System for non-contact, rapid ultrasonic testing of batteries

Abstract

The disclosure relates to a system for rapid, non-contact testing of batteries using ultrasound capable of producing real-time feedback. The system includes an array of transducers connected to an edge computing node capable of receiving the signals from the transducers and analyzing the data to identify the condition of the battery being tested. A user may view the battery parameters obtained from the test either onsite or remotely. This system facilitates real-time in-screening of batteries during manufacture or assembly. The systems and methods may also be used during formation of the battery / cell or during any electrical testing for the battery / cell. The system would allow rapid, non-destructive testing of batteries in a cost-effective manner. The invention complements the existing electrical and / or temperature testing methods that are currently used, for real-time effective inspection, with potential to improve current manufacturing methods.

Description

SYSTEM FOR NON-CONTACT, RAPID ULTRASONIC TESTING OF BATTERIESCROSS-REFERENCES TO RELATED APPLICATION

[0001] This application claims priority to Indian Patent Application No. 202341015890 entitled SYSTEM FOR NON-CONTACT, RAPID ULTRASONIC TESTING OF BATTERIES filed on 10 August, 2023.FIELD OF INVENTION

[0002] The present disclosure relates to testing of batteries, in particular it relates to noncontact, rapid testing of batteries to determine the state of the battery health.DESCRIPTION OF THE RELATED ART

[0003] Batteries are an energy storage device which stores energy and discharges it by converting chemical energy into electrical energy. There are different types of batteries such as alkaline, lithium-ion, lithium-polymer, and nickel-metal hydride manufactured from variety of materials. Lithium-ion batteries are used in electric vehicles as well as most commercially available consumer electronic devices which require charging at regular intervals.

[0004] Batteries in general and lithium-ion batteries in particular, are prone to plurality of variations such as their energy density, life cycle and safety. These batteries may also have accelerated degradation and failure due to a range of manufacturing defects including the presence of foreign bodies, misaligned / poor-quality electrodes, improper electrolyte fdling / wetting and gas formation. Effective identification of these manufacturing inconsistencies / defects at the time of manufacture are not available currently. To identify the defects that may occur in the batteries early electrical testing alone is not sufficient, while other commonly used techniques such as X Ray CT and UT scans are time consuming, expensive and hazardous in some cases. These are selectivelyperformed only for confirmation of potential defects that are identified using indirect techniques

[0005] Various publications are available are available for testing the state of batteries. PCT application 2022232663A2 discloses management for charging / discharging of an energy storage device and ultrasound interrogation for passing ultrasound energy through energy storage device during charge / discharge cycles, Chinese application 110108799A relates to detecting a lithium ion migration state of a battery, US application 11549919B2 describes prediction of state of charge (SOH), state of health (SOC) and other characteristics of batteries using acoustic signals. Various non-patent literature also discuss techniques for detecting the state of batteries. “Ultrasound Tech Offers Sophisticated Battery-Testing Intelligence” discloses measuring of SoC and SoH of batteries by sensing internal changes in the battery, “Ultrasonic Tester-Non-contact Ultrasonic Testing System” discusses non-contact, non-destructive, and dry inspection using ultrasonic means to identify air bubbles, peeling spots, and foreign materials inside batteries and “Ultrasonic Scanning System for Non-destructive Testing of Pouch / Prismatic Cells” relates to non-destructive testing of pouch / prismatic cells.

[0006] There is a requirement for an inexpensive, convenient, and rapid characterization technique to identify the electrolyte / gas related internal changes or defects inside cells and batteries, especially during manufacture and end / second life assessment of the said batteries without damaging the cells / batteries.SUMMARY OF THE INVENTION

[0007] The invention discloses systems and methods for rapid, non-contact testing of batteries using ultrasound configured for real-time feedback. In various embodiments, the system comprises a pair of identical 2-dimensional ultrasound transducer arrays (102a, 102b) placed on either side of a battery (114) to be tested and to cover a surface area thereof. The transducer arrays may be configured to have n x m array elements. One of the arrays (102a) may be a transmit array to transmit ultrasound through the batteryand the other (102b) a receive array configured to receive attenuated ultrasound on the other side of the battery.

