Apparatus and method for estimating the lifespan of a battery

Abstract

The present invention relates to an apparatus and method for estimating the life state of a battery, and more particularly to an apparatus and method for calculating a voltage balance state value more accurately by reflecting not only the voltage distribution of a battery but also SOC information, and for measuring the life state of a battery based on the voltage balance state value.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for estimating the state of life of a battery. More specifically, the present invention relates to a method for calculating a voltage balance state value more accurately by reflecting the SOC information of a battery and measuring the state of life of the battery based on the voltage balance state value.

Background Art

[0002] [[ID=,11]] A battery module or battery pack is a device that combines multiple battery cells together to protect them from physical impacts in the external environment and is manufactured to perform a specific role, but is generally simply referred to as a "battery". For example, a battery is typically an attached charger for a smartphone, wireless device, laptop computer, etc. When consuming high power, such as in an electric bicycle and an electric vehicle, at least one battery, and in many cases, two to dozens of batteries can be bundled together to design a single battery pack structure.

[0003] On the other hand, when the life of a battery decreases, if the degree of voltage deviation of the cells constituting the battery pack becomes large when operating in the form of a battery pack (Figure 1), overcharging or overdischarging of some cells will occur. Thus, if overcharged or overdischarged cells occur among the battery cells, the stability will be greatly reduced, and there is a risk of leading to a fire or explosion in an abnormal state. In addition, if some of the battery cells reach the upper limit voltage or the lower limit voltage first, there is a limit in that the use is restricted even though there is remaining capacity, and the full capacity of the battery cannot be realized.

[0004] Therefore, a method has been devised to calculate the degree of voltage equalization (State Of Balance (SOB) by voltage) based on the voltage distribution of a plurality of cells constituting a battery pack and calculate SOH based on it. However, it cannot reflect the voltage deviation due to the SOC (State Of Charge) of the cells, and there is a problem in that, although the SOB is the same, the SOB is distorted by the SOC and calculated differently.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The first problem to be solved by the present invention is to calculate the degree of voltage equalization (SOB) of cells constituting a battery pack, and to provide an apparatus and a method thereof that can accurately estimate the state of life of the battery by applying the SOB calculated as described above.

[0007] The second problem to be solved by the present invention is to provide an apparatus and a method thereof that can more accurately estimate the state of life of the battery by calculating the SOB reflecting the SOC information of the cells when calculating the degree of voltage equalization (SOB) of the cells constituting the battery pack.

[0008] The objectives of the present invention are not limited to those mentioned above, and other objectives and advantages of the present invention not mentioned can be understood from the following description, and should be more clearly understood from the embodiments of the present invention. Also, it should be easily understood that the objectives and advantages of the present invention can be realized by the means shown in the claims and combinations thereof.

Means for Solving the Problems

[0009] A battery life state estimation device according to one aspect of the present invention for achieving the above-described objective includes a memory for reading a program for calculating the equilibrium state value of the voltages of a plurality of cells constituting a battery and estimating the equilibrium life state value, which is the battery life state value to which the equilibrium state value of the voltages is applied, and a processor for executing instructions contained in the program read into the memory.

[0010] In this process, the processor executes the program to set an acceptable limit value for the voltage difference within the voltage difference between the fully charged voltage and the discharged voltage of the battery, sets an acceptable limit quantile that subdivides the acceptable limit range obtained by applying the acceptable limit value for the voltage difference to the average voltage value derived from the measured voltage value of the cell into one or more analysis intervals, calculates the voltage decrease rate within the acceptable limit range based on the average voltage value, calculates the quantile decrease rate based on the acceptable limit quantile as the voltage decrease rate, derives the quantile order which is the order of the analysis interval in which the measured voltage values ​​of each cell are first included within the acceptable limit quantile, calculates a voltage equilibrium state value reflecting the quantile decrease rate, quantile order and the state of charge information of the cell, and can estimate an equilibrium life state value by applying the voltage equilibrium state value to the life state value calculated based on the remaining capacity of the battery.

[0011] Furthermore, the processor may provide a user interface that allows the user to set at least one of the voltage difference tolerance limit and the tolerance limit quantile.

