Apparatus and method for battery diagnostics

Abstract

A battery diagnostic apparatus includes a temperature detector configured to detect a temperature of battery cells; an impedance detection device configured to generate an AC current signal flowing through the battery cells, detect an AC voltage signal corresponding to the AC current signal for each of the battery cells, and detect impedance data for each of the battery cells based on the AC current signal and the AC voltage signal; and a controller configured to activate or deactivate the impedance detection device according to a temperature deviation of the battery cells, and detect an abnormal battery cell among the battery cells based on the impedance data when the impedance detection device is activated.

Description

Technical Field

[0001] This disclosure relates to an apparatus and method for battery diagnostics. Background Technology

[0002] Unlike primary batteries, which cannot be recharged, secondary batteries can be repeatedly charged and discharged. Low-capacity secondary batteries are used in portable small electronic devices such as smartphones, feature phones, laptops, digital cameras, or camcorders. High-capacity secondary batteries are widely used as power sources for motors in hybrid vehicles, electric vehicles, etc., and as energy storage devices. A secondary battery includes an electrode assembly containing positive and negative electrodes, a housing of the electrode assembly, and electrode terminals connected to the electrode assembly.

[0003] Typically, an electrode assembly includes a positive electrode, a negative electrode, a separator inserted between the positive and negative electrodes, a housing containing the electrode assembly, and electrode terminals electrically connected to the electrode assembly. An electrolyte is injected into the housing to enable charging and discharging of the battery through an electrochemical reaction between the positive and negative electrodes and the electrolyte. The shape of the housing can vary depending on the application of the battery and can be, for example, cylindrical or rectangular.

[0004] Diagnostic methods based on electrochemical impedance spectroscopy (EIS) measure the battery's impedance by applying AC signals of various frequency bands to the battery and then analyzing the battery's current and voltage responses.

[0005] The information disclosed in this section is intended only to enhance understanding of the background of this disclosure. It may include information that does not constitute prior art. Summary of the Invention

[0006] This disclosure provides a battery diagnostic apparatus and method that minimizes power consumption caused by electrochemical impedance spectroscopy (EIS) diagnostics of a battery system.

[0007] However, the technical problems solved by this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the following description of this disclosure other technical problems not mentioned.

[0008] A battery diagnostic apparatus according to an embodiment of the present disclosure includes: a temperature detector configured to detect the temperature of a battery cell; an impedance detection device configured to generate an AC current signal flowing through the battery cell, detect an AC voltage signal corresponding to the AC current signal for each of the battery cells, and detect impedance data for each of the battery cells based on the AC current signal and the AC voltage signal; and a controller configured to activate or deactivate the impedance detection device based on the temperature deviation of the battery cells, and when the impedance detection device is activated, detect abnormal battery cells based on the impedance data.

[0009] The controller can be configured to activate the impedance detection device if the temperature deviation is greater than or equal to a predetermined value.

[0010] The controller can be configured to activate the impedance detection device if the temperature deviation is 3°C or greater.

[0011] The controller can be configured to disable the impedance detection device if no abnormal battery cell is detected in the battery cell.

[0012] The battery diagnostic device may also include a discharge device configured to connect between the two ends of a battery module comprising multiple battery cells, forming a discharge path through which an AC current signal flows. An impedance detection device may be configured to control the current flow in the discharge path to generate an AC current signal.

[0013] The discharge device may include: a switch configured to be connected to a first terminal of the battery module; and a discharge load configured to be connected between the switch and a second terminal of the battery module.

[0014] The impedance detection device may include: an AC signal generator configured to generate an AC signal and output the AC signal to a discharge device; and an impedance detector configured to detect an AC current signal and an AC voltage signal, generate impedance data based on the AC current signal and the AC voltage signal, and transmit the impedance data to a controller. Switching can be controlled by an AC signal, and the AC current signal can be generated based on the switching.

[0015] The AC signal generator can be configured to sequentially change the frequency of the AC signal output to the discharge device, and the AC current signal can have the same frequency as the AC signal.

