As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS IN BASE MAINTENANCE: 2L EMERGENCY BATTERY M33651 FAILS OP CHECK. MAINTENANCE REMOVED AND REPLACED EMERGENCY BATTERY PACK M33651 AT DOOR 2L, OPS CHECK GOOD. PER B777-3 AMM 25-21-07-000-801, AMM 33-51-06-960-802, AMM 25-21-07-400-801