A power battery temperature prediction model and modeling method based on liquid cooling

Abstract

The present invention discloses a power battery temperature prediction model and a modeling method based on a liquid cooling heat dissipation method. By experimentally calibrating the variation relationship of the equivalent heat dissipation parameters between the battery and the coolant with the flow rate and the equivalent heat dissipation parameters between the battery and the air, and correcting the calibration results, while considering the variation relationships of the battery internal resistance and the entropy heat coefficient representing the reversible heat of the battery with factors such as SOC and temperature, a prediction model for the temperatures of battery cells at different positions in the battery pack can be established for different thermal management stages. The model established according to the above method can be used for real-time estimation of the temperatures of battery cells inside the liquid-cooled power battery pack and thermal management control, and can, on the basis of ensuring the simulation accuracy, expand the applicable range of the model, reduce the complexity of the model, simplify the model input parameters, and improve the reliability of the model operation.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and relates to a power battery temperature prediction model and a modeling method based on a liquid cooling heat dissipation method. Background Art

[0002] With the continuous popularization of new energy vehicles, as an important part of the three-electric system of new energy vehicles, the safety, reliability, and durability of power batteries during their use have attracted more and more attention from professionals and end-users. Currently, lithium-ion batteries are mainly used in new energy vehicles on the market, and their performance is highly sensitive to temperature changes. The discharge energy and output power of the battery at different temperatures will vary, affecting the power performance and economy of the whole vehicle. At the same time, too high or too low temperature also has a certain impact on the service life of the battery. Therefore, during the use of the whole vehicle and the power battery, the battery temperature needs to be focused on.

[0003] During the actual driving process of users, they are more concerned about the remaining mileage displayed on the instrument. Inaccurate estimation of the remaining mileage is likely to affect the normal use of users and cause user complaints. The remaining mileage is directly related to the state of energy (SOE) of the battery, and the battery temperature directly affects the SOE. Therefore, accurately predicting the battery temperature helps to improve the accuracy of SOE estimation and reduce user complaints.

[0004] In addition, conditional judgment can be made on the prediction results of the battery temperature, and thermal management control of the battery can be carried out in advance to ensure that the battery works within an appropriate temperature range as much as possible, thereby extending the service life and reliability of the battery.

[0005] Existing models for predicting the temperature of power batteries are mainly divided into four categories: neural network models, electrochemical-thermal coupling models, electro-thermal coupling models, and thermal abuse models. The technical status is as follows:

[0006] 1) Neural network model

[0007] When applying the neural network method to predict the temperature of power batteries, multiple training units need to be established to perform the training steps, and a large amount of measured data is required for model training, which is laborious and not easy to operate. In addition, neural network models are mostly used for predicting the battery temperature under specific current conditions, while the current during the actual vehicle operation is usually dynamically changing, and this method is not applicable under such conditions. In the model and modeling method described in the present invention, the amount of measured data required for parameter calibration is much less than that of neural network models, and it is not restricted by specific current conditions, with less workload, wide application range, and easy to operate.

[0008] 2) Electrochemical-thermal coupling model

[0009] The electro-thermal coupling model describes the thermal model of the battery from the perspective of heat generation by electrochemical reactions. The establishment of such a model needs to be based on the assumption that the current density is evenly distributed throughout the battery cell. This assumption is more applicable to small batteries. For large batteries, due to the relatively complex actual current density distribution inside the battery cell, the accuracy of model calculation based on this assumption is usually much lower than that of small batteries, resulting in certain limitations in the use of this model. The model described in the present invention is not affected by the battery size and has a wider application range than this model.

[0010] 3) Electro-thermal coupling model

[0011] The electro-thermal coupling model is a battery thermal model that takes into account the current density distribution inside the battery cell. Before establishing such a model, an accurate model of the internal electric field of the battery cell needs to be obtained first. Although the model calculation accuracy is relatively high, it is not easy to accurately obtain the internal electric field model of the battery cell, and it is not very convenient to use. The method for obtaining the model parameters described in the present invention is simple, and the simulation accuracy is not lower than that of commonly used battery thermal models.

[0012] 4) Thermal abuse model

[0013] The thermal abuse model is mainly used to simulate the heat generation of the battery under high-temperature conditions, and to judge when the battery reaches the thermal runaway point and the state of the battery after the thermal runaway reaction occurs. It is a model dedicated to safety research and has limitations in the scope of use. Summary of the Invention

[0014] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a power battery temperature prediction model and a modeling method based on a liquid cooling heat dissipation method.

[0015] To achieve the above object, the present invention adopts the following technical solutions:

[0016] In the first aspect, the present invention provides a power battery temperature prediction model based on a liquid cooling heat dissipation method, and the temperature prediction model is:

[0017]

[0018] Wherein, and are the temperatures of the coolant at times t n and t n-1 respectively, and are the heat generation power and the total heat dissipation power of the battery at time t n-1 respectively, c b is the specific heat capacity of the battery, and m b is the weight of the battery.

[0019] The temperature prediction model of the present invention is applicable to a battery pack that uses liquid cooling as its heat dissipation method and has charging and heating functions.

[0020] Preferably, the heat generation power of the battery in the temperature prediction model is obtained by:

[0021] According to the Bernadi heat generation rate model, the heat generation rate of the battery Q p It is expressed as follows:

[0022] Q p =I 2 R+IT b k rev

[0023] Where: I is the battery current, R is the internal resistance of the battery; k rev is the entropy thermal coefficient of the battery,

[0024] By testing the internal resistance of the battery under different temperature and SOC conditions, the function R=f(SOC, T b ), and tested the entropy thermal coefficient k under different SOC conditions rev = g(SOC), and we get t n-1 The heat generation power of the battery at this moment is as follows:

[0025]

[0026] in, t n-1 The battery current at that moment.

[0027] The total heat dissipation power of the battery in the temperature prediction model is obtained as follows:

[0028] For liquid-cooled battery packs, the heat dissipation of the battery includes natural convection heat exchange with the outside air and forced convection heat exchange with the coolant. The total heat dissipation power of the battery is the sum of the heat dissipation power between the battery and the air and the heat dissipation power between the battery and the coolant, that is:

[0029]

[0030] in, and t n-1 The heat dissipation power between the battery and the air, the heat dissipation power between the battery and the coolant, and the total heat dissipation power of the battery at all times.

[0031] According to Newton's law of cooling, t n-1 Total heat dissipation power of the battery at all times Proportional to the temperature difference between the battery and the external heat exchange medium:

[0032] Among them, H is the heat dissipation parameter between the battery and the external heat exchange medium, and are respectively the temperatures of the battery and the external heat exchange medium at time t n-1 .

