Battery diagnosis device and method

Abstract

The invention discloses a battery diagnosis device and method. A battery diagnosis apparatus includes a configuration for diagnosing an abnormality of a battery cell in a manner that analyzes a behavioral change in a cell voltage change rate that occurs when the battery cell discharges in a state in which a state of charge of the battery cell has been formed to a predetermined reference state of charge.

Description

TECHNICAL FIELD

[0001] Aspects of embodiments of the present disclosure relate to a battery diagnostic device and method and a battery pack. BACKGROUND

[0002] Unlike primary batteries that cannot be recharged, secondary batteries are batteries that can be charged and discharged. Low-capacity secondary batteries can be used for small portable electronic devices such as smartphones, feature phones, laptop computers, digital cameras, and camcorders, while high-capacity secondary batteries are widely used as motor drive power sources in hybrid electric vehicles, electric vehicles, etc., power storage batteries, etc. These secondary batteries (i.e., battery cells) include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, a case that houses the electrode assembly, an electrode terminal connected to the electrode assembly, etc. Charging and discharging of the battery cell is performed in such a manner that an electrolyte is injected into the case of the battery cell, and an electrochemical reaction is performed between the positive electrode, the negative electrode, and the electrolyte. For example, depending on the use of the battery cell, the case of the battery cell can be implemented in any one of various shapes such as a cylindrical shape, a rectangular shape, etc.

[0003] In the battery cell, an internal short circuit phenomenon in which the positive electrode and the negative electrode in the battery cell are short-circuited due to a loss of function of the separator can occur. The internal short circuit in the battery cell can occur due to deformation caused by external impact, metal foreign matter introduced during a manufacturing process, or dendrite formation of lithium or copper due to an electrochemical reaction. Such an internal short circuit in the battery cell can cause a safety problem such as thermal runaway.

[0004] In addition, in the case of a secondary battery applied to an electric vehicle or a high-capacity system such as an energy storage system (ESS), due to the characteristics of the high-capacity system, long life, high output characteristics, and safety are desired. Specifically, in the case of a battery into which a waste-type foreign matter including an abnormal metal foreign matter or a base material has been introduced, lithium salt can grow around a region into which the foreign matter has been introduced, and a phenomenon in which the lithium salt penetrates the separator under pressurized conditions in which cell swelling is limited by the external separator can occur, and thus, there is a risk of thermal runaway occurring due to an internal short circuit in the battery cell.

[0005] The above information disclosed in this Background section is provided for enhancing the understanding of the background of the present disclosure, and therefore it can include information that does not constitute the related (or prior) art. SUMMARY

[0006] According to an aspect of one or more embodiments of the present disclosure, there is provided a battery diagnostic device and method capable of diagnosing a battery cell abnormality such as an internal short circuit in a cell due to lithium salt precipitation that can occur in a lithium ion battery in advance.

[0007] However, aspects and objectives of the present disclosure are not limited to the above-described aspects and objectives, and other aspects and objectives not described can be clearly understood by those skilled in the art from the following description.

[0008] According to one or more embodiments of the present disclosure, a battery diagnostic device includes a processor configured to diagnose an abnormality of a battery cell, and a memory for storing one or more commands executed by the processor, wherein the processor is configured to diagnose the abnormality of the battery cell by analyzing a behavior of a cell voltage change rate occurring when the battery cell is discharged in a state in which a state of charge (SOC) of the battery cell has been formed as a reference SOC (e.g., a pre-defined reference SOC). BRIEF DESCRIPTION OF DRAWINGS

[0009] The following drawings included in the specification illustrate some embodiments of the present disclosure, and together with the detailed description further describe the aspects and features of the present disclosure. However, the present disclosure should not be construed as being limited to the drawings, in which: Figure 1 A prismatic battery according to an embodiment of the present disclosure is illustrated; Figure 2 A cross-sectional view of a prismatic battery of Figure 1 is illustrated; Figure 3 A battery module according to an embodiment of the present disclosure is illustrated; Figure 4A A battery module according to an embodiment of the present disclosure is illustrated; Figure 4B A battery module according to an embodiment of the present disclosure is illustrated; Figure 5 A block configuration diagram of a battery diagnostic device according to an embodiment of the present disclosure is illustrated; Figure 6 A block configuration diagram of a battery diagnostic device according to an embodiment of the present disclosure is illustrated; Figure 7 A process of analyzing a behavior of a cell voltage change rate of a battery cell in a battery diagnostic device according to an embodiment of the present disclosure is illustrated; and Figure 8 A process of analyzing a behavior of a cell voltage change rate of a battery cell in a battery diagnostic device according to an embodiment of the present disclosure is illustrated; and Figure 9 A flowchart of a battery diagnostic method according to some embodiments of the present disclosure is illustrated. DETAILED DESCRIPTION

[0010] Hereinafter, some embodiments of the present disclosure will be described in greater detail with reference to the accompanying drawings. The terms or words used in the present specification and claims should not be interpreted as being limited to their typical meanings or dictionary definitions, but should be interpreted to have meanings and concepts consistent with the technical idea of the present disclosure based on the principle that the inventor can appropriately define the terms to best explain his / her own invention.

[0011] The embodiments described in this specification and the configurations shown in the drawings are merely some embodiments of the present disclosure, and do not necessarily represent all technical ideas, aspects, and features of the present disclosure. It will be understood, therefore, that there can be various equivalents and modifications of the embodiments described herein that can be substituted or modified at the time of filing this application.

[0012] It will be understood that when an element or layer is referred to as being “on” another element or layer, “connected to” or “coupled to” another element or layer, it can be directly on, directly connected to, or directly coupled to the other element or layer, or one or more intervening elements or layers can also be present. In contrast, when an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. By way of example, when a first element is described as being “coupled” or “connected” to a second element, the first element can be directly coupled or directly connected to the second element, or the first element can be indirectly coupled or indirectly connected to the second element via one or more intervening elements.

