Battery module online monitoring device based on ultrasonic waveguide and method thereof

Abstract

The application belongs to the technical field of nondestructive testing and new energy battery safety management, and specifically discloses a battery module online monitoring device based on an ultrasonic waveguide and a method thereof. In the device, a transmitting transducer is coupled to one end of a waveguide tube through a waveguide connecting piece. A pipe wall of the waveguide tube is arranged along an axial direction and is provided with a plurality of acoustic openings. An acoustic wedge block is coupled to the outside of each acoustic opening. The bottom surface of the acoustic wedge block is attached to the surface of a battery to be measured. The waveguide tube is used for transmitting ultrasonic signals in the waveguide tube, and the ultrasonic signals are leaked to the corresponding acoustic wedge block through the plurality of acoustic openings. The acoustic wedge block has a preset wedge block angle, which is used for converting the ultrasonic signals leaked through the acoustic openings into ultrasonic surface waves propagating along the surface of the battery to be measured. The application greatly reduces the hardware cost and wiring complexity.

Description

Technical Field

[0001] This application belongs to the field of non-destructive testing and new energy battery safety management technology, and more specifically, relates to an online monitoring device and method for battery modules based on ultrasonic conduction. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and high efficiency, have become a key carrier supporting the development of new power systems and new energy vehicles.

[0003] Existing battery management systems (BMS) primarily rely on external characteristic parameters such as voltage, current, and temperature for monitoring. However, these parameters often exhibit hysteresis, making it difficult to decouple microscopic physicochemical changes within the battery, such as micro-short circuits, lithium plating, gas generation from interfacial side reactions, and uneven electrolyte wetting. When voltage or temperature anomalies are detected, the battery is often already on the verge of thermal runaway, resulting in delayed early warning responses and failing to meet the intrinsic safety requirements of large-scale energy storage power stations.

[0004] Ultrasonic technology, with its high sensitivity to dielectric density, modulus, and interface state, is considered an important means of accurately sensing the internal state of batteries and providing early warning of thermal runaway. However, despite the great potential of ultrasonic technology in characterizing the internal state of batteries, the traditional single-point "one transmitter, one receiver" monitoring method faces severe challenges when applied to large-scale energy storage modules. On the one hand, this method requires individual sensors and wiring harnesses for each cell, resulting in extremely high system integration complexity and redundant wiring, making it difficult to meet the stringent constraints of lightweight and low-cost battery modules. On the other hand, to overcome the strong sound attenuation of multi-layer composite media, traditional solutions often require high-voltage AC excitation of tens of volts or more, which introduces safety hazards such as insulation failure and electromagnetic interference in the high-voltage DC environment inside the battery pack. In addition, simple waveguide attempts are limited by the exponential attenuation of sound energy along the path and the mechanical constraints of fixed cell spacing, making it difficult to achieve effective coverage of the energy of all cells in the module uniformly and without blind spots. To address these challenges, it is urgent to overcome the safety hazards and cost concerns caused by high-voltage excitation and redundant wiring harnesses in existing methods and propose new and efficient monitoring methods. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide an online monitoring device and method for battery modules based on ultrasonic conduction. This aims to solve the problem that when ultrasonic technology is used to characterize the internal state of batteries, a single transmitter and receiver monitoring method is required, which necessitates the separate configuration of sensors and wiring harnesses for each battery cell. This results in extremely high integration complexity and redundant wiring within the battery module, making it difficult to meet the requirements of lightweight and low-cost battery modules.