[0012] Furthermore, the processor can calculate the reference deviation voltage value per allowable limit quantile, calculate a correction factor value based on the standard deviation calculated based on the average voltage and the number of cells, the reference deviation voltage value, and the quantile order, calculate a secondary voltage equilibrium state value by adding the product of the correction factor value and the quantile decline rate to the primary voltage equilibrium state value, which is a voltage equilibrium state value calculated based on the quantile decline rate and the quantile order, and apply the secondary voltage equilibrium state value to the lifetime state value to estimate the equilibrium lifetime state value.

[0013] Furthermore, when the processor calculates the secondary voltage equilibrium state value, if the calculated correction factor value is negative, it can be changed to zero (0) and applied; if it is positive, the calculated correction factor value can be applied as is.

[0014] Furthermore, the processor is configured to calculate the amount of charge stored in the battery based on the current applied to the battery. The processor is also configured to convert a QV graph, which shows the relationship between the battery voltage and the amount of charge stored in the battery, into a V-dQ / dV graph, which shows the relationship between the battery voltage and the ratio of the change in the amount of charge stored to the change in the battery voltage. On the other hand, the processor can detect two feature points from the V-dQ / dV graph, including a reference point and a measurement point.

[0015] Furthermore, when the processor reflects the cell's SOC information in the voltage balance state, it uses the (dQ) at the reference point. 基準 / dV 基準 ) value, (dQ at the measurement point) 測定 / dV 測定 The system is configured to apply the value and calculate a voltage balance state that reflects the SOC information. Furthermore, the processor may set the permissible limit of the voltage difference to be greater than the value obtained by dividing the operating voltage range value, which is the difference between the voltage in the fully charged state and the voltage in the discharged state, by the number of cells, and less than the value obtained by dividing the operating voltage range value by 2.

[0016] Furthermore, the processor sequentially increases the variable quantile order in integer units within the range from 1 to the permissible limit quantile. It calculates a range of values ​​obtained by subtracting or adding the value obtained by dividing the permissible limit of the voltage difference by the permissible limit quantile and multiplying it by the quantile order, and derives the first quantile order in which all of the measured voltages for each cell are included within the calculated range. Based on the derived quantile order, it can calculate the voltage equilibrium state value.

[0017] Furthermore, the processor may determine the voltage equilibrium state value to zero (0) if, while the variable quantile order is increased up to the allowable limit quantile, none of the measured voltages for each cell fall within the calculated range.

[0018] On the other hand, a battery life state estimation method by a battery life state estimation device according to another aspect of the present invention includes the steps of: setting an allowable limit value for the voltage difference within the voltage difference between the fully charged state voltage and the discharged state voltage of a battery composed of multiple cells; setting an allowable limit quantile that subdivides the allowable limit range obtained by applying the allowable limit value for the voltage difference to an average voltage value derived from the measured voltage values ​​of the cells into one or more analysis intervals; calculating the voltage decrease rate within the allowable limit range based on the average voltage value, but calculating the voltage decrease rate as a quantile decrease rate based on the allowable limit quantile; and measuring the measured voltage of each cell within the allowable limit quantile. The method includes the steps of: deriving the order of quantiles, which is the order of the analysis interval in which the values ​​are initially all included; determining the amount of charge stored in the battery based on the current applied to the battery; converting a QV graph showing the relationship between the battery voltage and the amount of charge stored in the battery into a V-dQ / dV graph showing the relationship between the battery voltage and the ratio of the change in the amount of charge stored to the change in the battery voltage; and calculating a voltage equilibrium state value based on the rate of quantile decline, the order of quantiles, and the V-dQ / dV value of the feature point; and estimating an equilibrium life state value by applying the voltage equilibrium state value to a life state value calculated based on the remaining capacity of the battery.

[0019] In this case, the method for estimating the battery life state may further include the steps of: providing a user interface that allows the user to set at least one of the allowable limit value and the allowable limit quantile of the voltage difference, before the step of setting the allowable limit value of the voltage difference; and receiving at least one of the allowable limit value and the allowable limit quantile of the voltage difference as input via the user interface.

