Device and method for measuring internal temperature of secondary battery based on permanent magnet

Abstract

The invention discloses a device and a method for measuring the internal temperature of a secondary battery based on a permanent magnet, and relates to a secondary battery applied to the fields of power, energy storage, consumption and the like. The permanent magnet is arranged in the secondary battery, and the internal temperature of the battery is monitored in a magnetic field wireless transmission mode by utilizing the characteristic that the residual magnetism of the permanent magnet changes along with the temperature. The problem that the existing secondary battery internal temperature measurement technology needs to damage the structural integrity of the battery or influence the safety and performance of the battery is solved. The device is simple in structure, low in cost and compatible with an existing battery production process, the internal temperature of the battery can be monitored in real time, the temperature measurement range covers the working temperature range of the battery, and the thermal runaway risk exceeding the normal working temperature of the battery can be judged and early warned in time. The device can be integrated with a battery management system, effectively reduces the thermal runaway risk, and has a remarkable application prospect and industrialization potential.

Description

Technical Field

[0001] The present invention relates to secondary batteries used in the fields of power, energy storage and consumption, and in particular to a device and method for wirelessly monitoring the internal temperature of a secondary battery. Specifically, the present invention is a device and method for wirelessly transmitting a magnetic field to indicate the temperature based on placing a permanent magnet inside the secondary battery and utilizing the property that the residual magnetism of the permanent magnet changes with temperature. Background Art

[0002] With the rapid development of new energy technology, secondary batteries such as lithium-ion batteries have been widely used. At the same time, battery safety issues have attracted much attention. During the high-current charging and discharging process of the battery, irreversible changes will occur in the internal materials and structures, leading to battery aging and even thermal runaway. The direct cause of thermal runaway is that the internal temperature of the battery rises rapidly in a short period of time, triggering a chain of side reactions. Therefore, accurately monitoring the battery temperature, especially the internal temperature, has become an important means to improve battery safety.

[0003] At present, commercial battery temperature monitoring mainly relies on external temperature detection methods. Such methods usually install temperature sensors on the outside of the battery, such as thermistors, thermocouples, and infrared temperature measuring devices. For review literature (LH JRaijmakers, et al. A review on various temperature-indication methods for Li-ion batteries[J]. Applied Energy , 2019, 240: 918–945). However, this type of battery external detection method can only measure the temperature of the battery shell, but cannot reflect the temperature condition inside the battery. Under high current working conditions, the temperature difference between the inside and outside of the battery is significant. The external temperature measurement has a lag in response judgment and cannot reflect the changes in the working state of the battery in time, thereby increasing the risk of thermal runaway.

[0004] In order to solve this problem, researchers have proposed a variety of battery internal temperature measurement solutions, mainly including implantable temperature sensor technology. The existing battery internal temperature measurement methods mainly include:

[0005] 1. Obtain temperature information by implanting flexible thin film temperature sensors based on thermal resistors or thermocouples inside the battery, such as the research literature (Zhu SX, et al. A novel embedded method for in situmeasuring internal multi-point temperatures of lithium-ion batteries [J]. Journal of Power Sources, 2020, 456: 227981).

[0006] 2. Implant the optical fiber inside the battery and infer the temperature inside the battery by monitoring the physical phenomena such as reflection and scattering of light in the optical fiber as it changes with temperature. For example, the research literature (Huang JQ, et al. Operando decoding of chemical and thermal events in commercial Na(Li)-ion cells via optical sensors [J]. Nature Energy , 2020. 5: 674–683).

[0007] Although the above-mentioned implantable sensors can measure the internal temperature of the battery to a certain extent, they still have many shortcomings in practical applications. First, most of these sensors require modification of the battery structure, such as drilling holes or reserving wiring ports on the battery shell, which inevitably affects the packaging integrity of the battery and reduces the safety of the battery. Secondly, the production and installation process of the sensor is complicated and costly, which is not conducive to the widespread application of industry. Summary of the invention

[0008] The first purpose of the present invention is to propose a device for measuring the internal temperature of a secondary battery based on a permanent magnet, which is intended to solve the problem that when measuring the internal temperature of a secondary battery, a wire needs to be drawn out from the inside of the battery, thereby affecting the safety of the battery. By implanting a permanent magnet inside the battery and utilizing the characteristic that the residual magnetism of the permanent magnet changes with temperature, the disadvantages of traditional implantable sensors that require wires to be drawn out or the battery structure to be modified are avoided. The temperature measuring device has a simple structure, low cost, and is compatible with existing battery production processes without destroying the packaging integrity of the battery.

