A thermoelectric coupling-based motor-battery integrated thermal management system and method for electric vehicles

Abstract

The present application relates to the field of electric vehicle thermal management, in particular to a kind of electric vehicle motor-battery integrated thermal management system and method based on thermoelectric coupling;The system of the present application includes motor cooling circuit, battery thermal management circuit, thermoelectric coupling heat exchange module, sensor unit and controller.The present application adjusts the fluid distribution of multiple through proportional valve and the working mode of thermoelectric component by controller, realizes energy cross-circuit scheduling.In preheating, motor waste heat is preferentially transported to battery, and when waste heat is insufficient, thermoelectric module actively pumps heat, and when heating is not needed, energy is recovered by using temperature difference generation, the present application not only reduces the dependence on PTC heating, realizes waste heat recovery and electric energy regeneration, and at the same time, through dynamic threshold closed-loop control, the temperature control precision and system reliability are improved.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle thermal management, and specifically to an integrated thermal management system and method for electric vehicle motor-battery based on thermoelectric coupling. Background Technology

[0002] The power batteries and motors of electric vehicles generate a lot of heat during operation, and their thermal management performance directly affects the efficiency, safety and lifespan of the vehicle, which has become a key technical challenge in the industry. Especially under high load or fast charging conditions, excessively high battery and motor temperatures can easily lead to decreased efficiency, system damage and even safety hazards, so there is an urgent need for efficient and precise temperature control solutions.

[0003] Currently, the mainstream solution uses independent motor cooling circuits and battery thermal management circuits, which are liquid-cooled through pumps, radiators, and cooling plates, respectively. In addition, in recent years, there have been attempts to introduce thermoelectric modules to actively heat or cool using the Peltier effect and recover waste heat based on the Seebeck effect.

[0004] However, existing independent liquid cooling systems have the following drawbacks: low-temperature battery heating relies on high-energy-consuming PTC heaters, resulting in low energy efficiency; the motor and battery temperature control operate independently, and the lack of coordination leads to lag in response; a large amount of waste heat from the motor is not utilized, resulting in energy waste; while thermoelectric module solutions face the problems of low thermoelectric conversion efficiency and the need for complex control strategies to coordinate the module, liquid cooling system and battery. Summary of the Invention

[0005] To address the problems mentioned in existing technologies, this invention proposes an integrated thermal management system and method for electric vehicle motor-battery based on thermoelectric coupling. It employs a thermoelectric coupling heat exchange module for heat transfer between the motor and battery, utilizing waste heat from the motor circuit to preheat the battery, and enables efficient waste heat recovery and power generation through the thermoelectric module. Furthermore, by adjusting the flow distribution of the liquid cooling circuit and the operating mode of the thermoelectric module, the temperature of the motor and battery can be precisely controlled, improving the system's energy efficiency and safety. This solves the problems of low energy efficiency, imprecise control, and insufficient waste heat utilization in existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention proposes an integrated thermal management system for electric vehicle motor-battery based on thermoelectric coupling, comprising: The motor cooling circuit includes a drive motor, a motor circulation pump, a first multi-way proportional valve, a first radiator, and a motor cooling plate; The coolant outlet of the drive motor is connected to the first multi-way proportional valve through the motor circulation pump. The first multi-way proportional valve has a first outlet and a second outlet. The first outlet is connected to the inlet of the first radiator, and the second outlet is connected to the inlet of the first liquid-cooled heat exchange plate. The outlet of the first radiator and the outlet of the first liquid-cooled heat exchange plate merge and are connected to the inlet of the motor cooling plate. The outlet of the motor cooling plate is connected to the coolant inlet of the drive motor, forming a closed loop. The battery thermal management circuit includes a power battery pack, a battery circulation pump, a second multi-way proportional valve, a second radiator, and a battery pack cooling plate; The coolant outlet of the power battery pack is connected to the second multi-way proportional valve through the battery circulation pump. The second multi-way proportional valve has a third outlet and a fourth outlet. The third outlet is connected to the inlet of the second radiator, and the fourth outlet is connected to the inlet of the second liquid-cooled heat exchange plate. The outlet of the second radiator and the outlet of the second liquid-cooled heat exchange plate merge and are connected to the inlet of the battery pack cooling plate. The outlet of the battery pack cooling plate is connected to the coolant inlet of the power battery pack, forming a closed loop. A thermoelectric coupling heat exchange module is disposed between a motor cooling circuit and a battery thermal management circuit; it includes a thermoelectric component, a first liquid-cooled heat exchange plate attached to one side of the thermoelectric component and connected to the motor cooling circuit, and a second liquid-cooled heat exchange plate attached to the other side of the thermoelectric component and connected to the battery thermal management circuit; the thermoelectric component forms heat exchange between the motor cooling circuit and the battery thermal management circuit through the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate; The sensor unit is used to collect thermal parameters of the motor cooling circuit and the battery thermal management circuit; The controller is connected to the sensor unit, the first multi-way proportional valve, the second multi-way proportional valve, and the thermoelectric component, respectively. It is used to adjust the fluid distribution ratio of the motor cooling circuit and the battery thermal management circuit and the working mode of the thermoelectric component according to the thermal parameters collected by the sensor unit.

[0007] As a further improvement of the present invention, the sensor unit includes five temperature detectors, which are respectively located at: The coolant outlet of the drive motor is used to monitor the outlet temperature of the motor cooling circuit. The coolant outlet of the first radiator is used to monitor the inlet temperature of the motor cooling circuit; The inside or surface of the power battery pack is used to monitor the real-time temperature of the power battery pack; The coolant outlet of the second radiator is used to monitor the inlet temperature of the battery thermal management circuit. The coolant outlet of the power battery pack is used to monitor the outlet temperature of the battery thermal management circuit.

