Monitoring device for an electric accumulator

Abstract

Monitoring device for an electric accumulator This description relates to a system (5) comprising an electric accumulator (10) and a device (20) for detecting outgassing of said electric accumulator (10).The outgassing detection device (20) comprises a first electro-acoustic transducer (22) based on said electrical accumulator (10) and configured to emit ultrasonic waves (US) into said electrical accumulator (10), a second electro-acoustic transducer (24) for receiving the ultrasonic waves (US) emitted by the first electro-acoustic transducer (22), based on said electrical accumulator (10) and configured to convert the received ultrasonic waves (US) into an electrical signal (S), and an electrical signal (S) processing circuit (28) configured to determine a maximum amplitude (SA) of the electrical signal (S), and to detect outgassing by comparing the maximum amplitude (SA) or the temporal variation of the maximum amplitude (SA) to a threshold. Figure for the abstract: Fig. 1.

Description

Title of the invention: Device for monitoring an electric accumulator. Technical field

[0001] This description relates generally to a monitoring device for an electric accumulator, in particular for the detection of outgassing from an electric accumulator. Previous technique

[0002] Several phenomena during the operation of an electric battery can lead to the generation of gas, also known as outgassing, within the battery, including overheating or overcharging. Gas accumulation can lead to deterioration, or even destruction, of the battery, particularly through thermal runaway. It is desirable to be able to detect gas formation within an electric battery before gas accumulation causes damage.

[0003] To detect outgassing from an electric accumulator, it is known to have, within the electric accumulator or battery pack comprising a set of several accumulators electrically connected in series or parallel, a pressure sensor adapted to detect an increase in pressure within the electric accumulator. One drawback is that commercially available pressure sensors have a low signal-to-noise ratio. Furthermore, they are likely to detect pressure variations that are not due to outgassing, which can lead to false alarms.

[0004] An electric accumulator may include a safety valve that allows gas to escape. To detect outgassing from an electric accumulator, it is also known to use a gas sensor, in particular a carbon dioxide sensor or a hydrogen sensor, located near the electric accumulator. However, such a sensor can only detect the presence of gas when the gas begins to escape from the electric accumulator, that is, well after gas generation has started. This means that by the time detection occurs, the electric accumulator may already be damaged. It would be desirable to be able to detect gas generation in the electric accumulator before it causes damage to the accumulator. Summary of the invention

[0005] An embodiment overcomes all or part of the drawbacks of known devices for monitoring an electric accumulator, in particular for detecting the generation of gas in the electric accumulator.

[0006] An embodiment provides for a system comprising an electric accumulator or a group of electric accumulators and a device for detecting outgassing of said electric accumulator or of one of the electric accumulators of the group of electric accumulators, the outgassing detection device comprising: - a first electro-acoustic transducer based on said electric accumulator or one of the electric accumulators of the group of electric accumulators and configured to emit ultrasonic waves in said electric accumulator or the electric accumulators of the group of electric accumulators; - a second electro-acoustic transducer for receiving ultrasonic waves emitted by the first electro-acoustic transducer, based on said electrical accumulator or on another of the electrical accumulators in the electrical accumulator group and configured to convert the received ultrasonic waves into an electrical signal; and - an electrical signal processing circuit configured to determine a maximum amplitude of the electrical signal, and to detect outgassing from the comparison of the maximum amplitude or the time variation of the maximum amplitude to a threshold.

[0007] According to one embodiment, the system comprises the group of electric accumulators, the outgassing detection device comprising, for each electric accumulator in the group of electric accumulators, the first electro-acoustic transducer, based on said electric accumulator and configured to emit ultrasonic waves in said electric accumulator, and the second electro-acoustic transducer for receiving the ultrasonic waves emitted by the first electro-acoustic transducer, based on said electric accumulator, the outgassing detection device further comprising a multiplexer connecting each second electro-acoustic transducer to the processing circuit.

[0008] According to one embodiment, the system comprises, for each pair of electric accumulators in the group of electric accumulators, a solid or liquid interface layer in direct physical contact with the electric accumulators of the pair of electric accumulators, configured to promote the propagation of ultrasonic waves.

[0009] One embodiment also provides a method for detecting outgassing from an electric accumulator or from one of the electric accumulators in a group of electric accumulators, comprising the following steps: - emission of ultrasonic waves in said electric accumulator or the electric accumulators of the group of electric accumulators by a first electro-acoustic transducer resting on said electric accumulator or one of the electric accumulators of the group of electric accumulators; - reception of the ultrasonic waves emitted by the first electroacoustic transducer by a second electroacoustic transducer based on said electrical accumulator or on another of the electrical accumulators in the group of electrical accumulators, and conversion, by the second electroacoustic transducer, of the received ultrasonic waves into an electrical signal; and - determination of a maximum amplitude of the electrical signal, and detection of outgassing from the comparison of the maximum amplitude or the temporal variation of the maximum amplitude to a threshold.

[0010] According to one embodiment, outgassing is detected when the maximum amplitude or the temporal variation of the maximum amplitude becomes greater than the threshold.

[0011] According to one embodiment, the method further comprises the steps of: - successive emission of bursts of ultrasonic waves by the first electro-acoustic transducer; and - reception of each burst of ultrasonic waves by the second electroacoustic transducer and provision of the electrical signal including oscillations for each burst of ultrasonic waves received.

[0012] According to one embodiment, the method includes determining a new value for the maximum amplitude of the electrical signal for each burst of ultrasonic waves received by the second electro-acoustic transducer.

[0013] According to one embodiment, the method comprises, for one of the received ultrasonic wave bursts, determining, among the oscillations of the electrical signal, the oscillation of maximum amplitude of the electrical signal and the rank of the oscillation of maximum amplitude, and for each other received ultrasonic wave burst, determining the amplitude of the oscillation of the same rank, this amplitude corresponding to the maximum amplitude of the electrical signal for said received ultrasonic wave burst.

