A method and system for calculating the internal temperature of a power battery

Abstract

The present application discloses a method and system for calculating the internal temperature of a power battery. The method includes obtaining the starting temperature of the power battery and heating the power battery; if the temperature of the power battery is greater than a preset value, stopping heating and obtaining the peak temperature of the power battery; detecting the temperature of the power battery after stopping heating to form a display temperature of the power battery; if the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, determining the displayed temperature as the first internal temperature of the power battery; if the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time is less than the first preset time, calculating the second internal temperature of the power battery according to the displayed temperature. Since the second internal temperature of the power battery is calculated according to the displayed temperature when the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, the temperature of the power battery is more accurate, the risk of overcharging or over-discharging the battery is reduced, and the life of the power battery is increased.

Description

Technical Field

[0001] The present application relates to the technical field of new energy vehicles, and in particular to a method and system for calculating the internal temperature of a power battery. Background Art

[0002] At present, the battery temperature is generally measured by the battery surface temperature sensor. This method obtains the battery surface temperature, not the battery internal temperature, which has a large error with the battery internal temperature. For example, the battery cell temperature sensor in the battery pack is generally attached to the bus. Under normal use conditions, the temperature collected from the bus is close to the internal temperature of the battery cell. However, under low temperature conditions, the activity of the substances inside the battery is low, which affects the battery's charge and discharge performance. Therefore, the battery needs to be heated to increase the activity of the substances inside the battery and improve the battery's charge and discharge performance.

[0003] However, during the low-temperature heating process, the temperature rise of the bus is greater than the temperature rise of the battery cell. There is a deviation when the temperature of the bus is collected as the internal temperature of the battery cell. When the bus temperature is used to calculate the SOC (State of charge) of the electric vehicle power battery, it is easy to cause overcharging or over-discharging of the battery, causing capacity life problems. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a method and system for calculating the internal temperature of a power battery, so as to solve the problem that the temperature of the bus after heating is used as the internal temperature of the battery cell, which affects the accuracy of the power battery SOC calculation.

[0005] In order to solve the above problems, the present application adopts the following technical solutions:

[0006] The present application provides a method for calculating the internal temperature of a power battery, including:

[0007] Obtaining a starting temperature of a power battery and heating the power battery;

[0008] If the temperature of the power battery is greater than a preset value, the heating is stopped and the peak temperature of the power battery is obtained;

[0009] After stopping the heating, detecting the temperature of the power battery to form a displayed temperature of the power battery;

[0010] If the difference between the peak temperature and the starting temperature is less than or equal to a preset temperature difference, determining the displayed temperature as the first internal temperature of the power battery;

[0011] If the difference between the peak temperature and the starting temperature is greater than a preset temperature difference, and the stop time is less than a first preset time length, a second internal temperature of the power battery is calculated according to the displayed temperature.

[0012] Furthermore, the second internal temperature of the power battery and the display temperature satisfy the relationship:

[0013] Wherein, i≤k, t(i) is the time from the starting temperature to the i-th moment, t(i-1) is the time from the starting temperature to the i-1th moment, t(k) is the time from the starting temperature to the set kth moment, t(1) is the time from the starting temperature to the peak temperature, Y(i) is the displayed temperature at the i-th moment, and T2(i) is the second internal temperature at the i-th moment.

[0014] Furthermore, the time difference corresponding to two adjacent display temperatures is consistent.

[0015] Furthermore, the calculation method further includes:

[0016] If the difference between the peak temperature and the starting temperature is greater than a preset temperature difference, and the stop time dn is greater than or equal to the first preset duration dt, a third internal temperature T3 of the power battery is calculated according to the internal temperature corresponding to the first preset duration dt and the displayed temperature.

[0017] Furthermore, the internal temperature corresponding to the first preset time dt, the display temperature and the third internal temperature of the power battery satisfy the relationship:

[0018]

[0019] Wherein, dn is the stop time, dt is the first preset duration, Y(dn) is the displayed temperature corresponding to the stop time, and T2(dt) is the second internal temperature corresponding to the first preset duration.

