Early monitoring method and system for thermal runaway of battery pack

Abstract

The invention provides a battery pack thermal runaway early-stage monitoring method and system, and the method is applied to the battery pack thermal runaway early-stage monitoring system. The system comprises a signal demodulator and an F-P optical fiber pressure sensor arranged in a battery pack, the F-P optical fiber pressure sensor comprises an F-P optical interference cavity formed by an optical fiber end face and a movable diaphragm; the gas pressure change in the battery pack enables the movable diaphragm to move so as to change the physical length of the F-P optical interference cavity; the method comprises the steps that a signal demodulator transmits broadband light to an F-P optical interference cavity through a trunk optical fiber, the broadband light generates multi-beam interference in the F-P optical interference cavity, and an interference spectrum carrying gas pressure information in the battery pack is generated; and the signal demodulator receives the interference spectrum returned by the F-P optical interference cavity through the main optical fiber, and determines the gas pressure in the battery pack at the current moment according to the interference spectrum at the current moment. Through the method, extremely early warning is realized, and the monitoring safety is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery pack thermal runaway early monitoring method and system. BACKGROUND

[0002] Currently, when monitoring the state of the battery pack in the electric vehicle and the energy storage station and giving a thermal runaway warning, the temperature sensor is usually used to collect the surface temperature of the battery pack, which cannot directly perceive the key chemical change information (such as the volatilization and decomposition of the electrolyte) inside the battery pack, and these changes are the direct precursor of battery performance degradation and thermal runaway.

[0003] The existing temperature sensor can only trigger a warning after the battery cell has a significant temperature rise (usually 5-10 minutes later than the initial chemical reaction), so the surface temperature rise of the battery pack is the "result" of thermal runaway, not the "cause". It is too late to alarm when the surface temperature of the battery pack rises. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a battery pack thermal runaway early monitoring method and system to discover abnormalities in time through the pressure change inside the battery pack before the surface temperature of the battery pack rises significantly, and to achieve early warning. At the same time, since the F-P optical fiber pressure sensor does not need electricity and does not produce electric sparks, it fundamentally eliminates the risk of ignition and ensures the safety of monitoring.

[0005] In a first aspect, the embodiments of the present application provide a battery pack thermal runaway early monitoring method, which is applied to a battery pack thermal runaway early monitoring system; the monitoring system comprises a signal demodulator and an F-P optical fiber pressure sensor arranged inside the battery pack; the F-P optical fiber pressure sensor comprises an F-P optical interference cavity composed of an optical fiber end face and a movable diaphragm; wherein the gas pressure change inside the battery pack causes the movable diaphragm to move to change the physical length of the F-P optical interference cavity; the method comprises: The signal demodulator transmits broadband light to the F-P optical interference cavity through a main optical fiber, and the broadband light undergoes multi-beam interference in the F-P optical interference cavity to generate an interference spectrum carrying the gas pressure information inside the battery pack; The signal demodulator receives the interference spectrum returned by the F-P optical interference cavity through the main optical fiber to determine the gas pressure inside the battery pack at the current time according to the interference spectrum at the current time.

[0006] In conjunction with the first aspect, this application provides a first possible implementation of the first aspect, wherein the battery pack includes at least one battery module, and the FP fiber optic pressure sensor is deployed at a key location inside the battery pack; the key location includes any one or more of the following locations: the gas flow channel of the battery module, or near a specific battery cell identified as being prone to thermal runaway; The backbone optical fiber is led out from inside the battery pack to the outside of the battery pack through a sealed feedthrough on the battery pack cover, and the led-out backbone optical fiber is connected to the signal demodulator.

[0007] In conjunction with the first aspect, this application provides a second possible implementation of the first aspect, wherein determining the gas pressure inside the battery pack at the current moment based on the interference spectrum at the current moment includes: The gas pressure inside the battery pack at the current moment is determined based on the wavelength shift between the current interference spectrum and the reference interference spectrum of the battery pack, and the calibration relationship between the wavelength shift and gas pressure pre-stored in the signal demodulator; wherein the reference interference spectrum is measured when the battery pack thermal runaway early monitoring system is powered on and initialized.

[0008] In conjunction with the first aspect, this application provides a third possible implementation of the first aspect, wherein the monitoring system further includes a battery management system, and the signal demodulator is connected to the battery management system via a CAN bus; the method further includes: The battery management system receives the current gas pressure inside the battery pack from the signal demodulator; The battery management system calculates the first rate of change of the battery pack based on the gas pressure monitored within the first monitoring time window; wherein, the length of the first monitoring time window is T1; The battery management system calculates the second rate of change of the battery pack based on the gas pressure monitored within the second monitoring time window; wherein the length of the second monitoring time window is T2, T1 <T2; If the first rate of change is greater than the first-level alarm threshold, the battery management system executes a first-level alarm safety strategy; the first-level alarm safety strategy includes any one or more of the following: prompting the battery management system to limit charging or discharging power, or activating the liquid cooling system; If the second rate of change is greater than the secondary alarm threshold, or if the gas pressure inside the battery pack monitored at the current moment is greater than the absolute pressure threshold, the battery management system executes a secondary alarm safety strategy; the secondary alarm threshold is greater than the primary alarm threshold; the secondary alarm safety strategy has a higher priority than the primary alarm safety strategy; the secondary alarm safety strategy includes any one or more of the following: disconnecting the high-voltage main relay between the battery pack and the power system, starting the liquid cooling system at full power, and issuing a visual or audible alarm.