[0020] Furthermore, the step of estimating the equilibrium lifetime state value may include: calculating a reference deviation voltage value which is the voltage difference per allowable limit quantile; calculating a correction factor A value based on the standard deviation calculated based on the average voltage and the number of cells, the reference deviation voltage value and the quantile order; calculating a secondary voltage equilibrium state value by adding the product of the correction factor A value and the quantile decline rate to the primary voltage equilibrium state value which is the voltage equilibrium state value calculated based on the quantile decline rate and the quantile order; calculating the dQ / dV value of the reference point and the dQ / dV value of the measurement point based on the V-dQ / dV graph, and calculating a correction factor D by dividing the dQ / dV value of the measurement point by the dQ / dV value of the reference point; calculating a tertiary voltage equilibrium state value that reflects the correction factor D; and estimating the equilibrium lifetime state value by applying the tertiary voltage equilibrium state value to the lifetime state value.

[0021] The means of solving the aforementioned problems do not merely enumerate all of the features of the present invention. The diverse features of the present invention, and the resulting advantages and results, should be understood in more detail by referring to the specific examples below. [Effects of the Invention]

[0022] According to one embodiment of the present invention, the degree of voltage equalization between battery cells can be more accurately managed by reflecting the SOC information of the cells making up the battery pack, and it is possible to anticipate and take measures in advance before a battery with an unbalanced degree of cell voltage equalization reaches a dangerous situation. Along with the effects described above, the specific effects of the present invention will be described below while explaining the embodiments for carrying out the invention. [Brief explanation of the drawing]

[0023] [Figure 1] This is an example of a graph showing the capacity deviation of cells due to battery usage. [Figure 2] This is a diagram showing the configuration of a battery life state estimation device according to one embodiment of the present invention. [Figure 3]This is a step-by-step diagram illustrating a method for estimating battery life based on the degree of voltage equalization according to one embodiment of the present invention. [Figure 4] This is an example of a graph used to explain the voltage deviation due to the state of clock (SOC) of a cell. [Figure 5] This graph illustrates the V-dQ / dV graph (b) obtained from the QV graph (a). [Figure 6] This is an example graph illustrating a method for estimating battery life that reflects the voltage equilibrium state of cells according to one embodiment of the present invention. [Modes for carrying out the invention]

[0024] The principles of preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the drawings shown below and the description described later are of preferred methods of implementation among various methods for effectively explaining the features of the present invention, and the present invention is not limited to the drawings and description below.

[0025] On the other hand, terms such as "first" or "second" may be used to describe a variety of components, but such terms should be interpreted solely for the purpose of distinguishing one component from another. For example, the first component may be called the second component, and similarly, the second component may also be called the first component.

[0026] The singular form includes plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “includes” or “has” should be understood to indicate the presence of the described feature, figure, step, action, component, part, or combination thereof, without prejudice to the presence or possibility of adding one or more other features, figures, steps, actions, components, parts, or combination thereof.

[0027] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by someone with ordinary knowledge of the subject matter. Terms that are the same as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant technology, and not in an ideal or overly formal sense unless explicitly defined herein.

[0028] The following describes the process for estimating the battery life state according to an embodiment of the present invention, with reference to the attached drawings. First, Figure 2 is a diagram showing the configuration of a battery life state estimation device according to one embodiment of the present invention. The battery life estimation device 100 shown in Figure 2 may be a computing device operated by at least one processor. The battery life device 100 may execute a program that includes instructions described to perform the operations according to the present invention.

[0029] The device 100 may be included in a battery management system (BMS) (not shown) provided in the battery pack. As shown in Figure 2, the hardware of the battery life state estimation device 100 may include at least one processor 110, memory 120, storage 130, and communication interface 140, and each component may be connected by a bus.

[0030] In addition, the battery life estimation device 100 may further include hardware such as separate input and output devices. Furthermore, the battery life estimation device 100 may be equipped with various software, including an operating system capable of driving the program, on a storage device such as the storage device 130.

[0031] The processor 110 is a device that controls the operation of the computing device 100 and can be a variety of processors that process instructions included in a program (for example, a CPU (Central Processing Unit), an MPU (Micro Processor Unit), an MCU (Micro Controller Unit), a GPU (Graphics Processing Unit), etc.).

[0032] Memory 120 can load a program so that the instruction words written to perform the operations according to the present invention are processed by the processor 110. For example, memory 120 may be ROM (read-only memory), RAM (random access memory), etc. The storage 130 can store various data and programs required to perform the operations according to the present invention. In this case, the storage 130 can match the result data processed by the execution of the program and the measurement data input by a device that is linked or connected in advance (for example, a battery management system (BMS)) for each square battery, and store them in a database.

