Cell balancing device

Abstract

The present invention relates to a cell balancing device, and more specifically, to a cell balancing device that performs cell balancing by considering the cell's SOC, SOH, rated capacity, and usage area characteristics, thereby enabling accurate balancing even when different types of cells are mixed together, such as when each cell has a different SOH or rated capacity, and minimizing unnecessary balancing operations.

Description

Technology Field

[0001] The present invention relates to a cell balancing device, and more specifically, to a cell balancing device that performs cell balancing by considering the cell's SOC, SOH, rated capacity, and usage area characteristics, thereby enabling accurate balancing even when different types of cells are mixed together, such as when each cell has a different SOH or rated capacity, and minimizing unnecessary balancing operations. Background Technology

[0002] With economic development, the demand for vehicles is experiencing explosive growth. As this demand increases, exhaust emissions from vehicles are becoming a major cause of environmental pollution. Consequently, various studies aimed at reducing vehicle emissions are continuously underway, and as a result, electric vehicles (EVs) and hybrid electric vehicles (HEVs) are rapidly emerging as eco-friendly automobiles.

[0003] An electric vehicle (including electric motorcycles and special vehicles capable of operating via electric charging) refers to a vehicle that operates using electricity as a power source. It is a vehicle equipped with a rechargeable battery that serves as the power source, and operates by utilizing the power supplied from the installed battery. The composition of such an electric vehicle largely consists of basic functional parts that possess components identical to those of a conventional vehicle, a drive motor driven by electricity to operate the vehicle, and a battery that supplies electricity to the drive motor.

[0004] A battery is composed of multiple battery cells, and since the voltage of each battery cell must be uniform to ensure safety, improve lifespan, and obtain high output, a battery balancing device is used to ensure that each battery has an appropriate voltage while charging or discharging the battery cells. However, the multiple battery cells (hereinafter referred to as cells) experience SOC variations due to material characteristics such as internal resistance and artificial variations caused by the usage environment.

[0005] Accordingly, a battery management system (BMS) that manages the state of the battery continuously measures the SOC of the cells, and if a deviation exceeding a certain value occurs, it performs a balancing operation to eliminate the deviation, thereby eliminating or minimizing the deviation.

[0006] Figure 1 is a flowchart illustrating a conventional battery cell balancing method. As illustrated, the conventional cell balancing method involves converting the initial cell voltage measured upon power supply into SOC, comparing the deviation between the lowest SOC cell and the remaining cells, and for cells with a value exceeding 5%, calculating the balancing time based on the relationship between the balancing resistance and the cell voltage to reduce the deviation between cells.

[0007] For example, if the inter-cell deviation is 6%, 1% of the capacity is removed through the balancing resistor during the balancing time. However, in this case, errors are included at every step, so the actual balancing may be less than the initial calculation. Errors occur when converting the initially measured cell voltage to SOC, and since the balancing time is calculated based on the initial measured voltage, the error increases if the voltage changes during balancing. Additionally, errors caused by the resistance component of the balancing circuit may be included, so if the resistance characteristics of the balancing circuit differ for each cell, the amount of balancing performed becomes irregular.

[0008] In addition, according to this conventional method, even if the cells are balanced by performing a balancing operation, if the SOH or rated capacity of each cell is different, the balancing is repeated during charging and discharging, resulting in a problem of unnecessary balancing operations. That is, if the SOH or rated capacity of each cell is different, the capacity deviation between the cells cannot be matched even if balancing is performed, and there is a problem in that the available capacity of each cell decreases to a level below the available capacity of the cell with the minimum capacity. Prior art literature

[0009] Korean Published Patent Application No. 2012-0134415 (December 12, 2012) The problem to be solved

[0010] The present invention was devised to solve the above-mentioned problems, and more specifically, the purpose is to provide a cell balancing device that enables accurate balancing even when different types of cells are mixed together, such as when each cell has a different SOH or rated capacity, by performing cell balancing while considering the cell's SOC, SOH, rated capacity, and usage area characteristics, and to minimize unnecessary balancing operations. means of solving the problem

[0011] A cell balancing device according to an example of the present invention comprises: a data unit that acquires and stores information for each of a plurality of cells; and a balancing unit that receives information for each of the cells from the data unit and performs cell balancing based thereon, wherein the balancing unit receives SOC values ​​and SOH values ​​of each cell as information for each of the cells, and can select a cell to be balanced based on the SOC values ​​and SOH values ​​of each of the cells and perform balancing.

