Snowmobile power battery structure resistant to extremely cold environment and temperature management system thereof

Abstract

This invention relates to the field of power battery technology for special vehicles, and specifically discloses a power battery structure for snowmobiles resistant to extremely cold environments and its temperature management system. The structure includes: an outer casing, composed of an upper shell and a lower shell, both made of metal and fixedly connected by connectors, with a sealing structure at the joint between the upper and lower shells; a battery module housed within the outer casing, comprising multiple battery cells, a support structure, a protection board (BMS), electrical connectors, insulating components, and heating elements; heat insulation material covering the exterior of the battery module; and multiple temperature sensors distributed within the battery module at different locations and connected to the protection board (BMS). The protection board (BMS) is configured to control the start and stop of the heating elements based on the detection signals from the temperature sensors. The battery pack has a robust overall structure, excellent waterproof reliability, convenient assembly, high production efficiency, and meets drop and shock resistance requirements.

Description

Technical Field

[0001] This invention relates to the field of power battery technology for special vehicles, and in particular to a power battery structure for snowmobiles that is resistant to extremely cold environments and its temperature management system. Background Technology

[0002] Snowmobiles, as special vehicles designed for driving on snow, face severe challenges in extremely cold environments with their battery systems. Traditional battery systems experience significant performance degradation, charging difficulties, and reduced driving range in temperatures below -20°C.

[0003] In existing technologies, battery systems mostly employ a structure with a plastic casing and a rubber sealing ring. However, this structure has significant shortcomings in extremely cold environments: the plastic material becomes significantly brittle below -30°C, resulting in a decrease in impact strength; the elasticity of the rubber sealing ring weakens at low temperatures, leading to a decline in sealing performance; and conventional battery systems lack effective thermal insulation design and temperature monitoring systems, causing a significant reduction in battery performance in extremely cold environments.

[0004] On the other hand, while stainless steel possesses excellent mechanical properties and low-temperature resistance, effectively applying it to battery systems while ensuring its sealing and insulation remains a technical challenge. For instance, ultra-high-strength stainless steel, with its good ductility, is specifically developed for critical safety components in vehicle structures, but current technology does not offer an effective solution for its application in battery casings and for addressing sealing and insulation issues in extremely cold environments.

[0005] Furthermore, thermal management of battery systems is particularly important in extremely cold environments. Conventional battery systems are typically equipped with only simple temperature monitoring, lacking comprehensive temperature field monitoring and active heating functions, thus failing to achieve intelligent temperature management. In extremely cold environments, uneven temperature distribution, localized overcooling leading to electrolyte solidification, and lithium deposition can easily occur inside the battery, severely impacting battery performance and safety.

[0006] Therefore, there is an urgent need to develop a battery system specifically designed for the extreme environments of snowmobiles, which can meet multiple requirements such as low temperature resistance, high sealing and intelligent temperature control, and achieve reliable charging and discharging in ultra-low temperature environments below -30℃.

[0007] Therefore, this invention proposes a snowmobile power battery structure and its temperature management system that are resistant to extremely cold environments. Summary of the Invention

[0008] This invention provides a snowmobile power battery structure and its temperature management system that are resistant to extremely cold environments. By optimizing the battery casing structure, module design, insulation scheme, and temperature management strategy, it solves the core problems of sealing, insulation, and temperature control in existing technologies under extremely cold environments. It provides a snowmobile power battery structure and its temperature management system that are resistant to extremely cold, highly reliable, and easy to manufacture, ensuring that the battery can still charge and discharge stably in environments below -30°C, thus guaranteeing the snowmobile's range and safety.

[0009] This invention provides a snowmobile power battery structure resistant to extremely cold environments, comprising: The outer casing consists of an upper shell and a lower shell, which are made of metal and are fixedly connected by connectors. A sealing structure is provided at the joint between the upper shell and the lower shell. The battery module is housed in an outer casing and includes multiple battery cells, a support structure, a protection board (BMS), electrical connectors, insulating components, and heating elements. Thermal insulation material is used to cover the outside of the battery module; Multiple temperature sensors are distributed in different locations inside the battery module and connected to the BMS protection board. The protection board (BMS) is configured to control the start and stop of the heating element based on the detection signal from the temperature sensor.

[0010] Preferably, the metal material is stainless steel; the sealing structure includes a sealant groove formed on the joint surface of the upper and lower shells and sealant filling the sealant groove, and the connecting part is a screw, at least a portion of which is located in the sealant groove.

[0011] Preferably, the battery module includes at least two sub-modules, which are positioned to each other by a positioning structure and connected by screws.

[0012] Preferably, the positioning structure includes interlocking studs.

[0013] Preferably, the heating element is a plurality of independently controllable heating films, which are respectively attached to the surface of different battery cells or battery cell groups.

