Method of detecting defective battery cells and battery management system

Abstract

The present invention relates to a method of detecting a defective battery cell among a plurality of battery cells forming a battery and a battery management system providing the same, and the battery management system according to the present invention includes: a cell monitoring IC connected to opposite ends of each of the plurality of battery cells and measuring a cell voltage of each of the plurality of battery cells; and a main control circuit detecting, for each charge cycle of the battery, a charge battery cell in which the cell voltage among the plurality of battery cells first reaches a charge final voltage, detecting, for each discharge cycle of the battery, a discharge battery cell in which the cell voltage among the plurality of battery cells first reaches a discharge final voltage, and detecting, when a sum of a charge cycle count and a discharge cycle count satisfies a first reference count, a battery cell corresponding to a second reference count or more as a defective battery cell, the sum count being a sum of a first count in which the battery cell is detected as the charge battery cell and a second count in which the battery cell is detected as the discharge battery cell.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2021-0100431, filed with the Korean Intellectual Property Office on July 30, 2021, the entire contents of which are incorporated herein by reference.

[0003] This invention relates to a method for detecting defective battery cells among a plurality of battery cells and a battery management system providing the method. Background Technology

[0004] Electric vehicles are vehicles that operate using electrical energy output from batteries consisting of a predetermined number (e.g., two to four) of battery packs. A battery comprises multiple battery cells that can be charged / discharged and can undergo state changes due to external environmental factors and its own characteristics. Therefore, a battery management system (BMS) monitors and manages the multiple battery cells contained within the battery.

[0005] When each of the multiple battery cells has performance within a predetermined range (hereinafter referred to as a battery cell within the normal range), the cell voltage of each of the multiple battery cells varies similarly within the predetermined range during charging and discharging cycles. Therefore, even if the BMS terminates the charging cycle when the first battery cell whose voltage reaches the final charging voltage first appears, the battery can still utilize its full usable battery capacity.

[0006] On the other hand, when batteries are used for a long time, battery cells deteriorate, which may result in battery cells that deviate from their performance within the predetermined performance range (hereinafter referred to as defective battery cells). During charging or discharging cycles, the cell voltage of a defective battery cell may have the characteristic that it reaches the final charging voltage or the final discharging voltage faster than the cell voltage of other battery cells within the normal range.

[0007] When a defective battery cell reaches its final charging voltage, terminating the charging cycle, other cells within the normal range may be charged without being fully charged. This results in the battery not utilizing its full usable capacity. Furthermore, defective cells experience accelerated degradation due to repeated use of their entire usable capacity. Additionally, when defects occur in the battery cells—the basic units used to form the battery—the overall battery voltage drops, leading to frequent cell balancing and undervoltage fault (UV) diagnostics, thus threatening the overall stability of the battery. Summary of the Invention

[0008] Technical issues

[0009] The present invention aims to provide a method for detecting defective battery cells that cause battery performance degradation, and a battery management system that provides the method.

[0010] Technical solution

[0011] According to one aspect of the present invention, a battery management system detects defective battery cells in a battery comprising a plurality of battery cells, and includes: a cell monitoring IC connected to opposite ends of each of the plurality of battery cells and measuring the cell voltage of each of the plurality of battery cells; and a main control circuit that detects, for each charging cycle of the battery, rechargeable battery cells whose cell voltage first reaches the final charging voltage, and for each discharging cycle of the battery, discharging battery cells whose cell voltage first reaches the final discharging voltage, and detects battery cells whose cell voltage first reaches the final discharging voltage when the sum of the charging cycle count and the discharging cycle count satisfies a first reference count, and detects battery cells whose total count corresponds to a second reference count or greater as the defective battery cells, the total count being the sum of the first count of the battery cells detected as rechargeable battery cells and the second count of the battery cells detected as discharging battery cells.

[0012] When the rechargeable battery cell is detected, the main control circuit can terminate the charging cycle.

[0013] When the discharge battery cell is detected, the main control circuit can terminate the discharge cycle.