[0012] It may further include a setting unit for setting an SOC reference value that serves as a standard for the SOC values ​​of each of the above cells.

[0013] The above setting unit can set an SOC reference value individually for each of the above cells.

[0014] The above setting unit can set the SOC reference value using information on the usage area characteristics of each of the above cells.

[0015] The above setting unit can calculate the available capacity of each of the above cells and determine the actual SOC usage area of ​​the minimum cell having the minimum available capacity among the available capacities of each of the above cells.

[0016] The above setting unit can determine the actual SOC usage area of ​​each cell individually by considering the usage area characteristics of each cell and the actual SOC usage area of ​​the minimum cell.

[0017] The above setting unit can calculate the intermediate value between the lower limit and the upper limit of the actual usage range of each cell and set the calculated intermediate value as the SOC reference value of each cell.

[0018] The balancing unit can calculate the capacity deviation of each cell by multiplying the value obtained by subtracting the SOC reference value from the SOC value of each cell by the SOH value of each cell.

[0019] The balancing unit can calculate a balance value, which is the deviation between the capacity deviation of each cell and the minimum value, based on the minimum value among the capacity deviations of each cell.

[0020] The balancing unit can compare the sorting value of each cell with the balancing reference value, and if the sorting value of each cell exceeds the balancing reference value, select the cell as the cell to be balanced.

[0021] The balancing unit can further receive the rated capacity of each cell as information about each cell, and perform balancing by selecting a cell to be balanced based on the SOC value, SOH value, and rated capacity of each cell.

[0022] The balancing unit can calculate the capacity deviation of each cell by subtracting the SOC reference value, which serves as a reference for the SOC value of each cell, from the SOC value of each cell, multiplying the result by the SOH value of each cell, and then further multiplying by the rated capacity of each cell.

[0023] The balancing unit can perform a first balancing using the SOH values ​​of each cell at a first time point, and compare the SOH values ​​of each cell at a second time point with the SOH values ​​of each cell at the first time point for each cell, and perform a second balancing only when the amount of change in SOH value in at least one cell is greater than a preset threshold value. Effects of the invention

[0024] According to the present invention, unnecessary balancing operations can be minimized, and accordingly, cells are prevented from being unnecessarily charged or discharged for balancing, thereby increasing the energy efficiency of the battery unit and preventing the waste of resources for balancing.

[0025] In addition, by setting the actual usage area of ​​each cell considering the usage area characteristics of each cell, the degradation rate among the cells can be matched. Accordingly, in a battery module or battery pack composed of multiple cells, rapid degradation of a specific cell is prevented, thereby ensuring uniform power supply performance among the cells. Brief explanation of the drawing

[0026] Figure 1 is a flowchart illustrating a conventional battery cell balancing method. FIG. 2 is a conceptual block diagram illustrating a cell balancing device according to an example of the present invention. FIG. 3 is a conceptual diagram illustrating a balancing method according to an example of the present invention. FIG. 4 is a conceptual diagram illustrating the process of setting an SOC reference value according to an example of the present invention. FIG. 5 conceptually illustrates the balancing method of the present invention. Figure 6 conceptually illustrates a conventional balancing method. FIG. 7 is a table showing the balancing results according to an example of the present invention compared with the conventional balancing results. FIG. 8 is a graph showing the balancing result according to an example of the present invention compared with the conventional balancing result. Specific details for implementing the invention

[0027] Throughout this specification, terms such as “unit,” “device,” and “system” refer to a unit that processes an operation combining one or more functions, and this may be implemented in hardware, software, or a combination of hardware and software.

[0028] Terms such as "part," "device," and "system" as used in this specification may be treated as equivalent to computer-related entities, namely hardware, combinations of hardware and software, software, or software at runtime. Additionally, the application program executed in the present invention may be organized into "part" units and may be recorded in a single physical memory in a form that allows reading, writing, and erasing, or may be recorded distributed across two or more memories or recording media.

[0029] Hereinafter, the present invention will be described with reference to the attached drawings.

[0030] FIG. 2 is a conceptual block diagram of a cell balancing device according to an example of the present invention. As shown, the device (10) includes a data unit (100) and a balancing unit (200), may further include a setting unit (300), and may be connected to a battery unit (20).

