Battery internal short circuit diagnosis method and battery system using the method

Abstract

The present invention relates to a method for diagnosing an internal short circuit in a battery and a battery system that provides the method. The battery system of the present invention includes a battery including a plurality of battery cells, a cell monitoring integrated circuit (IC) that collects first cell voltages of the battery cells corresponding to a predetermined charging interval in a charging cycle for charging the battery, and a main control circuit that calculates a remaining charging time, which is the time required for a maximum value of the first cell voltage to reach a maximum value of a second cell voltage of a predetermined reference cell, calculates a remaining charge capacity, which is a capacity difference value between the battery cell and the reference cell, based on the remaining charging time, and diagnoses a short circuit in the battery cell based on a comparison result between the remaining charge capacity and a predetermined capacity reference value.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0183596 dated December 23, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method for diagnosing an internal short circuit in a battery and a battery system that provides the method. [Background technology]

[0003] Secondary batteries are batteries that can be charged and discharged. Secondary batteries are widely used in small portable electronic devices such as mobile phones and laptops, and as power sources for driving motors in power tools, automobiles, etc. The interior of a secondary battery may be composed of a positive electrode, a negative electrode, a separator, an electrolyte, etc., and the case may be made of a metal plate or a pouch.

[0004] However, secondary batteries with high energy density can pose various safety issues. For example, the separator can lose its function due to deformation caused by external impact, metallic foreign matter present during the manufacturing process, or the formation of lithium or copper dendrites due to electrochemical reactions, which can lead to an internal short circuit. If a short circuit occurs inside a secondary battery, it can lead to serious safety issues such as thermal runaway.

[0005] Therefore, it is necessary to effectively detect an internal short circuit phenomenon in a battery before the internal short circuit causes significant physical and thermal deformation of the battery. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a battery internal short circuit diagnosis method capable of accurately diagnosing an internal short circuit in a plurality of battery cells connected in series, and a battery system that provides the method. [Means for solving the problem]

[0007] According to one aspect of the present invention, a battery system includes a battery including a plurality of battery cells; a cell monitoring integrated circuit (IC) that collects first cell voltages of the battery cells corresponding to a predetermined charging interval in a charging cycle for charging the battery; and a main control circuit that calculates a remaining charging time, which is the time required for a maximum value of the first cell voltage to reach a maximum value of a second cell voltage of a predetermined reference cell, calculates a remaining charge capacity, which is a capacity difference value between the battery cell and the reference cell, based on the remaining charging time, and diagnoses a short circuit in the battery cell based on a comparison result between the remaining charge capacity and a predetermined capacity reference value.

[0008] The main control circuit may calculate the remaining charge capacity based on the remaining charging time and the magnitude of the charging current of the battery.

[0009] The reference cell may be a battery cell having the largest maximum value among the maximum values ​​of the first cell voltages of the plurality of battery cells or a battery cell corresponding to an average value of the first cell voltages of the plurality of battery cells.

[0010] The cell monitoring integrated circuit (IC) may collect a first cell voltage of the battery cell corresponding to the charging interval in a constant-current charging step of charging the battery with a preset charging current magnitude.

[0011] The plurality of battery cells may be connected in series.

[0012] The main control circuit may extract, for each charging cycle, a plurality of previous first charging cycles corresponding to a predetermined number of samples based on the charging cycle, calculate a moving average value that is an average of a plurality of remaining charge capacities corresponding to each of the plurality of first charging cycles, and calculate the capacity reference value by adding a predetermined error value to the moving average value.

[0013] The main control circuit may calculate a standard deviation based on the moving average value and the plurality of remaining charge capacities for each charging cycle, and calculate the error value by multiplying the standard deviation by a predetermined multiple.

[0014] According to another aspect of the present invention, a method for diagnosing an internal short circuit in a battery includes the steps of: collecting first cell voltages of the battery cells corresponding to a predetermined charging interval in a charging cycle for charging a battery including a plurality of battery cells; calculating a remaining charging time, which is a time required for a maximum value of the first cell voltage to reach a maximum value of a second cell voltage of a predetermined reference cell; calculating a remaining charge capacity, which is a capacity difference value between the battery cell and the reference cell, based on the remaining charging time; calculating a predetermined capacity reference value; and diagnosing a short circuit in the battery cell based on a result of comparing the remaining charge capacity with the capacity reference value.

[0015] The step of calculating the remaining charge capacity may calculate the remaining charge capacity based on the remaining charging time and the magnitude of a charging current of the battery.

[0016] The reference cell may be a battery cell having the largest maximum value among the maximum values ​​of the first cell voltages of the plurality of battery cells or a battery cell corresponding to an average value of the first cell voltages of the plurality of battery cells.

[0017] The step of collecting the first cell voltage of the battery cell may collect the first cell voltage of the battery cell corresponding to the charging interval in a constant-current charging step of charging the battery at a preset charging current magnitude.

[0018] The plurality of battery cells may be connected in series.

