A method, device and battery management system for estimating state of charge (SOC) of a battery pack

Abstract

The application discloses a method, device and battery management system for estimating the SOC of a battery pack (10), and belongs to the technical field of batteries. The battery pack (10) comprises first battery cells (11) without a platform region and second battery cells (12) with a platform region, and at least one first battery cell (11) is connected in series with a second battery cell. The method comprises determining the capacity variation of the battery pack (10) according to the SOC variation of the first battery cells (11) relative to the initial SOC of the first battery cells (11) and the nominal capacity of the first battery cells (11) (S101); obtaining the equalization capacity of the first battery cells (11) and the equalization capacity of the second battery cells (12) (S102); estimating the SOC of the second battery cells (12) according to the capacity variation of the battery pack (10), the nominal capacity of the first battery cells (11), the equalization capacity of the first battery cells (11) and the equalization capacity of the second battery cells (12), and the initial SOC of the second battery cells (12), and determining the SOC of the battery pack (10) according to the SOC of the second battery cells (12) (S103). The SOC of the second battery cells (12) can be accurately estimated by the method, and the problem of inaccurate SOC estimation is solved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a method, apparatus, and battery management system for estimating the state of charge (SOC) of a battery pack. Background Technology

[0002] As the power source for new energy vehicles, the state of the battery is strictly controlled by the Battery Management System (BMS). Among these parameters, the remaining charge (State of Charge, SOC) is a crucial parameter for estimating the driving range of new energy vehicles. The SOC value is the ratio of remaining capacity to the battery's total capacity, usually expressed as a percentage, and its value ranges from 0 to 1.

[0003] In existing technologies, the state of charge (SOC) is typically estimated based on voltage values ​​and the SOC-OCV curve. However, for cells with a plateau region (where voltage changes are very small, with each 1% change in SOC corresponding to a voltage change of less than 1mV), the accuracy of SOC estimation based on voltage is not high. Summary of the Invention

[0004] Therefore, the purpose of this application is to provide a method, apparatus and battery management system for estimating the state of charge (SOC) of a battery pack, so as to improve the problem that existing methods cannot accurately estimate the SOC of a battery.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, embodiments of this application provide a method for estimating the State of Charge (SOC) of a battery pack. The battery pack includes a first cell without a plateau region and a second cell with a plateau region, wherein at least one of the first cells is connected in series with the second cell. The method includes: determining the capacity change of the battery pack based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell; obtaining the balanced capacity of the first cell and the balanced capacity of the second cell; estimating the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell; and determining the SOC of the battery pack based on the SOC of the second cell.

[0007] In this embodiment, by introducing a first cell without a plateau region and connecting it in series with a second cell that has a plateau region, the capacity change of the battery pack can be determined based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell. Then, the balanced capacity of the first cell and the balanced capacity of the second cell are obtained. Finally, based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell, the SOC of the second cell can be accurately estimated. This solves the problem that estimating the SOC of a cell with a plateau region based on the existing voltage value and the SOC-OCV curve results in low accuracy.

[0008] In one possible implementation of the first aspect embodiment, determining the capacity change of the battery pack based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell includes: determining the capacity change of the battery pack based on the SOC change of the first cell relative to its initial SOC, the nominal capacity of the first cell, and the SOH of the first cell.

[0009] In this embodiment of the application, when determining the capacity change of the battery pack, the State of Health (SOH) of the first cell is also taken into account. This can eliminate the impact of battery wear or aging during use, thereby improving the accuracy of subsequent estimation of the SOC of the second cell.

[0010] In one possible implementation of the first aspect embodiment, estimating the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell includes: estimating the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the SOH of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell.

[0011] In this embodiment of the application, when estimating the SOC of the second cell, the State of Health (SOH) of the first cell is also taken into account. This can eliminate the impact of battery wear or aging during use, thereby improving the accuracy of estimating the SOC of the second cell.

[0012] In one possible implementation of the first aspect embodiment, the process of obtaining the SOC change of the first battery cell relative to its initial SOC includes: obtaining the SOC change of the first battery cell based on its current SOC and its initial SOC; wherein, if the current open-circuit voltage of the second battery cell is located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the initial SOC of the first battery cell obtained and stored when the open-circuit voltage of the second battery cell was not located in the plateau region of the SOC-OCV curve; if the current open-circuit voltage of the second battery cell is not located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the most recently obtained initial SOC.

[0013] In this embodiment, the initial SOC of the first cell is updated in real time. If the open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC is the initial SOC of the first cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve. If the open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve, the initial SOC is the latest obtained initial SOC. This ensures that the determined change in the battery pack is accurate and reliable, thereby ensuring the accuracy of the subsequent estimated SOC of the second cell.

[0014] In one possible implementation of the first aspect embodiment, if the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve of the second cell; if the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the latest obtained initial SOC.

[0015] In this embodiment, the initial SOC of the second cell is updated in real time. If the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve of the second cell. If the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the latest obtained initial SOC. This ensures that the determined change in the battery pack is accurate and reliable, thereby ensuring the accuracy of estimating the SOC of the second cell.

[0016] In one possible implementation of the first aspect embodiment, the method further includes obtaining the initial SOC of the first battery cell and the second battery cell. Obtaining the initial SOC of the first battery cell and the second battery cell includes: if the second battery cell is detected to be in a fully charged state, obtaining the initial SOC of the second battery cell, and obtaining the SOC of the first battery cell when the second battery cell is in a fully charged state as the initial SOC of the first battery cell; if the second battery cell is detected to be in a low-end idle state, obtaining the sampling voltage of the first battery cell, and obtaining the initial SOC of the first battery cell based on the SOC-OCV curve of the first battery cell; and obtaining the sampling voltage of the second battery cell, and obtaining the initial SOC of the second battery cell based on the SOC-OCV curve of the second battery cell.

[0017] In this embodiment of the application, by obtaining the initial SOC of the first and second cells when the second cell is fully charged, or by obtaining the initial SOC of the first and second cells when the second cell is in a low-end resting state, the SOC of the second cell can be accurately estimated, thereby ensuring the accuracy of the solution.

[0018] In one possible implementation of the first aspect embodiment, the second battery cell includes a plurality of individual battery cells; determining the SOC of the battery pack based on the SOC of the second battery cell includes: obtaining the maximum SOC and the minimum SOC from the plurality of SOCs of the second battery cell, wherein each individual battery cell corresponds to one SOC; obtaining the weighted SOC of the maximum SOC and the minimum SOC, and using the weighted SOC as the SOC of the battery pack.