[0014] According to another aspect of the present invention, a battery management system detects defective battery cells in a battery comprising a plurality of battery cells, and includes: a cell monitoring IC connected to opposite ends of each of the plurality of battery cells and measuring the cell voltage of each of the plurality of battery cells; and a main control circuit that detects, for each charging cycle of the battery, a rechargeable battery cell whose cell voltage first reaches the final charging voltage, and for each discharging cycle of the battery, a discharging battery cell whose cell voltage first reaches the final discharging voltage, and detects, for each discharging cycle of the battery, a battery cell that is detected as the rechargeable battery cell in the Nth charging cycle and subsequently as the discharging battery cell in the (N+1)th discharging cycle as the defective battery cell.

[0015] The main control circuit can detect a battery cell that was detected as a discharge battery cell in the Nth discharge cycle and subsequently as a recharge battery cell in the (N+1)th charging cycle as a defective battery cell.

[0016] When the rechargeable battery cell is detected, the main control circuit can terminate the charging cycle.

[0017] When the discharge battery cell is detected, the main control circuit can terminate the discharge cycle.

[0018] According to another aspect of the present invention, a method for detecting defective battery cells is used by a battery management system to detect defective battery cells in a battery comprising a plurality of battery cells, and includes the following steps: for each charging cycle of the battery, detecting rechargeable battery cells whose cell voltage first reaches the final charging voltage among the plurality of battery cells; for each discharging cycle of the battery, detecting discharging battery cells whose cell voltage first reaches the final discharging voltage among the plurality of battery cells; determining whether the sum of a charging cycle count and a discharging cycle count reaches a first reference count; and when it is determined that the sum reaches the first reference count, detecting battery cells whose total count corresponds to a second reference count or greater as the defective battery cells, the total count being the sum of a first count of the battery cells detected as the rechargeable battery cells and a second count of the battery cells detected as the discharging battery cells.

[0019] Detecting the rechargeable battery cell may include the following steps: when the rechargeable battery cell is detected, the charging cycle is terminated.

[0020] Detecting the discharged battery cell may include the following steps: when the discharged battery cell is detected, the discharge cycle is terminated.

[0021] According to another aspect of the present invention, a method for detecting defective battery cells is performed by a battery management system to detect defective battery cells in a battery comprising a plurality of battery cells, and includes: detecting, for each charging cycle of the battery, a rechargeable battery cell whose cell voltage first reaches a final charging voltage among the plurality of battery cells; detecting, for each discharging cycle of the battery, a discharging battery cell whose cell voltage first reaches a final discharging voltage among the plurality of battery cells; determining whether the sum of a charging cycle count and a discharging cycle count reaches a first reference count; and when it is determined that the sum reaches the first reference count, detecting the battery cell that was detected as the rechargeable battery cell in the Nth charging cycle and subsequently as the discharging battery cell in the (N+1)th discharging cycle as the defective battery cell.

[0022] Detecting a battery cell as defective may include the following steps: identifying a battery cell that was detected as a discharge battery cell in the Nth discharge cycle and subsequently as a rechargeable battery cell in the (N+1)th charging cycle as a defective battery cell.

[0023] Detecting the rechargeable battery cell may include the following steps: when the rechargeable battery cell is detected, the charging cycle is terminated.

[0024] Detecting the discharged battery cell may include the following steps: when the discharged battery cell is detected, the discharge cycle is terminated.

[0025] Technical effect

[0026] This invention can improve battery stability and prevent battery performance degradation by quickly and accurately detecting defective battery cells. Attached Figure Description

[0027] Figure 1 It is provided for the purpose of describing a battery system according to an embodiment.

[0028] Figure 2 This is a flowchart describing a method for detecting defective battery cells according to an embodiment.

