Cell balancing method and battery system for providing the method

Abstract

To provide a cell balancing method for raising accuracy of cell balancing by determining necessity of the cell balancing according to a reference value corresponding to cell capacity and a battery system for providing the method.SOLUTION: In a battery system, a main control circuit estimates a cell capacity of each of a plurality of battery cells on the basis of a battery including a plurality of battery cells, a cell monitoring IC which measures a cell voltage of each of the plurality of battery cells, a current sensor which measures a battery current flowing to the battery, the cell voltage, and the battery current, extracts a minimum cell capacity from the cell capacity of each of the plurality of battery cells, determines a balancing reference value corresponding to the minimum cell capacity, and determines necessity of cell balancing for each of the plurality of battery cells on the basis of the balancing reference value.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0171884, filed December 3, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a cell balancing method for performing customized cell balancing according to cell capacity (Cell SOC, Charge of Charge) and a battery system that provides the method. [Background technology]

[0003] Electric vehicles (EVs) and hybrid vehicles (HVs) use a battery pack as an energy source to drive a motor, which may include multiple battery cells connected in series and / or parallel.

[0004] When a battery pack is used for a long period of time, the degree of aging and internal resistance of each battery cell may change, resulting in cell deviation between the battery cells. At this time, cell deviation can indicate deviation in cell capacity (SOC, State of Charge) and deviation in cell voltage. As cell deviation increases, overcharging or over-discharging may occur, which may reduce the overall capacity of the battery pack and shorten its lifespan.

[0005] To solve this problem, battery systems perform cell balancing to reduce cell deviation. The battery system calculates a cell balancing current value based on an open circuit voltage (OCV) value and performs cell balancing for a balancing time calculated based on the balancing current value.

[0006] Meanwhile, the range of change in cell voltage may vary depending on the cell capacity. For example, in the case of a battery cell with a very small or large cell capacity, the change in cell voltage value according to the change in cell capacity may be large. That is, in the process of cell balancing, in the case of a battery cell with a large or small cell capacity, the cell voltage may drop significantly and the balancing current value may also be reduced. As a result, insufficient cell balancing may be performed for a battery cell with a large or small cell capacity within a preset balancing time. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a cell balancing method that performs optimal cell balancing according to the cell capacity (SOC, Charge of Charge) of battery cells to reduce cell deviation, and a battery system that provides the method. [Means for solving the problem]

[0008] According to one aspect of the present invention, a battery system includes a battery including a plurality of battery cells, a cell monitoring IC that measures a cell voltage of each of the plurality of battery cells, a current sensor that measures a battery current flowing through the battery, and a main control circuit that estimates a cell capacity of each of the plurality of battery cells based on the cell voltage and the battery current, extracts a minimum cell capacity from each of the plurality of battery cells, determines a balancing reference value corresponding to the minimum cell capacity, and determines the need for cell balancing for each of the plurality of battery cells based on the balancing reference value.

[0009] The main control circuit can classify the entire cell capacitance range into a plurality of SOC ranges according to a predetermined criterion, set a range reference value, which is a starting condition for cell balancing, for each of the plurality of SOC ranges according to the predetermined criterion, select an SOC range to which the minimum cell capacitance belongs from the plurality of SOC ranges, and determine the range reference value corresponding to the selected SOC range as the balancing reference value.

[0010] The main control circuit may classify the entire range of the cell capacity into the plurality of SOC ranges based on a point where a ratio of a cell voltage to a cell capacity is changed, and set the range reference value based on the ratio.

[0011] The main control circuit may calculate a difference between a cell capacity and the minimum cell capacity for each of the plurality of battery cells, and determine that cell balancing is required for a battery cell whose difference exceeds the balancing reference value.

[0012] According to another aspect of the present invention, the battery system further includes a cell balancing circuit including a plurality of switches and a plurality of resistors, and controlling a switching operation according to a corresponding switching signal among at least one switching signal supplied from the cell monitoring IC to perform cell balancing of the battery cells, and the cell monitoring IC discharges a battery cell determined to be a target for cell balancing among the plurality of battery cells through the cell balancing circuit according to a cell balancing control signal transferred from the main control circuit.