[0031] The battery unit (20) may be composed of a plurality of cells (21, 22, 23, …), and more specifically, the battery unit (20) may correspond to a battery module composed of a plurality of cells or a battery pack composed of a plurality of battery modules, and such battery module or battery pack may be mounted on or intended to be mounted on an electric vehicle.

[0032] The device (10) is connected to the battery unit (20) and performs balancing on each cell using information about each cell of the battery unit (20). The cell balancing device (10) of the present invention may correspond to, for example, a battery management device (BMS).

[0033] The data unit (100) can perform the function of acquiring and storing information for each of a plurality of cells. Here, the information for each cell may include the State of Charge (SOC), State of Health (SOH), rated capacity (C nominal), and usage area characteristics of each cell. SOC represents the charge state of the cell, where SOC 0% means a fully discharged state and SOC 100% means a fully charged state; SOH represents the health state of the cell, indicating the degree of deterioration of the cell, where a new cell may have an SOH of 100% and an aged cell may have a lower SOH %; rated capacity represents the nominal capacity of the cell, which may be a constant value determined during cell manufacturing; and usage area characteristics are based on the Depth of Discharge (DOD) of the cell, representing the characteristics of the charge or discharge area of ​​the cell and may be associated with the usage area of ​​the cell.

[0034] The characteristics of the operating range can be explained in more detail as follows. A cell has a physical upper limit for charging and a physical lower limit for discharging. Additionally, each cell may have unique characteristics within these upper charging limits; for example, some cells may exhibit good charge-discharge characteristics in the SOC 20–100% range, while others may exhibit good charge-discharge characteristics in the SOC 0–80% range. Good charge-discharge characteristics refer to the ability to perform charges and discharges effectively with a low degree of degradation when charging occurs within the corresponding operating range. For example, a cell having good charge / discharge characteristics in the SOC 20~100% range may mean a cell that is fine when fully charged (i.e., DOD 0%) but is unstable when fully discharged (i.e., DOD 100%), and conversely, a cell having good charge / discharge characteristics in the SOC 0~80% range may mean a cell that is fine when fully discharged (i.e., DOD 100%) but is unstable when fully charged (i.e., DOD 0%).

[0035] In addition, as described above, when using a cell, the entire range between the cell's SOC 0~100% range—that is, the range between the cell's physical limit discharge point and physical limit charge point—is not utilized; instead, a predetermined lower discharge limit and upper charge limit are set, and the cell is designed to perform charging and discharging within that range. For example, the cell's usage range can be set as SOC 3~97%, 5~97%, 10~90%, 20~80%, etc., and such usage ranges can be configured to be variable within a single cell. In this case, for aged cells, charging and discharging can be performed, for example, in the SOC 20~80% range, while for new cells, charging and discharging can be performed, for example, in the 3~97% range. Thus, considering the degree of aging and risk of the cell, the range of usage for aged cells can be designed or set so that it is reduced compared to new cells.

[0036] Referring again to FIG. 2, the data unit (100) can obtain information about each cell as described above, and for this purpose, it may include an SOC estimation unit (110), an SOH estimation unit (120), an input unit (130), etc., and may include a storage unit (140) for storing the obtained information.

[0037] The SOC and SOH of the cell can be estimated from the cell's current, voltage, temperature, etc., and the SOC estimation unit (110) and SOH estimation unit (120) can estimate the cell's SOC and SOH by receiving data such as the cell's current, voltage, and temperature. Although not illustrated, a sensing unit for sensing the cell's current, voltage, temperature, etc. may be provided. Additionally, the cell's rated capacity and usage area characteristics may be provided as initial information from the outside through the input unit (130), and in the case of usage area characteristics, modified information may be input through the input unit (130) so that changed characteristics are reflected considering the cell's aging, etc. Furthermore, such information regarding the cell may be stored in the storage unit (140).

[0038] The balancing unit (200) receives information about the cells from the data unit (100) and can perform cell balancing based on this. More specifically, the balancing unit (200) receives the SOC value and SOH value of each cell as information about each cell, selects the cells to be balanced, i.e., the cells that require balancing, based on this, and can perform balancing on at least one or all of the selected cells.

[0039] FIG. 3 is a conceptual diagram illustrating a balancing method according to an example of the present invention. As shown, a total of four cells may be provided, and these shall be referred to as the first to fourth cells (21, 22, 23, 24), respectively. At this time, the current SOC of the first cell (21) is 59 Ah and the current SOH is 80%, the current SOC of the second cell (22) is 53 Ah and the current SOH is 100%, the current SOC of the third cell (23) is 48 Ah and the current SOH is 80%, the current SOC of the fourth cell (24) is 48 Ah and the current SOH is 100%, and the rated capacity of the first to fourth cells (21, 22, 23, 24) may all be 100 Ah. The balancing unit (200) may receive information regarding each of these cells (S100).

