Power battery system super-low temperature charging and discharging heat management method

Abstract

The application discloses a kind of power battery system super low temperature charge-discharge heat management methods, comprising: starting fuel cell system under super low temperature environment, pull up the power of the fuel cell system, the electric energy generated is used to power heater and fuel cell auxiliary components;Control water pump to circulate cooling liquid between power battery pack and fuel cell system;According to the temperature of power battery pack, control electronic thermostat to switch cooling liquid circulation mode;When power battery pack reaches the first preset temperature, the fuel cell system is closed, and only rely on heater to provide heat for power battery pack;When heater cannot guarantee the temperature rise of power battery pack, restart fuel cell system.The power battery system super low temperature charge-discharge heat management method of the application uses the wide temperature range characteristics of fuel cell to heat the power battery pack under extremely cold conditions, so as to ensure the normal use of vehicle, solve the industry problem that power battery cannot charge and discharge below-40 DEG C, and improve the extreme cold adaptability of whole vehicle.

Description

Technical Field

[0001] This invention belongs to the field of automotive power battery technology. Specifically, this invention relates to a method for ultra-low temperature charging and discharging thermal management of a power battery system. Background Technology

[0002] The power battery system is the power source of an electric vehicle and serves as an energy storage device; its capacity affects the vehicle's driving range. However, power batteries are quite sensitive to temperature, especially in ambient temperatures below -30°C, where low temperatures can negatively impact their discharge performance. To ensure better battery discharge and extend its lifespan, the power battery needs to be heated during electric vehicle operation in low-temperature conditions. Traditionally, power battery heating involves using a fixed-power heating device to continuously heat the battery, stopping heating once a certain temperature is reached or after a specified period.

[0003] Fuel cells, as a novel energy source, have experienced rapid development in recent years. Based on the type of electrolyte, fuel cells can be categorized into proton exchange membrane fuel cells, solid oxide fuel cells, alkaline fuel cells, molten carbonate fuel cells, and phosphoric acid fuel cells. Each type of fuel cell has its specific operating scenarios and technological advantages. Proton exchange membrane fuel cells, due to their high energy conversion efficiency, environmental friendliness, low operating noise, relatively small size, fewer components, and good reliability and maintainability, have been demonstrated in small-scale applications. According to power rating, fuel cell systems can currently be classified into low-power fuel cell systems (watts (W) to tens of watts (W)), medium-power fuel cell systems (hundreds of watts (hundreds of W) to several kilowatts (several kW)), high-power fuel cell systems (several kilowatts (several kW) to tens of kilowatts (several kW)), and ultra-high-power fuel cell systems (tens of kilowatts (several kW) to megawatts (MW). Medium-power fuel cell systems have high energy density and can meet medium-scale energy needs, such as small vehicles (e.g., motorcycles, small trucks), small to medium-sized backup power supplies, and small boats.

[0004] In low-temperature environments, power battery systems experience problems such as short driving range, low discharge rate, and long charging / heating times. Especially when the ambient temperature is below -30℃, the power battery system can only discharge at a very low rate, and some systems are even designed to not discharge at all. When the ambient temperature is below -20℃, the power battery system can only be charged with a very low current when equipped with an auxiliary heating system, and the minimum allowable discharge temperature is -5℃. Furthermore, at low temperatures, the corresponding charge and discharge rates are both low, failing to address the issues of insufficient power for vehicle operation in low-temperature conditions and the inability or excessive charging time at low temperatures.

[0005] This invention provides a method for thermal management of power battery systems at ultra-low temperatures during charging and discharging, particularly concerning how to meet the charging and discharging requirements of power battery packs under low-temperature conditions and increase vehicle driving range. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for ultra-low temperature charging and discharging thermal management of a power battery system, with the purpose of meeting the charging and discharging requirements of the power battery pack under low-temperature conditions and increasing the vehicle's driving range.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an ultra-low temperature charging and discharging thermal management method for power battery systems, comprising:

[0008] In an ultra-low temperature environment, the fuel cell system is started, increasing its power output to power the heater and auxiliary components. A water pump is controlled to circulate coolant between the battery pack and the fuel cell system. Based on the battery pack temperature, an electronic thermostat switches the coolant circulation mode. When the battery pack reaches a first preset temperature, the fuel cell system is shut down, relying solely on the heater to provide heat. If the heater cannot guarantee a temperature increase for the battery pack, the fuel cell system is restarted.

[0009] The ultra-low temperature environment is an ambient temperature of -40℃.