[0033] According to the above formula, the total heat dissipation power of the battery at time t n-1 is expressed as:

[0034]

[0035] Among them, H air and H liquid are respectively the equivalent heat dissipation parameters between the battery and air and between the battery and coolant, and are respectively the temperatures of the coolant and air at time t n-1 .

[0036] As a preferred technical solution of the power battery temperature prediction model based on the liquid cooling heat dissipation method described in the present invention, the method further includes calibrating and correcting the equivalent heat dissipation parameter H air between the battery and air and the equivalent heat dissipation parameter H liquid between the battery and coolant, and respectively obtaining the corrected heat dissipation parameter H air-corr between the battery and air and the corrected heat dissipation parameter H liquid-corr between the battery and coolant;

[0037] The H air-corr is obtained through the following method:

[0038] For the convective heat transfer between the battery and air, first set the environmental chamber temperature to temperature T high , and let the battery pack stand still in it until all the monomer temperatures in the battery pack are stable at (T high - 2) °C to (T high + 2) °C. Then set the environmental chamber temperature to temperature T low , (T high - T low ) ≥ 15 °C, control the coolant flow rate to 0 L / min, start the test until all the monomer temperatures in the battery pack are in (T low - 2) °C to (T low + 2) °C and remain stable for ≥ 1 h, stop the test, and record the start and end times of the test, as well as the environmental temperature and battery temperature at different times during the test. According to the thermodynamic equation of the battery:

[0039]

[0040] Calculate the heat dissipation parameter between the battery and air at different times:

[0041]

[0042] Among them, represents the heat dissipation parameter between the battery and the air at time t n and represents the heat generation power of the battery at time t n-1 After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameter between the battery and the air:

[0043] Then the heat dissipation power between the battery and the air at time t

[0044]

[0045] is: n The battery temperatures at different times are calculated by the following formula:

[0046]

[0047] Substitute the calculation result of H

[0048]

[0049] back into the original test data according to the above formula to calculate the battery temperatures at different times air-initial Based on the error between and T and T b,tn,calc use the least squares method to correct the equivalent heat dissipation parameter between the battery and the air, and obtain the corrected equivalent heat dissipation parameter H air-corr .

[0050] The above-mentioned H liquid-corr is obtained through the following method:

[0051] For the convective heat transfer between the battery and the coolant, first set the environmental chamber temperature to temperature T high , and let the battery pack stand still in it until the battery temperature stabilizes at (T high - 2) °C to (T high + 2) °C. Control the coolant flow rate to be L1, start the test until the battery temperature remains stable for ≥1 h, stop the test, and record the start and end times of the test, as well as the temperatures of the environment, coolant, and battery at different times during the test. According to the thermodynamic equation of the battery:

[0052]

[0053] Calculate the heat dissipation parameters between the battery and the coolant at different times:

[0054]

[0055] Among them, represents the heat dissipation parameter between the battery and the coolant at time t. n-1

[0056] After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameter between the battery and the coolant:

[0057]

[0058] Then, the heat dissipation power of the battery at time t n is:

[0059]

[0060] The battery temperatures at different times are calculated by the following formula:

[0061]

[0062] Using the above formula, substitute the calculation result of H liquid-initial back into the original test data to calculate the battery temperatures at different times Based on the error between and use the least squares method to correct the equivalent heat dissipation parameter between the battery and the coolant, and obtain the corrected equivalent heat dissipation parameter H liquid-corr ;

[0063] Preferably, the method further includes successively adjusting the coolant flow rate and repeating the above test and parameter calibration and correction processes until the coolant flow rate is adjusted to the maximum flow rate L max that the water-cooled plate can withstand, to obtain the functional relationship between the corrected equivalent heat dissipation parameter between the battery and the coolant and the coolant flow rate under different coolant flow rate conditions:

[0064] H liquid-corr = h(L).

[0065] The present invention proposes a test calibration and correction method for the equivalent heat dissipation parameters between the battery and air and coolant, and uses the equivalent heat dissipation parameter H to characterize the heat dissipation performance of the battery pack. For a battery pack based on liquid cooling heat dissipation, first, by controlling the coolant flow rate to 0, record the changes in the battery and environmental chamber temperatures, calculate the heat dissipation parameter H air of natural convection between the battery and the external air at different times, take the average value to obtain the initial value H air-initial of the equivalent heat dissipation parameter, substitute it back into the original test data, calculate the battery temperature T b,tn,calc at different times, and based on the error between the true battery temperature T b,tn and T b,tn,calc use the least squares method to correct the equivalent heat dissipation parameter between the battery and air, and obtain the corrected equivalent heat dissipation parameter H​air-corr For the equivalent heat dissipation parameter H between the battery and the coolant liquid , the test calibration and correction method is basically the same as that of H air . The difference is that in this process, the flow rate of the coolant needs to be adjusted, the equivalent heat dissipation parameters under different flow rate conditions are calibrated, and the corrected equivalent heat dissipation parameter H liquid-corr is established as a function of the flow rate L. This method can effectively avoid the differences in the fitting results caused by different operators' judgment methods for the scattered points of the fitting data, and has high reliability at the method execution level.

[0066] As a preferred technical solution of the power battery temperature prediction model based on the liquid cooling heat dissipation method described in the present invention, the thermodynamic equation of the battery is:

[0067]

[0068] According to the Bernadi heat generation rate model, the heat generation power Q of the battery p can be expressed as follows:

[0069] Q p = I 2 R + IT b k rev

[0070] where: R is the internal resistance of the battery; k rev is the entropy heat coefficient of the battery, which is calculated by the following formula.

[0071]

[0072] where, U OCV is the open-circuit voltage of the battery.

[0073] Substitute into the battery heat generation rate model:

[0074]

[0075] Preferably, through the HPPC test under the conditions of -30 to 55 °C, the functional relationship between the equivalent DC internal resistance of the battery pack and the state of charge (SOC) and the battery temperature is obtained, that is: R = f(SOC, T b ).

[0076] Preferably, an SOC is selected as a measurement point every 10% within the range of 0% to 100%. First, the battery cell is charged to 100% SOC, and this SOC is fixed. The ambient temperature is adjusted in the order of 25°C → 55°C → 25°C → 0°C → -20°C → 25°C. After fully standing at each temperature point, the open circuit voltage of the battery cell is measured. After completing the test of one SOC point, the SOC is adjusted to another value, and this SOC is fixed again. The above operation is repeated until the entire test process is completed. The entropy thermal coefficient of the battery under different SOC conditions is calculated according to the following formula:

[0077]

[0078] Where n is a positive integer from 0 to 10, SOC n Indicates 11 SOC measurement points from SOC 100% to 0%; is the entropy thermal coefficient under specific SOC conditions; T n 6 temperature points corresponding to the temperature change sequence of the environmental chamber.

