Patent Description:
In the related art, the internal temperature of a power battery of a new energy vehicle is estimated in real time by collecting a current, a voltage, and a battery surface temperature. Alternatively, the internal temperature of the power battery of the new energy vehicle is estimated by obtaining a relationship between feature quantities of electrochemical impedance spectroscopy and an ambient temperature in a stable state and measured impedance values. However, in such methods, the effect of real-time charging and discharging states of the battery on the actually measured impedance values is not considered, and the obtained internal temperature is actually the average temperature of the entire battery rather than the actual temperature inside the battery, so that the estimation precision of the internal temperature of the battery is not high.

Document <CIT> relates to an inner temperature estimation method for a single cell, which comprises an offline part and an online part. The offline part executes the steps of a1) acquiring the internal resistance characteristic of the single cell at different temperatures; and a2) acquiring a standard relationship between the inner temperature of the cell and the internal resistance of the cell according to the internal resistance characteristic. The online part executes the steps of b1) performing online detection on the current, end voltage and surface temperature of a current working cell; b2) performing online estimation for the internal resistance of the current working cell according to the current and the end voltage; and b3) estimating the internal temperature of the current working cell according to the internal resistance acquired in the step b2), the surface temperature acquired in the step b1) and the standard relationship acquired in the step a2).

Document <CIT> provides a method of estimating secondary battery internal temperature based on electrochemical impedance.

<CIT> refers to a method and a system of estimating core temperatures of battery cells in a battery pack. In one step, a surface temperature of one or more battery cell(s) is received, a current of the one or more battery cell(s) is received, an inlet temperature of coolant provided to the battery pack is received, and a flow rate or velocity of the coolant is received. In another step, estimations are made including those of a cell-lumped internal electrical resistance of the battery cell(s), a cell-lumped conduction resistance between a core and a surface of the battery cell(s), and a cell- lumped convection resistance between the surface and the coolant. In yet another step, an estimation is made of a core temperature of the battery cell(s) based upon the received and estimated values of previous steps.

<CIT> discloses a battery control device and motor drive system. In a memory, the surface temperature and the internal resistance of an assembled battery detected under the condition where a difference between the surface and the internal temperature is within a predetermined value are stored, and an internal temperature diagnosis unit that diagnoses whether or not the internal temperature estimated by an internal temperature estimation unit is correct, detects the internal resistance with an internal resistance calculation unit when the internal temperature estimation unit estimates the internal temperature, searches for an internal resistance corresponding to the surface temperature equal to the estimated internal temperature value from among the stored internal resistances, and diagnoses the estimated internal temperature value based upon the result of comparison of a search result of the internal resistance and the internal resistance detected during internal temperature estimation.

The present invention refers to a battery temperature estimation method according to claim <NUM>, an apparatus according to claim <NUM>, a computer program according to claim <NUM>, and a storage medium according to claim <NUM>, which can estimate the internal temperature of the battery by using admittances that are measured in real time and surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

In the battery temperature estimation method provided in the embodiments of the present invention, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

In the battery temperature estimation apparatus provided in the embodiments of the present invention, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

In a computer program stored in the memory of an electronic device, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

In a computer-readable storage medium, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

The additional aspects and advantages of the present invention will be provided in the following description, some of which will become apparent from the following description or may be learned from practices of the present disclosure.

The foregoing and/or additional aspects and advantages of the present invention will become apparent and comprehensible in the description made with reference to the following accompanying drawings, where:.

The embodiments of the present invention are described below in detail. Examples of the embodiments are shown in the accompanying drawings, and same or similar reference signs in all the accompanying drawings indicate same or similar components or components having same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary, and are merely intended to explain the present invention and cannot be construed as a limitation to the present invention. On the contrary, the embodiments of the present invention include all changes, modifications, and equivalents falling within the scope of the appended claims.

To resolve the technical problem in the related art that the effect of real-time charging and discharging states of the battery on the actually measured impedance values is not considered, and the obtained internal temperature is actually the average temperature of the entire battery rather than the actual temperature inside the battery, so that the estimation precision of the internal temperature of the battery is not high, an embodiment of the present invention provides a battery temperature estimation method. When a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

<FIG> is a schematic flowchart of a battery temperature estimation method according to an embodiment of the present invention.

