As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: DURING PERIODIC SERVICE CHECK CIDS 1 EMERGENCY POWERS SUPPLY UNIT TEST, EMERGENCY POWER SUPPLY UNIT 13WL BATTERY FAILED TEST. REPLACED BATTERY AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38