Suggest to perform diagnose at work shop, usually the keypoints of diagnose are:
1. Check if the battery is faulty, replace if necessary.
2. Check if the alternator belting is broken due to aged, replace if necessary.
3. Check if the alternator wiring is open circuit or short circuit, replace if necessary.
4. Use measuring device to test the alternator see if its internal part is faulty. Replace if it is beyond repair.