Q: Car shut down due to low battery voltage

I was pulling into a parking space when my car completely shut down. The lights on the dashboard started blinking - it seemed like all of them. The most dominate flashing light, after others settled down, was the ABS brakes warning light. For four hours the car would not start. This was very dangerous since it had shut off while I was driving/moving into the parking space, fortunately at low speed. The dealer told me that the cause was low voltage from the battery. They had done a diagnostic test to find this problem; however, they did nothing about it. I was told not to use the radio if the car was off. My car should have charged fully after my ride, but it is still a problem. What will fix this problem?