[0079] After completing the calculation of the entropy thermal coefficient under all SOC conditions, the functional relationship between the entropy thermal coefficient and SOC can be obtained:

[0080] k rev =g(SOC)

[0081] Preferably, during the entropy thermal coefficient test, for temperature points above 0°C, the standing time is ≥3 hours; for temperature points below 0°C, the standing time is ≥5 hours.

[0082] Preferably, t n-1 The heat generation power of the battery at this moment is expressed as:

[0083]

[0084] The thermodynamic equation of the battery is expressed as:

[0085]

[0086] In a second aspect, the present invention provides a method for modeling a power battery temperature prediction model based on a liquid cooling heat dissipation method, the method comprising the following steps:

[0087] (1) Test the internal resistance of the battery under different temperature and SOC conditions, and establish the function R = f(SOC, T b ), test the entropy thermal coefficient k under different SOC conditions rev =g(SOC), establish the battery heat generation rate model:

[0088] Q p =I 2 R+ITb k rev = I 2 × f(SOC, T b ) + IT b × g(SOC)

[0089] (2) Adopt the battery heat generation rate model Q p and the heat dissipation power model Q s to establish a battery thermodynamic equation, where the heat dissipation power model is the total heat dissipation power described in the first aspect;

[0090] (3) Calculate the heat dissipation power between the battery cells at different positions and the corresponding coolant below them according to the inlet and outlet temperatures of the coolant, and substitute it into the battery thermodynamic equation described in step (2) to obtain the temperatures of the battery cells at different positions.

[0091] Preferably, step (1) includes:

[0092] (a) Through HPPC tests under the conditions of -30 to 55 °C, obtain the functional relationship between the equivalent DC internal resistance of the battery pack and the state of charge (SOC) and the battery temperature, that is: R = f(SOC, T b );

[0093] According to the Bernadi heat generation rate model, the heat generation rate Q p of the battery is expressed as follows:

[0094] Q p = I 2 R + IT b k rev

[0095] where: I is the current of the battery, and R is the internal resistance of the battery; k rev is the entropy heat coefficient of the battery, which is calculated by the following formula:

[0096]

[0097] where, U OCV is the open-circuit voltage of the battery;

[0098] (b) Select a SOC every 10% in the range of SOC from 0% to 100% as a measurement point. First, charge the battery cell to SOC 100%, fix this SOC, adjust the ambient temperature in the order of 25 °C → 55 °C → 25 °C → 0 °C → -20 °C → 25 °C, and measure the open-circuit voltage of the battery cell after fully standing at each temperature point; after completing the test at one SOC point, adjust the SOC to another value, fix this SOC again, and repeat the above operations until the entire test process is completed. For the entropy heat coefficient of the battery under different SOC conditions, calculate it according to the following formula:

[0099]

[0100] Among them, n is a positive integer from 0 to 10, and SOC n represents 11 SOC measurement points from 100% to 0% of SOC; is the entropy heat coefficient under a specific SOC condition; T n corresponds to 6 temperature points in the order of the temperature change of the environmental chamber;

[0101] After calculating the entropy heat coefficient under all SOC conditions, the functional relationship k between the entropy heat coefficient and SOC can be obtained rev = g(SOC);

[0102] Substitute it into the Bernadi heat generation rate model, t n-1 The heat generation rate of the battery at time t is expressed as:

[0103]

[0104] Preferably, in step (b), in order to ensure that the battery temperature is consistent with the temperature of the temperature chamber environment, for temperature points above 0 °C, the standing time ≥ 3 hours; for temperature points of 0 °C and -20 °C, the standing time ≥ 5 hours.

[0105] Preferably, the battery thermodynamic equation in step (2) is:

[0106]

[0107] Among them, represents the battery current at time t n-1 of the battery.

[0108] Preferably, step (3) includes:

[0109] Adopt a power battery based on a liquid cooling heat dissipation method. The power battery includes a battery pack, and the battery pack is composed of at least 2 battery modules and m parallelly arranged mouthpiece tubes. m is an integer not less than 1. The battery modules are located above each mouthpiece tube. The coolant flows from one side to the other along the cooling pipeline inside the mouthpiece tube. The battery module includes n battery cells. n is an integer not less than 2. The battery cells are not in direct contact with the mouthpiece tubes. Therefore, the heat dissipation situation between the battery and the coolant is characterized by an equivalent heat dissipation parameter;

[0110] For the internal battery cell arrangement and coolant flow direction schematic diagram of the power battery based on the liquid cooling heat dissipation method, see Figure 2 .

[0111] t n The heat dissipation power corresponding to the single cells at different positions at time t is calculated according to the following formula:

[0112]

[0113] It is determined that the coolant temperatures corresponding to different monomers increase approximately equally along the flow direction of the coolant. The coolant temperatures corresponding to different monomers are calculated according to the following formula:

[0114]

[0115] where j and k are positive integers (where k≠1), respectively representing the row number and column number where the battery monomer is located; T liquid,jk represents the temperature of the coolant below the battery monomer in the j-th row and k-th column; T liquid,inlet and T liquid,outlet are the inlet and outlet temperatures of the coolant, respectively.

[0116] When k = 1, the coolant temperature corresponding to the monomer below is the inlet temperature T liquid,inlet of the coolant.

[0117] Based on the law that the coolant temperatures corresponding to different monomers increase approximately equally along the flow direction of the coolant, the method of the present invention can calculate the coolant temperatures corresponding to different monomers only based on the inlet and outlet temperatures of the coolant, and then calculate the heat dissipation power between the monomers at different positions and the coolant, thus completing the calculation of the temperatures of the monomers at different positions.

[0118] As a further preferred technical solution of the method for modeling a power battery temperature prediction model based on a liquid cooling heat dissipation method according to the present invention, the method further includes judging the thermal management stage of the battery according to the battery temperature and the coolant flow rate, and calculating the temperatures of the battery monomers at different positions corresponding to different thermal management stages, specifically including:

[0119] (A) Set a cooling strategy and a charging heating strategy. The cooling strategy is: when the highest monomer temperature T b,max in the battery pack is higher than a certain specific temperature T c , battery cooling will be turned on; when the highest monomer temperature T b,max in the battery pack is lower than a certain specific temperature T c ', battery cooling will be turned off.

