my sister's iphone stopped charging. apple genius concluded that the iphone was corroded. no chargers worked, wall-plug, computer, or car-battery. but when i plugged the iphone into an ipod portable speaker it charged. i cannot find any difference between the iphone charger, ipod charger, or the portable speaker dock. they all look identical, same length, width, etc. any recommendations on how to connect the iphone to a computer again?