[0014] According to one embodiment, the method includes determining the envelope of the electrical signal and determining, for each burst of ultrasonic waves received, the maximum amplitude of the envelope corresponding to the maximum amplitude of the electrical signal for said burst of ultrasonic waves received.

[0015] According to one embodiment, the method further comprises determining the state of charge of said electric accumulator from the maximum amplitude.

[0016] According to one embodiment, the method includes determining the propagation time of the bursts of ultrasonic waves from the first electro-acoustic transducer to the second electro-acoustic transducer, called time of flight (ToF).

[0017] According to one embodiment, the method further comprises determining the state of charge of said electric accumulator from the time of flight.

[0018] According to one embodiment, the method further comprises determining the derivative of the time of flight as a function of the voltage across the terminals of the electric accumulator. Brief description of the drawings

[0019] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0020] [Fig.1] is a partial and schematic cross-sectional view of a system comprising an electric accumulator and an electric accumulator monitoring device according to one embodiment;

[0021] [Fig.2] is a partial and schematic cross-sectional view of a system comprising an electric accumulator and an electric accumulator monitoring device according to another embodiment;

[0022] [Fig.3] and [Fig.4] are each a partial and schematic cross-sectional view, illustrating embodiments of the connection between an electro-acoustic transducer and an electrical accumulator respectively in prismatic or pocket format ([Fig.3]) and in cylindrical format ([Fig.4]);

[0023] [Fig.5] is a partial and schematic cross-sectional view of a system comprising a battery of electrical accumulators and a monitoring device, according to one embodiment, for the electrical accumulators of the battery;

[0024] [Fig.6] is a partial and schematic cross-sectional view of a system comprising a battery of electrical accumulators and a monitoring device, according to another embodiment, for the electrical accumulators of the battery;

[0025] [Fig.7] represents a timing diagram of an electrical control signal of a first electro-acoustic transducer for the emission of a burst of ultrasonic waves and a timing diagram of an electrical signal emitted by a second electro-acoustic transducer upon reception of the burst of ultrasonic waves;

[0026] [Fig.8] is a block diagram of an embodiment of a method for monitoring an electric accumulator;

[0027] [Fig.9] and [Fig.10] each represent the timing diagrams of the maximum amplitude of an ultrasonic wave measurement signal and the voltage across the terminals of a battery for batteries according to two different technologies;

[0028] [Fig.1 1] is a block diagram of an embodiment of another method for monitoring an electric accumulator;

[0029] [Fig. 12] represents a timing diagram of the maximum amplitude of an ultrasonic wave measurement signal, a timing diagram of the voltage across the terminals of an electric accumulator, and a timing diagram of the time of flight of the ultrasonic wave measurement signal for a test;

[0030] [Fig. 13] represents a chronogram of the charge stored in an electric accumulator and a chronogram of the time of flight of an ultrasonic wave measurement signal for another test;

[0031] [Fig. 14] represents a chronogram of the voltage across the terminals of an electric accumulator and a chronogram of the time of flight of an ultrasonic wave measurement signal for another test;

[0032] [Fig. 15] represents a chronogram of the voltage across the terminals of an electric accumulator and a chronogram of the maximum amplitude of an ultrasonic wave measurement signal for another test;

[0033] Figure 16 is a block diagram of an embodiment of another method for monitoring an electric accumulator; and

[0034] [Fig. 17] represents a curve of evolution of the derivative of the charge stored in an electric accumulator chronogram with respect to the voltage across the terminals of the electric accumulator and a curve of evolution of the derivative of the time of flight of an ultrasonic wave measurement signal guided by the electric accumulator with respect to the voltage across the terminals of the electric accumulator. Description of the implementation methods

[0035] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0036] For the sake of clarity, only the steps and elements necessary for understanding the described embodiments have been shown and are detailed. In particular, the internal structure and operation of electric accumulators are known to those skilled in the art and are not described.

[0037] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0038] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0039] Unless otherwise specified, the expressions "approximately", "roughly", and "on the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0040] Fig. 1 is a partial, schematic cross-sectional view of a system 5 comprising an electric accumulator 10 and a monitoring device 20, according to one embodiment of the electric accumulator 10.

[0041] The electric accumulator 10 comprises an outer wall 12 having several faces 14, 16.

[0042] The monitoring device 20 comprises: - a first electro-acoustic transducer 22 for emitting ultrasonic waves US, resting on a first face 14 of the external wall 12, configured to receive an electrical control signal C and to convert the control signal C into ultrasonic waves US; - a second electro-acoustic transducer 24 for receiving ultrasonic waves US emitted by the first electro-acoustic transducer 22, resting on the first face 14 of the external wall 12 at a distance from the first electro-acoustic transducer 22, configured to convert the received ultrasonic waves US into an electrical measurement signal S; - a control circuit 26 for the first electro-acoustic transducer 22 configured to provide the control signal C; and - a processing circuit 28 for the measurement signal S supplied by the second electro-acoustic transducer 24, the processing circuit 28 being able to be connected to the control circuit 26.

[0043] In the embodiment illustrated in [Fig.1], the first electroacoustic transducer 22 and the second electroacoustic transducer 24 are located on the same face 14 of the outer wall 12.

[0044] Fig. 2 is a partial schematic cross-sectional view of a system 5 comprising an electric accumulator 10 and a monitoring device 20, according to another embodiment, of the electric accumulator 10.

[0045] The monitoring device 20 of the electric accumulator 10 shown in [Fig. 2] comprises all the elements of the monitoring device 20 of the electric accumulator 10 shown in [Fig. 1], with the difference that the first electroacoustic transducer 22 is located on a first face 14 of the outer wall 12 and that the The second electro-acoustic transducer 24 is located on a second face 16 of the external wall 12, opposite the first face 14, preferably aligned in a direction perpendicular to the first and second faces 14 and 16.