[0020] Furthermore, the starting temperature ranges from -20°C to 0°C.

[0021] Furthermore, the peak temperature of the power battery is greater than 0°C.

[0022] Furthermore, the displayed temperature of the power battery is obtained by measuring the power battery bus by a temperature sensor.

[0023] The present application also provides a system for calculating the internal temperature of a power battery, the system being used to execute any one of the above methods for calculating the internal temperature of a power battery, the system comprising a temperature acquisition module and a temperature calculation module, wherein:

[0024] The temperature acquisition module is used to acquire the display temperature and peak temperature of the power battery at different times;

[0025] The temperature calculation module is used to calculate the second internal temperature and the first internal temperature of the power battery according to the displayed temperature and the peak temperature.

[0026] The method for calculating the internal temperature of a power battery in an embodiment of the present application includes obtaining the starting temperature of the power battery and heating the power battery; if the temperature of the power battery is greater than a preset value, the heating is stopped and the peak temperature of the power battery is obtained; after the heating is stopped, the temperature of the power battery is detected to form a displayed temperature of the power battery; if the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, the displayed temperature is determined as the first internal temperature of the power battery; if the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time is less than the first preset time, the second internal temperature of the power battery is calculated according to the displayed temperature. Since the second internal temperature of the power battery is calculated according to the displayed temperature when the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, the temperature of the power battery is more accurate, the risk of overcharging or over-discharging of the battery is reduced, and the life of the power battery is increased.

[0027] The calculation system of the internal temperature of the power battery of the embodiment of the present application is used to execute any one of the above-mentioned calculation methods of the internal temperature of the power battery, and includes a temperature acquisition module and a temperature calculation module, wherein the temperature acquisition module is used to obtain the display temperature and peak temperature of the power battery at different times; the temperature calculation module is used to calculate the second internal temperature and the first internal temperature of the power battery according to the display temperature and the peak temperature. When the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, the second internal temperature of the power battery is calculated according to the display temperature, so that the temperature of the power battery is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic flow chart of a method for calculating the internal temperature of a power battery provided in an embodiment of the present application;

[0029] Figure 2 A system block diagram of a power battery internal temperature calculation system provided in an embodiment of the present application;

[0030] Figure 3 A schematic diagram of displaying temperature of a power battery provided in an embodiment of the present application; and

[0031] Figure 4 A schematic diagram of a second internal temperature of a power battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] The specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0033] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0034] It should be understood that the orientation or position relationship is based on the orientation or position relationship shown in the drawings. These orientation terms are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0035] In the description of the present application, the terms "first / second" involved are merely used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first / second" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0036] During the use of power batteries, accurate estimation of battery temperature plays an important role in ensuring the normal operation of the battery. For example, in the calculation of the SOC (State of charge) of the power battery of an electric vehicle, it is necessary to know the battery parameters such as battery capacity and coulomb efficiency at the corresponding temperature based on the battery temperature; in battery fault diagnosis, it is necessary to judge whether the battery is working within the specified temperature range based on the battery temperature to prevent the battery temperature from being too high or too low.

[0037] The use of new energy vehicles is affected by temperature, among which the key component - power battery is significantly affected by temperature. The evaluation and prediction of battery SOC (State of Charge), SOH (State of Health) and battery life all require accurate battery temperature support, and this battery temperature is the temperature of the active material inside the battery. During the use of the battery pack, the temperature sensor that measures the battery temperature can only be arranged outside the battery, such as at the battery pole. The field of power battery thermal management mainly focuses on the operating temperature range and temperature difference of each battery pack in the battery pack. Similarly, these temperature values ​​all refer to the temperature of the active material inside the battery. If the temperature value actually measured by the battery external temperature sensor is used as the input of battery thermal management, it will inevitably produce a large error. In the actual operation of new energy vehicles, the battery temperature is a distribution inside the battery. At this time, there is a difference between the measured temperature value and the required battery temperature. After obtaining this difference, the temperature of the active material inside the battery can be accurately estimated from the measured temperature.

