Battery diagnosis method based on resistance deterioration degree and battery system applying battery diagnosis method

Abstract

A battery diagnosis method is a method for diagnosing a battery pack including a plurality of battery groups and a battery system applying the method, the battery diagnosis method including: determining, by a battery management system (BMS), presence of a target battery group satisfying a discharge condition among the plurality of battery groups; discharging, by the BMS, the target battery group detected through the determining step for a certain time; storing, by the BMS, a first group voltage of the target battery group before discharging the target battery group and a second group voltage of the target battery group after discharging the target battery group; deriving, by the BMS, a current voltage variation amount based on the first group voltage and the second group voltage; estimating, by the BMS, a resistance degradation degree of the target battery group based on a reference voltage variation amount of the target battery group and the current voltage variation amount; and diagnosing, by the BMS, the plurality of battery groups based on the resistance degradation degree for each of the plurality of battery groups, wherein the discharge condition includes at least one of a group voltage, a group temperature, and a rest time of the battery group.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2021-0149028, filed with the Korean Intellectual Property Office on November 2, 2021, the entire contents of which are incorporated herein by reference.

[0003] This invention relates to a battery diagnostic method based on the degree of resistance degradation and a battery system using the battery diagnostic method. Background Technology

[0004] A battery pack may include multiple battery packs connected in series, and each battery pack may include multiple battery cells connected in parallel.

[0005] When a battery pack is repeatedly charged and discharged via external devices, the charging capacity of its internal battery cells may vary. If this variation is ignored during continued charging and discharging, resistance degradation or other abnormal conditions may occur in the battery cells.

[0006] When the resistance of a battery cell deteriorates or becomes abnormal, the battery pack may be unable to stably supply power to external devices. Summary of the Invention

[0007] Technical issues

[0008] This invention aims to provide a battery diagnostic method capable of detecting anomalies in each of multiple battery packs in a battery pack comprising multiple battery packs, and a battery system applying this battery diagnostic method.

[0009] Technical solutions

[0010] In a battery diagnostic method according to an embodiment of the present invention, a method for diagnosing a battery pack comprising multiple battery packs includes: determining, by a battery management system (BMS), whether a target battery pack that meets discharge conditions exists among the multiple battery packs; discharging the detected target battery pack by the BMS for a predetermined time; storing, by the BMS, a first set of voltages of the target battery pack before discharging the target battery pack and a second set of voltages of the target battery pack after discharging the target battery pack; deriving a current voltage change by the BMS based on the first set of voltages and the second set of voltages; estimating the degree of resistance degradation for the target battery pack by the BMS based on the reference voltage change and the current voltage change of the target battery pack; and diagnosing the multiple battery packs by the BMS based on the degree of resistance degradation for each of the multiple battery packs, wherein the discharge conditions include at least one of the group voltage, group temperature, and rest time for each of the multiple battery packs.

[0011] The reference voltage change of the target battery pack is the initial voltage change for the target battery pack stored in the BMS, and the initial voltage change is the voltage change of each of the multiple battery packs before and after the first discharge.

[0012] Diagnostic procedures for multiple battery packs include: deriving an overall representative value for the degree of resistance degradation based on multiple resistance degradation levels for multiple battery packs by the BMS; calculating a multi-parallel ideal factor based on the number of parallel connections of the multiple battery packs by the BMS; calculating an upper limit threshold for the normal range by the BMS based on the overall representative value of the degree of resistance degradation and the multi-parallel ideal factor; and deriving a normal range by the BMS based on the upper limit threshold, and diagnosing the state of each of the multiple battery packs based on the normal range.

[0013] The calculation of the upper limit threshold includes: the BMS setting multiple first battery packs whose resistance degradation degree is less than or equal to the overall representative value of the multiple resistance degradation degrees as target groups; the BMS deriving the target representative values ​​of the multiple resistance degradation degrees of the multiple first battery packs belonging to the target group; and the calculation of the upper limit threshold of the normal range based on the target representative values ​​and the multiple parallel ideal factors.

