Apparatus and method for diagnosing a battery

Abstract

According to the present invention, there is provided an apparatus for diagnosing whether an error has occurred in a plurality of battery cells by measuring a voltage of each of the plurality of battery cells. The present invention includes a voltage measurement circuit, a data processing circuit, and a diagnosis circuit. The voltage measurement circuit can measure a voltage of a battery cell. The data processing circuit calculates a target statistical value indicating a state of the battery cell based on the voltage measured by the voltage measurement circuit, and calculates a cumulative statistical value by accumulating the target statistical value of the battery cell during an analysis period. The diagnosis circuit determines whether an error has occurred in the battery cell through a cumulative determination operation of comparing the cumulative statistical value with a cumulative reference value, and counts a number of cumulative errors when it is determined that an error has occurred in the battery cell during the cumulative determination operation.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0058588, filed May 15, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

[0003] The present application relates to an apparatus for diagnosing a battery, and more particularly, to an apparatus for diagnosing whether an error has occurred in a plurality of battery cells by measuring a voltage of each of the plurality of battery cells. BACKGROUND

[0004] Recently, research and development on secondary batteries are being actively conducted. Here, the secondary battery is a battery capable of charging and discharging, including all conventional Ni / Cd batteries, Ni / MH batteries, etc., and recent lithium ion batteries. Among the secondary batteries, the lithium ion battery has an advantage of having much higher energy density than the conventional Ni / Cd battery, Ni / MH battery, etc. The lithium ion battery can be manufactured to be small in size and light in weight, and thus the lithium ion battery is used as a power source of a mobile device. In particular, the lithium ion battery can be used as a power source of an electric vehicle, and thus has attracted attention as a next-generation energy storage medium as its use range has been expanded to a power source for an electric vehicle.

[0005] In addition, the secondary battery is generally used as a battery pack including a battery module in which a plurality of battery cells are connected in series and / or in parallel. The state and operation of the battery pack are managed and controlled by a battery management system. The battery cells in the battery pack are charged by receiving power from the outside.

[0006] The charged battery cells provide power to various devices and / or circuits connected to the battery pack. When the battery cell malfunctions, power is not properly supplied to the various devices and / or circuits, and thus a fatal accident can occur. Therefore, it is important to monitor the battery cell to diagnose whether an error has occurred in the battery cell. In addition, for accurate diagnosis, there is a problem about which diagnostic criterion and which diagnostic method to use. SUMMARY

[0007] Technical Problem

[0008] The present application aims to solve the above technical problems, and an object thereof is to provide an apparatus for diagnosing a battery that determines whether an error has occurred in one battery cell based on a voltage trend of a plurality of battery cells and finally determines whether the one battery cell is defective by accumulating measured values of the one battery cell.

[0009] Technical Solution

[0010] The apparatus for diagnosing a battery according to embodiments of the present application can include a voltage measurement circuit, a data processing circuit, and a diagnosis circuit. The voltage measurement circuit can measure a voltage of a battery cell. The data processing circuit can calculate a target statistical value indicating a state of the battery cell based on the voltage measured by the voltage measurement circuit, and can calculate a cumulative statistical value by accumulating the target statistical value of the battery cell during an analysis period. The diagnosis circuit can determine whether an error has occurred in the battery cell through a cumulative determination operation of comparing the cumulative statistical value with a cumulative reference value, and count a number of cumulative errors when it is determined that an error has occurred in the battery cell in the cumulative determination operation.

[0011] The method for diagnosing a battery according to embodiments of the present application can include a voltage measurement step of measuring, by an apparatus for diagnosing a battery, a voltage between an input terminal and an output terminal of a battery cell, a calculation step of calculating, by the apparatus for diagnosing a battery, a target statistical value indicating a state of the battery cell based on the voltage measured in the voltage measurement step, and calculating a cumulative statistical value by accumulating the target statistical value of the battery cell during an analysis period, and a first diagnosis step of determining, by the apparatus for diagnosing a battery, whether an error has occurred in the battery cell through a cumulative determination operation of comparing the cumulative statistical value with a cumulative reference value, and counting a number of cumulative errors when it is determined that an error has occurred in the battery cell through the cumulative determination operation.

[0012] Advantages

[0013] According to the present application, whether an error has occurred in a battery cell can be determined through absolute determination, relative determination, and cumulative determination. According to the present application, whether a battery cell is defective can be more accurately determined by synthesizing results of the absolute determination, the relative determination, and the cumulative determination. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a block diagram illustrating a configuration of a battery control system;

[0015] Figure 2 is a block diagram illustrating a configuration of a battery pack 10 including the apparatus for diagnosing a battery of the present application;

[0016] Figure 3 is a flowchart for describing an operation of a battery management system of Figure 2

[0017] Figure 4 is a flowchart for describing a first absolute determination operation of a battery management system of Figure 2

[0018] ​​Figure 5 is a flowchart for describing a data preprocessing operation of a data processing circuit of Figure 2 ;

[0019] Figure 6a is a graph illustrating a method of performing sampling in order to remove a redundant signal of battery voltage data;

[0020] Figure 6b is a graph illustrating a result obtained by performing preprocessing on battery voltage data through sampling and smoothing a spline;

[0021] Figure 6c is a graph illustrating a differential curve of battery voltage data for each step of preprocessing;

[0022] Figure 6d is a histogram illustrating a differential signal of each charge cycle of a battery;

[0023] Figure 6e is a graph illustrating a standard deviation of each charge cycle of a battery;

[0024] Figure 6f is a graph illustratively describing an example of diagnosing a battery abnormality through a standard deviation of a differential signal in an apparatus for diagnosing a battery according to an embodiment of the present application;

[0025] Figure 7 is a flowchart for describing a second absolute determination operation of a battery management system of Figure 2 ;

[0026] Figure 8a illustrates a voltage change when a pressure drop due to an internal short circuit of a battery cell occurs over an entire section;

[0027] Figure 8b is a graph illustrating a voltage change when a pressure drop due to an internal short circuit of a battery cell occurs temporarily;

[0028] Figure 8c is a graph illustrating an actual rest voltage about 10 minutes after charging a battery, a voltage according to a fitted equation, and a difference therebetween;

[0029] Figure 8d illustrates a result detected by an apparatus for diagnosing a battery according to an embodiment of the present application that a pressure drop due to an internal short circuit of a battery cell occurs over an entire section;

[0030] Figure 8e illustrates a result detected that a pressure drop due to an internal short circuit of a battery cell occurs temporarily;

[0031] Figure 9 is a flowchart for describing a second absolute determination operation of a battery management system of Figure 2a flowchart of a relative determination operation of a battery management system of

[0032] Figure 10a is a graph illustrating a distribution of a first statistical value of a battery cell;

[0033] Figure 10b is a graph illustrating a number of times of relative errors of a battery cell;

[0034] Figure 11 is a flowchart of a cumulative determination operation of a battery management system of Figure 2 ; and

[0035] Figure 12 is a graph illustrating a hardware configuration of an apparatus for diagnosing a battery according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present application will be described clearly and in detail to the extent that a person having an ordinary skill in the art can easily implement the present application.

