Fiber bragg grating temperature sensing system and method for detecting temperature of lead-acid battery electrolyte

Abstract

The invention relates to a fiber bragg grating sensing system for detecting the temperature of a lead-acid battery electrolyte and a method thereof, and belongs to the technical field of lead-acid battery monitoring. Comprising a fiber grating sensor; the fiber bragg grating sensor is connected with the SM130 fiber bragg grating demodulator through a single-mode fiber jumper wire with an FC interface, and the SM130 fiber bragg grating demodulator is connected with the computer; the fiber bragg grating sensor comprises a fiber core, a fiber bragg grating area and a cladding; the length of the fiber bragg grating area is 1-1.5 cm, the fiber bragg grating area is located in the cladding and prepared on the surface of the fiber core, and the center wavelength is 1550 + / -0.3 nm. And the central wavelength and temperature data of the fiber bragg grating are read and recorded in real time by accessing the SM130 fiber bragg grating demodulator. According to the technical scheme that the running temperature of the lead-acid battery is monitored by the implanted FBG sensor, the temperature change of the electrolyte in the lead-acid battery can be monitored in real time, and the FBG sensor is high in sensitivity and good in stability and can be implanted into the lead-acid battery to be used for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of lead-acid battery monitoring, and in particular relates to a fiber grating sensing system and a method thereof for detecting the temperature of an electrolyte of a lead-acid battery. Background Art

[0002] Lead-acid batteries have the advantages of high energy density, long cycle life, low self-discharge rate, high safety, and no memory effect. They are widely used in electronic products, transportation, aerospace, energy storage and other fields, and are one of the energy storage technologies for sustainable development. However, in practical applications, especially in energy storage power stations, thermal runaway is very easy to occur. Energy storage power stations have a wide variety of batteries with a large number of them. Once thermal runaway occurs, it may evolve into a major safety accident of combustion and explosion. Safety issues have gradually become the primary issue for large-scale application of lead-acid battery energy storage.

[0003] The thermal runaway problem of lead-acid batteries has always been a major technical challenge. At present, in order to monitor the operating parameters of the battery and estimate its health state, the battery management system (BMS) is the most commonly used technology. BMS relies on the monitoring of external parameters such as voltage, current and external temperature. However, regardless of the acquisition rate used by the surface temperature sensor, the temperature sensor may not reflect the rapid fluctuation of the internal temperature due to the time required for thermal conduction of the battery, and this method cannot meet the requirements of early and accurate measurement of the internal temperature of the battery. Temperature is the most important part and monitoring indicator in the battery management system, so it is necessary to be able to monitor the internal temperature of the lead-acid battery in real time and accurately. In recent years, fiber Bragg grating (FBG) sensors have been proposed as an alternative monitoring method to achieve large-capacity, high-temperature, long-distance and high-reliability sensing. As an efficient monitoring method, FBG can monitor multiple parameters such as temperature, strain, and pressure in real time during the operation of lead-acid batteries. Summary of the invention

[0004] The present invention aims at the problems existing in the traditional BMS technology and provides an optical fiber sensing system which can monitor the internal temperature state of a lead-acid battery online during operation.

[0005] The present invention provides a fiber Bragg grating temperature sensing system, comprising a fiber Bragg grating sensor; the fiber Bragg grating sensor is connected to a fiber Bragg grating demodulator via a single-mode optical fiber jumper with an FC interface, and the fiber Bragg grating demodulator is connected to a computer;

[0006] The fiber grating sensor comprises a core, a fiber grating region and a cladding; the fiber grating region is located in the middle section between the core and the cladding, and the length of the fiber grating region is 1 to 1.5 cm; the fiber grating region is located inside the cladding, prepared on the surface of the core, and has a central wavelength of 1550±0.3 nm.

[0007] Furthermore, the fiber grating region is engraved with a grating on the surface of the fiber core by a femtosecond laser through a phase mask; the sum of the energies of the ±1st order diffraction beams in the phase mask accounts for 68.2% of the total energy, and the 0th order light energy accounts for only 3.8% of the total energy; the gratings are periodically arranged in the fiber grating region.

[0008] Furthermore, the preparation of the fiber grating sensor includes the following steps:

[0009] Step 1: The laser resonant cavity of the femtosecond laser is pumped by a solid laser with an output wavelength of 532nm, a power of 5W, and a temperature of 22°C; after the seed laser of the femtosecond laser is output through the titanium sapphire oscillator, it is mode-selected and mode-locked by the mode controller, and then enters the regenerative amplifier for optical amplification to output the femtosecond laser; the current of the regenerative amplifier pump is 18A to 22A.

