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Wall Connector overcharging my MY

cjxmtn

Member
May 22, 2021
165
199
SoCal
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.
 
Last edited:

jcanoe

Active Member
Oct 2, 2020
3,429
3,479
Maryland
I don't believe it is the Wall Connector. This has been observed before in Model Y, seems to be a software bug. It could be temperature related or it could be the result of cell re-balancing taking place. In my case 3% over the set charging limit disappeared as mysteriously as it appeared after a few weeks. (I use a non-Tesla EVSE to charge at home.) If it causes a warning issue or concern you can adjust the charging limit more precisely using the Tesla app on your phone than using the Charging screen set charging limit function.
 

cjxmtn

Member
May 22, 2021
165
199
SoCal
I don't believe it is the Wall Connector. This has been observed before in Model Y, seems to be a software bug. It could be temperature related or it could be the result of cell re-balancing taking place. In my case 3% over the set charging limit disappeared as mysteriously as it appeared after a few weeks. (I use a non-Tesla EVSE to charge at home.) If it causes a warning issue or concern you can adjust the charging limit more precisely using the Tesla app on your phone than using the Charging screen set charging limit function.
The fact that the Gen2 charger hit exactly 90% each time (4 separate charges) leads me to believe it's not cell rebalancing or temp. When charging at home however, it consistently charges over 90% every time with my Gen3 wall charger for the last month. Temperatures were similar between the two places I charged (also my car is garage kept when at home).
 

Toneus

Member
Apr 9, 2021
37
69
Atlanta
How are you setting 90%? In the app or the car?

If it's in the car on the Charging screen, and you're trying to lineup with the Daily/Trip grid, you're likely not setting exactly 70%, 80%, 90%. Check the Charging within the app, the granularity of 1% settings is visible there. Dragging the triangle will pop up the numerical value on the left of the battery display. You should be able to refine the target percentage selection to exactly 90% in the app.

Screenshot_20210816-115418.png
 

Toneus

Member
Apr 9, 2021
37
69
Atlanta
Do you have Charging notifications set on? What does the app tell you when charging is complete? What does it say? "Charging completed at <time> with battery at 90%." Or does it state the higher 93% or 95%. Depending on temperature, or a BMS recalculation a charge may settle higher.

I've recently had a charge finish at 90%, but the SOC report 92% a short time after. In the top Charge Details snip you can see the SOC Max is reported to be 90%. But a short time later in the Charge Level report the SOC settles at 92%.

charge_session.JPG
SOC.JPG
 

cjxmtn

Member
May 22, 2021
165
199
SoCal
I didn't catch the notification this morning, I dismissed it while I was still half asleep but I'm pretty sure it said 90%. I'll have to check again next time I charge, but the car is sitting at 91% right now. Every time this happens, in the charging page of the App the green SoC indicator is always past the white line set to 90%. And to reiterate, this didn't happen once during all my charging this weekend on the destination Gen2 wall connector, and prior to my update to 2021.4.18.10 it always stopped at exactly 90% as well, but now happens every time I charge with my home Gen3 wall connector.
 

cjxmtn

Member
May 22, 2021
165
199
SoCal
Being that it's the only variable that changes between charging to 90% and going over 90% it has some role in managing the charging process. It's not just a wire, it has firmware and charging logic in it as well or else I could just plug my extension cord in to the car without the need for a wall/mobile connector.
 

sgalla04

Member
Mar 24, 2021
553
532
Philadelphia, Pennsylvania
I’ve been setting my 14-30 adapter with mobile connector charging set via mobile app to 75% and the past couple weeks it has consistently been charging over… 77-78%. Not really an issue, but seeing that someone else is “over charging” I figured I’d mention.

When I got the car in June it has always stopped/showed SOC to what I’ve set it to charge to.
 
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cjxmtn

Member
May 22, 2021
165
199
SoCal
Thanks for the data point, leads me to believe moreso it might be a firmware issue. Are you vision only (assuming so since you're 203xxx) and which firmware are you on?
 