[0013] The main control circuit can calculate a balancing time based on the cell capacity of the battery cell determined to be the target of cell balancing, the difference between the cell capacity and the minimum cell capacity, and the cell voltage value, and transmit the cell balancing control signal including information about the balancing time to the cell monitoring IC.

[0014] According to another aspect of the present invention, a cell balancing method includes determining a balancing reference value based on a minimum cell capacity among the respective cell capacities of a plurality of battery cells; calculating a difference between the cell capacity of each of the plurality of battery cells and the minimum cell capacity, and comparing the difference with the balancing reference value to determine whether cell balancing is necessary for each of the plurality of battery cells; and, if it is determined that cell balancing is necessary for at least one battery cell, performing cell balancing on the battery cells determined to be targets for cell balancing.

[0015] The step of determining the balancing reference value may include the steps of: estimating a cell capacity of each of the plurality of battery cells based on a cell voltage of each of the plurality of battery cells; extracting a minimum cell capacity from each of the cell capacities of the plurality of battery cells; selecting an SOC range to which the minimum cell capacity belongs from a plurality of SOC ranges formed by classifying entire ranges of cell capacities according to a predetermined criterion; and determining a range reference value corresponding to the selected SOC range as the balancing reference value.

[0016] The plurality of SOC ranges are configured by classifying the entire range of the cell capacity based on the point where the ratio of the cell voltage to the cell capacity changes, and the range reference value can be set based on the ratio of the cell voltage to the cell capacity corresponding to the plurality of SOC ranges.

[0017] The cell balancing step may include calculating a balancing time based on the cell capacity of the battery cell determined to be the target of cell balancing, a difference between the cell capacity and the minimum cell capacity, and a cell voltage value, and performing cell balancing of the corresponding battery cell during the balancing time.

[0018] The determining whether cell balancing is necessary may determine that battery cells whose difference value exceeds the balancing reference value are to be subjected to cell balancing. [Effects of the Invention]

[0019] The present invention can improve the accuracy of cell balancing by determining the need for cell balancing according to a reference value corresponding to the cell capacity. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating a battery system that provides a cell balancing method according to an embodiment. [Figure 2] 10 is a diagram illustrating an example of a graph for explaining a reference value determined in accordance with a cell capacity according to an embodiment; [Figure 3] 1 is a flowchart illustrating a cell balancing method according to one embodiment. [Figure 4] 4 is a flowchart illustrating in detail the balancing reference value determination step S100 of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. Identical or similar components will be designated by the same or similar reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "section" used in the following description for components are given or used interchangeably solely for ease of description and do not have any distinct meanings or functions. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related prior art is deemed to obscure the gist of the embodiments disclosed herein, such a detailed description will be omitted. Furthermore, the accompanying drawings are intended to facilitate understanding of the embodiments disclosed herein, and the accompanying drawings should not be construed as limiting the technical concepts disclosed herein, and should be understood to include all modifications, equivalents, or alternatives within the concept and technical scope of the present invention.

[0022] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0023] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that it may be directly coupled or connected to the other component, but that there may be additional components in between. On the other hand, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0024] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but should be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0025] FIG. 1 is a diagram illustrating a battery system that provides a cell balancing method according to an embodiment, and FIG. 2 is a diagram illustrating an example of a graph illustrating a reference value determined according to a cell capacity according to an embodiment.

[0026] As shown in FIG. 1 , the battery system 1 includes a battery 2 , a BMS 3 , a relay 11 , and a current sensor 12 .

[0027] The battery 2 includes a plurality of battery cells connected in series / parallel and can supply necessary power to an external device. In FIG. 1, the battery 2 includes a plurality of battery cells Cell1-Celln connected in series and is connected between two output terminals OUT1 and OUT2 of the battery system 1. A relay 11 is connected between the positive terminal of the battery system 1 and the output terminal OUT1, and a current sensor 12 is connected between the negative terminal of the battery system 1 and the output terminal OUT2. The configuration and the connection relationship between the configurations shown in FIG. 1 are merely examples, and the present invention is not limited thereto.

