A battery self-preheating system and method for an electric vehicle

Abstract

The application relates to the technical field of electric vehicles, and discloses a battery self-preheating system and method for an electric vehicle, which comprises a photovoltaic power generation unit, an irradiance sensor, a heating unit, a temperature sensor, a DC-DC converter and a controller. The controller is used for controlling a relay to switch from a first mode to a second mode when the electric vehicle is in a locked state, the state of charge of a power battery is greater than or equal to a full charge threshold, the temperature of the power battery is less than or equal to a temperature starting threshold, and the irradiance is greater than or equal to a photovoltaic starting threshold, so that the photovoltaic power generation unit provides electric energy for the heating unit to heat the power battery. The first mode is that the photovoltaic power generation unit and an on-board charger are connected through the relay, and the second mode is that the photovoltaic power generation unit and the DC-DC converter are connected through the relay. The application can realize battery preheating without consuming battery energy storage and without relying on charging facilities.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle technology, and more specifically to a battery self-preheating system and method for electric vehicles. Background Technology

[0002] At low temperatures, the electrolyte viscosity of lithium-ion batteries increases and the ionic conductivity decreases, leading to a sharp increase in internal resistance and a significant reduction in usable capacity and discharge power. This, in turn, makes it difficult for electric vehicles to start in low-temperature environments, thus hindering the promotion of electric vehicles in cold regions.

[0003] Currently, the problem of electric vehicles struggling to start in low-temperature environments is addressed by using either a built-in PTC (Positive Temperature Coefficient) heating device in the power battery or pre-heating via external charging stations. The built-in PTC heating device preheats the battery using its own power, consuming a significant amount of battery energy and resulting in a substantial reduction in usable driving range. The external charging station pre-heating method utilizes grid power, relying on charging infrastructure and thus being unusable in locations without charging stations, such as parking lots or outdoors, while also increasing electricity costs for users. Summary of the Invention

[0004] This invention provides a battery self-preheating system and method for electric vehicles to solve the problems of consuming battery power or relying on the external power grid during preheating, which leads to limited application scenarios and increased costs.

[0005] In a first aspect, the present invention provides a battery self-preheating system for an electric vehicle, comprising: a photovoltaic power generation unit disposed on the electric vehicle at a location exposed to sunlight, connected to an on-board charger and a power battery via a relay; an irradiance sensor for detecting the irradiance of the photovoltaic power generation unit; a heating unit disposed within the power battery; a temperature sensor disposed within the power battery; a DC-DC converter, one end connected to the photovoltaic power generation unit via a relay, and the other end connected to the heating unit; and a controller connected to the irradiance sensor, the temperature sensor, and the relay, for controlling the relay to switch from a first mode to a second mode when the electric vehicle is locked, the state of charge of the power battery is greater than or equal to a full charge threshold, the temperature of the power battery is less than or equal to a temperature start-up threshold, and the irradiance is greater than or equal to a photovoltaic start-up threshold, thereby enabling the photovoltaic power generation unit to provide electrical energy to the heating unit to heat the power battery, wherein the first mode connects the photovoltaic power generation unit and the on-board charger via a relay, and the second mode connects the photovoltaic power generation unit and the DC-DC converter via a relay.

[0006] The battery self-preheating system for electric vehicles provided by this invention constructs a branch circuit between the photovoltaic power generation unit and the power battery, through a relay, to supply power to the heating unit via the photovoltaic power generation unit. This branch circuit is physically isolated from the main circuit that supplies power to the power battery via the photovoltaic power generation unit. The relay is only controlled to switch from the first mode to the second mode when the electric vehicle is parked, the state of charge of the power battery is greater than or equal to the full charge threshold, the temperature of the power battery is less than or equal to the temperature start-up threshold, and the irradiance is greater than or equal to the photovoltaic start-up threshold. This ensures that the preheating energy comes entirely from solar energy and does not consume the energy storage of the power battery.

[0007] Meanwhile, it can start electric vehicles in low ambient temperatures without relying on any external charging facilities, such as in remote areas and outdoor parking lots where there is no power grid, thus improving the vehicle's low-temperature start performance and enhancing its environmental adaptability. Furthermore, the system utilizes photovoltaic power that might otherwise be wasted after the battery is fully charged for preheating, maximizing the use of solar energy and avoiding energy waste.

[0008] In one optional embodiment, the system further includes multiple switches, the power battery includes multiple battery modules, the heating unit includes multiple heating elements corresponding to each of the multiple battery modules, the temperature sensor includes multiple temperature detection units corresponding to each of the multiple battery modules, and the multiple switches correspond to each of the multiple heating elements; the control terminals of the multiple switches are connected to a controller, the first connection terminals of the multiple switches are all connected to a DC-DC converter, and the second connection terminals of the multiple switches are connected to the corresponding heating elements; the controller is used to obtain multiple current temperatures corresponding to each of the multiple battery modules from the multiple temperature detection units, and determine the average temperature of the power battery and the temperature difference between any two battery modules in the multiple battery modules based on the multiple current temperatures; the controller is also used to adjust the duty cycle of each of the multiple switches according to the temperature difference when the average temperature is less than or equal to the temperature start-up threshold, so as to adjust the power supply provided by the DC-DC converter to the multiple heating elements, wherein the sum of the power supply corresponding to the multiple heating elements is the total power output by the DC-DC converter.

[0009] This embodiment sets up multiple switches, temperature detection units, and heating elements, and adjusts the duty cycle of the multiple switches to control the heating power of the heating elements, thereby achieving zoned and on-demand heating, avoiding the risk of overheating and energy waste; at the same time, balancing the power battery temperature can maintain the consistency of the battery module, which is beneficial to extending the service life of the entire power battery.

