Need Advice: NEMA 14-50 Sometimes Charges at only 16a

[Kevy Baby]

Hello all

I need some advice on where to start looking to track down the problem.

I have a 2019 SR+ with a little over 40M miles. The vast majority of my charging is on a NEMA 14-50 outlet at work using the original Mobile Connector and the proper adaptor. There is no damage to the cable or adaptor (at least that I know of). I also occasionally use a Supercharger (where I don't get any error messages). When I charge (when it is going correctly), I am getting the full 32A my car can accept at between 205-208V (7 kW) per the app (just my observation - I don't constantly monitor the app).

Occasionally, I get a notification on my phone that charging has been interrupted (with a time stamp and SOC). But it was infrequent enough that I did not worry about it.

But in the last month or so, I have now had 3-4 instances of discovering my car charging at only 16 amps. When I discover it, it always shows the same voltage (205-208V). I know today when I discovered it, I did NOT have an interruption notification (I just double-checked to ascertain). To correct it, I go out to unplug the cable going into the car re-plug it in. I generally feel as though I always firmly plug the car in, but of course, this could be the problem (not firmly seated enough). I see no signs of dirt or anything around/inside the plug. I do not have any third-party apps (such as Stats) installed at this time.

So, other than the inconvenience, is this a major problem where I should drop everything to get this fixed? How do I go about finding out if this is a car error or a supply issue?

Any tips are appreciated!

 

[Sklith]

When this happens, is your Mobile Connector (UMC) so hot at the plug you're barely able to hold it?

Your UMC has a thermometer to protect itself, and it's lowering the amps to avoid overheating. This overheating issue is likely happening due to improper wiring of the outlet or a loose/poor connection of the plug.

 

[Kevy Baby]

When this happens, is your Mobile Connector (UMC) so hot at the plug you're barely able to hold it?

I've never checked that - I will check that next. Are you saying at the 14-50 connector or the brick?

The connector where it goes in the car is always fine

 

[stonelance]

Where it connects to the 14-50 outlet. It is most likely a lose wire in the outlet, and it might start a fire. You should definitely have it looked at ASAP if it seems hot at all.

 

[Rocky_H]

Sounds to me like your onboard charger is failing.

I have a 2019 SR+

That has the 32A charger in it, but that is built with two 16A modules in it. Tesla builds them to be able to "fail gracefully", so if one of those goes out, the whole thing doesn't just quit. It will still be able to use the other one, so your car showing up only being able to use 16A seems to indicate that one of the modules is dying intermittently.

 

[Jeremy3292]

You are charging in the "wild" with a 14-50 outlet at your work. Many 14-50 outlets are not designed for a constant amperage draw over many hours. Are you positive this outlet is on it's own dedicated circuit? Are you positive this is an industrial grade outlet? It is unlikely (but possible) your onboard charger is bad. It is most likely the outlet is overheating and the car automatically reduces amperage when it detects an "anomaly" in the circuit. In fact your description of events is exactly what many others have reported on this forum. There are COUNTLESS 14-50 threads on here.

Good article: NEMA 14-50 Tesla Response | Seahurst Electric

 

[bedoig]

Check the error log in your car right after this happens (if it was recent enough it's still on the main screen, otherwise look under Service-->Notifications). It will specify if it was an overheat error at the plug. As @Rocky_H mentions it could potentially be a failing onboard charger, but if it's bouncing around my money is on the overheat protection built into the plug of your UMC.

Edit - if you have TeslaFi or other monitoring apps and you see something like this it's almost certainly the overheat protection cycling down to 16 amps to protect the outlet. I started noticing this pattern charging on a 14-50 at home after a couple years and had one seriously loose terminal in the outlet.

 

[Kevy Baby]

Sounds to me like your onboard charger is failing.

That has the 32A charger in it, but that is built with two 16A modules in it. Tesla builds them to be able to "fail gracefully", so if one of those goes out, the whole thing doesn't just quit. It will still be able to use the other one, so your car showing up only being able to use 16A seems to indicate that one of the modules is dying intermittently.

This is sounding like the most probable issue at this point, but I will research.

 

[Kevy Baby]

You are charging in the "wild" with a 14-50 outlet at your work. Many 14-50 outlets are not designed for a constant amperage draw over many hours. Are you positive this outlet is on it's own dedicated circuit? Are you positive this is an industrial grade outlet? It is unlikely (but possible) your onboard charger is bad. It is most likely the outlet is overheating and the car automatically reduces amperage when it detects an "anomaly" in the circuit. In fact your description of events is exactly what many others have reported on this forum. There are COUNTLESS 14-50 threads on here.

Good article: NEMA 14-50 Tesla Response | Seahurst Electric

I know for a fact that it is on its own circuit. Because of the high-current printing equipment we use (that runs on 440 and 220), we have a large capacity feed into our facility. The installers who put it in maintain all of our power and used top quality components - they aren’t some handyman off the streets.

That’s not to say that there isn’t a problem: just that the likelihood is lower.

 

[Kevy Baby]

Edit - if you have TeslaFi or other monitoring apps and you see something like this it's almost certainly the overheat protection cycling down to 16 amps to protect the outlet. I started noticing this pattern charging on a 14-50 at home after a couple years and had one seriously loose terminal in the outlet.