[0040] Subsequently, the balancing unit (200) can calculate the capacity deviation of each cell based on the SOC reference value (S200). The SOC reference value is a value that serves as a reference for the current SOC value of each cell, for example, the SOC reference value can be set to SOC 50% (details regarding the SOC reference value will be described later). In this case, the balancing unit (200) can calculate the capacity deviation of each cell by subtracting 50 Ah, which corresponds to the SOC reference value of SOC 50%, from the current SOC value of each cell, from the rated capacity of 100 Ah, and multiplying the result of the subtraction of the two by the current SOH value of each cell.

[0041] That is, the capacity deviation can be calculated as (current SOC value of each cell - SOC reference value) * (current SOH value of each cell). Taking FIG. 3 as an example, the capacity deviation of the first cell (21) is (59-50) * 80% = 7.2 (Ah), the capacity deviation of the second cell (22) is (53-50) * 100% = 3 (Ah), the capacity deviation of the third cell (23) is (48-50) * 80 = -1.6 (Ah), and the capacity deviation of the fourth cell (24) is (45-50) * 100% = -5 (Ah). As such, the capacity deviation can be both positive and negative, and more specifically, if the current SOC of the cell is less than the SOC reference value, the value can be negative.

[0042] Here, the present invention may further utilize information regarding the rated capacity of each cell to calculate the capacity deviation of each cell by taking into account cases where cells having different rated capacities are mixed. That is, the balancing unit (200) may receive additional information regarding the rated capacity of each cell in addition to the SOC value and SOH value of each cell as information regarding each cell, and may perform balancing based on the information regarding the SOC value, SOH value, and rated capacity of each cell. More specifically, the balancing unit (200) may calculate the capacity deviation of each cell considering the rated capacity of the cell by further multiplying the rated capacity by the above capacity deviation calculation formula, and accordingly, the capacity deviation in this example can be calculated through (current SOC value of each cell - SOC reference value) * (current SOH value of each cell) * (rated capacity of each cell). For example, if the rated capacity of the fourth cell (24) in FIG. 3 is assumed to be 50 Ah, then half of the capacity deviation of -5 (Ah) without considering the rated capacity, which is -2.5 (Ah), can be the final capacity deviation. In this way, by further considering the rated capacity of the cell, the present invention can perform accurate cell balancing even when different types of cells with different rated capacities are mixed.

[0043] After calculating the capacity deviation of each cell through the above process, the balancing unit (200) can calculate a sorted value by sorting the capacity deviation of each cell based on the minimum value among the capacity deviations (S300). Taking FIG. 3 as an example, since the capacity deviation of the fourth cell (24) is -5 (Ah) which corresponds to the minimum value, if the capacity deviations of the remaining cells are sorted based on this, the first cell (21) can be 12.2 (Ah), the second cell (22) can be 8 (Ah), the third cell (23) can be 3.4 (Ah), and the fourth cell (24) can be 0 (Ah). The value calculated by sorting the capacity deviation of each cell based on the minimum value of the capacity deviation is called the sorted value, and accordingly, the sorted values ​​of the first to fourth cells (21, 22, 23, 24) can be 12.2, 8, 3.4, and 0, respectively.

[0044] Subsequently, the balancing unit (200) can select a cell as a balancing cell when the cleanup value of each cell exceeds the balancing reference value, and perform a balancing operation to balance the selected balancing cell (S400). The balancing reference value is a predetermined threshold value and may be set by a user and stored in the balancing unit (200). For example, in the example of FIG. 3, if the balancing reference value is 5 (Ah), the cleanup values ​​of the first cell (21) and the second cell (22) are 12.2 and 8 (Ah), respectively, which exceed the balancing reference value, so the balancing unit (200) can select the first cell (21) and the second cell (22) as balancing cells and perform a balancing operation on the first cell (21) and the second cell (22). Balancing operation equalizes the current charge amount with other cells through charging or discharging of the cell. In this example, since the first and second cells are overcharged compared to other cells, balancing can be performed by discharging them.