[0008] As a further improvement of the present invention, the thermoelectric component is an array structure composed of multiple thermoelectric units, used to generate the Peltier effect based on the driving current to transfer heat between the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate; and used to recover waste heat for power generation based on the natural temperature difference between the motor cooling circuit and the battery thermal management circuit.

[0009] As a further improvement of the present invention, each of the thermoelectric units includes a thermoelectric pair, a conductive connection layer, and a ceramic insulating substrate: The thermoelectric couple includes a P-type thermoelectric semiconductor element and an N-type thermoelectric semiconductor element; A conductive connection layer is disposed between the P-type thermoelectric semiconductor element and the N-type thermoelectric semiconductor element to connect the P-type thermoelectric semiconductor element and the N-type thermoelectric semiconductor element in series. The ceramic insulating substrate is disposed at the top and bottom of the thermoelectric assembly to provide mechanical support and electrical insulation, and to conduct heat to the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate as a heat transfer medium.

[0010] As a further improvement of the present invention, the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate are further provided with an enhanced heat exchange structure. The high-heat-exchange structure includes a microchannel flow path, and the microchannel flow path is provided with turbulence columns or staggered fins.

[0011] As a further improvement to the present invention, a bidirectional power conversion circuit is also included: The bidirectional power conversion circuit is connected to the controller and is used to provide a drive current with adjustable polarity and amplitude for the thermoelectric components and to convert the electrical energy generated by the thermoelectric coupling heat exchange module and feed it back to the vehicle electrical system or power battery pack.

[0012] This invention proposes a method for an integrated thermal management system for electric vehicle motor-battery based on thermoelectric coupling. The system described above includes the following steps: S1. Parameter Sensing: The controller obtains the outlet temperature of the motor cooling circuit in real time through the sensor unit. T m,out Inlet temperature T m,in Real-time battery temperature and battery thermal management circuit T b outlet temperature T b,out and inlet temperature T b,in And preset the motor safety threshold. T m,max Battery preheating threshold T b,low Battery cooling threshold T b,highEffective temperature difference threshold for waste heat recovery Δ T pump and the power generation trigger temperature difference threshold Δ T gen ; S2, Motor Protection and Gradient Cooling: When detected... T m,out > T m,max At this time, the controller forces the first multi-way proportional valve to direct all the coolant in the motor cooling circuit to the first radiator; If detected T b > T b,high When the cooling is activated, the following gradient is applied: first, the second multi-way proportional valve is opened to passively dissipate heat using the second radiator; if the passive cooling power is insufficient, the thermoelectric component is instructed to actively transfer the heat from the battery thermal management circuit to the motor cooling circuit and dissipate it using the first radiator. S3. Active preheating based on effective temperature difference: The effective temperature difference Δ T = T m,out T b,out ; When detected T b < T b,low hour: If Δ T ≥Δ T pump If the motor has sufficient waste heat, it will enter the low-power induced waste heat recovery mode: the controller will send an induced current to the thermoelectric component and adjust the first multi-way proportional valve to increase the flow rate of the high-temperature coolant through the first liquid-cooled heat exchange plate, so as to actively transfer the motor waste heat to the battery thermal management circuit. If Δ T <Δ T pump If the motor is deemed to have insufficient residual heat, the system enters the large temperature difference active heat pumping mode: the controller applies a positive current to make the thermoelectric components work and generate the Peltier heating effect, forcibly absorbing heat from the motor cooling circuit and forcibly releasing heat to the battery thermal management circuit. At the same time, the first multi-way proportional valve and the second multi-way proportional valve are adjusted to guide the coolant to flow through the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate respectively, so that the Joule heat generated by the thermoelectric components and the latent heat extracted from the motor cooling circuit are injected into the power battery pack. S4. Waste heat power generation based on temperature polarization effect: When detected T b,low ≤ Tb ≤ T b,high And Δ T >Δ T ge At this time, the controller switches the thermoelectric component to Seebeck power generation mode and increases the temperature difference between the first liquid-cooled heat exchange plate and the second liquid-cooled heat exchange plate by adjusting the opening of the first multi-way proportional valve and the second multi-way proportional valve. At the same time, it adjusts the impedance matching of the bidirectional power conversion circuit to achieve maximum power point tracking power generation.

[0013] As a further improvement to this invention, it also includes system flexible control and reliability optimization strategies: The controller adjusts based on the real-time battery temperature. T b The variable frequency speed of the motor circulation pump and battery circulation pump is finely adjusted in real time by changing the slope of the pump. By matching the coolant flow rate and the drive current of the thermoelectric component, the thermal stress impact of the thermoelectric component during the switching of different modes is reduced. Furthermore, a hysteresis control algorithm is used to determine the switching threshold of each working mode in order to avoid the multi-way proportional valve from generating high-frequency oscillations at the critical point.

[0014] As a further improvement of the present invention, the controller executes a motor safety threshold. T m,max The dynamic correction logic is used for correction, and its expression is as follows:

[0015] In the formula: The corrected motor safety threshold; The reference safe temperature; k 1 represents the environmental impact coefficient; Ambient temperature; To match the overall vehicle speed V The relevant air volume compensation function; k 2 represents the air volume compensation coefficient; The controller executes a battery preheating threshold. T b,low The dynamic correction logic is used for correction, and its expression is as follows:

[0016] In the formula: The corrected battery preheating threshold; This is the battery reference preheating temperature; This is a correction term that increases the preheating target value as the ambient temperature decreases; The controller executes the effective temperature difference threshold Δ for waste heat recovery. T pump The dynamic correction logic is modified, including: The controller is based on the outlet temperature of the motor cooling circuit. T m,out To correct the effective temperature difference threshold Δ of waste heat recovery T pump ; when T m,out When the temperature rises, the controller decreases Δ T pump By triggering the low-power induced waste heat recovery mode in advance, the starting time and proportion of waste heat recovery are dynamically optimized based on the COP characteristics of the thermoelectric component in different temperature ranges.