[0009] The second object of the present invention is to provide a method for measuring the internal temperature of a secondary battery based on a permanent magnet, which uses the physical quantity of the residual magnet temperature coefficient of the permanent magnet to characterize the change of the residual magnet of the permanent magnet with temperature, and monitors the temperature inside the battery in real time through the wireless transmission of the magnetic field. The method can monitor the internal temperature of the battery in real time and accurately, and can be integrated with the battery management system to help better monitor the battery status and effectively reduce the risk of thermal runaway. The method has significant prospects for industrial application and can provide strong protection for the safe operation of secondary batteries.

[0010] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions.

[0011] In a first aspect, the present invention provides a secondary battery internal temperature measurement device using the permanent magnet remanence changing with temperature, comprising the following permanent magnet, magnetic attraction structure, magnetic field detection element and processor;

[0012] The permanent magnet is selected to have a larger residual magnetism temperature coefficient; the residual magnetism of the permanent magnet changes reversibly with the change of temperature;

[0013] The magnetic attraction structure uses a material with high magnetic permeability and low coercivity to increase the magnetic field size and uniformity near the magnetic field detection element, so as to improve the signal-to-noise ratio and dynamic range of the magnetic field signal; the magnetic attraction structure is installed outside the battery housing, close to the magnetic field detection element, to ensure the effective transmission and enhancement of the magnetic field;

[0014] The magnetic field detection element is an element for detecting and sensing the magnitude of the magnetic field. The magnetic field detection element is fixed outside the battery and is used to measure the change of the magnetic field and convert the magnetic signal into a magnetic-electrical signal for subsequent processing;

[0015] The processor is electrically connected to the magnetic field detection element, and is used to obtain the magnetic induction intensity at the detection component according to the electrical signal, and calculate the temperature at the location of the permanent magnet according to the magnetic induction intensity;

[0016] The processor includes a signal acquisition unit and an operation processing unit; wherein the signal acquisition unit is used for real-time and regular acquisition and recording of magnetic field data; the operation processing unit is used for correcting magnetic signals and converting magnetic field data into temperature data.

[0017] Furthermore, the permanent magnet is made of materials with a large residual magnetic temperature coefficient, such as neodymium iron boron and ferrite. The shape of the permanent magnet is designed to be miniaturized, thin-sheet or cylindrical according to the internal structure of the battery, so that it is easy to embed into the battery without affecting the integrity of the battery structure, and is implanted inside the battery during the battery production process.

[0018] Furthermore, the material of the magnetic attraction structure is a material with high magnetic permeability and low coercive force such as soft iron or Permalloy to concentrate and amplify the magnetic field generated by the permanent magnet and make the magnetic field distribution in the detection area more uniform. The shape of the magnetic attraction structure is set according to the results of finite element simulation optimization, and there are two optimization goals: 1. The magnetic field in the detection area is large enough, and 2. The magnetic field in the detection area is uniform enough.

[0019] Furthermore, the magnetic field detection element adopts a Hall element or a magnetoresistive element to accurately measure the change of the magnetic field. The magnetic field detection element adopts a waterproof, dustproof, shockproof, high and low temperature resistant design to ensure long-term stable operation.

[0020] Furthermore, the signal acquisition unit adopts a high-precision ADC to realize real-time acquisition of magnetic field data; the operation processing unit integrates a temperature-magnetic field conversion algorithm, including a linear or nonlinear correction model based on the residual magnetism temperature coefficient of the permanent magnet, and a current interference rejection algorithm, to convert the magnetic field data into temperature data, and integrate it with the battery management system (BMS) of the battery pack through a standard communication protocol (such as CAN, SPI or I2C).

[0021] In a second aspect, the present invention further provides a method for measuring the internal temperature of a secondary battery using the change in the residual magnetism of a permanent magnet with temperature, comprising the following steps:

[0022] 1) Permanent magnet selection: select a permanent magnet, initialize it, and measure the remanence temperature coefficient of the permanent magnet;

[0023] 2) Battery integration and testing: Before the secondary battery cell is filled and sealed, the permanent magnet is placed in the proper position inside the battery, the cell is encapsulated, and the integrated secondary battery is obtained, and its performance and reliability are tested;

[0024] 3) Installation of the measurement system: Install the magnetic attraction structure and magnetic field detection element at the appropriate position outside the battery. The magnetic field detection element is close to the magnetic attraction structure to ensure the effective transmission and measurement of the magnetic field. Connect the magnetic field detection element to the processor to complete the installation of the measurement system.