[0013] In the drawings, the size of various elements, layers, etc., can be exaggerated for clarity. Like reference numerals designate like elements. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. In addition, use of “may” in describing embodiments of the present disclosure relates to “one or more implementations of the present disclosure.” Expressions such as “at least one of,” and “one or more of,” when preceding a list of two or more items, cover the respective items individually as well as in any combination. When a phrase such as “at least one of A, B, and C” or “at least one of A, B, or C” is used, it is meant to include A, B, and C individually, as well as any combination of A, B, and C. As used herein, the term “use” and variations thereof can be considered synonymous with the term “utilize” and variations thereof. As used herein, the terms “substantially,” “approximately,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent variations in measurements or calculations that would be recognized by those of ordinary skill in the art.

[0014] It will be understood that, although the terms“first,”“second,”“third,” etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus,“a first element,”“a first component,”“a first region,”“a first layer,” or“a first portion” discussed below could be termed a“second element,”“a second component,”“a second region,”“a second layer,” or“a second portion” without departing from the teachings of example embodiments.

[0015] For ease of description, spatial relative terms, such as“below,”“under,”“lower,”“above,”“upper” and the like, can be used herein for describing the orientation of one element or feature to another element(s) or feature(s) as shown in the figures. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements described as“below” or“under” other elements or features would then be oriented“above” or“over” the other elements or features. Thus, the term“below” can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0016] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure. As used herein, the singular forms“a,”“an” and“the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms“comprises,”“comprising,”“includes” and / or“including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0017] Further, any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of "1.0 to 10.0" is intended to include all sub-ranges, half- ranges, etc. of the same precision, within the prescribed range, e.g., 2.4 to 7.6. Also, when any numerical range is recited, it is intended to include all sub-ranges of the same numerical precision, within the recited range, as if each numerical combination and sub-combination were individually recited. Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range including any of the specific integers within the ranges expressly recited.

[0018] Referring to two compared elements, features, etc. as "the same" can mean that they are identical or substantially identical. Thus, the phrase "the same" or "substantially the same" can include having a deviation that is considered low in the art, e.g., 5% or less. Additionally, where a parameter is referred to as being uniform in a given region, it can mean that it is uniform in terms of average value.

[0019] Throughout this specification, unless otherwise indicated, each element can be singular or plural.

[0020] When any element is referred to as being "on" or "above," or "below" a component, it can mean that the element is placed in contact with the upper or lower surface of the component, and it can also mean that another component can be interposed between the component and any element disposed on or below the component.

[0021] In addition, it will be understood that when an element is referred to as "coupled" or "linked" to another element, it can be directly coupled or linked to the other element or one or more intervening elements can exist between them such that the element and the other element are indirectly coupled or linked to each other. In addition, when a component is referred to as being "electrically coupled" to another component, the component can be directly connected to the other component, or one or more intervening components can exist between them such that the component and the other component are indirectly connected to each other.

[0022] Throughout this specification, unless otherwise stated, when stating "A and / or B," it means A, B, or A and B. That is, "and / or" includes any combination or all combinations of the plurality of listed items. When stating "C to D," unless otherwise stated, it means C or greater and D or less.

[0023] 1. Battery structure Before a detailed description of some embodiments, first, a structure of a battery that is a target of an abnormality diagnosis in one or more embodiments will be generally described.

[0024] Prismatic battery Figure 1 is a perspective view showing a secondary battery according to an embodiment; and Figure 2 is a sectional view along line II-II in Figure 1 .

[0025] Referring to Figure 1 and Figure 2 , a secondary battery C according to one or more embodiments of the disclosure can include at least one electrode assembly 10 that is wound with a separator 13 as an insulator interposed between a positive electrode 11 and a negative electrode 12, a case 20 that receives (or accommodates) the electrode assembly 10 therein, and a cap assembly 30 that is coupled to an opening of the case 20.

[0026] Now, a secondary battery C according to one or more embodiments shown in Figure 1 and Figure 2 will be described as an example of a prismatic lithium ion secondary battery. However, the disclosure is not limited thereto, and for example, suitable aspects, features, and principles described herein can be applied to various other types of batteries, such as lithium polymer batteries and / or cylindrical batteries.

[0027] Each of the positive electrode 11 and the negative electrode 12 can include a current collector made of a thin metal foil having a coated portion on which an active material is coated and a corresponding uncoated portion 11a, 12a on which the active material is not coated.

[0028] In an embodiment, the positive electrode 11 and the negative electrode 12 are wound after the separator 13 as an insulator is interposed therebetween. However, the disclosure is not limited thereto, and the electrode assembly 10 can have a structure in which the positive electrode 11 and the negative electrode 12 each made of a plurality of pieces are alternately stacked with the separator interposed therebetween.

[0029] The case 20 can form an overall appearance of the secondary battery C, and can be made of an electrically conductive metal such as aluminum, an aluminum alloy, or nickel-plated steel. In addition, the case 20 can provide a space in which the electrode assembly 10 is accommodated.

[0030] The cover assembly 30 can include a cover plate 31 covering an opening in the case 20, and the case 20 and the cover plate 31 can be made of an electrically conductive material. The positive electrode terminal 21 and the negative electrode terminal 22 electrically connected to the positive electrode 11 and the negative electrode 12, respectively, can be installed to penetrate (or extend through) the cover plate 31 and protrude outwardly therefrom.

[0031] In an embodiment, the outer peripheral surface (e.g., circumferential surface) of the upper column of the positive electrode terminal 21 and the negative electrode terminal 22 protruding outwardly from the cover plate 31 can have a screw thread and can be fixed to the cover plate 31 by using a nut.

[0032] However, the present disclosure is not limited thereto, and the positive electrode terminal 21 and the negative electrode terminal 22 can have a riveting structure and can be riveted or welded to the cover plate 31, for example.

[0033] In an embodiment, the cover plate 31 can be made of a thin plate and can be combined to the opening in the case 20, and the electrolyte injection port 32 to which the sealing stopper 33 can be installed can be positioned (e.g., formed) in the cover plate 31, and the exhaust portion 34 having the notch 34a can be installed or included.

[0034] The positive electrode terminal 21 and the negative electrode terminal 22 can be electrically connected to the current collectors including the first current collector 40 and the second current collector 50 (here, referred to as positive electrode current collector and negative electrode current collector) by being joined or combined (e.g., by welding) to the positive electrode uncoated portion 11a and the negative electrode uncoated portion 12a, respectively.

