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 BATTERY FAILED SYSTEM TEST IN REFERENCE WITH JOB CARD 26L00005005. MAINTENANCE REPLACED EMERGENCY POWER SUPPLY UNIT 13WL BATTERY IN REFERENCE WITH AMM 33-51-38, EPSU SYSTEM TEST OK.