Vehicle battery thermal management method

Abstract

The application provides a vehicle battery thermal management method. A battery cooling plate is arranged at the bottom of a battery, and a temperature sensor is arranged at the top of the battery. The vehicle battery thermal management method comprises the following steps: determining a predicted temperature of the bottom of the battery according to a top temperature of the battery measured by the temperature sensor; obtaining a correction temperature difference, wherein the correction temperature difference represents a difference between the predicted temperature of the bottom of the battery and an actual temperature of the bottom of the battery; when the correction temperature difference is less than a first temperature difference threshold, executing a first temperature difference strategy, wherein the first temperature difference strategy comprises: when a thermal management system is in a battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode; when the correction temperature difference is greater than or equal to the first temperature difference threshold, executing a second temperature difference strategy, wherein the second temperature difference strategy comprises: controlling the thermal management system to be in a battery waste heat recovery disabled mode. In this way, the risk of lithium precipitation of the battery during charging and discharging is reduced.

Description

Technical Field

[0001] This application relates to the field of vehicle thermal management, and more particularly to a method for thermal management of vehicle batteries. Background Technology

[0002] When the battery acts as a heat source to heat the passenger compartment (in waste heat recovery mode), the coolant actively absorbs heat from the battery to heat the passenger compartment circuitry. Current electric vehicle battery thermal management systems typically only place a limited number of temperature sensors (such as NTC thermistors) on the top of the battery pack to monitor battery temperature. This arrangement generally meets the requirements in conventional thermal management scenarios, but it has shortcomings in the operating mode where the battery acts as a heat source to heat the passenger compartment (battery waste heat recovery mode). When the system uses the heat stored in the battery to heat the passenger compartment circuitry, the low-temperature coolant flows through the battery cooling plate, actively absorbing heat from the battery, causing the temperature of the battery area near the cooling plate to drop. If the battery is charged at this time, the actual temperature at the bottom of the battery may already be below the safe charging temperature threshold, but the system mistakenly judges that high-rate charging is allowed based on the temperature detected by the temperature sensors, thus triggering the risk of lithium ion deposition on the surface of the battery's negative electrode. Summary of the Invention

[0003] This application provides a vehicle battery thermal management method and a vehicle battery thermal management system that can reduce the risk of lithium ion deposition on the surface of the battery negative electrode.

[0004] In a first aspect, this application provides a vehicle battery thermal management method, wherein a battery cooling plate is provided at the bottom of the battery, and the vehicle battery thermal management method includes: The expected temperature of the bottom of the battery is determined based on the temperature of the top of the battery measured by the temperature sensor. Obtain the corrected temperature difference, which represents the difference between the expected temperature at the bottom of the battery and the actual temperature at the bottom of the battery; When the corrected temperature difference is less than the first temperature difference threshold, the first temperature difference strategy is executed. The first temperature difference strategy includes: when the thermal management system is in the battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode, determining the battery charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference; and charging and discharging the battery based on the charging and discharging current. When the corrected temperature difference is greater than or equal to the first temperature difference threshold, a second temperature difference strategy is executed. The second temperature difference strategy includes controlling the thermal management system to be in a battery waste heat recovery disabled mode.

[0005] Optionally, the first temperature difference strategy includes a first low temperature difference strategy and a first medium temperature difference strategy; The execution of the first temperature difference strategy includes: When the corrected temperature difference is less than the second temperature difference threshold, the first low temperature difference strategy is executed, where the second temperature difference threshold is less than the first temperature difference threshold. The first low temperature difference strategy includes: when the thermal management system is in the battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode, determining the battery charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery based on the charging and discharging current; When the corrected temperature difference is greater than the second temperature difference threshold and less than the first temperature difference threshold, the first intermediate temperature difference strategy is executed; the first intermediate temperature difference strategy includes: controlling the thermal management system to maintain the current mode, the current mode being the battery waste heat recovery mode or the battery waste heat recovery disabled mode.

[0006] Optionally, the first low temperature difference strategy includes: When the thermal management system is in battery waste heat recovery disabled mode, determine whether the thermal management system meets the waste heat recovery conditions. When the thermal management system meets the waste heat recovery conditions, in response to the waste heat recovery request, the thermal management system is controlled to start the battery waste heat recovery mode.

[0007] Optionally, the battery cooling plate includes a coolant inlet and a coolant outlet; The waste heat recovery conditions include: the coolant temperature at the coolant inlet is lower than a set temperature and remains so for a first set duration; the coolant temperature at the coolant outlet is higher than the coolant temperature at the coolant inlet, and the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet is greater than an effective difference; and the coolant flow rate of the battery is greater than a set flow rate.

[0008] Optionally, the first low temperature difference strategy further includes: When the thermal management system is in battery waste heat recovery mode, it controls the water pump connected to the cooling plate to maintain its current speed.