[0033] The communication interface 140 may be a wireless communication module that handles communication between the components of the computing device 100 and communication with externally connected devices. Figure 3 is a sequence diagram illustrating the process by which a battery life state estimation device according to one embodiment of the present invention accurately estimates the battery life based on the degree of voltage equalization of the battery cells. Figure 4 is an example of a graph illustrating the voltage deviation due to the state of charge (SOC) of the cells.

[0034] A battery life state estimation device 100 according to one embodiment of the present invention reflects the state of charge (SOC) information to determine the voltage balance state between battery cells (SOB). voltage ) is calculated, and the reference lifetime state (State of Health, SOH) is determined by the thermodynamic reference capacity (i.e., SOC) of the battery. capacity) to apply the voltage balance state (SOB) of the battery cell voltage ) to calculate the balanced life state (SOH) balance ).

[0035] In a battery composed of a plurality of single cells (i.e., cells), the voltage balance state (SOB) is a factor indicating the degree of voltage equalization of the single cells. That is, it is a value that can confirm how much the voltage state of each single cell of the battery differs from the average voltage at any given time.

[0036] By calculating the state of health (SOH) of the balanced life state to which the actual voltage balance state between the single cells is applied balance it is possible to estimate the more accurate life of the battery in the actual usage environment. That is, if conventionally only information such as the average voltage and standard deviation of the cells was limited when estimating the life of the battery, the method for estimating the life of the battery according to an embodiment of the present invention can estimate the life of the battery by applying whether the voltage balance state between the battery cells is stable enough for the battery operation to be possible, and also the SOC information of the cells.

[0037] Regarding this, the conventional SOB was calculated based on the voltage distribution diagram of the cells at any given time, that is, the voltage distribution information such as the average voltage and the standard deviation of the voltage of the cells forming the battery pack. However, even if the deviation in the charge amount of the cells forming the battery pack shows the same distribution diagram, there may be a large difference in the voltage deviation depending on the arbitrary time point at which the voltage is measured, that is, depending on the arbitrary state of charge (SOC), and the SOB may be measured distorted.

[0038] For example, in the SOC-voltage curve of FIG. 4 showing the SOC and voltage of the cells, looking at the change in voltage according to the state of charge, it can be confirmed that the voltage difference (ΔV1) between SOC 5% and 10% and the voltage difference (ΔV2) between SOC 30% and 35% are very large. Although the charged capacity difference (SOC difference) of the cells forming the battery pack is the same, the voltage distribution of the cells varies greatly depending on the SOC at which the voltage of the battery is measured. In other words, assuming a battery pack consisting of two cells, a pack with one cell each with an SOC of 5% and an SOC of 10% and a pack with one cell each with an SOC of 35% and an SOC of 40% will only differ in their SOC at the time of measurement, but a severe distortion will occur in the voltage deviation. Therefore, in this invention, we have made every effort to complement the conventional method of calculating SOC based solely on voltage distribution, and have arrived at this invention.

[0039] On the other hand, referring to Figure 3, the processor 110 can execute a series of instructions included in the program to process the following operations, thereby reflecting the battery's balanced life state (SOH), which is the voltage balance state of the battery cells. balance It can estimate and output ). First, the values ​​of the pre-set parameters are derived based on the basic information and actual measurement information from the battery-specific information stored in storage 140.

[0040] In this case, the pre-set parameter is the "fully charged voltage V" applied to the individual cells of the battery. cha "The voltage in the discharged state is V" which applies to a single cell of a battery. dis "and among the measured voltages of each individual battery cell, "the maximum voltage V max "and the minimum voltage V of each individual battery cell min "and the "average voltage V" relative to the measured voltage of a single battery cell. avg " and the "number n" of individual cells that make up the battery, and the maximum "operating voltage range V" of the battery. f This may include the "voltage standard deviation σn" of the battery relative to a single cell.

[0041] For more details, see the voltage range over which the battery can be used, i.e., the maximum operating voltage range V. f It can be defined as shown in equation 1 below.

number

[0042] For example, referring to Figure 6, in any lithium-ion battery, the voltage V in the fully charged state is cha The voltage is set to 4.2V, and the discharge voltage is V dis If set to 3.0V, the operating voltage range V f This can be calculated to be 1.2V. Based on the parameters derived in this way, the following two parameters, dV and X, are determined in order to estimate the voltage equilibrium state value (SOB) for a single cell of the battery in question.

