Battery thermal management system and control method

Abstract

The application discloses a battery thermal management system and a control method, and belongs to the field of vehicle battery thermal management. The battery thermal management control method judges the state of the battery through the maximum and minimum values of the battery temperature. When the battery temperature is relatively high, the air conditioning unit is controlled to refrigerate, so that the efficient operation of the battery is ensured. When the battery temperature is relatively low, the air conditioning unit is controlled to heat, so that the reliable operation of the battery is ensured, and the defects of battery capacity attenuation, lithium precipitation and insufficient charging and discharging power in a low-temperature environment are eliminated. When the temperature of the battery is relatively normal, the refrigeration and heating do not need to be greatly controlled, and only the temperature difference needs to be adjusted. According to the different environmental temperatures, the temperature difference is controlled to be reduced to a corresponding degree, so that when the environmental temperature is relatively low, the requirement for the reduction degree of the temperature difference is relatively high, excessive energy consumption is avoided, and the phenomenon that the user's driving experience is affected is avoided.

Description

Technical Field

[0001] This invention belongs to the field of vehicle battery thermal management, and in particular relates to a battery thermal management system and control method. Background Technology

[0002] Electric vehicles have become a trend in the automotive industry due to their energy-saving and environmentally friendly advantages. However, the battery packs of electric vehicles generate a significant amount of heat during use. This heat not only affects battery performance but also threatens vehicle safety. To address this, liquid cooling technology for battery packs has been proposed. In existing passenger vehicles, the battery pack is generally placed as a single unit within the chassis, resulting in relatively small temperature differences within the battery system. However, in existing commercial vehicles, due to the large number of battery packs and considerations for overall vehicle space and cost, the battery packs are often distributed in various locations throughout the vehicle. This leads to uneven heat dissipation in different areas, resulting in excessive temperature differences. Large temperature differences not only affect battery performance and lifespan but also cause abnormal activation of battery cooling and heating systems, increasing energy consumption.

[0003] To address temperature differences, a common approach is to reduce system temperature variations through a temperature equalization strategy. This involves activating a water pump to circulate the coolant throughout the battery cooling system, thereby balancing the temperature difference across the entire circuit. However, temperature equalization strategies are typically set solely based on battery temperature. When relying solely on single battery temperature data for temperature equalization, prolonged operation of the water pump's self-circulation in low-temperature environments increases overall vehicle energy consumption and reduces the water pump's lifespan. Furthermore, in extremely low-temperature environments, the coolant temperature within the water pump is very low, potentially allowing this cold coolant to enter the battery's surroundings and posing a battery safety risk.

[0004] In summary, existing thermal management control methods that rely solely on battery temperature data have problems such as increasing vehicle energy consumption, reducing water pump lifespan, and threatening battery safety. Summary of the Invention

[0005] The purpose of this invention is to provide a battery thermal management system and control method to solve the technical problems of existing thermal management control methods that rely solely on battery temperature data, such as increased vehicle energy consumption, reduced water pump lifespan, and threats to battery safety.

[0006] To achieve the above objectives, the technical solution of the battery thermal management system and control method provided by the present invention is as follows:

[0007] A battery thermal management control method, the method comprising the following steps:

[0008] During the self-circulation start-up process of the water pump, when the ambient temperature is ≥ the first ambient threshold and the battery temperature difference is ≥ the first temperature difference activation threshold, the water pump self-circulation is controlled to shut down when the battery temperature difference is ≤ the first temperature difference stop threshold; if the first ambient threshold is > the ambient temperature is ≥ the second ambient threshold and the battery temperature difference is ≥ the second temperature difference activation threshold, the water pump self-circulation is controlled to shut down when the battery temperature difference is ≤ the second temperature difference stop threshold; the first ambient threshold is > the second ambient threshold; the first temperature difference activation threshold is < the second temperature difference activation threshold, and the first temperature difference stop threshold is < the second temperature difference stop threshold.

[0009] As a further improvement, during the water pump self-circulation process, if the minimum battery temperature minus the outlet water temperature is greater than or equal to the outlet water temperature difference threshold and the minimum battery temperature is less than or equal to the correction risk threshold, the temperature data of the battery temperature sampling point is subtracted from the set temperature value within the set time of the water pump self-circulation start-up to complete the temperature correction, and the outlet water temperature difference threshold is less than the correction risk threshold.

[0010] As a further improvement, the method also includes controlling the pump self-circulation to shut down if the pump self-circulation start-up duration is greater than the self-circulation duration threshold.

