Charge dropping to 30A

[BBB4000]

Our house recently had a 240V installed by the builder and I noticed that the car insists on charging at 30A. I will set the charging to 40A but the next time I charge it is back down to 30A. The voltage reads out at 240-245V by the car.

I saw some threads on this but it does not look like there is anything definitive on why this occurs. Any thoughts on how I should troubleshoot this?

 

[DrivingRockies]

Temporary voltage drops will cause the car to lower it's draw. Then you go and look later, and it looks fine. Might be a few neighbors having their A/C kick on at the same time. Maybe your A/C and dryer starting at the same time? Who knows. I never have the issue in the winter.

 

[yul sam]

The car senses the voltage drop between no charging and full charging currents, and reduces the current if the drop is too high. This is to protect your wiring from overheating.

 

[BBB4000]

Temporary voltage drops will cause the car to lower it's draw. Then you go and look later, and it looks fine. Might be a few neighbors having their A/C kick on at the same time. Maybe your A/C and dryer starting at the same time? Who knows. I never have the issue in the winter.

You think neighbors can cause temporary voltage drops? I have a direct line from the wall to my breaker and it's on a dedicated circuit. I don't get why anyone else would impact the charging?

 

[DrivingRockies]

You think neighbors can cause temporary voltage drops? I have a direct line from the wall to my breaker and it's on a dedicated circuit. I don't get why anyone else would impact the charging?

Definitely can. We deal with similar problems often at work (that's why some electric companies will offer you $50 to allow them to shut off your A/C whenever it pleases them). While you have a dedicated line to your panel, you're still sharing the lines coming into your neighborhood (lines, transformers, sectionalizers, etc.) with LOTS of other people.

 

[david_42]

You probably share a line transformer with 10-15 other homes. High demand will drop the voltage delivered to everyone. My home in Fullerton, CA used to brown-out in the summer, because there was an apartment building on the transformer and it had not been sized for most everyone having window A/C. The transformer was upgraded after I had been in the house for three years.

 

[John5396]

The tesla steps down the voltage when it sees a voltage drop because one cause for this is a fault in the wiring from the breaker panel to the 14-50 outlet. That is why it is stepping down the voltage to protect from a fire from a poor connection caused by the high current.

As others note the voltage fade could be from other items in your home, startup current on the AC or Dryer causing a momentary power drop at your breaker.

 

[demundus]

What gauge is your wire to the 240?

A 30A drop, as others have said, is treated like a watermark. Even one event that causes a drop in voltage or quality of electricity will be met with a permanent change by the car. If you're finding this keeps happening, and its happening overnight (when most people charge and most things are "off") my first bet would be improper wire gauge, followed by a bad breaker, followed by "unclean" bars on the panel. But start with the gauge...

 

[SabrToothSqrl]

I've had the same issue. Problem is outside my home/control.

Try setting your car to 38 amps for a few days. see if it holds. if not, try 37, 36, 35.

Significant annoyances later, mine's held 35 for months and months, and kicks to 30 very rarely.

I do wonder what would happen if I installed a HPWC, and 80 amps... but I've no need to spend the $.

 

[philgrocks]

I had a similar problem... The failure mode turned out to be a defective on-board charger. It was getting too hot. When it gets hot it self-projects and limits charging.

If you can try to charge someplace else this would eliminate your charging setup at home.

Otherwise take it into your service center and have them check.

 

[Lasttoy]

Find a Tesla destination charger, they are same as home 220v. See what happens

 

[JPUConn]

Gauge of wire?
Please say 6 awg copper

AMP breaker?
Please say 50

Distance to panel?
Please say less than 100 ft

 

[xyeahtony]

my voltage will drop as low as 219V but still maintains 48A using my hpwc. I suspect the voltage drop is due to the 74 houses in my subdivision all running their central A/C. When i first got my car in cooler weather, the car was charging at 248V.

And yes i know its not faulty wiring or voltage drop due to wiring, my hpwc is 7 feet away from my service panel.

 

[BBB4000]

There is a lot of good information here so thanks everyone. The builder checked with the electrician who said the wire is 6/4 AWG - although I have not independently verified. Yes, on a 50A breaker, about 8 feet away.

I am confident it is not an issue with the car b/c my previous home had a 240V and I could always charge it at 40A. This only happened at the new house.

Since we still have warranty through the builder the question I now have is, what do I tell the builder to look at? I will need to give them specific ideas to investigate otherwise I am afraid they are going to just pass the blame onto someone/something else. Or is there nothing they can do?

 

[brkaus]

It may be a question for the power company. Perhaps the builder has a contact?

Does it happen every time? Where you could watch the voltage on the screen until it kicks down?

 

[BBB4000]

Does it happen every time? Where you could watch the voltage on the screen until it kicks down?

It does happen every time but I don't know how long it takes before it happens. I can try looking tonight. I usually plug it in and go away until the morning..

 

[mbhforum]

OP, this happens to me also and like you I posted and was concerned. It’s not a big deal and very normal for the reasons mentioned above.

 

[DrivingRockies]

Power company won't care unless you have some amazing amount of money and time. They'll tell you to have an electrician put a recording meter on it. And then will probably still say it's within their limits.

Unfortunately power companies have VERY little overisght.

 

[BBB4000]

OP, this happens to me also and like you I posted and was concerned. It’s not a big deal and very normal for the reasons mentioned above.

Yeah I get that it's not a big deal but coming from a house where I consistently charged at 40A I don't like that I can't get 40A on demand with an even newer house. In general it makes no difference b/c I charge overnight but sometimes I want juice faster and in those cases it does matter.

 

[demundus]

There is a lot of good information here so thanks everyone. The builder checked with the electrician who said the wire is 6/4 AWG - although I have not independently verified. Yes, on a 50A breaker, about 8 feet away.

I am confident it is not an issue with the car b/c my previous home had a 240V and I could always charge it at 40A. This only happened at the new house.

Since we still have warranty through the builder the question I now have is, what do I tell the builder to look at? I will need to give them specific ideas to investigate otherwise I am afraid they are going to just pass the blame onto someone/something else. Or is there nothing they can do?

Take voltmeter measurements at several points along the 8 ft run. I have a 70 foot run and still pull about 32A at the end of it (idiot electrician used 8AWG... thats another story)