Silverado auxiliary battery

[chilson450]

2007 Chevy 3500 classic 6.0l gas

I recently had the auxiliary battery in my truck start smelling like rotten eggs. I could see it pushing fluid out the top vents. So I unhooked the battery and removed it from the truck and just left the cables unhooked for now. I'm just looking for clarification on how this system works. This is a gas truck that has an auxiliary battery, not dual batteries hooked in parallel like the diesels. It has an isolator that is supposed to disconnect the 2 batteries while the truck is off so it won't leave you with a dead battery if you are using it while the truck is off. When the truck is running, it's charging at the auxiliary cables at roughly 14.5. when I shut the truck off the auxiliary cables have around 6 volts.

So my questions are
1- Why was the battery smelling and pushing fluid?
2- Does this system use the 2 batteries together for starting and large loads like a snowplow?
3- Why am I getting the 6 volts at those auxiliary cables ends when the truck is off?

Thanks for any help given.

 

[64bawagon]

Sounds like the battery has an internal short. Make sure you put it outside, it's done.
My understanding is that the dual batteries on the gasser do not work together when starting. My main battery went bad on my 24 and the truck wouldn't start even with voltage in the 2nd battery.
The 2nd battery is more of a source for isolating high loads like a plow.