[0009] In conjunction with the third possible implementation of the first aspect, this application provides a fourth possible implementation of the first aspect, wherein the method further includes: The battery management system performs linear fitting on the gas pressure monitored over a predetermined long-term monitoring period to obtain a pressure trend line, and uses the slope of the pressure trend line as the average pressure change rate of the battery pack. If the average pressure change rate is less than 0, the battery management system generates an alarm indicating that the battery pack has deteriorated sealing.

[0010] In conjunction with the third possible implementation of the first aspect, this application provides a fifth possible implementation of the first aspect, wherein, after the battery management system receives the gas pressure inside the battery pack at the current moment from the signal demodulator, the method further includes: The battery management system determines the current gas pressure peak value during the current operating cycle based on the gas pressure continuously received during one or more complete charge-discharge cycles of the battery pack during the current operating cycle. The battery management system acquires the initial gas pressure peak value of the battery pack; the initial gas pressure peak value is the maximum gas pressure value monitored during one or more complete charge-discharge cycles when the battery pack is in a brand new healthy state. The battery management system calculates the growth rate of the gas pressure peak based on the current gas pressure peak and the initial gas pressure peak. The battery management system assesses the current health status of the battery pack based on the growth rate of the peak gas pressure, the internal resistance of the battery pack, and capacity decay data.

[0011] In conjunction with the third possible implementation of the first aspect, this application provides a sixth possible implementation of the first aspect, wherein a plurality of FP fiber optic pressure sensors are arranged inside the battery pack, and different FP fiber optic pressure sensors are arranged at different key positions inside the battery pack. The plurality of FP fiber optic pressure sensors arranged inside the battery pack are connected in series to the signal demodulator through a trunk fiber. After the signal demodulator determines the gas pressure inside the battery pack at the current moment, it also includes: Distinguish the interference spectra of the FP fiber optic pressure sensors from different key locations, and associate the calculated gas pressure with the corresponding key location markers; The battery management system receives the current gas pressure inside the battery pack from the signal demodulator, including: The battery management system receives the gas pressure inside the battery pack at the current moment, which is associated with a key location identifier of the FP fiber optic pressure sensor, sent by the signal demodulator. If the first rate of increase is greater than the first-level alarm threshold, the battery management system executes a first-level alarm safety strategy, including: If the battery management system determines, based on the gas pressure associated with the location identifier of the FP fiber optic pressure sensor, that the first rate of change of any critical location is greater than the first-level alarm threshold, then the battery management system generates first-level warning information containing that critical location and executes a first-level alarm safety strategy based on the first-level warning information.

[0012] In conjunction with the fourth possible implementation of the first aspect, this application provides a seventh possible implementation of the first aspect, wherein different FP fiber optic pressure sensors are arranged in different battery packs; After the signal demodulator determines the gas pressure inside the battery pack at the current moment, it also includes: The signal demodulator distinguishes the interference spectra of the FP fiber optic pressure sensors from different battery packs and associates the calculated gas pressure with the corresponding battery pack identifier; The battery management system receives the current gas pressure inside the battery pack from the signal demodulator, including: The battery management system receives the gas pressure inside the battery pack at the current moment, which is associated with the battery pack identifier of the FP fiber optic pressure sensor, sent by the signal demodulator. The battery management system performs linear fitting on the gas pressure monitored over a predetermined long-term monitoring period to obtain a pressure trend line, and uses the slope of the pressure trend line as the average pressure change rate of the battery pack, including: The battery management system performs linear fitting on the gas pressure monitored within a predetermined long-term monitoring period and time for the gas pressure associated with each battery pack identifier, to obtain the pressure trend line corresponding to each battery pack. The battery management system uses the slope of the pressure trend line corresponding to each battery pack as the average pressure change rate of that battery pack. If the average pressure change rate is less than 0, the battery management system generates an alarm indicating that the battery pack has deteriorated sealing, including: If the average pressure change rate of any battery pack is less than 0, the battery management system generates an alarm containing the battery pack identifier indicating that the battery pack has a deterioration in its seal.

[0013] In conjunction with the first aspect, this application provides an eighth possible implementation of the first aspect, wherein the FP fiber optic pressure sensor is encapsulated in a metal housing or a ceramic housing.

[0014] Secondly, embodiments of this application also provide a battery pack thermal runaway early monitoring system, the monitoring system comprising: a signal demodulator and an FP fiber optic pressure sensor disposed inside the battery pack; the FP fiber optic pressure sensor includes an FP optical interference cavity composed of an optical fiber end face and a movable diaphragm; wherein, changes in gas pressure inside the battery pack cause the movable diaphragm to move, thereby changing the physical length of the FP optical interference cavity; The signal demodulator is used to emit broadband light into the FP optical interference cavity through the trunk optical fiber. The broadband light undergoes multi-beam interference in the FP optical interference cavity to generate an interference spectrum carrying information about the gas pressure inside the battery pack. The signal demodulator is also used to receive the interference spectrum returned by the FP optical interference cavity through the backbone optical fiber, so as to determine the gas pressure inside the battery pack at the current moment based on the interference spectrum at the current moment.

