Dead Battery

In preparation for the drive back to Phoenix, I wanted to make sure my car was up for the long haul.  I suspected a bad battery due to the sad chug-a-lug sound that eminates when I turn the key.  Plus I had to jump it once when I left the radio on while vacuuming the interior...  The guy at autozone confirmed that the battery was bad and proceeded to look up a replacement battery in his system.  When the one he pulled off the shelf was about an inch wider than the original battery I pulled out, I became suspicious that there may be a reliability shortfall somewhere in the whole "which-part-do-I-need" autozone system.  Fortunately, the human aspect proved its worth in this instance when the attendant arbitrarily pulled an alternate battery down that was a similar size to the bad one and left the decision up to me.  I went with the one that would fit in my battery bay...