As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: EMERGENCY POWER SUPPLY UNIT 13WL FAULTING DURING SYSTEM TEST. MAINTENANCE REPLACED EMERGENCY POWER SUPPLY UNIT 13WL (AALA202312141769) AND THE BATTERY (AALA202312144809). A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.