Anyone Still Experiencing Charge Current Limiting (40A->30A)?

[DavidM]

While my 2 year old Model S was in for the routine annual service, I received a loaner Model S. It's a brand new car with about 700 miles on it. I have charged it three times at 40A (on my home circuit) using my UMC. NO CURRENT REDUCTION! So there is nothing wrong with my UMC or my home wiring. There is something going on with MY car (specifically). Maybe it's the master charger, maybe it's the receptacle on the side of the car. Maybe the software updates are not fully compatible with the older cars 2,xxx. Stay tuned. I'll get to the bottom of this if it takes all 4 years of the warranty period.

 

[randompersonx]

While my 2 year old Model S was in for the routine annual service, I received a loaner Model S. It's a brand new car with about 700 miles on it. I have charged it three times at 40A (on my home circuit) using my UMC. NO CURRENT REDUCTION! So there is nothing wrong with my UMC or my home wiring. There is something going on with MY car (specifically). Maybe it's the master charger, maybe it's the receptacle on the side of the car. Maybe the software updates are not fully compatible with the older cars 2,xxx. Stay tuned. I'll get to the bottom of this if it takes all 4 years of the warranty period.

On this loaner car, what does it report as voltage when at 1 amp and at 40 amps?

On a road trip my p85d backed off to 30 amp at a hotel but the voltage drop went from 208 to 193. I think it is reasonable for the car to consider a drop of more than 5% to be potentially risky.

 

[scaesare]

While my 2 year old Model S was in for the routine annual service, I received a loaner Model S. It's a brand new car with about 700 miles on it. I have charged it three times at 40A (on my home circuit) using my UMC. NO CURRENT REDUCTION! So there is nothing wrong with my UMC or my home wiring. There is something going on with MY car (specifically). Maybe it's the master charger, maybe it's the receptacle on the side of the car. Maybe the software updates are not fully compatible with the older cars 2,xxx. Stay tuned. I'll get to the bottom of this if it takes all 4 years of the warranty period.

Have you deleted the saved charging location in the nav favorites to see if it resets back up to 40? That works for me for me for a few weeks until it limits again...

 

[FlasherZ]

I can reliably make my car back off to 30A under 6.1, when I plug it into a 14-50 in a machine shed at our hunting lodge (237V); a combination of the long run to the transformer plus some appliances (this shed uses many 8-bulb T5 high-bay fluorescent fixtures) creates enough of a disturbance that the car backs off occasionally. Simply unplugging and replugging makes it go back to 40A.

 

[apacheguy]

Simply unplugging and replugging makes it go back to 40A.

That sounds new. It defaults back to 40? I've always had to manually reset the amperage on the touchscreen.

 

[FlasherZ]

That sounds new. It defaults back to 40? I've always had to manually reset the amperage on the touchscreen.

I've never had to, EXCEPT the case where you attempted to manually increase the amperage.

Scenario 1: You plug in, the current limiter kicks in, you see it's at 30A and try to manually increase it -- maybe even going down to 29A then back up to 30A... in this case, I've observed that plugging back in gives you the 30A current it was limited to.

Scenario 2: You plug in, the current limiter kicks in, you see it's at 30A. You don't touch the screen. In this case unplugging and re-plugging makes it go to 40A.

 

[jacobp]

Since the 5.8.4 software update, many Model S owners began to experience charging sessions where charging was randomly reduced from 40A to 30A. When it happens, there is usually a message on the dashboard that says "charging problems". The impact of this change is slower, and unpredictable refueling sessions. Personally, I have owned my Model S for 2 years. For a full year before the software change, I could charge at home (at 40A) unimpeded. Since the change, the software limits my charging to 30A (in most cases).

The power utility has checked the install and the transformer. Tesla has checked the install. Electricians have checked the install. Everything is within standard residential tolerances (but perhaps not within the new Tesla tolerances). Lots of head scratching. Tesla won't disclose the old (or new) tolerance levels to the power utility, which makes it difficult to troubleshoot the problem. I am using the Universal Mobile Connector (with the revised adapter).

Is anyone else still having this issue with the car randomly backing off to 30A while charging at home? If so, are you using the UMC cable, or the beefier Wall Connector?

I am in the same situation as the OP. I have also had the utility company, electrician, etc. come out to check the line, but I always get bumped to 30. This is the case even though i recently had my NEMA 14-50 isolated by the power company to a separate meter -- so they checked the line thoroughly.

