Dwn4BassAlan

if I could do what i wanted to my truck, I'd have no batteries under the hood

Alright.. Im half asleep, so dont be too rough on me lol

Your stock battery is most likely lead acid, and the XS batts are AGM. Lead acid batts generally have a lower resting voltage than AGM. When your car isn't running, the batts are resting. If your batteries are connected in parallel, the voltages between the batts try to level out to maintain the same voltage. As a result, your AGMs will rest lower. There's been controversy about the life span of the AGMs being shorter.