[0006] The first aspect of this application relates to an online monitoring device for a battery module based on ultrasonic waveguides, comprising: a waveguide, an acoustic excitation module, a transmitting transducer, a receiving sensor, a waveguide connector, several acoustic wedges, and a signal acquisition module; The output of the acoustic excitation module is connected to the transmitting transducer; the transmitting transducer is coupled to one end of the waveguide through a waveguide connector; several acoustic openings are arranged axially on the wall of the waveguide, and a sound-guiding wedge is coupled to the outside of each acoustic opening, with the bottom surface of the sound-guiding wedge in contact with the surface of the battery under test; the receiving sensor is located on the surface of the battery under test, and its output is connected to the signal acquisition module. The acoustic excitation module generates pulsed electrical signals; the transmitting transducer converts the pulsed electrical signals into ultrasonic signals; the waveguide allows the ultrasonic signals to be transmitted within it, and energy leakage occurs through several acoustic openings to the corresponding acoustic wedges; the acoustic wedges have preset wedge angles to convert the ultrasonic signals leaking through the acoustic openings into ultrasonic surface waves propagating along the surface of the battery under test; the receiving sensor receives the ultrasonic surface waves carrying battery status information and converts them into ultrasonic electrical signals, which are then transmitted to the signal acquisition module; the signal acquisition module extracts the three-dimensional feature parameters of the ultrasonic electrical signals and inputs them into a machine learning model to obtain quantitative evaluation values ​​of the battery's state of charge and health status.

[0007] In some implementations, the geometry of the acoustic openings is distributed in a gradient increasing manner along the propagation direction of the ultrasonic signal within the waveguide; or the distribution density of the acoustic openings increases along the propagation direction.

[0008] In some implementations, the center frequency of the pulsed electrical signal generated by the acoustic excitation module is determined according to the fixed distribution spacing of the batteries, satisfying the non-Bracket resonance condition, so that the ultrasonic signal maintains a traveling wave transmission state in the waveguide.

[0009] In some implementations, the preset wedge angle of the sound-guiding wedge is: ; in, The propagation speed of the ultrasonic signal in the sound-guiding wedge material; Let be the propagation velocity of the ultrasonic surface wave on the surface of the battery under test, and < .

[0010] In some embodiments, the waveguide is a hollow cylindrical structure filled with an acoustic coupling liquid medium; the waveguide connector is provided with a transition layer that matches the acoustic impedance of the acoustic coupling liquid medium.

[0011] In some embodiments, the waveguide is provided with a conical or wedge-shaped sound absorber at its end to absorb the residual ultrasonic signal energy incident on the end of the waveguide.

[0012] In some implementations, the transmitting transducer and acoustic excitation module are located on the external structure of the battery module and extend into the battery module through an insulated waveguide.

[0013] In some implementations, the three-dimensional feature parameters include: amplitude attenuation rate, center frequency offset, and time-of-flight distortion; Amplitude decay rate characterizes the enhanced reflection at the gas-solid interface caused by gas production or electrolyte drying; time-of-flight distortion characterizes the electrode volume expansion and shell stress changes caused by lithium-ion deintercalation during charging and discharging; center frequency offset characterizes the large deformation or bulging of the battery shell caused by abnormal gas production in the battery.

[0014] The second aspect of this application relates to an online monitoring method for battery modules based on ultrasonic conduction, comprising the following steps: The pulsed electrical signal is converted into an ultrasonic signal and incident into the waveguide at a specific angle, so that the ultrasonic signal propagates unidirectionally along the axis of the waveguide, and then propagates to the corresponding battery under test through the sound-guiding wedges. When the ultrasonic surface wave propagating along the surface of the battery under test interacts with the battery under test, the ultrasonic surface wave is converted into an ultrasonic electrical signal. The three-dimensional feature parameters of the ultrasonic electrical signal are extracted and input into the machine learning model, which outputs quantitative assessment values ​​of the battery's state of charge and health status.

[0015] In some implementations, the three-dimensional feature parameters include: amplitude attenuation rate, center frequency offset, and time-of-flight distortion; Amplitude decay rate characterizes the enhanced reflection at the gas-solid interface caused by gas generation or electrolyte drying; time-of-flight distortion characterizes the electrode volume expansion and shell stress changes caused by lithium-ion deintercalation during charging and discharging; center frequency offset characterizes the battery shell deformation caused by abnormal gas generation in the battery.

