Battery pack thermal management system and temperature control method

Abstract

The invention discloses a battery pack thermal management system and a temperature control method, and relates to the technical field of battery pack thermal management, and the battery pack thermal management system comprises a composite phase change material layer, a micro-channel heat transfer network, a temperature monitoring and auxiliary temperature adjusting system and an intelligent control system. According to the battery pack heat management system and the temperature control method, through cooperation of the composite phase change material, the enhanced heat transfer structure and intelligent regulation, the temperature of the battery cell is stabilized at 25 + / -2 DEG C in the working environment of-30 DEG C to 50 DEG C, the temperature difference is smaller than or equal to 2 DEG C, the temperature is reduced by 60-70% compared with that of traditional liquid cooling, the normal-temperature auxiliary energy consumption is smaller than 1% of the battery capacity, the energy consumption in the whole working condition is reduced by 40-50%, and the working efficiency is improved. The composite phase-change material covers the range of-10 DEG C to 55 DEG C, so that starting is carried out for only 5 minutes at the low temperature of-30 DEG C, the cycle life of the battery cell is prolonged by 30-50% through global constant temperature, the volume ratio of the phase-change material is 30%, leakage is avoided, the structure is compact and safe, and the strict requirement of a counterweight card is met.

Description

Technical Field

[0001] This invention relates to the field of battery pack thermal management technology, specifically to a battery pack thermal management system and temperature control method. Background Technology

[0002] Battery packs for heavy-duty electric trucks are characterized by large capacity, typically 300-600kWh, and hundreds or even thousands of cells. During charging and discharging, they generate a significant amount of heat, and due to the dense arrangement and enclosed space of the cells, localized overheating is likely to occur. Furthermore, the operating environment for heavy-duty trucks experiences large temperature variations, generally ranging from -30℃ to above 40℃. Low temperatures reduce battery activity, leading to capacity decay, while high temperatures pose a risk of thermal runaway.

[0003] Current battery pack thermal management systems mostly employ liquid cooling or air cooling, but these have significant drawbacks: liquid cooling systems rely on pipeline circulation, which can easily lead to cell temperature differences exceeding 5°C due to uneven flow distribution; air cooling systems have low heat exchange efficiency, and low-temperature heating requires additional power, accounting for 5-8% of the battery capacity; traditional single phase change materials (PCMs), while capable of heat storage, have fixed phase change points, such as paraffin-based materials at around 50°C, making them unsuitable for wide-temperature-range operation, and they also have low thermal conductivity, i.e., 0.2-0.5 W / (m²). K), heat transfer is slow, making it difficult to achieve uniform temperature across the entire area. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a battery pack thermal management system and temperature control method, solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a battery pack thermal management system, comprising a composite phase change material layer, a microchannel heat transfer network, a temperature monitoring and auxiliary temperature regulation system, and an intelligent control system; The composite phase change material layer is a sandwich structure composed of a low-temperature phase change unit, a high-temperature phase change unit, and a thermally conductive reinforcement. A microchannel heat transfer network is embedded inside the composite phase change material layer for circulating heat exchange medium; The temperature monitoring and auxiliary temperature control system is used to collect the cell temperature and realize heating or heat dissipation regulation; The intelligent control system receives temperature data and controls the operation of the auxiliary temperature control system.

[0006] Furthermore, the low-temperature phase change unit is composed of n-octadecane and decanoic acid in a 3:1 mass ratio. The n-octadecane has a phase change point of -10℃ and a latent heat of 200kJ / kg, while the decanoic acid has a phase change point of 10℃ and a latent heat of 180kJ / kg. The low-temperature phase change unit is filled at the bottom of the battery cell. The high-temperature phase change unit is composed of paraffin wax and stearic acid in a 2:1 mass ratio. The paraffin wax has a phase change point of 45℃ and a latent heat of 220kJ / kg, while the stearic acid has a phase change point of 55℃ and a latent heat of 190kJ / kg. The high-temperature phase change unit is wrapped around the top and sides of the battery cell.

[0007] Furthermore, the thermally conductive reinforcement is a graphene or expanded graphite composite sheet with a thickness of 2 mm and a thermal conductivity of 30-50 W / (m²). K), and embedded in the composite phase change material layer to form a three-dimensional heat transfer network.