[0037] Figure 1 is a block diagram illustrating a configuration of a battery control system.

[0038] Referring to Figure 1 , a battery management system including a battery pack 1 and a superior controller 2 included in a superior system according to an embodiment of the present application are schematically illustrated.

[0039] As illustrated in Figure 1 , the battery pack 1 includes a battery module 11 constituted by one or more battery cells and capable of charging and discharging, a switching unit 14 connected in series to a positive terminal side or a negative terminal side of the battery module 11 to control a charging and discharging current of the battery module 11, and a battery management system 20 monitoring a voltage, a current, a temperature, etc. of the battery pack 1 to control and manage the battery module to prevent overcharging, overdischarging, etc.

[0040] Here, the switching unit 14 is a switching element for controlling a current for charging or discharging of the battery module 11, and for example, a semiconductor switching element such as at least one MOSFET or a relay can be used.

[0041] In addition, the battery management system 20 can monitor a voltage, a current, a temperature, etc. of the battery pack 1, and can measure a current, a voltage, a temperature, etc. of the battery pack using a sensor 12 disposed adjacent to the semiconductor switching element 14. The battery management system 20 is an interface receiving values obtained by measuring the above-described various parameters, and can include a plurality of terminals and a circuit connected to the terminals to perform processing for input values.

[0042] In addition, the battery management system 20 can control the on / off of the switching element 14, for example, a MOSFET, and can be connected to the battery module 11 to monitor the state of the battery module 11.

[0043] The upper controller 2 can transmit a control signal for the battery module 11 to the battery management system 20. Accordingly, the operation of the battery management system 20 can be controlled based on the signal applied from the upper controller 2. The battery cell of the present application can be configured to be included in a battery pack used in an energy storage system (ESS) or a vehicle, etc. However, the battery cell is not limited to these uses.

[0044] Since the configuration of the battery pack 1 and the configuration of the battery management system 20 are known configurations, a more detailed description thereof will be omitted.

[0045] Figure 2 is a block diagram illustrating a configuration of a battery pack 10 including the apparatus for diagnosing a battery of the present application. Figure 2 The battery module 100 and the battery management system 200 of Figure 1 The battery module 11 and the battery management system 20 of

[0046] The battery pack 10 can include the battery module 100 and the battery management system 200. The "apparatus for diagnosing a battery" of the present application can be an apparatus including some or all components of the battery management system 200. For example, the "apparatus for diagnosing a battery" can include the voltage measurement circuit 210, the data processing circuit 220, the diagnosis circuit 230, and the memory 240.

[0047] The battery module 100 can include a plurality of battery cells B1 to BN. The plurality of battery cells B1 to BN can be configured to be connected in series and / or in parallel. Referring to Figure 2 , the battery pack 10 is illustrated as including one battery module 100, but the present application is not limited thereto, and the battery pack 10 can include one or more battery modules.

[0048] In the charging section, the battery module 100 can receive power from a power source (not illustrated). In the charging section, the voltage at both ends of each of the battery cells B1 to BN can increase. In the following description, the "voltage of a battery cell" refers to the "voltage between both ends of a battery cell". In the discharging section, the battery module 100 can supply power to an external device and / or a circuit. There can be a resting section between the charging section and the discharging section. In the resting section, the battery module 100 can stop the operation of receiving power or supplying power. Thus, in an ideal case, the voltage of the battery module 100 is maintained constant in the resting section. When the battery module 100 is included in an electric vehicle, the external device and / or the circuit can be a motor, a power control unit (PCU), an inverter, or the like.

[0049] Due to an internal short circuit or an external short circuit of a battery cell, an abnormal voltage drop phenomenon can be detected in the battery cell. The abnormal voltage drop phenomenon means that the voltage of the battery cell is abnormally decreased in the charging section, the discharging section, and / or the resting section. The battery management system 200 of the present application can monitor the battery cells B1 to BN to determine whether the abnormal voltage drop phenomenon has occurred in the battery cells B1 to BN.

[0050] The battery management system 200 can include a voltage measurement circuit 210, a data processing circuit 220, a diagnosis circuit 230, and a memory 240. The battery management system 200 can more accurately determine whether the abnormal voltage drop phenomenon has occurred in the battery cells B1 to BN through an absolute determination operation, a relative determination operation, and a cumulative determination operation. In the following description, checking whether an error has occurred in the battery cell B1 means checking whether the abnormal voltage drop phenomenon has occurred in the battery cell B1. In addition, in the following description, for the convenience of description, a method for inspecting the battery cell B1 by the battery management system 200 is collectively described. The battery management system 200 can also inspect the remaining battery cells B2 to BN in the same manner as the method for inspecting the battery cell B1.

[0051] First, a method for performing an absolute determination operation by the battery management system 200 is described. The absolute determination operation performed in the charging section and the discharging section can be different from the absolute determination operation performed in the resting section. In the following description, the absolute determination operation performed in the charging section and the discharging section is expressed as a first absolute determination operation. The absolute determination operation performed in the resting section is expressed as a second absolute determination operation.

[0052] Hereinafter, the first absolute determination operation is described. The voltage measurement circuit 210 can measure the voltage of the battery cell B1 in the charging section and the discharging section. The voltage measurement circuit 210 can output voltage data of the measured voltage to the data processing circuit 220.

[0053] The data processing circuit 220 can process the voltage data received from the voltage measurement circuit 210 to calculate a first statistical value. For example, the first statistical value can be a value obtained by differentiating the capacity of the battery cell B1 with respect to the voltage. To calculate the first statistical value, the capacity of the battery cell B1 can be measured by the battery management system 200. Reference will be made to Figures 4 to 6f The first statistical value is described in detail.

