Apparatus for managing a busbar fastening state of a battery pack and a welding state between battery cells and method for inspecting the same

Abstract

This invention relates to a management device for detecting defects in the busbar fastening and cell-to-cell welding conditions of a battery pack using electrochemical impedance spectroscopy (EIS) technology. The device comprises: a current generation unit for applying a set alternating current to the battery pack; a voltage measurement unit for measuring the voltage generated at each battery cell or across the busbars by means of the current; an impedance calculation unit for calculating impedance using the measured current and voltage values; and a data output unit for generating a Nyquist plot or Bode plot based on the calculated impedance and outputting the impedance change.

Description

Technical Field

[0001] This invention relates to a battery pack management device and inspection method, and more specifically, to a battery pack management device and inspection method for early detection of faulty busbar connections and defective inter-cell welding using onboard electrochemical impedance spectroscopy (EIS) technology. Background Technology

[0002] In small devices, individual battery cells are arranged directly, while in vehicles and the like, battery modules in which multiple battery cells are electrically connected, and battery packs in which battery modules are further connected, are used. Battery modules are designed such that multiple battery cells are connected in series or parallel to output a voltage at or above a certain level, and battery packs are designed such that multiple battery modules are connected via connecting members such as busbars to provide higher output and capacity.

[0003] In such cases, the performance and stability of the battery module may deteriorate when multiple battery cells within the module are not properly connected due to poor assembly. Additionally, because the battery pack is used in high-vibration environments (e.g., in automobiles), the fastening screws of the busbars connecting the battery module may loosen due to vibration, potentially further degrading the battery pack's performance and stability.

[0004] Furthermore, if abnormal conditions such as faulty busbar connections or defective welding between battery cells are not detected beforehand, contact resistance at points such as busbars and cell connections may increase. This can lead to electrical sparks or degradation, potentially causing battery cell failure or fire, which could result in serious accidents. In fact, in recent years, fires have frequently occurred at busbar connections within battery packs, resulting in the complete combustion of electric vehicles.

[0005] To address this issue, inspections are conducted after the welding between battery cells and the overlapping laser welding of busbars between battery modules to ensure weld quality. Weld inspection is primarily performed through visual inspection to examine the weld's appearance, including its depth, width, and penetration. However, existing visual inspection techniques may only check the weld's appearance (including depth, width, and penetration), but the problem is that they may not detect anomalies caused by problems within the substrate material, such as the presence of gaps between substrate materials, insufficient depth, or excessive internal porosity.

[0006] Furthermore, methods using photodiodes or similar devices to detect reflected light / plasma during the welding process to identify abnormal conditions have been studied. However, this suffers from reduced reliability of pass / fail detection due to external noise factors such as temperature, static electricity, radio waves, component tolerances, and blowers. In other words, when narrowing the specification range to minimize the impact of external noise, over-detection often occurs, or actually good products are identified as defective, leading to a decrease in production line operating speed. Conversely, when expanding the specification range, defective products may be missed, resulting in a trade-off between reduced quality competitiveness and potential issues.

[0007] Due to these issues, in recent years, it has become possible to detect abnormal conditions in the battery pack (i.e., poor welding, incorrect bolt assembly, etc.) by measuring the voltage of each battery cell through the vehicle's in-vehicle battery management system (BMS) during driving. However, the problem is that when using a BMS to measure the voltage of a battery cell, it is very difficult to detect abnormal conditions using only voltage unless the cell is completely disconnected.

[0008] Examples of related technologies include the following existing technical documents.

[0009] (Patent Document 1) Korean Patent Publication No. 10-2023-0034520 (Published on March 10, 2023)

[0010] (Patent Document 2) Korean Patent Publication No. 10-2016-0123173 (Published on October 25, 2016) Summary of the Invention

[0011] Technical issues

[0012] The present invention aims to provide a management device and inspection method for battery packs, which uses on-board electrochemical impedance spectroscopy (EIS) technology to detect poor busbar connections and defective welding between battery cells at an early stage.

