I have a Back-UPS Pro 900 from 2012 (BR900GI) that has failed with an F05 error. A local APC service center has quoted me $85 (labour included) for the board replacement. I have no idea what the board number for my model would be, but the 640-3078A-Z_REV07 mentioned above seems to cost about $75 second-hand.
I'd love to keep using this device, but given the fact that a repair ''and'' a new battery are needed (it's 4 years old) ... buying a new one may seem a better option? I hate it when this happens!!