Apparatus and method for estimating battery cell capacity

Abstract

A method for estimating a battery cell capacity can include deriving a discharge curve for each battery cell included in a module including a plurality of battery cells; deriving a charge curve for each battery cell included in the module; calculating an additional dischargeable capacity of a second battery cell based on a pattern of the discharge curve of a first battery cell; calculating an additional chargeable capacity of the second battery cell based on a transition of the charge curve of the first battery cell; and calculating a capacity of the second battery cell based on the additional dischargeable capacity and the additional chargeable capacity of the second battery cell.

Description

Technical Field

[0001] The present invention relates to apparatus and methods for estimating the capacity of a single battery cell, and more particularly, to apparatus and methods for more accurately calculating the capacity of each of a plurality of battery cells included in a module. Background Technology

[0002] With increasing demand for various portable electronic devices and the vigorous development of batteries for electric vehicles and energy storage systems, high-performance batteries capable of repeated charging and discharging are being actively researched. Specifically, batteries used in electric vehicles or energy storage systems can be configured into battery modules by connecting multiple battery cells, thereby enabling charging and discharging of high output and large capacity power.

[0003] Battery control technology can be crucial in devices or systems that use batteries as an energy source. As one such control technology, controlling battery charging and discharging based on remaining battery capacity can be used to improve the operational efficiency of the device or system.

[0004] Meanwhile, in a battery module consisting of several battery cells connected in series, the capacity of the entire module is determined by the battery cells that have experienced significant degradation or voltage deviation, and therefore, it may be impossible to clearly detect the battery capacity of the remaining cells. Summary of the Invention

[0005] [Technical Issues]

[0006] To avoid one or more problems of the prior art, embodiments of this disclosure provide an apparatus for calculating the capacity of a single battery cell, enabling accurate diagnosis of the degradation state of each battery cell by estimating the remaining capacity of all cells in a battery module.

[0007] To avoid one or more problems of the prior art, this disclosure also provides a method for calculating the capacity of a single battery cell.

[0008] [Technical Solution]

[0009] To achieve the objectives of this disclosure, an apparatus for estimating the capacity of a battery cell may include: at least one processor; and a memory for storing at least one instruction executed by the at least one processor, wherein the at least one instruction may include: instructions for deriving a discharge curve of each battery cell included in a module comprising a plurality of battery cells; instructions for deriving a charging curve of each battery cell included in the module; instructions for calculating an additional dischargeable capacity of a second battery cell based on a pattern of a discharge curve of a first battery cell; instructions for calculating an additional rechargeable capacity of a second battery cell based on a transition of a charging curve of the first battery cell; and instructions for calculating the capacity of a second battery cell based on the additional dischargeable capacity and the additional rechargeable capacity of the second battery cell.

[0010] In this embodiment, multiple battery cells can be connected in series and included in the module. The first battery cell can be the one with the most severe degradation among the multiple battery cells in the module.

[0011] The instruction for calculating the additional discharge capacity of the second battery cell may include the following instruction: extending the discharge curve of the second battery cell to the first battery cell when it is discharged to its maximum voltage based on the pattern of the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on the time axis.

[0012] The instruction for calculating the additional rechargeable capacity of the second battery cell may include the following instruction: extending the charging curve of the second battery cell to the first battery cell when it is charged to its maximum voltage based on the pattern of the charging curve of the first battery cell, wherein the extended portion of the charging curve of the first battery cell is derived by offsetting the charging curve of the first battery cell on the time axis.

[0013] The capacity of the second battery cell can be calculated based on the module's discharge capacity, the additional discharge capacity of the second battery cell, the additional rechargeable capacity of the second battery cell, and the charging and discharging efficiency.

[0014] The second battery cell can be any one of the remaining battery cells in the module, excluding the first battery cell.

[0015] According to another embodiment of this disclosure, a method for estimating the capacity of a battery cell may include: deriving a discharge curve for each battery cell included in a module comprising a plurality of battery cells; deriving a charging curve for each battery cell included in the module; calculating an additional dischargeable capacity of a second battery cell based on the pattern of the discharge curve of a first battery cell; calculating an additional rechargeable capacity of the second battery cell based on the transition of the charging curve of the first battery cell; and calculating the capacity of the second battery cell based on the additional dischargeable capacity and the additional rechargeable capacity of the second battery cell.

