Abnormal cell diagnosis method and battery system using differential capacity profile
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-11-03
- Publication Date
- 2026-08-13
Smart Images
Figure KR2025017820_13082026_PF_FP_ABST
Abstract
Description
Abnormal cell diagnosis method using differential capacity profile and battery system
[0001] Cross-citation with related application(s)
[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2025-0015854 dated February 7, 2025, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.
[0003] The present disclosure relates to a method for diagnosing an abnormal cell using a differential capacity profile and a battery system.
[0004] In battery packs containing multiple battery cells, there are various methods for diagnosing abnormal cells. Battery cell degradation can be diagnosed by utilizing key indicators on differential capacity profiles based on battery charge / discharge voltage and current data.
[0005] However, since the positions of key indicators on the differential capacitance profile change depending on the magnitude of the current, it is difficult to select a voltage range that does not depend on the current.
[0006] The present invention aims to provide a method and battery system capable of diagnosing abnormal cells by utilizing differential capacity profiles as key indicators.
[0007] A battery system according to one feature of the invention comprises: a battery pack including a plurality of battery cells; a current sensor connected to one end of the battery pack and generating a current signal indicating a module current flowing through the battery pack; and a battery management system (BMS) that, in a first charging cycle for charging the plurality of battery cells, generates battery state data including cell voltage and cell capacity of each of the plurality of battery cells based on signals received from the plurality of battery cells and the current sensor, generates a plurality of differential capacity profiles indicating a differential change in capacity with respect to a voltage change for the plurality of battery cells based on the battery state data, determines the valley with the lowest cell voltage among the valleys of each of the plurality of differential profiles as a target valley, determines the peak with the second lowest cell voltage among the peaks of each of the plurality of differential profiles as a target peak, and diagnoses the state of each of the plurality of battery cells based on the target valley and the target peak.
[0008] The first charging cycle above may be a charging cycle in which charging is performed on the battery pack within a predetermined cell voltage range.
[0009] The battery status data includes cycle information indicating which charging cycle among a plurality of charging cycles for the battery pack the data was measured in, and the BMS can generate each of the plurality of differential capacity profiles by calculating the differential change in capacity with respect to the voltage change for each of the plurality of battery cells based on the battery status data for a predetermined number of cycle periods based on the cycle information.
[0010] The above BMS can calculate a voltage interval representing the interval between the target low point and the target high point for each of the plurality of battery cells, and determine an abnormal cell among the plurality of battery cells based on the result of comparing the voltage interval with a predetermined reference value.
[0011] The above BMS determines a plurality of voltage intervals calculated for the plurality of battery cells in the first charging cycle as a voltage interval group, and if there is a voltage interval below a predetermined reference value among the voltage interval groups determined in correspondence with each of the plurality of charging cycles for the battery pack, the target battery cell corresponding to the voltage below the predetermined reference value can be determined as the abnormal cell.
[0012] The above BMS determines a plurality of voltage intervals calculated for the plurality of battery cells in the first charging cycle in correspondence with each of the plurality of predetermined charge / discharge rates as a voltage interval group, and if there is a voltage interval below a predetermined reference value among the voltage interval groups determined in correspondence with each of the plurality of charge / discharge rates in correspondence with each of the plurality of charging cycles for the battery pack, it determines one or more target battery cells corresponding to the voltage below the predetermined reference value as one or more abnormal candidate cells, and can determine at least one of the one or more abnormal candidate cells as an abnormal cell.
[0013] A method for diagnosing an abnormal cell according to another feature of the invention may include: generating battery state data including cell voltage and cell capacity of each of the plurality of battery cells in a first charging cycle in which the plurality of battery cells are charged based on a signal received from a current sensor connected to one end of a battery pack including the plurality of battery cells; generating a plurality of differential capacity profiles indicating a differential change in capacity with respect to a voltage change for the plurality of battery cells based on the battery state data; determining the lowest valley among the plurality of valleys of each of the plurality of differential profiles as a target valley where the cell voltage is lowest; determining the second lowest peak among the plurality of peaks of each of the plurality of differential profiles as a target peak; and diagnosing the state of each of the plurality of battery cells based on the target valley and the target peak.
[0014] The first charging cycle is a charging cycle in which charging is performed on the battery pack within a predetermined cell voltage range, and the battery status data includes cycle information indicating which charging cycle among a plurality of charging cycles for the battery pack the data was measured in, and the abnormal cell diagnosis method may further include the step of generating each of the plurality of differential capacity profiles by calculating the differential change in capacity with respect to the voltage change for each of the plurality of battery cells based on the battery status data for a predetermined number of cycle periods based on the cycle information.
[0015] The method may further include the step of calculating a voltage interval representing the interval between the target low point and the target high point for each of the plurality of battery cells, and the step of determining an abnormal cell among the plurality of battery cells based on the result of comparing the voltage interval with a predetermined reference value.
[0016] For the first charging cycle, the method may further include the step of determining a plurality of voltage intervals calculated for the plurality of battery cells as a single voltage interval group, the step of determining whether there is a voltage interval below a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charging cycles for the battery pack, and the step of determining a target battery cell corresponding to the target voltage interval as the ideal cell if there is a target voltage interval below a predetermined reference value among the voltage interval groups.
[0017] The method may further include the steps of: determining a plurality of voltage intervals calculated for the plurality of battery cells for each of the first charging cycles corresponding to each of the plurality of charging and discharging rates as a single voltage interval group; determining whether there is a voltage interval below a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charging cycles for the battery pack for each of the plurality of charging and discharging rates; if there is a target voltage interval below a predetermined reference value among the voltage interval groups, determining one or more target battery cells corresponding to the target voltage interval as one or more ideal candidate cells; and determining at least one of the one or more ideal candidate cells as the ideal cell.
[0018] According to the present invention, the voltage interval between the lowest point (valley1) and the second lowest point (peak2) of the differential capacity profile can be used as an indicator to distinguish between normal cells and abnormal cells. Furthermore, according to the present invention, even if the charging and discharging currents are different, the positions of the lowest point and the peak may change on the differential capacity profile each time, but the voltage interval between the lowest point (valley1) and the second lowest point (peak2) of the cell voltage can distinguish between abnormal cells and normal cells, and thus can be used as an indicator for diagnosing abnormal cells.