[0016] The AC signal generator can be configured to output an AC signal to the discharge device if the impedance detection device is activated, and the AC signal generator can be configured to output a blocking signal to the discharge device if the impedance detection device is deactivated. When the discharge device receives the blocking signal, the switch can be turned off.

[0017] The impedance detector can be configured to generate and transmit impedance data when the impedance sensing device is activated, and the impedance detector can be configured to stop generating and transmitting impedance data when the impedance sensing device is deactivated.

[0018] A battery system according to an embodiment of the present disclosure includes: a battery module comprising a plurality of battery cells; and a battery diagnostic device.

[0019] The battery diagnostic method according to embodiments of the present disclosure includes: calculating the temperature deviation of a battery cell; when the temperature deviation is greater than or equal to a predetermined value, activating an impedance detection device to detect the impedance data of each of the battery cells using electrochemical impedance spectroscopy; and detecting abnormal battery cells based on the impedance data.

[0020] Battery diagnostic methods may also include disabling the impedance detection device when no abnormal battery cell is detected in the battery cell.

[0021] Battery diagnostic methods may also include stopping the charging and discharging of a battery cell when an abnormal battery cell is detected.

[0022] According to this disclosure, power consumption caused by electrochemical impedance spectroscopy (EIS) diagnostics of a battery system can be minimized.

[0023] However, the effects that can be obtained through this disclosure are not limited to those described above, and those skilled in the art can clearly understand from the following description of this disclosure other technical effects not mentioned. Attached Figure Description

[0024] The accompanying drawings illustrate embodiments of the present disclosure and are used to further describe the technical ideas of the present disclosure together with the detailed description below. The present disclosure is not limited to the embodiments depicted in the drawings.

[0025] Figure 1 A battery system according to an embodiment of the present disclosure is shown.

[0026] Figure 2 This is a flowchart of a battery diagnostic method for a battery system according to an embodiment of the present disclosure. Detailed Implementation

[0027] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, but should be interpreted as conforming to the meaning and concepts of the technical spirit of this disclosure, based on the principle that the inventor can appropriately define the concepts of the terms to best describe their invention. The embodiments described in this specification and the configurations shown in the accompanying drawings are merely examples of this disclosure and do not represent all the technical ideas of this disclosure. Therefore, it should be understood that various equivalents and variations may exist that can replace the embodiments and configurations described herein.

[0028] When used in this specification, the terms "comprising" or "including" describe the presence of shapes, quantities, steps, operations, components, elements, and / or groups thereof, but do not exclude the presence or addition of one or more other shapes, one or more other quantities, one or more other operations, one or more other components, one or more other elements, and / or groups thereof. Furthermore, when describing embodiments of this disclosure, the use of "may" means "one or more embodiments of this disclosure".

[0029] To aid in understanding this disclosure, the accompanying drawings may not be shown to scale, and the dimensions of some components may be exaggerated in the drawings. Furthermore, the same reference numerals may be assigned to the same components in different embodiments.

[0030] When two objects are described as identical, it means that the objects are "substantially the same." Therefore, substantially identical objects can include those with what is considered to be low deviation in the art, for example, deviation within 5%. Furthermore, when describing certain parameters as uniform over a predetermined region, this can mean that the parameters are uniform in terms of their average value.

[0031] Although terms such as "first," "second," etc., are used to describe various components, components are not limited by these terms. Terms are only used to distinguish one component from another, and unless otherwise specified, the first component can be the second component.

[0032] Throughout this specification, unless otherwise stated, each component may be singular or plural.

[0033] Placing any component "above (or below)" or "on (or below)" another component may not only mean that the component is arranged to contact the upper (or lower) surface of the other component, but also that other components can be inserted between the other component and the component arranged above (or below) the other component.

[0034] When describing a component as "connected," "coupled," or "accessed" to another component, the components may be directly connected or accessed to each other. However, it should be understood that another component may be "inserted" between the components, or a component may be "connected," "coupled," or "accessed" through another component. Furthermore, when a part is described as electrically coupled or connected to another part, this includes not only the case where a part is directly coupled to another part, but also the case where a part is coupled to another part via an intermediate element.

