My new to me 06 expedition isnt holding a charge. Replaced battery 2 weeks ago. About a week ago I had to jump start the expy if it sits for more than 4-6 hours. Initially I figured it was just the extreme cold but it seems to be at any temp. After I jump start it the voltage indicator on dash is showing a normal charge. I can drive around all day but if it sits for more tha. 6 hours I have to jump start it. Any ideas....electrical is not a strong suit for me so I am a bit stumped.