[0015] This application provides a method and system for early monitoring of thermal runaway in a battery pack. The method considers that the direct precursor to battery pack performance degradation and thermal runaway is internal chemical change (such as electrolyte evaporation and decomposition), which generates gas within the battery pack, leading to increased internal pressure. In this embodiment, a fiber optic pressure sensor is deployed inside the battery pack. When the internal pressure increases, the movable diaphragm in the sensor is pushed, causing displacement and altering the physical length of the FP optical interference cavity. At this time, a signal demodulator transmits broadband light to the FP optical interference cavity via the backbone fiber. This broadband light undergoes multi-beam interference within the cavity, generating an interference spectrum carrying information about the internal gas pressure of the battery pack. The demodulator receives the interference spectrum returned from the cavity via the backbone fiber to determine the current internal gas pressure of the battery pack. Because the internal chemical changes in the battery pack occur before the external surface temperature rises (internal chemical reactions typically precede external surface temperature rise by 5-10 minutes), this embodiment can detect anomalies through changes in internal gas pressure before the external surface temperature of the battery pack has significantly increased, providing an early warning several minutes in advance and buying valuable time for personnel evacuation and emergency response. Furthermore, the FP fiber optic pressure sensor itself is a passive device (requiring no power supply). Internally, it only contains physical structures such as fiber end faces and movable diaphragms, without any electronic components, chips, or circuits. The FP fiber optic pressure sensor itself does not emit light or consume power; it simply borrows broadband light from the signal demodulator, modulates (interferes) internally, and then reflects the light back. Its energy comes entirely from the incident broadband light. This passive characteristic brings significant inherent safety benefits. In an environment like a battery pack where flammable gases may be present, it is absolutely impossible for it to generate an electric spark or become an ignition source, which is unmatched by traditional electronic sensors. Therefore, it fundamentally eliminates the risk of ignition, ensuring the safety of monitoring.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1This paper shows a schematic diagram of the structure of an early monitoring system for thermal runaway of a battery pack provided in an embodiment of this application; Figure 2 This paper shows a schematic diagram of the structure of an FP optical interference cavity provided in an embodiment of this application; Figure 3 A flowchart of an early monitoring method for thermal runaway of a battery pack provided in an embodiment of this application is shown; Figure 4 This illustration shows a schematic diagram of a battery pack containing multiple FP fiber optic pressure sensors connected in series, according to an embodiment of this application. Figure 5 This illustration shows a schematic diagram of the FP fiber optic pressure sensor connected in series in a different battery pack according to an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] Traditional electrical temperature sensors can only collect the temperature of the battery pack's outer surface and rely on this temperature to determine thermal runaway. Since a rise in the battery pack's outer surface temperature is a "result," not a "cause," of thermal runaway, waiting until the temperature rises before issuing an alarm is too late. Furthermore, electrical sensors may generate electrical sparks inside the battery pack, posing a risk of explosion.

[0021] Based on this, this application provides a method and system for early monitoring of thermal runaway in a battery pack, which can detect abnormalities in a timely manner by changing the internal pressure of the battery pack before the surface temperature of the battery pack rises significantly, thus achieving very early warning. At the same time, since the FP fiber optic pressure sensor does not require electricity and does not generate electrical sparks, it fundamentally eliminates the risk of ignition and ensures the safety of monitoring. The following is a description through embodiments.

[0022] To facilitate understanding of this embodiment, a method for early monitoring of thermal runaway in a battery pack, disclosed in this application, will first be described in detail. This method for early monitoring of thermal runaway in a battery pack is applied to an early monitoring system for thermal runaway in a battery pack; such asFigure 1 As shown, the early thermal runaway monitoring system for this battery pack includes: a signal demodulator and an FP fiber optic pressure sensor (Fabry-Pérot Cavity sensor) deployed inside the battery pack; as shown Figure 2 As shown, the FP fiber pressure sensor includes an FP optical interference cavity consisting of an optical fiber end face and a movable diaphragm; wherein, changes in gas pressure inside the battery pack cause the movable diaphragm to move, thereby changing the physical length of the FP optical interference cavity.

[0023] In this embodiment, the FP fiber optic pressure sensor mainly consists of the following parts: an optical fiber, a first reflecting surface, an FP optical interference cavity, a movable diaphragm, a second reflecting surface, and a housing. The FP optical interference cavity is the core structure of the FP fiber optic pressure sensor. It is composed of an "optical fiber end face" and a "movable diaphragm," which are precisely parallel to each other with a tiny gap in between. The space between these two parallel reflecting surfaces (the optical fiber end face and the movable diaphragm) constitutes the FP optical interference cavity.

[0024] The first reflecting surface is located at the end face of the optical fiber, and the second reflecting surface is located inside the movable diaphragm, parallel and opposite to the first reflecting surface. The outer shell is a metal (such as stainless steel) shell or a ceramic shell, meaning that the FP fiber optic pressure sensor is encapsulated in a metal or ceramic shell, providing excellent pressure resistance and corrosion resistance.

[0025] In the specific scenario of battery pack thermal runaway monitoring, the gas pressure monitored by the FP fiber optic pressure sensor refers to the gas pressure (i.e., air pressure) within the sealed cavity inside the battery pack. The FP fiber optic pressure sensor is exposed to the air between the battery modules inside the battery pack, and it directly senses the gas pressure acting on the movable diaphragm. This change in gas pressure originates from the chemical reactions within the battery pack.

[0026] like Figure 3 As shown, the method for early monitoring of thermal runaway in a battery pack includes the following steps S101-S102: S101: The signal demodulator emits broadband light into the FP optical interference cavity through the trunk optical fiber. The broadband light undergoes multi-beam interference in the FP optical interference cavity, generating an interference spectrum that carries information about the gas pressure inside the battery pack.

