Distributed fiber optic monitoring device for battery pack temperature and strain and battery pack

Abstract

This application relates to the field of battery state monitoring technology, providing a distributed optical fiber monitoring device for battery pack temperature and strain, and a battery pack. The distributed optical fiber monitoring device for battery pack temperature and strain includes: a fixing device; a sensing optical fiber, fixed to the sidewall of each battery cell by the fixing device, and passing through the gap between adjacent battery cells in an S-shaped path; the fixing device includes: a fixing plate with a straight groove on its surface to accommodate the sensing optical fiber; a spring pressure plate, fixed at both ends to the fixing plate by screws, with its middle part spanning over the straight groove and pressing against the surface of the sensing optical fiber; anchor blocks disposed at both ends of the sensing optical fiber; a fiber Bragg grating and a Fabry-Perot structure are connected in series on the sidewall of each battery cell; one end of the sensing optical fiber is connected to a broadband light source, and the other end is connected to a spectrometer. This application achieves integrated functions of reliable optical fiber fixing, separate temperature and strain measurement, and single-fiber multi-point distributed monitoring.

Description

Technical Field

[0001] This application relates to the field of battery status monitoring technology, and more specifically, to a distributed optical fiber monitoring device for battery pack temperature and strain, and a battery pack. Background Technology

[0002] Currently, fiber optic sensing technology is increasingly being applied to battery monitoring due to its advantages such as resistance to electromagnetic interference, small size, and cascaded multiplexing. However, existing fiber optic sensing solutions still have the following technical drawbacks: First, the fixing methods of optical fibers in battery packs are relatively simple, mostly using adhesive bonding or direct attachment, lacking reliable pre-tightening and anti-loosening structures. Under long-term vibration, they are prone to detachment or displacement, leading to measurement failure. Second, existing solutions mostly use a single sensor, only a fiber Bragg grating or only a Fabry-Perot structure, making it difficult to achieve high-precision measurement of temperature and strain simultaneously. Furthermore, there is a problem of cross-sensitivity between temperature and strain, making it impossible to effectively separate the responses of the two physical quantities. Third, for battery packs composed of multiple cells, existing solutions usually require multiple optical fibers or multi-channel demodulation equipment, resulting in complex systems and high costs. Utility Model Content

[0003] This application aims to at least address the technical problems in the related art, such as the susceptibility of battery monitoring devices to electromagnetic interference, complex wiring, poor installation reliability, difficulty in simultaneously measuring temperature and strain, and high cost of distributed monitoring.

[0004] To address the aforementioned technical problems, this application provides the following: Firstly, it offers a distributed optical fiber monitoring device for battery pack temperature and strain, comprising a fixing device and a sensing optical fiber. The fixing device is used to mount multiple battery cells arranged in a straight line; the sensing optical fiber is fixed to the sidewall of each battery cell via the fixing device and passes sequentially through the gap between adjacent battery cells in an S-shaped path. The fixing device includes a fixing plate, a spring clamping plate, and an anchoring block. The device includes a fixing plate for attaching to the sidewall of the battery cell, with a straight groove on its surface to accommodate the sensing fiber; a spring pressure plate with both ends fixed to the fixing plate by screws, the middle of which spans over the straight groove and presses against the surface of the sensing fiber; anchor blocks at both ends of the sensing fiber, with the ends of the sensing fiber fixed in the anchor blocks by adhesive; a fiber Bragg grating and a Fabry-Perot structure are connected in series on the sidewall of each battery cell, the fiber Bragg grating being used to measure temperature and the Fabry-Perot structure being used to measure strain; one end of the sensing fiber is connected to a broadband light source, and the other end is connected to a spectrometer.

[0005] This application provides a distributed optical fiber monitoring device for battery pack temperature and strain. Through the coordinated operation of a fixing device, an S-shaped single-fiber series layout, and an FBG / FP collaborative measurement mechanism, it achieves integrated functions of highly reliable optical fiber fixing, separate temperature and strain measurement, and multi-point distributed monitoring of a single fiber. It effectively solves the problems of existing battery monitoring devices being susceptible to electromagnetic interference, having complex wiring, poor installation reliability, difficulty in simultaneously measuring temperature and strain, and high cost of distributed monitoring, thereby improving the stability, accuracy, and system integration of battery pack status monitoring.

[0006] Secondly, this application proposes a battery pack, comprising: a plurality of battery cells arranged in a straight line; and a distributed optical fiber monitoring device for battery pack temperature and strain as described above, with the fixing device disposed on the battery cells.

[0007] The battery pack provided in this application includes the battery pack temperature and strain distributed optical fiber monitoring device of the above-mentioned technical solution, and therefore has all the beneficial effects of the battery pack temperature and strain distributed optical fiber monitoring device, which will not be repeated here.

[0008] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0009] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0010] Figure 1 This is a schematic diagram of the structure of a battery pack and a distributed optical fiber monitoring device for battery pack temperature and strain according to an embodiment of this application;

[0011] Figure 2 for Figure 1 A schematic diagram of the fixing device in the distributed optical fiber monitoring device for battery pack temperature and strain of the embodiment shown.

[0012] Figure 3 for Figure 1 A schematic diagram of the fiber Bragg grating and Fabry-Perot structure in the distributed fiber optic monitoring device for battery pack temperature and strain in the embodiment shown.

