Constant power test method and system of power battery pack liquid cooling system

Abstract

The invention relates to the technical field of power battery pack testing, in particular to a constant-power testing method and system for a liquid cooling system of a power battery pack, and the method comprises the steps: employing a constant-power testing device of the power battery pack, calculating a temperature difference T through a backflow flow G and a power set value Q, and carrying out the constant-power testing of the liquid cooling system of the power battery pack; and the cooling liquid medium is cooled or heated by detecting that the load power P connected with the power battery pack is larger than or smaller than the power set value Q, and then the power battery pack operates at constant power. The constant-power operation of the power battery pack has the beneficial effects of prolonging the service life of the battery, improving the cruising ability and ensuring the stable operation of the battery in different environments. Due to the beneficial effects, constant-power operation becomes an effective method for improving the performance of the power battery and prolonging the service life of the power battery.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery pack testing, and specifically to a constant power testing method and system for a liquid cooling system of a power battery pack. Background Art

[0002] In recent years, with the continuous support of the country for new energy, power battery technology has developed rapidly. Power batteries are mainly used in new energy vehicles and energy storage devices. Encouraged by national policies, power batteries have made great progress in high density, high power, fast charging and discharging, and there are increasingly high requirements for the battery capacity and charging and discharging power of power battery packs. Therefore, the use of a liquid cooling system to control the temperature of power batteries has replaced air-cooled heat dissipation.

[0003] In the prior art, the patent with the publication number CN112629770A discloses a testing method for a liquid cooling system of a power battery pack for a new energy vehicle. This patent discloses that by building a test bench, placing the battery pack on the table, and connecting the battery pack, the liquid cooling tester and the charge and discharge test cabinet together, airtight testing, flow resistance testing and temperature control testing can be carried out on the battery pack. Most importantly, the temperature control testing function of this patent is to verify the liquid cooling system control function and temperature control effect by using the charge and discharge test cabinet to simulate the vehicle charge and discharge conditions and the vehicle liquid cooling circulation system. However, in addition to the requirement for temperature control to achieve a constant temperature effect, during the charging and discharging process of the power battery pack, the power provided needs to maintain sufficient stability and will not fluctuate greatly due to insufficient battery power or internal resistance changes. This requires constant power testing of the battery pack, and the above patent does not disclose a technical solution for constant power testing of the battery pack. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a constant power testing method and system for a liquid cooling system of a power battery pack. By calculating the temperature difference △T from the reflux flow rate G and the power set value Q, and then detecting whether the load power P connected to the power battery pack is greater than or less than the power set value Q, the cooling liquid medium is cooled or heated, so that the power battery pack operates at a constant power, solving the technical problem in the prior art that there is a lack of constant power testing for power battery packs.

[0006] (2) Technical Solutions

[0007] To achieve the above object, the present invention provides the following technical solution: A constant power testing method for a liquid cooling system of a power battery pack, using a constant power testing device for a power battery pack, the method comprising the following steps:

[0008] S1. Select a cooling liquid medium and add it to the normal-temperature water storage tank, and start the constant-power test program;

[0009] S2. Turn on the external circulation pump, and inject the cooling liquid medium into the power battery pack through the external hose of the waterway system. After the cooling liquid medium flows through the power battery pack, it flows back into the buffer water box;

[0010] S3. Turn on the internal circulation pump, and inject the cooling liquid medium in the buffer water box into the heater and evaporator through the internal connection of the waterway system for circulating temperature control;

[0011] S4. Turn on the refrigeration system, and adjust the refrigerating capacity entering the evaporator in real time according to the power setting value Q in the constant-power test program;

[0012] S5. Turn on the heater, and adjust the heating amount in real time according to the power setting value Q in the constant-power test program;

[0013] S6. When the return flow rate of the cooling liquid medium reaches the set value G, the constant-power test program calculates the temperature difference △T through the return flow rate G and the power setting value Q;

[0014] S7. Monitor the return temperature T1 of the cooling liquid medium. The constant-power test program controls the outlet temperature T2 in real time through the return temperature T1 and the temperature difference △T to ensure that the actual outlet-return temperature difference is consistent with the calculated temperature difference;

[0015] S8. When the load power P connected to the power battery pack is less than the power setting value Q, the temperature of the cooling liquid medium will decrease at the refrigerating power of Q - P, and the outlet temperature T2 will show a downward trend;

