As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI ,APU BATTERY, NO STBY STATUS MESSAGE DISPLAYED. ADVISED BY MTC TO RETURN TO PARKING (BTB). MTX GROUNDED ACFT AND REMOVED AND REPLACED APU BATTERY IAW AMM 24-31-04 AND REMOVED AND REPLACED APU BATTERY CHARGER IAW AMM 24-31-04. OPS CHECK GOOD. ACFT REMAINS NO ETOPS.AND RETURNED AC TO SERVICE.