[mitmaks]

I have 01 Ram 5.9L Cummins and it has dual batteries. One of the batteries posts constantly oxidize, I'm not sure why. I cleaned posts, terminals, put insulators under terminals, sprayed with battery cleaner/protector.
It still oxidizes no matter what while 2nd battery hasn't oxidized since I've cleaned over a year ago.

[poncho62]

Make sure the connections are tight...at both ends of the cable.

I bet its the negative post

[SSedan64]

90's Chevy Diesels used to do the same thing where the 2 cables joined at Bat. Appeared the Cables were too small, they'd get hot, loose then corrode.

[S10 Racer]

Originally Posted by mitmaks

I have 01 Ram 5.9L Cummins and it has dual batteries. One of the batteries posts constantly oxidize, I'm not sure why. I cleaned posts, terminals, put insulators under terminals, sprayed with battery cleaner/protector.
It still oxidizes no matter what while 2nd battery hasn't oxidized since I've cleaned over a year ago.

Clean them again real good, check all connections at the battery and use a dielectric grease on the posts before you install the cables.

There is also the chance that the battery post is loose in the case allowing fumes to escape under the terminals. You might try switching the two batteries around. If the 2nd battery starts corroding, it has to be something with the battery.

[T-bucket23]

A bad connection or a weak battery. When a battery gets weak it needs more charging which results in more off gassing which causes the corrosion. A bad connection also has the same effect. Most likely if you replace the battery the issue will go away.