[0014] This invention provides a temperature management system for a snowmobile's power battery that is resistant to extremely cold environments, comprising: The protection board BMS is communicatively connected to multiple temperature sensors and heating components. The protection board BMS is configured to perform the following operations: In the charging state, when the temperature sensor detects that the battery temperature is lower than the first temperature threshold, the control power supply is used to supply power to the heating component; when the battery temperature is higher than the first temperature threshold, the power supply is switched to charge the battery module. In the discharge state, when the temperature sensor detects that the battery temperature is lower than the second temperature threshold, the discharge circuit is shut off and the external power supply is controlled to supply power to the heating component. When the battery temperature is higher than the second temperature threshold, the discharge circuit is activated.

[0015] Preferably, the protection board BMS is further configured to perform adaptive focus heating control: Based on data from multiple temperature sensors, local extreme cold focal regions in the three-dimensional temperature field of the battery module are reconstructed and identified in real time by using the Kriging space interpolation algorithm and solving the inverse problem of heat conduction. For each identified focal region, calculate the direction and intensity of the temperature gradient between the focal region and its adjacent regions; Based on the direction and intensity of the temperature gradient, one or more heating films closest to the focal region are dynamically generated and driven to implement gradient heating pulses with the focal region as the convergence target and the power decaying over time, until the temperature of the focal region reaches thermal equilibrium with the surrounding region.

[0016] Preferably, the protection board BMS is further configured to perform phase change interface synchronous preheating control: In the initial stage of heating or when a sudden drop in ambient temperature is predicted, the cells or regions inside the battery that may undergo phase change are identified based on real-time monitoring data of electrochemical impedance spectroscopy. For the identified high-risk battery cells, a low-amplitude AC preheating signal of 1-100Hz is applied to the heating film corresponding to the high-risk battery cell. At the same time, conventional DC preheating is applied to the adjacent non-high-risk cells to form a synergistic preheating field with high-risk cells as the core and consisting of AC preheating area and DC preheating area.

[0017] Preferably, the protection plate BMS is further configured to integrate vibrational spectrum matching heating enhancement: Real-time acquisition or reception of the vehicle body vibration spectrum under the current driving state of the snowmobile; Extract the characteristic frequency bands where the main energy is concentrated from the vehicle body vibration spectrum; The carrier frequency of the gradient heating pulse or preheating signal is modulated to a frequency band that matches the characteristic frequency band.

[0018] Preferably, the protection board BMS is further configured to run a digital twin-based policy self-evolution module, including: The digital twin model of the battery module is maintained in the protection board BMS or cloud. The digital twin model integrates three-dimensional geometry, material properties, electrochemical-thermal coupling characteristics and historical degradation data. In the actual heating control process, sensor data is synchronized to the digital twin model in real time, and the adaptive focus heating strategy, phase change interface synchronous preheating strategy and vibration spectrum matching strategy are simulated and evaluated in advance in the digital twin model. Based on a reinforcement learning framework, a new control strategy with better energy efficiency ratio is generated and screened using a digital twin simulation environment. After passing safety verification, the strategy is updated to the actual control loop.

[0019] The beneficial effects of this invention compared to the prior art are as follows: The stainless steel shell combined with a special adhesive sealing structure provides excellent low-temperature resistance and sealing performance, enabling it to resist snow water intrusion and mechanical impact in environments below -30℃, thus ensuring structural integrity. The battery module is covered with heat insulation material on all six sides, which effectively slows down heat loss, extends the heat preservation time in extremely cold environments, and reduces battery performance degradation. Eight distributed temperature sensors work together with an independently controllable heating film to achieve comprehensive temperature field monitoring and uniform heating, avoiding local overcooling problems. The intelligent temperature management strategy achieves precise temperature control and efficient heating through the collaboration of multiple algorithms, reduces energy consumption, and ensures reliable charging and discharging in ultra-low temperature environments; The integrated module and stud positioning structure design improves the battery's shock and drop resistance, making it suitable for snowmobile driving conditions. It also supports automated production, improving production efficiency and product consistency.

[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in this application.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the power battery structure for a snowmobile designed to withstand extremely cold environments, as described in an embodiment of the present invention. Figure 2 This is a diagram of the finished battery product in an embodiment of the present invention; Figure 3 This is a schematic diagram of the glue application structure in an embodiment of the present invention; Figure 4 This is a schematic diagram of the positioning structure in an embodiment of the present invention; Figure 5 This is a schematic diagram of the integrated module in an embodiment of the present invention; Figure 6 This is a schematic diagram of the 8-channel temperature sensor setup in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of two battery cell modules in an embodiment of the present invention; Figure 8 This is a schematic diagram of the battery module covering heat insulation material structure in an embodiment of the present invention; Figure 9 This is a control flowchart of the temperature management system in an embodiment of the present invention.