[0043] The aforementioned determined operating voltage range V f The maximum allowable voltage difference between individual cells is determined, i.e., the allowable voltage difference limit dV. This allowable voltage difference limit dV is a parameter that the user may specify to set a range for a suitable voltage equilibrium state (SOB), and its range value is not limited. In this case, the processor 110 may provide a user interface that allows a user (e.g., a battery inspector or a battery-using system designer) to select an acceptable voltage difference limit dV. The user interface provided by the processor 110 is a concept that includes a graphical user interface (GUI). Thus, the user interface provided by the processor 110 allows the allowable voltage difference limit dV value to be input in real time or in advance. Such a user interface may include recommended values ​​for the allowable voltage difference limit dV, and the user may select a dV value from among the recommended dV values ​​that is suitable for the desired degree of voltage balance of the battery cell.

[0044] The permissible limit dV for such a voltage difference can be determined by the conditions in Equation 2 below.

number

[0045] In the case of a lithium-ion battery as illustrated in Figure 6, the operating voltage range is V f This indicates that the allowable limit dV value for the voltage difference is 1.2V, and that the maximum value within the allowable limit range for the voltage difference, "1.2V / 2 = 0.6V", has been determined. Figure 6 shows that dV is at its maximum value V f I used the example of / 2, but this is not limited to this; the average voltage V avg The narrower the allowable limit range for applying dV based on this standard, the more efficient the application of the voltage equilibrium state can become.

[0046] Referring to Figure 6, the average voltage V is derived from the measured voltage of a single cell. avg The voltage is 3.6V, and the average voltage is V avg Based on this, the allowable voltage difference limit can be determined to be a range of up to 0.6V in the negative direction and up to 0.6V in the positive direction, respectively. Next, in order to determine the equilibrium precision of the dispersion within the allowable limit range of the voltage difference, we determine the allowable limit quantile X, which is the number of analysis intervals within the allowable limit range of the voltage difference.

[0047] For example, the permissible limit quantile X can be determined by the condition in equation 3 below.

number

[0048] In this case, the processor 110 may provide a user interface that allows a user (for example, a battery inspector or a battery-using system designer) to select the number of acceptable limit quantiles X. The user interface provided by the processor 110 is a concept that includes a graphical user interface (GUI). Thus, the user interface provided by the processor 110 allows the tolerance limit quantile X value to be entered in real time or in advance, and such a user interface includes recommended values ​​for tolerance limit quantile X, allowing the user to select an X value from the recommended X that fits the desired level of precision.

[0049] Thus, with the allowable limit range dV and the allowable limit quantile X of the voltage difference determined, the quantile fall rate Y is determined. The quantile fall rate Y represents the voltage fall rate within the allowable limit range relative to the average voltage. For example, the quantile fall rate Y can be defined as shown in equation 4 below.

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[0050] Furthermore, in the lithium-ion battery illustrated in Figure 6, the operating voltage range V f Since the voltage is 1.2V and the allowable voltage difference limit dV is 0.6V, the reference deviation voltage dV / X, which represents the voltage difference per allowable limit quantile, can be calculated as "0.6 / 25 = 0.024".

[0051] Next, the single cell V1 to V n Each measured voltage value V cell Based on the average voltage V avg Then, the standard deviation σn is determined. For example, the standard deviation σn can be calculated using the following formula 5.

number

[0052] In the lithium-ion battery illustrated in Figure 6, the measured voltage V is measured for each cell (i.e., a single cell). cell The average voltage V calculated based on this avgSince the voltage is 3.6V, the standard deviation σn can be calculated as 0.187.

[0053] Next, we calculate the quantile order N to which each measured cell's voltage value is contained. The quantile order N is an integer that increases sequentially from 1 to the acceptable limit quantile X. In this case, the quantile degree N can be determined using the following formula 6.

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[0054] In the lithium-ion battery illustrated in Figure 6, the average voltage V avg If the voltage is 3.6V and the reference deviation voltage dV / X is 0.024, then the first quantile order N, which includes the measured voltages of all cells, can be 5. In more detail, the initial quantile order N, which includes the voltage values ​​of all individual cells (i.e., single cells), is the value of V that satisfies the condition of equation 7 below when the variable quantile order N is sequentially increased in integer units from 1 to X. cell It can be determined by calculating the number of items.