[0019] In this embodiment of the application, when the second cell includes multiple individual cells, the maximum and minimum SOCs are obtained from the multiple SOCs of the second cell, and then the weighted SOC of the maximum and minimum SOCs is obtained. The weighted SOC is then used as the SOC of the battery pack. The SOC of the battery pack can be accurately estimated by weighting.

[0020] In one possible implementation of the first aspect embodiment, the method further includes: if the first battery cell is fully discharged preferentially relative to the second battery cell, then the second battery cell is subjected to equalization discharge to ensure that the second battery cell is fully discharged preferentially; if the first battery cell is fully charged preferentially relative to the second battery cell, then the first battery cell is subjected to equalization discharge to ensure that the second battery cell is fully charged preferentially.

[0021] In this embodiment, when balancing the first cell and the second cell, if the first cell is fully discharged first relative to the second cell, then the second cell is balanced and discharged to ensure that the second cell is fully discharged first. If the first cell is fully charged first relative to the second cell, then the first cell is balanced and discharged to ensure that the two cells are fully charged first. This ensures that the first cell will not affect the charging and discharging of the entire battery pack and will not become a cell that restricts the capacity of the battery pack. The charging and discharging of the entire battery pack is only related to the charging and discharging of the second cell, so that the SOC of the second cell can reflect the SOC of the entire battery pack.

[0022] In one possible implementation of the first aspect embodiment, the process of determining whether the first battery cell is preferentially fully discharged or fully charged relative to the second battery cell includes: determining the charging capacity required for the first battery cell to be fully charged or the discharge capacity to be fully discharged based on the initial SOC, nominal capacity, and SOH of the first battery cell; determining the charging capacity required for the second battery cell to be fully charged or the discharge capacity to be fully discharged based on the initial SOC, nominal capacity, and SOH of the second battery cell; if the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, then determining that the first battery cell is preferentially fully charged relative to the second battery cell; if the discharge capacity of the first battery cell is less than the discharge capacity of the second battery cell, then determining that the first battery cell is preferentially fully discharged relative to the second battery cell.

[0023] In this embodiment, the required charging capacity for a first cell to be fully charged or the required discharging capacity to be fully discharged is determined based on the initial SOC, nominal capacity, and SOH of the first cell. Then, based on the initial SOC, nominal capacity, and SOH of the second cell, the required charging capacity for the first cell to be fully charged is compared with that of the second cell, and the required discharging capacity for the first cell to be fully discharged is compared with that of the second cell. This allows for a rapid determination of whether the first cell should be fully charged or discharged first, relative to the second cell. Furthermore, when calculating the required charging capacity for full charging or the required discharging capacity for full discharging, the cell's State of Health (SOH) is also taken into account. This eliminates the impact of battery wear or aging during use, improving the reliability of the solution.

[0024] Secondly, embodiments of this application also provide an apparatus for estimating the State of Charge (SOC) of a battery pack. The battery pack includes a first cell without a plateau region and a second cell with a plateau region, and at least one of the first cells is connected in series with the second cell. The apparatus includes a processing module and an acquisition module. The processing module is configured to determine the capacity change of the battery pack based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell. The acquisition module is configured to acquire the balanced capacity of the first cell and the balanced capacity of the second cell. The processing module is further configured to estimate the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell, and determine the SOC of the battery pack based on the SOC of the second cell.

[0025] In one possible implementation of the second aspect embodiment, the processing module is specifically configured to: determine the capacity change of the battery pack based on the SOC change of the first cell relative to its initial SOC, the nominal capacity of the first cell, and the SOH of the first cell.

[0026] In one possible implementation of the second aspect embodiment, the processing module is specifically configured to: estimate the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the SOH of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell.

[0027] In a possible implementation of the second aspect embodiment, the processing module is further configured to: obtain the SOC change of the first battery cell based on the SOC of the first battery cell and the initial SOC of the first battery cell; wherein, if the current open-circuit voltage of the second battery cell is located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the initial SOC of the first battery cell obtained and stored when the open-circuit voltage of the second battery cell was not located in the plateau region of the SOC-OCV curve in the previous instance; if the current open-circuit voltage of the second battery cell is not located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the latest obtained initial SOC.

[0028] In one possible implementation of the second aspect embodiment, if the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve of the second cell; if the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the latest obtained initial SOC.

[0029] In a possible implementation of the second aspect embodiment, the processing module is further configured to: if the second battery cell is detected to be in a fully charged state, obtain the initial SOC of the second battery cell, and obtain the SOC of the first battery cell when the second battery cell is in a fully charged state as the initial SOC of the first battery cell; if the second battery cell is detected to be in a low-end idle state, obtain the sampling voltage of the first battery cell, and obtain the initial SOC of the first battery cell based on the SOC-OCV curve of the first battery cell, and obtain the sampling voltage of the second battery cell, and obtain the initial SOC of the second battery cell based on the SOC-OCV curve of the second battery cell.

[0030] In one possible implementation of the second aspect embodiment, the second battery cell includes a plurality of individual battery cells, and the processing module is further configured to: obtain the maximum SOC and the minimum SOC from the plurality of SOCs of the second battery cell, wherein each individual battery cell corresponds to one SOC; obtain the weighted SOC of the maximum SOC and the minimum SOC, and use the weighted SOC as the SOC of the battery pack.

[0031] In one possible implementation of the second aspect embodiment, the device further includes an equalization module, the equalization module being configured to: if the first battery cell is fully discharged preferentially to the second battery cell, then perform equalization discharge on the second battery cell to ensure that the second battery cell is fully discharged preferentially; if the first battery cell is fully charged preferentially to the second battery cell, then perform equalization discharge on the first battery cell to ensure that the second battery cell is fully charged preferentially.

[0032] In one possible implementation of the second aspect embodiment, the equalization module is further configured to: determine the charging capacity required for the first battery cell to be fully charged or the discharge capacity required for it to be fully discharged, based on the initial SOC, nominal capacity, and SOH of the first battery cell; determine the charging capacity required for the second battery cell to be fully charged or the discharge capacity required for it to be fully discharged, based on the initial SOC, nominal capacity, and SOH of the second battery cell; if the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, determine that the first battery cell is given priority to be fully charged relative to the second battery cell; if the discharge capacity of the first battery cell is less than the discharge capacity of the second battery cell, determine that the first battery cell is given priority to be fully discharged relative to the second battery cell.