[0019] According to the present invention, when a defect occurs in a battery connected to a vehicle, the safety of the battery pack can be improved by diagnosing the defect. According to the present invention, when a plurality of battery cells included in a battery pack can be divided into multiple cell groups, it is possible to detect which of the multiple cell groups an abnormal cell with a potential for ignition is located in. Furthermore, according to this, it is possible to prevent the entire defect caused by a partial defect in the battery pack.
[0020] FIG. 1 is a block diagram schematically illustrating a battery system according to one embodiment.
[0021] Figure 2 is an example of a differential capacity profile for a single battery cell.
[0022] Figure 3 is a graph to explain the voltage interval between the target low point and the target high point of Figure 2.
[0023] Figure 4 is a graph showing the voltage interval between the target low point and the target high point of each of the multiple battery cells in each of the multiple target charging cycles corresponding to the multiple target voltage groups.
[0024] FIG. 5 is a graph showing an example in another embodiment where the charge / discharge rate is 0.1C.
[0025] FIG. 6 is a graph showing an example in which the charge / discharge rate is 0.3C in another embodiment.
[0026] FIG. 7 is a graph showing an example in another embodiment where the charge / discharge rate is 0.5C.
[0027] FIG. 8 is a comparative example utilizing the lowest point indicator among the plurality of poles where the cell voltage is lowest for the battery cells shown in FIG. 5 to 7.
[0028] FIG. 9 is a comparative example utilizing the second lowest peak indicator among the plurality of poles for the battery cells shown in FIG. 5 to 7.
[0029] FIG. 10 is a flowchart of an abnormal cell diagnosis method according to one embodiment.
[0030] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Identical or similar components are assigned identical or similar reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "part" for components used in the following description are assigned or used interchangeably solely for the ease of drafting the specification and do not have distinct meanings or roles in themselves. Furthermore, in describing the embodiments disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the embodiments disclosed in this specification, such detailed description will be omitted. Additionally, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification; the technical concept disclosed in this specification is not limited by the attached drawings, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the invention.
[0031] Terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.
[0032] In this application, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.
[0033] In a configuration that controls another configuration under specific control conditions among the configurations according to one embodiment, a program implemented as a set of instructions specifying a control algorithm required to control the other configuration may be installed. The control configuration may generate output data by processing input data and stored data according to the installed program. The control configuration may include a non-volatile memory for storing the program and a memory for storing data.
[0034] FIG. 1 is a block diagram schematically illustrating a battery system according to one embodiment.
[0035] Referring to FIG. 1, the battery system (1) may include a battery pack (110), a battery management system (BMS) (120), and relays (101, 102).
[0036] The battery pack (110) may include a plurality of battery cells (C1-C6). Here, n is a natural number greater than or equal to 3. In FIG. 1, the number of battery cells is depicted as 6, but this is for convenience of explanation and the invention is not limited thereto. The battery pack (110) may include 2 or more battery cells. Also, in FIG. 1, the battery pack (110) is depicted as having a plurality of battery cells (C1-C6) connected in series, but this is for convenience of explanation and the invention is not limited thereto. The battery pack (110) may include 2 or more battery cells connected in series, a plurality of battery cells connected in series, or 2 or more battery cells connected in parallel.
[0037] One end of the relay (101, 102) is connected to the battery pack (110), and the other end of the relay (101, 102) is connected to at least one component of the external device (2). The closing and opening of the relay (101, 102) can be controlled according to relay control signals (RCS1, RCS2) supplied from the BMS (120).
[0038] The battery system (1) may be connected to an external device (2). The external device (2) may include a load and a charging device such as an inverter or a converter. If the external device (2) is a charger, both ends (P+, P-) of the battery system (1) may be connected to the charger to receive power from the charger and be charged. If the external device (2) is a load, both ends (P+, P-) of the battery system (1) may be connected to the load so that the power supplied by the battery pack (110) may be discharged through the load. Although FIG. 1 is illustrated as having the external device (2) connected to the battery system (1), this is merely an example to aid in understanding the battery system (1) and the invention is not limited thereto.
[0039] The BMS (120) can generate battery status data for multiple battery cells (C1-C6), generate differential capacity profiles for each of the multiple battery cells (C1-C6) based on the battery status data, analyze each differential capacity profile, and diagnose the status of each of the multiple battery cells (C1-C6) based on the results of the analysis.
[0040] The BMS (120) may include a state data generation unit (121) and a main control unit (MCU) (122). The MCU (122) may control the operation of the state data generation unit (121). The MCU (122) may include a differential capacitance calculation unit (1221), a pole extraction unit (1222), and a diagnostic unit (1223).
[0041] The battery system (1) may further include a current sensor (130). The current sensor (130) may be connected to one end of the battery pack (110). The current sensor (130) may generate a current signal indicating the module current flowing through the battery pack (110).
[0042] The state data generation unit (121) can generate battery state data for each of the plurality of battery cells (C1-C6) based on signals received from each of the plurality of battery cells (C1-C6) and signals received from the current sensor (130). In the following, the battery state data may include information indicating the cell voltage, cell current, and cell capacity of each battery cell. Here, the battery state data may be information corresponding to a predetermined charge / discharge rate (C-rate). Here, the predetermined charge / discharge rate may be a charge / discharge rate reference determined in advance as initial information.
[0043] The state data generation unit (121) can derive the cell voltage of each of the plurality of battery cells (C1-C6) based on voltage signals received from both ends of each of the plurality of battery cells (C1-C6). The state data generation unit (121) can derive the module current flowing through the battery pack (110) based on current signals received from the current sensor (130). The state data generation unit (121) can calculate the cell capacity of each of the plurality of battery cells (C1-C6) based on the derived module current.
