2007 battery issue

I have 2007 Sebring Touring V6 w/ abt 44K miles. Battery light started coming on intermittently. Car starts no problem, sometimes light comes on when I pull out of driveway, other times it doesn't come on until I've driven for a while. Some days I drive to/from work (10 miles) -- no light. Took it to a mech who said the alternator was over charging the battery (15.5 when its supposed to be around 14), and I needed a new alternator and battery. Bought a new DieHard @ Sears (675CCA - they looked it up in the computer), took it to Chrysler dealer, who said the alternator and starter were fine, and that I needed a new battery. I told them there was a new battery in the trunk, and to put that one in. Dealer says DieHard is too strong (should be 525 CCA), said I need their battery ($250 - forget that!). Talked to Chrysler mech on th "QT" and he told me either batter is ok. Sears won't take the DieHard back because they said that is the correct one, and they don't make DieHard in 525 CCA, so I had them install the new 675 I purchased originally. This morning, pulled out of my driveway, and light came back on. Can someone please tell me what the deal is? I don't know who's telling me the truth!! Thanks!  :)