Battery pack equalization control method and apparatus, vehicle and computer program product

Abstract

The present application relates to a method for equalization control of a battery pack, comprising: detecting an open-circuit voltage of each battery cell of the battery pack after a charging cycle of the battery pack is ended (S1); when the first open-circuit voltage of the first battery cell is lower than a predetermined voltage threshold value, a second battery cell with the highest open-circuit voltage is discharged, and the discharge amount W of the second battery cell is determined as the difference between the first deviation X and the discharge adjustment amount M. A first deviation X between a first charge state of charge of the first battery cell and a second charge state of charge of the second battery cell is determined on the basis of the charge SOC-OCV curve and the detected open circuit voltage of the battery cells, and a discharge adjustment amount M is determined on the basis of at least the charge and discharge SOC-OCV curve of the battery cells (S2). According to the invention, the charging and discharging cycle period number of the battery can be greatly reduced in the equalization process of the battery pack, and the efficiency of the equalization process of the battery pack is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a method for balancing control of a battery pack, a device for balancing control of a battery pack, a vehicle including the device according to the present application, and a computer program product for at least assisting in implementing the steps of the method according to the present application. Background Art

[0002] An electric vehicle is mainly powered by a battery pack, which is composed of a large number of battery cells. However, parameters such as the state of charge, capacity, and self-discharge rate of each battery cell may be inconsistent. Therefore, it is necessary to regularly balance each battery cell of the battery pack to improve the overall performance of the battery pack.

[0003] In existing battery balancing methods, the balancing strategy of the battery pack is usually formulated according to the open circuit voltage (abbreviated as OCV) and the state of charge (abbreviated as SOC) of each battery cell. However, due to the hysteresis effect of the battery cell, the balancing strategy formulated according to the existing technology often causes over-balancing or under-balancing of the battery pack, which greatly affects the overall performance of the battery pack, especially the available capacity.

[0004] Therefore, how to eliminate the influence of the hysteresis effect of the battery cell on battery balancing has become a technical problem to be solved at present. Summary of the Invention

[0005] The purpose of the present application is to provide a method for balancing control of a battery pack, a device for balancing control of a battery pack, a vehicle including the device according to the present application, and a computer program product to at least partially solve the problems in the prior art.

[0006] According to a first aspect of the present application, there is provided a method for balancing control of a battery pack, the method comprising:

[0007] - Step S1: After the end of a charging cycle of the battery pack, detecting the open circuit voltage of each battery cell of the battery pack; and

[0008] - Step S2: When the first open circuit voltage of the first battery cell is lower than a pre-given voltage threshold U rIn the case of, the second battery cell with the highest open-circuit voltage is discharged, wherein the discharge amount W of the second battery cell is determined as the difference between the first deviation X and the discharge adjustment amount M, wherein the first deviation X between the first state of charge of the first battery cell and the second state of charge of the second battery cell is determined based on the charging SOC-OCV curve and the detected open-circuit voltage of the battery cell, and wherein the discharge adjustment amount M is determined based at least on the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell.

[0009] The core concept of the present application lies in: when determining the discharge amount of the battery cell, the hysteresis effect caused by the difference between the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell is fully considered, thereby greatly reducing the number of charge and discharge cycles of the battery pack during the battery pack balancing process, thus reducing the time-consuming of the battery pack balancing process, avoiding repeated charging and discharging of the battery cell during the balancing process, and effectively improving the efficiency of the battery pack balancing process.

[0010] According to an optional embodiment of the present application, the discharge adjustment amount M can be determined based at least on the second deviation Y and the adjustment ratio Z, wherein the second deviation Y between the charging state of charge and the discharging state of charge of the battery cell at the voltage threshold U r is determined based on the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell, and the adjustment ratio Z is related to the voltage threshold U r is related.

[0011] According to another optional embodiment of the present application, the discharge adjustment amount M is determined as the product of the second deviation Y and the adjustment ratio Z, wherein the larger the voltage threshold U r is, the smaller the adjustment ratio Z is.

[0012] According to another optional embodiment of the present application, the method may further include:

[0013] - Step S3: After the discharge of the second battery cell is completed, the battery pack is charged until a battery cell with a charging state of charge of 100% appears in the battery pack to complete one charge and discharge cycle, and wherein steps S1 to S3 are repeatedly executed until the open-circuit voltages of all battery cells in the battery pack are higher than a pre-given voltage threshold U r .