[0013] The present invention aims to provide a battery pack management device and inspection method, which is designed to prevent fire accidents by detecting abnormal conditions of the battery pack such as poor busbar connections and defective welding between battery cells at an early stage.

[0014] The present invention aims to provide a battery pack management device and inspection method for detecting abnormal conditions of the battery pack based on impedance changes, which are calculated using current and voltage values ​​measured at both ends of the battery pack connected by a busbar.

[0015] Technical solution

[0016] According to an exemplary embodiment, a battery pack management device includes: a measuring current generation unit configured to generate a measuring current as an alternating current (AC) having a set measuring frequency, and to apply the measuring current to a positive (+) output terminal and a negative (-) output terminal of the battery pack; a voltage measuring unit configured to measure the voltage generated at both ends of any battery cell or busbar among a plurality of battery cells in the battery pack by the measuring current applied to the (+) and (-) output terminals of the battery pack; an impedance calculation unit configured to calculate impedance using the measuring current value generated by the measuring current generation unit and the voltage value measured by the voltage measuring unit; and a data output unit configured to output the impedance change of the busbar or the impedance change of the battery cell in the battery pack based on the calculated impedance.

[0017] The current measurement generation unit can connect the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) to the battery cells located at both ends of the battery pack, and apply the generated measurement current to the battery cells.

[0018] The current generation unit can generate two or more AC currents with different measurement frequencies as measurement currents.

[0019] The signal amplitude for measuring current can be set to an amplitude signal of 5 mV to 10 mV.

[0020] The data output unit may also include a defect detection unit configured to detect poor contact of the busbars based on impedance changes within the battery pack, or to detect poor contact between battery cells based on impedance changes within the battery cells.

[0021] The voltage measurement unit can connect the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) to the two ends of any battery cell or the two ends of a busbar, and measure the voltage at the connected ends.

[0022] The impedance calculation unit can calculate impedance using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0023] When the measured voltage value is the voltage across the busbar, the impedance can be the busbar impedance calculated from the busbar, and when the measured voltage value is the voltage across any battery cell, it can be the battery cell impedance of that arbitrary battery cell.

[0024] The data output unit can display the real and imaginary parts of the impedance in a Nyquist plot and the impedance magnitude and phase angle relative to frequency in a Bode plot.

[0025] Impedance calculation unit and data output unit can be located in a signal processing unit (DSP) that is independent of the microcontroller unit (MCU) of the battery management device.

[0026] According to an exemplary embodiment, a method for inspecting a battery pack includes the following steps: generating an AC current with a set measurement frequency as a measurement current by a measurement current generation unit, and applying the measurement current to the (+) output terminal and (-) output terminal of the battery pack; measuring the voltage generated at both ends of any battery cell or busbar in the battery pack by the measurement current applied to the (+) output terminal and (-) output terminal of the battery pack by a voltage measurement unit; calculating the impedance by an impedance calculation unit using the generated current value and the measured voltage value; and outputting the impedance change of the busbar or the impedance change of the battery cell in the battery pack based on the calculated impedance by a data output unit.

[0027] The method may further include the following steps before applying the measuring current: applying current to the terminals by connecting the first current applying electrode ((-) Forcing) and the second current applying electrode ((+) Forcing) to the (+) output terminal and (-) output terminal of the battery pack, respectively; and connecting the voltage measuring electrode by connecting the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) to the two ends of any battery cell in the battery pack or to the two ends of the busbar, respectively.

[0028] In the step of connecting the voltage measuring electrodes, when checking for faulty busbar connections, the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) can be connected to both ends of the busbar respectively, and when detecting welding between defective battery cells, each of the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) can be connected to any battery cell among the multiple battery cells located in the battery pack.

[0029] Impedance can be calculated using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0030] The measured current can be from two or more ACs with different measurement frequencies.

