110V charging, now even slower?

[cvrcv]

I've been watching my charges carefully for the past year, and it's been incredibly consistent. I charge with NEMA 5-20 all day at work because it's free and almost always available. I used to consistently pull 16A @ ~114V, and close to the end of the day the API would usually read a charge rate of 4.5 mph, and if divided the rated miles gained by the time charged, I would get a very consistent 4.56 mph, day after day after day.

Sometime in July the behavior changed, all of a sudden I'm getting 7% less charge rate, even though the car claims it's pulling the same 16A @ ~114V. I can't pin this down to a single software update, because I didn't have the car for a couple weeks as it bounced between the body shop and Tesla service. So I emailed ServiceNA a couple weeks ago and I've been basically stuck in a tier 1 tech support loop between them and my local service center unable to get a clear answer about what happened and if it's just my car or everybody. "Well the logs look fine", "110V charging is just a backup", "with spec", etc, is all I get.

So frustrated what I did eventually was I used multiple meters to confirm what the car was drawing, and surprise, the car is drawing 1A less than the chargers claim it is! Losing 1A/16A basically drops you 7%. It gets even worse if you use NEMA 5-15, because now you drop 1A/12A! With auxillary overheads, I except 12A charging to have dropped by a full 10%!!! when charging at 40A it's not such a big deal, because it's only 1/40th. I even have a workaround: I can use my custom NEMA 14-50 to NEMA 5-15 adapter, turn the charging amps down to 16A, and voila, we now have 4.56 mph charging again. Amazing.

So this seems like a software regression to me, because in any case, the car should not claim it's drawing x/x amps, when it clearly isn't. If they reduced it by one amp for some safety reason or whatever, then it should just report the right number.

Can anyone else confirm this?

 

[cvrcv]

Oh, and I'm currently running 2.28.60

 

[tnt1971]

I have noticed on really hot days the power company cuts back the power, mostly the volts, to deal with the higher demand. You say it started in July, so it is possible it is due to this, especially if where the outlet is is very far away from the source.

 

[kort677]

as noted, it might not be the car, it could be the power supply that you're using. could you find a different place to charge?

 

[cvrcv]

as noted, it might not be the car, it could be the power supply that you're using. could you find a different place to charge?

Several places, several sources, same behavior. Fundamentally the charger in the car reports a different number of amps drawn than I measure at the input.

 

[cvrcv]

I have noticed on really hot days the power company cuts back the power, mostly the volts, to deal with the higher demand. You say it started in July, so it is possible it is due to this, especially if where the outlet is is very far away from the source.

It's not the voltage, it's measured by both me and the car. The voltage is nominal and reported correctly, unlike the amps. I know the car will reduce amperage if the voltage falls 8%, and the car will report this in multiple ways, this is not happening. Car reports 16/16A, only pulls ~14.9A

 

[cvrcv]

I should add, the car pulls the right amount of current when using the wall connector, even at 80A.

If somebody could please measure what they're drawing from the UMC and what build you are on, that would be great.

 

[Zaphod]

I wonder if a rounding error was introduced in software version somewhere. This way the display shows the expected amps, but behind the scenes is lower like you are seeing. Like you mentioned, at higher amps, the difference would be not be that noticeable, but at your lower charge rate, that 1A difference is much more significant.

I know there were some reports at one time of people seeing 79A instead of 80A, but that was using the HPWC not the UMC. Not sure if there is/was anything similar going on.

 

[gaswalla]

It's most likely not the software.... The UMC can degrade rapidly - my guess is that this is hardware related. You may want to take your UMC to a service center to get checked out. Also, check the plug adapter on the UMC for degradation, melting, etc.. (the wall plug adapter side)

 

[cvrcv]

It's most likely not the software.... The UMC can degrade rapidly - my guess is that this is hardware related. You may want to take your UMC to a service center to get checked out. Also, check the plug adapter on the UMC for degradation, melting, etc.. (the wall plug adapter side)

It's not the plug itself. I always use the 5-20 adapter and never the 5-15. 5-15 shows the same problem when checked out. Maybe it's the UMC. But the charge current (not pilot current) is reported at the charger, not the UMC, everyone agrees? Then it shouldn't misreport.