[0025] 4) Temperature information conversion and processing: When the battery is charging and discharging, the processor receives the signal from the magnetic field detection element and converts it into temperature information.

[0026] Furthermore, in step 1), the permanent magnet is selected, initialized, and the residual magnetism temperature coefficient of the permanent magnet is measured. Specifically, the steps include:

[0027] 1.1) Based on the specific application scenario, select a permanent magnet with appropriate process, material and shape, such as NdFeB or ferrite permanent magnet;

[0028] 1.2) Place the permanent magnet in an environment slightly beyond the measurement temperature range and perform initialization processing on it to eliminate irreversible magnetic loss and ensure that the remanence of the permanent magnet is stable and highly consistent with temperature;

[0029] 1.3) Measure the remanence of the permanent magnet at multiple temperature points and calculate its remanence temperature coefficient, which is a key parameter for subsequent temperature calculations;

[0030] In step 2), the permanent magnet is placed in a battery and tested, and the specific steps may be:

[0031] 2.1) Before filling and sealing the secondary battery cell, place the permanent magnet in the proper position inside the battery to ensure that it does not affect the structural integrity and performance of the battery;

[0032] 2.2) Determine the optimal position of the permanent magnet inside the battery through simulation experiments to maximize the magnetic field strength and measurement accuracy; Complete the packaging of the battery cell to obtain an integrated secondary battery;

[0033] 2.3) Perform performance and reliability tests on the integrated secondary battery, including cycle charge and discharge tests, high temperature / low temperature storage tests, etc., to verify that the permanent magnet has no negative impact on the battery performance and ensure its normal and stable operation;

[0034] Furthermore, in step 3), after the installation of the measurement system is completed, debugging is performed, and the magnetic field background noise is measured and calibrated without battery current to improve the measurement accuracy.

[0035] Furthermore, in step 4), the processor receives the signal from the magnetic field detection element and converts it into temperature information, including:

[0036] 4.1) The magnetic field detection element is used to sense the magnetic field changes generated by the permanent magnet and convert the sensed magnetic field changes into corresponding electrical signals; the signal acquisition unit in the processor collects these electrical signals in real time and periodically, and uses its built-in working mechanism to convert the electrical signals into processable magnetic field information;

[0037] 4.2) During the battery charging and discharging process, the working current will generate a magnetic field around the battery. In addition to the magnetic field generated by the working current, there may also be stray magnetic fields in the device itself, which will also interfere with the temperature measurement results. In order to eliminate these interfering magnetic fields, the processor calculates the size and direction of the magnetic field generated by the working current based on the pre-established electromagnetic field physical model (such as Biot-Savart law, Faraday's law of electromagnetic induction, Maxwell equations), and uses signal processing technology (such as filtering, denoising, etc.) to identify and eliminate stray magnetic fields; at the same time, the processor works in coordination with the battery management system to obtain the current battery charging and discharging current information in real time, so as to more accurately calculate and eliminate the influence of the magnetic field generated by the working current;

[0038] 4.3) According to the remanence temperature coefficient and physical model of the permanent magnet, the magnetic field signal is converted into temperature information.

[0039] For an initialized permanent magnet, its remanence changes reversibly with temperature, and can be regarded as a linear change at the normal operating temperature of a secondary battery. This change relationship is described by the remanence temperature coefficient; the processor uses this coefficient and the physical model to convert the magnetic field signal into temperature information.

[0040] Alternatively, a method for measuring the internal temperature of a secondary battery using the change in the remanence of a permanent magnet with temperature further includes the following steps:

[0041] 5) Utilization of temperature information: Print or display temperature information for personnel to know; or transmit temperature information to the battery management system for further analysis to determine the battery working status.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The temperature measuring device provided by the present invention has a simple structure and low cost, is compatible with the existing battery production process, and measures temperature by placing a permanent magnet inside the battery and utilizing the property that the residual magnetism of the permanent magnet changes with temperature. It does not need to destroy the battery structure and does not affect the safety and performance of the battery.

