As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BEFORE PUSHBACK, FLT ATT REPORTED ACRID SMELL IN CABIN. EVACUATED AIRCRAFT VIA MAIN L2 DOOR. FOUND APU BATTERY DEFECTIVE, CAUSING FUMES IN AFT CARGO COMPARTMENT. REPLACED APU BATTERY AND APU BATTERY CHARGER PER MM. RAN APU, BATTERY AND CHARGER CHECKS OK PER MM.