[0008] The system further includes an ultrasound driver-receiver module (104) comprising circuitry to transmit electrical impulses to the elements of the transmit array (102a) for generating the ultrasound pulses, and to receive voltage signals from the receive array (102b), characteristic of the attenuated ultrasound. The system includes a visualization module comprising a display (108) to render information on the integrity of the battery over the surface area thereof, using the signals characteristic of the attenuated ultrasound.

[0009] In some embodiments, the system includes an edge computing node (106) configured to connect the ultrasound driver-receiver module (104) to the visualization module, or to a remote server (112), or both. In some embodiments, the system may form part of infrastructure comprising multiple ultrasound arrays (102a, 102b), ultrasound driver-receiver modules (104) and edge computing nodes (106), wherein the edge computing nodes are connected to the remote server (112) for monitoring a battery production line.

[0010] In various embodiments, the arrays (102a, 102b), include ultrasound transducers 121-1, 121-2... 121-n, in m rows of elements 122-1, 123-1... 12m-l. In various embodiments, the transducers are selected from one of piezoelectric transducers, or magnetostrictive transducers.

[0011] In various embodiments, a method for real time non-contact testing of a battery for internal defects, is disclosed. The method comprises providing a first 2-dimensional ultrasound transducer array covering one side of the battery, the transducer array configured to transmit pulses from one or more transducers in the array, transmitting pulses from at least one transducer in the array across a thickness of the battery, and receiving attenuated ultrasound pulses characteristic of an integrity of the battery over an area covered by the array. The receiving may comprise receiving attenuated ultrasound pulses transmitted through the cell at a second 2-dimensional ultrasound transducer arrayplaced on the other side of the battery, or receiving ultrasound pulses transmitted through the cell and reflected from a back wall of the cell at the first transducer array.

[0012] In some embodiments of the method, the receiving attenuated ultrasound pulses transmitted through the cell at a second 2-dimensional ultrasound transducer array placed on the other side of the battery comprises transmitting a single pulse from each element of the first array and receiving an attenuated signal at a corresponding receive element at the second array.

[0013] In some embodiments of the method, the receiving (205) ultrasound pulses transmitted through the cell and reflected from a back wall of the cell at the first transducer array comprises transmitting from one or more array elements and receiving attenuated signals at all the elements 121-1, 121-2... - 12m-n of the m x n array. In some embodiments of the method, the transmitting may comprise transmitting multiple signals separated in time.

[0014] In some embodiments, the method may comprise visualizing an integrity of the battery cell across an area thereof, in a display. In some embodiments, the method may comprise visualizing an integrity of the battery cell at intervals during a manufacturing cycle thereof.

[0015] In various embodiments, the method is applied to a pouch battery or a prismatic or a cylindrical battery cell. In various embodiments, the ultrasonic transducer array is operated at frequency between 20 kHz to 2 MHz. In various embodiments, the method comprises analyzing attenuated ultrasonic pulses using one or more parameters selected from peak signal amplitude, time of arrival, dominant frequency, ring down time and zero crossing rate. Using the analysis, the method may comprise identifying swelling, dendrite formation, electrolyte fill level, or gas formation within the battery. In some embodiments, the method may include computing SoC, or SoH of the battery using the attenuated ultrasonic pulses.

[0016] This, and other aspects are disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention has other advantages and features, which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:

[0018] FIG. 1A illustrates the system for non-contact testing of battery using ultrasound.

[0019] FIG. IB shows top view of ultrasound sensor array placed over a battery to be tested.

[0020] FIG. 2A shows a method of testing a battery using two transducer arrays on either side for transmitting ultrasound and receiving test results.

[0021] FIG. 2B shows a method of testing a battery from one side using a single transducer array.

[0022] FIG. 3 illustrates method of testing battery cells using the system disclosed.

[0023] FIG. 4 shows test setup and sample holder used in testing a battery.

[0024] FIG. 5A illustrates ultrasound amplitude vs. time obtained from a good battery without defects or discontinuities using two-sided inspection technique.

[0025] FIG. 5B shows ultrasound amplitude vs. time obtained from a defective battery with high attenuation because of defects using two-sided inspection technique.

[0026] FIG. 6A shows ultrasound amplitude vs. time obtained from a good battery without defects or discontinuities using one-sided inspection technique.

[0027] FIG. 6B shows ultrasound amplitude vs. time obtained from a defective battery with high attenuation because of defects using one-sided inspection technique.

[0028] FIG. 7A and 7B show ultrasound time of flight traces for good and defective battery respectively, using one-sided inspection technique.