[0013] Figure 4 This is a schematic diagram of the fiber Bragg grating and Fabry-Perot structure in a sensing fiber for monitoring state, according to one embodiment of this application.

[0014] in, Figures 1 to 4 The correspondence between the reference numerals and component names in the attached drawings is as follows:

[0015] 1. Distributed optical fiber monitoring device for battery pack temperature and strain; 2. Battery pack; 100. Battery cell; 200. Sensing optical fiber; 210. Fiber Bragg grating; 211. PDMS sensitizing layer; 220. Fabry-Perot structure; 221. Epoxy resin layer; 222. Metal reflection enhancement layer; 230. Single-mode optical fiber; 300. Fixing device; 310. Fixing plate; 311. Linear groove; 312. Thermally conductive silicone grease layer; 320. Spring pressure plate; 321. Screw; 330. Anchor block; 400. Broadband light source; 500. Spectrometer. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0018] The following reference Figures 1 to 4 This application describes a distributed optical fiber monitoring device for battery pack temperature and strain, and a battery pack, according to some embodiments thereof.

[0019] According to the first aspect of this application, Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, one embodiment of this application provides a distributed optical fiber monitoring device 1 for battery pack temperature and strain, comprising: a fixing device 300 for mounting on a plurality of battery cells 100 arranged in a straight line; and a sensing optical fiber 200 fixed to the sidewall of each battery cell 100 by the fixing device 300, passing sequentially through the gap between adjacent battery cells 100 in an S-shaped path; the fixing device 300 includes: a fixing plate 310 for fitting and fixing to the sidewall of the battery cell 100, the surface of the fixing plate 310 having a straight groove 311 for accommodating the sensing optical fiber 200; and a spring pressure plate 320, the two ends of which are respectively secured by screws 321. Fixed to the fixing plate 310, the middle part of the spring pressure plate 320 spans across the straight groove 311 and presses against the surface of the sensing fiber 200; the anchor block 330 is set at both ends of the sensing fiber 200, and the ends of the sensing fiber 200 are cured in the anchor block 330 by adhesive; the sensing fiber 200 has a fiber Bragg grating 210 and a Fabry-Perot structure 220 connected in series on the side wall of each battery cell 100, the fiber Bragg grating 210 is used to measure temperature, and the Fabry-Perot structure 220 is used to measure strain; one end of the sensing fiber 200 is used to connect to the broadband light source 400, and the other end is used to connect to the spectrometer 500.

[0020] Specifically, such as Figure 1 , Figure 2 and Figure 3 As shown, the distributed optical fiber monitoring device 1 for battery pack temperature and strain provided in the embodiments of this application includes a fixing device 300 and a sensing optical fiber 200. The fixing device 300 is disposed on a plurality of battery cells 100 arranged in a straight line. The sensing optical fiber 200 is fixed to the sidewall of each battery cell 100 by the fixing device 300 and passes through the gap between adjacent battery cells 100 in an S-shaped path. The fixing device 300 includes a fixing plate 310, a spring pressure plate 320, and an anchor block 330. The fixing plate 310 is used to adhere and fix to the side wall of the battery cell 100. The surface of the fixing plate 310 has a straight groove 311 for accommodating the sensing optical fiber 200. The two ends of the spring pressure plate 320 are respectively fixed to the fixing plate 310 by screws 321. The middle part of the spring pressure plate 320 spans over the straight groove 311 and presses against the surface of the sensing optical fiber 200. Anchor blocks 330 are disposed at both ends of the sensing optical fiber 200. The ends of the sensing optical fiber 200 are fixed in the anchor blocks 330 by adhesive. A fiber Bragg grating 210 and a Fabry-Perot structure 220 are connected in series on the side wall of each battery cell 100. The fiber Bragg grating 210 is used to measure temperature, and the Fabry-Perot structure 220 is used to measure strain. One end of the sensing optical fiber 200 is used to connect to the broadband light source 400, and the other end is used to connect to the spectrometer 500.

[0021] Thus, when the monitoring device is installed on the battery pack 2, the fixing plate 310 is attached to the side wall of each battery cell 100, and the straight groove 311 on its surface provides a precise positioning path for the sensing optical fiber 200; the two ends of the spring pressure plate 320 are fixed to the fixing plate 310 by screws 321, and the middle of the spring pressure plate 320 spans over the straight groove 311 and elastically presses the surface of the optical fiber, forming a stable positive pressure to ensure that the optical fiber does not shift or fall off under long-term vibration environment; the anchor block 330 is set at both ends of the sensing optical fiber 200, and the end of the optical fiber is fixed in the anchor block 330 by adhesive, providing initial preload for the optical fiber and preventing overall slippage. The sensing optical fiber 200 passes through the gap between adjacent battery cells 100 in an S-shaped path, and one optical fiber can cover all battery cells 100. Fiber Bragg gratings 210 and Fabry-Perot structures 220 are connected in series on the side wall of each battery cell 100, which are used to measure temperature and strain, respectively. When the light emitted by the broadband light source 400 enters the sensing fiber 200, the fiber Bragg grating 210 reflects narrowband light corresponding to temperature, and the Fabry-Perot structure 220 outputs an interference spectrum corresponding to strain. The spectrometer 500 receives and demodulates the above optical signals, thus realizing distributed online monitoring of the temperature and expansion strain of each cell in the battery pack 2. This monitoring device solves the problem of fiber optic cable loosening and falling off under vibration environment through the coordinated cooperation of the fixing plate 310, spring pressure plate 320 and anchor block 330; the S-shaped single-fiber series layout realizes multi-point distributed measurement of single fiber, which greatly simplifies the system structure; and the series connection of the fiber Bragg grating 210 and the Fabry-Perot structure 220 realizes the coordinated measurement of temperature and strain, avoiding cross-sensitive interference.