[0044] The battery status data may include cycle information (hereinafter "cycle information") indicating which charging cycle (hereinafter "multiple charging cycles") each included data was measured in among multiple charging cycles (hereinafter "multiple charging cycles") for multiple battery cells (C1-C6) and which discharge cycle (hereinafter "multiple discharge cycles") for multiple battery cells (C1-C6). Here, the charging cycle may represent the number of times a charging process is performed in which power is supplied to the multiple battery cells (C1-C6) to charge the multiple battery cells (C1-C6) from a discharged state to a charged state. Here, the discharge cycle may represent the number of times a discharge process is performed in which power is consumed from the multiple battery cells (C1-C6) to discharge the multiple battery cells (C1-C6) from a charged state to a discharged state. Here, the discharged state of multiple battery cells (C1-C6) may indicate a state in which the cell voltages of all multiple battery cells (C1-C6) are below a predetermined lower discharge limit voltage, and the charged state of multiple battery cells (C1-C6) may indicate a state in which the cell voltages of all multiple battery cells (C1-C6) are above a predetermined upper charge limit voltage. The predetermined upper charge limit voltage may be a predetermined value or a predetermined range indicating that the battery pack is fully charged. The predetermined lower discharge limit voltage may be a predetermined value or a predetermined range indicating that the battery pack is fully discharged. Battery state data may include current values flowing through the battery pack (110) in each of the multiple charging cycles.
[0045] The differential capacity calculation unit (1221) receives battery state data from the state data generation unit (121) and can generate a plurality of differential capacity profiles (dQ / dV profiles) based on the battery state data. Here, the plurality of differential capacity profiles can indicate a differential change in capacity with respect to a voltage change amount of a plurality of battery cells (C1-C6) corresponding to a predetermined charge / discharge rate. For example, the first differential capacity profile can indicate a differential change in capacity with respect to a voltage change for battery cell (C1). The second differential capacity profile can indicate a differential change in capacity with respect to a voltage change for battery cell (C2). The third differential capacity profile can indicate a differential change in capacity with respect to a voltage change for battery cell (C3). The fourth differential capacity profile can indicate a differential change in capacity with respect to a voltage change for battery cell (C4). The fifth differential capacity profile can indicate a differential change in capacity with respect to a voltage change for battery cell (C5). The sixth differential capacity profile can represent the differential change in capacity with respect to the voltage change for the battery cell (C6).
[0046] The differential capacity calculation unit (1221) can generate each differential capacity profile by expressing the change in capacity relative to the change in voltage as a graph with voltage as the x-axis.
[0047] The differential capacity calculation unit (1221) can determine whether the charging range of each of the plurality of charging cycles is within a predetermined cell voltage range based on state data. Here, the predetermined cell voltage range is a range from a predetermined lower limit reference voltage to a predetermined upper limit reference voltage. The predetermined lower limit reference voltage may be greater than or equal to a predetermined charging upper limit voltage, and the predetermined upper limit reference voltage may be less than or equal to a predetermined discharging lower limit voltage. Here, the charging range may be a range from the cell voltage at the time when each of the plurality of battery cells (C1-C6) started charging in each corresponding charging cycle to the cell voltage at the time when charging ended.
[0048] The differential capacity calculation unit (1221) can derive a plurality of target charging cycles (hereinafter referred to as "target charging cycles") among a plurality of charging cycles, wherein the charging range is within a predetermined cell voltage range. Each of the plurality of target charging cycles may be a cycle in which charging starts from a cell voltage below a predetermined lower limit reference voltage and is charged to a cell voltage above a predetermined upper limit reference voltage. For example, if the predetermined cell voltage range is 3.2V to 4.2V, the differential capacity calculation unit (1221) may determine a charging process among the plurality of charging cycles that starts charging from a cell voltage of 3.2V or lower and charges to a cell voltage of 4.2V or higher as a target charging cycle.
[0049] The differential capacity calculation unit (1221) can determine whether the discharge range of each of the plurality of discharge cycles is within a predetermined cell voltage range based on state data. Here, the discharge range may be a range from the cell voltage at the time when each of the plurality of battery cells (C1-C6) started discharging in each corresponding discharge cycle to the cell voltage at the time when the discharge ended.
[0050] The differential capacity calculation unit (1221) can derive a plurality of target discharge cycles (hereinafter referred to as "target discharge cycles") among a plurality of discharge cycles, wherein the discharge range is within a predetermined cell voltage range. Each of the plurality of target discharge cycles may be a cycle in which discharge begins from a cell voltage greater than or equal to a predetermined upper reference voltage and discharges to a cell voltage less than or equal to a predetermined lower reference voltage. For example, if the predetermined cell voltage range is 3.2V to 4.2V, the differential capacity calculation unit (1221) may determine a discharge process in which charging begins from a cell voltage greater than or equal to 4.2V and discharges to a cell voltage less than or equal to 3.2V among the plurality of discharge cycles as a target discharge cycle.
[0051] The differential capacity calculation unit (1221) can generate a differential capacity profile corresponding to each of a plurality of target charging cycles among a plurality of charging cycles. Each of the plurality of differential capacity profiles generated by the differential capacity calculation unit (1221) can be matched with each corresponding cycle information. The differential capacity calculation unit (1221) can generate a differential capacity profile corresponding to each of a plurality of target discharge cycles among a plurality of discharge cycles. Each of the plurality of differential capacity profiles generated by the differential capacity calculation unit (1221) can be matched with each corresponding cycle information.
[0052] In the following description, the MCU (122) derives a plurality of target charging cycles, generates a differential capacity profile for the plurality of target charging cycles, and determines an abnormal cell based on two poles of the differential capacity profile; however, this is for convenience of explanation and the invention is not limited thereto. The MCU (122) may derive a plurality of target charging cycles and a plurality of target discharging cycles based on state data, generate a differential capacity profile for the plurality of target charging cycles and a plurality of target discharging cycles, and determine an abnormal cell based on two poles of the differential capacity profile.
[0053] Alternatively, the differential capacity calculation unit (1221) may generate a plurality of differential capacity profiles for a plurality of battery cells corresponding to battery state data for each of a plurality of target charging cycles, based on cycle information, at a predetermined number of cycle periods among a plurality of charging cycles. Here, the predetermined number of cycle periods may be a number determined in advance by initial information. For example, the predetermined number of cycle periods may be 50 times. In an example where the predetermined number of cycle periods is 50 times, the differential capacity calculation unit (1221) may derive a plurality of target charging cycles for every 50 charging cycles and generate a plurality of differential capacity profiles for each of the plurality of target charging cycles. In the following description, the differential capacity calculation unit (1221) is described as assuming that it generates a plurality of differential capacity profiles at each of the plurality of target charging cycles in which charging occurs within a predetermined cell voltage range among the plurality of charging cycles, but the invention is not limited thereto.