[0029] FIG. 8A shows amplitude measured for an optimally fdled cell, while FIG. 8B shows amplitude for a cell without electrolyte.

[0030] FIG. 8C shows ultrasound amplitude for an under fdled cell with 50% fdling, while FIG. 8D illustrates amplitude measured for an overfilled cell with 150% fdling.

[0031] FIG. 9A shows measured and predicted voltage using contact ultrasound across charge-discharge cycles.

[0032] FIG. 9B shows measured and predicted voltage using non-contact ultrasound across one charge-discharge cycle.

[0033] Referring to the figures, like numbers indicate like parts throughout the various views.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope.

[0035] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of “a”, “an”, and “the” include plural references. The meaning of “in” includes “in” and “on.” Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein. The term cell is used to define a single electrochemical power producing unit having a pair of electrodes and an electrolyte therebetween. Battery means an array of cells interconnected in series or in parallel to form various configurations of power packs.

[0036] The present subject matter describes systems, devices and methods for noncontact testing of cells and batteries or other flat products using ultrasound capable of producing real-time feedback. The invention is intended to facilitate the 100% screening of batteries during manufacture or assembly, to identify defects or to identify progress or stage of production. The devices and methods disclosed herein may also be used during formation of the battery or during any electrical testing for the battery. The system consists of an array of ultrasonic transducers positioned around the battery,transmit / receive electronics, an edge computing node, and a display interface. The system would allow rapid, non-contact, non-destructive testing of batteries in a cost- effective manner, as further described with reference to the drawings.

[0037] In various embodiments, a system 100 for non-contact testing of batteries or cells, is disclosed. The system 100 includes an array of ultrasonic transducers 102a, and optionally a second array 102b for transmitting and receiving ultrasonic signals over the entire battery area, as disclosed with reference to FIG. 1A and FIG. IB. As illustrated in FIG. 1A, the system in one embodiment may have ultrasonic transducer arrays 102a and 102b placed on either side of the cell 114. In various embodiments, the arrays 102a and 102b are strategically placed to cover the entire surface area of the battery as illustrated in FIG. 2A, ensuring a uniform transmission and reception of ultrasonic waves across the battery's structure. In this configuration, the array of transducers may operate in pitch catch, i.e. transmit-receive signals using different transducers. One array 102a transmits ultrasound waves while the receive array 102b is configured to receive attenuated ultrasound on the other side of the battery. This dual-array setup enhances the detection accuracy by capturing the attenuation and reflection of the waves, which are indicative of the battery’s internal condition, such as the presence of defects, misalignments, or inconsistencies. The one or more arrays may receive instruction from an ultrasound driver-receiver module 104 comprising circuitry to transmit electrical impulses to the elements of the transmit array 102a for generating the ultrasound pulses, and to receive voltage signals from the receive array 102b, characteristic of the attenuated ultrasound.

[0038] In various embodiments, each array 102a or 102b may be configured in a rectangular matrix as illustrated in FIG. IB, to enable inspection of the entire battery area at one instant. Thus, the cell area may be divided into a m x n segments and each transducer may be configured to cover one segment. As illustrated in FIG. IB, the array of transducers utilized for testing the battery having transducers 121-1, 121-2... 121-m in a row and having n rows, with transistors up to 12n-l to 12n-m in the mthcolumn.

[0039] In one embodiment, the array of transducers 102a, may be placed on one side of the battery to be tested so that transmission and receiving may be done by the same sensors in pulse-echo mode, as illustrated in FIG. 2B. The array is placed on one side of the battery and is responsible for both transmitting and receiving the ultrasonic waves. In various embodiments, the transmitting transducer may be a single transducer or multiple transducers placed on one side of the cell, while all the array elements may be configured to receive the ultrasound signal for analysis after reflection from the back wall of the battery, as illustrated in FIG. 2B. This one-sided inspection configuration and method are particularly useful for scenarios where space constraints or battery cell design and / or manufacturing setup limit access to both sides of the cell. The embodiments illustrated by FIG. 2B emphasize the versatility of the system in adapting to various battery configurations while still providing reliable defect detection.

