PSA: If your Tesla app is giving you "charging interrupted" alerts for no obvious reason, something may be very wrong!!

[bro1999]

So quick backstory: I had a NEMA 14-50 outlet installed in my garage a little over 3 years ago as I had just moved into my new house and needed an outlet for my EVSE to charge my at-the-time Bolt. Used the outlet to charge @240V/32A with a Tesla Gen 2 UMC + Jdapter for over 2 years no problems. Then last year I took advantage of some state/utility rebates to upgrade to a Chargepoint Flex Home NEMA 14-50 plug-in version, and used that to charge my Bolt since last fall. In July of this year, I had Chevy buyback my Bolt due to the infamous battery recall and picked up a Model 3 and have been charging my 3 via the CP Home Flex and j1772 adapter that came with the car.

Starting maybe a week ago, I started getting "charge interrupted" alerts from the Tesla app (have my 3 set to charge at 11pm every night to take advantage of TOU pricing) 1-2 hours after it started charging for the night. I chalked it up to something going wonky with how the car and CP unit were trying to both handle TOU charging, as when I woke up the 3 was always at its target charge level.

Then last night I got another alert before midnight, so I went to my garage to see if something was up with my CP unit. That is when I smelled a plastic burning smell, and upon inspection of the NEMA 14-50 outlet I noticed some black soot marks above it! After shutting off the breaker, I saw that the CP unit's plug was starting to melt on 1 side. After much effort, I yanked out the outlet and one of the prongs looked charred and that side of the plug was starting to melt. Unscrewing the NEMA 14-50 receptacle, I saw obvious signs of melting wiring (the red wire's casing was completely burned and I could see exposed wire). Seems like I came very close to having a fire break out and potentially burn my house down!

I think I definitely need an electrician to come out to look at the outlet, but trying to figure out what went wrong. I charged my Bolt fine for almost 3 years using the outlet (probably some $10 Leviton one from Home Depot....local electrician installed it), and 6 weeks after I started charging my Model 3 with it, this happened. The Bolt and SR+ 3 both charge at a maximum 32 amps, so pretty sure the 3 was not pulling any extra juice from the wall compared to the Bolt. Also, if it was a poor install job, problems would have probably surfaced sooner than 3 years, right? I charged my Bolt (and then Model 3) at least 3-4 times a week using that outlet since it was installed in 2018.

Until an electrician looks at it and installs a new receptacle (ordered a Hubbell unit from Amazon) I'll have to resort to 120v trickle charging and probably some sessions at a local Supercharger as well.

 

[brkaus]

It might have been happening with the previous car too. Slowly getting worse.

 

[RedTesY]

The Chevy Bolt on-board Level 2 charger uses a maximum of 30 amps, while the Model 3 on-board Level 2 charger can use up to 48 amps. Our Module Y Mobile Connector, with NEMA 14-50 adapter, draws 40 amps. So a lot more amps going through the outlet. Also likely that the outlet wire terminals needed to be tightened. Great job diagnosing the problem and preventing a fire!!

 

[jjrandorin]

The Chevy Bolt on-board Level 2 charger uses a maximum of 30 amps, while the Model 3 on-board Level 2 charger can use up to 48 amps. Our Module Y Mobile Connector, with NEMA 14-50 adapter, draws 40 amps. So a lot more amps going through the outlet. Also likely that the outlet wire terminals needed to be tightened. Great job diagnosing the problem and preventing a fire!!

The OPs signature states they have a model 3 SR+, and the model 3 SR+ charges at a maximum charge rate (L2 Charging) of 32amps. Only the LR model 3 versions can charge at up to 48amps.

 

[ItsNotAboutTheMoney]

The OPs signature states they have a model 3 SR+, and the model 3 SR+ charges at a maximum charge rate (L2 Charging) of 32amps. Only the LR model 3 versions can charge at up to 48amps.

However, the Bolt was indeed 30A (7.2kW) charging, so it's possible that the slightly higher power of the SR+ has pushed things a bit harder.

 

[brkaus]

However, the Bolt was indeed 30A (7.2kW) charging, so it's possible that the slightly higher power of the SR+ has pushed things a bit harder.

If that’s the case with the bolt vs Tesla, the 30 to 32a would dissipate roughly 13% more heat in a wire, connector, etc.

 

[bro1999]

The OPs signature states they have a model 3 SR+, and the model 3 SR+ charges at a maximum charge rate (L2 Charging) of 32amps. Only the LR model 3 versions can charge at up to 48amps.

I checked the TeslaFi logs and nothing screwy was going on with the amperage...all recent sessions at 32A or slightly below. Wonder if it'll be prudent to dial down the amperage to like 24 even after I get a new 14-50 installed out of an abundance of caution.

 

[jjrandorin]

I checked the TeslaFi logs and nothing screwy was going on with the amperage...all recent sessions at 32A or slightly below. Wonder if it'll be prudent to dial down the amperage to like 24 even after I get a new 14-50 installed out of an abundance of caution.