[0008] Furthermore, the microchannel heat transfer network includes an aluminum alloy microchannel plate with a channel diameter of 3 mm and a spacing of 10 mm. Antifreeze flows through the channels, and the freezing point of the antifreeze is -40℃. The aluminum alloy microchannel plate is connected to the liquid cooling main pipeline outside the battery pack through branch pipes, and the contact area with the cell shell is ≥80%.

[0009] Furthermore, the temperature monitoring and auxiliary temperature control system includes 25 NTC temperature sensors, a PTC heater, a liquid cooling pump, and a two-way valve; the 25 NTC temperature sensors are arranged in a 5×5 array with an accuracy of ±0.5℃; the PTC heater has a power of 5kW and is installed at the inlet of the liquid cooling circuit; the liquid cooling pump has an adjustable flow rate of 5-15L / min; and the two-way valve is used to control the flow direction of the antifreeze to achieve switching between heating and heat dissipation modes.

[0010] Furthermore, the intelligent control system adopts a dual-core MCU controller with a main frequency of 120MHz. It receives temperature sensor data through the CAN bus and automatically starts auxiliary temperature adjustment when a local temperature difference >2℃ or the temperature deviates from the range of 25±2℃.

[0011] A temperature control method is provided, which is applied to the aforementioned battery pack thermal management system. The temperature control method includes wide-range adaptive adjustment, global temperature difference control, and charge-discharge coordinated regulation. The wide-range adaptive adjustment initiates different temperature regulation strategies according to the ambient temperature. The global temperature difference control balances the heat distribution through thermally conductive reinforcement and microchannel network. The charge-discharge coordinated regulation pre-activates the temperature regulation function according to the charge-discharge state.

[0012] Furthermore, the specific process of the wide temperature range adaptive adjustment is as follows: When the ambient temperature is < -10℃, the low-temperature phase change unit solidifies and releases heat, which, combined with PTC heating, raises the temperature of the antifreeze to 30℃, and heats the battery cell through microchannels; when the ambient temperature is 10-45℃, the phase change material regulates itself through heat absorption and release; when the ambient temperature is > 50℃, the high-temperature phase change unit melts and absorbs heat, and the liquid cooling pump operates at full load to remove the heat. The specific process for global temperature difference control is as follows: The graphene composite sheet rapidly conducts heat from local hot spots to the phase change material layer. The microchannel network dynamically distributes the flow, increasing the flow rate of the corresponding channel in the hot spot area by 20%, ensuring that the temperature difference between any two cells is ≤2℃. The specific process of the charge-discharge coordinated regulation is as follows: During charging, the liquid cooling pump is started in advance at 8L / min to absorb the heat generated during charging using the high-temperature phase change unit; during discharging, the liquid cooling system is pre-activated when the current is >300A to avoid overheating and saturation of the phase change material.

[0013] Furthermore, the battery pack thermal management system also includes: A phase change material performance real-time monitoring and adaptive compensation module is embedded in an intelligent control system. It assesses the latent heat decay state by collecting temperature change rate and expansion pressure data of the phase change material and dynamically adjusts auxiliary temperature control parameters. The phase change material performance real-time monitoring and adaptive compensation module includes a miniature pressure sensor embedded inside the phase change material layer, with an accuracy of ±1 kPa, used to monitor pressure changes caused by phase change or aging of the phase change material.

[0014] Furthermore, the specific process of the phase change material performance real-time monitoring and adaptive compensation module is as follows: The latent heat decay rate is calculated using temperature and pressure correlation data. When the decay rate is greater than 15%, the PTC heating power is increased by 10-20% or the liquid cooling pump flow rate is increased by 15-25%.

[0015] This invention provides a battery pack thermal management system and temperature control method, which have the following beneficial effects: 1. This battery pack thermal management system and temperature control method, through the synergy of composite phase change materials, enhanced heat transfer structure and intelligent regulation, achieves stable cell temperature of 25±2℃ in an operating environment of -30℃ to 50℃, with a temperature difference of ≤2℃, which is 60-70% lower than traditional liquid cooling. The auxiliary energy consumption at room temperature is <1% of the battery capacity, resulting in a 40-50% reduction in energy consumption under all operating conditions. The composite phase change material covers the range of -10℃ to 55℃, enabling startup in just 5 minutes at -30℃. The constant temperature across the entire range increases the cell cycle life by 30-50%. The phase change material accounts for 30% of the volume without leakage, and the structure is compact and safe, making it suitable for the stringent requirements of heavy trucks.

