Apparatus for managing busbar fastening state of battery pack and welding state between battery cells, and method for inspecting busbar fastening state of battery pack and welding state between battery cells

Abstract

The present invention relates to a management apparatus for detecting defects in a busbar fastening state and an inter-cell welding state of a battery pack by using an electrochemical impedance spectroscopy (EIS) technique. The apparatus of the present invention comprises: a measurement current generation unit for applying a set alternating current to a battery pack; a voltage measurement unit for measuring a voltage generated across each battery cell or across both ends of a busbar by means of the current; an impedance calculation unit for calculating impedance by using the measured current and voltage values; and a data output unit for generating a Nyquist or Bode plot on the basis of the calculated impedance, and outputting an impedance variation.

Description

Battery pack busbar connection and battery cell welding condition management device and inspection method

[0001] The present 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 busbar fastening and welding defects between battery cells using in-vehicle electrochemical impedance spectroscopy (EIS) technology.

[0002]

[0003] In small devices, individual battery cells are directly placed, whereas in automobiles and the like, battery modules consisting of multiple electrically connected battery cells, and battery packs formed by connecting these modules, are utilized. Battery modules are designed to output a voltage above a certain level by connecting multiple battery cells in series or parallel, while battery packs are designed to provide higher output and capacity by connecting multiple battery modules via connecting components such as busbars.

[0004] In this case, if multiple battery cells within the battery module are not properly connected due to assembly defects, the performance and stability of the battery module may be degraded. Additionally, since battery packs are used in environments with severe vibration, such as automobiles, vibrations can cause the fastening screws of the busbars connecting the battery modules to loosen, thereby degrading the performance and stability of the battery pack.

[0005] Furthermore, if abnormal conditions such as faulty busbar connections or welding defects between battery cells are not detected early, contact resistance may increase at the busbars or cell connections, leading to electrical sparks or degradation. This can result in battery cell failure and fire, potentially leading to a major accident. In fact, there have recently been frequent incidents where electric vehicles have been completely destroyed by fire caused by ignition at the busbar connections within battery packs.

[0006] To address these issues, quality assurance inspections are conducted after welding between battery cells and overlapping laser welding of busbars between battery modules. Welding inspections are primarily performed via visual and vision inspections to check the external appearance, such as the depth, width, and penetration of the weld bead. However, conventional visual and vision inspections can only confirm the external appearance of the weld bead's depth, width, and penetration, but they have the problem of being unable to detect abnormal conditions caused by internal issues within the base material, such as gaps between base materials, insufficient depth, or excessive internal porosity.

[0007] Meanwhile, methods for detecting abnormal conditions during the welding process using reflected light / plasma via photodiodes have been considered; however, this method has the problem of reduced reliability in detecting good / bad products due to significant influence from external noise such as temperature, static electricity, electromagnetic waves, component tolerances, and air blowers. In other words, there is a trade-off issue where narrowing the spec range to minimize the influence of external noise leads to frequent over-detection or cases where actual good products are judged as defective, causing a decrease in production line utilization; conversely, widening the spec range may result in the leakage of defective products, leading to a decline in quality competitiveness.

[0008] Due to these issues, recent advancements have enabled the measurement of each battery cell's voltage via a Battery Management System (BMS) both inside the vehicle and while driving, allowing for the detection of abnormal battery pack conditions (i.e., welding defects, incorrect bolt installation, etc.). However, measuring battery cell voltage in a BMS presents a significant challenge: it is very difficult to detect abnormal conditions based solely on voltage when the cells are not in a fully open state.

[0009] Regarding the prior art, the following prior art documents exist.

[0010] (Patent Document 1) Korean Published Patent Application No. 10-2023-0034520 (Published Mar. 10, 2023)

[0011] (Patent Document 2) Korean Published Patent Application No. 10-2016-0123173 (Published Oct. 25, 2016)

[0012]

[0013] The present invention aims to provide a battery pack management device and inspection method for detecting busbar fastening and welding defects between battery cells using in-vehicle electrochemical impedance spectroscopy (EIS) technology.