[0022] Compared with existing technologies, the distributed optical fiber monitoring device 1 for battery pack temperature and strain provided in this application has the following advantages: First, reliable fixation, vibration resistance, and anti-detachment. It adopts a fixing structure combining a fixing plate 310, a spring pressure plate 320, and an anchor block 330. The two ends of the spring pressure plate 320 are fixed to the fixing plate 310 by screws 321, while the middle elastically presses against the surface of the optical fiber. Combined with the adhesive curing of the anchor blocks 330 at both ends, a stable pre-tightening force and anti-loosening structure are formed, ensuring that the optical fiber does not shift or fall off under long-term vibration, effectively solving the problem of poor reliability in traditional adhesive or direct bonding methods. Second, distributed measurement, simplified system. A single sensing optical fiber 200 passes through the gaps between all battery cells 100 in an S-shaped path. An independent sensing unit is set on the side wall of each battery cell 100. Wavelength division multiplexing technology is used to achieve multi-point measurement on a single fiber, eliminating the need for multiple optical fibers or multi-channel demodulation equipment, significantly reducing system complexity and cost. Third, coordinated temperature and strain measurement, high accuracy. A fiber Bragg grating 210 and a Fabry-Perot structure 220 are sequentially connected in series on the sidewall of each battery cell 100, dedicated to measuring temperature and strain respectively. They are connected by a single-mode fiber 230 to avoid cross-sensitivity interference. Combined with a temperature compensation algorithm, temperature and strain signals can be accurately separated, achieving high-precision synchronous monitoring. Fourth, the structure is compact and easy to install. The fixing plate 310 is attached to the sidewall of the battery cell 100, and the spring pressure plate 320 is quickly fixed by screws 321. No complex encapsulation process is required. The overall structure is thin and lightweight, suitable for the confined space of the battery pack 2, and easy to install and operate, facilitating batch deployment and maintenance.

[0023] Specifically, current battery pack condition monitoring technologies mostly employ traditional electrical sensor solutions such as thermocouples for temperature measurement and resistance strain gauges for strain measurement, attaching the sensors to the surface of individual battery cells for data acquisition. While widely used, this approach has significant drawbacks. In the high-voltage, high-current operating environment of battery packs, electrical sensors are susceptible to electromagnetic interference, resulting in poor measurement stability and distortion of temperature and strain data. Furthermore, each sensor requires an independent signal line, leading to complex wiring and difficulties in distributed monitoring of multiple cells. In addition, traditional sensors are bulky, making installation difficult in the limited space between batteries, and after prolonged use, vehicle vibrations can cause sensors to loosen or detach, leading to measurement failure. In recent years, fiber optic sensing technology, due to its advantages such as resistance to electromagnetic interference, small size, and the ability to be serially multiplexed, has been increasingly applied in the field of battery monitoring. However, existing fiber optic sensing solutions still suffer from the following technical shortcomings: First, the fixing methods for optical fibers in battery packs are relatively simple, often using adhesive bonding or direct adhesion, lacking reliable pre-tightening and anti-loosening structures. Under long-term vibration, these fibers are prone to detachment or displacement, leading to measurement failure. Second, existing solutions mostly use a single sensor, making it difficult to simultaneously achieve high-precision measurements of temperature and strain. Furthermore, there is a cross-sensitivity issue between temperature and strain, making it impossible to effectively separate the responses of the two physical quantities. Third, for battery packs composed of multiple cells, existing solutions typically require multiple optical fibers or multi-channel demodulation equipment, resulting in complex systems and high costs. Therefore, there is an urgent need for a battery pack monitoring device that can reliably fix optical fibers, perform coordinated temperature and strain measurements, and support single-fiber multi-point distributed monitoring to improve the stability, accuracy, and system integration of battery pack condition monitoring.

