As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NOTICED ELEC BURNED ODOR AND SMOKE IN AFT CABIN AREA, FOUND APU BATTERY THERMAL DISCHARGED. REPLACED APU BATTERY AND CHARGER. FOUND APU BATTERY WITH BURN SPOT ON BACK AND IN CONTACT WITH INSULATION REPLACED APU BATTERY AND CHARGER PER MM. REMOVED BUR INSULATION. POSITIONED INSULATION CORRECTLY