[0010] Step 2: After the femtosecond laser is output, the light path is first collimated by two pinhole apertures and then enters the grating writing system;

[0011] Step 3: Use a cylindrical lens with a focal length of 60mm to write the grating; the period of the phase mask is 3200nm, the incident wavelength is 800nm, and periodic grating fringes can be formed in the overlapping area of ​​the ±1st order diffraction light behind the phase mask.

[0012] Furthermore, the fiber Bragg grating demodulator demodulates the temperature T in real time:

[0013] T=(FBG_A1-λ0)*1000 / 10+T0

[0014] Where FBG_A1 is the real-time center wavelength of the fiber grating region; λ0 is the initial center wavelength of the fiber grating region; T0 is the initial ambient temperature.

[0015] The present invention further provides an application of a fiber grating sensor system, wherein the fiber grating sensor system is applied to detect the temperature of electrolyte in a lead-acid battery; the test temperature of the fiber grating sensor is 10-70°C.

[0016] The present invention further provides an application method of a fiber grating sensing system, comprising the following steps:

[0017] Step 1: Connect the thermocouple to the computer, start the control program, and fix the temperature sensing element of the thermocouple on the surface of the lead-acid battery;

[0018] Step 2: Connect the fiber Bragg grating sensor to the fiber Bragg grating demodulator and start the operation; implant the fiber Bragg grating sensor into the lead-acid battery from the injection port, and the electrolyte completely immerses the fiber Bragg grating area on the fiber Bragg grating sensor;

[0019] Step 3: Connect the lead-acid battery to the charger and discharger, and record the surface temperature changes and internal temperature changes of the lead-acid battery during the charging and discharging process.

[0020] Furthermore, during the charge and discharge process of the lead-acid battery, the lead-acid battery electrodes undergo redox reactions, causing the electrolyte temperature to change; due to the heat conduction effect, the battery surface temperature will also change. The fiber grating demodulator and thermocouple can monitor the temperature changes of the lead-acid battery in real time through computer data acquisition.

[0021] Furthermore, when the lead-acid battery is discharged, dilute sulfuric acid reacts with the active substances on the cathode and anode plates to generate a new compound, lead sulfate; when the lead-acid battery is charged, the lead sulfate generated on the anode and cathode plates will decompose and reduce into sulfuric acid, lead and lead peroxide, and the concentration of the sulfuric acid solution will increase; the heat generated by the redox reaction during the charge and discharge of the lead-acid battery causes the electrolyte temperature to rise, and the thermo-optical effect causes the grating period and the core refractive index to change, and the temperature detected by the fiber grating sensor tends to gradually increase.

[0022] Furthermore, the fiber grating sensing system can monitor the temperature change of the lead-acid battery electrolyte in real time; when the monitored temperature value exceeds a preset temperature threshold, it can be determined that the battery is in a thermal runaway state.

[0023] The beneficial effects of the present invention are:

[0024] 1. The fiber grating sensing system of the present invention can be implanted inside a lead-acid battery without damaging the battery, and realizes online detection of the electrolyte temperature of the lead-acid battery. Due to the complex chemical environment inside the lead-acid battery, implanting metal devices such as thermocouples may cause significant damage to the battery. Compared with traditional sensors, fiber grating sensors have the advantages of anti-electromagnetic interference, electrical insulation, corrosion resistance, high sensitivity, fast response time, small size, low cost, etc., and can operate stably for a long time in the internal environment of the lead-acid battery.

[0025] 2. Compared with the fiber temperature sensor made by special fiber fusion splicing, the fiber Bragg grating sensor of the present invention has more quantifiable indicators in the manufacturing process, and its demodulation process is relatively simple. This feature makes the fiber Bragg grating sensor show unique advantages in related academic research and practical applications, and provides a more ideal solution for high-precision and convenient temperature measurement. Its quantifiable manufacturing indicators are conducive to standardized production and quality control, and the simple demodulation process reduces the difficulty of data acquisition and analysis, which is of great significance in the research scope of temperature sensing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of a fiber Bragg grating sensor for detecting the temperature of electrolyte in a lead-acid battery;

[0027] Figure 2 It is a schematic diagram of a fiber Bragg grating sensing system for detecting the electrolyte temperature of a lead-acid battery;

