If you are powering the system off the battery with the car parked, then you are simply running out of power. Add another battery for longer operation time. If you mean the system cuts out with the vehicle running, then it has nothing to do with the battery. It could be a number of issues including your setup, the integrity of your ground connections, needing to upgrade the Big 3, and needing a higher output alternator. Tell us more about your symptoms. What is the system voltage doing when the amps shut down?