I don't think I started another battery thread, but I would like to update my 12V battery issue.
After getting stranded about 4 times and using Ford Roadside assistance for a free jump, I took the car into the dealer (who assured me my 2017 12V battery was fine) and they tested it. Sure enough, it flunked the test and would not hold a charge. They replaced it under warranty and all is fine now. I also went on Amazon and found a portable battery jump starter for $30 bucks and bought one. It has a lithium ion battery and claims to be able to start up to a 2.5 liter engine. It fits in the glove box and will hold a charge for about 6 months. I feel confident it will get the relay closed and allow the car to engage the HVB the next time this happens. Hopefully the car will be good for 3-5 years until the new 12V battery wears out, but I will be ready with my portable battery.
One thing to point out to the OP that I don't think was mentioned, our electric motor is also a generator and charges the HVB regularly in hybrid mode, or when you step on the brake. While charging the HVB, I suspect the 12V battery is also getting charged. Maybe the 12V battery is always getting charged when the HVB is operating. I am not sure how that is controlled.
I do think either Ford buys low quality 12V batteries, or the load model for this car was not thought out well.
Edited by ScottB, 06 April 2019 - 07:26 AM.