What was found
DURING PREFLIGHT OVERHEAD ELEC LIGHT WAS ILLUMINATED. ACCOMPLISHED P5-13 BITE PROCEDURE IAW FIM TASK 24-31, TASK 801. FOUND FAULT MESSAGE FOR BATTERY CHARGER INOPERATIVE. CLEARED FAULT. ACCOMPLISHED BATTERY CHARGER OPERATIONAL TEST IAW AMM 24-31-21-710-801. NO DEFECTS NOTED. ACFT OK FOR SERVICE. REPLACED MAIN BATTERY & MAIN BATTERY CHARGER WITH SERVICEABLE ONES. REF MM 24-31-21. R & R NEW AUX BATTERY REF 24-31-11. PERFORMED BATTERY OPS CK 24-31-11, STEP I. SYS CKS NORMAL. PERFORMED MAIN BATTERY CHARGER REF. 24-31-21. SYS CKS NORMAL.