Hi all. I'm new to this forum, so I want to first thank everyone who has taken the time to detail & discuss their issues and fixes. I have a 2014 FFE with a 33.5 KWh battery (replaced under warranty by previous owner in Sept 2017) with 50K miles on it. I have owned this car for 11 months, and I have been dealing with 12V battery issues since October. As described by others on this post, my 12V battery seems to randomly die (dropping down to ~9V) after sitting unplugged for 7-8 hours. Ford has replaced my 12V battery twice under warranty, and assured me that it was just a bad battery, and there is nothing wrong with my car. But I'm quite sure this has nothing to do with the 12V battery.
I've noticed a pattern over the last 5 months that the 12V battery issues seem to correlate with MyFord Mobile issues (losing connection). I have to constantly pull the fuse on the Telematics Control Unit (fuse F1) to reset the TCU so that I can connect again. I recently used a Klein Tools model MM200 along with a Fuse Buddy 301M to measure current at the fuse level when the car is on and when the car is off. As per Triangles advice, I was sure to measure after 40 minutes as well. What I found was that all units that I tested (I only measured fuses that were 10A or lower) read zero amps when the car was shut down. But the TCU never shut off. It constantly bounced from 0.03A up to 1.3A, but mostly sitting round around 0.04A. I pulled the TCU fuse and left it out. It's been 3 days now, and so far, I have had no issues with the 12V battery.