[0019] The step of calculating the capacity reference value may include the steps of: extracting a plurality of previous first charging cycles corresponding to a predetermined number of samples based on the charging cycle; calculating a moving average value that is an average of a plurality of remaining charge capacities corresponding to each of the plurality of first charging cycles; calculating a standard deviation based on the moving average value and the plurality of remaining charge capacities; and multiplying the standard deviation by a predetermined multiple to calculate the error value, and adding the predetermined error value to the moving average to calculate the capacity reference value. [Effects of the Invention]

[0020] Since the present invention diagnoses an internal short circuit based on the cell voltage of a battery cell sensed during a battery charging cycle, a separate sleep mode for diagnosing an internal short circuit after the battery charging cycle is not required, and the operation schedule of a higher-level system (e.g., a vehicle) may not be affected.

[0021] The present invention calculates a reference range based on a moving average (MA), which is an average of data adjacent to the current diagnosis point, instead of a fixed reference range, and diagnoses an internal short circuit based on the calculated reference range, thereby reducing the problem of misdiagnosing battery aging as an internal short circuit and improving the accuracy of diagnosis. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a block diagram illustrating a battery system according to an embodiment. [Figure 2] 2 is an exemplary diagram showing a change in the voltage of a battery cell during a charge cycle and a discharge cycle of the battery of FIG. 1; [Figure 3] 3 is an enlarged view of a section Sam_Z of the charge cycle and the discharge cycle of FIG. 2. FIG. [Figure 4] 4 is an enlarged view of a sampling window (SW) in the constant current charging step of FIG. 3, and is an exemplary view illustrating a method for deriving the remaining charging time Δt. [Figure 5] 1 is a diagram illustrating an example of a graph corresponding to a remaining charge capacity RCC, a moving average MA, and a capacity reference value Th-rcc of a battery cell according to an embodiment. [Figure 6] 6 is an exemplary diagram showing an alarm message being generated in a section where the remaining charge capacity RCC is equal to or greater than the capacity reference value Th-rcc in FIG. 5. FIG. [Figure 7] 3 is a flowchart illustrating a method for diagnosing an internal short circuit in a battery according to an embodiment. [Figure 8] 8 is a flowchart illustrating in detail the step (S200) of calculating the remaining charge capacity RCC in FIG. 7. [Figure 9] 8 is a flowchart illustrating in detail the step (S300) of calculating the capacitance reference value Th-rcc in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. Identical or similar components will be designated by identical 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 assigned or used interchangeably solely for the convenience of writing the specification, and do not have any distinct meanings or roles. Furthermore, in describing the embodiments disclosed herein, if it is determined that a detailed description of related publicly known technology may obscure the gist of the embodiments disclosed herein, such a detailed description will be omitted. Furthermore, the accompanying drawings are intended only to facilitate understanding of the embodiments disclosed herein, and the accompanying drawings should not be construed as limiting the technical concepts disclosed herein, and all modifications, equivalents, or alternatives within the concept and technical scope of the present invention are intended to be included.

[0024] 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.

[0025] When a component is said to be "coupled" or "connected" to another component, it is understood that the component may be directly coupled or connected to the other component, but that there may be other components in between. Conversely, when a component is said to be "directly coupled" or "directly connected" to another component, it is understood that there are no other components in between.

[0026] In this application, the use of terms such as "comprises" or "having" is intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof stated in the specification, but is understood not to preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] FIG. 1 is a block diagram illustrating a battery system according to one embodiment.

[0028] Referring to FIG. 1, the battery system 1 includes a battery 10, a current sensor 20, a relay 30, and a battery management system (hereinafter referred to as "BMS") 40.

[0029] 1, a battery 10 is connected between two output terminals OUT1 and OUT2 of a battery system 1, a relay 30 is connected between the positive terminal of the battery 10 and the first output terminal OUT1, and a current sensor 20 is connected between the negative terminal of the battery 10 and the second output terminal OUT2. The configurations and connections between the configurations shown in FIG. 1 are merely examples, and the present invention is not limited thereto.

[0030] The battery 10 includes a plurality of battery cells Cell1 to Celln connected in series. In one embodiment, the battery cells may be rechargeable secondary batteries. Each of the plurality of battery cells Cell1 to Celln is electrically connected to the BMS 40 via wiring. The BMS 40 collects and analyzes various information related to the battery cells, including information about the plurality of battery cells Cell1 to Celln, to control charging, discharging, and protection operations of the battery cells, and to control the operation of the relay 30.

[0031] The current sensor 20 is connected in series to a current path between the battery 10 and an external device. The current sensor 20 measures the battery current, i.e., the charging current and discharging current, flowing through the battery 10 and transmits the measurement result to the BMS 40.

[0032] The relay 30 controls the electrical connection between the battery system 1 and the external device. When the relay 30 is turned on, the battery system 1 and the external device are electrically connected to each other and charging or discharging is performed. When the relay 30 is turned off, the battery system 1 and the external device are electrically disconnected. In this case, the external device may be a charger in a charging cycle that supplies power to the battery 10 for charging, or a load in a discharging cycle that the battery 10 supplies power to the external device.

