As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT IN BASE MAINTENANCE: EMERGENCY LIGHT BATTERY PACK M33409 FAILS OPERATIONAL TEST. REMOVED AND REPLACED AND PERFORMED GOOD OPERATIONS CHECK FOR EMERGENCY BATTERY PACK M33409 PER B777-AMM 33-51-06-960-803 AND B777-2 AMM 33-51-06-960-802.