What is running inside of my radio on 07 Tahoe? I here a motor sound in there when I turn the car off and leave the radio on with volume on mute. thanks.

 

Its a cooling fan...

 

ah ha! Thanks! How long can I run the radio with engine off before my 2007 tahoe battery dies? anyone know?

 

Its not just the radio that runs, there are several modules that are powered on at the same time.... I'd give it a max of 20 minutes before the battery indicator would light at start up...

 

i have been reading in these forums about adding a second battery but the wiring and charging issues of the second battery may be beyond my abilities. anyone have comments after completing this process or can offer instructions with pictures? thanks.

 

The charging system of your Tahoe is capable of charing 2 batteries without issue.. in fact its setup to charge an extra battery that would be on a trailer... that is what the extra fused stud is for on the under hood fuse box...
The options for you would be to have the battery isolated or to be in series with the factory one....

 

If you read the owners manual for the "tow haul" mode button it indicates that it enables the alternator to output a higher voltage for charging a trailer battery...

 

I hope you meant in "parallel" with the factory one. 24V would probably kill most, if not all, of the electrical stuff.

Brandon2007Tahoe: Search this forum as I recall someone posting some info on an isolated second battery. Also the noise may be the Nav DVD drive.

 

Correct, not literally in series but in a non-isolated state, meaning both batteries could/would drain down over time,

 

what are the pros/cons of placing a 2nd battery in parallel versus isolated? how many of you have gone to the trouble to add a second battery? thanks.