2013 Tesla Model S Long-Term Road Test

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2013 Tesla Model S: High Power Wall Connector Flaw

July 2, 2013

2013 Tesla Model S

More than one person has quizzed me about it over the last couple of weeks, including my boss's boss, whose title is a three-letter acronym beginning with "C" and ending with "O".

"Why is that still sitting on your desk?" they ask, pointing at the white cardboard box containing the HPWC (High Power Wall Connector) we bought with our 2013 Tesla Model S.

"Uhhh...it's complicated?"

A Tesla HPWC draws 240V single-phase power at 80 amps through a 100-amp circuit breaker, enough juice to refill an empty 85kWh Model S battery and restore its 265 miles of maximum driving range in just over four hours. Put another way, a Model S charges at up to 62 mph through a HPWC, as in 62 miles of driving for every hour on the plug.

Our Coulomb Level 2 charge station draws 30 amps through a 40-amp circuit, plenty for all other EVs on the market. But it takes over a dozen hours to refill an empty Model S. Slow as this sounds, it would do until we got our HPWC installed. Many Edmunds staffers drive less than 50 miles overnight, which the Coulomb can deal with in less than 3 hours.

That's great, but why is it still sitting on your desk, Dan?

The answer begins with delivery dates. We picked up our 2013 Tesla Model S in February of 2013, but the HPWC was not in the trunk as we had expected. We learned it would be shipped to us later.

Much later, as it turned out. The HPWC didn't land upon my desk until May, by which time we'd gotten accustomed to the ins and outs of charging with our Coulomb. Still, the lack of speed was hindering our ability to do full recharges every time, a necessity in our quest to track fuel consumption at every "tank" like we do with gasoline cars. It also sewed "will it be full enough?" doubts in the minds of those who were considering a longer trip.

With the HPWC in hand, I could finally kick off the installation process. Tesla sister company Solar City is the go-to installer, so I put in a call. But I was told to "go to" someone else once they realized I needed to install our HPWC in a commercial building instead of a private residence.

So I struck out on my own and begin seeking bids from commercial electricians. But a bigger problem soon stopped me in my tracks.

I'd begun reading an HPWC thread on a Tesla owner's forum, looking at pictures of other installations. As I read, I noticed that as more went in service they started chatting about a possible defect in the HPWC, with the first vague report dating back to early April, maybe even late March.

Fuses were blowing inside early in-service HPWC units left and right. Tesla became concerned enough to release a firmware update that went out to all Model S cars in the field.

Among other things, the quietly-released update limited the car's maximum charging draw to 60 amps instead of 80 amps. Our car apparently got it, too, at some point, but we never ran across the warning screen that others saw because we had not yet plugged our car into a Tesla HPWC.

At first I wasn't worried. Our HPWC had arrived in May, some five weeks after the problem first surfaced and the firmware update went out. Surely ours didn't have the problem at this later stage. Maybe that was the reason for our unit's delayed shipping.

But no resolution or official statement had come to light in posts with dates that matched the day our box arrived. Later in May folks were still swapping stories about buying the expensive fuses from third party electrical supply houses, replacing them on their own and charging at 60 amps.

Rumors of an impending HPWC swap-out program surfaced toward the end of May, with the stories suggesting they would appear in June. But from Tesla Motors we still heard nothing.

For my part, I still needed to figure out a suitable metering solution. Unlike our fleet-grade Coulomb charge station, the Tesla HPWC doesn't have a readout that displays the number of kWh dispensed in a given session. I would have to develop a work-around.

On June 11 a forum member posted pictures of his new unit with the cover off. Instead of two 100-amp fuses everyone had been talking about it had two 200-amp fuses sitting crossways, with a different busbar shape to match the new orientation.

Upon seeing this I went straight for a T-20 Torx wrench to remove our HPWC's cover and take a look inside.

2013 Tesla Model S

Sure enough, I found two 100-amp fuses sitting lengthwise. It seemed certain at this point that we had the "bad" one.

2013 Tesla Model S

There is a humungous irony here. Can you spot it? The cantankerous fuses in question that plague this Tesla component are made by?Edison.

At this point I had no further desire to play the anonymous role of Joe Consumer and let events play out at their own pace. I decided to play the Edmunds card. I contacted Tesla PR. After all, forum posters had implied that the squeaky wheels were getting the grease. I could squeak louder than anyone with kind words. "Hello, this is Dan Edmunds of Edmunds.com, and I was wondering?"

They said that there had been problems and, yes, the fuses and busbar had been redesigned. The affected units have a TPN number ending in 99-A and 99-B. The redesigned units end in 99-C. I checked ours: it's a 99-B, which was no surprise after my T-20 Torx expedition.

2013 Tesla Model S

So, what's next?

They explained that the early focus has been on sending out new replacement HPWC units to existing consumers as the supply of replacement parts built up. Now they're at a point where they have sufficient parts to have Solar City technicians upgrade existing in-service units in the field without undoing the entire installation, which is much less of a hassle, especially in localities where this would trigger a second round of permits and inspections.

In our situation they'd rather trade us for a new 99-C unit since ours is still mint-in-box. I expect to get a notification from the mailroom of a package for me any day now.

And so we're moving ahead with the installation process once more. We've zeroed in on an electrician and have gotten the blessing of building management. I've even worked out a metering solution (more on that later) so our drivers can record how many kWh of electricity were dispensed.

The new unit should arrive by the time the installation has been approved and permitted by the city of Santa Monica. I'm getting close to having my desk back.

Dan Edmunds, Director of Vehicle Testing @ 5,276 miles

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