GtiMart

Active Member
Nov 13, 2019
1,370
1,208
Quebec City, Canada
I am at least 95% sure that the car doesn't "overcharge" per se. IT targets the percentage you set. But, as the BMS cannot very precisely know the capacity of the battery, it stops when it thinks it's at 90% or whatever you set. Things can change/readjust afterwards, the BMS might later think you're actually at 92%. There's nothing wrong. Software versions can indeed change the calculation of capacity in some form.
Note that temperature changes can also change the SOC displayed, without you drawing current nor adding any.

I wouldn't fret it. I've seen it happen on mine too, over multiple software versions, varying 2-3%.
 

cjxmtn

Member
May 22, 2021
165
199
SoCal
I am at least 95% sure that the car doesn't "overcharge" per se. IT targets the percentage you set. But, as the BMS cannot very precisely know the capacity of the battery, it stops when it thinks it's at 90% or whatever you set. Things can change/readjust afterwards, the BMS might later think you're actually at 92%. There's nothing wrong. Software versions can indeed change the calculation of capacity in some form.
Note that temperature changes can also change the SOC displayed, without you drawing current nor adding any.

I wouldn't fret it. I've seen it happen on mine too, over multiple software versions, varying 2-3%.
I'll reiterate that this is a new thing, from purchase of the car to recently when it started overcharging, it stopped at 90% every single time, superchargers it stops at 90% every single time, and the gen2 stopped at 90% every single time, meaning not once did it charger more than what I had it set to. You're welcome to dismiss it, but it doesn't change the fact that something's recently changed that's causing this to happen. My charge on Wednesday night it went 5% over, from 90% to 95%, which to me is problematic.
 

sleepydoc

Member
Aug 2, 2020
268
239
Minneapolis
I’ve noticed a similar issue with my MY. I have a Clipper Creek charger and after charging it to 100% for a trip recently I set the charge limit back to 80 but it’s been charging to 83%. I thought I had just missed the mark but looking at my phone it was actually set to 80 so I’m guessing it’s a minor bug in the latest update.
 
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Toneus

Member
Apr 9, 2021
37
69
Atlanta
Being that it's the only variable that changes between charging to 90% and going over 90% it has some role in managing the charging process. It's not just a wire, it has firmware and charging logic in it as well or else I could just plug my extension cord in to the car without the need for a wall/mobile connector.
The Wall "Charger" is a Wire. All of the charging logic is in the Car. The Wall Charger will sense line faults, and overloads, and coordinate multiple chargers, but it doesn't CHARGE the car, nor does it stop the flow of electrons because 90% has been reached. It's not the wall charger unit.
 

Flybyglass

Member
Feb 2, 2020
113
87
New England
In my model 3 this is common. I also have a Gen 3 charger. The charger does communicate with the car but I am not sure if this is the cause of the slight overcharge. For fun I sent a not to Tesla support to get their explanation.
 

TomServo

Active Member
Apr 10, 2014
1,592
1,043
Belleville IL
My Y (charging with a Clipper Creek EVSE) has been “dead on” with regards to SOC limits. I do agree that setting the limit on the phone app is far more accurate especially with the haptic feedback my iPhone 12 provides.

I wish they would tweak the cars slider to act more like the phone app.
 

sgalla04

Member
Mar 24, 2021
553
532
Philadelphia, Pennsylvania
I’ve been setting my 14-30 adapter with mobile connector charging set via mobile app to 75% and the past couple weeks it has consistently been charging over… 77-78%. Not really an issue, but seeing that someone else is “over charging” I figured I’d mention.

When I got the car in June it has always stopped/showed SOC to what I’ve set it to charge to.
Interestingly enough, this morning it charged to / showed 75% SOC, as set to via the mobile app. Nothing new updated on my end, but didn't "overcharge' this time. Just reporting another data point for folks.
 

sleepydoc

Member
Aug 2, 2020
268
239
Minneapolis
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*
 

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