[0054] The diagnosis circuit 230 can receive information about the first statistical value. The diagnosis circuit 230 can compare the first statistical value with a first absolute reference value. The first absolute reference value can be a value set by a user. However, the present application is not limited thereto, and the first absolute reference value can be a value determined based on the state of the battery cell B1, such as the temperature of the battery cell B1 and the SOC of the battery cell B1. When the first statistical value is equal to or greater than the first absolute reference value, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1.

[0055] Hereinafter, a second absolute determination operation is described. The voltage measurement circuit 210 can measure the voltage of the battery cell B1 in the rest section. The voltage measurement circuit 210 can output voltage data of the measured voltage to the data processing circuit 220.

[0056] The data processing circuit 220 can process the voltage data received from the voltage measurement circuit 210 to calculate a second statistical value. The second statistical value can be a value calculated by substituting the voltage data into a voltage fitting equation. Reference will be made to Figures 7 to 8e The second statistical value is described in detail.

[0057] The diagnosis circuit 230 can receive information about the second statistical value. The diagnosis circuit 230 can compare the second statistical value with a second absolute reference value. The second absolute reference value can be a value set by a user. However, the present application is not limited thereto, and the second absolute reference value can be a value determined based on the state of the battery cell B1, such as the temperature of the battery cell B1 and the SOC of the battery cell B1. When the second statistical value is equal to or greater than the second absolute reference value, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1.

[0058] Second, a method for performing a relative determination operation by the battery management system 200 is described. The relative determination operation performed in the charge section and the discharge section can be different from the relative determination operation performed in the rest section. In the following description, the relative determination operation performed in the charge section and the discharge section is expressed as a first relative determination operation. The relative determination operation performed in the rest section is expressed as a second relative determination operation.

[0059] Hereinafter, the first relative determination operation is described. The voltage measurement circuit 210 can measure the voltage of each of the battery cells B1 to BN in the charge section and the discharge section. The voltage measurement circuit 210 can output voltage data of the measured voltage to the data processing circuit 220.

[0060] The data processing circuit 220 can process the voltage data received from the voltage measurement circuit 210 to calculate a first relative reference value. Specifically, the data processing circuit 220 can calculate the first statistical values of the battery cells B1 to BN in the same manner as the method of calculating the first statistical value of the battery cell B1 in the absolute determination operation. The data processing circuit 220 can determine the first relative reference value based on an ‘n’ sigma value of the first statistical values of the battery cells B1 to BN. Here, ‘n’ can be a positive number. As an example, the first relative reference value can be a +3 sigma value of the first statistical value.

[0061] The diagnosis circuit 230 can receive information on the first statistical value and the first relative reference value of the battery cell B1. The diagnosis circuit 230 can compare the first statistical value with the first relative reference value. When the first statistical value is equal to or greater than the first relative reference value, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1.

[0062] Hereinafter, the second relative determination operation is described. The voltage measurement circuit 210 can measure the voltage of each of the battery cells B1 to BN in the rest section. The voltage measurement circuit 210 can output voltage data of the measured voltage to the data processing circuit 220.

[0063] The data processing circuit 220 can process the voltage data received from the voltage measurement circuit 210 to calculate a second relative reference value. Specifically, the data processing circuit 220 can calculate the second statistical values of the battery cells B1 to BN in the same manner as the method of calculating the second statistical value of the battery cell B1 in the absolute determination operation. The data processing circuit 220 can determine the second relative reference value based on a ‘k’ sigma value of the second statistical values of the battery cells B1 to BN. Here, ‘k’ can be a positive number. As an example, the second relative reference value can be a +3 sigma value of the second statistical value.

[0064] The diagnosis circuit 230 can receive information on the second statistical value and the second relative reference value of the battery cell B1. The diagnosis circuit 230 can compare the second statistical value with the second relative reference value. When the second statistical value is equal to or greater than the second relative reference value, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1.

[0065] Next, a method for performing the cumulative determination operation by the battery management system 200 is described. The battery management system 200 can perform the absolute determination operation and the relative determination operation in each fixed cycle during the analysis period. By using the data generated in the absolute determination operation and the relative determination operation, the battery management system 200 can perform the cumulative determination operation.

[0066] The data processing circuit 220 can calculate the cumulative statistical value by accumulating statistical values related to the voltage of the battery cell B1. For example, the data processing circuit 220 can calculate the cumulative statistical value by accumulating all of the statistical values calculated during the analysis period. As another example, the data processing circuit 220 can calculate the cumulative statistical value by selecting some of the statistical values calculated during the analysis period and accumulating the selected statistical values. Specifically, the data processing circuit 220 can calculate the cumulative statistical value by accumulating the statistical values obtained in a specific time zone during the analysis period.

[0067] The data processing circuit 220 can calculate the cumulative reference value by accumulating the relative reference value in a similar manner to the manner of calculating the cumulative statistical value. However, the present application is not limited thereto, and the data processing circuit 220 can calculate the cumulative reference value based on the absolute reference value. In addition, the cumulative reference value can be a value set by a user.

[0068] The diagnosis circuit 230 can receive information about the cumulative statistical value and the cumulative reference value. The diagnosis circuit 230 can compare the cumulative statistical value with the cumulative reference value. When the cumulative statistical value is equal to or greater than the cumulative reference value, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1.

[0069] That is, the cumulative determination operation means a determination operation of performing a comparison operation using a value (e.g., cumulative statistical value, cumulative reference value) obtained by accumulating and adding data values (e.g., statistical value, relative reference value) for the relative determination operation during a specific period, or performing a comparison operation using a value (e.g., cumulative statistical value, cumulative reference value) obtained by accumulating and adding data values (e.g., statistical value, relative reference value) for the absolute determination operation during a specific period.

[0070] The data processing circuit 220 and the diagnosis circuit 230 can perform a first cumulative determination operation by accumulating the first statistical value of the battery cell B1, or perform a second cumulative determination operation by accumulating the second statistical value of the battery cell B1. In addition, the present application is not limited thereto, and the data processing circuit 220 and the diagnosis circuit 230 can perform both the first cumulative determination operation and the second cumulative determination operation.