[0120] The charging heating strategy is any one of Method 1 or Method 2. Method 1 is a heating strategy of heating first and then charging. Specifically, when the lowest monomer temperature T b,min in the battery pack is lower than a certain specific temperature T h , battery heating will be turned on; when the lowest monomer temperature T b,min in the battery pack is higher than a certain specific temperature T h ', battery heating will be turned off;

[0121] The second method is to heat first, then heat while charging, and finally charge without heating. Specifically, when the lowest cell temperature T b,min Below a certain temperature T h When the battery pack's lowest single cell temperature T b,min Above a certain temperature T h ″, the battery charging will start, the heating will not stop, and the battery will be heated while charging; when the lowest cell temperature T b,min Above a certain temperature T h ', the battery heating will stop and only charging will be performed;

[0122] (B) According to the battery thermodynamic equation, when the highest and lowest cell temperatures T b,max and T b,min When in different ranges, the thermal management stage of the battery is determined and the temperature of cells at different positions is calculated. Specifically:

[0123] ① When T b,max ≥T c When the battery pack is in the cooling stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0124]

[0125] ②When T c ′≤T b,max <T c When L≠0, the battery pack is in the cooling stage, t n The calculation method of monomer temperature at different positions at the same time is the same as that in ①;

[0126] ③When T c ′≤T b,max <T c When L=0, the battery pack is in the non-cooling stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0127]

[0128] ④ When T b,max <T c ′, the battery pack is in the non-cooling stage, t n The calculation method of monomer temperature at different positions at different times is the same as ③.

[0129] ⑤When T b,min <T h When L≠0, the battery pack is in the heating stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0130]

[0131] ⑥ When T b,min <T h and L = 0, the battery pack is in the stage of no cooling or no heating, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ③;

[0132] ⑦ When T b,min ≥T h and L≠0, for the strategy of heating first and then charging, when T h ≤T b,min <T h ′, the battery pack is in the heating stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ⑤; when T b,min ≥T h ′, the battery pack is in the charging stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as that in ③.

[0133] ⑧ When T b,min ≥T h and L≠0, for the heating strategy of heating first, then heating while charging, and finally only charging without heating, when T h ≤T b,min <T h ′, the battery pack is in the heating stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as that in ⑤; when T h ′≤T b,min <T h ″, the battery pack is in the stage of heating while charging, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ①; when T b,min ≥T h ″, the battery pack is in the charging stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ③.

[0134] ⑨ When T b,min ≥T h and L = 0, the battery pack is in the stage of no cooling or no heating, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ③.

[0135] The present invention determines the thermal management stage of the battery according to the battery temperature and the coolant flow rate, and proposes a calculation method that can calculate the single - cell temperatures of the battery at different positions in different thermal management stages only based on the battery current, SOC, coolant temperature and flow rate.

[0136] The battery pack based on the liquid cooling heat dissipation method of the present invention not only proposes a method for judging and predicting the battery thermal management state according to the results of battery temperature prediction and coolant flow rate, but also proposes a method for calculating the temperatures of single cells at different positions under different conditions according to this judgment result, expanding the applicable range of the model.

[0137] The present invention also provides a schematic diagram of the arrangement of battery single cells inside the battery pack of the power battery based on the liquid cooling heat dissipation method and the flow direction of the coolant.

[0138] In the present invention, the battery current at time t in the model is represented by I n , and for the discharge condition, it usually comes from the future condition predicted based on the historical condition, and based on this, the SOC of the battery at time t tn can be predicted. n

[0139] In the present invention, by combining the inlet and outlet coolant temperatures T liquid,inlet , T liquid,outlet collected by the sensor and the flow rate L, the temperatures of battery single cells at different positions at a certain moment can be predicted.

[0140] In the present invention, for the heat dissipation parameters between the battery and the coolant, they can also be obtained by the following method: based on the three-dimensional data of the battery pack, performing simulation calculations through simulation software, and correcting according to the test data to obtain the heat dissipation parameters between single cells at different positions and the coolant. This part is the prior art, and those skilled in the art can refer to the content disclosed in the prior art for actual operations; combining the calculation formula of the coolant temperature at different positions in the technical solution of the present invention, calculating the heat dissipation power between single cells at different positions and the coolant, and further calculating the temperatures of single cells at different positions.

[0141] Compared with the prior art, the present invention has the following beneficial effects:

[0142] (1) The present invention provides a battery pack based on the liquid cooling heat dissipation method. By experimentally calibrating the variation relationship of the equivalent heat dissipation parameters between the battery and the coolant with the flow rate and the equivalent heat dissipation parameters between the battery and the air, and correcting the calibration results, while considering the variation relationships of the battery internal resistance and the entropy heat coefficient representing the reversible heat of the battery with factors such as SOC and temperature, a prediction model for the temperatures of battery single cells at different positions in the battery pack for different thermal management stages is established. The model established by the above method can expand the applicable range of the model, reduce the complexity of the model, simplify the model input parameters, and improve the reliability of the model operation while ensuring the simulation accuracy.

[0143] (2) The method of the present invention can determine the thermal management stage of the battery based on the battery temperature and coolant flow rate. Furthermore, based solely on the battery current, SOC, coolant temperature, and flow rate, the temperature of battery cells at different locations corresponding to different thermal management stages can be predicted. The model input parameters are simple, and the calculation reliability is high. The prediction results can be used to estimate the remaining energy (SOE) of the battery. Thermal management control of the battery can also be performed in advance based on the predicted battery temperature to ensure that the battery operates within the appropriate temperature range as much as possible.

[0144] (3) The calculation method of the present invention is simple, and there is no repeated iteration of multiple parameters, which ensures the reliability of the model operation. In addition, the modeling method of the power battery temperature prediction model proposed by the present invention is based on the battery pack with liquid cooling. It is advanced in the experimental calibration and correction of the equivalent heat dissipation parameters between the battery and the air and coolant, and the calculation method of the corresponding coolant temperature under different cells. At the same time, considering that the battery pack has charging and heating functions, a calculation method for the temperature of battery cells at different locations in different thermal management stages is proposed, which has high reliability and convenience at the operational level. BRIEF DESCRIPTION OF THE DRAWINGS

[0145] Figure 1 This is a flow chart of the modeling of the power battery temperature prediction model based on the liquid cooling heat dissipation method of the present invention.