[0055]

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[0056] Next, the voltage equalization state value SOB for a single cell is based on the quantile order N calculated by the above formulas 6 and 7. voltage Calculate. SOB1 is the primary voltage equilibrium state value. voltage This is calculated using formula 8 below.

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[0057] Incidentally, when expressing the variable quantile degree N as a percentage of n until it reaches X, if the first quantile degree that becomes 100 does not appear, then SOB1 voltage The value is determined to be 0. In contrast, when expressing a variable as a percentage of n until the quantile degree N becomes X, if the first quantile degree N that becomes 100 is any one value from 1 to X, then SOB1 voltage It is calculated as 100 - Y*N as shown in equation 8, and Y = 100 / X.

[0058] In the lithium-ion battery illustrated in Figure 6, the quantile order N is 5 and Y is 4, therefore SOB1 voltage The answer is "100 - 4 * 5", which is calculated as 80. On the other hand, the intra-quantile equilibrium correction factor A is calculated from the standard deviation σn and the reference deviation voltage dV / X, and the secondary voltage equilibrium state value SOB2 is calculated using the correction factor A. voltage It is possible to calculate this. The correction factor A is obtained using equation 9 below, and the secondary voltage equilibrium state value SOB2 is obtained using equation 10. voltage This is required.

number

[0059] Correction factor A is the equilibrium correction factor for each quantile. In the lithium-ion battery illustrated in Figure 6, the quantile order N is 5, the reference deviation voltage dV / X is 0.024, and the standard deviation σn is 0.02. Therefore, the correction factor A is "(5*0.024-0.02) / (5*0.024)" and is determined to be 0.83.

number

[0060] As shown in equation 10, the secondary voltage equilibrium state value SOB2 voltageThis is the primary voltage equilibrium state value SOB1 voltage This is calculated based on the product of the correction factor A and the rate of decline of quantiles Y. In this case, if the correction factor A is negative, A' is set to 0, and if the value of A is positive, A' is set to the value of A.

[0061] In the lithium-ion battery illustrated in Figure 6, the correction factor A is a positive number, 0.83, so A' is set to 0.83. As a result, the secondary voltage equilibrium state value SOB2 voltage The answer is "80 + 0.83 * 4", which is determined to be "83.32". Meanwhile, SOB1 voltage and SOB2 voltage While it reflects the voltage distribution of the cells making up the battery pack, as mentioned above, it does not reflect the SOC information at the time the SOB is measured. Therefore, even if the cells show the same charge distribution, the voltage deviation of the cells may be large depending on the measured SOC, and thus the SOB may be calculated differently.

[0062] Therefore, the voltage balance state value SOB3 reflects the SOC information of the cells that make up the battery pack. voltage We need to calculate this. Referring to Figure 5, the processor 110 converts the battery's VQ graph (or a function corresponding to the VQ graph) into a V-dQ / dV graph. Here, dQ / dV represents the ratio of the change in the battery's charge amount dQ to the change in the battery's voltage dV. In other words, the processor 110 can generate the V-dQ / dV shown in Figure 5 by differentiating the VQ graph (or a function corresponding to the VQ graph) with respect to the battery voltage V. V-dQ / dV is a graph that shows the relationship between the battery voltage V and dQ / dV.

[0063] Next, the processor 110 can detect two feature points (reference point and measurement point) on the V-dQ / dV graph. Furthermore, in order to reflect the cell's SOC information in the voltage equilibrium state, the processor determines the (dQ) at the reference point. 基準 / dV 基準 ) value, (dQ at the measurement point) 測定 / dV 測定The system is configured to apply the value and calculate a voltage balance state that reflects the SOC information.

[0064] Here, SOB3 voltage To reflect the voltage change due to SOC, the correction factor D is calculated using the following formula 11, and then SOB3 is calculated based on this. voltage It is possible to calculate this. Here, the dQ / dV value is the ratio of the change in capacitance to the change in voltage. By applying the dQ / dV value of the voltage measurement point relative to a specific reference point to the SOB calculation, the difference in voltage change due to SOC can be offset.

