Battle droids are the main part the C.I.S army, using blaster rifles but not smarts. They were controlled via a control ship normally orbiting the planet, they also have their own ranking system. They also can man AATs and protect power generators. The battle droids are commanded by General Grievous and separatists such as Nute Gunray and Wat Tambor. They were various other models such as security droids, pilot droids, and commander droids. Before the Clone Wars the B1's were used as security for the Trade Federation. B1's were also manufactured by the Geonosians on the planet Geonosis. They were designed to look like their Geonosian creators.
After the execution of Order 66, Palpatine ordered that Vader use a turn off transmission to all the battle droids while on Mustafar. However some droids did not shut themselves down, such as the ship that general Kalani was in control of. And later he sided with the rebellion to try and defeat a squad of Stormtroopers.