As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DUIRNG AND OPERATIONAL CHECK OF THE EMERGENCY LIGHTING SYSTEM, EMERGENCY POWER SUPPLY UNIT 16WL DISPLAYS A BATTERY FAULT MESSAGE. REPLACED BATTERY FOR EMERGENCY POWER SUPPLY UNIT 16WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38.