First thing to do is give each cable clamp a good twist with channelocks at batt posts. Sounds llike a crappy bite on posts.
please don't take this as me picking on you, but that is a good way to break the posts away from the internal plates, as well as possibility of cracking the case in the area the posts protrude from it.
the connections don't need to be tightened to the specs of a head bolt.
it's best to remove the cable and clean both the post and the cable end good, then re-install. tighten snug until you can't move the cable end by hand, then a tick more.
a spray of wd-40 now and then prevents the green "stuff" from growing in and around the connection.
just my experience and opinion from 55+ years of playing with cars. your mileage will vary.
