Battery diagnostic device and battery diagnostic method

Abstract

The battery diagnostic device includes an information acquisition unit to which an output signal is transmitted from each of a plurality of battery cells of a battery pack to which an AC input signal is applied, and a controller that compares each of the output signals with a reference signal to determine whether correction is necessary, corrects the output signal to generate a correction signal if correction is necessary, and determines the state of each of the plurality of battery cells based on the characteristics of the correction signal.

Description

[Technical Field]

[0001] The present invention claims the benefit of priority based on Korean Patent Application No. 10-2023-0009736, filed January 25, 2023, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The embodiments disclosed herein relate to a battery diagnostic device and a battery diagnostic method. [Background technology]

[0002] In recent years, the widespread use of portable devices such as smartphones and laptop computers, transportation methods such as electric cars, electric scooters, and electric motorcycles, and devices for stable power supply and management such as energy storage systems (ESS) has led to increased interest in batteries and more active development.

[0003] As devices using batteries become more widespread, the market for not only general batteries but also battery recycling is expanding. For battery recycling, accurate diagnosis of the condition of batteries is necessary to determine whether they are recyclable.

[0004] One of the representative techniques for diagnosing batteries is a method using electrochemical impedance spectroscopy (EIS), in which a battery is diagnosed using a Nyquist plot of EIS measurement data. Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the embodiments disclosed herein to provide an apparatus and method for diagnosing the condition of each battery cell.

[0006] The technical problems of the embodiments described in this document are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0007] A battery diagnostic device according to one embodiment disclosed in this document includes an information acquisition unit to which an output signal is transmitted from each of a plurality of battery cells of a battery pack to which an AC input signal is applied, and a controller that compares each of the output signals with a reference signal to determine whether correction is necessary, and if correction is necessary, corrects the output signal to generate a correction signal, and determines the state of each of the plurality of battery cells based on the characteristics of the correction signal.

[0008] In one embodiment, the controller can compare the amplitude and phase of the output signal with the amplitude and phase of a reference signal, respectively, to determine whether correction is required, and if correction is required, correct the amplitude or phase of the output signal to generate a correction signal.

[0009] According to one embodiment, the plurality of battery cells may include n battery cells, the amplitude of the reference signal may correspond to the amplitude of the AC input signal divided by n, and the phase of the reference signal may correspond to the phase of the AC input signal.

[0010] In one embodiment, the controller is capable of correcting the amplitude or phase of the output signal to correspond to the amplitude or phase of the reference signal. According to an embodiment, the controller may calculate a frequency-specific impedance response of each of the plurality of battery cells based on the correction signal.

[0011] According to one embodiment, the controller may determine a state of each of the plurality of battery cells based on the frequency-specific impedance response. According to an embodiment, the controller may generate a Nyquist diagram based on the impedance response of each of the plurality of battery cells at different frequencies.

[0012] According to one embodiment, the controller may compare the Nyquist diagram with a reference diagram to determine the state of each of the plurality of battery cells. According to one embodiment, the controller may compare the slope, X-intercept, or inflection point of the Nyquist plot and the reference plot, respectively.

[0013] According to one embodiment, the sum of the amplitudes of the output signals obtained from each of the plurality of battery cells can correspond to the amplitude of the AC input signal applied to a battery pack including the plurality of battery cells. According to an embodiment, the information acquisition unit may be connected to each of the battery cells included in the plurality of battery cells.

[0014] A battery diagnostic method according to one embodiment disclosed herein includes the steps of applying an AC input signal to a plurality of battery cells, transmitting an output signal from each of the plurality of battery cells, correcting the output signal to generate a correction signal, and determining the state of each of the plurality of battery cells based on characteristics of the correction signal.

[0015] According to one embodiment, the step of generating the correction signal may involve comparing the amplitude and phase of the output signal with the amplitude and phase of a reference signal, respectively, to determine whether correction is necessary, and if correction is necessary, generating the correction signal.

[0016] According to one embodiment, the plurality of battery cells may include n battery cells, the amplitude of the reference signal may correspond to the amplitude of the AC input signal divided by n, and the phase of the reference signal may correspond to the phase of the AC input signal.

[0017] In one embodiment, generating the correction signal may include correcting the amplitude or phase of the output signal to correspond to the amplitude or phase of the reference signal.

[0018] According to one embodiment, the step of determining the state may be a step of calculating a frequency-specific impedance response of each of the plurality of battery cells based on the correction signal, and determining the state of each of the plurality of battery cells based on the frequency-specific impedance response.

[0019] According to one embodiment, the sum of the amplitudes of the output signals obtained from each of the plurality of battery cells can correspond to the amplitude of the AC input signal applied to a battery pack including the plurality of battery cells. [Effects of the Invention]

[0020] According to the battery diagnostic device and battery diagnostic method of the embodiments disclosed herein, it is possible to diagnose the state of each of the plurality of battery cells included in a battery pack.