[0044] 2. The temperature measurement method provided by the present invention realizes real-time monitoring of the internal temperature information of the secondary battery by means of wireless transmission of the magnetic field, and the temperature measurement range covers the operating temperature range of the secondary battery, and can make timely judgments and early warnings on the risk of thermal runaway that exceeds the normal operating temperature of the battery; within the normal operating temperature range of the battery, the magnetic field corresponds to the temperature inside the battery. Furthermore, if the battery thermally runs away, the internal temperature of the battery rises sharply in a short period of time, causing the magnetic field signal to suddenly drop. Such a rate of change of the magnetic field is more significant and sensitive than the traditional battery surface temperature measurement. Therefore, the present invention can make a more timely judgment on the risk of thermal runaway.

[0045] 3. The present invention provides a reliable and economical secondary battery internal temperature monitoring solution and thermal runaway judgment method, which can be integrated with the existing battery management system, and is expected to help better understand the battery working status, and has significant application prospects and industrialization potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic structural diagram of a secondary battery internal temperature measurement device based on a permanent magnet provided in an embodiment of the present invention.

[0047] Figure 2 The CT scan of a commercial 18650 battery after being placed in a cylindrical NdFeB permanent magnet provided by an embodiment of the present invention. The left image is a three-dimensional scan image, and the right image is a cross-sectional scan image along the battery axis.

[0048] Figure 3 The present invention provides a flow chart of a method for measuring the internal temperature of a secondary battery based on a permanent magnet.

[0049] Figure 4 A graph showing the relationship between the magnetic flux density at the magnetic field detection element and the internal temperature of the battery after a commercial 18650 battery is placed in a cylindrical NdFeB permanent magnet provided in an embodiment of the present invention. The horizontal axis represents the temperature inside the battery (unit: Celsius), and the vertical axis represents the magnetic flux density at the magnetic field detection element (unit: Gauss). DETAILED DESCRIPTION

[0050] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Note that the following contains many specific details in order to fully understand the present invention. However, the following are only preferred embodiments of the present invention. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that it is possible for those skilled in the art to make various significant changes, readjustments and alternative promotions to the device and method based on the specific embodiments without departing from the scope of protection of the present invention.

[0051] Figure 1 A schematic diagram of a temperature measuring device for measuring the internal temperature of a commercial 18650 battery provided by an embodiment of the present invention. Figure 1 The embodiment of the present invention provides a secondary battery internal temperature measurement device that utilizes the change of permanent magnet remanence with temperature, and its components include a permanent magnet 1, a magnetic attraction structure 2, a magnetic field detection element 3, a processor 4, and a display screen or a battery management system 5.

[0052] For example, the permanent magnet 1 is a NdFeB magnet bar with a diameter of 2.5 mm and a length of 15 mm, and is brand N42M. The permanent magnet 1 can be placed exactly in the central hole inside a commercial 18650 lithium battery without affecting the performance and structural integrity of the battery. The property of residual magnetism changing with temperature is used to measure the internal temperature of the battery. Figure 2 , showing a CT scan of an 18650 shaped lithium battery into which a permanent magnet 1 has been placed. Figure 2 The left picture in the figure is a 3D scan of the battery, showing the overall shape of the battery and the location of the permanent magnet inside the battery. The permanent magnet is cylindrical and located in the reserved hole in the center of the battery; Figure 2 The right picture in the figure is a cross-sectional scan along the battery axis, which more clearly shows the cross-sectional position of the permanent magnet inside the battery, as well as the structural details of the battery and the permanent magnet.

[0053] Exemplarily, the magnetizing structure 2 uses Permalloy with a grade of 1J85, and is processed to obtain a rod with a diameter of 4 mm and a length of 4 mm and a rod with a diameter of 4 mm and a length of 7 mm. The magnetizing structure 2 is used to enhance and transfer the magnetic field generated by the permanent magnet 1 to the magnetic field detection element 3. The magnetizing structure 2 is installed and fixed on the outside of the positive pole of the battery to ensure that the magnetic field detection element 3 is between two pieces of Permalloy to optimize the magnetic field transfer effect. Exemplarily, the magnetic field detection element 3 uses a high-precision Hall element to receive the magnetic field signal generated by the permanent magnet 1 and enhanced by the magnetizing structure 2, and convert the magnetic field signal into an electrical signal for output. The Hall element is calibrated regularly to ensure measurement accuracy.

