QC/T 1206.2-2024Thermal management systems for electric vehicle traction batteries - Part 2: Liquid cooling systems (English PDF)

3.1 Liquid cooling system

A system that uses a coolant (such as a mixed solution of ethylene glycol and water) as a heat exchange medium to cool the battery.

NOTE: It is generally composed of liquid cooling plate, liquid cooling pipe, joint, water inlet and outlet assembly and other components, as shown in Figure 1.

Flow resistance

After the flow resistance test is carried out in accordance with 5.4, the flow resistance of the liquid cooling system shall meet the technical requirements specified by the manufacturer.

4.3 Safety performance

4.3.1 Sealing

After the sealing test is carried out in accordance with 5.5, one of the following requirements shall be met:

a) Wet test: no visible bubbles;

b) Dry test: leakage is no more than 2.5 mL/min;

c) Helium test: leakage rate is no more than 2 x 10^-6 Pa·m3/s.

4.3.2 Flame retardancy

After the flame retardancy test is carried out in accordance with 5.6, the horizontal combustion grade of non-metallic parts of the liquid cooling system shall meet the requirements for grade HB in GB/T 2408-2021.

4.4 Technical requirements

4.4.1 Pressure resistance

After the pressure test according to 5.7, the liquid cooling system shall be leak-free.

The deformation in the deformation direction shall not exceed 10% of the original size.

4.4.2 Vibration

After the vibration test is carried out in accordance with 5.8, the liquid cooling system shall meet the requirements of 4.3.1.

4.4.3 Welding strength

After the welding strength test is carried out in accordance with 5.9, there shall be no damage or cracks at the joint welding.

4.4.4 Burst pressure

During the burst pressure test according to 5.10, the liquid cooling plate and liquid cooling pipeline shall not be damaged or loose.

4.4.5 High and low temperature cycle

After the high and low temperature cycle test is carried out in accordance with 5.11, the liquid cooling system shall meet the requirements of 4.3.1.

5.6 Flame retardancy

5.6.1 Test object: liquid cooling system.

5.6.2 Test content: non-metallic parts of the liquid cooling system shall be subjected to horizontal combustion test in accordance with the provisions of Chapter 8 of GB/T 2408-2021.

5.7 Pressure resistance

5.7.1 Test object: liquid cooling system.

5.7.2 Perform the test according to the following steps:

a) Continuously introduce gas greater than or equal to 250 kPa into the liquid cooling system. Immerse in water and observe for 1 h;

b) Observe whether there are bubbles. Finally, take the liquid cooling system out of the water and check its appearance.

5.8 Vibration

5.8.1 Test object: battery system.

5.8.2 Perform the test according to the following steps:

a) Test the battery system according to the vibration test method specified in 8.2.1 of GB 38031-2020;

b) Perform a sealing test on the battery liquid cooling system after vibration according to 5.5.

5.9 Welding strength

5.9.1 Test object: liquid cooling plate.

5.9.2 Perform the test according to the following steps:

a) Fix the liquid cooling plate on the test bench according to the actual assembly method. Use the fixture to press the liquid cooling plate body instead of the battery.

Drill holes on the joints of the liquid cooling plate. The pull-out force test hook is vertically hooked on the joint hole. The tensile machine slowly pulls to 500 N;

b) Check the appearance of the jointer and the liquid cooling plate welding point.

5.10 Burst pressure

5.10.1 Test object: liquid cooling system.

5.13 Pressure alternation

5.13.1 Test object: liquid cooling system.

5.13.2 Perform the test according to the following steps:

a) At 25°C±2°C, introduce pressure alternating coolant into the liquid cooling system;

b) The pressure of the coolant rises from 30 kPa to 200 kPa, and then drops to 30 kPa after holding the pressure, which is a pressure cycle. The cycle period is 6 s~10 s. The holding time is 3 s~6 s. The coolant temperature is 45°C±2°C;

c) The test cycle is 5 x 10^4 times;

d) After the test, carry out a sealing test in accordance with 5.5.

5.14 Multiple plugging and unplugging

5.14.1 Test object: liquid cooling pipe joint.

5.14.2 Perform the test according to the following steps:

a) Install the pipe jointer on the liquid cooling plate. Place at 80°C for 30 min. Let in 205 kPa air. Then cool to 25°C±2°C. Remove the jointer and reinstall it according to the operating specifications;

b) Repeat step a) 20 times. Let in 205 kPa of air. Maintain the pressure at 25°C±2°C for 10 min;

c) After the test, carry out a sealing test in accordance with 5.5.

5.15 Jointer installation force

5.15.1 Test object: liquid cooling pipe joint.

5.15.2 Perform the test according to the following steps:

a) At 25°C ±2°C, insert the joint into the liquid cooling plate at a speed of 50 mm/min±5 mm/min until it is plugged into place;

b) Record the installation force of the joint during installation.

5.16 Jointer pull-off force

5.16.1 Test object: liquid cooling pipeline jointer.

5.16.2 Perform the test according to the following steps:

a) Install the jointer on a tensile testing machine at 25°C±2°C. Apply tensile force at a rate of 50 mm/min±5 mm/min until the quick-connect jointer is pulled out of the liquid cooling plate jointer;

b) Record the pull-off force when the jointer is installed.

5.17 Negative pressure resistance

5.17.1 Test object: liquid cooling system.

5.17.2 Perform the test according to the following steps:

a) At 25°C±2°C, assemble the liquid cooling plate and liquid cooling pipeline according to the actual state;

b) Apply a pressure of -(90±2) kPa to the inside of the liquid cooling system. Maintain the pressure for 60 s and then return to normal pressure;

c) Repeat steps a)~b) 5 times;

d) After the test, perform a sealing test according to 5.5.

6.1 Inspection items

See Table 3 for inspection items and requirements.