[0017] As a further improvement of the present invention, a predictive thermal scheduling step is also included: According to the preset terminal charging plan, the controller will trigger the low-power induced waste heat recovery mode or the large temperature difference active heat pumping mode in advance within the preset time window before the vehicle arrives at the charging pile. The controller will use the waste heat of the motor cooling circuit and the active heat pumping of the thermoelectric module to preheat the power battery pack to the optimal fast charging temperature range.

[0018] Compared with the prior art, the present invention achieves the following technical effects: In this invention, the motor cooling circuit and the battery thermal management circuit operate independently, preventing heat exchange. The thermoelectric coupling heat exchange module is positioned between these two circuits and utilizes first and second multi-way proportional valves to dynamically adjust the coolant flow, thus constructing an energy bridge between the motor and the battery. When the battery requires preheating, the residual heat generated in the motor circuit can be proactively transferred to the battery circuit, achieving closed-loop sharing and cascaded utilization of energy within the powertrain. This significantly reduces reliance on external energy sources such as PTC heating and improves overall vehicle energy efficiency. Furthermore, this invention utilizes the Peltier effect of the thermoelectric components to actively absorb heat from the motor circuit and release it to the battery circuit when the motor's residual heat is insufficient. Joule heat and extracted latent heat are injected into the battery pack, overcoming the limitations of traditional heating methods in terms of energy efficiency. While ensuring effective battery preheating, this significantly reduces additional energy consumption and optimizes energy utilization efficiency.

[0019] This invention utilizes the Seebeck effect of thermoelectric components to directly convert the natural temperature difference between the motor and the battery circuit into electrical energy when the battery does not require heating or cooling. This energy is then fed back to the vehicle's electrical system or power battery pack through a bidirectional power conversion circuit, thus realizing a shift from simple energy-consuming temperature control to energy-saving and energy-enhancing systems, further improving the overall energy utilization rate of the system.

[0020] This invention collects five temperature points in real time through a sensor unit. The controller dynamically adjusts the fluid distribution ratio of the multi-way proportional valve and the working mode of the thermoelectric components according to the thermal parameters, realizing high-precision closed-loop temperature control under multiple operating conditions. The system can automatically optimize based on ambient temperature, vehicle speed and real-time temperature difference to avoid local thermal shock. It reduces transient thermal stress on the thermoelectric components through frequency conversion control, thereby improving the quality of temperature control while ensuring the long service life of the thermal management system and the power battery. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the thermoelectric coupling heat exchange module of the present invention; Figure 3 This is a schematic diagram of the internal unit structure of the thermoelectric unit of the present invention; Figure 4 This is a schematic diagram illustrating the working principle of the thermoelectric unit of the present invention, which is based on the Peltier effect for active cooling and preheating, and on the Seebeck effect for waste heat power generation. Figure 5 This is a logic flowchart of the control method of the present invention.

[0022] Reference numerals: 1. Drive motor; 2. Motor circulation pump; 3. First multi-way proportional valve; 4. First radiator; 5. Motor cooling plate; 6. Power battery pack; 7. Battery circulation pump; 8. Second multi-way proportional valve; 9. Second radiator; 10. Battery pack cooling plate; 11. Thermoelectric coupling heat exchange module; 11a. Thermoelectric component; 11b. First liquid-cooled heat exchange plate; 11c. Second liquid-cooled heat exchange plate. Detailed Implementation

[0023] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0028] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0029] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0031] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] like Figure 1 As shown in the figure, this embodiment of an electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling includes: The motor cooling circuit includes a drive motor 1, a motor circulation pump 2, a first multi-way proportional valve 3, a first radiator 4, and a motor cooling plate 5; The coolant outlet of the drive motor 1 is connected to the first multi-way proportional valve 3 through the motor circulation pump 2. The first multi-way proportional valve 3 has a first outlet and a second outlet. The first outlet is connected to the inlet of the first radiator 4, and the second outlet is connected to the inlet of the first liquid-cooled heat exchange plate 11b. The outlet of the first radiator (4) merges with the outlet of the first liquid-cooled heat exchange plate 11b and is connected to the inlet of the motor cooling plate 5. The outlet of the motor cooling plate 5 is connected to the coolant inlet of the drive motor 1 to form a closed loop. The battery thermal management circuit includes a power battery pack 6, a battery circulation pump 7, a second multi-way proportional valve 8, a second radiator 9, and a battery pack cooling plate 10. The coolant outlet of the power battery pack 6 is connected to the second multi-way proportional valve 8 through the battery circulation pump 7. The second multi-way proportional valve 8 has a third outlet and a fourth outlet. The third outlet is connected to the inlet of the second radiator (9), and the fourth outlet is connected to the inlet of the second liquid-cooled heat exchange plate 11c. The outlet of the second radiator 9 merges with the outlet of the second liquid-cooled heat exchange plate 11c and is connected to the inlet of the battery pack cooling plate 10. The outlet of the battery pack cooling plate 10 is connected to the coolant inlet of the power battery pack 6, forming a closed loop. A thermoelectric coupling heat exchange module 11 is disposed between the motor cooling circuit and the battery thermal management circuit; it includes a thermoelectric component 11a, a first liquid-cooled heat exchange plate 11b attached to one side of the thermoelectric component 11a and connected to the motor cooling circuit, and a second liquid-cooled heat exchange plate 11c attached to the other side of the thermoelectric component 11a and connected to the battery thermal management circuit; the thermoelectric component 11a forms heat exchange between the motor cooling circuit and the battery thermal management circuit through the first liquid-cooled heat exchange plate 11b and the second liquid-cooled heat exchange plate 11c; Sensor unit 13 is used to collect thermal parameters of the motor cooling circuit and the battery thermal management circuit; The controller 12 is connected to the sensor unit 13, the first multi-way proportional valve 3, the second multi-way proportional valve 8 and the thermoelectric component 11a respectively, and is used to adjust the fluid distribution ratio of the motor cooling circuit and the battery thermal management circuit and the working mode of the thermoelectric component 11a according to the thermal parameters collected by the sensor unit 13.

