A B2-series super battle droid was stranded on a scrap pile sometime between 4 BBY and 2 BBY.
At some point, this B2-series super battle droid ended up stranded and deactivated in a scrap pile somewhere in the galaxy. Between 4 BBY and 2 BBY, a droid by the named C1-10P, nicknamed Chopper, ended up stranded in the scrap pile after being lost in a fight just before that. When the droid tried to escape after realizing he would be turned into scrap by the owner of the scrap pile, he stole the activation codes and transmitted it throughout the scrap pile, allowing this B2-series super battle droid and many other droids to slowly activate.
When the owner, Bidvel, was about to incinerate the droid, the battle droid awoke with many other droids and worked together to help save their new friend. As Davil was being swarmed with droids, Bidvel was held at gunpoint by this droid and ordered to release Chopper. Bidvel ignored the droid, and ordered Davil to shoot all the droids, but this battle droid turned around and stunned Davil before he could continure to shoot droids. Bidvel took the opportunity to drop Chopper, but Chopper was saved after a nearby Droideka closed the hatch that would incinerate Chopper. Bidvel was succumbed by the droid and ordered to be released by them as he was their owner, but the battle droid replied that him and the rest of the droids were nothing to him, but now have a purpose.
As the Ghost arrived, Hera Syndulla, Sabine Wren, and Garazeb Orrelios marched on out to welcome Chopper back. Chopper told Syndulla that Bidvel knew about Chopper Base, as well as other useful things the Empire would want, and ordered Syndulla to erase Bidvel's mind. Chopper then went over to thank the battle droid for their help, and the battle droid said it was the least they could do, but was confused at what they do now. Chopper suggested that they would form a group to helping other droids, as another droid pitched in saying that Chopper should be their leader. Chopper refused, as his friends were more imprtant, which the droid understood and wished to meet Chopper again.
The B2-series super battle droid first appeared in "Escaping the Scrap Pile," the nineteenth issue of the comic series Star Wars Rebels Magazine', which originally released on June 29, 2016.