[0146] Figure 2 This is a schematic diagram of the arrangement of battery cells inside a battery pack and the flow of coolant in a power battery based on liquid cooling. DETAILED DESCRIPTION

[0147] The present invention provides a power battery temperature prediction model and modeling method based on liquid cooling heat dissipation. The modeling process is as follows:

[0148] (1) Establish the thermodynamic equation of the battery:

[0149]

[0150] Among them, c b is the specific heat capacity of the battery, m b is the weight of the battery, and t n and t n-1 The temperature of the coolant at all times, and t n-1 The heat generation power and total heat dissipation power at each moment.

[0151] (2) According to the Bernadi heat generation rate model, the heat generation rate of the battery Q p It can be expressed as follows:

[0152] Q p = I 2 R + IT b k rev

[0153] Where: R is the internal resistance of the battery; k rev is the entropy heat coefficient of the battery and is calculated by the following formula.

[0154]

[0155] Where, U OCV is the open-circuit voltage of the battery.

[0156] Substitute into the battery heat generation rate model:

[0157]

[0158] (3) Through the HPPC test under the conditions of -30 to 55 °C, obtain the functional relationship between the equivalent DC internal resistance of the battery pack and the state of charge (SOC) and the battery temperature, that is: R = f(SOC, T b ).

[0159] (4) Select one SOC every 10% within the range of SOC from 0% to 100% as the measurement point. First, charge the battery cell to SOC 100%, fix this SOC, adjust the ambient temperature in the order of 25 °C → 55 °C → 25 °C → 0 °C → -20 °C → 25 °C. After fully standing at each temperature point, measure the open-circuit voltage of the battery cell; after completing the test at one SOC point, adjust the SOC to another value, fix this SOC again, and repeat the above operations until the entire test process is completed. For the entropy heat coefficient of the battery under different SOC conditions, calculate according to the following formula:

[0160]

[0161] Where, n is a positive integer from 0 to 10, SOC n represents 11 SOC measurement points from SOC 100% to 0%; is the entropy heat coefficient under a specific SOC condition; T n corresponds to 6 temperature points in the order of the ambient chamber temperature change.

[0162] After completing the calculation of the entropy heat coefficient under all SOC conditions, the functional relationship between the entropy heat coefficient and SOC can be obtained:

[0163] k rev = g(SOC)

[0164] Preferably, during the entropy heat coefficient test, for temperature points above 0°C, the standing time ≥ 3 hours; for temperature points below 0°C, the standing time ≥ 5 hours.

[0165] (5) According to steps (2) to (4), the heat generation rate of the battery at time t n-1 is expressed as:

[0166]

[0167] (6) For the battery pack with liquid cooling heat dissipation method, the total heat dissipation power of the battery is the sum of the heat dissipation power between the battery and the air and the heat dissipation power between the battery and the coolant, that is:

[0168] (15)

[0169] where and are the heat dissipation power between the battery and the air, the heat dissipation power between the battery and the coolant, and the total heat dissipation power of the battery at time t n-1 respectively.

[0170] According to Newton's law of cooling, the total heat dissipation power of the battery at time t n-1 is proportional to the temperature difference between the battery and the external heat exchange medium:

[0171] where H is the heat dissipation parameter between the battery and the external heat exchange medium, and are the temperatures of the battery and the external heat exchange medium at time t n-1 respectively.

[0172] According to the above formula, the total heat dissipation power of the battery at time t n-1 is expressed as:

[0173]

[0174] where H air and H liquid are the equivalent heat dissipation parameters between the battery and the air and the coolant respectively, and are the temperatures of the coolant and the air at time t n-1 respectively.

[0175] As a preferred technical solution of the power battery temperature prediction model based on the liquid cooling heat dissipation method of the present invention, the method further includes calibrating and correcting the equivalent heat dissipation parameter H air between the battery and the air and the equivalent heat dissipation parameter H liquid between the battery and the coolant, and respectively obtaining the corrected heat dissipation parameter H air-corr, and the corrected heat dissipation parameter H between the battery and the coolant liquid-corr ;

[0176] The said H air-corr is obtained by the following method:

[0177] For the convective heat transfer between the battery and the air, first set the temperature of the environmental chamber to temperature T high , and let the battery pack stand still in it until all the monomer temperatures in the battery pack are stable at (T high -2) °C to (T high +2) °C. Then set the temperature of the environmental chamber to temperature T low , (T high -T low ) ≥ 15 °C, control the coolant flow rate to 0 L / min, start the test until all the monomer temperatures in the battery pack are in (T low -2) °C to (T low +2) °C and remain stable for ≥ 1 h. Stop the test and record the start and end times of the test, as well as the environmental temperature and battery temperature at different times during the test. According to the thermodynamic equation of the battery:

[0178]

[0179] Calculate the heat dissipation parameter between the battery and the air at different times:

[0180]

[0181] where, represents the heat dissipation parameter between the battery and the air at time t n , represents the heat generation power of the battery at time t n-1 .

[0182] After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameter between the battery and the air:

[0183]

[0184] Then the heat dissipation power between the battery and the air at time t n is:

[0185]

[0186] The battery temperature at different times is calculated by the following formula:

[0187]

[0188] Use the above formula to calculate H air-initialSubstitute the calculation results back into the original test data (i.e., substitute the calculation results of the heat dissipation parameters into the original test data, and according to the calculation formula of the battery temperature at different times, obtain the calculated values of the battery temperature at different times), and calculate the battery temperature at different times Based on and the error between them, use the least squares method to correct the equivalent heat dissipation parameter between the battery and the air, and obtain the corrected equivalent heat dissipation parameter H air-corr .

[0189] The above-mentioned H liquid-corr is obtained through the following method:

[0190] For the convective heat transfer between the battery and the coolant, first set the environmental chamber temperature to temperature T high , and let the battery pack stand still in it until the battery temperature stabilizes at (T high -2) °C to (T high +2) °C. Control the coolant flow rate to be L1, start the test until the battery temperature remains stable for ≥1 h, stop the test, and record the start and end times of the test, as well as the temperatures of the environment, coolant, and battery at different times during the test. According to the thermodynamic equation of the battery:

[0191]

[0192] Calculate the heat dissipation parameter between the battery and the coolant at different times:

[0193]

[0194] where, H liquid,tn-1 represents the heat dissipation parameter between the battery and the coolant at time t n-1 .