[0014] According to another optional embodiment of the present application, during the repeated execution of steps S1 to S3, the discharge adjustment amount M can be adjusted based at least on the number of charge and discharge cycles, the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell, so as to reduce until the open-circuit voltages of all battery cells in the battery pack are higher than a pre-given voltage threshold U rThe total number of charge and discharge cycles to be completed.

[0015] According to another alternative embodiment of the present application, the discharge adjustment amount M can be adjusted by an artificial intelligence model at least based on the number of charge and discharge cycles, the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell. The artificial intelligence model includes, for example, a machine learning model, a deep learning model, a large language model, and / or a reinforcement learning model, etc.

[0016] According to a second aspect of the present application, there is provided a device for balancing control of a battery pack, wherein the device may include the following components:

[0017] - An open-circuit voltage detection unit configured to detect the open-circuit voltage of each battery cell of the battery pack;

[0018] - A discharge unit configured to discharge the second battery cell with the highest open-circuit voltage;

[0019] and

[0020] - A control unit configured to execute the method according to the present application.

[0021] According to a third aspect of the present application, there is provided a vehicle, and the vehicle may include the device according to the present application.

[0022] According to a fourth aspect of the present application, there is provided a computer program product, such as a computer-readable program carrier, containing or storing computer program instructions, and when the computer program instructions are executed by a processor, at least assist in implementing the steps of the method according to the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The principles, features and advantages of the present application can be better understood by describing the present application in more detail with reference to the accompanying drawings. The drawings show:

[0024] Figure 1 A flowchart showing the operation of a method for balancing control of a battery pack according to an exemplary embodiment of the present application;

[0025] Figure 2 Show an OCV-SOC curve of an exemplary battery cell;

[0026] Figure 3 Show an OCV-SOC curve of another exemplary battery cell;

[0027] Figure 4 A flowchart showing the operation of a method for balancing control of a battery pack according to another exemplary embodiment of the present application;

[0028] Figure 5A schematic block diagram of an apparatus for balancing control of a battery pack according to an exemplary embodiment of the present application; and

[0029] Figure 6 A schematic diagram of a vehicle according to an exemplary embodiment of the present application is shown. Detailed Description of the Invention

[0030] In order to make the technical problems to be solved, technical solutions and beneficial technical effects of the present application more clearly understood, the present application will be further described in detail below with reference to the accompanying drawings and a plurality of exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, rather than to limit the protection scope of the present application.

[0031] Figure 1 A working flowchart of a method for balancing control of a battery pack according to an exemplary embodiment of the present application is shown. The following exemplary embodiments describe the method according to the present application in more detail.

[0032] As Figure 1 shown, the method may include steps S1 and S2. In step S1, after the end of a charging cycle of the battery pack, the open-circuit voltage of each battery cell of the battery pack can be detected. In the current embodiment of the present application, the battery pack is composed of a large number of battery cells. When there is a fully charged battery cell in the battery pack, that is, the charging state of charge of the battery cell is 100%, the end of a charging cycle of the battery pack occurs. In the control unit 13 of the apparatus 10 for balancing control of the battery pack, the charging SOC-OCV curve and the discharging SOC-OCV curve of the open-circuit voltage corresponding to the charging state of charge and the discharging state of charge of this type of battery cell are stored. The relationship between the voltage and current of the battery cell during charge and discharge shows an asymmetry. As Figure 2 shown by an exemplary OCV-SOC curve of a battery cell, the charging SOC-OCV curve (marked with a solid line) and the discharging SOC-OCV curve (marked with a dashed line) of the battery cell do not coincide. At the same state of charge, the open-circuit voltage of the battery cell during charging is higher than that during discharging. This hysteresis effect of the battery cell may be caused by factors such as electrode material characteristics, electrolyte characteristics, and temperature. After the battery pack is left static for a pre-given period of time, especially a sufficiently long period of time, the open-circuit voltage of the battery cell will gradually decrease from the open-circuit voltage value corresponding to the charging SOC-OCV curve to the open-circuit voltage value corresponding to the discharging SOC-OCV curve.

[0033] In step S2, when the first open-circuit voltage of the first battery cell is lower than a pre-given voltage threshold U rIn this case, the second battery cell with the highest open-circuit voltage can be discharged. For clarity, assume that the battery cell with the lowest open-circuit voltage is called the first battery cell, and the battery cell with the highest open-circuit voltage is called the second battery cell. A pre-given voltage threshold U r For example, it can be set to 3.36V. According to Figure 2 the charging SOC-OCV curve shown, when the open-circuit voltage of the battery cell is lower than 3.36V, the charging state of charge of this battery cell will be lower than 98.5%, thereby triggering the balancing process of the battery pack, especially the passive balancing process.