[0021] According to the battery diagnostic device and battery diagnostic method of the embodiments disclosed herein, it is possible to diagnose the state of each individual cell in a battery pack without disassembling the battery pack. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 illustrates a battery pack according to one embodiment disclosed herein. [Figure 2] 1 illustrates a battery diagnostic device according to one embodiment disclosed herein. [Figure 3] FIG. 10 is a diagram illustrating a battery diagnostic device according to another embodiment disclosed herein. [Figure 4] 10 is a diagram illustrating a correction process when the output signal of a battery cell has a normal waveform according to an embodiment disclosed herein. [Figure 5]FIG. 2 is a diagram illustrating a process for correcting an amplitude error in an output signal of a battery cell according to an embodiment disclosed herein. [Figure 6] FIG. 2 is a diagram illustrating a process for correcting a phase error in an output signal of a battery cell according to an embodiment disclosed herein. [Figure 7] FIG. 1 is a diagram illustrating a diagnostic method of a battery diagnostic device according to an embodiment disclosed herein. [Figure 8] 1 is a flowchart illustrating a battery diagnostic method according to one embodiment disclosed herein. [Figure 9] FIG. 1 illustrates a computing system for implementing an embodiment of a battery diagnostic method disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. When assigning reference numerals to components in each drawing, it should be noted that the same reference numerals are assigned to the same components as long as possible when they appear in other drawings. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related known structures or functions is deemed to hinder understanding of the embodiments disclosed herein, such detailed description will be omitted.

[0024] When describing components of the embodiments disclosed herein, terms such as "first," "second," etc. may be used. Such terms are merely used to distinguish the component from other components and do not limit the nature, order, or sequence of the components. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments disclosed herein belong. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

[0025] FIG. 1 is a diagram illustrating a battery pack according to one embodiment disclosed herein. Referring to FIG. 1, a battery control system including a battery pack 1 according to an embodiment disclosed herein and a host controller 2 included in the host system is schematically shown.

[0026] As shown in FIG. 1, the battery pack 1 may include one or more battery cells 11, a switching unit 14 connected in series to a first terminal side and / or a second terminal side of the battery cell 11 for controlling the flow of charge / discharge current of the battery cell 11, and a battery management system 20 that monitors the voltage, current, temperature, etc. of the battery pack 1 and manages it to prevent overcharging and over-discharging, etc.

[0027] In this case, the battery pack 1 may be provided with a plurality of battery cells 11, sensors 12, switching units 14, and battery management systems 20. For example, the first terminal may be the (+) terminal of the battery cell 11, and the second terminal may be the (-) terminal.

[0028] The battery cell 11 may include a plurality of battery cells. The plurality of battery cells may form one battery pack 1, but is not limited to this. According to an embodiment, the battery cell 11 may be one battery pack 1. According to another embodiment, the battery cell 11 may not form a pack, but may be a collection of multiple battery cells. The multiple battery cells included in the battery cell 11 are connected to each other and can be operated as a single unit.

[0029] Here, the switching unit 14 is an element for controlling the flow of current for charging or discharging the multiple battery cells 11, and for example, at least one relay, electromagnetic contactor, etc. can be used depending on the specifications of the battery pack 1.

[0030] The battery management system 20 is an interface that receives input of measured values ​​of the various parameters described above, and may include a plurality of terminals and circuits connected to these terminals for processing the received input values. The battery management system 20 may also control the ON / OFF of a switching unit 14, such as a relay or contactor, and may be connected to the battery cells 11 to monitor the status of each battery cell 11.

[0031] The upper controller 2 can transmit a control signal for the battery cells 11 to the battery management system 20. As a result, the operation of the battery management system 20 can be controlled based on the signal applied from the upper controller 2.

[0032] According to an embodiment, the battery management system 20 may include the battery diagnostic device 100 of Fig. 2. According to another embodiment, the battery management system 20 may be a system different from the battery diagnostic device 100 of Fig. 2. That is, the battery diagnostic device 100 of Fig. 2 may be included in the battery pack 1, or may be configured as a separate device external to the battery pack 1. For convenience of explanation, the following description will be given on the assumption that the battery diagnostic device 100 is configured as a separate device external to the battery pack 1.

[0033] The battery diagnostic device 100 can diagnose the states of the plurality of battery cells 11. Furthermore, the battery diagnostic device 100 can be connected to each of the battery cells included in the plurality of battery cells 11. That is, the battery diagnostic device 100 can be connected directly or indirectly to each of the terminals of the battery cells included in the plurality of battery cells 11.

[0034] FIG. 2 is a diagram illustrating a battery diagnostic device according to an embodiment disclosed herein. FIG. 3 is a diagram illustrating a battery diagnostic device according to another embodiment disclosed herein. FIG. 4 is a diagram illustrating a correction process when the output signal of a battery cell according to an embodiment disclosed herein has a normal waveform. FIG. 5 is a diagram illustrating a correction process for an amplitude error in the output signal of a battery cell according to an embodiment disclosed herein. FIG. 6 is a diagram illustrating a correction process for a phase error in the output signal of a battery cell according to an embodiment disclosed herein. FIG. 7 is a diagram illustrating a diagnostic method of a battery diagnostic device according to an embodiment disclosed herein.

[0035] First, referring to FIG. 2, the battery diagnostic device 100 may include an information acquisition unit 110, a storage unit 120, and a controller . The information acquisition unit 110 can measure the voltage of each battery cell 11. To this end, the information acquisition unit 110 can be connected to each individual battery cell included in each of the plurality of battery cells 11. That is, the information acquisition unit 110 is connected to a first terminal and a second terminal of each battery cell included in the plurality of battery cells 11, and can acquire the voltage between the first terminal and the second terminal. Here, the first terminal may be a (+) terminal and the second terminal may be a (-) terminal, but is not limited thereto. The voltage of each battery cell 11 acquired by the information acquisition unit 110 can be defined as an output signal 210.