[0054] In one embodiment, the differential capacity calculation unit (1221) can generate a plurality of differential capacity profiles for the plurality of battery cells corresponding to a predetermined charge / discharge rate. Here, the predetermined charge / discharge rate may be a plurality of charge / discharge rate references predetermined as initial information. For example, the predetermined charge / discharge rate may be 0.1C.
[0055] The pole extraction unit (1222) can extract multiple poles from each of the multiple differential capacitance profiles generated from the differential capacitance calculation unit (1221). Here, the multiple poles may include multiple valleys and multiple peaks included in each differential capacitance profile. Each of the multiple poles extracted by the pole extraction unit (1222) can be matched with corresponding cycle information. The pole extraction unit (1222) can extract multiple poles through various methods. For example, the pole extraction unit (1222) can extract a maximum value in a predetermined first voltage range (x-axis range) as a peak and extract a minimum value in a predetermined second voltage range as a valley.
[0056] The diagnostic unit (1223) can determine an abnormal cell among a plurality of battery cells (C1-C6) based on the voltage interval between two poles, which are major features among the plurality of poles of each differential capacity profile extracted from the pole extraction unit (1222). Hereinafter, an abnormal cell refers to a battery cell in which a defect has occurred. The diagnostic unit (1223) can determine an abnormal cell based on the result of comparing the voltage interval calculated for the plurality of battery cells (C1-C6) corresponding to each of the plurality of charging cycles with a predetermined reference value.
[0057] When the diagnostic unit (1223) determines an abnormal cell, it can transmit a message indicating the abnormal cell to the electronic control unit (ECU) of the vehicle connected to the battery system (1) to perform an alert operation. The vehicle can display the diagnostic alarm message on the screen of a terminal equipped in the vehicle or on the screen of a user terminal connected to the vehicle. A user of the vehicle who checks the alarm message from the screen can take follow-up measures to have the vehicle inspected.
[0058] The diagnostic unit (1223) can derive a target low point and a target peak among a plurality of poles. Based on the derived target low point and target peak, the diagnostic unit (1223) can diagnose the state of each of the plurality of battery cells (C1-C6).
[0059] Figure 2 is an example of a differential capacity profile for a single battery cell.
[0060] Referring to FIG. 2, the differential capacity profile for each of the plurality of battery cells (C1-C6) can be represented as a graph of the differential capacity value with respect to the cell voltage (V_CELL) of the corresponding battery cell (e.g., C1) among the plurality of battery cells (C1-C6). Hereinafter, the differential capacity profile shown in FIG. 2 is described assuming that it is a profile for the battery cell (C1) shown in FIG. 1.
[0061] Referring to FIG. 2, the differential capacity profile for a single battery cell may include three valleys (valley1-valley3) and three peaks (peak1-peak3). FIG. 2 is illustrated with three valleys and three peaks, but this is for convenience of explanation and the invention is not limited thereto.
[0062] The pole extraction unit (1222) can extract multiple low points and multiple peaks from each generated differential capacitance profile. The diagnosis unit (1223) can determine the low point with the lowest cell voltage among the multiple low points extracted for each differential capacitance profile as the target low point. The diagnosis unit (1223) can determine the peak with the second lowest cell voltage among the multiple peaks extracted for each differential capacitance profile as the target peak.
[0063] In the example of FIG. 2, the diagnostic unit (1223) can determine the lowest cell voltage among the three low points (valley1-valley3) for the battery cell (C1) as the target low point (valley1), and the second peak (peak2) among the three peaks (peak1-peak3) in order of lowest potential as the target peak. In the example of FIG. 2, the target low point (valley1) of the battery cell (C1) is approximately 3.55V, and the target peak (peak2) of the battery cell (C1) is approximately 3.68V.
[0064] The diagnostic unit (1223) can calculate a voltage interval representing the interval between a target low point and a target peak for each of the plurality of battery cells. Hereinafter, the voltage interval may represent the interval between a target low point and a target peak. The diagnostic unit (1223) can determine a target battery cell among the plurality of battery cells (C1-C6) whose voltage interval is less than a predetermined reference value as an abnormal cell. Here, the predetermined reference value may be a voltage value determined in advance as initial information. For example, the predetermined reference value may be 0.11V. Alternatively, the predetermined reference value may be an appropriate threshold value selected by the diagnostic unit (1223) using a method using Z-score, a method using interquartiles (IQR), etc.
[0065] The dQ / dV value changes depending on the magnitude of the current, and accordingly, the position of each pole (peak, valley) in the differential capacitance profile may change. However, even if the magnitude of the current changes, the abnormal cell and the normal cell that is not the abnormal cell can be distinguished by the voltage interval, which is the interval between the target low point and the target peak among the multiple poles. Therefore, according to one embodiment, the BMS (120) can diagnose the abnormal cell even with a change in the magnitude of the current.
[0066] Figure 3 is a graph to explain the voltage interval between the target low point and the target high point of Figure 2.
[0067] Referring to FIG. 3, since the target low point (valley1) is approximately 3.55V and the target peak (peak2) is approximately 3.68V, the diagnostic unit (1223) can calculate the voltage interval for the battery cell (C1) as 3.68-3.55=3.13(V), which is the interval between the target low point (valley1) and the target peak (peak2). Each voltage interval calculated by the diagnostic unit (1223) can be matched with each corresponding cycle information.
[0068] Corresponding to each of a plurality of target charging cycles in which the charging range is within a predetermined cell voltage range, the diagnostic unit (1223) can determine a plurality of voltage intervals calculated for a plurality of battery cells (C1-C6) as a single voltage interval group. For example, if the first charging cycle is a charging cycle in which charging is performed on the battery pack (110) within a predetermined cell voltage range, the diagnostic unit (1223) can determine a plurality of voltage intervals calculated for a plurality of battery cells (C1-C6) in the first charging cycle as a single voltage interval group.
