As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PREPERATION FOR APU RELAY REMOVAL FOUND BURNED SIGNES ON M2709004 BATTERY 10 MIN-R CASING. REMOVED R FCE BATTERY REMOVED ACC AMM 27-02-09-00A-520A. RH FCU 10 MIN BATTERY REPLACED AS PER AMM DMC-B787-A-27-09-00A-720A-A. OLD FCU BATTERY WAS SCRAPPED LOCALLY DUE TO RUNAWAY.