[0065]

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[0066] In this case, calculations were performed at the same reference point within the same cell or battery (dQ). 基準 / dV 基準 ) in order to apply (dQ 基準 / dV 基準 Even if the SOB is measured at any point, the relative SOB can be calculated within the same cell or the same battery. On the other hand, the processor 110 can use a noise filter to remove noise components from the V-dQ / dV graph before detecting feature points on the V-dQ / dV graph. By preventing the phenomenon of misdetection of feature points from the V-dQ / dV graph in Figure 5 due to noise components present in the V-dQ / dV in Figure 3, the accuracy of feature point detection can be improved. Of course, flattening the V-dQ / dV graph is a selective process. Figure 5 shows an example in which the processor 110 detects two feature points located on the V-dQ / dV graph.

[0067] Then, as shown in equation 12 below, the third voltage equilibrium state value SOB3voltage This is the primary voltage equilibrium state SOB1 voltage Value and secondary voltage equilibrium state SOB2 voltage The value is calculated by reflecting the correction factor D.

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[0068] Battery life (SOH) applied to battery voltage balance state balance This can be calculated using the following formula 13.

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[0069] As mentioned above, the mean, standard deviation, and critical quantile alone cannot accurately represent the equilibrium state of the battery cell in question. Therefore, by reflecting the cell's SOC, a more accurate voltage equilibrium state can be applied to estimate the battery's lifespan. Refer to Tables 1 and 2 below to determine the voltage equilibrium state (SOB) of the battery. Tables 1 and 2 below were measured using the same battery, and the SOB was calculated at different voltage ranges after complete discharge. [Table 1] [Table 2]

[0070] Tables 1 and 2 show data collected during the charging process following the complete discharge of all cells in the battery pack. Since the SOB was measured immediately after complete discharge, the balance should not have been significantly disrupted, and therefore, it can be assumed that the SOB deviation is not large.

[0071] Table 1 shows the voltage distribution of cells measured near 3.1V, a region where voltage changes due to SOC are very large. In this case, SOB2, calculated simply by reflecting only the cell voltage distribution and critical quantile, was 64.917, but SOB3, calculated by reflecting the correction factor D related to SOC, was calculated to be 97.314. In other words, it can be confirmed that there is a very large difference in the value between SOB that reflects SOC information and SOB that does not.

[0072] In contrast, Table 2 shows the data for the voltage distribution of the cells measured near 4.0V, a region where the voltage change due to SOC is small. Here, SOB2 was calculated as 95.295, and SOB3, reflecting the correction factor D, was calculated as 98.594. While this suggests similar SOB values, it can be confirmed that the difference in calculated SOB depending on the time of measurement is very large, and that more accurate measurements are possible by reflecting the correction factor D in the calculation.

[0073] Although preferred embodiments of the present invention have been described in detail, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, utilizing the basic concepts of the present invention as defined in the following claims, also fall within the scope of the present invention. [Explanation of Symbols]

[0074] 100: Battery life status estimation device 110: Processor 120: Memory 130: Storage 140: Communication Interface

Claims

1. In a battery life status estimation device, A memory for loading a program that calculates the equilibrium state value of the voltage of multiple cells constituting a battery and estimates the equilibrium life state value, which is the life state value of the battery to which the equilibrium state value of the voltage is applied, A processor that executes instructions contained in the program loaded into the memory, The aforementioned processor, By executing the program, an acceptable limit value for the voltage difference is set within the voltage difference between the fully charged state voltage and the discharged state voltage of the battery, and an acceptable limit quantile is set which subdivides the acceptable limit range obtained by applying the acceptable limit value for the voltage difference to the average voltage value derived from the measured voltage value of the cell into one or more analysis intervals. The rate of voltage decrease within the permissible limit range, which is the quantile decline rate, is calculated based on the average voltage value. The order of the analysis interval in which the measured voltage values ​​for each cell are initially included within the permissible limit quantile is derived. The amount of charge stored in the battery is determined based on the current applied to the battery, and the Q-V graph showing the relationship between the battery voltage and the amount of charge stored in the battery is converted into a V-dQ / dV graph showing the relationship between the battery voltage and the ratio of the change in the amount of charge stored to the change in the battery voltage. Two feature points, including a reference point and a measurement point, are detected from the V-dQ / dV graph. A voltage equilibrium state value is calculated based on the quantile decline rate, quantile order, and V-dQ / dV value of the feature point, and the equilibrium life state value is estimated by applying the voltage equilibrium state value to the life state value calculated based on the remaining capacity of the battery. The aforementioned quantile decline rate is a battery life state estimation device calculated by the following formula. Y is the quantile decline rate of the battery, meaning the voltage decline rate within the permissible limit range based on the average voltage, and X is the permissible limit quantile.