 

[EarlyAdopter]

I think I may have had the same problem on my old P85.

It would consistently drop back from 40A to 30A after an hour of charging at home. I triple checked every connection and ruled out house loads. I was ready to start involving the power company to check the transformer supplying my house.

Then I get a new P85D and lo and behold, it will charge for hours at 40A on end, never once dropping the amperage.

I had the local SC check the old car for faults on the onboard charger, and they charged it fine at 40A for hours there at the SC. Likewise, I was able to charge for hours at 40A on a NEMA 14-50 at work. Here's the rub though - in both cases it was on 208V commercial power, not 240V residential. That means the car was only drawing 8kW, not the full 10kW, and thus wasn't maxing out the onboard charger.

 

[tfinan]

I had this problem starting in June 2014. The firmware update and problem aligned with the beginning of full time air conditioning season here in NJ. Here is some information about the troubleshooting path was used for my situation:

I was a March 2014 Model S delivery and still had the original 14-50 adapter to the UMC, I never received a replacement in the mail. The revised adapter was provided and later the UMC was replaced.

The drop down problem could be recreated by turning on the older of the two central a/c units in my house.

Tesla charged my car successfully over night at the service center without any issue. Tesla brought a loaner to my house and we were able to recreate the voltage drop down on that vehicle(turned on a/c unit).

After that, I contacted the utility and also had a Tesla recommended electrician come to the house. He found a grounding issue and installed a new ground from the main panel to the cold water pipe. There was also a loose connection at one of the air conditioning circuit breakers. I also had a soft start capacity added to the older a/c unit and replaced its contactors which were burnt. This work did not resolve the issue.

After three or so calls to the utilities, they had an engineering person call me. He listened to the Tesla log provided information about transient spikes and the work I had already done at the house to clean things up. An in-person assessment of the neighborhood was made by this engineering and they decided to replace two poles, wiring and the transformer on my street. I am awaiting for a new thicker gauge service wire from the transformer( there is a patch in my current line). This thicker wire which requires replacing the circa 1936 lift pole on my property and adding a guy-wire(one had existed but had been removed). i needed to sign an easement form since the previous easement (if any) could not be located.

The voltage step problem has not occurred since the transformer upgrade but the weather has also been cold so no a/c use. I will only know for sure once I pass through an entire summer charging season. I am pleased with both Tesla's and the utility company's effort to help resolve the problem.

====
the first lineman who visited the house with a few hours of my call replaced the split nuts connecting the house to the street feed. He said if that didn't work to keep calling it in since it was old infrastructure supporting lots of upgraded houses and needed replacing.

 

[jerry33]

In my area the utility company has had this issue as long as I've lived here (over 15 years). As the utility company is in Chapter 11, I don't see this changing anytime soon. I've found that charging at 33 amps almost never drops and isn't noticeably slower. Of course, it still drops if I turn on the air compressor while charging, but that's no one's fault other than my own.

 

[DavidM]

Thanks to everyone for their feedback and personal experiences with this issue. My issues with reduced amperage continue. The ball is in Tesla's court to resolve the issue since this never occurred my entire first year of ownership. I am of the opinion that the software tolerances which were applied in the 5.8.4 download are too aggressive. The cause of the problem for many owners might simply be that the UMC (or wall connector) and the Trident (charge port on the car) don't make a tight enough connection to inhibit tripping the tolerances.

Software companies go through this all the time. Provide a software update to fix a problem, but the update causes one or more other problems. I would think that by now, Tesla has a database of cases where they determined what course of action finally resolved the issue for each customer. In some cases, Tesla may have replaced one or more parts and resolved the problem. In other cases, the owner or the power company may have made some change(s) to resolve the problem. With this information and knowledge of the new tolerances, Tesla should specifically know what to look for. Everybody else is taking stabs in the dark, wasting time and money, and living in a 30A existence, when they paid for 40A.

 

[islandbayy]

I've got a perfect install of a 80 amp HPWC at Parents Motel. It's on a 75kW transformer. Fed by 2/0 wire to the breaker box, from breaker box 2awg to the HPWC. Thought, during the summer when the Motel was open, the current limiting from 80 to 60 was due to voltage drop or something from the Transformer. Since the Motel had 4x200 amp drops from this transformer, then, 2 more houses with 200 amp drops from it. Well, now it's winter, Model is Closed for winter. Power usage for the Motel is next to nothing. Just two houses that have intermittent electric baseboard heat.
The HPWC is STILL being limited to 60 Amps. Though, during the summer, it would take only seconds to get limited from 80 to 60. Now, it takes about 30 seconds to a Minute Disappointing.