[0024] To address the shortcomings of existing technologies, such as Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, this application provides a distributed optical fiber monitoring device 1 for battery pack temperature and strain. Through the cooperation of a fixing device 300, an S-shaped single-fiber series layout, and an FBG / FP collaborative measurement mechanism, it achieves multiple functions including high-reliability optical fiber fixing, separate temperature and strain measurement, and distributed monitoring. Specifically, in the high-reliability optical fiber fixing scenario, the fixing device 300 adopts a combination structure of a fixing plate 310, a spring pressure plate 320, and an anchor block 330. The fixing plate 310 is attached to the side wall of the battery cell 100, and its surface has a straight groove 311 that accommodates the sensing optical fiber 200. The two ends of the spring pressure plate 320 are fixed to the fixing plate 310 by screws 321, with its middle portion spanning above the straight groove 311 and elastically pressing against the surface of the optical fiber to form a stable positive pressure. The anchor blocks 330 are disposed at both ends of the sensing optical fiber 200, and the ends of the optical fibers are cured in the anchor blocks 330 with adhesive, providing initial preload and preventing the optical fiber from slipping. This structure maintains the fiber optic cable's stability and prevents detachment under long-term vibration, while ensuring efficient transmission of battery expansion strain, effectively solving the reliability problems of traditional adhesive or direct bonding methods. In distributed measurement and system simplification scenarios, the sensing fiber 200 passes sequentially through the gaps between adjacent battery cells 100 in an S-shaped path, allowing a single fiber to cover all battery cells 100 in the battery pack 2. By setting fiber Bragg gratings 210 with different center wavelengths and Fabry-Perot structures 220 with different cavity lengths on the sidewall of each battery cell 100, combined with wavelength division multiplexing technology, single-fiber multi-point measurement is achieved, eliminating the need for multiple fibers or multi-channel demodulation equipment, significantly reducing system complexity and cost. In temperature and strain co-measurement scenarios, the sensing fiber 200 has fiber Bragg gratings 210 and Fabry-Perot structures 220 connected in series on the sidewall of each battery cell 100. The fiber Bragg grating 210 is used to measure temperature. Its outer surface is coated with a PDMS sensitizing layer 211, which amplifies the temperature response by utilizing the high thermal expansion coefficient of PDMS. The Fabry-Perot structure 220 is used to measure strain. Its outer surface is coated with a high elastic modulus epoxy resin layer 221 to ensure strain transfer efficiency. The fiber in this area adopts a reduced diameter design, and a silver film reflection enhancement layer is provided on a pair of reflective surfaces, which significantly improves the strain measurement sensitivity. Through the series layout of the two sensors and the temperature compensation algorithm, the interference of temperature on strain measurement is effectively separated, and accurate synchronous monitoring of temperature and strain is achieved. In the case of rapid thermal response, a thermally conductive silicone grease layer 312 with a thickness of 0.05mm~0.1mm and a thermal conductivity ≥3.0W / m·K is provided between the fixing plate 310 and the sensing fiber 200. This ensures that the battery heat is quickly transferred to the fiber Bragg grating 210 area without affecting strain transfer, significantly shortening the temperature response time.In summary, this application achieves integrated functions of high-reliability fiber optic fixing, separate temperature and strain measurement, and multi-point distributed monitoring of single fibers through the coordinated cooperation of the fixing device 300, S-shaped single-fiber series layout, and FBG / FP collaborative measurement mechanism. It effectively solves the problems of existing battery monitoring devices being susceptible to electromagnetic interference, having complex wiring, poor installation reliability, difficulty in simultaneously measuring temperature and strain, and high cost of distributed monitoring, thereby improving the stability, accuracy, and system integration of battery pack 2 status monitoring.

[0025] In some embodiments, optionally, such as Figure 1 and Figure 3 As shown, a thermally conductive silicone grease layer 312 is provided between the fixing plate 310 and the sensing optical fiber 200. The thickness of the thermally conductive silicone grease layer 312 is 0.05mm~0.1mm, and the thermal conductivity is ≥3.0W / m·K.

[0026] Specifically, such as Figure 1 and Figure 3 As shown, a thermally conductive silicone grease layer 312 is provided between the fixing plate 310 and the sensing optical fiber 200. The thickness of the thermally conductive silicone grease layer 312 is 0.05mm~0.1mm, and the thermal conductivity is ≥3.0W / m·K. The heat generated by the charging and discharging of the battery cell 100 is sequentially transferred through the fixing plate 310 and the thermally conductive silicone grease layer 312 to the sensing optical fiber 200, and then to the fiber Bragg grating 210 region. The thermally conductive silicone grease layer 312 has good thermal conductivity, which can significantly reduce contact thermal resistance and ensure that the temperature change of the battery sidewall is quickly and accurately sensed by the fiber Bragg grating 210, thereby shortening the temperature response lag time. At the same time, its thickness is controlled within the range of 0.05mm~0.1mm, which ensures sufficient thermal conductivity without affecting the strain transfer accuracy between the fixing plate 310 and the sensing optical fiber 200 due to excessive thickness. In this way, by setting up the thermally conductive silicone grease layer 312, the temperature measurement response speed is improved without affecting the strain measurement performance, thus achieving efficient compatibility between temperature and strain sensing functions.

[0027] In some embodiments, optionally, such as Figure 3 and Figure 4 As shown, the fiber Bragg grating 210 and the Fabry-Perot structure 220 are connected by a single-mode fiber 230, the length of which is 1mm to 5mm.

[0028] Specifically, such as Figure 3 and Figure 4As shown, the fiber Bragg grating 210 and the Fabry-Perot structure 220 are connected by a single-mode fiber 230, the length of which is 1mm to 5mm. The single-mode fiber 230 serves as a connecting segment, cascading the fiber Bragg grating 210 and the Fabry-Perot structure 220 onto the same sensing fiber 200, making them spatially adjacent but optically independent. When broadband light passes sequentially through the fiber Bragg grating 210 and the Fabry-Perot structure 220, it generates a narrowband reflection signal for temperature measurement and an interference signal for strain measurement, respectively. The length of the single-mode fiber 230 is controlled within the range of 1mm to 5mm. This ensures sufficient physical spacing between the two sensing units, avoiding signal crosstalk or spectral overlap, and also ensures that their temperature and strain fields are essentially consistent, thus providing a reliable physical basis for subsequent algorithmic separation of the effects of temperature and strain on their respective signals. In this way, by setting a suitable length of single-mode fiber 230 as the connection segment, the independence and clarity of temperature and strain signals are ensured, and conditions are created for the decoupling of the two parameters, thereby improving the measurement accuracy.

