response voltage curve, as shown below. Figure 2 , Figure 3 As shown.

[0085] Adopting such Figure 4 The schematic diagram shown illustrates the construction of a battery thermo-electric coupling model. Given the initial battery temperature T... init In this case, combined with the already determined equivalent circuit parameters R0 and R of the lithium-ion battery p C p The battery's heat generation power is calculated based on the battery heat generation formula, and the battery temperature T is obtained through a fluid heat transfer model. batt This model takes the applied current and the initial temperature of the battery as inputs and the battery temperature after a period of operation as output.

[0086] A Z-groove air-cooled model of a lithium-ion battery pack was built using COMSOL Multiphysics. The physical field simulation conditions of the battery pack model were set at three interfaces: laminar flow, fluid heat transfer, and lumped cell. Ultra-fine free tetrahedral network elements were used on the outer shell of the battery pack cooling model, and quadrilateral meshes were automatically generated for the individual cells inside the cooling structure of the battery pack model by sweeping.

[0087] The established battery pack heat generation model was used to analyze the temperature distribution of the battery pack under different inlet air velocities of the cooling structure, different discharge rates, and different aging degrees. A battery pack composed of 12 ISR18650-2.5Ah cells was selected, and an experimental platform was built. The aging degree of the battery pack followed a normal distribution X~N(0.99, 0.01302). Based on... Figure 5 The heat dissipation strategy shown was tested, and the highest temperature and maximum temperature difference at the end of discharge under the initial conditions of the battery pack were measured. The heat dissipation strategy was implemented using an established simulation model, and the simulation yielded the inlet air velocity and discharge rate of the cooling structure that suppressed the highest temperature and maximum temperature difference at the end of discharge within the ideal range. Based on the simulation results, a discharge experiment was conducted on the battery pack, setting the discharge rate to 1C and the inlet air velocity to 1.97 m / s. The temperature distribution cloud map of the battery pack at the end of discharge is shown below. Figure 6 Battery pack T max Equal to 27.7℃, ΔT max The temperature reached 3.9℃, achieving the target set by the heat dissipation strategy and verifying the effectiveness of the heat dissipation strategy in suppressing the highest temperature and maximum temperature difference at the end of battery discharge.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0089] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a lithium-ion battery pack heat dissipation control method.

[0090] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing a lithium-ion battery pack heat dissipation control method.

[0091] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0092] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0093] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0094] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0095] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for heat dissipation control of a lithium-ion battery pack, characterized in that: The temperature of all individual cells at the end of the battery pack discharge is collected. The highest temperature of the individual cells is taken as the highest temperature of the battery pack at the end of the discharge, and the maximum temperature difference between the individual cells is taken as the maximum temperature difference of the battery pack at the end of the discharge. If the highest temperature and maximum temperature difference at the end of battery discharge are not within the set ideal range, then the pre-built battery heat dissipation model is used to conduct simulation tests by gradually increasing the inlet wind speed of the battery heat dissipation cooling structure to obtain the inlet wind speed corresponding to the highest temperature and maximum temperature difference at the end of battery discharge within the set ideal range, and the inlet wind speed of the battery heat dissipation cooling structure is adjusted to the inlet wind speed obtained from the simulation test. If increasing the inlet air velocity of the battery pack heat dissipation cooling structure to its maximum value still cannot bring the highest temperature and maximum temperature difference at the end of the battery pack discharge into the set ideal range, then the battery pack discharge rate will be gradually reduced for simulation testing to obtain the battery pack discharge rate that brings the highest temperature and maximum temperature difference at the end of the battery pack discharge into the set ideal range. Adjust the battery pack's discharge rate to the discharge rate obtained from the simulation test.