[0038] The following is an explanation using lithium batteries. Under low temperature conditions, the activity of lithium ions decreases, and high-current DC charging easily causes lithium accumulation on the negative electrode surface, resulting in lithium plating. As the AC excitation frequency increases, the electrochemical reaction cycle becomes shorter, and lithium insertion and removal occur alternately on the negative electrode surface, preventing lithium plating from occurring and causing no permanent damage to the battery capacity.

[0039] At present, the battery temperature is generally measured by the battery surface temperature sensor. This method obtains the battery surface temperature, not the battery internal temperature, and has a large error with the battery internal temperature. For example, the battery cell temperature sensor in the battery pack is generally attached to the bus. The material is aluminum, which has a small specific heat capacity, small volume and weight. Under normal use conditions, the temperature collected from the bus is close to the internal temperature of the battery cell, so the industry generally uses the collected temperature as the battery cell temperature. However, under pulse current heating conditions, when a large current flows, the bus temperature rise is greater than the battery cell temperature rise. Therefore, under this condition, the battery cell temperature is inaccurate. Therefore, the temperature collected at this location needs to be corrected to represent the actual temperature of the battery cell, so as to avoid using a falsely high temperature as the actual temperature, causing the battery to overcharge or over-discharge, and causing capacity life problems.

[0040] In view of this, if Figure 1 and Figure 4 As shown, the embodiment of the present application provides a method for calculating the internal temperature of a power battery, including:

[0041] S1. Obtaining the starting temperature of the power battery and heating the power battery;

[0042] S2. If the temperature of the power battery is greater than a preset value, the heating is stopped and the peak temperature of the power battery is obtained;

[0043] S3. After stopping heating, detecting the temperature of the power battery to form a display temperature of the power battery;

[0044] S4. If the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, the displayed temperature is determined as the first internal temperature of the power battery;

[0045] S5. If the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time is less than the first preset time length, calculate the second internal temperature of the power battery according to the displayed temperature.

[0046] Specifically, the starting temperature of the power battery is obtained through a temperature sensor, and the starting temperature of the power battery is stored and recorded before the power battery is heated. The starting temperature of the power battery is used for calculation in subsequent steps. The temperature of the power battery is compared with a preset value. If the temperature of the power battery is greater than the preset value, heating is stopped. For example, if the preset value is 5°C, heating is stopped after the temperature of the power battery is greater than 5°C. It should be noted that the preset value is adapted to the temperature required by the active material inside the power battery, so that the temperature to which the power battery is heated is greater than the temperature required by the active material, thereby improving the charging and discharging effect of the power battery.

[0047] When heating is stopped, the peak temperature of the power battery is obtained through the temperature sensor. It should be understood that after heating the power battery is stopped, the temperature of the power battery will drop with the passage of time, and the temperature at the moment when heating is stopped, then the power battery temperature obtained at this moment, becomes the peak temperature of the power battery.

[0048] After the power battery stops heating, the temperature of the power battery will drop as time passes. The temperature of the power battery is detected to form the displayed temperature of the power battery. Specifically, the temperature of the power battery drops as time passes. The temperature of the power battery is continuously detected to form the displayed temperature of the power battery. For example, the temperature of the power battery is detected at the sampling frequency of the temperature sensor, and the displayed temperature of the power battery is formed. Alternatively, the temperature of the power battery is detected at a certain time interval, and the displayed temperature of the power battery is formed.

[0049] If the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, the displayed temperature is determined as the first internal temperature of the power battery. Specifically, the peak temperature is subtracted from the starting temperature, and the difference between the peak temperature and the starting temperature is compared with the preset temperature difference. If the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, the displayed temperature is determined as the first internal temperature of the power battery.

[0050] It should be noted that the difference between the peak temperature and the starting temperature is less than or equal to the preset temperature difference, which indicates that the power battery heating time is short, or the detection time after stopping heating is short, the temperature of the power battery has not changed significantly for the time being, and the temperature change is less than the preset temperature difference. The internal temperature of the power battery is close to the detection temperature of the power battery, and the displayed temperature can be determined as the first internal temperature of the power battery.

