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M3 Mobile Connector (UMC) Charging Fluctuations

elecTED

Member
Jun 21, 2019
325
320
Bristol, UK
I use the UMC cable for home charging (and have been doing so for a number of months) and used to see a steady 10 mi/hr 231-235 V 10/10 A charging rate.

In the last few weeks I've noticed the charging rate using the UMC cable fluctuate between 5 to 10 mi/hr and 5/5A to 10/10A. The charging rate changes several times a minute and sometimes only stays on the lower charging values for just a few seconds.

I've tried a 3 pin socket in other locations/houses and similar fluctuations and unsteady behaviour from the mobile connector.

Anyone else seen this type of continuous fluctuating charging behaviour from your UMC cable?

Time to get the cable checked out with SC?
 

OfficialMark_H

VLOGGER
Jan 1, 2020
192
129
Somerset UK
I also use the UMC for charging at home and get 10mph, if however you’ve got a lot of other items drawing current at the same time the car knocks it down from 10a to 5amps.
 

Louis0w

Member
Mar 6, 2020
127
111
Bridgend, Wales, UK
After 10 mths, I had an issue with my UMC. It developed a thermal fault whereby the T would flash red. Tested with multiple adapters and different sockets but problem persisted. It would still charge, but was limited to 4kw. Reported to Tesla via the App and they were happy to replace under warranty. No issues.
 
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Columbo

Member
May 23, 2020
65
29
Uk
I also use the UMC for charging at home and get 10mph, if however you’ve got a lot of other items drawing current at the same time the car knocks it down from 10a to 5amps.
How does the UMC know your house load? If you were drawing too much at the same time the main fuse / trip would go. Unless you've got some sort of monitoring system talking to your smart meter?
 
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VanillaAir_UK

Supporting Member
Jun 17, 2019
7,973
5,466
Surrey, UK
How does the UMC know your house load? If you were drawing too much at the same time the main fuse / trip would go. Unless you've got some sort of monitoring system talking to your smart meter?

It doesn't know your house load but can be influenced by it. As load on local electrical area goes up, voltage often drops. If it starts getting too low, car may think there is a problem and starts to throttle rate. Also, power is proportional to voltage, so low voltage gives less power and slower charge rate. Also, difference between charging at 220v vs 250v is around 12% slower charge.
 

Jason71

Active Member
May 8, 2019
2,838
2,712
Shropshire
After 10 mths, I had an issue with my UMC. It developed a thermal fault whereby the T would flash red. Tested with multiple adapters and different sockets but problem persisted. It would still charge, but was limited to 4kw. Reported to Tesla via the App and they were happy to replace under warranty. No issues.
Do you mean 4amps not 4KW? The UMC can only do 2KW even when working properly?
 

Columbo

Member
May 23, 2020
65
29
Uk
It doesn't know your house load but can be influenced by it. As load on local electrical area goes up, voltage often drops. If it starts getting too low, car may think there is a problem and starts to throttle rate. Also, power is proportional to voltage, so low voltage gives less power and slower charge rate. Also, difference between charging at 220v vs 250v is around 12% slower charge.
Yes that's right, the local area load will effect the voltage not the house load. If the house load is then their is a serious issue with the house circuit.
 

Louis0w

Member
Mar 6, 2020
127
111
Bridgend, Wales, UK
My T is intermittently flashing red too and the UMC handle button no longer opens the charging port flap.

Time to report to SC.

Definitely report it. With my UMC fault, I tested it on different sockets and even at a different property; T still flashed red. I was then confident the issue was with the UMC and not my socket or supply. It took 2-3 weeks for Tesla to supply the replacement; thankfully I had purchased a spare UMC shortly after delivery, so was still able to charge whilst I waited. Check your in car notifications too:

79290950-6484-4464-AC5A-D9E05BD6C2BB.jpeg
 
Last edited:

R5scott

Member
Apr 23, 2020
42
15
Bath
Seem to be having exactly the same problem. Tried at a different property so definitely car or cable. Logged with Tesla a week ago and still waiting for them to get back to me
 

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