[0035] For example, the positive electrode terminal 21 and the negative electrode terminal 22 can be combined by being welded to the positive electrode current collector 40 and the negative electrode current collector 50, respectively. However, the present disclosure is not limited thereto, and in one or more embodiments, the positive electrode terminal 21 and the positive electrode current collector 40 can be integrally formed, and the negative electrode terminal 22 and the negative electrode current collector 50 can be integrally formed.

[0036] In addition, an insulating member can be installed between the electrode assembly 10 and the cover plate 31. The insulating member can include a first lower insulating member 60 and a second lower insulating member 70, and each of the first lower insulating member 60 and the second lower insulating member 70 can also have a portion positioned between the electrode assembly 10 and the case 20.

[0037] According to one or more embodiments of the present disclosure, one end of the separation member can face one side of the electrode assembly 10, and can be installed between the insulating member and the positive electrode terminal 21 or the negative electrode terminal 22.

[0038] In one or more embodiments, the separation member can include a first separation member 80 and a second separation member 90.

[0039] In such an embodiment, the first end of the first separation member 80 installed on the side facing the electrode assembly 10 and the first end of the second separation member 90 installed on the side facing the electrode assembly 10 can be installed between the first lower insulating member 60 and the positive electrode terminal 21 and between the second lower insulating member 70 and the negative electrode terminal 22, respectively.

[0040] Accordingly, the positive electrode terminal 21 and the negative electrode terminal 22, which can be bonded to the positive electrode current collector 40 and the negative electrode current collector 50 by welding, can be bonded to the first end of the first lower insulating member 60 and the first end of the second lower insulating member 70, and the first end of the first separation member 80 and the first end of the second separation member 90.

[0041] Battery module Figure 3 is a perspective view showing a battery module according to an embodiment of the disclosure.

[0042] Referring to Figure 3 , the battery module M according to one or more embodiments of the disclosure includes electrode units 110, 120, a plurality of battery cells C arranged in one direction, a connection tab 200 connecting a battery cell 10a to an adjacent battery cell 10b, and a protection circuit module 300 having one end connected to the connection tab 200. In an embodiment, the protection circuit module 300 can include a battery management system (BMS). In addition, the connection tab 200 can include a main body portion in contact with the electrode units 110, 120 between the adjacent battery cells 10a, 10b, and an extension portion extending from the main body portion and connected to the protection circuit module 300. The connection tab 200 can be, for example, a bus bar.

[0043] Each battery cell C can include a battery case, an electrode assembly received (or housed) in the battery case, and an electrolyte. The electrode assembly and the electrolyte undergo an electrochemical reaction to store and release (e.g., generate) energy. The electrode units or terminal portions 110, 120 electrically connected to the connection tab 200 and the exhaust port 130 as a discharge passage for gas generated inside the battery case can be provided at one side (e.g., an upper side) of the battery cell C. The terminal portions 110, 120 of the battery cell C can be a positive electrode terminal 110 and a negative electrode terminal 120 having different polarities from each other, and the terminal portions 110, 120 of the adjacent battery cells 10a, 10b can be electrically connected in series or in parallel with each other by the connection tab 200, which will be described in more detail below. Although a series connection is shown as an example, the connection structure is not limited thereto and any one of various connection structures can be employed as desired or needed. In addition, the number and arrangement of the battery cells are not limited to the structure shown in FIG. 1 and can be changed as desired or needed. Figure 3 ​

[0044] The plurality of battery cells C can be arranged (e.g., can be stacked) in a direction in which the wide surfaces of the battery cells C face each other, and the plurality of battery cells C can be fixed by the housings 61, 62, 63, 64. The housings 61, 62, 63, and 64 can include a pair of end plates 61, 62 facing the wide surfaces of the battery cells C and a side plate 63 and a bottom plate 64 connecting the pair of end plates 61, 62 to each other. The side plate 63 can support the side surfaces of the battery cells C, and the bottom plate 64 can support the bottom surfaces of the battery cells C. In an embodiment, the pair of end plates 61, 62, the side plate 63, and the bottom plate 64 can be connected by bolts 65 and / or any other suitable fastening members and methods known to one of ordinary skill in the art.

[0045] The protection circuit module 300 can have electronic components and protection circuits mounted thereon and can be electrically connected to the connection tabs 200, which will be described in greater detail later. In an embodiment, the protection circuit module 300 includes a first protection circuit module 300a and a second protection circuit module 300b extending in a direction in which the plurality of battery cells C are arranged at different positions. The first protection circuit module 300a and the second protection circuit module 300b can be spaced apart from each other by a suitable interval (e.g., a predetermined interval) and arranged in parallel to each other to be electrically connected to adjacent connection tabs 200, respectively. In an embodiment, for example, the first protection circuit module 300a extends in the direction in which the plurality of battery cells C are arranged at one side of an upper portion of the plurality of battery cells C, and the second protection circuit module 300b extends in the direction in which the plurality of battery cells C are arranged at the other side of the upper portion of the plurality of battery cells C. The second protection circuit module 300b can be spaced apart from the first protection circuit module 300a by a suitable interval (e.g., a predetermined interval) with the exhaust port 130 disposed therebetween, and the second protection circuit module 300b can be disposed in parallel to the first protection circuit module 300a. As such, the two protection circuit modules are disposed in parallel to and spaced apart from each other in the direction in which the plurality of battery cells C are arranged, thereby reducing or minimizing the area of a printed circuit board (PCB) constituting the protection circuit module 300. By separately configuring the protection circuit module 300 as two protection circuit modules, unnecessary PCB area can be reduced or minimized. The first protection circuit module 300a and the second protection circuit module 300b can be connected to each other by a conductive connection member 500. One side of the conductive connection member 500 is connected to the first protection circuit module 300a, and the other side of the conductive connection member 500 is connected to the second protection circuit module 300b, such that the two protection circuit modules 300a, 300b can be electrically connected to each other.

[0046] The connection can be performed by any one of soldering, resistance welding, laser welding, projection welding, and / or any other suitable connection method known to those of ordinary skill in the art.