[0033] Thirdly, embodiments of this application also provide a battery management system, including: at least one processor; and a memory communicatively connected to the at least one processor; the battery management system is connected to a battery pack, the battery pack including a first cell without a plateau region and a second cell with a plateau region, and at least one of the first cells and the second cell are connected in series; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform a method for estimating the state of charge (SOC) of the battery pack provided in conjunction with a possible implementation of the second aspect embodiments.

[0034] Fourthly, embodiments of this application also provide a storage medium storing a computer program thereon, which, when run by a processor, performs the method provided by any possible implementation of the first aspect embodiments and / or in combination with the first aspect embodiments.

[0035] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0037] Figure 1 A schematic diagram of the structure of a battery pack provided in an embodiment of this application is shown.

[0038] Figure 2A schematic diagram of the SOC-OCV curve of an LFP cell provided in an embodiment of this application is shown.

[0039] Figure 3 A schematic diagram of the SOC-OCV curve of an NCM battery cell provided in an embodiment of this application is shown.

[0040] Figure 4 A flowchart illustrating a method for estimating the state of charge (SOC) of a battery pack according to an embodiment of this application is shown.

[0041] Figure 5 A block diagram of an apparatus for estimating the state of charge (SOC) of a battery pack, provided in an embodiment of this application, is shown.

[0042] Figure 6 A schematic diagram of a battery management system provided in an embodiment of this application is shown. Detailed Implementation

[0043] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0044] The method for estimating the State of Charge (SOC) of a battery pack provided in this application can be applied to electric vehicles. This method allows for the estimation of the SOC of the battery pack in electric vehicles. Of course, this method can also be applied to other electric devices, i.e., devices that use batteries or battery packs as power sources. This method allows for the estimation of the SOC of the battery packs in other electric devices.

[0045] Whether it's an electric vehicle or other electric equipment, they are typically equipped with a Battery Management System (BMS). The BMS and battery pack constitute the battery system, and the BMS is used to manage various parameters of the battery pack, such as voltage, current, and temperature. The hardware environment used in the embodiments of this application can be the BMS corresponding to the battery pack. In addition to connecting to the battery pack to manage it, the BMS also connects to other modules of the electric vehicle or electric equipment, including electrical connections, physical connections, and other feasible connections. Data can be transmitted between the BMS and these modules. For example, the electric vehicle's BMS sends relevant parameter information of the battery pack to the central control system, which then provides feedback, such as direct display; or the BMS receives relevant instructions from the central control system and manages the battery pack accordingly.

[0046] Figure 1As an example of the battery pack 10 involved in this application, the battery pack 10 includes two different types of cells: a first cell 11 without a plateau region and a second cell 12 with a plateau region. In this configuration, at least one first cell 11 and at least one second cell 12 are connected in series in the battery pack 10. The first cell 11 may include a single cell 111, and the second cell 12 may include multiple single cells 121 connected in series.

[0047] The state of charge (SOC) and open-circuit voltage (OCV) curves of the first cell 11 and the second cell 12 are different. The SOC-OCV curve represents the change between the open-circuit voltage and the state of charge of the cell. The first cell 11 is a cell without a plateau region; it can be a ternary lithium battery cell (also known as an NCM cell, where NCM is an abbreviation for nickel (Ni), cobalt (Co), and manganese (Mn)). A ternary lithium battery cell is one whose positive electrode material is primarily made of nickel (Ni), cobalt (Co), and manganese (Mn), and the ratio of nickel, cobalt, and manganese can be adjusted according to actual needs. The second cell 12 is a cell with a plateau region; it can be a lithium iron phosphate (LiFePO4) cell, abbreviated as LFP cell.

[0048] The following example illustrates the difference in SOC-OCV curves between two different types of battery cells. Assume the first cell, 11, is an NCM cell, and the second cell, 12, is an LFP cell. The SOC-OCV curve of the LFP cell is as follows: Figure 2 As shown, the SOC-OCV curve of the NCM cell is as follows: Figure 3 As shown. From Figure 2 It can be seen that the SOC-OCV curve of the LFP cell has two plateau regions: Plateau Region 1 and Plateau Region 2. In the curve portions corresponding to Plateau Region 1 and Plateau Region 2, the voltage remains basically constant, that is, the voltage change in the plateau region is very small. For example, the voltage change corresponding to each 1% change in SOC is less than 1mV.

[0049] contrast Figure 2 and Figure 3 It can be seen that the slope of the SOC-OCV curve of LFP cells is greater than that of ternary cells when the state of charge is 0% to 8%. However, from approximately 8% to 95% of the state of charge, the slope of the SOC-OCV curve of LFP cells is less than that of ternary cells. The SOC-OCV curve of LFP cells shows a trend of first rising sharply and then rising smoothly, while the SOC-OCV curve of ternary cells shows a trend of rising gradually.

[0050] In existing technologies, State of Charge (SOC) is typically estimated based on voltage values ​​and SOC-OCV curves. However, for cells with plateau regions, the voltage change corresponding to each 1% change in SOC is less than 1mV, which may cause an SOC estimation error of 5% or more, resulting in low accuracy. Therefore, in this embodiment, by introducing a first cell without a plateau region and connecting it in series with a second cell that has a plateau region, combined with the battery pack SOC estimation method provided in this embodiment, the accuracy of SOC estimation can be improved.

[0051] The following will combine Figure 4 This application describes a method for estimating the state of charge (SOC) of a battery pack, as provided in an embodiment. The method includes:

[0052] Step S101: Determine the capacity change of the battery pack during use based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell.

[0053] In step S101, "usage process" includes possible scenarios during battery pack use, such as changes in SOC caused by the battery pack being installed in an electric vehicle, during charging, driving, or sitting. For ease of understanding, the SOC change of the first cell relative to its initial SOC is expressed as (SOC... B -SOC B_initial The nominal capacity of the first cell is expressed as C. B The change in battery pack capacity during use can be expressed as ΔCap = (SOC) / (SOC) B -SOC B_initial )*C B Among them, SOC B The SOC of the first cell is obtained when it is necessary to estimate the SOC of the battery pack. B_initial This is the initial SOC of the first battery cell. The nominal capacity of the first battery cell is the capacity marked at the factory, which is a preset known value.

[0054] Among them, the SOC of the first battery cell during use can be used as a reference. B And the initial SOC of the first cell, i.e., SOC B_initial This allows us to obtain the SOC change of the first cell during use.