[0034] According to the balancing strategy of the prior art, usually, 1.5% of the charge amount of the second battery cell with the highest open-circuit voltage is discharged - that is, the difference between the 100% second charging state of charge of the second battery cell and the 98.5% first charging state of charge of the first battery cell. The second battery cell is discharged from the 100% state of charge to the 98.5% state of charge as shown by the arrow in Figure 2 - which is marked with a hollow circle. According to Figure 2 the discharge SOC-OCV curve shown, the open-circuit voltage value of the second battery cell after being discharged will be much lower than the voltage threshold U r . Charge the battery pack for the next charging cycle until a fully charged battery cell appears in the battery pack. In this charging cycle, the state of charge of the second battery cell increases from 98.5% to 99.2% for example - which is marked with a hollow square. The open-circuit voltage value of the second battery cell in the discharged state may still be lower than the voltage threshold U r - that is, the second battery cell is over-balanced, thereby triggering a new round of battery charge and discharge process. Usually, after experiencing multiple charge and discharge cycle sequences, the open-circuit voltages of all battery cells in the battery pack can be made higher than the pre-given voltage threshold U r , and this balancing strategy will cause the battery cells to be repeatedly charged and discharged and take a long time.

[0035] According to the current embodiment of the present application, the discharge amount W of the second battery cell can be determined as the difference between the first deviation X and the discharge adjustment amount M. Here, the first deviation X between the first charging state of charge of the first battery cell and the second charging state of charge of the second battery cell can be determined based on the charging SOC-OCV curve and the detected open-circuit voltage of the battery cell. Specifically, the first charging state of charge SOC1 of the first battery cell and the second charging state of charge SOC2 of the second battery cell can be determined based on the charging SOC-OCV curve and the detected open-circuit voltage of the battery cell. As shown in Figure 3The OCV-SOC curve of another exemplary battery cell is shown. At the end of a charging cycle of the battery pack, the first state of charge SOC1 of the first battery cell is, for example, 98.5%, and the second state of charge SOC2 of the second battery cell is, for example, 100%. Thus, the first deviation X can be calculated as the difference between the first state of charge SOC1 and the second state of charge SOC2:

[0036] X = SOC2 - SOC1 = 100% - 98.5% = 1.5%.

[0037] The discharge adjustment amount M can be determined based at least on the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell. Specifically, the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell can be used to determine the second deviation Y between the charging state of charge and the discharging state of charge of the battery cell at the voltage threshold U r At a voltage threshold U of, for example, 3.36V, according to the charging SOC-OCV curve of the battery cell, the charging state of charge SOC3 of the battery cell is determined to be 98.5%, and according to the discharging SOC-OCV curve of the battery cell, the discharging state of charge SOC4 of the battery cell is determined to be 99.5%. Thus, the second deviation Y between the charging state of charge and the discharging state of charge of the battery cell at the voltage threshold U of 3.36V can be calculated as follows: r At a voltage threshold U of, for example, 3.36V, according to the charging SOC-OCV curve of the battery cell, the charging state of charge SOC3 of the battery cell is determined to be 98.5%, and according to the discharging SOC-OCV curve of the battery cell, the discharging state of charge SOC4 of the battery cell is determined to be 99.5%. Thus, the second deviation Y between the charging state of charge and the discharging state of charge of the battery cell at the voltage threshold U of 3.36V can be calculated as follows: r At a voltage threshold U of, for example, 3.36V, according to the charging SOC-OCV curve of the battery cell, the charging state of charge SOC3 of the battery cell is determined to be 98.5%, and according to the discharging SOC-OCV curve of the battery cell, the discharging state of charge SOC4 of the battery cell is determined to be 99.5%. Thus, the second deviation Y between the charging state of charge and the discharging state of charge of the battery cell at the voltage threshold U of 3.36V can be calculated as follows:

[0038] Y = SOC4 – SOC3 = 99.5% - 98.5% = 1%.

[0039] Next, the discharge adjustment amount M can be determined based at least on the second deviation Y and the adjustment ratio Z, that is, the discharge adjustment amount M is set as a function f(Y,Z) of the second deviation Y and the adjustment ratio Z. Thus, the discharge amount W of the second battery cell can be determined by the following expression:

[0040] W = X - M = X – f(Y,Z),

[0041] wherein, the adjustment ratio Z is related to the voltage threshold U r Exemplarily, the discharge adjustment amount M can be determined as the product of the second deviation Y and the adjustment ratio Z. Thus, the discharge amount W of the second battery cell can be determined by the following expression:

[0042] W = X - M = X – Y*Z,

[0043] wherein, the voltage threshold U r The larger the voltage threshold U is, the smaller the adjustment ratio Z is. At a voltage threshold U of, for example, 3.36V rThe adjustment ratio Z can be set to 0.5. Thus, the discharge capacity W of the second battery cell can be calculated as follows:

[0044] W=XM=X–Y*Z=1.5%-1%*0.5=1%.