[0071] The diagnosis circuit 230 can repeatedly perform the absolute determination operation, the relative determination operation, and the cumulative determination operation. The diagnosis circuit 230 can count the number of times of the absolute error in which it is determined that an error has occurred in the battery cell B1 in the absolute determination operation. The diagnosis circuit 230 can count the number of times of the relative error in which it is determined that an error has occurred in the battery cell B1 in the relative determination operation. The diagnosis circuit 230 can count the number of times of the cumulative error in which it is determined that an error has occurred in the battery cell B1 in the cumulative determination operation.

[0072] The diagnosis circuit 230 can finally determine whether the battery cell B1 is defective based on the number of times of the absolute error, the number of times of the relative error, and the number of times of the cumulative error. For example, when the number of times of the absolute error, the number of times of the relative error, and the number of times of the cumulative error of the battery cell B1 are equal to or greater than a first number, a second number, and a third number, respectively, the diagnosis circuit 230 can determine that the battery cell B1 is defective. The first number, the second number, and the third number can be values set by a user. In addition, the first number, the second number, and the third number can be determined based on the number of times of the absolute error, the number of times of the relative error, and the number of times of the cumulative error of the battery cells B1 to BN, respectively. For example, the first number can be the number of times of the absolute error corresponding to the top 2% among the number of times of the absolute error of the battery cells B1 to BN.

[0073] The memory 240 can store data necessary for the absolute determination operation, the relative determination operation, and the cumulative determination operation. In addition, the memory 240 can store data generated by the data processing circuit 220 and the diagnosis circuit 230. Specifically, the memory 240 can store data related to the statistical value, the cumulative statistical value, the number of times of the absolute error, the number of times of the relative error, and the number of times of the cumulative error. When it is determined that the battery cell B1 is defective, the memory 240 can store information about the battery cell B1, information about a defect occurring in the battery cell B1, etc.

[0074] Figure 3 is a flowchart for describing an operation of the battery management system. Figure 2

[0075] Referring to Figure 3 , a method for determining whether the battery cell B1 is defective by the battery management system 200 through the absolute determination operation, the relative determination operation, and the cumulative determination operation by the battery management system 200 is described. Referring to Figure 2 Figure 3 ​​In the description of the battery management system 200, the fact that the battery management system 200 performs the absolute determination operation means that it performs the first absolute determination operation and / or the second absolute determination operation. The fact that the battery management system 200 performs the relative determination operation means that it performs the first relative determination operation and / or the second relative determination operation. In addition, the fact that the battery management system 200 performs the cumulative determination operation means that it performs the first cumulative determination operation and / or the second cumulative determination operation.

[0076] In operation S110, the battery management system 200 can measure the voltage of each of the battery cells B1 to BN.

[0077] In operation S120, the battery management system 200 can generate data for the absolute determination operation, the relative determination operation, and the cumulative determination operation based on the measured voltage. Specifically, the battery management system 200 can calculate the statistical value of the battery cell B1, the cumulative statistical value, etc. based on the measured voltage, and can calculate the relative reference value, the cumulative reference value, etc.

[0078] In operation S130, the battery management system 200 can perform the absolute determination operation. The battery management system 200 can compare the statistical value of the battery cell B1 with the absolute reference value. When the statistical value of the battery cell B1 is equal to or greater than the absolute reference value, the battery management system 200 can increase the number of absolute errors by one.

[0079] In operation S140, the battery management system 200 can perform the relative determination operation. The battery management system 200 can compare the statistical value of the battery cell B1 with the relative reference value. When the statistical value of the battery cell B1 is equal to or greater than the relative reference value, the battery management system 200 can increase the number of relative errors by one.

[0080] In operation S150, the battery management system 200 can perform the cumulative determination operation. The battery management system 200 can compare the cumulative statistical value of the battery cell B1 with the cumulative reference value. When the cumulative statistical value of the battery cell B1 is equal to or greater than the cumulative reference value, the battery management system 200 can increase the number of cumulative errors by one.

[0081] In operation S160, the battery management system 200 can determine whether the number of absolute errors, the number of relative errors, and the number of cumulative errors satisfy the condition. As described with reference to FIG. 1, the battery management system 200 can determine whether the number of absolute errors, the number of relative errors, and the number of cumulative errors satisfy the condition based on the number of absolute errors, the number of relative errors, and the number of cumulative errors. Figure 2The described condition may be whether the number of absolute errors, the number of relative errors, and the number of cumulative errors are equal to or greater than the first count, the second count, and the third count, respectively. Satisfying the condition may mean that the number of errors (the number of absolute errors, the number of relative errors, and the number of cumulative errors) should be equal to or greater than the corresponding counts (the first count, the second count, and the third count), but is not limited to this. Satisfying the condition may be sufficient when at least one of the error counts (e.g., the number of cumulative errors) is equal to or greater than the corresponding count (the third count). Alternatively, satisfying the condition may mean that the sum of some of the error counts (e.g., the sum of the number of absolute errors and the number of relative errors) is equal to or greater than the sum of the corresponding counts (the sum of the first count and the second count), and the remaining error count (the number of cumulative errors) is equal to or greater than the corresponding count (the third count). Furthermore, the condition may be modified differently depending on the comparison of the error count with the corresponding count.

[0082] When the number of absolute errors, the number of relative errors, and the number of cumulative errors meet the above conditions, operation S170 is executed. In operation S170, the battery management system 200 can finally determine that the battery cell B1 is defective.

[0083] If the number of absolute errors, the number of relative errors, and the number of cumulative errors do not meet the above conditions, operation S180 is executed. In operation S180, the battery management system 200 can finally determine that the battery cell B1 is free of defects.

[0084] Figure 4 It is used to describe Figure 2 The flowchart of the first absolutely certain operation of the battery management system. Figure 2 The battery management system 200 can perform a first absolutely certain operation in both the charging and discharging phases.

[0085] In operation S210, the voltage measurement circuit 210 can measure the voltage of the battery cell B1.

[0086] In operation S220, the data processing circuit 220 can convert the voltage of the battery cell B1 measured by the voltage measurement circuit 210 into a differential signal. In this case, the data processing circuit 220 can calculate the differential signal (e.g., dQ / dV) relative to the capacity and voltage of the battery cell B1. To calculate the differential signal, the battery management system 200 can measure the capacity of the battery cell B1.

