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 ACCOMPLISHMENT OF TASK CARD 26L00005005 EMERGENCY POWER SUPPLY UNIT SYSTEM TEST EMERGENCY POWER SUPPLY UNIT 13WL BATTERY FAILED. REPLACED BATTERY AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38.