[0055] In one implementation, when obtaining the SOC of the first battery cell, the battery management system may obtain the current SOC of the first battery cell when a preset time interval for estimating the SOC is reached, such as 1 minute, but not limited to this, or when the battery management system receives an instruction from another module, such as the central control system, to estimate the SOC of the battery pack, or when other triggering conditions are met.

[0056] The method for obtaining the SOC of the first cell is consistent with existing methods for obtaining the SOC of a battery pack containing only one type of cell. It can be based on a nonlinear Kalman filter to determine the SOC of the first cell. Simultaneously, the SOC of the first cell is corrected based on its static voltage and SOC-OCV curve in a static state (no current), and its open-circuit voltage and SOC-OCV curve when current is flowing through it, thus obtaining the final SOC of the first cell. B This process is well known to those skilled in the art and will not be described in detail here.

[0057] In one implementation, when obtaining the initial SOC of the first battery cell, it can be determined whether the open-circuit voltage of the current second battery cell is located in the plateau region of the SOC-OCV curve of the second battery cell. If the open-circuit voltage of the current second battery cell is located in the plateau region of the SOC-OCV curve of the second battery cell, then the SOC... B_initial The initial SOC of the first cell was obtained and stored when the open-circuit voltage of the second cell was not in the plateau region of the SOC-OCV curve in the previous instance; if the open-circuit voltage of the second cell is not in the plateau region of the SOC-OCV curve of the second cell, then the SOC mentioned above... B_initial This is the latest obtained initial SOC. If there is no previous initial SOC for the first cell obtained and stored when the open-circuit voltage of the second cell was not in the plateau region of the SOC-OCV curve, then the initial SOC of the first cell is the system default initial SOC. It should be noted that initially, the system sets a default initial SOC for the first cell. When estimating the SOC of the battery pack for the first time, if the open-circuit voltage of the second cell is in the plateau region of the second cell's SOC-OCV curve, then the initial SOC of the first cell is the system default initial SOC.

[0058] To facilitate understanding, an example is given. At time 1 (Clock 1), when the open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the first cell is obtained and stored. At time 2 (Clock 2), when it is necessary to estimate the SOC of the battery pack, it is determined whether the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell. If the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the first cell is obtained again, and the stored SOC of the first cell is updated. B_initial This refers to the latest obtained initial SOC. If the open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, then the SOC... B_initialThis refers to the initial SOC of the first cell, which is acquired and stored at Clock 1. It should be noted that the initial SOC of the first cell is updated in real time. The initial SOC of the first cell will be updated whenever the open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell.

[0059] As one possible implementation, the process of obtaining the initial SOC of the first battery cell can be as follows: If the second battery cell is detected to be fully charged, the SOC of the first battery cell is obtained as the initial SOC of the first battery cell. That is, when the second battery cell is fully charged, it is not necessary to obtain the sampling voltage of the first battery cell; the SOC of the first battery cell is directly used as the initial SOC of the first battery cell. If the second battery cell is detected to be in a low-end idle state, the sampling voltage of the first battery cell is obtained, and the initial SOC of the first battery cell is obtained based on the SOC-OCV curve of the first battery cell. It should be noted that the initial SOC of the first battery cell is updated whenever the second battery cell is detected to be fully charged or in a low-end idle state.

[0060] If the second battery cell includes multiple individual battery cells, that is, two or more individual battery cells, the second battery cell is considered to be fully charged as long as any one of the individual battery cells is detected to be fully charged; the second battery cell is considered to be in a low-end static state only when all the individual battery cells in the second battery cell are detected to be in a low-end static state.

[0061] Optionally, the plateau region of the SOC-OCV curve of the second cell is not located in the second cell when the second cell is fully charged or when the second cell is in a low-end static state.

[0062] Among them, "fully charged state" refers to the state where the SOC of the battery cell reaches a preset maximum value during the charging process, such as 100%. "Low-end resting state" means that the voltage value of the second battery cell must not exceed, i.e., be less than or equal to, the minimum voltage value corresponding to the plateau region of the SOC-OCV curve. Figure 2 Vmin in the middle, and the second cell is in a static state.

[0063] If the first battery cell comprises multiple individual cells, i.e., two or more individual cells, optionally, the individual cell with the lowest voltage during the resting process can be selected from the multiple individual cells of the first battery cell for calculation. That is, the initial SOC, the SOC of the first battery cell, and the change in SOC of the first battery cell are all corresponding parameters of this selected individual cell. It should be noted that selecting the individual cell with the lowest voltage during the resting process is the preferred solution in this application example. Theoretically, it can be any cell from multiple individual cells. Therefore, the above example of selecting the individual cell with the lowest voltage during the resting process for calculation should not be construed as a limitation of this application.

[0064] In one alternative implementation, considering that batteries may experience wear and tear or aging during use, resulting in the actual storage capacity of the cells being less than their nominal capacity, in order to improve the accuracy of SOC estimation, the state of health (SOH) of the cells is also taken into account when estimating the SOC of the battery pack in this embodiment.

[0065] In one optional implementation, the process of determining the capacity change of the battery pack during use, based on the change in SOC of the first cell relative to its initial SOC and the nominal capacity of the first cell, includes: determining the capacity change of the battery pack during use based on the change in SOC of the first cell relative to its initial SOC, the nominal capacity of the first cell, and the SOH of the first cell. This can be expressed by the formula: ΔCap=(SOC) B -SOC B_initial )*C B *SOH B SOH B The health of the first battery cell.

[0066] Step S102: Obtain the equalization capacity of the first battery cell and the equalization capacity of the second battery cell.

[0067] In step S102, to obtain the equalization capacity in real time, the equalization capacity of each type of cell can be obtained by integrating the equalization time and equalization current with respect to the ampere-hour, i.e., integrating the equalization current with respect to the equalization time. Each time the first cell is updated, the equalization capacity of the first cell and the second cell is automatically reset to zero.

[0068] The balancing current can be calculated during balancing based on the passive balancing resistor and the cell voltage at the time of balancing, using the formula I = U / R. The passive balancing resistor is a known value, and the cell voltage at the time of balancing can be obtained through BMS voltage sampling. The balancing time can be obtained statistically by starting a balancing timer when balancing begins, thus obtaining the balancing time t.

[0069] If the first battery cell comprises multiple individual cells, the aforementioned equalization capacity of the first battery cell can be the equalization capacity of the selected individual cell from the multiple individual cells of the first battery cell. To obtain the equalization capacity of the first battery cell, it is only necessary to determine the equalization time and equalization current of the selected individual cell.