[0023] In the diagram: 1. Handle; 2. Explosion-proof valve; 3. Upper housing; 4. EVA; 5. Sealant; 6. Waterproof plug; 7. BMS; 8. B-nickel plate; 9. B2 nickel plate; 10. B4 nickel plate; 11. Cell bracket A; 12. NTC (temperature sensor); 13. Cell; 14. Cell bracket B; 15. B1 nickel plate; 16. B3 nickel plate; 17. B5 nickel plate; 18. PC sheet; 19. B7 nickel plate; 20. B9 nickel plate; 21. B+ nickel plate; 22. B8 nickel plate; 23. B6 nickel plate; 24. Protective cotton; 25. Heating film 1; 26. Lower housing; 27. PC board; 28. Heating film 2; 29. ​​Temperature control switch. Detailed Implementation

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] like Figures 1 to 8 As shown, this invention provides a snowmobile power battery structure resistant to extremely cold environments, including an outer casing, battery module, heat insulation material, temperature sensor, heating element, temperature control switch, and explosion-proof valve. The specific configuration and connection relationship of each component are as follows: The outer casing structure includes: The outer casing consists of two parts: the upper shell 3 and the lower shell 26. Both the upper shell 3 and the lower shell 26 are made of 1.2mm thick ultra-high strength stainless steel through bending and welding. The yield strength of the stainless steel is not less than 1000MPa, ensuring that it still has good mechanical strength and ductility in extremely cold environments below -30℃, and avoiding embrittlement and cracking.

[0026] The upper housing 3 and the lower housing 26 are fixedly connected by screws, forming a 3.5mm wide and 25mm high sealant area at the joint, with the screws embedded within this area. During assembly, the screws are pre-fixed to the upper housing 3 and the lower housing 26. After adjusting the sealant thickness, sealant 5 is filled into the sealant area, completely covering the embedded portion of the screws. This structure ensures the IP67 protection rating test requirements, avoids full-circumference sealant application on the battery pack housing joint surface, saves sealant costs, and facilitates subsequent battery maintenance. The screws are embedded in the sealant, ensuring a secure connection and preventing them from loosening during prolonged battery vibration.

[0027] The outer box is also equipped with a handle structure. The handle is fixed to the upper shell with 8 M4 screws, which facilitates the handling and installation of the power battery. The handle 1 is integrally formed with the upper shell 3 or the lower shell 26 to ensure the connection strength.

[0028] The battery module structure includes: The battery module is housed in the outer casing and includes two sub-modules (cell module 1 and cell module 2). Cell module 1 and cell module 2 are positioned by interlocking studs of different sizes and are locked in place by eight screws to enhance structural reliability and meet the requirements for drop and shock resistance during snowmobile operation.

[0029] The battery module specifically includes the following components: Battery cells: Multiple 21700 steel-cased battery cells 13; Support structure: including cell support A11 and cell support B14, used to fix and support 21700 steel shell cell 13; BMS7 Protection Board: As the control core of the entire battery system, it is electrically connected to various electrical components; Electrical connectors include nickel plates B- (8), B2 (9), B4 (10), B1 (15), B3 (16), B5 (17), B7 (19), B9 (20), B+ (21), B8 (22), and B6 (23), used to achieve series and parallel connections of the 21700 steel-cased battery cells 13 to ensure stable current transmission. Insulating components: including PC sheet 18 and PC board 27. PC sheet 18 is disposed between the cells and the contact surface between the cells and the bracket. PC board 27 covers the outside of the module to effectively prevent short circuit faults. Other components: screws, waterproof plug 6, temperature control switch 29, explosion-proof valve 2. The waterproof plug 6 is used to connect an external power source. The temperature control switch 29 helps control the on / off state of the heating circuit. The explosion-proof valve 2 is used to ensure the safety of battery use and avoid risks caused by excessive internal pressure.

[0030] The battery module adopts an integrated design, which enables fully automated production of battery cells and nickel sheets, resulting in high production efficiency and good product consistency.

[0031] The heating component includes: The heating components consist of two independent and controllable heating films (heating film 125 and heating film 228). Heating film 125 covers the surface of cell module 1, and heating film 228 covers the surface of cell module 2. Each heating film is completely attached to the surface of each 21700 steel shell cell 13 in the corresponding sub-module, which can heat each cell synchronously, avoid uneven heating of the cells, and ensure heating efficiency and temperature consistency.

[0032] Among them, the thermal insulation materials include: The battery module is completely covered with heat-insulating material on all six sides, including heat-insulating film and EVA protective cotton (protective cotton 24). This fully enclosed design reduces heat loss from the battery, maintains a suitable operating temperature, and blocks extreme external low temperatures to prevent internal short circuits caused by lithium plating due to overcooling. When parked overnight in an environment of -20℃, this insulation design can keep the battery temperature above 10℃ for more than 14 hours, greatly improving the driving experience the next day.