[0028] Figure 3 is the linear response of fiber Bragg grating temperature;

[0029] Figure 4 It is the change in fiber Bragg grating wavelength recorded by the fiber Bragg grating demodulator during the charging process of the lead-acid battery;

[0030] Figure 5 It is the comparison between the internal temperature of the lead-acid battery detected by the fiber grating and the external temperature of the lead-acid battery detected by the thermocouple during the charging process of the lead-acid battery. Figure 5 a The temperature variation curve of fiber grating and thermocouple during the charge and discharge process of lead-acid battery. Figure 5 b Difference gradient diagram of the temperature change of fiber Bragg grating and thermocouple during the charge and discharge process of lead-acid battery.

[0031] Description of Reference Numerals

[0032] In the figure: 1. Fiber core, 2. Fiber Bragg grating region, 3. Cladding, 4. SM130 Fiber Bragg grating demodulator, 5. Computer, 6. Fiber Bragg grating sensor, 7. Thermocouple, 8. Lead-acid battery, 9. Charger and discharger. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings.

[0034] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art, unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0035] The present invention provides a fiber grating sensing system for online detection of the electrolyte temperature of a lead-acid battery, comprising an SM130 fiber grating demodulator 4, a computer 5, a fiber grating sensor, a lead-acid battery 8, and a charger and discharger 9; the fiber grating sensor is connected to the SM130 fiber grating demodulator 4 through a single-mode optical fiber jumper with an FC interface, and the SM130 fiber grating demodulator 4 is connected to the computer 5; and a thermocouple 7 is also included, one end of the thermocouple 7 is connected to the computer 5, and a temperature sensing element of the thermocouple 7 is fixed on the surface of the lead-acid battery.

[0036] The fiber grating sensor comprises a core 1, a fiber grating region 2, and a cladding 3; the fiber grating region 2 is located in the middle area between the core 1 and the cladding 3, and the axial length of the fiber grating region 2 is 1 to 1.5 cm; the fiber grating region 2 is located inside the cladding 3 and is prepared on the surface of the core 1, and the central wavelength of the fiber grating region 2 is 1550±0.3 nm.

[0037] The fiber grating sensor is prepared by SMF-28e single-mode optical fiber, written by femtosecond laser method, and phase mask plate method; 800nm ​​infrared femtosecond laser is passed through the center of the cylindrical lens, and the light intensity is adjusted by Glan prism and half-wave plate combination; the focused light spot enters the center of the small hole and the center of the phase mask plate, and the position of the cylindrical lens and the optical fiber is precisely adjusted to form uniform grating fringes on the optical fiber core; specifically, the following steps are included:

[0038] Step S1, the laser resonator of the femtosecond laser used is pumped by a solid laser with an output wavelength of 532nm. The power is locked at 5W during normal operation and the temperature is set at 22°C. After the seed laser of the femtosecond laser is output through the titanium sapphire oscillator, it is mode-selected and mode-locked by the mode controller, and then enters the regenerative amplifier for optical amplification to output the femtosecond laser. The regenerative amplifier is pumped by an Evolution 30 laser, and the pump current is set between 18A and 22A;

[0039] Step S2, after the femtosecond laser is output, it is first collimated by two pinhole apertures and then enters the grating writing system. The core part of the grating writing system is mainly composed of a plano-convex cylindrical lens, a third-order phase mask and a pair of high-precision optical fiber adjustment frames;

[0040] Step S3, a cylindrical lens with a focal length of 60 mm is selected to write the grating; the period of the phase mask is 3200 nm, the incident wavelength is set to 800 nm, and periodic grating fringes can be formed in the overlapping area of ​​the ±1st order diffraction light behind the phase mask; the optical fiber adjustment frame has a built-in optical fiber V-groove, the optical fiber sample can be clamped and fixed in the V-groove, and the optical fiber can be precisely adjusted;

[0041] Step S4, use a fiber optic cutter to cut one end of the single-mode optical fiber with the fiber grating area inscribed, and fusion-splice it with a single-mode optical fiber jumper with an FC interface through a commercial fusion splicer, and connect the jumper to channel 1 of the SM130 fiber grating demodulator; the other end is a free end, and the excess pigtail can be cut.

