Battery loss when away from home

[chyuan]

I have experienced multiple times that when I'm away from home and leave the car parked the SOC can drop by as much as 5% over the course of 3 hours. This is the most consistent when I go to work, and here's a typical timeline (I only go to work like once every other week usually):

1. In the morning departure SOC is 80%
2. Drive to work is about 45 miles, SOC would be around 64%, time is about 9:30AM
3. Car is parked, no sentry, no cabin overheat protection
4. Return to car ~12:30PM, SOC would drop to like 59%, app shows inside temp ~115F
5. Eat lunch in the car with AC on for about 30m, SOC will be ~58%
6. Back to work and returns after 6PM, SOC will remain at 58%
7. Drive back home SOC is like 43%

This same pattern has happened multiple times, two times last week alone. Checked TeslaMates afterwards car goes to sleep normally (like within an hour after left car each time). Any suggestion on what might have caused the battery to drop? (like why does it drop in the morning but not in the afternoon? And if car is parked at home this does not happen)

 

[jcanoe]

If you normally leave Sentry Mode set to be ON at your home location the Tesla Model Y will never enter sleep mode. If the Tesla Model Y never enters sleep the Tesla battery management system can't measure the open cell voltage (OCV) of the cells within the battery pack. (The battery management system can't perform this calibration step unless the high voltage battery is disconnected from the rest of the Tesla Model Y vehicle.)

Maybe the battery management system is using this time (when the Tesla Model Y is parked with Sentry Mode turned off) as an opportunity to perform the OCV measurement (it takes several hours to complete.) Afterwards, the Tesla battery management system has a better estimate of the state of charge of the battery and that is why the displayed state of charge is so much lower after just a few hours.

Alternately, a bad temperature sensor unit within the battery pack could have the battery management system using extra power from the battery to cool the battery when this cooling is not actually required.

Also, consider if you purchased FSD if Smart Summon is being left set to ON. This would also prevent the Tesla Model Y from entering sleep mode (although the battery consumption would be similar to Sentry Mode, that is 6 to 7% over 24 hours not over just a few hours.

 

[chyuan]

First of all thanks for your input.

If you normally leave Sentry Mode set to be ON at your home location the Tesla Model Y will never enter sleep mode. If the Tesla Model Y never enters sleep the Tesla battery management system can't measure the open cell voltage (OCV) of the cells within the battery pack. (The battery management system can't perform this calibration step unless the high voltage battery is disconnected from the rest of the Tesla Model Y vehicle.)

Sentry is OFF at home. I only turn it on occasionally when going to places I felt not as safe.

Maybe the battery management system is using this time (when the Tesla Model Y is parked with Sentry Mode turned off) as an opportunity to perform the OCV measurement (it takes several hours to complete.) Afterwards, the Tesla battery management system has a better estimate of the state of charge of the battery and that is why the displayed state of charge is so much lower after just a few hours.

Since Sentry is always off unless I manually turn it on this shouldn't be the problem?

Alternately, a bad temperature sensor unit within the battery pack could have the battery management system using extra power from the battery to cool the battery when this cooling is not actually required.

How would one be able to diagnose this to the point where I can bring this into SC and have some evidence of a potential problem? If it's due to bad sensor, I would think the SOC will also go down between noon and the evening in my original example work schedule but that doesn't seem to be the case, outside temperature I think it wouldn't be any cooler between 1-4pm compare to 9-12 in the morning.

Also, consider if you purchased FSD if Smart Summon is being left set to ON. This would also prevent the Tesla Model Y from entering sleep mode (although the battery consumption would be similar to Sentry Mode, that is 6 to 7% over 24 hours not over just a few hours.

No FSD, and based on TeslaMate the car went to sleep after ~45m after I left the car each time so doesn't seem to be a going into sleep type of problem.

 

[jjrandorin]

45 minutes sounds like a long time to me (to go to sleep).

 

[chyuan]

45 minutes sounds like a long time to me (to go to sleep).

Is it not normal? I typically see it stays online for ~1h after drive before it sleeps. (based on my TeslaMate history within the last week it takes between 32m to 1h15m to go to sleep after any drive regardless of location.