[0010] The electronic thermostat is controlled to switch the coolant circulation mode according to the power battery pack temperature. Specifically, when the power battery pack temperature is below -20℃, the electronic thermostat is controlled to switch to small circulation so that the coolant does not pass through the radiator.

[0011] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0012] When the heater fails, the fuel cell system is started in an ultra-low temperature environment, increasing the power of the fuel cell system to a preset power range, and using the heat generated by the fuel cell system to heat the power battery pack; when the temperature of the fuel cell system continues to rise and the heat dissipation through the cooling pipes cannot meet the heat dissipation requirements of the fuel cell system itself, the cooling fan is turned on; when the temperature of the power battery pack rises to a second preset temperature, the fuel cell system is shut down; when the temperature of the power battery pack drops below a set value, the fuel cell system is restarted.

[0013] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0014] When the power battery pack is charged by an external power source, it draws power directly from the external power supply equipment and uses the heater to heat the power battery pack.

[0015] When the power battery pack is within the dischargeable temperature range, power is drawn from the power battery pack to shut down the fuel cell system and heat the power battery pack to a third preset temperature.

[0016] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0017] When the power battery pack is depleted and cannot support the vehicle's pure electric driving, the fuel cell system is activated, and the vehicle enters electric-electric hybrid mode. The fuel cell system outputs a portion of its power to the electric drive system to drive the vehicle, and supplies the excess energy to the power battery pack for recharging.

[0018] The cooling pipeline includes a first cooling branch and a second cooling branch. The fuel cell system is connected to the battery pack cooling pipeline through the first cooling branch, and the battery pack cooling pipeline is connected to the power battery pack. The fuel cell system is connected to the water pump through the second cooling branch, and the water pump is connected to the battery pack cooling pipeline.

[0019] A first solenoid valve is installed in the first cooling branch, and a second solenoid valve is installed in the second cooling branch.

[0020] The first cooling branch is connected to the radiator via the fourth cooling branch, the water pump is connected to the electronic thermostat via the fifth cooling branch, the electronic thermostat is connected to the radiator via the third cooling branch, and the heater is connected to the electronic thermostat and the fourth cooling branch.

[0021] The ultra-low temperature charging and discharging thermal management method for power battery systems of the present invention has the following beneficial effects:

[0022] 1) Utilizing the wide temperature range characteristics of fuel cells, the power battery pack can be heated under extremely cold conditions, thereby ensuring the normal use of the vehicle, solving the industry problem that power batteries cannot be charged and discharged below -40℃, and improving the vehicle's extreme cold adaptability.

[0023] 2) The fuel cell system can replenish the energy of the vehicle and the power battery system when the power battery is at a low SOC, reducing the risk of accidental failure and alleviating user concerns;

[0024] 3) The power battery system features dual heating via liquid heat and heater, with each heat source operating independently. This design improves system reliability and increases the heating rate of the battery system, shortening the heating time for low-temperature charging and thus accelerating the charging rate.

[0025] 4) Utilize waste heat from fuel cells to reduce additional energy consumption, and combine this with control strategies to achieve efficient energy distribution;

[0026] 5) The system features integrated functions, combining waste heat utilization, low-temperature energy replenishment, and dynamic heating control into a single solution. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the thermal management principle for low-temperature charging of power batteries;

[0028] The markings in the above diagrams are as follows: 001, fuel cell; 002, intake pipe; 003, air system; 004, hydrogen system; 005, heater; 006, power battery pack; 007, first cooling branch; 008, radiator; 009, cooling fan; 010, water pump; 011, electronic thermostat; 012, first solenoid valve; 013, second solenoid valve; 014, first pressure sensor; 016, second pressure sensor; 015, first temperature sensor; 017, second temperature sensor; 018, expansion tank; 019, second cooling branch; 020, battery pack cooling branch; 021, fourth cooling branch; 022, fifth cooling branch; 023, third cooling branch. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0030] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," and similar expressions used in this document are for illustrative purposes only.

[0031] It should be noted that in the following embodiments, the terms "first", "second", "third", "fourth" and "fifth" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution, but are merely for the convenience of description.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] This invention provides a method for ultra-low temperature charging and discharging thermal management of a power battery system, comprising:

[0034] In an ultra-low temperature environment, the fuel cell system is started, increasing its power output to power the heater and auxiliary components. A water pump is controlled to circulate coolant between the battery pack and the fuel cell system. Based on the battery pack temperature, an electronic thermostat switches the coolant circulation mode. When the battery pack reaches a first preset temperature, the fuel cell system is shut down, relying solely on the heater to provide heat. If the heater cannot guarantee a temperature increase for the battery pack, the fuel cell system is restarted.

[0035] The ultra-low temperature environment is an ambient temperature of -40℃.

