What was found
STATUS MESSAGE "MAIN BAT CHGR". REPEAT WRITE-UP. AIR RETURN TO EWR. PERFORMED T/S PER FIM 24-31-00-815-802 PG 2; BLOCK 19. HARD FAULT REMOVED. REPLACED MAIN & APU BAT. AS PRECAUTIONARY ACMX MEASURE PER TOMC MAA #7993 IAW 777-200 AMM TASK 24-31-01 & 03. ALSO R&R'D MAIN BAT. SHUNT BLOCK PN MS91586-7AS PRECAUTIONARY. SYSTEM TEST GOOD. ROTABLE PARTS CHANGE WAS INDICATED - TT # 1474345 S/N OFF 05981 TT # 1485303 S/N OFF 02005 BATTERY, AIRCRAFT OFF 99-2431-9-9001 5981 ON 99-2431-9-9001 0424 BATTERY, AIRCRAFT OFF 99-2431-9-9001 2005 ON 99-2431-9-9001 6796.