[0016] In this embodiment, multiple battery cells can be connected in series and included in the module. The first battery cell can be the one with the most severe degradation among the multiple battery cells in the module.

[0017] Calculating the additional discharge capacity of the second battery cell may include extending the discharge curve of the second battery cell to the first battery cell when it is discharged to its maximum voltage, based on a pattern of the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on the time axis.

[0018] Calculating the additional rechargeable capacity of the second battery cell may include: extending the charging curve of the second battery cell to the first battery cell when it is charged to its maximum voltage based on a pattern of the charging curve of the first battery cell, wherein the extended portion of the charging curve of the first battery cell is derived by offsetting the charging curve of the first battery cell on the time axis.

[0019] Calculating the capacity of the second battery cell may include: calculating the capacity of the second battery cell based on the module's discharge capacity, the additional discharge capacity of the second battery cell, the additional rechargeable capacity of the second battery cell, and the charge / discharge efficiency.

[0020] The capacity of the second battery cell can be calculated based on the module's discharge capacity, the additional discharge capacity of the second battery cell, the additional rechargeable capacity of the second battery cell, and the charging and discharging efficiency.

[0021] The second battery cell can be any one of the remaining battery cells in the module, excluding the first battery cell.

[0022] [Beneficial Effects]

[0023] According to embodiments of the present invention, the remaining capacity of all cells in a battery module in which multiple battery cells are connected in series can be estimated.

[0024] Therefore, the degradation status of each battery cell included in the battery module can be accurately checked. Attached Figure Description

[0025] Figure 1 This is a block diagram of a typical battery module.

[0026] Figure 2 It is a graph showing the voltage changes during the charging / discharging operation of multiple battery cells connected in series.

[0027] Figure 3 This illustrates the concept of deriving the additional discharge capacity of each battery cell from the behavior curve of the cell with the lowest discharge capacity according to an embodiment of the present invention.

[0028] Figure 4 This illustrates the concept of deriving the additional rechargeable capacity of each battery cell from the behavior curve of the lowest charging capacity cell according to an embodiment of the present invention.

[0029] Figure 5 This is a graph showing a comparison between the estimated capacity of a single battery cell according to an embodiment of the present invention and the actual measured value.

[0030] Figure 6 This is a block diagram of an apparatus for estimating the capacity of a single battery cell according to an embodiment of the present invention.

[0031] Figure 7 This is a flowchart of a method for estimating the capacity of a single battery cell according to an embodiment of the present invention. Detailed Implementation

[0032] This invention can be modified in various ways and has different embodiments, specific of which are illustrated by way of example in the accompanying drawings and will be described in detail below. However, it should be understood that the invention is not intended to be limited to the specific embodiments; rather, the invention is intended to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention. Throughout the description of the drawings, similar reference numerals denote similar elements.

[0033] It should be understood that although terms such as first, second, A, B, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element without departing from the scope of the invention, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes a combination of multiple associated listed items or any one of multiple associated listed items.

[0034] It will be understood that when an element is said to be "coupled" or "connected" to another element, it can be directly coupled or connected to the other element, or there can be an intermediary element. In contrast, when an element is said to be "directly coupled" or "directly connected" to another element, there is no intermediary element.

[0035] The terminology used herein is for describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” also include the plural forms, unless the context clearly specifies otherwise. Furthermore, it will be understood that the terms “comprising,” “including,” and / or “having” as used herein specify the presence of the stated features, integers, steps, operations, constituent elements, components, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, constituent elements, components, and / or combinations thereof.

[0036] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it will be understood that terms—such as those defined in common dictionaries—should be interpreted as having the same meaning as they have in the context of the relevant field, and should not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0037] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0038] Figure 1 This is a block diagram of a typical battery module.