[0029] Figure 3 This is a flowchart describing a method for detecting another defective battery cell according to another embodiment. Detailed Implementation

[0030] In the following description, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings. The same or similar reference numerals are used for the same or similar constituent elements, and repeated descriptions will be omitted. The suffixes "module" and / or "part" used for constituent elements in the following description are given or used interchangeably only for convenience of writing the specification, and they do not have a clear meaning or function in themselves. Furthermore, when describing the embodiments disclosed in this specification, detailed descriptions of related known technologies are omitted where it is determined that such detailed descriptions might obscure the essence of the embodiments disclosed in this specification. Moreover, the accompanying drawings are only for ease of understanding of the embodiments disclosed in this specification; the technical ideas disclosed in this specification are not limited by the drawings, and all variations contained within the spirit and scope of the invention should be understood to include equivalents or substitutions.

[0031] Various constituent elements may be described using ordinal terms such as first, second, etc., but constituent elements are not limited by these terms. These terms are used only for the purpose of distinguishing one constituent element from another.

[0032] It should be understood that when a component is described as "connected to" or "connected to" another component, the component can be directly connected to or connected to the other component, but there may also be intervening factors. In contrast, when a component is described as "directly connected to" or "directly connected to" another component, it should be understood that there are no intermediary factors.

[0033] In this application, it should be understood that the terms "comprising" and "having" are intended to indicate the presence of the features, quantities, steps, operations, constituent elements and components or combinations thereof described in the specification, and do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, constituent elements and components or combinations thereof.

[0034] Figure 1 It is provided for the purpose of describing a battery system according to an embodiment.

[0035] Reference Figure 1 The battery system 1 includes a battery 10, a current sensor 20, a relay 30, and a battery management system (hereinafter referred to as BMS) 40.

[0036] Battery 10 may include multiple battery cells Cell1 to Celln electrically connected in parallel and series. In some embodiments, the battery cells may be rechargeable batteries. A predetermined number of battery cells are connected in series to form a battery module, a predetermined number of battery modules are connected in series to form a battery pack, and a predetermined number of battery packs are connected in parallel to form a battery bank, thereby providing the required power. Figure 1 The image shows a battery 10 with multiple battery cells Cell1 to Celln connected in series, but this is not limiting. The battery 10 can be formed as a battery module, battery pack, or battery library.

[0037] Each of the multiple battery cells Cell1 to Celln is electrically connected to BMS40 via wires. BMS40 collects and analyzes various information related to the battery cells, including information about the multiple battery cells Cell1 to Celln, to control the charging and discharging of the battery cells, protection operation, etc., and controls the operation of relay 30.

[0038] exist Figure 1 In the battery 10, a plurality of battery cells Cell1 to Celln are connected in series and connected between the two output terminals OUT1 and OUT2 of the battery system 1. The relay 30 is connected between the first output terminal OUT1 of the battery system 1 and the positive terminal, and the current sensor 20 is connected between the second output terminal OUT2 of the battery system 1 and the negative terminal. Figure 1 The components shown and the connections between them are an example of the present invention, and the present invention is not limited thereto.

[0039] The current sensor 20 is connected in series to the current path between the battery 10 and the external device. The current sensor 20 can measure the battery current flowing through the battery 10, that is, the charging current and discharging current of the battery 10, and can send the measurement results to the BMS40.

[0040] Relay 30 controls the electrical connection between battery system 1 and an external device. When relay 30 is open, battery system 1 is electrically connected to the external device to perform charging and discharging, and when relay 30 is closed, battery system 1 is electrically disconnected from the external device. In this case, the external device can be a charger in the charging cycle where the battery 10 is charged by a power supply, and a load in the discharging cycle where the battery 10 discharges to the external device.

[0041] BMS40 includes a unit monitoring IC 41 and a main control circuit 43.

[0042] The cell monitoring IC 41 is electrically connected to the positive and negative terminals of each of the multiple battery cells Cell1 to Celln, and measures the cell voltage of each of the multiple battery cells Cell1 to Celln. The battery current value measured by the current sensor 20 can be sent to the cell monitoring IC 41. The cell monitoring IC 41 sends information about the measured cell voltage and battery current to the main control circuit 43. Specifically, the cell monitoring IC 41 can measure the cell voltage of each of the multiple battery cells Cell1 to Celln at predetermined intervals during rest periods when no charging or discharging occurs, and calculate the cell current based on the measured cell voltage. The cell monitoring IC 41 can send the cell voltage and cell current of each of the multiple battery cells Cell1 to Celln to the main control circuit 43.

