Thermal Characterization of an Automotive High Voltage Junction Box

The high voltage battery junction box (HVJB) controls and protects the high voltage connections of the battery pack to the traction, auxiliary, and charging systems. HVJBs are composed of busbars, contactors, fuses, and other protection systems. The health of the HVJB is paramount to ensure performance of electric vehicles. However, sensing and monitoring in the HVJB are often lacking due to packaging cost, causing limited capability of the vehicle controller to estimate the status and health of the unit. This publication focuses on the experimentation of an automotive HVJB to characterize the operation and build the foundation for the development of prognostic algorithms for HVJB. A production HVJB has been acquired and heavily instrumented. Extensive testings are performed in adiabatic and in ambient conditions at various current levels for various durations of operation. The testing setup was calibrated and iterated based on preliminary results, and the testing conditions were adjusted to increase the accuracy of the data. These results were analyzed to identify patterns in the behavior of the heat generation for each individual component and the heat exchange between them. The analysis of these results allows for the calibration of an electrothermal model of the HVJB using MATLAB Simulink. Upon finalizing model calibration, the model will be able to accurately predict the electrothermal behavior of the HVJB, allowing for critical feedback data that can be used by production engineers to assist in reducing overall pack failures.