[0051] If the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time is less than the first preset duration, the second internal temperature of the power battery is calculated according to the displayed temperature. Specifically, the stop time is the duration after the power battery heating stops, the stop time is less than the first preset duration, and the difference between the peak temperature and the starting temperature is greater than the preset temperature difference. The second internal temperature of the power battery is calculated according to the displayed temperature, for example, after linear interpolation of the displayed temperature, the second internal temperature of the power battery is calculated. The displayed temperature is linearly correlated with the second internal temperature of the power battery.

[0052] When the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, the second internal temperature of the power battery is calculated according to the displayed temperature, so that the power battery temperature is more accurate, the risk of battery overcharge or over discharge is reduced, and the life of the power battery is increased.

[0053] It should be understood that the first preset can often be determined based on multiple tests and from result graphs of the multiple tests.

[0054] It should be noted that in the existing calculations for estimating the internal temperature of the power battery, the effect of the stop time after the battery temperature heating is stopped on the internal temperature of the power battery is not taken into account. In the method for calculating the internal temperature of the power battery in the embodiment of the present application, the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time is less than the first preset time length. The second internal temperature of the power battery is calculated based on the displayed temperature, so that the calculation of the internal temperature of the power battery is more accurate and effective.

[0055] In one embodiment, the starting temperature ranges from -20°C to 0°C. Specifically, the starting temperature is taken from -20°C to 0°C, and multiple calculations are performed according to the above S1 to S5 at different starting temperatures in the intervals. For example, the starting temperature is set to -20°C, -15°C, -10°C, -5°C or 0°C, and the power battery is heated by a pulse current. The starting temperature can be set at a certain temperature interval. The above is only performed at intervals of 5°C. In other cases, other temperature intervals can be used for division, so as to obtain starting temperatures at different temperatures, and further determine different second internal temperatures of the power battery based on different starting temperatures.

[0056] In one embodiment, the peak temperature of the power battery is greater than 0°C. Specifically, when the peak temperature of the power battery is greater than 0°C, the active material inside the power battery operates better at the peak temperature, which is beneficial to the charging and discharging of the power battery. In particular, the displayed temperature of the power battery is obtained by measuring the power battery bus through a temperature sensor.

[0057] In one embodiment, the second internal temperature of the power battery and the display temperature satisfy the relationship:

[0058] Wherein, i≤k, t(i) is the time from the starting temperature to the i-th moment, t(i-1) is the time from the starting temperature to the i-1th moment, t(k) is the time from the starting temperature to the set kth moment, t(1) is the time from the starting temperature to the peak temperature, Y(i) is the displayed temperature at the i-th moment, and T2(i) is the second internal temperature at the i-th moment.

[0059] Specifically, the time from the start temperature heating to the calculation of the internal temperature of the power battery is calculated according to the above formula for the displayed temperature Y(i) at each moment, so that the second internal temperature of the power battery takes into account the influence of the cooling time after stopping heating.

[0060] It should be noted that the shorter the time interval between two adjacent displayed temperatures Y(i), the more displayed temperature Y(i) data are used, and the more accurate the calculated second internal temperature T2(i) is.

[0061] For example, taking the initial temperature X=-10°C as an example, the pulse current heating technology is turned on, and the first preset time is 25 minutes.

[0062] Heating t(1) = 20 min, the temperature rises to Y(1) = 10°C.

[0063] During the time period t(2)=21 min, the displayed temperature Y(2) was stabilized at 9°C.

[0064] During the time period t(3)=23 min, the displayed temperature Y(3) was stabilized at 8°C.

[0065] During the time period t(4)=25 min, the displayed temperature Y(4) was stabilized at 7°C.

[0066] During the time period t(5)=36 min, the displayed temperature Y(5) was stabilized at 5°C.

[0067] The actual temperature at time t(4) is

[0068] T2(4)=9*(21-20) / (25-21)+8*(23-21) / (25-21)=6.25°C.

[0069] In one embodiment, the time difference corresponding to two adjacent displayed temperatures is consistent. Specifically, when calculating the second internal temperature at different moments, the calculation is performed according to the above formula at equal intervals.