[0016] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application provides an ultrasonic-guided online monitoring device for battery modules. By setting up a waveguide, the traditional complex transducer array is simplified into a single waveguide structure, which greatly reduces hardware costs and wiring complexity. It achieves isolation between the excitation device (acoustic excitation module and transmitting transducer) and the battery cell under test. By placing the excitation device (acoustic excitation module and transmitting transducer) outside the battery module, the potential for insulation failure and electromagnetic interference caused by high voltage pulses introduced into the battery pack is eliminated. Combined with gradient aperture energy compensation and surface wave mode conversion technology, it effectively overcomes the problems of acoustic energy attenuation along the path and fixed spacing coupling, and achieves uniform coverage of the acoustic field energy of the entire module and high sensitivity capture of early thermal runaway characteristics. Attached Figure Description

[0017] Figure 1 This is the waveguide structure provided in the embodiments of this application.

[0018] Figure 2 This is the structure of the online monitoring device for battery modules provided in the embodiments of this application.

[0019] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is the transmitting transducer; 2 is the waveguide connector; 3 is the sound-guiding wedge; 4 is the waveguide; 5 is the sound-absorbing structure; 6 is the battery module; 7 is the electrode connector; 8 is the receiving sensor. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0022] In this application, the terms “first” and “second” are used to distinguish different objects, rather than to describe a specific order of objects.

[0023] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0024] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0025] The embodiments of this application are described below with reference to the accompanying drawings.

[0026] like Figure 1 and Figure 2 As shown, this application provides an online monitoring device for battery modules based on ultrasonic guides, including: a waveguide 4, an acoustic excitation module, a transmitting transducer 1, a receiving sensor 8, a waveguide connector 2, several sound-guiding wedges 3, a sound-absorbing structure 5, and a signal acquisition module; Transmitting transducer 1 is coupled to one end of waveguide 4 through waveguide connector 2. Acoustic excitation module drives transmitting transducer 1 to generate ultrasonic signal. Acoustic excitation module is used to generate pulse electrical signal. Transmitting transducer 1 is used to convert pulse electrical signal into ultrasonic signal. Ultrasonic signal propagates axially in waveguide 4. The waveguide 4 is an integral acoustic guiding component. Its structure is an acoustic leakage waveguide. Several acoustic openings are arranged along the axial direction on its tube wall. An acoustic wedge 3 is coupled to the outside of each acoustic opening. The bottom surface of the acoustic wedge 3 is used to fit the surface of the battery under test. During the transmission of the ultrasonic signal within the waveguide 4, controlled energy leakage occurs through several acoustic openings and enters the corresponding acoustic wedge 3. The sound guide wedge 3 has a preset wedge angle and is configured to convert the leakage sound wave from the acoustic opening into an ultrasonic surface wave that propagates along the surface of the battery under test. The ultrasonic surface wave carries the battery status information and is received by the receiving sensor 8. The receiving sensor 8 is used to receive ultrasonic surface waves and convert them into ultrasonic electrical signals for transmission to the signal acquisition module; The signal acquisition module is used to extract the three-dimensional feature parameters of the ultrasonic electrical signal and input them into the machine learning model to obtain quantitative evaluation values ​​of the battery's state of charge and health status.

[0027] In some embodiments, the battery arrangement spacing d within the battery module 6 is fixed and cannot be changed. In order to compensate for the energy attenuation of the ultrasonic signal during transmission and to ensure that the acoustic energy amplitude obtained at each acoustic wedge 3 is consistent, the geometric dimensions of several acoustic openings (including aperture size, opening depth, or slit length) are distributed in a gradient increasing manner along the propagation direction of the ultrasonic guided wave within the waveguide; or, the distribution density of several acoustic openings increases along the propagation direction.

[0028] In some implementations, the center frequency f of the ultrasonic pulse signal generated by the acoustic excitation module is selected according to a fixed distribution spacing d to satisfy the non-Bracket resonance condition, so as to ensure that the ultrasonic signal maintains a traveling wave transmission state in the waveguide 4 and avoids the formation of standing wave nodes at specific openings.

[0029] In some implementations, the center frequency range of the transmitting transducer 1 is 20 kHz to 300 kHz.

