Wall Connector charging decreases amperage over a long charge

[CubedRoot]

These past few weeks, I've noticed some odd behavior on my Model 3 charging via AC on a Wall Connector. It will start at 48 amps, and charge at 48a for a decent chunk of the charge cycle (say 10% to 50%), and then it will slowly start dropping the amperage from 48 down to around 40 amps. Sometimes it does this with the battery in the 20 to 40% range after a few minutes of charging. When I check the car, or the app, I can't even raise the limit back to 48.

Here's the details:
2018 Model 3 long range. I've had this car for 3 years, and its been using this same exact wall connector the whole time.

Gen 3 wall connector on a 60amp breaker. This has ALWAYS charged my car at a full 48amps for the past 3 years of ownership, up until recently

I've noticed the amperage drop off when looking at the app, or the car, and I can verify it in Teslafi. The charging cables aren't getting hot, and the car is kept in a garage. The voltage never drops below 239.

Is this something new with the latest updates? I can't tell if its the car asking for a lower amperage or the wall connector.

 

[GtiMart]

I don't think there's anything new doing this. Do you have any error message on the car screen when the drop happens? Or maybe in the service menu for a more detailed log?

 

[ATPMSD]

Easy thing to check. Trip the breaker and open the wall connector, then ensure all three connections are tight, they should be torqued to 50 lbf . in (5.6 Nm). If loose this can cause the problem you are seeing.

 

[Tronguy]

Yeah, and just to be clear about this: The wall connector is just that: a connector that hooks the car to city power. In fact, there’s a big honking contactor (read: relay) in there that goes, “Clunk!” when the power is applied and, “Clunk!” In the other direction when power is removed. The only bit of electronics in there is a protocol processor. The car goes, “How much voltage/current ya good for?” The WC says, “Yea much.”, which is set when you commissioned the thing. The car says, “Gimmie.”, and the WC goes, “Clunk.”

This is unlike a Supercharger where the DC potential is variable and set by the SC electronics and hand-waving between the car and the SC. The SC is legitimately a battery Charger; the WC, not so much.

The amount of current the car draws from a WC is pretty much under control of the car and its electronics.

Now, it’s well known that if the city power voltage applied to the car from the WC or, especially, from a Mobile Connector droops, a Tesla will reduce its current draw in order to prevent excessive power dissipation and heating at the point where the droop is occurring. Like in a loose wall socket, wire in a breaker box, or from someone trying to use a cheapie extension cord that can’t handle the current. Which is what most of the posters above are thinking.

But, there’s another possibility: Teslas have three 16A AC to DC rectifiers built in that convert city power to battery voltage. You’ll see the side effects of this when you watch a car start charging: first the car will zip up to 16A; then drop a bit, then rise to 32A; then do it again and run at 48A.

It’s known that these modules sometime fail, so people only get 16A or 32A instead of the full 46A. So some form of that might be happening to you, maybe. If your car is under warranty, Tesla will fix that problem.

Note: those with Standard Range Teslas and thus smaller battery packs only get two of those modules, sizing the charging rate to the battery size. But that does limit max charge rate for those cars on L2 to 32A.

So, yeah, make sure all those screws are torqued down in the WC and breaker panel. Then start worrying about loose wires and bad electronics in the car.

 

[CubedRoot]

So, I went out, verified that the connections are torqued down to the proper torque and checked the messages screen on the car. I didn't see anything, but I also wasnt charging at the time. I'll check it later tonight as its charging.

I did install the "wall monitor" app and it found some very interesting data. I am seeing 148 "Thermal Foldbacks" which is where the Wall Connector will tell the car to lower its amperage draw. See FAQ - Lifetime Statistics | Wall Monitor

So, @Tronguy it seems that the Gen3 Wall Connector does a bit more than just "clunk" as a relay. Apparently if there is some thermal problem the Wall Connector will command the car to reduce its amperage draw. Now I need to find out why all of a sudden my Wall Connector is having Thermal Foldbacks when its in a garage that barely gets over 82 degrees in the dead of summer.

 

[Mike1080i]

What revision is your WC? I recall reading that -F revision gen 3 units had an issue with some internal relays.

 

[CubedRoot]

What revision is your WC? I recall reading that -F revision gen 3 units had an issue with some internal relays.

My part number: 1457768-01-G
So It appears I have a post -F revision.

 

[davewill]

The Gen3 wall connectors have temperature sensors monitoring the wire connections. The connections are likely getting too hot. Check the wire connections again. Look for signs of excessive heating (melting, scorching, etc...) anywhere inside the wall connector. Verify that you have the right size wire, and that the strands were not cut or nicked. If they were, you might trim them back, restrip, and connect them again.

