I have a 2009 Tahoe with what looks like a battery tray on the right front looking at motor from front, battery using is on the left rear ,what is the empty one for and why?

 

2nd battery

 

but will it give 12v or 24v and what is the purpose,just bought it.

 

It's a 12 volt system. The batteries will be a parallel circuit.

 

This same chassis is used for diesels. They require two batteries for starting. Police package Tahoes also get two batteries.

I've actually converted both of my trucks to dual batteries. My daughter has the one at college in upstate New York, and I don't want her stuck with a dead battery in the middle of winter. We do a lot of camping with my Suburban, so I like the second battery when we're boondocking. Kinda hard to call AAA for a jump start when you're in the middle of the woods. All factory parts were used, so they each have the ignition-switched battery isolators, to prevent any possible drain of both batteries.

 

thank for the answer, what the extra cost except battery ,and could interstate batteries do it. Or take it to dealer? Wonder what cost would be after purchase of battery..

 

I did it myself. Probably $350 in parts, bought online, plus the cost of the second battery.

Here's the thread I used as a reference: TP2 Upgrade

 

I have an Optima yellow top in my 09. It's now 8 years old with 125,000 on it, and have never had an issue starting it.
I do run dual batteries on my boat though

 

My last Silverado was set up for two batteries like intheburbs posted. I don't remember it having cables just the base for one. It was a company truck.

 

Got me thinking about mu 03 suburban if it set up for a second battery?