[0014] The present invention aims to provide a battery pack management device and inspection method that prevent fire accidents by early detection of abnormal conditions in the battery pack, such as busbar connection defects and welding defects between battery cells.

[0015] The present invention aims to provide a battery pack management device and inspection method for detecting abnormal conditions of a battery pack based on impedance changes calculated using current and voltage values ​​measured at both ends of a battery pack connected by a busbar.

[0016]

[0017] A battery pack busbar connection and battery cell inter-welding state management device according to an embodiment of the present invention comprises, in a battery management device, a measurement current generating unit that generates a measurement current, which is an alternating current having a set measurement frequency, and applies it to a (+) output terminal and a (-) output terminal of the battery pack; a voltage measuring unit that measures a voltage generated at either end of any battery cell or busbar among a plurality of battery cells in the battery pack by the measurement current applied to the (+) output terminal and the (-) output terminal of the battery pack; an impedance calculating unit that calculates an impedance using a measurement current value generated by the measurement current generating unit and a voltage value measured by the voltage measuring unit; and a data output unit that outputs a change in impedance between a busbar or each battery cell in the battery pack based on the calculated impedance.

[0018] The above measurement current generating unit connects the first current application electrode ((-)Forcing) and the second current application electrode ((+)Forcing) to battery cells located at both ends of the battery pack, respectively, and applies the generated measurement current to the battery cells.

[0019] The above-mentioned measurement current generation unit generates two or more alternating currents having different measurement frequencies as measurement currents.

[0020] The above-mentioned measured current sets its signal amplitude to an amplitude signal of 5 mV to 10 mV.

[0021] The above data output unit further includes a defect detection unit that detects a busbar contact failure or a battery cell contact failure from a change in impedance between the busbar or between each battery cell within the battery pack.

[0022] The above voltage measuring unit connects a first voltage measuring electrode ((-)Sensing) and a second voltage measuring electrode ((+)Sensing) to both ends of any battery cell or both ends of the busbar, respectively, and measures the voltage at both ends of the connected terminals.

[0023] The above impedance calculation unit calculates the 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.

[0024] The above impedance calculation unit is characterized in that, when the measured voltage value is a voltage applied across the ends of the busbar, it is a busbar impedance calculated from the busbar, and when the measured voltage value is a voltage applied across the ends of any battery cell, it is a battery cell impedance calculated from any battery cell.

[0025] The above data output unit displays the real and imaginary impedances in the Nyquist plot and displays the impedance magnitude and phase angle according to frequency in the Bode plot.

[0026] The above impedance calculation unit and data output unit are configured in a signal processing unit (DSP) separate from the MCU (Micro-Controller Unit) of the battery management device.

[0027] A method for inspecting the busbar connection and welding status between battery cells of a battery pack according to an embodiment of the present invention comprises: a step of generating an alternating current having a set measurement frequency as a measurement current in a measurement current generation unit and applying the measurement current to a (+) output terminal and a (-) output terminal of the battery pack; a step of measuring the voltage at both ends of any battery cell or busbar within the battery pack by means of the measurement current applied to the (+) output terminal and the (-) output terminal of the battery pack in a voltage measurement unit; a step of calculating an impedance using the generated current value and the measured voltage value in an impedance calculation unit; and a step of outputting a change in impedance between the busbar or each battery cell within the battery pack based on the calculated impedance in a data output unit.

[0028] Prior to the step of applying the measurement current, the method further includes a current application electrode step of connecting a first current application electrode ((-)Forcing) and a second current application electrode ((+)Forcing) to the (+) output terminal and the (-) output terminal, respectively, of the battery pack, and a voltage measurement electrode connection step of connecting a first voltage measurement electrode ((-)Sensing) and a second voltage measurement electrode ((+)Sensing) to both ends of any battery cell or busbar within the battery pack, respectively.

