RESOLVED 14-50 Breaker keeps tripping when charging my DE (Solved)

[Anil Saigal]

Recently, I discovered that my Lucid DE won't accept charge. The info screen would say charging at 38 MPH, but charge level would not climb in %age or Miles. I also noticed that my 240V/50A circuit breaker started tripping. I suspected the HV battery pack or the charging system were at fault. Lucid came out and said the battery system diagnostics showed no error codes related to charging, but that they had an HV battery replacement campaign pending for my car. During the replacement work they provided a Lucid GT which showed exact same issue with charging. Suspecting that the charging cable electronics may be the issue, I asked the drop-off driver to bring a charging cable (none was included with the loaner). With sustained charging, same thing happened with the replacement charging cable. In order to order the right circuit breaker (I have a Square D 50A circuit breaker), i opened the electrical panel (I am an EE and use proper procedure and safety equipment) and discovered that one of the two phase wires was loose under the screw plate. It made sense that the loose cable would result in increased resistance, which in turn would drop voltage available to the Lucid charger which demanded more current to keep charging at 9KW, which in turn would trip the breaker. I also noticed slight discoloration on the copper strands in the "stripped" portion of the cable.

After cleaning the cable with 00 sand paper and tightening the breaker screw for that wire, charging completed successfully. During the 15 min charging period, I noticed that the terminal with loose wire was hotter than the other phase wire terminal (I suggest using an IR thermometer as I did). I haven't measured the wire contact resistance at each terminal to see if there is a difference between the two live phase wires. I am suspecting that the original installer had tightened both screws properly, but due to non-symmetric current draw by the Lucid charger, constant heating/cooling of the one breaker terminal caused the screw to become progressively loose over time.

Hope this post helps someone having a similar issue.

 

[Anil Saigal]

Recently, I discovered that my Lucid DE won't accept charge. The info screen would say charging at 38 MPH, but charge level would not climb in %age or Miles. I also noticed that my 240V/50A circuit breaker started tripping. I suspected the HV battery pack or the charging system were at fault. Lucid came out and said the battery system diagnostics showed no error codes related to charging, but that they had an HV battery replacement campaign pending for my car. During the replacement work they provided a Lucid GT which showed exact same issue with charging. Suspecting that the charging cable electronics may be the issue, I asked the drop-off driver to bring a charging cable (none was included with the loaner). With sustained charging, same thing happened with the replacement charging cable. In order to order the right circuit breaker (I have a Square D 50A circuit breaker), i opened the electrical panel (I am an EE and use proper procedure and safety equipment) and discovered that one of the two phase wires was loose under the screw plate. It made sense that the loose cable would result in increased resistance, which in turn would drop voltage available to the Lucid charger which demanded more current to keep charging at 9KW, which in turn would trip the breaker. I also noticed slight discoloration on the copper strands in the "stripped" portion of the cable.

After cleaning the cable with 00 sand paper and tightening the breaker screw for that wire, charging completed successfully. During the 15 min charging period, I noticed that the terminal with loose wire was hotter than the other phase wire terminal (I suggest using an IR thermometer as I did). I haven't measured the wire contact resistance at each terminal to see if there is a difference between the two live phase wires. I am suspecting that the original installer had tightened both screws properly, but due to non-symmetric current draw by the Lucid charger, constant heating/cooling of the one breaker terminal caused the screw to become progressively loose over time.

Hope this post helps someone having a similar issue.

Be sure to mind the following edits for your personal safety:

If you are having similar symptoms with charging your Lucid, be sure to call a certified electrician to work on your electrical panel to troubleshoot the issue I described above. Unless you are trained or are certified as an electrician, don't do this work yourself. Being electrocuted is serious business and can be fatal.

 

[DeaneG]

Great catch. I think many EVSEs (or is it the car?) check for voltage drop as the charging current is slowly ramped up, and stop with an error if the voltage drop becomes excessive.