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: 4L DOOR EMERGENCY BATTERY M33406 FAILS OP CHECK. MAINTENANCE REMOVED AND REPLACED EMERGENCY BATTERY PACK M33406 AT 4L DOOR, S/N OFF 310818, S/N ON 341465 OPS CHECK GOOD. PER B777-3 AMM 33-51-06-960-802.