What was found
*GROUND RETURN* EICAS ADVISORY ELEC STBY SYS AND STATUS ELEC MAIN BATTERY DISPLAYED ON TAXI OUT. MAINT MSG 24-40361. CHKD CMC AND FOUN MMSG 24-40361 AND FOLLOWED THE FIM TASK 24-30-F1-26A-421.THE MAIN BATTERY AND APU BATTERYCHARGER SWPPED BUT NO HELP. CURRENLTY MAIN BATTERY CHARGER S/N#130119AND APU BATERY CHARGER S/N#1301049 P/N C3808-902.BRWD THE BATTERY FROM AIRINDIA ENGINEERING SERVICES LTD. AND REPLACED THE BATTERY PER BATTERY OFF S/N#00005836 B787-A-24-31-01-02C-720AA P/N#B3856-904 BATTERY ON S/N#00004465 AMM B787-A-24-31-01-01-02C-520A-A AND INSTALLATION PER AMM BATTERY, AIRCRA OFF 78-2431-9-9005 5836 ON 78-2431-9-9005 4465