What was found
EMERGENCY DECLARED, WHILE IN CRUISE FL 350 JUST AFTER TOC A FAINT ACRID SMELL WAS NOTICEABLE AND VISIBLE. RAN SMOKE, FIRE, FUMES CHECKLIST. IRO SEARCHED FOR POSSIBLE SOURCE BUR COULD NOT LOCATE. REPLACED THE MAIN BATTERY CHARGER IAW AMM 34-31-02/401. OK FOR SERVICE. REPLACED MAIN BATTERY PRECAUTIONARY IAW AMM 24-31-01/401 DUE TO HISTORY WITH MAIN BATTERY CHARGER. BATTERY AND CHARGER ARE FUNCTIONING NORMALLY IAW AMM 24-31-01-710-801. OK FOR SERVICE.