[0014] The diagnosis of the state of each of the multiple battery packs includes: the BMS identifying battery packs with resistance degradation equal to or less than the upper limit threshold as normal states; and the BMS identifying battery packs with resistance degradation greater than the upper limit threshold as abnormal states.

[0015] A battery system according to another embodiment of the present invention includes: a plurality of battery packs, in each of the plurality of battery packs a plurality of battery cells connected in parallel; a discharge circuit connected in parallel between the positive and negative terminals of each of the plurality of battery packs and configured to discharge each of the battery packs; and a battery management system (BMS) configured to: determine whether a target battery pack exists among the plurality of battery packs that meets discharge conditions; discharge the target battery pack detected by the discharge circuit; store a first set of voltages of the target battery pack before the target battery pack is discharged and a second set of voltages of the target battery pack after the target battery pack is discharged; derive a current voltage change based on the first set of voltages and the second set of voltages; estimate the degree of resistance degradation for the target battery pack based on the reference voltage change and the current voltage change of the target battery pack; and diagnose the plurality of battery packs based on the degree of resistance degradation for each of the plurality of battery packs, wherein the discharge conditions include at least one of the group voltage, group temperature and rest time of each of the plurality of battery packs.

[0016] The reference voltage change of the target battery pack is the initial voltage change for the target battery pack stored in the BMS, and the initial voltage change is the voltage change of each of the multiple battery packs before and after the first discharge.

[0017] The BMS calculates an upper threshold of the normal range based on the degree of resistance degradation for multiple battery packs; derives the normal range based on the upper threshold; and diagnoses the state of each of the multiple battery packs based on the normal range.

[0018] The upper limit threshold is calculated by the BMS based on the overall representative value of multiple resistance degradation levels and the multiple parallel ideal factor through the following steps: deriving the overall representative value of multiple resistance degradation levels based on multiple resistance degradation levels for multiple battery packs respectively; and calculating the multiple parallel ideal factor based on the number of parallel connections of multiple battery packs.

[0019] The BMS identifies battery packs with resistance degradation levels equal to or less than the upper limit threshold as normal states; and identifies battery packs with resistance degradation levels greater than the upper limit threshold as abnormal states.

[0020] BMS diagnoses the condition of multiple battery packs by distinguishing whether each of the multiple battery packs is in an abnormal state.

[0021] Beneficial effects

[0022] For a battery pack comprising multiple battery cells, each of which can be discharged under specific conditions, the voltage change of each of the multiple battery cells before and after discharge can be determined; the degree of resistance degradation of each of the multiple battery cells can be calculated based on the voltage change; and anomalies in each of the multiple battery cells can be detected based on the degree of resistance degradation of each of the multiple battery cells. Attached Figure Description

[0023] Figure 1 This is a diagram illustrating a battery system according to an embodiment.

[0024] Figure 2 This is a flowchart illustrating a battery diagnostic method according to an embodiment.

[0025] Figure 3 It is a waveform diagram showing the changes in switch control signals, group voltage, and group current according to the discharge of each of the multiple battery groups.

[0026] Figure 4 This is a detailed flowchart illustrating the steps involved in diagnosing multiple battery packs based on the degree of degradation of multiple resistors. Detailed Implementation

[0027] In the following description, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings. However, identical or similar components will be given identical or similar reference numerals, and redundant descriptions will be omitted. The suffixes "module" and / or "part" used for components in the following description are given or combined merely for ease of writing this specification, and they do not inherently have different meanings or functions from each other. Furthermore, when describing the embodiments disclosed in this specification, detailed descriptions of relevant known technologies will be omitted if it is determined that such detailed descriptions may obscure the essential points of the embodiments disclosed in this specification. Additionally, the accompanying drawings are only for the purpose of facilitating understanding of the embodiments disclosed in this specification and do not limit the technical ideas disclosed in this specification. They should be understood to include all variations, equivalents, or substitutions included within the spirit and scope of this disclosure.