[0070] Since the time difference between two adjacent displayed temperatures is consistent, the second internal temperature is also roughly linearly correlated (see Figure 3 and Figure 4 ).

[0071] In one embodiment, the calculation method further includes: if the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, and the stop time dn is greater than or equal to the first preset duration dt, then the third internal temperature T3 of the power battery is calculated according to the internal temperature corresponding to the first preset duration dt and the displayed temperature.

[0072] Specifically, if the difference between the peak temperature and the starting temperature is greater than the preset temperature difference, for example, the preset temperature difference is 3°C, the peak temperature is Y1, and the difference between the peak temperature and the starting temperature is Y1-X. If Y1-X>3°C, the third internal temperature T3 of the power battery is calculated based on the internal temperature T2(dt) corresponding to the first preset time length dt and the displayed temperature Y(dn).

[0073] It should be understood that the current moment exceeds the first preset time dt, and the stop time dn represents the temperature of the power battery at the current moment.

[0074] It should be noted that when the stop time dn is greater than or equal to the first preset time dt, the temperature of the power battery has exceeded the ramp-down stage and entered a slowly smoothing stage. The third internal temperature T3 of the power battery is calculated based on the internal temperature corresponding to the first preset time dt and the displayed temperature, so that the temperature of the power battery in the stage where the stop time dn is greater than or equal to the first preset time dt is more accurate.

[0075] In one embodiment, the internal temperature corresponding to the first preset time dt, the display temperature and the third internal temperature of the power battery satisfy the relationship:

[0076]

[0077] Wherein, dn is the stop time, dt is the first preset duration, Y(dn) is the display temperature corresponding to the stop time, and T2(dt) is the second internal temperature corresponding to the first preset duration.

[0078] Specifically, when the moment when the power battery temperature needs to be calculated exceeds the first preset time dt, the temperature of the power battery has passed the ramp-down stage and entered the slow smoothing stage. Based on the second internal temperature T2(dt) of the first preset time dt and the displayed temperature Y(dn) corresponding to the stop time, the formula Calculation is performed to obtain the third internal temperature T3 of the power battery, so that when the first preset time dt is exceeded, the internal temperature of the power battery is calculated using the formula of the third internal temperature, so that the power battery temperature greater than the first preset time dt stage is more accurate.

[0079] like Figure 2As shown, the embodiment of the present application also provides a calculation system 100 for the internal temperature of a power battery. The calculation system 100 is used to execute a calculation method for the internal temperature of a power battery. The calculation system 100 includes a temperature acquisition module 110 and a temperature calculation module 120, wherein the temperature acquisition module 110 is used to obtain the display temperature and peak temperature of the power battery at different times. The temperature calculation module 120 is used to calculate the second internal temperature and the first internal temperature of the power battery according to the display temperature and the peak temperature. According to the display temperature and peak temperature of the power battery obtained by the temperature acquisition module 110 at different times, a suitable formula is selected for calculation, and the temperature calculation module 120 calculates the internal temperature of the power battery, so that the temperature of the power battery is more accurate, the risk of overcharging or over-discharging of the battery is reduced, and the life of the power battery is improved.

[0080] In order to better understand the power generation control method for a hybrid vehicle according to the embodiment of the present application, Figure 3 and Figure 4 Each step of the power generation control method is described in detail.

[0081] After the pulse current heating is turned on for a while and then turned off, the collected battery temperature curve is as follows: Figure 3 As shown in the figure, the collected battery temperature will experience a rapid rise, then drop sharply after the heating is turned off, and finally stabilize within a certain range.

[0082] The battery temperature drops sharply during the stage where it is not the actual temperature of the battery cell. The heat loss during the later stable stage is not the actual temperature of the battery cell during the heating process because it has been standing still for a period of time. Therefore, it is extremely important to design a method to estimate the actual temperature within a certain period of time before and after pulse current heating.