[0031] The output impedance variation step also includes the following steps: analyzing the impedance variation using visualized Nyquist plots or Bode plots to assess the electrochemical characteristics and performance of the busbar or battery cell, and detecting abnormal conditions including poor busbar connections and defective welding between battery cells.

[0032] The Nyquist plot shows the real and imaginary parts of the impedance, while the Bode plot shows the magnitude of the impedance and the phase angle relative to the frequency.

[0033] Beneficial effects

[0034] According to embodiments of the present invention, fire accidents can be prevented by early detection of abnormal conditions in the battery pack, such as faulty busbar connections and defective welding between battery cells.

[0035] According to an embodiment of the present invention, by detecting impedance changes calculated from current and voltage values ​​measured at both ends of a battery pack connected via a busbar, the internal state of the battery pack can be diagnosed very quickly, thereby improving the performance and stability of the battery pack. Attached Figure Description

[0036] Figure 1 is a diagram showing the configuration of a management device for the state of busbar connection and welding between battery cells in a battery pack according to an embodiment of the present invention.

[0037] Figure 2 It is shown in detail Figure 1a and Figure 1b A diagram of the components of the management device.

[0038] Figure 3 This is a flowchart describing a method for inspecting the state of the welding between the busbar connection and the battery cell in a battery pack according to an embodiment of the present invention. Detailed Implementation

[0039] In the following, exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings. However, the invention is not limited to the exemplary embodiments disclosed below, but will be implemented in various different forms. Exemplary embodiments of the invention are provided only to allow the invention to be complete and to fully inform those skilled in the art of the scope of this disclosure. The drawings may be exaggerated to describe the disclosure in detail, and the same reference numerals denote the same elements in the drawings.

[0040] Figure 1a and Figure 1b This diagram illustrates the configuration of a management device for the state of the busbar connection and the welding between the battery cells in a battery pack, according to an embodiment of the present invention. In this case, Figure 1a The configuration for detecting faulty busbar connections is shown, and Figure 1b The configuration for detecting defective welding between battery cells is shown.

[0041] Reference Figure 1a and Figure 1b According to an embodiment of the present invention, the battery pack management device 100 detects abnormal conditions of the battery pack based on impedance changes, which are calculated using current and voltage values ​​measured in the battery pack 10, in which multiple battery modules 12 are connected via busbars 13.

[0042] In the battery pack 10, multiple battery cells 11 constitute a battery module 12, and a first battery module 12a and a second battery module 12b are connected via a busbar 13. In this case, as shown in the figures, the battery module 12 is composed of three battery cells 11 connected in series, but it is not limited to this and can be composed of three or more battery cells connected in series or in parallel, or three or fewer battery cells. Furthermore, when multiple busbars 13 are provided, two or more units corresponding to the number of busbars 13 can be used to arrange a pair of battery modules 12 connected to the busbars 13 in series or in parallel.

[0043] When required by the experiment, the battery cell 11 can be set to a specific state. For example, the battery cell 11 can be set to a charging or discharging state. In addition, when a reference electrode and auxiliary electrode are needed, the battery cell 11 can be installed in an appropriate position.

[0044] The management device 100 may be an electrochemical impedance spectroscopy (EIS) device.

[0045] The battery pack management device 100 connects the electrodes to the battery cell 11. The electrodes can be two electrodes (working electrode (RE) and counter electrode (CE)) or three electrodes (working electrode (RE), counter electrode (CE) and reference electrode (WE)).

[0046] The battery pack management device 100 connects current application electrodes (Forcing) to both ends of the battery cells 11 and voltage measurement electrodes (Sensing) to either end of any battery cell 11 or the busbar 13. Furthermore, by applying a measurement current (alternating current (AC)) to the battery cells 11 within a set measurement frequency range, the impedance of any battery cell 11 or busbar 13 is measured. The management device 100 can record the measured impedance data according to the set measurement frequency and output the data as a Nyquist plot or Bode plot for visualization. As an example, the frequency range is set from 1 mHz to 1 MHz, and the signal amplitude is set to a small signal from 5 mV to 10 mV. Additionally, the measurement potential is set to match the potential of the battery cells 11.