[0028] The relay 11 controls the electrical connection between the battery system 1 and an external device. When the relay 11 is turned on, the battery system 1 and the external device are electrically connected to each other to perform charging or discharging. When the relay 11 is turned off, the battery system 1 and the external device are electrically disconnected. The external device may be a load or a charger.

[0029] The current sensor 12 is connected in series to a current path between the battery 2 and an external device. The current sensor 12 measures the current flowing through the battery 2, i.e., the charging current and discharging current, and can transmit the measurement result to the BMS 3.

[0030] The BMS 3 includes a cell balancing circuit 10, a cell monitoring IC 20, and a main control circuit 30.

[0031] The cell balancing circuit 10 includes multiple switches SW1-SWn and multiple resistors R1-Rn. Each of the multiple switches SW1-SWn performs a switching operation in accordance with a corresponding one of multiple switching signals SC[1]-SC[n] supplied from the cell monitoring IC 20. For each of the multiple battery cells Cell1-Celln, a corresponding switch SWi and resistor Ri are connected in series between the positive and negative electrodes of the corresponding cell Cell1. When the switch SWi is turned on, a discharge path is formed between the corresponding cell Cell1, the switch SWi, and the resistor Ri, and the corresponding cell Cell1 is discharged. Here, i is a natural number from 1 to n.

[0032] The cell monitoring IC 20 is electrically connected to the positive and negative electrodes of each of the plurality of battery cells Cell1-Celln and measures the cell voltage. The current value (hereinafter referred to as battery current) measured by the current sensor 12 can be transmitted to the cell monitoring IC 20. The cell monitoring IC 20 transmits information regarding the measured cell voltage and battery current to the main control circuit 30. Specifically, the cell monitoring IC 20 measures the cell voltage of each of the plurality of battery cells Cell1-Celln at predetermined intervals during a rest period when no charging or discharging occurs, and transmits the measurement results to the main control circuit 30.

[0033] The cell monitoring IC 20 can discharge cells targeted for cell balancing among the plurality of battery cells Cell1-Celln via the cell balancing circuit 10 in accordance with a cell balancing control signal transferred from the main control circuit 30. For example, the cell monitoring IC 20 can generate a plurality of switching signals SC[1] to SC[n] in accordance with the cell balancing control signal from the main control circuit 30. Each of the switching signals SC[1] to SC[n] can control the switching operation of a corresponding switch SWi. When an on-level switching signal SC[i] is supplied to the corresponding switch SWi, the switch SWi is turned on and the corresponding cell Celli is discharged.

[0034] The main control circuit 30 determines a balancing reference value based on the minimum cell capacity (min SOC) among the cell capacities Csoc of the plurality of battery cells Cell1-Celln. At this time, the balancing reference value may be a reference value for determining (judging) which of the plurality of battery cells Cell1-Celln is to be subjected to cell balancing.

[0035] The main control circuit 30 can classify the entire range of cell capacitance Csoc into a plurality of SOC ranges according to a predetermined criterion, and set a range reference value, which is a cell balancing start condition for each of the plurality of SOC ranges, according to the predetermined criterion. In addition, the main control circuit 30 can select an SOC range to which the minimum cell capacitance (min SOC) belongs from the plurality of SOC ranges, and determine the range reference value corresponding to the selected SOC range as the balancing reference value.

[0036] 2, the main control circuit 30 can divide the entire cell capacity range (0% to 100%) into a plurality of SOC ranges A, B, and C according to a predetermined criterion. For example, in FIG. 2, the main control circuit 30 can divide the entire cell capacity range (0% to 100%) into a first SOC range (0% to less than 16%), a second SOC range (16% to less than 51%), and a third SOC range (51% to 100%) according to the slope of a capacity-voltage correlation graph (SOC-Voltage Correlation Graph, hereinafter referred to as S-VCG). The capacity-voltage correlation graph (S-VCG) is a graph that displays cell voltage values ​​corresponding to cell capacity Csoc.

[0037] According to one embodiment, the main control circuit 30 may divide the entire range of the cell capacitance Csoc into a plurality of SOC ranges A, B, and C based on points at which the ratio of the cell voltage to the cell capacitance Csoc is changed. The points at which the ratio of the cell voltage to the cell capacitance Csoc is changed may be points at which the slope value of the capacitance-voltage relationship graph (S-VCG) is changed.