[0043] When the number of charge / discharge cycles meets the first reference count, the main control circuit 43 can detect defective battery cells based on the charging battery cells and the discharging battery cells.

[0044] A rechargeable battery cell can indicate the battery cell whose cell voltage first reaches the final charging voltage during a charging cycle. A discharging battery cell can indicate the discharging battery cell whose cell voltage first reaches the final discharging voltage during a discharging cycle. For example, the main control circuit 43 can use the electrical position of the battery cell within the battery 10 as an identification factor for the battery cell.

[0045] Figure 2 This is a flowchart describing a method for detecting defective battery cells according to an embodiment.

[0046] In the following text, reference will be made to Figure 1 and Figure 2This document details a method for detecting defective battery cells according to an embodiment and a battery management system that provides the detection method.

[0047] First, for each charging cycle in which the battery 10 is charged using power from an external device, the BMS40 detects the rechargeable battery cell (S110) among multiple battery cells Cell1 to Celln that first reaches the final charging voltage Vmax.

[0048] The final charging voltage Vmax can be the maximum voltage at which battery 10 can be charged within a non-hazardous range. A higher final charging voltage Vmax allows for a higher capacity of battery 10, but overcharging may pose a danger to battery 10. Therefore, the final charging voltage should be appropriately set considering the capacity and stability of battery 10.

[0049] The BMS40 can use the electrical position of the battery cell as an identification factor. For example, in the Nth charging cycle, the BMS40 can check the electrical position of the battery cell whose cell voltage first reaches the final charging voltage Vmax among multiple battery cells Cell1 to Celln, and add a detection count to the cell at the corresponding position.

[0050] When a rechargeable battery cell is detected, the BMS40 can terminate the charging cycle. Subsequently, it can prevent accelerated degradation of the rechargeable battery cell by blocking the overcharge state, in which the rechargeable battery cell continues to charge until the cell voltage of the remaining battery cells reaches the final charging voltage Vmax.

[0051] Next, BMS40 detects the battery cell whose cell voltage first reaches the final discharge voltage Vmin during the discharge cycle that supplies discharge power to the external device from the battery 10 (S120).

[0052] The final discharge voltage Vmin can be the minimum voltage at which battery 10 can be discharged without being in a dangerous situation. When the final discharge voltage Vmin decreases, the capacity of battery 10 may increase, but over-discharge may put battery 10 in a dangerous situation. Therefore, the final discharge voltage Vmin can be appropriately set considering the capacity and stability of battery 10. For example, the final discharge voltage can be called the cutoff voltage.

[0053] BMS40 can use the electrical location of the battery cell within battery 10 as an identification factor for the battery cell. For example, in the Nth discharge cycle, BMS40 checks the location of the battery cell whose cell voltage first reaches the final discharge voltage Vmin among multiple battery cells Cell1 to Celln, and increments the detection count of the battery cell at the corresponding location by one.

[0054] When a discharging battery cell is detected, the BMS40 can terminate the discharge cycle. Then, the over-discharge state of the discharging battery cell is blocked until the cell voltage of the remaining battery cells reaches the final discharge voltage, thereby preventing accelerated degradation of the discharging battery cells.

[0055] Next, BMS40 determines whether the sum of the charge cycle count and the discharge cycle count satisfies the first reference count (S130).

[0056] The first reference count can correspond to the optimal number of charge cycles and discharge cycles used to detect defective battery cells. For example, the first reference count can be derived through predetermined experiments.

[0057] When the result shows that the sum of the charge cycle count and the discharge cycle count does not meet the first reference count (S130, No), BMS40 repeats from step S110.

