Battery cell balancing system and method

Abstract

A battery cell balancing system and method are disclosed. A battery cell balancing system according to the present invention may comprise: a state of charge (SOC) estimation unit for estimating the SOC of each battery cell included in a battery assembly; a state of health (SOH) estimation unit for estimating the SOH of each battery cell; and a cell balancing unit for calculating a balancing reference SOC reflecting a difference in the degree of deterioration of each battery cell on the basis of the SOC and the SOH, and performing balancing for each battery cell on the basis of the balancing reference SOC.

Description

Battery cell balancing system and method

[0001] The present invention relates to a battery cell balancing system and method, and more specifically to a battery cell balancing system and method that performs balancing for each battery cell by reflecting the difference in degradation degree between battery cells.

[0002]

[0003] An Energy Storage System (ESS) is a system that increases energy usage efficiency by storing a large amount of electrical energy and supplying the stored electrical energy when it is needed. An ESS may include a battery system, a Battery Management System (BMS) that manages the battery system by monitoring the voltage, current, temperature, etc. of the battery system, a Power Conversion System (PCS) that performs AC-DC conversion and power distribution functions, and an Energy Management System (EMS) that controls the energy flow of the ESS and collects and manages information on the status of the ESS, thereby providing integrated control of the entire ESS system.

[0004] Typically, an ESS battery system comprises multiple electrically interconnected battery racks, each containing dozens to hundreds of series-connected cells. The cells constituting a single battery rack undergo degradation and characteristic differences due to environmental variations, such as manufacturing processes or operating temperatures. These degradation and characteristic differences lead to voltage imbalances between cells, resulting in unusable capacity corresponding to the voltage imbalance. Cell balancing is performed to resolve these voltage imbalances and increase capacity; however, conventional balancing methods match the voltage by consuming the capacity of the remaining cells based on the cell with the lowest voltage at the rest point. This method of balancing, however, has the problem of failing to account for voltage imbalances caused by differences in degradation between battery cells.

[0005] The information described above disclosed in the background technology of this invention is intended only to enhance understanding of the background of the present invention and may therefore include information that does not constitute prior art.

[0006]

[0007] The problem that the present invention aims to solve is to provide a battery cell balancing system and method that performs balancing for each battery cell by reflecting the difference in degradation degree between battery cells to solve the above-mentioned problems.

[0008] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems can be clearly understood by those skilled in the art from the description of the invention below.

[0009]

[0010] A battery cell balancing system according to one embodiment of the present invention may include: an SOC estimation unit that estimates the State of Charge (SOC) of each battery cell included in a battery assembly; an SOH estimation unit that estimates the State of Health (SOH) of each battery cell; and a cell balancing unit that calculates a balancing reference SOC reflecting the difference in degradation of each battery cell based on the SOC and SOH, and performs balancing for each battery cell based on the balancing reference SOC.

[0011] In one embodiment, the SOC estimation unit can estimate the SOC of each battery cell based on the Open Circuit Voltage (OCV) when the rest state of each battery cell is maintained for a certain period of time.

[0012] In one embodiment, the cell balancing unit can calculate the maximum SOH among the SOHs of each battery cell included in the battery assembly.

[0013] In one embodiment, the cell balancing unit can calculate the SOH deviation relative to the maximum SOH of each battery cell.

[0014] In one embodiment, the cell balancing unit can calculate the SOC deviation of each battery cell based on the SOH deviation of each battery cell.

[0015] In one embodiment, the cell balancing unit has a SOC deviation of each battery cell D SOC,k , the SOH deviation of each battery cell is D SOH,k , the SOC of each battery cell is SOC k In this case, the SOC deviation of each battery cell can be calculated by the following mathematical formula.

[0016] [Mathematical Formula]

[0017]

[0018] In one embodiment, the cell balancing unit can calculate the corrected SOC of each battery cell by adding the SOC deviation of each battery cell to the SOC of each battery cell.

[0019] In one embodiment, the cell balancing unit may determine the smallest value among the corrected SOCs of each battery cell as the balancing reference SOC.

[0020] In one embodiment, the cell balancing unit may determine the balancing performance capacity by subtracting the balancing reference SOC from the corrected SOC of each battery cell.

[0021] In one embodiment, the cell balancing unit can perform balancing for each battery cell by the balancing performance capacity.