[0011] As a further improvement, the method also includes controlling the water pump self-circulation to shut down when the minimum battery temperature is less than or equal to the self-circulation temperature threshold during the water pump self-circulation process.

[0012] As a further improvement, the method also includes prohibiting the start of the water pump self-circulation during the water pump self-circulation start-up process when the ambient temperature is ≤ a second ambient temperature threshold.

[0013] As a further improvement, the water pump self-circulation start-up condition is: the minimum battery temperature is greater than the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold.

[0014] As a further improvement, the method also includes controlling the air conditioning unit to start the cooling mode when the maximum battery temperature is ≥ the battery high temperature threshold and the minimum battery temperature is > the battery low temperature threshold, until the maximum temperature is ≤ the battery high temperature stop threshold and the minimum battery temperature is > the battery low temperature threshold; the battery high temperature threshold > the battery high temperature stop threshold > the battery low temperature threshold.

[0015] As a further improvement, when the minimum battery temperature is less than or equal to the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold, the air conditioning unit is controlled to start the heating mode until the maximum temperature is greater than or equal to the battery low temperature stop threshold and the minimum battery temperature is less than the battery high temperature threshold; where the battery high temperature threshold is greater than the battery low temperature stop threshold and the battery low temperature threshold is greater than the battery low temperature threshold.

[0016] The present invention also discloses a battery thermal management system, including an air conditioning unit, an air conditioning unit controller, and a battery management system. The battery management system uses the above-described battery thermal management control method embodiment to control the air conditioning unit controller in order to achieve switching between different modes of the air conditioning unit.

[0017] The beneficial effects of the battery thermal management control method of this invention are: during the water pump self-circulation process, i.e., when the current battery temperature is relatively normal, there is no need for significant cooling or heating; only temperature difference adjustment is required. The temperature difference is controlled to a corresponding degree according to different ambient temperatures, avoiding the excessive energy consumption and negative impact on the user's driving experience caused by the high requirement for a smaller temperature difference when the ambient temperature is low. This solves the problems of increased vehicle energy consumption, reduced water pump lifespan, and threats to battery safety inherent in thermal management control methods based solely on battery temperature data. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating an embodiment of the battery thermal management control method of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Example of battery thermal management control method:

[0021] This method controls the water pump's self-circulation to stop under different conditions based on varying ambient temperatures during the pump's self-circulation process. It classifies the battery's current state by setting low-temperature and high-temperature thresholds, and then, in conjunction with ambient temperature data, controls the air conditioning unit accordingly to achieve precise temperature regulation of the battery.

[0022] like Figure 1 As shown, the battery thermal management control method includes the following steps:

[0023] 1) When the battery system temperature meets condition one, control the air conditioning unit to turn on the cooling mode until the maximum temperature is less than or equal to the battery high-temperature stop threshold and the minimum battery temperature is greater than the battery low-temperature threshold. Specifically, when the battery temperature meets condition one, it means that the battery temperature is already very high. If the battery is used at a high temperature for a long time, its lifespan will be severely affected. In addition, it may also lead to high-temperature charging and discharging current limiting or power limiting, affecting the normal use of the customer. Therefore, it is necessary to control the air conditioning unit to turn on liquid cooling to cool the battery. At the same time, the liquid cooling itself has a similar effect to the self-circulation of a water pump, which can effectively reduce the temperature difference in the system.

[0024] 2) When the battery system temperature meets condition two, control the air conditioning unit to turn on the heating mode until the maximum temperature is greater than or equal to the battery low-temperature stop threshold and the minimum battery temperature is less than the battery high-temperature threshold. Specifically, when the battery temperature meets condition two, it means that the battery temperature is already very low and needs to be heated by controlling the PTC to turn on. If the battery is not heated when this limit is reached, as the battery temperature further decreases, not only will the battery's discharge capacity decay more and more severely, leading to a significant reduction in the vehicle's driving range, but it will also further limit the vehicle's charging / regenerative power, affecting the customer's driving experience; in addition, there is a risk of lithium plating during charging.