[0027] S102: The signal demodulator receives the interference spectrum returned by the FP optical interference cavity through the backbone fiber, so as to determine the gas pressure inside the battery pack at the current moment based on the interference spectrum at the current moment.

[0028] In step S101, the broadband light source in the signal demodulator emits broadband light (i.e., emits optical signal) into the FP optical interference cavity through the trunk optical fiber. The broadband light is reflected multiple times between the first and second reflecting surfaces of the FP optical interference cavity, resulting in multi-beam interference. The characteristics of the returned interference spectrum (such as wavelength or frequency) are determined by the physical length of the FP optical interference cavity. This physical length changes with the gas pressure inside the battery pack, thus the interference spectrum carries information about the gas pressure inside the battery pack.

[0029] Broadband light, also known as white light or continuous spectrum light, refers to light whose spectrum encompasses a very wide range of wavelengths (or frequencies), rather than just one or a few specific wavelengths. Specifically, the spectral width of broadband light is not less than 10 nm, and preferably between 20 nm and 100 nm.

[0030] In step S102, the signal demodulator receives the interference spectrum returned by the FP optical interference cavity through the backbone optical fiber, and calculates the real-time gas pressure inside the battery pack (i.e. the gas pressure at the current moment) based on the drift of the interference spectrum.

[0031] In this embodiment, the battery pack can specifically be the battery pack in the power battery of an electric vehicle. In this case, the signal conditioner can be installed below the vehicle's instrument panel.

[0032] In another embodiment, the battery pack can be a battery pack in a battery cluster of an energy storage power station, in which case the signal conditioner can be a centralized demodulator installed on the top of the cabinet.

[0033] In one possible implementation, step S102 can be performed according to the following steps: The gas pressure inside the battery pack at the current moment is determined based on the wavelength shift between the current interference spectrum and the reference interference spectrum of the battery pack, as well as the calibration relationship between the wavelength shift and gas pressure pre-stored in the signal demodulator. The reference interference spectrum is measured when the battery pack thermal runaway early monitoring system is powered on and initialized.

[0034] In this embodiment, the reference interferometric spectrum is the interferometric spectrum measured when the battery pack is in a safe state and the internal gas pressure of the battery pack is within the normal range. Each battery pack has its own reference interferometric spectrum, and the reference interferometric spectrum of each battery pack only needs to be measured once.

[0035] In one possible implementation, the battery pack includes at least one battery module, and FP fiber optic pressure sensors are deployed at key locations inside the battery pack; key locations include any one or more of the following: gas flow channels of the battery module, and the vicinity of specific battery cells identified as being prone to thermal runaway. The backbone optical fiber is led out from inside the battery pack to the outside of the battery pack through the sealed feedthrough on the top cover of the battery pack, and the led-out backbone optical fiber is connected to the signal demodulator.

[0036] In this embodiment, considering that after thermal runaway of the battery pack generates gas, the gas will first diffuse along the gas flow channel, placing monitoring points here will capture the gas pressure change faster than placing points directly on the surface of the cell.

[0037] The area near a specific battery cell identified as prone to thermal runaway is defined as a high-risk cell based on the battery pack's thermal management characteristics and historical data. "Area near" refers to a straight-line distance between the FP fiber optic pressure sensor and the outer surface of the specific battery cell within the range of [0, 50] mm, preferably [0, 20] mm.

[0038] In one possible implementation, the battery pack thermal runaway early detection system further includes a battery management system (BMS), and the signal demodulator is connected to the battery management system via a CAN bus; the battery pack thermal runaway early detection method can also be performed according to the following steps S104-S208: S104: The battery management system receives the current gas pressure inside the battery pack from the signal demodulator.

[0039] S105: The battery management system calculates the first rate of change of the battery pack based on the gas pressure monitored within the first monitoring time window; wherein, the length of the first monitoring time window is T1.

[0040] S106: The battery management system calculates the second rate of change of the battery pack based on the gas pressure monitored within the second monitoring time window; wherein, the length of the second monitoring time window is T2, T1 <T2。

[0041] S107: If the first rate of change is greater than the first alarm threshold, the battery management system executes the first alarm safety strategy; the first alarm safety strategy includes any one or more of the following: prompting the battery management system to limit the charging or discharging power, or activating the liquid cooling system.

[0042] S108: If the second rate of change is greater than the secondary alarm threshold, or if the gas pressure inside the battery pack monitored at the current moment is greater than the absolute pressure threshold, the battery management system executes the secondary alarm safety strategy; the secondary alarm threshold is greater than the primary alarm threshold; the secondary alarm safety strategy has a higher priority than the primary alarm safety strategy; the secondary alarm safety strategy includes any one or more of the following: disconnecting the high-voltage main relay between the battery pack and the power system, starting the liquid cooling system at full power, and issuing a visual or audible alarm.

[0043] In this embodiment, two alarm thresholds are set in the battery management system. Level 1 alarm (early warning): Pressure rises >1 kPa within 1 second, prompting the battery management system to limit charging / discharging power and enhance heat dissipation. Level 2 alarm (emergency): Pressure rises >5 kPa within 100 milliseconds, or the absolute gas pressure exceeds 150 kPa (relative pressure).

[0044] In other words, the length of the first monitoring time window, T1, is 1 second, and the length of the second monitoring time window, T2, is 100 milliseconds. The first-level alarm threshold corresponds to a pressure increase of 1 kPa within 1 second, the second-level alarm threshold corresponds to a pressure increase of 5 kPa within 100 milliseconds, and the absolute pressure threshold is 150 kPa.