[0029] In some embodiments, optionally, such as Figure 1 and Figure 3 As shown, the outer surface of the fiber Bragg grating 210 is covered with a PDMS sensitizing layer 211, and the thermal expansion coefficient of the PDMS sensitizing layer 211 is ≥300×10⁻⁶. -6 K -1 .

[0030] Specifically, such as Figure 1 and Figure 3 As shown, the outer surface of the fiber Bragg grating 210 is covered with a PDMS sensitizing layer 211, which has a thermal expansion coefficient ≥300×10⁻⁶. -6 K -1 Because polydimethylsiloxane polymer has a much higher coefficient of thermal expansion than optical fiber, when the temperature of the battery cell 100 changes, the PDMS sensitizing layer 211 undergoes significant thermal expansion or contraction. This volume change directly stretches or releases the fiber Bragg grating 210, causing significant changes in the grating's period and effective refractive index, resulting in a significant shift in the reflection center wavelength. By encapsulating the fiber Bragg grating 210 in the high-expansion-coefficient PDMS material, the temperature response is mechanically amplified, transforming the originally temperature-insensitive fiber Bragg grating 210 into a highly sensitive temperature sensing unit. In this way, the PDMS sensitizing layer 211 effectively improves the temperature response sensitivity of the fiber Bragg grating 210, ensuring accurate capture of even minute temperature changes. Simultaneously, its encapsulation on the outer surface of the grating does not affect the independent strain measurement of the adjacent Fabry-Perot structure 220, achieving synergistic optimization of temperature and strain sensing performance.

[0031] In some embodiments, optionally, such as Figure 1 and Figure 3 As shown, the outer surface of the Fabry-Perot structure 220 is covered with an epoxy resin layer 221, and the elastic modulus of the epoxy resin layer 221 is ≥2 GPa.

[0032] Specifically, such as Figure 1 and Figure 3 As shown, the outer surface of the Fabry-Perot structure 220 is covered with an epoxy resin layer 221, which has an elastic modulus ≥ 2 GPa. The epoxy resin layer 221 has a high elastic modulus, enabling it to efficiently transfer the strain generated by the expansion of the battery cell 100 to the Fabry-Perot structure 220 region. When the battery cell 100 expands and deforms, the fixing plate 310 protrudes outward along the battery sidewall, the spring pressure plate 320 is lifted, and the sensing fiber 200 is stretched axially. The high elastic modulus epoxy resin layer 221 transfers the tensile stress to the Fabry-Perot structure 220 with almost no loss, causing a corresponding change in the cavity length of the Fabry-Perot structure 220, thereby causing a characteristic wavelength shift in the interference spectrum. In this way, by coating with a high elastic modulus epoxy resin layer 221, the efficient and faithful transmission of strain from the battery sidewall to the Fabry-Perot structure 220 is ensured, which significantly improves the sensitivity and accuracy of strain measurement. At the same time, the epoxy resin layer 221 also protects the Fabry-Perot structure 220 from external mechanical damage.

[0033] In some embodiments, optionally, such as Figure 1 and Figure 3 As shown, the sensing fiber 200 in the region where the Fabry-Perot structure 220 is located is a reduced-diameter fiber with a diameter ≤ 70 μm.

[0034] Specifically, such as Figure 1 and Figure 3As shown, the sensing fiber 200 in the region where the Fabry-Perot structure 220 is located is a reduced-diameter fiber with a diameter ≤70μm. The diameter of a conventional single-mode fiber 230 is typically 125μm. By using processes such as hydrofluoric acid etching or femtosecond laser-assisted tapering, the fiber diameter in the region of the Fabry-Perot structure 220 is reduced to below 70μm, significantly reducing the cross-sectional area of ​​the fiber in this region. According to the principles of materials mechanics, under the same axial tensile force, the smaller the cross-sectional area, the greater the stress generated inside the fiber, resulting in a larger change in the cavity length of the Fabry-Perot structure 220 and a higher sensitivity to strain response. In this way, by processing the optical fiber in the region where the Fabry-Perot structure 220 is located into a reduced-diameter optical fiber, the strain measurement sensitivity of the Fabry-Perot structure 220 is significantly improved without changing other structural parameters. This allows even the minute expansion and deformation of the battery cell 100 to be accurately captured. At the same time, the reduced-diameter region is limited to the location of the Fabry-Perot structure 220 and does not affect the mechanical strength and optical transmission performance of other parts of the sensing optical fiber 200.

[0035] In some embodiments, optionally, such as Figure 1 and Figure 4 As shown, a metal reflection enhancement layer 222 is provided on a pair of reflective surfaces along the axial direction of the Fabry-Perot structure 220. The metal reflection enhancement layer 222 is a silver film.

[0036] Specifically, such as Figure 1 and Figure 4 As shown, a metallic reflection enhancement layer 222, which is a silver film, is provided on a pair of reflective surfaces along the axial direction of the Fabry-Perot structure 220. The working principle of the Fabry-Perot structure 220 is based on multi-beam interference between the two reflective surfaces. The reflectivity of the reflective surfaces directly affects the intensity and contrast of the interference signal. The reflectivity of a conventional fiber end face is only about 4%, resulting in a very weak interference signal. By using processes such as vacuum evaporation or magnetron sputtering, a silver film is deposited on the pair of reflective surfaces. The silver film has a reflectivity of over 90% in the visible and near-infrared bands, which can efficiently reflect the incident light back into the Fabry-Perot cavity, significantly enhancing the multi-beam interference effect and greatly improving the fringe contrast and signal-to-noise ratio of the output interference spectrum. At the same time, as a metallic reflective layer, the silver film has good chemical stability and adhesion, and can maintain high reflectivity for a long time. In this way, by setting a silver film as a metal reflection enhancement layer 222 on a pair of reflective surfaces, the interference signal intensity and demodulation accuracy of the Fabry-Perot structure 220 are effectively improved, enabling the demodulator to more stably and accurately identify the minute drift of the interference fringes, thereby improving the resolution, signal-to-noise ratio and long-term stability of strain measurement.