[0070] If the second cell comprises multiple individual cells, when obtaining the balanced capacity of the second cell, it is necessary to determine the balanced time and balanced current of each individual cell in the second cell, so as to obtain the balanced capacity of each individual cell.

[0071] In one optional implementation, when balancing the first and second battery cells, if the first battery cell is fully discharged before the second battery cell, then the second battery cell is subjected to equalization discharge, and the discharge capacity is the equalization capacity of the second battery cell, ensuring that the second battery cell is fully discharged before the second battery cell. Conversely, if the first battery cell is fully charged before the second battery cell, then the first battery cell is subjected to equalization discharge, and the discharge capacity is the equalization capacity of the first battery cell, ensuring that the second battery cell is fully charged before the second battery cell. During equalization discharge, a passive equalization resistor can be used to discharge the battery cell that needs to be discharged; this part is well known to those skilled in the art and will not be described in detail here.

[0072] In one optional implementation, the process of determining whether the first battery cell is preferentially fully charged or fully discharged relative to the second battery cell includes: determining the required charging capacity for full charging or the discharge capacity for full discharge of the first battery cell based on its initial SOC, nominal capacity, and SOH; determining the required charging capacity for full charging or the discharge capacity for full discharge of the second battery cell based on its initial SOC, nominal capacity, and SOH; comparing the required charging capacity for full charging of the first battery cell with the required charging capacity for full charging of the second battery cell; if the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, then determining that the first battery cell is preferentially charged relative to the second battery cell; and comparing the discharge capacity for full discharge of the first battery cell with the discharge capacity for full discharge of the second battery cell; if the discharge capacity of the first battery cell is less than the discharge capacity of the second battery cell, then determining that the first battery cell is preferentially discharged relative to the second battery cell.

[0073] For ease of understanding, let B represent the first battery cell and A represent the second battery cell. The charging capacity required for the first battery cell to be fully charged can be expressed as (1 - SOC). B )*C B *SOH B The charging capacity required for the second battery cell to be fully charged can be expressed as (1-SOC). A )*C A *SOH AThe discharge capacity of the first cell when fully discharged can be expressed as SOC (State of Charge). B *C B *SOH B The discharge capacity of the second cell when fully discharged can be expressed as SOC. A *C A *SOH A Among them, C A The nominal capacity of the second battery cell is the capacity marked at the factory, which is a preset known value. SOH A The State of Health (SOH) of the second cell. B The health of the first battery cell.

[0074] Among them, "priority full charge" means that the first battery cell reaches the full charge state first in time compared to the second battery cell, or the second battery cell reaches the full charge state first in time compared to the first battery cell; "priority full discharge" means that the first battery cell reaches the full discharge state first in time compared to the second battery cell, or the second battery cell reaches the full discharge state first in time compared to the first battery cell.

[0075] The term "fully discharged" refers to the state of charge (SOC) of the battery cell reaching a preset minimum value, such as 5%, but it is not limited to this. For example, when the SOC of the battery cell falls below 5% during discharge, it stops discharging, reaching the fully discharged state.

[0076] Step S103: Based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell, estimate the SOC of the second cell, and determine the SOC of the battery pack based on the SOC of the second cell.

[0077] In step S103, for ease of understanding, the change in battery pack capacity is expressed as ΔCap, and the nominal capacity of the first cell is expressed as C. B The balanced capacity of the first cell is represented by C. b The balanced capacity of the second cell is expressed as C. a The initial SOC of the second cell is denoted as SOC. A_initial The SOC of the second cell is denoted as SOC. A Then there is

[0078] When obtaining the initial SOC of the second cell, it is determined whether the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve. If the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve. If the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve, the initial SOC of the second cell is the latest obtained initial SOC. If there is no previous initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve, the initial SOC of the second cell is the system default initial SOC. It should be noted that at the beginning, the system will set a default initial SOC for the second cell. When estimating the SOC of the battery pack for the first time, if the open circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, then the initial SOC of the second cell is the system's default initial SOC.

[0079] To facilitate understanding, an example is given. At time 1 (Clock 1), when the open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is obtained and stored. At time 2 (Clock 2), when it is necessary to estimate the SOC of the battery pack, it is determined whether the current open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell. If the current open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell at this time is obtained again, and the stored initial SOC of the second cell is updated. A_initial This refers to the latest obtained initial SOC. If the open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, then the SOC... A_initial This refers to the initial SOC of the second battery cell acquired and stored at Clock 1. It should be noted that the initial SOC of the second battery cell is updated in real time. The initial SOC of the second battery cell is updated whenever the open-circuit voltage of the second battery cell is not located in the plateau region of the SOC-OCV curve. In one implementation, the process of obtaining the initial SOC of the second battery cell can be as follows: if the second battery cell is detected to be fully charged, the initial SOC of the second battery cell is acquired; if the second battery cell is detected to be in a low-end resting state, the sampled voltage of the second battery cell is acquired, and the initial SOC of the second battery cell is obtained based on the SOC-OCV curve. It should be noted that the initial SOC of the second battery cell is updated whenever the second battery cell is detected to be fully charged or in a low-end resting state.

[0080] If the second battery cell is a single cell (i.e., it consists of only one cell), its initial SOC is 100% when it is detected to be fully charged. If the second battery cell comprises multiple cells (i.e., two or more cells), its initial SOC is an array containing the initial SOCs of each individual cell. When a cell in the second battery cell is detected to be fully charged, its SOC is corrected to 100%, meaning all fully charged cells have an initial SOC of 100%. The SOCs of the remaining cells not fully charged are also corrected by the same amount, and the modified SOCs are used as the initial SOCs of these cells. When the second battery cell is in a low-end resting state, the initial SOC of each individual cell is obtained based on its own sampled voltage and the SOC-OCV curve of the second battery cell.

[0081] To facilitate understanding, let's take the second battery cell, which consists of three individual cells: cell 1, cell 2, and cell 3. Assume cell 1 is detected as fully charged, with an actual SOC of 98%. In this case, the initial SOC of cell 1 is corrected to 100%, a correction of 2%. The other cells not fully charged are also corrected by the same amount, increasing their SOC by 2%. For cell 2, if its actual SOC is 97%, the corrected SOC is 99%. Similarly, for cell 3, if its actual SOC is 96%, the corrected SOC is 98%. When the second cell is in a low-end static state, the initial SOC of single cell 1 is obtained based on the sampled voltage of single cell 1 and the SOC-OCV curve of the second cell; the initial SOC of single cell 2 is obtained based on the sampled voltage of single cell 2 and the SOC-OCV curve of the second cell; and the initial SOC of single cell 3 is obtained based on the sampled voltage of single cell 3 and the SOC-OCV curve of the second cell. It should be noted that the above examples are for ease of understanding only and should not be construed as limiting this application.

