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

Kevy Baby

Dis-Member
Supporting Member
Aug 11, 2019
2,247
2,369
Brea, CA
Interesting development today.

As mentioned earlier, the electrician came out a couple of weeks ago and reran the wires so that we could have two outlets (on two separate 50A circuits). At the same time, I had gone to the service center where they pointed out that NEMA 14-50 pigtail was not fully seated into the Controller. Since then, I've had no problems: charging never dropped to 16A. And I was always making sure the pigtail was fully seated.

No problems until today that is.

I had been watching the charging carefully since the updates: always charging at 32A. Today, when I was about to go to lunch and went to turn my AC on remotely, I noticed that I was only charging at 16A. So when I went out, I started touching everything:
  • The plug where it goes into the outlet was cool to the touch
  • the Controller was cool
  • the short cable between the two was warm. Not hot - easy to hold - but decidedly warm.
So on Wednesday (when I will charge next, I will have an IR thermometer (good tip @a64pilot) with me and take a measurement. Armed with the info, I will go to the Service Center and see if they will replace the pigtail. Worst case is I buy another one and I'm out $45.
 

jwharnish

Member
Aug 30, 2021
26
19
AZ
Well, we did a couple of things at the same time, so I am not 100% certain, but I suggest you do one simple thing: make sure the NEMA 14-50 adaptor is FULLY seated into the Controller (I call it the the brick) of the Mobile Connector Cable. When I stopped by the service center, they pointed out that mine was sticking out by about 1/16" +/- and that MAY have contributed. But that was discovered on the same day the updated outlets were installed, so I can't be 100% certain. I have not had any charging issues since then.
You indicate that "updated outlets were installed". Which brand outlets were installed? I do believe some make outlets work better than others for EV charging. From all of the responses regarding this issue, all makes outlets seem to work ok at first, but over time overheating become an issue with certain outlets.
This was my experience with a cheap outlet vs an expensive outlet.
 

Kevy Baby

Dis-Member
Supporting Member
Aug 11, 2019
2,247
2,369
Brea, CA
You indicate that "updated outlets were installed". Which brand outlets were installed? I do believe some make outlets work better than others for EV charging. From all of the responses regarding this issue, all makes outlets seem to work ok at first, but over time overheating become an issue with certain outlets.
This was my experience with a cheap outlet vs an expensive outlet.
Previously posted, but the outlets are Hubbell, which is considered one of the more solid brands.

At this point, I am fairly certain that it is the pigtail, given the warmth of the cable when I checked earlier.
 
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rrolsbe

Member
Feb 18, 2017
305
191
Albuquerque
Having the charging speed dropping off in increments of 16A frequently means a module in the onboard charger in the car is failing. The 32A charger has two of those modules, and the 48A charger has three of them, so if it drops off by 16, that sometimes means part of it is failing, but the car can continue to use what's left instead of just quitting entirely.
My June build 2018 M3 would not AC charge over 32A. The PCS board was replace under warranty Aug 2021 and it can now charge at 48A. The modules discussed by Rocky_H are located on the Power Conversion System board (PCS). The replacement cost of the PCS board, outside of the warranty period, can be north of $2500.
 

jwharnish

Member
Aug 30, 2021
26
19
AZ
Previously posted, but the outlets are Hubbell, which is considered one of the more solid brands.

At this point, I am fairly certain that it is the pigtail, given the warmth of the cable when I checked earlier.
Sorry missed that previous post. When using the Hubbell outlets, I'd look elsewhere for the problem. Hubbells are top notch.
 
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Kevy Baby

Dis-Member
Supporting Member
Aug 11, 2019
2,247
2,369
Brea, CA
Was having issues again this morning. After it dropped to 16A, I unplugged and re-plugged and then went out about 45 minutes later (was showing charging at 32A). The pigtail was definitely very warm. So I took the cable in to the Service Center (Irvine - Barranca). Was planning on replacing just the pigtail but they replaced the whole cable and the NEMA 14-50 connector under warranty. Hopefully this is the end of my problems.

I'm going to go out and check again in about a half hour to see how the new cable is doing.
 

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