For the past month I've been getting the Battery Saver message almost constantly, so last week I had my dealer check it out. I have put my 12v on a trickle charge twice with the BS message coming back in two days, so when the dealer said they just charged the battery and it was fine, I was a little upset. But I'm glad I didn't make a big issue of it. The message has not been seen for a week now, and I am now getting 2 mpg better mileage. On my 600+mile trip this past weekend, the HV SOC rarely got below 70% unless I intentionally drained it going up a grade. My FFH was more effecient while cruising in the 65-70 mph range.
Before the trip I did increase the tire pressure from 34 psi to 39 psi, and the temperatures while driving ranged from 52-65 degrees, so these may be a factor, but seeing my lifetime average now at 37.5 instead of the 35.4 from two weeks ago makes me feel much better. I have a feeling the dealer did more than just charge the battery, since they had it all day.