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 LIGHTS BATTERY PACK M33408 FAILS OPERATIONAL CHECK. REMOVED AND REPLACED AND PERFORMED GOOD OPERATIONS CHECKS FOR EMERGENCY BATTERY PACK M33408 PER B777-2 AMM 33-51-06-960-803 AND B777-2 AMM 33-51-06-760-802.