This is bad, right?

[coinneach]

Past 3-4 charges, I've gone out to unplug my car and been greeted with the "charging problem" dash message. The charge port is green, the UMC LEDs are flowing, and it's charging at 30A rather than 40. I went to clean the contacts on the car and the UMC tonight and saw this.

I have a new CMC coming. The outlet, wiring, breaker, etc is new, and I tested it myself with the installer watching.

So. Faulty UMC, or something more sinister?

 

[Tam]

..something more sinister?

It's just old fashion heat.

I wouldn't use those at the first sign of heat damage.

That's why permanent HPWC might be a better idea than Mobile Connector.

 

[gsteele]

Another first gen UMC bites the dust. On the slim chance that you get another first-gen UMC, you should turn the amperage down to 32. There is a reason why the second-gen ones max out at 32.

 

[coinneach]

Another first gen UMC bites the dust. On the slim chance that you get another first-gen UMC, you should turn the amperage down to 32. There is a reason why the second-gen ones max out at 32.

*sigh* Neat. Guess I shouldn't complain too loudly; most of the googles for "Charging problem" were all "Oh yeah, your master charger is dying, gonna cost $2500."

 

[davewill]

Remove the cover plate and check the outlet. Copper conducts heat, not just electricity. The heat could have damaged the outlet. The outlet could even be the SOURCE of the heat. Check the screw connections on the back of the outlet for signs of trouble like discoloration, looseness, or insulation trapped under the screw. If there's any damage at all, replace the outlet.

 

[coinneach]

Remove the cover plate and check the outlet. Copper conducts heat, not just electricity. The heat could have damaged the outlet. The outlet could even be the SOURCE of the heat. Check the screw connections on the back of the outlet for signs of trouble like discoloration, looseness, or insulation trapped under the screw. If there's any damage at all, replace the outlet.

No visible damage to the outlet, all connections are secure. I Fluke'd it again this morning and everything is nominal.

 

[coinneach]

Well, crap.

My new CMC came today. I plugged it into the outlet, watched it turn green, plugged it into the car (which responded immediately, unlike the multiple clicks required to wake it up with the old UMC), watched it start charging, went to check on it 30 minutes later...

Same error.

I disconnected/reconnected it, left it at 30A, estimated charge time 1:55. I checked it just now and it shows 10 minutes left and no errors.

 

[ac_power]

Yep, Gen1 is notorious for that.
Somebody got to explain me how those skinny pins inside the adapter are supposed to be transferring 40A continuously. And they seem to be even hollow inside, plastic filled.
Tesla used to blame NEMA sockets for overheating due to poor contact, but one look is enough to identify weak point (and it's not the socket).
So is the problem finally gone with CMC ?

 

[ac_power]

Another first gen UMC bites the dust. On the slim chance that you get another first-gen UMC, you should turn the amperage down to 32. There is a reason why the second-gen ones max out at 32.

Sure enough Gen2 could have been improved to handle 40A.
Reason for the drop is that in Canada NEMA 14-50 are normally installed into 40A rated / 32A continuous circuit (unlike USA 50A rated / 40A continuous), and running Gen1 at full power would often overload the wiring without tripping the breaker.

 

[coinneach]

So is the problem finally gone with CMC ?

Nope, same behavior as before. The plug doesn't feel warm and there's no discoloration, it just kicked down to 30A and finished there. I can deal with it until I swap out the breaker for a 60A or get the car checked out. Still don't have the plate so Tesla won't put it on my account.

 

[tga]

How did you test the outlet? Are you just testing the no-load voltage at the outlet? That doesn't tell you much. You need to monitor voltage under load, ideally while the charge current ramps up. If voltage sags "too much" under load (I don't think the limit has been publicized), the car will cut charge current 25% and display that error on the dash. Based on other reports here, it seems like the car may also do it if (a) the starting voltage is to low (<200V?) or (b) power fluctuations occur during charging (brownouts, a sag when your A/C compressor turn on, etc).

My suspicion is that you have two separate issues here -

• Your UMC had a loose pin and overheated. You've fixed that.
• You have a loose connection elsewhere or a utility/power supply issue. The first step is to monitor the voltage while the current ramps up and see if it drops more than 8-9V. If so, you need to figure out where the voltage drop is occurring (bad connection, small wire, etc). See if anything is getting hot while charging (you should wait an hour or two to warm) - note, your breaker will be warm, but not hot (you should be able to hold your hand on the breaker indefinitely without getting burned).

If you know what you are doing and can take proper safety precautions, you can measure the voltage under load at various points going back to the panel to find the loss point. If the voltage drop also occurs at the main panel bus bars, you likely have an undersized utility feeder. If you don't know how to do this safely, get help from a pro.

Sure enough Gen2 could have been improved to handle 40A.
Reason for the drop is that in Canada NEMA 14-50 are normally installed into 40A rated / 32A continuous circuit (unlike USA 50A rated / 40A continuous), and running Gen1 at full power would often overload the wiring without tripping the breaker.

This is also a potential problem in the US. NEC allows a 14-50 on a 40A circuit if you are plugging in an appliance with a nameplate rating of 40A or less. But that doesn't apply to the UMC.

 

[coinneach]

When I first connect the CMC, I watch the charge progress on the touchscreen as it ramps up. It smoothly increases to 40A/240V and holds there for at least 10 minutes (I also supercharged to 95% the day I took it home and saw no errors). I've not sat and timed it so I don't know exactly when it kicks down. If I discon/recon the CMC after it throws the error and set it back to 40A, it completes successfully.

 

[tga]

Watch the voltage displayed as the current ramps up. It will drop; the question is how much.

AC charging is completely different than supercharging - no errors while supercharging doesn't really tell you anything.

 

[ac_power]

To clarify - supercharger bypasses onboard charger.
Voltage drop is a first thing to check for sure, and it's relatively easy. The closer to the CMC plug, the better.
If voltage drop is within reasonable limits (3V should be a good starting point), then high chance it's voltage inconsistency during charging. Unfortunately, the only way to investigate further is to run power quality logger I guess.

 

[Evoforce]

Also make sure that you do not have to much tension (cord stretch) from the cord pulling against the socket of the car.

 

[tga]

The car should tolerate a higher drop than 3V @ 40A. I go from 247V-248V (yes, it's a bit hot in my neighborhood) to 241V-242V at 24A. That's all on the utility side; I get the same reading at the car and at the main panel bus bars. I got the same voltage drop before and after the utility replaced my feed when I upgraded from 100 to 200A service.

 

[ac_power]

The car should tolerate a higher drop than 3V @ 40A.

I think your original estimate of 8..10 A may be about right.
Running 40A, my system shows voltage drop of ~2.4 V at the socket, and 4..5V from the dashboard (i.e. measured by the UMC itself).
Dependent on the wiring, both numbers can potentially go up by 0.5..1.5V, but anything above would indicate a potential issue.

 

[coinneach]

Thanks for the great advice and feedback, all.

Tesla support pulled the car's logs this afternoon and saw no issues on that side. I have the electrician who installed the outlet coming out this weekend to run a load test.

 

[scaesare]

*sigh* Neat. Guess I shouldn't complain too loudly; most of the googles for "Charging problem" were all "Oh yeah, your master charger is dying, gonna cost $2500."

FYI that's often a $10 fix if you are willing to dig in to your car.

 

[tga]

FYI that's often a $10 fix if you are willing to dig in to your car.

Explain, please?