2011 Sierra HD dual battery question

DaBomb6988 · September 6, 2014

I have a 2011 Sierra 2500HD 6.0 gasser with the TP2 factory dual batteries. What does the second battery do? When does it get charged? And how can I tell if it is being charged? Here's what brought these questions on. Last weekend I put the second battery on a battery tender. It took over 24hrs to bring the battery back to about 12.6v. Not knowing it would take that long to charge I never tested the battery to see what the volts were. So I am wondering if the second battery is being charged.

MORSNO · September 7, 2014

They should be wired in parrallel and work and charged together.

DaBomb6988 · September 7, 2014

Ok thanks. I hooked a volt meter to both batteries when the truck was running and the aux battery was only showing 12.38v. So I will have to dig a little deeper.

dewfpo · September 10, 2014

With Option TP2, the second battery is used for auxiliary loads (lights, snowplows, winches, etc... It is not used to start the engine. When the engine is running, it is being charged along with the primary battery.

DEWFPO