[0038] 2, the slope of the graph changes at a cell capacity Csoc value of approximately 16%, and then changes again at approximately 51%. Specifically, the cell voltage change (i.e., the slope of the graph) is large in the first SOC range (0% or more but less than 16%) and the third SOC range (51% or more but less than 100%), while the cell voltage change (i.e., the slope of the graph) is small in the second SOC range (16% or more but less than 51%).

[0039] The section reference value may be a condition for determining battery cells that require cell balancing or a starting condition (reference value) for performing cell balancing. That is, the section reference value may be a condition for determining whether or not cell balancing of battery cells is required in each of a plurality of SOC sections. The balancing reference value may be a section reference value corresponding to a selected SOC section from the plurality of SOC sections.

[0040] 3, for example, the interval reference value for each of the first SOC interval A and the third SOC interval C may be 1.5%, and the interval reference value for the second SOC interval B may be 3%. Furthermore, when the second SOC interval B is selected using the method described below, the interval reference value of 3% for the second SOC interval B may be determined as the balancing reference value.

[0041] The main control circuit 30 determines the necessity of cell balancing for each of the plurality of battery cells Cell1-Celln using the method described below, and if the determination result indicates that there is at least one battery cell that requires cell balancing (hereinafter, referred to as a cell balancing target), the main control circuit 30 can perform cell balancing. A more detailed description will be given below with reference to Figures 3 and 4.

[0042] FIG. 3 is a flowchart illustrating a cell balancing method according to an embodiment, and FIG. 4 is a flowchart illustrating in detail the balancing reference value determination step (S100) of FIG.

[0043] Hereinafter, a cell balancing method and a battery system that provides the method will be described with reference to FIGS.

[0044] Referring to FIG. 3, first, the main control circuit 30 determines a balancing reference value, which is a starting condition for cell balancing (S100).

[0045] The balancing reference value may be a starting condition (reference value) for determining whether cell balancing is necessary for each of the plurality of battery cells Cell1-Celln. According to one embodiment, the main control circuit 30 may determine a balancing reference value corresponding to the cell capacity Csoc of the plurality of battery cells Cell1-Celln, rather than a fixed balancing reference value.

[0046] 3 and 4, in step S100, the main control circuit 30 estimates the cell capacity (SOC, Charge of Charge) for each of the plurality of battery cells Cell1-Celln based on at least one of the cell voltage and the battery current for each balancing period (S110).

[0047] The balancing period is a period during which cell balancing is performed, and may be a preset time period, but is not limited to this. The balancing period may include a rest period during which the battery 2 is not charged or discharged. For example, the main control circuit 30 may estimate the cell capacity (hereinafter referred to as Csoc) of each of the plurality of battery cells Cell1-Celln for each preset balancing period or for each rest period using various conventionally known methods.

[0048] In step S100, the main control circuit 30 extracts the minimum cell capacity (min SOC) from the cell capacities Csoc of each of the plurality of battery cells Cell1-Celln (S130).

[0049] In step S100, the main control circuit 30 selects an SOC section including a minimum cell capacitance (min SOC) from among a plurality of SOC sections that are configured by classifying all sections of the cell capacitance according to a predetermined criterion (S150).

[0050] In step S100, the main control circuit 30 determines the section reference value corresponding to the selected SOC section as the balancing reference value (S170).

[0051] For example, the battery 2 includes first to fourth battery cells Cell1 to Cell4, and the first to fourth cell capacities C soc_1 , C soc_2 , C soc_3 , C soc_4 2, the section reference values ​​corresponding to the first SOC section A and the third SOC section C are assumed to be 1.5%, and the section reference value corresponding to the second SOC section B is assumed to be 3%. The main control circuit 30 controls the first to fourth cell capacitances C soc_1 , C soc_2 , C soc_3 , C soc_4 The first cell capacitance C soc_1 As shown in FIG. 2, the main control circuit 30 extracts the first cell capacitance C soc_1 The second SOC zone B, which includes the value 26%, is selected. The main control circuit 30 can determine the zone reference value 3% corresponding to the second SOC zone B as the balancing reference value.

