I dunno, man. I just use it to describe module frameworks or collections that add a whole lot of utility on their own, or dramatically simplify getting started with your everyday tasks. First popped into my head when trying to describe Mojolicious, but more folks would probably understand Rails and that whole Active* collection of libraries as a battery pack.
Battery packs are usually more polished than what you get with Batteries Included, especially if they’re filling in some perceived gap in the standard library.