[0009] Optionally, the first temperature difference strategy further includes: When the thermal management system is in battery waste heat recovery mode, the speed of the water pump connected to the cooling plate of the thermal management system is controlled to be higher than the speed threshold.

[0010] Optionally, the battery has multiple temperature difference filtering modes, and the second temperature difference strategy further includes: When the thermal management system is in the battery waste heat recovery disabled mode, the thermal management system is controlled to start the temperature difference filtering mode so that the corrected temperature difference decays to the correction threshold within a set time.

[0011] Optionally, the temperature difference filtering mode includes a fast filtering mode, a medium-speed filtering mode, and a slow filtering mode; The control of the thermal management system to activate the temperature difference filtering mode includes: When the battery is in heating / cooling mode, the thermal management system is controlled to start the fast filtering mode so that the corrected temperature difference decays to the correction threshold within a second set time period. When the battery is in the temperature equalization mode, the thermal management system is controlled to start the medium-speed filtering mode so that the corrected temperature difference decays to the correction threshold within a third set time period. When the battery is in idle mode, the thermal management system is controlled to start the slow filtering mode so that the corrected temperature difference decays to the correction threshold within a fourth set time period. Wherein, the second set duration is less than the third set duration; the third set duration is less than the fourth set duration.

[0012] Optionally, the second temperature difference strategy further includes: When the thermal management system is in the temperature difference filtering mode, the corrected temperature difference has not decreased to 0, and the vehicle is powered off, record the timestamp of the vehicle being powered off and the corrected temperature difference at the time of power off; When the vehicle is powered on again, the duration of the power-off is determined based on the timestamp of the vehicle being powered off and the timestamp of the vehicle being powered on again. Based on the power-off duration and the corrected temperature difference at the time of power-off, the temperature difference filtering mode after the thermal management system is powered on again, and the corrected temperature difference of the battery after power-on are determined.

[0013] Optionally, obtaining the corrected temperature difference includes: Obtain battery temperature difference correction parameter values, which include the coolant temperature at the coolant inlet of the cooling plate, the coolant temperature at the coolant outlet, the coolant flow rate, and the maximum temperature of the battery. The corrected temperature difference is determined based on the battery temperature difference correction parameter value.

[0014] Optionally, determining the corrected temperature difference based on the battery temperature difference correction parameter value includes: The corrected temperature difference is determined based on the battery temperature difference correction parameter value and the temperature difference expression; The temperature difference expression includes the sum of the first, second, and third terms, and the product of the difference between the cell temperature of the battery and the coolant temperature at the coolant inlet. The first item is the product of the first weighting coefficient and the coolant flow rate; the second item includes the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet, plus the second weighting coefficient; the third item includes the difference between the cell temperature and the coolant temperature at the coolant inlet, plus the third weighting coefficient.

[0015] In this application, when the corrected temperature difference is less than a first temperature difference threshold, the difference between the expected temperature and the actual temperature at the bottom of the battery is small. The thermal management system is in battery waste heat recovery mode, and the system is controlled to maintain this mode. The charging and discharging current is determined based on the expected bottom temperature and the corrected temperature difference, and the battery is charged or discharged according to this current. The corrected temperature difference represents the difference between the expected bottom temperature and the actual bottom temperature of the battery. The expected bottom temperature and the measured top temperature of the battery are related. Therefore, the charging and discharging current can be adjusted based on the actual bottom temperature, avoiding high current charging and discharging when the actual bottom temperature is too low, thus reducing the risk of lithium plating during charging and discharging.

[0016] When the corrected temperature difference is greater than or equal to the first temperature difference threshold, the difference between the expected temperature at the bottom of the battery and the actual temperature at the bottom of the battery is large, resulting in a large difference between the actual temperature at the bottom of the battery and the temperature at the top of the battery. The actual temperature at the bottom of the battery may be too low. At this time, the thermal management system is controlled to be in the battery waste heat recovery disabled mode, thereby reducing the risk of lithium plating in the battery during charging and discharging caused by the actual temperature at the bottom of the battery being too low. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0018] Figure 1 The diagram shown is a schematic representation of an embodiment of the vehicle battery thermal management method of this application.

[0019] Figure 2 As shown Figure 1 A detailed schematic diagram of the vehicle battery thermal management method is shown.

[0020] Figure 3 As shown Figure 1 A detailed schematic diagram of the vehicle battery thermal management method is shown.

[0021] Figure 4 As shown Figure 1 A detailed schematic diagram of the vehicle battery thermal management method is shown.

[0022] Figure 5 The diagram shown is a schematic representation of an embodiment of the vehicle battery thermal management system of this application.