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] Figure 1 As shown, the motor cooling circuit in this embodiment is designed to prevent the drive motor 1 from overheating during operation. The motor cooling circuit consists of the drive motor 1, motor circulation pump 2, first multi-way proportional valve 3, first radiator 4, and motor cooling plate 5 connected in series, ultimately returning to the drive motor 1 to form a closed loop. In actual operation, the coolant, driven by the motor circulation pump 2, first flows out from the coolant outlet of the drive motor 1, passes through the inlet of the motor circulation pump 2, and then is sent to the first multi-way proportional valve 3 from the pump outlet. The first multi-way proportional valve 3 in this embodiment has three interfaces, including one inlet and two outlets; the first outlet is connected to the inlet of the first radiator 4 via a pipe, and the second outlet is connected to the inlet of the first liquid-cooled heat exchange plate 11b in the thermoelectric coupling heat exchange module 11.

[0035] The coolant flowing from the first radiator 4 and the coolant flowing from the first liquid-cooled heat exchange plate 11b merge in the pipeline and flow together into the inlet of the motor cooling plate 5. After passing through the cooling plate 5, it returns to the coolant inlet of the drive motor 1 from the outlet of the cooling plate 5. It should be noted that the first multi-way proportional valve 3 dynamically adjusts the ratio of the coolant flow to the first radiator 4 and the coolant flow to the first liquid-cooled heat exchange plate 11b according to the needs of the controller 12. Figure 1As shown, the battery thermal management circuit in this embodiment ensures that the power battery pack 6 always operates within a suitable temperature range. The battery thermal management circuit consists of the power battery pack 6, battery circulation pump 7, second multi-way proportional valve 8, second radiator 9, and battery pack cooling plate 10 connected in series, and finally returning to the power battery pack 6, forming a closed loop. Driven by the battery circulation pump 7, the coolant flows from the coolant outlet of the power battery pack 6, passes through the battery circulation pump 7, and enters the second multi-way proportional valve 8. The second multi-way proportional valve 8 has the same structure: one inlet and two outlets; the third outlet is connected to the inlet of the second radiator 9, and the fourth outlet is connected to the inlet of the second liquid-cooled heat exchange plate 11c in the thermoelectric coupling heat exchange module 11. The coolant flowing from the second radiator 9 merges with the coolant flowing from the second liquid-cooled heat exchange plate 11c and enters the inlet of the battery pack cooling plate 10 together, passing through the cooling plate 10 before returning to the coolant inlet of the power battery pack 6. Similarly, the second multi-way proportional valve 8 can also dynamically adjust the flow ratio to the second radiator 9 and the second liquid-cooled heat exchange plate 11c according to the controller's instructions, thereby flexibly switching between multiple modes such as independent heat dissipation, thermoelectric coupling heating, and thermoelectric coupling cooling.

[0036] It should be noted that in the motor cooling circuit and the battery thermal management circuit, the outlet of the first radiator 4 and the outlet of the first liquid-cooled heat exchange plate 11b merge before being connected to the inlet of the motor cooling plate 5. Similarly, the outlet of the second radiator 9 and the outlet of the second liquid-cooled heat exchange plate 11c also merge before being connected to the inlet of the battery pack cooling plate 10. This ensures that no matter how the first multi-way proportional valve 3 or the second multi-way proportional valve 8 distributes the flow, the coolant in both branches can eventually return to the main circulation, and there will be no situation where the coolant cannot circulate after a branch is completely cut off. like Figure 2 As shown, in this embodiment, the thermoelectric coupling heat exchange module 11 has a thermoelectric component 11a in the middle. A first liquid-cooled heat exchange plate 11b is attached and fixed to the upper side of the thermoelectric component 11a, and a second liquid-cooled heat exchange plate 11c is attached and fixed to the lower side. The first liquid-cooled heat exchange plate 11b has internal flow channels, and the inlet and outlet of the flow channels are connected to the motor cooling circuit. The second liquid-cooled heat exchange plate 11c also has internal flow channels, and the inlet and outlet of the flow channels are connected to the battery thermal management circuit.

[0037] Therefore, the temperature of the first liquid-cooled heat exchange plate 11b represents the temperature on the motor cooling circuit side, the temperature of the second liquid-cooled heat exchange plate 11c represents the temperature on the battery thermal management circuit side, and the thermoelectric component 11a can actively transfer heat between the two sides. It should be noted that the thermoelectric component 11a is not a single piece of thermoelectric material, but is composed of an array of multiple independent thermoelectric units. Each thermoelectric unit can be controlled individually.

[0038] like Figure 3As shown, each thermoelectric unit consists of a pair of P-type thermoelectric semiconductor elements and an N-type thermoelectric semiconductor element, which are connected in series electrically and in parallel thermally through a conductive connection layer. The conductive connection layer is preferably a copper conductor. A ceramic insulating substrate is provided at the top and bottom of the thermoelectric assembly 11a. The ceramic insulating substrate provides mechanical support for the internal thermoelectric pairs, provides electrical insulation, and also serves as a heat transfer medium to transfer heat from the first liquid-cooled heat exchange plate 11b and the second liquid-cooled heat exchange plate 11c to the thermoelectric unit.