[0087] In addition, the data processing circuit 220 can convert the voltage of the battery cell B1 into a differential signal with respect to a region in which the voltage is 4V to 4.2V. This is because an unstable voltage curve due to an internal short circuit inside the battery can be detected in a high voltage region in which the voltage of the battery cell B1 is 4V to 4.2V and an influence on a differential peak value change due to other factors such as a deviation between the battery cells (B1) or deterioration can be excluded. However, the differential signal converted by the data processing circuit 220 according to the embodiment of the present application is not necessarily limited to the voltage range of 4V to 4.2V, and in addition, it can be converted into a differential signal with respect to any voltage range.

[0088] The data processing circuit 220 can perform preprocessing on the voltage data of the battery cell B1 before calculating the differential signal, thereby converting the voltage of the battery cell B1 to be differentiable in a predetermined section. It will be described with reference to FIG. 4. Figure 5 The preprocessing operation of the data processing circuit 220 will be described in detail.

[0089] In operation S230, the data processing circuit 220 can calculate a first statistical value with respect to the converted differential signal. In this case, the first statistical value of the differential signal calculated by the data processing circuit 220 is used to determine abnormal behavior of the battery in a sliding window (or moving window) method, as will be described later. For example, the first statistical value of the differential signal can include a standard deviation.

[0090] In operation S240, the diagnosis circuit 230 can diagnose the battery cell B1 based on the differential signal converted by the data processing circuit 220.

[0091] When the first statistical value with respect to the differential signal of the battery voltage is equal to or greater than a first absolute reference value, operation S250 is performed. In operation S250, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1. The diagnosis circuit 230 can diagnose the battery cell B1 with respect to the first statistical value of the differential signal related to the battery voltage in a sliding window method. As described above, when the diagnosis circuit 230 diagnoses the battery cell B1 in a sliding window method, the size of the window can be arbitrarily set by a user. When the first statistical value with respect to the differential signal of the battery voltage is less than the first absolute reference value, operations S210 to S540 are performed again.

[0092] Figure 5 is a flowchart for describing Figure 2 the data preprocessing operation of the data processing circuit. Figure 2 The data processing circuit 220 of

[0093] In operation S310, the voltage measurement circuit 210 can measure the voltage of the battery cell B1.

[0094] The data processing circuit 220 can perform preprocessing on the voltage data of the battery cell B1 before calculating the differential signal, thereby converting the voltage of the battery cell B1 to be differentiable in a predetermined section. In general, there can be a case where differential analysis cannot be performed on the measured voltage data of the battery due to redundant signals, discontinuous sections, etc. Accordingly, the data processing circuit 220 can perform preprocessing on the voltage data of the battery cell B1 before conversion of the differential signal, thereby converting the voltage of the battery cell B1 to be differentiable in a predetermined section.

[0095] In operation S320, the data processing circuit 220 can convert the voltage of the battery cell B1 into data in the form of a monotonically increasing or monotonically decreasing by sampling the voltage data. For example, the data processing circuit 220 can perform voltage sampling by classifying the capacity values of the battery cell B1 having the same voltage amplitude and calculating the average of the capacity values of the battery cell B1 for each voltage amplitude.

[0096] In operation S330, the data processing circuit 220 can convert to satisfy continuity between adjacent data by a smoothing spline. Through this, the curve of the slope of the voltage data of the battery cell B1 can be converted into a gentle form.

[0097] Figure 6a is a diagram illustrating a method of performing sampling to remove redundant signals of battery voltage data.

[0098] Referring to Figure 6a , the measured data of the voltage and capacity of the battery for each time is illustrated. Here, the voltage is the same as 3.23V in the sections where the battery capacity is 43 Ah, 44 Ah, 46 Ah, and the voltage is the same as 3.24V in the sections where the battery capacity is 45 Ah and 47 Ah. Accordingly, a redundant signal of the voltage data can be generated, thereby making differential analysis impossible.

[0099] In this case, the battery voltage data can be sampled by classifying the capacity values of the battery for the capacity and voltage data of the battery based on the voltage of a certain amplitude and calculating the average thereof. For example, as Figure 6a illustrated, the average of the capacity values corresponding to each voltage can be calculated based on 3.23V and 3.24V which are overlapping battery voltages. For example, when the voltage is 3.23V, 44.3 Ah which is the average of the battery capacities 43 Ah, 44 Ah, and 46 Ah can be determined as the capacity value, and when the voltage is 3.24V, 46 Ah which is the average of the battery capacities 45 Ah and 47 Ah can be determined as the capacity value.

[0100] As described above, the apparatus for diagnosing a battery according to an embodiment of the present application can diagnose the battery byFigure 6a The illustrated method performs sampling to convert voltage data into a monotonically increasing (or monotonically decreasing) form based on the measured voltage.

[0101] Figure 6b is a graph illustrating the result of performing pre-processing on battery voltage data through sampling and smoothing spline, and Figure 6c is a graph illustrating the differential curve of battery voltage data for each pre-processing step. In this case, Figure 6b the horizontal axis of indicates the capacity (Ah) of the battery, while the vertical axis indicates the measured voltage (V) of the battery. In addition, Figure 6c the horizontal axis of indicates the voltage (V) of the battery, while the vertical axis indicates the differential signal (Ah / V) related to the capacity and voltage of the battery.

[0102] As Figure 6b illustrated, redundant signals and noise are generated in the case of original voltage data, but it can be seen that the voltage data according to Figure 6a sampling appears in a monotonically increasing form.

[0103] On the other hand, even when the sampling process is performed on the original data of the voltage, a differential-impossible section can occur due to the slope difference between adjacent data. In this regard, referring to Figure 6c when only the sampling process is performed on the original data of the voltage, it can be seen that the value of the differential signal does not completely occur.

[0104] Therefore, by performing smoothing spline on the sampled voltage data, it is possible to convert the slope of the voltage data of the battery to satisfy continuity. For example, the calculation equation for smoothing spline can be expressed as follows.

[0105]

[0106] Through the smoothing spline equation, it is possible to prevent the slope of the sampled voltage data from rapidly changing, and to be converted into a continuous curve. In this case, as the value of λ increases, the curve becomes smoother. For example, the λ values can be 0.001 (V) and 0.01 (Q), respectively.

[0107] Figure 6d illustrates a histogram of the differential signal for each charge cycle of the battery, and Figure 6e illustrates the standard deviation for each charge cycle of the battery. In this case, Figure 6d the horizontal axis of indicates the interval of the differential signal value, while the vertical axis indicates the number of each differential signal value. In addition, Figure 6d the horizontal axis of indicates the voltage (V) while the vertical axis indicates the standard deviation of the differential signal. Meanwhile, in Figure 6d and Figure 6eIn this case, the results obtained by setting the size of the moving (sliding) window to 60 are illustrated.