[0028] Terms including ordinal numbers such as first, second, etc., can be used to describe various components, but these components are not limited by these terms. These terms are only used for the purpose of distinguishing one component from another.

[0029] It will also be understood that when the terms “comprising” and / or “including” are used in this specification, they specify the presence of the stated features, integers, steps, operations, components and / or portions, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, portions and / or combinations thereof.

[0030] In a configuration according to an embodiment that controls other configurations under specific control conditions, a program implementing a set of instructions for controlling the other configurations can be installed. The control configuration can process input data and stored data according to the installed program to generate output data. The control configuration may include non-volatile memory for storing the program and memory for storing the data.

[0031] In the following description, with reference to the accompanying drawings, a method for diagnosing a battery by estimating the degree of resistance degradation of the battery pack and considering multiple parallel ideal factors of the resistance degradation degree, and a battery system applying this method, will be described. The method for diagnosing a battery by considering multiple parallel ideal factors of the resistance degradation degree can be implemented as software installed in a battery management system or as a program including a combination of software. The corresponding program can be stored in a storage medium of the battery management system. The storage medium can be implemented as various types of memory, such as high-speed random access memory, flash memory devices, non-volatile memory such as other non-volatile solid-state memory devices, etc.

[0032] Figure 1 This is a diagram illustrating a battery system according to an embodiment.

[0033] Battery system 1 includes battery pack 10, battery management system 20, discharge circuit 30, and relays 40 and 41. Hereinafter, battery management system 20 is referred to as BMS. Figure 1 The invention is shown to have one battery pack 10, but the invention is not limited thereto, and the battery system 1 may include two or more battery packs.

[0034] External device 2 may include loads such as inverters and converters, as well as charging devices. When external device 2 is a charger, the two ends of battery system 1 (e.g., Figure 1 The P+ and P- terminals of the battery system 1 can be connected to a charger to receive power and be charged. When the external device 2 is a load, the two ends of the battery system 1 can be connected to the load so that the power supplied by the battery pack 10 can be discharged through the load.

[0035] The battery pack 10 includes multiple battery packs 101 to 103 and multiple temperature sensors 111 to 113. Figure 1 The invention is shown to contain three battery packs, but the invention is not limited thereto, and the battery pack 10 may include two or more battery packs.

[0036] Each of the multiple battery packs 101 to 103 (e.g., 101) includes multiple battery cells (e.g., 11 and 12) connected in parallel. Figure 1 Each battery pack (e.g., 101) is shown to include two battery cells (e.g., 11 and 12) connected in parallel, but the invention is not limited thereto, and each battery pack may include two or more battery cells connected in parallel.

[0037] Each of the plurality of temperature sensors 111 to 113 (e.g., 111) can detect the group temperature of a corresponding battery pack (e.g., 101) among the plurality of battery packs 101 to 103 and generate a temperature measurement signal (e.g., TS1). Figure 1 The invention illustrates that multiple temperature sensors 111 to 113 are positioned to correspond to multiple battery packs 101 to 103 respectively, and generate multiple temperature measurement signals TS1 to TS3. However, the invention is not limited thereto, and the number and position of the temperature sensors in the battery pack 10 can be changed.

[0038] The BMS20 can monitor the group voltage and group temperature of multiple battery packs 101 to 103 based on multiple voltage measurement signals and multiple temperature measurement signals; estimate the degree of resistance degradation of the battery pack by determining whether the battery pack meets the discharge conditions based on the group voltage, group temperature and rest time; and diagnose the battery pack by detecting anomalies in each battery pack based on the degree of resistance degradation of each battery pack.

