recommended charging habit

[hybrid>EV]

Tesla site shows >> The most important way to preserve the high voltage Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it.

I have time of day electrical rates, so I set the schedule to start charging at 8pm daily. I don't drive much, especially on weekdays, but I leave it plugged in 24/7 unless I need to drive it. I noticed that even if I don't drive, the battery % will drop 1 and sometimes 2 % by 8 pm the next day. Then it would be charged up to my set maximum in minutes. My question is shouldn't the battery maintain its charge since the car is plugged in? I read the car would use wall power (instead of batter power) when plugged in so I am wondering why it would lose some charge.

 

[Ken_Y]

If you set charge to start at 8pm, it will not charge even if you are plugged in. IMO, that is fine. You don't have to constantly be charging it. Charging it nightly is perfectly sufficient for battery health.

 

[ATPMSD]

shouldn't the battery maintain its charge since the car is plugged in?

Here is what I believe happens:

The answer to your question is no, the car goes to sleep and the low voltage system is supported by the low voltage battery. The Battery Management Systems (BMS) monitors the low voltage battery and when it gets below a pre-defined threshold the car wakes up. Power from the HV battery goes through a DC-DC converter that supplies power to the low voltage system, which then chargers the battery and draws down the HV battery a bit. When the low voltage battery charge is complete the car goes back to sleep.

The HV battery is monitored separately and when it gets a few percentage points below the SOC level you have set, the HV battery is charged back to the desired SOC level.

Drops in the range you stated are typically if Sentry is on. You may wish to ensure Sentry is set to not be used at home.

 

[jcanoe]

Sentry mode will use more than 1 to 2 % per 24 hours, ~6% per 24 hours. Repeatedly opening the Tesla app will cause the Tesla Model Y to wake from sleep mode, this uses additional power as it takes ~20 minutes before the Tesla Model Y will re-enter sleep mode if not being driven.

Set Sentry Mode to be OFF at the Home location (Home location is set in the Tesla Navigation system.)

Since you don't drive the Tesla Model Y much during the week you can lower the maximum charge setting to ~60% to 70% and still have plenty of driving range for daily use. You can bump this up on the weekend if you know you will be needing additional range or else on a trip plan to use the Supercharger network.

 

[ATPMSD]

Sentry mode will use more than 1 to 2 % per 24 hours, ~6% per 24 hours

@hybrid>EV

I agree with @jcanoe, Sentry is more like 6% per day, but a 1-2% per day is not typical. Do you add a camera or radar detector and if so, where did you wire it into the system? Are you running any third party apps? If so turn them off and see if that makes a difference.

 

[hybrid>EV]

OK it is probably me opening the app on my phone. I will lower max charge to 70%. I have sentry mode off at home and favorite locations. Thanks

 

[SkyDog]

... I noticed that even if I don't drive, the battery % will drop 1 and sometimes 2 % by 8 pm the next day.

The battery % is really just an estimate. It can easily go up or down 1 or 2% as the outside temperature changes (causing the battery temperature to change).

 

[hybrid>EV]

I think what you state makes sense.

I intemperate the below statement on user manual as I can sit in the car parked at home, watch 10 hours of movies with max brightness and max volume turned on, and the battery shouldn't loose any charge over it as power should be coming from the wall outlet, not the battery. However, I may see 1 or 2% drop due to temperate change and car recalculating and displaying the updated and lower (maybe sometimes higher) %.

From Tesla site - Model Y Owner's Manual | Tesla

Whenever Model Y is plugged in but not actively charging, it draws energy from the wall outlet instead of using energy stored in the Battery. For example, if you are sitting in Model Y and using the touchscreen while parked and plugged in, Model Y draws energy from the wall outlet instead of the Battery.

 

[jcanoe]

Whenever Model Y is plugged in but not actively charging, it draws energy from the wall outlet instead of using energy stored in the Battery. For example, if you are sitting in Model Y and using the touchscreen while parked and plugged in, Model Y draws energy from the wall outlet instead of the Battery.

Power always comes from the high voltage battery and is replenished as needed when plugged in. Need proof? The HVAC compressor runs at ~360V and can draw more than 8kW. All 120V charging is under 2kW (TT-30 receptacle, (2.88kW) excepted), so how does the HVAC system get powered from the power grid while the Tesla Model Y is plugged in? Answer; from the high voltage battery. Stator heating for warming the battery consumes 3.5 kW per drive unit, for a total of 7kW when warming the battery. Stator heating for the battery and warming the cabin can consume more than 11kW. Even if you have 240V/48A charging at 11kW that power is not coming from the grid. The high voltage battery will be replenished over time depending on your charging setup. It could take less than 10 minutes or more than 1 hour. If you trace the high voltage wiring from the HVAC compressor it only receives power from the high voltage battery. Running separate high voltage wiring from the onboard charger to the HVAC compressor would add to cost, weight and and complexity, is not part of the design.

 

[ucmndd]

I think what you state makes sense.

I intemperate the below statement on user manual as I can sit in the car parked at home, watch 10 hours of movies with max brightness and max volume turned on, and the battery shouldn't loose any charge over it as power should be coming from the wall outlet, not the battery. However, I may see 1 or 2% drop due to temperate change and car recalculating and displaying the updated and lower (maybe sometimes higher) %.

From Tesla site - Model Y Owner's Manual | Tesla

Whenever Model Y is plugged in but not actively charging, it draws energy from the wall outlet instead of using energy stored in the Battery. For example, if you are sitting in Model Y and using the touchscreen while parked and plugged in, Model Y draws energy from the wall outlet instead of the Battery.

When the car is “on” - high voltage contactors closed, HVAC on, someone sitting in the seat, etc - it will draw power from the wall if connected.

If the car is off, it does not do this continuously. This is to allow the car to sleep and avoid the constant ~300 watt power draw required to keep the car and charging circuitry “on”.

When you set a charging schedule, it further limits charging in any case to respect your wishes. Put another way, do you really want your car unnecessarily drawing power during your peak electricity time to replenish 1 or 2% of the battery? I don’t.