[0033] The temperature sensor includes: The battery pack is equipped with 8 temperature sensors (NTC sensors 12, including NTC1-NTC8) to comprehensively monitor the temperature of each battery cell. The specific placement is as follows: The six temperature sensors are located between the first and second strings of cells, the third and fourth strings of cells, the fourth and fifth strings of cells, the sixth and seventh strings of cells, the seventh and eighth strings of cells, and the ninth and tenth strings of cells, respectively. The remaining two temperature sensors are respectively set at the upper and lower positions at both ends of the battery cell to achieve comprehensive monitoring of the temperature field of the battery module.

[0034] The protection board BMS7 is connected to 8 temperature sensors 12, heating films (25, 28), temperature control switches 29, explosion-proof valves 2 and other components. It is configured to control the start and stop of the heating components and the switching of the charging and discharging circuit based on the detection signals of the temperature sensors.

[0035] like Figure 9 As shown, a temperature management system for a snowmobile power battery that is resistant to extremely cold environments is further provided, which is applied to the battery structure described in Example 1.

[0036] The system includes a protection board BMS7, which is communicatively connected to eight temperature sensors 12, two heating films (25, 28), a temperature control switch 29, and a waterproof connector 6, and is configured to perform the following operations: During charging, when the temperature sensor 12 detects that the battery temperature is below 0°C (first temperature threshold), the protection board BMS7 controls the charger to first supply power to the heating film (25, 28), and the temperature control switch 29 assists in turning on the heating circuit to preheat the battery cell; when the battery temperature is above 0°C, it switches to the charging circuit to charge the battery pack to avoid damage to battery performance caused by low-temperature charging.

[0037] In the discharge state, when the temperature sensor 12 detects that the battery temperature is below -20℃ (the second temperature threshold), the protection board BMS7 immediately shuts off the discharge circuit. At this time, an external power supply can be connected through the waterproof plug 6. The protection board BMS7 controls the external power supply to supply power to the heating film (25, 28). The temperature control switch 29 adjusts the heating power according to the temperature change. When the battery temperature is above -20℃, the discharge circuit is started to achieve reliable charging and discharging in ultra-low temperature environments below -30℃.

[0038] Further optimize the control strategy of the temperature management system to solve the problem of insufficient heating in extremely cold areas of the battery module.

[0039] The protection board BMS7 is further configured to perform adaptive focus heating control: Based on discrete temperature data collected by 8 temperature sensors 12 (NTC1-NTC8), the three-dimensional temperature field of the battery module is reconstructed in real time by using the Kriging space interpolation algorithm and solving the inverse problem of heat conduction. This accurately identifies local extremely cold focal areas in the three-dimensional temperature field (such as cell gaps, module edges, and other areas where the temperature is significantly lower than the surrounding area). For each identified focal region, calculate the direction (i.e. the direction of temperature increase) and intensity (i.e. the magnitude of temperature difference) of the temperature gradient between the focal region and its neighboring regions. Based on the direction and intensity of the temperature gradient, a gradient heating pulse is dynamically generated: one or more heating films (25, 28) closest to the focal area are selected, and a heating pulse with power decaying over time is applied with the focal area as the convergence target to avoid energy waste caused by overheating; heating continues until the temperature of the focal area reaches thermal equilibrium with the surrounding area to ensure uniform temperature distribution of the entire battery module.

[0040] Further optimize the battery preheating strategy in extremely cold environments to prevent phase change of the electrolyte inside the battery.

[0041] The protection board BMS7 is further configured to perform phase change interface synchronous preheating control: In the initial stage of heating or when a sudden drop in ambient temperature is predicted by the ambient temperature sensor, the protection board BMS7 monitors the impedance change data of the battery in real time through electrochemical impedance spectroscopy, and identifies high-risk cells or areas where the internal electrolyte may undergo phase change (solidification) based on the impedance change. For high-risk cells identified, the protection board BMS7 controls the corresponding heating film (25 or 28) to apply a low-amplitude AC preheating signal of 1-100Hz to prevent the electrolyte from freezing locally and forming a phase change interface. At the same time, for adjacent non-high-risk cells, the corresponding heating film (25 or 28) is controlled to apply conventional DC preheating, forming a synergistic preheating field with the high-risk cells as the core and consisting of AC preheating area and DC preheating area, to ensure the temperature stability of the entire battery module and prevent phase change diffusion.

[0042] Further utilize the vibration characteristics of snowmobiles during operation to enhance the heating effect and improve heat transfer efficiency.