[0029] The above voltage measuring electrode connection step involves connecting the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) to each end of the busbar, respectively, when inspecting for fault detection of the busbar connection, and connecting the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) to any battery cell among a plurality of battery cells located inside the battery pack, respectively, when detecting faulty welding between battery cells.

[0030] The above 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.

[0031] The above-mentioned measured current is two or more alternating currents having different measurement frequencies.

[0032] The step of outputting the impedance change further includes the step of analyzing the impedance change through a visualized Nyquist or Bode plot to evaluate the electrochemical characteristics and performance of the busbar or the battery cell, and detecting abnormal conditions including busbar connection and welding defects between battery cells.

[0033] The real and imaginary impedances are displayed in the Nyquist plot above, and the impedance magnitude and phase angle according to frequency are displayed in the Bode plot above.

[0034]

[0035] According to an embodiment of the present invention, abnormal conditions of a battery pack, such as busbar connection failures and welding defects between battery cells, can be detected early to prevent ignition accidents.

[0036] The present invention can provide performance and stability of a battery pack by detecting changes in impedance calculated using current and voltage values ​​measured at both ends of a battery pack connected by a busbar, thereby enabling very rapid diagnosis of the internal state of the battery pack.

[0037]

[0038] FIG. 1 is a diagram showing the configuration of a busbar connection and battery cell welding status management device of a battery pack according to an embodiment of the present invention.

[0039] Figure 2 is a detailed diagram showing the configuration of the management device in Figures 1a and 1b.

[0040] FIG. 3 is a flowchart illustrating a method for inspecting the busbar connection and welding status between battery cells of a battery pack according to an embodiment of the present invention.

[0041]

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and the embodiments of the present invention are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. To explain the invention in detail, the drawings may be exaggerated, and like reference numerals in the drawings refer to like elements.

[0043] FIGS. 1A and 1B are diagrams showing the configuration of a busbar connection and battery cell welding status management device for a battery pack according to an embodiment of the present invention. In this case, FIG. 1A is a configuration for detecting busbar connection defects, and FIG. 1B is a configuration for detecting welding defects between battery cells.

[0044] Referring to FIG. 1a and FIG. 1b, a battery pack management device (100) according to an embodiment of the present invention detects an abnormal condition of the battery pack based on an impedance change calculated using current and voltage values ​​measured in a battery pack (10) in which a plurality of battery modules (12) are connected by a bus bar (13).

[0045] A battery pack (10) comprises a plurality of battery cells (11) as one battery module (12) and connects the first battery module (12a) and the second battery module (12b) with a bus bar (13). In the drawing, the battery module (12) is configured with three battery cells (11) connected in series, but it is not limited thereto, and the number of battery cells (11) can be three or more, or three or fewer, configured in series or in parallel. Also, when the bus bar (13) is configured with multiple units, a pair of battery modules (12) connected thereto can be configured in series or in parallel with two or more units corresponding to the number of bus bars (13).

[0046] The battery cell (11) can be set to a specific state if necessary for the experiment. For example, it can be set to a charging or discharging state. Additionally, the battery cell (11) can be installed in appropriate locations if a reference electrode and an auxiliary electrode are required.

[0047] The management device (100) may be an electrochemical impedance spectroscopy (EIS) device.

[0048] The battery pack management device (100) connects the electrodes to the battery cell (11). The electrodes may use two electrodes, an operating electrode (RE) and a counter electrode (CE), or three electrodes, an operating electrode (RE), a counter electrode (CE), and a reference electrode (WE).

[0049] A battery pack management device (100) connects current application electrodes (Forcing) to both ends of a battery cell (11) and voltage measurement electrodes (Sensing) to both ends of any battery cell (11) or busbar (13). Then, a measurement current, which is an alternating current, is applied to the battery cell (11) within a frequency range of a set measurement frequency to measure the impedance of any battery cell (11) or busbar (13). The management device (100) records the measured impedance data according to the set measurement frequency and can visualize it by outputting it as a Nyquist or Bode plot. For example, the frequency range is set from 1 mHz to 1 MHz, and the signal amplitude is set to a small signal of 5 mV to 10 mV. The measurement potential is set to match the potential of the battery cell (11).