[0022] A battery cell balancing method according to one embodiment of the present invention may include: a State of Charge (SOC) estimation step of estimating the State of Charge (SOC) of each battery cell included in a battery assembly through an SOC estimation unit; a State of Health (SOH) estimation step of estimating the State of Health (SOH) of each battery cell through an SOH estimation unit; and a cell balancing step of calculating a balancing reference SOC that reflects the difference in degradation degree of each battery cell based on the SOC and SOH through a cell balancing unit, and performing balancing for each battery cell based on the balancing reference SOC.

[0023] In one embodiment, the SOC estimation step may include a step of estimating the SOC of each battery cell based on the Open Circuit Voltage (OCV) when the rest state of each battery cell is maintained for a certain period of time.

[0024] In one embodiment, the cell balancing step may include a step of calculating the maximum SOH among the SOHs of each battery cell included in the battery assembly.

[0025] In one embodiment, the cell balancing step may further include a step of calculating the SOH deviation relative to the maximum SOH of each battery cell.

[0026] In one embodiment, the cell balancing step may further include a step of calculating the SOC deviation of each battery cell based on the SOH deviation of each battery cell.

[0027] In one embodiment, the cell balancing step is such that the SOC deviation of each battery cell is D SOC,k , the SOH deviation of each battery cell is D SOH,k , the SOC of each battery cell is SOC k In this case, the method may include a step of calculating the SOC deviation of each battery cell using the following mathematical formula.

[0028] [Mathematical Formula]

[0029]

[0030] In one embodiment, the cell balancing step may further include a step of calculating a corrected SOC of each battery cell by adding the SOC deviation of each battery cell to the SOC of each battery cell.

[0031] In one embodiment, the cell balancing step may further include the step of determining the smallest value among the corrected SOCs of each battery cell as the balancing reference SOC.

[0032] In one embodiment, the cell balancing step may further include a step of determining the balancing performance capacity by subtracting the balancing reference SOC from the corrected SOC of each battery cell.

[0033] In one embodiment, the cell balancing step may further include the step of performing balancing for each battery cell by the balancing performance capacity.

[0034]

[0035] According to one embodiment of the present invention, unlike conventional battery cell balancing methods that determine only whether there is a voltage imbalance at a specific point in time and perform balancing based on the minimum voltage cell, the degree of voltage imbalance caused by the difference in degradation between battery cells is identified, and balancing is performed excluding that part, thereby providing excellent balancing effect and increasing capacity by the amount of the balancing part.

[0036] However, the effects obtainable through the present invention are not limited to those described above, and other unmentioned technical effects will be clearly understood by those skilled in the art from the description of the invention below.

[0037]

[0038] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0039] Figure 1 is a graph illustrating voltage imbalance caused by the difference in capacity between battery cells.

[0040] Figure 2 is a graph showing voltage imbalance due to differences in degradation between battery cells.

[0041] FIG. 3 is a schematic diagram illustrating a battery cell balancing system according to one embodiment of the present invention.

[0042] FIGS. 4a to 4c are graphs illustrating simulation results for comparing the state before and after the introduction of a battery cell balancing system according to one embodiment of the present invention.

[0043] FIG. 5 is a flowchart illustrating a battery cell balancing method according to an embodiment of the present invention.

[0044]

[0045] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe their invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0046] Additionally, as used herein, “comprise, include” and / or “comprising, including” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0047] Additionally, to aid in understanding the invention, the attached drawings are not drawn to actual scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be assigned to identical components in different embodiments.

[0048] The statement that two subjects of comparison are 'identical' means that they are 'substantially identical.' Therefore, substantial identity may include deviations considered low in the industry, for example, deviations within 5%. Additionally, the statement that a parameter is uniform in a given area may mean that it is uniform from an average perspective.

[0049] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0050] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0051] The fact that any configuration is placed on the “upper (or lower)” of a component or on the “upper (or lower)” of a component may mean not only that the any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0052] Furthermore, where one component is described as being "on," "connected to," or "coupled to" another component, it should be understood that while the components may be directly connected or coupled to each other, another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "coupled" through another component.

[0053] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Additionally, the use of “may” when describing embodiments of the invention relates to “one or more embodiments of the invention.” Expressions such as “one or more” and “one or more” preceding a list of elements modify the entire list of elements and do not modify individual elements of the list.

[0054] Throughout the specification, “A and / or B” means A, B, or A and B unless specifically stated otherwise, and “C to D” means C or more and D or less, unless specifically stated otherwise.