[0039] Battery module 10 typically includes multiple battery cells connected in series with each other. Figure 1 In a battery module, N individual battery cells are connected in series to form a battery module. A battery cell is the smallest unit of a battery used to store energy. Depending on the device, system, or environment in which the battery is used, series or parallel combinations of battery cells can form a battery module, and multiple battery modules can form a battery rack or battery pack.

[0040] Here, the battery pack may include not only multiple battery cells connected in series, but also various components for charging and discharging the battery pack, such as busbars, cables, relays and control circuits.

[0041] Furthermore, even among battery cells arranged and used in the same group, the degree of degradation of individual cells may vary over time, and therefore, the voltage deviations of battery cells may differ from one another. When a load is applied to a weak cell, energy may be consumed faster than that of a strong cell. Additionally, during the charging process, weak cells with smaller charging capacity reach full charge before strong cells, leading to the problem of weak cells being in an overcharged state for extended periods. Moreover, during the discharging process, weak cells discharge first and may be affected by strong cells.

[0042] Figure 2It is a graph showing the voltage changes during the charging / discharging operation of multiple battery cells connected in series.

[0043] Figure 2 Each curve in the diagram shows the change in the measured voltage of each battery cell over time. For each curve, the first time segment 21 represents the period during which charging occurs, and the second time segment 22 represents the period during which discharging occurs.

[0044] exist Figure 2 In this circuit, the upper charging limit voltage is the maximum voltage at which a single battery cell can be safely charged, and it can be preset. Similarly, the lower discharging limit voltage is the minimum voltage at which a single battery cell can be safely discharged, and it can also be preset.

[0045] refer to Figure 2 The dashed curve represents the voltage behavior of the battery cell with the most severe degradation. The most severely degraded battery cell reaches its upper charging voltage limit first during charging, at which point charging of all battery cells in the module ceases. Conversely, during discharging, the most severely degraded battery cell discharges the fastest, causing its voltage to reach its lower discharge limit first. Here, not only is discharging of the most severely degraded battery cell stopped, but discharging of all other battery cells also ceases.

[0046] In other words, the capacity of the entire module is determined by the capacity of the battery cell with the most severe degradation. Therefore, when multiple battery cells in a module are connected in series, the module's capacity is the same as the capacity of the single battery cell with the most severe degradation among all the battery cells in the module.

[0047] Here, because charging or discharging has not yet reached the upper limit voltage of the remaining battery cell or the lower limit voltage of the discharge, the following problem arises: it is difficult to accurately determine how much charge / discharge capacity each cell has before reaching the upper limit voltage of the charge or the lower limit voltage of the discharge.

[0048] Figure 3 This illustrates the concept of deriving the additional discharge capacity of each battery cell from the behavior curve of the cell with the lowest discharge capacity according to an embodiment of the present invention.

[0049] Figure 3 Curve 300 shows the voltage behavior of the cell with the lowest discharge capacity, measured over time during discharge. Here, the cell with the lowest discharge capacity can be the cell in the module that experiences the most severe degradation. In curve 310, the portion corresponding to the line above point Pd shows the discharge behavior of one of the battery cells in the module other than the cell with the lowest discharge capacity.

[0050] Here, according to an embodiment of the present invention, a virtual curve of a first battery cell, which is one of the battery cells in the module, can be generated (in... Figure 3 (Indicated by the dashed line below Pd). The virtual curve can be seen from the point where the discharge stops at the actual discharge line of the first cell—that is, Figure 3 Point Pd in ​​the diagram represents the starting point, extending along the direction of decreasing voltage. The virtual discharge curve of the first battery cell can be set to the same pattern as the discharge curve 300 of the cell with the lowest discharge capacity. In other words, the virtual discharge curve of the first battery cell can extend from point Pd along the direction of decreasing battery cell voltage over time, following the line of the discharge curve 300 of the cell with the lowest discharge capacity as it moves along the time axis. Figure 3 In this diagram, the virtual discharge curve of the first battery cell, indicated by a dashed line, is represented as an extrapolated voltage behavior. Here, the additional dischargeable capacity of the first battery cell can be the amount of time by which the virtual discharge curve of the first battery cell shifts from the discharge curve 300 of the cell with the lowest discharge capacity on the time axis.

