my battery is not keeping a charge all the time. most of the time after you shut off the car it will need a jump to start it again. but not ALL of the time. 2 mechanics have said that the alternator is good one has said it was bad. the battery does not ever lose power while i'm driving it, only when i turn it off . and for the first time the other day the battery light did come on while i was driving it. could it really be the alternator or could it be something else like a short in the electrical system somewhere? no one can seem to figure it out. does anyone out there have any theories. help!