120v Mobile Charger reducing amps

[Triple D]

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.

 

[lUtriaNt]

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]

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.

 

[brkaus]

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.

 

[Triple D]

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.

 

[brkaus]

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.

 

[lUtriaNt]

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..

 

[mongo]

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

 

[Rocky_H]

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.

 

[Triple D]

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.

 

[brkaus]

Here is an example of a melted plug. In this case the 14-50 outlet.

Melted adapter and outlet

 

[M3BlueGeorgia]

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.

 

[NimroWA]

My 120V charging goes to 6a in 70 degree F weather after several hours. Unplugging Tesla cable will reset it. Stopping charging with the app causes no change.

 

[20221229 3RWD]

We have only had our Tesla Model 3 RWD for a couple of weeks now. Yesterday was my first Level 1 charging effort. I plugged in the Tesla Mobile Charger into an available NEMA 5-20 outlet (on a 20amp breaker) using a NEMA 5-15 Adapter. I have a NEMA 5-20 Adapter on order.

For the first hour it charged at 12amps but then dropped to 8amps. After a few hours at 8amps per out I went out and clicked the connector button on the Tesla plug (the piece that plugs into the car) and it started charging at 12amps again. I did the same the earlier this morning after the overnight charging dropped to 8amps and sure enough it started charging at 12amps again.

Trying to trouble shoot, can you help with any ideas regarding why the drop to 8amps and then why back to 12amps after I click the connector button on the Tesla plug?

 

[brkaus]

Clicking the button is stopping the charge and resetting the cycle.

It is dropping the current because it is detecting something it thinks is dangerous. It could be heat at the plug, it could be the voltage is sagging.

You can check for heat after it’s been charging for a while and before the amps drop. Ideally with an IR temp sensor, but hand also works.

You can also look at the voltage on the screen immediately once it starts charging and see how much it changes as the amps get higher. It will drop, it shouldn’t drop too much.

Finally, you can charge at 10a and see if it will hold that overnight.

But, in all likelihood you have a marginality in your charging circuit that should be looked at by a professional. (Before the smoke gets out)

 

[mongo]

We have only had our Tesla Model 3 RWD for a couple of weeks now. Yesterday was my first Level 1 charging effort. I plugged in the Tesla Mobile Charger into an available NEMA 5-20 outlet (on a 20amp breaker) using a NEMA 5-15 Adapter. I have a NEMA 5-20 Adapter on order.

For the first hour it charged at 12amps but then dropped to 8amps. After a few hours at 8amps per out I went out and clicked the connector button on the Tesla plug (the piece that plugs into the car) and it started charging at 12amps again. I did the same the earlier this morning after the overnight charging dropped to 8amps and sure enough it started charging at 12amps again.

Trying to trouble shoot, can you help with any ideas regarding why the drop to 8amps and then why back to 12amps after I click the connector button on the Tesla plug?

What are the status lights doing on the mobile connector when this happens?
8 amps with five red flashes indicates an internal connector failure. Have you tried unplugging the wall end (and reseating the adapter)?

 

[20221229 3RWD]

What are the status lights doing on the mobile connector when this happens?
8 amps with five red flashes indicates an internal connector failure. Have you tried unplugging the wall end (and reseating the adapter)?
View attachment 895366

Understood, thank you. All green lights flashing in series. The outlet, nor the socket nor any part of the cable feels hot. Average of 115.33 volts and 9.39 amps over the last 20 hours and 9 minutes of charging via TeslaFi website.

 

[20221229 3RWD]

Clicking the button is stopping the charge and resetting the cycle.

It is dropping the current because it is detecting something it thinks is dangerous. It could be heat at the plug, it could be the voltage is sagging.

You can check for heat after it’s been charging for a while and before the amps drop. Ideally with an IR temp sensor, but hand also works.

You can also look at the voltage on the screen immediately once it starts charging and see how much it changes as the amps get higher. It will drop, it shouldn’t drop too much.

Finally, you can charge at 10a and see if it will hold that overnight.

But, in all likelihood you have a marginality in your charging circuit that should be looked at by a professional. (Before the smoke gets out)

Understood, thank you. Sure that makes sense regarding "resetting the cycle". Hmmm ... nothing appears to be warm and volts and amps seem to be fine?

Average of 115.33 volts and 9.39 amps over the last 20 hours and 9 minutes of charging via TeslaFi website.

 

[brkaus]

Understood, thank you. All green lights flashing in series. The outlet, nor the socket nor any part of the cable feels hot. Average of 115.33 volts and 9.39 amps over the last 20 hours and 9 minutes of charging via TeslaFi website.

Since you have the graph, what did the voltage start at? I’m not sure if it samples enough to be useful.

 

[Rocky_H]

Sounds like voltage drop because of the telltale 8 amps. The car measures the voltage at first, before beginning charging, and then it will check how much it drops as it ramps up the current. If it sees drop more than a certain amount, then it will drop the current to 3/4 of what it was using. So that is what the 8 amps instead of 12 would show.

It's probably not just the heat sensor, because that almost always throws a visible error on the display.

A lot of builders put in those 120V outlets using the part on the back of the outlets called "stab-in". They are holes with little sharp teeth along the edges of the inside of the holes. You can strip the wire, and then just shove it in there, and the teeth scrape into the wire to kinda, sorta, make a weak connection. It's faster to get a bunch of outlets installed, but is generally crummy because those tiny teeth connections are a very small point of contact and are resistive, and after several years will usually stop working right.

So maybe pull that outlet and check. The outlets do still have the screw terminals on the side. So if it's using the stab-in holes, pull the wires out of that and wrap it around the screw on the side and tighten it up to make it a much better connection, and it won't have as much voltage drop, and that may fix that issue.

Or the wires may be loose at the other end where they are screwed into the breaker. Or, it may just be a really long run of the wire that is just going to have significant voltage drop regardless. That's not bad, but will keep dropping the current down to 8A. As @brkaus suggested, you might be able to turn the amps down to around 9 or 10 to start with, and that may keep it sustained without triggering that lowering.