[0023] Explanation of reference numerals in the attached figures: 10, Vehicle battery thermal management system; 11, Processor; 12, Storage medium; 13, Memory; 14, Interface. Detailed Implementation

[0024] The technical solutions in the embodiments (or "implementations") of this application will be clearly and completely described herein with reference to the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0025] If the embodiments of this application contain terms relating to directional indications or positional relationships (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationships and movement of the components in a specific posture (as shown in the attached figures); if the specific posture changes, the directional indications or positional relationships will also change accordingly. Furthermore, the terms "first" and "second" used in the embodiments of this application are only for descriptive convenience and should not be construed as indicating or implying relative importance.

[0026] This application provides a vehicle battery thermal management method. The vehicle battery thermal management method of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0027] This application provides a vehicle battery thermal management system, applied to a vehicle, specifically a pure electric vehicle or a hybrid vehicle. The vehicle also includes a battery. The thermal management system includes a passenger compartment circuit and a battery circuit. The passenger compartment circuit and the battery circuit are interconnected, and the excess heat generated during battery operation is recovered through coolant flowing in both circuits for heating the passenger compartment. This process is the battery waste heat recovery mode of the thermal management system. Specifically, the battery circuit is located within the battery and is used to heat or cool the battery; the passenger compartment circuit is located within the vehicle's passenger compartment and is used to heat or cool the passenger compartment.

[0028] The battery features a temperature sensor at its top, which acquires the temperature of the top of the battery and uses this temperature to predict the temperature of the bottom, thus obtaining the predicted bottom temperature. A battery cooling plate is located at the bottom of the battery, with coolant channels within the cooling plate forming the battery circuit. These coolant channels include a coolant inlet and a coolant outlet. The thermal management system achieves heat exchange between the battery and the coolant in the channels, and heats the passenger compartment circuit by delivering the coolant that absorbs heat from the battery.

[0029] The thermal management system implements vehicle battery thermal management methods. See also Figure 1 As shown, the vehicle battery thermal management method includes steps S10, S20, S30 and S40.

[0030] In step S10, the expected temperature of the bottom of the battery is determined based on the temperature of the top of the battery measured by the temperature sensor. There is a specific relationship between the expected temperature of the bottom of the battery and the temperature of the top of the battery. The expected temperature of the bottom of the battery can be the temperature of the top of the battery plus or minus a fixed value. This fixed value can be determined according to the characteristics of the battery or obtained through experimentation.

[0031] In step S20, the corrected temperature difference is obtained. The corrected temperature difference represents the difference between the expected temperature and the actual temperature at the bottom of the battery. Due to heat exchange between the battery cooling plate and the bottom of the battery, the actual temperature and the expected temperature at the bottom of the battery are inconsistent. The corrected temperature difference can be obtained when the thermal management system is in battery waste heat recovery mode. In response to a waste heat recovery request, the thermal management system enters battery waste heat recovery mode if the waste heat recovery conditions are met.

[0032] In step S30, when the corrected temperature difference is less than the first temperature difference threshold, the first temperature difference strategy is executed. The first temperature difference strategy includes: when the thermal management system is in battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode; determining the battery's charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery according to the charging and discharging current. The first temperature difference threshold can be 10℃, 12℃, or 15℃, and can be adjusted according to the battery type, size, etc. Specifically, the actual temperature at the bottom of the battery is obtained through the expected temperature and the corrected temperature. The battery management system determines the safe charging and discharging current corresponding to the current actual temperature at the bottom of the battery by querying the current limit table, and charges or discharges the battery according to the charging and discharging current. This ensures that the battery's charging and discharging current is more consistent with the actual temperature at the bottom of the battery, reducing the risk of lithium plating during charging and discharging due to excessively low actual bottom temperature.

[0033] In step S40, when the corrected temperature difference is greater than or equal to the first temperature difference threshold, a second temperature difference strategy is executed. The second temperature difference strategy includes controlling the thermal management system to be in a battery waste heat recovery disabled mode. When the thermal management system is in the battery waste heat recovery mode, the thermal management system will stop the currently running battery waste heat recovery mode, or, without responding to a battery waste heat recovery request, activate the battery waste heat recovery disabled mode.

[0034] When the corrected temperature difference is less than the first temperature difference threshold, the difference between the expected temperature and the actual temperature at the bottom of the battery is small. In this case, the thermal management system is in battery waste heat recovery mode, maintaining this mode and determining the charging / discharging current based on the expected bottom temperature and the corrected temperature difference. The corrected temperature difference represents the difference between the expected bottom temperature and the actual bottom temperature, which is related to the measured top temperature. Therefore, the charging / discharging current can be adjusted based on the actual bottom temperature, avoiding high current charging / discharging when the actual bottom temperature is too low, thus reducing the risk of lithium plating during charging / discharging. When the corrected temperature difference is greater than or equal to the first temperature difference threshold, the difference between the expected bottom temperature and the actual bottom temperature is large, resulting in a significant difference between the actual bottom temperature and the top temperature. The actual bottom temperature may be too low. In this case, the thermal management system is in battery waste heat recovery disabled mode, further reducing the risk of lithium plating during charging / discharging caused by an excessively low bottom temperature.