[0069] A voltage interval group may include voltage intervals for multiple battery cells (C1-C6) corresponding to a single charging cycle. The diagnostic unit (1223) may derive multiple target charging cycles in which the charging range is within a predetermined cell voltage range for a predetermined number of cycle periods based on cycle information, and may determine a voltage interval group for each of the voltage intervals of the multiple target charging cycles. For example, the diagnostic unit (1223) may determine a voltage interval corresponding to each of the multiple battery cells (C1-C6) for the first target charging cycle as a first voltage interval group, and determine a voltage interval corresponding to each of the multiple battery cells (C1-C6) for the second target charging cycle as a second voltage interval group.
[0070] The diagnostic unit (1223) can determine a voltage interval group including a plurality of voltage intervals of a plurality of battery cells (C1-C6) corresponding to each of a plurality of target charging cycles. The diagnostic unit (1223) can determine the voltage interval groups determined for a plurality of target charging cycles for a predetermined number of cycle periods as a plurality of target voltage interval groups. The diagnostic unit (1223) can determine whether a voltage interval less than a predetermined reference value is included in the plurality of target voltage interval groups. For example, the first target voltage interval group may include voltage interval groups corresponding to each of the 11th, 12th, 14th, and 15th charging cycles in which the charging range is within a predetermined cell voltage range among the 1st to 50th charging cycles, and the second target voltage interval group may include voltage interval groups corresponding to each of the 58th, 61st, and 62nd charging cycles in which the charging range is within a predetermined cell voltage range among the 51st charging cycles. The diagnostic unit (1223) can determine an abnormal cell among a plurality of battery cells (C1-C6) based on the result of comparing each voltage interval included in a plurality of target voltage interval groups with a predetermined reference value.
[0071] The diagnostic unit (1223) may determine the target battery cell as an abnormal cell if there is a target battery cell corresponding to a voltage interval below a predetermined reference value among a plurality of target voltage interval groups. Alternatively, the diagnostic unit (1223) may determine the target battery cell corresponding to a voltage interval below a predetermined reference value as an abnormal cell if there is a battery cell corresponding to a voltage interval below a predetermined reference value in all of the plurality of target charging cycles of the plurality of target voltage interval groups. Alternatively, the diagnostic unit (1223) may determine the target battery cell corresponding to a voltage interval below a predetermined reference value as an abnormal cell if there are a predetermined number or more of battery cells corresponding to a voltage interval below a predetermined reference value among the plurality of target charging cycles of the plurality of target voltage interval groups. For example, if a plurality of target voltage interval groups include voltage interval groups corresponding to each of the first, second, third, and fourth charging cycles, the diagnostic unit (1223) may determine that a battery cell is an abnormal cell if there is a battery cell that exhibits a voltage interval below a predetermined reference value in three or more charging cycles among the first, second, third, and fourth charging cycles. Hereinafter, for convenience of explanation, the diagnostic unit (122) is described as determining that a battery cell exhibiting a voltage interval below a predetermined reference value in all of the plurality of target charging cycles corresponding to the plurality of target voltage interval groups is an abnormal cell, but the invention is not limited thereto.
[0072] Figure 4 is a graph showing the voltage interval between the target low point and the target high point of each of the multiple battery cells in each of the multiple target charging cycles corresponding to the multiple target voltage groups.
[0073] Referring to FIG. 4, the diagnostic unit (1223) can determine first to fourth voltage interval groups (VG1-VG4) corresponding to four target charging cycles. The first voltage interval group (VG1) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 1, and the second voltage interval group (VG2) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 2. The third voltage interval group (VG3) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 3, and the fourth voltage interval group (VG4) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 4.
[0074] In FIG. 4, the horizontal axis represents the identification number of each of the multiple target charging cycles corresponding to the multiple target voltage interval groups, and a predetermined reference value (Vth) is assumed to be 0.11V.
[0075] In the example of FIG. 4, the diagnostic unit (1223) can determine an abnormal cell among a plurality of battery cells (C1-C6) based on voltage intervals included in the first to fourth voltage interval groups (VG1-VB4) corresponding to four target charging cycles.
[0076] In FIG. 4, among the voltage intervals included in the first to fourth voltage interval groups (VG1-VB4), the voltage interval of the battery cell (C1) is less than a predetermined reference value. The diagnostic unit (1223) can determine the voltage interval of the battery cell (C1) as the target voltage interval and determine the battery cell (C1) as the target battery cell. The diagnostic unit (1223) can determine the battery cell (C1), which is the target battery cell, as an abnormal cell.
[0077] Meanwhile, in another embodiment, the BMS (120) may calculate a voltage interval corresponding to a predetermined plurality of charge / discharge rates and determine an abnormal cell based on the result of comparing the voltage interval with a predetermined reference value. For example, if the first charging cycle is a charging cycle in which charging is performed on the battery pack (110) within a predetermined cell voltage range, the diagnostic unit (1223) may determine a plurality of voltage intervals calculated for a plurality of battery cells (C1-C6) in the first charging cycle as a single voltage interval group corresponding to each of the predetermined plurality of charge / discharge rates. In the following description of another embodiment using a predetermined plurality of charge / discharge rates, descriptions of configurations identical to or corresponding to the previously described embodiment may be omitted. Here, the predetermined plurality of charge / discharge rates may be a plurality of charge / discharge rate references predetermined as initial information. For example, the predetermined plurality of charge / discharge rates may include 0.1C, 0.3C, and 0.5C.
[0078] The state data generation unit (121) can generate multiple battery state data for each of the multiple battery cells (C1-C6) corresponding to a predetermined plurality of charge / discharge rates. In the following, the multiple battery state data may include information indicating the cell voltage, cell current, and cell capacity of each battery cell corresponding to a predetermined plurality of charge / discharge rates. In this case, the differential capacity calculation unit (1221) can generate multiple differential capacity profiles corresponding to each of the predetermined plurality of charge / discharge rates based on the multiple battery state data received from the state data generation unit (121).
[0079] The pole extraction unit (1222) can extract multiple poles from each of a plurality of differential capacity profiles corresponding to each of a predetermined plurality of charge / discharge rates generated from the differential capacity calculation unit (1221).
[0080] The diagnostic unit (1223) can derive target low points and target peaks among the multiple poles of each differential capacity profile extracted from the pole extraction unit (1222). The diagnostic unit (1223) can diagnose the state of multiple battery cells based on the derived target low points and target peaks.