Referring to <FIG>, the method includes the following steps:
S101. Fit, when a battery is in an offline state, a first function relationship according to corresponding admittances of the battery at different test temperatures.

The offline state indicates that the battery is currently in a test environment, or may indicate that the battery is not charged or discharged. This is not limited.

During specific execution, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures.

During specific execution, real parts of the corresponding admittances of the battery at different test temperatures may be determined, and the first function relationship is fitted according to the different test temperatures and the real parts of the corresponding admittances. The first function relationship is used for describing a correspondence between different test temperatures and the real parts of the corresponding admittances of the battery. The concept of admittance is introduced to simplify the calculation formula and reduce the calculation amount, thereby reducing the requirement on the chip calculation capacity.

During specific execution, the first function relationship may be fitted according to the different test temperatures, the real parts of the corresponding admittances, and an Arrhenius formula.

For example, according to the Arrhenius formula, G' = AeRT//Ea, where A is a constant, Ea is activation energy, and R is a universal gas constant. The relationship between the real parts of the admittances and temperatures may be represented as G' = AebT. Fitting is performed according to testing data, to obtain parameters A= <NUM>, and b = <NUM>. <FIG> is a schematic diagram of a curve of a first function relationship according to an embodiment of the present invention.

Obtain a temperature distribution model of the battery according to the shape and the size of the battery, and determine a second function relationship corresponding to internal temperatures and a surface temperature by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery.

In this embodiment, when a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the first function relationship may be integrated and the second function relationship of the battery may be determined according to the temperature distribution model and the integrated first function relationship.

The temperature distribution model is used for describing a correspondence among temperatures at different locations inside the battery, the highest internal temperature of the battery, and the surface temperature of the battery.

During specific execution, a function relationship among temperatures T(x) at different locations, the highest internal temperature of the battery, and the surface temperature of the battery may be determined according to a one-dimensional steady heat-conduction equation and used as the temperature distribution model, for example, T(x) = f(Tmax, T<NUM>, x) = <MAT>, where Tmax indicates the highest internal temperature of the battery, T<NUM> indicates the surface temperature of the battery, x indicates different locations inside the battery, h is the thickness of the battery, Φ is a current heat flow rate of the battery, and λ is a thermal conductivity coefficient of the battery.

The shape of the battery may be, for example, regular or irregular. The shape of the battery may be, for example, hexahedral. In the embodiments of the present invention, an example in which the shape of the battery is square is given, and this is not limited.

In an example, the square battery may be regarded as being formed by a plurality of battery sheets that are discretized along a thickness direction of the battery. The plurality of battery sheets are, for example, N battery sheets, where N is a positive integer greater than or equal to <NUM>. The battery may be discretized in advance into N battery sheets along the thickness direction. <FIG> is a schematic diagram of discretization of a square battery in an embodiment of the present invention. The square battery is discretized into N battery sheets along the thickness direction, each battery sheet may correspond to a corresponding location on an x coordinate axis, and a plurality of corresponding locations may correspond to x in the foregoing temperature distribution model T(x).

During specific execution, when the temperature distribution model of the battery is obtained according to the shape and the size of the battery, and the second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the first function relationship may be integrated and the second function relationship of the battery may be determined according to the temperature distribution model and the integrated first function relationship.

In an example, the real part of the admittance measured in the first function relationship in the foregoing step is the accumulation of all the real parts of the admittances of the battery, that is, <MAT>, where k ∈ [<NUM>,∞], Tk indicates the temperature corresponding to the kth battery sheet, a specific value of Tk is related to a location of the battery sheet in the battery, and h is a thickness value of the battery. After that, according to the temperature distribution model, that is, T(x) = f(Tmax,T<NUM>,x), the temperature T(x) at different locations is a function of the highest internal temperature and the surface temperature of the battery, where Tmax indicates the highest internal temperature of the battery, T<NUM> indicates the surface temperature of the battery, and x indicates different locations inside the battery. T(x) = f(Tmax,T<NUM>,x) is substituted into the integrated first function relationship <MAT>, the function relationship obtained after substitution is used as the second function relationship, and the second function relationship is used for fitting a correspondence among the surface temperature of the battery, the admittances of the battery, and the internal temperature of the battery.

In this embodiment, when a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

<FIG> is a schematic flowchart of a battery temperature estimation method according to another embodiment of the present invention.