[0040] The system further includes an edge computing node 106 configured to connect the ultrasound driver-receiver module 104 to the visualization module or display 108, or to a remote server 112, or both. In some embodiments, the node 106 employs advanced analytics for automatic defect recognition, defect quantification and remaining useful life predictions. The edge computing node 106 may in some embodiments, have its own display and may be provided with an IOT gateway 110. The visualization module 108 is configured to render information on the integrity of the battery over the entire area thereof, using the signals characteristic of the attenuated ultrasound.

[0041] In some embodiments, the system may form part of infrastructure comprising multiple ultrasound arrays 102a, 102b, ultrasound driver-receiver modules 104 and edge computing nodes 106, wherein the edge computing nodes are connected to the remote server 112 for monitoring a battery production line. The IOT gateway 110 may interface with a central dashboard or a cloud database for monitoring of such large production or refurbishment operations of cells or batteries.

[0042] In various embodiments, the invention discloses a method 200 for real time noncontact testing of a battery for internal defects with reference to FIG. 3. The methodcomprises the steps of providing 201 a first 2-dimensional ultrasound transducer array covering one side of the battery cell, the transducer array configured to transmit pulses from one or more transducers in the array, transmitting 202 pulses from at least one transducer in the array across a thickness of the battery cell, and receiving attenuated ultrasound pulses characteristic of an integrity of the battery over an area covered by the array.

[0043] In some embodiments where one transmit array 102a and one receive array 102b are used, the method comprises receiving 203 attenuated ultrasound pulses transmitted through the cell at a second 2-dimensional ultrasound transducer array placed on the other side of the battery.

[0044] In some embodiments where a single array 102a is used both for transmitting and receiving, the method comprises receiving 205 attenuated signals transmitted through the cell and reflected from a back wall of the cell at at all the elements 121-1, 121-2. . . - 12m- n of the m x n array. In some embodiments, the method comprises transmitting multiple signals separated in time.

[0045] In various embodiments, the method may comprise visualizing an integrity of the battery cell across an area thereof, in a display, as may be present at a monitoring station in a manufacturing facility. The method may thus facilitate visualizing an integrity of the battery cell at intervals during a manufacturing cycle thereof. The system and method disclosed are general enough to test any kind of battery such as a pouch battery, a prismatic or a cylindrical battery cell.

[0046] In various embodiments of the method, the ultrasonic transducer array is operated at frequency between 20 kHz to 2 MHz. In various embodiments, the method comprises analyzing 206 attenuated ultrasonic pulses using one or more parameters selected from peak signal amplitude, time of arrival, dominant frequency, ring down time and zero crossing rate. Analysis of these parameters may enable identifying 207 defects or manufacturing or operating characteristics of the battery. In some embodiments, the identifying may include detecting swelling, dendrite formation, electrolyte fdl level, orgas formation within the battery. In some embodiments, the detecting of electrolyte fill level may include identifying defects such as uneven distribution of electrolyte, or uneven wetting across the battery. In one embodiment, the method may include using peak signal amplitude to identify defects or electrolyte fill level.

[0047] In some embodiments of the method, the analyzing step 207 may include computing state of charge or SoC, or state of health (SoH) of the battery using the attenuated ultrasonic pulses. In some embodiments, estimating state of charge of the battery may involve analyzing one or more of peak signal amplitude, time of arrival, dominant frequency, ring down time and zero crossing rate and measure SoC using these parameters. In one embodiment, the SoC is measured using peak amplitude. In some embodiments, the method of measuring SoC may include using an artificial neural network (ANN) to eliminate noise from the measured signals and to improve accuracy.

[0048] The array of ultrasound transducers 102a, 102b, in various embodiments may utilize longitudinal or shear waves, or a combination of waveforms for determining the condition of the battery 114 being tested. The devices and methods of the invention are, configured to provide integrity information of the battery 114 without the need for scanning as well as to dispense with contact, thereby avoiding contamination of the battery 114 due to use of a couplant. The devices and methods of the invention are thus intended for use either continuously or intermittently during production cycle of battery cells, without hindrance to the production processes.

