If your empeg displays a battery icon it means the whole car's voltage has dropped seriously.

The reason things get quiet is probably because your amplifiers also drop into "protect" mode in that case.

You should be checking your car battery/alternator/wiring and finding out why your car can't supply enough voltage to run your amps.

It could be something as simple as a loose wiring connection, a blown fuse where you don't know about it, or that you're using too-thing wiring to your amplifier. Or even something as simple as you need a new battery or voltage regulator for the car.

___________
Tony Fabris