[0030] In some embodiments, the preset wedge angle of the sound-guiding wedge 3 The following conditions must be met: ; in, The propagation speed of the ultrasonic signal in the sound guide wedge 3 material; Let be the propagation velocity of the ultrasonic surface wave on the surface of the battery under test, and < .

[0031] In some embodiments, the waveguide 4 is a hollow cylindrical structure filled with an acoustic coupling liquid medium; the waveguide connector 2 is provided with a transition layer that matches the acoustic impedance of the acoustic coupling liquid medium; and the end of the waveguide 4 is provided with a conical or wedge-shaped sound absorber to absorb the residual acoustic wave energy incident on the end of the waveguide 4.

[0032] This application provides an online monitoring method for battery modules based on ultrasonic conduction, specifically including the following steps: Step S1: The acoustic excitation module generates a pulsed electrical signal, which is converted into an ultrasonic signal by the transmitting transducer 1, and emitted at a specific angle. The ultrasonic signal is incident into the waveguide 4, where it propagates unidirectionally along the axial direction and is transmitted to the corresponding battery under test through the sound-guiding wedge 3; after the ultrasonic surface wave interacts with the battery, it is received by the receiving sensor 8. Step S2: Record the ultrasonic electrical signals at different battery locations, respectively , , The three-dimensional feature parameters of the ultrasonic electrical signal were extracted, including amplitude attenuation rate, center frequency shift, time-of-flight distortion, and other features; among them, the acoustic signals of the battery pack in the initial healthy state were recorded as follows: , , … ; Step S3: Input the three-dimensional feature parameters into the trained machine learning model, and combine the weighted fusion results of amplitude decay rate, center frequency offset and time-of-flight distortion to simultaneously output the quantitative evaluation values ​​of battery state of charge (SOC) and state of health (SOH); where the input of the machine learning model is the three-dimensional feature parameters; the output is the battery state of charge and state of health.

[0033] It should be noted that the three-dimensional feature parameters of batteries in different health states, along with the corresponding known battery state of charge and health states, are input into the machine learning model for training.

[0034] Example This application proposes an online monitoring device for battery modules based on ultrasonic waveguides. It is suitable for energy storage modules consisting of 16 strings of 280 Ah square aluminum-cased lithium iron phosphate batteries arranged in a double-row linear configuration, with the center-to-center spacing of the battery cells fixed at d=45mm. The main structure of the device includes a waveguide serving as the acoustic transmission backbone, preferably a hollow stainless steel tube with an outer diameter of 10mm and a wall thickness of 1mm. The tube is filled with a 100 cc dimethyl silicone oil liquid medium via vacuum injection. A transmitting transducer is coupled to the starting end of the waveguide through a waveguide connector with an acoustic impedance matching transition layer (such as an acoustic rubber layer). Notably, the transmitting transducer is physically installed on the external structure of the battery module, extending only into the battery module through an insulated waveguide. This structural design completely isolates the high-voltage excitation signal source from the high-voltage DC environment inside the battery pack, eliminating safety hazards caused by insulation failure.

[0035] In this embodiment, several circular acoustic openings are formed along the axial direction of the waveguide, corresponding to the center position of each individual cell, and a gradient design of geometric dimensions is adopted. Specifically, along the propagation direction of the ultrasonic guided wave, the diameter of the acoustic openings increases linearly or exponentially. For example, the diameter of the first opening closest to the transmitting end is designed to be 1.5 mm to limit excessive acoustic energy leakage at the near end; while the diameter of the last opening furthest from the transmitting end is increased to 4.5 mm to maximize the acoustic energy leakage rate at the far end. Through this gradient compensation mechanism, the energy loss of the guided wave during transmission within the tube is effectively offset, ensuring that the amplitude of the acoustic energy radiated from each position from the beginning to the end remains highly consistent, achieving uniform coverage of the sound field of the entire module. To eliminate standing wave interference formed by the superposition of reflected waves within the tube, a conical rubber sound absorber with a length of approximately 20 mm is installed inside the end of the waveguide. Its acoustic impedance matches that of the silicone oil inside the tube, and it is used to completely absorb the remaining acoustic wave energy incident to the end, ensuring that the sound field inside the tube maintains a unidirectional traveling wave transmission state.

