As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TRANSIT CHECK, THE CENTER EMERGENCY LIGHTS ROWS 29 TO 33 TURNED OFF. MAINTENANCE PERSONNEL PERFORMED REVISION DETECTING THE BATTERY PACK FAILED; SO THE BATTERY PACK WAS REPLACED IAW AMM DMC-B787-A-33-51-07-02B-520A-A / 720A-A AND EMERGENCY LIGHT TEST WAS PERFORMED IAW AMM DMC B787-A-33-51-00-00B-320-A, TESTED CORRECT.