[0035] Throughout this specification, when “A and / or B” is mentioned, it means A, B, or A and B, unless otherwise specified. That is, the term “and / or” includes any and all combinations of the listed items. When “C to D” is mentioned, it means greater than or equal to C and less than or equal to D, unless otherwise specified.

[0036] Figure 1 A battery system according to an embodiment is illustrated schematically.

[0037] refer to Figure 1 According to an embodiment, the battery system 1 may include a battery module 10 and a battery diagnostic device. The battery module 10 may include a plurality of battery cells 11 connected in series and / or in parallel with each other.

[0038] The battery diagnostic device can monitor the temperature of each of the battery cells 11, and can selectively perform electrochemical impedance spectroscopy (EIS) diagnostic functions based on the temperature monitoring results. The battery diagnostic device may include a temperature detector 20, an impedance detection device 30, a discharge device 40, and a controller 50.

[0039] Temperature detector 20 can detect the temperature of each of the battery cells 11 included in the battery module 10. Temperature detector 20 may include various temperature sensors capable of measuring the temperature of the battery cells 11, such as thermocouples, thermistors, resistance temperature detectors (RTDs), bimetallic devices, and strain gauges.

[0040] Impedance detection device 30 can detect the impedance of each of the battery cells 11 based on EIS diagnostic methods. Impedance detection device 30 may include: AC signal generator 31 for making an AC current signal flow through the battery cell 11; and impedance detector 32 for detecting the impedance of each of the battery cells 11 when the AC current signal flows through the battery cell 11.

[0041] If the EIS diagnostic function is activated, the AC signal generator 31 can generate AC signals for EIS diagnostics. The AC signal generator 31 can generate AC signals by changing the frequency of the AC signals, and can sequentially output the generated AC signals of different frequencies. For example, the AC signal generator 31 can generate multiple AC signals with frequencies of 0.01 Hz or greater and 4 kHz or less, and the AC signal generator 31 can sequentially output the generated multiple AC signals.

[0042] The AC signal output by the AC signal generator 31 can be transmitted to the discharge device 40 (described below). The AC signal transmitted to the discharge device 40 can control the discharge device 40 to generate an AC current signal flowing through the battery cell 11.

[0043] If the EIS diagnostic function is disabled, the AC signal generator 31 can output a blocking signal. In this case, the AC signal generator 31 can maintain the output of the blocking signal while the EIS diagnostic function remains inactive. The blocking signal output by the AC signal generator 31 can be transmitted to the discharge device 40. The blocking signal transmitted to the discharge device 40 can block the current signal from flowing to the battery cell 11.

[0044] When the EIS diagnostic function is activated, causing an AC current signal to flow through the battery cell 11, the impedance detector 32 can measure the AC current signal flowing through the battery module 10 and the AC voltage signal of each of the battery cells 11. If the AC current signal flows through the battery cell 11, the voltage signal output from each of the battery cells 11 can be an AC voltage signal corresponding to the AC current signal. The impedance detector 32 can detect the impedance of each of the battery cells 11 by analyzing the measured AC current signal and the measured AC voltage signal. The impedance of each of the battery cells 11 can include, for example, the electrolyte resistance (Rs), film resistance (Rf), charge transfer resistance (Rct), film capacitance (Cf), charge double layer capacitance (Cdl), constant phase element (CPE), Warburg impedance (Zw), etc., of the battery cell 11. Determining the impedance of the battery cell 11 using the AC current signal and AC voltage signal measured from the battery cell 11 can use techniques known in the field of EIS diagnostic technology, and therefore their detailed description is omitted.

[0045] Whenever the frequency of the AC signal output from the AC signal generator 31 changes, the impedance detector 32 can repeatedly perform the process of measuring the AC current signal flowing through the battery module 10 and the AC voltage signal of each of the battery cells 11. Furthermore, the impedance detector 32 can perform the process of determining the impedance of each of the battery cells 11 based on the measured AC current signal and the measured AC voltage signal. By repeating this process, the impedance detector 32 can determine the impedance of each of the battery cells 11 at each frequency. When determining the impedance of each of the battery cells 11 at each frequency, the impedance detector 32 can transmit impedance data, including the impedance value of each of the battery cells 11 at each frequency, to the controller 50. If the EIS diagnostic function is disabled, the impedance detector 32 can stop the impedance detection operation.

