The Edge requires a buffer battery between it and the dynamo otherwise it is a right pain in the rear-end if my speed drops off, e.g., climbing up a hill. As to the tablet not interested in having it in an exposed position to charge. Using the battery I just need to top it up during the day and really don't need to but do it, but I do simply because I can. It works out well, being fairly secure in my handlebar bag. Overnight charging of the other devices is a simple process in the tent where I can charge two devices at once if I desire.