[0050] The battery pack management device (100) can evaluate the internal resistance, ion mobility, interface characteristics, etc. of the battery pack (10) by analyzing the change in impedance of the busbar (13) or battery cell (11) based on the measured impedance through the output Nyquist or Bode plot. At this time, the Nyquist plot displays the real and imaginary impedances, and the Bode plot displays the magnitude of the impedance and the phase angle according to frequency, thereby allowing the electrochemical characteristics of the battery pack (10) to be interpreted.

[0051] As illustrated in FIG. 1a, the battery pack management device (100) connects a first current application electrode ((-)Forcing) and a second current application electrode ((+)Forcing) to each of the battery cells (11) located at both ends to detect a fault in connection of the bus bar (13), and connects a first voltage measurement electrode ((-)Sensing) and a second voltage measurement electrode ((+)Sensing) to each of the ends of the bus bar (13).

[0052] The battery pack management device (100) applies a measurement current, which is an alternating current, to the battery cell (11) within a set frequency range through a current application electrode (Forcing), and measures the voltage generated at both ends of the bus bar (13) by the applied measurement current through a voltage measurement electrode (Sensing). At this time, the applied current is stored. Then, the management device (100) calculates the impedance using the measured voltage and current data. At this time, the impedance is a value measured at the R1 portion of the bus bar (13), and is calculated by measuring the voltage change caused by the current passing 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.

[0053] The battery pack management device (100) can analyze the change in impedance of the bus bar (13) according to frequency based on the calculated impedance, and through this, can evaluate the electrochemical characteristics and performance of the bus bar (13) and detect a faulty connection of the bus bar (13).

[0054] Additionally, as illustrated in FIG. 1b, 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, respectively, to detect welding defects between battery cells (11), and connects a first voltage measurement electrode ((-)Sensing) and a second voltage measurement electrode ((+)Sensing) to the ends of any battery cell (11) among a plurality of battery cells located inside the battery pack (10), respectively. At this time, any battery cell (11) connected to the first voltage measurement electrode ((-)Sensing) and the second voltage measurement electrode ((+)Sensing) may be a battery cell (11) selected to detect welding defects.

[0055] The battery pack management device (100) applies a measurement current, which is an alternating current, to the battery cell (11) within a set frequency range through a current application electrode (Forcing), and measures the voltage generated at both ends of the battery cell (11) by the applied measurement current through a voltage measurement electrode (Sensing). The voltage measured at this time is a voltage that appears as a reaction to the applied measurement current. At this time, the applied current is stored.

[0056] And the battery pack management device (100) calculates the impedance using the measured voltage and current data. At this time, 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.

[0057] The battery pack management device (100) can analyze the impedance change of the battery cell (11) according to frequency based on the calculated impedance. At this time, in the low frequency range (from about 0.1 Hz or less to several Hz (e.g., 0.1 Hz to 10 Hz)), the total resistance and capacitance components of the battery cell (11) can be measured mainly, and in the high frequency range (above several kHz (e.g., 1 kHz to 1 MHz)), the electric double layer effect and the intrinsic resistance inside the battery cell (11) can be measured mainly. In addition, in the intermediate frequency range (e.g., 10 Hz to 1 kHz), the charge transfer resistance of the battery cell (11) and the electrochemical reaction of an intermediate rate can be measured.

[0058] Through this, the electrochemical characteristics and performance of the battery cells (11) can be evaluated, and welding defects between the battery cells (11) can be detected.

[0059]

[0060] Figure 2 is a detailed diagram showing the configuration of the management device in Figures 1a and 1b.

[0061] Referring to FIG. 2, a battery pack management device (100) according to an embodiment of the present invention includes a measurement current generation unit (110), a voltage measurement unit (120), an impedance calculation unit (130), and a data output unit (140).