[0039] It should be noted that, in this embodiment, microchannel flow paths are also processed inside the first liquid-cooled heat exchange plate 11b and the second liquid-cooled heat exchange plate 11c, and turbulence columns or staggered fins are provided on the inner wall of the microchannels. The purpose is to induce turbulence in the coolant, thereby reducing the contact thermal resistance between the thermoelectric component and the coolant and improving the heat exchange efficiency.

[0040] The system in this embodiment also includes a bidirectional power conversion circuit 14, which is controlled by the controller 12. When the thermoelectric component 11a operates in Peltier mode (active heating or cooling mode), the bidirectional power conversion circuit 14 provides the thermoelectric component 11a with a drive current whose polarity and amplitude can be adjusted. When the thermoelectric component 11a operates in Seebeck mode (i.e., thermoelectric power generation mode), the bidirectional power conversion circuit 14 converts the electrical energy generated by the thermoelectric component 11a into voltage and feeds it back to the vehicle low-voltage electrical system or recharges it back into the power battery pack 6.

[0041] like Figure 4 As shown, when a forward current is applied to the thermoelectric component (11a), based on the Peltier effect, heat absorption or release occurs when the current flows through the junction of the P-type and N-type semiconductors, causing the temperature on the first liquid-cooled heat exchange plate (11b) to decrease and the temperature on the second liquid-cooled heat exchange plate (11c) to increase, thereby actively transporting heat from the motor cooling circuit (100) to the battery thermal management circuit (200); when a reverse current is applied, the heat transport direction is reversed, and the heat from the battery thermal management circuit (200) can be transported to the motor cooling circuit (100) for heat dissipation; when there is a natural temperature difference between the two ends of the thermoelectric component (11a) and no external driving current, based on the Seebeck effect, an electromotive force is generated inside the thermoelectric component (11a), which directly converts the temperature difference energy into electrical energy.

[0042] In this embodiment, sensor unit 13 specifically employs five temperature detectors. The first temperature detector is installed on the coolant outlet pipe of the drive motor 1 to monitor the outlet temperature of the motor cooling circuit in real time. T m,outA second temperature sensor is installed on the coolant outlet pipe of the first radiator 4 to monitor the inlet temperature of the motor cooling circuit. T m,in The third temperature sensor is attached to the inside or surface of the power battery pack 6 to monitor the real-time temperature of the battery. T b The fourth temperature sensor is installed on the coolant outlet pipe of the second radiator 9 to monitor the inlet temperature of the battery thermal management circuit. T b,in The fifth temperature sensor is installed on the coolant outlet pipe of the power battery pack 6 to monitor the outlet temperature of the battery thermal management circuit. T b,out .

[0043] The controller 12 receives the temperature signal transmitted by the sensor unit 13 at its input terminal, and its output terminals are respectively connected to the first multi-way proportional valve 3, the second multi-way proportional valve 8, the motor circulation pump 2, the battery circulation pump 7, the thermoelectric component 11a, and the bidirectional power conversion circuit 14. The controller 12 has a preset motor safety threshold. T m,max Battery preheating threshold T b,low Battery cooling threshold T b,high The temperature difference threshold Δ used to determine whether residual heat is sufficient T pump And the temperature difference threshold Δ used to determine whether thermoelectric power generation is possible. T gen .

[0044] under Figure 5 As shown, the working process and control logic of the entire system under different operating conditions are described in detail.

[0045] First, the controller 12 continuously acquires the values ​​of the five temperature points mentioned above through the sensor unit 13.

[0046] When controller 12 detects the outlet temperature of the motor cooling circuit T m,out Exceeding the preset motor safety threshold T m,max When this occurs, the system will enter the motor safety priority protection mode. At this time, regardless of the battery temperature, the controller 12 will forcibly switch the outlet of the first multi-way proportional valve 3 completely to the first radiator 4, guiding all the coolant in the motor cooling circuit to the first radiator 4. After cooling, the coolant will return to the drive motor 1, reducing the motor temperature in the shortest possible time. In this mode, if the real-time battery temperature is detected simultaneously... T b It also exceeded the battery cooling threshold.T b,high The system will employ a composite gradient cooling strategy.

[0047] First, controller 12 opens the second multi-way proportional valve 8, allowing the coolant in the battery thermal management circuit to flow preferentially to the second radiator 9, using ambient temperature for passive heat dissipation. Then, controller 12 further instructs thermoelectric component 11a to activate the reverse Peltier operating mode. Specifically, heat is actively transported from the second liquid-cooled heat exchange plate 11c (battery side) to the first liquid-cooled heat exchange plate 11b (motor side), and then dissipated by the first radiator 4 in the motor cooling circuit. During this process, controller 12 also monitors the inlet temperature of the motor circuit. T m,in If the inlet temperature of the motor circuit T m,in The temperature is close to the ambient temperature, indicating that the first radiator 4 still has sufficient heat dissipation capacity. At this time, the controller 12 will appropriately increase the speed of the motor circulation pump 2 to enhance the heat dissipation capacity of the first radiator 4 and the thermoelectric component 11a for the heat transferred from the battery.

[0048] When the battery needs heating, the control logic switches to preheating mode. Preheating mode is based on the effective temperature difference Δ. T Determined, where the effective temperature difference Δ T = T m,out T b,out .