[0049] The array of transducers 102a, 102b may be connected to a receiver unit 104 adapted to receive the signals generated by the array of transducers 102a, 102b. Alternatively, the receiver unit 104 may be integrated with the transducers 102a, or 102b. The receiver unit 104 is connected to an edge computing node 106, which is configured to receive parallel streams of data generated from the signals received from the array of transducers 102. These parallel streams of data are analysed to quantify variation within and in between different area elements within the cell area. The edge computing node 106 is configured to allow real time direct feedback on the health of thebatery. The feedback may be both quantitative and qualitative, such as directly identifying changes in the electrode structural integrity including swelling or dendrite formation, electrolyte distribution / weting, gas formation, state of charge / state of health estimation etc. The edge computing node 106 is connected to a local display 108 which allows the user to observe the outcome of the batery test instantaneously. The data streams generated during the testing of the batery may be used for further analytics at the edge computing node 106 which provides real time analysis of the data. The data may further be provided to a central location for data analysis, such as a central dashboard 112, or for storage and archival.

[0050] The central dashboard 112 maybe connected to the edge computing node 106 by an IOT gateway 110 for facilitating transfer of data from the edge computing node 106, since the ultrasonic imaging array systems may be configured to be deployed at multiple locations in the batery manufacturing workflow. The system may be used for testing the bateries during the manufacture of the batery such as during formation, integration, and other electrical testing, batery cycling without interfering to any of these processes, this facilitates in reducing the wastage caused due to batery damage encountered during its process of manufacture. The said system may also be applied to test a completely formed batery and its components such as anode, cathode, separator, housing etc. or during cell fabrication including electrolyte filling stage. Further, the system may be used to test the batery in free state or under pressure, wherein the pressure is applied by specially designed fixtures for non-contact inspection of bateries. The system is particularly suitable for testing bateries having flat geometry such as pouch. The methods of inspection proposed herein are equally applicable for other batery configurations in electrode manufacturing such as prismatic or cylindrical cells.

[0051] In various embodiments, the transducers 121-1... 121-n-m etc. may be one of piezoelectric transducers, laser-generated ultrasound, electromagnetic or magnetostrictive transducers. The transducers may utilize any mode of non-contact actuation, independently or in combination with other sensing techniques including laseror vision or microwave. The transducers 121-1 maybe shaped differently to suit the geometry of the battery being tested. For instance, a curved surface may be inspected with elements either having curvature, or arranged with corresponding curvature. The frequency for operation of the array of transducers maybe varied to suit a given application such as varied battery size, stack complexity, etc. which may vary between 20 kHz at the lower end to 2 MHz at the higher end. In various embodiments, the thicker the battery, the lower the frequency used, and the higher frequencies are used for inspection of thinner batteries.

[0052] The signals that are captured from array of transducers may be used to making plurality of measurements that facilitate in identifying issues such as gas formation, electrolyte wetting and its inconsistencies, defects to electrodes and alignment problems within the battery 114 being tested. Further, the system is real-time, since no scanning is required. The surface of the article requires minimal preparation and no contamination of the cell surfaces takes place because there is no need for a liquid or gel couplant. The system is useful to provide real time direct feedback of quantitative and qualitative defects that directly affect structural integrity of the cell, including swelling, dendrite formation, electrolyte distribution / wetting, gas formation, and for SoC, SoH estimation of the cell. The data stream obtained from the inspection may be used for analytics at the edge node or at a central location for further analysis.

[0053] The systems, devices and methods may be applied to a test cell as it is being manufactured, at any stage during formation, integration and other electrical testing, charge-discharge battery cycling etc. without interfering with any of the processes or manufacturing stages. The invention complements the existing electrical and / or temperature testing methods that are currently used, for real-time effective inspection, with potential to improve current manufacturing methods. The systems and methods could be applied to test a finished cell and or its internals and components such as anode, cathode, separator, housing etc. and / or during cell fabrication, including electrolyte filling stage. The method could also be applied to a cell under pressure, with suitablydesigned special fixtures. The technique may also be used for second life assessment of used batteries, i.e. for assessing the recycling or reclamation potential, as well. For instance, batteries at the end of life may be assessed for reclamation or rejuvenation using various available techniques, using the methods of the invention. This could potentially increase the effectiveness of the reclamation process.

[0054] The present disclosure presents several advantages over prior art such as noncontact one-sided or two-sided inspection of batteries with minimal or no scanning. Further, real time feedback is received by the user indicating both the qualitative and quantitative parameters of the battery being tested. Additionally, the system is useful for screening of batteries during manufacture or assembly as they may be easily integrated into the manufacturing / assembly process of batteries. A user may view the outcome of battery testing either onsite or even from a remote location. The real-time output could be used as a control parameter to optimise the cell / battery fabrication - such as electrolyte filling, formation or cycling.EXAMPLES

[0055] EXAMPLE 1: Testing Batteries using Two Ultrasound Transducer Arrays

[0056] Batteries were tested using a setup as illustrated in FIG. 4, which also shows sample holder used in testing a battery. A distance was maintained between the transmit array and the battery and also between the battery and the receive array. The setup is designed to maintain the battery in a stable position, ensuring consistent and accurate ultrasonic measurements. The test setup is configured to minimizing external variables that could affect the test results, such as vibration or misalignment of the battery during inspection.