[0045] Level 1 alarm safety strategies include any one or more of the following: prompting the battery management system to limit charging or discharging power, or activating the liquid cooling system (to enhance heat dissipation).

[0046] Level 2 alarm safety strategies include any one or more of the following: disconnecting the high-voltage main relay between the battery pack and the power system, starting the liquid cooling system at full power, and issuing a visual or audible alarm.

[0047] In this embodiment, the high-voltage main relay is a power switch connecting the battery pack and the vehicle's powertrain (motor, air conditioning, etc.). Since thermal runaway itself generates heat, if the motor is still drawing a large current from the battery pack, or the charging station is still charging, this will drastically accelerate the spread of thermal runaway. Therefore, immediately disconnecting the high-voltage main relay between the battery pack and the powertrain isolates the entire high-voltage system from the dangerous battery pack, preventing further electrical fires or electric shock risks.

[0048] Full-power start-up of the liquid cooling system involves activating the liquid cooling system at maximum power to cool the battery pack and lower its temperature.

[0049] The system issues visual or auditory alerts, such as displaying a "Risk Warning, Please Stop Safely Immediately" message to the driver via the in-vehicle screen. This process provides occupants with over 3 minutes of emergency response time, far exceeding the less than 1 minute of traditional temperature warning systems, significantly improving occupant safety.

[0050] In one possible implementation, such as Figure 4 As shown, the battery pack is equipped with multiple FP fiber optic pressure sensors. Different FP fiber optic pressure sensors are deployed at different key locations inside the battery pack. The multiple FP fiber optic pressure sensors deployed inside the battery pack are connected in series to the signal demodulator through a main fiber optic cable.

[0051] If the battery pack contains multiple battery modules, after determining the gas pressure inside the battery pack at the current moment in step S102, the process further includes: S103: The signal demodulator distinguishes the interference spectra of FP fiber optic pressure sensors from different key locations and associates the calculated gas pressure with the corresponding key location markers.

[0052] When the battery management system receives the current gas pressure inside the battery pack from the signal demodulator in step S104, the specific steps can be performed as follows: The battery management system receives the gas pressure inside the battery pack at the current moment, which is sent by the signal demodulator and associated with the key location marker of the FP fiber optic pressure sensor.

[0053] If the first rate of change is greater than the first-level alarm threshold in step S107, the battery management system will execute the first-level alarm safety strategy, which can be done in the following steps: If the battery management system determines, based on the gas pressure associated with the location identifier of the FP fiber optic pressure sensor, that the first rate of change of any critical location is greater than the first-level alarm threshold, the battery management system generates a first-level warning message containing that critical location and executes a first-level alarm safety strategy based on the first-level warning message.

[0054] In this embodiment, when the battery pack contains multiple battery modules, the above method can more accurately locate the individual battery module that first experiences abnormal gas production, providing precise information for fault diagnosis and maintenance.

[0055] In one possible implementation, the battery pack thermal runaway early monitoring method can also be performed according to the following steps S201-S202: S201: The battery management system performs linear fitting on the gas pressure monitored over a predetermined long-term monitoring period to obtain a pressure trend line, and uses the slope of the pressure trend line as the average pressure change rate of the battery pack.

[0056] S202: If the average pressure change rate is less than 0, the battery management system generates an alarm indicating that the battery pack has deteriorated sealing.

[0057] In this embodiment, the predetermined long-term monitoring cycle is two weeks. Alarms indicating deterioration in sealing are used to guide maintenance personnel in locating and replacing battery packs with compromised sealing.

[0058] In one possible implementation, such as Figure 5 As shown, different FP fiber optic pressure sensors are deployed in different battery packs; if there are multiple battery packs, after determining the gas pressure inside the battery pack at the current moment in step S102, the process further includes: S200: The signal demodulator distinguishes the interference spectra of FP fiber optic pressure sensors from different battery packs and associates the calculated gas pressure with the corresponding battery pack identifier.

[0059] When the battery management system receives the current gas pressure inside the battery pack from the signal demodulator in step S104, the specific steps can be performed as follows: The battery management system receives the current gas pressure inside the battery pack, which is associated with the battery pack identifier of the FP fiber optic pressure sensor, sent by the signal demodulator.

[0060] When performing step S201, the battery management system performs linear fitting of the gas pressure monitored over a predetermined long-term monitoring period with time to obtain a pressure trend line, and uses the slope of the pressure trend line as the average pressure change rate of the battery pack, the specific steps can be as follows: The battery management system performs linear fitting on the gas pressure and time monitored within a predetermined long-term monitoring period for each battery pack identifier to obtain the pressure trend line corresponding to each battery pack. The battery management system uses the slope of the pressure trend line corresponding to each battery pack as the average pressure change rate of that battery pack.

[0061] If the average pressure change rate is less than 0 during step S202, and the battery management system generates an alarm indicating that the battery pack has deteriorated sealing, the following steps can be followed: If the average pressure change rate of any battery pack is less than 0, the battery management system generates an alarm containing the battery pack identifier indicating that the battery pack has a deteriorated seal.

[0062] In this embodiment, when a slow but continuous decline in the gas pressure of a battery pack is detected over two weeks, an automatic sealing degradation alarm is generated for that battery pack. Maintenance personnel can accurately locate the battery pack with the most significant pressure drop, isolate and replace it, thus preventing permanent damage to the entire battery cluster due to moisture intrusion.