[0016] 2. The battery pack thermal management system and temperature control method integrate a phase change material performance real-time monitoring and adaptive compensation module to construct a full life cycle performance degradation response mechanism: a micro pressure sensor and an NTC temperature sensor work together to collect the pressure change peak and temperature change rate during the phase change process. The latent heat degradation degree is accurately quantified through a temperature and pressure correlation analysis algorithm. When the degradation degree exceeds the threshold of 15%, the system immediately starts dynamic compensation and regulation, thereby ensuring that even if the latent heat of the phase change material decays by more than 15%, the cell temperature can still be stably controlled within the target range of 25±2℃, and the temperature difference between any two cells is always ≤2℃. This completely avoids the risk of temperature runaway caused by material degradation in traditional systems and fundamentally maintains the core temperature control accuracy. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the cross-sectional structure of a battery pack according to the present invention, which describes a battery pack thermal management system and temperature control method. Figure 2 This is a logic block diagram of the battery pack thermal management and temperature control method under low temperature environment according to the present invention. Figure 3 This is an adaptive logic block diagram of a battery pack thermal management system and temperature control method under normal temperature conditions according to the present invention. Figure 4 This is a block diagram of the battery pack thermal management and temperature control logic under high temperature environment according to the present invention, which describes a battery pack thermal management system and temperature control method. Figure 5 This is a comparison table of cell temperature difference control between the present invention and traditional liquid cooling systems; Figure 6 This is a comparison table of energy consumption control between the present invention and traditional pure liquid cooling systems; Figure 7 This is a comparison table of the temperature range adaptability of the present invention with that of traditional thermal management systems (liquid cooling, air cooling); Figure 8 This is a comparison table of the cell cycle life of the present invention and traditional thermal management systems; Figure 9 This table compares the structural safety and volume of the present invention with those of traditional liquid cooling systems. Detailed Implementation

[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0019] like Figures 1-9 As shown, the present invention provides a technical solution: a battery pack thermal management system, comprising a composite phase change material layer, a microchannel heat transfer network, a temperature monitoring and auxiliary temperature regulation system, and an intelligent control system; The composite phase change material layer is a sandwich structure composed of a low-temperature phase change unit, a high-temperature phase change unit, and a thermally conductive reinforcement. The low-temperature phase change unit is composed of a 3:1 mass ratio of n-octadecane and decanoic acid. The n-octadecane has a phase change point of -10℃ and a latent heat of 200 kJ / kg, while the decanoic acid has a phase change point of 10℃ and a latent heat of 180 kJ / kg. This low-temperature phase change unit is located at the bottom of the battery cell. The high-temperature phase change unit is composed of a 2:1 mass ratio of paraffin wax and stearic acid. The paraffin wax has a phase change point of 45℃ and a latent heat of 220 kJ / kg, while the stearic acid has a phase change point of 55℃ and a latent heat of 190 kJ / kg. This high-temperature phase change unit is wrapped around the top and sides of the battery cell. The thermal conductivity enhancement material is graphene or expanded graphite composite sheet with a thickness of 2 mm and a thermal conductivity of 30-50 W / (m²). K), and embedded in the composite phase change material layer to form a three-dimensional heat transfer network. A microchannel heat transfer network is embedded inside the composite phase change material layer for circulating heat exchange medium; The microchannel heat transfer network includes an aluminum alloy microchannel plate with a channel diameter of 3mm and a spacing of 10mm. Antifreeze flows through the channels, and the freezing point of the antifreeze is -40℃. The aluminum alloy microchannel plate is connected to the liquid cooling main pipeline outside the battery pack through branch pipes, and the contact area with the cell shell is ≥80%. The temperature monitoring and auxiliary temperature control system is used to collect the cell temperature and realize heating or heat dissipation regulation; The temperature monitoring and auxiliary temperature control system includes 25 NTC temperature sensors, a PTC heater, a liquid cooling pump, and a two-way valve. The 25 NTC temperature sensors are arranged in a 5×5 array with an accuracy of ±0.5℃. The PTC heater has a power of 5kW and is installed at the inlet of the liquid cooling circuit. The flow rate of the liquid cooling pump is adjustable from 5-15L / min. The two-way valve is used to control the flow direction of the antifreeze to achieve switching between heating and heat dissipation modes. The intelligent control system receives temperature data and controls the operation of the auxiliary temperature control system; The intelligent control system uses a dual-core MCU controller with a main frequency of 120MHz. It receives temperature sensor data via CAN bus and automatically starts auxiliary temperature adjustment when a local temperature difference >2℃ or the temperature deviates from the range of 25±2℃.

