2013 owner here. Moved from Sunny San Diego to Upstate NY a few years ago which then started giving me battery troubles. I went from mild weather, 40 mile each way commutes to less than a mile, a lot of sitting since I just walked my commute most of the time, winters with low temps.
I had to eventually replace my battery once at a ford dealership, but still suffer 2 years later, every winter. It dies in less than a week. The voltage after a jumpstart is still "healthy" right now though.
Some tips and things I noticed over the years
Tie a rope to the trunk handle and bring it to your rear seat, like others have mentioned
Your 12V needs to be functioning for your HVB to be charged. Why? Because physics.
When your HVB is fully charged, then your 12V is allowed to charge.
Thus, if you leave your car plugged in using your charging cable, your car battery should theoretically be able to be topped off
If you are locked out with car not functioning, the driver door handle can be opened basically using your key to pry it open. A piece of plastic pops off. That kind of chipped/break off a piece with cold weather
Your battery is in your trunk. The hood has connections to it but if you can access your trunk, use that, it's an easier terminal to use
The older units had I think a deprecated 3G antenna or something that got deprecated. It's used with MyFordMobile and other remote connections for your car. Anyway, how I understand it is that, with less towers to ping, it was constantly reaching out and thus draining the battery. They had a recall for an update and I noticed an improvement. So if you got the notice, get that updated to what I believe is the 4G model now.
I still don't know how the 12V outlets in the car work. I have a dash cam that sometimes auto shuts off when I turn the car off, and sometimes it just stays on. I notice the camera one when I check my car like an hour later. I would have thought power to those ports would be killed but I'm not sure. I do see my voltmeter drops voltage immediately after I power off, but not completely.
I got a car alarm notification to my phone from MyFordMobile somehow when I got into my car with a dead 12V battery... so the cell unit in the car was still powered but the rest of the car wasn't.
Hope that helps. I know this forum goes months/years with people not replying but people use this as reference so I'll put in my 2c