[0033] The BMS 40 includes a cell monitoring integrated circuit (IC) 41 and a main control circuit 43 .

[0034] The cell monitoring integrated circuit (IC) 41 is electrically connected to the positive and negative electrodes of each of the plurality of battery cells Cell1 to Celln and measures the cell voltage of each of the plurality of battery cells Cell1 to Celln. In some embodiments, during a charging cycle in which the battery 10 is charged with power from an external device, the cell monitoring integrated circuit (IC) 41 may measure the cell voltage of each of the plurality of battery cells Cell1 to Celln corresponding to a predetermined sampling period W. The battery current value measured by the current sensor 20 may be transmitted to the cell monitoring integrated circuit (IC) 41. The cell monitoring integrated circuit (IC) 41 transmits information regarding the measured cell voltage and battery current to the main control circuit 43.

[0035] The main control circuit 43 can diagnose an internal short circuit in each of the battery cells Cell1 to Celln for each charging cycle. For example, assuming that all of the battery cells Cell1 to Celln are in a normal state, if the same amount of current flows through the battery cells Cell1 to Celln, the charge capacities of the battery cells Cell1 to Celln will be the same within a predetermined error range. If some of the battery cells are in an abnormal state, for example, have an internal short circuit, the charge capacity of the battery cell with the internal short circuit may be smaller than the charge capacity of a non-defective battery cell, even if the same amount of current flows through the battery cells Cell1 to Celln. In other words, the charge capacities of the series-connected battery cells Cell1 to Celln may differ depending on whether an internal short circuit occurs.

[0036] In some embodiments, the main control circuit 43 can compare the charge capacities of each of the plurality of battery cells Cell1 to Celln for each charging cycle and diagnose which battery cell among the plurality of battery cells Cell1 to Celln has an internal short circuit defect.

[0037] A method for diagnosing a battery cell in which an internal short circuit defect has occurred based on the remaining charge capacity (RCC) of each of the plurality of battery cells Cell1 to Celln by the main control circuit 43 will be described in detail below.

[0038] FIG. 2 is an exemplary diagram showing a change in the voltage of a battery cell in a charge cycle and a discharge cycle of the battery of FIG. 1, and FIG. 3 is an enlarged diagram of a section Sam_Z of a charge cycle and a discharge cycle of FIG.

[0039] FIG. 2 is an exemplary diagram showing a change in voltage of one of the battery cells Cell1 to Celln during a charge cycle and a discharge cycle of the battery.

[0040] Referring to FIG. 2, during a charge cycle of the battery 10, the cell voltage of each of the battery cells Cell1 to Celln included in the battery 10 may increase as charging proceeds. Also, during a discharge cycle of the battery 10, the cell voltage of each of the battery cells Cell1 to Celln included in the battery 10 may decrease as discharging proceeds. Hereinafter, a charge cycle may refer to the period from the start of charging the battery 10 to the end of charging. Also, a discharge cycle may refer to the period from the start of discharging the battery 10 to the end of discharging.

[0041] Referring to FIG. 3, which is an enlarged view of a portion Sam_Z of the charge cycle and discharge cycle shown in FIG. 2, it is assumed that the battery 10 is charged using a constant current (CC) charging method until time t1, charged using a constant voltage (CV) charging method from time t1 to time t2, is in a sleep mode in which no charging or discharging is performed from time t2 to time t3, and is discharged using a constant current (CC) discharging method from time t3 onwards.

[0042] The constant current CC charging method is a method of charging the battery 10 by maintaining a constant magnitude of the charging current Ic to prevent overcurrent charging. When charging the battery 10 using the constant current CC charging method, the magnitude of each cell voltage of the plurality of serially connected battery cells Cell1 to Celln increases as charging proceeds. The constant voltage CV charging method is a method of charging the battery 10 by maintaining a constant magnitude of the charging voltage Vc to prevent overcharging. When charging the battery 10 using the constant voltage CV charging method, the cell voltage of each of the plurality of battery cells Cell1 to Celln can be maintained constant within a predetermined range even during charging.

[0043] The charging method shown in FIG. 3 is a constant current, constant voltage (CCCV) charging method that uses both constant current charging (CC) and constant voltage charging (CV) within one charging cycle.

[0044] 2 and 3, the solid line A is a graph showing the change in cell voltage of a battery cell in an abnormal state, for example, a battery cell with an internal short circuit defect. The dotted line B is a graph showing the change in cell voltage of a battery cell in a normal state. It can be seen that even when the same current flows, a battery cell with an internal short circuit defect cannot be charged as fully as a battery cell in a normal state.

[0045] FIG. 4 is an enlarged view of a sampling window (SW) in the constant current charging step of FIG. 3, and is an exemplary view illustrating a method for deriving the remaining charging time Δt.