[0047] The battery pack management device 100 can analyze the impedance changes of the busbar 13 or battery cell 11 based on the measured impedance by outputting a Nyquist plot or Bode plot, and evaluate the internal resistance, ion mobility, interface characteristics, etc. of the battery pack 10. In this case, the Nyquist plot can show the real and imaginary parts of the impedance, and the Bode plot can show the magnitude of the impedance and the phase angle relative to the frequency, which can be used to interpret the electrochemical characteristics of the battery pack 10.

[0048] like Figure 1a As shown, the battery pack management device 100 connects the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) to the battery cells 11 located at both ends, and connects the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) to both ends of the busbar 13, in order to detect poor connections of the busbar 13.

[0049] The battery pack management device 100 applies a measuring current (AC) to the battery cell 11 within a set frequency range via a current application electrode (Forcing), and measures the voltage generated across the busbar 13 by the applied measuring current via a voltage measurement electrode (Sensing). In this case, the applied current is stored. Additionally, the management device 100 uses data related to the measured voltage and current to calculate impedance. In this case, the impedance is the value measured at the R1 portion of the busbar 13, and is calculated by measuring the voltage change caused by the current flowing through the entire battery pack 10, using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0050] The battery pack management device 100 can analyze the impedance of the busbar 13 relative to the frequency based on the calculated impedance, and in this way, the electrochemical characteristics and performance of the busbar 13 can be evaluated, thereby detecting poor connections of the busbar 13.

[0051] In addition, such as Figure 1bAs shown, the battery pack management device 100 connects a first current application electrode ((-) Forcing) and a second current application electrode ((+) Forcing) to the battery cells 11 located at both ends, and connects a first voltage measurement electrode ((-) Sensing) and a second voltage measurement electrode ((+) Sensing) to both ends of any one of the multiple battery cells 11 located inside the battery pack 10, to detect defective welds between the battery cells 11. In this case, any battery cell 11 connected to the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) can be a battery cell 11 selected to detect defective welds.

[0052] The battery pack management device 100 applies a measuring current (AC) to the battery cell 11 within a set frequency range via a current application electrode (Forcing), and measures the voltage generated across the terminals of the battery cell 11 by the applied measuring current via a voltage measurement electrode (Sensing). The measured voltage is a voltage that reflects the response to the applied measuring current. In this case, the applied current is stored.

[0053] Additionally, the battery pack management device 100 uses data related to the measured voltage and current to calculate the impedance. In this case, the impedance is calculated using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0054] The battery pack management device 100 can analyze the impedance variation of the battery cell 11 with respect to frequency based on the calculated impedance. In this case, in the low-frequency range (from about 0.1 Hz or less to a few Hz (e.g., 0.1 Hz to 10 Hz)), the overall resistance and capacitance components of the battery cell 11 can be measured primarily, and in the high-frequency range (a few kHz or greater (e.g., 1 kHz to 1 MHz)), the double-layer effect and intrinsic resistance within the battery cell 11 can be measured primarily. Additionally, in the mid-frequency range (e.g., 10 Hz to 1 kHz), the charge transfer resistance and medium-rate electrochemical reactions of the battery cell 11 can be measured.

[0055] In this way, the electrochemical characteristics and performance of the battery cell 11 can be evaluated, and defective welds between the battery cells 11 can be detected.

[0056] Figure 2 It is shown in detail Figure 1a and Figure 1b A diagram of the components of the management device.

[0057] Reference Figure 2According to an embodiment of the present invention, the battery pack management device 100 includes a current generation unit 110, a voltage measurement unit 120, an impedance calculation unit 130, and a data output unit 140.

