I'd have the battery load-tested. Tis' the season for battery problems. I just had one go bad in my other car. It would go dead and I'd stick it on the charger for a few hours, but in the next couple of days, it would be dead again. Wal-Mart tested it with their "small" tester and said it was good. I mentioned having no luck with it after trying to recharge it, and that I wasn't going to take it home again just to have it go dead again, so they put it on the "big" tester. Sure enough, 20 minutes later when the test was finished they told me it was bad. I had only had it for about 4 months too. It's the easiest thing to check too, aside from checking across the battery terminals for current draw with a voltmeter.