[0051] Figure 4 This illustrates the concept of deriving the additional rechargeable capacity of each battery cell from the behavior curve of the lowest charging capacity cell according to an embodiment of the present invention.

[0052] Figure 4 Curve 400 shows the voltage behavior of the lowest charge capacity cell measured over time during charging. Here, the lowest charge capacity cell can be the cell in the module that experiences the most severe degradation. In curve 410, the portion of the line corresponding to point Pc indicates the charging behavior of one of the battery cells in the module other than the lowest charge capacity cell.

[0053] According to an embodiment of the present invention, a virtual curve of a first battery cell, which is one of the battery cells in a module, can be generated (in... Figure 4 (Indicated by the dashed line above Pc). The virtual curve can be seen from the actual charging curve of the first battery cell at the point where charging stops—that is, Figure 4 Point Pc in the diagram extends along the direction of voltage increase. Here, the virtual charging curve of the first battery cell can be set to the same pattern as the charging curve 400 of the lowest charging capacity cell. In other words, the virtual charging curve of the first battery cell can extend from point Pc along the direction of voltage increase over time, and follow the curve of the lowest charging capacity cell 400 offset on the time axis. Figure 4 In this embodiment, the virtual charging curve of the first battery cell, indicated by the dashed line, is represented as an extrapolated voltage behavior. Here, the additional rechargeable capacity of the first battery cell can be the amount of time by which the virtual charging curve of the first battery cell shifts from the charging curve 400 of the lowest charging capacity cell on the time axis.

[0054] Then, it can be based on reference Figure 3 and Figure 4 The method derives the additional discharge capacity and additional rechargeable capacity to calculate the capacity of each battery cell. The capacity of each cell can be defined by the following Equation 1.

[0055] [Equation 1]

[0056] The individual capacity of each unit in the module = module discharge capacity + additional discharge capacity + (additional charging capacity * charging and discharging efficiency).

[0057] Here, the individual capacity of each cell can indicate the electrical power (Ah) that can be output assuming the cell is charged to the upper limit voltage and discharged to the lower limit voltage. Furthermore, the charge / discharge efficiency can be defined as the value obtained by dividing the module's discharge capacity by its charge capacity.

[0058] Figure 5 This is a graph showing a comparison between the estimated capacity of a single battery cell according to an embodiment of the present invention and the actual measured value.

[0059] exist Figure 5 In the diagram, line 51 includes the capacity of each individual battery cell calculated as described in the above embodiments using the charge / discharge curves of each of the 12 battery cells in the module, which are connected in series. In contrast, graph 53 shows the values ​​obtained by measuring the capacity of each individual battery cell separately by disassembling the module.

[0060] Lines 51 and 53 show an average difference of 1% and a maximum difference of 3%. Therefore, there is no significant difference between the actual measured capacity of a battery cell and the estimated capacity of a battery cell according to the invention. Thus, the method for calculating battery cell capacity proposed according to the invention can accurately determine the actual degradation state of a battery cell without disassembling the module and measuring each disassembled battery cell.

[0061] Figure 6 This is a block diagram of an apparatus for estimating the capacity of a single battery cell according to an embodiment of the present invention.

[0062] refer to Figure 6 An apparatus for calculating the capacity of a single battery cell includes a memory 100, at least one processor 200, a transceiver 300, and a storage device 600. Each of the components 100, 200, 300, and 600 included in the apparatus for calculating the capacity of a single battery cell can be connected via a bus 700 to communicate with each other.

[0063] The device for calculating the capacity of a single battery cell according to the present invention can be implemented as a battery management system (BMS), or included in a battery management system, which can be part of a battery system or a separate device.

[0064] The memory 100 and the storage device 600 can be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 100 and the storage device 600 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0065] The memory 100 may store at least one instruction or command executed by the processor 200. The processor 200 may include a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that executes the methods according to embodiments of the present invention thereon.

[0066] The processor 200 can execute at least one program command or instruction stored in the memory 100.