[0082] In one alternative implementation, considering that batteries may experience wear and tear or aging during use, resulting in the actual storage capacity of the battery cell being less than its nominal capacity, in order to improve the accuracy of SOC estimation, the health of the battery cell is also taken into account when estimating the SOC of the battery pack in this embodiment.

[0083] In one optional implementation, the process of estimating the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity and balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell includes: estimating the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the SOH of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell. This can be expressed by the following formula:

[0084] If the second cell includes multiple individual cells, that is, two or more individual cells, then when estimating the SOC of the second cell, it is necessary to estimate the SOC of each of the multiple individual cells.

[0085] When balancing the first and second cells, if the first cell is fully discharged before the second cell, the second cell is then balanced to ensure it is fully discharged first. Conversely, if the first cell is fully charged before the second cell, the first cell is balanced to ensure it is fully charged first. This ensures that the first cell does not affect the overall charging and discharging of the battery pack and does not become a limiting factor in the battery pack's capacity. The charging and discharging of the entire battery pack is only related to the charging and discharging of the second cell. Therefore, the SOC of the second cell can reflect the SOC of the entire battery pack. Thus, when estimating the SOC of the battery pack, only the SOC of the second cell needs to be estimated. Once the SOC of the second cell is obtained, the SOC of the entire battery pack can be determined based on it.

[0086] If the second cell is a single cell, its SOC can be used as the SOC of the battery pack after obtaining its SOC. If the second cell comprises multiple single cells (two or more), its SOC is an array containing the SOCs of each single cell. The process of determining the SOC of the battery pack based on the second cell's SOC can be as follows: obtain the maximum and minimum SOCs from the multiple SOCs of the second cell; then obtain the weighted SOC of the maximum and minimum SOCs, and use this weighted SOC as the SOC of the battery pack. For ease of understanding, the maximum SOC is denoted as SOC_max, the minimum SOC as SOC_min, and the SOC of the battery pack as SOC_pack. One feasible weighted calculation method is: SOC_pack = SOC_min / (1 - (SOC_max - SOC_min)) * 100%.

[0087] In this embodiment, by introducing a first cell without a plateau region and connecting it in series with a second cell that has a plateau region, the capacity change of the battery pack during use can be determined based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell. Then, the balanced capacity of the first cell and the balanced capacity of the second cell are obtained. Finally, based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell, the SOC of the second cell can be accurately estimated. This solves the problem that estimating the SOC of a cell with a plateau region based on the existing voltage value and the SOC-OCV curve results in low accuracy.

[0088] Based on the same inventive concept, please refer to Figure 5 This application embodiment also provides a device 100 for estimating the state of charge (SOC) of a battery pack, which includes a processing module 110 and an acquisition module 120.

[0089] The processing module 110 is used to determine the capacity change of the battery pack during use based on the SOC change of the first cell relative to its initial SOC and the nominal capacity of the first cell.

[0090] The acquisition module 120 is used to acquire the equalization capacity of the first battery cell and the equalization capacity of the second battery cell.

[0091] The processing module 110 is also used to estimate the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell, and to determine the SOC of the battery pack based on the SOC of the second cell.

[0092] In this embodiment of the application, the processing module 110 is specifically used to: determine the capacity change of the battery pack during use based on the SOC change of the first cell relative to the initial SOC of the first cell during use, the nominal capacity of the first cell, and the SOH of the first cell.

[0093] In this embodiment of the application, the processing module 110 is specifically used to: estimate the SOC of the second cell based on the capacity change of the battery pack, the nominal capacity of the first cell, the balanced capacity of the first cell, the SOH of the first cell, the balanced capacity of the second cell, and the initial SOC of the second cell.

[0094] In this embodiment of the application, the processing module 110 is further configured to: obtain the SOC change of the first battery cell during use based on the SOC of the first battery cell during use and the initial SOC of the first battery cell; wherein, if the current open-circuit voltage of the second battery cell is located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC is the initial SOC of the first battery cell obtained and stored when the open-circuit voltage of the second battery cell was not located in the plateau region of the SOC-OCV curve of the second battery cell; if the current open-circuit voltage of the second battery cell is not located in the plateau region of the SOC-OCV curve of the second battery cell, the initial SOC is the latest obtained initial SOC.

[0095] In this embodiment, if the open-circuit voltage of the second cell is located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open-circuit voltage of the second cell was not located in the plateau region of the SOC-OCV curve of the second cell in the previous instance; if the open-circuit voltage of the second cell is not located in the plateau region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the latest obtained initial SOC.

[0096] In this embodiment of the application, the processing module 110 is further configured to: if the second battery cell is detected to be in a fully charged state, obtain the initial SOC of the second battery cell, and obtain the SOC of the first battery cell when the second battery cell is in a fully charged state as the initial SOC of the first battery cell; if the second battery cell is detected to be in a low-end static state, obtain the sampling voltage of the first battery cell, and obtain the initial SOC of the first battery cell based on the SOC-OCV curve of the first battery cell, and obtain the sampling voltage of the second battery cell, and obtain the initial SOC of the second battery cell based on the SOC-OCV curve of the second battery cell.

[0097] In this embodiment of the application, the second battery cell includes multiple individual battery cells, and the processing module 110 is further configured to: obtain the maximum SOC and the minimum SOC from the multiple SOCs of the second battery cell, wherein each individual battery cell corresponds to one SOC; obtain the weighted SOC of the maximum SOC and the minimum SOC, and use the weighted SOC as the SOC of the battery pack.

[0098] In this embodiment of the application, the device 100 for estimating the SOC of the battery pack further includes an equalization module. The equalization module is configured to: if the first cell is fully discharged before the second cell, then perform equalization discharge on the second cell to ensure that the second cell is fully discharged before the first cell; if the first cell is fully charged before the second cell, then perform equalization discharge on the first cell to ensure that the second cell is fully charged before the second cell.