[0055] When syntax such as "at least one of A, B, and C", "at least one of A, B, or C", "at least one selected from the group of A, B, and C", or "at least one selected from A, B, and C" is used to specify a list of elements A, B, and C, the syntax can refer to any suitable combination.

[0056] The term "use" may be considered synonymous with the term "utilize." As used herein, terms such as "substantially," "about," and similar terms are used as terms of approximation rather than degree, and are intended to account for the inherent variation of a measured or calculated value that would be recognized by a person skilled in the art.

[0057] In this specification, terms such as first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or sections, but these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Accordingly, the first element, component, region, layer, or section discussed below may be named the second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0058] Spatial relative terms such as "beneath," "below," "lower," "above," and "upper" may be used in the specification for ease of description to explain the relationship between one element or feature and other element(s) or feature(s) as illustrated in the drawings. Spatially relative positions are to be understood as encompassing different orientations of the device in use or operation, in addition to the orientations depicted in the figures. For example, if the device in the drawing is inverted, the other element is understood as "below" or "below," and the described element is understood as "above" or "upper" of the other element. Thus, the term "below" may encompass both the up and down directions.

[0059] The terms used in this specification are for describing embodiments of the invention and are not intended to limit the invention.

[0060]

[0061] The present invention will be described in detail below with reference to the attached drawings.

[0062]

[0063] Figure 1 is a graph showing voltage imbalance due to capacity difference between battery cells, and Figure 2 is a graph showing voltage imbalance due to degradation difference between battery cells.

[0064] Referring to FIGS. 1 and 2, cell balancing is performed to increase capacity by resolving voltage imbalances between battery cells constituting a battery assembly, for example, a battery rack, and conventional balancing is performed by consuming the capacity of the remaining cells based on the minimum voltage cell at the rest time to match the voltage.

[0065] However, there are two cases of voltage imbalance between cells: voltage imbalance caused by a difference in actual capacity as shown in Fig. 1, and voltage imbalance caused by a difference in the degree of degradation between cells as shown in Fig. 2. In the case of voltage imbalance caused by a difference in capacity between cells as shown in Fig. 1, it can be seen that the voltage difference between the charging and discharging of the battery cells is maintained. However, in the case of voltage imbalance caused by a difference in the degree of degradation between cells as shown in Fig. 2, it can be seen that due to the difference in the degree of degradation between cells, the battery cell that had a minimum voltage during discharge has a maximum voltage after charging.

[0066] Accordingly, the voltage imbalance caused by the difference in capacity between cells in Fig. 1 can be increased by the capacity of the balancing process, but the voltage imbalance caused by the difference in degradation between cells in Fig. 2 is not resolved even if balancing is performed; rather, unnecessary balancing is performed, and there may be a decrease in capacity by the amount of balancing.

[0067] Therefore, if balancing is performed by considering only the voltage imbalance situation at a specific point in time, as in conventional cell balancing methods, it is impossible to know whether it corresponds to the case of Fig. 1 or the case of Fig. 2, so there is a problem in that balancing is performed even in a situation where it is ineffective, as in the case of Fig. 2.

[0068]

[0069] FIG. 3 is a schematic diagram illustrating a battery cell balancing system according to one embodiment of the present invention.

[0070] Referring to FIG. 3, a battery cell balancing system (100) according to one embodiment of the present invention may be connected to tens to hundreds of battery cells (11) in a battery assembly (10) to perform balancing between each battery cell. In one embodiment, the battery assembly (10) refers to an assembly formed by gathering a plurality of batteries, and may be a concept that includes a battery module, a battery pack, and a battery rack. In one embodiment, the battery cell balancing system (100) according to one embodiment of the present invention may be included in a Battery Management System (BMS). The BMS manages the battery assembly (10), such as by monitoring the voltage, current, temperature, etc. of the battery assembly (10), and can monitor the State of Charge (SOC), State of Health (SOH), etc. In addition, the BMS can perform control functions (e.g., temperature control, cell balancing control, charge / discharge control, etc.) and protection functions (e.g., over-discharge, over-charge, over-current protection, etc.) based on the results of the status monitoring.