[0036] On the outer side of each acoustic opening, a sound-guiding wedge made of PMMA (polymethyl methacrylate) is coupled and connected. Its bottom surface is tightly attached to the surface of the battery under test via a flexible dry coupling sheet coated with acoustic coupling agent. The core function of this sound-guiding wedge is to achieve wave mode conversion, that is, to convert the volume wave leaking from the waveguide opening into an ultrasonic surface wave (Rayleigh wave) propagating along the surface of the battery's aluminum casing, thereby improving the detection sensitivity of casing stress and internal minute defects. The preset wedge angle of the sound-guiding wedge is [not specified in the original text]. The calculations and settings are strictly based on Snell's law, and the longitudinal wave velocity within the PMMA wedge in this embodiment is known. The Rayleigh wave velocity on the surface of the battery's aluminum casing is approximately 2750 m / s. The speed is approximately 2950 m / s, so the wedge angle is... The center frequency f of the ultrasonic pulse signal generated by the acoustic excitation module is set to 200kHz. This frequency selection must avoid the Bragg resonant frequency point related to the fixed spacing d to ensure the purity of the monitoring signal.

[0037] The online monitoring process based on the above device is as follows: When the battery module is in an initial healthy state and is stationary, the system first drives the transmitting transducer to generate a 200kHz narrowband pulse excitation through the acoustic excitation module. The sound wave propagates along the liquid-filled waveguide and leaks in a controlled manner through the gradient opening. After being converted into a surface wave by the wedge, it propagates along the battery casing and is finally received by the PVDF piezoelectric film receiving sensor attached to the other end of the battery. The signals of each channel are recorded as reference acoustic features.

[0038] During battery module operation, the system periodically acquires signals. The host computer compares and analyzes the real-time acquired signals with a reference signal to extract three-dimensional feature parameters: amplitude decay rate, time-of-flight distortion, and center frequency offset. Amplitude decay rate primarily characterizes enhanced gas-solid interface reflection caused by trace gas generation or electrolyte drying. Time-of-flight distortion primarily characterizes electrode volume expansion and shell stress changes caused by lithium-ion intercalation / deintercalation during charging and discharging. Center frequency offset characterizes significant deformation or bulging of the battery shell caused by abnormal gas generation. The feature parameters are input into a pre-trained machine learning model (such as a convolutional neural network), and after weighted fusion calculation, the system synchronously outputs quantitative evaluation values ​​of the state of charge (SOC) and state of health (SOH) for each individual battery cell. When an abnormality is detected in the feature parameters of a certain channel (such as a sudden increase in amplitude decay rate or a non-periodic step in time of flight), the system immediately determines that the battery has a risk of thermal runaway and issues a warning. Through the above implementation method, this application achieves high-precision online monitoring of the state of all cells within the module in a low-cost and high-safety manner without altering the original structure of the battery module.

[0039] In summary, this application has the following advantages compared with the prior art: This application simplifies the traditional complex transducer array into a single waveguide structure through waveguide design, significantly reducing hardware costs and wiring complexity. It achieves isolation between the excitation device and the cell under test, places the high-voltage excitation source outside the module, and eliminates the risk of insulation failure and electromagnetic interference caused by high-voltage pulses introduced into the battery pack. Combined with gradient aperture energy compensation and surface wave mode conversion technology, it effectively overcomes the problems of acoustic energy attenuation along the path and fixed-spacing coupling, achieving uniform coverage of the acoustic field energy of the entire module and high sensitivity capture of early thermal runaway characteristics.

[0040] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0041] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0042] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium.

[0043] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are all limitations relative to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are allowed, and approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable.