[0036] The electronic thermostat is controlled to switch the coolant circulation mode according to the power battery pack temperature. Specifically, when the power battery pack temperature is below -20℃, the electronic thermostat is controlled to switch to small circulation so that the coolant does not pass through the radiator.

[0037] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0038] When the heater fails, the fuel cell system is started in an ultra-low temperature environment, increasing the power of the fuel cell system to a preset power range, and using the heat generated by the fuel cell system to heat the power battery pack; when the temperature of the fuel cell system continues to rise and the heat dissipation through the cooling pipes cannot meet the heat dissipation requirements of the fuel cell system itself, the cooling fan is turned on; when the temperature of the power battery pack rises to a second preset temperature, the fuel cell system is shut down; when the temperature of the power battery pack drops below a set value, the fuel cell system is restarted.

[0039] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0040] When the power battery pack is charged by an external power source, it draws power directly from the external power supply equipment and uses the heater to heat the power battery pack.

[0041] When the power battery pack is within the dischargeable temperature range, power is drawn from the power battery pack to shut down the fuel cell system and heat the power battery pack to a third preset temperature.

[0042] The aforementioned method for ultra-low temperature charge and discharge thermal management of power battery systems also includes:

[0043] When the power battery pack is depleted and cannot support the vehicle's pure electric driving, the fuel cell system is activated, and the vehicle enters electric-electric hybrid mode. The fuel cell system outputs a portion of its power to the electric drive system to drive the vehicle, and supplies the excess energy to the power battery pack for recharging.

[0044] The cooling pipeline includes a first cooling branch and a second cooling branch. The fuel cell system is connected to the battery pack cooling pipeline through the first cooling branch, and the battery pack cooling pipeline is connected to the power battery pack. The fuel cell system is connected to the water pump through the second cooling branch, and the water pump is connected to the battery pack cooling pipeline.

[0045] A first solenoid valve is installed in the first cooling branch, and a second solenoid valve is installed in the second cooling branch.

[0046] The first cooling branch is connected to the radiator via the fourth cooling branch, the water pump is connected to the electronic thermostat via the fifth cooling branch, the electronic thermostat is connected to the radiator via the third cooling branch, and the heater is connected to the electronic thermostat and the fourth cooling branch.

[0047] Specifically, the fuel cell system exhibits good low-temperature performance and can operate within a wide temperature range of -40℃ to 90℃. This invention integrates the fuel cell system with the thermal management of the power battery system. Building upon existing power battery system heating solutions, it uses the fuel cell system as a parallel energy source to preheat the battery at extremely low temperatures and replenish it at low SOC levels, thereby meeting the charging and discharging requirements of the vehicle under low-temperature conditions and increasing its driving range.

[0048] This invention utilizes a fuel cell system as both an energy and heat source to preheat the battery during charging at low temperatures and to replenish it at low state of charge (SOC). A 10kW fuel cell system is considered optimal in terms of both size and price. However, any power rating can be used as a preheating device, not limited to 10kW. Due to its excellent low-temperature performance, the fuel cell system can self-start without auxiliary heating in environments as low as -40°C. Specifically, the fuel cell system is an energy conversion device, providing oxygen for the chemical reaction via an air system and hydrogen via a hydrogen system. During the electrochemical reaction of H2 and O2 to produce water, in addition to providing electrical energy to the external circuit, a significant amount of heat is released. Since the overall efficiency of the fuel cell system is approximately 45% (converted to electrical efficiency), the remainder is dissipated as heat, including through exhaust and radiative heat dissipation from the casing. However, these two forms of heat are negligible. The vast majority of the heat is carried away by the coolant.

[0049] like Figure 1 As shown, the fuel cell system includes a fuel cell 001, a hydrogen system for supplying hydrogen to the fuel cell 001, an air system for supplying air to the fuel cell 001, and a cooling path for supplying coolant to the fuel cell 001. The cooling path includes cooling pipes, a heater 005, a water pump 010, an electronic thermostat 011, a cooling fan 009, and a radiator 008. The heater 005 is a PTC heater. The cooling pipes include a first cooling branch 007 and a second cooling branch 019. The fuel cell 001 is connected to the battery pack cooling pipes via the first cooling branch 007, and the battery pack cooling pipes are connected to the power battery pack 006. The fuel cell 001 is connected to the water pump 010 via the second cooling branch 019, and the water pump 010 is connected to the battery pack cooling pipes. A first solenoid valve 012 is installed in the first cooling branch 007, and a second solenoid valve 013 is installed in the second cooling branch 019. The first cooling branch 007 is connected to the radiator 008 via the fourth cooling branch 021. The water pump 010 is connected to the electronic thermostat 011 via the fifth cooling branch 022. The electronic thermostat 011 is connected to the radiator 008 via the third cooling branch 023. The heater 005 is connected to the electronic thermostat 011 and the fourth cooling branch 021.