[0049] When Δ T ≥Δ T pump This indicates that a significant amount of waste heat has accumulated in the motor cooling circuit, and directly utilizing this waste heat is sufficient to meet the battery's preheating requirements. At this point, the system enters a low-power induced waste heat recovery mode, such as... Figure 5 The diagram shows the S2a mode. In this mode, the controller 12 applies a small induced current to the thermoelectric component 11a. The Peltier effect generated by the induced current can counteract the inherent thermal resistance of the thermoelectric component 11a. Simultaneously, the controller 12 adjusts the first multi-way proportional valve 3 to increase the flow rate of the high-temperature coolant flowing from the drive motor 1 into the first liquid-cooled heat exchange plate 11b. In this way, the high-temperature coolant in the motor cooling circuit carries residual heat into the first liquid-cooled heat exchange plate 11b. With the help of the induced current, the heat can more easily pass through the thermoelectric component 11a to the second liquid-cooled heat exchange plate 11c, where it is carried away by the coolant in the battery thermal management circuit and finally injected into the power battery pack 6. The advantage of this mode is extremely low energy consumption, because only a small induced current is needed to significantly improve the efficiency of residual heat transfer.

[0050] When Δ T<Δ T pump This indicates that the residual heat in the motor cooling circuit is insufficient to support the battery's temperature rise requirements. At this point, the system enters a large temperature difference active heat pump mode, which is... Figure 5 In S2b mode, the controller 12 supplies a large drive current to the thermoelectric component 11a, causing it to operate in a powerful Peltier pumping state. Specifically, on the side of the first liquid-cooled heat exchange plate 11b, the thermoelectric component generates a forced heat absorption effect, extracting heat from the motor coolant flowing through the first liquid-cooled heat exchange plate 11b; on the side of the second liquid-cooled heat exchange plate 11c, the thermoelectric component generates a forced heat release effect, releasing the absorbed heat and the Joule heat generated during its operation to the battery coolant flowing through the second liquid-cooled heat exchange plate 11c. Simultaneously, the controller 12 coordinates the actions of two proportional valves: the first multi-way proportional valve 3 guides the motor coolant through the first liquid-cooled heat exchange plate 11b, providing a cold end for the thermoelectric component 11a to absorb heat, and also actively drawing heat from the motor circuit to prevent the motor from overcooling due to heat loss; the second multi-way proportional valve 8 guides the battery coolant through the second liquid-cooled heat exchange plate 11c, sending the Joule heat generated by the thermoelectric component 11a and the latent heat extracted from the motor cooling circuit into the power battery pack 6. In this mode, the controller 12 also monitors the battery circuit inlet temperature in real time. T b,in ,if T b,in If the current rises too quickly or exceeds the battery's tolerance limit, the controller 12 will dynamically reduce the driving current of the thermoelectric component 11a to prevent local thermal shock from damaging the battery.

[0051] When the battery temperature is within a relatively comfortable range, that is T b,low ≤ T b ≤ T b,high The system does not require cooling or heating. However, if Δ T >Δ T ge Controller 12 will put the system into waste heat power generation mode, which is... Figure 5The controller 12 switches the thermoelectric component 11a to Seebeck power generation mode and connects the bidirectional power conversion circuit 14. Simultaneously, the controller 12 adjusts the opening of the first multi-way proportional valve 3 and the second multi-way proportional valve 8 to maximize the temperature difference between the first liquid-cooled heat exchange plate 11b and the second liquid-cooled heat exchange plate 11c, while ensuring the basic cooling flow rates of the motor and battery. The greater the temperature difference, the higher the Seebeck power generation. The controller 12 also calculates the actual heat exchange power on both sides of the thermoelectric component 11a in real time and adjusts the equivalent input impedance of the bidirectional power conversion circuit 14 accordingly to achieve maximum power point tracking (MPPT) power generation, feeding the generated electrical energy back to the vehicle's electrical system or recharging it back to the power battery pack 6.

[0052] The controller 12 in this embodiment also executes optimization strategies. For example, a flexible control strategy: the controller 12 adjusts the control based on the real-time battery temperature. T b The rate of change of the variable frequency drive (VFD) of the motor circulation pump 2 and the battery circulation pump 7 is adjusted in real time to match the flow rate of the coolant with the drive current of the thermoelectric component 11a, thereby reducing the thermal stress impact on the thermoelectric component during the switching between different modes. In addition, to avoid frequent operation of the proportional valve near the critical point, the controller 12 uses a hysteresis control algorithm to determine the switching conditions of each working mode. The trigger temperature point for switching from one mode to another is not the same as the temperature point for switching back, and a certain buffer interval is left in between.

[0053] In this embodiment, a predictive thermal scheduling function is also implemented. The controller 12 can communicate with the vehicle navigation system to obtain the preset destination charging station location and estimated arrival time. When the vehicle is about to arrive at the charging station, the controller 12 will trigger the aforementioned low-power induced waste heat recovery mode (S2a) or large temperature difference active heat pumping mode (S2b) in advance within a preset time window before arrival. By utilizing the waste heat generated by the motor circuit during the last leg of the journey and the active heat pumping of the thermoelectric components, the power battery pack 6 is preheated to the temperature range most suitable for fast charging, reducing the heating waiting time in the early stage of charging.

[0054] The controller 12 in this embodiment also employs dynamic threshold correction logic, such as a motor safety threshold. T m,max The dynamic correction logic is used for correction, and its expression is as follows:

[0055] In the formula: The corrected motor safety threshold; The reference safe temperature; k 1 represents the environmental impact coefficient; Ambient temperature; To match the overall vehicle speed V The relevant air volume compensation function; k 2 represents the air volume compensation coefficient; The above formula can be used to determine the motor's safety threshold based on ambient temperature. T m,max Make real-time corrections.