[0081] The diagnostic unit (1223) can calculate a voltage interval representing the interval between a target low point and a target high point for each of the plurality of battery cells, corresponding to each of the predetermined plurality of charge / discharge rates.
[0082] FIG. 5 is a graph showing an example in another embodiment where the charge / discharge rate is 0.1C.
[0083] FIG. 6 is a graph showing an example in which the charge / discharge rate is 0.3C in another embodiment.
[0084] FIG. 7 is a graph showing an example in another embodiment where the charge / discharge rate is 0.5C.
[0085] The diagnostic unit (1223) can determine the voltage interval groups determined for a plurality of target charging cycles at a predetermined number of cycle periods for each of the predetermined multiple charge / discharge rates as a plurality of target candidate voltage interval groups. The diagnostic unit (1223) can determine whether the plurality of target candidate voltage interval groups include a voltage interval that is less than a predetermined reference value corresponding to each charge / discharge rate. The diagnostic unit (1223) can determine one or more abnormal candidate cells among the plurality of battery cells (C1-C6) based on the result of comparing each voltage interval included in each of the plurality of target candidate voltage interval groups with a predetermined reference value corresponding to each charge / discharge rate. If there is one or more target battery cells among the plurality of target candidate voltage interval groups that correspond to a voltage interval less than a predetermined reference value corresponding to each charge / discharge rate, the diagnostic unit (1223) can determine the one or more target battery cells as one or more abnormal candidate cells, and determine at least one of the one or more abnormal candidate cells as an abnormal cell.
[0086] Hereinafter, with reference to FIGS. 5 to 7, the operation of the diagnostic unit (1223) determining an abnormal cell based on a voltage interval corresponding to each of a predetermined plurality of charge / discharge rates is explained.
[0087] Referring to FIGS. 5 to 7, the diagnostic unit (1223) derives a plurality of target charging cycles in which the charging range is within a predetermined cell voltage range based on cycle information at each of a predetermined plurality of charge / discharge rates, and can determine a plurality of voltage intervals calculated for a plurality of battery cells (C1-C6) corresponding to each of the plurality of target charging cycles as a plurality of target candidate voltage interval groups. The plurality of target candidate voltage interval groups may include voltage intervals for a plurality of battery cells (C1-C6) corresponding to a single charge / discharge rate and a single charging cycle. In FIGS. 5 to 7, the horizontal axis represents the identification number of each of the plurality of target charging cycles corresponding to the plurality of target candidate voltage interval groups.
[0088] The diagnostic unit (1223) can determine whether each voltage interval group includes a voltage interval that is less than a predetermined reference value.
[0089] The diagnostic unit (1223) can determine an abnormal cell among a plurality of battery cells (C1-C6) based on the result of comparing each voltage interval included in each voltage interval group with a predetermined reference value. For example, the diagnostic unit (1223) can determine a target battery cell as an abnormal cell if there is a target battery cell among the plurality of battery cells (C1-C6) in which the voltage interval in all of the plurality of voltage interval groups is less than a predetermined reference value. Here, the predetermined reference value may be determined differently corresponding to each of the predetermined multiple charge / discharge rates. For example, the predetermined reference value corresponding to a charge / discharge rate of 0.1C may be 0.155V, the predetermined reference value corresponding to a charge / discharge rate of 0.3C may be 0.12V, and the predetermined reference value corresponding to a charge / discharge rate of 0.5C may be 0.09V.
[0090] Referring to FIG. 5, the diagnostic unit (1223) can determine 11th to 14th voltage interval groups (VG11-VG14) corresponding to 4 target charging cycles corresponding to a charge / discharge rate of 0.1C. The 11th voltage interval group (VG11) may include the voltage interval of each of the plurality of battery cells (C1-C6) in a charging cycle corresponding to identification number 1, and the 12th voltage interval group (VG12) may include the voltage interval of each of the plurality of battery cells (C1-C6) in a charging cycle corresponding to identification number 2. The 13th voltage interval group (VG13) may include the voltage interval of each of the plurality of battery cells (C1-C6) in a charging cycle corresponding to identification number 3, and the 14th voltage interval group (VG14) may include the voltage interval of each of the plurality of battery cells (C1-C6) in a charging cycle corresponding to identification number 4.
[0091] In the example of FIG. 5, the diagnostic unit (1223) can determine an abnormal candidate cell among a plurality of battery cells (C1-C6) based on voltage intervals included in the 11th to 14th voltage interval groups (VG11-VG14) corresponding to four target charging cycles. In FIG. 5, a predetermined reference value (Vth1) corresponding to a charge / discharge rate of 0.1C is assumed to be 0.155V.
[0092] In FIG. 5, among the voltage intervals included in the 11th to 14th voltage interval groups (VG11-VG14), the voltage interval of each of the three battery cells (C1-C3) is less than a predetermined reference value. The diagnostic unit (1223) can determine each voltage interval of the three battery cells (C1-C3) as a target voltage interval and determine the three battery cells (C1-C3) as target battery cells. The diagnostic unit (1223) can determine the three battery cells (C1-C3) that are target battery cells as a first or more candidate cell.
[0093] Referring to FIG. 6, the diagnostic unit (1223) can determine 21 to 24 voltage interval groups (VG21-VG24) corresponding to four target charging cycles corresponding to a charge / discharge rate of 0.3C. The 21st voltage interval group (VG21) may include the voltage interval of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 1, and the 22nd voltage interval group (VG22) may include the voltage interval of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 2. The 23rd voltage interval group (VG23) may include the voltage interval of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 3, and the 24th voltage interval group (VG24) may include the voltage interval of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 4.
[0094] In the example of FIG. 6, the diagnostic unit (1223) can determine an abnormal candidate cell among a plurality of battery cells (C1-C6) based on voltage intervals included in the 21st to 24th voltage interval groups (VG21-VG24) corresponding to four target charging cycles. In FIG. 6, a predetermined reference value (Vth2) corresponding to a charge / discharge rate of 0.3C is assumed to be 0.12V.
