Thermal Performance Tests

[pasrom]

Introduction:

Our aim was to conduct a thermal investigation of the BMS to determine how hot it gets at a current of 100 A or more.

Test Setup:

The picture below illustrates the BMS setup during the testing phase (with heatsink). The tests were performed without actual battery, as described here.

Used Devices:

• Power source: E/A Power Supply PSB 10750-120
• Sink: Deutronic xxx
• Temperature measurements: "TIM QVGA/HD" thermal imaging camera
• Linux & Windows Computer

Boundary Conditions:

• Ambient Temperature: ~24°C

Test Scenarios:

Three different scenarios were tested:

1. Without Heatsink:

   • Current: 100 A
   • Measured Temperature: ~91°C after 35 minutes
   • BMS Position: horizontally on the table
   • The thermal camera image below displays the temperature distribution upon concluding the test, highlighting the MOSFETs as the area of highest temperature.

2. With Heatsink (1):

   • Current: 100 A
   • Measured Temperature: ~49°C after 25 minutes
   • BMS Position: 5 cm above the table (floating, cooling fins facing down to the table)
   • The thermal camera image below displays the temperature distribution upon concluding the test, with the PCB layer of the shunt being the hottest area.

3. With Heatsink (2):

   • Current: 122 A

   • Measured Temperature: ~66°C after 4 hours

   • BMS Position: identical to Measurement 2

   • The thermal camera image below displays the temperature distribution upon concluding the test, with the PCB layer of the shunt being the hottest area.

   • Below graph shows the current profile, temperature rise of the internal sensors and thermal camera temperature areas over time (area 2: small rectangle, area 3: big rectangle).

Conclusion

The BMS can comfortably manage over 100 A while maintaining a temperature within an acceptable range. If feasible, the PCB layer should have a thickness greater than 70 µm to minimize the heating around the shunt. Further work could involve identifying the maximum current that results in a temperature of around 80°C.