[0010] In one optional implementation, the controller is configured to adjust the duty cycle of multiple switches to the first duty cycle when the maximum value of the temperature difference corresponding to multiple battery modules is less than a first equalization threshold. The first duty cycle is determined based on the average value of the total output power of the DC-DC converter. The controller is also configured to adjust the duty cycle of the switches corresponding to the battery modules according to the current temperature and average temperature of the battery modules when the maximum value is greater than or equal to the first equalization threshold and less than a second equalization threshold, so that the power supply of the heating element corresponding to the battery modules with different current temperatures is different. Furthermore, the controller is configured to adjust the duty cycle of the switch corresponding to the target battery module to the maximum value when the maximum value is greater than or equal to the second equalization threshold, wherein the target battery module is the battery module with the lowest current temperature among the multiple battery modules.

[0011] This embodiment divides the temperature difference into three intervals. When the temperature difference is small, the heating is uniform, and when the temperature difference is large, the heating is differentiated to balance the battery module temperature. This optimizes the energy efficiency ratio of the heating system and ensures that the temperature field of the power battery is more uniform under low temperature conditions, thereby improving the discharge capacity and power output capability of the power battery.

[0012] In one optional implementation, the controller is configured to determine the priority of the battery module based on the absolute value of the difference between the current temperature and the average temperature of the battery module when the maximum value is less than or equal to a first equilibrium threshold and the maximum value is less than a second equilibrium threshold. Specifically, when the current temperature is less than the average temperature, the priority is directly proportional to the absolute value of the difference; when the current temperature is greater than or equal to the average temperature, the priority is inversely proportional to the absolute value of the difference. The controller is also configured to adjust the duty cycle of the corresponding switch based on the priority of the battery module, wherein the duty cycle is directly proportional to the priority.

[0013] This embodiment introduces a priority determination rule, which can adapt to different ambient temperatures, realize priority heating of low-temperature modules and suppression of high-temperature modules, reduce the temperature difference between modules as quickly as possible, and the algorithm structure is simple and has strong engineering practicality.

[0014] In one optional implementation, the system further includes a maximum power point tracking controller, a voltage sampling unit, and a current sampling unit connected to the DC-DC converter; the voltage sampling unit is used to collect the output voltage of the photovoltaic power generation unit; the current sampling unit is used to collect the output current of the photovoltaic power generation unit; and the maximum power point tracking controller is used to determine the maximum output power of the photovoltaic power generation unit based on the output voltage and output current, and control the total output power of the DC-DC converter to be the maximum output power.

[0015] This embodiment uses a DC-DC converter paired with a high-power point tracking controller to track the maximum power point of the photovoltaic power generation unit in real time under the current irradiance and temperature, thereby maximizing the utilization of photovoltaic energy.

[0016] In one optional implementation, the system further includes a maximum power point tracking controller and a power sensor connected to the DC-DC converter; the power sensor is used to detect the current power generation of the photovoltaic power generation unit; the maximum power point tracking controller is used to determine the maximum output power of the photovoltaic power generation unit based on the current power generation and control the total output power of the DC-DC converter to be the maximum output power.

[0017] This embodiment improves the synchronization and accuracy of power feedback by configuring a power sensor to directly detect the real-time power generation of the photovoltaic power generation unit.

[0018] In one alternative implementation, the photovoltaic power generation unit is a silicon-based perovskite tandem photovoltaic cell.

[0019] This embodiment uses silicon-based perovskite tandem photovoltaic cells as photovoltaic power generation units, achieving a photoelectric conversion efficiency higher than that of monocrystalline silicon photovoltaic cells, and significantly improving output power under the same installation area. At the same time, this type of cell has a better temperature coefficient and weak light response characteristics in low-temperature environments, which is highly compatible with the low-temperature heating requirements of battery modules and can effectively extend the effective heating time in winter. In addition, its lightweight and flexible characteristics improve the engineering applicability of the system in vehicle environments.

[0020] In one alternative implementation, a capacitor is connected in parallel across the two ends of the DC-DC converter.

[0021] This embodiment uses a parallel capacitor scheme to buffer the instantaneous power of the circuit, reduce energy conversion loss, effectively suppress heating power fluctuations, and at the same time, it does not interact with the power battery throughout the process, ensuring battery preheating without loss of range.

[0022] Secondly, the present invention provides a self-preheating method for an electric vehicle battery, comprising: acquiring the operating status of the electric vehicle, the state of charge of the power battery, the temperature of the power battery, and the irradiance of the photovoltaic power generation unit; when the electric vehicle is locked, the state of charge of the power battery is greater than or equal to a full charge threshold, the temperature of the power battery is less than or equal to a temperature start-up threshold, and the irradiance is greater than or equal to a photovoltaic start-up threshold, controlling a relay to switch from a first mode to a second mode, so that the photovoltaic power generation unit provides electrical energy to the heating unit to heat the power battery; wherein, the first mode connects the photovoltaic power generation unit and the on-board charger through the relay, and the second mode connects the photovoltaic power generation unit and the DC-DC converter through the relay.

[0023] In an optional implementation, the method further includes: acquiring multiple current temperatures corresponding one-to-one with multiple battery modules from multiple temperature detection units; determining the average temperature of the power battery and the temperature difference between any two battery modules based on the multiple current temperatures; when the average temperature is less than or equal to a temperature start-up threshold, adjusting the duty cycle of each switch among the multiple switches based on the temperature difference to adjust the power supply provided by the DC-DC converter to the multiple heating elements, wherein the sum of the power supply corresponding to the multiple heating elements is the total power output by the DC-DC converter. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a battery self-preheating system for an electric vehicle according to an embodiment of the present invention; Figure 2 This is another schematic diagram of a battery self-preheating system for an electric vehicle according to an embodiment of the present invention; Figure 3 This is yet another schematic diagram of a battery self-preheating system for an electric vehicle according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the operation of a battery self-preheating system for an electric vehicle according to an embodiment of the present invention. Figure 5 This is a schematic flowchart of a battery self-preheating method for an electric vehicle according to an embodiment of the present invention; Figure 6 This is another schematic flowchart of a battery self-preheating method for an electric vehicle according to an embodiment of the present invention; Figure 7 This is a comparison diagram of the effects of embodiments of the present invention and related technologies.