[0020] A temperature control method is applied to the above-mentioned battery pack thermal management system. The temperature control method includes wide-range adaptive adjustment, global temperature difference control, and charge-discharge coordinated regulation. The wide-range adaptive adjustment activates different temperature regulation strategies according to the ambient temperature. The global temperature difference control balances the heat distribution through thermally conductive reinforcement and microchannel network. The charge-discharge coordinated regulation pre-activates the temperature regulation function according to the charge-discharge state. The specific process for wide-temperature-range adaptive regulation is as follows: When the ambient temperature is < -10℃, the low-temperature phase change unit solidifies and releases heat, which, combined with PTC heating, raises the temperature of the antifreeze to 30℃, and heats the battery cell through microchannels; when the ambient temperature is 10-45℃, the phase change material regulates itself through heat absorption and release; when the ambient temperature is > 50℃, the high-temperature phase change unit melts and absorbs heat, and the liquid cooling pump operates at full load to remove the heat. The specific process for global temperature difference control is as follows: The graphene composite sheet rapidly conducts heat from local hot spots to the phase change material layer. The microchannel network dynamically distributes the flow, increasing the flow rate of the corresponding channel in the hot spot area by 20%, ensuring that the temperature difference between any two cells is ≤2℃. The specific process of the charge-discharge coordinated regulation is as follows: During charging, the liquid cooling pump is started in advance at 8L / min to absorb the heat generated during charging using the high-temperature phase change unit; during discharging, the liquid cooling system is pre-activated when the current is >300A to avoid overheating and saturation of the phase change material.

[0021] The battery pack thermal management system also includes: A phase change material performance real-time monitoring and adaptive compensation module is embedded in an intelligent control system. It assesses the latent heat decay state by collecting temperature change rate and expansion pressure data of the phase change material and dynamically adjusts auxiliary temperature control parameters. The phase change material performance real-time monitoring and adaptive compensation module includes a miniature pressure sensor, which is embedded inside the phase change material layer and has an accuracy of ±1 kPa. It is used to monitor pressure changes caused by phase change or aging of the phase change material. The specific process of the real-time monitoring and adaptive compensation module for phase change material properties is as follows: The latent heat decay rate is calculated using temperature and pressure correlation data. When the decay rate is greater than 15%, the PTC heating power is increased by 10-20% or the liquid cooling pump flow rate is increased by 15-25%.