[0043] The BMS7 protection plate is further configured to integrate vibrational spectrum matching heating enhancement: The vehicle's vibration spectrum is collected in real time by onboard sensors, or the vehicle vibration data is received through the communication module. The characteristic frequency bands where the main energy is concentrated are extracted from the vehicle body vibration spectrum. These frequency bands reflect the main vibration characteristics of the snowmobile during operation. By modulating the carrier frequency of the gradient heating pulse in adaptive focus heating control or the preheating signal in phase change interface synchronous preheating control to a frequency band that matches the characteristic frequency band, and utilizing the synergistic effect of vibration and heating, the traditional heat conduction limit is broken, the heating time is shortened, and energy consumption is reduced.

[0044] Furthermore, an intelligent temperature management strategy optimization method is provided to achieve continuous iterative upgrades of the control strategy.

[0045] The protection board BMS7 is further configured to run a digital twin-based policy self-evolution module: The digital twin model of the battery module is maintained on the protection board BMS7 or in the cloud. This model integrates the three-dimensional geometry of the battery module, the thermophysical properties of the stainless steel shell and heat insulation materials, the electrochemical-thermal coupling characteristics of the cells, and the battery's historical degradation data (such as the number of charge-discharge cycles, historical heating energy consumption, etc.). In the actual heating control process, the real-time data of the working status of the 8 temperature sensors 12, heating film (25, 28), and temperature control switch 29 are synchronized to the digital twin model. Based on these data, the digital twin model performs advanced simulation of the adaptive focus heating strategy, phase change interface synchronous preheating strategy and vibration spectrum matching strategy to evaluate the heating efficiency and energy consumption level of different strategies under the current working conditions. Based on a reinforcement learning framework, a simulation environment is constructed using a digital twin model to generate multiple candidate control strategies. By comparing the energy efficiency ratios of different candidate strategies through simulation, the optimal strategy is selected. After safety verification (such as simulating abnormal scenarios like short circuits, overheating, and explosion-proof valve triggering), the optimal strategy is updated to the actual control loop, realizing the self-evolution and optimization of the heating control strategy and continuously improving the temperature management performance in extremely cold environments.

[0046] Based on the above embodiments, additional functions of heat flux topology optimization and intelligent phase change prediction are added to achieve more precise thermal intervention control: The BMS7 protection board includes a heat flow topology optimization module and a phase change intelligent prediction unit, which are implemented as follows: The heat flow topology optimization module is based on the principle of electrical impedance tomography. It uses temperature data collected by 8 temperature sensors 12 and impedance response data of the battery module to reversely reconstruct the three-dimensional heat conduction network inside the battery, clearly showing the heat flow distribution between components such as cells, nickel plates, and brackets.

[0047] Using the continuous cohomology method in topology data analysis, topological features are extracted from the three-dimensional heat conduction network. By tracking the connectivity changes of the heat conduction path, the bottleneck regions with extremely low heat transfer efficiency are accurately identified, such as areas with excessively large gaps between battery cells or areas blocked by insulating components. The influence weight of the bottleneck regions on the overall heat conduction efficiency is quantified, with the influence weight ranging from 60% to 90%.

[0048] The phase change intelligent prediction unit integrates Markov random field theory and electrochemical thermocoupled model to construct an electrolyte phase change prediction model: Using battery temperature, charging and discharging current, and electrolyte concentration as state variables, a spatiotemporal transition probability matrix of the state variables is established through Markov random field theory, which clearly describes the spatiotemporal correlation of phase transition behavior inside the cell. By combining an electrochemical thermocoupled model, the dynamic change of the freezing point of the electrolyte with temperature and current is accurately calculated. The phase transition driving force is quantified by the potential function, and the potential energy of the potential function is between 0 and 10 J / mol. Based on the model constructed above, the evolution path of the electrolyte solid-liquid interface is dynamically predicted within the next 5-10 minutes, and the interface movement speed and evolution range are output. The interface movement speed is in micrometers per second.

[0049] The system calculates a heat flow redistribution strategy based on topological entropy based on the identified heat conduction bottleneck regions (regions with an influence weight of 70% or more are given priority) and the predicted phase change interface evolution path: The topological entropy is calculated by statistically analyzing the distribution probability of heat flow along each path, using the basic definition of entropy. The goal is to minimize the topological entropy, keeping the entropy value below 0.5. Based on the redistribution strategy, the heating films (25, 28) corresponding to the bottleneck region and the phase transition interface evolution path are controlled, and adaptive morphological thermal intervention is implemented. Focused high-power heating is applied to the bottleneck region, with the power density controlled at 2-3 watts per square centimeter; gradient power heating is applied to the phase transition interface evolution region, with the power density varying linearly with the interface distance, ranging from 0.5-2 watts per square centimeter, to ensure efficient heat transfer and suppress phase transition.

