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 BATTERY FAILED EMERGENCY POWER SUPPLY UNIT SYSTEM TEST IN REF WITH JOB CARD 26L00005005. REMOVED AND REPLACED EMERGENCY POWER SUPPLY UNIT 10WL BATTERY AT DOOR 1L PER AMM 33-51-38.