[0047] In an embodiment, the connection member 500 can be, for example, an electric wire. In addition, the connection member 500 can be made of a material having elasticity or flexibility. Through the connection member 500, it can be possible to check and manage whether the voltage, temperature, and / or current of the battery cell C is normal. For example, information such as voltage, current, and / or temperature received by the first protection circuit module 300a from the connection tab adjacent to the first protection circuit module 300a and information such as voltage, current, and / or temperature received by the second protection circuit module 300b from the connection tab adjacent to the second protection circuit module 300b can be integrated and managed by the protection circuit module 300 through the connection member 500.

[0048] In addition, if the battery cell C swells, the impact can be absorbed by the elasticity or flexibility of the connection member 500, thereby preventing or substantially preventing the first protection circuit module 300a and the second protection circuit module 300b from being damaged.

[0049] However, the shape and structure of the connection member 500 are not limited to Figure 3 the shape and structure shown in FIG. 1.

[0050] As described above, since the protection circuit module 300 is provided as the first protection circuit module 300a and the second protection circuit module 300b, it is possible to reduce or minimize the area of the PCB constituting the protection circuit module, and it is possible to secure the space inside the battery module, thereby improving work efficiency by facilitating the fastening work for connecting the connection tab 200 and the protection circuit module 300 and the repair work if (or when) an abnormality is detected in the battery module M.

[0051] Battery pack Figure 4A and Figure 4B are views showing a battery pack according to an embodiment of the disclosure.

[0052] The battery pack P can include a plurality of battery modules M and a housing H for accommodating the plurality of battery modules M. For example, the housing H can include a first housing H1 and a second housing H2 combined in opposite directions throughout the plurality of battery modules M. The plurality of battery modules M can be electrically connected to each other using bus bars 51, and the plurality of battery modules M can be electrically connected to each other in a series / parallel or a hybrid series-parallel method, thereby obtaining a desired (e.g., required) electric output.

[0053] 2. Battery diagnosis apparatus Based on the above-described battery structure, hereinafter, a method of diagnosing a battery cell abnormality will be described in more detail in embodiments.

[0054] Figure 5 is a block configuration diagram of a battery diagnosis apparatus according to an embodiment of the disclosure; and Figure 6 and Figure 7 is a diagram of a process of analyzing a behavior of a cell voltage change rate of a battery cell in a battery diagnosis apparatus according to an embodiment of the disclosure.

[0055] Referring to Figure 5 , the battery diagnosis apparatus of the embodiment can include a memory 100 and a processor 400, and each of the components 100, 400 can constitute a battery pack together with battery cells (and a plurality of battery modules composed of a plurality of battery cells) that are a target of abnormality diagnosis in the embodiment.

[0056] At least one command to be executed by the processor 400 to be described hereinafter can be stored in the memory 100. The memory 100 can be implemented as a volatile storage medium and / or a non-volatile storage medium, and can be implemented as, for example, a read-only memory (ROM) and / or a random access memory (RAM).

[0057] Further, a plurality of types of threshold data required in a process of diagnosing a battery cell abnormality by the processor 400 can be stored in the memory 100, and the plurality of types of threshold data can include a reference state of charge (SOC), a reference voltage change rate, a reference open circuit voltage (OCV) change rate, and first to third count values. As will be described hereinafter, the plurality of types of threshold data stored in the memory 100 can be utilized in a process of designating an abnormal cell candidate or finally classifying an abnormal cell. The value of each type of threshold data can be predefined based on the specification of the battery system and the experimental results of the designer.

[0058] The processor 400 is an entity that diagnoses an abnormality of a battery cell, and can be implemented as a central processing unit (CPU) or a system on chip (SoC), controls a plurality of hardware or software components connected to the processor 400 by driving an operating system or an application, and can perform various types of data processing and calculation. The processor 400 can be configured to execute at least one command stored in the memory 100, and store execution result data in the memory 100. In the embodiment, as is well known, the processor 400 can be implemented as a battery management system (BMS) or a micro controller unit (MCU) in the BMS provided in the battery pack, and can be configured to detect a current, a voltage, an open circuit voltage (OCV), and a temperature of the battery cell. The sensing function of the BMS can support a sensing operation of parameters (cell voltage and OCV) considered when diagnosing a battery cell abnormality.

[0059] In an embodiment, the abnormality of the battery cell to be diagnosed can refer to an internal short circuit in the cell due to, for example, lithium precipitation occurring on the negative electrode surface of the battery cell. Two embodiments of a method for diagnosing this battery cell abnormality are presented below, and the respective embodiments will be distinguished in the description.

[0060] (1) First Embodiment The first embodiment focuses on a configuration for improving the reliability of battery cell abnormality diagnosis using a change in behavior of the cell voltage change rate of the battery cell as a basic analysis factor and using the maximum value of the cell voltage change rate of the battery cell and the change rate of the open circuit voltage as additional analysis factors.

[0061] First, the processor 400 can determine whether the state of charge (SOC) of the battery cell has been formed as a reference SOC (e.g., a pre-defined reference SOC) in the memory 100. This embodiment is configured to diagnose a battery cell abnormality based on a change in behavior of the cell voltage change rate occurring during self-discharge due to an internal short circuit of the battery cell, and assumes that the state in which the SOC of the battery cell has been formed as a reference SOC (e.g., a pre-defined reference SOC) as an initial state of self-discharge of the battery cell.

[0062] If the SOC of the battery cell has been formed lower than the reference SOC, the processor 400 can operate to form the SOC of the battery cell as the reference SOC by a certain charging method (e.g., a constant current-constant voltage (CC-CV) charging method). In this case, considering that there can be fluctuations in the cell voltage of the battery cell for a certain period of time after the completion of charging of the battery cell, the processor 400 can be configured to wait for a reference time (e.g., a pre-defined reference time) to stabilize the cell voltage of the battery cell, and then start the abnormality diagnosis operation. The state of cell voltage stabilization can be a state in which the fluctuation range of the cell voltage of the battery cell is within an allowable range (e.g., a pre-defined allowable range), and the above-mentioned reference time required to enter this cell voltage stabilization state can be selected as a specific value according to the specifications of the battery system, and can be pre-defined in the memory 100 (e.g., 5 hours).

[0063] When the SOC of the battery cell has been formed as the reference SOC and the cell voltage enters a stabilized state after the reference time has elapsed, the factor that changes the cell voltage formed in the battery cell can be designated as an abnormality of the battery cell itself such as an internal short circuit, and thus the processor 400 can start the abnormality diagnosis operation of the battery cell. In this embodiment, a change in behavior of the cell voltage change rate of the battery cell is used as a basic consideration factor for diagnosing a battery cell abnormality.

