Lost tribe of Westwood

I going to try to figure out how smart I am. The batteries on the stratus and the truck crapped out this week. I'm hoping it is only the batteries. I will first try to start up the truck. This one has the oldest battery. Both vehicles have the same symptoms and will start with the help of a jump. They just won't hold a charge. Car repair may be easy to some, but to me it is rocket science.