2013 Tesla Model S: Our Thermally-Fused NEMA 14-50 Adaptor Has Finally Arrived
June 5, 2014
A package came today, and it was from Tesla Motors. Inside was a replacement NEMA 14-50 charge cord adaptor for our 2013 Tesla Model S.
Don't remember the story? It dates back to late last year and involved a couple of near-miss fire incidents during charging with a 240-volt NEMA 14-50 wall receptacle and the matching plug adaptor that Tesla provides with each Model S charge cord.
The incidents were ultimately blamed on faulty NEMA 14-50 wall receptacle installations, possible DIY jobs by amateur electricians. Indeed the parts required to install a NEMA 14-50 receptacle are temptingly cheap at places like Home Depot and Lowes. Thing is, you can't buy experience and an electrician's training at those places.
Tesla came up with two new safeguards to deal with this scenario. The first was an over-the-air software update (v5.8.4) that would dial the charge rate back by 25 percent if a certain type of wonky current fluctuation was detected by the onboard charging system. We received that update in late December before I headed out on my holiday road trip.
The second was the new NEMA 14-50 plug-end adaptor that came in the box today.
Word from Elon Musk back on January 10th was that the new adaptor would be mailed out to Tesla owners in two weeks' time. I just eyeballed my calendar: it's the second of June.
The new piece is dimensionally identical to the original part, but there's a thermal fuse buried somewhere inside. This fuse is designed to trip and terminate the charging process if overheating is detected. It's a triple-redundancy behind the software tweak and the charge cord's own circuit breaker.
Tesla made it ridiculously easy to tell the new 14-50 plug-end from the old one. The new piece has a light-gray socket, the old one is black.
Tesla wants the old parts back, perhaps for no other reason than to ensure they're out of circulation. Or maybe they'll inspect them for signs of near-miss overheating. To that end the box contains a pre-addressed return shipping label. I've already re-packed the now-obsolete part and handed the box to the FedEx guy for delivery back to Tesla.
Dan Edmunds, Director of Vehicle Testing @ 22,206 miles