[0064] The monomer voltage change rate is a rate of change of the monomer voltage of the battery monomer with respect to time, i.e., can correspond to a first derivative (here, referred to as a first derivative) of the monomer voltage of the battery monomer with respect to time. Also, the behavior change of the monomer voltage change rate can correspond to a second derivative of the battery monomer with respect to time. When the battery monomer is normal, the monomer voltage tends to decrease due to self-discharge, and assuming the above steady state, the rate of decrease of the monomer voltage (i.e., the rate of decrease of the monomer voltage with respect to time) gradually decreases (i.e., the first derivative gradually decreases).

[0065] If a short circuit occurs in a normal battery monomer as described above, the amount of self-discharge due to internal short circuit can sharply increase, and thus the monomer voltage decrease rate increases (i.e., the first derivative increases).

[0066] That is, in the case of an abnormal battery monomer in which a short circuit has occurred, the first derivative changes from a decreasing trend to an increasing trend, and the processor 400 of the embodiment is configured to diagnose the battery monomer abnormality based on the behavior change of the first derivative (i.e., the behavior change of the monomer voltage change rate).

[0067] The processor 400 can determine whether the sign of the slope of the monomer voltage change rate with respect to time changes to designate an abnormal monomer candidate composed of one or more battery monomers predicted to have an abnormality. That is, the change in the sign of the slope of the monomer voltage change rate with respect to time means that the above first derivative changes from a decreasing trend (negative sign) to an increasing trend (positive sign), and since this means that there is a possibility that an internal short circuit has occurred in the battery monomer, if the sign of the slope of the monomer voltage change rate with respect to time has changed, the processor 400 can classify the corresponding battery monomer as an abnormal monomer candidate. This has the same meaning as classifying a battery monomer having an inflection point of the monomer voltage with respect to time (i.e., a second derivative having a value of 0) as an abnormal monomer candidate. Figure 6 Experimental data showing the monomer voltage curve of a normal battery monomer and the monomer voltage curve of four abnormal battery monomers over time are shown.

[0068] When the abnormal monomer candidate is designated, the processor 400 can discharge the battery monomer classified as the abnormal monomer candidate and then prevent subsequent charging of the discharged battery monomer. Accordingly, the risk of thermal runaway and fire due to continuous use of a battery monomer suspected of having an internal short circuit can be eliminated or reduced.

[0069] To more accurately diagnose the battery monomer abnormality, the processor 400 can diagnose the battery monomer abnormality by further considering the maximum value of the monomer voltage change rate and the change rate of the open circuit voltage together with whether the slope of the monomer voltage change rate has changed.

[0070] If the sign of the slope of the cell voltage change rate of the battery cell with respect to time (i.e., the second derivative) has changed (i.e., if an inflection point is formed) and if the maximum value of the cell voltage change rate of the battery cell with respect to time (i.e., the first derivative) is greater than or equal to a reference voltage change rate stored in the memory 100 (e.g., predefined in the memory 100), the processor 400 can classify the battery cell as an abnormal cell candidate.

[0071] That is, the case where the maximum value of the first derivative is greater than or equal to the reference voltage change rate means that the self-discharge rate of the corresponding battery cell is high, and since such a phenomenon can be caused by an internal short circuit of the battery cell, the processor 400 can more accurately diagnose the battery cell abnormality by additionally considering the maximum value of the first derivative along with whether the sign of the second derivative has changed. Figure 7 Experimental data of the first derivative of a normal battery cell and the first derivative of four abnormal battery cells are shown.

[0072] In addition, if the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed and if the change rate of the open circuit voltage of the battery cell (the rate of decrease of the open circuit voltage with respect to time) is greater than or equal to a reference OCV change rate (e.g., a predefined reference OCV change rate), the processor 400 can classify the battery cell as an abnormal cell candidate.

[0073] That is, since the case where the rate of decrease of the open circuit voltage of the battery cell is greater than or equal to the reference OCV change rate can also be regarded as a state in which the self-discharge rate has increased due to an internal short circuit of the battery cell, the processor 400 can more accurately diagnose the battery cell abnormality by additionally considering the rate of decrease of the open circuit voltage along with whether the sign of the second derivative has changed.

[0074] In addition, the following embodiment can be provided: if the sign of the slope of the cell voltage change rate of the battery cell with respect to time changes, the maximum value of the cell voltage change rate of the battery cell with respect to time is greater than or equal to a reference voltage change rate, and the change rate of the open circuit voltage of the battery cell is greater than or equal to a reference OCV change rate, the battery cell is classified as an abnormal cell candidate.

[0075] To improve the accuracy of the abnormal battery cell diagnosis, the processor 400 can determine whether a state in which a point of inflection is formed for which the second derivative has a value of 0 has occurred as many times as a first count value defined in the memory 100, can determine whether a state in which a maximum value of the first derivative is greater than or equal to a reference voltage change rate has occurred as many times as a second count value defined in the memory 100, and can determine whether a state in which a change rate of the open circuit voltage is greater than or equal to a reference OCV change rate has occurred as many times as a third count value defined in the memory 100. In an embodiment, the processor 400 can be configured to classify a corresponding battery cell as an abnormal cell candidate only in the case where each of the above states has occurred as many times as the count value.

[0076] Table 1 below shows experimental data comparing whether a point of inflection is formed, the number of times a point of inflection is formed, a maximum value of the first derivative, and a change rate of the open circuit voltage of four abnormal battery cells with whether a point of inflection is formed, the number of times a point of inflection is formed, a maximum value of the first derivative, and a change rate of the open circuit voltage of normal battery cells.

[0077] Table 1

[0078] Based on the experimental data as shown in Table 1, the reference SOC, the reference voltage change rate, the reference OCV change rate, and the first to third count values, which are presented as threshold data in an embodiment, can be selected as specific numerical values and predefined in the memory 100, and for example, the reference SOC can be predefined as a value of 80 [%], the reference voltage change rate can be predefined as a value of 4 [mV / 5 hours], the reference OCV change rate can be predefined as a value of 0.7 [mV / hour], and the first to third count values can be predefined as values of 2, 3, 2, respectively.