[0037] In some embodiments, optionally, such as Figure 1 and Figure 2As shown, the spring pressure plate 320 is made of stainless steel with a thickness of 0.1mm~0.3mm.

[0038] Specifically, such as Figure 1 and Figure 2 As shown, the spring clamp 320 is made of stainless steel with a thickness of 0.1mm to 0.3mm. Stainless steel has excellent elasticity, corrosion resistance, and mechanical strength, maintaining stable elastic recovery force during long-term use and is not prone to plastic deformation or fatigue fracture. The two ends of the spring clamp 320 are fixed to the fixing plate 310 by screws 321, and the middle part spans over the straight groove 311 and presses against the surface of the sensing optical fiber 200. Its elastic clamping force mainly depends on the material and thickness. By controlling the thickness of the spring clamp 320 within the range of 0.1mm to 0.3mm, sufficient elastic clamping force is ensured, allowing the sensing optical fiber 200 to maintain close contact with the thermally conductive silicone grease layer 312 at the bottom of the fixing plate 310 and the battery sidewall, ensuring effective transmission of temperature and strain signals, while preventing damage to the optical fiber or affecting its optical performance due to excessive pressure. Simultaneously, the stainless steel material is resistant to electrolyte corrosion and high-temperature aging, making it suitable for the complex working environment of the battery pack 2. In this way, by using stainless steel and setting an appropriate thickness, the spring plate 320 can maintain stable and reliable elastic clamping performance under long-term vibration and temperature cycling conditions, effectively solving the problem of fiber optic loosening and falling off, and extending the service life of the device.

[0039] According to the second aspect of this application, such as Figure 1 As shown, a battery pack 2 is also proposed, comprising: a plurality of battery cells 100 arranged in a straight line; and a distributed optical fiber monitoring device 1 for battery pack temperature and strain as described in the above embodiment, wherein a fixing device 300 is disposed on the battery cells 100.

[0040] Specifically, such as Figure 1 As shown, the battery pack 2 proposed in the second aspect of this application includes multiple battery cells 100 arranged in a straight line and a distributed optical fiber monitoring device 1 for battery pack temperature and strain. The monitoring device is fixed to each battery cell 100 by a fixing device 300. Specifically, a fixing plate 310 is attached to the side wall of the battery cell 100, a spring pressure plate 320 is fixed to the fixing plate 310 by screws 321 and presses against the sensing optical fiber 200, and anchor blocks 330 are disposed at both ends of the sensing optical fiber 200 and fixed within the anchor blocks 330. The sensing optical fiber 200 is fixed to the side wall of each battery cell 100 by the fixing device 300 and passes through the gaps between adjacent battery cells 100 in an S-shaped path. In this way, the monitoring device and multiple battery cells 100 are integrated into a whole, forming a complete functional unit that can be directly applied to new energy vehicles or energy storage systems to achieve distributed online monitoring of the temperature and expansion strain of each cell in the battery pack 2.

[0041] The battery pack 2 provided in this application includes the battery pack temperature and strain distributed optical fiber monitoring device 1 of the above embodiment, and therefore has all the beneficial effects of the battery pack temperature and strain distributed optical fiber monitoring device 1, which will not be repeated here.

[0042] In some embodiments, optionally, such as Figure 1 As shown, there are six battery cells 100, and the center wavelengths of the fiber Bragg gratings 210 corresponding to the six battery cells 100 are 1540.00nm, 1545.00nm, 1550.00nm, 1555.00nm, 1560.00nm, and 1565.00nm, respectively; the cavity lengths of the Fabry-Perot structures 220 corresponding to the six battery cells 100 are 50μm, 55μm, 60μm, 65μm, 70μm, and 75μm, respectively.

[0043] Specifically, such as Figure 1 As shown, there are six battery cells 100. The center wavelengths of the fiber Bragg gratings 210 corresponding to the six battery cells 100 are 1540.00nm, 1545.00nm, 1550.00nm, 1555.00nm, 1560.00nm, and 1565.00nm, respectively. The cavity lengths of the Fabry-Perot structures 220 corresponding to the six battery cells 100 are 50μm, 55μm, 60μm, 65μm, 70μm, and 75μm, respectively. By assigning different center wavelengths of the fiber Bragg gratings 210 and different cavity lengths of the Fabry-Perot structures 220 to different battery cells 100, the sensing signal corresponding to each battery cell 100 has unique spectral characteristics. When light emitted from the broadband light source 400 is transmitted through the sensing fiber 200, fiber Bragg gratings 210 with different center wavelengths reflect narrowband light of different wavelengths, and Fabry-Perot structures 220 with different cavity lengths output interference spectra with different interference periods. The demodulation device can accurately identify which battery cell 100 the signal comes from based on the received wavelength and interference spectrum characteristics, thereby achieving a combination of wavelength division multiplexing and space division multiplexing. The center wavelength spacing of adjacent fiber Bragg gratings 210 is 5 nm, and the cavity length spacing of adjacent Fabry-Perot structures 220 is 5 μm. The channel spacing is sufficient to ensure that there is no overlap or crosstalk between the signal spectra. In this way, by setting a stepped increase in center wavelength and cavity length for the six battery cells 100, the single sensing fiber 200 can distinguish and locate the signals of the six battery cells 100. This allows the demodulation device to simultaneously and independently acquire the temperature and strain data of each battery cell 100, providing a reliable data foundation for the refined management and safety early warning of the battery pack 2.