[0016] S9. When the load power P connected to the power battery pack is greater than the power setting value Q, the temperature of the cooling liquid medium will increase at the refrigerating power of P - Q, and the outlet temperature T2 will show an upward trend;

[0017] S10. When the load power P connected to the power battery pack is equal to the set power G, the refrigerating capacity output by the equipment can just offset the load completely, and the temperature of the cooling liquid medium will remain constant at a certain temperature point, and the outlet temperature T2 will show a stable trend;

[0018] S11. When the external load is continuously greater than or continuously less than the power setting value Q, the increase or decrease of the outlet temperature T2 is limited. When reaching the upper limit or the lower limit, the refrigerating capacity will be automatically adjusted to perform constant-temperature control at the set temperature of the upper limit or the lower limit until the load power changes again;

[0019] S12. The constant-power test program continuously executes steps S1 - S11 to realize the constant-power test of the liquid cooling system of the power battery pack.

[0020] Further, the cooling liquid medium is one of pure water, 30% ethylene glycol, 50% ethylene glycol or 60% ethylene glycol.

[0021] Further, the waterway system includes a normal temperature water storage tank. A liquid adding port is provided above the normal temperature water storage tank, and a liquid level gauge for checking the liquid level in the normal temperature water storage tank is arranged on its side. The normal temperature water storage tank is connected to a buffer water box through a pipeline. The water outlet on one side of the buffer water box is connected to an external circulation pump, an outlet temperature sensor, an outlet flow sensor, and an outlet pressure sensor through the main pipeline of the waterway system, and then accesses the inside of the power battery pack from the inlet of the power battery pack. After passing through the inside of the power battery pack, the main pipeline of the waterway system is led out from the outlet of the power battery pack, and after being led out, the main pipeline of the waterway system is connected to a return temperature sensor and then connected back into the buffer water box.

[0022] Further, a heater is installed in the buffer water box, and a temperature control sensor is connected to one end thereof.

[0023] Further, the water outlet on the other side of the buffer water box is connected to an internal circulation pump through a secondary pipeline of the waterway system and then accesses the inside of the refrigeration system from the inlet of the refrigeration system. The cooling liquid medium flows out from the outlet of the refrigeration system and accesses the secondary pipeline of the waterway system, and then is connected to a back pressure sensor and then connected back into the buffer water box.

[0024] Further, the refrigeration system includes an evaporator. The inlet and outlet provided on one side of the evaporator are respectively connected to the secondary pipeline of the waterway system, and the outlet provided on the other side is connected to the main pipeline of the refrigeration system, which is connected to a throttling element, an air condenser and a compressor, and then is connected back into the evaporator from the inlet provided on the other side of the evaporator.

[0025] Further, the temperature difference △T in step S6 is calculated by the following formula:

[0026]

[0027] In the formula: 3.6 is the unit conversion coefficient,

[0028] Q is the set power,

[0029] M is the mass flow rate,

[0030] C is the specific heat capacity.

[0031] Further, M is calculated by the following formula:

[0032] M = ρ×G

[0033] In the formula: ρ is the medium density,

[0034] G is the return flow rate.

[0035] To achieve the above object, a constant power test method of a liquid cooling system for a power battery pack as described above is compiled into a corresponding constant power test system for a liquid cooling system for a power battery pack or made into a hardware device, and the system is an embedded software system.

[0036] (III) Beneficial effects

[0037] Compared with the prior art, the present invention provides a constant power test method and system for a liquid cooling system of a power battery pack, having the following beneficial effects:

[0038] In the constant power test method for the liquid cooling system of the power battery pack, a constant power test device for the power battery pack is used to calculate the temperature difference △T through the reflux flow rate G and the power set value Q, and then by detecting whether the load power P connected to the power battery pack is greater than or less than the power set value Q, the cooling liquid medium is cooled or heated, so that the power battery pack operates at a constant power. The beneficial effects of the constant power operation of the power battery pack include extending the battery life, improving the endurance ability, and ensuring the stable operation of the battery in different environments. These beneficial effects make the constant power operation an effective method for improving the performance and extending the service life of the power battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of a constant power test method for a liquid cooling system of a power battery pack according to the present invention;

[0040] Figures 2 to 4 is an operation screen of a constant power test system for a liquid cooling system of a power battery pack according to the present invention;

