Currently, I have a USB charge cord for a 1st gen iPod touch, 2nd gen iPod nano, and 1st gen iPad. I have a wall charger that i purchased to use with my touch and nano, and a wall charger that came with the iPad. Are all these cords and chargers interchangeable? If not, what is the problem? Does the iPad wall charger have too much power output that will fry the touch and nano? Will the wall charger for the touch and nano provide enough power to charge the iPad without hurting the battery? Thanks.