[0036] The storage unit 120 can store the voltage of each battery cell 11 acquired by the information acquisition unit 110. That is, the storage unit 120 can receive the output signal 210 from the information acquisition unit 110 and store the output signal 210. According to the embodiment, the storage unit 120 can store not only the output signal 210 but also a reference signal 220 for determining whether correction of the output signal 210 is necessary and a correction signal 230 generated by the controller 130. Meanwhile, the storage unit 120 can transmit the output signal 210 to the controller 130.

[0037] The controller 130 can control the waveform generator 30. The controller 130 can control the waveform generator 30 to apply an AC input signal to the plurality of battery cells 11. That is, the controller 130 can transmit an instruction to the waveform generator 30 to generate an AC input signal, and the waveform generator 30 can apply the AC input signal to the plurality of battery cells 11 based on the instruction transmitted from the controller 130. According to an embodiment, the waveform generator 30 is not included in the battery diagnostic device 100, but can be configured as a device separate from the battery diagnostic device 100. Thus, the controller 130 can be connected to the waveform generator 30 and transmit an instruction to generate an AC input signal to the waveform generator 30 via a wired connection, or can transmit an instruction to generate an AC input signal using wireless communication without a separate connection.

[0038] The controller 130 controls the waveform generator 30 to control the frequency of the AC input signal applied to the plurality of battery cells 11. According to the embodiment, the controller 130 controls the waveform generator 30 to gradually increase the frequency of the AC input signal applied to the plurality of battery cells 11. By the controller 130 controlling the frequency of the AC input signal, the controller 130 can control the frequency of the output signal 210 that the information acquisition unit 110 acquires from the plurality of battery cells 11.

[0039] The controller 130 can receive the output signal 210 from the information acquisition unit 110. Here, the output signal 210 may be the voltage of each battery cell included in the plurality of battery cells 11, thereby allowing the controller 130 to receive the voltage of each battery cell included in the plurality of battery cells 11. According to an embodiment, the controller 130 can also receive the output signal 210 from the storage unit 120.

[0040] The controller 130 can determine whether correction of the output signal 210 is necessary. That is, the controller 130 can compare the output signal 210 with the reference signal 220 and determine whether correction of the output signal 210 is necessary. Here, the controller 130 can determine that correction is not necessary if the output signal 210 corresponds to the reference signal 220, and can determine that correction of the output signal 210 is necessary if the output signal 210 does not correspond to the reference signal 220. As a result, if correction of the output signal 210 is necessary, the controller 130 can correct the output signal 210 to generate the correction signal 230. Furthermore, if correction of the output signal 210 is not necessary, the controller 130 can regard the output signal 210 as the correction signal 230.

[0041] 3, the battery diagnostic device 100_1 may include an information acquiring unit 110_1, a storage unit 120_1, a controller 130_1, and a waveform generator 140_1. That is, according to various embodiments, the battery diagnostic device 100_1 may include the waveform generator 140_1. In this case, the controller 130_1 included in the battery diagnostic device 100_1 may transmit a command to the waveform generator 140_1 to generate an AC input signal within the same device. In this way, the controller 130_1 may control the waveform generator 140_1.

[0042] The controller 130_1 controls the waveform generator 140_1 to control the frequency of the AC input signal applied to the plurality of battery cells 11. According to the embodiment, the controller 130_1 controls the waveform generator 140_1 to gradually increase the frequency of the AC input signal applied to the plurality of battery cells 11. By the controller 130_1 controlling the frequency of the AC input signal, the controller 130_1 can control the frequency of the output signal 210 acquired by the information acquisition unit 110_1 from the plurality of battery cells 11.

[0043] That is, the battery diagnostic device 100_1 according to the embodiment of Fig. 3 may be substantially similar to the battery diagnostic device 100 according to the embodiment of Fig. 2, except that it includes a waveform generator 140_1. For convenience of explanation, the following description will be given on the assumption that the battery diagnostic device 100 and the waveform generator 30 are configured as separate devices as shown in Fig. 2.

[0044] Referring to FIG. 4, the controller 130 may receive an output signal 210 from the information acquisition unit 110 . The controller 130 can compare the output signal 210 with a reference signal 220. Here, the reference signal 220 can be defined as a signal that has been set in advance to check for an error in the amplitude or phase of the output signal 210.

[0045] According to an embodiment, the reference signal 220 may be a signal arbitrarily set by a user to check an error in the amplitude or phase of the output signal 210. For example, a user may define the reference signal 220 as a signal whose amplitude is a value obtained by dividing the amplitude of the AC input signal by the number of battery cells included in the plurality of battery cells and whose phase is the same as the phase of the AC input signal. That is, if the plurality of battery cells 11 includes n battery cells, the amplitude of the reference signal 220 may correspond to the value obtained by dividing the amplitude of the AC input signal by n, and the phase of the reference signal 220 may correspond to the phase of the AC input signal. In this case, the sum of the amplitudes of the output signals 210 acquired by the information acquisition unit 110 from each of the plurality of battery cells 11 may correspond to the amplitude of the AC input signal applied to the battery pack including the plurality of battery cells 11.