[0022] Specific examples are as follows: Preparation of composite phase change materials: 99% pure n-octadecane and decanoic acid (analytical grade) were melted and stirred at 80℃ in a 3:1 mass ratio, and 5% expanded graphite (50 μm) was added. The mixture was stirred at 500 r / min for 30 minutes. Preparation of high-temperature phase change unit: Paraffin and stearic acid are mixed in a 2:1 ratio, 8% graphene microsheets (5nm) are added, and the mixture is ultrasonically dispersed at 300W for 20 minutes; Preparation of thermal conductivity reinforcement: 300-mesh expanded graphite and graphene were pressed in a 1:1 ratio at a pressing pressure of 5 MPa to form a 2 mm thick sheet with a thermal conductivity of 42 W / (m²). K); Battery pack structure: It adopts a 2P120S cell arrangement, with a total of 240 cells, 280Ah, and filled with 80kg of composite phase change material; the bottom is a 5mm low temperature unit, the top and the sides are 3mm high temperature units, and graphene composite sheets are inserted between every two cells. The microchannel plate is made of 6061 aluminum alloy die casting, with 30 strips on each plate, and the contact parts are roughened to enhance heat transfer. Auxiliary temperature control system parameters: NTC sensor sampling at 1Hz; PTC is a ceramic heating element with a size of 100mm×80mm, and its power is adjusted via PWM; the liquid cooling pump is a DBP50 model with a head of 5m, and its flow rate is adjusted via a 0-5V signal; the two-way valve response is <50ms. Control flow example: Low temperature start-up: When the cell temperature is <10℃ at an ambient temperature of -20℃, the low temperature phase change unit is activated, the antifreeze is heated to 30℃ by PTC, the liquid cooling pump runs at 5L / min, and the temperature rises to 23℃ within 15 minutes, with a temperature difference ≤1.5℃. High-temperature fast charging: At an ambient temperature of 40℃, using a current of 500A, the liquid cooling pump is started 5 minutes before charging. The liquid cooling pump runs at 8L / min. When the local temperature reaches 30℃, the flow rate of the corresponding channel increases to 10L / min, with a maximum temperature difference of 1.8℃. Heavy-load discharge: Using 400A current and 35℃ ambient temperature, adjust the pump speed to 10L / min 30 seconds in advance, and use microchannels to remove 10% of the unabsorbed heat to maintain the temperature at 26℃. Based on the above description, such as Figure 5 As shown in the comparison table, compared to traditional liquid cooling systems that rely on pipe circulation to distribute coolant, which are limited by differences in flow resistance and uneven local heat exchange efficiency, resulting in temperature differences between battery cells often exceeding 5°C, and even reaching 8-10°C under extreme conditions, causing some battery cells to be in a state of high or low temperature fluctuations for a long time, accelerating aging and increasing the risk of thermal runaway, this invention uses a sandwich structure in the composite phase change material layer. In this structure, graphene composite sheets form a three-dimensional heat transfer network, which can quickly conduct heat from local hot spots to the entire phase change material layer within 10 seconds, avoiding heat accumulation. The aluminum alloy microchannel network dynamically distributes the flow rate through an intelligent control system. The flow rate of the corresponding channel in the hot spot area is automatically increased by 20%, which precisely enhances heat dissipation. In a wide temperature range environment of -30℃ to 50℃, the low temperature phase change unit changes phase at -10℃ to 10℃ and the high temperature phase change unit changes phase at 45℃ to 55℃. Through heat absorption and heat release, the temperature fluctuation is buffered. With the assistance of PTC heating and liquid cooling pump speed regulation, the temperature of the entire cell is stabilized at 25±2℃. The temperature difference between any two cells is strictly controlled within 2℃. Compared with the temperature difference of more than 5℃ in the traditional liquid cooling system, the temperature difference of this invention is reduced by 60-70%, providing the cell with an extremely stable working temperature environment. like Figure 6As shown in the comparison table, traditional pure liquid cooling systems require continuous coolant circulation. Even under normal operating conditions (10-45℃), auxiliary equipment such as liquid cooling pumps and valves still consume power continuously, with auxiliary energy consumption accounting for 2-3% of the battery capacity. During low-temperature heating, the PTC consumes an additional 5-8% of power, further exacerbating the loss of battery life. This invention significantly reduces energy consumption through the energy-saving logic of phase change materials autonomously regulating temperature and auxiliary systems starting on demand. Within the normal temperature range of 10-45℃, the composite phase change material achieves autonomous balance through the phase change characteristics of heat release in the low-temperature unit and heat absorption in the high-temperature unit. The battery cell generates heat, eliminating the need for PTC heating or high-load operation of the liquid cooling pump. At this time, the auxiliary system maintains only the minimum power consumption, i.e., sensor monitoring and controller standby, with energy consumption accounting for less than 1% of the battery capacity. Only in extreme low temperatures (<-10℃) or high temperatures (>50℃) is the PTC activated or the liquid cooling pump speed increased. Compared with the traditional pure liquid cooling system's high-energy-consumption mode throughout, this invention reduces overall energy consumption by 40-50% under all operating conditions. Especially in the normal temperature range scenario of long-distance heavy truck transportation, the energy-saving effect can be directly converted into a range increase of 10-15km. like Figure 7 The comparison table shows that heavy-duty trucks operate in environments with extreme temperature differences, ranging from -30°C in northern winters to over 50°C in southern summers. Traditional thermal management systems are difficult to adapt to these conditions. For example, single liquid cooling systems experience a sharp drop in heating efficiency below -20°C due to decreased coolant fluidity, often resulting in start-up times exceeding 30 minutes. Single air cooling systems suffer from insufficient heat exchange at high temperatures, easily leading to overheating of the battery cells. The composite phase change material layer of this invention, through its layered design, covers a wide temperature range: the low-temperature phase change unit is composed of a 3:1 mixture of n-octadecane (phase change point -10°C) and decanoic acid (phase change point 10°C), which solidifies and releases heat below -10°C, providing basic heat for the battery cells; the high-temperature phase change unit is composed of paraffin wax (phase change point 45°C) and stearic acid (phase change point 10°C). Mixing phase change materials (at a temperature of 55℃) in a 2:1 ratio, the material melts and absorbs heat above 45℃, buffering high-temperature heat generation. Combined with intelligent auxiliary temperature control: at extreme low temperatures of -30℃, the low-temperature phase change unit solidifies and releases heat, working in conjunction with a PTC heater (5kW) to heat the antifreeze to 30℃. This heat is then rapidly conducted to the battery cell through microchannels, raising the cell temperature from -30℃ to above 20℃ in just 5 minutes, meeting startup requirements. At temperatures above 50℃, the high-temperature phase change unit continuously absorbs heat, and the liquid cooling pump operates at full load (15L / min) to remove excess heat. This phase change material heat storage combined with auxiliary temperature control and energy replenishment mode achieves stable operation in environments ranging from -30℃ to 50℃, completely breaking through the temperature range limitations of traditional systems. like Figure 8As shown in the comparison table, the cycle life of the battery cell is closely related to the operating temperature: when the temperature fluctuation exceeds ±5℃, the rate of side reactions inside the battery cell increases by 2-3 times, leading to accelerated capacity decay; long-term high temperature (>30℃) will cause electrolyte decomposition, while low temperature (<15℃) will exacerbate lithium dendrite growth. Due to the large temperature difference and unstable temperature in traditional systems, the cycle life of the battery cell is usually only about 1500 times. However, this invention delays the aging of the battery cell from the root by controlling the temperature across the entire range (25±2℃): the uniform control of temperature difference ≤2℃ avoids excessive decay of local battery cells and ensures that the performance of the entire battery pack decays synchronously. Actual test data shows that the cycle life of the battery pack using this invention is increased from the traditional 1500 times to 2000-2250 times, an increase of 30-50%. Based on the average annual charge and discharge of heavy trucks of 300 times, the traditional battery pack needs to be replaced every 5 years, while the battery pack of this invention can be extended to 6.5-7.5 years, reducing the cost of a single replacement by about 40,000 yuan, significantly reducing the total life cycle cost. like Figure 9 The comparison table shows that traditional liquid cooling systems rely on complex piping that occupies 15-20% of the battery pack volume. Pipe joints are prone to coolant leakage due to vibration and aging, posing a short-circuit risk. Single phase change materials account for less than 20% of the total volume, resulting in limited heat storage capacity and poor thermal conductivity, making it difficult to dissipate heat during thermal runaway. In contrast, this invention employs high-density phase change material filling and an integrated structural design: composite phase change materials account for 30% of the volume, enabling solid or semi-solid phase change heat storage without a flowing medium, completely eliminating leakage risks. Graphene, expanded graphite composite sheets, and aluminum alloy microchannel plates are embedded in the phase change material layer to form heat storage. The integrated structure for heat transfer and dissipation reduces the overall volume by 10% compared to traditional liquid cooling systems, making it suitable for the compact installation space of heavy-duty trucks. In terms of thermal runaway safety protection, the microchannel network can quickly conduct heat from the phase change material layer when the battery cell generates abnormal heat, with a heat dissipation rate of 200W / m². Combined with the melting and heat absorption of the high-temperature phase change unit, the latent heat of 220kJ / kg delays the thermal runaway propagation time to more than 15 minutes, providing sufficient time for the vehicle's fire protection system to respond. Compared with the risk of heat dissipation failure after the rupture of traditional liquid cooling pipes, the safety of this invention is significantly improved, meeting the stringent safety standards of heavy-duty trucks. Therefore, this invention achieves stable cell temperature of 25±2℃ with a temperature difference of ≤2℃ in an operating environment of -30℃ to 50℃ through the synergy of composite phase change materials, enhanced heat transfer structure and intelligent regulation. This reduces the temperature by 60-70% compared to traditional liquid cooling, and the auxiliary energy consumption at room temperature is <1% of the battery capacity, resulting in a 40-50% reduction in energy consumption under all operating conditions. The composite phase change material covers the range of -10℃ to 55℃, enabling startup in just 5 minutes at -30℃. The constant temperature across the entire range increases the cell cycle life by 30-50%. The phase change material accounts for 30% of the volume without leakage, and the structure is compact and safe, making it suitable for the stringent requirements of heavy trucks.

