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 (10WL) FAULTED DURING EMERGENCY LIGHT TEST. MAINTENANCE REPLACED EMERGENCY POWER SUPPLY UNIT AND BATTERY PACK (SEE AALA201801109017) PER MM 33-51-38-400-001-A AND PERFORMED SATISFACTORY OPERATIONAL CHECK.