[0041] In the figure: 1, cooling liquid medium; 2, normal temperature water storage tank; 3, external circulation pump; 4, external connection hose; 5, power battery pack; 6, buffer water box; 7, internal circulation pump; 8, heater; 9, evaporator; 10, liquid filling port; 11, liquid level gauge; 12, main pipeline of the water circuit system; 13, outlet temperature sensor; 14, outlet flow sensor; 15, outlet pressure sensor; 16, return temperature sensor; 17, temperature control sensor; 18, secondary pipeline of the water circuit system; 19, return pressure sensor; 20, throttling element; 21, air condenser; 22, compressor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1, a constant power test method for a liquid cooling system of a power battery pack, using a constant power test device for the power battery pack. The method includes the following steps:

[0044] S1. Select cooling liquid medium 1 and add it to the normal temperature water storage tank 2. Cooling liquid medium 1 is one of pure water, 30% ethylene glycol, 50% ethylene glycol, or 60% ethylene glycol. Start the constant power test program;

[0045] S2. Turn on the external circulation pump 3, and inject cooling liquid medium 1 into the power battery pack 5 through the external hose 4 of the water circuit system. After cooling liquid medium 1 flows through the power battery pack 5, it flows back into the buffer water box 6;

[0046] S3. Turn on the internal circulation pump 7, and circulate and control the temperature of cooling liquid medium 1 in the buffer water box 6 by injecting it into the heater 8 and the evaporator 9 through the internal connection of the water circuit system;

[0047] S4. Turn on the refrigeration system, and adjust the refrigeration capacity entering the evaporator 9 in real time according to the power setting value Q in the constant power test program;

[0048] S5. Turn on the heater 8, and adjust the heating amount in real time according to the power setting value Q in the constant power test program;

[0049] S6. When the return flow rate of cooling liquid medium 1 reaches the set value G, the constant power test program calculates the temperature difference △T through the return flow rate G and the power setting value Q;

[0050] △T is calculated by the following formula:

[0051]

[0052] In the formula: 3.6 is the unit conversion coefficient,

[0053] Q is the set power,

[0054] M is the mass flow rate,

[0055] C is the specific heat capacity.

[0056] M is calculated by the following formula:

[0057] M = ρ × G

[0058] In the formula: ρ is the medium density,

[0059] G is the return flow rate.

[0060] S7. Monitor the return temperature T1 of cooling liquid medium 1. The constant power test program controls the outlet temperature T2 in real time through the return temperature T1 and the temperature difference △T to ensure that the actual outlet-return temperature difference is consistent with the calculated temperature difference;

[0061] S8. When the load power P connected to the power battery pack 5 is less than the power set value Q, the temperature of the cooling liquid medium 1 will decrease at a refrigeration power of Q - P, and the outlet temperature T2 will show a downward trend;

[0062] S9. When the load power P connected to the power battery pack 5 is greater than the power set value Q, the temperature of the cooling liquid medium 1 will increase at a refrigeration power of P - Q, and the outlet temperature T2 will show an upward trend;

[0063] S10. When the load power P connected to the power battery pack 5 is equal to the set power G, the refrigerating capacity output by the equipment can just completely offset the load, and the temperature of the cooling liquid medium 1 will remain constant at a certain temperature point, and the outlet temperature T2 will show a stable trend;

[0064] S11. When the external load is continuously greater than or continuously less than the power set value Q, the rise or fall of the outlet temperature T2 is limited. When reaching the upper limit or lower limit, the refrigerating capacity will be automatically adjusted to perform constant temperature control at the set temperature of the upper limit or lower limit until the load power changes again;

[0065] S12. The constant power test program continuously executes steps S1 - S11 to realize the constant power test of the liquid cooling system of the power battery pack 5.

[0066] In the above embodiment, the water circuit system includes a normal temperature water storage tank 2. A liquid filling port 10 is provided above the normal temperature water storage tank 2, and a liquid level gauge 11 for checking the liquid position in the normal temperature water storage tank 2 is provided on its side. The normal temperature water storage tank 2 is connected to a buffer water box 6 through a pipeline. The water outlet on one side of the buffer water box 6 is connected to an external circulation pump 3, an outlet temperature sensor 13, an outlet flow sensor 14, and an outlet pressure sensor 15 through the main pipeline 12 of the water circuit system, and then accesses the inside of the power battery pack 5 from the inlet of the power battery pack 5. After passing through the inside of the power battery pack 5, the main pipeline 12 of the water circuit system is connected to a return temperature sensor 16 and then connected back to the buffer water box 6; a heater 8 is installed in the buffer water box 6, and a temperature control sensor 17 is connected to one end thereof; the water outlet on the other side of the buffer water box 6 is connected to an internal circulation pump 7 through a secondary pipeline 18 of the water circuit system and then accesses the inside of the refrigeration system from the inlet of the refrigeration system. The cooling liquid medium 1 flows out from the outlet of the refrigeration system and is connected to the secondary pipeline 18 of the water circuit system, and then connected to a return pressure sensor 19 and then connected back to the buffer water box 6; the refrigeration system includes an evaporator 9. The inlet and outlet provided on one side of the evaporator 9 are respectively connected to the secondary pipeline 18 of the water circuit system, and the outlet provided on the other side is connected to a main pipeline 19 of the refrigeration system, which is connected to a throttling element 20, an air condenser 21, and a compressor 22, and then connected back to the inside from the inlet provided on the other side of the evaporator 9.