I suppose the bad connection could even be in a nearby junction box, with the heat being conducted into the wall connector, but I doubt it.

If nothing is getting hot, it could be a faulty sensor or other electronics failure in the wall connector.

 

[ATPMSD]

Open a ticket with Tesla and have them check the logs in the connector to isolate which sensor is reporting the overheat.

 

[ewoodrick]

These past few weeks, I've noticed some odd behavior on my Model 3 charging via AC on a Wall Connector. It will start at 48 amps, and charge at 48a for a decent chunk of the charge cycle (say 10% to 50%), and then it will slowly start dropping the amperage from 48 down to around 40 amps. Sometimes it does this with the battery in the 20 to 40% range after a few minutes of charging. When I check the car, or the app, I can't even raise the limit back to 48.

Here's the details:
2018 Model 3 long range. I've had this car for 3 years, and its been using this same exact wall connector the whole time.

Gen 3 wall connector on a 60amp breaker. This has ALWAYS charged my car at a full 48amps for the past 3 years of ownership, up until recently

I've noticed the amperage drop off when looking at the app, or the car, and I can verify it in Teslafi. The charging cables aren't getting hot, and the car is kept in a garage. The voltage never drops below 239.

Is this something new with the latest updates? I can't tell if its the car asking for a lower amperage or the wall connector.

A car slowing charging is basically one thing, the voltage is dropping. Since you indicate that it is the wall charger showing the errors as temperature, then that's where to go.

And you indicate that the voltage is always 239V, where and when are you measuring it. Even a bad circuit that will catch on fire next time will show full voltage when no load is present. It's only when load exists that the voltage will drop, and that's what the car measures.

 

[CubedRoot]

A car slowing charging is basically one thing, the voltage is dropping. Since you indicate that it is the wall charger showing the errors as temperature, then that's where to go.

And you indicate that the voltage is always 239V, where and when are you measuring it. Even a bad circuit that will catch on fire next time will show full voltage when no load is present. It's only when load exists that the voltage will drop, and that's what the car measures.

I’m going by the voltage that the car shows on the display when it’s charging.

 

[ewoodrick]

I’m going by the voltage that the car shows on the display when it’s charging.

Then that definitely suggest that it is the wall charger.

 

[ATPMSD]

Open a ticket with Tesla and have them check the logs in the connector to isolate which sensor is reporting the overheat.

Instead of opening a ticket, try sending an email here: [email protected]

They have been responsive in the past.

 

[zoomer0056]

Thanks for calling it a wall connector. Most people incorrectly call it a wall charger. Torqued connections all around are essential maintenance. With temperature changes and AC voltage, wires do move. This includes the whole electrical path that you have access to, not just the wall connector.

 

[CubedRoot]

Update: Its the Wall Connector.
I opened a service request, and they advised me to call 877-798-3752 and follow the prompts for "Home charging / Wall Connector support". I called that number they had me give them the TSN and TPN numbers from the side of the wall connector and he remotely diagnosed it as having "internal failures" in about 3 minutes. I asked if it was thermal related and he said yeah, he was seeing thermal PCB errors. So the Thermal Foldback errors I saw in Wall Monitor app was dead on. The Wall Connector was getting these thermal issues, and then telling the car to reduce its current draw.

Thankfully, Wall Connectors (Gen3 at least) have a 4 year warranty. They're sending me a new unit to replace this one. So for anyone else thats seeing this error and behavior, give Tesla a call and have them remotely diagnose it or download the "Wall Monitor" app from the Apple App store and check for Thermal Foldback errors.

 

[Tronguy]

Update: Its the Wall Connector.
I opened a service request, and they advised me to call 877-798-3752 and follow the prompts for "Home charging / Wall Connector support". I called that number they had me give them the TSN and TPN numbers from the side of the wall connector and he remotely diagnosed it as having "internal failures" in about 3 minutes. I asked if it was thermal related and he said yeah, he was seeing thermal PCB errors. So the Thermal Foldback errors I saw in Wall Monitor app was dead on. The Wall Connector was getting these thermal issues, and then telling the car to reduce its current draw.

Thankfully, Wall Connectors (Gen3 at least) have a 4 year warranty. They're sending me a new unit to replace this one. So for anyone else thats seeing this error and behavior, give Tesla a call and have them remotely diagnose it or download the "Wall Monitor" app from the Apple App store and check for Thermal Foldback errors.

Good. Glad to hear it's fixed; and my apologies for not figuring that it could be in the WC.

