Back2Ford

My fusion is still on it's first tank of gas and I have noticed that the battery voltage gauge often reads full and is never below the halfway mark. Is this normal? I thought it was supposed stay around the half-way position. I am a bit concerned about this. When I was on the freeway today and the car made a 3 tone (I think) alert sound for about 10 to 15 seconds. I couldn't see any warning anywhere and it stopped before I could pull over. Should I be concerned about this?

We paid 28,885 before tax and reg. for a white platinum with 502A package. We're in southern CA.