I have an 07 Chrysler Sebring

I have an 07 chrysler sebring. I was having problems with it about a month ago, and had my alternator, serpentine belt and battery replaced. Then was acting like it wante to stall a couple times after but didn't actually stall. Then I cleaned my car and waxed it yesterday took about an hour and I had my key turned to accessories so I could listen to my radio and also had my doors open. I went to start it and it took a min to turn over but then it did. Drove it then it say for about a half hour and went to start it and it was turning over but wouldn't actually start. Did that a couple times, tried jumping it but nothing. I have about half a tank of gas. Well it sat over night and I started it tpday and it started perfect. Drove it around turned it off and then on again just fine. Brought it to auto zone and they tested my alternator, that was good, tested battery and they said it was bad. So now I don't know what to do. Replace the battery again? But how is my car starting of my battery is bad?