usually.....all your sound system is hooked up sa battery....once you start your engine......the alternator charges your battery.....now.....since you are using up your battery....your alternator will not stop charging the battery.....acting like the power source you are using is the alternator.....for better performance.....upgrade you allternator to a higher rate.....like ranging from 90 to 120 ampereHour rating so that it will take the alternator a short time to charge your battery if you cannot afford to buy those costly 1 farrad Capacitors.......