Battery internal temperature assessment method and device, terminal equipment and storage medium

Abstract

The invention discloses a battery internal temperature assessment method and device, terminal equipment and a storage medium. The method comprises the following steps of: when any one of a first Bit number, a second Bit number and a third Bit number is smaller than or equal to a preset Bit number threshold value, constructing a Fourier heat conduction equation of the battery according to the density, the constant-pressure specific heat, a first heat conduction coefficient, current, voltage, volume and open-circuit potential; wherein the Fourier heat conduction equation is used for representing the change relation of the internal temperature of the battery along with time and position; and solving the Fourier heat conduction equation according to the to-be-evaluated position and the working duration to obtain the internal temperature of the battery at the to-be-evaluated position. The differential equation is solved by adopting the mathematical analysis method to calculate the internal temperature of the battery, so that the technical problem of inaccurate internal temperature detection caused by replacing the internal temperature of the battery with the surface temperature of the battery in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery management, and in particular to a method, device, terminal equipment and storage medium for evaluating the internal temperature of a battery. Background Art

[0002] Temperature is an important indicator that affects the performance, life and safety of lithium-ion batteries. With the expansion of battery application scenarios and the innovation of battery materials, lightweight, compact, and high system energy density battery systems have become the main development direction for power systems and large-scale energy storage. Large-capacity and large-size batteries have emerged. Compared with small-capacity batteries, single-point temperature measurement on the outer surface of the battery under complex application conditions can no longer reflect the true thermal state and corresponding safety state of large-capacity batteries.

[0003] In order to balance performance and economy brought by space utilization, the existing energy storage system cannot accurately monitor the battery temperature of each single cell in the battery system through a temperature sensor, resulting in the temperature value of the local measurement point being difficult to truly reflect the temperature state of the adjacent or thermal field "dead zone", which poses a more serious safety hazard to the management and operation of the battery system. At present, the application scenarios of electric vehicles, energy storage power stations, and electric ship batteries have adopted active thermal management strategies to minimize the temperature inconsistency of the battery system as much as possible, and detect the battery surface temperature as the internal temperature of the battery. However, under conditions of high power output and poor heat exchange conditions, the large temperature gradient inside the battery cannot be avoided, which makes the difference between the battery surface temperature and the internal temperature of the battery too large, resulting in inaccurate measurement of the internal temperature of the battery. How to detect or calculate the internal temperature of the battery at low cost, accurately, and in real time has become one of the difficulties and major challenges in the reliability monitoring and analysis of existing lithium-ion battery systems. Summary of the invention

[0004] The present invention provides a battery internal temperature evaluation method, device, terminal equipment and storage medium to solve the technical problem of inaccurate battery internal temperature detection in the prior art.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a method for evaluating the internal temperature of a battery, comprising:

[0006] Obtaining a first Biot number in a thickness direction, a second Biot number in a width direction, and a third Biot number in a height direction of the battery;

[0007] When any one of the first Biot number, the second Biot number and the third Biot number is less than or equal to a preset Biot number threshold, the following operations are performed:

[0008] Obtain the battery's density, specific heat at constant pressure, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and operating time;

[0009] Constructing a Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, first thermal conductivity, current, voltage, volume and open circuit potential; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position;

[0010] The Fourier heat conduction equation is solved according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated.

[0011] As a preferred solution, the Fourier heat conduction equation is:

[0012]

[0013] In the formula, t represents the working time of the battery; x represents the position of the battery to be evaluated; T represents the internal temperature of the battery, which is a binary function of time t and position x; k x represents the first thermal conductivity of the battery in the thickness direction; ρ represents the density of the battery; c p represents the constant pressure specific heat of the battery; g(t) represents the time-varying heat source of the battery; I represents the current of the battery; V represents the volume of the battery; E oc It represents the open circuit potential of the battery; U represents the voltage of the battery; ± takes a positive sign when the battery is discharging and a negative sign when the battery is charging.