Interestingly, this is the second time I've heard of quick action by Tesla on a WC. Back in 2019, one of my co-workers bought a Tesla, a WC (gen 2), and hired an electrician to do the wiring and install. The electrician (not a Tesla-approved guy) did his bit, got his money, and left quickly. And my co-worker and I think that that quick exit was because when the co-worker tried using the WC, it failed immediately.

Me being me, I had read the installation manual on the WC cover-to-cover. And one of the warnings in there was to Never Change The Rotary Switch Settings With The Power On. My co-worker and I are convinced that that's precisely what that electrician probably did.

In any case, the interesting part was that my co-worker called the number in the manual. Somebody answered on the second ring (!). They immediately got into diagnostics, the guy said the WC was dead, and drop-shipped him a new one immediately. The new one worked.

 

[zoomer0056]

Update: Its the Wall Connector.
I opened a service request, and they advised me to call 877-798-3752 and follow the prompts for "Home charging / Wall Connector support". I called that number they had me give them the TSN and TPN numbers from the side of the wall connector and he remotely diagnosed it as having "internal failures" in about 3 minutes. I asked if it was thermal related and he said yeah, he was seeing thermal PCB errors. So the Thermal Foldback errors I saw in Wall Monitor app was dead on. The Wall Connector was getting these thermal issues, and then telling the car to reduce its current draw.

Thankfully, Wall Connectors (Gen3 at least) have a 4 year warranty. They're sending me a new unit to replace this one. So for anyone else thats seeing this error and behavior, give Tesla a call and have them remotely diagnose it or download the "Wall Monitor" app from the Apple App store and check for Thermal Foldback errors.

Awesome to have a definitive fix!

 

[CubedRoot]

Started a short charge tonight so I could watch the Wall Monitor app. Check out the PCB temp in the Wall Connector. It’s 203.2 degrees! And only after a few minutes of charging. This is also about the time I started seeing the thermal foldbacks happen.

 

[Tronguy]

Started a short charge tonight so I could watch the Wall Monitor app. Check out the PCB temp in the Wall Connector. It’s 203.2 degrees! And only after a few minutes of charging. This is also about the time I started seeing the thermal foldbacks happen.

OK: I'm a-gonna make a random, long-distance predictions, all of which are likely to be wrong:

1. Bad solder joint. Cracked, overheated, "cold": eventually, corrosion catches up with that and one ends up with a high-resistance joint.
2. Bad crimp. A crimped connector can handle a ton of current if done properly. The words, "Gas tight" end up being bandied around by the people selling the crimping tool. Bad insertion, insulation in the wrong place, not enough force on the crimp, and high resistance R Us.
3. The contactor. Contactors have big, round, plated contacts (hence the name) that make contact and have micro- or milli-ohm resistances. Don't build the contactor, with the wrong metals? Counterfeit components are a thing, especially when they're expensive. Open and close contacts and one gets arcs and sparks as the contacts open and shut; the contacts are designed with Plenty of Expensive Metals so they'll last, but that doesn't work if one has the wrong contactor. Or a counterfeit one.
4. I believe you when you say you torqued all the wire clamps down. But if one of those blocks of metal that the clamp is built out of isn't secured to whatever-it's-supposed-to-be-secured-to properly, then high resistance and overheating is a-gonna occur.

Properly diagnosing something like this usually involves a heck of a lot of close eye inspection, up to and including microscopes, not to mention putting it on a jig, running some test current through same, and figuring out what went wrong with a voltmeter/ammeter. That's too much work for a homeowner, no kidding, so drop-shipping you a new one is the Right Thing To Do.

One last thought, though. If I were engineering a Wall Connector, I'd go out of my way to zero the current before closing or opening the contactor, the idea being to reduce the arcs and sparks as the contactor opened and closed. As I implied earlier, contactors are kind of designed to handle arcs and sparks, but they last a lot longer if they're aren't any. Given that the car is the load on the WC, it kind of seems to me that it would be trivial to enforce this with the car's software. So, nothing, but.. hmmm...

 

[Bob2C]

I was charging today at 48 amps and the app said it would take 3.5 hours to get to 90%. Was heading out the door and noticed the car still charging 4 hours later. Went to the app and noticed it was reduced to 24 amps. Contacted Tesla Wall Connector support. They immediately answered the phone, did a diagnostic as well as me sending then pictures of my charge port on the car and the handle of the cable. They determined the wall connector to be at fault and are shipping a new one for free. Still under warranty after 2 years of use. I asked if i can still use it and he recommended not to. Not that there was a fire risk but something how it can corrupt the data in the car. Overall very please with Tesla support