[0058] When the result shows that the sum of the charging cycle count and the discharging cycle count meets the first reference count (S130, yes), the BMS40 determines whether there is a battery cell with a total count corresponding to the second reference count or greater, the total count being the sum of the first count detected as a charging battery cell and the second count detected as a discharging battery cell (S140).

[0059] For example, assuming battery 10 includes five battery cells Cell1, Cell2, Cell3, Cell4, and Cell5, the first reference count is 500 times, and the second reference count is 300 times. When it is determined that the third battery cell has been detected a total of 400 times (e.g., 200 times for rechargeable battery cells and 200 times for dischargeable battery cells), and the first, second, fourth, and fifth battery cells have each been detected 25 times (e.g., 12 times for rechargeable battery cells and 13 times for dischargeable battery cells), BMS40 can determine that there are battery cells with reference counts corresponding to two or more.

[0060] Next, when the results show that there are battery cells whose total count corresponds to the second reference count (S140, yes), BMS40 diagnoses that there are defective battery cells among the multiple battery cells (S150).

[0061] For example, BMS40 can detect a third battery cell, Cell3, whose total count corresponds to the second reference count, as a defective battery cell. According to an embodiment, a defective battery cell can be a battery cell with performance lower than predetermined performance due to battery cell degradation.

[0062] Next, the results show that there are no battery cells whose total count corresponds to the second reference count (S140, No), and the BMS40 diagnoses that there are no defective battery cells among the multiple battery cells (S160).

[0063] Figure 3 This is a flowchart describing a method for detecting another defective battery cell according to another embodiment.

[0064] In the following text, reference will be made to Figure 1 and Figure 3 This document details a method for detecting defective battery cells and provides a battery management system that incorporates this method.

[0065] First, the BMS40 detects the rechargeable battery cell whose cell voltage first reaches the final charging voltage Vmax during a charging cycle in which the battery 10 is charged with power from an external device (S210).

[0066] The final charging voltage Vmax can be the maximum voltage (MaxVoltage) that allows battery 10 to be charged within a non-hazardous range. A higher final charging voltage Vmax allows for a higher capacity of battery 10, but overcharging may put battery 10 at risk. Therefore, the final charging voltage Vmax should be appropriately set considering the capacity and stability of battery 10.

[0067] The BMS40 can use the electrical location of the battery cell as an identification factor. For example, in the Nth charging cycle, the BMS40 checks the location of the battery cell whose cell voltage first reaches the final charging voltage Vmax among multiple battery cells Cell1 to Celln, and adds a detection count to the battery cell at the corresponding location.

[0068] When a rechargeable battery cell is detected, the BMS40 can terminate the charging cycle. Subsequently, the overcharge state of the rechargeable battery cell is blocked until the cell voltage of the remaining battery cells reaches the final charging voltage Vmax, thereby preventing accelerated degradation of the rechargeable battery cells.

[0069] Next, BMS40 detects the battery cell whose cell voltage first reaches the final discharge voltage Vmin during the discharge cycle that supplies discharge power to the external device from the battery 10 (S220).

[0070] The final discharge voltage Vmin can be the minimum voltage (MinVoltage) that allows battery 10 to discharge within a non-hazardous range. While a lower final discharge voltage Vmin can increase the capacity of battery 10, over-discharge may endanger it. Therefore, the final discharge voltage Vmin can be appropriately set considering the capacity and stability of battery 10. For example, the final discharge voltage can be referred to as the cutoff voltage.

[0071] BMS40 can use the electrical location of the battery cell within battery 10 as an identification factor for the battery cell. For example, in the Nth discharge cycle, BMS40 checks the location of the battery cell whose cell voltage first reaches the final discharge voltage Vmin among multiple battery cells Cell1 to Celln, and adds a detection count to the battery cell at the corresponding location.

[0072] When a discharging battery cell is detected, the BMS40 can terminate the discharge cycle. Then, the over-discharge state of the discharging battery cell is blocked until the cell voltage of the remaining battery cells reaches the final discharge voltage, thereby preventing accelerated degradation of the discharging battery cells.