[0050] A further nonlinear vibration thermal enhancement module is added to improve heating efficiency through the nonlinear coupling of mechanical vibration and heat conduction. The system also includes a nonlinear vibration thermal enhancement module, which is implemented as follows: Vibration data was collected under different driving conditions (constant speed, climbing, and bumpy roads) using vibration sensors mounted on snowmobiles, covering a frequency range of 10-1000Hz, to establish a multi-scale vibration spectrum database for the battery module. The database contains key parameters such as vibration frequency, amplitude, and phase, and is stored according to driving conditions, supporting real-time retrieval and updates.

[0051] The vibration spectrum data was decomposed into three levels using the wavelet packet decomposition algorithm to extract the characteristic frequency components related to heat conduction efficiency. The characteristic frequency components are mainly concentrated between 50-200Hz. The energy proportion of each component was calculated, and the energy proportion of the characteristic components was required to reach 60% or more.

[0052] A Lyapunov exponential field is constructed to describe the nonlinear coupling relationship between external mechanical vibration and internal heat conduction: the changes in heat conduction coefficient at different vibration frequencies are calibrated experimentally, and the Lyapunov exponent is calculated. The exponent value is between 0.1 and 0.8. The larger the exponent, the stronger the coupling effect and the more significant the improvement in heat conduction efficiency.

[0053] When the system detects specific operating conditions (such as the energy proportion of the vibration characteristic frequency component reaching 70% or more, or the battery temperature being below -15℃), it controls the heating film (25, 28) to output a thermal power modulation waveform that resonates with the vibration characteristic frequency: The modulation waveform uses a sine wave superimposed with a DC component, the carrier frequency is consistent with the vibration characteristic frequency, i.e., 50-200Hz, and the modulation depth is controlled between 30% and 50%. By inducing micro-vibrations inside the battery through parametric resonance, the thermal boundary layer is disrupted. Through the vibration-thermal synergistic effect, the thermal conduction efficiency is improved by more than 40%, breaking through the traditional thermal conduction limit.

[0054] This embodiment details the implementation process of adaptive focus heating control in the protection board BMS7. This control method is executed cyclically once per second, aiming to eliminate localized low-temperature regions within the battery module.

[0055] The protection board BMS7 first reads the real-time temperature values ​​from all eight NTC temperature sensors 12. Simultaneously, BMS7 has pre-stored the specific coordinates of each sensor's location within the battery module's three-dimensional space. These coordinates, determined based on the battery design drawings, are used to map the temperature values ​​to specific points in space.

[0056] BMS7 uses a calculation method called Kriging space interpolation. This method uses the actual temperature and location measurements from eight sensors as a basis, and through algorithms, estimates the temperature of thousands of virtual points inside the battery module, thus constructing a continuous three-dimensional temperature distribution map covering the entire battery module within BMS7. This temperature field can show which areas are hot and which areas are cold.

[0057] BMS7 scans and analyzes the newly reconstructed 3D temperature field. It sets a threshold, such as 5 degrees Celsius. The system examines every small region in the temperature field. If it finds that the temperature of a small region is significantly lower than the average temperature of all its surrounding regions, and the difference exceeds 5 degrees Celsius, then this small region is marked as an extreme cold focal area. These focal areas typically appear in the gaps between battery cells, the corners of modules, or near the casing.

[0058] For each identified focal region, BMS7 will conduct further analysis: Gradient direction: Identify the dominant direction from the focal region to the surrounding areas with higher temperatures. This direction is where heat is most likely to be transferred.

[0059] Gradient strength: Calculates the difference between the temperature of the focal region and the highest temperature within a certain surrounding range. The larger the difference, the colder the point is, and the greater the heating required.

[0060] Heater Selection: Based on the location of the focal area in three-dimensional space, BMS7 calculates which of the two heating films (heating film 125 and heating film 228) is closer. The nearest heating film is selected for heating. If both heating films are approximately close, both are activated simultaneously.

[0061] Determine the heating parameters: Initial power: The initial heating power is proportional to the gradient intensity calculated in step four. For example, for every 1 degree Celsius increase in gradient intensity, the initial heating power increases by approximately 1.8 watts.

[0062] Power decay method: Heating is not a continuous constant power process. The BMS7 controls the heating power to be output in an exponential decay mode, starting strong and then weakening. The specific decay rate is determined by the gradient direction: if the low-temperature region extends in only one direction (direction concentrated), the decay is slow, providing gentle and sustained heating; if the low-temperature region is scattered (direction dispersed), the decay is rapid, providing short-term strong heating to avoid ineffective diffusion.