[0044] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An online monitoring device for battery modules based on ultrasonic conduction, characterized in that, include: Waveguide, acoustic excitation module, transmitting transducer, receiving sensor, waveguide connector, several acoustic wedges and signal acquisition module; The output of the acoustic excitation module is connected to the transmitting transducer; the transmitting transducer is coupled to one end of the waveguide through a waveguide connector; several acoustic openings are arranged axially on the wall of the waveguide, and a sound-guiding wedge is coupled to the outside of each acoustic opening, with the bottom surface of the sound-guiding wedge in contact with the surface of the battery under test; the receiving sensor is located on the surface of the battery under test, and its output is connected to the signal acquisition module. The acoustic excitation module generates pulsed electrical signals; the transmitting transducer converts the pulsed electrical signals into ultrasonic signals; the waveguide allows the ultrasonic signals to be transmitted within it, and energy leakage occurs through several acoustic openings to the corresponding acoustic wedges; the acoustic wedges have preset wedge angles to convert the ultrasonic signals leaking through the acoustic openings into ultrasonic surface waves propagating along the surface of the battery under test; the receiving sensor receives the ultrasonic surface waves carrying battery status information and converts them into ultrasonic electrical signals, which are then transmitted to the signal acquisition module; the signal acquisition module extracts the three-dimensional feature parameters of the ultrasonic electrical signals and inputs them into a machine learning model to obtain quantitative evaluation values ​​of the battery's state of charge and health status. The preset wedge angle of the sound guide wedge is: ； in, The propagation speed of the ultrasonic signal in the sound-guiding wedge material; Let be the propagation velocity of the ultrasonic surface wave on the surface of the battery under test, and < ; The geometric dimensions of the acoustic apertures increase in a gradient along the direction of ultrasonic signal propagation within the waveguide; or the distribution density of the acoustic apertures increases along the propagation direction. The three-dimensional characteristic parameters include: amplitude attenuation rate, center frequency offset, and time-of-flight distortion; Amplitude decay rate characterizes the enhanced reflection at the gas-solid interface caused by gas generation or electrolyte drying; time-of-flight distortion characterizes the electrode volume expansion and shell stress changes caused by lithium-ion deintercalation during charging and discharging; center frequency offset characterizes the battery shell deformation caused by abnormal gas generation in the battery.

2. The online monitoring device for battery modules according to claim 1, characterized in that, The center frequency of the pulsed electrical signal generated by the acoustic excitation module is determined according to the fixed distribution spacing of the batteries, satisfying the non-Bracket resonance condition so that the ultrasonic signal maintains a traveling wave transmission state in the waveguide.

3. The online monitoring device for battery modules according to claim 1, characterized in that, The waveguide is a hollow cylindrical structure filled with an acoustic coupling liquid medium; the waveguide connector is provided with a transition layer that matches the acoustic impedance of the acoustic coupling liquid medium.

4. The online monitoring device for battery modules according to claim 3, characterized in that, The waveguide is equipped with a conical or wedge-shaped sound absorber at its end to absorb the residual ultrasonic signal energy incident on the end of the waveguide.

5. The online monitoring device for battery modules according to claim 1, characterized in that, The transmitting transducer and acoustic excitation module are located on the external structure of the battery module and extend into the battery module through an insulated waveguide.

6. A method for online monitoring of a battery module based on ultrasonic conduction, using the online monitoring device for battery modules according to claim 1, characterized in that, Includes the following steps: The pulsed electrical signal is converted into an ultrasonic signal and incident into the waveguide at a specific angle, so that the ultrasonic signal propagates unidirectionally along the axis of the waveguide, and then propagates to the corresponding battery under test through the sound-guiding wedges. When the ultrasonic surface wave propagating along the surface of the battery under test interacts with the battery under test, the ultrasonic surface wave is converted into an ultrasonic electrical signal. The three-dimensional feature parameters of the ultrasonic electrical signal are extracted and input into the machine learning model, and the quantitative evaluation values ​​of the battery's state of charge and health status are output. The three-dimensional characteristic parameters include: amplitude attenuation rate, center frequency offset, and time-of-flight distortion; Amplitude decay rate characterizes the enhanced reflection at the gas-solid interface caused by gas generation or electrolyte drying; time-of-flight distortion characterizes the electrode volume expansion and shell stress changes caused by lithium-ion deintercalation during charging and discharging; center frequency offset characterizes the battery shell deformation caused by abnormal gas generation in the battery.

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