[0050] like Figure 1 As shown, the cooling circuit can form a small cooling water circulation loop that does not flow through the radiator 008 and a large cooling water circulation loop that flows through the radiator 008. One end of the heater 005 is connected to the first working port of the electronic thermostat 011, the other end of the heater 005 is connected to the fourth cooling branch 021, the second working port of the electronic thermostat 011 is connected to the water pump 010, and the third working port of the electronic thermostat 011 is connected to the radiator 008.

[0051] When the temperature of fuel cell 001 is low, the cooling circuit can form a small circulation loop of cooling water that does not flow through radiator 008. Heater 005 works to generate heat. The coolant flowing out of fuel cell 001 flows sequentially through water pump 010, electronic thermostat 011, and heater 005 before returning to fuel cell 001. When the temperature of fuel cell 001 rises, the cooling circuit can form a large circulation loop of cooling water that flows through radiator 008. The coolant flowing out of fuel cell 001 flows sequentially through water pump 010, electronic thermostat 011, and radiator 008 before returning to fuel cell 001. Radiator 008 cools the coolant, and cooling fan 009 cools radiator 008.

[0052] When fuel cell 001 is started in an ultra-low temperature environment, it generates heat, which circulates in the cooling circuit, providing heat to the power battery pack 006. The battery temperature continuously rises as the fuel cell system continues to operate. Data from temperature and pressure sensors in the system is used to adjust the power of fuel cell 001 and determine whether to switch to a larger circulation mode. The first and second pressure sensors are primarily used to detect water pressure in the pipeline to determine if the water pump 010 is functioning correctly.

[0053] Example 1

[0054] In this embodiment, the ultra-low temperature environment is an ambient temperature of -40°C or an ambient temperature below -40°C.

[0055] The fuel cell system can start normally at an ambient temperature of -40℃. At this point, the power of fuel cell 001 is rapidly increased to power heater 005 and fuel cell auxiliary components. Because the temperature of the power battery pack 006 is extremely low, it cannot store the electrical energy generated by the fuel cell system. Therefore, a control strategy is needed to ensure that all generated electrical energy is used to power heater 005 and fuel cell auxiliary components. Water pump 010 is activated to its maximum speed to rapidly circulate coolant between the battery pack and the fuel cell.

[0056] In the initial stage, when the temperature is below -20℃, the electronic thermostat 011 switches to a small circulation mode, so that the coolant does not pass through the radiator 008, and the cooling circuit forms a small circulation loop of cooling water that does not flow through the radiator 008.

[0057] When the temperature rises to the fast-charging temperature of the power battery pack 006, i.e., the temperature of the power battery pack 006 reaches the first preset temperature, the fuel cell 001 is shut down, and the first solenoid valve 012 and the second solenoid valve 013 are closed, relying solely on the heater 005 to provide heat to the power battery pack 006. If the heater 005 alone cannot guarantee the temperature rise of the battery pack under low-temperature conditions, it is necessary to promptly activate the fuel cell 001 to ensure that the heat can continuously meet the requirements of fast charging.

[0058] Example 2

[0059] In this embodiment, the fuel cell system starts by heating the power battery pack 006 with its own cooling water.

[0060] When heater 005 fails, the fuel cell system can be used to heat the power battery pack 006. Specifically, at an ambient temperature of -40℃, fuel cell 001 starts working. Through control, the power of fuel cell 001 is quickly increased to an appropriate power range. The main reason for this is that the heat generated by the stack varies with different power levels. In the initial stage, the heat generated is dissipated through cooling water in the cooling pipes without needing to turn on the cooling fan 009. This cooling water can then flow through the power battery pack 006, thereby heating the power battery pack 006 while also reducing the cooling pressure on the fuel cell system.

[0061] If the fuel cell temperature continues to rise and the cooling pipes are insufficient to meet the heat dissipation needs of fuel cell 001, then cooling fan 009 will be activated to cool the system and prevent overheating. When the temperature of the power battery pack 006 reaches the required temperature, fuel cell 001 will be shut down. If it is found that the temperature of the power battery pack 006 is extremely low, and although it is discharging, the temperature drop of the power battery pack 006 is significant due to the extremely low ambient temperature, then fuel cell 001 needs to be restarted.