[0026] Reference numerals: 10. Battery self-preheating system for electric vehicles; 11. Photovoltaic power generation unit; 12. Relay; 13. DC-DC converter; 14. Heating unit; 15. Temperature sensor; 16. Controller; 17. Irradiance sensor; 21. On-board charger; 22. Power battery; 31. Maximum power point tracker; 32. Voltage sampling unit; 33. Current sampling unit; 41. Supercapacitor. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] 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 technical features indicated. 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.

[0029] This invention provides a battery self-preheating system and method for electric vehicles. By using a relay, a branch circuit is constructed between the photovoltaic power generation unit and the power battery, which supplies power to the heating unit through the photovoltaic power generation unit. This branch circuit is physically isolated from the main circuit that supplies power to the power battery through the photovoltaic power generation unit. Furthermore, the power supply module is switched based on four conditions: the vehicle's operating status, the power battery's state of charge, the power battery's temperature, and the irradiance. This allows preheating to be completed without losing power battery energy or relying on charging facilities, thus solving the problem of difficult starting of electric vehicles in low-temperature environments.

[0030] The battery self-preheating system for electric vehicles provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the battery self-preheating system 10 for electric vehicles provided by the present invention includes a photovoltaic power generation unit 11, a relay 12, a DC-DC converter 13, a heating unit 14, a temperature sensor 15, a controller 16, and an irradiance sensor 17.

[0032] The photovoltaic power generation unit 11 is installed on the electric vehicle at a position exposed to sunlight and is connected to the on-board charger 21 and the power battery 22 via a relay 12. One end of the DC-DC converter 13 is connected to the photovoltaic power generation unit 11 via the relay 12, and the other end is connected to the heating unit 14. The DC-DC converter is used to convert the first voltage output by the photovoltaic power generation unit into a second voltage that matches the working requirements of the heating unit.

[0033] Irradiance sensor 17 is used to detect the irradiance of photovoltaic power generation unit 11; heating unit 14 is installed inside power battery 22 and is used to heat power battery under the drive of power provided by photovoltaic power generation unit; temperature sensor 15 is installed inside power battery 22 and is used to detect the temperature of power battery; controller 16 connects irradiance sensor 17, temperature sensor 15 and relay 12.

[0034] This invention does not specifically limit the type and location of the photovoltaic power generation unit 11. For example, the material of the photovoltaic power generation unit 11 can be monocrystalline silicon or perovskite; the photovoltaic power generation unit 11 can be installed on parts that can be directly exposed to sunlight, such as the roof or hood of a vehicle. Since the irradiance received by the photovoltaic power generation unit directly depends on its relative angle with the sunlight, the irradiance sensor 17 is usually set at the same tilt and azimuth angle as the photovoltaic power generation unit, thereby ensuring that the measured irradiance data can accurately reflect the actual solar radiation received by the photovoltaic power generation unit.

[0035] The present invention does not impose specific limitations on the number and material of the heating unit 14, as long as it can achieve the heating of the power battery. For example, there can be one or more heating units 14, and the heating unit 14 can be made of PTC material or other materials that are easy to integrate into the power battery, are insulating and resistant to high temperature.

[0036] The controller 16 is used to control the relay 12 to switch from a first mode to a second mode when the electric vehicle is locked, the state of charge of the power battery 22 is greater than or equal to the full charge threshold, the temperature of the power battery 22 is less than or equal to the temperature start-up threshold, and the irradiance is greater than or equal to the photovoltaic start-up threshold. This allows the photovoltaic power generation unit 11 to provide electrical energy to the heating unit 14 to heat the power battery. In the first mode, the relay 12 connects the photovoltaic power generation unit 11 and the on-board charger 21; in the second mode, the relay 12 connects the photovoltaic power generation unit 11 and the DC-DC converter 13.

[0037] Specifically, the locked state of an electric vehicle refers to the static safety mode when the vehicle power is cut off, all doors and the trunk are locked, and the engine immobilizer system and body control module are in alert mode. It's understandable that this condition does not include situations where the vehicle is parked but unlocked, because in this case, the vehicle's low-voltage electrical systems (central control, lights, in-vehicle entertainment, door sensors, seat ventilation, etc.) are in standby or ready to be turned on at any time. If the second mode is switched to, the photovoltaic output power will be diverted to the vehicle's low-voltage load, potentially causing voltage fluctuations and insufficient heating power. Furthermore, in this situation, no one can get in or out of the vehicle at any time, or touch components around the battery pack, and the high-power heating of the heating unit will increase the risk of thermal safety management issues. In addition, when temporarily parked without locking (waiting for someone, short-term stop), the user may unlock and drive at any time without needing to preheat the battery. This condition avoids the waste of photovoltaic energy caused by accidentally activating the second mode.

[0038] The full charge threshold refers to the maximum charge level at which charging stops to protect battery life; it can be set to 95%. The temperature start-up threshold can be adjusted according to the environment; it can be set to 5℃. The photovoltaic start-up threshold refers to the minimum voltage at which the DC-DC converter starts operating, which is usually achievable under conditions of sunlight (photovoltaic irradiance greater than 0).

[0039] By default, the electric vehicle is in the first mode. Relay 12 switches from the first mode to the second mode only when all four conditions are met simultaneously: the electric vehicle is locked, the state of charge (SOC) of the power battery 22 is greater than or equal to the full charge threshold, the temperature of the power battery 22 is less than or equal to the temperature start-up threshold, and the irradiance is greater than or equal to the photovoltaic start-up threshold. This allows the photovoltaic power generation unit 11 to provide electrical energy to the heating unit 14 to heat the power battery. When any one of the following conditions is met—the electric vehicle is in an unlocked state (driving, parked, etc.), the SOC of the power battery 22 is less than the full charge threshold, the temperature of the power battery 22 is greater than the temperature start-up threshold, or the irradiance is less than the photovoltaic start-up threshold—then the vehicle switches back from the second mode to the first mode.

