I’ll leave the hood open and my fob inside the house, then let the vehicle sit for a while to get into a “rest” condition before I check the battery again.

I re-read the manual again, the section on the battery management system. It needs 8 hrs of uninterrupted off time to calibrate, but it specifically says the doors need to be locked. I keep it garaged overnight but unlocked.

The battery is in the engine compartment in a conventional gas version. I haven’t verified yet, but the manual says the part number is BAGM-48H6-760, a 760 amp battery.

 

Yeah, you've got the 70Ah AGM. Ford gives the PHEV a much smaller battery because it is not used for ignition.

 

Here is an update from the OP. Last week I finally brought the car into the dealership. Despite two different hand-held load testers reporting the battery was OK, the dealer's tests showed it was bad. They replaced the battery.

The new battery seems to be working well. I have been checking the 12v every morning, with the car at rest. We've barely driven it. The readings were like this this 12.5, 12.15, 12.25, 12.45. Based on at one point getting a Ford Pass message that I should plug in my PHEV to address a low 12v battery, and based on the battery gaining charge overnight without us driving it, I conclude, contrary to what I read on this forum, that in a PHEV the EV charging system does charge the 12v.

I think that the whole time the problem might have been a bum battery. Time will tell.

 

Not sure where you read that "that in a PHEV the EV charging system does charge the 12v. is not true". But the fact is 100% true that in a PHEV the EV charging system does charge the 12v. It does this any time you are plugged in to recharge the HVB. The power from your charger, Leve 1 or 2 will provide power to the AC to DC converter as part of the HVB system and will push 12v to the small 12v battery. Remember your car does not have a traditional generator/alternator. All power comes from the Level 1 or 2 charger or from the ICE power converter.

 

45 deg in the garage. Opened the hood and let the car sit for about 10-15 minutes so anything triggered when I opened and closed the doors would reset. I left the fob in the house and saw 12.1V.

That still seems low, I think it should be closer to 12.6V. I have enough of a warranty punch list now that it’s probably time to call the dealer and let them take a look.

 

Just drove over to the dealer to have them test the battery. They said it’s good, and that a lot of people have been coming in for the same thing. I’m going to let them have it for a day next week and dig into a few other items. And I will have them retest the battery and the battery saver mode.

As of now: battery is 12.4v. Battery saver mode is still on. I’m going to get some highway driving tonight, not much, but some. If it doesn’t clear up on its own then I’ll let it sit, locked, overnight and check again in the morning. If that doesn’t do it then I’ll reset the battery monitoring system manually. And if that doesn’t work then the dealer will be seeing it next week anyway.

Also - now my Ford Pass app won’t connect and the exterior door lock/unlock function is disabled. I think this is battery saver related.

 

FYI the Ford Pass app was down yesterday and down for some a couple days ago

 

I'd love to put a trickle charger on the 12 Volt battery, but it doesn't want to accept a charge when the ignition is not on. Any way to circumvent this?

 

Has to be connected to the jump post under the hood or directly to the battery.