As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW REPORTED THAT THE BATTERY FEED TEST DID NOT TEST CORRECTLY DURING PREFLIGHT CHECKS, FLIGHT WAS CANCELLED. THE MAINTENANCE VENDOR TROUBLESHOT AND FOUND A FAULTY BATTERY FEEDER PROTECTOR UNIT P/N 50284-003 S/N 98054. THE UNIT WAS REMOVED AND A NEW UNIT WAS REMOVED AND A NEW UNIT WAS INSTALLED. OPERATIONAL CHECKS WERE SATISFACTORY. THE AIRCRAFT WAS THEN RETURN TO SERVICE.