[0062] The measurement current generating unit (110) generates a measurement current, which is an alternating current having a predetermined set measurement frequency, and applies it to the (+) output terminal and the (-) output terminal of the battery pack (10). To this end, the measurement current generating 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 measurement current to the battery cells (11).

[0063] In the case of 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 of 5 mV to 10 mV. The measurement potential is set to match the potential of the battery cell (11). At this time, the measurement frequency can be divided into a low frequency range having a frequency range of about 0.1 Hz or less to several Hz (e.g., 0.1 Hz to 10 Hz), a high frequency range having a frequency range of several kHz or more (e.g., 1 kHz to 1 MHz), and an intermediate frequency range having a frequency range of several Hz to several kHz (e.g., 10 Hz to 1 kHz).

[0064] In the low frequency range, the total resistance and capacity components of the battery pack (10) can be measured primarily. The impedance at low frequency is related to the electrochemical reactions, charging / discharging processes, and diffusion processes within the battery pack (10). Therefore, it is useful for analyzing the overall electrochemical characteristics of the battery pack (10). Additionally, in the high frequency range, the electric double layer effect and the intrinsic resistance within the battery cell (11) can be measured primarily. The impedance at high frequency is related to the electric double layer capacity and internal resistance at the electrode-electrolyte interface of the battery cell (11). Therefore, it is useful for analyzing the internal resistance and fast response characteristics of the battery cell (11). Additionally, in the medium frequency range, the charge transfer resistance and medium-speed electrochemical reactions of the battery cell (11) can be analyzed.

[0065] This frequency range may vary slightly depending on the type and condition of the battery pack (10), and the frequency range of the measurement frequency is appropriately set according to the characteristics to be measured or the abnormal condition of the battery pack (10) (i.e., busbar connection and welding defects between battery cells, etc.).

[0066] The voltage measuring unit (120) measures the voltage generated at either end of any battery cell (11) or bus bar (13) among a plurality of battery cells in the battery pack (10) by the measurement current applied to the (+) output terminal and the (-) output terminal of the battery pack (10). To this end, the voltage measuring unit (120) connects a first voltage measuring electrode ((-)Sensing) and a second voltage measuring electrode ((+)Sensing) to either end of any battery cell (11) or to either end of the bus bar (13), respectively, and measures the voltage at the connected ends.

[0067] That is, as shown in FIG. 1a, the voltage measuring unit (120) has the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) connected to both ends of the bus bar (13), respectively, to measure the voltage applied to both ends of the bus bar (13). Or, as shown in FIG. 1b, the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) are connected to both ends of any battery cell (11), respectively, to measure the voltage applied to both ends of the battery cell (11).

[0068] The impedance calculation unit (130) calculates the impedance using the current value generated by the measurement current generation unit (110) and the voltage value measured by the voltage measurement unit (120). At this time, the impedance is calculated using the phase difference and magnitude between the measurement current and the measured voltage, or the ratio between the measurement current and the measured voltage.

[0069] At this time, if the measured voltage value is the voltage applied across the ends of the bus bar (13), the impedance calculated by the impedance calculation unit (130) is the value measured at the R1 portion of the bus bar (13), and is the bus bar (13) impedance. Additionally, if the measured voltage value is the voltage applied across the ends of any battery cell (11), the impedance calculated by the impedance calculation unit (130) is the value measured at the portion of any battery cell (11), and is the battery cell (11) impedance.

[0070] The data output unit (140) generates a Nyquist or Bode plot based on the calculated impedance to output the impedance change between the busbar (13) or each battery cell (11) within the battery pack (10). By analyzing the impedance change, the electrochemical characteristics and performance of the busbar (13) or battery cell (11) are evaluated to detect abnormal conditions such as busbar connection failures or welding defects between battery cells. At this time, the Nyquist plot displays the real and imaginary impedances, and the Bode plot displays the impedance magnitude and phase angle according to frequency, thereby allowing the electrochemical characteristics of the battery pack (10) to be interpreted.