[0046] To facilitate understanding, it is assumed that the amplitude of the AC input signal is 100 and the plurality of battery cells 11 includes 100 battery cells. In this case, the amplitude of the reference signal 220 is 1, which is the amplitude 100 of the AC input signal divided by 100, which is the number of battery cells included in the plurality of battery cells 11, and the phase of the reference signal 220 can be the same as the phase of the AC input signal.

[0047] While the above description is based on the assumption that the controller 130 sets the reference signal 220 based on the AC input signal, this is not limiting. In other embodiments, the amplitude and phase of the reference signal 220 may be the amplitude and phase of any signal that has already been set, separate from the amplitude and phase of the AC input signal.

[0048] The controller 130 can compare the amplitude and phase of the output signal 210 with the amplitude and phase of the reference signal 220, respectively. For example, if the amplitude of the output signal 210 and the amplitude of the reference signal 220 are identical and the phase of the output signal 210 and the phase of the reference signal 220 are identical, the controller 130 can determine that the output signal 210 is a normal waveform. In this case, the controller 130 can determine that correction of the output signal 210 is not necessary. This allows the controller 130 to regard the output signal 210 itself as the correction signal 230.

[0049] According to various embodiments, the controller 130 can determine that the output signal 210 has a normal waveform not only when the amplitude and phase of the output signal 210 are identical to those of the reference signal 220, but also when the amplitude and phase of the output signal 210 do not deviate from a predetermined range when compared with the amplitude and phase of the reference signal 220. In this regard, the controller 130 can set a range related to the amplitude and phase for determining that the output signal 210 has a normal waveform. That is, the controller 130 can set a range for determining that the output signal 210 has a normal waveform, taking into consideration the type of battery pack and battery cells, the number of battery cells included in the battery pack, and the intended use of the battery pack.

[0050] Referring to FIG. 5, the controller 130 can correct the amplitude of the output signal 210 . The controller 130 receives the output signal 210 from the information acquiring unit 110 and can compare the output signal 210 with the reference signal 220. In this case, the controller 130 can compare the amplitude of the output signal 210 with the amplitude of the reference signal 220. According to an embodiment, the controller 130 can calculate a ratio between the amplitude of the output signal 210 and the amplitude of the reference signal 220. If the ratio between the amplitude of the output signal 210 and the amplitude of the reference signal 220 calculated by the controller 130 exceeds a preset ratio, the controller 130 can determine that the output signal 210 has an abnormal amplitude.

[0051] If the output signal 210 is determined to have an abnormal amplitude, the controller 130 can correct the amplitude of the output signal 210. According to the embodiment, the controller 130 can correct the amplitude of the output signal 210 by multiplying the output signal 210 by the inverse of the ratio of the output signal 210 to the reference signal 220 to generate the corrected signal 230. In this way, the amplitudes of the corrected signals 230 generated by the controller 130 based on the output signals 210 of the respective battery cells included in the plurality of battery cells 11 can all be corrected to be the same as the amplitude of the reference signal 220.

[0052] For ease of explanation, it is assumed that the amplitude of the reference signal 220 is 1 and the amplitude of the output signal 210 is 0.8. The controller 130 can calculate the ratio between the output signal 210 and the reference signal 220 to derive 0.8 / 1. In this case, the controller 130 determines that 0.8 / 1 exceeds the preset ratio, and can multiply the amplitude of the output signal 210 by 1 / 0.8 to correct the amplitude of the output signal 210 to 1, thereby generating the correction signal 230. In this way, the controller 130 can correct the amplitude of the correction signal 230 of each of the battery cells included in the multiple battery cells 11 to 1.

[0053] Meanwhile, according to various embodiments, the controller 130 can also determine whether the output signal 210 has an amplitude abnormality based on the difference between the amplitude of the output signal 210 and the amplitude of the reference signal 220 .

[0054] Referring to FIG. 6, the controller 130 can correct the phase of the output signal 210 . The controller 130 receives the output signal 210 from the information acquisition unit 110 and can compare the output signal 210 with the reference signal 220. In this case, the controller 130 can compare the phase of the output signal 210 with the phase of the reference signal 220.

[0055] According to an embodiment, the controller 130 compares the phase of the output signal 210 with the phase of the reference signal 220, and if the difference between the phase of the output signal 210 and the phase of the reference signal 220 is outside a predetermined range, the controller 130 can determine that the output signal 210 has a phase abnormality.

[0056] If the output signal 210 is determined to have a phase abnormality, the controller 130 can correct the phase of the output signal 210. According to the embodiment, the controller 130 can correct the phase of the output signal 210 to generate the correction signal 230 so that the phase of the output signal 210 corresponds to the phase of the reference signal 220. In this way, the phases of the correction signals 230 generated by the controller 130 based on the output signals 210 of the respective battery cells included in the plurality of battery cells 11 can all be corrected to be the same as the phase of the reference signal 220.

[0057] The controller 130 can adjust the frequency of the AC input signal while repeatedly correcting the output signal 210. This allows the controller 130 to obtain corrected signals 230 with various frequencies.