[0014] As a preferred solution, solving the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated includes:

[0015] Obtaining the initial temperature, ambient temperature and thermal diffusion coefficient of the battery; wherein the initial temperature refers to the temperature of the battery when it is not working;

[0016] Constructing a heat transfer boundary condition of the Fourier heat conduction equation according to the ambient temperature and the first thermal conductivity;

[0017] According to the initial temperature, constructing the initial condition of the Fourier heat conduction equation;

[0018] Constructing an excess temperature expression of the battery according to the ambient temperature;

[0019] According to the thermal diffusion coefficient and the first Biot number, using Duhamel's theorem, the excess temperature expression is converted into a homogeneous term to obtain an internal temperature expression of the battery;

[0020] Substitute the position to be evaluated and the working time into the internal temperature expression to solve it, so as to obtain the internal temperature of the battery at the position to be evaluated.

[0021] As a preferred solution, the formula for the heat exchange boundary condition is:

[0022]

[0023] Where, T f Indicates the ambient temperature of the battery; L indicates the thickness of the battery;

[0024] The formula for the initial condition is:

[0025] T(x,t)=T0 at t=0;

[0026] Where, represents the initial temperature of the battery;

[0027] The excess temperature expression is:

[0028] θ(x,t)=T(x,t)-T f ;

[0029] Where θ represents the excess temperature of the battery, which is a binary function of time t and position x;

[0030] The internal temperature expression is:

[0031]

[0032] Where α represents the thermal diffusion coefficient of the battery; Bi x represents the first Biot number of the battery in the thickness direction; θ0 represents the initial temperature T0 and the ambient temperature T f The difference between δ and L; τ represents the intermediate variable used to deal with time-varying heat sources; β n is the eigenvalue corresponding to a solution of β.

[0033] As a preferred solution, when the first Biot number, the second Biot number and the third Biot number are all greater than the Biot number threshold, the surface temperature of the battery is obtained;

[0034] The surface temperature is taken as the internal temperature of the battery at any location.

[0035] As a preferred solution, before obtaining the first Biot number of the battery in the thickness direction, the second Biot number in the width direction, and the third Biot number in the height direction, the method further includes:

[0036] Obtaining the thickness, width, height, first thermal conductivity in the thickness direction, second thermal conductivity in the width direction, third thermal conductivity in the height direction, and convection heat transfer coefficient of the battery;

[0037] Calculating the first Biot number according to the thickness, the first thermal conductivity and the convection heat transfer coefficient;

[0038] Calculating the second Biot number according to the width, the second thermal conductivity and the convection heat transfer coefficient;

[0039] The third Biot number is calculated according to the height, the third thermal conductivity and the convection heat transfer coefficient.

[0040] As a preferred solution, the calculation formula of the first Biot number is:

[0041]

[0042] In the formula, Bi x represents the first Biot number of the battery in the thickness direction; h represents the convection heat transfer coefficient; L represents the thickness of the battery; k x Indicates the first thermal conductivity of the battery in the thickness direction;

[0043] The calculation formula of the second Biot number is:

[0044]

[0045] In the formula, Bi y represents the second Biot number of the battery in the width direction; L represents the width of the battery; k x Represents the second thermal conductivity of the battery in the width direction;

[0046] The calculation formula of the third Biot number is:

[0047]

[0048] In the formula, Bi y represents the third Biot number of the battery in the height direction; L represents the height of the battery; k x Represents the third thermal conductivity of the battery in the height direction.

[0049] Based on the above embodiment, another embodiment of the present invention provides a battery internal temperature evaluation device, including: a data acquisition module and an internal temperature calculation module;

[0050] The data acquisition module is used to obtain a first Biot number in the thickness direction, a second Biot number in the width direction, and a third Biot number in the height direction of the battery; when any one of the first Biot number, the second Biot number, and the third Biot number is less than or equal to a preset Biot number threshold, obtain the density, constant pressure specific heat, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and working time of the battery;

[0051] The internal temperature calculation module is used to construct the Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, the first thermal conductivity, the current, the voltage, the volume and the open circuit potential; and solve the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position.

[0052] Based on the above embodiments, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, the battery internal temperature evaluation method described in the above invention embodiment is implemented.

[0053] Based on the above embodiment, another embodiment of the present invention provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the battery internal temperature evaluation method described in the above invention embodiment.