Referring to <FIG>, the method includes the following steps:
S401. Determine a feature test frequency when the battery is in the offline state, where the feature test frequency is within a target frequency range, and in the target frequency range, impedance of the battery does not change with a state of charge of the battery.

The feature test frequency is obtained through pre-testing, and is a frequency within a target frequency range, and in the target frequency range, impedance of the battery does not change with a state of charge of the battery. The feature test frequency is used for performing in-situ admittance testing on the battery.

During specific execution, in the process of determining the feature test frequency, electrochemical impedance spectroscopy testing may be performed on the battery in a preset frequency range in different states of charge, the target frequency range is determined from the preset frequency range according to a result of the testing, response values of electrochemical impedance spectroscopy of the battery are tested in a preset state of charge at different temperatures, the response values are converted into the corresponding admittances, and a frequency at which real parts of the admittances change most with temperatures in the target frequency range is determined as the feature test frequency. By performing in-situ admittance testing on the battery based on the feature test frequency, a standard relationship between in-situ admittance testing data and ambient temperature data can be effectively established, thereby reducing an estimation error and improving the estimation precision.

Certainly, during actual execution, the feature test frequency may be determined in any other possible manners. For example, the feature test frequency may be determined by using the conventional programming technology (such as a simulation method and an engineering method). In another example, the feature test frequency may be determined by using a genetic algorithm and an artificial neural network method.

The preset frequency range may be preset according to actual testing experience, and the preset frequency range may be <NUM> to <NUM>.

In an example, electrochemical impedance spectroscopy testing is performed on the battery in a preset frequency range in different states of charge, and the target frequency range is determined from the preset frequency range according to a result of the testing. For example, at room temperature (<NUM>), the states of charge (SOC) of a square battery cell having a capacity of <NUM> Ah are adjusted respectively to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% at a rate of <NUM> C, and then electrochemical impedance spectroscopy (EIS) testing is performed. The preset frequency range is <NUM> to <NUM>, and a frequency interval in which impedance does not change with the state of charge is obtained by analyzing a testing result and is used as a target frequency range. The target frequency range is <NUM> to <NUM>. <FIG> is a schematic diagram of an EIS curve according to an embodiment of the present invention.

In an example, response values of electrochemical impedance spectroscopy of the battery are tested in a preset state of charge at different temperatures, the response values are converted into the corresponding admittances, and a frequency at which real parts of the admittances change most with temperatures in the target frequency range is determined as the feature test frequency. For example, in the SOC of <NUM>%, after the square battery is placed in environments with respective temperatures of -<NUM>, -<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> to fully stand, response values of electrochemical impedance spectroscopy at different temperatures are tested, and the response values of the impedance are converted into the corresponding admittances. A frequency at which real parts of the admittances change most with temperatures is determined in the foregoing determined target frequency range of <NUM> to <NUM>, and the frequency is determined as the feature test frequency f<NUM> = <NUM>. <FIG> is a schematic diagram of response curves of the admittances with temperatures in a state of charge of <NUM>% according to an embodiment of the present invention.

Determine real parts of the corresponding admittances of the battery at different test temperatures according to the feature test frequency.

In an example, the feature test frequency is f<NUM> = <NUM>. In-situ testing is performed on admittances of the battery in charging and discharging states in environments with temperatures of -<NUM>, -<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and real parts G' of the admittances are extracted. After that, step S403 is triggered.

Fit the first function relationship according to the different test temperatures and the real parts of the corresponding admittances.

Obtain a temperature distribution model of the battery according to the shape and the size of the battery, and determine a second function relationship corresponding to * internal temperatures and a surface temperature by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery.

In an example, the real part of the admittance measured in the first function relationship in the foregoing step is the accumulation of all the real parts of the admittances of the battery, that is, <MAT>, where k ∈ [<NUM>, ∞], Tk indicates the temperature corresponding to the kth battery sheet, a specific value of Tk is related to a location of the battery sheet in the battery, and h is a thickness value of the battery. After that, according to the temperature distribution model, that is, T(x) = f(Tmax,T<NUM>,x), the temperature T(x) at different locations is a function of the highest internal temperature and the surface temperature of the battery, where Tmax indicates the highest internal temperature of the battery, T<NUM> indicates the surface temperature of the battery, and x indicates different locations inside the battery. T(x) = f(Tmax,T<NUM>,x) is substituted into the integrated first function relationship <MAT>, the function relationship obtained after substitution is used as the second function relationship, and the second function relationship is used for fitting a correspondence among the surface temperature of the battery, the admittances of the battery, and the internal temperature of the battery.

