I just got a sharp ms-md702. i'm a noob, and hoping to use it next week to record some jam sessions on a camping trip. the guy who sold it said the battery would charge in the unit. it works plugged in, but no light or display indicates charging. it's been plugged in three hours and does nothing without the adaptor. if anyone's had this unit, should it be charging, or do i need an external charger? does anyone know how to get a AA adaptor for it, or how to make one? i was hoping to use it for multiple nights of recording. thanks!