[0054] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0055] The present invention constructs the Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, first thermal conductivity, current, voltage, volume and open circuit potential when any one of the first Biot number, the second Biot number and the third Biot number is less than or equal to the preset Biot number threshold; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position; then, according to the position to be evaluated and the working time, the Fourier heat conduction equation is solved to obtain the internal temperature of the battery at the position to be evaluated. The present invention uses a mathematical analytical method to solve the differential equation to calculate the internal temperature of the battery, which solves the technical problem of inaccurate internal temperature detection caused by using the battery surface temperature instead of the internal temperature of the battery in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a flow chart of a method for evaluating internal temperature of a battery provided by one embodiment of the present invention;

[0057] Figure 2 This is a structural diagram of a square single lithium-ion battery provided by an embodiment of the present invention;

[0058] Figure 3 It is a structural schematic diagram of a battery internal temperature evaluation device provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0059] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] Embodiment 1

[0061] Please refer to Figure 1 , a method for evaluating the internal temperature of a battery provided by an embodiment of the present invention, comprising:

[0062] S1. Obtain a first Biot number in a thickness direction, a second Biot number in a width direction, and a third Biot number in a height direction of the battery.

[0063] It should be noted that the thickness, width and height directions of the battery are as follows: Figure 2 As shown, the thickness direction is the direction of the x-axis, the width direction is the direction of the y-axis, and the height direction is the direction of the z-axis.

[0064] S2. When any one of the first Biot number, the second Biot number and the third Biot number is less than or equal to a preset Biot number threshold, perform operations from steps S3 to S5.

[0065] It should be noted that if any one of the first Biot number, the second Biot number and the third Biot number is less than or equal to the preset Biot number threshold, it means that the internal thermal resistance of the battery cannot be ignored and there is a temperature gradient inside the battery.

[0066] S3. Obtain the density, specific heat at constant pressure, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and working time of the battery.

[0067] It should be noted that the position to be evaluated refers to the position of the target point in the thickness direction where the internal temperature is to be calculated. For example, if the target point is the center point of the battery, then the position to be evaluated is the 1 / 2 position of the thickness. If the thickness is l, the value of the position to be evaluated is l / 2. The working time refers to the time from the start of the battery working to the present moment.

[0068] S4. Constructing the Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, first thermal conductivity, current, voltage, volume and open circuit potential; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the change of time and position.

[0069] It should be noted that in the process of constructing the Fourier heat conduction equation, the following initial Fourier heat conduction equation is first constructed:

[0070]

[0071] In the formula, k x Indicates the first thermal conductivity of the battery in the thickness direction; k y k represents the second thermal conductivity of the battery in the width direction; z represents the third thermal conductivity of the battery in the height direction; ρ represents the density of the battery; c p represents the constant-pressure specific heat of the battery; g(t) represents the time-varying heat source of the battery.

[0072] The initial Fourier heat conduction equation is a three-dimensional, non-homogeneous, non-steady-state equation with a time-varying heat source, which is inconvenient to solve. Since the battery thickness direction is the direction of battery cell stacking, the thermal resistance value is the largest. Therefore, based on the heat transfer characteristics, the initial Fourier heat conduction equation is first simplified to a one-dimensional, non-homogeneous, non-steady-state Fourier heat conduction equation with an event-varying heat source. The simplified Fourier heat conduction equation only needs to solve the temperature distribution in the battery thickness direction to characterize the temperature distribution of the entire battery.

[0073] In a preferred embodiment, the Fourier heat conduction equation is:

[0074]

[0075] In the formula, t represents the working time of the battery; x represents the position of the battery to be evaluated; T represents the internal temperature of the battery, which is a binary function of time t and position x; k x represents the first thermal conductivity of the battery in the thickness direction; ρ represents the density of the battery; c p represents the constant pressure specific heat of the battery; g(t) represents the time-varying heat source of the battery; I represents the current of the battery; V represents the volume of the battery; E oc It represents the open circuit potential of the battery; U represents the voltage of the battery; ± takes a positive sign when the battery is discharging and a negative sign when the battery is charging.

[0076] In this embodiment, a simplified Fourier heat conduction equation is given.

[0077] S5. Solve the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated.