[0083] According to the temperature rise curve characteristics of the pulse current heating battery, calibration is performed based on the test data. After accumulating a large amount of test data, it is written into the BMS software program to facilitate obtaining accurate battery cell temperature when using pulse current heating. When conducting the test, the following data needs to be recorded:

[0084] The initial battery temperature is X. The pulse current heating is turned on for t1 minute and then turned off. At this time, the displayed battery temperature is Y(1). After t(2) time, it drops to Y(2), and ..., after t(n) time, the temperature drops to Y(n). After tn+1 time, the temperature is basically stable at Y(n+1). According to the test data, when the time is within 0~t(n), when Y1-X≤3℃, the temperature difference is not large and has little effect on battery overcharge and overdischarge. The current displayed temperature Y(i) is assumed to be the current real battery temperature T1, that is, the displayed temperature is determined as the first internal problem T1 of the power battery. When Y1-X≤3℃, T1=Y(i). It should be noted that in order to simplify the expression, Y(3) and Y3 have the same meaning, Y(2) and Y2, or Y(n) and Yn, etc.

[0085] When the time is between 0 and t(n), and Y1-X>3i℃, where i=1, 2, 3, ..., the battery temperature collected by BMS is discrete data rather than continuous data, so the following algorithm is used:

[0086] The real battery temperature is also the second internal temperature of the power battery. The second internal temperature of the power battery satisfies the following relationship:

[0087] T2(i)=[Y(2)*[t(2)-t(1)]] / [t(n)-t(1)]+[Y(3)*[t(3)-t(2)]] / [t(n)-t(1)]+……+

[0088] [Y(n)*[t(n)-t(n-1)]] / [t(n)-t(1)];

[0089] When 3i≤Y1-X<3(i+1), where i=1, 2, 3, ..., the data of 3i at the previous moment is taken as the real temperature of the battery.

[0090] After time tn~tn+1, the actual temperature of the power battery is Y3=(Y2+Yn+1) / 2 in the above formula.

[0091] When the elapsed time is greater than tn+1 and the displayed temperature remains stable for a long time, the actual battery temperature is the displayed temperature.

[0092] The test plan can be set as follows: the starting temperature X is set to -20℃, -15℃, -10℃, -5℃, 0℃, etc. The pulse current heating display temperature target can be set to -20℃+3i℃ where i=1, 2, 3, ..., to carry out the test calibration work.

[0093] Due to the special temperature performance of pulse current heating technology, based on the above real temperature calculation method, the temperature detection strategy in BMS is:

[0094] When the user turns on pulse current heating, the temperature displayed after the temperature rise is within 3°C of the initial temperature, and the default displayed temperature is the real temperature; when the temperature difference between the displayed temperature and the real temperature increases, correction is performed according to the above idea. Regardless of whether the pulse current heating technology remains on or is immediately turned off, the BMS internally controls the battery charging and discharging current according to the threshold value at the real temperature, but the displayed temperature seen by the user remains unchanged; when the user turns off the pulse current heating technology, and the shutdown time does not exceed the first preset time dt, the user still sees that the displayed temperature remains unchanged. At this time, the BMS internally controls the battery charging and discharging current according to the threshold value at the real temperature; when the shutdown time is greater than the first preset time dt, the displayed temperature approaches the real temperature at a certain rate k until the displayed temperature is equal to the real temperature, and then exits the temperature correction mode of this special state.

[0095] Take an example to illustrate, the initial temperature X = -30°C as an example, and start the pulse current heating technology.

[0096] Heating t(1) = 20 min, the temperature rises to Y(1) = 10°C.

[0097] During the time period t(2)=21 min, the displayed temperature Y(2) was stabilized at 9°C.

[0098] During the time period t(3)=23 min, the displayed temperature Y(3) was stabilized at 8°C.

[0099] During the time period t(4)=26 min, the displayed temperature Y(4) was stabilized at 7°C.

[0100] During the time period t(5)=30 min, the displayed temperature Y(5) was stabilized at 6°C.

[0101] During the time period t(6)=40 min, the displayed temperature Y(6) was stabilized at 5°C.