[0058] The controller 130 may calculate a frequency-specific impedance response based on the corrected signal 230 of each battery cell included in the plurality of battery cells 11. According to an embodiment, the controller 130 may calculate the impedance response using electrochemical impedance spectroscopy (EIS). According to an embodiment, electrochemical impedance spectroscopy may be understood as a method for generating and interpreting a Nyquist diagram 320 based on the results obtained by applying an AC power source to a battery.

[0059] Specifically, the controller 130 calculates the impedance response calculated based on the correction signal 230 of each battery cell included in the plurality of battery cells 11 as a real part (Z real ) and the imaginary part (Z imag ) and the controller 130 can generate an impedance profile based on the real and imaginary parts of each impedance response. As a result, one impedance profile can include impedance information generated based on the corrected signals 230 of the battery cells at various frequencies.

[0060] 7, the controller 130 can generate a Nyquist diagram 320 based on the impedance profile. That is, the controller 130 can generate a Nyquist diagram 320 where the X-axis represents the real part of the impedance response (Z real ), and the Y-axis is the imaginary part of the impedance response (Z imag ), the frequency of the AC input signal, the real part of the impedance, and the imaginary part of the impedance can be represented by a single point based on the impedance profile. Here, the impedance response at a specific frequency can be represented by a single point on the Nyquist diagram 320. In this manner, the controller 130 can repeat the same operation for multiple frequencies and connect the multiple points formed thereby to represent a single graph.

[0061] The controller 130 can compare the Nyquist diagram 320 with the reference diagram 420 to determine the state of each of the plurality of battery cells 11. The Nyquist diagram 320 generated by the controller 130 can be divided into a second line 321 and a third line 322 based on a first line 310. Here, the first line 310 can be defined as a line drawn perpendicular to the X-axis at an inflection point of the Nyquist diagram 320. The second line 321 can be defined as the Nyquist diagram 320 located in the opposite direction to the X-axis based on the first line 310. The third line 322 can be defined as the Nyquist diagram 320 located in the X-axis direction based on the first line 310.

[0062] The reference line diagram 420 set by the controller 130 may be divided into a fifth line 421 and a sixth line 422 based on the fourth line 410. Here, the fourth line 410 may be defined as a line drawn perpendicular to the X-axis at an inflection point of the reference line diagram 420. The fifth line 421 may be defined as the reference line diagram 420 located in the opposite direction to the X-axis direction based on the fourth line 410. The sixth line 422 may be defined as the reference line diagram 420 located in the X-axis direction based on the fourth line 410.

[0063] Hereinafter, the preset range for each case may be set in consideration of the type of battery pack and battery cells, the number of battery cells included in the battery pack, and the intended use of the battery pack.

[0064] The controller 130 can compare the X-intercept of the Nyquist diagram 320 with the X-intercept of the reference diagram 420. The X-intercept of the Nyquist diagram 320 can be defined as a first X-intercept 330. The reference diagram 420 can be defined as a second X-intercept 430. The controller 130 can compare the position of the first X-intercept 330 with the position of the second X-intercept 430. If the position of the first X-intercept 330 deviates from the position of the second X-intercept 430 by more than a predetermined range, the controller 130 can determine that the corresponding battery cell is defective. Because the first X-intercept 330 and the second X-intercept 430 each indicate a case where the impedance is a pure real number, the controller 130 can determine that the corresponding battery cell has a problem with internal resistance.

[0065] The controller 130 can compare the slope of the third line 322 with the slope of the fifth line 421. If the slope of the third line 322 is outside a preset range from the slope of the fifth line 421, the controller 130 can determine that the corresponding battery cell is defective. In this case, the controller 130 can determine that there is a problem with the diffusion effect inside the corresponding battery cell.

[0066] Meanwhile, an inflection point of the Nyquist diagram 320 may be defined as a first inflection point 340. An inflection point of the reference diagram 420 may be defined as a second inflection point 440. The controller 130 may compare the radius of curvature and the first inflection point 340 of the second line 321 with the radius of curvature and the second inflection point of the fifth line 421. If the radius of curvature or the position of the first inflection point of the second line 321 deviates from the radius of curvature or the second inflection point of the fifth line 421 by more than a predetermined range, the controller 130 may determine that the corresponding battery cell is defective. In this case, the controller 130 may determine that the corresponding battery cell has a problem with charge transfer.

[0067] The controller 130 may determine that the battery cell is normal if the Nyquist diagram 320 corresponds to the reference diagram 420. Specifically, the controller 130 may determine that the battery cell is normal if the position of the first X-intercept 330 does not deviate from a predetermined range from the position of the second X-intercept 430, the slope of the third line 322 does not deviate from a predetermined range from the slope of the fifth line 421, and the radius of curvature of the second line 321 and the position of the first inflection point 340 do not deviate from a predetermined range from the radius of curvature of the fifth line 421 and the position of the second inflection point 440.

[0068] FIG. 8 is a flowchart illustrating a battery diagnostic method according to one embodiment disclosed herein. The embodiment shown in FIG. 8 is just one embodiment, and the order of operations according to various embodiments of the present invention may differ from that shown in FIG. 8, and some steps shown in FIG. 8 may be omitted, the order between steps may be changed, or steps may be merged.