[0067] To achieve the above object, a constant power test system for a liquid cooling system of a power battery pack or a hardware device is compiled by using the above constant power test method for a liquid cooling system of a power battery pack, and the system is an embedded software system.

[0068] Embodiment:

[0069] During use, pure water is selected as the cooling liquid medium 1. The constant power test program sets the initial temperature to 25°C, the power set value Q to 2 kW, monitors the return flow rate G to reach 8 L / min, and calculates the temperature difference ΔT through the formula: In the formula: the unit conversion system is 3.6, the power is 2 kW, the flow rate is 8 L / min, 16.667 is the flow rate conversion coefficient, 8 / 16.667 = 0.48 T / h, the medium density is 1000 kg / m 3 , the specific heat capacity of the pure water medium is 4.2 kJ / kg·°C, and the calculated ΔT: = 3.5715°C,

[0070] When the load power P connected to the power battery pack 5 is less than 2 kW, the temperature of the cooling liquid medium 1 will decrease at the refrigeration power of Q - P, and the outlet temperature T2 will show a downward trend. If the return liquid temperature is 25°C, the control temperature is 25°C - 3.5715°C = 21.4285°C, and the control temperature is updated in real time, but the control temperature needs to be less than or equal to the limit value of the decreasing temperature;

[0071] When the load power P connected to the power battery pack 5 > 2 kW, the temperature of the cooling liquid medium 1 will increase at the refrigeration power of P - Q, and the outlet temperature T2 will show an upward trend. If the liquid addition temperature is still 25°C, the control temperature is: 25°C + 3.5715°C = 28.5715°C, and the control temperature is updated in real time, but the control temperature needs to be greater than or equal to the limit value of the increasing temperature;

[0072] After the above cooling or heating operations, when the load power P connected to the power battery pack 5 = the set power G, that is, both are 2 kW in this example, the refrigerating capacity output by the device can just offset the load completely, and the temperature of the cooling liquid medium 1 will remain constant at the 25°C temperature point, and the outlet temperature T2 will show a stable trend;

[0073] If the external load is continuously greater than or continuously less than the power set value of 2 kW, there are upper and lower limits for the rise or fall of the outlet temperature T2. When reaching the upper or lower limit, the refrigerating capacity will be automatically adjusted to perform constant temperature control at the set temperature of the upper or lower limit until the load power changes again.