[0058] The measuring current generation unit 110 generates a measuring current, which is an AC current with a predetermined measuring frequency, and applies the AC current to the (+) output terminal and (-) output terminal of the battery pack 10. For this purpose, the measuring current generation unit 110 connects the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) to the battery cells 11 located at both ends of the battery pack 10, respectively, and applies the generated measuring current to the battery cells 11.

[0059] For the measurement frequency, the frequency range is set from 1 mHz to 1 MHz, and the signal amplitude is set to a small amplitude signal from 5 mV to 10 mV. Additionally, the measurement potential is set to match the potential of the battery cell 11. In this case, the measurement frequency can be divided into a low-frequency range with a frequency range from approximately 0.1 Hz or less to several Hz (e.g., 0.1 Hz to 10 Hz), a high-frequency range with a frequency range of several kHz or greater (e.g., 1 kHz to 1 MHz), and a mid-frequency range with a frequency range from several Hz to several kHz (e.g., 10 Hz to 1 kHz).

[0060] In the low-frequency range, the overall resistance and capacitance components of battery pack 10 can be measured. The impedance at low frequencies is related to the electrochemical reactions, charge / discharge processes, and diffusion processes within battery pack 10. Therefore, the low-frequency range is useful when analyzing the overall electrochemical characteristics of battery pack 10. In the high-frequency range, the double-layer effect and intrinsic resistance within battery cell 11 can be primarily measured. The impedance at high frequencies is mainly related to the double-layer capacitance and internal resistance at the electrode-electrolyte interface of battery cell 11. Therefore, the high-frequency range is useful when analyzing the internal resistance and fast response characteristics of battery cell 11. Furthermore, in the mid-frequency range, the charge transfer resistance and medium-rate electrochemical reactions of battery cell 11 can be analyzed.

[0061] These frequency ranges may vary slightly depending on the type and condition of the battery pack 10, and the frequency range for setting the measurement frequency is appropriately set according to the characteristics to be measured or the abnormal condition of the battery pack 10 (i.e., poor busbar connection, defective welding between battery cells, etc.).

[0062] The voltage measurement unit 120 measures the voltage generated at both ends of any one of the battery cells 11 or at both ends of the busbar 13 among the plurality of battery cells in the battery pack 10 by a measurement current applied to the (+) and (-) output terminals of the battery pack 10. For this purpose, the voltage measurement unit 120 connects a first voltage measurement electrode ((-) Sensing) and a second voltage measurement electrode ((+) Sensing) to both ends of any one of the battery cells 11 or to both ends of the busbar 13, and measures the voltage at the connected terminals or ends.

[0063] In other words, such as Figure 1a As shown, the voltage measurement unit 120 connects the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) to the two ends of the busbar 13 respectively, and measures the voltage across the busbar 13. Alternatively, as... Figure 1b As shown, the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) are respectively connected to the two ends of any battery cell 11, and the voltage at the two ends of the battery cell 11 is measured.

[0064] The impedance calculation unit 130 uses the current value generated by the current generation unit 110 and the voltage value measured by the voltage measurement unit 120 to calculate the impedance. In this case, the impedance is calculated using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0065] In this case, when the measured voltage value is the voltage across the two ends of the busbar 13, the impedance calculated by the impedance calculation unit 130 is the value measured at the R1 portion of the busbar 13, and is the impedance of the busbar 13. Furthermore, when the measured voltage value is the voltage across the two ends of any battery cell 11, the impedance calculated by the impedance calculation unit 130 is the value measured on any battery cell 11, and is the impedance of the battery cell 11.

[0066] The data output unit 140 generates a Nyquist plot or Bode plot based on the calculated impedance and outputs the impedance change of the busbar 13 or the battery cell 11 within the battery pack 10. In this way, the impedance change is analyzed, and the electrochemical characteristics and performance of the busbar 13 or battery cell 11 are evaluated, thereby detecting abnormal conditions such as poor busbar connections and defective inter-cell welding. In this case, the Nyquist plot can show the real and imaginary parts of the impedance, and the Bode plot can show the impedance magnitude and phase angle relative to frequency, through which the electrochemical characteristics of the battery pack 10 can be interpreted.

