I've been wrestling with this question every winter since I got my M3 in 2019. Is it better to warm the battery by charging--timing my charge so that it finishes just before I leave? Or is it better to turn on the heat before I go? And for how long? And at what temp? Lately I have been doing a combination of all this stuff. I have my charging start at 4:30 am, but my departing/commuting time varies, so it could be a couple hours before I drive off. Not ideal? No big deal? And then I set the heat to 60 degrees for 20 minutes or so, basically to just start warming the battery, because there doesn't seem to be any other method of officially sending heat to the battery, (if charging is done.) And then about 10 minutes before I get in the car, I increase to 74 degrees just so the cabin is toasty. Then I reduce to 68. But even when I time all of this perfectly, with a long (~50%) charge, I still have many dots in the region indicator. I guess that's unavoidable? Sometimes I even increase the battery charge target a bit for the last 20 or so minutes before I leave just to heat it even more. Problem with that is that I can forget and overcharge the next day. None of this is ideal!!! Surely Tesla could come up with a less complicated solution. And yes, I have tried the Departure Precondition setting, but have been late to work because the battery wasn't even close to the set point when I needed to leave! Been hesitant to use it since then.
Please, experts, weigh in? How should I prepare my car given that I don't have a set departure time every day?