[0044] In specific applications, there can be multiple battery cells 100. The center wavelength of the fiber Bragg grating 210 and the cavity length of the Fabry-Perot structure 220 corresponding to multiple battery cells 100 can also be multiple. This embodiment only takes six battery cells 100 as an example, but it is not limited to this. It can be selected according to the specific actual use, and will not be listed here.

[0045] In specific applications, such as Figure 1 As shown, this application provides a distributed optical fiber monitoring device 1 for battery pack temperature and strain, which is disposed on a plurality of battery cells 100 arranged in a straight line. A fixing device 300 is disposed on the side wall of each battery cell 100. A sensing optical fiber 200 is fixed to the side wall of each battery cell 100 by the fixing device 300, and passes through the gap between adjacent battery cells 100 in an S-shaped path. One end of the sensing optical fiber 200 is connected to a broadband light source 400 with a wavelength range of 1525nm~1565nm.

[0046] like Figure 2 As shown, the fixing device 300 includes a fixing plate 310, a spring pressure plate 320, and an anchor block 330. The fixing plate 310 is attached to the side wall of the battery cell 100 by thermally conductive adhesive or mechanical means, and its surface has a straight groove 311 for accommodating the sensing optical fiber 200. The two ends of the spring pressure plate 320 are respectively fixed to the fixing plate 310 by screws 321, and the middle part of the spring pressure plate 320 spans over the straight groove 311, elastically pressing the sensing optical fiber 200 into the groove. The spring pressure plate 320 is made of stainless steel with a thickness of 0.2mm, and has good elasticity and corrosion resistance.

[0047] Anchor blocks 330 are provided at both ends of the sensing optical fiber 200. After the end of the sensing optical fiber 200 passes through the anchor block 330, it is fixed by an adhesive such as epoxy resin to prevent the optical fiber from slipping and to maintain the initial preload.

[0048] like Figure 3 As shown, a thermally conductive silicone grease layer 312 with a thickness of 0.08 mm and a thermal conductivity of 6.0 W / m·K is provided between the fixing plate 310 and the coating layer of the sensing optical fiber 200. This layer is used to quickly transfer the battery heat to the sensing optical fiber 200 without affecting strain transmission. The sensing optical fiber 200 consists of a core, a cladding, and a coating layer from the inside out.

[0049] Specifically, the sensing fiber 200 is fabricated by segmented processing followed by fusion splicing, with the specific steps as follows:

[0050] First, the FBG segment is prepared. A section of single-mode fiber 230 is selected, and an FBG is etched in its middle to form a Bragg grating. Then, the FBG-etched area is immersed in PDMS prepolymer, degassed under vacuum, and cured in an 80℃ oven for 2 hours to form a PDMS sensitizing layer 211 with a thickness of approximately 0.3 mm. The coefficient of thermal expansion of the PDMS sensitizing layer 211 is 310 × 10⁻⁶. -6 K -1 This is used to amplify the temperature response sensitivity of the FBG. After curing, the fiber coating at both ends of the FBG segment is peeled off to expose the glass cladding for later use.

[0051] Next, the FP segment is fabricated. Another single-mode fiber 230 is selected, and a Fabry-Perot cavity is formed on the fiber using femtosecond laser micromachining technology. Specifically, two reflective surfaces are etched into the fiber core using a femtosecond laser; the distance between the two reflective surfaces is the FP cavity length. In this embodiment, Fabry-Perot structures 220 with cavity lengths of 50μm, 55μm, 60μm, 65μm, 70μm, and 75μm are fabricated according to the battery number. After fabrication, the fiber in the region containing the Fabry-Perot structure 220 is further processed into a reduced-diameter fiber. The fiber diameter is reduced to 70μm through hydrofluoric acid etching or femtosecond laser-assisted tapering to improve strain sensitivity. Subsequently, a silver film with a thickness of approximately 50nm is deposited on the reflective surface of the Fabry-Perot structure 220 using a vacuum evaporation process, serving as a metal reflection enhancement layer 222 to improve the interference signal intensity. Finally, an epoxy resin layer 221, specifically 353ND epoxy resin, is coated on the outer surface of the Fabry-Perot structure 220. After coating, it is placed in an oven at 100°C for 1 hour to cure. The elastic modulus after curing is 2.5 GPa.

[0052] Finally, the prepared FBG and FP segments are fused together using a fiber optic fusion splicer, with a 3mm long single-mode fiber 230 connecting them. The splice joint is protected with heat-shrink tubing to ensure mechanical strength.

[0053] like Figure 4 As shown, at the side wall position of each battery cell 100, a fiber Bragg grating 210 and a Fabry-Perot structure 220 are connected in series on the sensing fiber 200, and the fiber Bragg grating 210 and the Fabry-Perot structure 220 are connected by a single-mode fiber 230.