 

[jjrandorin]

My car (which has no third party apps) seems to fall asleep within 15 -20 minutes. I can tell when its sleep as it takes a while for the app to connect to it when its sleep.

Back when I used teslafi (for the first few months I had my car), it used to fall asleep in 15 minutes. That was the teslafi sleep timer back then. I have never setup teslamate although I am familiar with what it is. 45 minutes just sounds like a long time for the car to fall asleep to me, on a regular basis.

 

[jcanoe]

First of all thanks for your input.

Sentry is OFF at home. I only turn it on occasionally when going to places I felt not as safe.

Since Sentry is always off unless I manually turn it on this shouldn't be the problem?

How would one be able to diagnose this to the point where I can bring this into SC and have some evidence of a potential problem? If it's due to bad sensor, I would think the SOC will also go down between noon and the evening in my original example work schedule but that doesn't seem to be the case, outside temperature I think it wouldn't be any cooler between 1-4pm compare to 9-12 in the morning.

No FSD, and based on TeslaMate the car went to sleep after ~45m after I left the car each time so doesn't seem to be a going into sleep type of problem.

My 2020 LRMY usually enters sleep mode within 15 minutes after arriving at Home. Having ruled out Sentry Mode, Summon, and COP as the source of the power drain perhaps Teslamate is causing the Model Y to remain awake longer than it should. You could change your Tesla credentials to keep Teslamate locked out and see what happens over a period of time.

 

[GtiMart]

I very often see 30 minutes to an hour of idle time before my car goes to sleep. Could be because the fans run after I used the AC to dry the evaporator. There are also some shorter times, it varies. I would say this is still within normal parameters.

 

[chyuan]

My 2020 LRMY usually enters sleep mode within 15 minutes after arriving at Home. Having ruled out Sentry Mode, Summon, and COP as the source of the power drain perhaps Teslamate is causing the Model Y to remain awake longer than it should. You could change your Tesla credentials to keep Teslamate locked out and see what happens over a period of time.

I may give that a try, but even with potentially Teslamate keeping it from sleeping sooner it still doesn't explain the 5% SOC drop over ~3hrs, and it oddly follows a pattern (especially when I'm at work since the schedule is usually pretty similar).

Also to note, if I'm not driving the car and just having to wake up the car at home by opening the App or door it's usually quick to go back to sleep, ~15m or so not sure if TeslaMate is the real problem there.

 

[jcanoe]

I may give that a try, but even with potentially Teslamate keeping it from sleeping sooner it still doesn't explain the 5% SOC drop over ~3hrs, and it oddly follows a pattern (especially when I'm at work since the schedule is usually pretty similar).

Also to note, if I'm not driving the car and just having to wake up the car at home by opening the App or door it's usually quick to go back to sleep, ~15m or so not sure if TeslaMate is the real problem there.

What year is the Model Y? Does it have the 12V lead-acid battery or the newer lithium starting battery module? The reason I asked about the age and about the 12V battery is a failing 12V battery can cause all sorts of gremlins especially as relates to the vehicle's sensors.

It could be a bad sensor. Possibly the outside air temperature (OAT) sensor that is located in the front right wheel well and is susceptible to rodent damage of the sensor wire harness. As previously noted it could be the temperature sensing unit in the high voltage battery (here there are multiple temperature sensors so one bad sensor won't brick the vehicle.) There is also a sensor that detects if there is a passenger in the driver's seat that would affect the Tesla vehicle being able to enter sleep mode.

 

[ATPMSD]

And if car is parked at home this does not happen)

Sure sounds heat related

like why does it drop in the morning but not in the afternoon? And if car is parked at home this does not happen

A guess - when you arrive the battery is hot and the battery cooling system is running. Eventually, the battery is cooled and the car settles down. This could be an issue with the battery cooling system.

To check this, when you get home do not put the car on charge. Instead leave it alone for 3-hours and then check the SOC to see if you get the same kind of drop. Try to do this on a day when you can leave work early when it is still hot, or at least the same temperature as when you drive to work.