[0067] As described above, the impedance changes of the busbar 13 or battery cell 11 can be analyzed based on the measured impedance by outputting a Nyquist plot or Bode plot, and the internal resistance, ion mobility, interface characteristics, etc. of the battery pack 10 can be evaluated, thereby detecting abnormal states of the battery pack 10 (that is, poor busbar connection, defective welding between battery cells, etc.).

[0068] Therefore, the data output unit 140 may further include a defect detection unit (not shown) that detects poor contact of the busbar 13 or poor contact between the battery cells 11 based on impedance changes in the busbar 13 or battery cells 11 within the battery pack 10. During EIS measurement, when a value different from the impedance corresponding to each cell is measured for a cell, or a value different from the normal impedance of the busbar is detected, the defect detection unit detects poor contact of the busbar, poor contact of the battery cells, or poor contact between the battery cells.

[0069] In this case, the battery pack management device 100 can detect the impedance change of the busbar 13 or the battery cell 11 in the battery pack 10, so as to perform early detection in case of abnormal conditions (such as poor busbar connection, defective welding between battery cells, etc.).

[0070] Furthermore, the data output unit 140 can change the characteristics obtained through impedance analysis according to the frequency range of the measurement frequency set for generating the measurement current.

[0071] In other words, the data output unit 140 can primarily measure the overall resistance and capacitance components of the battery pack 10 in the low-frequency region (e.g., 0.1 Hz to 10 Hz). The impedance at low frequencies is related to the electrochemical reactions, charge / discharge processes, and diffusion processes within the battery pack 10. Therefore, the low-frequency region is useful when analyzing the overall electrochemical characteristics of the battery pack 10. Additionally, the data output unit 140 can primarily measure the double-layer effect and intrinsic resistance within the battery cell 11 in the high-frequency region (e.g., 1 kHz to 1 MHz). The impedance at high frequencies is primarily related to the double-layer capacitance and internal resistance at the electrode-electrolyte interface of the battery cell 11. Therefore, the high-frequency region is useful when analyzing the internal resistance and fast response characteristics of the battery cell 11. Furthermore, the data output unit 140 can analyze the charge transfer resistance and medium-rate electrochemical reactions of the battery cell 11 in the mid-frequency region (e.g., 10 Hz to 1 kHz).

[0072] The following describes a method for inspecting the state of the welding between the busbar connection and the battery cell in a battery pack according to an embodiment of the present invention. The method for inspecting the state of the welding between the busbar connection and the battery cell in a battery pack according to an embodiment of the present invention can be a method for processing signals received using the aforementioned management device for the state of the welding between the busbar connection and the battery cell in a battery pack. Therefore, the content described in the management device for the state of the welding between the busbar connection and the battery cell in a battery pack is equally applicable here, and therefore, its repeated description can be omitted.

[0073] Figure 3 This is a flowchart describing a method for inspecting the state of the welding between the busbar connection and the battery cell in a battery pack according to an embodiment of the present invention.

[0074] Reference Figure 3 In the method for inspecting a battery pack according to an embodiment of the present invention, firstly, a first current application electrode ((-) Forcing) and a second current application electrode ((+) Forcing) are respectively connected to the (+) output terminal and (-) output terminal of the battery pack 10, and a first voltage measurement electrode ((-) Sensing) and a second voltage measurement electrode ((+) Sensing) are respectively connected to the two ends of any one of the plurality of battery cells 11 in the battery pack 10 or to the two ends of the bus bar 13 (S10).

[0075] In this case, when inspecting for poor connections in the busbar 13, the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) are respectively connected to both ends of the busbar 13, and when inspecting for defective welding between battery cells 11, each of the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) is connected to any battery cell 11 located within the battery pack 10.