[0035] When the corrected temperature difference is less than the first temperature difference threshold, the thermal management system is in battery waste heat recovery mode, and the system maintains this mode. A corrected temperature difference less than the first threshold indicates a small difference between the expected temperature and the actual temperature at the bottom of the battery. This means the difference between the actual bottom temperature and the top temperature measured by the temperature sensor is also small. In this case, if the thermal management system is in battery waste heat recovery mode, the top temperature meets the requirements, and therefore the actual bottom temperature also meets the requirements, thus maintaining the battery waste heat recovery mode.

[0036] In an optional embodiment, see Figure 2 As shown, the first temperature difference strategy includes a first low temperature difference strategy and a first medium temperature difference strategy.

[0037] Step S30: Execute the first temperature difference strategy, including steps S31 and S32.

[0038] In step S31, when the corrected temperature difference is less than the second temperature difference threshold, the first low temperature difference strategy is executed. The second temperature difference threshold is less than the first temperature difference threshold, and the second temperature difference threshold can be 5℃, 7℃, or 10℃. The second temperature difference threshold can be adjusted according to the battery type, size, etc. The first low temperature difference strategy includes: when the thermal management system is in battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode, determining the battery charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery according to the charging and discharging current.

[0039] In step S32, when the corrected temperature difference is greater than the second temperature difference threshold and less than the first temperature difference threshold, a first temperature difference strategy is executed. The first temperature difference strategy includes: controlling the thermal management system to maintain the current mode, which is either battery waste heat recovery mode or battery waste heat recovery disabled mode. The first temperature difference strategy may further include: when the current mode is battery waste heat recovery mode, determining the battery's charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery according to the charging and discharging current.

[0040] A corrected temperature difference less than the second temperature difference threshold indicates a very small temperature difference, classified as a low temperature difference. A corrected temperature difference greater than the second temperature difference threshold but less than the first temperature difference threshold indicates a relatively small temperature difference, classified as a medium temperature difference. When the corrected temperature difference is less than the second temperature difference threshold, the difference between the expected temperature and the actual temperature at the bottom of the battery is small. If the thermal management system is in battery waste heat recovery mode, it can continue in this mode to utilize the heat generated by the battery operation to heat the passenger compartment, thereby reducing energy consumption during vehicle operation. Furthermore, the charging and discharging current of the battery can be determined based on the expected temperature and the corrected temperature difference at the bottom of the battery, and the battery can be charged and discharged accordingly. This also reduces the risk of lithium plating in the battery.

[0041] When the corrected temperature difference is greater than or equal to the second temperature difference threshold and less than the first temperature difference threshold, the thermal management system is controlled to maintain the current mode, avoiding frequent switching between battery waste heat recovery mode and battery waste heat recovery disabled mode, thereby improving the stability of the thermal management system during operation and reducing the energy consumption of the thermal management system.

[0042] In an optional embodiment, see Figure 3 As shown, the first low temperature difference strategy includes steps S311 and S312.

[0043] In step S311, when the thermal management system is in the battery waste heat recovery disabled mode, it is determined whether the thermal management system meets the waste heat recovery conditions.

[0044] In step S312, when the thermal management system meets the waste heat recovery conditions, in response to a waste heat recovery request, the thermal management system is controlled to start the battery waste heat recovery mode. The battery waste heat recovery mode is entered when the waste heat recovery conditions are met and a waste heat recovery request is received. If the waste heat recovery conditions are not met, and / or a waste heat recovery request is not received, the battery waste heat recovery mode is not entered, and the battery waste heat recovery is disabled in the disabled mode, without recovering any waste heat from the battery.

[0045] When the corrected temperature difference is less than the second temperature difference threshold and the thermal management system meets the waste heat recovery conditions, the thermal management system is controlled to start the battery waste heat recovery mode in response to the waste heat recovery request, so as to use the heat generated by the battery operation to heat the passenger compartment and reduce the energy consumption generated by the vehicle during driving. At this time, the risk of lithium plating during battery charging and discharging is relatively small, which is conducive to comprehensively considering the utilization of battery waste heat and the guarantee of battery health.

[0046] In an optional embodiment, the waste heat recovery conditions include: the coolant temperature at the coolant inlet is lower than a set temperature and remains so for a first set duration; the coolant temperature at the coolant outlet is higher than the coolant temperature at the coolant inlet, and the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet is greater than an effective difference; and the coolant flow rate of the battery is greater than a set flow rate.

