Charging issue

[Kalex]

Whenever I switch charging from 2017 MS 75D to 2017 MX 100D ( both set at 32Amp rate), the 50 amp breaker trips. When I check the MCU, the amp rate is changed to 72 amp. I tried both UMC cables, but still does the same. After resetting the breaker, they charge fine. Both cars appears to retain the geofenced @32amp as my preferred charging rate. There is a camco 14-50 extension cord between the NEMA 14-50 outlet and the Gen 1 UMC, if this makes a difference.
After charging the MS, do I have to unplug the UMC for 60 seconds to reset the UMC, then plugging in to the MX to avoid the issue?
Hopefully the experts can chime in.
This issue started when my wife got the MX in March. The MS is 9 months and so far very happy with it.
Thanks

 

[Rocky_H]

Huh. That is a tough one--nothing really jumping out at me yet. But here are some ideas:

The Model X seems to be trying to use a higher current setting for some unknown reason. Now the gen1 UMC should only be capable of pulling 40A current maximum anyway, so there should only be 40A total through that Camco cord and the outlet. Now it is possible, that maybe the full 40A is enough to trip the breaker. Does it trip immediately or after a few hours? So one thing you could check is to have your Model S use 40A charging rate for a while to see if that will also trip the breaker. So even though the Model X is still doing something weird in ignoring your current setting, you might be able to figure out why the breaker is tripping, unrelated to which model of car is doing it.

I am a little curious and concerned about something which I hope isn't even possible. The UMC is supposed to send the proper pilot signal to the car telling it the maximum amps it can request. That is supposed to be 40A, since it has a 14-50 plug attached. Surely there is not a way that the car can override that the other direction? If the car glitches and tries to draw 60 or 72 amps, I really hope the UMC won't try to pull that much from the outlet. Obviously the UMC wouldn't last long doing that, and that would trip the breaker, but I would think the UMC would have some kind of safeguard to block that from happening anyway.

 

[Kalex]

Update:
After charging the 75D yesterday afternoon without any issue. I unplugged the UMC from the 14-50 adapter and left for work. I arrived tonight and plugged the UMC to the 14-50, and then charged the Model X with no issues..the 32 Amp rate stayed the same. I think the UMC get "confused", or does not recognize the change from a 48 amp max to 72amp max. I just have to unplug the UMC after each charging to avoid tripping the breaker.. I read in the charging manual somewhere that if the UMC throws an error, try the reset button, but if it does not work, unplug the adapter from the 14-50 outlet to reset. I will reach out to Service about my findings and see what they say and report back. I think I should be able to just unplug from one car and then plug to the other car without no issues. The UMC and car should recognize and adjust the amperage set at the MCU.

I would like to hear what others that has 2 teslas (72 amp and 48 amp) do with regards to charging.

 

[GOPJEW]

Update:
After charging the 75D yesterday afternoon without any issue. I unplugged the UMC from the 14-50 adapter and left for work. I arrived tonight and plugged the UMC to the 14-50, and then charged the Model X with no issues..the 32 Amp rate stayed the same. I think the UMC get "confused", or does not recognize the change from a 48 amp max to 72amp max. I just have to unplug the UMC after each charging to avoid tripping the breaker.. I read in the charging manual somewhere that if the UMC throws an error, try the reset button, but if it does not work, unplug the adapter from the 14-50 outlet to reset. I will reach out to Service about my findings and see what they say and report back. I think I should be able to just unplug from one car and then plug to the other car without no issues. The UMC and car should recognize and adjust the amperage set at the MCU.

I would like to hear what others that has 2 teslas (72 amp and 48 amp) do with regards to charging.

You max capability has nothing to do with it - when I switched between my S and X I had no problems.

Reality - as @Rocky_H pointed out - the Gen 1UMC is only capable of 40 amp regardless of my vehicle's capabilities. I had them both set to 40 amp on a 50 amp circuit and have no problems.

Now, every once in a while when I get a voltage drop the vehicle automatically reduces it's pull to 30 amp (it is a well designed safety protocol built into the vehicles) and I have to go back in and reset each vehicle back to 40 amp...

My guess is you may have a loose connection somewhere in your charge line - perhaps the extension cord is your culprit - that is causing your breaker to trip. For the breaker to trip it has to be exceeding it's capacity, which typically means a short somewhere since the vehicles AUTOMATICALLY gauge the amount they can pull and reduce it (i.e. 40 amps on a 50 amp circuit, 32 amps on a a40 mp circuit, etc).

 

[Kalex]

I am going to try to plug the UMC directly to the 14-50 and see if it the extension cord is causing the problem.
Thanks

 

[mongo]

The UMC doesn't directly control charge current. It provides a control signal (based on the adapter plug type) indicating the maximum the car should draw, but the only power delivery related parts inside it are for Ground Fault protection. If the car decides to pull 72Amps, the UMC can't stop it (unless it also does current sense, then it could trip the GF relay).

I assume the circuit breaker isn't a GFCI type.
Is the first car done charging when you switch to the second? The breaker could be going bad, and/or has a loose connection that causes it to heat up when charging the S. Then, when connected to the X, the inrush trips it. Could test by plugging in to the X, letting it charge for a while, then unplug and replug to the X.

 

[Kalex]

Would this cause the issue? Some corrosion on the prongs. I guess water was getting into the outlet.

 

[mongo]

Would this cause the issue? Some corrosion on the prongs. I guess water was getting into the outlet.

If the connection is intermittent, then the contact resistance goes down (better connection) it could cause a spike in current (depending on charge controller response time) but I would expect worse discoloration if that were the case.