[0099] In this embodiment, the equalization module is further configured to: determine the charging capacity required for a full charge of the first battery cell or the discharge capacity required for a full discharge based on the initial SOC, nominal capacity, and SOH of the first battery cell; determine the charging capacity required for a full charge of the second battery cell or the discharge capacity required for a full discharge based on the initial SOC, nominal capacity, and SOH of the second battery cell; if the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, then determine that the first battery cell is prioritized for full charge relative to the second battery cell; if the discharge capacity of the first battery cell is less than the discharge capacity of the second battery cell, then determine that the first battery cell is prioritized for full discharge relative to the second battery cell.

[0100] The device 100 for estimating the SOC of a battery pack provided in this application embodiment has the same implementation principle and technical effect as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the device embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0101] Based on the same inventive concept, such as Figure 6 As shown, Figure 6 A structural block diagram of a battery management system 200 provided in an embodiment of this application is shown. The battery management system 200 includes: a processor 210; and a memory 220 communicatively connected to the processor 210. The memory 220 stores instructions executable by the processor, which are executed by the processor 210 to enable the processor 210 to perform the method for estimating the state of charge (SOC) of a battery pack provided in an embodiment of this application.

[0102] The processor 210 and memory 220 are electrically connected directly or indirectly to enable data transmission or interaction. For example, these components can be electrically connected via one or more communication buses 530 or signal buses 530. Methods for estimating the battery pack's State of Charge (SOC) include at least one software functional module that can be stored in memory 220 in the form of software or firmware.

[0103] Processor 210 can be an integrated circuit chip with signal processing capabilities. Processor 210 can be a general-purpose processor, including a CPU (Central Processing Unit), NP (Network Processor), etc.; it can also be a digital signal processor, application-specific integrated circuit, off-the-shelf programmable gate array or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor.

[0104] The memory 220 can store various software programs and modules, such as the program instructions / modules corresponding to the method and apparatus for estimating the SOC of a battery pack provided in the embodiments of this application. The processor 210 executes various functional applications and data processing by running the software programs and modules stored in the memory 220, thereby implementing the method in the embodiments of this application.

[0105] The memory 220 may include, but is not limited to, RAM (Random Access Memory), ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electric Erasable Programmable Read-Only Memory), etc.

[0106] The various implementation methods and specific examples in the methods for estimating the state of charge (SOC) of the battery pack described in the foregoing embodiments are also applicable to... Figure 6 The battery management system 500 shown above, through the foregoing detailed description of the method for estimating the battery pack's state of charge (SOC), will be clearly understood by those skilled in the art. Figure 6 The implementation method of the battery management system 500 is not detailed here for the sake of brevity.

[0107] Based on the same inventive concept, this application also provides a vehicle, which is an electric vehicle, including... Figure 1 The battery pack 10 shown is Figure 6 The battery management system 200 shown.

[0108] Based on the same inventive concept, embodiments of this application also provide an electric device, including... Figure 1 The battery pack 10 shown is Figure 6 The battery management system 200 shown.

[0109] Based on the same inventive concept, this application also provides a non-volatile computer-readable storage medium (hereinafter referred to as the storage medium), on which a computer program is stored. When the computer, such as the battery management system 200 described above, runs the computer program, it executes the ring network configuration method described above. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0110] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0111] It should be noted that relational terms such as "first" and "second" in the description of this application are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0112] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0113] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for estimating a state of charge (SOC) of a battery pack, the battery pack comprising a first cell without a platform region and a second cell with a platform region, and at least one of the first cell and the second cell being connected in series; the method comprising: determining a capacity variation of the battery pack according to a SOC variation of the first cell relative to an initial SOC of the first cell and a nominal capacity of the first cell; obtaining an equalization capacity of the first cell and an equalization capacity of the second cell; the equalization capacity being obtained according to an integration of an equalization current with respect to an equalization time; estimating an SOC of the second cell according to the capacity variation of the battery pack, the nominal capacity of the first cell, the equalization capacity of the first cell, the equalization capacity of the second cell, and an initial SOC of the second cell, and determining an SOC of the battery pack according to the SOC of the second cell. The method further comprises: determining the capacity variation of the battery pack according to the SOC variation of the first cell relative to the initial SOC of the first cell and the nominal capacity of the first cell and a state of health (SOH) of the first cell. The method further comprises: estimating the SOC of the second cell according to the capacity variation of the battery pack, the nominal capacity of the first cell, the equalization capacity of the first cell, the equalization capacity of the second cell, and the initial SOC of the second cell. The method further comprises: obtaining the SOC variation of the first cell relative to the initial SOC of the first cell according to a SOC of the first cell and the initial SOC of the first cell. If the open circuit voltage of the second cell is currently located in the platform region of the SOC-OCV curve of the second cell, the initial SOC of the first cell is the initial SOC of the first cell obtained and stored when the open circuit voltage of the second cell was not located in the platform region of the SOC-OCV curve of the second cell last time.

2. The method of claim 1, wherein, If the open circuit voltage of the second cell is not currently located in the platform region of the SOC-OCV curve of the second cell, the initial SOC of the first cell is the initial SOC obtained most recently. If the open circuit voltage of the second cell is currently located in the platform region of the SOC-OCV curve of the second cell, the initial SOC of the second cell is the initial SOC of the second cell obtained and stored when the open circuit voltage of the second cell was not located in the platform region of the SOC-OCV curve of the second cell last time.

3. The method of claim 2, wherein, ​ ​ 4. The method of claim 1, wherein, ​ ​ ​ ​ 5. The method of claim 1, wherein, ​ If the open circuit voltage of the second battery cell is not in the flat region of the SOC-OCV curve of the second battery cell, the initial SOC of the second battery cell is the latest obtained initial SOC.

6. The method of claim 1, wherein, Further comprising, obtaining the initial SOCs of the first battery cell and the second battery cell, wherein the obtaining the initial SOCs of the first battery cell and the second battery cell comprises: If it is detected that the second battery cell is in a full charge state, obtaining the initial SOC of the second battery cell, and obtaining the SOC of the first battery cell when the second battery cell is in the full charge state as the initial SOC of the first battery cell; If it is detected that the second battery cell is in a low-end static state, obtaining the sampling voltage of the first battery cell, and obtaining the initial SOC of the first battery cell based on the SOC-OCV curve of the first battery cell, and obtaining the sampling voltage of the second battery cell, and obtaining the initial SOC of the second battery cell based on the SOC-OCV curve of the second battery cell.

