Hello, and thank you for allowing me the opportunity to help you. If I am not online when you are, please allow me time to return. If the terminals are clean and if the battery tests fine then you more than likely have a bad alternator. I would start by making sure that the belt is tight on the engine. If it is tight then you need to have the alternator checked. You can have this checked for free at most auto parts stores. Please let me know if you need more help.