Maybe the alternator. You can take a test light, connect it to the disconnected positive cable and the battery positive terminal. Make sure everything in the car is turned off, and the doors are closed. If the test light lights, something is draining the battery. You can go to the fusebox and pull 1 fuse at a time, when the light goes out, the problem is in that circuit.
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Maybe the alternator. You can take a test light, connect it to the disconnected positive cable and the battery positive terminal. Make sure everything in the car is turned off, and the doors are closed. If the test light lights, something is draining the battery. You can go to the fusebox and pull 1 fuse at a time, when the light goes out, the problem is in that circuit.