[0078] In a preferred embodiment, solving the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated includes:

[0079] Obtaining the initial temperature, ambient temperature and thermal diffusion coefficient of the battery; wherein the initial temperature refers to the temperature of the battery when it is not working;

[0080] Constructing a heat transfer boundary condition of the Fourier heat conduction equation according to the ambient temperature and the first thermal conductivity;

[0081] According to the initial temperature, constructing the initial condition of the Fourier heat conduction equation;

[0082] Constructing an excess temperature expression of the battery according to the ambient temperature;

[0083] According to the thermal diffusion coefficient and the first Biot number, using Duhamel's theorem, the excess temperature expression is converted into a homogeneous term to obtain an internal temperature expression of the battery;

[0084] Substitute the position to be evaluated and the working time into the internal temperature expression to solve it, so as to obtain the internal temperature of the battery at the position to be evaluated.

[0085] In a preferred embodiment, the formula for the heat exchange boundary condition is:

[0086]

[0087] Where, T f Indicates the ambient temperature of the battery; L indicates the thickness of the battery;

[0088] The formula for the initial condition is:

[0089] T(x,t)=T0 at t=0;

[0090] Where, represents the initial temperature of the battery;

[0091] The excess temperature expression is:

[0092] θ(x,t)=T(x,t)-T f ;

[0093] Where θ represents the excess temperature of the battery, which is a binary function of time t and position x;

[0094] The internal temperature expression is:

[0095]

[0096] Where α represents the thermal diffusion coefficient of the battery; Bi x represents the first Biot number of the battery in the thickness direction; θ0 represents the initial temperature T0 and the ambient temperature T f The difference between δ and L; τ represents the intermediate variable used to deal with time-varying heat sources; β n is the eigenvalue corresponding to a solution of β.

[0097] In this embodiment, in order to complete the mathematical description of the heat generation problem during the battery working process, the heat exchange boundary conditions and initial conditions of the Fourier heat conduction equation are first constructed. To facilitate the solution, the excess temperature expression of the battery is constructed to eliminate the non-homogeneous term T in the heat exchange boundary condition. f . Then, the Duhamel Theorem is used to transform the excess temperature expression into a homogeneous expression, and the internal temperature expression of the battery is obtained. By directly solving the internal temperature expression, we can get the analytical solution of the excess temperature changing with time and position, and further get the analytical solution of the internal temperature changing with time and position, and then substitute the position to be evaluated and the working time to solve the internal temperature of the battery at the position to be evaluated.

[0098] It should be noted that the present invention uses a mathematical analytical method to solve the differential equation to calculate the internal temperature of the battery, which is the fastest and most accurate method. The present invention avoids the errors caused by physical modeling and physical measurement calculations, and can obtain the internal temperature value of any point in the thickness direction of the battery. At the same time, the present invention uses a non-destructive and rapid detection method that can be quickly integrated into the battery management system for use in different energy storage system application scenarios. In addition, the present invention can directly calculate the internal temperature of the battery under conditions such as aging due to long-term use by only correcting the physical properties, while physical detection and model calculations are difficult to achieve adaptive calculation of aging.

[0099] In a preferred embodiment, when the first Biot number, the second Biot number and the third Biot number are all greater than the Biot number threshold, the surface temperature of the battery is obtained;

[0100] The surface temperature is taken as the internal temperature of the battery at any location.

[0101] It should be noted that if the first Biot number, the second Biot number and the third Biot number are all greater than the preset Biot number threshold, it means that the internal thermal resistance of the battery can be ignored, the internal temperature tends to be constant, and the battery surface temperature approximately represents the internal temperature of the battery. Then the internal temperature of any position of the battery at any time is equal to the surface temperature of the battery.

[0102] In a preferred embodiment, before obtaining the first Biot number of the battery in the thickness direction, the second Biot number in the width direction, and the third Biot number in the height direction, the method further includes:

[0103] Obtaining the thickness, width, height, first thermal conductivity in the thickness direction, second thermal conductivity in the width direction, third thermal conductivity in the height direction, and convection heat transfer coefficient of the battery;

[0104] Calculating the first Biot number according to the thickness, the first thermal conductivity and the convection heat transfer coefficient;

[0105] Calculating the second Biot number according to the width, the second thermal conductivity and the convection heat transfer coefficient;

[0106] The third Biot number is calculated according to the height, the third thermal conductivity and the convection heat transfer coefficient.

