IF they were ran in parallel, I agree. The yellow top has an isolator between it and the starting battery.
Been there, done that....on my 06 Gm 5.3 and now this 2010 5.3.....I spent the large on both of them having a proper draw test(s) done....3 computers that shut off at different times and have different milliamp draws....radar detector, stereo memory, command start(s), and whatever else lurks....both these trucks just EAT batteries. When you let everything go "to sleep" there is still 45 (?...going by memory) milliamps. If you do the math, it will draw the battery below 12v in 3 days....then it won't start without a boost. In the winter it is two days. Both my GM's were like this. By adding an isolated second batt, I can always "self boost". If I hit the command start (factory) and it doesn't go, means the main batt is below a certain voltage. I generally just have to go out with the key and hit it....the isolated battery kicks over when the main batt is low, but won't work with the command start. This past weekend with the main batt frozen solid, even the "self boost" didn't work.
Just plugs into cig lighter. I tell ya, I've jumped through the hoops on these GM's. The aftermarket stereo in my old one....found out that when you open the door, or hit the auto locks (or any draw occurs for whatever reason) it would turn the amps on, because the door chimes and beeps go through the stereo....the stereo powers up, the amps power up.....sooooo I had the stereo shop set the amps up to only come on with the key on ONLY. That helped some of the draw....but not all. I likes me my Gm 1/2 ton car-trucks, but gonna be a Dodge in the driveway soon if I gotta keep doing this.....