[0023] The phase change material performance real-time monitoring and adaptive compensation module structure is integrated into the intelligent control system. It includes a miniature pressure sensor embedded in the phase change material layer. The miniature pressure sensor model is MSP-10. There is one miniature pressure sensor in every 10 cell areas. The accuracy is ±1kPa and the sampling frequency is 5Hz. It also includes a temperature and pressure correlation analysis algorithm. The specific algorithm for temperature and pressure correlation analysis is as follows: During the system initialization phase (when the phase change material is in a brand new state), the temperature change rate of the phase change material under standard operating conditions is collected by an NTC temperature sensor and recorded as the initial temperature change rate. Simultaneously, the peak expansion pressure of the phase change material during this stage was collected using a miniature pressure sensor and recorded as the initial peak pressure. ; Real-time data acquisition: During daily system operation, the NTC temperature sensor continuously collects the temperature change rate during the phase transition stage of the phase change material. , ,in This represents the temperature change during the phase transition phase. To correspond to the change over time, a miniature pressure sensor synchronously acquires the peak expansion pressure during this phase. ; Attenuation calculation: based on real-time data acquisition and initial parameters The latent heat decay of phase change materials is calculated using an algorithmic formula, as follows: Compensation Judgment and Execution: If the calculated attenuation is >15%, the intelligent control system will trigger adaptive compensation regulation, increasing the PTC heating power by 10-20% in low-temperature conditions and increasing the liquid cooling pump flow rate by 15-25% in high-temperature conditions; if the attenuation is ≤15%, the original temperature control strategy will be maintained.