[0045] Thus, in performing balancing, the present invention, unlike conventional balancing based only on the SOC value of a cell, takes into account the SOH value of the cell, thereby preventing unnecessary balancing caused by differences in SOH between cells, and furthermore, by taking into account the rated capacity of the cell, accurate balancing is possible even when heterogeneous cells with different rated capacities are mixed.

[0046] Meanwhile, referring again to FIG. 2, the device (10) may further include a setting unit (300) in addition to the data unit (100) and the balancing unit (200). The setting unit (300) performs the function of setting an SOC reference value, and the SOC reference value refers to a predetermined value that serves as a reference for the SOC value of each cell when calculating the capacity deviation of each cell as described above. In the previous example, SOC 50% was uniformly applied as the SOC reference value to all cells, but the device (10) can set an SOC reference value individually for each cell by further including the setting unit (300).

[0047] FIG. 4 is a conceptual diagram illustrating the process of setting an SOC reference value according to an example of the present invention. In the example of FIG. 4, three battery cells are described as reference, and these are referred to as the first to third battery cells (21, 22, 23), respectively. At this time, the current SOH of the first cell (21) is 100%, the current SOH of the second cell (22) is 80%, the current SOH of the third cell (23) is 90%, and the rated capacity of the first to third cells (21, 22, 23) may all be 100 Ah.

[0048] First, the setting unit (300) can calculate the available capacity of each cell and determine the SOC usage area of ​​the minimum cell having the minimum available capacity among the available capacities of each cell. The available capacity of each cell can be calculated by multiplying the cell's rated capacity by the cell's current SOH. Taking FIG. 4 as an example, the available capacity of the first cell (21) is (100 Ah) * (100%) = 100 Ah, the available capacity of the second cell (22) is 80 Ah, and the available capacity of the third cell (23) is 90 Ah. Among these, the minimum available capacity is 80 Ah, which corresponds to the available capacity of the second cell (22). The setting unit (300) can determine the actual SOC usage area of ​​the second cell (22) within the available capacity of the second cell (22). For example, as illustrated in FIG. 4, the actual SOC usage area of ​​the second cell (22) can be determined as SOC 5~95%, and the actual SOC usage area of ​​the second cell (22) can be determined by considering the usage area characteristics of the second cell (22). Specifically, information that the second cell (22) has excellent charge / discharge characteristics at SOC 5~95% can be stored in the data unit (100) as a usage area characteristic of the second cell (22), and the setting unit (300) can determine the actual SOC usage area of ​​the second cell (22) as 5~95% based on this.

[0049] Afterward, the setting unit (300) can determine the actual SOC usage area of ​​each cell individually by considering the usage area characteristics of each cell and the actual SOC usage area of ​​the minimum capacity cell determined above. First, when considering the actual SOC usage area of ​​the second cell (22), the maximum actual available capacity of the second cell becomes (80Ah) * (95% - 5%) = 72Ah. Based on this, the actual SOC usage area of ​​the first cell (21) is determined. In order for the maximum actual available capacity of the first cell (21) and the maximum actual available capacity of the second cell (22) to be the same, the range of the actual SOC usage area of ​​the first cell (22) must be 72% since the current SOH of the first cell (21) is 100%. At the same time, the setting unit (300) can determine the actual SOC usage area of ​​the first cell (21) to be closer to the full discharge area than the full charge area by considering the usage area characteristics of the first cell (21), for example, if the usage area characteristics of the first cell (21) have conditions that are more suitable for the full discharge area than the full charge area (for example, the full charge is more stable than the full discharge, or there are other reasons why the full charge area should be emphasized). Considering these relationships, the actual SOC usage area of ​​the first cell (21) can be determined to be SOC 4~76%.

[0050] The actual SOC usage area of ​​the third cell (23) can also be determined in the same way. More specifically, since the current SOH of the third cell (23) is 90%, the range of the actual SOC usage area of ​​the third cell should be 80%. If the third cell (23), unlike the first cell (21), has conditions that are more suitable for the full charge area than the full discharge area (e.g., the full discharge is more stable than the full charge, or there are other reasons why the full discharge area should be emphasized), the setting unit (300) can determine that the actual SOC usage area of ​​the third cell (23) is more focused on the full charge area than the full discharge area. Considering these relationships, the actual SOC usage area of ​​the third cell (23) can be determined to be 15.6% to 95.6%.