[0039] BMS20 is connected to each of a plurality of battery packs 101 to 103 and receives a plurality of voltage measurement signals VS1 to VS4, measured from both ends of the plurality of battery packs 101 to 103, via a plurality of input terminals P1 to P4. The positive terminal of each of the plurality of battery packs 101 to 103 (e.g., 101) is connected via wiring to a corresponding input terminal (e.g., P1) among the plurality of input terminals P1 to P3, and the negative terminal of each of the plurality of battery packs 101 to 103 (e.g., 101) is connected via wiring to a corresponding input terminal (e.g., P2) among the plurality of input terminals P2 to P4. For example, measurement signal VS1 is the positive voltage of battery pack 101 and is input to BMS20 via input terminal P1, and measurement signal VS2 is the voltage of the negative terminal of battery pack 101 or the voltage of the positive terminal of battery pack 102 and is input to BMS20 via input terminal P2.

[0040] The BMS20 can receive multiple temperature measurement signals TS1 to TS3, determined based on the temperatures sensed by multiple temperature sensors 111 to 113, through multiple input terminals P8 to P10.

[0041] The discharge circuit 30 may include a plurality of discharge switches 31 to 33 and a plurality of discharge resistors 301 to 303. The discharge switches 31 and 301, connected in series, are connected in parallel between the positive and negative terminals of the battery pack 101; the discharge switches 32 and 302, connected in series, are connected in parallel between the positive and negative terminals of the battery pack 102; and the discharge switches 33 and 303, connected in series, are connected in parallel between the positive and negative terminals of the battery pack 103. The number of discharge switches 31 to 33 and the number of discharge resistors 301 to 303 may be increased or decreased depending on the number of battery packs 101 to 103.

[0042] The opening and closing of multiple discharge switches 31 to 33 can be controlled according to the switch control signals SCS1 to SCS3 supplied from BMS20. Each of the multiple switch control signals SCS1 to SCS3 (e.g., SCS1) is sent to the corresponding switch 31 among the multiple discharge switches 31 to 33 through the corresponding output terminal (e.g., P5) among the multiple output terminals P5 to P7 of BMS20.

[0043] When a corresponding discharge switch (e.g., 31) among the plurality of discharge switches 31 to 33 is turned on, each of the plurality of discharge resistors 301 to 303 (e.g., 301) causes a corresponding battery pack (e.g., 101) among the plurality of battery packs 101 to 103 to discharge.

[0044] One end of each of relays 40 and 41 is connected to the battery pack 10, and the other end of each of relays 40 and 41 is connected to at least one component of the external device 2. The closing and opening of relays 40 and 41 are controlled according to relay control signals RSC1 and RSC2 supplied from BMS 20.

[0045] In the following text, it will be based on Figure 2 The flowchart shown sequentially describes the operation of each component of the BMS20 used to diagnose the state of the battery pack 10.

[0046] Figure 2 This is a flowchart illustrating a battery diagnostic method according to an embodiment.

[0047] In BMS20, multiple reference voltage variations (ΔV) for multiple battery packs 101 to 103 are pre-stored. 参考 (S1).

[0048] The voltage change will be described below in step S6, which calculates the voltage change. The reference voltage change may be the initial voltage change. The initial voltage change may refer to the voltage change before and after discharge when each of the plurality of battery packs 101 to 103 is initially discharged.

[0049] BMS20 determines whether there is a battery pack among the multiple battery packs 101 to 103 that has a pack voltage, pack temperature and rest time that meet the discharge conditions (S2).

[0050] In the following text, the battery pack among the multiple battery packs 101 to 103 that has a group voltage, group temperature, and rest time that meet the discharge conditions is referred to as the target battery pack. The BMS20 can detect the target battery pack based on the group voltage, group temperature, and rest time of each of the multiple battery packs 101 to 103.

[0051] BMS20 can derive multiple group voltages for each of the multiple battery packs 101 to 103 based on multiple voltage measurement signals VS1 to VS4. For example, BMS20 can derive the group voltage of battery pack 101 based on the voltage difference between voltage measurement signal VS1 and voltage measurement signal VS2. BMS20 can derive the same number of group voltages as the number of battery packs 101 to 103 included in battery pack 10.