Also, at my home, I installed a HPWC for the rare times I need 80 amp.
Not sure what my home transformer is, it's shared by a number of houses though. HPWC is literally opposite side of the wall as the breaker box. Connected to breaker box by exactly 14 inches of 2awg. Breaker box is connected to the meter 5 ft away with 2/0.
Charging voltage starts at 242, at 40 amps drops to 220, and stays at 220 all the way to 80 amps. It will maintain voltage at 220 at 80 amps indefinitely. After about 5 minutes it will drop it down to 60 amps, despite no voltage fluctuations or changes what so ever. And it's not a matter of overloading the utility. I could maintain charging at 60 amps last summer, even with the car charging at 60 + Electric dryer running + Air Conditioner + The other 5 houses on my transformer having there AC's cranked too. Voltages are slightly higher during winter here (no AC usage), limiting still occurs.

This feature needs to be made OPTIONAL!!! Or give a option after a warning screen and waiver of liability check box to disable the limiter function due to "nuisance tripping".

 

[scaesare]

I've got a perfect install of a 80 amp HPWC at Parents Motel. It's on a 75kW transformer. Fed by 2/0 wire to the breaker box, from breaker box 2awg to the HPWC. Thought, during the summer when the Motel was open, the current limiting from 80 to 60 was due to voltage drop or something from the Transformer. Since the Motel had 4x200 amp drops from this transformer, then, 2 more houses with 200 amp drops from it. Well, now it's winter, Model is Closed for winter. Power usage for the Motel is next to nothing. Just two houses that have intermittent electric baseboard heat.
The HPWC is STILL being limited to 60 Amps. Though, during the summer, it would take only seconds to get limited from 80 to 60. Now, it takes about 30 seconds to a Minute Disappointing.

Also, at my home, I installed a HPWC for the rare times I need 80 amp.
Not sure what my home transformer is, it's shared by a number of houses though. HPWC is literally opposite side of the wall as the breaker box. Connected to breaker box by exactly 14 inches of 2awg. Breaker box is connected to the meter 5 ft away with 2/0.
Charging voltage starts at 242, at 40 amps drops to 220, and stays at 220 all the way to 80 amps. It will maintain voltage at 220 at 80 amps indefinitely. After about 5 minutes it will drop it down to 60 amps, despite no voltage fluctuations or changes what so ever. And it's not a matter of overloading the utility. I could maintain charging at 60 amps last summer, even with the car charging at 60 + Electric dryer running + Air Conditioner + The other 5 houses on my transformer having there AC's cranked too. Voltages are slightly higher during winter here (no AC usage), limiting still occurs.

This feature needs to be made OPTIONAL!!! Or give a option after a warning screen and waiver of liability check box to disable the limiter function due to "nuisance tripping".

That's a 9% loss... that might be a bit much....

 

[David99]

Wow, just found this discussion. Looks like I'm not alone. I never had issues until I had my car at the service center for other issues and they swapped out my old UMC with a newer version. After that I started to see it happen here and there. My house it right next to the transformer and even with heavy load from AC and pool pump, the voltage never drops below 233 or so. But what really shows that is nothing to do with too much load is the fact that I only charge at night (off peak) where the voltage is on average 244 under 40 Amp load. But that's exactly where I see the car adjusting down to 30 Amp. Reading through all the messages here it doesn't seem to be related to grid load or voltage. It's plain and simple a bug on Tesla's side being too cautious about the charge current.

 

[randompersonx]

I'm not sure what the tolerance is for HPWC setups, but in my P85D, The maximum voltage drop that Tesla seems to tolerate before dropping amperage is 5% on circuits that advertise 32A or 40A charge speed.
I would expect it to back off at 242 -> 220 (9% drop).

That said, it sounds like perhaps the voltage drop is due to an issue at the transformer rather than the wiring. Can you try starting a high power 240V load before starting the charging on the car and see if the starting voltage is lower, and therefore the drop isn't as severe? (eg: start up an electric clothes drier for a few minutes?)

 

[linkster]

This feature needs to be made OPTIONAL!!! Or give a option after a warning screen and waiver of liability check box to disable the limiter function due to "nuisance tripping".