[0195] After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameter between the battery and the coolant:

[0196]

[0197] Then the heat dissipation power of the battery at time t n is:

[0198]

[0199] The battery temperature at different times is calculated by the following formula:

[0200]

[0201] Substitute the calculation results of H liquid-initial back into the original test data using the above formula, and calculate the battery temperature at different times Based on the error between and, the equivalent heat dissipation parameter between the battery and the coolant is corrected by the least square method, and the corrected equivalent heat dissipation parameter H liquid-corr ;

[0202] Preferably, the method further includes sequentially adjusting the coolant flow rate, and repeating the above tests and parameter calibration and correction processes until the coolant flow rate is adjusted to the maximum flow rate L that the water-cooled plate can withstand max , to obtain the functional relationship between the corrected equivalent heat dissipation parameter between the battery and the coolant and the coolant flow rate under different coolant flow rate conditions:

[0203] H liquid-corr = h(L).

[0204] (7) According to (1) to (6), the thermodynamic equation of the battery is expressed as:

[0205]

[0206] (8) According to the schematic diagram of the arrangement of battery cells inside the battery pack and the coolant flow direction of the power battery based on the liquid cooling heat dissipation method in the appendix Figure 2 , the heat dissipation power corresponding to different positions of the monomers at time t n is calculated according to the following formula:

[0207]

[0208]

[0209] It is judged that the coolant temperature corresponding to different monomers approximately increases in an equal amplitude along the flow direction of the coolant. The coolant temperature corresponding to different monomers is calculated according to the following formula:

[0210]

[0211] where j and k are positive integers (where k≠1), respectively representing the row number and column number where the battery cell is located;

[0212] T liquid,jk represents the temperature of the coolant below the battery cell in the j-th row and k-th column; T liquid,inlet and T liquid,outlet are the inlet and outlet temperatures of the coolant respectively.

[0213] When k = 1, the coolant temperature corresponding to the monomer below is the inlet temperature T liquid,inlet .

[0214] (9) Based on step (8), the thermal management stage of the battery is determined according to the battery temperature and the coolant flow rate, and the temperature of the battery cells corresponding to different thermal management stages and different positions is calculated, specifically including:

[0215] (A) Setting cooling strategy and charging heating strategy: When the highest cell temperature T b,max Above a certain temperature T c When the battery pack's highest single cell temperature T b,max Below a certain temperature T c ', the battery cooling will exit.

[0216] The charging heating strategy is either one of the first or second methods. The first method is a heating strategy that heats first and then charges. Specifically, when the lowest cell temperature T b,min Below a certain temperature T h When the battery pack's lowest single cell temperature T b,min Above a certain temperature T h ', the battery heating will exit;

[0217] The second method is to heat first, then heat while charging, and finally charge without heating. Specifically, when the lowest cell temperature T b,min Below a certain temperature T h When the battery pack's lowest single cell temperature T b,min Above a certain temperature T h ″, the battery charging will start, the heating will not stop, and the battery will be heated while charging; when the lowest cell temperature T b,min Above a certain temperature T h ', the battery heating will stop and only charging will be performed;

[0218] (B) According to the battery thermodynamic equation, when the highest and lowest cell temperatures T b,max and T b,min When in different ranges, the thermal management stage of the battery is determined and the temperature of cells at different positions is calculated. Specifically:

[0219] ① When T b,max ≥T c When the battery pack is in the cooling stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0220]

[0221] ②When T c ′≤T b,max <Tc When L≠0, the battery pack is in the cooling stage, t n The calculation method of monomer temperature at different positions at the same time is the same as that in ①;

[0222] ③When T c ′≤T b,max <T c When L=0, the battery pack is in the non-cooling stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0223]

[0224] ④ When T b,max <T c ′, the battery pack is in the non-cooling stage, t n The calculation method of monomer temperature at different positions at different times is the same as ③.

[0225] ⑤When T b,min <T h When L≠0, the battery pack is in the heating stage, t n The monomer temperature at different positions at the same time is calculated as follows:

[0226]

[0227] ⑥When T b,min <T h When L=0, the battery pack is in the non-cooling or non-heating stage, t n The calculation method of monomer temperature at different positions at the same time is the same as that in ③;

[0228] ⑦When T b,min ≥T h When L≠0, for the strategy of heating first and then charging, when T h ≤T b,min <T h ′, the battery pack is in the heating stage, t n The calculation method of monomer temperature at different positions at the same time is the same as that in ⑤; when T b,min ≥T h ′, the battery pack is in the charging stage, t n The calculation method of monomer temperature at different positions at different times is the same as ③.

[0229] ⑧When T b,min ≥T h When L≠0, the heating strategy is to heat first, then charge and heat at the same time, and finally charge without heating. h ≤T b,min <T h ′, the battery pack is in the heating stage, t nThe calculation method of the monomer temperature at different positions at a moment is the same as that in ⑤; when T h ′ ≤ T b,min <T h ″, the battery pack is in the stage of heating and charging simultaneously, and the calculation method of the monomer temperature at different positions at time t n is the same as the calculation method in ①; when T b,min ≥ T h ″, the battery pack is in the charging stage, and the calculation method of the monomer temperature at different positions at time t n is the same as the calculation method in ③.

[0230] ⑨ When T b,min ≥ T h and L = 0, the battery pack is in the stage of no cooling or no heating, and the calculation method of the monomer temperature at different positions at time t n is the same as the calculation method in ③.

[0231] (10) Regarding the input of the battery SOC in the model, for the discharging condition, first, based on the future condition predicted from the historical condition, predict the battery current at time t n , and then predict the SOC of the battery at time t n accordingly.

[0232] (11) Combine the coolant inlet and outlet temperatures T liquid,inlet , T liquid,outlet and the flow rate L collected by the sensor, and predict the temperatures of the battery monomers at different positions at a certain moment according to the above method.

