Well the easiest thing to do would be to pull the F1 fuse which supplies power to the TCU. If the problem goes away then you know it's your TCU.
Ford's procedure is to do a draw down test as I described in my linked thread above. This checks battery drain and finds the culprit.
I only use the LVD in winter when I want to use go times as running the battery down to 12.1V is hard on a lead acid battery. It is like 40% SOC. Otherwise like now I just pull the fuse and not care about the lack of TCU.
I realized my 12V battery was nearing it's end of life when I tried to jumpstart my motorcycle and it didn't have enough to power to turn over the motorcycle engine. The motorcycle battery is only 160 CCA. I replaced my 12V with a LiFePO4 battery. probably a bad idea because LiFePO4 chemistry pretty much stops below freezing. Then I realized I don't need current, just enough juice to energize the contactors. Than and I put a LiFePO4 starter battery in another motorcycle I rode often in winter, 8 years ago and it is still works just fine.