[0057] The batteries were 199x152x10 mm in dimension pouch batteries. One good battery cell and another known to be defective were tested. Ultrasound amplitude vs. time obtained from a good battery without defects or discontinuities using two-sided inspection technique is shown in FIG. 5A. The clear and strong signal depicted in thegraph indicates that the ultrasound waves have passed through the battery with minimal attenuation, confirming the absence of structural anomalies. FIG. 5B shows ultrasound amplitude vs. time obtained from a defective battery with high attenuation because of defects. The graph reveals significant attenuation in the ultrasound signal, which is a direct consequence of defects within the battery. This attenuation may be due to issues such as internal voids, misaligned components, or foreign material presence, making this graph a critical tool for identifying battery health problems.

[0058] EXAMPLE 2: Testing Batteries using a Single Ultrasound Transducer Array

[0059] Batteries were tested using one-sided battery testing technique as shown in FIG. 2B. Ultrasound amplitude vs. time obtained from a good battery without defects or discontinuities using one-sided inspection technique, as shown in FIG. 6A. The graph shows a strong, undistorted signal, indicating that the battery's internal structure is intact and free from defects that would otherwise absorb or scatter the ultrasound waves. FIG. 6B shows ultrasound amplitude vs. time obtained from a defective battery with high attenuation because of defects using one-sided inspection technique. The significant attenuation observed in the graph suggests the presence of internal defects, such as poor electrode alignment or gas pockets, which compromise the battery's structural integrity and performance.

[0060] FIG. 7A and 7B show ultrasound time of flight traces for good and defective battery respectively, using one-sided inspection technique. The time series is a combined signal generated by inspecting a cell in multiple locations at a given time and provides insight into the time it takes for the ultrasound waves to travel through the battery and return. A consistent, predictable trace indicates that the battery is free from defects that disrupt the wave propagation. This combined data could also be used to extract a fitness score for battery that could be used to assess overall cell quality.

[0061] EXAMPLE 3: Testing Batteries for Fill Level

[0062] Ultrasound wave signals were recorded by scanning through multiple sites over batteries of various quality - dry stack (no electrolyte), optimally fdled, under-filled (50% optimal) and over-filled (150% optimal) with liquid electrolyte. Pouch cells with nominal thickness of 2mm and 50x60mm dimensions were used in these experiments. The sampling rate of this data is 25MHz and for feature extraction, we focus on the first signal, as this represents the observed reflected ultrasound signal, which within this dataset occurs between measurement indices 9000-11500. Examples of reflected ultrasound signal event within four different battery cells that differ by amount of liquid electrolyte, as shown in FIG. 8 A to 8D. FIG. 8 A shows results for optimally filled cell, while FIG. 8B shows measurement for empty cell without electrolyte. FIG. 8C shows cell with 50%, i.e. underfilled cell, while FIG. 8D shows results for 150% filled or overfilled cell. The results show that amplitude of received signal could be correlated easily to electrolyte fill level.

[0063] EXAMPLE 4: Measuring State of Charge of a Battery

[0064] Voltage characteristics of battery cells were tested by continuously cycling Lithium-Ion Battery Cells while collecting ultrasound signal. The cell dimensions were 60x80 mm x 2.5 mm maximum thickness. The signals were collected using single-sided inspection. Both contact testing and non-contact testing using a single ultrasonic transmitter / receiver was used. Contact testing was done as reference to calibrate the noncontact testing results.