[0054] The processor 4 includes a signal acquisition unit 41 and an operation processing unit 42. The signal acquisition unit 41 is responsible for acquiring the voltage signal of the Hall element; the operation processing unit 42 is responsible for converting the voltage signal into magnetic flux density, subtracting the magnetic field generated by the current and the stray magnetic field of the device, and finally obtaining temperature information.

[0055] The display screen or battery management system 5 is used to display the temperature information processed by the processor 4, or transmit the temperature information to the battery management system for further analysis.

[0056] The device can be integrated with the existing battery management system to achieve comprehensive monitoring of the battery status.

[0057] The following is the working principle of the present invention:

[0058] The permanent magnet 1 is first placed in the reserved hole of the 18650 battery, and then the battery is assembled. The magnetic attraction structure 2 is installed and fixed on the outside of the positive pole of the battery to ensure that the Hall element 3 is located between the two Permalloys. The processor 4 is connected to the Hall element 3 through a wire and is responsible for collecting and processing signals. The display screen or battery management system 5 is connected to the processor 4 to display or transmit temperature information. When in use, the residual magnetism of the permanent magnet 1 changes with temperature, and the magnetic field signal is received by the magnetic field detection element 3, and the temperature information inside the battery is obtained after being processed by the algorithm of the processor 4.

[0059] Figure 3 A flow chart of a temperature measurement method for measuring the internal temperature of a commercial 18650 battery provided by an embodiment of the present invention. Figures 1 to 3 The embodiment of the present invention further provides a method for measuring the internal temperature of a secondary battery using the change in the remanence of a permanent magnet with temperature, which specifically includes the following steps:

[0060] (S11) Selecting a permanent magnet, and initializing and testing the permanent magnet.

[0061] Select a suitable permanent magnet, specifically and exemplarily, select a neodymium iron boron magnet bar to ensure that its remanence changes with temperature and its characteristics are obvious and stable. In step S11, the permanent magnet is initialized, the neodymium iron boron magnet bar is placed in a 90 degree Celsius incubator for 2 hours, and then placed in a minus 10 degree Celsius environment for 2 hours. The above process is repeated 3 times to eliminate the irreversible magnetic loss of the permanent magnet and stabilize its performance. After initialization, the remanence temperature coefficient of the permanent magnet is measured, which is used for subsequent temperature calculations.

[0062] (S12) Placing a permanent magnet into a secondary battery.

[0063] Specifically and exemplarily, in the step S12, in the production of 18650 lithium batteries, when the wound electrode is placed in the steel shell, a polytetrafluoroethylene rod with a thickness of 2.5 mm is placed in the central hole of the wound electrode, and then the permanent magnet is embedded therein. The polytetrafluoroethylene rod plays a supporting role to ensure that the position of the permanent magnet inside the battery is stable, and at the same time will not affect the battery performance and magnetic field measurement. After the permanent magnet is placed, the battery continues to be filled, sealed, and tested.

[0064] (S13) Install the measurement system.

[0065] Specifically and exemplarily, in the step S13, a magnetic attraction structure is installed and fixed outside the positive pole of the battery. That is, a Permalloy with a diameter of 4mm and a length of 4mm is placed outside the center of the positive terminal surface of the 18650 lithium battery, a Hall sensor is placed on this side as a magnetic field detection element, and a Permalloy with a diameter of 4mm and a length of 7mm is placed on this side. The Hall sensor is placed between two Permalloys. Ensure that the gap between the components mentioned in the above system is as small as possible to optimize the magnetic field transfer effect. Fix the above components to ensure that the relative positions of the components remain unchanged. Thereafter, use a wire to connect the Hall sensor and the processor, and use a wire to connect the processor and the display screen or battery management system. Ensure that the processor can receive and process the data of the magnetic field detection element, and can transmit the processed temperature data to the display screen or battery management system.

[0066] (S14) The magnetic field detection element receives the signal.

[0067] (S23) The battery management system obtains the current.

[0068] (S24) The processor estimates the magnitude of the magnetic field generated by the current.