[0069] Referring to FIG. 8, the battery diagnosis method may include an operation of applying an AC input signal to a battery cell 11 (S110), an operation of acquiring an output signal 210 from the battery cell 11 (S120), an operation of determining whether correction of the output signal 210 is necessary (S130), an operation of treating the output signal 210 as a correction signal 230 (S140), an operation of generating the correction signal 230 (S150), and an operation of determining the state of the battery cell 11 based on the characteristics of the correction signal 230 (S160).

[0070] The operations S110 to S160 will be specifically described below with reference to FIGS. In operation S110, the battery diagnostic device 100 can control the waveform generator to apply an AC input signal to the plurality of battery cells 11. That is, the battery diagnostic device 100 can transmit an instruction to the waveform generator to generate an AC input signal, and the waveform generator can apply the AC input signal to the plurality of battery cells 11 based on the instruction transmitted from the battery diagnostic device 100.

[0071] The battery diagnostic device 100 can control the waveform generator to control the frequency of the AC input signal applied to the plurality of battery cells 11. According to the embodiment, the battery diagnostic device 100 can control the waveform generator to gradually increase the frequency of the AC input signal applied to the plurality of battery cells 11. Operation S110 may be followed by operation S120.

[0072] In operation S120, the battery diagnostic device 100 can acquire an output signal 210 from the battery cell 11. To this end, the battery diagnostic device 100 can be connected to each of the individual battery cells included in each of the plurality of battery cells 11. That is, the battery diagnostic device 100 is connected to a first terminal and a second terminal of each of the battery cells included in the plurality of battery cells 11, and can acquire a voltage between the first terminal and the second terminal. Here, the first terminal may be a (+) terminal, and the second terminal may be a (-) terminal, but is not limited thereto. The voltage of each battery cell 11 acquired by the battery diagnostic device 100 can be defined as an output signal 210. Operation S120 may be followed by operation S130.

[0073] In operation S130, the battery diagnostic device 100 can determine whether correction of the output signal 210 is necessary. That is, the battery diagnostic device 100 can compare the output signal 210 with the reference signal 220 and determine whether correction of the output signal 210 is necessary. Here, the battery diagnostic device 100 can determine that correction is not necessary if the output signal 210 corresponds to the reference signal 220, and can determine that correction of the output signal 210 is necessary if the output signal 210 does not correspond to the reference signal 220. More specifically, the battery diagnostic device 100 can compare the amplitude and phase of the output signal 210 with the amplitude and phase of the reference signal 220. If the amplitude of the output signal 210 and the amplitude of the reference signal 220 are identical and the phase of the output signal 210 and the phase of the reference signal 220 are identical, the battery diagnostic device 100 can determine that the output signal 210 has a normal waveform. In this case, the battery diagnostic device 100 can determine that correction of the output signal 210 is not necessary. Furthermore, the battery diagnostic device 100 can determine that correction of the output signal 210 is necessary when the amplitude or phase of the output signal 210 does not correspond to the amplitude or phase of the reference signal 220. When the battery diagnostic device 100 determines that correction of the output signal 210 is not necessary, operation S140 can be performed. When the battery diagnostic device 100 determines that correction of the output signal 210 is necessary, operation S150 can be performed.

[0074] In operation S140, the battery diagnostic device 100 can regard the output signal 210 as the correction signal 230. That is, the battery diagnostic device 100 regards the output signal 210 as the correction signal 230, and in the operation of making a determination based on the correction signal 230 in the subsequent process, regards the output signal 210 itself as the correction signal 230, and can determine the state of the battery cell based on the output signal 210. Operation S140 may be followed by operation S160.

[0075] In operation S150, the battery diagnostic device 100 can generate the correction signal 230. The battery diagnostic device 100 can generate the correction signal 230 by correcting the amplitude of the output signal 210. To this end, the battery diagnostic device 100 can compare the amplitude of the output signal 210 with the amplitude of the reference signal 220. According to an embodiment, the battery diagnostic device 100 can calculate a ratio between the amplitude of the output signal 210 and the amplitude of the reference signal 220. If the ratio between the amplitude of the output signal 210 and the amplitude of the reference signal 220 calculated by the battery diagnostic device 100 exceeds a predetermined ratio, the battery diagnostic device 100 can determine that the output signal 210 has an amplitude abnormality. If the output signal 210 is determined to have an amplitude abnormality, the battery diagnostic device 100 can correct the amplitude of the output signal 210. According to the embodiment, the battery diagnostic device 100 can correct the amplitude of the output signal 210 by multiplying the output signal 210 by the inverse of the ratio between the output signal 210 and the reference signal 220 to generate the corrected signal 230. As a result, the amplitudes of the corrected signals 230 generated by the battery diagnostic device 100 based on the output signals 210 of the respective battery cells included in the plurality of battery cells 11 can all be corrected to be the same as the amplitude of the reference signal 220.

[0076] Furthermore, the battery diagnostic device 100 can correct the phase of the output signal 210 to generate the correction signal 230. To this end, the battery diagnostic device 100 compares the phase of the output signal 210 with the phase of the reference signal 220, and if the difference between the phase of the output signal 210 and the phase of the reference signal 220 is outside a preset range, the battery diagnostic device 100 can determine that the output signal 210 has a phase abnormality. If the output signal 210 is determined to have a phase abnormality, the battery diagnostic device 100 can correct the phase of the output signal 210. According to an embodiment, the battery diagnostic device 100 can correct the phase of the output signal 210 to generate the correction signal 230 so that the phase of the output signal 210 corresponds to the phase of the reference signal 220. As a result, the phases of the correction signals 230 generated by the battery diagnostic device 100 based on the output signals 210 of the plurality of battery cells 11 can all be corrected to be the same as the phase of the reference signal 220. Operation S150 may be followed by operation S160.