[0051] Afterward, the setting unit (300) calculates the midpoint between the lower limit and the upper limit of the actual SOC usage area of ​​each cell, and sets the calculated midpoint as the SOC reference value of each cell, thereby finally setting the SOC reference value individually for each cell. For example, in FIG. 4, the SOC reference value of the first cell (21) corresponds to (4+76) / 2=40(%), the SOC reference value of the second cell (22) corresponds to (5+95) / 2=50(%), and the SOC reference value of the third cell (23) corresponds to (15.6+95.6) / 2=55.6(%).

[0052] As such, the present invention allows for the individual setting of an SOC reference value for each cell using information regarding the usage area characteristics of each cell through a setting unit. Accordingly, an accurate reference point can be set for each cell by considering the degree of degradation of each cell, and at the same time, the degradation rate among the cells can be uniformly matched when repeating the charging and discharging of each cell after balancing. Meanwhile, although not separately explained, it goes without saying that the setting unit can further consider the rated capacity of each cell during the process of setting the SOC reference value for each cell.

[0053] When the SOC reference value is set by the setting unit (300), the balancing unit (200) can perform the selection of balancing cells and cell balancing operations using the SOC reference value set by the setting unit (300), which is the same as the explanation of the balancing operation of the balancing unit (200) described above. That is, unlike the previous case where the SOC reference value was uniformly set to the same value, i.e., SOC 50%, for all cells, in this embodiment, the SOC reference value can be individually set for each cell through the setting unit (300).

[0054] More specifically, the balancing unit (200) may calculate the capacity deviation of each cell by multiplying the value obtained by subtracting the aforementioned SOC reference value from the SOC value of each cell by the SOH of each cell, or by further multiplying the value by the rated capacity of each cell. After calculating the capacity deviation in this way, the balancing unit (200) calculates a balance value, which is the deviation between the capacity deviation of each cell and the minimum value among the capacity deviations of each cell, based on the minimum value among the capacity deviations of each cell, and compares the balance value of each cell with the balancing reference value; if the balance value of each cell exceeds the balancing reference value, the cell can be balanced.

[0055] Furthermore, the balancing unit (200) may perform first balancing using the SOH values ​​of each cell at a first time point, and compare the SOH values ​​of each cell at a second time point with the SOH values ​​of each cell at the first time point for each cell, and perform second balancing only when the amount of change in the SOH value of at least one cell is greater than a threshold value. Here, the second time point may mean any time point after the first time point. That is, the balancing unit (200) may not perform balancing further if there is no change in the SOH of each cell, or even if there is, the amount of change in the value is smaller than a predetermined threshold value. For example, assuming there are first to third cells, and the SOH of the first to third cells at the first time point is 100%, 90%, and 80%, respectively, and the SOH at the second time point is 95%, 88%, and 73%, respectively, the change in SOH values ​​of the first to third cells between the two time points can be 5, 2, and 7 (%), respectively. In this case, if the threshold value is 10%, the change in SOH values ​​of all first to third cells does not exceed the threshold value, so the balancing unit may not perform additional balancing. On the other hand, if the threshold value is 3%, even if the change in SOH value of the second cell does not exceed the threshold value, the change in SOH values ​​of the first and third cells exceeds the threshold value, so the balancing unit may perform additional balancing. In this case, the threshold value may be set by the user and stored inside the balancing unit. In this way, according to the present invention, since additional balancing operations are not performed until a significant level of SOH change occurs in each cell, the number of balancing operations can be significantly reduced.