[0071] A battery cell (11) that is subject to charging control of a battery cell balancing system (100) according to one embodiment of the present invention is a battery cell capable of charging and discharging, in which an electrode assembly having a positive / separator / negative structure is impregnated with a lithium electrolyte and sealed inside a battery case. Such electrode assemblies generally have a jelly-roll structure (wound type) in which a long sheet-type positive and negative electrode, with active material coated on both sides, is wound in a circular shape with a separator interposed therebetween, and a stack type (stacked type) structure in which a plurality of positive and negative electrodes of a predetermined size, with active material coated on both sides, are sequentially stacked with a separator interposed therebetween.

[0072] Depending on the shape of the battery, cylindrical and prismatic types in which the electrode assembly is embedded in a metal can battery case, and pouch-type battery cells in which the electrode assembly is embedded in an aluminum laminate sheet battery case can all be used as battery cells (11).

[0073] A battery cell balancing system (100) according to one embodiment of the present invention may include an SOC estimation unit (110), an SOH estimation unit (120), and a cell balancing unit (130).

[0074] The SOC estimation unit (110) estimates the State of Charge (SOC) of each battery cell (11) included in the battery assembly (10). In one embodiment, the SOC estimation unit (110) can estimate the SOC of each battery cell (11) based on the Open Circuit Voltage (OCV) when the rest state of each battery cell (11) is maintained for a certain period of time. The OCV is the battery voltage in a stable state where no load is applied, and since the OCV and SOC have a constant relationship, the SOC can be estimated by drawing an OCV-SOC graph and matching it to a SOC table. The voltage measurement method for estimating the SOC based on the OCV is one of the methods by which the SOC estimation unit (110) estimates the SOC, but is not limited thereto, and the SOC estimation unit (110) can estimate the SOC in various ways, such as the total current integration method, chemical measurement method, and pressure measurement method.

[0075] The SOH estimation unit (120) estimates the State of Health (SOH) of each battery cell (11). The SOH estimation unit (120) can estimate the SOH in various ways, including a direct measurement method that directly measures battery parameters such as impedance, internal resistance, OCV, and charge / discharge current, a model-based method that uses a battery model developed to evaluate the battery aging process, and a data-based method that uses a learning algorithm by continuously collecting a large amount of battery parameters.

[0076] The cell balancing unit (130) calculates a balancing reference SOC that reflects the difference in the degree of degradation of each battery cell (11) based on SOC and SOH, and performs balancing for each battery cell (11) based on the balancing reference SOC. In one embodiment, the cell balancing unit (130) calculates the maximum SOH among the SOHs of each battery cell (11) included in the battery assembly (10). Then, the cell balancing unit (130) calculates the SOH deviation relative to the maximum SOH of each battery cell (11). Then, the cell balancing unit (130) calculates the SOC deviation of each battery cell (11) based on the SOH deviation of each battery cell (11). At this time, the calculated SOC deviation of each battery cell (11) is the SOC deviation due to degradation of each battery cell (11) and corresponds to the SOC deviation for which balancing will not be performed. In one embodiment, the cell balancing unit (130) has a SOC deviation of each battery cell (11) D SOC,k , the SOH deviation of each battery cell (11) is D SOH,k , the SOC of each battery cell (11) is SOC k In this case, the SOC deviation of each battery cell (11) can be calculated by the following mathematical formula.

[0077]

[0078]

[0079]

[0080] In this way, when the SOC deviation of each battery cell (11) is calculated, the cell balancing unit (130) calculates the corrected SOC of each battery cell (11) by adding the SOC deviation of each battery cell (11) to the SOC of each battery cell (11). Then, the cell balancing unit (130) determines the smallest value among the corrected SOCs of each battery cell (11) as the balancing reference SOC. Then, the cell balancing unit (130) determines the value obtained by subtracting the balancing reference SOC from the corrected SOC of each battery cell (11) as the balancing performance capacity, and performs balancing for each battery cell (11) by the balancing performance capacity.

[0081]

[0082] Below, a cell balancing process by a battery cell balancing system (100) according to an embodiment of the present invention will be described according to the SOH and SOC conditions of Tables 1 and 2.

[0083]

[0084] Cell 1 Cell 2 Cell 3 Cell 4 SOH (%) 90 95 100 100 Current SOC (%) 40 45 55 55

[0085] Referring to Table 1, the SOC estimation unit (110) estimates the SOC of each battery cell (11) included in the battery assembly (10). At this time, the SOC of each battery cell (11) is 40% for cell 1, 45% for cell 2, 55% for cell 3, and 55% for cell 4.