[0046] The operation of the monitoring device 20 for the electric battery 10 shown in [Fig. 1] and [Fig. 2] is as follows. The control circuit 26 provides the control signal C to the first electro-acoustic transducer 22 for the emission of ultrasonic waves US. The ultrasonic waves US propagate through the electric battery 10 and are captured by the second electro-acoustic transducer 24, which provides the measurement signal S. The processing circuit 28 analyzes the measurement signal S and determines an operating parameter of the electric battery 10 from the analysis of the measurement signal S.

[0047] In the embodiment illustrated in [Fig. 1], the ultrasonic waves propagate preferentially on the surface of the electrical accumulator 10. In the embodiment illustrated in [Fig. 2], the ultrasonic waves propagate preferentially inside the electrical accumulator 10. According to one embodiment, the frequency range of the ultrasonic waves is between 16 kHz and 10 MHz. According to one embodiment, the distance between the first electroacoustic transducer 22 and the second electroacoustic transducer 24 is between 10 mm and 150 mm.

[0048] The first and second electro-acoustic transducers 22, 24 may each comprise a single ultrasonic wave generation / reception element, also referred to hereafter as an electro-acoustic element, two ultrasonic acoustic wave generation / reception elements, or more than two ultrasonic acoustic wave generation / reception elements. In the embodiments illustrated in Figures 1 and 2, each electro-acoustic transducer 22, 24 comprises a single ultrasonic acoustic wave generation / reception element.

[0049] Each electroacoustic element is adapted to convert an electrical signal (current, voltage, electric charge) into ultrasonic waves. Conversely, each electroacoustic element is adapted to convert an ultrasonic wave into an electrical signal (current, voltage, electric charge). Each electroacoustic element is, for example, made of a plate of single-crystal or polycrystalline piezoelectric material, for example PZT (Zirconium-Lead Titanate), the thickness of which varies when a voltage is applied between two faces of the plate. Each electroacoustic element is, for example, a microelectromechanical system (MEMS) that uses microelectronic manufacturing technologies. This microelectromechanical system is, for example, made of a deformable membrane suspended above a cavity. The deformable membrane is, for example, driven by capacitive action using an electrode. attached to the membrane and separated by an electrode within the cavity. This type of transducer is known by the acronym CMUT, for Capacitive Micro-machined Ultrasonic Transducer. The deformable membrane is, for example, driven by the piezoelectric effect using a layer of piezoelectric material equipped with two electrodes attached to the membrane. This type of transducer is known by the acronym PMUT, for Piezoelectric Micro-machined Ultrasonic Transducer. Each electroacoustic element is, for example, a magnetostrictive transducer made of a material that changes slightly in size when exposed to a magnetic field. Depending on the type of electroacoustic element, the control signal C of the electroacoustic element can correspond to a voltage, a current, or an electrical charge.

[0050] The electric accumulator 10 can correspond to a prismatic cell, a cylindrical cell, or a pouch cell.

[0051] Fig. 2 and Fig. 4 are each a partial and schematic cross-sectional view, illustrating an embodiment of the connection between the electro-acoustic transducer 22 or 24 and the electrical accumulator 10, when the electrical accumulator 10 corresponds to a prismatic cell or a pocket cell (Fig. 3) or a cylindrical cell (Fig. 4).

[0052] In these embodiments, the electro-acoustic transducer 22 or 24 is fixed to an electronic circuit 30, for example a printed circuit board. A layer 32 of a coupling material is disposed between the electro-acoustic transducer 22 or 24 and the face 14 of the electrical accumulator 10. The coupling material is in liquid form, for example acoustic transmission gel (standard product for ultrasound diagnosis), or in solid form (in particular the product marketed by Parker Laboratories under the name AquaFlex®), or in silicone grease form (in particular the product marketed by Eleco Panacol-EFD under the name G641), or in the form of glue or adhesive allowing the propagation of ultrasound waves.

[0053] In the embodiment illustrated in [Fig. 3], the face 14 can be substantially flat. The electronic circuit 30 can then be a rigid printed circuit board.

[0054] In the embodiment illustrated in [Fig. 4], the face 14 can be curved, for example cylindrical with a circular base. The electronic circuit 30 can then be a flexible printed circuit board, and the electro-acoustic transducer 22 or 24 can be flexible or rigid with a curvature corresponding to the curvature of the face 14.

[0055] Figure 5 is a partial, schematic cross-sectional view of a system 40 comprising a battery 42 of electrical accumulators 10 and a monitoring device 50, according to one embodiment, for the electrical accumulators 10 of the battery 42. The battery 42 comprises N electrical accumulators 10, where N is an integer greater than or equal to 2, for example in the range from 2 to several hundred, or even several thousand. For example, in [Fig. 5], only three electrical accumulators 10 are shown. The electrical accumulators 10 are electrically connected to each other, in series and / or in parallel, by conductive elements 44. For example, in [Fig. 5], the electrical accumulators 10 are electrically connected in parallel by two conductive elements 44.

[0056] The monitoring device 50 comprises: - for each electric accumulator 10, the first electro-acoustic transducer 22 for emitting ultrasonic waves US resting on the electric accumulator 10, adapted to receive the control signal C and to convert the control signal C into ultrasonic waves US; - for each electric accumulator 10, the second electro-acoustic transducer 24 receives the ultrasonic US waves emitted by the first electro-acoustic transducer 22, and is configured to convert the received ultrasonic US waves into the measurement signal S; - a first multiplexer 52 comprising one input and N outputs, each output of the first multiplexer 52 being coupled, preferably connected, to one of the first N electro-acoustic transducers 22; - a second multiplexer 54 comprising N inputs and one output, each input of the second multiplexer 54 being coupled, preferably connected, to one of the N second electro-acoustic transducers 24; - the control circuit 26 of the first N electro-acoustic transducers 22, configured to provide successive control signals C and comprising, for example, a signal generator 261 and an amplifier 262 connecting the signal generator 261 to the first multiplexer 52; and - the processing circuit 28 of the N electrical measurement signals S provided by the N second electro-acoustic transducers 24 and comprising, for example, an amplifier 281, a low-pass filter 282, an analog-to-digital converter 283, a digital processing circuit 284, and an interface 285.