 

[cvrcv]

I wonder if a rounding error was introduced in software version somewhere. This way the display shows the expected amps, but behind the scenes is lower like you are seeing. Like you mentioned, at higher amps, the difference would be not be that noticeable, but at your lower charge rate, that 1A difference is much more significant.

I know there were some reports at one time of people seeing 79A instead of 80A, but that was using the HPWC not the UMC. Not sure if there is/was anything similar going on.

That's my guess. The behavior is clearly been changing. For example at the start of charge sometimes it reports 17/16A draw. It used to do this for almost a full minute near the start of charging with the last known working build, newest build does it very briefly.

I think the charging thinks it's drawing full current when it isn't, and then also logs the wrong number.

 

[Chopr147]

Charger say's i'm getting 1 mile per hour
Over 24 hours to charge!
Just putting this out there because it's kinda funny. I just haven't gotten to installing the 14-50 yet at the lake

house. I do have an electric stove I am going to tap into but the plug is the old 10-50 so can't use that

 

[kort677]

the problem more than likely is the extension cord. you need to get a 12guage cord rated to 15amps.

 

[GSP]

Charger say's i'm getting 1 mile per hour
Over 24 hours to charge!
Just putting this out there because it's kinda funny. I just haven't gotten to installing the 14-50 yet at the lake

house. I do have an electric stove I am going to tap into but the plug is the old 10-50 so can't use that
View attachment 191753

I have purchased the following to charge at our vacation cottage. The range and dryer both use 10-50 plugs.

https://www.amazon.com/gp/product/B00TCYBG2G/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B00192QB9M/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

This is just temporary until I have a HPWC installed. I don't like using the 10-50 on a regular basis since it does not have a dedicated ground wire.

GSP

 

[TexasEV]

the problem more than likely is the extension cord. you need to get a 12guage cord rated to 15amps.

Agree. Using the typical orange outdoor cord (16ga) is dangerous if it even charges at all. Maybe you should RTFM? Can't you plug in directly by switching the position of the cars? If you use an extension cord use the shortest possible 10 or 12ga to minimize voltage drop.

 

[mikeash]

Charger say's i'm getting 1 mile per hour

If you looked at it shortly after you plugged in, check again in a couple of hours and you should see a higher number. The MPH figure is an average, and seems to count the time it takes to set up, so the initial figure can be really low. Typically you'll get more like 3MPH long term.

I did plug into an outdoor outlet at a hotel a couple of weeks ago that had severe voltage sag. I forget the exact numbers, but it was something like 118V when idle, and 102V when drawing 12A. I figured that couldn't be a good sign, so I dialed the car back to 6A. Now that was slow!

Note that if you want to take the easy way out, you should be able to build a 10-50 to 14-50 adapter to use your existing oven outlet. Not that I'll try too hard to talk you out of installing the proper one....

 

[Chopr147]

This is just a temporary problem but you're right. It is charging 3 MPH now. On Monday I plan on putting a 14-50 exterior outlet in, tapping off the oven range which has a 50 amp breaker. I will just unplug anytime we cook. I already have the supplies but I have been busy relaxing with the family one last weekend before school starts up. For now it's running 12 amps and not getting hot but I keep checking it anyway. Thanks for the responses

 

[Cosmacelf]

Cvrcv, I'll check when I get home on 5-15 and 5-20, Model S and Model X. I have a clamp on ammeter so I can get the actual amps being drawn. How old/what kind of car do you have?

 

[Cosmacelf]

Well I just measured actual amps being pulled using my clamp on ammeter on a 5-15, 5-20 adapters and HPWC. All three reported way lower amp draw than shown on the screen (like 25% less). It is so off that I suspect my ammeter is wrong. Time to get a new ammeter! Will report back...

 

[mach.89]

Interesting you brought this up, I think I've observed similar behavior with 120V charging. I keep careful logs of charging and prior to July I was getting a pretty consistent 3.7-3.8 mph charge rate in the same location (I only charge 120V 15A at work and typically leave my car for 24-36 hours when I fly off for work). Since July, I've had 5/6 times where I was plugged into same outlet at work and getting 3.3-3.5 mph. But once was 3.8mph average, so go figure. Maybe a charging algorithm changed with a software update? I remember the console always saying charging at a rate of 4mph, now says 3mph. I have a Nov 2015 85D on 2.32.23