[0086] The SOH estimation unit (120) estimates the SOH of each battery cell (11), and the cell balancing unit (130) calculates the maximum SOH among the SOHs of each battery cell (11) included in the battery assembly (10). At this time, the maximum SOH is 100%.

[0087] The cell balancing unit (130) calculates the SOH deviation relative to the maximum SOH of each battery cell (11). At this time, the SOH deviation relative to the maximum SOH of each battery cell (11) is 10% for cell 1, 5% for cell 2, 0% for cell 3, and 0% for cell 4.

[0088] And the cell balancing unit (130) calculates the SOC deviation of each battery cell (11) corresponding to the SOC deviation due to degradation of each battery cell (11) by the above mathematical formula 1. At this time, the SOC deviation of each battery cell (11) is 1% = 10%*(50%-40%) for cell 1, 0.25% = 5%*(50%-45%) for cell 2, 0% for cell 3, and 0% for cell 4.

[0089] When the SOC deviation of each battery cell (11) is calculated, the cell balancing unit (130) calculates the corrected SOC of each battery cell (11) by adding the SOC deviation of each battery cell (11) to the SOC of each battery cell (11). At this time, the corrected SOC of each battery cell (11) is 41% for cell 1, 45.25% for cell 2, 55% for cell 3, and 55% for cell 4.

[0090] Then, the cell balancing unit (130) determines the smallest value among the corrected SOCs of each battery cell (11) as the balancing reference SOC. At this time, the balancing reference SOC is 41%, which is the SOC of cell 1, the smallest value.

[0091] Then, the cell balancing unit (130) determines the balancing performance capacity by subtracting the balancing reference SOC from the corrected SOC of each battery cell (11). At this time, cell 1 is 0%, cell 2 is 4.25%, cell 3 is 14%, and cell 4 is 14%.

[0092] When the balancing performance capacity is determined, the cell balancing unit (130) performs balancing for each battery cell (11) by the balancing performance capacity. At this time, after balancing, the SOC is 40% for cell 1, 40.75% for cell 2, 41% for cell 3, and 41% for cell 4.

[0093]

[0094] Cell 1 Cell 2 Cell 3 Cell 4 SOH (%) 90 95 100 100 Current SOC (%) 100 98 95 95

[0095] Referring to Table 2, the SOC estimation unit (110) estimates the SOC of each battery cell (11) included in the battery assembly (10). At this time, the SOC of each battery cell (11) is 100% for cell 1, 98% for cell 2, 95% for cell 3, and 95% for cell 4.

[0096] The SOH estimation unit (120) estimates the SOH of each battery cell (11), and the cell balancing unit (130) calculates the maximum SOH among the SOHs of each battery cell (11) included in the battery assembly (10). At this time, the maximum SOH is 100%.

[0097] The cell balancing unit (130) calculates the SOH deviation relative to the maximum SOH of each battery cell (11). At this time, the SOH deviation relative to the maximum SOH of each battery cell (11) is 10% for cell 1, 5% for cell 2, 0% for cell 3, and 0% for cell 4.

[0098] And the cell balancing unit (130) calculates the SOC deviation of each battery cell (11) corresponding to the SOC deviation due to degradation of each battery cell (11) by the above mathematical formula 1. At this time, the SOC deviation of each battery cell (11) is -5% = 10%*(50%-100%) for cell 1, -2.4% = 5%*(50%-98%) for cell 2, 0% for cell 3, and 0% for cell 4.

[0099] When the SOC deviation of each battery cell (11) is calculated, the cell balancing unit (130) calculates the corrected SOC of each battery cell (11) by adding the SOC deviation of each battery cell (11) to the SOC of each battery cell (11). At this time, the corrected SOC of each battery cell (11) is 95% for cell 1, 95.6% for cell 2, 95% for cell 3, and 95% for cell 4.

[0100] Then, the cell balancing unit (130) determines the smallest value among the corrected SOCs of each battery cell (11) as the balancing reference SOC. At this time, the balancing reference SOC is 95%, which is the SOC of cell 1, the smallest value.

[0101] Then, the cell balancing unit (130) determines the balancing performance capacity by subtracting the balancing reference SOC from the corrected SOC of each battery cell (11). At this time, cell 1 is 0%, cell 2 is 0.6%, cell 3 is 0%, and cell 4 is 0%.