[0056] The controller 12 executes the battery preheating threshold. T b,low The dynamic correction logic is used for correction, and its expression is as follows:

[0057] In the formula: The corrected battery preheating threshold; This is the battery reference preheating temperature; This is a correction term that increases the preheating target value as the ambient temperature decreases; The above formula can be used to determine the motor's safety threshold based on ambient temperature. Make real-time corrections.

[0058] The controller 12 executes the effective temperature difference threshold Δ for waste heat recovery. T pump The dynamic correction logic is modified, including: Controller 12 based on the outlet temperature of the motor cooling circuit T m,out To correct the effective temperature difference threshold Δ of waste heat recovery T pump ; when T m,out When the temperature rises, the controller decreases Δ T pump By triggering the low-power induced waste heat recovery mode in advance, the starting time and proportion of waste heat recovery are dynamically optimized based on the COP characteristics of the thermoelectric component 11a in different temperature ranges.

[0059] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0060] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A thermoelectric coupling-based integrated thermal management system for electric vehicle motor-battery, characterized in that, include: The motor cooling circuit includes a drive motor (1), a motor circulation pump (2), a first multi-way proportional valve (3), a first radiator (4), and a motor cooling plate (5). The coolant outlet of the drive motor (1) is connected to the first multi-way proportional valve (3) via the motor circulation pump (2). The first multi-way proportional valve (3) has a first outlet and a second outlet. The first outlet is connected to the inlet of the first radiator (4), and the second outlet is connected to the inlet of the first liquid-cooled heat exchange plate (11b). The outlet of the first radiator (4) merges with the outlet of the first liquid-cooled heat exchange plate (11b) and is connected to the inlet of the motor cooling plate (5). The outlet of the motor cooling plate (5) is connected to the coolant inlet of the drive motor (1) to form a closed loop. The battery thermal management circuit includes a power battery pack (6), a battery circulation pump (7), a second multi-way proportional valve (8), a second radiator (9), and a battery pack cooling plate (10). The coolant outlet of the power battery pack (6) is connected to the second multi-way proportional valve (8) via the battery circulation pump (7). The second multi-way proportional valve (8) has a third outlet and a fourth outlet. The third outlet is connected to the inlet of the second radiator (9), and the fourth outlet is connected to the inlet of the second liquid-cooled heat exchange plate (11c). The outlet of the second radiator (9) merges with the outlet of the second liquid-cooled heat exchange plate (11c) and is connected to the inlet of the battery pack cooling plate (10). The outlet of the battery pack cooling plate (10) is connected to the coolant inlet of the power battery pack (6) to form a closed loop. A thermoelectric coupling heat exchange module (11) is disposed between the motor cooling circuit and the battery thermal management circuit; it includes a thermoelectric component (11a), a first liquid-cooled heat exchange plate (11b) attached to one side of the thermoelectric component (11a) and connected to the motor cooling circuit, and a second liquid-cooled heat exchange plate (11c) attached to the other side of the thermoelectric component (11a) and connected to the battery thermal management circuit; the thermoelectric component (11a) forms heat exchange between the motor cooling circuit and the battery thermal management circuit through the first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c); Sensor unit (13) is used to collect thermal parameters of motor cooling circuit and battery thermal management circuit; The controller (12) is connected to the sensor unit (13), the first multi-way proportional valve (3), the second multi-way proportional valve (8) and the thermoelectric component (11a) respectively, and is used to adjust the fluid distribution ratio of the motor cooling circuit and the battery thermal management circuit and the working mode of the thermoelectric component (11a) according to the thermal parameters collected by the sensor unit (13).

2. The electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling according to claim 1, characterized in that, The sensor unit (13) includes five temperature detectors, each of which is located at: The coolant outlet of the drive motor (1) is used to monitor the outlet temperature of the motor cooling circuit. The coolant outlet of the first radiator (4) is used to monitor the inlet temperature of the motor cooling circuit; The inside or surface of the power battery pack (6) is used to monitor the real-time temperature of the power battery pack (6); The coolant outlet of the second radiator (9) is used to monitor the inlet temperature of the battery thermal management circuit; The coolant outlet of the power battery pack (6) is used to monitor the outlet temperature of the battery thermal management circuit.

3. The electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling according to claim 1, characterized in that, The thermoelectric component (11a) is an array structure composed of multiple thermoelectric units, used to generate the Peltier effect based on the driving current to transfer heat between the first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c); and used to recover waste heat for power generation based on the natural temperature difference between the motor cooling circuit and the battery thermal management circuit.

4. The electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling according to claim 3, characterized in that, Each of the thermoelectric units includes a thermocouple, a conductive connection layer, and a ceramic insulating substrate: The thermoelectric couple includes a P-type thermoelectric semiconductor element and an N-type thermoelectric semiconductor element; A conductive connection layer is disposed between the P-type thermoelectric semiconductor element and the N-type thermoelectric semiconductor element to connect the P-type thermoelectric semiconductor element and the N-type thermoelectric semiconductor element in series. The ceramic insulating substrate is disposed at the top and bottom of the thermoelectric assembly (11a) to provide mechanical support and electrical insulation, and to conduct heat to the first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c) as a heat transfer medium.

5. The electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling according to claim 1, characterized in that, The first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c) are also provided with enhanced heat exchange structures. The high-heat-exchange structure includes a microchannel flow path, and the microchannel flow path is provided with turbulence columns or staggered fins.

6. The electric vehicle motor-battery integrated thermal management system based on thermoelectric coupling according to claim 1, characterized in that, It also includes a bidirectional power conversion circuit (14): The bidirectional power conversion circuit (14) is connected to the controller (12) and is used to provide the thermoelectric component (11a) with a drive current of adjustable polarity and amplitude and to convert the electrical energy generated by the thermoelectric coupling heat exchange module and feed it back to the vehicle electrical system or power battery pack (6).