[0067] At least one instruction may include: an instruction to derive the discharge curve of each battery cell included in a module comprising multiple battery cells; an instruction to derive the charging curve of each battery cell included in the module; an instruction to calculate the additional discharge capacity of a second battery cell based on the pattern of the discharge curve of a first battery cell; an instruction to calculate the additional rechargeable capacity of a second battery cell based on the transition of the charging curve of a first battery cell; and an instruction to calculate the capacity of a second battery cell based on the additional discharge capacity and the additional rechargeable capacity of the second battery cell.

[0068] Here, multiple battery cells can be connected in series and included in the module. The first battery cell can be the one with the most severe degradation among the multiple battery cells in the module. The second battery cell can be any one of the remaining battery cells in the module other than the first battery cell.

[0069] Instructions for calculating the additional discharge capacity of the second battery cell may include instructions for extending the discharge curve of the second battery cell to the maximum voltage of the first battery cell based on the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on the time axis.

[0070] The instruction for calculating the additional rechargeable capacity of the second battery cell may include an instruction to extend the charging curve of the second battery cell to the first battery cell when it is charged to its maximum voltage, based on a pattern of the charging curve of the first battery cell, wherein the extended portion of the charging curve of the first battery cell is derived by offsetting the charging curve of the first battery cell on the time axis.

[0071] The capacity of the second battery cell can be calculated based on the module's discharge capacity, the additional discharge capacity of the second battery cell, the additional rechargeable capacity of the second battery cell, and the charging and discharging efficiency.

[0072] The memory 100 or storage device 600 can store information about the charging and discharging curves of individual battery cells and battery modules calculated by the processor.

[0073] Figure 7 This is a flowchart of a method for estimating the capacity of a single battery cell according to an embodiment of the present invention.

[0074] Figure 7 The method illustrated for calculating the capacity of a single battery cell relates to a method for calculating the capacity of each battery cell in a battery module comprising multiple battery cells, and can be performed by means of means for calculating the capacity of a single battery cell. In some embodiments, the means for calculating the capacity of a single battery cell may be a battery management system (BMS). Furthermore, multiple battery cells may be connected in series and included in the battery module.

[0075] refer to Figure 7 The device for calculating the capacity of individual battery cells can derive the discharge curve S711 for each individual battery cell included in the battery module. The device for calculating the capacity of individual battery cells can also derive the charging curve S712 for each individual battery cell included in the battery module.

[0076] Then, the additional discharge capacity S721 of the second battery cell can be calculated based on the transition pattern of the discharge curve of the first battery cell. More specifically, the discharge curve of the second battery cell can be extended to the instruction that the first battery cell is discharged to its maximum voltage based on the pattern of the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on the time axis.

[0077] Here, the first battery cell can be the battery cell with the most severe degradation among the multiple battery cells in the module. The second battery cell can be any of the remaining battery cells in the module other than the first battery cell.

[0078] Furthermore, the additional rechargeable capacity S722 of the second battery cell can be calculated based on the transition pattern of the charging curve of the first battery cell. More specifically, the charging curve of the second battery cell can be extended to the point where the first battery cell is charged to its maximum voltage based on the pattern of the charging curve of the first battery cell, wherein the extended portion of the charging curve of the first battery cell is derived by shifting the charging curve of the first battery cell on the time axis.

[0079] For ease of explanation, steps 711, 712, 721, and 722 are shown in sequence, but steps 711 and 712 can be performed simultaneously, or the order can be reversed. The same applies to steps 721 and 722. However, step 721 should be performed after step 711, and step 722 should be performed after step 712.

[0080] Once the additional discharge capacity and additional rechargeable capacity of the second battery cell are calculated, the capacity of the second battery (S730) can be calculated based on these calculated values. More specifically, the capacity of the second battery cell can be calculated based on the module's discharge capacity, the derived additional discharge capacity of the second battery cell, the additional rechargeable capacity of the second battery cell, and the charge / discharge efficiency. Here, the charge / discharge efficiency can be defined as the value obtained by dividing the module's discharge capacity by its charge capacity.

[0081] While some aspects of the invention have been described in the context of apparatus, the description may also be presented according to a corresponding method, wherein a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of method may also represent features of corresponding blocks or items or corresponding apparatuses. Some or all of the method steps may be performed by (or using) hardware devices such as, for example, microprocessors, programmable computers, or electronic circuits. In some embodiments, one or more of the most important method steps may be performed by such apparatus.