[0076] Subsequently, in the measurement current generation unit 110, a measurement current with a preset measurement frequency is generated, and the measurement current is applied to the (+) output terminal and (-) output terminal of the battery pack 10 through the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) (S20).

[0077] In this configuration, the measurement frequency is set to a range of 1 mHz to 1 MHz, and the signal amplitude is set to a small amplitude signal ranging from 5 mV to 10 mV. Additionally, the measurement potential is set to match the potential of the battery cell 11. These frequency ranges may vary slightly depending on the type and condition of the battery pack 10, and the frequency range for setting the measurement frequency can be appropriately determined based on the characteristics to be measured or any abnormal conditions of the battery pack 10 (i.e., poor busbar connections, defective welding between battery cells, etc.).

[0078] Subsequently, in the voltage measurement unit 120, the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) are used to measure the voltage generated at both ends of any battery cell 11 among the plurality of battery cells in the battery pack 10 or at both ends of the busbar 13 by the measurement current applied to the (+) output terminal and (-) output terminal of the battery pack 10 (S30).

[0079] In this case, the voltage measurement unit 120 measures the voltage of the busbar 13 when checking for poor connections, and measures the voltage of the battery cell 11 when detecting defective welds between the battery cells 11.

[0080] Subsequently, in the impedance calculation unit 130, the generated current value and the measured voltage value are used to calculate the impedance (S40).

[0081] In this case, when the measured voltage value is the voltage of busbar 13, the value measured at the R1 portion of busbar 13 is the impedance of busbar 13, and when the measured voltage value is the voltage of battery cell 11, the value measured at any battery cell 11 is the impedance of battery cell 11. The impedance can be calculated using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

[0082] Subsequently, in the data output unit 140, a Nyquist plot or Bode plot is generated based on the calculated impedance, thereby visualizing the impedance changes of the busbar 13 or battery cell 11 within the battery pack 10 (S50).

[0083] In this way, impedance changes are analyzed and the electrochemical characteristics and performance of busbar 13 or battery cell 11 are evaluated, thereby detecting abnormal conditions such as poor busbar connections and defective welding between battery cells.

[0084] Furthermore, the battery pack management device 100 constructed in the BMS can detect impedance changes of the busbar 13 or battery cell 11 within the battery pack 10, enabling early detection in abnormal conditions such as poor busbar connections or defective welding between battery cells.

[0085] In the foregoing, while specific terminology has been used to describe and illustrate preferred embodiments of the invention, these terms are for the purpose of clearly describing the invention only, and it will be apparent that various modifications and changes can be made to the exemplary embodiments of the invention and the described terminology without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. These modified embodiments should not be construed as departing from the spirit and scope of the invention, but should be interpreted as falling within the scope of the claims of the invention.

[0086] The names of the symbols used in the detailed description of the invention and the accompanying drawings are as follows.

[0087] 10: Battery pack 11: Battery cells

[0088] 12: Battery module 13: Busbar

[0089] 100: Battery pack management device; 110: Current generation unit.

[0090] 120: Voltage measurement unit; 130: Impedance calculation unit

[0091] 140: Data Output Unit

Claims

1. A battery management device, the management device comprising: A current generation unit is configured to generate a measurement current as an alternating current (AC) with a set measurement frequency, and to apply the measurement current to the positive and negative output terminals of the battery pack. A voltage measurement unit configured to measure the voltage generated at both ends of any one of the battery cells or at both ends of a busbar among a plurality of battery cells in the battery pack by the measurement current applied to the positive output terminal and the negative output terminal of the battery pack; An impedance calculation unit is configured to calculate impedance using a measured current value generated by the measured current generation unit and a voltage value measured by the voltage measurement unit. as well as A data output unit is configured to output the impedance change of the busbar in the battery pack or the impedance change between the battery cells based on the calculated impedance.

