Coming from an iphone 4, i recently picked up a used ipod touch 4th gen. I restored by iphone backup to it and kept all the same apps and settings. However i am very dissapointed by the battery life. Overall it seems poor. As a particular example, a 20-minute facetime conversation took the battery from ~65% to 30%. Charging overnight only reaches a maximum of 96%. Any advice? is the hardware defective or are my expectations too high?