[0073] Next, BMS40 determines whether the sum of the charge cycle count and the discharge cycle count satisfies the first reference count (S230).

[0074] The first reference count can correspond to the optimal charge cycle count and discharge cycle count used to detect defective battery cells. For example, the first reference count can be derived through predetermined experiments.

[0075] When the result shows that the sum of the charge cycle count and the discharge cycle count does not meet the first reference count (S230, No), BMS40 repeats from step S210.

[0076] When the result shows that the sum of the charging cycle count and the discharging cycle count meets the first reference count (S230, Yes), BMS40 determines whether the charging battery cell and the discharging battery cell correspond to the same battery cell consecutively (S240).

[0077] According to the implementation, when there is a battery cell that is detected as a rechargeable battery cell in the Nth charging cycle and subsequently as a discharge battery cell in the (N+1)th discharging cycle, the BMS40 can determine that the rechargeable battery cell and the discharge battery cell continuously correspond to the same battery cell.

[0078] According to another embodiment, when there is a battery cell that is detected as a discharge battery cell in the Nth discharge cycle and as a rechargeable battery cell in the (N+1)th charging cycle, the BMS40 can determine that the rechargeable battery cell and the discharge battery cell continuously correspond to the same battery cell.

[0079] Assume battery 10 includes five battery cells: Cell1, Cell2, Cell3, Cell4, and Cell5, and the first reference count is 500. For example, when the fourth battery cell, Cell4, is detected as a rechargeable battery cell in the 35th charging cycle and subsequently as a discharging battery cell in the 36th discharging cycle, BMS40 can determine that the rechargeable and discharging battery cells consecutively correspond to the same battery cell. Similarly, for example, when the fifth battery cell, Cell5, is detected as a discharging battery cell in the 37th discharging cycle and subsequently as a rechargeable battery cell in the 38th charging cycle, BMS40 can determine that the rechargeable and discharging battery cells consecutively correspond to the same battery cell.

[0080] Next, when the results show that the rechargeable battery cell and the discharge battery cell correspond to the same battery cell consecutively (S240, yes), the BMS40 diagnoses that there is a defective battery cell among the multiple battery cells (S250).

[0081] For example, BMS40 may identify the fourth battery cell, Cell4, which is detected as a rechargeable battery cell in the 35th charging cycle and subsequently as a discharge battery cell in the 36th discharging cycle, as a defective battery cell. As another embodiment, BMS40 may identify the fifth battery cell, Cell5, which is detected as a discharge battery cell in the 37th discharging cycle and subsequently as a rechargeable battery cell in the 38th charging cycle, as a defective battery cell. According to the embodiment, a defective battery cell may be a battery cell with performance lower than predetermined performance due to battery cell degradation.

[0082] Next, when the results show that the rechargeable battery cell and the discharge battery cell do not correspond to the same battery cell consecutively (S240, No), the BMS40 diagnoses that there is no defective battery cell among the multiple battery cells (S260).

[0083] While the invention has been described in conjunction with what is now considered to be the actual implementation, it should be understood that the invention is not limited to the disclosed embodiments. Rather, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A battery management system that detects defective battery cells in a battery comprising a plurality of battery cells, the battery management system comprising: A cell monitoring IC is connected to the opposite end of each of the plurality of battery cells and measures the cell voltage of each of the plurality of battery cells; as well as The main control circuit: (1) detects, for each charging cycle of the battery, the rechargeable battery cell whose cell voltage first reaches the final charging voltage among the plurality of battery cells; (2) detects, for each discharging cycle of the battery, the discharging battery cell whose cell voltage first reaches the final discharging voltage among the plurality of battery cells; and (3) when the sum of the charging cycle count and the discharging cycle count satisfies a first reference count, detects the battery cell whose total count corresponds to a second reference count or greater as the defective battery cell, the total count being the sum of the first count of the battery cell being detected as the rechargeable battery cell and the second count of the battery cell being detected as the discharging battery cell.

