100D wants to charge at 72 Amps which trips Tesla home charger

[smartypnz]

My wife's MS 100D (her 2nd MS) which has 51k miles in 15 months has been tripping the Tesla home charger.
Our power has always been iffy and normal charge would be set to 40 Amps, but with her previous Model S (185k miles in 5 years) we lowered it to 30 Amps because our power would drop below 200 volts and the charger would go 'red'. That worked well for the 5 years. Plus she never needed to charge any quicker.

New MS 100D - We continued that method - setting it to charge but only at 30 Amps. But, we have been getting Faults from the charger which cease (middle of night of course) and she winds up with insufficient miles to get to work - I wind up running to nearby Supercharger to get her to work.

What we have noticed is that the car sets itself to 72 Amps shortly after she plugs in and sets it to 30 Amps ??? Setting it back to 30 Amps would make it stay - but maybe it is resetting to 72 later in the night? I believe this is causing the problem - making the home charger max out at 40 Amps and it fails when night voltage drops.

Ok - I have a M3, and although I normally charge at home with a 110v outlet (dedicated circuit in Garage - nothing else connected) as I normally drive less than 50 miles/day). When she is out of town (weekly) I will connect my Tesla to the Home Charger and charge at 30 Amps - never had a problem. Even when I occasionally need to charge 200+ miles.

OK - baffled.... do I suspect her newer MS or the wall charger?

 

[brkaus]

What device are you using to connect the car to the power?

A wall connector?

A Gen1 UMC?

A Gen2 UMC?

Other -

 

[smartypnz]

What device are you using to connect the car to the power?

A wall connector?

A Gen1 UMC?

A Gen2 UMC?

Other -

Gen 1 - also have a "Signature" unit and had toyed with the idea of a "Master/Slave" connection, but really don't need for my M3 charging. Not worth money to pay electrician to connect. Still in box.

 

[brkaus]

Interesting. That's really strange. I don't see how the Gen1 would ever be able to show 72a as it's max is 40a. I also don't know how a new car could select 72a. There is also no good way to force a Gen1 to be 30a.

I would be concerned about the voltage dropping that much. Did you have anyone look at why it was doing it? I would be concerned about that much drop on a outlet rated for 50a.

Options that I would see -
- Replace 14-50 with a 14-30 outlet. Get the adaptor for the Gen1. It would limit to 24A
- Use the Gen2 UMC that came with the M3. It will limit the charge rate to 30a (or 32a, I don't remember 100%)
- If that works, you could buy another Gen2
- Add a 14-50 plug on the WC and set the breaker size in the unit to 40a. That will limit the current.


Sorry, not offering much insight as to why the car is displaying what it is displaying.

And, again, if the circuit hasn't been looked at I would have it checked. While it is running at 40a I would check the voltage at various points back to the panel. Also look at the wiring gauge.

 

[TMeister]

Let's start over... You call it a home charger but answered that you have a Gen1 UMC. Just to be clear do you have a wall charger that is wired into your house directly, hangs on the wall or are you using a UMC that plugs into an outlet? Toying with hooking up a signature unit implies you have a wall charger.

The wall charger, of course, is configurable. Was that done correctly? What is your wire size and run length?

The UMC will work up to 40 amps on a 14-50 plug and it will present itself to the car as that limit.

 

[ewoodrick]

If the voltage is dropping that much I would suggest having an electrician check the circuit out instead of possibly burning your house down.
Yes, it can be this serious.

 

[Twiglett]

sounds much more like a power issue that has been worked around by playing with car settings.
Much safer to fix the power issues before something burns out

 

[smartypnz]

OK... our wall charger is a UMC Gen 1 connected to a dedicated panel which only has a 50 amp breaker in the Garage. Nothing else is using AC from that panel. Feeding the panel is a 6 gauge cable (approx 75 ft run) from our main Panel connected to a 50 Amp circuit. That is connected to a 50 Amp breaker in the main house panel.

