Truck has two batteries. I don't row or have AC essories to power do if need the 2nd battery. If I keep the 2nd battery what kind and how should it be hooked up? Thanks in advance for your time.

 

So the 2nd battery isn’t hooked up? A lot of those hd trucks came with two battery trays but only one battery. If it’s diesel then you will need two batteries.

 

Chevy k3500. Battery isn't hooked up now. Truck finally started. But if I decide to hook up 2nd battery what's the best way to do it.

 

You’ll need a cable to link + to +. - to the frame or block. You should load test both batteries first, a weak battery will slowly kill a good one. The batteries should really be replaced at the same time and paired for life.