[0052] BMS20 can obtain multiple group temperatures for multiple battery packs 101 to 103 based on multiple temperature measurement signals TS1 to TS3. BMS20 can obtain the same number of group temperatures as the number of battery packs 101 to 103 included in battery pack 10. Figure 1Three temperature sensors are shown positioned to correspond to multiple battery packs 101 to 103, but the battery pack 10 may include fewer temperature sensors than the number of battery packs. In this case, the BMS 20 can estimate the group temperature of each of the multiple battery packs 101 to 103 based on the temperature measurement signal sensed by each of the temperature sensors.

[0053] BMS20 can determine whether the rest time during which the battery pack is not charged / discharged meets the conditions regarding rest time included in discharge conditions.

[0054] Discharge conditions may include at least those related to group voltage, group temperature, and rest time. For example, discharge conditions may include the following: group voltage in the range of 3.6V to 3.65V, group temperature in the range of 20°C to 30°C, and rest time equal to or greater than 2 hours.

[0055] When there is no battery pack among the multiple battery packs 101 to 103 that has a group voltage, group temperature and rest time that meet the discharge conditions, the BMS20 can periodically repeat step S2.

[0056] When there is a target battery pack among the multiple battery packs 101 to 103 that has a group voltage, group temperature and rest time that meet the discharge conditions, the BMS20 can store the group voltage of the target battery pack as a first voltage indicating the voltage of the battery pack before discharge (S3).

[0057] In the following text, battery pack 101 will be described as a target battery pack that meets the discharge conditions.

[0058] BMS20 can determine the group voltage VB1 of the target battery pack 101 before the discharge of the target battery pack 101 begins, and store the obtained group voltage VB1 as the first voltage.

[0059] BMS20 can turn on the discharge switch 31 via the switch control signal SCS1 and cause the target battery pack 101 to discharge for a predetermined time (S4).

[0060] When each of the multiple switch control signals SCS1 to SCS3 (e.g., SCS1) is at a high level, which is an on level, a corresponding one of the multiple discharge switches 31 to 33 (e.g., 31) is turned on; and when each of the multiple switch control signals SCS1 to SCS3 (e.g., SCS1) is at a low level, which is an off level, a corresponding one of the multiple discharge switches 31 to 33 (e.g., 31) is turned off. For example, when the switch control signal SCS1 is at a high level, the discharge switch 31 can be turned on.

[0061] The scheduled time can be a fixed time that is predetermined as the initial information.

[0062] When the discharge of the target battery pack 101 ends after a predetermined time, the BMS20 can store the pack voltage of the target battery pack as a second voltage indicating the voltage of the battery pack after discharge (S5).

[0063] After the target battery pack 101 finishes discharging, the BMS20 can obtain the group voltage VB1 of the target battery pack 101 and store the obtained group voltage VB1 as the second voltage.

[0064] BMS20 can derive the current voltage change (ΔV) based on the first and second voltages, indicating the change in the group voltage caused by the discharge of the target battery pack 101. 当前 (S6).

[0065] Referring to [Equation 1], the current voltage change (ΔV) 当前 It can be derived based on the first voltage and the second voltage.

[0066] [Formula 1]

[0067] ΔV 当前 =V2-V1

[0068] ΔV 当前 The current voltage change of the battery pack is indicated by V1, which indicates the voltage stored as the first voltage, and V2, which indicates the voltage stored as the second voltage.

[0069] In the following text, reference will be made to Figure 3 Describe the process by which BMS20 obtains the current voltage change of the target battery pack 101.

[0070] Figure 3 It is a waveform diagram showing the changes in switch control signal, group voltage, and group current as the battery pack discharges.