7. The method of claim 1, wherein, The second battery cell comprises a plurality of single battery cells; Determining the SOC of the battery pack according to the SOC of the second battery cell comprises: Obtaining the maximum SOC and the minimum SOC from the plurality of SOCs of the second battery cell, wherein each single battery cell corresponds to one SOC; Obtaining the weighted SOC of the maximum SOC and the minimum SOC, and taking the weighted SOC as the SOC of the battery pack.

8. The method of claim 1, wherein, The method further comprises: If the first battery cell is preferentially fully discharged relative to the second battery cell, performing equalization discharge on the second battery cell to ensure that the second battery cell is preferentially fully discharged; If the first battery cell is preferentially fully charged relative to the second battery cell, performing equalization discharge on the first battery cell to ensure that the second battery cell is preferentially fully charged.

9. The method of claim 8, wherein, The process of determining that the first battery cell is preferentially fully discharged or fully charged relative to the second battery cell comprises: Determining the charging capacity required when the first battery cell is fully charged or the discharge capacity discharged when the first battery cell is fully discharged according to the initial SOC, the nominal capacity and the SOH of the first battery cell; Determining the charging capacity required when the second battery cell is fully charged or the discharge capacity discharged when the second battery cell is fully discharged according to the initial SOC, the nominal capacity and the SOH of the second battery cell; If the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, it is determined that the first battery cell is preferentially fully charged relative to the second battery cell; if the discharge capacity of the first battery cell is less than the discharge capacity of the second battery cell, it is determined that the first battery cell is preferentially fully discharged relative to the second battery cell.

10. An apparatus for estimating a state of charge (SOC) of a battery pack, the battery pack comprising first cells without a plateau region and second cells with a plateau region, and at least one of the first cells being connected in series with the second cells; The device comprises: The processing module is configured to determine the capacity variation of the battery pack according to the SOC variation of the first battery cell relative to the initial SOC of the first battery cell, and the nominal capacity of the first battery cell; The obtaining module is configured to obtain the equalization capacity of the first battery cell and the equalization capacity of the second battery cell; the equalization capacity is obtained by integrating the equalization current with respect to the equalization time. The processing module is further configured to estimate the SOC of the second battery cell according to the capacity change amount of the battery pack, the nominal capacity of the first battery cell, the equalization capacity of the first battery cell, the equalization capacity of the second battery cell, and the initial SOC of the second battery cell, and determine the SOC of the battery pack according to the SOC of the second battery cell.

11. The apparatus of claim 10, wherein, The processing module is specifically configured to: determine the capacity change amount of the battery pack according to the SOC change amount of the first battery cell relative to the initial SOC of the first battery cell, and the nominal capacity of the first battery cell and the SOH of the first battery cell.

12. The apparatus of claim 11, wherein, The processing module is specifically configured to: estimate the SOC of the second battery cell according to the capacity change amount of the battery pack, the nominal capacity of the first battery cell, the equalization capacity of the first battery cell, the SOH of the first battery cell, and the equalization capacity of the second battery cell and the initial SOC of the second battery cell.

13. The apparatus of claim 10, wherein, The processing module is further configured to: obtain the SOC change amount of the first battery cell according to the SOC of the first battery cell and the initial SOC of the first battery cell; wherein, if the open circuit voltage of the second battery cell currently is located in the platform region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the initial SOC of the first battery cell obtained and stored last time when the open circuit voltage of the second battery cell is not located in the platform region of the SOC-OCV curve; if the open circuit voltage of the second battery cell currently is not located in the platform region of the SOC-OCV curve of the second battery cell, the initial SOC of the first battery cell is the initial SOC obtained currently.

14. The apparatus of claim 10, wherein, if the open circuit voltage of the second battery cell currently is located in the platform region of the SOC-OCV curve of the second battery cell, the initial SOC of the second battery cell is the initial SOC of the second battery cell obtained and stored last time when the open circuit voltage of the second battery cell is not located in the platform region of the SOC-OCV curve of the second battery cell; if the open circuit voltage of the second battery cell currently is not located in the platform region of the SOC-OCV curve of the second battery cell, the initial SOC of the second battery cell is the initial SOC obtained currently.

15. The apparatus of claim 10, wherein, The processing module is further configured to: if it is detected that the second battery cell is in a full charge state, obtain the initial SOC of the second battery cell, and obtain the SOC of the first battery cell when the second battery cell is in the full charge state as the initial SOC of the first battery cell; if it is detected that the second battery cell is in a low-end static state, obtain the sampling voltage of the first battery cell, and obtain the initial SOC of the first battery cell based on the SOC-OCV curve of the first battery cell, and obtain the sampling voltage of the second battery cell, and obtain the initial SOC of the second battery cell based on the SOC-OCV curve of the second battery cell.

16. The apparatus of claim 10, wherein, The second battery cell includes a plurality of single battery cells, and the processing module is further configured to: obtain the maximum SOC and the minimum SOC from the plurality of SOCs of the second battery cell, wherein each single battery cell corresponds to one SOC; obtaining a weighted SOC of the maximum SOC and the minimum SOC, and taking the weighted SOC as the SOC of the battery pack.

17. The apparatus of claim 10, wherein, The device further comprises a balancing module, configured to: if the first battery cell is preferentially discharged to full capacity relative to the second battery cell, performing a balancing discharge on the second battery cell to ensure that the second battery cell is preferentially discharged to full capacity; if the first battery cell is preferentially charged to full capacity relative to the second battery cell, performing a balancing discharge on the first battery cell to ensure that the second battery cell is preferentially charged to full capacity.

18. The apparatus of claim 17, wherein, The balancing module is further configured to: determine the charging capacity required for the first battery cell to be fully charged or the discharging capacity discharged by the first battery cell to be fully discharged according to the initial SOC, the nominal capacity and the SOH of the first battery cell; determine the charging capacity required for the second battery cell to be fully charged or the discharging capacity discharged by the second battery cell to be fully discharged according to the initial SOC, the nominal capacity and the SOH of the second battery cell; if the charging capacity of the first battery cell is less than the charging capacity of the second battery cell, determine that the first battery cell is preferentially charged to full capacity relative to the second battery cell; if the discharging capacity of the first battery cell is less than the discharging capacity of the second battery cell, determine that the first battery cell is preferentially discharged to full capacity relative to the second battery cell.

19. A battery management system comprising: at least one processor; and a memory connected to the at least one processor in communication; The battery management system is connected to a battery pack, the battery pack comprising first battery cells without a platform region and second battery cells with a platform region, and at least one of the first battery cells and the second battery cells are connected in series; The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method for estimating the SOC of the battery pack according to any one of claims 1 to 9.

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