[0063] Execution and Real-time Control: The BMS7 drives the selected heating film (25 or 28) to output varying heating power according to the above settings. Simultaneously, it continuously estimates the real-time temperature of the focal area using an interpolation algorithm. Once it detects that the temperature in that area has risen to within 2 degrees Celsius of the average temperature of the surrounding area (reaching thermal equilibrium), it immediately stops targeted heating of that point.

[0064] After completing a round of heating treatment on all key areas, BMS7 returns to step one and begins a new round of temperature monitoring and calculation. Through this repeated cycle, the temperature inside the battery module is adjusted to be more and more uniform, ultimately ensuring that the maximum temperature difference of the entire module does not exceed 5 degrees Celsius.

[0065] The specific implementation of the phase change interface synchronous preheating control is further elaborated. This function is automatically activated in two main situations: first, within the first 90 seconds after any heating process begins; and second, when the ambient temperature sensor detects a rapid drop in air temperature.

[0066] Step 1: Diagnose high-risk battery cells using electrochemical impedance spectroscopy: Impedance measurement: The BMS7 protection board uses its built-in precision measurement circuit to apply a series of very weak high, medium and low frequency AC signals to the battery module and measure the voltage response of the battery, thereby calculating the electrochemical impedance spectrum inside the battery.

[0067] Risk Identification: BMS7 focuses on the rate of impedance change of the battery at a specific frequency (e.g., 5 Hz). At low temperatures, when the electrolyte begins to thicken or near solidification, this impedance value increases abnormally rapidly. The system sets a risk threshold, such as an impedance increase exceeding 15% per minute. If the impedance rate of a cell exceeds this threshold, BMS7 determines it as a high-risk cell, and its electrolyte is likely undergoing or about to undergo a phase change (solidification).

[0068] Step 2: Establish an AC + DC coordinated preheating field: Based on the diagnostic results, BMS7 adopts a differentiated heating strategy: For high-risk cells: Preheating is achieved by applying a low-frequency, small-amplitude AC voltage to the heating film (25 or 28) attached to the cell surface. The frequency of the AC signal is selected between 10 Hz and 80 Hz (preferably the frequency most sensitive to impedance changes), and the voltage amplitude is only about 15% of the normal DC heating voltage (e.g., using 1.8 volts of AC voltage). This periodic micro-thermal disturbance generated by the AC current is designed to agitate the electrolyte at the molecular level, delaying or preventing its solidification into a solid interface.

[0069] For surrounding normal cells: control their heating films to apply a conventional DC voltage preheating (e.g., 7.2 volts DC) to provide stable background heat for the entire module and prevent heat from being absorbed too quickly by high-risk areas.

[0070] This combination creates a collaborative preheating field centered on high-risk battery cells: the core area is protected from freezing by AC micro-stirring, while the outer area is supported by DC insulation.

[0071] Step 3: Dynamic Monitoring and Exit: The BMS7 continuously monitors the impedance change rate of high-risk cells. Once the rate of increase falls below the safe threshold and remains stable for more than 30 seconds, or the cell's temperature has risen above -5 degrees Celsius, the phase change risk is considered eliminated. At this point, the BMS7 smoothly switches the cell's heating mode to the same DC preheating mode as the surrounding cells. The entire phase change warning heating process ends when all cells have returned to normal and the overall temperature reaches the preheating target (e.g., 0 degrees Celsius).

[0072] The specific implementation of vibration spectrum matching heating enhancement is further elaborated. This function is used as an enhancer for the aforementioned focus heating or phase change preheating control.

[0073] The specific implementation of the strategy self-evolution module based on digital twins is further elaborated. This module runs within BMS7 or on a connected cloud server, enabling the system to continuously learn and evolve.

[0074] Step 1: BMS7 establishes and maintains a high-precision virtual model (digital twin) of a battery system, which includes: 3D geometric model: accurately replicates the shape and assembly relationship of every component (cell, bracket, casing, heating film, etc.) of a real battery.

[0075] Material property database: Stores the physical parameters of all materials (such as stainless steel, insulation cotton, electrode materials, electrolytes) at different temperatures, such as thermal conductivity and heat storage.

[0076] Electro-thermal coupling simulation model: It can simulate the entire process of internal electrochemical reactions and heat generation and transfer of batteries during charging, discharging and heating.

[0077] Historical Archives: Records all important data since the battery was put into use, such as power consumption per heating cycle, temperature change curve, and cycle life degradation.

[0078] The second step: During the actual heating process, BMS7 synchronously inputs real-time data (8-channel temperature, heating film status, ambient temperature, etc.) measured by real-world sensors into the digital twin model. Then, in this virtual laboratory of the digital twin, planned or newly conceived heating strategies (such as new focal heating parameters, new phase change early warning thresholds) can be implemented.