[0045] In this discharge cycle, the second battery cell is discharged from, for example, 100% state of charge to 99% state of charge. Figure 3 In the case where there is only one second battery cell with the highest open circuit voltage, 1% of the charge can be discharged to the second battery cell with the highest open circuit voltage; in the case where there are multiple second battery cells with the same and highest open circuit voltages, 1% of the charge can be discharged to all the second battery cells with the highest open circuit voltages.

[0046] like Figure 4 A workflow diagram of a method for balancing control of a battery pack according to another exemplary embodiment of another exemplary embodiment of the present application is shown, and the method may further include step S3. In step S3, after the discharge of the second battery cell is completed, the battery pack is charged until a battery cell with a charge state of 100% appears in the battery pack to complete a round of charge and discharge cycle. For example, after each battery cell of the battery pack is charged with 0.7% of the charge, a fully charged battery cell appears in the battery pack, thereby increasing the charge state of the second battery cell from 99% to 99.7% - which is in Figure 3 Marked with a hollow square.

[0047] Here, steps S1 to S3 may be executed cyclically. In step S1, after the next charging cycle of the battery pack is completed, the open circuit voltage of each battery cell of the battery pack may be detected again after being left to stand for a long enough time. r In the case of the battery pack, step S2 is executed again to discharge the battery cell with the highest open circuit voltage by the discharge amount W calculated in the above manner, and the battery cell is charged again after the discharge is completed, and so on, until the open circuit voltage of each battery cell of the battery pack is higher than the predetermined voltage threshold U r Only then does the loop of steps S1 to S3 exit, thus completing the balancing process of the battery pack. Figure 3 Only one charge and discharge cycle is shown in the figure. After this charge and discharge cycle, the open circuit voltage of the second battery cell in the discharge state is higher than the voltage threshold U r , thus the charge and discharge cycle of the battery pack is no longer repeatedly triggered by the second battery cell.

[0048] Since the battery pack includes a large number of battery cells, even if the open-circuit voltage of the second battery cell in the discharged state remains higher than the voltage threshold U after one or more charge-discharge cycles r , there may still be other battery cells with an open-circuit voltage lower than the voltage threshold U in the discharged state r . Therefore, it may be necessary to perform multiple charge-discharge cycles before the equalization process of the battery pack can be completed. To accelerate the equalization process of the battery pack, the discharge adjustment amount M can be adjusted at least based on the number of charge-discharge cycles, the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell, so as to reduce until the open-circuit voltages of all battery cells in the battery pack are higher than a pre-given voltage threshold U r The total number of charge-discharge cycles required to complete. Such adjustment can be achieved especially through an artificial intelligence model, including but not limited to machine learning models, deep learning models, large language models, and / or reinforcement learning models, etc. Specifically, the number of charge-discharge cycles, the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell can be input into the artificial intelligence model, and the artificial intelligence model can learn the changes in battery parameters during the equalization process of the battery pack and adjust the functional expression of the discharge adjustment amount M, thereby achieving a reduction in the total number of charge-discharge cycles required to achieve battery pack equalization.

[0049] According to the equalization strategy of the present application, the difference in the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell, that is, the hysteresis effect, is fully considered when determining the discharge amount of the battery cell. Thereby, the number of charge-discharge cycles of the battery pack is greatly reduced during the equalization process of the battery pack, thereby reducing the time-consuming of the equalization process of the battery pack, avoiding repeated charge and discharge of the battery cell during the equalization process, and effectively improving the efficiency of the equalization process of the battery pack.

[0050] In addition, it should be noted that the step numbers described herein do not necessarily represent the order of sequence, but are merely a kind of reference numeral. According to the specific situation, the order can be changed as long as the technical purpose of the present application can be achieved.

[0051] Figure 5 FIG. shows a schematic block diagram of a device 10 for equalization control of a battery pack according to an exemplary embodiment of the present application.