7. A method for an integrated thermal management system for an electric vehicle motor-battery based on thermoelectric coupling, characterized in that, The system according to any one of claims 1 to 6 comprises the following steps: S1, Parameter sensing: The controller (12) obtains the outlet temperature of the motor cooling circuit in real time through the sensor unit (13). T m,out Inlet temperature T m,in Real-time battery temperature and battery thermal management circuit T b outlet temperature T b,out and inlet temperature T b,in And preset the motor safety threshold. T m,max Battery preheating threshold T b,low Battery cooling threshold T b,high Effective temperature difference threshold for waste heat recovery Δ T pump and the power generation trigger temperature difference threshold Δ T gen ; S2, Motor Protection and Gradient Cooling: When detected... T m,out > T m,max At that time, the controller (12) forces the first multi-way proportional valve (3) to direct the coolant of the motor cooling circuit to the first radiator (4) in full. If detected T b > T b,high When the cooling is performed, the following gradient is applied: first, the second multi-way proportional valve (8) is opened to passively dissipate heat using the second radiator (9); if the passive heat dissipation power is insufficient, the thermoelectric component (11a) is instructed to actively transfer the heat from the battery thermal management circuit to the motor cooling circuit and dissipate it through the first radiator (4). S3. Active preheating based on effective temperature difference: The effective temperature difference Δ T = T m,out T b,out ; When detected T b < T b,low hour: If Δ T ≥Δ T pump If the motor has sufficient waste heat, it will enter the low-power induced waste heat recovery mode: the controller (12) will pass an induced current to the thermoelectric component (11a) and adjust the first multi-way proportional valve (3) to increase the flow rate of the high-temperature coolant through the first liquid-cooled heat exchange plate (11b) to actively transfer the motor waste heat to the battery thermal management circuit. If Δ T <Δ T pump If the motor is deemed to have insufficient residual heat, the system enters the large temperature difference active pumping mode: the controller (12) applies a positive current to make the thermoelectric component (11a) work to generate the Peltier heating effect, forcibly absorbs heat from the motor cooling circuit and forcibly releases heat to the battery thermal management circuit, and at the same time adjusts the first multi-way proportional valve (3) and the second multi-way proportional valve (8) to guide the coolant to flow through the first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c) respectively, and injects the Joule heat generated by the thermoelectric component (11a) and the latent heat extracted from the motor cooling circuit into the power battery pack (6). S4. Waste heat power generation based on temperature polarization effect: When detected T b,low ≤ T b ≤ T b,high And Δ T >Δ T ge At that time, the controller (12) switches the thermoelectric component (11a) to Seebeck power generation state, and increases the temperature difference between the first liquid-cooled heat exchange plate (11b) and the second liquid-cooled heat exchange plate (11c) by adjusting the opening of the first multi-way proportional valve (3) and the second multi-way proportional valve (8), while adjusting the impedance matching of the bidirectional power conversion circuit (14) to achieve maximum power point tracking power generation.

8. The method for an integrated thermal management system for an electric vehicle motor-battery based on thermoelectric coupling according to claim 7, characterized in that, It also includes system flexibility control and reliability optimization strategies: The controller (12) adjusts the battery temperature based on real-time temperature. T b The variable frequency speed of the motor circulation pump (2) and the battery circulation pump (7) is adjusted in real time by changing the slope of the variable frequency. By matching the coolant flow rate and the driving current of the thermoelectric component (11a), the thermal stress impact of the thermoelectric component (11a) at the moment of switching between different modes is reduced. The hysteresis control algorithm is used to determine the switching threshold of each working mode in order to avoid the multi-way proportional valve from generating high frequency oscillation at the critical point.

9. The method for an integrated thermal management system for an electric vehicle motor-battery based on thermoelectric coupling according to claim 7, characterized in that, The controller (12) executes the motor safety threshold. T m,max The dynamic correction logic is used for correction, and its expression is as follows: In the formula: The corrected motor safety threshold; The reference safe temperature; k 1 represents the environmental impact coefficient; Ambient temperature; To match the overall vehicle speed V The relevant air volume compensation function; k 2 represents the air volume compensation coefficient; The controller (12) executes the battery preheating threshold. T b,low The dynamic correction logic is used for correction, and its expression is as follows: In the formula: The corrected battery preheating threshold; This is the battery reference preheating temperature; This is a correction term that increases the preheating target value as the ambient temperature decreases; The controller (12) executes the effective temperature difference threshold Δ for waste heat recovery. T pump The dynamic correction logic is modified, including: The controller (12) determines the outlet temperature of the motor cooling circuit based on the temperature of the motor cooling circuit. T m,out To correct the effective temperature difference threshold Δ of waste heat recovery T pump ; when T m,out When the temperature rises, the controller decreases Δ T pump By triggering the low-power induced waste heat recovery mode in advance, the starting time and proportion of waste heat recovery are dynamically optimized based on the COP characteristics of the thermoelectric component (11a) in different temperature ranges.

10. The method for an integrated thermal management system for an electric vehicle motor-battery based on thermoelectric coupling according to claim 7, characterized in that, It also includes predictive thermal scheduling steps: According to the preset terminal station charging plan, the controller (12) triggers the low power consumption induced waste heat recovery mode or the large temperature difference active heat pumping mode in advance within the preset time window before the vehicle arrives at the charging pile. The controller uses the waste heat of the motor cooling circuit and the active heat pumping of the thermoelectric module (11a) to preheat the power battery pack (6) to the optimal fast charging temperature range.

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