[0102] When the balancing performance capacity is determined, the cell balancing unit (130) performs balancing for each battery cell (11) by the balancing performance capacity. At this time, after balancing, the SOC is 100% for cell 1, 97.4% for cell 2, 95% for cell 3, and 95% for cell 4.

[0103]

[0104] In the case of performing balancing based on a conventional minimum voltage cell, the SOC of the entire cell becomes uniformly 95% when based on the SOC of cell 3, which is the minimum voltage cell. However, according to the battery cell balancing system (100) according to one embodiment of the present invention, cell 1 can secure an additional 5% capacity and cell 2 can secure an additional 2.4% capacity.

[0105]

[0106] FIGS. 4a to 4c are graphs illustrating simulation results for comparing the state before and after the introduction of a battery cell balancing system according to one embodiment of the present invention.

[0107] Referring to Fig. 4a, this is a graph showing the voltage change between battery cells before balancing is performed. As shown in Fig. 4a, balancing is performed when the battery cell with SOH 100% and the battery cell with SOH 90% are fully charged.

[0108] Referring to FIG. 4b, this is a graph showing the voltage change between battery cells before the introduction of a battery cell balancing system (100) according to one embodiment of the present invention. As shown in FIG. 4b, when balancing is performed at the time of full charge, since balancing is performed based on the minimum voltage cell, the deviation due to the SOH difference between battery cells is maintained even after balancing is performed, and the capacity is wasted by the capacity of the balancing.

[0109] Referring to FIG. 4c, this is a graph illustrating the voltage change between battery cells after the introduction of a battery cell balancing system (100) according to one embodiment of the present invention. As shown in FIG. 4c, the voltage difference between battery cells that occurs at the full charge point after balancing is a portion that occurs due to capacity difference, and it can be seen that there is no waste of capacity because balancing is not performed uniformly based on the cell with the lower charge capacity.

[0110]

[0111] FIG. 5 is a flowchart illustrating a battery cell balancing method according to an embodiment of the present invention.

[0112] As illustrated in FIG. 5, a battery cell balancing method according to one embodiment of the present invention may include steps S210 to S230.

[0113] Step S210 is a SOC estimation step that estimates the SOC of each battery cell included in the battery assembly through the SOC estimation unit. In one embodiment, Step S210 may include a step of estimating the SOC of each battery cell based on OCV when the standby state of each battery cell is maintained for a certain period of time.

[0114] Step S220 is an SOH estimation step that estimates the SOH of each battery cell through the SOH estimation unit.

[0115] Step S230 is a cell balancing step that calculates a balancing reference SOC reflecting the difference in the degree of degradation of each battery cell based on SOC and SOH through a cell balancing unit, and performs balancing for each battery cell based on the balancing reference SOC. In one embodiment, Step S230 may include a step of calculating the maximum SOH among the SOHs of each battery cell included in the battery assembly and calculating the SOH deviation relative to the maximum SOH of each battery cell. Additionally, Step S230 may include a step of calculating the SOC deviation of each battery cell based on the SOH deviation of each battery cell, and calculating the corrected SOC of each battery cell by adding the SOC deviation of each battery cell to the SOC of each battery cell. Additionally, step S230 may include the step of determining the smallest value among the corrected SOCs of each battery cell as the balancing reference SOC, determining the value obtained by subtracting the balancing reference SOC from the corrected SOC of each battery cell as the balancing performance capacity, and performing balancing for each battery cell by the balancing performance capacity.

[0116]

[0117] The battery cell balancing method according to one embodiment of the present invention described above has been explained with reference to the flowchart presented in the drawings. For simplicity of explanation, the method has been illustrated and described in a series of blocks; however, the present invention is not limited to the order of said blocks, and some blocks may occur in a different order or simultaneously with other blocks as illustrated and described herein, and various other branches, flow paths, and sequences of blocks that achieve the same or similar results may be implemented. Furthermore, not all illustrated blocks may be required for the implementation of the method described herein.

[0118]

[0119] Meanwhile, in the description with reference to FIG. 5, each step may be further divided into additional steps or combined into fewer steps according to an embodiment of the present invention. Also, some steps may be omitted as necessary, and the order between steps may be changed. Furthermore, even if other omitted details are included, the contents of FIG. 1 to 4c may be applied to the contents of FIG. 5. Also, the contents of FIG. 5 may be applied to the contents of FIG. 1 to 4c.