[0054] Specifically, to distinguish the sensing signals of different battery cells 100, the center wavelengths of the fiber Bragg gratings 210 corresponding to the six battery cells 100 are set to 1540.00nm, 1545.00nm, 1550.00nm, 1555.00nm, 1560.00nm, and 1565.00nm, respectively, with adjacent wavelengths spaced 5nm apart. The cavity lengths of the corresponding Fabry-Perot structures 220 are set to 50μm, 55μm, 60μm, 65μm, 70μm, and 75μm, respectively, with adjacent cavity lengths spaced 5μm apart.

[0055] Specifically, after the broadband light emitted by the broadband light source 400 enters the sensing fiber 200, each fiber Bragg grating 210 reflects narrowband light corresponding to its center wavelength. Each fiber Bragg grating 210 and the Fabry-Perot structure 220 generate an interference spectrum corresponding to its cavity length. The demodulation device, such as a spectrometer 500, simultaneously receives all reflected signals. By identifying different center wavelengths and interference spectral characteristics, the signals of each battery cell 100 can be distinguished, and temperature and strain changes can be calculated separately.

[0056] Specifically, when the battery cell 100 generates heat during charging and discharging, the heat is transferred to the sensing optical fiber 200 via the thermally conductive silicone grease layer 312, and then to the PDMS sensitization layer 211. The PDMS expands and stretches the fiber Bragg grating 210 due to heat, causing a significant shift in its center wavelength. After demodulation, a highly sensitive temperature value is obtained.

[0057] Specifically, when the battery cell 100 expands and deforms, the fixing plate 310 protrudes outward along the sidewall of the battery, the spring pressure plate 320 is lifted and drives the optical fiber to stretch axially, the cavity length of the Fabry-Perot structure 220 changes accordingly, the wavelength of the interference peak shifts, and the strain is obtained after demodulation. Since the fiber Bragg grating 210 and the Fabry-Perot structure 220 are connected in series in the same optical fiber and are located close to each other, the temperature compensation algorithm can effectively separate the interference of temperature on strain measurement, and realize accurate synchronous monitoring of temperature and strain.

[0058] In the description of this application, the term "multiple" refers to two or more. Unless otherwise expressly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0059] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A distributed optical fiber monitoring device for battery pack temperature and strain, characterized in that, include: A fixing device for mounting on multiple battery cells arranged in a straight line; The sensing optical fiber is fixed to the sidewall of each of the battery cells by the fixing device, and passes through the gap between adjacent battery cells in an S-shaped path. The fixing device includes: A fixing plate is used to fit and fix the battery cell to the side wall, and the surface of the fixing plate is provided with a straight groove to accommodate the sensing optical fiber. A spring pressure plate, the two ends of which are respectively fixed to the fixing plate by screws, and the middle part of the spring pressure plate spans over the straight groove and presses against the surface of the sensing optical fiber; Anchor blocks are disposed at both ends of the sensing optical fiber, and the ends of the sensing optical fiber are fixed in the anchor blocks by adhesive. The sensing fiber has a fiber Bragg grating and a Fabry-Perot structure connected in series on the sidewall of each battery cell. The fiber Bragg grating is used to measure temperature, and the Fabry-Perot structure is used to measure strain. One end of the sensing optical fiber is used to connect to a broadband light source, and the other end is used to connect to a spectrometer.

2. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, A thermally conductive silicone grease layer is provided between the fixing plate and the sensing optical fiber. The thickness of the thermally conductive silicone grease layer is 0.05mm~0.1mm, and the thermal conductivity is ≥3.0W / m·K.

3. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, The fiber Bragg grating is connected to the Fabry-Perot structure via a single-mode fiber with a length of 1mm to 5mm.

4. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, The fiber Bragg grating is coated with a PDMS sensitizing layer, and the coefficient of thermal expansion of the PDMS sensitizing layer is ≥300×10⁻⁶. -6 K -1 .

5. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, The outer surface of the Fabry-Perot structure is covered with an epoxy resin layer, the elastic modulus of which is ≥2 GPa.

6. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, The sensing fiber in the region where the Fabry-Perot structure is located is a reduced-diameter fiber with a diameter ≤70μm.

7. The distributed optical fiber monitoring device for battery pack temperature and strain according to claim 1, characterized in that, A metal reflection enhancement layer, which is a silver film, is provided on a pair of reflective surfaces along the axial direction of the Fabry-Perot structure.

8. The distributed optical fiber monitoring device for battery pack temperature and strain according to any one of claims 1 to 7, characterized in that, The spring pressure plate is made of stainless steel with a thickness of 0.1mm to 0.3mm.

9. A battery pack, characterized in that, include: Multiple battery cells arranged in a straight line; And the distributed optical fiber monitoring device for battery pack temperature and strain as described in any one of claims 1 to 8, wherein the fixing device is disposed on the battery cell.

10. The battery pack according to claim 9, characterized in that, The number of battery cells is six, and the center wavelengths of the fiber Bragg gratings corresponding to the six battery cells are 1540.00nm, 1545.00nm, 1550.00nm, 1555.00nm, 1560.00nm, and 1565.00nm, respectively; the cavity lengths of the Fabry-Perot structures corresponding to the six battery cells are 50μm, 55μm, 60μm, 65μm, 70μm, and 75μm, respectively.

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