In this embodiment, by performing in-situ admittance testing on the battery based on the feature test frequency, a standard relationship between in-situ admittance testing data and ambient temperature data can be effectively established, thereby reducing an estimation error and improving the estimation precision. When a battery is in an offline state, a first function relationship is fitted according to corresponding admittances of the battery at different test temperatures, a temperature distribution model of the battery is obtained according to the shape and the size of the battery, and a second function relationship corresponding to internal temperatures and a surface temperature is determined by combining with the first function relationship, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the admittances of the battery. Therefore, the internal temperature of the battery can be estimated by using the admittances that are measured in real time and the surface temperature of the battery, thereby effectively improving the estimation precision of the internal temperature of the battery.

Referring to <FIG>, the method includes the following steps:
S701. Detect a target surface temperature of the to-be-estimated battery, and detect a target admittance of the to-be-estimated battery.

A temperature sensor may be disposed on the to-be-estimated battery in advance, to detect a target surface temperature of the to-be-estimated battery in real time, and detect a target admittance of the to-be-estimated battery in real time.

Determine the internal temperature of the to-be-estimated battery according to the target surface temperature and the target admittance by using the second function relationship.

During specific execution, T(x) = f(Tmax,T<NUM>,x) is substituted into the integrated first function relationship <MAT>, and the function relationship obtained after substitution is used as the second function relationship, where Tmax indicates the highest internal temperature of the battery, and T<NUM> indicates the surface temperature of the battery. Therefore, the target surface temperature and the target admittance may be substituted into the second function relationship to determine Tmax, and Tmax obtained through calculation is used as the actual temperature inside the battery, thereby estimating the highest internal temperature of the battery.

During specific execution of the embodiments of the present invention, for temperatures tested through experiments and the result of estimation in the embodiments of the present invention, reference may be made to <FIG> is a schematic diagram of a temperature change curve in a battery charging process according to an embodiment of the present invention. Four temperature time curves respectively represent the internal temperature Test of the battery that is estimated in the embodiments of the present invention, equivalent temperature Teq of the entire battery, internal temperature Ti of the battery that is actually tested, and surface temperature T<NUM> of the battery. Compared with the surface temperature of the battery and the equivalent temperature of the entire battery, the internal temperature of the battery that is estimated in the embodiments of the present invention is closer to the internal temperature of the battery that is actually measured.

In this embodiment, the target surface temperature of the to-be-estimated battery and the target admittance of the to-be-estimated battery are detected, and the internal temperature of the to-be-estimated battery is determined according to the target surface temperature and the target admittance by using the second function relationship. The internal temperature distribution of the battery is considered, and the highest internal temperature can be accurately given for estimation of the internal temperature of the field test battery. Therefore, a battery management system may further optimize the working status of the battery according to the internal temperature, thereby ensuring that the battery works in a safe temperature range, eliminating the hidden dangers of flammability and explosiveness, and improving the safety and reliability of battery operation.

<FIG> is a schematic structural diagram of a battery temperature estimation apparatus according to an embodiment of the present invention.

Referring to <FIG>, the apparatus <NUM> includes:.

In some embodiments, referring to <FIG>, the fitting module <NUM> includes:.

Optionally, in some embodiments, referring to <FIG>, the apparatus <NUM> further includes:.

In some embodiments, the first determination sub-module <NUM> is specifically configured to:
perform electrochemical impedance spectroscopy testing on the battery in a preset frequency range in different states of charge; determine the target frequency range from the preset frequency range according to a result of the testing; test response values of electrochemical impedance spectroscopy of the battery in a preset state of charge at different temperatures, and convert the response values into the corresponding admittances; and determine a frequency at which real parts of the admittances change most with temperatures in the target frequency range as the feature test frequency.

In some embodiments, the fitting sub-module <NUM> is specifically configured to:
fit the first function relationship according to the different test temperatures, the real parts of the corresponding admittances, and an Arrhenius formula.