[0063] In one possible implementation, after the battery management system receives the current gas pressure inside the battery pack from the signal demodulator in step S104, the following steps S301-S304 can also be performed: S301: The battery management system determines the current gas pressure peak value during the current operating cycle based on the gas pressure continuously received during one or more complete charge-discharge cycles of the battery pack during the current operating cycle.

[0064] S302: The battery management system obtains the initial gas pressure peak value of the battery pack; the initial gas pressure peak value is the maximum gas pressure value monitored during one or more complete charge-discharge cycles when the battery pack is in a brand new healthy state.

[0065] S303: The battery management system calculates the growth rate of the gas pressure peak based on the current gas pressure peak and the initial gas pressure peak.

[0066] S304: The battery management system assesses the current health status of the battery pack based on the growth rate of peak gas pressure, the internal resistance of the battery pack, and capacity decay data.

[0067] In this embodiment, the growth rate = (current gas pressure peak - initial gas pressure peak) / initial gas pressure peak × 100%.

[0068] The current operating cycle is nearly one year. By comparing the pressure fluctuation amplitude during the charge-discharge cycle when the battery was first put into operation and after one year of operation, it was found that the peak pressure increased by 15%. This data serves as an important auxiliary parameter, and together with the battery pack's internal resistance and capacity decay data, it is used to accurately assess the overall SOH (State of Health) of the battery pack.

[0069] Based on the same technical concept, this application also provides a battery pack thermal runaway early monitoring system, which includes: a signal demodulator and an FP fiber optic pressure sensor deployed inside the battery pack; the FP fiber optic pressure sensor includes an FP optical interference cavity composed of an optical fiber end face and a movable diaphragm; wherein, changes in gas pressure inside the battery pack will cause the movable diaphragm to move, thereby changing the physical length of the FP optical interference cavity; The signal demodulator is used to emit broadband light into the FP optical interference cavity through the trunk optical fiber. The broadband light undergoes multi-beam interference in the FP optical interference cavity to generate an interference spectrum carrying information about the gas pressure inside the battery pack. The signal demodulator is also used to receive the interference spectrum returned by the FP optical interference cavity through the backbone optical fiber, so as to determine the gas pressure inside the battery pack at the current moment based on the interference spectrum at the current moment.

[0070] Optionally, the battery pack includes at least one battery module, and the FP fiber optic pressure sensor is deployed at key locations inside the battery pack; the key locations include any one or more of the following: the gas flow channel of the battery module, or the vicinity of a specific battery cell identified as being prone to thermal runaway; The backbone optical fiber is led out from inside the battery pack to the outside of the battery pack through a sealed feedthrough on the battery pack cover, and the led-out backbone optical fiber is connected to the signal demodulator.

[0071] Optionally, when the signal demodulator is used to determine the gas pressure inside the battery pack at the current moment based on the interference spectrum at the current moment, it is specifically used for: The gas pressure inside the battery pack at the current moment is determined based on the wavelength shift between the current interference spectrum and the reference interference spectrum of the battery pack, and the calibration relationship between the wavelength shift and gas pressure pre-stored in the signal demodulator; wherein the reference interference spectrum is measured when the battery pack thermal runaway early monitoring system is powered on and initialized.

[0072] Optionally, the monitoring system further includes a battery management system, and the signal demodulator is connected to the battery management system via a CAN bus; the battery management system is further configured to: Receive the current gas pressure inside the battery pack from the signal demodulator; The first rate of change of the battery pack is calculated based on the gas pressure monitored within the first monitoring time window; wherein, the length of the first monitoring time window is T1. The second rate of change of the battery pack is calculated based on the gas pressure monitored within the second monitoring time window; wherein the length of the second monitoring time window is T2, T1 <T2; If the first rate of change is greater than the first-level alarm threshold, then the first-level alarm safety strategy is executed; the first-level alarm safety strategy includes any one or more of the following: prompting the battery management system to limit charging or discharging power, or activating the liquid cooling system; If the second rate of change is greater than the secondary alarm threshold, or if the gas pressure inside the battery pack monitored at the current moment is greater than the absolute pressure threshold, then the secondary alarm safety strategy is executed; the secondary alarm threshold is greater than the primary alarm threshold; the secondary alarm safety strategy has a higher priority than the primary alarm safety strategy; the secondary alarm safety strategy includes any one or more of the following: disconnecting the high-voltage main relay between the battery pack and the power system, starting the liquid cooling system at full power, and issuing a visual or audible alarm.

[0073] Optionally, the battery management system is further configured to: The gas pressure monitored over a predetermined long-term monitoring period is linearly fitted with time to obtain a pressure trend line, and the slope of the pressure trend line is used as the average pressure change rate of the battery pack. If the average pressure change rate is less than 0, an alarm is generated indicating that the battery pack has deteriorated sealing.

[0074] Optionally, after receiving the current gas pressure inside the battery pack from the signal demodulator, the battery management system is further configured to: The current peak gas pressure in the current operating cycle is determined based on the gas pressure continuously received during one or more complete charge-discharge cycles in the current operating cycle of the battery pack. Obtain the initial gas pressure peak value of the battery pack; the initial gas pressure peak value is the maximum gas pressure value monitored during one or more complete charge-discharge cycles when the battery pack is in a brand new healthy state. Calculate the growth rate of the gas pressure peak based on the current peak gas pressure and the initial peak gas pressure. The current health status of the battery pack is assessed based on the growth rate of peak gas pressure, the internal resistance of the battery pack, and capacity decay data.

