I dont think you have a charging problem. When your car dies, is it while your driving? The radio could play for 4 days without killing the battery. If your car shuts down while you are driving, it could very well be the connector from the ignition switch. They have a tendency of overheating and breaking contact, that would shut the car down because your main power loom, including all of your electrical runs through your ignition switch. The switch is located i believe on the steering post. See if you can get to it and check to see if it looks like it got hot. I had a car that would just cut out while driving and that is what it was. Even your charging system goes through that ignition switch connector.