In some embodiments, the first determination module <NUM> is specifically configured to:
integrate the first function relationship; and determine the second function relationship of the battery according to the temperature distribution model and the integrated first function relationship.

In some embodiments, the battery is square.

It should be noted that the explanation of the embodiment of the battery temperature estimation method in the above embodiments of <FIG> is also applicable to the battery temperature estimation apparatus <NUM> of this embodiment, and the implementation principle thereof is similar, so that details are omitted herein.

<FIG> is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

The electronic device <NUM> includes: a memory <NUM>, a processor <NUM>, and a computer program stored in the memory <NUM> and executable on the processor <NUM>. The processor <NUM>, when executing the program, implements the battery temperature estimation method in the foregoing embodiments.

In a possible implementation, the electronic device further includes a communication interface <NUM>, configured to perform communication between the memory <NUM> and the processor <NUM>.

This embodiment further provides a computer-readable storage medium, storing a computer program, the computer program, when executed by a processor, implementing the foregoing battery temperature estimation method.

It should be noted that in the description of the present invention, the terms "first", "second", and the like are merely used for description, and shall not be understood as an indication or implication of relative importance. In addition, in the description of the present disclosure, unless otherwise stated, "a plurality of" means two or more than two.

Any process or method in the flowcharts or described herein in another manner may be understood as indicating a module, a segment, or a part including code of one or more executable instructions for implementing a particular logical function or process step. In addition, the scope of exemplary embodiments of the present invention includes other implementations which do not follow the order shown or discussed, including performing, according to involved functions, the functions basically simultaneously or in a reverse order, which should be understood by technical personnel in the technical field to which the embodiments of the present invention belong.

It should be understood that, parts of the present invention can be implemented by using hardware, software, firmware, or a combination thereof. In the foregoing implementations, a plurality of steps or methods may be implemented by using software or firmware that are stored in a memory and are executed by a proper instruction execution system. For example, if hardware is used for implementation, same as in another implementation, implementation may be performed by any one of the following technologies well known in the art or a combination thereof: a discrete logic circuit of a logic gate circuit for realizing a logic function for a data signal, an application-specific integrated circuit having a suitable combined logic gate circuit, a programmable gate array (PGA), and a field programmable gate array (FPGA).

A person of ordinary skill in the art may understand that all or some of the steps of the methods in the foregoing embodiments may be implemented by a program instructing relevant hardware. The program may be stored in a computer-readable storage medium. When the program is executed, one or a combination of the steps of the method embodiments are performed.

In addition, the functional modules in the embodiments of the present invention may be integrated into one processing module, or each of the units may exist alone physically, or two or more units may be integrated into one module. The integrated module may be implemented in the form of hardware, or may be implemented in a form of a software functional module. If implemented in the form of software functional modules and sold or used as an independent product, the integrated module may also be stored in a computer-readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic disk, an optical disc, or the like.

In the description of the present specification, reference to the description of the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", and the like means that specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, exemplary descriptions of the foregoing terms do not necessarily refer to the same embodiment or example. In addition, the described specific features, structures, materials, or characteristics may be combined in a proper manner in any one or more of the embodiments or examples.

Claim 1:
A computer-implemented battery temperature estimation method, comprising:
fitting, when a battery is in an offline state, a first function relationship according to different test temperatures, real parts of corresponding admittances of the battery at the different test temperatures, and an Arrhenius formula;
obtaining a temperature distribution model of the battery according to the shape and the size of the battery, wherein the temperature distribution model is used for describing the internal temperatures at different locations inside the battery as a function of a highest internal temperature of the battery, and a surface temperature of the battery; and
determining a second function relationship, wherein the second function relationship is derived by substituting the temperature distribution model into the first relationship and integrating the first relationship over the different locations inside the battery, the second function relationship being used for estimating the internal temperature of the battery by using the surface temperature and the real part of the admittance of the battery;
wherein the fitting of the first function relationship according to corresponding real parts of the admittances of the battery at different test temperatures comprises:
determining a feature test frequency when the battery is in the offline state, wherein the feature test frequency is within a target frequency range, and in the target frequency range, impedance of the battery does not change with a state of charge of the battery;
determining the corresponding real parts of the admittances of the battery at the different test temperatures according to the feature test frequency; and
fitting the first function relationship according to the different test temperatures and the corresponding real parts of the admittances.