[0233] The applicant declares that the present invention illustrates the detailed method of the present invention through the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for predicting the temperature of a power battery based on a liquid cooling heat dissipation method, characterized in that, The method is based on a temperature prediction model for power batteries with liquid cooling heat dissipation, and the temperature prediction model is as follows: Among them, and are the battery temperatures at times t n and t n-1 respectively, and are the heat generation power and total heat dissipation power of the battery at time t n-1 respectively, c b is the specific heat capacity of the battery, m b is the weight of the battery; In the temperature prediction model, the heat generation power of the battery is obtained in the following way: According to the Bernadi heat generation rate model, the heat generation rate Q of the battery p is expressed as follows: Q p = I 2 R + IT b k rev Where: I is the current of the battery, R is the internal resistance of the battery; k rev is the entropy heat coefficient of the battery, By testing the internal resistance of the battery under different temperatures and SOC conditions, a function R = f(SOC, T b ) is established, and the entropy heat coefficient k rev = g(SOC) is tested under different SOC conditions, and the heat generation power of the battery at time t n-1 is obtained as follows: Among them, is the current of the battery at time t; n-1 ​ In the temperature prediction model, the total heat dissipation power of the battery is obtained in the following way: For a battery pack with liquid cooling heat dissipation, the heat dissipation of the battery includes natural convection heat transfer with the external air and forced convection heat transfer with the coolant. The total heat dissipation power of the battery is the sum of the heat dissipation power between the battery and the air and the heat dissipation power between the battery and the coolant, that is: Among them, and are respectively the heat dissipation power between the battery and the air, the heat dissipation power between the battery and the coolant, and the total heat dissipation power of the battery at time t n-1 ; According to Newton's law of cooling, the total heat dissipation power of the battery at time t n-1 is proportional to the temperature difference between the battery and the external heat exchange medium: ​ where H is the heat dissipation parameter between the battery and the external heat exchange medium, and are the temperatures of the battery and the external heat exchange medium at time t n-1 respectively; According to the total heat dissipation power formula of the above battery, t n-1 The total heat dissipation power of the battery at the moment is expressed as: Among them, H air and H liquid are respectively the equivalent heat dissipation parameters between the battery and air and coolant, and are respectively the temperatures of the coolant and air at time t n-1 . The temperature prediction model further includes calibrating and correcting the equivalent heat dissipation parameter H between the battery and the air air and the equivalent heat dissipation parameter H between the battery and the coolant liquid , and respectively obtaining the corrected equivalent heat dissipation parameter H between the battery and the air air-corr , and the corrected equivalent heat dissipation parameter H between the battery and the coolant liquid-corr , The said H air-corr is obtained by the following method: For the convective heat transfer between the battery and the air, first set the temperature of the environmental chamber to temperature T high , and let the battery pack stand still in it until the temperatures of all the monomers in the battery pack are stable at (T high -2) °C to (T high +2) °C. Then set the temperature of the environmental chamber to temperature T low , (T high -T low ) ≥ 15 °C, control the coolant flow rate to be 0 L / min, start the test, and continue until the temperatures of all the monomers in the battery pack are in the range of (T low -2) °C to (T low +2) °C and remain stable for ≥ 1 h. Stop the test, record the start and end times of the test, as well as the environmental temperature and battery temperature at different times during the test. According to the thermodynamic equation of the battery: Calculate the heat dissipation parameters between the battery and the air at different times: Among them, represents the heat dissipation parameter between the battery and the air at time t, n and represents the heat generation power of the battery at time t. n-1 ​ After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameters between the battery and the air: Then t n The heat dissipation power between the battery and the air at this moment is: The battery temperature at different times is calculated by the following formula: Substitute the calculation result of H into the original test data using the above formula air-initial to calculate the battery temperature at different times Based on and the error between them, use the least squares method to correct the equivalent heat dissipation parameter between the battery and the air, and obtain the corrected equivalent heat dissipation parameter H air-corr ; The said H liquid-corr is obtained by the following method: For the convective heat transfer between the battery and the coolant, first set the environmental chamber temperature to temperature T high , and let the battery pack stand still in it until the battery temperature stabilizes at (T high - 2) °C to (T high + 2) °C. Control the coolant flow rate to be L1, start the test, and stop the test until the battery temperature remains stable for ≥1 h. Record the start and end times of the test, as well as the temperatures of the environment, coolant, and battery at different times during the test. According to the thermodynamic equation of the battery: Calculate the heat dissipation parameters between the battery and the coolant at different times: Among them, represents the heat dissipation parameter between the battery and the coolant at time n-1 t, After that, calculate the average value of the heat dissipation parameters at different times to obtain the initial value of the equivalent heat dissipation parameters between the battery and the coolant: Then t n The heat dissipation power of the battery at the moment is: The battery temperature at different times is calculated by the following formula: Substitute the calculation result of H into the original test data using the above formula liquid-initial to calculate the battery temperature at different times Based on and the error between them, use the least squares method to correct the equivalent heat dissipation parameter between the battery and the coolant, and obtain the corrected equivalent heat dissipation parameter H liquid-corr ; The temperature prediction model further includes successively adjusting the coolant flow rate and repeating the above tests and parameter calibration and correction processes until the coolant flow rate is adjusted to the maximum flow rate L that the water-cooled plate can withstand. max to obtain the functional relationship between the corrected equivalent heat dissipation parameter between the battery and the coolant and the coolant flow rate under different coolant flow rate conditions: H liquid-corr = h(L).

2. A modeling method for the power battery temperature prediction method based on liquid cooling heat dissipation as described in claim 1, characterized in that, The method includes the following steps: (1) Test the internal resistance of the battery under different temperatures and SOC conditions, and establish the function R = f(SOC, T b ), test the entropy heat coefficient k rev = g(SOC), and establish a battery heat generation rate model: Q p = I 2 R + IT b k rev = I 2 × f(SOC, T b ) + IT b × g(SOC) (2)Adopt the battery heat generation rate model Q described in step (1) p and the heat dissipation power model Q s to establish the battery thermodynamics equation: The total heat dissipation power is: (3) According to the inlet water temperature and outlet water temperature of the coolant, calculate the heat dissipation power between the battery cells at different positions and the corresponding coolant below them, and substitute it into the battery thermodynamics equation described in step (2) to obtain the temperatures of the battery cells at different positions; A power battery with liquid cooling heat dissipation is adopted. The power battery includes a battery pack, and the battery pack is composed of at least 2 battery modules and m parallelly arranged corrugated tubes, where m is an integer not less than 1. The battery modules are located above each corrugated tube, and the coolant flows from one side to the other along the cooling pipes inside the corrugated tubes. The battery module includes n battery cells, where n is an integer not less than 2. The battery cells are not in direct contact with the corrugated tubes, so the heat dissipation situation between the battery and the coolant is characterized by equivalent heat dissipation parameters; t n The heat dissipation power corresponding to monomers at different positions at different times is calculated according to the following formula: where k≠1; and respectively represent the temperature of the battery cell located in the j-th row and k-th column at time t n-1 and the heat dissipation power corresponding to time t n ; and are the inlet and outlet temperatures of the coolant at time t n-1 ; Among them, k = 1; Judge that the coolant temperatures corresponding to different monomers below show a law of approximately equal-amplitude increase along the flow direction of the coolant. The coolant temperatures corresponding to different monomers below are calculated by the following formula: where j and k are positive integers, with k≠1, representing the row number and column number of the battery cell respectively; T liquid,jk represents the temperature of the coolant below the battery cell in the j-th row and k-th column; T liquid,inlet and T liquid,outlet are the inlet and outlet temperatures of the coolant respectively; When k = 1, the temperature of the coolant corresponding to the lower part of the monomer is the inlet temperature T of the coolant liquid,inlet .