[0077] In operation S160, the battery diagnostic device 100 can determine the state of the battery cell 11 based on the characteristics of the correction signal 230. The battery diagnostic device 100 can calculate a frequency-specific impedance response based on the correction signal 230 of each battery cell included in the plurality of battery cells 11. According to an embodiment, the battery diagnostic device 100 can calculate the impedance response using electrochemical impedance spectroscopy (EIS).

[0078] Specifically, the battery diagnostic device 100 calculates the impedance response calculated based on the correction signal 230 of each battery cell included in the plurality of battery cells 11 as a real part (Z real ) and the imaginary part (Z imag ) can be generated. As a result, one impedance profile can include impedance information generated based on the corrected signals 230 of the battery cells at various frequencies. In other words, the battery diagnostic device 100 can use the impedance profile to form pairs in which the frequency of the AC input signal, the real part of the impedance, and the imaginary part of the impedance correspond to each other.

[0079] 7, the battery diagnostic device 100 can generate a Nyquist diagram 320 based on the impedance profile. That is, the battery diagnostic device 100 generates a Nyquist diagram 320 in which the X axis represents the real part of the impedance response (Z real ), and the Y-axis is the imaginary part of the impedance response (Z imag), the frequency of the AC input signal, the real part of the impedance, and the imaginary part of the impedance can be represented by a single point based on the impedance profile. Here, the impedance response at a specific frequency can be represented by a single point on the Nyquist diagram 320. In this manner, the battery diagnostic device 100 repeats the same operation for multiple frequencies and can connect the multiple points formed thereby to represent a single graph.

[0080] The battery diagnostic device 100 can compare the Nyquist diagram 320 with the reference diagram to determine the state of each of the plurality of battery cells 11. The Nyquist diagram 320 generated by the battery diagnostic device 100 can be divided into a second line 321 and a third line 322 based on a first line 310.

[0081] The battery diagnostic device 100 can compare the X-intercept of the second line 321 with the X-intercept of the reference diagram. The battery diagnostic device 100 can compare the position of the X-intercept of the second line 321 with the position of the X-intercept of the reference diagram. If the position of the X-intercept of the second line 321 deviates from the position of the X-intercept of the reference diagram by more than a predetermined range, the battery diagnostic device 100 can determine that the corresponding battery cell is defective. Since the X-intercept of the Nyquist diagram 320 indicates that the impedance is a pure real number, in this case the battery diagnostic device 100 can determine that the corresponding battery cell has a problem with its internal resistance.

[0082] The battery diagnostic device 100 can compare the slope of the third line 322 with the slope of the portion of the reference diagram that corresponds to the third line 322. If the slope of the third line 322 deviates from a preset range from the slope of the portion of the reference diagram that corresponds to the third line 322, the battery diagnostic device 100 can determine that the battery cell is defective. In this case, the battery diagnostic device 100 can determine that there is a problem with the diffusion effect inside the battery cell.

[0083] The battery diagnostic device 100 can compare the radius of curvature of the second line 321 and the inflection point of the Nyquist diagram 320 with the radius of curvature and the inflection point of the portion of the reference diagram that corresponds to the second line 321. If the radius of curvature of the second line 321 or the position of the inflection point of the Nyquist diagram 320 deviates from the radius of curvature or the inflection point of the portion of the reference diagram that corresponds to the second line 321 by more than a predetermined range, the battery diagnostic device 100 can determine that the corresponding battery cell is defective. In this case, the battery diagnostic device 100 can determine that the corresponding battery cell has a problem with charge transfer.

[0084] The battery diagnostic device 100 can determine that the battery cell is normal if the Nyquist diagram 320 corresponds to the reference diagram 420. Specifically, the battery diagnostic device 100 can determine that the battery cell is normal if the position of the first X-intercept 330 does not deviate from a predetermined range from the position of the second X-intercept 430, the slope of the third line 322 does not deviate from a predetermined range from the slope of the fifth line 421, and the radius of curvature of the second line 321 and the position of the first inflection point 340 do not deviate from a predetermined range from the radius of curvature of the fifth line 421 and the position of the second inflection point 440.

[0085] FIG. 9 illustrates a computing system that executes one embodiment of the battery diagnostic method disclosed herein. Referring to FIG. 8, a computing system 500 according to one embodiment disclosed herein may include an MCU 510, a memory 520, an input / output I / F 530, and a communication I / F 540.

[0086] The MCU 510 may be a processor that executes various programs (e.g., an SOH calculation program, a cell balancing execution target determination program, etc.) stored in the memory 520, processes various data including the SOC, SOH, etc. of the multiple battery cells 11 through such programs, and performs the functions of the battery diagnostic device 100 described above with reference to Figures 1 to 7.

[0087] The memory 520 can store various programs related to calculating the SOH of the battery cells 11 and determining which cells are to be subjected to cell balancing. The memory 520 can also store various data such as SOC and SOH data for each battery cell 11.