2. The aforementioned processor, The reference deviation voltage value, which is the voltage difference per per per-allowable limit quantile, is calculated. Based on the average voltage and the number of cells, the standard deviation, the reference deviation voltage value, and the quantile order, the correction factor A value is calculated. A secondary voltage equilibrium value is calculated by adding the product of the correction factor A value and the quantile decline rate to the primary voltage equilibrium value, which is the voltage equilibrium value calculated based on the quantile decline rate and quantile order. Based on the V-dQ / dV graph, the dQ / dV values ​​of the reference point and the dQ / dV values ​​of the measurement point are calculated. The correction factor D is calculated by dividing the dQ / dV value of the measurement point by the dQ / dV value of the reference point. The third voltage equilibrium state value is calculated, reflecting the aforementioned correction factor D. The battery life state estimation device according to claim 1, wherein the third voltage equilibrium state value is applied to the life state value to estimate the equilibrium life state value.

3. The battery life state estimation device according to claim 2, wherein the processor, when calculating the secondary voltage equilibrium state value, changes the calculated correction factor A value to zero (0) if it is negative and applies it, and applies the calculated correction factor A value as is if it is positive.

4. The battery life state estimation device according to claim 1, wherein the processor sets the permissible limit of the voltage difference to a value greater than the operating voltage range value, which is the difference between the voltage in the fully charged state and the voltage in the discharged state, divided by the number of cells, and less than the value obtained by dividing the operating voltage range value by 2.

5. In a method for estimating the battery life state using a battery life state estimation device, The steps include setting an allowable limit for the voltage difference within the voltage difference between the fully charged state voltage and the discharged state voltage of a battery composed of multiple cells, The steps include setting an allowable limit quantile that subdivides the allowable limit range obtained by applying the allowable limit value of the voltage difference to the average voltage value derived from the measured voltage value of the cell into one or more analysis intervals, A step of calculating the quantile decline rate, which is the voltage decline rate within the allowable limit range, based on the average voltage value, based on the allowable limit quantiles, The steps include: deriving the order of quantiles, which is the order of the analysis interval in which the measured voltage values ​​for each cell are initially all included within the aforementioned permissible limit quantiles; The steps include: determining the amount of charge stored in the battery based on the current applied to the battery, converting a Q-V graph showing the relationship between the battery voltage and the amount of charge stored in the battery into a V-dQ / dV graph showing the relationship between the battery voltage and the ratio of the change in the amount of charge stored to the change in the battery voltage; The steps include detecting feature points including reference points and measurement points from the V-dQ / dV graph, A method for estimating the life state of a battery, comprising the steps of: calculating a voltage equilibrium state value based on the quantile decline rate, quantile order, and dQ / dV value of the feature point; and applying the voltage equilibrium state value to a life state value calculated based on the remaining capacity of the battery to estimate an equilibrium life state value, wherein the quantile decline rate is calculated by the following formula. Y is the quantile decline rate of the battery, meaning the voltage decline rate within the permissible limit range based on the average voltage, and X is the permissible limit quantile.

6. The step of estimating the equilibrium lifetime state value is: The steps include: calculating the reference deviation voltage value, which is the voltage difference per per per-allowable limit quantile; A step of calculating a correction factor A value based on the standard deviation calculated based on the average voltage and the number of cells, the reference deviation voltage value and the quantile order, The steps include: calculating a secondary voltage equilibrium value by adding the product of the correction factor A value and the quantile decline rate to the primary voltage equilibrium value, which is the voltage equilibrium value calculated based on the quantile decline rate and quantile order; The steps include: calculating the dQ / dV value of the reference point and the dQ / dV value of the measurement point based on the V-dQ / dV graph, and calculating the correction factor D by dividing the dQ / dV value of the measurement point by the dQ / dV value of the reference point; The steps include: calculating the third voltage equilibrium state value reflecting the correction factor D; The step includes applying the tertiary voltage equilibrium state value to the lifetime state value to estimate the equilibrium lifetime state value, A method for estimating the lifespan of a battery according to claim 5.

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