[0057] The operation of the monitoring device 50 shown in [Fig. 5] is as follows. The control circuit 26 provides the control signal C for one of the N accumulators 10 and commands the first multiplexer 52 to connect its input to the output corresponding to the accumulator 10 in question. Under the control of the signal C, the first electro-acoustic transducer 22 attached to the accumulator 10 in question emits ultrasonic waves US. The ultrasonic waves US propagate through the electric accumulator 10 in question and are captured by the second electro-acoustic transducer 24 attached to the accumulator 10 in question, which provides the measurement signal S. The processing circuit 28 commands the second multiplexer 54 to connect its input, which is connected to the accumulator 10 in question, to its output. The processing circuit 28 then receives the measurement signal S provided by the second electroacoustic transducer 24 attached to the accumulator 10 considered and analyzes the measurement signal S and determines an operating parameter of the electric accumulator 10 considered from the analysis of the measurement signal S. This operation can be repeated for each electric accumulator 10 of the battery 42.

[0058] In the preceding description, the number N of accumulators 10 is equal to the number of channels of the detection circuit 50. For a number N of accumulators 10 greater than the number of channels of the detection circuit 50, a part of the N accumulators 10 is connected to a first detection circuit 50 and the remaining accumulators 10 are connected to at least a second detection circuit 50.

[0059] Figure 6 is a partial, schematic cross-sectional view of a system 60 comprising a battery 42 of electrical accumulators 10 and a monitoring device 65, according to one embodiment, of the electrical accumulators 10 of the battery 42, the battery 42 and the monitoring device 65 being only partially shown in Figure 6. The battery 42 comprises at least one group of M electrical accumulators 10, where M is an integer greater than or equal to 2, for example in the range from 2 to several hundred, or even several thousand. By way of example, in Figure 6, only one group of six electrical accumulators 10 is shown. The battery 42 may comprise several groups of electrical accumulators 10. The electrical accumulators 10 are electrically connected to each other, in series and / or in parallel, by conductive elements not shown in Figure 6.The battery 42 further comprises an interface layer 44 between each pair of adjacent electrical accumulators 10 in the group, the interface layers 44 each being made of a material that promotes the propagation of ultrasonic waves. Each interface layer 44 is, for example, an ultrasonic conducting gel in solid or liquid form. Each interface layer 44 can also be a coolant such as water.

[0060] Each group of electric accumulators 10 of the battery 42 comprises first and second end electric accumulators 10, which are the two electric accumulators 10 of the group of electric accumulators 10 that are not interposed between two other electric accumulators 10.

[0061] The monitoring device 65 comprises the first electro-acoustic transducer 22 attached to the first end electric accumulator 10 and the second electro-acoustic transducer 24 attached to the second end electric accumulator 10. The first and second electro-acoustic transducers 22 and 24 are preferably arranged opposite each other. The monitoring device 65 further comprises the control circuit 26 supplying the control signal C to the first transducer electro-acoustic 22 and the processing circuit 28 of the measurement signal S supplied by the second electro-acoustic transducer 24.

[0062] The operation of the monitoring device 65 shown in [Fig. 6] is as follows. The control circuit 26 supplies the control signal C to the first electro-acoustic transducer 22. Under the control of the signal C, the first electro-acoustic transducer 22, attached to the first end accumulator 10, emits ultrasonic waves US. The ultrasonic waves US propagate through the electrical accumulators 10 of the group of electrical accumulators 10, from the first end electrical accumulator 10 to the second end electrical accumulator 10, and are received by the second electro-acoustic transducer 24 of the second end electrical accumulator 10, which provides the measurement signal S.The processing circuit 28 then receives the measurement signal S and analyzes the measurement signal S and determines an operating parameter of the electrical accumulators 10 of the group of electrical accumulators 10 which have been traversed by the ultrasonic waves.

[0063] According to one embodiment, the control circuit 26 provides the control signal C to the first electro-acoustic transducer 22 for the emission of at least one burst of ultrasonic waves US.

[0064] Figure 7 is a DC timing diagram, in normalized amplitude, of the electrical signal C is the control signal of the first electroacoustic transducer 22 for the emission of a burst of ultrasonic waves, and a normalized amplitude chronogram CS is the measurement signal S emitted by the second electroacoustic transducer 24 upon reception of the burst of ultrasonic waves. As shown in [Fig. 7], the chronogram CC comprises several successive oscillations of increasing and then decreasing amplitude, and the chronogram CS comprises several oscillations of varying amplitudes. There is an attenuation of the maximum amplitudes of the oscillations of the measurement signal S relative to the maximum amplitudes of the oscillations of the control signal C due to the propagation of the ultrasonic waves in the electrical accumulator 10. Furthermore, a time interval separates the first oscillation of the measurement signal S from the first oscillation of the control signal C due to the distance between the first and second electroacoustic transducers 22 and 24.

[0065] According to one embodiment, a method for monitoring an electric accumulator 10 or electric accumulators comprises the following steps: - emission of several bursts of ultrasonic waves spaced in time by the first electro-acoustic transducer 22; - for each burst of ultrasonic waves emitted, a measurement signal S is provided by the second electro-acoustic transducer 24 upon reception of the burst of ultrasonic waves - for each burst of ultrasonic waves captured by the second electroacoustic transducer 24, determination by the processing circuit 28 of a parameter of the measurement signal S; - determination of the evolution of the measurement signal parameter S over time for the group of acquired ultrasonic wave bursts; and - determination of the evolution of a characteristic of the electric accumulator 10 or of the electric accumulators from the analysis of the evolution of the parameter of the measurement signal S.

