it begins with the usb not working, than the whole radio sy

The first time it happened I didn't take much notice. Just thought the desert heat killed my battery, which was about 1 year old. The second time it happened, I took notice to the string of events. First the USB not wording for a couple days, than the media center acting weird. ?. Then the dead battery. Both times, auto zone and O'rileys, checked alternator n some other possibilities, and they said all was ok. So both times I just bought a new battery. Now I wait until it happens again. I don't have a bunch of money to put into a car that I bought used and have only had for 2 years! These are not issues of normal wear and tear! I do not mistreat my auto.