[0046] The impedance detection device 30 may include at least one integrated circuit (IC). For example, the impedance detection device 30 may include one IC (e.g., an analog front-end (AFE) IC) for performing the functions of the AC signal generator 31 and the impedance detector 32. Alternatively, the impedance detection device 30 may include multiple ICs for performing the functions of the AC signal generator 31 and the impedance detector 32. Each IC may be configured to perform one of the individual functions of the AC signal generator 31 and the impedance detector 32, or each IC may be configured to perform all the functions of the AC signal generator 31 and the impedance detector 32. In the latter case, the battery cells 11 may be classified into multiple battery cell groups, and the IC for each battery cell group may be configured to perform the impedance detection function.

[0047] The impedance detection device 30 may include electronic circuitry for performing the functions of the AC signal generator 31 and the impedance detector 32.

[0048] The discharge device 40 can be connected between the ends (or the positive and negative electrodes) of the battery module 10 to form a discharge path between the ends of the battery module 10. When the EIS diagnostic function is activated, the discharge device 40 can selectively generate a current signal flowing through the battery module 10.

[0049] When the EIS diagnostic function is activated, the discharge device 40 can receive an AC signal from the AC signal generator 31. The discharge device 40 can generate an AC current signal flowing through the battery module 10 based on the received AC signal. The AC current signal flowing through the battery module 10 can have the same frequency as the AC signal output from the AC signal generator 31.

[0050] When the EIS diagnostic function is disabled, the discharge device 40 can receive a blocking signal from the AC signal generator 31. If a blocking signal is received, the discharge device 40 can block the discharge path corresponding to the blocking signal, so that no AC current signal is generated.

[0051] exist Figure 1 In the example shown, the discharge device 40 includes a switch 41 and a discharge load 42. The switch 41 and the discharge load 42 can be connected between the ends of the battery module 10 to form a discharge path for the battery module 10.

[0052] Switch 41 can be connected between one end of battery module 10 (e.g., the positive electrode) and discharge load 42. If switch 41 is in the off state (e.g., open or non-conductive), the electrical connection between the end of battery module 10 and discharge load 42 can be blocked at switch 41. If switch 41 is in the on state (e.g., closed or conductive), the electrical connection between the end of battery module 10 and discharge load 42 is not blocked at switch 41.

[0053] The output signal (e.g., an AC signal or a blocking signal) from the AC signal generator 31 can control the on state (e.g., closed state or conducting state) and off state (e.g., open state or non-conducting state) of the switch 41. When an AC signal is received from the AC signal generator 31, the switch 41 can repeatedly switch according to the received AC signal (e.g., from the on state to the off state and from the off state to the on state). Therefore, while receiving the AC signal, an AC current signal can flow between the two ends of the battery module 10.

[0054] If a blocking signal is received from AC signal generator 31, switch 41 can be turned off in response to the received blocking signal. This state can then be maintained.

[0055] Switch 41 may include various types of switching elements. For example, switch 41 may include a field-effect transistor (FET).

[0056] The discharge load 42 can be connected between the switch 41 and one end of the battery module 10 (e.g., the negative electrode). If the switch 41 is in the ON state, the discharge load 42 can form a discharge path between the two ends of the battery module 10 to generate a discharge current signal flowing through the battery module 10. The discharge load 42 may include a discharge resistor.