[0088] A plurality of such memories 520 may be provided as necessary. The memories 520 may be volatile memories or nonvolatile memories. As the volatile memories 520, RAM, DRAM, SRAM, etc. may be used. As the nonvolatile memories 520, ROM, PROM, EAROM, EPROM, EEPROM, flash memory, etc. may be used. The examples of the memories 520 listed above are merely illustrative and are not limited to these examples.

[0089] The input / output I / F 530 can provide an interface that connects input devices (not shown) such as a keyboard, mouse, or touch panel, and output devices such as a display (not shown), to the MCU 510, enabling data to be sent and received.

[0090] The communication I / F 540 is configured to be able to send and receive various data to and from a server, and may be any device that supports wired or wireless communication. For example, programs and various data for calculating the SOH of the battery cells 11 and determining which cells are to be balanced can be sent and received from a separately provided external server via the communication I / F 540. In this manner, the battery diagnostic method according to one embodiment disclosed herein can be stored in the memory 520 and executed by the MCU 510.

[0091] The above description is merely an illustrative example of the technical ideas disclosed in this document, and various modifications and variations are possible within the scope of those skilled in the art to which the embodiments disclosed in this document pertain without departing from the essential characteristics of the embodiments disclosed in this document.

[0092] Therefore, the embodiments disclosed in this document are intended to illustrate, not limit, the technical ideas disclosed in this document, and such embodiments do not limit the scope of the technical ideas disclosed in this document. The scope of protection of the technical ideas disclosed in this document should be interpreted according to the claims below, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of rights of this document.

Claims

1. an information acquisition unit to which an output signal is transmitted from each of a plurality of battery cells of a battery pack to which an AC input signal is applied; a controller that compares each of the output signals with a reference signal to determine whether correction is necessary, and if correction is necessary, corrects the output signal to generate a correction signal, and determines the state of each of the plurality of battery cells based on characteristics of the correction signal; A battery diagnostic device comprising:

2. 2. The battery diagnostic device according to claim 1, wherein the controller compares the amplitude and phase of the output signal with the amplitude and phase of the reference signal, respectively, to determine whether correction is necessary, and if correction is necessary, corrects the amplitude or phase of the output signal to generate the correction signal.

3. the plurality of battery cells includes n battery cells, 3. The battery diagnostic device according to claim 2, wherein the amplitude of the reference signal corresponds to a value obtained by dividing the amplitude of the AC input signal by n, and the phase of the reference signal corresponds to the phase of the AC input signal.

4. 4. The battery diagnostic device according to claim 3, wherein the controller corrects the amplitude or phase of the output signal so that the amplitude or phase corresponds to the amplitude or phase of the reference signal.

5. The battery diagnostic device according to claim 1 , wherein the controller calculates an impedance response for each frequency of each of the plurality of battery cells based on the correction signal.

6. The battery diagnostic device according to claim 5 , wherein the controller determines the state of each of the plurality of battery cells based on the frequency-specific impedance response.

7. The battery diagnostic device according to claim 5 , wherein the controller generates a Nyquist diagram based on the impedance response of each of the plurality of battery cells at different frequencies.

8. The battery diagnostic device according to claim 7 , wherein the controller compares the Nyquist diagram with a reference diagram to determine the state of each of the plurality of battery cells.

9. The battery diagnostic device according to claim 8 , wherein the controller compares the slope, the X-intercept, or the inflection point of the Nyquist diagram with that of the reference diagram.

10. 10. The battery diagnostic device according to claim 1, wherein a sum of amplitudes of the output signals acquired from the plurality of battery cells corresponds to an amplitude of the AC input signal applied to the battery pack including the plurality of battery cells.

11. The battery diagnostic device according to claim 1 , wherein the information acquisition unit is connected to each of the battery cells included in the plurality of battery cells.

12. applying an AC input signal to a plurality of battery cells; receiving an output signal from each of the plurality of battery cells and correcting the output signal to generate a correction signal; determining a state of each of the plurality of battery cells based on a characteristic of the correction signal; A battery diagnostic method comprising:

13. 13. The battery diagnostic method according to claim 12, wherein the step of generating the correction signal is a step of comparing the amplitude and phase of the output signal with the amplitude and phase of a reference signal, respectively, to determine whether correction is necessary, and generating the correction signal if correction is necessary.

14. the plurality of battery cells includes n battery cells, 14. The battery diagnostic method according to claim 13, wherein the amplitude of the reference signal corresponds to a value obtained by dividing the amplitude of the AC input signal by n, and the phase of the reference signal corresponds to the phase of the AC input signal.

15. 15. The battery diagnostic method according to claim 14, wherein the step of generating the correction signal includes the step of correcting the amplitude or phase of the output signal so as to correspond to the amplitude or phase of the reference signal.

16. The step of determining the state includes calculating a frequency-specific impedance response of each of the plurality of battery cells based on the correction signal; The battery diagnostic method according to claim 12 , further comprising determining a state of each of the plurality of battery cells based on the frequency-specific impedance response.

17. 16. The battery diagnosis method according to claim 12, wherein a sum of amplitudes of the output signals acquired from the plurality of battery cells corresponds to an amplitude of the AC input signal applied to a battery pack including the plurality of battery cells.

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