[0107] In a preferred embodiment, the calculation formula of the first Biot number is:

[0108]

[0109] In the formula, Bi x represents the first Biot number of the battery in the thickness direction; h represents the convection heat transfer coefficient; L represents the thickness of the battery; k x Indicates the first thermal conductivity of the battery in the thickness direction;

[0110] The calculation formula of the second Biot number is:

[0111]

[0112] In the formula, Bi y represents the second Biot number of the battery in the width direction; L represents the width of the battery; k x Represents the second thermal conductivity of the battery in the width direction;

[0113] The calculation formula of the third Biot number is:

[0114]

[0115] In the formula, Bi y represents the third Biot number of the battery in the height direction; L represents the height of the battery; k x Represents the third thermal conductivity of the battery in the height direction.

[0116] Embodiment 2

[0117] Please refer to Figure 2 , a battery internal temperature evaluation device provided by an embodiment of the present invention comprises: a data acquisition module and an internal temperature calculation module;

[0118] The data acquisition module is used to obtain a first Biot number in the thickness direction, a second Biot number in the width direction, and a third Biot number in the height direction of the battery; when any one of the first Biot number, the second Biot number, and the third Biot number is less than or equal to a preset Biot number threshold, obtain the density, constant pressure specific heat, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and working time of the battery;

[0119] The internal temperature calculation module is used to construct the Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, the first thermal conductivity, the current, the voltage, the volume and the open circuit potential; and solve the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position.

[0120] Embodiment 3

[0121] Accordingly, an embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, the battery internal temperature evaluation method described in the above-mentioned embodiment of the invention is implemented.

[0122] Embodiment 4

[0123] Accordingly, an embodiment of the present invention provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute the battery internal temperature evaluation method described in the above-mentioned embodiment of the invention.

[0124] It should be noted that the device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which may be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art may understand and implement it without paying any creative effort.

[0125] Those skilled in the art can clearly understand that for the sake of convenience and brevity, the specific working process of the device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0126] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0127] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the device, and various interfaces and lines are used to connect various parts of the entire device.

[0128] The memory can be used to store the computer program, and the processor realizes various functions of the device by running or executing the computer program stored in the memory and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required for a function, etc.; the data storage area can store data created according to the use of the mobile phone, etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (FlashCard), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0129] The storage medium is a storage medium, and the computer program is stored in the storage medium. When the computer program is executed by the processor, the steps of each method embodiment described above can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer readable media do not include electric carrier signals and telecommunication signals.

[0130] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for evaluating the internal temperature of a battery, characterized in that: include: Obtaining a first Biot number in a thickness direction, a second Biot number in a width direction, and a third Biot number in a height direction of the battery; When any one of the first Biot number, the second Biot number and the third Biot number is less than or equal to a preset Biot number threshold, the following operations are performed: Obtain the battery's density, specific heat at constant pressure, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and operating time; Constructing a Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, first thermal conductivity, current, voltage, volume and open circuit potential; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position; The Fourier heat conduction equation is solved according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated.

2. The battery internal temperature evaluation method according to claim 1, characterized in that: The Fourier heat conduction equation is: In the formula, t represents the working time of the battery; x represents the position of the battery to be evaluated; T represents the internal temperature of the battery, which is a binary function of time t and position x; k x represents the first thermal conductivity of the battery in the thickness direction; ρ represents the density of the battery; c p represents the constant pressure specific heat of the battery; g(t) represents the time-varying heat source of the battery; I represents the current of the battery; V represents the volume of the battery; E oc It represents the open circuit potential of the battery; U represents the voltage of the battery; ± takes a positive sign when the battery is discharging and a negative sign when the battery is charging.