[0042] The SM130 fiber Bragg grating demodulator 4 is used to connect the fiber Bragg grating sensor, and the demodulation formula of the SM130 fiber Bragg grating demodulator 4 can be used to demodulate the central wavelength change of the fiber Bragg grating area 2 of the fiber Bragg grating sensor into the temperature change of the electrolyte of the lead-acid battery 8. The temperature demodulation formula of the SM130 fiber Bragg grating demodulator 4 is:

[0043] T=(FBG_A1-λ0)*1000 / 10+T0

[0044] Where FBG_A1 is the real-time center wavelength of the fiber Bragg grating region; λ0 is the initial center wavelength of the fiber Bragg grating region; T and T0 are the real-time demodulation temperature and the initial ambient temperature, respectively.

[0045] Thermocouple 7 is used to detect the surface temperature of lead-acid battery 8. The temperature is monitored by sticking thermocouple on the surface of the battery. Regardless of the acquisition rate of the surface temperature sensor, due to the polarization and heat conduction of the battery, monitoring the temperature change by sticking thermocouple on the surface of the battery cannot meet the requirements of early accurate measurement of the internal temperature of the battery. Implanting optical fiber sensor inside the battery is of great significance for real-time online monitoring of the functional state of the battery. The effective combination of monitoring the outer surface temperature of the lead-acid battery with thermocouple and the internal temperature with fiber grating sensor can show that there is a difference between the surface temperature and the internal temperature during the operation of the battery, and the internal temperature can better reflect the working state of the battery than the external temperature. Monitoring the internal temperature can detect abnormal temperature changes earlier and take necessary measures in time, while the increase in external temperature may indicate that serious faults have occurred inside the battery. The computer is used to run the SM130 fiber grating demodulator 4 control program and the thermocouple control program to complete the collection and recording of internal and external temperature data during the operation of the lead-acid battery 8 and perform preliminary analysis of the temperature information. The charger 9 is used to charge and discharge the lead-acid battery 8.

[0046] A method for detecting the temperature of a lead-acid battery electrolyte using a fiber grating sensing system comprises the following steps:

[0047] Step S1, connect the thermocouple 7 to the computer 5, start the control program, fix the temperature sensing element on the battery surface, and record the surface temperature change of the lead-acid battery 8 during the charging and discharging process; the temperature sensing module of the thermocouple 7 is a metal component, so it cannot be placed in the electrolyte of the lead-acid battery 8.

[0048] Step S2, connect the fiber grating sensor to the SM130 fiber grating demodulator 4, and run the control program. The fiber grating sensor is implanted into the lead-acid battery 8 from the injection port, and the electrolyte completely immerses the fiber grating area 2. The fiber grating area 2 is placed in an unfixed manner, eliminating the strain crosstalk caused by external force fixation.

[0049] Step S3, connect the lead-acid battery 8 to the charger and discharger 9, and start the charger and discharger 9 to perform a charge and discharge cycle on the battery.

[0050] The electrolyte of the lead-acid battery 8 is dilute sulfuric acid. When the lead-acid battery 8 is charged, the current will convert electrical energy into chemical energy when passing through the battery, thereby causing the temperature inside the battery to rise. However, factors such as overcharging of the lead-acid battery 8 or battery aging will cause the chemical reaction inside the battery to get out of control, causing the battery to react abnormally, generating a large amount of heat energy, and causing the heating phenomenon to become more obvious. Due to the thermo-optical effect, the temperature change of the electrolyte of the lead-acid battery 8 affects the grating period and the effective refractive index of the fiber core, so the reason for the wavelength response is the influence of temperature.

[0051] When the lead-acid battery 8 is charged, the lead sulfate produced on the anode plate and the cathode plate will be decomposed and reduced into sulfuric acid, lead and lead peroxide, and the redox reaction will generate a lot of heat. When the lead-acid battery 8 is discharged, the dilute sulfuric acid will react with the active substances on the cathode and anode plates to generate the compound lead sulfate, and the internal chemical reaction will generate heat. Therefore, the temperature of the electrolyte in the lead-acid battery gradually increases, and the central wavelength of the fiber grating will produce a red shift.

[0052] During battery operation, no matter what factors induce thermal runaway, its external manifestation is that the peak temperature is significantly higher than that of normal operation. The design of implanting fiber grating sensors inside the battery can realize real-time monitoring of battery temperature changes. A temperature threshold can be set in the SM130 fiber grating demodulator 4. When the fiber grating sensing system detects that the temperature value exceeds the preset temperature threshold, it can be determined that the battery is in a thermal runaway state.

