Charging question -- MS ignoring 24amp charging limit

[HankLloydRight]

I've been charging my MS in my garage with the UMC for at least a year now on a 30-amp 14-30 socket at 24 amps without incident.

Today I plug in and the car started charging fine and I went inside. About 10 minutes later, I get a mobile alert that charging has been interrupted.

There's a sub-panel breaker box in my garage with a 30-amp breaker for 14-30 socket, and that runs to my main breaker box with another 30-amp breaker for the garage sub-panel. The main breaker was tripped. I reset it, and then went to the car and the charging limit was set at 24 amps as I had last set it. I don't know why the breaker tripped. So I dialed the car down to 20 amps for a little extra headroom and started up charging again. The car starts to charge at 20 amps.

Now I go back to check my power monitor, and see that the car was charging at 40 amps@238 volts (10kW) for 10 minutes! (see graph):

So my questions are:
1. Why did the car start to charge at the full 40 amps, when it was clearly set to limit to 24 amps at this location?
2. Why didn't either circuit breaker trip during the first 10 minutes of pulling 40 amps?
3. Do I need to worry about either/both of these circuit breakers not tripping for 10 minutes at 40 amps?
4. Has anyone else seen their car ignore the charging amperage setting and charge at the full 40 amps?

thanks.

 

[Max*]

Are you using a 14-50 with a converter, or Tesla's 14-30 adapter?

 

[HankLloydRight]

Are you using a 14-50 with a converter, or Tesla's 14-30 adapter?

My own dogbone adapter.

 

[FlasherZ]

No idea why it went to charge at 40A; I've had cases where - when I arrived home - the car's location had me at a different spot (my street address has been off by 16 numbers, e.g. 136 Any Street instead of my real address, 120 Any Street). It's very possible that when you plugged in, or started to charge, that the car thought it was in a different location -- then it got a GPS lock and shifted.

By UL standard, circuit breakers must trip within 2 hours at 135% of rating; a 30A breaker won't trip at 30.0001A. That's why it's dangerous to rely upon the breaker to protect the case where the car resets to the higher current, because they can allow an overload to occur for a while before tripping.

No need to worry about the breakers not tripping unless it occurred far longer.

I've never seen the car ignore the maximum; I've only ever seen it reset to the default based on software updates or location issues.

 

[HankLloydRight]

Thanks.

 

[miimura]

Stories like this are exactly why Tesla should continue/resume making adapters for all common outlets. If the OP had been using a proper Tesla 14-30 adapter or 10-30 adapter with a home-made "dogbone", this could not have happened. The user did their best to set the car to the proper charging current but the car still went into an unsafe condition.

 

[HankLloydRight]

I totally agree!

 

[GSP]

Stories like this are exactly why Tesla should continue/resume making adapters for all common outlets. If the OP had been using a proper Tesla 14-30 adapter or 10-30 adapter with a home-made "dogbone", this could not have happened. The user did their best to set the car to the proper charging current but the car still went into an unsafe condition.

I agree. Tesla should make at least one 30 A adapter for the UMC. I don't understand why they stopped selling them. Even if they were slow sellers, the people that charge from a 30 A circuit really need them.

GSP

PS. If I had a 30 A circuit and could not find one of Tesla's 30 A UMC adapters, I would purchase a Clipper Creek LCS-30, or other 30 A EVSE, and use Tesla's J1772 adapter.

 

[FlasherZ]

I can understand a strategy that would suggest someone buy a wall connector for a 30A circuit (now that they can be configured as such). However, from the surveys that I've seen done here, the use of a 14-30 at a rental or vacation home is a big chunk of 30A circuit usage. I'm not going to carry around a 30A-configured HPWC.

Another option that Tesla could pursue at some point is a multi-point switch to "dial-down" on the UMC itself that would override (only to the lower side) the charge current, sending a pilot signal indicating a lower current.

 

[Rocky_H]

I can understand a strategy that would suggest someone buy a wall connector for a 30A circuit (now that they can be configured as such). However, from the surveys that I've seen done here, the use of a 14-30 at a rental or vacation home is a big chunk of 30A circuit usage. I'm not going to carry around a 30A-configured HPWC.

Another option that Tesla could pursue at some point is a multi-point switch to "dial-down" on the UMC itself that would override (only to the lower side) the charge current, sending a pilot signal indicating a lower current.

Whoa, that current reducing switch is a great idea!

