I think you can create a custom post type of brands and inside that post type, you can add a repeater field of the Battery Types. This way you can set the URL slug, and it’s accessible as a post. On the Battery subpages, you can add a repeater with Post Object Field in it which is assigned for the Brands custom post type.
I hope this makes sense.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users