[0071] In this way, by analyzing the change in impedance of the busbar (13) or battery cell (11) based on the measured impedance through the output Nyquist or Bode plot, the internal resistance, ion mobility, interface characteristics, etc. of the battery pack (10) can be evaluated, and abnormal conditions of the battery pack (10) (i.e., busbar connection and welding defects between battery cells, etc.) can be detected.

[0072] To this end, the data output unit (140) may further include a defect detection unit (not shown) that detects a contact failure of the bus bar (13) or a contact failure between the battery cells (11) from a change in impedance between the bus bar (13) or each battery cell (11) within the battery pack (10). The defect detection unit detects that, when measuring the EIS, if a value different from the impedance corresponding to each cell is measured or a value different from the normal impedance of the bus bar is detected, it is a contact failure of the bus bar or a contact failure between the battery cells or cells.

[0073] At this time, the battery pack management device (100) can detect changes in impedance between the busbar (13) or each battery cell (11) within the battery pack (10), so that early detection of abnormal conditions such as busbar connection failure or welding failure between battery cells may be possible.

[0074] Meanwhile, the data output unit (140) can have different characteristics analyzed through impedance depending on the frequency range of the measurement frequency set to generate the measurement current.

[0075] That is, the data output unit (140) can measure the total resistance and capacitance components of the battery pack (10) mainly in the low frequency range (e.g., 0.1 Hz to 10 Hz). The impedance at low frequency is related to the electrochemical reactions, charging / discharging processes, and diffusion processes inside the battery pack (10). Therefore, the low frequency range is useful for analyzing the overall electrochemical characteristics of the battery pack (10). Additionally, the data output unit (140) can measure the electric double layer effect and the intrinsic resistance inside the battery cell (11) mainly in the high frequency range (e.g., 1 kHz to 1 MHz). The impedance at high frequency is mainly related to the electric double layer capacitance and internal resistance at the electrode-electrolyte interface of the battery cell (11). Therefore, the high frequency range is useful for analyzing the internal resistance and fast response characteristics of the battery cell (11). Additionally, the data output unit (140) can analyze the charge transfer resistance of the battery cell (11) and the electrochemical reaction of the medium speed in the medium frequency range (e.g., 10 Hz to 1 kHz).

[0076] Hereinafter, a method for inspecting the busbar connection and inter-cell welding status of a battery pack according to an embodiment of the present invention will be described. The method for inspecting the busbar connection and inter-cell welding status of a battery pack according to an embodiment of the present invention may be a method for processing a signal received using the aforementioned battery pack busbar connection and inter-cell welding status management device. Since the aforementioned details regarding the battery pack busbar connection and inter-cell welding status management device can be applied as is, the description of redundant details may be omitted.

[0077] FIG. 3 is a flowchart illustrating a method for inspecting the busbar connection and welding status between battery cells of a battery pack according to an embodiment of the present invention.

[0078] Referring to FIG. 3, a method for inspecting a battery pack according to an embodiment of the present invention first connects a first current application electrode ((-)Forcing) and a second current application electrode ((+)Forcing) to the (+) output terminal and the (-) output terminal of the battery pack (10), respectively, and connects a first voltage measurement electrode ((-)Sensing) and a second voltage measurement electrode ((+)Sensing) to the ends of any battery cell (11) or bus bar (13) among a plurality of battery cells in the battery pack (10), respectively (S10).

[0079] At this time, in order to detect a fault in the connection of the bus bar (13), the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) are each connected to both ends of the bus bar (13), and in order to detect a fault in the welding between battery cells (11), the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) are each connected to any battery cell (11) located inside the battery pack (10).

[0080] Next, the measurement current generating unit (110) generates a measurement current having a preset measurement frequency, and applies the measurement current to the (+) output terminal and the (-) output terminal of the battery pack (10) through the first current application electrode ((-)Forcing) and the second current application electrode ((+)Forcing) (S20).