[0069] Specifically and exemplarily, in step S24, the operation processing unit in the processor estimates the magnetic field generated by the battery operating current and the stray magnetic field of the device based on the constructed physical electromagnetic model (that is, based on the specific mechanical structure of the battery, the Biot-Savart law is used to calculate the magnetic field distribution generated by the current, the Maxwell equations are used to describe the changes of the electromagnetic field with time and space, and the finite element method is applied to numerically solve the above equations).

[0070] (S15) The processor processes the signal received by the magnetic field detection element and converts the signal into temperature information.

[0071] The electrical signal is transmitted to the processor through the wire, and the signal acquisition unit in the processor is used to collect these signals. The operation processing unit converts the voltage signal into magnetic flux density, and calculates the temperature information inside the battery based on the known residual magnetism temperature coefficient and physical model. The processor is also responsible for real-time monitoring of temperature information, and triggering the early warning mechanism when the temperature exceeds the preset safety threshold. The early warning mechanism can be implemented in a variety of ways, such as lighting up indicator lights, sounding sound alarms, or sending early warning information to the battery management system or remote monitoring platform wirelessly. The early warning information contains key information such as the current temperature information of the battery, whether it exceeds the safety range, and possible thermal runaway risks.

[0072] Specifically and exemplarily, in step S15, the signal acquisition unit collects the voltage of the Hall element once every 1 second. The operation processing unit converts the voltage into magnetic flux density, subtracts the magnetic field generated by the current estimated in step S24 and the stray magnetic field of the device, and filters and estimates the magnetic field measurement value based on the historical acquisition data, and finally obtains the current temperature information. The integrated 18650 lithium battery is subjected to temperature measurement experiments under different temperature conditions, and the experimental results are recorded. At each temperature point, the voltage signal output by the magnetic field detection element (such as the Hall element) is recorded, and the signal is proportional to the magnetic flux density. The voltage signal is converted into a magnetic flux density value through the known sensor characteristics and circuit parameters. The magnetic flux density values ​​at different temperatures are plotted as a graph, with the horizontal axis being the temperature and the vertical axis being the magnetic flux density. Figure 4 The graph shows the change in magnetic flux density at the corresponding magnetic field detection element when the internal temperature of the integrated 18650 lithium battery rises from 0 degrees Celsius to 80 degrees Celsius. Figure 4 It can be seen that the change trend of the magnetic flux density value received by the magnetic field detection element. As the temperature increases, the remanence of the permanent magnet gradually decreases, causing the magnetic flux density value received by the magnetic field detection element to decrease accordingly. Through this curve, the corresponding relationship between temperature and magnetic flux density can be established, thereby realizing temperature measurement. According to the following formula, the remanence temperature coefficient of the graph is calculated to be approximately 0.122%.

[0073]

[0074] In the above formula, α represents the remanence temperature coefficient, J r (T) represents the remanence at temperature T, T 0 represents the starting temperature, and T represents the end temperature.

[0075] This system uses a linear magnetic field-temperature model and realizes temperature measurement through reference point calibration. Specifically: 1. Calibration process: When the battery is in a static state (when the internal and external temperatures are consistent), the surface temperature and the corresponding magnetic field signal are collected as reference points to establish a linear correspondence. 2. Temperature measurement principle: Based on the linear characteristics of the permanent magnet remanence temperature coefficient, the real-time temperature is calculated using the reference point data and the temperature coefficient. 3. Calibration mechanism: Considering that long-term use may cause the reference magnetic field signal to drift, the system automatically calibrates the reference point every time the battery is static to ensure measurement accuracy.

[0076] (S16) Printing the temperature information or transmitting the temperature information to the battery management system for further analysis to determine the working status of the battery.

[0077] Printing temperature information allows operators to directly view and record the current temperature status of the battery. Through paper or electronic output, operators can intuitively understand the operating temperature of the battery, so as to make preliminary judgments and records to help determine whether the battery has overheating or abnormal temperature problems.

[0078] The temperature information is transmitted to the battery management system for higher-level monitoring and management. The battery management system can evaluate the working status of the battery in real time based on the received temperature information, so as to take corresponding protection measures or adjustment strategies. The temperature information can be transmitted to the battery management system via wired or wireless methods. Wired methods may include serial communication (such as RS-232, RS-485, CAN bus), Ethernet, etc.; wireless methods may include Wi-Fi, Bluetooth, Zigbee, etc. The transmission protocol is customized according to the specific requirements of the battery management system to ensure the accuracy and reliability of the data.