[0079] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A power battery structure for snowmobiles resistant to extremely cold environments, characterized in that, include: The outer casing is composed of an upper shell (3) and a lower shell (26). The upper shell (3) and the lower shell (26) are made of metal and are fixedly connected by connectors. A sealing structure is provided at the joint between the upper shell (3) and the lower shell (26). The sealing structure includes a glue groove formed on the joint surface of the upper shell (3) and the lower shell (26) and a sealant (5) filling the glue groove. The connector is a screw, and at least a part of the screw is located in the glue groove. The battery module is housed in an outer casing. The battery module includes multiple battery cells (13), a support structure, a protection board BMS (7), electrical connectors, insulating components, and heating components. Thermal insulation material is used to cover the outside of the battery module; Multiple temperature sensors (12) are distributed in different positions inside the battery module and connected to the protection board BMS (7); Among them, the protection board BMS (7) is configured to control the start and stop of the heating component based on the detection signal of the temperature sensor (12); Among them, the heating component consists of multiple independently controllable heating films (25, 28), which are respectively attached to the surface of different cells (13) or cell groups; Among them, the protection board BMS (7) is connected to multiple temperature sensors (12) and heating components in communication; The protection board BMS (7) is configured to perform the following operations: In the charging state, when the temperature sensor (12) detects that the battery temperature is lower than the first temperature threshold, the control power supply supplies power to the heating component. When the battery temperature is higher than the first temperature threshold, the control power supply switches to charging the battery module. In the discharge state, when the temperature sensor (12) detects that the battery temperature is lower than the second temperature threshold, the discharge circuit is turned off and the external power supply is controlled to supply power to the heating component. When the battery temperature is higher than the second temperature threshold, the discharge circuit is started. The protection board BMS (7) is further configured to perform adaptive focus heating control: Based on data from multiple temperature sensors (12), the local extreme cold focal region in the three-dimensional temperature field of the battery module is reconstructed and identified in real time by using the Kriging space interpolation algorithm and solving the inverse problem of heat conduction. For each identified focal region, calculate the direction and intensity of the temperature gradient between the focal region and its adjacent regions; Based on the direction and intensity of the temperature gradient, one or more heating films (25, 28) closest to the focal region are dynamically driven to implement gradient heating pulses with the focal region as the convergence target and the power decaying over time, until the temperature of the focal region reaches thermal equilibrium with the surrounding region.

2. The snowmobile power battery structure for extreme cold environments according to claim 1, characterized in that, The metal material is stainless steel.

3. The snowmobile power battery structure for extreme cold environments according to claim 1, characterized in that, The battery module includes at least two sub-modules, which are positioned to each other by a positioning structure and connected by screws.

4. The snowmobile power battery structure for extreme cold environments according to claim 3, characterized in that, The positioning structure includes interlocking studs.

5. The snowmobile power battery structure for extreme cold environments according to claim 1, characterized in that, The protection board BMS (7) is further configured to perform phase change interface synchronous preheating control: In the initial stage of heating or when a sudden drop in ambient temperature is predicted, the cells (13) or regions where the electrolyte inside the battery may undergo phase change are identified based on real-time monitoring data of electrochemical impedance spectroscopy. For the identified high-risk battery cell (13), a low-amplitude AC preheating signal of 1-100Hz is applied to the heating film (25, 28) corresponding to the high-risk battery cell (13); At the same time, conventional DC preheating is applied to the adjacent non-high-risk cells (13) to form a synergistic preheating field with the high-risk cells (13) as the core and consisting of AC preheating area and DC preheating area.

6. The snowmobile power battery structure for extreme cold environments according to claim 1, characterized in that, The protection plate BMS (7) is further configured to integrate vibrational spectrum matching heating enhancement: Real-time acquisition or reception of the vehicle body vibration spectrum under the current driving state of the snowmobile; Extract the characteristic frequency bands where the main energy is concentrated from the vehicle body vibration spectrum; The carrier frequency of the gradient heating pulse or preheating signal is modulated to a frequency band that matches the characteristic frequency band.

7. The snowmobile power battery structure for extreme cold environments according to claim 1, characterized in that, The protection board BMS (7) is further configured to run a digital twin-based policy self-evolution module, including: The digital twin model of the battery module is maintained in the protection board BMS (7) or the cloud. The digital twin model integrates three-dimensional geometry, material properties, electrochemical-thermal coupling characteristics and historical degradation data. In the actual heating control process, sensor data is synchronized to the digital twin model in real time, and the adaptive focus heating strategy, phase change interface synchronous preheating strategy and vibration spectrum matching strategy are simulated and evaluated in advance in the digital twin model. Based on a reinforcement learning framework, a new control strategy with better energy efficiency ratio is generated and screened using a digital twin simulation environment. After passing safety verification, the strategy is updated to the actual control loop.

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