I am just adding to the conversation. Funny timing- I never saw this message before even when 1 battery went bad over the summer. I read this post on the 31st, I got in my truck after it sat for 3 day and what do I get -“ Battery Saver Mode”. The message is saved in the EVIC under stored messages.
Background- I have a ‘14 Laramie. The original batteries went bad in June, (1 month after 3yearsmark). No messages then, just went. Was traveling at the time, the local dealer would not cover under warranty because of mileage, (60k), and they did not have any available. I went to the local Advanced and picked up 2 850CCA AGM batteries, (originals are 730CCA). When I installed them I immediately noticed the charge voltage went from 14 to 13.8 and was pretty consistant there. I remote started the truck this morning as it was a bit colder this morning-for GA, I know this is nothing for some of you

. When I got in I saw the message and noticed it was back up to 14v charge.
I have not been able to look into more yet with work but I will see if I can find out anything more this afternoon.
I realize this does not answer any questions but I wanted to give my experience to see if this could help narrow things down.
If anyone else has any recommendations I am all ears.