[0074] It should be noted that, in this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0075] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A constant power test method for a liquid cooling system of a power battery pack, using a constant power test device for the power battery pack, characterized in that: The method includes the following steps: S1. Select a cooling liquid medium (1) and add it to a normal temperature water storage tank (2), and start a constant power test program; S2. Turn on the external circulation pump (3), inject the cooling liquid medium (1) into the power battery pack (5) through an external hose (4) of the water circuit system, and the cooling liquid medium (1) flows back into the buffer water box (6) after flowing through the power battery pack (5); S3. Turn on the internal circulation pump (7), and inject the cooling liquid medium (1) in the buffer water box (6) into the heater (8) and the evaporator (9) through the internal connection of the water circuit system for circulating temperature control; S4. Turn on the refrigeration system, and adjust the refrigerating capacity of the refrigerant entering the evaporator (9) in real time according to the power setting value Q in the constant power test program; S5. Turn on the heater (8), and adjust the heating amount in real time according to the power setting value Q in the constant power test program; S6. When the return flow rate of the cooling liquid medium (1) reaches the set value G, the constant power test program calculates the temperature difference △T through the return flow rate G and the power setting value Q; S7. Monitor the return temperature T1 of the cooling liquid medium (1), and the constant power test program controls the outlet temperature T2 in real time through the return temperature T1 and the temperature difference △T to ensure that the actual outlet-return temperature difference is consistent with the calculated temperature difference; S8. When the load power P connected to the power battery pack (5) is less than the power setting value Q, the temperature of the cooling liquid medium (1) will be cooled at a refrigerating power of Q - P, and the outlet temperature T2 will show a downward trend; S9. When the load power P connected to the power battery pack (5) is greater than the power setting value Q, the temperature of the cooling liquid medium (1) will be heated at a refrigerating power of P - Q, and the outlet temperature T2 will show an upward trend; S10. When the load power P connected to the power battery pack (5) is equal to the set power G, the refrigerating capacity output by the equipment can just offset the load completely, and the temperature of the cooling liquid medium (1) will continue to be constant at a certain temperature point, and the outlet temperature T2 will show a stable trend; S11. When the external load is continuously greater than or continuously less than the power setting value Q, there are upper and lower limits for the rise or fall of the outlet temperature T2. When the upper limit or the lower limit is reached, the refrigerating capacity will be automatically adjusted to perform constant temperature control at the set temperature of the upper limit or the lower limit until the load power changes again; S12. The constant power test program continuously executes steps S1 - S11 to realize the constant power test of the liquid cooling system of the power battery pack (5).

2. The constant power test method for the liquid cooling system of a power battery pack according to claim 1, wherein: The cooling liquid medium (1) is one of pure water, 30% ethylene glycol, 50% ethylene glycol or 60% ethylene glycol.

3. A constant power test method for a liquid cooling system of a power battery pack according to claim 1, characterized in that: The waterway system includes a normal-temperature water storage tank (2). A liquid filling port (10) is provided above the normal-temperature water storage tank (2), and a liquid level gauge (11) for checking the liquid level in the normal-temperature water storage tank (2) is arranged on its side. The normal-temperature water storage tank (2) is connected to a buffer water box (6) through a pipeline. The water outlet on one side of the buffer water box (6) is connected to an external circulation pump (3), an outlet temperature sensor (13), an outlet flow sensor (14), and an outlet pressure sensor (15) through the main waterway pipeline (12) of the waterway system, and then accesses the inside of the power battery pack (5) from the inlet of the power battery pack (5). The main waterway pipeline (12) passes through the inside of the power battery pack (5) and then is led out through the outlet of the power battery pack (5). The main waterway pipeline (12) after being led out is connected to a return temperature sensor (16) and then connected back into the buffer water box (6).

4. The constant power test method for the liquid cooling system of a power battery pack according to claim 3, characterized in that: A heater (8) is installed in the buffer water box (6), and a temperature control sensor (17) is connected to one end of the heater (8).

5. The constant power test method for a liquid cooling system of a power battery pack according to claim 3, characterized in that: The water outlet on the other side of the buffer water box (6) is connected to an internal circulation pump (7) through a secondary waterway pipeline (18) of the waterway system, and then accesses the inside of the refrigeration system from the inlet of the refrigeration system. The cooling liquid medium (1) flows out from the outlet of the refrigeration system and accesses the secondary waterway pipeline (18), and then is connected to a back pressure sensor (19) and then connected back into the buffer water box (6).

6. A constant power test method for a liquid cooling system of a power battery pack according to claim 5, characterized in that: The refrigeration system includes an evaporator (9). The inlet and outlet provided on one side of the evaporator (9) are respectively connected to the secondary waterway pipeline (18). The outlet provided on the other side of the evaporator (9) is connected to the main refrigeration pipeline (19), which is connected to a throttling element (20), an air condenser (21), and a compressor (22), and then is connected back into the evaporator (9) from the inlet provided on the other side of the evaporator (9).

7. A constant power test method for a liquid cooling system of a power battery pack according to claim 1, characterized in that: The temperature difference △T in step S6 is calculated by the following formula: △T＝ 3.6Q MC In the formula: 3.6 is a unit conversion coefficient, Q is the set power, M is the mass flow rate, C is the specific heat capacity.

8. A constant power test method for a liquid cooling system of a power battery pack according to claim 7, characterized in that: The M is calculated by the following formula: M = ρ×G In the formula: ρ is the medium density, G is the return flow rate.

9. A constant power test system for a liquid cooling system of a power battery pack, characterized in that: A system compiled by using the constant power test method of a liquid cooling system for a power battery pack described in any one of claims 1-8, and the system is an embedded software system.

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