[0024] Implementation example: During system initialization, record the new phase change material. Such as the initial phase change unit at high temperature =0.8 and , as initially =3 ; Real-time data collection during daily operation and Dynamically calculate the attenuation rate; When the attenuation rate is greater than 15%, compensation regulation is triggered: under low temperature conditions, the PTC heating power is increased by 10-20%, such as from 3kW to 3.3-3.6kW; under high temperature conditions, the liquid cooling pump flow rate is increased by 15-25%, such as from 15L / min to 17.25-18.75L / min, to compensate for the insufficient heat storage capacity of the phase change material by strengthening auxiliary temperature regulation. Based on the above description, this invention constructs a full-lifecycle performance degradation response mechanism by integrating a phase change material performance real-time monitoring and adaptive compensation module: a micro pressure sensor and an NTC temperature sensor work together to collect the peak pressure change and temperature change rate during the phase change process, and accurately quantify the latent heat degradation degree through a temperature and pressure correlation analysis algorithm. When the degradation degree is detected to exceed the threshold of 15%, the system immediately starts dynamic compensation and control, thereby ensuring that even if the latent heat degradation of the phase change material is more than 15%, the cell temperature can still be stably controlled within the target range of 25±2℃, and the temperature difference between any two cells is always ≤2℃. This completely avoids the risk of temperature runaway caused by material degradation in traditional systems and fundamentally maintains the core temperature control accuracy.

[0025] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A battery pack thermal management system, characterized in that: It includes a composite phase change material layer, a microchannel heat transfer network, a temperature monitoring and auxiliary temperature control system, and an intelligent control system; The composite phase change material layer is a sandwich structure composed of a low-temperature phase change unit, a high-temperature phase change unit, and a thermally conductive reinforcement. A microchannel heat transfer network is embedded inside the composite phase change material layer for circulating heat exchange medium; The temperature monitoring and auxiliary temperature control system is used to collect the cell temperature and realize heating or heat dissipation regulation; The intelligent control system receives temperature data and controls the operation of the auxiliary temperature control system.

2. The battery pack thermal management system according to claim 1, characterized in that: The low-temperature phase change unit is composed of n-octadecane and decanoic acid in a 3:1 mass ratio. The n-octadecane has a phase change point of -10℃ and a latent heat of 200kJ / kg, while the decanoic acid has a phase change point of 10℃ and a latent heat of 180kJ / kg. The low-temperature phase change unit is filled at the bottom of the battery cell. The high-temperature phase change unit is composed of paraffin wax and stearic acid in a 2:1 mass ratio. The paraffin wax has a phase change point of 45℃ and a latent heat of 220kJ / kg, while the stearic acid has a phase change point of 55℃ and a latent heat of 190kJ / kg. The high-temperature phase change unit is wrapped around the top and sides of the battery cell.