[0108] Referring to FIG. 10, Figure 6d histograms of the differential signal for cases in which the number of charge cycles is 113, 135, and 140, respectively, are illustrated. As Figure 6d illustrated, it can be seen that, when the number of charge cycles is 113, a normal charge curve is illustrated, but when the number of charge cycles is 135 and 140, it can be confirmed that an unstable open-circuit curve occurs.

[0109] On the other hand, referring to FIG. 11, Figure 6e when the standard deviation of the differential signal is uniform with respect to the voltage, it means that a normal voltage behavior occurs, and when the standard deviation of the differential signal sharply rises in a specific voltage section, it means that an unstable behavior of the voltage occurs.

[0110] As described above, whether the voltage is unstable can be detected through a change in the standard deviation within an analysis window of the differential signal with respect to the battery voltage. Therefore, according to the apparatus for diagnosing a battery according to an embodiment of the present application, a determination condition for quantifying a normal behavior or an abnormal behavior of the battery voltage can be made.

[0111] Figure 6f is a graph illustratively describing an example of diagnosing an abnormality in a battery through the standard deviation of a differential signal in the apparatus for diagnosing a battery according to an embodiment of the present application. In this case, Figure 6f the results derived by setting the size of the moving (sliding) window to 10 are illustrated, with the horizontal axis representing the voltage (V) and the vertical axis representing the standard deviation of the differential signal.

[0112] As Figure 6f illustrated, the apparatus for diagnosing a battery according to an embodiment of the present application can diagnose an abnormal voltage drop due to an internal short circuit of the battery based on whether the standard deviation of the differential signal is equal to or greater than a preset reference value. For example, referring to FIG. 12, Figure 6f it can be determined that an abnormal voltage drop occurs in a region in which the battery voltage is 4.16 V to 4.18 V.

[0113] On the other hand, in the case of using the standard deviation of the differential signal as Figure 6f illustrated, as the size of the sliding window is smaller, the discrimination ability of the unstable behavior increases, so that the voltage drop phenomenon can be more easily and accurately detected.

[0114] In addition, in the above description, it has been described that the standard deviation of the differential signal of the battery voltage is used to determine whether it is normal, but the present application is not limited thereto, and various statistical values, such as the mean, median, kurtosis, and skewness of the differential signal, can be used in addition to the standard deviation.

[0115] Figure 7 is a flowchart for describing a second absolute determination operation of a battery management system. Figure 2

[0116] In operation S410, the voltage measurement circuit 210 can measure the voltage of the battery cell B1. In this case, the voltage measurement circuit 210 can measure the voltage of the battery cell B1 at a predetermined time interval.

[0117] In operation S420, the data processing circuit 220 can calculate a fitting equation of the voltage of the battery cell B1. In this case, the fitting equation calculated by the data processing circuit 220 can be a model voltage that represents a voltage profile of the battery cell B1. For example, the fitting equation can be an exponential equation. In addition, the data processing circuit 220 can calculate the fitting equation through least square estimation. However, this is only an example, and the present application is not limited thereto, but the data processing circuit 220 can calculate the fitting equation in various ways. The data processing circuit 220 can calculate the fitting equation of the voltage in a stationary section in which a voltage drop phenomenon due to an internal short circuit of the battery occurs after charging of the battery cell B1 is completed. The second statistical value can be calculated based on the fitting equation of the voltage of the battery cell B1 calculated by the data processing circuit 220. The second statistical value can be a difference between the measured voltage of the battery cell B1 and the voltage according to the fitting equation calculated by the data processing circuit 220.

[0118] In operation S430, the diagnosis circuit 230 can diagnose whether an error has occurred in the battery cell B1 based on the fitting equation of the voltage of the battery cell B1 calculated by the data processing circuit 220.

[0119] When the second statistical value is equal to or greater than the second absolute reference value, operation S440 is performed. In this case, the second absolute reference value can be set based on a predetermined measurement error value of the voltage measurement circuit 210. In operation S440, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1. When the second statistical value is less than the second absolute reference value, operations S410 to S430 are performed again.

[0120] Figure 8a is a graph of a voltage change when a voltage drop due to an internal short circuit of a battery cell occurs over an entire section, and Figure 8b is a graph illustrating a voltage change when a voltage drop due to an internal short circuit of a battery cell occurs temporarily. Here, in Figure 8a and Figure 8b , the horizontal axis represents time (sec) and the vertical axis represents the voltage (V) of the battery.

[0121] Referring to Figure 8a ​It can be seen that, for the case of the 113th, 135th, 140th, 149th, and 150th charge cycles, the voltage drop due to the internal short circuit of the battery cell gradually occurs in the stationary section after charging the battery during the entire period.

[0122] In addition, referring to Figure 8b It can be seen that, for the case of the 73rd, 74th, 82nd, and 105th charge cycles, the voltage drop due to the internal short circuit of the battery cell temporarily occurs in the stationary section after charging the battery in the section of about 1500 seconds, the section of 2300 seconds, etc.

[0123] Figure 8c is a graph illustrating the actual stationary voltage after charging the battery for about 10 minutes, the voltage according to the fitted equation, and the difference therebetween. In this case, Figure 8c The horizontal axis of indicates time (seconds), the vertical axis (left) indicates the voltage of the battery (V), and the vertical axis (right) indicates the absolute value of the difference between the actually measured voltage of the battery and the voltage according to the fitted equation (mV).

[0124] Figure 8c The fitted equation of the battery voltage in is derived through least square estimation. In this case, the fitted equation of the battery voltage can be expressed as follows.

[0125] Y flt = a x exp(b.t) + c

[0126] In the apparatus for diagnosing a battery according to the embodiment of the present application, the fitted equation of the battery voltage can be completed by calculating the constants of a, b, and c in the above equation, respectively. However, the above equation is illustrated only as an example, the present application is not limited thereto, and various equations capable of fitting the voltage of the battery can be used.

[0127] Referring to Figure 8c The absolute value of the difference between the actually measured stationary voltage of the battery (raw) and the voltage according to the fitted equation (Exp. fitted) is indicated by |V error | of the center of the graph. As described above, the absolute value of the difference between the actually measured voltage of the battery and the voltage according to the fitted equation means the second statistical value. The apparatus for diagnosing a battery according to the present application can detect the voltage drop due to the internal short circuit in the stationary section of the battery by comparing the second statistical value with the second absolute reference value.

