The very first thing I would recommend is switching chargers. Try using a different adapter to charge your phone. It's highly probable that you have a defective adapter. If after trying multiple chargers the phone still does not charge, then it could be a faulty mini-usb port. There is a small chance the battery could be the issue, but I doubt it; the reason being that even with a bad battery the phone should still charge, but the battery should not be able to keep the charge.