[0046] The sampling window (SW) may refer to a period during which the cell voltage of a battery cell is sampled in a constant current charging CC step of a charging cycle. The size of the sampling window SW may be determined experimentally or may vary depending on the specifications of the battery 10. For example, in FIG. 4, the size of the sampling window SW may correspond to the period from the start point T_a to the end point T_b.

[0047] 3 and 4, for a given battery cell, among the cell voltages extracted in the sampling window SW, the cell voltage corresponding to the start point T_a may have the smallest magnitude, and the cell voltage V_b corresponding to the end point T_b may have the largest magnitude. Hereinafter, the cell voltage V_b corresponding to the end point T_b is defined as the end voltage.

[0048] The first cell voltage V_A may represent the cell voltage of a battery cell that is to be determined as having an internal short circuit. The second cell voltage V_B may represent the cell voltage of a reference cell that serves as a diagnostic reference. For example, the first end voltage may be the first cell voltage corresponding to the end time T_b for the battery cell. The second end voltage V_Bb may be the second cell voltage corresponding to the end time T_b for the reference cell.

[0049] In some embodiments, the main control circuit 43 can calculate the remaining charging time Δt, which is the time further required for the first end voltage V_Ab value of the battery cell to reach the second end voltage V_Bb of the reference cell.

[0050] The reference cell may be defined as a battery cell that serves as a reference for diagnosing an internal short circuit. In Fig. 4, a first voltage graph A for one of the plurality of battery cells Cell1 to Celln that is to be determined as having an internal short circuit may be represented by a solid line.

[0051] Also, the second voltage graph B for the reference cell may be represented by a dotted line. In one embodiment, the battery cell having the largest first end voltage among the plurality of battery cells Cell1 to Celln constituting the battery 10 may be determined as the reference cell. However, the present invention is not limited thereto, and the reference cell may be determined according to various criteria.

[0052] Table 1 below shows an example of the first cell voltage measured at predetermined intervals for each of the first battery cell Cell1, the second battery cell Cell2, and the third battery cell Cell3 in the sampling window SW, assuming that the battery 10 consists of three battery cells, Cell1, Cell2, and Cell3.

[0053] [Table 1]

[0054] Referring to Table 1 above, the first end voltage V_Ab of the first battery cell is 4.1 V, the first end voltage V_Ab of the second battery cell is 3.9 V, and the first end voltage V_Ab of the third battery cell is 3.95 V. In some embodiments, among the first to third battery cells Cell1, Cell2, and Cell3 constituting the battery 10, the first battery cell Cell1, which corresponds to the highest first end voltage V_Ab of 4.1 V, may be determined as the reference cell. In this case, the magnitude of the first cell voltage measured in the period before the end time point T_b may be ignored.

[0055] In another embodiment, a voltage graph may be calculated based on the average value of the first cell voltages of the plurality of battery cells Cell1 to Celln during the sampling window SW, and a virtual battery cell corresponding to the calculated voltage graph may be determined as a reference cell. For example, based on the average value of the first cell voltages of the first battery cell Cell1, the second battery cell Cell2, and the third battery cell Cell3 disclosed in Table 1 above, a second cell voltage for the reference cell may be calculated as shown in Table 2 below.

[0056] [Table 2]

[0057] Referring to Table 2 above, the second end voltage V_Bb of the reference cell can be calculated as the average of the first end voltages V_Ab of the first battery cell Cell 1, the second battery cell Cell 2, and the third battery cell Cell 3. Referring to Table 2 and FIG. 4, the second end voltage V_Bb of the reference cell in second voltage graph B may be 3.983V.

[0058] In another embodiment, in the sampling window SW, among the first end voltages V_Ab of each of the plurality of battery cells Cell1 to Celln, battery cells corresponding to a first end voltage V_Ab that exceeds a value obtained by multiplying the standard deviation by a predetermined multiple are excluded, and a voltage graph is calculated based on the average value of each of the first cell voltages of the remaining plurality of battery cells Cell1 to Celln, and a virtual battery cell corresponding to the calculated voltage graph can be determined as a reference cell.

[0059] For example, referring to Table 1, the average value of the first end voltage V_Ab of each of the first battery cell Cell1, the second battery cell Cell2, and the third battery cell Cell3 is 3.983V. Assume that the standard deviation is 0.05 and the predetermined multiple α is 1. Then, the first end voltage V_Ab (4.1V) of the first battery cell exceeds the result of multiplying the standard deviation by the predetermined multiple from the average value (3.983 + 0.05 = 4.033), so it may be excluded from the calculation of the reference cell. Then, a voltage graph for a hypothetical reference cell, as shown in Table 3 below, can be calculated based on the average values ​​of the first cell voltages of each of the second and third battery cells.

[0060] [Table 3]

[0061] 4, the main control circuit 43 may calculate the remaining charging time Δt based on the slope of the first voltage graph A of the battery cell in the sampling window SW and the difference between the first end voltage and the second end voltage (ΔV=V_Bb-V_Ab). However, the main control circuit 43 may calculate the remaining charging time Δt using various known arithmetic methods, without being limited thereto.