[0047] When all the above waste heat recovery conditions are met, it means that the heat generated by the battery operation has been effectively removed. On this basis, the thermal management system enters the waste heat recovery mode and uses the heat generated by the battery operation to heat the passenger compartment, thereby reducing the energy consumption generated by the vehicle during driving.

[0048] In a further embodiment, the vehicle battery thermal management method further includes: acquiring the corrected temperature difference again at regular monitoring intervals. The monitoring interval can be set to 5 to 10 seconds. During the operation of the thermal management system, the battery temperature also changes, and the corrected temperature difference may also change. By acquiring the corrected temperature difference again at regular intervals, the strategy is adjusted based on the corrected temperature difference. This allows the thermal management system's operating mode to be adjusted in real time according to the corrected temperature difference, which is beneficial for comprehensively considering the utilization of battery waste heat and ensuring battery health, and can further reduce the risk of lithium plating in the battery.

[0049] In an optional embodiment, the first low-temperature difference strategy further includes: when the thermal management system is in battery waste heat recovery mode, controlling the water pump connected to the thermal management system and the cooling plate to maintain its current rotation speed. The water pump is used to circulate the coolant in the cooling plate.

[0050] Thus, when the risk of temperature difference between the expected temperature at the bottom of the battery and the actual temperature at the bottom of the battery is low, the water pump that maintains the connection between the thermal management system and the cooling plate maintains its current speed to maximize the use of the heat generated by the battery operation to heat the passenger compartment, thereby reducing the energy consumption generated by the vehicle during driving.

[0051] In an optional embodiment, the first temperature difference strategy further includes: when the thermal management system is in battery waste heat recovery mode, controlling the speed of the water pump connected to the cooling plate of the thermal management system to be higher than a speed threshold.

[0052] By using the above method, when the corrected temperature difference is greater than or equal to the second temperature difference threshold and less than the first temperature difference threshold, the risk of further increase in the corrected temperature difference can be reduced, thereby ensuring the waste heat recovery conditions and maintaining the thermal management system in waste heat recovery mode to maximize the use of the heat generated by battery operation to heat the crew cabin.

[0053] In optional embodiments, the battery has multiple temperature difference filtering modes. The second temperature difference strategy further includes: when the thermal management system is in a battery waste heat recovery disabled mode, controlling the thermal management system to activate the temperature difference filtering mode so that the corrected temperature difference decays to a correction threshold within a set time period. In some of the cases mentioned above where the thermal management system enters the battery waste heat recovery disabled mode, the temperature difference filtering mode is activated after the thermal management system enters the battery waste heat recovery disabled mode. The thermal management system operates in the temperature difference filtering mode, causing the corrected temperature difference to decay to a correction threshold within a set time period. In some embodiments, the correction threshold is 0°C.

[0054] By activating the temperature difference filtering mode, the difference between the expected temperature and the actual temperature at the bottom of the battery is reduced, resulting in a smaller temperature difference between the bottom and top of the battery. This leads to a more uniform overall battery temperature, which is beneficial for both utilizing residual heat and ensuring battery health.

[0055] The temperature difference filtering modes include fast filtering mode, medium-speed filtering mode, and slow filtering mode. Controlling the thermal management system to activate the temperature difference filtering mode includes: When the battery is in heating / cooling mode, the thermal management system activates a fast filtering mode to reduce the corrected temperature difference to the correction threshold within a second set time period. Specifically, the second set time period can be set to 10 to 20 seconds.

[0056] When the battery is in the equalization mode, the thermal management system activates the medium-speed filtering mode to reduce the temperature difference to the correction threshold within a third set time period. Specifically, the second set time period is shorter than the third set time period, which can be set to 3 to 5 minutes.

[0057] When the battery is in idle mode, the thermal management system activates a slow filtering mode to allow the corrected temperature difference to decay to the correction threshold within a fourth set time period. When the battery is in idle mode, the vehicle is powered on, but there is no need to activate the thermal management system. Specifically, the third set time period is shorter than the fourth set time period, which can be set to 20 to 30 minutes.

[0058] Depending on the battery's operating power, the actual temperature rise rate at the bottom of the battery varies. Three filtering modes—fast, medium, and slow—are used to adjust the temperature difference correction. The higher the battery's operating power, the faster the temperature difference filtering mode operates, and the shorter the set duration. The battery's operating power in heating / cooling mode is greater than that in the equal-temperature mode, and the battery's operating power in the equal-temperature mode is greater than that in the idle mode.

