What was found
LIGHTS TESTED NORMAL FIRST FLIGHT OF DAY YESTERDAY & TODAY. WHILE IN MDW, ANOTHER LATITUDE CAPTAIN ASKED TO CHECK EMER LIGHTS TO COMPARE BRIGHTNESS, TURNED OUR EMER LIGHTS SWITCH ON AND NOTHING ILLUMINATED. CONTACTED MX AND ASKED TO ATTEMPT W2 POWER DOWN, WHICH I DID, AND AGAIN NO ILLUMINATION OF ANY LIGHTS. REMOVED INOP BATTERY CHARGER AND INSTALLED A NEW BATTERY CHARGER IAW MM 33-50-06. OPS CHECK GOOD NO DEFECTS NOTED.