[0071] like Figure 3 As shown, the group voltage VB1 of the target battery pack 101 can be reduced by discharging. Figure 3 In the diagram, waveform (a) shows the switching control signal SCS1 corresponding to the target battery pack 101 among multiple switching control signals SCS1 to SCS3, waveform (b) shows the group voltage VB1 of the target battery pack 101 over time, and waveform (c) shows the group current IB flowing in the target battery pack 101 over time.

[0072] according to Figure 3 As shown in the waveform diagram, the discharge switch 31 can be turned on by a high-level signal, which serves as the on-state of the switch control signal SCS1.

[0073] The switch control signal SCS1 can be held as a low-level signal (off level), transitions to a high-level signal at time t1, and remains high until time t2. Afterward, the switch control signal SCS1 can transition back to a low-level signal at time t2 and remain high.

[0074] Reference Figure 3 The BMS20 can synchronously derive the group voltage VB1 at the discharge start time t1 of the target battery pack 101. The group voltage VB1 derived at time t1 is voltage V1.

[0075] The BMS20 can synchronously calculate the group voltage VB1 at time t2, the end time of discharge of the target battery pack 101. The group voltage VB1 calculated at time t2 is voltage V2. The BMS20 can calculate the difference (V2-V1) between the group voltage at time t1 and the group voltage at time t2, and can also calculate the current voltage change (ΔV) of the group voltage VB1 caused by the discharge of the target battery pack 101. 当前 ).

[0076] During discharge, the group current IB can be constantly controlled at the current level I. 放电 .

[0077] The BMS20 can be based on a reference voltage change (ΔV) 参考 ) and current voltage change (ΔV 当前 (S7) is used to estimate the degree of resistance degradation of the target battery pack 101.

[0078] The degree of increase in the resistance of a battery pack due to the increase in the internal resistance of the battery cells is called the degree of resistance degradation.

[0079] BMS20 can, based on pre-stored reference voltage changes (ΔV) of a target battery pack 101 among multiple reference voltage changes for multiple battery packs 101 to 103, respectively. 参考 ) and the current voltage change (ΔV) of the target battery pack 101 当前 This is used to estimate the degree of resistance degradation of the target battery pack 101.

[0080] Referring to [Equation 2], the degree of resistance degradation of the battery pack can be estimated by calculating the ratio of the current voltage change to the reference voltage change.

[0081] [Equation 2]

[0082]

[0083] BMS20 can repeat steps S1 to S7 until the degree of resistance degradation of all the multiple battery packs 101 to 103 included in the battery pack 10 is estimated.

[0084] BMS20 can diagnose the multiple battery packs 101 to 103 included in the battery pack 10 based on the multiple resistance degradation levels for the multiple battery packs 101 to 103 respectively (S8).

[0085] In the following text, reference will be made to Figure 4 This describes the process by which BMS20 diagnoses multiple battery packs 101 to 103 based on multiple resistance degradation levels.

[0086] Figure 4 This is a detailed flowchart illustrating the steps involved in diagnosing multiple battery packs based on the degree of degradation of multiple resistors.

[0087] BMS20 derives an overall representative value of the resistance degradation degree based on multiple resistance degradation degrees for multiple battery packs 101 to 103 respectively (S81).

[0088] As a method for obtaining an overall representative value of the degree of resistance degradation, one can use methods such as obtaining the median, average, etc., of the degree of resistance degradation for multiple battery packs 101 to 103 respectively. In the following text, it will be described that the overall representative value of the degree of resistance degradation is the median of multiple degrees of resistance degradation.

[0089] BMS20 calculates the multi-parallel ideal factor (S82) based on the number of parallel connections of multiple battery packs 101 to 103.

[0090] The number of parallel connections is the number of multiple battery cells (e.g., 11 and 12) connected in parallel in one of the multiple battery packs 101 to 103 (e.g., 101).

[0091] like Figure 1 As shown, each of the multiple battery packs 101 to 103 can have the same number of parallel connections.

[0092] exist Figure 1 In the example, the multiple battery packs 101 to 103 each include two battery cells 11-12, 13-14 and 15-16 connected in parallel, and the BMS20 can determine the number of parallel connections of the multiple battery packs 101 to 103.