[0052] The device 10 can be especially integrated into a battery management system. As Figure 5 shown, the device 10 can include the following components:

[0053] - An open-circuit voltage detection unit 11, which is configured to detect the open-circuit voltage of each battery cell in the battery pack, and is configured as a voltmeter, for example;

[0054] - A discharging unit 12, which is configured to discharge one or more second battery cells with the highest open-circuit voltage, and is configured, for example, as a resistor connected in parallel with each battery cell;

[0055] and

[0056] - A control unit 13, which is configured to execute the method according to the present application.

[0057] Figure 6 A schematic diagram showing a vehicle 1 according to an exemplary embodiment of the present application.

[0058] As Figure 6 shown, the vehicle 1 may include the device 10, whereby a battery pack equalization strategy according to the present application can be executed on the battery pack of the vehicle 1 during vehicle use.

[0059] It should be understood that in this text, expressions such as "first", "second", etc. are only for descriptive purposes, and should not be construed as indicating or implying relative importance, nor should they be construed as implicitly specifying the quantity of the indicated technical features.

[0060] If an embodiment includes an "and / or" association between a first feature and a second feature, it should be interpreted as follows: according to one embodiment, this embodiment has both the first feature and the second feature, and according to another embodiment, this embodiment has either only the first feature or only the second feature.

[0061] Although specific implementation schemes have been described above, these implementation schemes are not intended to limit the scope of the present application disclosure, even when only describing a single implementation scheme with respect to a specific feature. The feature examples provided in the present application disclosure are for illustrative purposes only and not for limitation, unless otherwise stated. In specific implementations, multiple features can be combined with each other according to actual needs and when technically feasible. Various substitutions, changes, and modifications can also be conceived without departing from the spirit and scope of the present application.

Claims

1. A method for balancing control of a battery pack, the method comprising: Step S1: After a charging cycle of the battery pack is completed, detecting the open circuit voltage of each battery cell of the battery pack; as well as Step S2: When the first open circuit voltage of the first battery cell is lower than a predetermined voltage threshold value U r , the second battery cell with the highest open circuit voltage is discharged, wherein the discharge amount W of the second battery cell is determined as the difference between the first deviation X and the discharge adjustment amount M, wherein the first deviation X between the first charging state of charge of the first battery cell and the second charging state of charge of the second battery cell is determined based on the charging SOC-OCV curve and the detected open circuit voltage of the battery cell, wherein the discharge adjustment amount M is determined based on at least the charging SOC-OCV curve and the discharging SOC-OCV curve of the battery cell.

2. The method according to claim 1, wherein: The discharge adjustment amount M is determined based on at least the second deviation Y and the adjustment ratio Z, wherein the discharge adjustment amount M is determined based on the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell. r The second deviation Y between the charging state of charge and the discharging state of charge of the battery cell, the adjustment ratio Z is r Related.

3. The method according to claim 2, wherein: The discharge adjustment amount M is determined as the product of the second deviation Y and the adjustment ratio Z, wherein the voltage threshold U r The larger it is, the smaller the adjustment ratio Z is.

4. The method according to any one of claims 1 to 3, wherein: The method further comprises: Step S3: After the discharge of the second battery cell is completed, the battery pack is charged until a battery cell with a charge state of 100% appears in the battery pack to complete a charge and discharge cycle, wherein steps S1 to S3 are executed repeatedly until the open circuit voltage of each battery cell of the battery pack is higher than the predetermined voltage threshold U r .

5. The method according to claim 4, wherein: In the process of cyclically executing steps S1 to S3, the discharge adjustment amount M is adjusted based on at least the number of charge and discharge cycles, the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell, so as to reduce the open circuit voltage of each battery cell of the battery pack until it is higher than the predetermined voltage threshold U r The total number of charge and discharge cycles required to be completed.

6. The method according to claim 5, wherein: The discharge adjustment amount M is adjusted by an artificial intelligence model based at least on the number of charge and discharge cycles, the charge SOC-OCV curve and the discharge SOC-OCV curve of the battery cell.

7. The method according to claim 6, wherein: The artificial intelligence model includes a machine learning model, a deep learning model, a large language model and / or a reinforcement learning model.

8. A device (10) for equalization control of a battery pack, wherein: The device (10) comprises the following components: An open circuit voltage detection unit (11) configured to detect the open circuit voltage of each battery cell of the battery pack; a discharge unit (12) configured to discharge a second battery cell having the highest open circuit voltage; and A control unit (13) configured to carry out the method according to any one of the preceding claims.

9. A vehicle (1) comprising a device (10) according to claim 8. 10 . A computer program product, such as a computer-readable program carrier, comprising or storing computer program instructions, which, when executed by a processor, at least assist in implementing the steps of the method according to claim 1 .

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