[0075] Optionally, the battery pack is equipped with a plurality of FP fiber optic pressure sensors, which are located at different key positions inside the battery pack. The plurality of FP fiber optic pressure sensors installed in the battery pack are connected in series to the signal demodulator through a trunk fiber. After determining the gas pressure inside the battery pack at the current moment, the signal demodulator is also used for: Distinguish the interference spectra of the FP fiber optic pressure sensors from different key locations, and associate the calculated gas pressure with the corresponding key location markers; When the battery management system receives the current gas pressure inside the battery pack from the signal demodulator, it is specifically used for: The battery management system receives the gas pressure inside the battery pack at the current moment, which is associated with a key location identifier of the FP fiber optic pressure sensor, sent by the signal demodulator. When the battery management system is configured to execute a level-one alarm safety policy if the first rate of increase is greater than the level-one alarm threshold, it is specifically configured to: If, based on the gas pressure associated with the location identifier of the FP fiber optic pressure sensor, it is determined that the first rate of increase in any critical location is greater than the first-level alarm threshold, then a first-level warning message containing that critical location is generated, and a first-level alarm safety strategy is executed based on the first-level warning message.

[0076] Optionally, different FP fiber optic pressure sensors are arranged in different battery packs; After determining the gas pressure inside the battery pack at the current moment, the signal demodulator is also used for: Distinguish the interference spectra of the FP fiber optic pressure sensors from different battery packs, and associate the calculated gas pressure with the corresponding battery pack identifier; When the battery management system receives the current gas pressure inside the battery pack from the signal demodulator, it is specifically used for: Receive the gas pressure inside the battery pack at the current moment, which is associated with the battery pack identifier of the FP fiber optic pressure sensor and sent by the signal demodulator; When the battery management system performs linear fitting on the gas pressure monitored over a predetermined long-term monitoring period to obtain a pressure trend line, and uses the slope of the pressure trend line as the average pressure change rate of the battery pack, it is specifically used for: For the gas pressure associated with each battery pack identifier, the gas pressure monitored within a predetermined long-term monitoring period is linearly fitted with time to obtain the pressure trend line corresponding to each battery pack. The slope of the pressure trend line corresponding to each battery pack is taken as the average pressure change rate of that battery pack. When the battery management system generates an alarm indicating sealing degradation of the battery pack if the average pressure change rate is less than 0, it is specifically used for: If the average pressure change rate of any battery pack is less than 0, an alarm is generated that includes the identifier of the battery pack, indicating that the battery pack has a deteriorated seal.

[0077] Optionally, the FP fiber optic pressure sensor is encapsulated in a metal or ceramic housing.

[0078] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the system described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0079] In the several embodiments provided in this application, it should be understood that the disclosed system can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and there may be other division methods in actual implementation. Furthermore, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interfaces; the indirect coupling or communication connection between devices or modules may be electrical, mechanical, or other forms.

[0080] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0081] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0082] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0083] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

Claims

1. A battery pack thermal runaway early monitoring method, characterized in that, The method is applied to a battery pack thermal runaway early monitoring system; the monitoring system comprises a signal demodulator and an F-P optical fiber pressure sensor arranged in the battery pack; the F-P optical fiber pressure sensor comprises an F-P optical interference cavity composed of an optical fiber end face and a movable diaphragm; wherein, the change of the gas pressure in the battery pack causes the movable diaphragm to move, so as to change the physical length of the F-P optical interference cavity; the method comprises: The signal demodulator transmits broadband light to the F-P optical interference cavity through a main trunk optical fiber, and the broadband light produces multi-beam interference in the F-P optical interference cavity to generate an interference spectrum carrying the gas pressure information in the battery pack; The signal demodulator receives the interference spectrum returned by the F-P optical interference cavity through the main trunk optical fiber, so as to determine the gas pressure in the battery pack at the current moment according to the interference spectrum at the current moment.

2. The method of claim 1, wherein, The battery pack comprises at least one battery module, and the F-P optical fiber pressure sensor is arranged at a key position in the battery pack; the key position comprises any one or more of the following positions: a gas flow channel of the battery module, a specific battery cell determined to be prone to thermal runaway; The main trunk optical fiber is led out from the inside of the battery pack to the outside of the battery pack through a sealing feeder of the battery pack upper cover, and the led-out main trunk optical fiber is connected to the signal demodulator.

3. The method of claim 1, wherein, The determination of the gas pressure in the battery pack at the current moment according to the interference spectrum at the current moment comprises: determining the gas pressure in the battery pack at the current moment according to the wavelength drift amount between the interference spectrum at the current moment and a reference interference spectrum of the battery pack, and a calibration relationship between the wavelength drift amount and the gas pressure pre-stored in the signal demodulator; wherein, the reference interference spectrum is measured when the battery pack thermal runaway early monitoring system is powered on.