If its installed correctly, you shouldnt have to do that. We have no idea what wiring etc was used in your setup, but if its all setup properly there shouldnt be any safety related reason to turn the charging speed down.

 

[dhrivnak]

I have seen this if a connection is not properly tightened down, or possibly too tight where the threads are stripped. It can work for years but then with repeated heating and cooling the connections become lose and when lose things go bad fast. So it is always good to touch your your outlet every 6 months to see if you feel heat. If you do have it checked.

 

[Frank99]

I have seen this if a connection is not properly tightened down, or possibly too tight where the threads are stripped. It can work for years but then with repeated heating and cooling the connections become lose and when lose things go bad fast. So it is always good to touch your your outlet every 6 months to see if you feel heat. If you do have it checked.

This exactly. If not installed correctly and torqued properly, the connection can slowly get worse. It starts with getting a bit warmer than it should, which causes a bit more expansion and contraction than should be there every time you charge (heats up when charging starts, cool down when charging stops), which loosens up the connection a wee bit. This causes more heat, which causes more expansion and contraction, which loosens things up even faster. Eventually, there's no pressure on the wire - it's essentially just sitting up against the screw, which makes for a high resistance connection which creates a LOT of heat which causes wire insulation to melt, char, and eventually catch fire.

I am an engineer and not an electrician. But after looking at the construction of both the $10 Home Depot outlet and the $100 Hubbell, my conclusions were:
1. Either could be used for a safe installation.
2. The $10 outlet would require a great deal more care in installation to be safe. It appeared much easier to under/over tighten the wire screws, either of which would make for an iffy connection that might eventually fail. Using a torque wrench and knowing the manufacturer torque specifications appeared almost a requirement to get a reliable connection. Nobody ever uses a torque wrench on an outlet.
3. The Hubbell had solid, robust wire connections that appeared much more likely to work reliably with the average "calibrated elbow" tightening them down. It's built much more solidly than the $10 outlet, which means it probably cost $2 more to construct - I hate paying $90 more for that, but it's the way it is today. Someone here (who appears to be an electrician) suggested the Bryant 9450R as a significantly cheaper but equivalently robust outlet to the Hubbell.

 

[bro1999]

Photos of the outlet

And plug

 

[brkaus]

Very scary.

 

[Gauss Guzzler]

Ouch! Another Leviton bites the dust!

You'll probably find that the red wire is a bit loose in the terminal. The stress from folding and shoving the wiring into the box can wiggle them loose a little during installation if the clamps weren't tightened enough. And once they're below a certain torque, they can very slightly unscrew themselves with each temperature cycle. You may have inadvertently accelerated that loosening if you wiggled the plug recently.

Don't pay $100 for an outlet - the online vendors are just price gouging because they see all these Tesla people suddenly buying their $25 outlets. Just get any reputable industrial grade model like the Bryant mentioned by @Frank99 and be sure to get a 2.5" faceplate cover to go with it as your old one won't fit. Your electrician should be able to supply one at a fair price - just ask for an industrial grade model with a 2.5" diameter.

Your Chargepoint plug should clean up just fine with a little scotchbrite, it's just brass. But if you're nervous note that the Tesla UMC includes a temperature sensor in the plug specifically intended to prevent this scenario so you might want to switch back to it.

 

[Sophias_dad]

Just a guess, but if you happen to have a micrometer try checking the thickness of the blades on the UMC vs Chargepoint plugs. If the chargepoint is ever-so-slightly thinner the cheap-ass Leviton plug would have made a worse connection, which means more heat. Even a bit of random crap on the blade could be enough to cause a hotspot if the outlet isn't right.

 

[dogmodes]

Wow glad you caught that! I'm about to install a HomeFlex and for some reason thought it had a temp sensor like the UMC. Seems like it really should. I was planning on hardwiring it in to get the extra couple amps.

In your case I'm wondering do they need to pull new cable?

 

[theothertom]

However, the Bolt was indeed 30A (7.2kW) charging, so it's possible that the slightly higher power of the SR+ has pushed things a bit harder.

Actually the Bolt charges at 32 amps max.

 

[DOOLMTR]

Glad you caught it man! I was getting the temp warnings when charging on hot nights but my wiring and outlet were fine. My issue was the house A/C and EVSE breakers were next to each other. I finally switched to a wall connector that is setup for 60amps and no longer worry about those temp alerts or charging interrupted.

 

[bro1999]

A (different) electrician came out and installed a new, heavier duty outlet with separate metal box and everything. Cost $400 but he said hes done tons of Tesla installs and I feel fine paying extra to have it done properly this time.
Don't cheap out!

 

[KenC]

A (different) electrician came out and installed a new, heavier duty outlet with separate metal box and everything. Cost $400 but he said hes done tons of Tesla installs and I feel fine paying extra to have it done properly this time.
Don't cheap out!

which brand outlet and box?

 

[bro1999]

which brand outlet and box?

I believe it was this.