[0062] First, the main control circuit 43 may generate a virtual voltage graph A' by extending the first voltage graph A to the second end voltage V_Bb based on the slope of the first voltage graph A. In this case, the main control circuit 43 may extend the graph using various algorithms known in the art. In FIG. 4, the virtual voltage graph A' is represented by a dashed line.

[0063] Next, the main control circuit 43 can calculate a virtual end point T_b+Δt, which is the horizontal axis coordinate that matches the second end voltage V_Bb of the virtual voltage graph A'. The main control circuit 43 can calculate the remaining charging time Δt based on the difference between the end point T_b of the sampling window SW and the virtual end point T_b+Δt.

[0064] FIG. 5 is an example of a graph corresponding to the remaining charge capacity RCC, moving average value MA, and capacity reference value Th-rcc of a battery cell according to an embodiment, and FIG. 6 is an example of a graph showing that an alarm message is generated in an area in FIG. 5 where the remaining charge capacity RCC is equal to or greater than the capacity reference value Th-rcc.

[0065] The following description will be given focusing on one of the plurality of battery cells Cell1 to Celln, but the method described below can be equally applied to each of the plurality of battery cells Cell1 to Celln.

[0066] Referring to FIG. 3, in some embodiments, the same amount of charging current Ic flows through each of the plurality of battery cells Cell1 to Celln connected in series. As described above, when the same amount of current flows through the plurality of battery cells Cell1 to Celln, the charge capacities of each of the plurality of battery cells Cell1 to Celln are the same within a predetermined error range. If a battery cell has an internal short circuit defect, the charge capacity of the battery cell may differ significantly from the charge capacities of other battery cells (e.g., reference cells). In some embodiments, the main control circuit 43 can diagnose the internal short circuit defect of the battery cell based on the difference in charge capacity.

[0067] The remaining charge capacity (RCC) may correspond to the difference in charge capacity between a reference cell and a battery cell under the same charging conditions. The larger the difference, the more likely there is a short circuit defect inside the battery cell.

[0068] The main control circuit 43 can calculate the remaining charge capacity RCC based on the remaining charging time Δt and the charging current Ic. Specifically, the main control circuit 43 can calculate the remaining charge capacity RCC of the battery cell based on the following Equation 1:

[0069] [Formula 1] RCC=Ic×Δt×(1h / 3600s)[Ah]

[0070] In the formula, Ic is the charging current supplied to the battery 10 in the constant current charging CC step of the charging cycle, Δt is the remaining charging time in seconds S, and the remaining charge capacity RCC can be expressed in "Ah," which is the capacity unit of the battery 10.

[0071] For each charging cycle, the main control circuit 43 calculates the remaining charge capacity RCC of the battery cell and compares the calculated remaining charge capacity RCC with a capacity reference value Th-rcc.

[0072] Referring to Figure 5, from the 330th charging cycle, the remaining charge capacity RCC of the battery cell is equal to or greater than the capacity reference value Th-rcc. When the remaining charge capacity RCC is equal to or greater than the capacity reference value Th-rcc, the main control circuit 43 can generate an alarm message. Referring to Figures 5 and 6, the main control circuit 43 continues to generate an alarm message from the 330th charging cycle.

[0073] The capacity reference value Th-rcc is a reference value used to diagnose an internal short circuit defect. As described above, if the remaining charge capacity RCC, which corresponds to the difference in charge capacity between the reference cell and the battery cell, increases by more than a predetermined reference value, it can indicate that the battery cell is not in a normal state. The reference value at this time is the capacity reference value Th-rcc.

[0074] In some embodiments, for each charging cycle, the main control circuit 43 calculates a moving average (MA), a capacity reference value Th-rcc that is greater than the moving average M value by a predetermined value, and a remaining charge capacity RCC corresponding to the current charging cycle N.

[0075] First, the main control circuit 43 can determine a sample group by extracting a plurality of charge cycles included in a preset number of samples (SN) when counting charge cycles in the direction of previous charge cycles based on the current charge cycle N. Here, the sample number SN is the number of charge cycles included in the sample group, and can be determined as an optimal number based on experiments, etc. The sample group may be a subset of a plurality of past charge cycles, which is a population, and may be a group for calculating a moving average value MA, which will be described below.

[0076] Table 4 below shows an example of the remaining charge capacity RCC, the moving average value MA, and the capacity reference value Th-rcc calculated for each of a plurality of charging cycles. Assume that the number of samples SN is 4.

[0077] [Table 4]

[0078] In some embodiments, when counting charge cycles in the direction of previous charge cycles based on the current charge cycle N, the main control circuit 43 can extract the Nth charge cycle, the N-1th charge cycle, the N-2nd charge cycle, and the N-3rd charge cycle, which correspond to the four sample numbers SN, and determine the sample population.

[0079] In another embodiment, the main control circuit 43 may determine the sample group by extracting the (N-1)th, (N-2)th, (N-3)th, and (N-4)th charge cycles, which correspond to four sample numbers SN, when counting charge cycles in the direction of previous charge cycles based on the current charge cycle N. That is, the current charge cycle N may be included in the sample group, but this is not limiting, and the current charge cycle N may be excluded. The following description will be given assuming that the current charge cycle N is included in the sample group.