[0053] Embodiment 1:

[0054] Combination Figure 1 This embodiment is described. A fiber grating sensor for detecting the electrolyte temperature of a lead-acid battery includes a core 1, a fiber grating region 2, and a cladding 3. When the temperature of the external electrolyte changes, the fiber grating region 2 will change the grating period of the fiber grating sensor and the effective refractive index of the core accordingly due to the thermo-optical effect, resulting in a change in the central wavelength of the fiber grating. The fiber grating sensor pigtail is a single-mode optical fiber, the core 1 has a diameter of 9um, and the fiber grating region 2 is engraved into the core 1 with an axial length of 1cm. The main material of the core 1 is silicon dioxide, which has a stable structure, is resistant to strong acids and alkalis, and has a small size, and can be used for a long time in lead-acid batteries.

[0055] Embodiment 2:

[0056] Combination Figure 2The present embodiment is described. The present embodiment is a fiber optic sensing system for detecting the electrolyte temperature of a lead-acid battery. The fiber optic Bragg grating sensor for detecting the electrolyte temperature of a lead-acid battery is used. The fiber optic Bragg grating sensor for detecting the electrolyte temperature of a lead-acid battery comprises an SM130 fiber optic Bragg grating demodulator 4, a computer 5, a fiber optic Bragg grating sensor, a thermocouple 7, a lead-acid battery 8, and a charger and discharger 9. The SM130 fiber optic Bragg grating demodulator 4, the computer 5, the fiber optic Bragg grating sensor, the thermocouple 7, the lead-acid battery 8, and the charger and discharger 9 are connected in sequence. The computer 5 runs the thermocouple 7 and the SM130 fiber optic Bragg grating demodulator 4 control program to realize real-time display and collection of the external and internal temperature data of the lead-acid battery 8. One end of the fiber optic Bragg grating sensor is connected to the channel 1 of the SM130 fiber optic Bragg grating demodulator 4 through an FC single-mode optical fiber jumper. The fiber optic Bragg grating area 2 of the fiber optic Bragg grating sensor is implanted into the lead-acid battery 8 through the lead-acid battery injection port and is completely immersed in the electrolyte. The charger and discharger 9 is connected to and controls the charging and discharging of the lead-acid battery 8.

[0057] Embodiment 3:

[0058] Combination Figure 3 This embodiment is described. The temperature calibration test of the fiber Bragg grating sensor in this embodiment has a temperature test range of 10 to 70°C. The fiber Bragg grating center wavelength shows a uniform increase trend with increasing temperature, with high linearity and a sensitivity of 10pm / °C. The fiber Bragg grating temperature and center wavelength data in this embodiment are provided by the SM130 fiber Bragg grating demodulator 4.

[0059] Embodiment 4:

[0060] Combination Figure 4 The present embodiment is described as a method for detecting the temperature of the electrolyte of a lead-acid battery. The fiber Bragg grating sensor detects the temperature change during the charging of the lead-acid battery 8. During charging, the lead sulfate is oxidized to lead dioxide at the positive electrode and reduced to pure lead at the negative electrode. At the same time, the concentration of the sulfuric acid solution increases, and the heat generated by the oxidation-reduction reaction causes the electrolyte temperature to rise. Therefore, the temperature detected by the fiber Bragg grating sensor shows a trend of gradually increasing.

[0061] Embodiment 5:

[0062] Combination Figure 5 This embodiment is described. This embodiment is to compare the internal temperature of the lead-acid battery 8 detected by the fiber grating sensor with the external temperature of the lead-acid battery detected by the thermocouple 7 during the charging process of the lead-acid battery 8. During the charging process, it can be seen from the temperature curve and the temperature gradient diagram that the temperature difference between the inside and outside of the lead-acid battery 8 increases significantly with the increase of charging time, such as Figure 5a and 5b. This is due to the polarization and heat conduction of the battery. The method of monitoring the temperature change by sticking a thermocouple on the surface of the battery obviously cannot meet the requirements of early and accurate measurement of the internal temperature of the battery. The fiber grating sensor implanted in the electrolyte has high acquisition frequency, high stability and accuracy, so it is suitable for lead-acid battery temperature monitoring.

[0063] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A fiber Bragg grating temperature sensing system, characterized in that: The invention comprises a fiber grating sensor; the fiber grating sensor is connected to a fiber grating demodulator; the fiber grating sensor comprises a fiber core, a fiber grating region (2), and a cladding; the fiber grating region (2) is located in the middle section between the fiber core and the cladding, and the length of the fiber grating region (2) is 1 to 1.5 cm; the fiber grating region (2) is located inside the cladding, prepared on the surface of the fiber core, and has a central wavelength of 1550±0.3 nm.