[0066] According to one embodiment, the processing circuit 28 is configured to determine a data representative of the maximum amplitude of the ultrasonic waves in a burst of ultrasonic waves received by the second electroacoustic transducer 24. According to one embodiment, the parameter of the measurement signal S provided by the second electroacoustic transducer 24 upon receipt of a burst of ultrasonic waves corresponds to the maximum amplitude SA of the measurement signal S.

[0067] According to one embodiment, in an initial phase, the processing circuit 28 is configured to count the number of oscillations of the measurement signal S provided by the second electro-acoustic transducer 24 upon reception of the first burst of ultrasonic waves and to determine, among all the oscillations of the measurement signal S, which oscillation has the maximum amplitude as well as the value of the maximum amplitude SA of this oscillation, which is hereafter referred to as the reference oscillation. In a subsequent phase, the processing circuit 28 is configured to determine the amplitude of the reference oscillation for each subsequent burst of ultrasonic waves received, this amplitude corresponding to the maximum amplitude SA for the burst of ultrasonic waves received by the second electro-acoustic transducer 24.

[0068] According to another embodiment, the processing circuit 28 is configured to determine the envelope of the measurement signal S provided by the second electro-acoustic transducer 24 upon receipt of a burst of ultrasonic waves and to determine the maximum amplitude of the envelope, this amplitude corresponding to the maximum amplitude SA for the burst of ultrasonic waves received by the second electro-acoustic transducer 24.

[0069] According to one embodiment, the monitored characteristic of the electric accumulator 10 or a group of electric accumulators 10 is outgassing. Several phenomena during the operation of an electric accumulator 10 can lead to the generation of gas within the accumulator 10, including overheating or overloading of the accumulator 10. The accumulation of gas can lead to deterioration, or even destruction, of the electric accumulator 10, particularly through thermal runaway. It is desirable to be able to detect the formation of gas. within an electric accumulator 10 before the accumulation of gas leads to deterioration of the electric accumulator 10.

[0070] The inventors have demonstrated that outgassing in an electric battery 10 leads to a significant and rapid increase in the maximum amplitude SA. Monitoring the evolution of the maximum amplitude SA or the temporal variation of the maximum amplitude SA therefore makes it possible to detect outgassing in an electric battery 10 before this outgassing leads to deterioration of the electric battery 10.

[0071] The [Fig.8] is a block diagram of an embodiment of a method for detecting, by the monitoring device 20, 50, and 65, outgassing in an electric accumulator 10 or in a group of electric accumulators 10.

[0072] In step 70, the control circuit 26 commands the emission of a burst of ultrasonic waves by the first electro-acoustic transducer 22. The burst of ultrasonic waves propagates through the electrical accumulator 10 or accumulators 10 to the second electro-acoustic transducer 24, which emits the measurement signal S. The processing circuit 28 determines the maximum amplitude SA of the measurement signal S, as described previously, for the burst of ultrasonic waves received by the second electro-acoustic transducer 24. The process continues in step 71.

[0073] In step 71, the processing circuit 28 compares the maximum amplitude SA or the time variation of the maximum amplitude SA to a degassing detection threshold. If the maximum amplitude SA or the time variation of the maximum amplitude SA is less than the degassing detection threshold, the process continues to step 70. If the maximum amplitude SA or the time variation of the maximum amplitude SA is greater than the degassing detection threshold, this means that degassing is taking place in the electrical accumulator 10 or at least in one of the electrical accumulators in the electrical accumulator group, and the process continues to step 72.

[0074] At step 72, the processing circuit 28 performs an action, such as issuing an alert, disconnecting the electric accumulator 10 or all the electric accumulators in the group of electric accumulators.

[0075] First and second tests were carried out for the outgassing detection method of an electric battery 10. For the first and second tests, the electric battery 10 corresponds to a pocket cell and the monitoring device is according to the embodiment illustrated in [Fig. 1]. For the first test, the electric battery 10 is placed under overload conditions according to a charging cycle comprising a constant current charge corresponding to the current required to charge the empty electric battery 10 in 2 hours, such a current being usually called C / 2, where C is the capacity of the battery (in Ah). For In the second test, the battery 10 is subjected to an overload condition using a charging cycle that includes charging at a constant voltage and limiting the current to a current called 2C, which corresponds to the current required to charge the battery 10 from empty in 30 minutes. For both the first and second tests, the charging cycle is performed at 20 °C. Furthermore, the voltage E across the terminals of the battery 10 is measured. For the first test, the battery 10 is a lithium-ion battery of the NMC (nickel-manganese-cobalt) type. For the second test, the battery 10 is a lithium-ion battery of the LiCo (lithium-cobalt) type.

[0076] Figures 9 and 10 each represent a timing diagram of the maximum amplitude SA and a timing diagram of the voltage E across the terminals of the electrical accumulator 10. Figure 9 was obtained for the first test and Figure 10 for the second test. For the first and second tests, the waveform of the bursts of ultrasonic waves received by the second electro-acoustic transducer 24 is shown in Figures 9 and 10, in an inset at the top left.

[0077] Each timing diagram of the maximum amplitude SA successively comprises a first phase PI, a second phase PII, and a third phase P1. In the first phase PI, as long as the electrical accumulator 10 under overload conditions (in current or voltage) does not exhibit mechanical deformation, the maximum amplitude SA remains generally stable at a low value, below the outgassing detection threshold. Just before the onset of cell swelling, which corresponds to the end of phase I, a decrease in the signal amplitude can be observed. In phase III, which corresponds to deformation of the electrical accumulator 10, saturation of the maximum amplitude SA at a high value, above the outgassing detection threshold, is observed. The end of phase III corresponds to the end of the test. The test ends when the deformation of the electrical accumulator 10, or even its outgassing, or even its explosion, is visually observed.In all three cases, the electric accumulator 10 is considered to be permanently damaged.