[0040] The battery self-preheating system for electric vehicles provided by this invention constructs a branch circuit between the photovoltaic power generation unit and the power battery, through a relay, to supply power to the heating unit via the photovoltaic power generation unit. This branch circuit is physically isolated from the main circuit that supplies power to the power battery via the photovoltaic power generation unit. The relay is only controlled to switch from the first mode to the second mode when the electric vehicle is parked, the state of charge of the power battery is greater than or equal to the full charge threshold, the temperature of the power battery is less than or equal to the temperature start-up threshold, and the irradiance is greater than or equal to the photovoltaic start-up threshold. This ensures that the preheating energy comes entirely from solar energy and does not consume the energy storage of the power battery.

[0041] Meanwhile, it can start electric vehicles in low ambient temperatures without relying on any external charging facilities, such as in remote areas and outdoor parking lots where there is no power grid, thus improving the vehicle's low-temperature start performance and enhancing its environmental adaptability. Furthermore, the system utilizes photovoltaic power that might otherwise be wasted after the battery is fully charged for preheating, maximizing the use of solar energy and avoiding energy waste.

[0042] In one alternative implementation, such as Figure 2 As shown, the battery self-preheating system 10 of the electric vehicle also includes multiple switches, the power battery 22 includes multiple battery modules, the heating unit 14 includes multiple heating elements corresponding to the multiple battery modules, the temperature sensor 15 includes multiple temperature detection units corresponding to the multiple battery modules, and the multiple switches correspond to the multiple heating elements. The control terminals of the multiple switches are connected to the controller 16, the first connection terminals of the multiple switches are all connected to the DC-DC converter 13, and the second connection terminals of the multiple switches are connected to the corresponding heating elements.

[0043] Among them, multiple switches are shown in the figure. Figure 2 The first switch K1, the second switch K2, ..., the nth switch Kn; for multiple battery modules, see [reference needed]. Figure 2 The first battery module 22-1, the second battery module 22-2, ..., the nth battery module 22-n; see multiple heating elements. Figure 2 The first heating element 14-1, the second heating element 14-2, ..., the nth heating element 14-n; multiple temperature detection units are shown in the figure. Figure 2 The first temperature detection unit 15-1, the second temperature detection unit 15-2, ..., the nth temperature detection unit 15-n. Figure 2 Taking the first switch K1 corresponding to the first heating element 14-1, the first heating element corresponding to the first battery module 22-1, and the first battery module 22-1 corresponding to the first temperature detection unit 15-1 as an example.

[0044] The controller 16 is used to acquire multiple current temperatures corresponding to multiple battery modules from multiple temperature detection units, and to determine the average temperature of the power battery 22 and the temperature difference between any two battery modules based on the multiple current temperatures. The controller 16 is also used to adjust the duty cycle of each of the multiple switches based on the temperature difference when the average temperature is less than or equal to the temperature start-up threshold, so as to adjust the power supply provided by the DC-DC converter 13 to the multiple heating elements.

[0045] The duty cycle refers to the proportion of the total time a switch is in the on state within a switching cycle, usually expressed as a percentage. Duty cycle D = (T...) on / (T) on +T off ))×100%, T on The duration (T) indicates the time the switch is in the ON state. on +T off T represents the total cycle duration. off This indicates the duration the switch is in the off state. A higher duty cycle means a higher power supply from the DC-DC converter 13 to the corresponding heating element. It should be noted that the sum of the power supplies to multiple heating elements is the total output power of the DC-DC converter 13.

[0046] For example, the switch can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The controller 16 can independently adjust the duty cycle of the switch through a PWM (Pulse Width Modulation) signal, and the states (on / off) of multiple switches do not affect each other.

[0047] This embodiment sets up multiple switches, temperature detection units, and heating elements, and adjusts the duty cycle of the multiple switches to control the heating power of the heating elements, thereby achieving zoned and on-demand heating, avoiding the risk of overheating and energy waste; at the same time, balancing the power battery temperature can maintain the consistency of the battery module, which is beneficial to extending the service life of the entire power battery.

[0048] Furthermore, the controller 16 is used to adjust the duty cycle of multiple switches to the first duty cycle when the maximum value of the temperature difference corresponding to multiple battery modules is less than the first equalization threshold. The first duty cycle is determined based on the average value of the total power output by the DC-DC converter 13. The controller 16 is used to adjust the duty cycle of the switches corresponding to the battery modules according to the current temperature and average temperature of the battery modules when the maximum value is greater than or equal to the first equalization threshold and less than the second equalization threshold, so that the power supply of the heating element corresponding to the battery modules with different current temperatures is different. The controller 16 is used to adjust the duty cycle of the switch corresponding to the target battery module to the maximum value when the maximum value is greater than or equal to the second equalization threshold. The target battery module is the battery module with the lowest current temperature among the multiple battery modules.

[0049] Specifically, the first and second equalization thresholds can be flexibly adjusted according to the environment. For example, the first equalization threshold can be 1°C, the second equalization threshold can be 3°C, and the maximum temperature difference between multiple battery modules is T. max At this time, if T max When the temperature is <1℃, the power battery temperature is considered to be good, and the power supply is evenly distributed among the heating elements; if 1℃ ≤ T max ≤3℃ indicates poor temperature uniformity in power batteries, necessitating temperature balancing. A mapping relationship can be established between the current temperature of the battery module and the switch duty cycle, allowing different heating elements to operate with different heating powers. This mapping relationship can be flexibly set based on factors such as ambient temperature or battery materials; for example, the current temperature of the battery module and the switch duty cycle could be inversely proportional. If T max If the temperature exceeds 3℃, the power battery temperature becomes severely uneven, requiring concentrated heating of the low-temperature battery modules.