4. The method of claim 1, wherein, The monitoring system further comprises a battery management system, and the signal demodulator is connected to the battery management system through a CAN bus; the method further comprises: The battery management system receives the gas pressure in the battery pack at the current moment from the signal demodulator; The battery management system calculates a first rising change rate of the battery pack according to the monitored gas pressure in a first monitoring time window; wherein, the length of the first monitoring time window is T1; The battery management system calculates a second rising change rate of the battery pack according to the monitored gas pressure in a second monitoring time window; wherein, the length of the second monitoring time window is T2, and T1 If the first rising change rate is greater than a first alarm threshold, the battery management system executes a first alarm safety strategy; the first alarm safety strategy comprises any one or more of the following: prompting the battery management system to limit the charging or discharging power, starting the liquid cooling system. if the second rising rate is greater than a secondary alarm threshold, or the gas pressure inside the battery pack monitored at the current time is greater than an absolute pressure threshold, the battery management system executes a secondary alarm safety strategy; the secondary alarm threshold is greater than the primary alarm threshold; the priority of the secondary alarm safety strategy is higher than that of the primary alarm safety strategy; the secondary alarm safety strategy includes any one or more of the following: cutting off the high-voltage main relay between the battery pack and the power system, starting the liquid cooling system at full power, and issuing a visual or audible alarm.

5. The method of claim 4, wherein, The method further comprises: The battery management system linearly fits the gas pressure monitored in a predetermined long-term monitoring period and time to obtain a pressure trend line, and takes the slope of the pressure trend line as the average pressure change rate of the battery pack; if the average pressure change rate is less than 0, the battery management system generates an alarm indicating that the battery pack has a seal degradation.

6. The method of claim 4, wherein, After the battery management system receives the gas pressure inside the battery pack at the current time from the signal demodulator, the method further comprises: The battery management system determines the current gas pressure peak value in the current operation cycle of the battery pack based on the continuously received gas pressure in one or more complete charge and discharge cycles in the current operation cycle of the battery pack; The battery management system obtains an initial gas pressure peak value of the battery pack; the initial gas pressure peak value is the maximum gas pressure monitored in one or more complete charge and discharge cycles when the battery pack is in a brand-new healthy state; The battery management system calculates the growth rate of the gas pressure peak value according to the current gas pressure peak value and the initial gas pressure peak value; The battery management system evaluates the current health status of the battery pack based on the growth rate of the gas pressure peak value, the internal resistance of the battery pack, and the capacity attenuation data.

7. The method of claim 4 wherein, A plurality of F-P optical fiber pressure sensors are arranged inside the battery pack, different F-P optical fiber pressure sensors are arranged at different key positions inside the battery pack, and the plurality of F-P optical fiber pressure sensors arranged inside the battery pack are connected in series to the signal demodulator through a main fiber; After the signal demodulator determines the gas pressure inside the battery pack at the current time, it further comprises: The signal demodulator distinguishes the interference spectrum of the F-P optical fiber pressure sensor from different key positions, and associates the calculated gas pressure with the corresponding key position identifier; The battery management system receives the gas pressure inside the battery pack at the current time from the signal demodulator, which comprises: The battery management system receives the gas pressure inside the battery pack at the current time sent by the signal demodulator and associated with the key position identifier of the F-P optical fiber pressure sensor; The if the first rising rate is greater than a primary alarm threshold, the battery management system executes a primary alarm safety strategy, which comprises: If the battery management system determines that the first rising rate of any critical position is greater than the first alarm threshold according to the gas pressure associated with the F-P optical fiber pressure sensor position identifier, the battery management system generates a first warning information containing the critical position, and executes a first alarm safety strategy based on the first warning information.

8. The method of claim 5, wherein, Different F-P optical fiber pressure sensors are arranged in different battery packs. After the signal demodulator determines the gas pressure inside the battery pack at the current time, it further includes: The signal demodulator distinguishes the interference spectrum from the F-P optical fiber pressure sensor of different battery packs, and associates the calculated gas pressure with the corresponding battery pack identifier; The battery management system receives the gas pressure inside the battery pack at the current time from the signal demodulator, including: The battery management system receives the gas pressure inside the battery pack at the current time sent by the signal demodulator, which is associated with the battery pack identifier of the F-P optical fiber pressure sensor; The battery management system linearly fits the monitored gas pressure and time in a predetermined long-term monitoring period to obtain a pressure trend line, and takes the slope of the pressure trend line as the average pressure change rate of the battery pack, including: The battery management system linearly fits the monitored gas pressure and time in a predetermined long-term monitoring period for the gas pressure related to each battery pack identifier, respectively, to obtain the corresponding pressure trend line of each battery pack; The battery management system takes the slope of the pressure trend line corresponding to each battery pack as the average pressure change rate of the battery pack; If the average pressure change rate is less than 0, the battery management system generates an alarm indicating that the battery pack has a sealing deterioration, including: If the average pressure change rate of any battery pack is less than 0, the battery management system generates an alarm indicating that the battery pack has a sealing deterioration containing the battery pack identifier.

9. The method of claim 1, wherein, The F-P optical fiber pressure sensor is packaged in a metal shell or a ceramic shell.

10. A battery pack thermal runaway early monitoring system, characterized in that, The monitoring system includes a signal demodulator and an F-P optical fiber pressure sensor arranged inside the battery pack; the F-P optical fiber pressure sensor contains an F-P optical interference cavity composed of an optical fiber end face and a movable diaphragm; wherein the change of the gas pressure inside the battery pack will cause the movable diaphragm to move, changing the physical length of the F-P optical interference cavity; The signal demodulator is used to emit broadband light to the F-P optical interference cavity through the main fiber, and the broadband light undergoes multi-beam interference in the F-P optical interference cavity to generate an interference spectrum carrying the gas pressure information inside the battery pack; The signal demodulator is also used to receive the interference spectrum returned by the F-P optical interference cavity through the main fiber, to determine the gas pressure inside the battery pack at the current time according to the interference spectrum at the current time.

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