[0078] One possible explanation for this observation lies in the sudden increase in the surface acoustic impedance of the electrical accumulator 10 due to the presence of gas inside the accumulator 10. This gas prevents the penetration of ultrasonic waves into the active layers of the accumulator 10, limiting the attenuation of the ultrasonic waves and thus generating a measurement signal S with a very high amplitude. Phase II corresponds to a rapid increase in the maximum amplitude SA from the low value to the high value, when outgassing has begun but the electrical accumulator 10 has not yet deformed in a way that is perceptible to the naked eye.

[0079] According to one embodiment, the outgassing detection threshold is chosen between a low and a high value, such that outgassing detection occurs during phase PII. Consequently, the emission of an alert when the maximum amplitude SA rises above the outgassing detection threshold provides sufficiently early warning of the onset of thermal runaway in the electric battery 10. This advantageously allows for the detection of the beginning of an anomaly in the operation of the electric battery 10 before any effects are visible, particularly before the electric battery explodes. This can advantageously prevent damage to the electric battery.

[0080] According to one embodiment, the measurement signal parameter S corresponds to the time of flight ToF of the ultrasonic waves. The time of flight ToF of the ultrasonic waves corresponds to the time elapsed between the emission of an ultrasonic wave by the first electro-acoustic transducer 22 and the reception of this ultrasonic wave by the second electro-acoustic transducer 24. The processing circuit 28 is configured to determine a representative data of the temporal evolution of the time of flight of the ultrasonic waves received by the second electro-acoustic transducer 24 from an analysis of the measurement signal S.

[0081] According to one embodiment, in an initial phase, the processing circuit 28 is configured to count the number of oscillations of the measurement signal S provided by the second electroacoustic transducer 24 upon receiving the first burst of ultrasonic waves and to determine, among all the oscillations of the measurement signal S, which oscillation has the maximum amplitude, this oscillation of maximum amplitude being referred to hereafter as the reference oscillation. In a subsequent phase, the first electroacoustic transducer 22 is controlled to emit bursts of ultrasonic waves periodically. The processing circuit 28 is configured to determine the time between two oscillations of the same rank of the measurement signal S, corresponding to the rank of the reference oscillation, of two successive bursts of ultrasonic waves.Since the bursts of ultrasonic waves are emitted periodically by the first electroacoustic transducer 22, a variation in the time between two reference oscillations of the measurement signal S corresponding to two successive bursts of ultrasonic waves is equal to the variation in the propagation time of the bursts of ultrasonic waves from the first electroacoustic transducer 22 to the second electroacoustic transducer 24, that is, the variation in the time of flight of the ultrasonic waves. Alternatively, the processing circuit 28 exchanges signals with the control circuit 26 so that the processing circuit 28 knows the time of emission of each burst of ultrasonic waves by the first electroacoustic transducer 22. The processing circuit 28 can then directly determine the time of flight of the reference oscillation. In the following description, we refer to... regardless of the time of flight of the ultrasonic waves or the time of flight of the measurement signal S.

[0082] According to one embodiment, the monitored characteristic of the electric accumulator 10 is the state of charge SoC (English abbreviation for State of Charge) of the electric accumulator 10. The method uses the monitoring device 50 of [Fig. 5] for monitoring the state of charge SoC of an electric accumulator 10. When the electric accumulators 10 of the battery 42 of electric accumulators 10 are balanced, the monitoring device 65 of [Fig. 6] can be used to monitor the state of charge of the battery 42, which corresponds to the state of charge of each electric accumulator 10.

[0083] The inventors have demonstrated that the time of flight (ToF) of ultrasonic waves in an electric battery 10 varies substantially linearly with the state of charge of the electric battery 10, either proportionally or inversely, depending on the chemical reactions occurring in the electric battery 10, for the most common electric battery technologies. Monitoring the evolution of the time of flight (ToF) therefore makes it possible to monitor the evolution of the state of charge of the electric battery 10. The inventors have further demonstrated that the maximum amplitude (SA) of the measurement signal (S) of the ultrasonic wave bursts in an electric battery 10 varies substantially linearly with the state of charge of the electric battery 10. Monitoring the evolution of the maximum amplitude (SA) therefore makes it possible to monitor the evolution of the state of charge of the electric battery 10.

[0084] According to one embodiment, the processing circuit 28 can determine a time-of-flight or time-of-flight variation value for the reference oscillation of the measurement signal S and determine a state-of-charge value from the determined time-of-flight or time-of-flight variation value. According to another embodiment, the processing circuit 28 can determine a maximum amplitude SA value for the reference oscillation of the measurement signal S and determine a state-of-charge value from the determined maximum amplitude SA value. According to yet another embodiment, the processing circuit 28 can determine a maximum amplitude SA value and a time-of-flight or time-of-flight variation value for the reference oscillation of the measurement signal S and determine a state-of-charge value from the determined maximum amplitude SA value and the determined time-of-flight or time-of-flight variation value.

[0085] The [Fig. 11] is a block diagram of an embodiment of a method for determining, by the monitoring device 20, 50, and 65, the state of charge of an electric accumulator 10.