 

[miimura]

I think there is a general reluctance to have anything user-adjustable. Having the plug adapter that physically fits hard coded to the correct allowable current is truly idiot proof and a brilliant design. However, it only works if all the adapters are available.

 

[FlasherZ]

I think there is a general reluctance to have anything user-adjustable. Having the plug adapter that physically fits hard coded to the correct allowable current is truly idiot proof and a brilliant design. However, it only works if all the adapters are available.

I sent this thread already to some of my contacts at Tesla as an example why the adapters are needed!

 

[HankLloydRight]

No idea why it went to charge at 40A; I've had cases where - when I arrived home - the car's location had me at a different spot (my street address has been off by 16 numbers, e.g. 136 Any Street instead of my real address, 120 Any Street). It's very possible that when you plugged in, or started to charge, that the car thought it was in a different location -- then it got a GPS lock and shifted.

I was thinking about this, but the car had properly popped up the Homelink button at exactly the same spot it always does (15 feet from my driveway). So the car knew where it was. Now the Homelink and Charging modules are different, but I think the GPS info was correct.

 

[Kalud]

I was thinking about this, but the car had properly popped up the Homelink button at exactly the same spot it always does (15 feet from my driveway). So the car knew where it was. Now the Homelink and Charging modules are different, but I think the GPS info was correct.

That makes me think, there is an outstanding bug affecting an unknown number of cars (that should be another thread) where the car GPS (or its interpretation) is wrong when going in reverse. The car position continue forward while you actually go in reverse. Its easy to test, just zoom-in the map to the maximum setting and go in reverse in a parking lot (or in the street). If you always, for example, back in your garage and had reset the Homelink position to the correct location it works just fine. But I can imagine that this wrong location thing could be at work in your issue. Like Homelink position being ok but charging location being wrong.

If you back in you garage (or driveway) you could also just have a quick glance at you phone app, check the current car's location. My car is currently falsely parked in my front neighbor's pool while being actually inside my garage. If have at least one Tesla friend that has the exact same issue and went to the service center for this, they couldn't fix it, even replaced the gyro board. They've escalated it to engineering. It happened sometimes in 7.0 or 7.1 and as of build 2.14.66 it still there.

For example, if you back in your driveway 50 foot from the street, you final reported location would be 50 foot in front of your actual location. Homelink could be ok with that (if reset at that position) but charging location could be seen as out of the original spot.

 

[HankLloydRight]

I don't back into the driveway or garage. It's all forward. And it's worked 100% since last year, until this time.

 

[FlasherZ]

If you back in you garage (or driveway) you could also just have a quick glance at you phone app, check the current car's location. My car is currently falsely parked in my front neighbor's pool while being actually inside my garage. If have at least one Tesla friend that has the exact same issue and went to the service center for this, they couldn't fix it, even replaced the gyro board. They've escalated it to engineering. It happened sometimes in 7.0 or 7.1 and as of build 2.14.66 it still there.

Watched as my wife did this the other day in Model S. Wife backed out of friend's driveway but app showed her driving through the house.

 

[Andyw2100]

I was thinking about this, but the car had properly popped up the Homelink button at exactly the same spot it always does (15 feet from my driveway). So the car knew where it was. Now the Homelink and Charging modules are different, but I think the GPS info was correct.

The car knew where it was when it opened the garage door. That doesn't mean it still knew where it was a minute or two later when you started charging. If there was some momentary loss of GPS signal at the time when the car had to make the decision on "this is or is not a previous charging location" that would explain the 40 amp charging, right?

Another possibility is that GPS was working just fine, but somehow your home charging location was simply erased from the history. Stranger things have happened!

 

[HankLloydRight]

I'll go out later and see if it stored a secondary "close" charging location that reset (temporarily) the charging limit, but I don't think that's it. It was a clear day, so I don't know if/how the GPS could have been temporarily disrupted as such.

My home location wasn't erased, since when I went back out to the car to reset the charging, the screen did have the proper 24 amp limit set.

The only way to really know would be to have Tesla pull the logs to see what transpired second-by-second, which I suspect they might already be doing since FlasherZ notified them of this anomaly.

 

[HankLloydRight]

I checked the Nav map, and no secondary charging location was found/created that would have reset the charging to 40 amps.

 

[Andyw2100]

I checked the Nav map, and no secondary charging location was found/created that would have reset the charging to 40 amps.

Sorry I can't help you solve your mystery as easily as you helped me solve mine.