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My accidental overnight unplugged reservation

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I have a 2019 Model 3 LR AWD and I usually keep my car plugged in to follow the motto .."a happy Tesla is a plugged in Tesla", but yesterday after I made a lunch run (I went from 80% battery to 77%) I forgot to plug my car back in upon parking back in my non-heated garage. Temps were in the low-to mid 20's all night for my area. So, I just checked my app this morning and after 20+ hours of sitting overnight in my garage it still shows 77% on the battery. I'm not sure if that's normal (to not lose any percentage over that period of time) but I'll gladly take it. I know my phone or iPad battery can't do that just sitting around not being used for 20+ hours and keep the same battery percentage. Side note... Sentry Mode is not on in my garage but I figured other small battery draining features would, at least bring it down 1% overnight.

EDIT: Title should be "My accidental overnight unplugged observation" ... NOT "reservation". I couldn't see anywhere to edit the title after posting.
 
If the car goes to sleep it loses very little battery. I left mine for 3 days in a parking garage on vacation and lost 1% IIRC probably just from waking it up to check battery level from the app once or twice a day.
That makes sense. I forgot about the going to sleep process. I guess once it does that the battery is conditioned for very little battery drain.
 
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According to Stats, I've been losing 0.1mi/hr, so maybe your car is doing the same. At 20hrs, that's 2 miles, and 2 miles, is 0.6%. I suppose that should round up to 1%, but your car could have been at 77.3%, showing 77%, and losing 0.6% would bring it down to 76.7%, rounding to 77%. You're losing charge, but very little, which is as it should be if the car is mostly sleeping.
 
If you follow these setup rules (+ change your password and disallow access to 3rd party apps and disable the new "always on" default summon feature with v10, if you have summon) you will loose less than a % each day. Actually, having the car in % will not show you the actuall battery usage. You should switch to km to see it since 1% is about 750Watts, which if you follow the advices should be enough for 2-3 days of unplugged also.

Also, the advise "a happy Tesla is a plugged in Tesla" is not 100% scientifically correct. First, there is a difference between a "Tesla" and a "Tesla" - for example Model 3 has different cells chemistry and BMS than older Model S/X.
Second, it seems the Model 3's BMS is more prone the "defects" if you charge it only in the high %-iles. Meaning if you just charge it from 60%-80%, like you probably did, you will "break" the BMS (the software that calculates the capacity) and it will think you have less capacity than you have. This is evident by a lot of posts around here and a Like Tesla video.
Ideally you wanna keep the battery around 65% always, but since this is not possible (unless you go on vacation - leave it around 65% and disable all the vampire drain things I explained in the video) you should try and drive it down to 30% and then charge to 80% or 90% if you can drive right away in the morning, only if you reach the 30-40%. Every once and a while (each month or so, try going to charge from 10-90 or even 100%)

But if you want more technical details on you rbattery you should check the other videos.
https://www.youtube.com/watch?v=3JqLIGOnV0c