[0025] 3) When the battery system temperature meets condition three, if the ambient temperature ≥ the first ambient threshold and the battery temperature difference ≥ the first temperature difference activation threshold, then the water pump is controlled to start self-circulation until the battery temperature difference ≤ the first temperature difference stop threshold; if the first ambient threshold > the ambient temperature ≥ the second ambient threshold and the battery temperature difference ≥ the second temperature difference activation threshold, then the water pump is controlled to start self-circulation until the battery temperature difference ≤ the second temperature difference stop threshold. Specifically, when the ambient temperature is relatively high and the temperature difference between the battery operating temperature and the water temperature is relatively small, the battery temperature difference can be adjusted appropriately. Based on the battery temperature difference data, the water pump self-circulation is controlled to start until the system temperature difference is reduced to the target value. The self-circulation activation can reduce the system temperature difference to the target temperature difference in a short time. When the ambient temperature is relatively low and the temperature difference between the battery and the ambient temperature is relatively large, the coolant will dissipate a lot of heat during the circulation of the liquid cooling system through the pipes and cold plates. In this case, it will take longer for the system temperature difference to drop to the same target value, and the energy consumption of the water pump will be greater. Therefore, in order to balance the relationship between temperature difference and energy consumption, the target value for self-circulation is often appropriately relaxed to avoid excessive energy consumption of the water pump or failure to reduce the water temperature to the target temperature if self-circulation is continuously activated.

[0026] Among them, condition 1: maximum battery temperature ≥ battery high temperature threshold and minimum battery temperature > battery low temperature threshold; condition 2: minimum battery temperature ≤ battery low temperature threshold and maximum battery temperature < battery high temperature threshold; condition 3: minimum battery temperature > battery low temperature threshold and maximum battery temperature < battery high temperature threshold. Specifically, battery high temperature threshold > battery high temperature stop threshold > battery low temperature stop threshold > battery low temperature threshold; the first environmental threshold > the second environmental threshold; the first temperature difference activation threshold is greater than the first temperature difference stop threshold, the second temperature difference activation threshold is greater than the second temperature difference stop threshold, the first temperature difference activation threshold < the second temperature difference activation threshold, and the first temperature difference stop threshold < the second temperature difference stop threshold.

[0027] 4) This method also includes controlling the water pump self-circulation to shut down if the self-circulation start-up duration exceeds a self-circulation duration threshold. The reason is that during actual water pump self-circulation startup, uneven distribution of different branch pipes, pipe blockage, water pump malfunction, etc., may prevent the self-circulation from continuously reducing the temperature to the target value. If self-circulation continues, the system temperature difference may never decrease, leading to increased energy consumption from continuous water pump operation; it may also cause the system temperature difference to increase instead of decrease, triggering a vehicle system temperature difference alarm. Therefore, self-circulation should be shut down within the self-circulation duration threshold. Preferably, the self-circulation duration threshold is approximately 60 minutes.

[0028] The method also includes controlling the water pump self-circulation to shut off if the minimum battery temperature is less than or equal to the self-circulation temperature threshold during the water pump self-circulation process. When the coolant temperature is too low, or if the vehicle system piping is too long, there is too much coolant, or the battery's insulation performance is insufficient, the self-circulation may continuously lower the minimum battery temperature after it is activated. If the self-circulation is not shut off, it may cause premature heating, increasing the number of times heating is activated and leading to increased vehicle energy consumption.

[0029] 5) The method also includes prohibiting the water pump self-circulation when the battery system temperature meets condition three and the ambient temperature is ≤ the second ambient temperature threshold. At this time, the ambient temperature is already very low. If the excessively low coolant is introduced into the battery pack, it will not only fail to achieve temperature equalization, but will also lead to low-temperature lithium plating and accelerate the triggering of heating, increasing energy consumption.

[0030] 6) During the water pump self-circulation process, the air conditioner outlet water temperature is determined. If the minimum battery temperature minus the outlet water temperature is greater than or equal to the outlet water temperature difference threshold and the minimum battery temperature is less than or equal to the correction risk threshold, low-temperature correction is initiated. This outlet water temperature difference threshold is less than the correction risk threshold. Low-temperature correction refers to reducing the set temperature value of the battery temperature sampling point within the first set time after the water pump self-circulation starts. The reason is that when the low-temperature water pump self-circulation is in progress, the coolant temperature is very low at the start. The excessively low-temperature coolant quickly enters the battery system, rapidly cooling the bottom temperature of the battery. Due to the thermal resistance between the sampling point and the bottom of the cell, the temperature cannot be reflected to the sampling point in time. As a result, when the battery is charged or fed back according to the actual temperature of the sampling point, the actual bottom temperature of the cell exceeds the cell's relevant limits, leading to lithium plating safety issues during charging / feedback. Therefore, low-temperature correction is used to modify the temperature data of the sampling point. Preferably, the set temperature value is approximately 5°C.

[0031] To illustrate further, let's take a concrete example: First, collect battery temperature data and ambient temperature data from the battery system.