[0128] Figure 8d illustrates the result that the voltage drop due to the internal short circuit of the battery cell is detected to occur over the entire section by the apparatus for diagnosing a battery according to the embodiment of the present application, and Figure 8eFIG. 13 illustrates a result that a voltage drop due to an internal short circuit of a battery cell temporarily occurs, which is detected by the device for diagnosing a battery according to an embodiment of the present application.

[0129] In this case, Figure 8d and Figure 8e The horizontal axis thereof indicates the number of charge cycles of a battery, and the vertical axis thereof indicates the maximum value (V) of the difference between the actually measured voltage of the battery and the voltage according to the fitted equation.

[0130] Referring to Figure 8d , the device for diagnosing a battery can compare the second statistical value with the second absolute reference value when a voltage drop due to an internal short circuit of a battery cell occurs over the entire section, and can determine that a voltage drop due to an internal short circuit of a battery has occurred when the second statistical value is equal to or greater than the second absolute reference value.

[0131] Similarly, referring to Figure 8e , the device for diagnosing a battery can compare the second statistical value with the second absolute reference value even when a voltage drop due to an internal short circuit of a battery cell temporarily occurs, and can determine that a voltage drop due to an internal short circuit of a battery has occurred when the second statistical value is equal to or greater than the second absolute reference value. In this case, the reference value of Figure 8d and Figure 8e may be determined based on the measurement range of the voltage sensor itself.

[0132] Figure 9 is a flowchart for describing a relative determination operation of a battery management system for Figure 2 . In a method corresponding to the relative determination operation described with reference to Figure 9 , the first relative determination operation and the second relative determination operation can be performed.

[0133] In operation S510, the voltage measurement circuit 210 can measure the voltage of each of the battery cells B1 to BN. In this case, the voltage measurement circuit 210 can measure the voltage of the battery cells B1 to BN at a predetermined time interval.

[0134] In operation S520, the data processing circuit 220 can calculate a statistical value of the battery cell B1 based on the measured voltage of the battery cell B1. The statistical value is an index value indicating the voltage state of the battery cell B1 and can be calculated in various ways. For example, in the first relative determination operation, the data processing circuit 220 can calculate the standard deviation of the differential signal of the voltage of the battery cell B1. When the voltage of the battery cell B1 is measured several times at a predetermined time interval, the data processing circuit 220 can calculate the standard deviation of the differential signal of the voltage of the battery cell B1 in each time section. In this case, the first statistical value can be the maximum value among the calculated standard deviations.

[0135] In operation S530, the data processing circuit 220 can calculate the statistical values of the battery cells B1 to BN based on the measured voltages of the battery cells B1 to BN. The statistical values of the battery cells B1 to BN can also be calculated in substantially the same manner as described with reference to operation S520.

[0136] In operation S540, the data processing circuit 220 can calculate a relative reference value based on the statistical values of the battery cells B1 to BN. The relative reference value can be an 'n' sigma value of the statistical values of the battery cells B1 to BN. Here, 'n' can be a positive number.

[0137] In operation S550, the diagnosis circuit 230 can compare the statistical value of the battery cell B1 with the relative reference value.

[0138] When the statistical value of the battery cell B1 is greater than or equal to the relative reference value, operation S560 is performed. In operation S560, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1. When the statistical value of the battery cell B1 is less than the relative reference value, operation S570 is performed. In operation S570, the diagnosis circuit 230 can determine that an error has not occurred in the battery cell B1.

[0139] Figure 10a is a graph illustrating a distribution of a first statistical value of a battery cell.

[0140] Figure 10a The horizontal axis of indicates the first statistical value, and the vertical axis indicates the number of battery cells. Referring to Figure 10a The first statistical value of any battery cell described means the maximum value (max(std(dQ / dV))) among standard deviations of values obtained by differentiating the voltage of the battery cell.

[0141] When the relative reference value is determined as a 3 sigma value of the statistical values of the battery cells B1 to BN, it can be determined that an error has occurred in Figure 10a In the graph of, the battery cells included on the right side of the 3 sigma value have an error.

[0142] Figure 10b is a graph illustrating the number of relative errors of a battery cell.

[0143] Figure 10b The horizontal axis of indicates the number of relative errors of a battery cell, and the vertical axis indicates the number of battery cells. The diagnosis circuit 230 can perform a relative determination operation at a predetermined time interval. The diagnosis circuit 230 can accumulate the number of relative errors of a battery cell while performing the relative determination operation. The greater the number of relative errors of a battery cell, the higher the probability that the battery cell is determined to be defective.

[0144] Figure 11 is a flowchart for describing a cumulative determination operation of the battery management system of Figure 2 . In a method corresponding to the cumulative determination operation described with reference to Figure 11 , a first cumulative determination operation and a second cumulative determination operation can be performed.

[0145] In operation S610, the voltage measurement circuit 210 can measure the voltage of the battery cell B1 at a predetermined time interval.

[0146] In operation S620, the data processing circuit 220 can calculate a statistical value of the battery cell B1 based on the voltage of the battery cell B1 measured at the predetermined time interval.

[0147] In operation S630, the data processing circuit 220 can calculate a cumulative statistical value by accumulating the statistical values of the battery cell B1. The data processing circuit 220 can select some of the statistical values calculated during the analysis period, and can calculate the cumulative statistical value by accumulating the selected statistical values.

[0148] In operation S640, the diagnosis circuit 230 can compare the cumulative statistical value with a cumulative reference value. The cumulative reference value can be a value calculated by accumulating the relative reference value, a value set by a user, or a value set based on the state of the battery cell.

[0149] When the cumulative statistical value is equal to or greater than the cumulative reference value, operation S650 is performed. In operation S650, the diagnosis circuit 230 can determine that an error has occurred in the battery cell B1. When the cumulative statistical value is less than the cumulative reference value, operation S660 is performed. In operation S660, the diagnosis circuit 230 can determine that an error has not occurred in the battery cell B1.

[0150] As described above, the apparatus for diagnosing a battery of the present application can finally determine whether a battery cell is defective by comprehensively considering the results of the absolute determination operation, the relative determination operation, and the cumulative determination operation. Accordingly, according to the present application, it is possible to improve the accuracy of determining a defect in a battery cell. In addition, in the present application, an operation of diagnosing an error of a battery cell occurring in a charging section and a discharging section and an operation of diagnosing an error of a battery cell occurring in a stationary section can be performed, and the above-described diagnosis operations can be selectively performed according to a situation.