2. The fiber Bragg grating temperature sensing system according to claim 1, characterized in that: The fiber grating region (2) is used to write gratings on the surface of the fiber core by a femtosecond laser through a phase mask; the gratings are periodically arranged in the fiber grating region (2).

3. The fiber Bragg grating temperature sensing system according to claim 2, characterized in that: The sum of the energies of ±1-order diffraction beams in the phase mask accounts for 68.2% of the total energy, and the energy of the 0-order light accounts for only 3.8% of the total energy.

4. The fiber Bragg grating temperature sensing system according to claim 2, characterized in that: The following steps are involved: Step 1: The laser resonant cavity of the femtosecond laser is pumped by a solid laser with an output wavelength of 532nm, a power of 5W, and a temperature of 22°C; after the seed laser of the femtosecond laser is output through the titanium sapphire oscillator, the mode controller performs mode selection and mode locking, and then enters the regenerative amplifier for optical amplification to output the femtosecond laser; the current of the regenerative amplifier pump is 18A to 22A; Step 2: After the femtosecond laser is output, the optical path is first collimated by two pinhole apertures and then enters the grating writing system; Step 3: Use a cylindrical lens with a focal length of 60mm to write the grating; the period of the phase mask is 3200nm, the incident wavelength is 800nm, and periodic grating fringes can be formed in the overlapping area of ​​the ±1st order diffraction light behind the phase mask.

5. The fiber Bragg grating temperature sensing system according to claim 1, characterized in that: The fiber Bragg grating demodulator real-time demodulates the temperature T: T=(FBG_A1-λ0)*1000 / 10+T0 Where FBG_A1 is the real-time center wavelength of the fiber grating region; λ0 is the initial center wavelength of the fiber grating region; T0 is the initial ambient temperature.

6. An application of the fiber Bragg grating temperature sensing system as claimed in claim 1, characterized in that: The fiber grating temperature sensing system is used to detect the electrolyte temperature of a lead-acid battery; the test temperature of the fiber grating sensor is 10-70°C.

7. The use of the fiber Bragg grating temperature sensing system according to claim 6, characterized in that: The following steps are involved: Step 1: Connect the thermocouple (7) to the computer (5), start the control program, and fix the temperature sensing element of the thermocouple (7) on the surface of the lead-acid battery (8); Step 2: Connect the fiber grating sensor to the fiber grating demodulator (4) and start operation; implant the fiber grating sensor into the lead-acid battery (8) from the injection port, and completely immerse the fiber grating area (2) on the fiber grating sensor in the electrolyte; Step 3: Connect the lead-acid battery (8) to the charger (9), and record the surface temperature change and internal temperature change of the lead-acid battery during the charging and discharging process.

8. The use of a fiber Bragg grating temperature sensing system according to claim 7, characterized in that: During the charge and discharge process of the lead-acid battery (8), an oxidation-reduction reaction occurs at the lead-acid battery electrodes, causing the electrolyte temperature to change; due to the heat conduction effect, the battery surface temperature also changes. The fiber grating demodulator (4) and the thermocouple (7) can monitor the temperature change of the lead-acid battery (8) in real time through data collection by the computer (5).

9. The use of a fiber Bragg grating temperature sensing system according to claim 8, characterized in that: When the lead-acid battery (8) is discharged, dilute sulfuric acid reacts with active substances on the cathode and anode plates to generate a new compound, lead sulfate; when the lead-acid battery (8) is charged, the lead sulfate generated on the anode and cathode plates is decomposed and reduced into sulfuric acid, lead and lead peroxide, and the concentration of the sulfuric acid solution increases at the same time; the heat generated by the redox reaction during the charge and discharge of the lead-acid battery causes the electrolyte temperature to rise, and the thermo-optical effect causes the grating period and the fiber core refractive index to change, and the temperature detected by the fiber grating sensor shows a trend of gradually increasing.

10. The use of a fiber Bragg grating temperature sensing system according to claim 7, characterized in that: The fiber grating temperature sensing system can monitor the temperature change of the lead-acid battery electrolyte in real time; when the monitored temperature value exceeds the preset temperature threshold, it can be determined that the battery is in a thermal runaway state.

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