[0081] At this time, 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 of 5 mV to 10 mV. The measurement potential is set to match the potential of the battery cell (11). This frequency range may vary slightly depending on the type and condition of the battery pack (10), and the frequency range of the measurement frequency can be appropriately set according to the characteristics to be measured or abnormal conditions of the battery pack (10) (i.e., busbar connection and welding defects between battery cells, etc.).

[0082] Next, in the voltage measuring unit (120), the voltage generated at either end of any battery cell (11) or bus bar (13) among the plurality of battery cells in the battery pack (10) by the measurement current applied to the (+) output terminal and the (-) output terminal of the battery pack (10) is measured using the first voltage measuring electrode ((-)Sensing) and the second voltage measuring electrode ((+)Sensing) (S30).

[0083] At this time, the voltage measuring unit (120) measures the voltage of the bus bar (13) when inspecting for faulty connection of the bus bar (13), and measures the voltage of the battery cell (11) when detecting faulty welding between the battery cells (11).

[0084] Next, the impedance calculation unit (130) calculates the impedance using the generated current value and the measured voltage value (S40).

[0085] At this time, if the measured voltage value is the busbar (13) voltage, the value measured at the R1 portion of the busbar (13) is the busbar (13) impedance, and if the measured voltage value is the battery cell (11) voltage, the value measured at any portion of the battery cell (11) is the battery cell (11) impedance. 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.

[0086] Next, at the data output unit (140), a Nyquist or Bode plot is generated based on the calculated impedance to visualize the change in impedance between the busbar (13) or each battery cell (11) within the battery pack (10) (S50).

[0087] Through this, changes in impedance are analyzed to evaluate the electrochemical characteristics and performance of the busbar (13) or battery cell (11), thereby detecting abnormal conditions such as busbar connection failures and welding defects between battery cells.

[0088] Meanwhile, a battery pack management device (100) is configured within the BMS, and a change in impedance between the busbar (13) or each battery cell (11) within the battery pack (10) can be detected, so that an abnormal condition such as busbar connection failure or welding defect between battery cells can be detected early.

[0089] In the foregoing, preferred embodiments of the present invention have been described and illustrated using specific terms, but such terms are intended solely to clarify the present invention, and it is obvious that various modifications and changes may be made to the embodiments and described terms of the present invention without departing from the technical spirit and scope of the following claims. Such modified embodiments should not be understood separately from the spirit and scope of the present invention, but should be considered to fall within the scope of the claims of the present invention.

[0090] The names of the symbols used in the detailed description of the invention and each drawing are as follows.

[0091] 10: Battery pack 11: Battery cell

[0092] 12: Battery module 13: Busbar

[0093] 100: Battery pack management device 110: Measurement current generation unit

[0094] 120: Voltage measurement unit 130: Impedance calculation unit

[0095] 140: Data output section

Claims

1. In a battery management device, A measurement current generating unit that generates a measurement current, which is an alternating current having a set measurement frequency, and applies it to the (+) output terminal and the (-) output terminal of a battery pack; A voltage measuring unit that measures the voltage generated at both ends of any battery cell or busbar among a plurality of battery cells in the battery pack by a measuring current applied to the (+) output terminal and the (-) output terminal of the battery pack, and An impedance calculation unit that calculates impedance using the measurement current value generated by the measurement current generation unit and the voltage value measured by the voltage measurement unit, and A battery pack management device comprising: a data output unit that outputs a change in impedance between a busbar or each battery cell within the battery pack based on the calculated impedance.

2. In Paragraph 1, The above-described measurement current generating unit is a battery pack management device that connects a first current application electrode ((-)Forcing) and a second current application electrode ((+)Forcing) to battery cells located at both ends of the battery pack, respectively, and applies the generated measurement current to the battery cells.

3. In Paragraph 1 or 2, The above-mentioned measurement current generating unit is, A battery pack management device that generates two or more alternating currents having different measurement frequencies as measurement currents.

