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UMC Charger AMP went down from 32 to 16

Hi all,

Not sure if anyone has experienced this but today I plugged in home l to charge and got the usual 32amps. After a while the amp went down to 16.

I unplugged the charger from the car and plugged it back in, and it returned to normal…until I checked a bout an hour later it went down to 16amps again.

Charger wasn’t stifling hot, just slightly warm but barely. Mobile charger is located in the garage and is plugged in to a 240.

There was a notification that the charger is getting hot but it wasn’t hot at all. Just slightly lukewarm. I was able to touch it for a while without any issues.

Anyone have any idea why?

This is the first time that it’s happened to me.
 

jeremymc7

Active Member
Feb 3, 2013
2,276
1,369
U.S.
I had this happen before. Eventually went away.

However I also see this happen to others for loose outlet / plug, not dedicated circuit and other items also drawing a load, undersized panel getting close to main breaker tripping, damaged charging cable due to being twisted back and forth too many time or stepped on.

There’s a bunch of possible things. I’m sure others will chime in.
 
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jcanoe

Well-Known Member
Oct 2, 2020
6,030
6,711
Maryland
If it is a 14-50 receptacle it is must be on a dedicated circuit. It is most likely the power plug adapter that is overheating.

Make sure that the power plug adapter is fully inserted into the Mobile Connector chassis.

Fully insert the plug into the 14-50 receptacle. Leave it plugged in, only unplug if you need to take the Mobile Connector with you for a trip.

Don't let the Mobile Connector hang supported by the power plug adapter pigtail. Support the Mobile Connector chassis brick. You can find cable organizer kits from Tesla, also on Amazon that include a mounting bracket for the Mobile Connector chassis. You can make your own support that takes the strain off of the plug.

If the problem persists have an electrician check the 14-50 receptacle for signs of overheating. (Do not use a cheap 14-50 receptacle from a home improvement store. Use only quality receptacles from Hubbell/Bryant or Cooper. Do not use the cheap Leviton 14-50 receptacle for charging an EV.)
 
The mobile connector has a temperature sensor built in to there plug. It was probably only warm because the sensor tripped and limited the current. It would have been burning hot had it been running at 32A.

Note that 2x the amps means 4x the heat due to resistance. Also note that as wires get warmer, the resistance increases, which leads to greater heat.

The most likely culprit is the outlet itself, so it would be good to get it checked out if it happens again. It's possible that the weight of the charger when it's hanging is causing a poor connection.
 
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ATPMSD

Active Member
Mar 12, 2021
1,611
1,518
Atlanta, GA
Couple of additional points to check:

  • If the outlet is a Leviton replace it! Those are consumer grade and should not be used for EV charging. Get a commercial / industrial grade outlet, such as:
Hubbell part # HBL9450A,
Cooper part #5754N

These list for around $50-90. You will also need a new faceplate.
  • Trip the breaker and check the connections on the outlet, make sure they are tight.
  • If you are comfortable doing so, open the breaker box and ensure those connections are tight was well.
 
Last edited:

Red Ryder 3

Now known as: "REDAZY22"
Mar 9, 2021
132
187
Phoenix, AZ USA
This happened yesterday morning with my Model Y wall charger and my wife's Mustang Mach E charger (Only trying one at a time!)
The electrical panel has separate 240V feeds to each charger.
The panel is mounted on an east-facing exterior wall on the other side of a concrete block wall from the chargers.
BUT, it was 100° ambient temperature in Phoenix yesterday morning!
Both provided 32 Amp later that evening.
Any other reason why this happened?
 

jeremymc7

Active Member
Feb 3, 2013
2,276
1,369
U.S.
Read the thread above there couple be numerous over potential causes.

In your specific case it sounds like likely the temp.

What was the actual temp in the car.

I have a digital thermometer mounted mid way up the way near my two chargers to keep track of these things.

That said the Tesla app is great for telling you what the temp in the garage is outside the car as well as inside. Complement that with the other thermometers I have in the garage, around the inside of the house for the zoned HVAC and outside gives a fuller picture.
 

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