[0057] The controller 50 can receive temperature values ​​from the temperature detector 20 for each of the battery cells 11. The controller 50 can analyze the temperature values ​​received from the temperature detector 20 to determine whether the EIS diagnostic function should be activated. For example, the controller 50 can control the driving of the impedance detection device 30 and the driving of the discharge device 40 based on the temperature values ​​received from the temperature detector 20. The controller 50 can calculate the temperature deviation among the battery cells 11 constituting the battery module 10, and the controller 50 can determine whether the EIS diagnostic function is activated based on the calculated temperature deviation. If the temperature deviation of the battery cell 11 is greater than or equal to a predetermined value (e.g., 3°C), the controller 50 can activate the EIS diagnostic function. If the temperature deviation of the battery cell 11 is less than the predetermined value, the controller 50 can deactivate the EIS diagnostic function. As used herein, the term "temperature deviation" can refer to the temperature difference between battery cells 11. Therefore, the condition "temperature deviation equal to or greater than a predetermined value (e.g., 3°C)" can be satisfied when the difference between the highest and lowest temperatures in the battery cells 11 is equal to or greater than a predetermined value.

[0058] The controller 50 can activate the EIS diagnostic function by activating the impedance detection device 30. If it is determined that the EIS diagnostic function should be activated, the controller 50 can control the AC signal generator 31 to output an AC signal for EIS diagnostics by sending a control signal to the AC signal generator 31. Furthermore, the controller 50 can control the impedance detector 32 to perform impedance detection by sending a control signal to the impedance detector 32. If the AC signal generator 31 outputs an AC signal, the discharge function of the discharge device 40 is activated, causing an AC current signal to flow through the battery module 10.

[0059] If it is determined that the EIS diagnostic function should be disabled, the controller 50 can send a control signal to the AC signal generator 31 to stop the output of the AC signal used for EIS diagnostics. Therefore, the AC signal generator 31 will stop the output of the AC signal and output a blocking signal. The controller 50 can also control the impedance detector 32 to stop its impedance detection operation by sending a control signal to it. When the AC signal generator 31 outputs a blocking signal, the discharge function of the discharge device 40 is disabled, thus blocking the discharge path formed by the discharge device 40.

[0060] When the impedance detection device 30 is activated to obtain impedance data for each of the battery cells 11, the controller 50 can analyze the impedance data to diagnose the state of each of the battery cells 11. For example, the controller 50 can diagnose the internal state of each of the battery cells 11, such as conductivity (e.g., ionic conductivity or electronic conductivity), based on the impedance data of each of the battery cells 11. The controller can also diagnose internal resistance, electrode reaction rate, degradation state, state of charge (SOC), internal short circuit, lithium plating, etc., based on the impedance data of each of the battery cells 11. Diagnosing the internal state of battery cells 11 based on impedance data is known in the field of EIS diagnostic technology. Therefore, its detailed description is omitted.

[0061] The controller 50 can detect abnormal battery cells among the battery cells 11 based on the diagnostic results of the internal state of each of the battery cells 11. For example, the controller 50 can detect that one of the battery cells 11 has an internal short circuit. In some embodiments, the controller 50 can detect that one of the battery cells 11 is abnormally degraded or has a high degree of degradedness.

[0062] When an abnormal battery cell is detected, the controller 50 can perform protective functions. For example, the controller 50 can stop the charging and discharging of the battery system 1 by blocking the electrical connection between the battery system 1 and an external device (e.g., a load, charger, or power system). The controller 50 can also send a notification signal indicating that an abnormal battery cell has been detected to a higher-level controller (not shown).

[0063] The controller 50 may include at least one processor for performing the functions of the controller 50 described above. The processor may refer to a data processing device such as a microprocessor, central processing unit (CPU), processor core, multiprocessor, application-specific integrated circuit (ASIC), or field-programmable gate array (FPGA) having physically structured circuitry to perform functions represented by code or commands included in a program. However, the processing device according to this disclosure is not limited to these examples.

[0064] Figure 2 This is a flowchart of a battery diagnostic method for a battery system 1 according to an embodiment of the present disclosure. Figure 2 The method can be found in the above reference. Figure 1 The controller 50 described is executed.

[0065] refer to Figure 2During the initial operation of battery system 1, in step S10, controller 50 can disable impedance detection device 30. That is, controller 50 can disable impedance detection device 30 by controlling AC signal generator 31 to stop outputting AC signals for EIS diagnostics, and controller 50 can control impedance detector 32 to stop impedance detection operation. If AC signal generator 31 outputs a blocking signal, the discharge function of discharge device 40 can be stopped by blocking the discharge path formed by discharge device 40.