4. In Paragraph 3, A battery pack management device that sets the signal amplitude of the above-mentioned measured current to an amplitude signal of 5 mV to 10 mV.

5. In Paragraph 3, The above data output unit is, A battery pack management device further comprising: a defect detection unit that detects a busbar contact failure or a battery cell contact failure from a change in impedance between a busbar or between each battery cell within the battery pack.

6. In Paragraph 1, The above voltage measuring unit is a battery pack management device that connects a first voltage measuring electrode ((-)Sensing) and a second voltage measuring electrode ((+)Sensing) to both ends of any battery cell or both ends of the busbar, respectively, and measures the voltage of both connected ends.

7. In Paragraph 1, The above impedance calculation unit is a battery pack management device that calculates 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.

8. In Paragraph 1, The above impedance calculation unit is, A battery pack management device characterized in that, when the measured voltage value is a voltage applied across the ends of the busbar, it is a busbar impedance calculated from the busbar, and when the measured voltage value is a voltage applied across the ends of any battery cell, it is a battery cell impedance calculated from any battery cell.

9. In Paragraph 1, The above data output unit is, A battery pack management device that interprets the electrochemical characteristics of the battery pack through the real and imaginary impedances shown in the Nyquist plot and the impedance magnitude and phase angle according to frequency shown in the Bode plot.

10. In Paragraph 1, The above impedance calculation unit and data output unit are configured in a signal processing unit (DSP) separate from the Micro-Controller Unit (MCU) of the battery management device, in a battery pack management device.

11. In a measurement current generation unit, an alternating current having a set measurement frequency is generated as a measurement current, and the measurement current is applied to the (+) output terminal and the (-) output terminal of a battery pack, and In a voltage measuring unit, the step of measuring the voltage across any one of any battery cell or busbar among a plurality of battery cells in the battery pack by means of a measuring current applied to the (+) output terminal and the (-) output terminal of the battery pack, and In the impedance calculation unit, a step of calculating impedance using the generated current value and the measured voltage value, and A method for inspecting a battery pack, comprising the step of outputting a change in impedance between a busbar or each battery cell within the battery pack based on the calculated impedance in a data output unit.

12. In Paragraph 11, Prior to the step of applying the above-mentioned measuring current, A current application electrode step of connecting a first current application electrode ((-)Forcing) and a second current application electrode ((+)Forcing) to the (+) output terminal and the (-) output terminal of the battery pack, respectively, and A method for inspecting a battery pack, further comprising a voltage measurement electrode connection step of connecting a first voltage measurement electrode ((-)Sensing) and a second voltage measurement electrode ((+)Sensing) to each end of any battery cell or busbar within the battery pack.

13. In Paragraph 12, The above voltage measurement electrode connection step is, In order to inspect for fault detection in the connection of the above busbar, a first voltage measuring electrode ((-)Sensing) and a second voltage measuring electrode ((+)Sensing) are respectively connected to both ends of the busbar, and A method for inspecting a battery pack in which, for detecting welding defects between the battery cells, a first voltage measuring electrode ((-)Sensing) and a second voltage measuring electrode ((+)Sensing) are respectively connected to any battery cell located inside the battery pack.

14. In Paragraph 11, A battery pack inspection method in which the above 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. In Paragraph 11 or Paragraph 14, A method for inspecting a battery pack in which the above-mentioned measured current is two or more alternating currents having different measurement frequencies.

16. In Paragraph 11, The step of outputting the above impedance change is, A method for inspecting a battery pack, further comprising the step of detecting abnormal conditions including busbar connection defects and welding defects between battery cells by analyzing impedance changes through a visualized Nyquist or Bode plot to evaluate the electrochemical characteristics and performance of the busbar or the battery cell.

17. In Paragraph 16, A method for inspecting a battery pack, which displays the real and imaginary impedances in the above Nyquist plot and displays the magnitude of the impedance and the phase angle according to frequency in the above Bode plot.

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