[0079] The battery management system monitors the battery's temperature information in real time to ensure that the battery operates within a safe and efficient range. When the battery temperature exceeds the preset threshold, the battery management system can trigger an alarm or take cooling measures. By accumulating and analyzing temperature data over a long period of time, the battery management system can also be used to predict the battery's life and performance changes, providing a scientific basis for battery maintenance and replacement. After receiving the temperature information, the battery management system can judge the battery's working status based on the preset algorithm and threshold. When the battery temperature exceeds or falls below the preset range, an alarm is triggered and corresponding protective measures are taken. The battery's performance status is evaluated based on the temperature information.

[0080] During battery production, permanent magnets and fiber Bragg gratings are placed inside the battery at the same time, and then the battery is packaged. The battery is charged and discharged under different temperature conditions, and the internal temperature of the battery rises as the battery is charged and discharged. During this process, the internal temperature of the battery obtained by the permanent magnet and the internal temperature of the battery obtained by the fiber Bragg grating are recorded simultaneously.

[0081] The differences in the internal temperature of the battery measured by the two methods were compared to evaluate the accuracy of the temperature measuring device.

[0082] Although the present invention is described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention. The scope of the present invention is determined by the scope of the attached claims.

Claims

1. A secondary battery internal temperature measurement device based on permanent magnets, characterized in that It includes the following permanent magnets, magnetic attraction structures, magnetic field detection elements and processors; The permanent magnet is selected to have a larger residual magnetism temperature coefficient; the residual magnetism of the permanent magnet changes reversibly with the change of temperature; The magnetic attraction structure uses a material with high magnetic permeability and low coercivity to increase the magnetic field size and uniformity near the magnetic field detection element, so as to improve the signal-to-noise ratio and dynamic range of the magnetic field signal; the magnetic attraction structure is installed outside the battery housing, close to the magnetic field detection element, to ensure the effective transmission and enhancement of the magnetic field; The magnetic field detection element is an element for detecting and sensing the magnitude of the magnetic field. The magnetic field detection element is fixed outside the battery and is used to measure the change of the magnetic field and convert the magnetic signal into a magnetic-electrical signal for subsequent processing; The processor is electrically connected to the magnetic field detection element, and is used to obtain the magnetic induction intensity at the detection component according to the electrical signal, and calculate the temperature at the location of the permanent magnet according to the magnetic induction intensity; The processor includes a signal acquisition unit and an operation processing unit; wherein the signal acquisition unit is used for real-time and regular acquisition and recording of magnetic field data; the operation processing unit is used for correcting magnetic signals and converting magnetic field data into temperature data.

2. A secondary battery internal temperature measurement device based on a permanent magnet as claimed in claim 1, characterized in that The permanent magnet is made of a material with a large residual magnetic temperature coefficient, such as neodymium iron boron or ferrite; the shape of the permanent magnet can be designed to be miniaturized, thin-sheet or cylindrical according to the internal structure of the battery, so that it is easy to embed into the battery without affecting the structural integrity of the battery, and can be implanted inside the battery during the battery production process.

3. A secondary battery internal temperature measurement device based on a permanent magnet as claimed in claim 1, characterized in that The material of the magnetic attraction structure is a material with high magnetic permeability and low coercive force, such as soft iron or Permalloy, to concentrate and amplify the magnetic field generated by the permanent magnet and make the magnetic field distribution in the detection area more uniform; the shape of the magnetic attraction structure can be optimized according to finite element simulation.

4. A secondary battery internal temperature measurement device based on a permanent magnet as claimed in claim 1, characterized in that The magnetic field detection element adopts a Hall element or a magnetoresistive element to accurately measure the change of the magnetic field; the magnetic field detection element adopts a waterproof, dustproof, shockproof, high and low temperature resistant design to ensure long-term stable operation.

5. A device for measuring the internal temperature of a secondary battery based on a permanent magnet as claimed in claim 1, characterized in that The signal acquisition unit adopts a high-precision ADC to realize real-time acquisition of magnetic field data; the operation processing unit integrates a temperature-magnetic field conversion algorithm, including a linear or nonlinear correction model based on the permanent magnet residual magnetism temperature coefficient, and a current interference rejection algorithm, to convert the magnetic field data into temperature data, and integrate it with the battery management system of the battery pack through a standard communication protocol.

