B1-0516, also known as Bats, was a B1-series battle droid serving within the droid army of the Confederacy of Independent Systems. During the era of the Clone Wars, B1-0516 participated in a battle on Horain against the forces of the Galactic Republic, where a random blaster shot caused a short circuit in his processor. Due to this damage, B1-0516 began fighting alongside the Republic army, offering assistance to General Obi-Wan Kenobi and Captain Rex, who decided to call the battle droid "Bats" for the sake of easier communication.
During the Clone Wars in 20 BBY, B1-0516 was a member of a unit belonging to the Separatist Droid Army stationed on the planet Horain within the Crantori system. While engaged in a battle against the Galactic Republic, B1-0516 encountered Jedi Master Obi-Wan Kenobi and Clone Captain Rex accompanied by a group of droids. The Separatists clashed with the pair, and during the conflict, Kenobi's deflection of a blaster bolt resulted in damage to B1-0516's processor. As the droid began to process the situation, it started to question the reason for so many battle droids attacking them. It voiced its opinion that the skirmish seemed unfair, given the overwhelming number of droids compared to the two individuals. This reasoning led the droid to choose to support the pair in repelling the advancing Separatist forces.
B1-0516 saluted his new commanders and offered his services to the Republic, receiving the nickname "Bats" in the process. As a fresh wave of Separatist reinforcements started moving toward their position, Bats drew the attention of the droid commander, appearing from behind a destroyed All Terrain Attack Pod alongside Kenobi and Rex. He claimed that the two were his prisoners, and the commander praised Bats for his efforts, stating that the pair needed to be taken to Count Dooku without delay. Revealing his newfound malfunction, Bats quickly turned against the Separatists, wielding two E-5 blaster rifles and destroying several droids while his superiors made their escape. Despite putting up a considerable fight, Bats was eventually overpowered and captured, being transported to a nearby Separatist garrison for analysis.
At the garrison, the commanding tactical droid suggested that Bats' original programming should be restored by wiping his memory, mentioning that there were still numerous clone troopers on Horain who needed to be eliminated. Bats resisted this attempt, fighting off the nearby guards using a detached arm from another battle droid. The tactical droid tried to reason with Bats, ordering him to immediately submit to reprocessing. Continuing his resistance, Bats prepared to fight off his oppressors until an unregistered Armored Assault Tank broke through the garrison's defenses. Assuming the infiltration was caused by another malfunctioning battle droid, the tactical droid ordered the tank to be destroyed, only to see Kenobi emerge from the tank, swiftly eliminating an OOM command droid and rescuing Bats, who had taken the opportunity to attack the T-1 with the detached arm. Entering the hijacked tank, Bats and his companions quickly left the garrison and returned to the Republic Evacuation Point. Upon reuniting with Anakin Skywalker and his forces, Kenobi and Rex introduced Skywalker to Bats and suggested that an undercover battle droid could be valuable for future missions. Bats then boarded a Republic gunship with his companions, begging Skywalker to give him his own lightsaber.