[0050] The maximum duty cycle means that all the electrical energy output by the photovoltaic power generation unit is supplied to the heating element corresponding to the target battery module, so that it works at the maximum heating power, thereby raising the temperature of the lowest temperature battery module as quickly as possible and rapidly eliminating extreme temperature differences.

[0051] The temperature detection unit synchronously collects the real-time temperature values ​​of all battery modules at a fixed period (e.g., 1 second). After each round of temperature collection, the controller recalculates the temperature difference between any two battery modules and continuously and dynamically adjusts the power supply of each heating element. For example, after a period of concentrated heating of the low-temperature battery modules, the maximum temperature difference falls back to within the first-level equilibrium threshold. At this time, the system automatically switches to the equal power synchronous heating mode.

[0052] This embodiment divides the temperature difference into three intervals. When the temperature difference is small, the heating is uniform, and when the temperature difference is large, the heating is differentiated to balance the battery module temperature. This optimizes the energy efficiency ratio of the heating system and ensures that the temperature field of the power battery is more uniform under low temperature conditions, thereby improving the discharge capacity and power output capability of the power battery.

[0053] Furthermore, the controller 16 is used to determine the priority of the battery module based on the absolute value of the difference between the current temperature and the average temperature of the battery module when the maximum value is less than or equal to the first equalization threshold and the maximum value is less than the second equalization threshold; the controller 16 is used to adjust the duty cycle of the corresponding switch according to the priority of the battery module.

[0054] Specifically, when the current temperature is lower than the average temperature, the priority is directly proportional to the absolute value of the difference; when the current temperature is greater than or equal to the average temperature, the priority is inversely proportional to the absolute value of the difference; the duty cycle is directly proportional to the priority.

[0055] Specifically, this embodiment sorts all battery modules in real time, assigning the highest power supply priority to the module with the lowest temperature and the lowest power supply priority to the module with the highest temperature. For example, the system can set a range of allowable duty cycles, such as a minimum of 5% and a maximum of 85%; the highest power supply priority battery module has a switch conduction duty cycle of 85%, the lowest power supply priority battery module has a switch conduction duty cycle of 5%, and the intermediate priority battery modules are allocated conduction duty cycles between 5% and 85% proportionally according to their priority order.

[0056] This embodiment introduces a priority determination rule, which can adapt to different ambient temperatures, realize priority heating of low-temperature modules and suppression of high-temperature modules, reduce the temperature difference between modules as quickly as possible, and the algorithm structure is simple and has strong engineering practicality.

[0057] In one alternative implementation, such as Figure 3As shown, the system also includes a maximum power point tracking controller 31, a voltage sampling unit 32, and a current sampling unit 33 connected to the DC-DC converter 13; the voltage sampling unit 32 is used to collect the output voltage of the photovoltaic power generation unit 11; the current sampling unit 33 is used to collect the output current of the photovoltaic power generation unit 11; the maximum power point tracking controller 31 is used to determine the maximum output power of the photovoltaic power generation unit 11 based on the output voltage and output current, and control the total output power of the DC-DC converter 13 to be the maximum output power.

[0058] The current-voltage curve of a photovoltaic (PV) power generation unit exhibits nonlinear characteristics. Its output power varies with the operating voltage, exhibiting a unique extreme point, known as the maximum power point (MPP). The location of this point dynamically shifts due to the influence of light intensity and ambient temperature. The Maximum Power Point Tracking Controller (MPPT) samples the terminal voltage and output current of the PV power generation unit at fixed intervals. Using MPPT algorithms such as the perturbation-observation method (applying periodic perturbations to the operating voltage and observing the direction of power change) or the incremental conductance method (comparing instantaneous conductance with incremental conductance), it calculates the control signal and adjusts the PWM duty cycle of the DC-DC converter. This continuously locks the operating point of the PV power generation unit within the neighborhood of the MPP under the current environmental conditions, maximizing energy capture efficiency.

[0059] In this embodiment, the input terminal of the DC-DC transformer continuously collects the real-time output voltage and current of the photovoltaic power generation unit and calculates the instantaneous power generation. The maximum power point tracking algorithm is then used to lock in the maximum output power of the photovoltaic unit under the current illumination. Subsequently, the duty cycle of the internal main switch is linearly adjusted based on the real-time photovoltaic output power to regulate the total output power delivered to multiple heating units, thereby matching the fluctuation characteristics of solar irradiance. The DC-DC converter performs primary control of the overall total power, while multiple switches perform secondary power allocation for each zone of heating units. These two levels of regulation work in concert to ensure that the total heating power of the heating units never exceeds the real-time photovoltaic power generation.

[0060] This embodiment uses a DC-DC converter paired with a high-power point tracking controller to track the maximum power point of the photovoltaic power generation unit in real time under the current irradiance and temperature, thereby maximizing the utilization of photovoltaic energy.

[0061] In an optional implementation, the system further includes a maximum power point tracking controller and a power sensor connected to the DC-DC converter 13; the power sensor is used to detect the current power generation of the photovoltaic power generation unit 11; the maximum power point tracking controller is used to determine the maximum output power of the photovoltaic power generation unit 11 based on the current power generation and control the total output power of the DC-DC converter 13 to be the maximum output power.

[0062] This embodiment improves the synchronization and accuracy of power feedback by configuring a power sensor to directly detect the real-time power generation of the photovoltaic power generation unit.

[0063] In one alternative implementation, the photovoltaic power generation unit 11 is a silicon-based perovskite tandem photovoltaic cell.