[0151] Figure 12 is a diagram illustrating a hardware configuration of an apparatus for diagnosing a battery according to an embodiment of the present application.

[0152] Reference will now be made to Figure 12The apparatus 800 for diagnosing a battery includes a microcontroller (MCU) 810 for controlling various processes and each configuration, a memory 820 in which an operating system program and various programs (e.g., a battery diagnosis program, a voltage approximation calculation program, etc.) are recorded, an input / output interface 830 that provides an input interface and an output interface between a battery cell module and / or a semiconductor switching element, and a communication interface 840 that can communicate with the outside through a wired or wireless communication network. In this way, the computer program according to the present application can be implemented as a module that performs, for example Figure 2 each of the illustrated functional blocks.

[0153] The above matters are specific embodiments for implementing the present application. The present application will not only include the above embodiments, but also include embodiments to which simple design changes or easy changes are made. In addition, the present application will include technologies that can be easily modified and implemented using the embodiments. Therefore, the scope of the present application should not be limited to the above embodiments.

Claims

1. An apparatus for diagnosing a battery, the apparatus comprising: a voltage measurement circuit configured to measure a voltage of a battery cell; a data processing circuit configured to calculate a target statistical value indicative of a state of the battery cell based on the voltage measured by the voltage measurement circuit, and to calculate a cumulative statistical value by accumulating the target statistical value of the battery cell during an analysis period; and a diagnostic circuit configured to determine whether an error has occurred in the battery cell by a cumulative determination operation of comparing the cumulative statistical value with a cumulative reference value, and to count a number of cumulative errors when it is determined in the cumulative determination operation that an error has occurred in the battery cell, wherein the data processing circuit is further configured to calculate a relative reference value based on target statistical values of a plurality of battery cells, the diagnostic circuit is further configured to determine whether an error has occurred in the battery cell by a relative determination operation of comparing the target statistical value with the relative reference value, and to count a number of relative errors when it is determined in the relative determination operation that an error has occurred in the battery cell, and the plurality of battery cells are a plurality of battery cells of a battery module including the plurality of battery cells.

2. The apparatus according to claim 1, wherein the data processing circuit is further configured to set an ‘n’ sigma value of the target statistical value as the relative reference value, and the ‘n’ is a positive number.

3. The apparatus according to claim 1, wherein the data processing circuit is further configured to calculate the cumulative reference value by accumulating the relative reference value calculated during the analysis period.

4. The apparatus according to claim 1, wherein the data processing circuit is further configured to select a target statistical value corresponding to a specific time zone of the analysis period from among the target statistical values of the battery cell, and to calculate the cumulative reference value by accumulating the selected target statistical value.

5. The apparatus according to claim 1, wherein the diagnostic circuit is further configured to determine whether an error has occurred in the battery cell by an absolute determination operation of comparing the target statistical value with an absolute reference value, and to count a number of absolute errors when it is determined in the absolute determination operation that an error has occurred in the battery cell.

6. The apparatus according to claim 1, wherein when measuring the voltage of the battery cell in a charge section and a discharge section of the battery cell, the data processing circuit is further configured to convert the voltage of the battery cell into a differential signal with respect to a capacity and a voltage of the battery cell, and to calculate the target statistical value based on the differential signal.

7. The apparatus according to claim 6, wherein The data processing circuit is further configured to convert the voltage of the battery cell into voltage data in a monotonically increasing or monotonically decreasing form by sampling the voltage of the battery cell, calculate a differential value by differentiating the converted voltage data, and set a standard deviation of the differential value as the target statistical value.

8. The apparatus according to claim 1, wherein The data processing circuit is further configured to calculate a fitting value of the voltage of the battery cell when measuring the voltage of the battery cell in a stationary section of the battery cell, and set an absolute value of a difference between the voltage measured by the voltage measurement circuit and the fitting value as the target statistical value.

9. The apparatus according to claim 8, wherein The data processing circuit is further configured to calculate the fitting value according to a least square estimation.

10. The apparatus according to claim 5, wherein The diagnostic circuit is further configured to determine that the battery cell is defective when the number of absolute errors, the number of relative errors, and the number of cumulative errors satisfy a diagnostic condition.

11. The apparatus according to claim 10, wherein the diagnostic condition is that the number of absolute errors is greater than or equal to a first number, the number of relative errors is greater than or equal to a second number, and the number of cumulative errors is greater than or equal to a third number, the first number is related to the number of absolute errors of the plurality of battery cells, the second number is related to the number of relative errors of the plurality of battery cells, and the third number is related to the number of cumulative errors of the plurality of battery cells.

12. A method for diagnosing a battery, comprising: a voltage measurement step of measuring a voltage between an input terminal and an output terminal of a battery cell by an apparatus for diagnosing a battery; a calculation step of calculating, by the apparatus for diagnosing a battery, a target statistical value indicating a state of the battery cell based on the voltage measured in the voltage measurement step, and calculating a cumulative statistical value by accumulating the target statistical value of the battery cell during an analysis period; and a first diagnostic step of determining, by the apparatus for diagnosing a battery, whether an error has occurred in the battery cell through a cumulative determination operation of comparing the cumulative statistical value with a cumulative reference value, and counting a number of cumulative errors when it is determined through the cumulative determination operation that an error has occurred in the battery cell, wherein the calculation step further includes calculating a relative reference value based on target statistical values of a plurality of battery cells including the battery cell, the method further includes a second diagnostic step of determining, by the apparatus for diagnosing a battery, whether an error has occurred in the battery cell through a relative determination operation of comparing the target statistical value with the relative reference value, and counting a number of relative errors when it is determined through the relative determination operation that an error has occurred in the battery cell.

13. The method according to claim 12, wherein the method further includes a third diagnosis step of determining whether an error has occurred in the battery cell by an absolute determination operation of comparing the target statistical value with an absolute reference value by the device for diagnosing a battery, and counting the number of absolute errors when it is determined that an error has occurred in the battery cell by the absolute determination operation, and a final diagnosis step of determining that the battery cell is defective when the number of absolute errors, the number of relative errors, and the number of accumulated errors satisfy a diagnosis condition, and providing a warning for the defect of the battery cell.

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