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 EMERGENCY LIGHTING SYSTEM TEST LEFT-HAND OVERWING EMEPRGENCY POWER SUPPLY UNIT BATTERY WAS INOPERATIVE. MAINTENANCE REPLACED THE LEFT-HAND OVERWING EMEPRGENCY POWER SUPPLY UNIT PER AMM 33-51-38 AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK.