As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHILE ACCOMPLISHING OPERATIONAL TEST OF EMERGENCY LIGHTING SYSTEM BAT/EPSU (12WL) OWD R FAULT MESSAGE DISPLAYED. MAINTENANCE REPLACED THE EMERGENCY POWER SUPPLY UNIT 17WL BATTERY (AALA202410076043) AND EMERGENCY POWER SUPPLY UNIT 16WL BATTERY (AALA202410076891). A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO FAULTS NOTED,