[0082] The present invention has been described above with reference to exemplary embodiments thereof; however, those skilled in the art will understand that various corrections and modifications may be made to the invention within the scope of the appended claims without departing from the spirit and scope of the invention as described therein.

Claims

1. An apparatus for estimating a battery cell capacity, comprising: at least one processor; and a memory for storing at least one instruction executed by the at least one processor, wherein the at least one instruction comprises: an instruction to derive a discharge curve of each battery cell included in a module comprising a plurality of battery cells; an instruction to derive a charge curve of each battery cell included in the module; an instruction to calculate an additional dischargeable capacity of a second battery cell based on a pattern of a discharge curve of a first battery cell; an instruction to calculate an additional chargeable capacity of the second battery cell based on a transition of a charge curve of the first battery cell; and an instruction to calculate a capacity of the second battery cell based on the additional dischargeable capacity and the additional chargeable capacity of the second battery cell, wherein the capacity of the second battery cell is calculated based on an equation of: the capacity of the second battery cell = a discharge capacity of the module + the additional dischargeable capacity of the second battery cell + (the additional chargeable capacity of the second battery cell * a charge-discharge efficiency).

2. The apparatus of claim 1, wherein, the plurality of battery cells are connected in series and included in the module.

3. The apparatus of claim 1, wherein, the first battery cell is a battery cell among the plurality of battery cells in the module, in which a deterioration progresses most severely.

4. The apparatus of claim 1, wherein, the instruction to calculate the additional dischargeable capacity of the second battery cell comprises an instruction to: extend a discharge curve of the second battery cell to a maximum voltage at which the first battery cell is discharged based on a pattern of the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on a time axis.

5. The apparatus of claim 1, wherein, the instruction to calculate the additional chargeable capacity of the second battery cell comprises an instruction to: extend a charge curve of the second battery cell to a maximum voltage at which the first battery cell is charged based on a pattern of the charge curve of the first battery cell, wherein the extended portion of the charge curve of the first battery cell is derived by shifting the charge curve of the first battery cell on a time axis.

6. The apparatus of claim 1, wherein, the second battery cell is any one of the remaining battery cells among all battery cells in the module except for the first battery cell.

7. A method for estimating a battery cell capacity, comprising: deriving a discharge curve of each battery cell included in a module comprising a plurality of battery cells; deriving a charge curve of each battery cell included in the module; calculating an additional dischargeable capacity of a second battery cell based on a pattern of a discharge curve of a first battery cell; calculating an additional chargeable capacity of the second battery cell based on a transition of a charge curve of the first battery cell; and calculating a capacity of the second battery cell based on the additional dischargeable capacity and the additional chargeable capacity of the second battery cell, wherein the capacity of the second battery cell is calculated based on an equation of: ​ The capacity of the second battery cell = the discharge capacity of the module + the additional dischargeable capacity of the second battery cell + (the additional chargeable capacity of the second battery cell * charge-discharge efficiency).

8. The method of claim 7, wherein, The plurality of battery cells are connected in series and included in the module.

9. The method of claim 7, wherein, The first battery cell is a battery cell among the plurality of battery cells in the module, in which deterioration progresses most severely.

10. The method of claim 7, wherein, Calculating the additional dischargeable capacity of the second battery cell includes: extending a discharge curve of the second battery cell to a maximum voltage at which the first battery cell is discharged based on a pattern of the discharge curve of the first battery cell, wherein the extended portion of the discharge curve of the second battery cell is derived by shifting the discharge curve of the first battery cell on a time axis.

11. The method of claim 7, wherein, Calculating the additional chargeable capacity of the second battery cell includes: extending a charge curve of the second battery cell to a maximum voltage at which the first battery cell is charged based on a pattern of the charge curve of the first battery cell, wherein the extended portion of the charge curve of the first battery cell is derived by shifting the charge curve of the first battery cell on a time axis.

12. The method of claim 7, wherein, The second battery cell is any one of the remaining battery cells among all battery cells in the module except for the first battery cell.

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