Chad R. Mittelstadt

Electric vehicle conductive charge couplers

The overall performance of listed Electric vehicle conductive charge couplers varies greatly based on engineering observations. In the field, excessive temperature rise at the connection between the charging station cord and the vehicle inlet has been noted. The temperature rise can be severe enough to damage the plastic coupler housings on both sides of the connection, and can occur in products that have been in the field for less than a year. In a laboratory environment, the variation can be measured more precisely with temperature and voltage drop across the connection. Laboratory results show resistance and temperature can increase rapidly with low cycling if the right conditions are present. The conditions can include intermixed contact technologies, insufficient crimping processes, thermal cycling, and elevated ambient temperatures. Changes may be needed to the standards that govern EV coupler connector design to better reflect these situations. A more demanding standard would help deliver charging systems that maintain low resistance and interchangeability across manufacturers, end of life safeguards, and increased longevity.

Silver Tungsten vs Silver Tungsten Carbide Contact Performance in Environmental Testing

The conductive performance of contact pairs varies greatly in testing due to their materials and to the probabilistic nature of how two parts can interface together. Contact pairs with different combinations of silver tungsten and silver tungsten carbide were exposed to salt spray test ASTM B117 for one week and two week intervals. Their resistance was then measured and analyzed using automated acquisition equipment and statistical methods. A simple probabilistic parallel resistor model was also created to simulate the range of results seen. The results are useful to other engineers working in this field to show the importance of taking multiple readings and using replicates in testing to account for normal variation. The model is helpful in visualizing what is perhaps happening in the contact interface.