2013 Tesla Model S Long-Term Road Test

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2013 Tesla Model S: Wall Adapter Replacement Program

January 14, 2013

2013 Tesla Model S

Last Friday, Tesla Motors announced a replacement program for wall charger adapters. Apparently there have been several reports of smoke in the vicinity of the wall plug, and at least one owner was burned when trying to unplug his car when he saw said smoke.

And while the issue is related to the home charge cord that comes with the car, the cord itself is fine, too. The issue is instead related to the use of the NEMA 14-50 wall adapter that can be snapped onto the end of it. That's the part that's being replaced.

That's the adapter I was using at Dad's place in Oregon. In fact, I had a minor charge issue myself while I was there. See the next page for more on that.

Early media reports were all over the map, with accompanying photos depicting the High Powered Wall Connector (HPWC) or a Tesla Supercharger. Neither is involved. They're fine.

Tesla says the adapter isn't really at issue. They instead blame the incidents on substandard or faulty home wiring.

"These are very rare events, but occasionally the wiring isn't done right," CEO Elon Musk said. "We want people to have absolute comfort, so we're going to be providing them with an upgraded adapter."

The upgraded adapter, which will be mailed to Tesla owners in the next two weeks, is functionally identical to the one pictured above, but with a thermal fuse imbedded inside to cut power if overheating is detected.

2013 Tesla Model S

It makes sense. Tesla isn't in a position to control the upstream home wiring environment, and standardized electrical codes can only guarantee so much. The necessary NEMA 14-50R receptacle costs less than $10 at Home Depot. The other parts are cheap and available, too. I imagine there are more than a few DIY wiring jobs out there. In fact, I've read more than one forum post where owners boasted of how easy it was to install the NEMA 14-50 socket themselves.

Tesla has always recommended the job be done by a qualified electrician, but they're unable to force the issue. Also, I'm not sure there's a standard definition of "qualified electrician."

Maybe that's why the adapter upgrade is part of a two-pronged affair, if you'll pardon the pun. A couple of weeks ago Tesla sent out a software update to enable the car's onboard charging circuitry to cut the power draw by 25 percent in the event of unusual input power fluctuations. This update (v5.8.4) popped up just a day or two before I headed north to Oregon, about 2 hours after I downloaded update v5.8, in fact.

I didn't know the history of this update at the time, but the description sounded good in light of what I knew about the variability of home wiring. My own house was built in 1966, and who knows what's in my walls? I don't. For its part, Tesla says there have been no reports of overheating since the update went out.

2013 Tesla Model S

This all came together at Dad's place in Oregon, well before the issue was publicly announced on January10th.

After unloading our luggage, we put the car to bed down behind his shop and plugged it into his NEMA 14-50 socket. Later, after dinner, we went back to the shop to see how it was doing. (There's no 3G reception there and his home Wi-Fi doesn't cover his shop, so the iPhone app couldn't communicate with the car.)

Charging had stopped. The green light on the charge cord's transformer had gone red. The car displayed a "charge cord fault" message in the cluster. But whatever it was hadn't happened right away because about 60 miles of range had been added before things came to a halt.

There wasn't a whiff of smoke, no sign that heat had ever been present. The cord's internal breaker had done its job as designed.

2013 Tesla Model S

I unplugged everything, including the wall connection to the cord. Then I plugged it back in and pressed the "reset" button on the charge cord's housing. The green light was back.

Then I plugged it back into the car and dialed the draw down from the NEMA 14-50 default of 40 amps to 30 amps.

Everything worked great from then on. I successfully charged it each of the next four nights, and the only difference on those subsequent charges was 30 amps was the default. I didn't have to manually dial it down from 40 amps each time.

This raises several questions. If the cord has internal protection built in, and the internal breaker functioned properly for me, why are the incidents happening at all? Why is additional thermal protection necessary at the plug end? Perhaps a qualified electrician can enlighten me.

And what's up with Dad's wiring? Well, the distance from the panel to his 14-50 is a long run. And the duty cycle of Tesla EV battery charging through a NEMA 14-50 is a fairly atypical 100 percent at 9.6 kilowatts, more or less. His NEMA 14-50 was added by repurposing an existing circuit years after the initial construction, but they did downgrade it from a 60-amp to a 50-amp breaker, so I'd have thought the conductors would be oversized.

Also, the cord's own breaker tripped before the v8.5.4 Automatic Charge Current Reduction software kicked in. The car was still at 40 amps when I came upon the scene and the system did not auto-detect a problem after I reset the cord's breaker. I set it down to 30 amps myself.

Maybe the wiring and the electrician are fine. Maybe there was a weird isolated power surge on the local grid, the kind of fluctuation the charge cord designers had foreseen. Maybe that's why the breaker tripped and the Automatic Charge Current Reduction software didn't.

What's clear is there are lots of outside-the-car variables in play. I don't think my incident matches those in the reports, but the new software and the thermally-fused NEMA 14-50 plug-end seem like prudent steps anyway. And whatever you do, don't DIY your NEMA 14-50 installation unless you are a qualified electrician.

Dan Edmunds, Director of Vehicle Testing @ 16,318 miles

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