[0066] Subsequently, in step S11, the controller 50 can use the temperature detector 20 to detect the temperature of the battery cells 11 included in the battery module 10. In step S12, the controller 50 can calculate the temperature deviation between the battery cells 11 based on the temperature of the battery cells detected in step S11. In step S13, the controller 50 can determine whether the temperature deviation calculated in step S12 is greater than or equal to a predetermined value. For example, the controller 50 can determine whether the temperature deviation between the battery cells 11 is 3°C or greater.

[0067] If the temperature deviation of the battery cell 11 is greater than or equal to a predetermined value, in step S14, the controller 50 can activate the impedance detection device 30 to obtain the impedance data of each of the battery cells 11. In step S14, the controller 50 can activate the drive of the impedance detection device 30 by causing the AC signal generator 31 to output an AC signal for EIS diagnostics. The controller 50 can control the impedance detector 32 to perform impedance detection operations. When the AC signal generator 31 outputs an AC signal, the discharge function of the discharge device 40 can be activated, causing an AC current signal to flow through the battery module 10.

[0068] The controller 50 can analyze the impedance data obtained in step S14 to diagnose the state of each of the battery cells 11 (S15). For example, the controller 50 can diagnose the conductivity (e.g., ionic conductivity or electronic conductivity), internal resistance, electrode reaction rate, degradation state, state of charge (SOC), internal short circuit, lithium plating, etc. of each of the battery cells 11 based on the impedance data of each of the battery cells 11. In step S16, the controller 50 can determine whether there are any abnormal battery cells among the battery cells 11 based on the diagnostic results in step S15.

[0069] If no abnormal battery cell is detected, in step S10, the controller 50 may again deactivate the impedance detection device 30. If at least one abnormal battery cell is detected, in step S17, the controller 50 may execute the protection function of the battery system 1. For example, the controller 50 may stop the charging and discharging of the battery system 1. The controller 50 may output a notification signal indicating that an abnormal battery cell has been detected to a higher-level controller (not shown).

[0070] Figure 2 An example is shown where the controller 50 controls the impedance detection device 30 to be inactive during the initial drive of the battery system 1. However, in other embodiments, the drive of the impedance detection device 30 can be deactivated without the control of the controller 50 during the initial drive of the battery system 1. In such an embodiment, the impedance detection device 30 can be configured to be automatically inactive during the initial drive and then switched to an active state by a control signal received from the controller 50.

[0071] According to the above embodiment, the battery diagnostic device can quickly detect when there is a high probability of an abnormal battery cell based on the temperature of the battery cell 11. When it is determined that there is a high probability of an abnormal battery cell (e.g., if the temperature deviation is higher than 3°C), the battery diagnostic device can activate the impedance detection device 30 to accurately diagnose the state of the battery cell 11. Therefore, the detection speed and accuracy of abnormal battery cells are improved.

[0072] According to the above embodiments, the battery diagnostic device can generate an AC current signal for EIS diagnostics by discharging the battery module 10 via the discharge device 40, instead of applying an AC current signal generated using a separate power supply to the battery module 10. If the impedance detection device 30 operates continuously, not only the power consumption of the impedance detection device 30 itself but also the power consumption due to the discharge of the discharge device 40 may occur continuously, potentially resulting in significant power loss in the battery system 1. However, as in the above embodiments, by disabling the impedance detection device 30 when the battery module 10 is in a normal state and activating the impedance detection device 30 only when there is a high probability of an abnormal battery cell, the power loss caused by EIS diagnostics can be significantly reduced.

[0073] The above embodiments can be implemented by the above-described apparatus and / or methods, and can also be implemented by a program that implements the functions corresponding to the configuration of each embodiment, or by a computer-readable recording medium on which the program is recorded. Based on the description of the above embodiments, those skilled in the art to which this disclosure pertains can readily implement such implementations. Computer-readable recording media can include all types of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, DVD-ROM, DVD-RAM, magnetic tape, floppy disk, hard disk, optical data storage devices, etc.