[0032] 1) If Tmax≥40℃ and Tmin>15℃, the liquid cooling system is turned on by controlling the air conditioning unit to cool the battery and reduce the system temperature difference until Tmax≤35℃ and Tmin>15℃, then it is turned off.

[0033] 2) When Tmin≤15 and Tmax<40℃, control the PTC to turn on to heat the battery and reduce the system temperature difference. When Tmin≥20℃ and Tmax<40℃, turn off the PTC.

[0034] 3) When 15℃ < Tmin and Tmax < 40℃, the ambient temperature is collected and determined by the air conditioning unit controller.

[0035] a. If the ambient temperature is ≥5℃ and Tmax-Tmin is ≥10℃, control the water pump to start self-circulation to equalize the temperature until Tmax-Tmin ≤5℃.

[0036] b. If 5℃ > ambient temperature ≥ -20℃ and Tmax-Tmin ≥ 20℃, control the water pump to start self-circulation to equalize the temperature until Tmax-Tmin ≤ 10℃.

[0037] C. If the ambient temperature is <-20℃, the coolant and ambient temperature are already very low, so it is forbidden to start the water pump self-circulation.

[0038] 4) During the water pump self-circulation process, if the water pump self-circulation start-up duration is >60min or the minimum battery temperature is ≤18℃, the water pump self-circulation will be turned off.

[0039] 5) During the water pump self-circulation process, continue to monitor the air conditioner outlet water temperature. If the difference between the minimum battery temperature and the air conditioner outlet water temperature is ≥10℃ and the minimum battery temperature is ≤25℃, control the activation of low-temperature correction. Low-temperature correction refers to reducing the temperature data at the battery temperature sampling point by 5℃ within 60 minutes of the water pump self-circulation starting.

[0040] The various thresholds in this invention are adaptively set according to the actual size, model, and application scenario of the battery system. This invention is not only applicable to commercial vehicles but also to other types of vehicles with similar problems. This application determines the battery state by using the maximum and minimum battery temperatures. When the battery temperature is high, the air conditioning unit is controlled to cool, ensuring efficient battery operation; when the battery temperature is low, the air conditioning unit is controlled to heat, ensuring reliable battery operation and eliminating defects such as battery capacity decay, lithium plating, and insufficient charge / discharge power in low-temperature environments.

[0041] Battery thermal management system example:

[0042] The battery thermal management system includes an air conditioning unit, an air conditioning unit controller, and a battery management system (BMS). The battery management system uses the battery thermal management control method embodiment described above to control the air conditioning unit controller, thereby enabling the switching of different modes of the air conditioning unit. This embodiment is implemented with reference to the battery thermal management control method embodiment described above, and will not be repeated here.

[0043] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery thermal management control method, characterized in that, The method includes the following steps: During the self-circulation start-up of the water pump, if the ambient temperature is greater than or equal to the first ambient threshold and the battery temperature difference is greater than or equal to the first temperature difference activation threshold, the water pump self-circulation will be shut off when the battery temperature difference is less than or equal to the first temperature difference stop threshold. If the first ambient threshold is greater than or equal to the ambient temperature, greater than or equal to the second ambient threshold and the battery temperature difference is greater than or equal to the second temperature difference activation threshold, the water pump self-circulation will be shut off when the battery temperature difference is less than or equal to the second temperature difference stop threshold. If the minimum battery temperature minus the outlet water temperature is greater than or equal to the outlet water temperature difference threshold and the minimum battery temperature is less than or equal to the correction risk threshold, the temperature data of the battery temperature sampling point will be subtracted from the set temperature value within the set time of the water pump self-circulation start-up to complete the temperature correction. The outlet water temperature difference threshold is less than the correction risk threshold. The first environmental threshold is greater than the second environmental threshold; the first temperature difference activation threshold is less than the second temperature difference activation threshold; and the first temperature difference stop threshold is less than the second temperature difference stop threshold.

2. The battery thermal management control method according to claim 1, characterized in that, The first temperature difference start threshold is greater than the first temperature difference stop threshold, and the second temperature difference start threshold is greater than the second temperature difference stop threshold.

3. The battery thermal management control method according to claim 1, characterized in that, The method also includes controlling the pump self-circulation to shut down if the pump self-circulation start-up duration is greater than the self-circulation duration threshold.

4. The battery thermal management control method according to claim 1, characterized in that, The method also includes controlling the water pump self-circulation to shut down when the minimum battery temperature is less than or equal to the self-circulation temperature threshold during the water pump self-circulation process.

5. The battery thermal management control method according to claim 1, characterized in that, The method also includes prohibiting the start of the water pump self-circulation during the water pump self-circulation start-up process when the ambient temperature is ≤ a second ambient temperature threshold.