Power in our area is notoriously horrendous. At night I see voltage drop to 225, with no connection. As I said, when we first started using - back in 2013 with the 1st MS we noticed when charging set to 40 Amps, the voltage reading in the car was in the 190's (during the day, about 238v). So to compensate, we would lower the setting in the MS to 30A - voltage went back up. This worked fine and I remember no cutoff during those years. When the M3 arrived, I would occasionally charge at night (setting it to 30A - no problems ever with the M3).

Traded in wife's MS for a new one Sept 2018 and she continued the process of charging at 30 A. We had the UMC go 'red' and shutoff a few months ago and reset by using Breaker in Garage panel. Thought maybe try lowering the Amps to 28. Still, occasional shutdowns.

Then my wife noticed car display showed it was set to 72 Amps. She set it back to the lower amount. It worked fine. But even ocasionally, as she parks, sets charge rate to 28 or 30 Amps - the UMC will go red before she gets out of the garage. Then she noticed that the MS shows it is set to 72 Amps. Not sure why it switches back.

Next move I guess would be to replace the UMC Gen 1 with our unopened UMC Signature (which I assume is a Gen 2). Gotta get an electrician to do that.

 

[MorrisonHiker]

OK... our wall charger is a UMC Gen 1 connected to a dedicated panel which only has a 50 amp breaker in the Garage. Nothing else is using AC from that panel. Feeding the panel is a 6 gauge cable (approx 75 ft run) from our main Panel connected to a 50 Amp circuit. That is connected to a 50 Amp breaker in the main house panel.

Power in our area is notoriously horrendous. At night I see voltage drop to 225, with no connection. As I said, when we first started using - back in 2013 with the 1st MS we noticed when charging set to 40 Amps, the voltage reading in the car was in the 190's (during the day, about 238v). So to compensate, we would lower the setting in the MS to 30A - voltage went back up. This worked fine and I remember no cutoff during those years. When the M3 arrived, I would occasionally charge at night (setting it to 30A - no problems ever with the M3).

Traded in wife's MS for a new one Sept 2018 and she continued the process of charging at 30 A. We had the UMC go 'red' and shutoff a few months ago and reset by using Breaker in Garage panel. Thought maybe try lowering the Amps to 28. Still, occasional shutdowns.

Then my wife noticed car display showed it was set to 72 Amps. She set it back to the lower amount. It worked fine. But even ocasionally, as she parks, sets charge rate to 28 or 30 Amps - the UMC will go red before she gets out of the garage. Then she noticed that the MS shows it is set to 72 Amps. Not sure why it switches back.

Next move I guess would be to replace the UMC Gen 1 with our unopened UMC Signature (which I assume is a Gen 2). Gotta get an electrician to do that.

If it shows 72 amps before you plug in, that's merely showing what the car is capable of charging at since you have the upgraded charger built into the car. Once you plug in, doesn't it return to the 30 amps or whatever you previously charged at?

You should probably contact your utility company and have them perform a test on your line. If the voltage to your house is fine then you need to check your wiring. If they aren't providing consistent voltage to the house then they should probably upgrade your transformer. They probably are required to keep it within 10% of 240 Volts.

 

[TMeister]

OK. Understand you have a wall connector. The term "UMC" is reserved for the mobile connector. So terms are confused.

If the wall connector goes red (solid, not flashing) then it is claiming a hardware fault. Your plan to swap out the original with your new one is a good call.

But just to be more helpful than that...

Your Model S I believe falls into the time when 72A charging was available so that's why the car will always show 72A charging when not plugged in. That is unless you have set it to something lower in that location in which case it will show that new number. When the wall connector goes red, the car should again show 72A.

Since your wall connector is properly installed (6 gauge and a 50amp circuit) it should only max output 40 amps. The rotary switch should be set to "8" for this case.

Next would be to see what happens when a load is applied to see if you have any high resistance connections. You can use the car to help. As you start a charging session, observe the voltage reading as the car ramps up the current draw. It will drop and voltage drop up to 5 or so volts at 40 amps is probably OK. Higher than that you probably have some loose connections along the way.

Since it appears that the wall connector faults while you are not able to observe, it could be likely that one of the line connections has gotten loose. Since you've had this unit for a long time that's the first place I'd look. A thermal fault is supposed to show with flashing red lights so maybe that's what's happening?