[0064] Silicon-based perovskite tandem solar cells connect two materials with different band gaps in series. The wide-bandgap perovskite top cell is responsible for efficiently absorbing short-wavelength ultraviolet-visible light, while the narrow-bandgap crystalline silicon bottom cell is responsible for absorbing near-infrared light, effectively broadening the spectral response range. In addition, the perovskite film is very thin, insensitive to temperature changes, and has an extremely high light absorption coefficient. Compared with monocrystalline silicon cells, the silicon-based perovskite tandem structure can significantly improve power generation efficiency.

[0065] By using silicon-based perovskite tandem photovoltaic cells as photovoltaic power generation units, a photoelectric conversion efficiency higher than that of monocrystalline silicon photovoltaic cells is achieved, resulting in a significant increase in output power within the same installation area. At the same time, this type of cell has a better temperature coefficient and weak light response characteristics in low-temperature environments, which is highly compatible with the low-temperature heating requirements of battery modules and can effectively extend the effective heating time in winter. In addition, its lightweight and flexible characteristics enhance the engineering applicability of the system in vehicle environments.

[0066] In one alternative implementation, a capacitor is connected in parallel across the two ends of the DC-DC converter.

[0067] The capacitor is used to absorb power spikes caused by sudden changes in sunlight and to temporarily supplement the photovoltaic power gap; the capacitor can be a supercapacitor. The capacitor can be connected to a controller, which can regulate the charging and discharging of the capacitor according to the state of charge of the power battery, the voltage of the capacitor, and the power of the photovoltaic power generation unit. For example, if the photovoltaic output power decreases due to cloud cover, the DC-DC converter synchronously reduces the total output power, while the parallel-connected supercapacitor instantaneously releases electrical energy to smooth out the power drop and ensure continuous heating.

[0068] This embodiment uses a parallel capacitor scheme to buffer the instantaneous power of the circuit, reduce energy conversion loss, effectively suppress heating power fluctuations, and at the same time, it does not interact with the power battery throughout the process, ensuring battery preheating without loss of range.

[0069] The following is combined Figure 4 The working process of the battery self-preheating system for electric vehicles provided by the present invention will be described in detail.

[0070] The system has two operating modes, which are switched via relays.

[0071] The first mode is the conventional charging mode, with the circuit path being photovoltaic power generation unit 11 → on-board charger 21 → power battery 22. It is activated when the power battery's state of charge is below 95% while the vehicle is in motion or parked, and the photovoltaic energy is used to supplement the range.

[0072] The second mode is the photovoltaic direct-supply PTC heating mode, with the circuit path being photovoltaic power generation unit 11 → DC-DC converter 13 → PTC heating element 14. When the vehicle is locked, the power battery's state of charge is above 95%, the power battery temperature is below 5℃, and the photovoltaic irradiance is above the start-up threshold, the system switches from the first mode to the second mode, where photovoltaic power bypasses the power battery and is directly and fully used for battery heating.

[0073] The controller collects real-time temperature data of all battery modules every second through temperature detection units arranged on the surface of each battery module. It stores the temperature data of each battery module and calculates the average temperature of the power battery and the temperature difference between any two battery modules. At the same time, it marks the low-temperature module with the lowest temperature and the high-temperature module with the highest temperature, and establishes a one-to-one correspondence data table between modules and temperatures.

[0074] The controller has two preset temperature difference thresholds: the first equalization threshold can be 1℃, and the second equalization threshold can be 3℃. The maximum temperature difference between multiple battery modules is T. max .

[0075] If T max When the temperature is less than 1℃, the power battery temperature is considered to be well consistent, and the power supply is evenly distributed among the heating elements.

[0076] If 1℃≤T max At temperatures ≤3℃, the power battery temperature consistency is poor, requiring temperature balancing. Following the core rule of "lower temperature, higher power supply priority," all battery modules are sorted in real-time, with the lowest-temperature module assigned the highest power supply priority and the highest-temperature module assigned the lowest. The system sets a minimum duty cycle of 5% and a maximum of 85%. The highest-priority battery module has an 85% duty cycle to allocate more photovoltaic output power and improve the heating rate; the lowest-priority battery module has a 5% duty cycle for only minor supplementary heating to avoid localized overheating; intermediate-priority battery modules are allocated duty cycles between 5% and 85% proportionally according to their priority. The total heating power of all zones is matched in real-time to the current total output power of the DC-DC converter, not exceeding the real-time output limit of the photovoltaic power generation unit, without consuming any power battery energy throughout the process.

[0077] If T maxIf the temperature exceeds 3℃, the power battery temperature becomes severely uneven. The duty cycle of the switch corresponding to the low-temperature battery module is adjusted to the maximum value to provide concentrated heating for the low-temperature battery module.

[0078] After each round of temperature data acquisition, the controller recalculates the module temperature difference, updates the power supply priority and duty cycle parameters of each branch, and continuously and dynamically corrects the PTC power supply power of each zone until the maximum temperature difference between all modules falls back to within the first-level balancing threshold. At this point, the system automatically switches to the equal power synchronous heating mode. For example, after a period of concentrated heating of the low-temperature battery modules, if the maximum temperature difference falls back to within the second-level balancing threshold, the system switches to the differentiated photovoltaic power allocation mode until the maximum temperature difference between all modules falls back to within the first-level balancing threshold.

[0079] During this process, if the photovoltaic output power decreases, the DC-DC converter 13 will simultaneously reduce the total output power, and the parallel supercapacitor 41 will release electrical energy instantaneously to smooth out the power drop and ensure that the heating process is continuous and uninterrupted.

[0080] The controller continuously monitors the vehicle status (driving / locking), the state of charge of the power battery, the temperature of the power battery, and the irradiance of the photovoltaic power generation unit.

[0081] When all conditions for the second mode are met, the controller issues a command to switch the system from the first mode to the second mode. Closed-loop temperature control is adopted, with the average temperature of the power battery or the lowest module temperature as the control object, and the target is the preset optimal start-up temperature of 15℃.