2. The method for heat dissipation control of a lithium-ion battery pack according to claim 1, characterized in that, The battery pack heat dissipation model includes a battery internal resistance test model, and the construction process of the battery internal resistance test model includes: A battery pack of the same model as the lithium-ion battery pack was subjected to different number of aging cycle tests. Charging experiments were conducted on the brand-new battery pack of the same model and the battery pack under different number of aging cycle tests. The internal resistance of the battery pack was measured every 5% increase in SOC. The internal resistance-SOC curve of the battery pack under different aging states was obtained by fitting. The current aging state of the battery pack was characterized by the internal resistance of the battery pack.

3. The method for heat dissipation control of a lithium-ion battery pack according to claim 1, characterized in that, The battery pack heat dissipation model includes a battery pack thermal-electric coupling model. This thermal-electric coupling model uses a hybrid pulse power test experiment to identify the parameters of the battery's equivalent circuit model, including: Discharge the battery pack and charge it fully using a constant current and constant voltage charging method with a 1C charging current and a 0.05C cutoff current. Discharge the battery pack at 1C for 10 seconds, let it rest for 40 seconds, then charge it at 1C for 10 seconds. After that, let it rest for 1 hour. Repeat this step a predetermined number of times. Collect battery pack charge and discharge data to obtain battery pack test current curves and response voltage curves; The parameters of the battery equivalent circuit model are determined based on the battery pack test current curve and response voltage curve.

4. The method for heat dissipation control of a lithium-ion battery pack according to claim 3, characterized in that, The process of calculating the battery pack temperature using the battery pack thermal-electric coupling model is as follows: Given the initial temperature T of the battery pack init In this case, combined with the already determined equivalent circuit parameters R0 and R of the lithium-ion battery p and C p The heat generation power of the battery pack is calculated based on the heat generation formula, and the battery pack temperature T is obtained through the heat transfer equation of the battery pack. batt ,in: The heat generation formula of the battery pack is: ； Where Q is the total heat generation power of the battery pack; The heat of reaction is expressed in J. Electromotive force (EMF), measured in J; T e The ambient temperature is expressed in Kelvin (K). is the temperature coefficient of the galvanic cell's electromotive force; n is the amount of charge passing through the separator at the end of charging and discharging, in C; F is the Faraday constant. ; Polarization heat, measured in J. This is the branch current across the polarization internal resistance during charging and discharging, expressed in amperes (A). and C p Polarization resistance, in Ω; Joule heating is expressed in J, and I is the branch current across the internal resistance of a single cell during charging and discharging, expressed in A. This represents the internal resistance of a single cell, measured in Ω. The heat of side reaction is expressed in J, where the heat of polarization is... and Joule heat It is a scalar quantity, heat of reaction. The size is determined by the battery's charge and discharge state; The temperature gradient is along the normal direction of the textured surface, in K / m. The heat transfer equation for the battery pack is: ； in: Battery pack density, in kg / m³ 3 ;T batt Battery pack temperature, in Kelvin (K). , and The battery pack is divided into cylindrical coordinates r, Φ, and Φ respectively. Thermal conductivity on the axis, in W / (m·K); u is the internal heat generation rate of the battery pack, in m / s.

5. The method for heat dissipation control of a lithium-ion battery pack according to claim 1, characterized in that, The battery pack heat dissipation model includes a three-dimensional thermal simulation model of the battery pack. The construction process of the three-dimensional thermal simulation model of the battery pack is as follows: A battery pack cooling structure model was built using COMSOL Multiphysics; The physical field simulation conditions for the battery pack cooling structure model are set at three interfaces: laminar flow, fluid heat transfer, and lumped cell. Ultra-fine free tetrahedral network elements are used on the outer shell of the battery pack cooling structure model, and quadrilateral meshes are automatically generated for the individual cells inside the cooling structure of the battery pack cooling structure model by sweeping.

6. The method for heat dissipation control of a lithium-ion battery pack according to claim 1, characterized in that, The battery pack discharge rate is gradually reduced in 0.1C increments.

7. A computer-readable storage medium for storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the steps of the method according to any one of claims 1 to 6.

8. A computing device, characterized in that, include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing the method of any one of claims 1 to 6.

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