[0080] Next, the main control circuit 43 determines the Nth capacity reference value Th-rcc_n, which is a reference value for diagnosing battery defects in the Nth charging cycle, based on the remaining charge capacity RCC calculated for each of the multiple charging cycles N-3, N-2, N-1, and N belonging to the sample population.

[0081] The following Table 5 shows an example of a method for calculating the Nth moving average value MA_n, the Nth standard deviation Std_n, and the Nth capacity reference value Th-rcc_n calculated in the Nth charging cycle. In Table 5, the predetermined multiple α is assumed to be a natural number 4.

[0082] [Table 5]

[0083] Using the methods described above in Tables 4 and 5, the main control circuit 43 can calculate the remaining charge capacity RCC and the capacity reference value Th-rcc for each of the battery cells Cell1 to Celln for each charging cycle. The main control circuit 43 can also calculate a moving average MA and a standard deviation Std to calculate the capacity reference value Th-rcc. For example, assuming that approximately 338 charging cycles have been performed, the graph shown in FIG. 5 can be derived.

[0084] FIG. 7 is a flowchart illustrating a method for diagnosing an internal short circuit in a battery according to one embodiment, FIG. 8 is a flowchart illustrating in detail the step (S200) of calculating the remaining charge capacity RCC in FIG. 7, and FIG. 9 is a flowchart illustrating in detail the step (S300) of calculating the capacity reference value Th-rcc in FIG. 7.

[0085] A method for diagnosing an internal short circuit in a battery and a battery system that provides the method will be described in detail below with reference to Figures 1 to 9. A method for diagnosing an internal short circuit defect in any one of the plurality of battery cells Cell1 to Celln will be described below. However, the method described below can be equally applied to each of the plurality of battery cells Cell1 to Celln.

[0086] Referring to FIG. 7, first, in a charging cycle in which the battery 10 is charged with power from an external device, the main control circuit 43 collects a first cell voltage of a battery cell corresponding to a sampling window, which is a predetermined charging period (S100).

[0087] The sampling window may be determined as a predetermined size in a constant-current charging step in which the battery 10 is charged with a preset charging current. Referring to FIG. 3, the size of the sampling window may be defined as a charging interval from a start point T_a to an end point T_b. The cell monitoring integrated circuit (IC) 41 may transmit the first cell voltage of the battery cell measured in the sampling window at predetermined intervals or in real time to the main control circuit 43.

[0088] Next, the main control circuit 43 calculates the remaining charge capacity RCC, which is the difference between the charge capacity of the reference cell and the charge capacity of the battery cell in the sampling window (S200).

[0089] The remaining charge capacity RCC may correspond to the charge capacity that the battery cell should have to meet the maximum charge capacity of the reference cell during the sampling window. That is, the remaining charge capacity RCC may be the deficiency of the charge capacity of the battery cell relative to the charge capacity of the reference cell.

[0090] When charging the battery 10 using the constant current charging method (CC), the same charging current Ic is supplied to each of the plurality of battery cells Cell1 to Celln connected in series. Therefore, the charge capacity of each of the plurality of battery cells Cell1 to Celln is the same within a predetermined error range. If any of the plurality of battery cells Cell1 to Celln has a defect such as an internal short circuit, the charge capacity of the battery cell may differ from the charge capacities of the other battery cells. In this case, the other battery cell serving as a basis for comparison may be the reference cell.

[0091] Referring to FIG. 8, in step S200, the main control circuit 43 determines a second end voltage V_Bb of the reference cell, which is a battery cell that serves as a reference for diagnosing an internal short circuit defect (S210).

[0092] In one embodiment, the main control circuit 43 may determine, as a reference cell, a battery cell having the highest first end voltage V_Ab among the plurality of battery cells Cell1 to Celln that constitute the battery 10. For example, referring to Table 1, among the first to third battery cells Cell1, Cell2, and Cell3 that constitute the battery 10, the first battery cell Cell1 having the highest first end voltage V_Ab may be determined as the reference cell.

[0093] In another embodiment, the main control circuit 43 may calculate a virtual voltage graph based on the average value of the first cell voltages of each of the plurality of battery cells Cell1 to Celln during the sampling window SW, and determine a virtual battery cell corresponding to the calculated virtual voltage graph as the reference cell. For a specific example, refer to Table 2 described above.

[0094] In another embodiment, the main control circuit 43 may calculate a virtual voltage graph based on the average value of the first cell voltages of the remaining battery cells Cell1 to Celln, excluding battery cells whose first end voltages V_Ab exceed a value obtained by multiplying the standard deviation by a predetermined multiple, among the battery cells Cell1 to Celln during the sampling window SW, and determine the virtual battery cell corresponding to the calculated virtual voltage graph as the reference cell. For a specific example, see Table 3 described above.