+1
....and it wouldn't be the first time I have signed a Tesla waiver

- - - Updated - - -

That's a 9% loss... that might be a bit much....

But isn't that just life with imperfect grids, transformers and sometimes safe necessary long runs? I wouldn't think a 9% or more loss is necessarily an unsafe charging condition that should warrant a mandatory amperage reduction without an override option/waiver/warning.

- - - Updated - - -

Tesla's side being too cautious about the charge current.

Especially since some owners have reported amp reduction issues with commercially installed J1772s.

 

[randompersonx]

Especially since some owners have reported amp reduction issues with commercially installed J1772s.

Just because it is commercially installed does not mean that it is safe or to code.

At the parking garage closest to my office, there is a J1172 that advertises 32A. at 1A the car detects 208V, but as soon as it ramps up to 24A, the voltage is already down to 197V and the car limits amperage to 24A.
It's quite clear that the conduit is >600 Feet long, and the conduit is so small that there's no way the wiring inside is larger than 8 Gauge (And I would suspect it is actually #10). Further, there are two J1772 chargers there, so it's also clear that the conduit is stuffed with the conductors from the two.

When I am charging there, the feeder conduit is notably warm to the touch, but with a Nissan Leaf charging, the conductor gets even warmer -- likely that car is not stepping down. Most likely the conductors are overheating, and over time the jackets will fail, and eventually lead to a short.

That said, like you said -- it's a commercial installation, and the risk is going to be the owners of the garage's problem. But Tesla would prefer to not be in the news story if it starts a fire.

 

[islandbayy]

I'm not sure what the tolerance is for HPWC setups, but in my P85D, The maximum voltage drop that Tesla seems to tolerate before dropping amperage is 5% on circuits that advertise 32A or 40A charge speed.
I would expect it to back off at 242 -> 220 (9% drop).

That said, it sounds like perhaps the voltage drop is due to an issue at the transformer rather than the wiring. Can you try starting a high power 240V load before starting the charging on the car and see if the starting voltage is lower, and therefore the drop isn't as severe? (eg: start up an electric clothes drier for a few minutes?)

Ive actually done this. Dryer, AC and 3 space heaters last summer. The starting voltage was then about 226-228. Then, car going up to full power, limited it. I then did again, and as soon as the car got to full power I shut down the other loads, voltage was stabil, still limited it. The fluctuation then was only about 1-2% if even that much.

 

[youlikeadajuice]

I'm not sure what the tolerance is for HPWC setups, but in my P85D, The maximum voltage drop that Tesla seems to tolerate before dropping amperage is 5% on circuits that advertise 32A or 40A charge speed.
I would expect it to back off at 242 -> 220 (9% drop).

That said, it sounds like perhaps the voltage drop is due to an issue at the transformer rather than the wiring. Can you try starting a high power 240V load before starting the charging on the car and see if the starting voltage is lower, and therefore the drop isn't as severe? (eg: start up an electric clothes drier for a few minutes?)

5% does seem to be about the limit with the Tesla. My car flirts with this limit while charging...about 1/3 of the time I end up limited to 30 amps. I have a very short run from the panel to the 14-50 outlet (literally about 6") as well from the panel to the electrical line (about 20') and everything including the panel and meter was new when I got the car. No problems charging for about the first year until the software started limiting things.

I also think it has something to do with the transformer. I've called the power company about it, and they offered to adjust something at the substation that would increase the voltage (my starting voltage changed from about 236 to 241), but the problem doesn't seem to be with the starting voltage but the drop. I've been told by a licensed electrician that anything less than about an 8% drop is considered acceptable. I'm not quite seeing an 8% drop, so I'm not sure there's much I can really do. Fortunately, I don't often need to charge up quickly.

 

[scaesare]

Well... I have the .116 flavor of 6.1, and my occasional charge reduction is still occurring. I managed to grab pics of the issue yesterday morning:

The car would not let me raise the charging current above 30A. It's interesting that the logic in the car "resets" the max down to 30, despite my HPWC sending a pilot current of 40A.

My house voltage is typically about 244V... so the 10V shown there only represents 4% drop. When charging at a full 40A, it typically only drops to about 243-242, which is only a 5% drop or so.

This happens infrequently... so I'm not sure if there's some other load elsewhere in my house or on the neighborhood transformer that causes a momentary sag in voltage... but I haven't seen it. I typically delete my home charging location in the nav system, and it will then happily charge at 40A for another several weeks...