[0056] FIG. 5 conceptually illustrates the balancing method of the present invention and shows the balancing method of the first to third cells (21, 22, 23). As initial conditions for each cell, the rated capacity of the first to third cells (21, 22, 23) is the same at 100 Ah, the current SOH of the first to third cells (21, 22, 23) is 100%, 80%, and 90%, respectively, and the current SOC of the first to third cells (21, 22, 23) is 72%, 90%, and 80%, respectively. When charging (CHA) proceeds in the current state, even if the second cell (22) is fully charged to SOC 100%, the first cell (21) and the third cell (23) are not fully charged to SOC 80% and SOC 89%, respectively. At this time, the present invention performs balancing based on the SOC reference value. In this example, for the convenience of calculation, it is assumed that the SOC reference values ​​of each cell set by the setting unit are all the same at SOC 50%. According to this, based on the reference value SOC 50%, the capacity deviation of the first cell (21) is (80-50)*100%=30 (Ah), the capacity deviation of the second cell (22) is (100-50)*80=40 (Ah), and the capacity deviation of the third cell (23) is (89-50)*90%=35.1 (Ah). Among these, balancing (BAL) is performed by discharging the second cell (22) and the third cell (23) based on the capacity deviation of the first cell (21), which has the smallest capacity deviation, which is 30 (Ah). Accordingly, the second cell (22) and the third cell (23) are balanced to SOC 87.5% and SOC 83.3%, respectively, and the available capacity of the first to third cells (21, 22, 23) is uniformly adjusted. Subsequently, even if the discharge (DCH) proceeds and the second cell (22) is completely discharged to SOC 0%, there is no capacity difference between the cells when calculated based on the reference value SOC of each cell, which is 50%, so no further balancing operation is required.At this time, it can be seen that the SOC usage range of the first cell (21) is set to 10~90%, the SOC usage range of the second cell (22) is set to 0~100%, and the SOC usage range of the third cell (23) is set to 5.6~94.2%. At this time, regarding the SOC reference value, as previously explained through FIG. 4, the SOC usage range is set to be concentrated on one side of the full charging range or the full discharging range of each cell by considering the usage range characteristics of each cell, and accordingly, the SOC reference value of each cell can be set differently. According to the present invention, even if charging and discharging are repeated after balancing, the available capacity of each cell converges to a constant maximum available capacity of the second cell (22), which is 80 Ah.

[0057] FIG. 6 conceptually illustrates a conventional balancing method and shows the balancing method of the first to third cells (21, 22, 23). The initial conditions of each cell are the same as the initial conditions of FIG. 5, and more specifically, the rated capacity of the first to third cells (21, 22, 23) is all the same at 100 Ah, the current SOH of the first to third cells (21, 22, 23) is 100%, 80%, and 90%, respectively, and the current SOC of the first to third cells (21, 22, 23) is 72%, 90%, and 80%, respectively. When charging (CHA) proceeds in the current state, even if the second cell (22) is fully charged to SOC 100%, the first cell (21) and the third cell (23) are not fully charged to SOC 80% and SOC 89%, respectively. At this time, in the conventional method, balancing is performed based only on SOC, and the second cell (22) and the third cell (23) are discharged based on the SOC of the first cell (21) having the lowest SOC of 80% to uniformly balance the SOC of the cells. Subsequently, when discharge (DCH) proceeds, even if the second cell (22) is completely discharged to SOC 0%, the first cell (21) and the third cell (23) are not completely discharged to SOC 16% and SOC 8.9%, respectively. At this time, in the conventional method, balancing is performed again based on SOC, and the first cell (21) and the third cell (23) are discharged based on the SOC of the second cell (22) having the lowest SOC of 0% to uniformly balance the SOC of the cells. Then, when charging and discharging are repeated, the above balancing operation is repeated again to continuously perform balancing. As such, according to the conventional method, the SOH or rated capacity of each cell is not taken into account, so even if a balancing operation is performed, the actual available capacity between the cells cannot be matched, and consequently, unnecessary balancing is performed continuously, and furthermore, as the balancing time increases, the available capacity of each cell gradually decreases from a maximum of 80 Ah to a minimum of 64 Ah.

[0058] In contrast, the present invention allows the available capacity between each cell to be matched even if the current SOH or rated capacity differs from each other as described above, and prevents unnecessary balancing by eliminating the need for further balancing with only one balancing operation, and allows the available capacity of each cell to be maintained at a constant maximum actual available capacity.

[0059] FIG. 7 is a table showing the balancing results according to an example of the present invention compared with the conventional balancing results, and FIG. 8 is a graph showing the balancing results according to an example of the present invention compared with the conventional balancing results.

[0060] As illustrated in FIG. 7, the present invention calculates a capacity deviation by considering the SOC, SOH, and rated capacity of each cell, calculates a sorted value by aligning it based on the minimum value, and performs balancing by selecting a balancing cell by comparing the sorted value with a balancing reference value. Accordingly, the sorted values ​​of the 1st to 12th cells are 0, 0, 5, 5, 0, 0, 0, 0, 4, 3, 2, and 0, respectively, and if the balancing reference value is 3, the 4th, 5th, and 9th cells having values ​​5, 5, and 4, which exceed this value, can be selected as cells to be balanced.

