Weapons Batteries are the main armament of many Imperial warships. They are large numbers of weapons such as heavy Plasma Cannons, large shell firing guns and similar heavy weapons grouped together for combined fire and improved efficiency.
Weapons batteries on cruiser sized vessels and larger, consist of large linear accelerators. These weapons accelerate fusion warheads to an appreciable fraction of the speed of light. The warheads are designed to detonate at predetermined ranges (useful for destroying ordinance), or upon impact with a massive object. In ranges of less than 15,000 kilometers, the linear accelerators are augmented by ranks of las/plasma/melta cannons. The addition of these weapons, while less destructive than the linear accelerators, vastly improves the fire power of the ship.
Chaos ships employ the same linear accelerators that the Imperial Navy uses, with a couple of key differences. The Chaos ships use more efficient linear accelerators. The linear accelerators are smaller, have greater range and are mounted in individual turrets. This coupled with logic engines that are more or less sentient, allow a Chaos ship to pack more of them in a given amount of space than the Imperial equivalent, and to fire them with a higher degree of precision.
Ork ships mount weapons that are essentially primitive cannons that use chemical explosions to hurl immense quantities of rock at the enemy. Occasionally an Ork vessel with cannabalized Imperial technology is encountered, but they are rare and most ships mount weapons not far removed from those on wooden ships in the seas of Earth forty thousand years before.
Tau ships utilise powerful railguns similar to the ones used by their ground forces but on a naval scale. Due to enormous power requirements power is routed to one barrel at a time and the sequence is timed so that the first barrel is reloaded by the time power is routed back to it.