[0052] Next, the main control circuit 30 determines whether cell balancing is necessary for each of the plurality of battery cells Cell1-Celln (S200).

[0053] The main control circuit 30 calculates the difference between the cell capacity of each of the plurality of battery cells Cell1-Celln and the minimum cell capacity (min SOC). The main control circuit 30 can determine the battery cell whose difference exceeds the balancing reference value as a cell balancing target.

[0054] For example, the first to fourth cell capacitances C soc_1 , C soc_2 , C soc_3 , C soc_4 When the battery voltages are 26%, 29%, 30%, and 31%, the difference values ​​of the first to fourth battery cells Cell1-Cell4 are 0%, 3%, 4%, and 5%, respectively. The main control circuit 30 can determine that the second to fourth battery cells Cell2-Cell4 whose difference values ​​exceed the balancing reference value (3%) are to be subjected to cell balancing. In this case, the balancing reference value (3%) is the balancing reference value determined in step S100.

[0055] Next, if the determination result indicates that cell balancing is necessary (S200, Yes), the main control circuit 30 performs cell balancing on the battery cells determined to be subject to cell balancing (S300).

[0056] In step S300, the main control circuit 30 determines a balancing time T based on the cell capacity of the battery cell determined to be the target of cell balancing, the difference between the cell capacity and the minimum cell capacity, and the cell voltage value. B Calculate.

[0057] Balancing time T B is the time required to balance the battery cells. B can be calculated by the following equations (1) and (2). For example, the main control circuit 30 calculates the balancing current I B Calculate the value and calculate the balancing time T according to the following formula (2): B can be calculated.

[0058] [Number 1] TIFF2025157289000002.tif34132

[0059] According to the above formula (1), the main control circuit 30 calculates the cell voltage V C value and balancing resistor R B Balancing current based on the value I B The value can be calculated by referring to Figure 1. C can correspond to the cell voltages of multiple battery cells Cell1-Celln, and the balancing resistor R B can correspond to each of the plurality of resistors R1-Rn. That is, when the cell voltage values ​​of the plurality of battery cells Cell1-Celln are different, the respective balancing currents I B The values ​​are also different.

[0060] [Number 2] TIFF2025157289000003.tif24160

[0061] According to the above formula (2), the main control circuit 30 calculates the cell capacitance Csoc value, the balancing current I B value, and the balancing time T based on the capacity loss Dsoc. B The cell capacity Csoc can correspond to the cell capacity of each of the multiple battery cells Cell1-Celln. The balancing current I B The value is the balancing current I calculated by the above formula (1). B The capacity loss Dsoc may be a difference between the cell capacity of each of the battery cells Cell1-Celln and the minimum cell capacity (min SOC). That is, the capacity loss Dsoc may correspond to a capacity value discharged from the battery cell during the cell balancing process.

[0062] In step S300, the main control circuit 30 determines the balancing time T BThe cell balancing control signal including the function information is transmitted to the cell monitoring IC 20, and the cell balancing control signal is controlled to perform cell balancing on the battery cells determined to be the target of cell balancing.

[0063] For example, as discussed above, when the second to fourth battery cells Cell2-Cell4 are determined to be the cell balancing targets, the main control circuit 30 determines the balancing time T B The main control circuit 30 calculates the balancing times T B The cell monitoring IC 20 can be controlled so that cell balancing is performed according to the

[0064] The cell monitoring IC 20 can perform cell balancing by discharging battery cells determined to be the target of cell balancing among the plurality of battery cells Cell1-Celln through the cell balancing circuit 10 in accordance with the cell balancing control signal transferred from the main control circuit 30.

[0065] Next, if it is determined that cell balancing is not necessary (S200, No) or if cell balancing has ended, the main control circuit 30 counts the next balancing cycle. When the balancing cycle arrives (S400), the main control circuit 30 can repeat the process from step S100.

[0066] According to one embodiment, the main control circuit 30 may determine a new balancing reference value each time it determines whether to perform cell balancing. For example, the main control circuit 30 may determine a balancing reference value at each preset period or each rest period of the battery 2 (e.g., a period when charging or discharging is not performed), and determine whether to perform cell balancing based on the determined balancing reference value.