[0095] In FIG. 6, among the voltage intervals included in the 21st to 24th voltage interval groups (VG21-VG24), the voltage interval of each of the three battery cells (C1-C3) is less than a predetermined reference value. The diagnostic unit (1223) can determine the voltage interval of each of the three battery cells (C1-C3) as the target voltage interval and determine the three battery cells (C1-C3) as the target battery cells. The diagnostic unit (1223) can determine the three battery cells (C1-C3) that are the target battery cells as the second or higher candidate cells.
[0096] Referring to FIG. 7, the diagnostic unit (1223) can determine 31 to 34 voltage interval groups (VG31-VG34) for four target charging cycles corresponding to a charge / discharge rate of 0.5C. The 31st voltage interval group (VG31) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 1, and the 32nd voltage interval group (VG32) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 2. The 33rd voltage interval group (VG33) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 3, and the 34th voltage interval group (VG34) may include the voltage intervals of each of the plurality of battery cells (C1-C6) in the charging cycle corresponding to identification number 4.
[0097] In the example of FIG. 7, the diagnostic unit (1223) can determine an abnormal candidate cell among a plurality of battery cells (C1-C6) based on voltage intervals included in the 31st to 34th voltage interval groups (VG31-VG34) corresponding to four target charging cycles. In FIG. 7, a predetermined reference value (Vth3) corresponding to a charge / discharge rate of 0.5C is assumed to be 0.09V.
[0098] In FIG. 7, among the voltage intervals included in the 31st to 34th voltage interval groups (VG31-VG34), the voltage interval of each of the three battery cells (C1-C3) is less than a predetermined reference value. The diagnostic unit (1223) can determine the voltage interval of each of the three battery cells (C1-C3) as the target voltage interval and determine the three battery cells (C1-C3) as the target battery cells. The diagnostic unit (1223) can determine the three battery cells (C1-C3) that are the target battery cells as the third or higher candidate cells.
[0099] The diagnostic unit (1223) can determine at least one of a first candidate cell corresponding to a charge / discharge rate of 0.1C, a second candidate cell corresponding to a charge / discharge rate of 0.3C, and a third candidate cell corresponding to a charge / discharge rate of 0.5C as an ideal cell. For example, the diagnostic unit (1223) can determine a battery cell included in all of the first to third candidate cells among a plurality of battery cells (C1-C6) as an ideal cell. Or, for example, the diagnostic unit (1223) can determine a battery cell included in at least one of the first to third candidate cells among a plurality of battery cells (C1-C6) as an ideal cell.
[0100] Unlike the embodiments of the present invention, if other indicators among multiple poles are used instead of the voltage interval between the lowest cell voltage point (valley1) and the second lowest cell voltage point (peak2), it may be difficult to identify an abnormal cell.
[0101] FIG. 8 is a comparative example utilizing the lowest point indicator among the plurality of poles where the cell voltage is lowest for the battery cells shown in FIG. 5 to 7.
[0102] FIG. 9 is a comparative example utilizing the second lowest peak indicator among the plurality of poles for the battery cells shown in FIG. 5 to 7.
[0103] Referring to FIGS. 8 and 9, if only the lowest point (valley1) with the lowest cell voltage among the multiple poles is utilized, or only the peak (peak2) with the second lowest cell voltage is utilized, it is difficult to distinguish three battery cells (C1-C3) that are abnormal cells among the multiple battery cells (C1-C6).
[0104] In contrast, referring to FIGS. 4 to 7, in an embodiment of the present invention, the lowest point (valley1) with the lowest cell voltage and the peak (peak2) with the second lowest cell voltage among a plurality of poles are considered as key indicators, and by utilizing the voltage interval between the lowest point (valley1) with the lowest cell voltage and the peak (peak2) with the second lowest cell voltage, an abnormal cell among a plurality of battery cells (C1-C6) can be identified.
[0105] FIG. 10 is a flowchart of an abnormal cell diagnosis method according to one embodiment.
[0106] Below, descriptions of each component of the battery system (1) that overlap with the descriptions above may be omitted.
[0107] The BMS (120) can generate battery status data based on signals received from a plurality of battery cells (C1-C6) and a current sensor (130) (S101). The status data may include cycle information indicating which cycle of the plurality of charging cycles for the battery pack each included data corresponds to the data measured during.
[0108] The BMS (120) can determine whether the charging range of each charging cycle is within a predetermined cell voltage range based on the status data (S102).
[0109] If the charging range of the corresponding charging cycle in step S102 is within a predetermined cell voltage range (e.g., in S102), the BMS (120) can generate multiple differential capacity profiles for multiple battery cells (C1-C6) corresponding to each of the multiple target charging cycles in which the charging range is within a predetermined cell voltage range (S103).
[0110] The BMS (120) can extract multiple low points and multiple peaks from each of the generated multiple differential capacitance profiles, and extract target low points and target peaks from multiple poles (S104).
[0111] In step S104, if a target low point, which is the lowest cell voltage among the multiple poles, and a target peak, which is the second lowest cell voltage among the multiple poles are extracted (e.g., in S104), the BMS (120) can calculate the voltage interval between the target low point and the target peak for each of the multiple battery cells (C1-C6) (S105).
[0112] The BMS (120) can determine whether there is a voltage interval among the plurality of battery cells (C1-C6) that is less than a predetermined reference value, calculated in step S105 (S106). In each charging cycle, the BMS (120) can determine a plurality of voltage intervals for the plurality of battery cells (C1-C6) as a single voltage interval group, and determine whether there is a voltage interval in each voltage interval group that is less than a predetermined reference value.
[0113] If there is a voltage interval below a predetermined threshold in step S106 (e.g., in S106), the battery cell corresponding to the voltage interval below the predetermined threshold among the plurality of battery cells (C1-C6) can be determined as an ideal cell (S107).
[0114] If, in step S102, the charging range of the corresponding charging cycle is outside the predetermined cell voltage range (in S102, no), if, in step S104, the target low point which is the lowest cell voltage among the plurality of poles and the target peak which is the second lowest cell voltage among the plurality of poles are not extracted (in S104, no), or if, in step S106, there is no voltage interval below a predetermined reference value (in S106, no), the BMS (120) may terminate the steps of the abnormal cell diagnosis method according to one embodiment.
