As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE LOWER CARGO COMPARTMENT FIRE DETECTOR SN FA2392 HAS LOW BATTERY FAULT. SMOKE DECTOR REMOVED AND REPLACED BATTERIES AT DETECTOR FA2392. FOUND D BATTERY LEVELS LOW. REPLACED BATTERIES, LOWER CARGO SMOKE DETECTOR SYSTEM OPS CKS NORMAL, DEFERRAL M210845 CLEARED.