[0067] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art to which the present invention pertains also fall within the scope of the present invention. [Item 1] a battery including a plurality of battery cells; a cell monitoring IC for measuring the cell voltage of each of the plurality of battery cells; a current sensor for measuring a battery current flowing through the battery; a main control circuit that estimates a cell capacity of each of the plurality of battery cells based on the cell voltage and the battery current, extracts a minimum cell capacity from the cell capacities of each of the plurality of battery cells, determines a balancing reference value corresponding to the minimum cell capacity, and determines the need for cell balancing for each of the plurality of battery cells based on the balancing reference value. [Item 2] The main control circuit is The entire cell capacity range is divided into a plurality of SOC ranges according to a predetermined standard, setting a section reference value, which is a start condition for cell balancing, for each of the plurality of SOC sections in accordance with a predetermined standard; selecting an SOC section to which the minimum cell capacitance belongs from among the plurality of SOC sections; 2. The battery system according to item 1, wherein a section reference value corresponding to the selected SOC section is determined as the balancing reference value. [Item 3] The main control circuit is The entire range of the cell capacity is divided into the plurality of SOC ranges based on a point where a ratio of the cell voltage to the cell capacity is changed; Item 3. The battery system according to item 2, wherein the section reference value is set based on the ratio. [Item 4] The main control circuit is calculating a difference between the cell capacity of each of the plurality of battery cells and the minimum cell capacity; 4. The battery system according to item 3, wherein the battery system determines that cell balancing is necessary for battery cells whose difference value exceeds the balancing reference value. [Item 5] a cell balancing circuit including a plurality of switches and a plurality of resistors, and controlling a switching operation according to at least one corresponding switching signal supplied from the cell monitoring IC to perform cell balancing of the battery cells; The above cell monitoring IC is 5. The battery system according to any one of items 1 to 4, wherein a battery cell determined to be a target for cell balancing among the plurality of battery cells is discharged via the cell balancing circuit in accordance with a cell balancing control signal transferred from the main control circuit. [Item 6] The main control circuit is Calculating a balancing time based on the cell capacity of the battery cell determined to be the target of cell balancing, the difference between the cell capacity and the minimum cell capacity, and the cell voltage value; 6. The battery system of item 5, wherein the cell balancing control signal including information regarding the balancing time is transmitted to the cell monitoring IC. [Item 7] determining a balancing reference value based on a minimum cell capacity among the respective cell capacities of the plurality of battery cells; calculating a difference between the cell capacity of each of the plurality of battery cells and the minimum cell capacity, and comparing the difference with the balancing reference value to determine whether cell balancing is necessary for each of the plurality of battery cells; If it is determined that cell balancing is required for at least one battery cell as a result of the determination, performing cell balancing on the battery cells determined to be targets of cell balancing. [Item 8] The step of determining the balancing reference value comprises: estimating a cell capacity of each of the plurality of battery cells based on a cell voltage of each of the plurality of battery cells; extracting a minimum cell capacity from among the respective cell capacities of the plurality of battery cells; selecting an SOC section including the minimum cell capacity from among a plurality of SOC sections that are configured by classifying all cell capacity sections according to a predetermined criterion; and determining an interval reference value corresponding to the selected SOC interval as the balancing reference value. [Item 9] The above multiple SOC sections are: The entire range of the cell capacity is classified based on the point where the ratio of the cell voltage to the cell capacity is changed, The above section reference values ​​are: 9. The cell balancing method according to item 8, wherein the cell balancing is set based on the ratio of cell voltage to cell capacity corresponding to the plurality of SOC intervals. [Item 10] The cell balancing step includes: Calculating a balancing time based on the cell capacity of the battery cell determined to be the target of cell balancing, the difference between the cell capacity and the minimum cell capacity, and the cell voltage value; 10. The cell balancing method according to any one of items 7 to 9, wherein cell balancing of the corresponding battery cells is performed during the balancing time. [Item 11] The step of determining the need for cell balancing includes: 10. The cell balancing method according to any one of items 7 to 9, wherein a battery cell whose difference value exceeds the balancing reference value is determined to be a target for cell balancing.