3. The modeling method according to claim 2, wherein Step (1) includes: (a) Through HPPC tests under the condition of -30 to 55 °C, the functional relationships between the equivalent DC internal resistance of the battery pack, the state of charge SOC, and the battery temperature are obtained, namely: R = f(SOC, T b ); According to the Bernadi heat generation rate model, the heat generation rate Q of the battery p is expressed as follows: Q p = I 2 R + IT b k rev Where: I is the current of the battery, R is the internal resistance of the battery; k rev is the entropy heat coefficient of the battery and is calculated by the following formula: Among them, U OCV is the open-circuit voltage of the battery; (b) Select a SOC every 10% within the range of SOC from 0% to 100% as a measurement point. First, charge the battery cell to SOC 100%, fix this SOC, adjust the ambient temperature in the order of 25°C → 55°C → 25°C → 0°C → -20°C → 25°C, and after fully standing at each temperature point, measure the open-circuit voltage of the battery cell; (c) After completing the test at one SOC point, adjust the SOC to another value, fix this SOC again, and repeat step (b) until the entire test process is completed. For the entropy heat coefficient of the battery under different SOC conditions, it is calculated according to the following formula: where n is a positive integer from 0 to 10, and SOC n represents 11 SOC measurement points from 100% to 0% of SOC; is the entropy heat coefficient under a specific SOC condition; T n corresponds to 6 temperature points in the order of the ambient chamber temperature change; After calculating the entropy heat coefficient under all SOC conditions, the functional relationship k between the entropy heat coefficient and SOC can be obtained rev = g(SOC); Substitute into the Bernadi heat generation rate model, the heat generation rate of the battery at time t n-1 is expressed as:

4. According to the modeling method described in claim 3, in step (b), in order to ensure that the battery temperature is consistent with the temperature of the temperature chamber environment, for temperature points above 0°C, the standing time ≥ 3 hours; for temperature points of 0°C and -20°C, the standing time ≥ 5 hours.

5. The modeling method according to claim 2, characterized in that The battery thermodynamics equation described in step (2) is: Among them, represents the battery current at n-1 time t.

6. The modeling method according to claim 2, wherein The method further includes determining the thermal management stage of the battery according to the battery temperature and the coolant flow rate, and calculating the temperatures of the battery cells at different positions corresponding to different thermal management stages, specifically including: (A) Set a cooling strategy and a charging and heating strategy. The cooling strategy is as follows: When the highest single-cell temperature T in the battery pack b,max is higher than a specific temperature T c , battery cooling will be turned on; when the highest single-cell temperature T in the battery pack b,max is lower than a specific temperature T c ', battery cooling will be turned off; The charging and heating strategy is any one of Method 1 or Method 2. Method 1 is a heating strategy of heating first and then charging. Specifically: when the lowest single-cell temperature T in the battery pack b,min is lower than a specific temperature T h , battery heating will be turned on; when the lowest single-cell temperature T in the battery pack b,min is higher than a specific temperature T h ', battery heating will be turned off; The second method is a heating strategy of first heating, then heating while charging, and finally only charging without heating. Specifically: when the lowest single-cell temperature T in the battery pack b,min is lower than a specific temperature T h , battery heating will be turned on; when the lowest single-cell temperature T in the battery pack b,min is higher than a specific temperature T h , battery charging will start, and heating will not stop, and heating will be carried out while charging; when the lowest single-cell temperature T in the battery pack b,min is higher than a specific temperature T h ', battery heating will stop and only charging will be carried out; (B) According to the thermodynamic equation of the battery, when the highest and lowest single-cell temperatures T b,max and T b,min are in different ranges, determine the thermal management stage of the battery and calculate the temperatures of single cells at different positions. Specifically: ①When T b,max ≥T c , the battery pack is in the cooling stage, and the temperatures of the single cells at different positions at time t n are calculated according to the following formula: where k≠1; where k = 1; ②When T c ′≤T b,max <T c and L≠0, the battery pack is in the cooling stage, and the calculation method of the monomer temperature at different positions at time t n is the same as that in ①; ③ When T c ′ ≤ T b,max <T c and L = 0, the battery pack is in the non-cooling stage, and the temperatures of the cells at different positions at time t n are calculated according to the following formula: ④When T b,max <T c ′, the battery pack is in the non-cooling stage, and the calculation method of the single-cell temperature at different positions at time t n is the same as that in ③; ⑤When T b,min <T h and L≠0, the battery pack is in the heating stage, and the temperatures of the cells at different positions at time t n are calculated according to the following formula: where k≠1; where k = 1; ⑥ When T b,min < T h and L = 0, the battery pack is in the stage of no cooling or no heating, and the calculation method of the monomer temperature at different positions at time t n is the same as the calculation method in ③; ⑦ When T b,min ≥ T h and L ≠ 0, for the strategy of heating first and then charging, when T h ≤ T b,min < T h ′, the battery pack is in the heating stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as the calculation method in ⑤; when T b,min ≥ T h ′, the battery pack is in the charging stage, and the calculation method of the single - cell temperature at different positions at time t n is the same as ③; ⑧When T b,min ≥T h and L≠0, the heating strategy is to heat first, then heat while charging, and finally only charge without heating. When T h ≤T b,min <T h ′, the battery pack is in the heating stage, and the calculation method of the single-cell temperature at different positions at time t n is the same as that in ⑤; when T h ′≤T b,min <T h ″, the battery pack is in the stage of heating while charging, and the calculation method of the single-cell temperature at different positions at time t n is the same as the calculation method in ①; when T b,min ≥T h ″, the battery pack is in the charging stage, and the calculation method of the single-cell temperature at different positions at time t n is the same as the calculation method in ③; ⑨When T b,min ≥ T h and L = 0, the battery pack is in the stage of no cooling or no heating, and the calculation method of the monomer temperature at different positions at time t n is the same as the calculation method in ③.

7. The modeling method according to claim 2, wherein The method further includes predicting the SOC of the battery.

8. The modeling method according to claim 6, characterized in that In the model of the described modeling method, the battery current at time t n is represented by . For the discharging condition, it is derived from the future condition predicted based on the historical condition, and based on this, the SOC of the battery at time t n is predicted.

9. The modeling method according to claim 2, wherein the method includes predicting the temperatures of the battery cells at different positions at a certain moment.

10. The modeling method according to claim 2, wherein the method includes combining the coolant inlet and outlet temperatures T liquid,inlet , T liquid,outlet and the flow rate L to predict the temperatures of battery cells at different positions at a certain moment.

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