7080 battery box battery connections

Hi I have a 7080 and Im running with 2 batteries.  The problem I have is that the batteries ground through the battery box individually with a bolt.  I have cleaned up the holes and even used new bolts but it seams like I have a hard time maintaining a ground with one of the batteries? The inside battery the bolt goes threw the battery box and into another ground strap that goes to the casting on the transmition (good connection) The outer battery is set up to ground through the box in which I get a terrible connection and the tractor ends up cranking on just one battery which isnt enough. Any ideas?  Would grease around the bolt and the surface help maintain a good clean connection?

ok thanks steve I was thinking about that but was looking for something simple that I could of missed.  and your right it would be a easy solution

For what it’s worth, I have gotten rid of the lug style and went with stud bolt batteries. (7045 & 7080) The front battery has the pos + in front and same for the rear. That puts the negative stud out first when they swing out. I undo one nut and they are disconnected. 8000’s have negatives in front and they are undone as well. Old tractors, trucks, and combines aren’t getting any newer. And neither are their wiring.