[0082] When the controller detects that the battery temperature reaches 15°C, or the photovoltaic irradiance drops to zero, or the vehicle is unlocked, or the state of charge of the power battery drops below 95% due to other static losses, the system exits the second mode and switches to the first mode.

[0083] According to an embodiment of the present invention, a self-preheating method for an electric vehicle battery is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0084] This embodiment provides a self-preheating method for electric vehicle batteries, which can be used in the controller of electric vehicles. Figure 5 This is a flowchart of a self-preheating method for an electric vehicle battery according to an embodiment of the present invention, such as... Figure 5 As shown, the process includes the following steps: Step S501: Obtain the operating status of the electric vehicle, the state of charge of the power battery, the temperature of the power battery, and the irradiance of the photovoltaic power generation unit.

[0085] In step S502, when the electric vehicle is in a locked state, the state of charge of the power battery is greater than or equal to the full charge threshold, the temperature of the power battery is less than or equal to the temperature start threshold, and the irradiance is greater than or equal to the photovoltaic start threshold, the control relay switches from the first mode to the second mode, so that the photovoltaic power generation unit 11 provides electrical energy to the heating unit to heat the power battery.

[0086] The first mode connects the photovoltaic power generation unit and the on-board charger via a relay, while the second mode connects the photovoltaic power generation unit and the DC-DC converter via a relay.

[0087] This embodiment provides a self-preheating method for electric vehicle batteries, which can be used in the controller of electric vehicles. Figure 6 This is a flowchart of a self-preheating method for an electric vehicle battery according to an embodiment of the present invention, such as... Figure 6 As shown, the process includes the following steps: Step S601: Obtain the operating status of the electric vehicle, the state of charge of the power battery, the temperature of the power battery, and the irradiance of the photovoltaic power generation unit.

[0088] In step S602, when the electric vehicle is locked, the state of charge of the power battery is greater than or equal to the full charge threshold, the temperature of the power battery is less than or equal to the temperature start threshold, and the irradiance is greater than or equal to the photovoltaic start threshold, the control relay switches from the first mode to the second mode, so that the photovoltaic power generation unit provides electrical energy to the heating unit to heat the power battery.

[0089] Step S603: Obtain multiple current temperatures corresponding to multiple battery modules from multiple temperature detection units.

[0090] Step S604: Based on multiple current temperatures, determine the average temperature of the power battery and the temperature difference between any two battery modules among the multiple battery modules.

[0091] Step S605: When the average temperature is less than or equal to the temperature start-up threshold, adjust the duty cycle of each of the multiple switches according to the temperature difference to adjust the power supply provided by the DC-DC converter to the multiple heating elements.

[0092] The sum of the power supplied to the multiple heating elements is the total power output of the DC-DC converter.

[0093] Taking an electric vehicle equipped with a 3.1-square-meter Si / perovskite tandem roof photovoltaic panel (peak power of approximately 860W) in winter as an example, the battery self-preheating method for electric vehicles provided by this invention will be described in detail.

[0094] The temperature dropped to -10℃ overnight, and the vehicle was locked in an outdoor parking lot. At 9:00 AM the next morning, the power battery was at 100% charge and the battery temperature was -5℃.

[0095] At this time, the sunlight intensifies, and the photovoltaic power generation unit begins generating electricity, outputting approximately 800W. The controller detects that the vehicle is locked, the battery's state of charge is 100% (greater than the full charge threshold), the battery temperature is -5℃ (less than the preset temperature start-up threshold of 5℃), and the photovoltaic irradiance is greater than 0, automatically switching the system to the second mode. The 860W of electrical energy generated by the photovoltaic panels is directly delivered to the 1000W PTC heating unit of the power battery via a dedicated DC-DC converter. Under continuous solar heating of approximately 860W, the power battery temperature steadily rises from -5℃. After about 40 minutes of solar heating, the power battery temperature reaches 12℃.

[0096] At 9:40 AM, the user prepares to use the vehicle, remotely unlocks it, and exits the heating mode. At this point, the battery is in a highly active state, the vehicle's power response is rapid, and the driving range is the same as when fully charged, achieving a rapid low-temperature start with zero loss.

[0097] like Figure 7 As shown, in the battery self-powered preheating scheme (i.e., the comparative example), the low temperature environment limits the battery's discharge capacity, resulting in low initial heating power. After 50 minutes, the temperature only reaches about 5°C, still below the optimal starting temperature, and the power output remains limited. However, by using the self-preheating method for electric vehicle batteries provided by this invention, the battery can immediately operate at rated power with a stable energy supply and constant heating power. The optimal starting temperature is reached in 20 minutes, and the power battery enters its optimal operating state in 30 minutes. Furthermore, in the battery self-heating scheme, the usable range is significantly reduced after preheating. This invention offers higher preheating efficiency, does not consume battery energy storage, and maintains the same driving range after preheating.

[0098] The changes in battery life between this embodiment and the comparative example are shown in Table 1.

[0099] Table 1. Comparison of battery life between the present invention and battery self-powered preheating.

[0100] In battery self-powered systems, battery discharge capacity is limited at low temperatures, and initial heating power is low, reaching only about 5°C after 50 minutes, still below the optimal start-up temperature, thus limiting power output. In this embodiment, the PTC heating unit can immediately operate at its rated power, providing stable energy supply with constant heating power. The optimal start-up temperature is reached in 20 minutes, and the battery enters its optimal operating state in 30 minutes. Furthermore, in battery self-heating systems, usable range is significantly reduced after preheating. This invention offers higher preheating efficiency, does not consume battery energy storage, and maintains the same driving range after preheating.

