From Lexicanum

Weapons Batteries is a catch-all name for the majority of weapons present on star ships. Most vessels (especially Imperial ones) are pock-marked with gun ports and weapons housings. Within each one is a range of weaponry including plasma projectors, laser cannons, missile launchers, rail guns, fusion beamers and graviton pulsars. Batteries tend to be fired in one concentrated blast or following a pattern determined by the captain for maximum effect.¹

Sources

• ¹:Battlefleet Gothic Rulebook - p.20