6. The battery thermal management control method according to claim 1, characterized in that, The conditions for the water pump to start self-circulation are: the minimum battery temperature is greater than the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold.

7. The battery thermal management control method according to claim 1, characterized in that, The method further includes controlling the air conditioning unit to start the cooling mode when the maximum battery temperature is greater than or equal to the battery high temperature threshold and the minimum battery temperature is greater than the battery low temperature threshold, until the maximum temperature is less than or equal to the battery high temperature stop threshold and the minimum battery temperature is greater than the battery low temperature threshold; wherein the battery high temperature threshold is greater than the battery high temperature stop threshold and the battery low temperature threshold is greater than the battery low temperature threshold.

8. The battery thermal management control method according to claim 1, characterized in that, When the minimum battery temperature is less than or equal to the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold, the air conditioning unit is controlled to start the heating mode until the maximum temperature is greater than or equal to the battery low temperature stop threshold and the minimum battery temperature is less than the battery high temperature threshold; wherein the battery high temperature threshold is greater than the battery low temperature stop threshold and the battery low temperature threshold is greater than the battery low temperature threshold.

9. A battery thermal management system, characterized in that, It includes an air conditioning unit, an air conditioning unit controller, and a battery management system. The battery management system uses battery thermal management control methods to control the air conditioning unit controller to switch between different modes of the air conditioning unit, including the following steps: During the self-circulation start-up of the water pump, if the ambient temperature is greater than or equal to the first ambient threshold and the battery temperature difference is greater than or equal to the first temperature difference activation threshold, the water pump self-circulation will be shut off when the battery temperature difference is less than or equal to the first temperature difference stop threshold. If the first ambient threshold is greater than or equal to the ambient temperature, greater than or equal to the second ambient threshold and the battery temperature difference is greater than or equal to the second temperature difference activation threshold, the water pump self-circulation will be shut off when the battery temperature difference is less than or equal to the second temperature difference stop threshold. If the minimum battery temperature minus the outlet water temperature is greater than or equal to the outlet water temperature difference threshold and the minimum battery temperature is less than or equal to the correction risk threshold, the temperature data of the battery temperature sampling point will be subtracted from the set temperature value within the set time of the water pump self-circulation start-up to complete the temperature correction. The outlet water temperature difference threshold is less than the correction risk threshold. The first environmental threshold is greater than the second environmental threshold; the first temperature difference activation threshold is less than the second temperature difference activation threshold; and the first temperature difference stop threshold is less than the second temperature difference stop threshold.

10. The battery thermal management system according to claim 9, characterized in that, The first temperature difference start threshold is greater than the first temperature difference stop threshold, and the second temperature difference start threshold is greater than the second temperature difference stop threshold.

11. The battery thermal management system according to claim 9, characterized in that, The method also includes controlling the pump self-circulation to shut down if the pump self-circulation start-up duration is greater than the self-circulation duration threshold.

12. The battery thermal management system according to claim 9, characterized in that, The method also includes controlling the water pump self-circulation to shut down when the minimum battery temperature is less than or equal to the self-circulation temperature threshold during the water pump self-circulation process.

13. The battery thermal management system according to claim 9, characterized in that, The method also includes prohibiting the start of the water pump self-circulation during the water pump self-circulation start-up process when the ambient temperature is ≤ a second ambient temperature threshold.

14. The battery thermal management system according to claim 9, characterized in that, The conditions for the water pump to start self-circulation are: the minimum battery temperature is greater than the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold.

15. The battery thermal management system according to claim 9, characterized in that, The method further includes controlling the air conditioning unit to start the cooling mode when the maximum battery temperature is greater than or equal to the battery high temperature threshold and the minimum battery temperature is greater than the battery low temperature threshold, until the maximum temperature is less than or equal to the battery high temperature stop threshold and the minimum battery temperature is greater than the battery low temperature threshold; wherein the battery high temperature threshold is greater than the battery high temperature stop threshold and the battery low temperature threshold is greater than the battery low temperature threshold.

16. The battery thermal management system according to claim 9, characterized in that, When the minimum battery temperature is less than or equal to the battery low temperature threshold and the maximum battery temperature is less than the battery high temperature threshold, the air conditioning unit is controlled to start the heating mode until the maximum temperature is greater than or equal to the battery low temperature stop threshold and the minimum battery temperature is less than the battery high temperature threshold; wherein the battery high temperature threshold is greater than the battery low temperature stop threshold and the battery low temperature threshold is greater than the battery low temperature threshold.

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