[0093] In the following text, referring to [Equation 3], BMS20 can derive the multi-parallel ideal factor based on the number of parallel connections of multiple battery packs 101 to 103.

[0094] [Formula 3]

[0095]

[0096] μ indicates the ideal factor for multiple parallel connections. P indicates the number of parallel connections. Figure 1 In the example, since the number of parallel connections is 2, μ is 2 / 1 = 2.

[0097] BMS20 can calculate the upper limit threshold of the normal range based on the overall representative value of the resistance degradation and the multiple parallel ideal factors (S83).

[0098] When multiple battery packs 101 to 103 are in normal condition, the range of resistance degradation for each battery pack is referred to as the normal range. Battery packs with resistance degradation that does not fall within the normal range can be identified as being in an abnormal state with high resistance degradation.

[0099] First, BMS20 can set the battery packs whose resistance degradation degree is equal to or less than the overall representative value among multiple resistance degradation degrees for multiple battery packs 101 to 103 respectively as target packs.

[0100] BMS20 can determine the target representative value for the degree of resistance degradation of battery packs belonging to the target group.

[0101] As a method for deriving the target representative value, one can use methods such as obtaining the median or average value of the resistance degradation degree of the battery packs belonging to the target group. In the following text, the target representative value based on the resistance degradation degree of the battery packs belonging to the target group will be described as the median value of the resistance degradation degree of multiple battery packs belonging to the target group.

[0102] In the following text, referring to [Equation 4], BMS20 can calculate the upper limit threshold by multiplying the target representative value, which is obtained as the median of the resistance degradation degree of multiple battery packs belonging to the target group, by the multi-parallel ideal factor.

[0103] [Formula 4]

[0104]

[0105] Upper indicates the upper threshold of the normal range. B indicates the degree of resistance degradation of the battery pack. T(B) indicates the degree of resistance degradation of the battery pack belonging to the target group. X T (T(B)) indicates the target representative value of B. μ indicates the multi-parallel ideal factor. P indicates the number of parallel connections.

[0106] BMS20 can determine the normal range based on the upper limit threshold and diagnose the state of each of the multiple battery packs 101 to 103 based on the normal range (S84).

[0107] The normal range can have a calculated upper limit threshold.

[0108] When the normal range has an upper threshold, the BMS20 can determine that a battery pack with a resistance degradation level equal to or less than the upper threshold is in a normal state. Conversely, when the resistance degradation level of a battery pack exceeds the upper threshold, the BMS20 can determine that the battery pack is in an abnormal state.

[0109] BMS20 can diagnose the state of the battery pack 10 by distinguishing whether each of the multiple battery packs 101 to 103 included in the battery pack 10 is in a normal state and / or whether each of the multiple battery packs 101 to 103 is in an abnormal state.

[0110] While the invention has been described in conjunction with exemplary embodiments now considered practical, it should be understood that the invention is not limited to the disclosed embodiments. Rather, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for diagnosing a battery pack comprising multiple battery modules, the method comprising: The battery management system (BMS) determines whether there is a target battery pack among the plurality of battery packs that meets the discharge conditions. The BMS causes the target battery pack, as determined by the BMS, to discharge for a predetermined time. The BMS stores a first set of voltages of the target battery pack before the target battery pack is discharged and a second set of voltages of the target battery pack after the target battery pack is discharged; The BMS derives the current voltage change based on the first set of voltages and the second set of voltages; The BMS estimates the degree of resistive degradation of the target battery pack based on the reference voltage change and the current voltage change of the target battery pack. as well as The BMS diagnoses the plurality of battery packs based on the degree of resistance degradation for each of the plurality of battery packs. The discharge conditions include at least one of the following for each of the plurality of battery packs: pack voltage, pack temperature, and rest time: in: Diagnostics for the multiple battery packs include: The BMS calculates an upper threshold of the normal range based on multiple resistance degradation levels for the plurality of battery packs; and The BMS derives the normal range based on the upper limit threshold and diagnoses the state of each of the plurality of battery packs based on the normal range.