[0079] (2) Second Embodiment The second embodiment focuses on a configuration in which an abnormal battery cell is accurately diagnosed within a range in which the battery system is ensured to operate normally by performing a discharge operation and an additional charge prevention operation only on a battery cell that is finally classified as having an abnormality through a stepwise monitoring and classification operation that monitors the "second derivative" and the "maximum value of the first derivative" of the above-described plurality of battery cells to preliminarily classify abnormal cell candidates, and monitors the "open circuit voltage" of the preliminarily classified abnormal cell candidates to finally classify an abnormal battery cell.

[0080] First, the terms used in the second embodiment will be defined. The first parameter indicated below can be defined as a behavior of a rate of change of a cell voltage occurring when a battery cell is discharged, and can include a change in the rate of change of the cell voltage (i.e., a second derivative) and a maximum value of the rate of change of the cell voltage (i.e., a maximum value of a first derivative) described in the first embodiment. In addition, the second parameter can be defined as a rate of change of an open circuit voltage occurring when a battery cell is discharged.

[0081] The processor 400 can diagnose a battery cell abnormality in a stepwise manner by stepwise monitoring the above-described first parameter and second parameter. That is, the processor 400 can operate to designate an abnormal cell candidate by first monitoring the first parameter among the first parameter and the second parameter and determining one or more battery cells predicted (suspected) to have an abnormality among the plurality of battery cells, and then finally classify a battery cell in which an abnormality has occurred by subsequently monitoring the second parameter with respect to the designated abnormal cell candidate. In this case, as in the first embodiment, the operations of determining whether the SOC of the battery cell has been formed as the reference SOC and waiting for the reference time can also be equally applied to the second embodiment.

[0082] The operation of the processor 400 will be described in further detail.

[0083] First, the processor 400 can monitor the first parameter in a manner of determining whether a sign of a slope of a rate of change of a cell voltage of a battery cell with respect to time changes, and whether a maximum value of the rate of change of the cell voltage of the battery cell with respect to time is greater than or equal to a pre-defined reference voltage change rate. That is, the processor 400 can monitor the first parameter in a manner of determining whether a first derivative has changed from a decreasing trend (negative sign) to an increasing trend (positive sign) (whether a turning point of a cell voltage with respect to time has been formed) and whether a maximum value of the first derivative is greater than or equal to a reference voltage change rate.

[0084] In the above-described process, if it is determined that the sign of the slope of the rate of change of the cell voltage of the battery cell with respect to time changes and the maximum value of the rate of change of the cell voltage of the battery cell with respect to time is greater than or equal to the pre-defined reference voltage change rate (i.e., if it is determined that the turning point of the cell voltage with respect to time has been formed and the maximum value of the first derivative is greater than or equal to the reference voltage change rate), the processor 400 can preliminarily classify the battery cell as an abnormal cell candidate. Unlike the first embodiment, in the second embodiment, the discharging operation and the additional charge prevention operation with respect to the battery cell classified as the abnormal cell candidate are excluded.

[0085] If the abnormal cell candidate is initially classified, the processor 400 can monitor the second parameter with respect to the initially classified abnormal cell candidate, and if the rate of change of the open circuit voltage of the battery cell included in the abnormal cell candidate is greater than or equal to a predefined reference OCV change rate, the battery cell can be finally classified as an abnormal cell. Thereafter, the processor 400 can operate to discharge the battery cell corresponding to the finally classified abnormal cell, and then prevent subsequent charging of the battery cell.

[0086] In the above-described second embodiment, the first parameter corresponding to the "behavior of the cell voltage change rate" is used as a parameter for detecting a sign of an abnormality such as an internal short circuit of the battery, and the second parameter corresponding to the "rate of change of the open circuit voltage" is used as a parameter for detecting a result of the abnormality. If a sign of an abnormality in the battery cell is detected through the monitoring of the first parameter, the battery cell is classified as an abnormal cell candidate and normal operation of the battery cell is maintained, and if a result of an abnormality in the battery cell is detected through the monitoring of the second parameter of the battery cell belonging to the abnormal cell candidate, the battery cell is finally classified as an abnormal battery cell and a discharge operation and an additional charge prevention operation with respect to the corresponding battery cell are performed. Accordingly, even if a sign of an abnormality is detected, normal operation of the battery system is maintained until the abnormal battery cell is finally confirmed, and thus, unnecessary discharge operations and additional charge prevention operations with respect to the battery cell can be prevented.

[0087] 3. Battery diagnosis method Figure 8 is a flowchart of the battery diagnosis method according to the above-described first embodiment. Referring to Figure 8 A battery diagnosis method according to the first embodiment will be described, and a detailed description of a configuration repeated with the above-described content can be omitted, and the description will focus on a time series configuration.

[0088] First, the processor 400 determines whether the SOC of the battery cell has been formed into a reference SOC (e.g., a predefined reference SOC) in the memory 100 (S810). If it is determined in operation S810 that the SOC of the battery cell has been formed to be lower than the reference SOC, the processor 400 forms the SOC of the battery cell to be the reference SOC through a certain charging method (e.g., a constant current-constant voltage (CC-CV) charging method) (S820).

[0089] If it is determined in operation S810 that the SOC of the battery cell has been formed to be the reference SOC, or if the SOC of the battery cell has been formed to be the reference SOC through operation S820, the processor 400 waits for a reference time to stabilize the cell voltage of the battery cell (S830).

[0090] At the time point at which the reference time has elapsed, the processor 400 diagnoses the battery cell abnormality in a manner of analyzing a change in behavior of the cell voltage change rate occurring when the battery cell is discharged (S840).

[0091] In operation S840, the processor 400 can determine whether the sign of the slope of the cell voltage change rate with respect to time has changed to designate an abnormal cell candidate composed of one or more battery cells predicted to have an abnormality, and can classify the battery cell as an abnormal cell candidate if the sign of the slope of the cell voltage change rate with respect to time of the battery cell has changed.

