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120v Mobile Charger reducing amps

Triple D

Member
Jun 1, 2020
54
81
Los Angeles, CA
I am having trouble determining why my Tesla mobile charger is reducing the amps while charging on 120v.

I charge while at work. I work 12 hour shifts and I am using a 120v 15 amp standard outlet. When I plug in the app shows I am charging at 122v 12/12amp and getting 5 mi / hour.

Then a few hours later I check the app and it shows my charging is at 122v 6/6amp 2mi/hr. Why does this happen? It usually goes down to 6/6amp for 4-6 hours a day then later goes back up to 12amps.
Is it temperature related? I have only had this car for 1 month and It’s been hot, 100 degrees most days.

I allow the fan in the car to run while I’m working but no A/C.
 
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lUtriaNt

Member
Mar 16, 2020
624
551
Los Angeles
yes most likely heat related and/or dirty power on that circuit.

i only have level 1 nema 5-20 (16AMPs) at my parking spot at my flat and sometimes it will drop down from 2kw (i dont use miles, i use percentage) to 1kw. i usually see 110-112 volts.

if i see this i will stop charging (using the app). wait a few seconds then start up charging again and this outputs the full 16amps/2kw on level 1.

its hot here in LA and if you park your car outside the heat may certainly cause this. i have garage parking but the car can get warm with that huge battery pack under it and if the circuit is dirty (dirty power) it could also make the charger drop down.

to me it sounds like its normal.

how are you charging habits at home? do you see the same phenomenon?
 

Triple D

Member
Jun 1, 2020
54
81
Los Angeles, CA
To be honest, I don’t really charge at home. I work 60 hours a week and with a 35 mile round trip commute, charging at work 12 hours daily should be all I need.

So I guess everything is working as designed. Is the reduction in amps because of the temperature of the mobile charger body, or the plug handle? Maybe I can shade the part that gets too hot. Are there any tricks I should try?
I have seen people maintain maximum Tesla supercharger kWh by wrapping the charging plug with a wet rag. The superchargers reduce power if the handle that plugs into the car gets too hot, afaik.
 
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brkaus

Well-Known Member
Jul 8, 2014
7,742
6,275
Austin, TX
It could be caused by the temperature sensors in the wall plug, the body, or the plug into the car.

At 120v / 12a, I doubt it would be the plug into the car or the body of the charger.

is the outlet getting hot?

it might also be voltage drop if some other part of the circuit is heating up and causing resistance. The car measures the voltage when it has no load and then if it drops significantly as the current increases it will throttle.
 
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Triple D

Member
Jun 1, 2020
54
81
Los Angeles, CA
It could be caused by the temperature sensors in the wall plug, the body, or the plug into the car.

Wow, I did not know there were temp sensors in all 3 parts.
It is plugged in with direct sunlight and 100*+ temperature. So that makes sense that it works fast during the early morning and afternoon but slows down during the hottest part of the day.
 
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brkaus

Well-Known Member
Jul 8, 2014
7,742
6,275
Austin, TX
Wow, I did not know there were temp sensors in all 3 parts.
It is plugged in with direct sunlight and 100*+ temperature. So that makes sense that it works fast during the early morning and afternoon but slows down during the hottest part of the day.

the biggest issues, I think, have been around the plug on the wall side melting. Not as common on 12a, but at higher current levels a poorly installed or warn out outlet can get very hot. The outlet transfers the heat into the plug and bad things happen.

I would think sitting in full sun at 12a should be fine. Does it say anything in the screen when it kicks down? I’m not sure if there is a history of error messages.
 
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lUtriaNt

Member
Mar 16, 2020
624
551
Los Angeles
its the temps outside mate. the charger is throttling. i think what you are seeing is fine. temps have been crazy hot here.

if your home parking situation is much better (garage, shaded, etc), id at least just charge at home for 12 hours or whatever you can and see if there is a difference.

like i said, i have seen this happen once or thrice on the charger and its usually when its 110 degrees here in the valley. :)

in case you wanna know what's in that thing.. :)

 
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mongo

Well-Known Member
May 3, 2017
13,033
39,213
Michigan
I am having trouble determining why my Tesla mobile charger is reducing the amps while charging on 120v.

I charge while at work. I work 12 hour shifts and I am using a 120v 15 amp standard outlet. When I plug in the app shows I am charging at 122v 12/12amp and getting 5 mi / hour.

Then a few hours later I check the app and it shows my charging is at 122v 6/6amp 2mi/hr. Why does this happen? It usually goes down to 6/6amp for 4-6 hours a day then later goes back up to 12amps.
Is it temperature related? I have only had this car for 1 month and It’s been hot, 100 degrees most days.

I allow the fan in the car to run while I’m working but no A/C.
The second number '/12' or '/6' is the max current the EVSE (wall adapter) will provide. So it looks like the plug is heating up (the adapters have a temp sensor in them). It could also be that the plug adapter is not fully seated.
The unit will report which section is hot during the 6/6 behavior:
Five is an internal hw fault.
Four red flashes indicate a plug temperature issue.
Three red flashes indicate a unit temperature issue.
2 is the cord to unit connection
1 is the vehicle connection
https://www.tesla.com/sites/default...bile_connector_owners_manual_32_amp_en_US.pdf
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,271
7,328
Boise, ID
And you could try starting with it at 9 or 10 amps instead of 12, and that might keep the heat low enough that it won't have to reduce it. And then 9 is higher than 6.
 
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Triple D

Member
Jun 1, 2020
54
81
Los Angeles, CA
The second number '/12' or '/6' is the max current the EVSE (wall adapter) will provide. So it looks like the plug is heating up (the adapters have a temp sensor in them). It could also be that the plug adapter is not fully seated.
The unit will report which section is hot during the 6/6 behavior:
Five is an internal hw fault.
Four red flashes indicate a plug temperature issue.
Three red flashes indicate a unit temperature issue.
2 is the cord to unit connection
1 is the vehicle connection
https://www.tesla.com/sites/default...bile_connector_owners_manual_32_amp_en_US.pdf

Thank you for this info. I had no idea that there was a red light and that it indicates a code.

Today I was planning to go take a look at the light to see exactly what the problem was. But, it stayed below 100 degrees in the valley and the charger never dropped below 12amps. So I am confident that the charging problem is temperature related. I will definetley find the issue next time its over 100.
But maybe temperatures will be cool for the rest of they year and I will have to investigate next spring /summer.

Thanks again.
 
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M3BlueGeorgia

Active Member
Dec 10, 2018
1,375
1,083
Atlanta, GA
Are you using an extension cord?

If so, you need 12 gauge not some thinner cable.

What you are seeing is the car recognizing a problem with cabling delivering electricity to the charging system. It thinks the cabling is overheating, so the car is reducing the current drawn.

Also, make sure the mobile connector control unit is shaded from direct sunlight. Otherwise the overload detection software gets tricked and reduces current draw.
 

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