[0095] The main control circuit 43 may determine the reference cell B according to the various embodiments described above. Referring to FIG. 4, the main control circuit 43 may determine the cell voltage V_b of the reference cell B corresponding to the end point T_b of the sampling window SW as the second end voltage V_Bb.

[0096] In step S200, the main control circuit 43 calculates the remaining charging time Δt, which is the time required for the first end voltage V_Ab value of the battery cell to reach the second end voltage V_Bb value of the reference cell (S230).

[0097] Referring to FIG. 4, the main control circuit 43 can calculate the remaining charging time Δt based on the slope of the first voltage graph A of the battery cell in the sampling window SW and the difference value (ΔV=V_Bb-V_Ab) between the end voltages of the battery cell and the reference cell.

[0098] First, the main control circuit 43 may generate a virtual voltage graph A' by extending the first voltage graph A to the second end voltage V_Bb based on the slope of the first voltage graph A. In this case, the main control circuit 43 may extend the graph using various algorithms known in the art. In FIG. 4, the virtual voltage graph A' is represented by a dashed line.

[0099] Next, the main control circuit 43 can calculate a virtual end point T_b+Δt, which is the horizontal axis coordinate that matches the second end voltage V_Bb of the virtual voltage graph A'. The main control circuit 43 can calculate the remaining charging time Δt based on the difference between the end point T_b of the sampling window SW and the virtual end point T_b+Δt.

[0100] In step S200, the main control circuit 43 calculates the remaining charge capacity RCC based on the remaining charging time Δt and the magnitude of the battery charging current Ic (S250).

[0101] The magnitude of the charging current Ic may correspond to the magnitude of the charging current supplied to the battery 10 during the sampling window SW. In some embodiments, the main control circuit 43 may calculate the remaining charge capacity RCC of the battery cell based on Equation 1.

[0102] Next, the main control circuit 43 calculates a capacitance reference value Th-rcc (S300).

[0103] The capacity reference value Th-rcc is a reference value used to diagnose internal short circuit faults. In some embodiments, for each charging cycle, the main control circuit 43 calculates the remaining charge capacity RCC and the capacity reference value Th-rcc of the battery cell.

[0104] In step S300, the main control circuit 43 extracts a predetermined number of previous charging cycles based on the current charging cycle to form a sample group, and calculates a moving average value MA by averaging the remaining charge capacities RCC corresponding to each charging cycle belonging to the sample group (S310).

[0105] The main control circuit 43 may determine a sample group by extracting a plurality of charge cycles included in a predetermined number of samples (SN) when counting charge cycles in the direction of the previous charge cycle based on the current charge cycle N. In this case, the sample number SN is the number of charge cycles included in the sample group, and may be determined as an optimal number based on experiments, etc. The sample group may be a subset of the previous plurality of charge cycles, which is the population, and may be a population for calculating a moving average value MA.

[0106] In step S300, the main control circuit 43 calculates the standard deviation Sdt based on the extracted remaining charge capacity RCC of each previous charging cycle and the calculated moving average value MA (S330).

[0107] In some embodiments, the sample population for calculating the moving average MA and the sample population for calculating the standard deviation Sdt may be the same, while in other embodiments, the sample population for calculating the moving average MA and the sample population for calculating the standard deviation Sdt may be different.

[0108] For example, the first sample collection for calculating the moving average value MA may have a sample number SN of 3. The main control circuit 43 may calculate the moving average value MA based on the remaining charge capacities RCC corresponding to the (N-3)th charging cycle (N-3), the (N-2)th charging cycle (N-2), and the (N-1)th charging cycle (N-1). The second sample collection for calculating the standard deviation Sdt may include the first charging cycle through the current charging cycle N. The main control circuit 43 may calculate the standard deviation Sdt based on the remaining charge capacities RCC corresponding to the first charging cycle through the (N-1)th charging cycle (N-1), and the moving average value MA calculated based on the first sample collection. However, the number of samples is not limited to this, and the sample collection may be determined using various numbers of samples.

[0109] In step S300, the main control circuit 43 calculates the capacitance reference value Th-rcc by adding an error value obtained by multiplying the standard deviation Sdt by a predetermined multiple α to the moving average value MA (S350).

[0110] The predetermined multiple α can be calculated experimentally depending on various circumstances such as the specifications and usage period of the battery 10. For example, the predetermined multiple α may be a predetermined integer.

[0111] Next, the main control circuit 43 determines whether the remaining charge capacity RCC is equal to or greater than a capacity reference value Th-rcc (S400).

[0112] If the remaining charge capacity RCC is equal to or greater than the capacity reference value Th-rcc, the main control circuit 43 can generate an alarm message indicating this and transmit the generated signal message to a higher-level system.

[0113] Next, if the result of the determination is that the remaining charge capacity RCC is equal to or greater than the capacity reference value Th-rcc (S400, YES), the main control circuit 43 determines whether the cumulative number of charging cycles corresponding to the remaining charge capacity RCC being equal to or greater than the capacity reference value Th-rcc is equal to or greater than a reference value (S500).