I just spent some time searching but kind find an answer: what exactly is TeslaFi? I know that it is something that allows you to collect data on your Tesla, but I don’t see anything in the IPhone App Store, and I couldn’t find much info on how to get started on the web site About TeslaFi.com

I tried searching here but just got info about users experiences and challenges.

 

[bedoig]

I just spent some time searching but kind find an answer: what exactly is TeslaFi? I know that it is something that allows you to collect data on your Tesla, but I don’t see anything in the IPhone App Store, and I couldn’t find much info on how to get started on the web site About TeslaFi.com

I tried searching here but just got info about users experiences and challenges.

It's all web based, they don't have native Android/iOS apps. You sign up through the site, provide your Tesla credentials or your own self-generated auth token (some people have security concerns with this, which I can understand) and it starts scraping all the data available through Tesla's API (driving stats, energy usage, charging data, firmware updates, etc). Also allows activation of all the vehicle controls (lock, unlock, set charge limit, start charging, etc), lets you set schedules, and more. Pretty cool if your into looking at the data. I think you can get a free trial if you use someone's referral code.

In my screenshot I posted you can see the amps cycling between 32 and 16 repeatedly. When I checked my car's errors it did show a whole bunch of "charging current reduced due to temperature at outlet" or something along those lines. IIRC the error was one that was silently logged in the car though rather than presenting to the user automatically. I had to go digging for it. You'd think something along those lines would be enough of a risk to make the user acknowledge it. I mean, I can't drive for more than 30 minutes without a persistent USB error message, but something that might burn my house down just logs silently in the background...

 

[Kevy Baby]

Awesome: thank you so much for the insight @bedoig!

 

[Kevy Baby]

You are charging in the "wild" with a 14-50 outlet at your work.

Well, I admit when I’m wrong and my initial speculation was wrong on this one. I was able to catch my error log and it is now looking like it IS the power outlet. Just weird for it to come up after two years. And nothing was even warm to the touch.

I’ll update after the electrician comes out.

 

[Jeremy3292]

Well, I admit when I’m wrong and my initial speculation was wrong on this one. I was able to catch my error log and it is now looking like it IS the power outlet. Just weird for it to come up after two years. And nothing was even warm to the touch.

I’ll update after the electrician comes out.

View attachment 723855

No worries, I learn things every day on this forum!

It actually makes more sense that it failed after 2 years of you using it than if you just started using it. 14-50 outlets fail at a high rate over time. Like I said, there are countless threads on this forum where people have this exact issue you're having. Tesla doesn't really recommend them but they also recognize people need multiple ways to charge. A hard wired charger is always the fastest, safest, and cheapest option over time. But obviously this is at your work and it is unlikely you would install a hard wired charger there. I'm lucky bc we have J1772 chargers where I work in the garage.

 

[t.e.s.l.a_dude]

Following this threat since I had an earlier issue with a NEMA outlet as well.

 

[Kevy Baby]

But obviously this is at your work and it is unlikely you would install a hard wired charger there.

This exactly. Prior to getting my Tesla, there was someone who had a Chevy Volt and had a hard-wired charger. When he left, he made the company pay to have it removed (since the device was his). When I got my Tesla, it was after a crash that totaled my previous car and the decision to get the Tesla was a quick one and I had to make a lot of fast decisions on very limited education. Putting the NEMA 14-50 in seemed like the safest route (nothing would need to be removed if I left and was generic enough to be used by others).

Besides, the company paid to have it installed (and they'll pay for the maintenance) and I charge for free, so I can put up with minor issues like this. I wasn't even going to charge today anyways (the electrician will be in today).

 

[Jeremy3292]

This exactly. Prior to getting my Tesla, there was someone who had a Chevy Volt and had a hard-wired charger. When he left, he made the company pay to have it removed (since the device was his). When I got my Tesla, it was after a crash that totaled my previous car and the decision to get the Tesla was a quick one and I had to make a lot of fast decisions on very limited education. Putting the NEMA 14-50 in seemed like the safest route (nothing would need to be removed if I left and was generic enough to be used by others).

Besides, the company paid to have it installed (and they'll pay for the maintenance) and I charge for free, so I can put up with minor issues like this. I wasn't even going to charge today anyways (the electrician will be in today).

More than likely it is just a new outlet replacement and checking the wires. Just want to use a very high quality industrial grade outlet, like Hubbell brand. There is nothing "bad" about using a 14-50 outlet to charge, however you have just experienced why it is not considered the "best" option.

 

[Rocky_H]

There are generally the two main categories of bad versus good outlets:
Leviton is cheap and pretty bad.
Cooper, Hubbel, or Bryant are all much better and are good choices.

 

[Kevy Baby]

Ours is a Hubbell

 

[Kevy Baby]

So here's the update: The electricians have been out twice and say the circuit is fine. I am charging this morning and when I checked after it had been charging for a while, it was at 16 amps again.

I checked the error log and saw a "Charge rate reduced - wall plug temperature high". I had just unplugged and replugged a couple of minutes prior, so I went back to the card and NEMA 14-50 adaptor cable was warm to the touch (not blazing hot, but I feel warmer than it should be). The outlet and the brick were both fine temperature-wise.

So, I am going to go buy another 14-50 adaptor and see if that makes a difference.