[0062] Example 3

[0063] In this embodiment, the fuel cell system is not started. When the power battery pack 006 draws power from the charging pile or external circuit, it is heated by the heater 005.

[0064] When the vehicle charges the power battery pack 006 through an external power source, the fuel cell 001 does not need to be started. Power can be drawn directly from external power supply equipment (charging pile, etc.), and the heater 005 is used to heat the coolant. When the heated coolant flows through the power battery pack 006, it can heat the power battery pack 006, thereby meeting the vehicle's charging needs.

[0065] When the power battery pack 006 is within its discharge temperature range, power can still be drawn directly from the power battery pack 006 without utilizing the fuel cell 001, and the power battery pack 006 can be heated to its optimal discharge temperature range. This method, on the one hand, allows the power battery pack 006 to be heated even in the event of a fuel cell 001 failure, ensuring smooth vehicle operation. On the other hand, it conserves the energy of the fuel cell 001, allowing it to be used in emergency situations.

[0066] Example 4

[0067] In this embodiment, when the power battery pack 006 is depleted, the fuel cell system charges the power battery pack 006 on one hand and supplies power to the electric drive system on the other to drive the vehicle.

[0068] When the power battery pack 006 is depleted and cannot support the vehicle's pure electric driving, the fuel cell 001 is activated, starting the electric-electric hybrid mode. On the one hand, the fuel cell 001 can output a portion of its power to the vehicle for driving, and on the other hand, it can supply excess energy to the power battery pack 006 to recharge it, thereby increasing the vehicle's driving range, reducing user anxiety, and optimizing the user experience.

[0069] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for ultra-low temperature charge and discharge thermal management of a power battery system, characterized in that, include: The fuel cell system is started in an ultra-low temperature environment, the power of the fuel cell system is increased, and the generated electrical energy is used to power the heater. The system controls the water pump to circulate coolant between the power battery pack and the fuel cell system; it controls the electronic thermostat to switch the coolant circulation mode according to the power battery pack temperature; when the power battery pack reaches a first preset temperature, the fuel cell system is shut down, and the power battery pack is heated only by the heater; when the heater cannot guarantee the temperature rise of the power battery pack, the fuel cell system is restarted.

2. The method of claim 1, wherein, The ultra-low temperature environment is an ambient temperature of -40℃.

3. The method of claim 1, wherein, The electronic thermostat is controlled to switch the coolant circulation mode according to the power battery pack temperature. Specifically, when the power battery pack temperature is below -20℃, the electronic thermostat is controlled to switch to small circulation so that the coolant does not pass through the radiator.

4. The method of claim 1 to 3, wherein, Also includes: When the heater fails, the fuel cell system is started in an ultra-low temperature environment, and the power of the fuel cell system is increased to a preset power range. The heat generated by the fuel cell system is used to heat the power battery pack. When the temperature of the fuel cell system continues to rise and the heat dissipation through the cooling pipes cannot meet the heat dissipation requirements of the fuel cell system itself, the cooling fan is turned on. When the temperature of the power battery pack rises to a second preset temperature, the fuel cell system is shut down. When the temperature of the power battery pack drops below a set value, the fuel cell system is restarted.

5. The method of claim 1 to 3, wherein, Also includes: When the power battery pack is charged by an external power source, it draws power directly from the external power supply equipment and uses the heater to heat the power battery pack.

6. The method of claim 5, wherein, When the power battery pack is within the dischargeable temperature range, power is drawn from the power battery pack to shut down the fuel cell system and heat the power battery pack to a third preset temperature.

7. The method of claim 1 to 3, wherein, Also includes: When the power battery pack is depleted and cannot support the vehicle's pure electric driving, the fuel cell system is activated, and the vehicle enters electric-electric hybrid mode. The fuel cell system outputs a portion of its power to the electric drive system to drive the vehicle, and supplies the excess energy to the power battery pack for recharging.

8. The method of claim 1 to 3, wherein, The cooling pipeline includes a first cooling branch and a second cooling branch. The fuel cell system is connected to the battery pack cooling pipeline through the first cooling branch, and the battery pack cooling pipeline is connected to the power battery pack. The fuel cell system is connected to the water pump through the second cooling branch, and the water pump is connected to the battery pack cooling pipeline.

9. The method of claim 8, wherein, A first solenoid valve is installed in the first cooling branch, and a second solenoid valve is installed in the second cooling branch.

10. The method of claim 8, wherein, The first cooling branch is connected to the radiator via the fourth cooling branch, the water pump is connected to the electronic thermostat via the fifth cooling branch, the electronic thermostat is connected to the radiator via the third cooling branch, and the heater is connected to the electronic thermostat and the fourth cooling branch.

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