3. The battery internal temperature evaluation method according to claim 2, characterized in that: The step of solving the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated includes: Obtaining the initial temperature, ambient temperature and thermal diffusion coefficient of the battery; wherein the initial temperature refers to the temperature of the battery when it is not working; Constructing a heat transfer boundary condition of the Fourier heat conduction equation according to the ambient temperature and the first thermal conductivity; According to the initial temperature, constructing the initial condition of the Fourier heat conduction equation; Constructing an excess temperature expression of the battery according to the ambient temperature; According to the thermal diffusion coefficient and the first Biot number, using Duhamel's theorem, the excess temperature expression is converted into a homogeneous term to obtain an internal temperature expression of the battery; Substitute the position to be evaluated and the working time into the internal temperature expression to solve it, so as to obtain the internal temperature of the battery at the position to be evaluated.

4. The battery internal temperature evaluation method according to claim 3, characterized in that: The formula for the heat exchange boundary condition is: Where, T f Indicates the ambient temperature of the battery; L indicates the thickness of the battery; The formula for the initial condition is: T(x,t)=T0 at t=0; Where, represents the initial temperature of the battery; The excess temperature expression is: θ(x,t)=T(x,t)-T f ; Where θ represents the excess temperature of the battery, which is a binary function of time t and position x; The internal temperature expression is: Where α represents the thermal diffusion coefficient of the battery; Bi x represents the first Biot number of the battery in the thickness direction; θ0 represents the initial temperature T0 and the ambient temperature T f The difference between δ and L; τ represents the intermediate variable used to deal with time-varying heat sources; β n is the eigenvalue corresponding to a solution of β.

5. The battery internal temperature evaluation method according to claim 1, characterized in that: When the first Biot number, the second Biot number and the third Biot number are all greater than the Biot number threshold, obtaining the surface temperature of the battery; The surface temperature is taken as the internal temperature of the battery at any location.

6. The method according to claim 1, wherein: Before obtaining the first Biot number of the battery in the thickness direction, the second Biot number in the width direction, and the third Biot number in the height direction, the method further includes: Obtaining the thickness, width, height, first thermal conductivity in the thickness direction, second thermal conductivity in the width direction, third thermal conductivity in the height direction, and convection heat transfer coefficient of the battery; Calculating the first Biot number according to the thickness, the first thermal conductivity and the convection heat transfer coefficient; Calculating the second Biot number according to the width, the second thermal conductivity and the convection heat transfer coefficient; The third Biot number is calculated according to the height, the third thermal conductivity and the convection heat transfer coefficient.

7. The method according to claim 6, wherein: The calculation formula of the first Biot number is: In the formula, Bi x represents the first Biot number of the battery in the thickness direction; h represents the convection heat transfer coefficient; L represents the thickness of the battery; k x Indicates the first thermal conductivity of the battery in the thickness direction; The calculation formula of the second Biot number is: In the formula, Bi y represents the second Biot number of the battery in the width direction; L represents the width of the battery; k x Represents the second thermal conductivity of the battery in the width direction; The calculation formula of the third Biot number is: In the formula, Bi y represents the third Biot number of the battery in the height direction; L represents the height of the battery; k x Represents the third thermal conductivity of the battery in the height direction.

8. A battery internal temperature evaluation device, characterized in that: include: Data acquisition module and internal temperature calculation module; The data acquisition module is used to obtain a first Biot number in the thickness direction, a second Biot number in the width direction, and a third Biot number in the height direction of the battery; when any one of the first Biot number, the second Biot number, and the third Biot number is less than or equal to a preset Biot number threshold, obtain the density, constant pressure specific heat, first thermal conductivity in the thickness direction, current, voltage, volume, open circuit potential, position to be evaluated, and working time of the battery; The internal temperature calculation module is used to construct the Fourier heat conduction equation of the battery according to the density, constant pressure specific heat, the first thermal conductivity, the current, the voltage, the volume and the open circuit potential; and solve the Fourier heat conduction equation according to the position to be evaluated and the working time to obtain the internal temperature of the battery at the position to be evaluated; wherein the Fourier heat conduction equation is used to characterize the relationship between the internal temperature of the battery and the time and position.

9. A terminal device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, the method for evaluating the internal temperature of a battery according to any one of claims 1 to 7 is implemented.

10. A storage medium, characterized in that: The storage medium includes a stored computer program, wherein when the computer program is executed, the device where the storage medium is located is controlled to execute the battery internal temperature evaluation method according to any one of claims 1 to 7.

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