[0059] By employing the above method, the battery can operate and release heat when it is in heating / cooling mode, temperature equalization mode, and idle mode, depending on different vehicle driving conditions. During this process, the thermal management system is in a battery waste heat recovery disabled mode, and there is no longer heat exchange between the bottom of the battery and the cooling plate. This causes the actual temperature of the bottom of the battery to rise, reducing the difference between the expected temperature and the actual temperature of the bottom of the battery. This results in a smaller temperature difference between the bottom and top of the battery, making the overall battery temperature uniform, ensuring battery health, extending battery life, and reducing the risk of lithium plating during subsequent charging and discharging processes.

[0060] In an optional embodiment, the second temperature difference strategy further includes: when the thermal management system is in temperature difference filtering mode, the corrected temperature difference has not decreased to the correction threshold, and the vehicle is powered off, recording the timestamp of the vehicle being powered off and the corrected temperature difference at the time of power off; when the vehicle is powered on again, determining the duration of the vehicle being powered off based on the timestamp of the vehicle being powered off and the timestamp of the vehicle being powered on again; and determining the temperature difference filtering mode of the thermal management system after being powered on again and the corrected temperature difference of the battery after being powered on again based on the duration of the power off and the corrected temperature difference at the time of power off.

[0061] In this way, the battery temperature gradually decreases after power-off. Based on the duration of power-off, it is helpful to accurately determine the corrected temperature difference between the expected temperature and the actual temperature at the bottom of the battery after power-on. This helps to accurately determine the actual temperature at the bottom of the battery. Furthermore, based on the battery status after power-off and the next power-on, the temperature difference filtering mode of the thermal management system can be further determined. This is beneficial for controlling the mode of the thermal management system and controlling the charging and discharging of the battery based on a more accurate corrected temperature difference, thus helping to comprehensively consider the utilization of battery waste heat and the guarantee of battery health.

[0062] In an optional embodiment, see Figure 4As shown, step S20 involves obtaining the corrected temperature difference between the expected temperature at the bottom of the battery and the actual temperature at the bottom of the battery, including steps S21 and S22.

[0063] In step S21, the battery temperature difference correction parameter values ​​are obtained. The battery temperature difference correction parameter values ​​include the coolant temperature at the coolant inlet of the cooling plate, the coolant temperature at the coolant outlet, the coolant flow rate, and the maximum battery temperature.

[0064] In step S22, the corrected temperature difference is determined based on the battery temperature difference correction parameter value.

[0065] The corrected temperature difference is determined based on the coolant temperature at the coolant inlet, the coolant temperature at the coolant outlet, the coolant flow rate, and the maximum temperature of the battery. Taking into account the degree of heat exchange between the coolant and the battery and the battery temperature, the corrected temperature difference can be determined more accurately.

[0066] In an optional embodiment, see Figure 4 As shown, step S22, determining the corrected temperature difference based on the battery temperature difference correction parameter value, includes step S221.

[0067] In step S221, the corrected temperature difference is determined based on the battery temperature difference correction parameter value and the temperature difference expression.

[0068] The temperature difference expression includes the sum of the first, second, and third terms, and the product of the difference between the cell temperature and the coolant temperature at the coolant inlet.

[0069] The first term is the product of the first weighting coefficient and the coolant flow rate; the second term includes the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet, and the second weighting coefficient; the third term includes the difference between the cell temperature and the coolant temperature at the coolant inlet, and the third weighting coefficient.

[0070] In this embodiment, an equivalent thermal resistance network model is used to accurately describe the temperature distribution of the battery under waste heat recovery mode. The equivalent thermal resistance network model simplifies the heat transfer path from the battery to the coolant into three series thermal resistances: the internal thermal resistance of the battery cell and the internal thermal resistance of the battery itself. -Contact thermal resistance - Convection thermal resistance - Coolant. Based on the equivalent thermal resistance network model, the actual temperature at the bottom of the battery. With cell temperature The relationship can be represented as:

[0071] Where Q represents the heat power absorbed by the coolant. ,in, This refers to the flow rate of the coolant. This refers to the coolant outlet temperature. This refers to the coolant inlet temperature. Specific heat capacity of coolant, representing the amount of heat required to raise the temperature by 1°C per unit mass of coolant. Internal thermal resistance of battery. Contact thermal resistance is used to represent the resistance to heat conduction within battery materials and is related to the battery materials and structure. This represents the thermal resistance at the interface between the battery and the cold plate. Convection thermal resistance. The convective thermal resistance used to represent the convective thermal resistance between the coolant and the cold plate is related to the coolant flow state, the cold plate structure, the coolant flow rate, and the flow channel dimensions. The convective heat transfer coefficient is inversely proportional to the product of the convective heat transfer coefficient and the area. The convective heat transfer coefficient can be solved based on the flow state of the coolant using empirical correlations.

