my pickup seems to have a problem. it kills my batteries while running it started last week the original battery i had in there went dead so i replaced it with a known new and good battery as i was driving today my battery light comes on and a little bit down the road my truck shutoff so i had my buddy bring me another battery to get me home i finally got home pulled the alternator and took it into autozone they tested the alternator and it checked out o.k. i fully charged the dead battery and it is now good but i am confused as to what else it may be and are the bench testers at autozone reliable i can see one battery going bad but two any help appreciated..