The plug is outside? So is it a GFCI breaker?

 

[Kalex]

Discoloration, no corrosion. I guess yes GCFI.
I can interrupt and restart charging with no problem, it's an issue if I unplug from one car , then plug in to the other, that's when the breaker trips. It's okay though if I disconnect from the camco and then replug to charge, I guess it give chance to reset.
Thanks for everyone's help.

 

[mongo]

Discoloration, no corrosion. I guess yes GCFI.
I can interrupt and restart charging with no problem, it's an issue if I unplug from one car , then plug in to the other, that's when the breaker trips. It's okay though if I disconnect from the camco and then replug to charge, I guess it give chance to reset.
Thanks for everyone's help.

Yah, that's a GFCI, it may be the root of your problem. The UMC self test/ vehicle charger EMI suppression can cause a >5mA current imbalance which will trip a standard GFCI (UMC GFCI is 20mA). If you are going to plug/ unplug a bunch, keep an eye on the health of the plug/socket, they are not build for high numbers of cycles and will eventually loosen which can cause excess heating.

 

[Kalex]

Should I get rid of the camco and plug directly on the 14-50?
I would still be plugging and unplugging daily. I guess during the winter, some water got in even with the cover, which is really water tight. I am going to test later when the MX is home, and see if I could charge them alternately without tripping the breaker.

 

[mongo]

Should I get rid of the camco and plug directly on the 14-50?
I would still be plugging and unplugging daily. I guess during the winter, some water got in even with the cover, which is really water tight. I am going to test later when the MX is home, and see if I could charge them alternately without tripping the breaker.

The plugging/ unplugging at any connection will wear out the socket, so doing it between the cord and UMC will make the outlet last longer. Were you leaving the UMC connected originally?
The slight greening of the plug doesn't look bad, That could just be from being outdoors with humidity.
My suggestion would be to turn off the breaker and open the outlet to check for moisture. If it is dry, pick up a new GFCI breaker, (anecdotally) they can go bad/ get trippyer over time.

 

[Kalex]

Prior to the arrival of the X, the UMC was connected to the Camco semi permanent, and no issues charging the S. (9 months) When the X arrived, that's when the breaker started tripping, when I connect to it after charging the S. We will see later when I charge the X immediately after the S.
The cars should be able to adjust to the set amp (32, 40) automatically, correct?
Who needs the Service center when you guys are more knowledgeable
Thanks

 

[mongo]

Prior to the arrival of the X, the UMC was connected to the Camco semi permanent, and no issues charging the S. (9 months) When the X arrived, that's when the breaker started tripping, when I connect to it after charging the S. We will see later when I charge the X immediately after the S.
The cars should be able to adjust to the set amp (32, 40) automatically, correct?
Who needs the Service center when you guys are more knowledgeable
Thanks

UMC with the 14-50 adapter should cause the car to limit to 40 Amps max, with potentially lower geofenced setting.

 

[Need]

UMC with the 14-50 adapter should cause the car to limit to 40 Amps max, with potentially lower geofenced setting.

Maybe a combination of

1) MX's geofenced setting failure
2) UMC's got confused by the extension cord + switching between MS/MX

 

[mongo]

Maybe a combination of

1) MX's geofenced setting failure
2) UMC's got confused by the extension cord + switching between MS/MX

UMC shouldn't (if SW is right) be able to request more than 40 Amp draw (and car should not be able to go above that). Extension cord and cars swaps should not confuse it either. (again caveat of SW being correct)

OP tried two UMCs, so it doesn't seem like a one off HW issue.
If there is a bad connection, that might be able to do it.
I'm going with the fact that the X has a higher power charger and the circuit is on a GFCI breaker is causing the issue. Hypothetically: after the initial breaker trip, the charger internals are already pre-charged, so the second attempt works.

 

[Kalex]

On one occasion while charging, I accidentally bumped the area where the UMC adapter was attached to the 14-50 camco outlet, the UMC green light turned red. It happened only ones.

 

[Rocky_H]

Yah, that's a GFCI, it may be the root of your problem. The UMC self test/ vehicle charger EMI suppression can cause a >5mA current imbalance which will trip a standard GFCI (UMC GFCI is 20mA).

@Kalex , I'm ready to make my diagnosis, and I think this is it; it's a GFCI thing. The extension shouldn't make any difference for this. I had no idea you had a GFCI on this at first and didn't think of it. The UMC does a ground test either when it's first plugged in, or when it's about to start charging--don't remember which. It's supposed to be very low level, but that is using the type of behavior that a GFCI is supposed to be watching out for. Usually that's below the threshold, but I have heard of this a few times where an old GFCI breaker just gets too sensitive and will trip from a Tesla charging cable doing that ground test.

The thing of it happening when you switch cars may be from it running for a while, which gets the breaker a little bit warm, and then when you start up again, it runs that ground test again, and then from it being warm makes it just a little more sensitive somehow, which pushes it over the edge. I would say you might need to replace that breaker.

 

[Kalex]

Should I ask the electrician to switch the breaker to a non GFCI even with the outlet outside?
The 200 amp panel and breakers was just installed last May before the MS arrived.
Tesla charging installation Program Manager is also on it. He mentioned that the breaker might be the issue.
I will post later what happens when I charge the X this evening.

Thank you again for your assistance.

 

[Rocky_H]

Should I ask the electrician to switch the breaker to a non GFCI even with the outlet outside?

You can ask I guess, but I doubt you will be able to. Remember the green stuff on those pins from moisture? That's why electric code requires GFCI on outlets that are outdoors. It's a protection for electrocution from water around an outlet.