Claims

1. a battery including a plurality of battery cells; a cell monitoring IC for measuring a cell voltage of each of the plurality of battery cells; a current sensor for measuring a battery current flowing through the battery; a main control circuit that estimates a cell capacity of each of the plurality of battery cells based on at least one of the cell voltage and the battery current, extracts a minimum cell capacity from the cell capacities of the plurality of battery cells, determines a balancing reference value corresponding to the minimum cell capacity, and determines whether cell balancing is necessary for each of the plurality of battery cells based on the balancing reference value, wherein the balancing reference value differs depending on which of a plurality of SOC ranges the minimum cell capacity belongs to.

2. The main control circuit classifying the entire range of cell capacity into the plurality of SOC ranges according to a predetermined criterion; setting a section reference value, which is a start condition for cell balancing, for each of the plurality of SOC sections in accordance with a predetermined standard; selecting an SOC range to which the minimum cell capacity belongs from among the plurality of SOC ranges; The battery system of claim 1 , wherein a section reference value corresponding to the selected SOC section is determined as the balancing reference value.

3. The main control circuit classifying the entire range of the cell capacity into the plurality of SOC ranges based on a point where a ratio of a cell voltage to a cell capacity is changed; The battery system according to claim 2 , wherein the section reference value is set based on the ratio.

4. The main control circuit calculating a difference between a cell capacity and the minimum cell capacity for each of the plurality of battery cells; The battery system according to claim 3 , wherein it is determined that cell balancing is necessary for battery cells whose difference value exceeds the balancing reference value.

5. a cell balancing circuit including a plurality of switches and a plurality of resistors, the cell balancing circuit controlling a switching operation according to at least one corresponding switching signal supplied from the cell monitoring IC to perform cell balancing of the battery cells; The cell monitoring IC includes:

5. The battery system according to claim 1, wherein a battery cell determined to be a target of cell balancing among the plurality of battery cells is discharged via the cell balancing circuit in accordance with a cell balancing control signal transferred from the main control circuit.

6. The main control circuit calculating a balancing time based on a cell capacity of a battery cell determined to be a target for cell balancing, a difference between the cell capacity and the minimum cell capacity, and a cell voltage value; The battery system of claim 5 , wherein the cell balancing control signal including information regarding the balancing time is transmitted to the cell monitoring IC.

7. determining a balancing reference value based on a minimum cell capacity among the respective cell capacities of the plurality of battery cells; calculating a difference between the cell capacity of each of the plurality of battery cells and the minimum cell capacity, and comparing the difference with the balancing reference value to determine whether cell balancing is necessary for each of the plurality of battery cells; If the determination result indicates that cell balancing is necessary for at least one battery cell, performing cell balancing on the battery cells determined to be targets for cell balancing, wherein the balancing reference value differs depending on a range to which the minimum cell capacity belongs among a plurality of SOC ranges.

8. The step of determining the balancing reference value comprises: estimating a cell capacity of each of the plurality of battery cells based on a cell voltage of each of the plurality of battery cells; extracting a minimum cell capacity from among the cell capacities of the plurality of battery cells; selecting an SOC range including the minimum cell capacity from among the plurality of SOC ranges that are configured by classifying all ranges of cell capacity according to a predetermined criterion; 8. The cell balancing method of claim 7, further comprising: determining a section reference value corresponding to the selected SOC section as the balancing reference value.

9. The plurality of SOC sections are: The entire range of the cell capacity is classified based on the point where the ratio of the cell voltage to the cell capacity is changed, The interval reference value is The cell balancing method according to claim 8 , wherein the cell balancing is set based on a ratio of cell voltage to cell capacity corresponding to the plurality of SOC ranges.

10. The step of performing cell balancing includes: calculating a balancing time based on a cell capacity of a battery cell determined to be a target for cell balancing, a difference between the cell capacity and the minimum cell capacity, and a cell voltage value; The cell balancing method according to claim 7 , further comprising: performing cell balancing of corresponding battery cells during the balancing time.

11. The step of determining the need for cell balancing includes: The cell balancing method according to claim 7 , wherein a battery cell whose difference value exceeds the balancing reference value is determined to be a cell balancing target.

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