[0072] in, The convective heat transfer coefficient represents the heat transfer power per unit area under a unit temperature difference, and can be calibrated experimentally or using empirical formulas. is the thermal conductivity of the coolant, used to represent the thermal conductivity of the coolant; is the hydraulic diameter, used to represent the characteristic dimension of the coolant flow channel cross section; Re is the Reynolds number, a dimensionless number used to characterize the flow state and to determine whether it is laminar or turbulent flow; Pr is the Prandtl number, used to characterize the ratio of momentum diffusion to thermal diffusivity.

[0073] Furthermore, correct the temperature difference. It can be represented as:

[0074]

[0075] Among them, the first item First weighting coefficient and coolant flow rate The product of these two terms reflects the impact of flow rate on heat exchange efficiency; the second term... Coolant outlet temperature and coolant inlet temperature The difference, divided by the reference temperature difference Then, with the second weighting coefficient The product of these terms reflects the actual amount of heat exchanged; the third term... Battery top temperature With coolant inlet temperature The difference, divided by the reference temperature difference Then, with the third weighting coefficient The product of these terms is used to reflect the nonlinear temperature gradient effect. Wherein, the reference temperature difference... This is the calibration constant.

[0076] To meet the computational requirements of the vehicle controller, a multi-dimensional lookup table can be established. Inputting the coolant inlet temperature, coolant outlet temperature, coolant flow rate, and the battery's maximum temperature as battery temperature correction parameters, the corrected temperature value can be obtained by looking up the table. In practical applications, if the input parameters are not exactly equal to discrete points in the table, bilinear or trilinear interpolation methods can be used to obtain the correction value, thereby reducing the computational process for correcting the temperature difference during actual vehicle operation.

[0077] In other embodiments, the corrected temperature difference can also be determined directly at the vehicle end based on the battery temperature difference correction parameter value and the temperature difference expression.

[0078] In this embodiment, in response to a waste heat recovery request, a corrected temperature difference is obtained, and it is determined that the thermal management system meets the waste heat recovery conditions. When the waste heat recovery conditions are met, the thermal management system activates the battery waste heat recovery mode, while simultaneously monitoring the corrected temperature difference. When the corrected temperature difference is less than a second temperature difference threshold, a first low temperature difference strategy is executed; when the corrected temperature difference is greater than the second temperature difference threshold but less than the first temperature difference threshold, a first medium temperature difference strategy is executed. When the corrected temperature difference is greater than or equal to the first temperature difference threshold, a second temperature difference strategy is executed, i.e., the thermal management system is controlled to be in a battery waste heat recovery disabled mode. Furthermore, when the thermal management system is in the battery waste heat recovery disabled mode, the thermal management system is controlled to activate a temperature difference filtering mode to cause the corrected temperature difference to decay to the corrected threshold within a set time period.

[0079] Figure 5 This is a schematic diagram of a vehicle battery thermal management system provided in one embodiment of this application. The vehicle battery thermal management system includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements a vehicle thermal management control method.

[0080] exist Figure 5 In the illustrated embodiment, the vehicle battery thermal management system may include a storage medium 12, which may store a program that can be called by the processor 11, and may include a non-volatile storage medium. In some embodiments, the vehicle thermal management control system 3 may include memory 13 and an interface 14. In some embodiments, the vehicle battery thermal management system may also include other hardware depending on the actual application.

[0081] The storage medium 12 stores a program that, when executed, implements a vehicle thermal management control method. In some embodiments, it may take the form of a computer program product implemented on one or more storage media 12 containing program code (including but not limited to disk storage, CD-ROM, optical storage, etc.). The storage medium 12 includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information may be computer-readable instructions, data structures, program modules, or other data. Examples of storage media 12 include, but are not limited to: phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information that can be accessed by a computing device.

[0082] It should be noted that the technical solutions or features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the accompanying drawings; all modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A vehicle battery thermal management method, a bottom of a battery is provided with a battery cooling plate, a top of the battery is provided with a temperature sensor, characterized in that, The vehicle battery thermal management method includes: The expected temperature of the bottom of the battery is determined based on the temperature of the top of the battery measured by the temperature sensor. Obtain the corrected temperature difference, which represents the difference between the expected temperature at the bottom of the battery and the actual temperature at the bottom of the battery; When the corrected temperature difference is less than the first temperature difference threshold, the first temperature difference strategy is executed. The first temperature difference strategy includes: when the thermal management system is in the battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode, determining the battery charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery based on the charging and discharging current. When the corrected temperature difference is greater than or equal to the first temperature difference threshold, a second temperature difference strategy is executed. The second temperature difference strategy includes controlling the thermal management system to be in a battery waste heat recovery disabled mode.

