Battery replacement

[HWright]

Both battery indicators are black. They are original so 3yrs old. I will be spending three weeks in Colorado in March. How far can I push them?

 

[WBusa]

Both battery indicators are black. They are original so 3yrs old. I will be spending three weeks in Colorado in March. How far can I push them?

A better question is prolly... how far can you push your truck? :-laf If the answer is "not very far" and you have doubts about your batteries, then you need to get new ones. Cheap insurance.