2. The management device according to claim 1, wherein, The current measurement generation unit connects the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) to the battery cells located at both ends of the battery pack, and applies the generated measurement current to the battery cells.

3. The management device according to claim 1 or 2, wherein, The measuring current generation unit generates two or more AC currents with different measuring frequencies as the measuring current.

4. The management device according to claim 3, wherein, The amplitude of the measured current signal is set to an amplitude signal of 5 mV to 10 mV.

5. The management device according to claim 3, wherein, The data output unit further includes a defect detection unit, which is configured to detect poor contact of the busbar or poor contact between the battery cells based on impedance changes between the busbars or the battery cells within the battery pack.

6. The management device according to claim 1, wherein, The voltage measurement unit connects the first voltage measurement electrode (-) Sensing and the second voltage measurement electrode (+) Sensing to the two ends of any battery cell or the two ends of the busbar, and measures the voltage at the connected ends.

7. The management device according to claim 1, wherein, The impedance calculation unit uses the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage, to calculate the impedance.

8. The management device according to claim 1, wherein, The impedance calculated in the impedance calculation unit is the busbar impedance calculated from the busbar when the measured voltage value is the voltage across the two ends of the busbar, and is the battery cell impedance of any battery cell when the measured voltage value is the voltage across the two ends of any battery cell.

9. The management device according to claim 1, wherein, The data output unit analyzes the electrochemical characteristics of the battery pack by using the real and imaginary parts of the impedance shown in the Nyquist plot and the impedance magnitude and phase angle relative to frequency shown in the Bode plot.

10. The management device according to claim 1, wherein, The impedance calculation unit and the data output unit are located in a signal processing unit (DSP) that is independent of the microcontroller unit (MCU) of the battery management device.

11. A method for inspecting a battery pack, the method comprising the following steps: An alternating current (AC) with a set measurement frequency is generated by a measurement current generation unit as a measurement current, and the measurement current is applied to the positive output terminal and the negative output terminal of the battery pack. The voltage generated at both ends of any battery cell or busbar among a plurality of battery cells in the battery pack is measured by the voltage measuring unit through the measuring current applied to the positive output terminal and the negative output terminal of the battery pack; The impedance calculation unit uses the generated current value and the measured voltage value to calculate the impedance; as well as The data output unit outputs the impedance change of the busbar in the battery pack or the impedance change between the battery cells based on the calculated impedance.

12. The method of claim 11, further comprising the step of applying the measuring current before: The step of connecting the first current application electrode ((-) Forcing) and the second current application electrode ((+) Forcing) to the positive output terminal and the negative output terminal of the battery pack, respectively; as well as The voltage measurement electrode connection step involves connecting the first voltage measurement electrode ((-) Sensing) and the second voltage measurement electrode ((+) Sensing) to the two ends of any battery cell in the battery pack or to the two ends of the busbar, respectively.

13. The method according to claim 12, wherein, In the step of connecting the voltage measuring electrodes, if a faulty busbar connection is detected, the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) are respectively connected to both ends of the busbar. If defective battery cell welding is detected, each of the first voltage measuring electrode ((-) Sensing) and the second voltage measuring electrode ((+) Sensing) is connected to any battery cell located in the battery pack.

14. The method according to claim 11, wherein, The impedance is calculated using the phase difference and magnitude between the measured current and the measured voltage, or the ratio between the measured current and the measured voltage.

15. The method according to claim 11 or 14, wherein, The measuring current is two or more ACs with different measuring frequencies.

16. The method according to claim 11, wherein, The step of outputting the impedance change further includes the following steps: analyzing the impedance change by visualizing the Nyquist plot or Bode plot to evaluate the electrochemical characteristics and performance of the busbar or the battery cell, and detecting abnormal conditions including poor busbar connections and defective welding between battery cells.

17. The method according to claim 16, wherein, The real and imaginary parts of the impedance are shown in the Nyquist plot, and the magnitude of the impedance and the phase angle relative to the frequency are shown in the Bode plot.

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