[0061] At this time, the present invention can perform balancing on at least one of the cells selected as the balancing target cells. For example, in the case of the third and fourth cells, the sorting value is 5, which corresponds to a value exceeding the balancing reference value, but since the third and fourth cells are immediately adjacent cells, balancing is performed on only one of them, and then the process of selecting the balancing target cells is repeated again. If the remaining cells still satisfy the criteria for the balancing target cells, the remaining cells are selected as the balancing target cells in that process, and then balancing is performed.

[0062] Figure 8 shows the results of these in a graph, where the x-axis represents time and the y-axis represents the number of balancing cycles. As illustrated, according to the conventional method, balancing is performed based solely on the SOC of the cells, so even if balancing is performed, the available capacity between the cells cannot be matched, and thus the number of balancing cycles continues to increase in proportion to the passage of time. In contrast, the present invention considers the SOC, SOH, and rated capacity of the cells and performs balancing based on the SOC reference value. Therefore, it can be seen that after a certain period of time, balancing is no longer required, and the number of balancing cycles does not increase but converges to a constant value.

[0063] As seen above, according to the present invention, unnecessary balancing operations can be minimized, and accordingly, the cells are prevented from being unnecessarily charged or discharged for balancing, thereby increasing the energy efficiency of the battery unit and preventing the waste of resources for balancing.

[0064] In addition, by setting the actual usage area of ​​each cell considering the usage area characteristics of each cell, the degradation rate among the cells can be matched. Accordingly, in a battery module or battery pack composed of multiple cells, rapid degradation of a specific cell is prevented, thereby ensuring uniform power supply performance among the cells.

[0065] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. Explanation of the symbols

[0066] 10: Cell balancing device 100: Data Department 200: Balancing section 300: Settings section 20: Battery section

Claims

Claim 1 A cell balancing device comprising: a data unit for acquiring and storing information for each of a plurality of cells; a setting unit for setting an SOC reference value that serves as a standard for the SOC value of each cell; and a balancing unit for receiving information for each of the cells from the data unit and performing cell balancing based thereon, wherein the setting unit receives usage area characteristics considering the Depth of Discharge (DOD) of each cell as information for each cell and sets an SOC reference value individually for each cell using the usage area characteristics for each cell, and the balancing unit receives the SOC value and SOH value of each cell as information for each cell, and selects a cell to be balanced based on the set SOC reference value, the received SOC value, and the SOH value of each cell and performs balancing. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A cell balancing device according to claim 1, wherein the setting unit calculates the available capacity of each of the cells and determines the actual SOC usage area of ​​the minimum cell having the minimum available capacity among the available capacities of each of the cells. Claim 6 A cell balancing device according to claim 5, wherein the setting unit determines the actual SOC usage area of ​​each cell individually for each cell by considering the usage area characteristics of each cell and the actual SOC usage area of ​​the minimum cell. Claim 7 A cell balancing device according to claim 6, wherein the setting unit calculates an intermediate value between a lower limit and an upper limit among the actual usage ranges of each cell, and sets the calculated intermediate value as the SOC reference value of each cell. Claim 8 A cell balancing device according to claim 1, wherein the balancing unit calculates the capacity deviation of each cell by multiplying the value obtained by subtracting the SOC reference value from the SOC value of each cell by the SOH value of each cell. Claim 9 In claim 8, the cell balancing device, wherein the balancing unit calculates a balance value which is the deviation between the capacity deviation of each cell and the minimum value among the capacity deviations of each cell, based on the minimum value among the capacity deviations of each cell. Claim 10 A cell balancing device according to claim 9, wherein the balancing unit compares the sorting value of each cell with a balancing reference value and selects the cell as a balancing target cell if the sorting value of each cell exceeds the balancing reference value. Claim 11 A cell balancing device according to claim 1, wherein the balancing unit further receives the rated capacity of each cell as information regarding each cell, and selects a cell to be balanced based on the SOC value, SOH value, and rated capacity of each cell to perform balancing. Claim 12 A cell balancing device according to claim 11, wherein the balancing unit calculates the capacity deviation of each cell by multiplying the value obtained by subtracting the SOC reference value, which serves as a reference for the SOC value of each cell, from the SOC value of each cell by the SOH value of each cell, and then further multiplying by the rated capacity of each cell. Claim 13 A cell balancing device according to claim 1, wherein the balancing unit performs first balancing using the SOH values ​​of each cell at a first time point, compares the SOH values ​​of each cell at a second time point with the SOH values ​​of each cell at the first time point for each cell, and performs second balancing only when the amount of change in SOH value in at least one cell is greater than a preset threshold value.

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