[0115] In FIG. 10, it is illustrated that if the charging range of the corresponding charging cycle in step S102 is outside the predetermined cell voltage range (in S102, no), if the target low point which is the lowest cell voltage among the plurality of poles and the target peak which is the second lowest cell voltage among the plurality of poles are not extracted in step S104 (in S104, no), or if there is no voltage interval below a predetermined reference value in step S106 (in S106, no), the BMS (120) terminates the steps of the abnormal cell diagnosis method according to one embodiment, but this is for convenience of explanation and the invention is not limited thereto.
[0116] In some embodiments, if the charging range of the corresponding charging cycle in step S102 is outside the predetermined cell voltage range (in S102, no), if the target low point which is the lowest cell voltage among the plurality of poles and the target peak which is the second lowest cell voltage among the plurality of poles are not extracted in step S104 (in S104, no), or if there is no voltage interval below a predetermined reference value in step S106 (in S106, no), the BMS (120) may perform step S101.
[0117] Although embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modified and improved forms 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 pack comprising multiple battery cells; A current sensor connected to one end of the battery pack and generating a current signal indicating a module current flowing through the battery pack; and A battery management system (BMS) that, in a first charging cycle for charging the plurality of battery cells, generates battery state data including cell voltage and cell capacity of each of the plurality of battery cells based on signals received from the plurality of battery cells and the current sensor, generates a plurality of differential capacity profiles indicating a differential change in capacity with respect to a voltage change for the plurality of battery cells based on the battery state data, determines the valley with the lowest cell voltage among the valleys of each of the plurality of differential profiles as a target valley, determines the peak with the second lowest cell voltage among the peaks of each of the plurality of differential profiles as a target peak, and diagnoses the state of each of the plurality of battery cells based on the target valley and the target peak. A battery system including 2. In Paragraph 1, The above first charging cycle is, A charging cycle in which charging is performed for the above battery pack within a predetermined cell voltage range, Battery system.
3. In Paragraph 2, The above battery status data is, It includes cycle information indicating which charging cycle among a plurality of charging cycles for the battery pack the data was measured in, and The above BMS is, Based on the above cycle information, the differential change in capacity with respect to the voltage change for each of the plurality of battery cells based on the battery state data for a predetermined number of cycle periods, and each of the plurality of differential capacity profiles are generated. Battery system.
4. In Paragraph 1, The above BMS is, Calculating a voltage interval representing the distance between the target low point and the target high point for each of the plurality of battery cells, and determining an abnormal cell among the plurality of battery cells based on the result of comparing the voltage interval with a predetermined reference value. Battery system.
5. In Paragraph 4, The above BMS is, In the first charging cycle, a plurality of voltage intervals calculated for the plurality of battery cells are determined as a voltage interval group, and if there is a voltage interval below a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charging cycles for the battery pack, the target battery cell corresponding to the voltage below the predetermined reference value is determined as the abnormal cell. Battery system.
6. In Paragraph 4, The above BMS is, A plurality of voltage intervals calculated for the plurality of battery cells in the first charging cycle corresponding to each of the plurality of predetermined charge / discharge rates are determined as a voltage interval group; if there is a voltage interval below a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charge cycles for the battery pack corresponding to each of the plurality of charge / discharge rates, one or more target battery cells corresponding to the voltage below the predetermined reference value are determined as one or more abnormal candidate cells; and at least one of the one or more abnormal candidate cells is determined as an abnormal cell. Battery system.
7. A step of generating battery status data including cell voltage and cell capacity of each of the plurality of battery cells in a first charging cycle for charging the plurality of battery cells based on a signal received from a current sensor connected to one end of a battery pack comprising the plurality of battery cells; A step of generating a plurality of differential capacity profiles that indicate a differential change in capacity with respect to a voltage change for the plurality of battery cells based on the battery status data above; A step of determining the lowest valley among the multiple valleys of each of the above multiple differential profiles, where the cell voltage is the lowest, as the target valley; A step of determining the peak with the second lowest cell voltage among the plurality of peaks of each of the plurality of differential profiles as the target peak; and An abnormal cell diagnosis method comprising the step of diagnosing the state of each of the plurality of battery cells based on the above-mentioned target low point and the above-mentioned target high point.
8. In Paragraph 7, The above first charging cycle is a charging cycle in which charging is performed on the battery pack within a predetermined cell voltage range, and The above battery status data is, It includes cycle information indicating which charging cycle among a plurality of charging cycles for the battery pack the data was measured in, and The above abnormal cell diagnosis method is, The method further includes the step of generating each of the plurality of differential capacity profiles by calculating the differential change in capacity with respect to the voltage change for each of the plurality of battery cells based on the battery state data with respect to the cycle information based on the above-mentioned cycle information and a predetermined number of cycle periods. Abnormal cell diagnosis method.
9. In Paragraph 7, A step of calculating a voltage interval representing the interval between the target low point and the target high point for each of the plurality of battery cells; and A method for diagnosing an abnormal cell, further comprising the step of determining an abnormal cell among the plurality of battery cells based on the result of comparing the above voltage interval with a predetermined reference value.
10. In Paragraph 9, For the first charging cycle, a step of determining a plurality of voltage intervals calculated for the plurality of battery cells as a single voltage interval group; A step of determining whether there is a voltage interval below a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charging cycles for the battery pack; and If there is a target voltage interval among the above voltage interval groups that is less than a predetermined reference value, the method further includes the step of determining a target battery cell corresponding to the above target voltage interval as the above abnormal cell. Abnormal cell diagnosis method.
11. In Paragraph 9, A step of determining a plurality of voltage intervals calculated for the plurality of battery cells for the first charging cycle, corresponding to each of a predetermined plurality of charge / discharge rates, into a single voltage interval group; A step of determining whether there is a voltage interval less than a predetermined reference value among the voltage interval groups determined corresponding to each of the plurality of charge / discharge rates and corresponding to each of the plurality of charge cycles for the battery pack; If there is a target voltage interval among the above voltage interval groups that is less than a predetermined reference value, a step of determining one or more target battery cells corresponding to the target voltage interval as one or more ideal candidate cells; and A step further comprising determining at least one of the above one or more abnormal candidate cells as the abnormal cell, Abnormal cell diagnosis method.