2. The battery management system according to claim 1, wherein, When the rechargeable battery cell is detected, the main control circuit terminates the charging cycle.

3. The battery management system according to claim 1, wherein, When the discharged battery cell is detected, the main control circuit terminates the discharge cycle.

4. A battery management system that detects defective battery cells in a battery comprising a plurality of battery cells, the battery management system comprising: A cell monitoring IC is connected to the opposite end of each of the plurality of battery cells and measures the cell voltage of each of the plurality of battery cells; as well as The main control circuit: (1) detects the rechargeable battery cell whose cell voltage first reaches the final charging voltage in each charging cycle of the battery; (2) detects the discharge battery cell whose cell voltage first reaches the final discharging voltage in each discharging cycle of the battery; and (3) when the sum of the charging cycle count and the discharging cycle count satisfies the first reference count, the battery cell that is detected as the rechargeable battery cell in the Nth charging cycle and subsequently as the discharge battery cell in the (N+1)th discharging cycle is detected as the defective battery cell.

5. The battery management system according to claim 4, wherein, The main control circuit detects the battery cell that is the discharge battery cell in the Nth discharge cycle and subsequently the recharge battery cell in the (N+1)th charging cycle as the defective battery cell.

6. The battery management system according to claim 4, wherein, When the rechargeable battery cell is detected, the main control circuit terminates the charging cycle.

7. The battery management system according to claim 4, wherein, When the discharged battery cell is detected, the main control circuit terminates the discharge cycle.

8. A method for detecting defective battery cells by a battery management system, said defective battery cells being in a battery comprising a plurality of battery cells, the method for detecting defective battery cells comprising the following steps: For each charging cycle of the battery, the rechargeable battery cell whose cell voltage first reaches the final charging voltage among the plurality of battery cells is detected. For each discharge cycle of the battery, the cell voltage of the battery cell that first reaches the final discharge voltage among the plurality of battery cells is detected. Determine whether the sum of the charging cycle count and the discharging cycle count reaches the first reference count; as well as When the sum reaches the first reference count, the battery cell corresponding to the second reference count or greater is detected as the defective battery cell, the total count being the sum of the first count of the battery cell being detected as the rechargeable battery cell and the second count of the battery cell being detected as the discharge battery cell.

9. The method for detecting defective battery cells according to claim 8, wherein, The step of detecting the rechargeable battery cell includes the following steps: when the rechargeable battery cell is detected, the charging cycle is terminated.

10. The method for detecting defective battery cells according to claim 8, wherein, The step of detecting the discharged battery cell includes the following steps: when the discharged battery cell is detected, the discharge cycle is terminated.

11. A method for detecting defective battery cells by a battery management system, said defective battery cells being in a battery comprising a plurality of battery cells, said method comprising the steps of: For each charging cycle of the battery, the rechargeable battery cell whose cell voltage first reaches the final charging voltage among the plurality of battery cells is detected. For each discharge cycle of the battery, the cell voltage of the battery cell that first reaches the final discharge voltage among the plurality of battery cells is detected. Determine whether the sum of the charging cycle count and the discharging cycle count reaches the first reference count; as well as When the first reference count is reached, the battery cell that was detected as the rechargeable battery cell in the Nth charging cycle and subsequently as the discharge battery cell in the (N+1)th discharging cycle is detected as the defective battery cell.

12. The method for detecting defective battery cells according to claim 11, wherein, The steps for detecting the defective battery cell include the following: The battery cell that is detected as the discharge battery cell in the Nth discharge cycle and subsequently as the recharge battery cell in the (N+1)th charge cycle is detected as the defective battery cell.

13. The method for detecting defective battery cells according to claim 11, wherein, The step of detecting the rechargeable battery cell includes the following steps: when the rechargeable battery cell is detected, the charging cycle is terminated.

14. The method for detecting defective battery cells according to claim 11, wherein, The step of detecting the discharged battery cell includes the following steps: when the discharged battery cell is detected, the discharge cycle is terminated.

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