[0086] In step 80, the control circuit 26 triggers the emission of a burst of ultrasonic waves by the first electroacoustic transducer 22. The burst of ultrasonic waves propagates through the electric accumulator 10 to the second electroacoustic transducer 24, which emits the measurement signal S. The processing circuit 28 determines the time of flight or the change in time of flight of the measurement signal S and the state of charge of the electric accumulator 10 from the time of flight or the change in time of flight as described previously. In one embodiment, the processing circuit 28 determines the maximum amplitude SA of the measurement signal S and the state of charge of the electric accumulator 10 from the maximum amplitude SA as described previously.According to another variant, the processing circuit 28 determines the maximum amplitude SA of the measurement signal S and the time of flight or the change in time of flight of the measurement signal S, determines a first value of the state of charge of the electric accumulator 10 from the time of flight or the change in time of flight as described previously, determines a second value of the state of charge of the electric accumulator 10 from the maximum amplitude SA as described previously, and determines a third value of the state of charge from the first and second values. The process continues in step 81.

[0087] In step 81, the processing circuit 28 stores the determined charge state value. A charge state display can also be provided. The process continues in step 80.

[0088] First, second, third, and fourth tests were carried out for the method of determining the state of charge of an electric accumulator 10. For the first, second, third, and fourth tests, the electric accumulator 10 corresponds to a pocket cell. For the first, second, third, and fourth tests, the monitoring device is according to the embodiment illustrated in [Fig. 1].

[0089] For the first test, the voltage E across the battery 10 is measured, and the time of flight ToF and the maximum amplitude SA for each burst of received ultrasonic waves are measured. For the first test, the battery 10 is a lithium-ion battery of the LiCo (lithium-cobalt) type. For the second test, the electric charge Q contained in the battery 10 is measured, and the time of flight ToF for each burst of received ultrasonic waves is measured. For the second test, the battery 10 is a lithium-ion battery of the LFP (lithium iron phosphate) type. For the third test, the voltage E across the battery 10 is measured, and the time of flight ToF for each burst of received ultrasonic waves is measured. For the third test, the electrical accumulator 10 is a lithium-ion accumulator of the NMC (nickel-manganese-cobalt) type.For the fourth test, the voltage E across the terminals of the electric accumulator. 10 is measured, and the maximum amplitude SA for each burst of received ultrasonic waves is measured. For the fourth test, the electrical accumulator 10 is an NMC (nickel-manganese-cobalt) type lithium-ion accumulator.

[0090] Fig. 12 represents a chronogram C_SA of the maximum amplitude SA of ultrasonic waves, a chronogram C_E of the voltage E across the terminals of the electric accumulator 10, and a chronogram C_ToF of the time of flight ToF for the first test.

[0091] Fig. 13 represents a chronogram C_Q of the charge Q stored in the electric accumulator 10, and a chronogram C_ToF of the time of flight for the second test.

[0092] Fig. 14 represents a timing diagram C_E of the voltage E across the terminals of the electric accumulator 10, and a timing diagram C_ToF of the time of flight ToF for the third test.

[0093] Fig. 15 represents a chronogram C_E of the voltage E across the terminals of the electric accumulator 10, and a chronogram C_SA of the maximum amplitude SA of ultrasonic waves for the fourth trial.

[0094] According to one embodiment, the monitored characteristic of the electric accumulator 10 is the incremental capacity of the electric accumulator 10. The incremental capacity corresponds to the derivative of the function relating the capacity charged in the electric accumulator 10 to the voltage across the terminals of the electric accumulator 10. The evolution curve of the incremental capacity of the electric accumulator 10 allows in particular the determination of the state of health (SoH), in particular the implementation of an incremental capacity analysis (ICA), in particular by an analysis of the peaks of this curve.

[0095] The inventors have shown that the derivative of the time of flight of the bursts of ultrasonic waves in an electric accumulator 10 with respect to the voltage across the terminals of the electric accumulator 10 varies substantially like the incremental capacity of the electric accumulator 10. Monitoring the evolution of the time of flight therefore makes it possible to monitor the evolution of the incremental capacity of the electric accumulator 10.

[0096] According to one embodiment, the processing circuit 28 can determine a time-of-flight value of the reference oscillation for each burst of ultrasonic waves and determine the value of the voltage across the terminals of the electric accumulator upon receipt of the burst of ultrasonic waves by the second electro-acoustic transducer 24. From the collected values, the processing circuit 28 can determine the derivative of the charge collected by the electric accumulator 10 as a function of the voltage across the terminals of the electric accumulator.

[0097] Figure 16 is a block diagram of an embodiment of a method for determining, by the monitoring device 20, 50, and 65, the capacity incremental of an electric accumulator 10. This method uses interchangeably the monitoring device 50 of [Fig.5] or the monitoring device 65 of [Fig.6].

[0098] In step 90, a voltage E of determined value is applied to the terminals of the electric accumulator 10. The process continues in step 91.

[0099] In step 91, the control circuit 26 triggers the emission of a burst of ultrasonic waves by the first electroacoustic transducer 22. The burst of ultrasonic waves propagates through the electrical accumulator 10 or accumulators 10 to the second electroacoustic transducer 24, which emits the measurement signal S. The processing circuit 28 determines the time of flight of the measurement signal S as described previously. The determined time of flight value and the value of the voltage E are stored. The process continues in step 92.

[0100] In step 92, an increment is applied to the value of the voltage E across the terminals of the electric accumulator 10. The process continues in step 91 as long as the voltage E is not equal to a given maximum value. The process is terminated when the voltage E is equal to the given maximum value.

[0101] A test was carried out for the method of determining the incremental capacity of an electric accumulator 10. For this test, the electric accumulator 10 corresponds to a pocket cell. For this test, the monitoring device is according to the embodiment illustrated in [Fig. 1]. The electric accumulator 10 is a lithium-ion LiPo (lithium-polymer) battery. For this test, the voltage E across the terminals of the electric accumulator 10 was varied between a minimum value of 2.8 V and a maximum value of 4.2 V for LiCo batteries, between 2.75 V and 4.35 V for solid-state batteries, between 2 V and 3.65 V for LFP batteries, and between 2.75 V and 4.2 V for NMC batteries, with an increment of 5 minutes.

