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 OPERATIONAL TEST OF EMERGENCY LIGHTING SYSTEM PER JOB CARD 26L00025010 FOUND EMERGENCY POWER SUPPLY UNIT BATTERY MID RIGHT INOPERATIVE. REMOVED AND REPLACED MID RIGHT EMERGENCY POWER SUPPLY UNIT BATTERY PER AMM 33-51-38.