2003 Chevy Impala Head and taillights blink when the car is

Rently after starting my car I noticed that my battery warning light kept flashing on the instrument panel of the car. I noticed an hour later that my headlights and taillights were still flashing on the car as well as the battery warning light while the car was off. My husband thought that the altenator may have been going out so he replaced it. The car ran fine for about 50 miles than it started to act up again. This time I noticed as I was driving it that the battery warning liight and all the insturment panel lights were blinking on and off every couple of miles. And once again while the car was off the lights all kept blinking on and off again. Other than the flashing lights the car starts up with no problem. I just hate to drive it to far as I'm not sure if the battery would die from all the flashing lights. What could be causing this to happen?