[0102] Figure 17 shows a curve C_dQ / dV of the incremental capacity dQ / dV of the electric battery and a curve C_dTof / dV of the derivative dTof / dV of the time of flight ToF as a function of the voltage E across the electric battery 10 obtained for the test. The two curves are substantially identical.

[0103] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to those skilled in the art. By way of example, a method for monitoring an electric battery may include implementing a method for detecting outgassing of the electric battery and a method for determining the state of charge of the electric battery according to the embodiments described above. According to another example, a method for monitoring an electric battery This may include implementing a method for detecting outgassing of an electric battery and a method for determining the incremental capacity of the electric battery according to the embodiments described above. In another example, a method for monitoring an electric battery may include implementing a method for determining the state of charge of the electric battery and a method for determining the incremental capacity of the electric battery according to the embodiments described above.

[0104] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. System (5; 40; 60) comprising an electric accumulator (10) or a group of electric accumulators (10) and a device (20; 50; 65) for detecting outgassing of said electric accumulator (10) or of one of the electric accumulators (10) of the group of electric accumulators (10), the outgassing detection device (20; 50; 65) comprising: - a first electro-acoustic transducer (22) resting on said electric accumulator (10) or one of the electric accumulators (10) of the group of electric accumulators (10) and configured to emit ultrasonic (US) waves in said electric accumulator (10) or the electric accumulators (10) of the group of electric accumulators (10);- a second electro-acoustic transducer (24) for receiving ultrasonic (US) waves emitted by the first electro-acoustic transducer (22), based on said electrical accumulator (10) or on another of the electrical accumulators (10) of the group of electrical accumulators (10) and configured to convert the received ultrasonic (US) waves into an electrical signal (S); and - an electrical signal (S) processing circuit (28) configured to determine a maximum amplitude (SA) of the electrical signal (S), and to detect outgassing from the comparison of the maximum amplitude (SA) or the temporal variation of the maximum amplitude (SA) to a threshold.

2. System (5) according to claim 1, comprising the group of electric accumulators (10), the outgassing detection device (50) comprising, for each electric accumulator (10) of the group of electric accumulators (10), the first electro-acoustic transducer (22), based on said electric accumulator (10) and configured to emit ultrasonic (US) waves into said electric accumulator (10), and the second electro-acoustic transducer (24) for receiving the ultrasonic (US) waves emitted by the first electro-acoustic transducer (22), based on said electric accumulator (10), the outgassing detection device (50) further comprising a multiplexer (54) connecting each second electro-acoustic transducer (24) to the processing circuit (28).

3. System (5) according to claim 1, comprising, for each pair of electric accumulators (10) of the group of electric accumulators (10), an interface layer (44), solid or liquid, in direct physical contact with the electric accumulators of the pair of electric accumulators (10), configured to promote the propagation of ultrasonic waves.

4. Method for detecting outgassing of an electric accumulator (10) or of one of the electric accumulators (10) of a group of electric accumulators (10), comprising the following steps: - emission of ultrasonic (US) waves in said electric accumulator (10) or the electric accumulators (10) of the group of electric accumulators (10) by a first electroacoustic transducer (22) resting on said electric accumulator (10) or one of the electric accumulators (10) of the group of electric accumulators (10); - reception of ultrasonic waves (US) emitted by the first electro-acoustic transducer (22) by a second electro-acoustic transducer (24) based on said electrical accumulator (10) or on another of the electrical accumulators (10) of the group of electrical accumulators (10) and conversion, by the second electro-acoustic transducer (24), of the received ultrasonic waves (US) into an electrical signal (S);and - determination of a maximum amplitude (SA) of the electrical signal (S), and detection of outgassing from the comparison of the maximum amplitude (SA) or the temporal variation of the maximum amplitude (SA) to a threshold.;

5. A method according to claim 4, wherein outgassing is detected when the maximum amplitude (SA) or the time variation of the maximum amplitude (SA) becomes greater than the threshold.

6. A method according to claim 4 or 5, further comprising the steps of: - successive emission of bursts of ultrasonic (US) waves by the first electro-acoustic transducer (22); and - reception of each burst of ultrasonic (US) waves by the second electro-acoustic transducer (24) and provision of the electrical signal (S) comprising oscillations for each burst of ultrasonic (US) waves received.

7. Method according to claim 6, comprising determining a new value of the maximum amplitude (SA) of the electrical signal for each burst of ultrasonic (US) waves received by the second electro-acoustic transducer (24).

8. A method according to claim 7, comprising, for one of the received ultrasonic (US) wave bursts, determining, among the oscillations of the electrical signal (S) the oscillation of maximum amplitude of the electrical signal (S) and the rank of the oscillation of maximum amplitude, and for each other received ultrasonic wave burst, determining the amplitude of the oscillation of the same rank, this amplitude corresponding to the maximum amplitude (SA) of the electrical signal (S) for said received ultrasonic (US) wave burst.

9. A method according to claim 7, comprising determining the envelope of the electrical signal and determining, for each burst of ultrasonic waves received, the maximum amplitude of the envelope corresponding to the maximum amplitude (SA) of the electrical signal (S) for said burst of ultrasonic waves (US) received.

10. A method according to any one of claims 4 to 9, further comprising determining the state of charge of said electric accumulator (10) from the maximum amplitude (SA).

11. Method according to claim 6, comprising determining the propagation time of the ultrasonic wave bursts from the first electro-acoustic transducer (22) to the second electro-acoustic transducer (24), called time of flight (ToF).

12. A method according to claim 11, further comprising determining the state of charge of said electric accumulator (10) from the time of flight (ToF).

13. A method according to any one of claims 4 to 12, further comprising determining the derivative (dTof / dV) of the time of flight (ToF) as a function of the voltage (E) across the terminals of the electric accumulator (10).

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