[0101] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A battery self-preheating system for electric vehicles, characterized in that, The system includes: A photovoltaic power generation unit is installed on the electric vehicle at a location exposed to sunlight and is connected to the on-board charger and the power battery via a relay. An irradiance sensor is used to detect the irradiance of the photovoltaic power generation unit; A heating unit is installed inside the power battery; A temperature sensor is installed inside the power battery; A DC-DC converter, one end of which is connected to the photovoltaic power generation unit via the relay, and the other end of which is connected to the heating unit; The controller, connected to the irradiance sensor, the temperature sensor, and the relay, is used to control the relay to switch from a first mode to a second mode when the electric vehicle is locked, the state of charge of the power battery is greater than or equal to a full charge threshold, the temperature of the power battery is less than or equal to a temperature start-up threshold, and the irradiance is greater than or equal to a photovoltaic start-up threshold. This allows the photovoltaic power generation unit to provide electrical energy to the heating unit to heat the power battery. In the first mode, the photovoltaic power generation unit and the on-board charger are connected through the relay. In the second mode, the photovoltaic power generation unit and the DC-DC converter are connected through the relay.

2. The system according to claim 1, characterized in that, The system also includes multiple switches, the power battery includes multiple battery modules, the heating unit includes multiple heating elements corresponding to each of the multiple battery modules, the temperature sensor includes multiple temperature detection units corresponding to each of the multiple battery modules, and the multiple switches correspond to each of the multiple heating elements. The control terminals of the plurality of switches are connected to the controller, the first connection terminals of the plurality of switches are all connected to the DC-DC converter, and the second connection terminals of the plurality of switches are connected to the corresponding heating elements. The controller is used to obtain multiple current temperatures corresponding to the multiple battery modules from the multiple temperature detection units, and to determine the average temperature of the power battery and the temperature difference between any two battery modules in the multiple battery modules based on the multiple current temperatures. The controller is further configured to, when the average temperature is less than or equal to the temperature start-up threshold, adjust the duty cycle of each of the plurality of switches according to the temperature difference, so as to adjust the power supply provided by the DC-DC converter to the plurality of heating elements, wherein the sum of the power supply corresponding to the plurality of heating elements is the total power output by the DC-DC converter.

3. The system according to claim 2, characterized in that, The controller is configured to adjust the duty cycle of all the switches to a first duty cycle when the maximum value of the temperature difference corresponding to the plurality of battery modules is less than a first equalization threshold. The first duty cycle is determined based on the average value of the total power output by the DC-DC converter. The controller is configured to adjust the duty cycle of the switch corresponding to the battery module according to the current temperature and the average temperature of the battery module when the maximum value is greater than or equal to the first equalization threshold and the maximum value is less than the second equalization threshold, so that the power supply of the heating element corresponding to the battery module with different current temperatures is different. The controller is configured to adjust the duty cycle of the switch corresponding to the target battery module to the maximum value when the maximum value is greater than or equal to the second equalization threshold, wherein the target battery module is the battery module with the lowest current temperature among the plurality of battery modules.

4. The system according to claim 3, characterized in that, The controller is configured to determine the priority of the battery module based on the absolute value of the difference between the current temperature and the average temperature of the battery module when the maximum value is less than or equal to the first equalization threshold and the maximum value is less than the second equalization threshold. The priority is proportional to the absolute value of the difference when the current temperature is less than the average temperature, and inversely proportional to the absolute value of the difference when the current temperature is greater than or equal to the average temperature. The controller is used to adjust the duty cycle of the corresponding switch according to the priority of the battery module, wherein the duty cycle is proportional to the priority.

5. The system according to any one of claims 1 to 4, characterized in that, The system also includes a maximum power point tracking controller, a voltage sampling unit, and a current sampling unit connected to the DC-DC converter; The voltage sampling unit is used to collect the output voltage of the photovoltaic power generation unit; The current sampling unit is used to collect the output current of the photovoltaic power generation unit; The maximum power point tracking controller is used to determine the maximum output power of the photovoltaic power generation unit based on the output voltage and the output current, and to control the total output power of the DC-DC converter to be the maximum output power.

6. The system according to any one of claims 1 to 4, characterized in that, The system also includes a maximum power point tracking controller and a power sensor connected to the DC-DC converter; The power sensor is used to detect the current power generation of the photovoltaic power generation unit; The maximum power point tracking controller is used to determine the maximum output power of the photovoltaic power generation unit based on the current power generation, and control the total output power of the DC-DC converter to be the maximum output power.

7. The system according to any one of claims 1 to 4, characterized in that, The photovoltaic power generation unit is a silicon-based perovskite tandem photovoltaic cell.

8. The system according to any one of claims 1 to 4, characterized in that, A capacitor is connected in parallel across the two ends of the DC-DC converter.

9. A method for self-preheating a battery in an electric vehicle, characterized in that, A controller applied to a battery self-preheating system of an electric vehicle according to any one of claims 1 to 8, the method comprising: The operating status of the electric vehicle, the state of charge of the power battery, the temperature of the power battery, and the irradiance of the photovoltaic power generation unit are obtained. When the electric vehicle is locked, the state of charge of the power battery is greater than or equal to the full charge threshold, the temperature of the power battery is less than or equal to the temperature start threshold, and the irradiance is greater than or equal to the photovoltaic start threshold, the relay is controlled to switch from the first mode to the second mode, so that the photovoltaic power generation unit provides electrical energy to the heating unit to heat the power battery. In the first mode, the photovoltaic power generation unit and the on-board charger are connected through the relay; in the second mode, the photovoltaic power generation unit and the DC-DC converter are connected through the relay.

10. The method according to claim 9, characterized in that, The method further includes: Multiple current temperatures, each corresponding to a specific battery module, are obtained from multiple temperature detection units. Based on the multiple current temperatures, determine the average temperature of the power battery and the temperature difference between any two battery modules among the multiple battery modules; When the average temperature is less than or equal to the temperature start-up threshold, the duty cycle of each of the multiple switches is adjusted according to the temperature difference to adjust the power supply provided by the DC-DC converter to the multiple heating elements, wherein the sum of the power supply corresponding to the multiple heating elements is the total power output by the DC-DC converter.

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