[0092] In operation S840, the processor 400 can classify the corresponding battery cell as an abnormal cell candidate if i) the sign of the slope of the cell voltage change rate with respect to time of the battery cell has changed and if the maximum value of the cell voltage change rate with respect to time of the battery cell is greater than or equal to a reference voltage change rate (e.g., a pre-defined reference voltage change rate); or ii) the sign of the slope of the cell voltage change rate with respect to time of the battery cell has changed, and if the rate of change of the open circuit voltage of the battery cell is greater than or equal to a reference OCV change rate.

[0093] If the abnormal cell candidate is designated through operation S840, the processor 400 discharges the battery cell classified as the abnormal cell candidate (S850), and prevents subsequent charging of the discharged battery cell (S860).

[0094] Figure 9 is a flowchart of a battery diagnosis method according to the second embodiment described above. Referring to Figure 9 A battery diagnosis method according to the second embodiment will be described.

[0095] First, the processor 400 determines whether the SOC of the battery cell has been formed into a reference SOC (e.g., a pre-defined reference SOC) in the memory 100 (S910). If it is determined in operation S910 that the SOC of the battery cell has been formed lower than the reference SOC, the processor 400 forms the SOC of the battery cell into the reference SOC by a certain charging method (e.g., a constant current-constant voltage (CC-CV) charging method) (S920).

[0096] If it is determined in operation S910 that the SOC of the battery cell has been formed into the reference SOC, or if the SOC of the battery cell has been formed into the reference SOC through operation S920, the processor 400 waits for a reference time to stabilize the cell voltage of the battery cell (S930).

[0097] At the time point at which the reference time has elapsed, the processor 400 diagnoses the battery cell abnormality by monitoring the first parameter defined as the behavior of the rate of change of the cell voltage when the battery cell is discharged and the second parameter defined as the rate of change of the open circuit voltage that occurs when the battery cell is discharged (S940).

[0098] In operation S940, the processor 400 can monitor the first parameter in a manner of determining whether the sign of the slope of the rate of change of the cell voltage of the battery cell with respect to time is changed and whether the maximum value of the rate of change of the cell voltage of the battery cell with respect to time is greater than or equal to a reference voltage change rate (e.g., a pre-defined reference voltage change rate). In this case, if the sign of the slope of the rate of change of the cell voltage of the battery cell with respect to time has been changed and if the maximum value of the rate of change of the cell voltage of the battery cell with respect to time is greater than or equal to the reference voltage change rate, the processor 400 can preliminarily classify the battery cell as an abnormal cell candidate.

[0099] Thereafter, the processor 400 can monitor the second parameter with respect to the preliminarily classified abnormal cell candidate, and when the rate of change of the open circuit voltage of the battery cell included in the abnormal cell candidate is greater than or equal to a reference OCV change rate, the processor 400 can finally classify the battery cell as an abnormal cell.

[0100] When the abnormal cell is finally classified through operation S940, the processor 400 can cause the battery cell corresponding to the finally classified abnormal cell to be discharged (S950) and prevent subsequent charging of the battery cell (S960).

[0101] Accordingly, according to one or more embodiments of the disclosure, since the battery cell abnormality is diagnosed in a manner of analyzing the behavior of the rate of change of the cell voltage (i.e., the inflection point of the cell voltage with respect to time) that occurs when the battery cell having a certain state of charge (SOC) is discharged, the battery cell abnormality (such as an internal short circuit in the battery cell due to lithium precipitation) can be diagnosed in advance, and the risk of thermal runaway and fire of the battery cell can be effectively eliminated or reduced through a discharge operation and an additional charge prevention operation with respect to the battery cell predicted to have an abnormality.

[0102] Further, according to one or more embodiments of the disclosure, since the battery cell abnormality is diagnosed by comprehensively considering the maximum value of the rate of change of the cell voltage with respect to time and the rate of change of the open circuit voltage and the inflection point of the cell voltage with respect to time, the accuracy of the abnormality diagnosis can be improved.

[0103] In addition, according to one or more embodiments of the present disclosure, since the battery cell abnormality is diagnosed in a manner of monitoring the first parameter, which is defined as a behavior of a cell voltage change rate occurring when the battery cell is discharged, and the second parameter, which is defined as a change rate of an open circuit voltage occurring when the battery cell is discharged, in a step-by-step manner, and the discharge operation and the additional charge prevention operation are performed only on the battery cell classified as having an abnormality, it is possible to eliminate or reduce the risk of thermal runaway and fire by diagnosing the battery cell abnormality in advance within a range of ensuring normal operation of the battery system.

[0104] According to one or more embodiments of the present disclosure, since the battery cell abnormality is diagnosed in a manner of analyzing a behavior of a cell voltage change rate (i.e., an inflection point of the cell voltage with respect to time) occurring when the battery cell having a certain state of charge (SOC) is discharged, it is possible to diagnose a battery cell abnormality (such as an internal short circuit in the cell due to metal dendrites or lithium salt growing as a charging / discharging cycle proceeds) in advance, and it is possible to effectively eliminate or reduce the risk of thermal runaway and fire of the battery cell through a discharge operation and an additional charge prevention operation for the battery cell predicted to have an abnormality.

[0105] In addition, according to one or more embodiments of the present disclosure, since the battery cell abnormality is diagnosed by comprehensively considering the maximum value of the cell voltage change rate with respect to time and the change rate of the open circuit voltage, and the inflection point of the cell voltage with respect to time, it is possible to improve the accuracy of the abnormality diagnosis.

[0106] In addition, according to one or more embodiments of the present disclosure, since the battery cell abnormality is diagnosed in a manner of monitoring the first parameter, which is defined as a behavior of a cell voltage change rate occurring when the battery cell is discharged, and the second parameter, which is defined as a change rate of an open circuit voltage occurring when the battery cell is discharged, in a step-by-step manner, and the discharge operation and the additional charge prevention operation are performed only on the battery cell classified as having an abnormality, it is possible to eliminate or reduce the risk of thermal runaway and fire by diagnosing the battery cell abnormality in advance within a range of ensuring normal operation of the battery system.

[0107] However, aspects and effects that can be achieved by the present application are not limited to the above-described aspects and effects, and other aspects and effects not described can be clearly understood from the detailed description by those skilled in the art.

