To everyone having 12V issues due to the TCU I have found a Pseudo fix. No, I have no solution for Ford's shitty TCU but at least I have found a reasonable way to prevent it from killing my 12V battery.
Over the last 11 months since I pulled the F1 fuse I have pondered various ways of powering the TCU separately from the car's 12V system. Everything I came up with from using an arduino microprocessor and an auxiliary 12V battery was some combination of too expensive, too complicated, or just plain not a good idea. Then it hit me I was overthinking the problem. If I could only find an "affordable" low voltage disconnect that itself would not drain my 12V battery (ie. draw practically no current) and I could set it at a relatively high disconnect voltage, that would be the simple solution. I set out to see if this magical unicorn of a device existed. I found many cheap low voltage disconnects but their current draw was unacceptably high.
Then the clouds parted and angels sang as I stumbled upon this little gem from Galley Power.
It was a little more than I wanted to spend at $46 but it fit what I was looking for almost perfectly. On the high end it can be set to disconnect if the voltage drops below 12.1V and will reconnect at 13V. From what I have read on the interwebs 12.1V is approximately a 50% SOC for a 12V battery. The next lowest setting is 11.7V which I believe is about 40% SOC. Anyway when the unit is in the "connected mode" it only draws 3.5mA. Ford's spec for the car when it is off is a 50mA or less load on the battery. I have measured mine at about 20mA so when my car is off It will now have a 23.5mA load on the 12V battery which is still in spec by a long shot and in theory should be able to sit for at least a month. When the unit disconnects due to low voltage the load drops to an amazingly low 0.26mA
I wanted to do this all without hacking and cutting any wires. I happened to have one of those add a circuit things that you plug into a fuse slot laying around similar to this.
I ran the power thru the "added circuit" fuse and to the disconnect. I then fed the output from the disconnect back into the fuse slot for the TCU. In other words I used the added circuit fuse as the fuse for my TCU, then fed this power to the disconnect and the output of the disconnect back into the fuse slot for the TCU. Sorry I neglected to take any pictures and if you don't understand how these add a circuit things work this all probably makes no sense. If I remember I'll add some pictures when I get a chance. Anyway this all seemed great, I soldered everything together to essentially plug into the F1 fuse slot. Then Murphy reared his ugly head. The damned fuse sockets are recessed and the prongs wouldn't reach the socket!
Still not wanting to start chopping wires I resigned my self to breaking out the dremel and carving away the extra plastic on the fuse block that was preventing me from plugging in the add a circuit. I used a nearby bolt that is one of the battery retention bolts for the disconnect's ground wire.
Well it has been nearly a week and knock on wood, I have had no issues with the TCU or a dead 12V battery. I had tossed around going to a lower disconnect voltage setting, 11.7V since that is supposedly about 40% SOC and I would think that would be enough to still start the car. Hopefully it doesn't come to that and things work just fine at the 12.1V setting. I'm not certain if it has disconnected or not but every time I've tried to connect to the car via MFM I have been able to do so.
I updated the details in my 8-22-17 timeline post.