2. The vehicle battery thermal management method of claim 1, wherein, The first temperature difference strategy includes a first low temperature difference strategy and a first medium temperature difference strategy; The execution of the first temperature difference strategy includes: When the corrected temperature difference is less than the second temperature difference threshold, the first low temperature difference strategy is executed, where the second temperature difference threshold is less than the first temperature difference threshold. The first low temperature difference strategy includes: when the thermal management system is in the battery waste heat recovery mode, controlling the thermal management system to maintain the battery waste heat recovery mode, determining the battery charging and discharging current based on the expected temperature at the bottom of the battery and the corrected temperature difference, and charging and discharging the battery based on the charging and discharging current; When the corrected temperature difference is greater than the second temperature difference threshold and less than the first temperature difference threshold, the first intermediate temperature difference strategy is executed; the first intermediate temperature difference strategy includes: controlling the thermal management system to maintain the current mode, the current mode being the battery waste heat recovery mode or the battery waste heat recovery disabled mode.

3. The vehicle battery thermal management method of claim 2, wherein, The first low temperature difference strategy includes: When the thermal management system is in battery waste heat recovery disabled mode, determine whether the thermal management system meets the waste heat recovery conditions. When the thermal management system meets the waste heat recovery conditions, in response to the waste heat recovery request, the thermal management system is controlled to start the battery waste heat recovery mode.

4. The vehicle battery thermal management method of claim 3, wherein, The battery cooling plate includes a coolant inlet and a coolant outlet; The waste heat recovery conditions include: the coolant temperature at the coolant inlet is lower than a set temperature and remains so for a first set duration; the coolant temperature at the coolant outlet is higher than the coolant temperature at the coolant inlet, and the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet is greater than an effective difference; and the coolant flow rate of the battery is greater than a set flow rate.

5. The vehicle battery thermal management method according to claim 2, characterized in that, The first low temperature difference strategy also includes: When the thermal management system is in battery waste heat recovery mode, the water pump connected to the cooling plate of the thermal management system is controlled to maintain its current speed; and / or The first temperature difference strategy also includes: When the thermal management system is in battery waste heat recovery mode, the speed of the water pump connected to the cooling plate of the thermal management system is controlled to be higher than the speed threshold.

6. The vehicle battery thermal management method according to claim 1, characterized in that, The battery has multiple temperature difference filtering modes, and the second temperature difference strategy further includes: When the thermal management system is in the battery waste heat recovery disabled mode, the thermal management system is controlled to start the temperature difference filtering mode so that the corrected temperature difference decays to the correction threshold within a set time.

7. The vehicle battery thermal management method according to claim 6, characterized in that, The temperature difference filtering modes include fast filtering mode, medium-speed filtering mode and slow filtering mode; The control of the thermal management system to activate the temperature difference filtering mode includes: When the battery is in heating / cooling mode, the thermal management system is controlled to start the fast filtering mode so that the corrected temperature difference decays to the correction threshold within a second set time period. When the battery is in the temperature equalization mode, the thermal management system is controlled to start the medium-speed filtering mode so that the corrected temperature difference decays to the correction threshold within a third set time period. When the battery is in idle mode, the thermal management system is controlled to start the slow filtering mode so that the corrected temperature difference decays to the correction threshold within a fourth set time period. Wherein, the second set duration is less than the third set duration; the third set duration is less than the fourth set duration.

8. The vehicle battery thermal management method according to claim 7, characterized in that, The second temperature difference strategy also includes: When the thermal management system is in the temperature difference filtering mode, the corrected temperature difference has not decreased to 0, and the vehicle is powered off, record the timestamp of the vehicle being powered off and the corrected temperature difference at the time of power off; When the vehicle is powered on again, the duration of the power-off is determined based on the timestamp of the vehicle being powered off and the timestamp of the vehicle being powered on again. Based on the power-off duration and the corrected temperature difference at the time of power-off, the temperature difference filtering mode after the thermal management system is powered on again, and the corrected temperature difference of the battery after power-on are determined.

9. The vehicle battery thermal management method according to claim 1, characterized in that, The process of obtaining the corrected temperature difference includes: Obtain battery temperature difference correction parameter values, which include the coolant temperature at the coolant inlet of the cooling plate, the coolant temperature at the coolant outlet, the coolant flow rate, and the maximum temperature of the battery. The corrected temperature difference is determined based on the battery temperature difference correction parameter value.

10. The vehicle battery thermal management method according to claim 9, characterized in that, The step of determining the corrected temperature difference based on the battery temperature difference correction parameter value includes: The corrected temperature difference is determined based on the battery temperature difference correction parameter value and the temperature difference expression; The temperature difference expression includes the sum of the first, second, and third terms, and the product of the difference between the cell temperature of the battery and the coolant temperature at the coolant inlet. The first item is the product of the first weighting coefficient and the coolant flow rate; the second item includes the difference between the coolant temperature at the coolant outlet and the coolant temperature at the coolant inlet and the second weighting coefficient; and the third item includes the difference between the cell temperature and the coolant temperature at the coolant inlet and the third weighting coefficient.

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