[0108] The embodiments described herein can be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single type of implementation (for example, discussed only in the context of a method), the features discussed herein can be implemented in other forms (for example, an apparatus or program). An apparatus can be implemented in, for example, appropriate hardware, software, and firmware. The methods can be implemented on an apparatus such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, a programmable logic device, and the like. A processor includes communication devices, such as a computer, a cell phone, a personal digital assistant (PDA), and other devices that facilitate communication of information between end-users and other devices.

[0109] Although the present disclosure has been described with reference to certain embodiments and illustrative aspects shown in the drawings, it is understood that the present disclosure is not limited thereto. Various modifications and changes can be made by those skilled in the art which fall in the spirit and scope of the techniques of the present disclosure, and the claims hereinafter, and their equivalents.

Claims

1. A battery diagnostic apparatus comprising: a processor configured to diagnose an abnormality of a battery cell; and a memory for storing one or more commands executed by the processor, wherein the processor is configured to diagnose the abnormality of the battery cell by analyzing a behavior change in a cell voltage change rate occurring when the battery cell is discharged in a state in which a state of charge of the battery cell has been formed into a reference state of charge.

2. The battery diagnostic apparatus according to claim 1, wherein The processor is configured to start an abnormality diagnosis operation of the battery cell at a time point at which a reference time for stabilizing a cell voltage of the battery cell has elapsed after the state of charge of the battery cell has been formed into the reference state of charge.

3. The battery diagnostic apparatus according to claim 1, wherein The processor is configured to, when analyzing the behavior change in the cell voltage change rate of the battery cell, determine whether a sign of a slope of the cell voltage change rate with respect to time changes to designate an abnormal cell candidate composed of one or more battery cells predicted to have an abnormality.

4. The battery diagnostic apparatus according to claim 3, wherein The processor is configured to classify the battery cell as an abnormal cell candidate if the sign of the slope of the cell voltage change rate with respect to time has changed.

5. The battery diagnostic apparatus according to claim 3, wherein The processor is configured to classify the battery cell as an abnormal cell candidate if the sign of the slope of the cell voltage change rate with respect to time has changed and if a maximum value of the cell voltage change rate with respect to time of the battery cell is greater than or equal to a reference voltage change rate.

6. The battery diagnostic apparatus according to claim 3, wherein The processor is configured to classify the battery cell as an abnormal cell candidate if the sign of the slope of the cell voltage change rate with respect to time has changed and if a rate of change of an open circuit voltage of the battery cell is greater than or equal to a reference open circuit voltage change rate.

7. The battery diagnostic apparatus according to claim 3, wherein The processor is configured to discharge the battery cell classified as the abnormal cell candidate and then prevent a subsequent charge to the discharged battery cell. 8.A battery diagnostic apparatus comprising: a processor configured to diagnose an abnormality of a battery cell; and a memory for storing one or more commands executed by the processor, wherein the processor is configured to diagnose the abnormality of the battery cell by monitoring a first parameter defined as a behavior of a cell voltage change rate occurring when the battery cell is discharged and a second parameter defined as a rate of change of an open circuit voltage occurring when the battery cell is discharged step by step.

9. The battery diagnostic apparatus according to claim 8, wherein The processor is configured to, when monitoring the first parameter, determine whether a sign of a slope of the cell voltage change rate with respect to time of the battery cell changes and whether a maximum value of the cell voltage change rate with respect to time of the battery cell is greater than or equal to a reference voltage change rate.

10. The battery diagnostic apparatus according to claim 9, wherein The processor is configured to monitor the first parameter among the first and second parameters first and to preliminarily classify the battery cell as an abnormal cell candidate if the sign of the slope of the cell voltage change rate with respect to time has changed and if the maximum value of the cell voltage change rate with respect to time of the battery cell is greater than or equal to the reference voltage change rate.

11. The battery diagnostic apparatus according to claim 10, wherein The processor is configured to monitor a second parameter with respect to the preliminary classified abnormal cell candidate, and to finally classify the battery cell as an abnormal cell when a rate of change of an open circuit voltage of the battery cell included in the abnormal cell candidate is greater than or equal to a predefined reference open circuit voltage change rate.

12. The battery diagnostic apparatus of claim 11, wherein, The processor is configured to discharge the battery cell corresponding to the finally classified abnormal cell, and then to prevent a subsequent charge to the discharged battery cell.

13. The battery diagnostic apparatus of claim 8, wherein, The processor is configured to monitor the first parameter and the second parameter occurring in the discharging process of the battery cell after a state of charge of the battery cell has been formed into a reference state of charge. 14.A battery diagnosis method, the battery diagnosis method comprising the steps of: determining, by a processor, whether a state of charge of a battery cell has been formed into a reference state of charge; and diagnosing, by the processor, an abnormality of the battery cell by analyzing a change in behavior of a cell voltage change rate, the change in behavior of the cell voltage change rate occurring if the battery cell is discharged in a case where the state of charge of the battery cell has been formed into the reference state of charge.

15. The battery diagnostic method according to claim 14, further comprising the steps of: After the determining step, determining, by the processor, whether a reference time for stabilizing a cell voltage of the battery cell has elapsed, wherein the diagnosing step is performed at a time point where the reference time has elapsed.

16. The battery diagnostic method of claim 14, wherein, In the diagnosing step, when analyzing the change in behavior of the cell voltage change rate of the battery cell, the processor determines whether a sign of a slope of the cell voltage change rate with respect to time has changed to designate an abnormal cell candidate composed of one or more battery cells predicted to have an abnormality.

17. The battery diagnostic method of claim 16, wherein, In the diagnosing step, if the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed, the processor classifies the battery cell as the abnormal cell candidate.

18. The battery diagnostic method of claim 16, wherein, In the diagnosing step, if the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed, and if a maximum value of the cell voltage change rate of the battery cell with respect to time is greater than or equal to a reference voltage change rate, the processor classifies the battery cell as the abnormal cell candidate.

19. The battery diagnostic method of claim 16, wherein, In the diagnosing step, if the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed, and if a rate of change of an open circuit voltage of the battery cell is greater than or equal to a reference open circuit voltage change rate, the processor classifies the battery cell as the abnormal cell candidate. 20.The battery diagnosis method of claim 16, further comprising the steps of: discharging, by the processor, the battery cell classified as the abnormal cell candidate; and preventing, by the processor, a subsequent charge to the discharged battery cell.

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