Hello All and Happy New Year!

I went to start my truck today. Hit my remote start and usually I hear my truck, can wake the dead with it. Nothing. I head outside and I can open the doors and lights go on but dead battery, won't turn over. I jumped it with my wife's Envoy and its fine now. I am in sales and do sit in my truck a lot and fire up the macbook for work and stuff. Some times I keep it running some times I don't. I do charge my iPhone, macbook and blue tooth daily, not at all the same time and macbook only when driving.

My truck is a 2011 GMC 2500HD Crew 6.0 and has 47K on it. I have the original factory battery. I do have a spot for a 2nd battery and wanted to know the best way to hook it up. I will likely buy 2 new batteries (Interstate or Optima), just not sure how to wire it. Ideally in series I'm thinking to give a longer time to drain. I do not want to have to pop the hood and connect the 2nd battery as a jumper. Just looking to have more power for the gadgets I use daily. Not even sure if its factory wired for a 2nd battery. I do have the snowplow prep package with bigger alternator.

Any and all ideas and schematics would be helpful and appreciated. I can do most work on my vehicles just not the most comfortable with electrical.

Thanks in advance