6. A method for measuring the internal temperature of a secondary battery using the change in the remanence of a permanent magnet with temperature, characterized in that The following steps are involved: 1) Permanent magnet selection: select a permanent magnet, initialize it, and measure the remanence temperature coefficient of the permanent magnet; 2) Battery integration and testing: Before the secondary battery cell is filled and sealed, the permanent magnet is placed in the proper position inside the battery, the cell is encapsulated, and the integrated secondary battery is obtained, and its performance and reliability are tested; 3) Installation of the measurement system: Install the magnetic attraction structure and magnetic field detection element at the appropriate position outside the battery. The magnetic field detection element is close to the magnetic attraction structure to ensure the effective transmission and measurement of the magnetic field. Connect the magnetic field detection element to the processor to complete the installation of the measurement system. 4) Temperature information conversion and processing: When the battery is charging and discharging, the processor receives the signal from the magnetic field detection element and converts it into temperature information.

7. A method for measuring the internal temperature of a secondary battery using the change in the residual magnetism of a permanent magnet with temperature as claimed in claim 6, characterized in that In step 1), the permanent magnet is selected, initialized, and the residual magnetism temperature coefficient of the permanent magnet is measured. The specific steps include: 1.1) Based on the specific application scenario, select a permanent magnet with appropriate process, material and shape, such as NdFeB or ferrite permanent magnet; 1.2) Place the permanent magnet in an environment slightly beyond the measurement temperature range and perform initialization processing on it to eliminate irreversible magnetic loss and ensure that the remanence of the permanent magnet is stable and highly consistent with temperature; 1.3) Measure the remanence of the permanent magnet at multiple temperature points and calculate its remanence temperature coefficient, which is the key parameter for subsequent temperature calculations.

8. A method for measuring the internal temperature of a secondary battery using the change in the residual magnetism of a permanent magnet with temperature as claimed in claim 6, characterized in that In step 2), the permanent magnet is placed in a battery and tested, and the specific steps may be: 2.1) Before filling and sealing the secondary battery cell, place the permanent magnet in the proper position inside the battery to ensure that it does not affect the structural integrity and performance of the battery; 2.2) Determine the optimal position of the permanent magnet inside the battery through simulation experiments to maximize the magnetic field strength and measurement accuracy; Complete the packaging of the battery cell to obtain an integrated secondary battery; 2.3) Conduct performance and reliability tests on the integrated secondary battery, including cycle charge and discharge tests, high temperature / low temperature storage tests, etc., to verify that the permanent magnet has no negative impact on the battery performance and ensure its normal and stable operation.

9. A method for measuring the internal temperature of a secondary battery using the change in the residual magnetism of a permanent magnet with temperature as claimed in claim 6, characterized in that In step 4), the processor receives the signal from the magnetic field detection element and converts it into temperature information, including: 4.1) The magnetic field detection element is used to sense the magnetic field changes generated by the permanent magnet and convert the sensed magnetic field changes into corresponding electrical signals; the signal acquisition unit in the processor collects these electrical signals in real time and periodically, and uses its built-in working mechanism to convert the electrical signals into processable magnetic field information; 4.2) During the battery charging and discharging process, the working current will generate a magnetic field around the battery. In addition to the magnetic field generated by the working current, there may also be stray magnetic fields in the device itself, which will also interfere with the temperature measurement results. In order to eliminate these interfering magnetic fields, the processor calculates the size and direction of the magnetic field generated by the working current based on the pre-established electromagnetic field physical model, and uses signal processing technology to identify and eliminate stray magnetic fields; at the same time, the processor works in coordination with the battery management system to obtain the current battery charging and discharging current information in real time, so as to more accurately calculate and eliminate the influence of the magnetic field generated by the working current; 4.3) Convert the magnetic field signal into temperature information according to the remanence temperature coefficient and physical model of the permanent magnet; For an initialized permanent magnet, its remanence changes reversibly with temperature, and can be regarded as a linear change at the normal operating temperature of a secondary battery. This change relationship is described by the remanence temperature coefficient. The processor uses this coefficient and the physical model to convert the magnetic field signal into temperature information.

10. A method for measuring the internal temperature of a secondary battery using the change in the residual magnetism of a permanent magnet with temperature as claimed in claim 6, characterized in that The following steps are also included: 5) Utilization of temperature information: Print or display temperature information for personnel to know; or transmit temperature information to the battery management system for further analysis to determine the battery working status.

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