[0074] Although the present disclosure has been described above with reference to embodiments and accompanying drawings, the present disclosure is not limited thereto, and those skilled in the art can make various modifications and changes within the equivalent scope of the technical concept of the present disclosure.

[0075] <Explanation of Symbols>

[0076] 1: Battery System

[0077] 10: Battery Module

[0078] 11: Battery cell

[0079] 20: Temperature detector

[0080] 30: Impedance detection device

[0081] 31: AC signal generator

[0082] 32: Impedance detector

[0083] 40: Discharge device

[0084] 41: Switch

[0085] 42: Discharge load

[0086] 50: Controller

Claims

1. A battery diagnostic device, comprising: A temperature detector is configured to detect the temperature of individual battery cells; An impedance detection device is configured to generate an AC current signal flowing through the battery cell, detect an AC voltage signal corresponding to the AC current signal for each of the battery cells, and detect impedance data for each of the battery cells based on the AC current signal and the AC voltage signal. and The controller is configured to activate or deactivate the impedance detection device based on the temperature deviation of the battery cell, and when the impedance detection device is activated, to detect abnormal battery cells based on the impedance data.

2. The battery diagnostic device according to claim 1, wherein, The controller is configured to activate the impedance detection device if the temperature deviation is greater than or equal to a predetermined value.

3. The battery diagnostic device according to claim 2, wherein, The controller is configured to activate the impedance detection device if the temperature deviation is 3°C or greater.

4. The battery diagnostic device according to claim 2, wherein, The controller is configured to disable the impedance detection device if no abnormal battery cell is detected among the battery cells.

5. The battery diagnostic device according to claim 1 further includes a discharge device, the discharge device being configured to connect between the two ends of a battery module comprising a plurality of battery cells, and forming a discharge path through which the AC current signal flows. in, The impedance detection device is configured to control the current flow in the discharge path to generate the AC current signal.

6. The battery diagnostic device according to claim 5, wherein, The discharge device includes: A switch is configured to connect to a first terminal of the battery module; and A discharge load is configured to be connected between the switch and the second terminal of the battery module.

7. The battery diagnostic device according to claim 6, wherein, The impedance detection device includes: An AC signal generator is configured to generate an AC signal and output the AC signal to the discharge device; and An impedance detector is configured to detect the AC current signal and the AC voltage signal, generate impedance data based on the AC current signal and the AC voltage signal, and transmit the impedance data to the controller. The switching of the switch is controlled by the AC signal, and the AC current signal is generated according to the switching of the switch.

8. The battery diagnostic device according to claim 7, wherein, The AC signal generator is configured to sequentially change the frequency of the AC signal output to the discharge device, and the AC current signal has the same frequency as the AC signal.

9. The battery diagnostic device according to claim 7, wherein, The AC signal generator is configured to output the AC signal to the discharge device if the impedance detection device is activated, and the AC signal generator is configured to output a blocking signal to the discharge device if the impedance detection device is deactivated, and the switch is set to the off state when the discharge device receives the blocking signal.

10. The battery diagnostic device according to claim 7, wherein, The impedance detector is configured to generate and transmit the impedance data when the impedance detection device is activated, and the impedance detector is configured to stop generating and transmitting the impedance data when the impedance detection device is deactivated.

11. A battery system, comprising: A battery module consists of multiple individual battery cells; and The battery diagnostic device according to any one of claims 1-10.

12. A battery diagnostic method, comprising: Calculate the temperature deviation of individual battery cells; When the temperature deviation is greater than or equal to a predetermined value, the impedance detection device is activated to detect the impedance data of each of the battery cells using electrochemical impedance spectroscopy; and Abnormal battery cells are detected based on the impedance data.

13. The battery diagnostic method according to claim 12, further comprising: When no abnormal battery cell is detected in the battery cell, the impedance detection device is deactivated.

14. The battery diagnostic method according to claim 12, further comprising: When the abnormal battery cell is detected, the charging and discharging of the battery cell shall be stopped.

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