only sometimes though. Mods are in sig. XM will completely cut out when I press the brake sometimes, even if the charge is at 13.5-14 volts. What gives? I know my battery isn't the greatest right now but it's enough to start the car and all that jazz. If I run the car in accessory mode, the XM radio will stay on for about 5 mins before it turns itself off for lack of juice.

The radio will cut out with the headlights on or off.

 

how's it wired? to a cig lighter? or hardwired to the vehicle wiring?

 

the power wire is through the fm-modulator. It is piggy-backed to the radio power line.

 

bump

 

ttt

 

what brand is it? delphi?
most newer car audio products have a safety cut off if there is a voltage drop. It could be dipping enough to trigger it. If the XM only runs for 5 minutes in acc, you definitely need a higher CCA battery. Most average systems (500-1000watts) require at least an 800 CCA battery. Since your stock alternator only puts out an extra 10-15 amps for accessories, there has to be a buffer (battery, capacitor) for extensive add ons.