If you are comfortable with a multimeter, you could check voltages back along the line. You'd have to open your main panel to do this and you might find where the loss is happening.

A 40 amp load should not affect your voltage read at the main breaker. If it does that you have an undersized feed line or your distribution transformer is undersized or failing. That's the time to call your utility.

If you have an IR temperature meter you can also look for hot spots. I have found that a FLIR adaptor for the phone works very well for this sort of thing. I have found loose connections this way. The voltage tests are easier since you don't have to wait for things to heat up.

 

[smartypnz]

Thanks, will meter all locations, and since I will need to get an electrician to swap the Tesla Wall Chargers, I will have that person tighten all connections along the route.

Will do IR test but only if all else fails. The 6 awg may have experienced some damage - will check.

Side note: as I mentioned, the M3 never had a symptom of this problem and I have charged it at the full 40 amps - but as I noted - voltage drop was significant.

Thnx for the suggestions.

 

[LCR1]

Why not just set the wall charger to 30A instead of changing the settings in the car?

 

[animorph]

LCR1 has the best solution, other than checking the connections carefully. Turn the dial inside the HPWC to the 30A output setting. That will enforce your best current limit. But do check the connections, even if this solution works.

It could be a car problem. The charge current is remembered by the car using GPS. If the GPS or computer was flaky it might be forgetting your charge setting (or location) and reverting back to the full 72A and using the full 40A the HPWC is willing to supply.

 

[LCR1]

LCR1 has the best solution, other than checking the connections carefully. Turn the dial inside the HPWC to the 30A output setting. That will enforce your best current limit. But do check the connections, even if this solution works.

It could be a car problem. The charge current is remembered by the car using GPS. If the GPS or computer was flaky it might be forgetting your charge setting (or location) and reverting back to the full 72A and using the full 40A the HPWC is willing to supply.

Happens at the girls house all the time. I rigged a 14-50 split off the dryer so I'm plugging the gen2, 32a plug into the 30a wired outlet. I reduce the amps in the car around 20-24 and it usually remembers that setting but every now and then when I get to her house it'll be back to 32a (gen 2 umc max) it's a crap shoot whether the car will say 24 or 32.

 

[Electric700]

Thanks, will meter all locations, and since I will need to get an electrician to swap the Tesla Wall Chargers, I will have that person tighten all connections along the route.

Will do IR test but only if all else fails. The 6 awg may have experienced some damage - will check.

Side note: as I mentioned, the M3 never had a symptom of this problem and I have charged it at the full 40 amps - but as I noted - voltage drop was significant.

Thnx for the suggestions.

If you use the center screen to set a maximum amperage of 30 A, your car shouldn't go over that for the same location / connected charging cable. I would contact Tesla too through the app and explain the issue.

 

[smartypnz]

If you use the center screen to set a maximum amperage of 30 A, your car shouldn't go over that for the same location / connected charging cable. I would contact Tesla too through the app and explain the issue.

Yeah, will check all possible supply source problems and then attack her MS, since my M3 has never seen the problem on her charger.

 

[Decibelle]

What number is your rotary dial in the WC set to?

 

[boaterva]

Yeah, not sure why the car isn’t remembering the setting. We have dual HPWCs, I have my X with 72 amp charger set to max at 32 amps at home and it has never forgotten it, through power outages, reboots, upgrades, etc.

 

[smartypnz]

What number is your rotary dial in the WC set to?

Will have to wait till I get ahold of a Torx 20 screwdriver. I do remember 7 years ago I had the electrician set it for 40 amps.
My version uses dip switches not a rotary dial. In our users manual there is pencilling indicating which dip switch setting he used. Choices were 12, 16, 24, 32, 40, 64, and 80. Our circuit being 50 Amp, we set it to 80% or 40 Amps.

 

[smartypnz]

Yeah, not sure why the car isn’t remembering the setting. We have dual HPWCs, I have my X with 72 amp charger set to max at 32 amps at home and it has never forgotten it, through power outages, reboots, upgrades, etc.

This is why I am leaning toward a car problem. Since I haven't had an issue with my wife's previous MS or my M3 on the same charger.