[0114] Next, if the cumulative number is equal to or greater than the reference value (S500, YES), the main control circuit 43 diagnoses an internal short circuit in the battery cell (S600).

[0115] Next, if the determination result shows that the remaining charge capacity RCC is less than the capacity reference value Th-rcc (S400, NO) or the cumulative number is less than the reference value (S500, NO), the main control circuit 43 diagnoses that no internal short-circuit defect will occur in the battery cell (S700).

[0116] 6, an event corresponding to the remaining charge capacity RCC being equal to or greater than the capacity reference value Th-rcc first occurs at the 330th charging cycle, and then an event also occurs at the 330th charging cycle. In one embodiment, if the reference value is 1, the main control circuit 43 can generate an alarm message and diagnose an internal short circuit in the battery cell at the 330th charging cycle. In another embodiment, if the reference value is 10, the main control circuit 43 can continue to generate an alarm message from the 330th charging cycle, but can diagnose an internal short circuit in the battery cell at the 340th charging cycle.

[0117] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these, 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.

Claims

1. a battery including a plurality of battery cells; a cell monitoring integrated circuit for collecting a first cell voltage of the battery cell corresponding to a predetermined charging interval in a charging cycle for charging the battery; a main control circuit that calculates a remaining charge time, which is the time required for the maximum value of the first cell voltage to reach a maximum value of the second cell voltage of a predetermined reference cell, calculates a remaining charge capacity, which is a capacity difference value between the battery cell and the reference cell, based on the remaining charge time, and diagnoses a short circuit of the battery cell based on a comparison result between the remaining charge capacity and a predetermined capacity reference value.

2. 2. The battery system according to claim 1, wherein the main control circuit calculates the remaining charge capacity based on the remaining charging time and the magnitude of the charging current of the battery.

3. 2. The battery system of claim 1, wherein the reference cell is a battery cell having the largest maximum value among the maximum values ​​of the first cell voltages of the plurality of battery cells, or a battery cell corresponding to an average value of the first cell voltages of the plurality of battery cells.

4. 2. The battery system of claim 1, wherein the cell monitoring integrated circuit collects a first cell voltage of the battery cell corresponding to the charging interval in a constant current charging step of charging the battery with a preset charging current magnitude.

5. The battery system according to claim 1 , wherein the plurality of battery cells are connected in series.

6. 2. The battery system of claim 1, wherein the main control circuit extracts, for each charging cycle, a plurality of previous first charging cycles corresponding to a predetermined number of samples based on the charging cycle, calculates a moving average value that is an average of a plurality of remaining charge capacities corresponding to each of the plurality of first charging cycles, and calculates the capacity reference value by adding a predetermined error value to the moving average value.

7. 7. The battery system according to claim 6, wherein the main control circuit calculates a standard deviation based on the moving average value and the plurality of remaining charge capacities for each charging cycle, and multiplies the standard deviation by a predetermined multiple to calculate the error value.

8. collecting first cell voltages of the battery cells corresponding to a predetermined charging interval in a charging cycle for charging a battery including a plurality of battery cells; Calculating a remaining charge time, which is the time required for the maximum value of the first cell voltage to reach the maximum value of the second cell voltage of a predetermined reference cell, and calculating a remaining charge capacity, which is a capacity difference value between the battery cell and the reference cell, based on the remaining charge time; calculating a predetermined capacitance reference value; and diagnosing a short circuit in the battery cell based on a comparison result between the remaining charge capacity and the capacity reference value.

9. 9. The method for diagnosing an internal short circuit in a battery according to claim 8, wherein the step of calculating the remaining charge capacity calculates the remaining charge capacity based on the remaining charging time and the magnitude of the charging current of the battery.

10. 9. The method for diagnosing an internal short circuit in a battery according to claim 8, wherein the reference cell is a battery cell having the largest maximum value among the maximum values ​​of the first cell voltages of the plurality of battery cells, or a battery cell corresponding to an average value of the first cell voltages of the plurality of battery cells.

11. 9. The method of diagnosing an internal short circuit in a battery according to claim 8, wherein the step of collecting the first cell voltage of the battery cell comprises collecting the first cell voltage of the battery cell corresponding to the charging section in a constant current charging step of charging the battery at a predetermined charging current magnitude.

12. The method of diagnosing an internal short circuit in a battery according to claim 8 , wherein the plurality of battery cells are connected in series.

13. The step of calculating the predetermined capacitance reference value includes: extracting a plurality of first charging cycles corresponding to a predetermined number of samples from the previous charging cycle, and calculating a moving average value that is an average of a plurality of remaining charge capacities corresponding to each of the plurality of first charging cycles; calculating a standard deviation based on the moving average value and the plurality of remaining charge capacities; 9. The method for diagnosing an internal short circuit in a battery according to claim 8, further comprising the steps of: multiplying the standard deviation by a predetermined multiple to calculate a predetermined error value; and adding the error value to the moving average value to calculate the capacity reference value.

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