[0065] Signal peak amplitudes along with their time of arrival and dominant frequency, ring down time and zero crossing rate were used as features for characterization of charge. Two different artificial neural network (ANN) models were trained to predict voltage of the battery, corresponding to contact and non-contact ultrasound measurement methods. A simple ANN topology with 1 hidden layer was used. The ANN was mainly useful in eliminating noise from the signal and improving accuracy. Grid search was used to optimize the models. The voltage predicted vs actual voltage through charge and discharge cycling is shown in FIG. 9A-9B. FIG. 9A shows results for contact testing,upper part of FIG. 9A shows measured voltage, while the lower part of the figure shows voltage predicted by the ANN model 1 through charge-discharge cycles using parameters extracted from attenuated ultrasound signals. Results for non-contact ultrasound experiments through a single charge -hold-discharge cycle are shown in FIG. 9B. The results in FIG. 9A and 9B illustrate that non-contact measurements using the claimed sensor are effective in accurate measurement of charge of the battery. Further, the results show that non-contact measurements are comparable or better than contact measurements for assessing state of charge or SoC.

[0066] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material the teachings of the invention without departing from its scope, which should be according to the claims appended here.

Claims

We claim:

1. A system (100) for rapid, non-contact testing of batteries using ultrasound configured for real-time feedback, comprising: a pair of identical 2-dimensional ultrasound transducer arrays (102a, 102b) placed on either side of a battery (114) to be tested and to cover a surface area thereof, the transducer arrays configured to have n x m array elements, wherein one of the arrays (102a) is a transmit array to transmit ultrasound through the battery and the other (102b) is a receive array configured to receive attenuated ultrasound on the other side; an ultrasound driver-receiver module (104) comprising circuitry to transmit electrical impulses to the elements of the transmit array (102a) for generating the ultrasound pulses, and to receive voltage signals from the receive array (102b), characteristic of the attenuated ultrasound; and a visualization module comprising a display (108) to render information on the integrity of the battery over the surface area thereof, using the signals characteristic of the attenuated ultrasound.

2. The system as claimed in claim 1, comprising an edge computing node (106) configured to connect the ultrasound driver-receiver module (104) to the visualization module, or to a remote server (112), or both.

3. The system as claimed in claim 2, comprising multiple ultrasound arrays (102a, 102b), ultrasound driver-receiver modules (104) and edge computing nodes (106), wherein the edge computing nodes are connected to the remote server (112) for monitoring a battery production line.

4. The system as claimed in claim 1, wherein the arrays (102a, 102b), include ultrasound transducers 121-1, 121-2... 121 -n, in m rows of elements 122-1, 123-1...

5. The system as claimed in claim 4, wherein the transducers are selected from one of piezoelectric transducers, electromagnetic or magnetostrictive transducers.

6. A method (200) for real time non-contact testing of a battery for internal defects, comprising: providing (201) a first 2-dimensional ultrasound transducer array covering one side of the battery, the transducer array configured to transmit pulses from one or more transducers in the array; transmitting (202) pulses from at least one transducer in the array across a thickness of the battery; receiving attenuated ultrasound pulses characteristic of an integrity of the battery over an area covered by the array, wherein the receiving comprises: receiving (203) attenuated ultrasound pulses transmitted through the cell at a second 2-dimensional ultrasound transducer array placed on the other side of the battery, wherein the method comprises transmitting a single pulse from each element of the first array and receiving an attenuated signal at a corresponding receive element at the second array, or receiving (205) ultrasound pulses transmitted through the cell and reflected from a back wall of the cell at the first transducer array wherein the method comprises transmitting from one or more array elements and receiving attenuated signals at all the elements 121-1, 121-2...- 12m -n of the m x n array..

7. The method as claimed in claim 6, wherein the receiving (205) comprises receiving multiple transmitted signals separated in time.

8. The method as claimed in claim 6, comprising visualizing an integrity of the battery cell across an area thereof, in a display.

9. The method as claimed in claim 6. comprising visualizing an integrity of the battery cell at intervals during a manufacturing cycle thereof.

10. The method as claimed in claim 6, wherein the battery is a pouch battery, a prismatic or a cylindrical battery cell.

11. The method as claimed in claim 6, wherein the ultrasonic transducer array is operated at frequency between 20 kHz to 2 MHz.

12. The method as claimed in claim 6, wherein the method comprises analyzing(206) attenuated ultrasonic pulses using one or more parameters selected from peak signal amplitude, time of arrival, dominant frequency, ring down time and zero crossing rate.

13. The method as claimed in claim 12, wherein the analyzing comprises identifying(207) swelling, dendrite formation, electrolyte fdl level, or gas formation within the battery.

14. The method as claimed in claim 12, wherein the analyzing comprises computing SoC, or SoH of the battery using the attenuated ultrasonic pulses.

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