2. The method according to claim 1, wherein: The reference voltage change of the target battery pack is the initial voltage change for the target battery pack stored in the BMS, and The initial voltage change is the voltage change of each of the plurality of battery packs before and after the first discharge.

3. The method according to claim 1, wherein: The diagnostics for the multiple battery packs also include: The BMS derives an overall representative value of the multiple resistance degradation degrees based on the multiple resistance degradation degrees of the multiple battery packs; The BMS calculates the multi-parallel ideal factor based on the number of parallel connections of the plurality of battery packs; and The upper limit threshold of the normal range is calculated by the BMS based on the overall representative value of the multiple resistor degradation degrees and the multiple parallel ideal factors.

4. The method according to claim 3, wherein: The calculation of the upper limit threshold includes: The BMS sets a plurality of first battery packs whose resistance degradation degree is less than or equal to the overall representative value of the plurality of resistance degradation degrees as target groups; The BMS derives target representative values ​​for the resistance degradation of the plurality of first battery packs belonging to the target group; and The upper limit threshold of the normal range is calculated based on the target representative value and the multiple parallel ideal factors.

5. The method according to claim 1, wherein: The diagnosis of the state of each of the plurality of battery packs includes: The BMS determines that battery packs with resistance degradation equal to or less than the upper threshold are in a normal state; and The BMS identifies battery packs whose resistance degradation exceeds the upper limit threshold as being in an abnormal state.

6. A battery system, comprising: Multiple battery packs, in each of the multiple battery packs, multiple battery cells are connected in parallel; A discharge circuit is connected in parallel between the positive and negative terminals of each of the plurality of battery packs and is configured to discharge each of the battery packs. as well as The battery management system (BMS) is configured to determine whether there is a target battery pack among the plurality of battery packs that meets the discharge conditions. The target battery pack, which has been detected and determined, is discharged by the discharge circuit. The target battery pack stores a first set of voltages before the target battery pack is discharged and a second set of voltages after the target battery pack is discharged; The current voltage change is determined based on the first set of voltages and the second set of voltages; The degree of resistance degradation for the target battery pack is estimated based on the reference voltage change and the current voltage change of the target battery pack. And to diagnose the plurality of battery packs based on the degree of resistance degradation for each of the plurality of battery packs. The discharge conditions include at least one of the following for each of the plurality of battery packs: pack voltage, pack temperature, and rest time: in: The BMS is configured as follows: Calculate an upper threshold of the normal range based on multiple resistance degradation levels for the plurality of battery packs; derive the normal range based on the upper threshold; and diagnose the state of each of the plurality of battery packs based on the normal range.

7. The battery system according to claim 6, wherein: The reference voltage change of the target battery pack is the initial voltage change for the target battery pack stored in the BMS, and The initial voltage change is the voltage change of each of the plurality of battery packs before and after the first discharge.

8. The battery system according to claim 6, wherein: The upper limit threshold The BMS calculates the following based on the overall representative value of multiple resistance degradation degrees and the multiple parallel ideal factor: the overall representative value of the multiple resistance degradation degrees is derived based on the multiple resistance degradation degrees for the multiple battery packs respectively, and the multiple parallel ideal factor is calculated based on the number of parallel connections of the multiple battery packs.

9. The battery system according to claim 6, wherein: The BMS is configured as follows: Battery packs with resistance degradation levels equal to or less than the upper limit threshold of the resistance degradation level are identified as being in a normal state; and battery packs with resistance degradation levels greater than the upper limit threshold of the resistance degradation level are identified as being in an abnormal state.

10. The battery system according to claim 9, wherein: The BMS is configured as follows: The state of the multiple battery packs is diagnosed by distinguishing whether each of the multiple battery packs is in the abnormal state.

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