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Wall Connector overcharging my MY

Flybyglass

Member
Feb 2, 2020
127
93
New England
I updated to 2021.24.3 a couple days ago, so I don't know if that affects things, but I plugged in my MY last night. When I came out this morning the display read "fully charged" and the battery was at 79% despite the charging limit being set to 80% on the phone. I'll see what it does next time.

*shrug*
If you have a Gen 3 charger it communicates with the car. I had both Gen 2 and 3. The Gen 2 it would charge to 80% and stay. The Gen 3 allows the car to run down a bit before bringing it back up to 80% possibly to allow the BMC's to balance the batteries. What you describe is common with gen 3 charger.
 

sleepydoc

Member
Aug 2, 2020
413
393
Minneapolis
If you have a Gen 3 charger it communicates with the car. I had both Gen 2 and 3. The Gen 2 it would charge to 80% and stay. The Gen 3 allows the car to run down a bit before bringing it back up to 80% possibly to allow the BMC's to balance the batteries. What you describe is common with gen 3 charger.
I have a clipper creek charger.
 

Stavinski

Member
Jan 31, 2021
148
167
USA
Ours has never charged exactly to the set level since we got it 6 months ago fluctuates a percent or two. We have a juicebox level 2 charger.
 
Sep 18, 2012
196
159
San Diego, CA, United States
I have seen/witnessed this wonky behavior on my Model S, However, the car is now ~5 years old and has ~125K miles, so maybe it's the age?

The repeatable behavior is created by doing the following:
  • Keep your car set to 90% SOC
  • Supercharge at a a busy Supercharger (which defaults/overrides the SOC down to 70-80%)
  • Override this moments later at either the display or on the app (done both) and put it back up 90% where you always have it
  • Charge to 90% at the Supercharger
  • Drive 100+ miles that day after the Supercharge event
  • Get home that night and leave the settings alone (they are still set 90%)
  • Charge overnight (Tesla brand charger, no more than 3 years old)
  • The following morning, the car will charge to 93-95%
  • SMH and and wonder why you have unnecessarily degraded your already very aging battery
The scenario can also be repeated by Supercharging and telling the car to supercharge up to 100% (whether it charges that far or not) and then bringing it down to 90% after the Supercharge event. Then home charging later on. It'll often overcharge to 93-95% in this scenario too.

In all cases, it involves Supercharging and in all cases the car is NEVER set above 90% at the home charge event. Yet it overcharges. I really HATE it that this happens. Maybe I'll try bringing down the overnight charge event to 80% for the next charge and see if that helps.

Either way, it's buggy and beneath a great car/company like Tesla to have these shenanigans.
 

GtiMart

Active Member
Nov 13, 2019
1,577
1,440
Quebec City, Canada
I think your reasoning hinges on a few assumptions that are not quite right. You are expecting to be able to set a precise state of charge percentage, and you are expecting that the car can figure out exactly the current state of charge of the battery. Those are not possible, not at the precision you're asking for. If you are interested, you can read all the literature around battery voltages and how that voltage fluctuates, depending on battery chemistry. You would see that temperature plays a role, and that good measures can only be achieved in an open circuit, that sort of thing.

To make things simple, and because I am not an actual expert, I will say this: the car estimates the current total capacity of the battery and the current SOC, and it's pretty good at it, but it might be off by a few percent. That estimate will be constantly adjusted. In your specific case, by supercharging and driving etc you're raising the battery temperature. At home, eventually the battery temperature goes back down and the car starts thinking that the battery cannot hold quite as much energy. Since the charge is done, with the current voltage and less potential capacity, the overall SOC looks higher.

Said another way: it's not a bug where the car decides to charge more than you asked for. Would I prefer that it be perfectly precise? Yes. Is it technically possible? No.
 
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Xopster

New Member
Nov 27, 2021
1
0
British Columbia
I posted about this on Reddit but didn't get much love. Ever since sometime around the update update to 2021.4.18.10, my Wall Connector has been overcharging my car. I have it set to 90%, but I've been getting 93%. Since the 2021.4.21.3 update that I just recently got it actually charged to 95% on my latest home charge and gave me the warning about charging to high and battery degradation, even though I have the limit set to 90%. Previously it always charged to exactly 90% and stopped.

I thought this might be the car (someone on reddit even mentioned battery calibration), but this weekend I stayed at a hotel that had the older Gen2 wall connectors available for charging. Each night it successfully charged to 90% and stopped.

Has anyone else been experiencing this? I'm wondering if it's the wall connector's software that's causing the problem.
 

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