3. The battery pack thermal management system according to claim 1, characterized in that: The thermal conductivity enhancement material is graphene or expanded graphite composite sheet with a thickness of 2 mm and a thermal conductivity of 30-50 W / (m²). K), and embedded in the composite phase change material layer to form a three-dimensional heat transfer network.

4. The battery pack thermal management system according to claim 1, characterized in that: The microchannel heat transfer network includes an aluminum alloy microchannel plate with a channel diameter of 3 mm and a spacing of 10 mm. Antifreeze flows through the channels, and the freezing point of the antifreeze is -40℃. The aluminum alloy microchannel plate is connected to the liquid cooling main pipeline outside the battery pack through branch pipes, and the contact area with the cell shell is ≥80%.

5. A battery pack thermal management system according to claim 3, characterized in that: The temperature monitoring and auxiliary temperature control system includes 25 NTC temperature sensors, a PTC heater, a liquid cooling pump, and a two-way valve. The 25 NTC temperature sensors are arranged in a 5×5 array with an accuracy of ±0.5℃. The PTC heater has a power of 5kW and is installed at the inlet of the liquid cooling circuit. The flow rate of the liquid cooling pump is adjustable from 5 to 15L / min. The two-way valve is used to control the flow direction of the antifreeze to achieve switching between heating and heat dissipation modes.

6. A battery pack thermal management system according to claim 1, characterized in that: The intelligent control system uses a dual-core MCU controller with a main frequency of 120MHz. It receives temperature sensor data via CAN bus and automatically starts auxiliary temperature adjustment when a local temperature difference >2℃ or the temperature deviates from the range of 25±2℃.

7. A battery pack thermal management system according to claim 1, characterized in that: The battery pack thermal management system also includes: A phase change material performance real-time monitoring and adaptive compensation module is embedded in an intelligent control system. It assesses the latent heat decay state by collecting temperature change rate and expansion pressure data of the phase change material and dynamically adjusts auxiliary temperature control parameters. The phase change material performance real-time monitoring and adaptive compensation module includes a miniature pressure sensor embedded inside the phase change material layer, with an accuracy of ±1 kPa, used to monitor pressure changes caused by phase change or aging of the phase change material.

8. A battery pack thermal management system according to claim 7, characterized in that: The specific process of the phase change material performance real-time monitoring and adaptive compensation module is as follows: The latent heat decay rate is calculated using temperature and pressure correlation data. When the decay rate is greater than 15%, the PTC heating power is increased by 10-20% or the liquid cooling pump flow rate is increased by 15-25%.

9. A temperature control method, applied to a battery pack thermal management system according to any one of claims 1-8, characterized in that: The temperature control method includes wide-range adaptive adjustment, global temperature difference control, and charge-discharge coordinated regulation; the wide-range adaptive adjustment activates different temperature regulation strategies according to the ambient temperature, the global temperature difference control balances heat distribution through thermally conductive reinforcement and microchannel network, and the charge-discharge coordinated regulation pre-activates the temperature regulation function according to the charge-discharge state.

10. A temperature control method according to claim 9, characterized in that: The specific process of the wide temperature range adaptive adjustment is as follows: When the ambient temperature is < -10℃, the low-temperature phase change unit solidifies and releases heat, which, combined with PTC heating, raises the temperature of the antifreeze to 30℃, and heats the battery cell through microchannels; when the ambient temperature is 10-45℃, the phase change material regulates itself through heat absorption and release; when the ambient temperature is > 50℃, the high-temperature phase change unit melts and absorbs heat, and the liquid cooling pump operates at full load to remove the heat. The specific process for global temperature difference control is as follows: The graphene composite sheet rapidly conducts heat from local hot spots to the phase change material layer. The microchannel network dynamically distributes the flow, increasing the flow rate of the corresponding channel in the hot spot area by 20%, ensuring that the temperature difference between any two cells is ≤2℃. The specific process of the charge-discharge coordinated regulation is as follows: During charging, the liquid cooling pump is started in advance at 8L / min to absorb the heat generated during charging using the high-temperature phase change unit; during discharging, the liquid cooling system is pre-activated when the current is >300A to avoid overheating and saturation of the phase change material.

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