[0120]

[0121] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

1. A State of Charge (SOC) estimation unit that estimates the State of Charge (SOC) of each battery cell included in a battery assembly; A SOH estimation unit for estimating the State of Health (SOH) of each of the above battery cells; and A battery cell balancing system characterized by including a cell balancing unit that calculates a balancing reference SOC reflecting the difference in degradation degree of each battery cell based on the above SOC and SOH, and performs balancing for each battery cell based on the balancing reference SOC.

2. In Paragraph 1, The above SOC estimation unit is, A battery cell balancing system characterized by estimating the SOC of each battery cell based on the Open Circuit Voltage (OCV) when the rest state of each battery cell is maintained for a certain period of time.

3. In Paragraph 1, The cell balancing unit above is, A battery cell balancing system characterized by calculating the maximum SOH among the SOHs of each battery cell included in the battery assembly.

4. In Paragraph 3, The cell balancing unit above is, A battery cell balancing system characterized by calculating the SOH deviation relative to the maximum SOH of each of the above battery cells.

5. In Paragraph 4, The cell balancing unit above is, A battery cell balancing system characterized by calculating the SOC deviation of each battery cell based on the SOH deviation of each battery cell.

6. In Paragraph 5, The cell balancing unit above is, The SOC deviation of each battery cell is D SOC,k , the SOH deviation of each battery cell is D SOH,k , the SOC of each battery cell is SOC k A battery cell balancing system characterized by calculating the SOC deviation of each battery cell according to the following mathematical formula in the case where... [Mathematical Formula] 7. In Paragraph 5, The cell balancing unit above is, A battery cell balancing system characterized by calculating a corrected SOC of each battery cell by adding the SOC deviation of each battery cell to the SOC of each battery cell.

8. In Paragraph 7, The cell balancing unit above is, A battery cell balancing system characterized by determining the smallest value among the corrected SOCs of each of the above battery cells as the balancing reference SOC.

9. In Paragraph 8, The cell balancing unit above is, A battery cell balancing system characterized by determining the balancing performance capacity by subtracting the balancing reference SOC from the corrected SOC of each battery cell.

10. In Paragraph 9, The cell balancing unit above is, A battery cell balancing system characterized by performing balancing for each battery cell to the extent of the balancing performance capacity.

11. A State of Charge (SOC) estimation step for estimating the State of Charge of each battery cell included in a battery assembly through an SOC estimation unit; A SOH estimation step for estimating the State of Health (SOH) of each battery cell through a SOH estimation unit; and A battery cell balancing method characterized by including a cell balancing step of calculating a balancing reference SOC that reflects the difference in the degree of degradation of each battery cell based on the SOC and SOH through a cell balancing unit, and performing balancing for each battery cell based on the balancing reference SOC.

12. In Paragraph 11, The above SOC estimation step is, A battery cell balancing method characterized by including a step of estimating the SOC of each battery cell based on the Open Circuit Voltage (OCV) when the rest state of each battery cell is maintained for a certain period of time.

13. In Paragraph 11, The cell balancing step described above is, A battery cell balancing method characterized by including the step of calculating the maximum SOH among the SOHs of each battery cell included in the battery assembly.

14. In Paragraph 13, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of calculating the SOH deviation relative to the maximum SOH of each of the above battery cells.

15. In Paragraph 14, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of calculating the SOC deviation of each battery cell based on the SOH deviation of each battery cell.

16. In Paragraph 15, The cell balancing step described above is, The SOC deviation of each battery cell is D SOC,k , the SOH deviation of each battery cell is D SOH,k , the SOC of each battery cell is SOC k A battery cell balancing method characterized by including the step of calculating the SOC deviation of each battery cell according to the following mathematical formula in the case where. [Mathematical Formula] 17. In Paragraph 15, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of calculating a corrected SOC of each battery cell by adding the SOC deviation of each battery cell to the SOC of each battery cell.

18. In Paragraph 17, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of determining the smallest value among the corrected SOCs of each battery cell as the balancing reference SOC.

19. In Paragraph 18, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of determining the value obtained by subtracting the balancing reference SOC from the corrected SOC of each battery cell as the balancing performance capacity.

20. In Paragraph 19, The cell balancing step described above is, A battery cell balancing method characterized by further including the step of performing balancing for each battery cell by the balancing performance capacity.

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