[0102] The actual temperature at time t(5) is

[0103] T2(5)=9*(21-20) / (30-21)+8*(23-21) / (30-21))+7*(26-23) / (30-21)+)+6*(30-26) / (30-21)=7.8℃.

[0104] During the time period from t(5) to t(6), the actual temperature is T3 = (7.8 + 5) / 2 = 6.4°C, that is, T3 = [T2(5) + Y(6)] / 2 = 6.4°C.

[0105] After t(6) time, the actual temperature is 5℃

[0106] During the time period t(0) to t(1), the actual temperature needs to be first tested on a test bench according to the above method before it can be known. It should be noted that the first preset time dt used in the above example is 30 minutes.

[0107] The above is a data point calibrated by a test bench. According to this principle, other points are tested, and the data from heating from -30℃ to -24℃, -21℃, -18℃, ... 9℃, 12℃, etc. are formed into a MAP table. When used on the actual vehicle, when encountering the same scenario, you can directly look up the table to retrieve the actual temperature and write it directly into the vehicle system.

[0108] When the actual vehicle is heated to -23°C or -22°C and continues to heat, the data calculated when heated to -24°C is directly taken as the actual temperature. Other similar situations (3i<Y1-X<3(i+1)) are similarly deduced.

[0109] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the same. Although the present application has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present application.

Claims

1. A method for calculating the internal temperature of a power battery, characterized in that: include: Obtaining a starting temperature of a power battery and heating the power battery; If the temperature of the power battery is greater than a preset value, heating is stopped, and a peak temperature of the power battery is obtained; the peak temperature of the power battery is the temperature at the moment when heating is stopped; After stopping the heating, detecting the temperature of the power battery to form a displayed temperature of the power battery; If the difference between the peak temperature and the starting temperature is less than or equal to a preset temperature difference, determining the displayed temperature as a first internal temperature of the power battery; If the difference between the peak temperature and the starting temperature is greater than a preset temperature difference, and the stop time is less than a first preset time length, a second internal temperature of the power battery is calculated according to the displayed temperature.

2. The calculation method according to claim 1, characterized in that: The second internal temperature of the power battery and the display temperature satisfy the relationship: Wherein, i≤k, t(i) is the time from the starting temperature to the i-th moment, t(i-1) is the time from the starting temperature to the i-1th moment, t(k) is the time from the starting temperature to the set kth moment, t(1) is the time from the starting temperature to the peak temperature, Y(i) is the displayed temperature at the i-th moment, and T2(i) is the second internal temperature at the i-th moment.

3. The calculation method according to claim 2, characterized in that: The time difference corresponding to two adjacent displayed temperatures is consistent.

4. The calculation method according to claim 2, characterized in that: The calculation method also includes: If the difference between the peak temperature and the starting temperature is greater than a preset temperature difference, and the stop time dn is greater than or equal to the first preset duration dt, a third internal temperature T3 of the power battery is calculated according to the internal temperature corresponding to the first preset duration dt and the displayed temperature.

5. The calculation method according to claim 4, characterized in that: The internal temperature corresponding to the first preset time dt, the display temperature and the third internal temperature of the power battery satisfy the relationship: Wherein, dn is the stop time, dt is the first preset duration, Y(dn) is the displayed temperature corresponding to the stop time, and T2(dt) is the second internal temperature corresponding to the first preset duration.

6. The calculation method according to claim 1, characterized in that: The starting temperature ranges from -20°C to 0°C.

7. The calculation method according to claim 1, characterized in that: The peak temperature of the power battery is greater than 0°C.

8. The calculation method according to claim 1, characterized in that: The displayed temperature of the power battery is obtained by measuring the power battery bus by a temperature sensor.

9. A system for calculating the internal temperature of a power battery, characterized in that: The computing system is used to execute the method for calculating the internal temperature of the power battery according to any one of claims 1 to 8, and the computing system includes a temperature acquisition module and a temperature calculation module, wherein: The temperature acquisition module is used to acquire the display temperature and peak temperature of the power battery at different times; The temperature calculation module is used to calculate the second internal temperature and the first internal temperature of the power battery according to the displayed temperature and the peak temperature.

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