Backup Battery

[wh4tig0t]

I was thinking of constructing a backup battery for my 6700 useing recharables or AA's maybe 9v's (hasn't arrived yet, but I'm already thinkning) I would use it mostly on plane trips or just in case I can't charge my phone for some reason. Anyways what does the 6700 draw when its chargeing off of usb, any more then 5v 500ma? Also could you switch batteries while power is applied to the USB port? Has anyone made one of these before?

Edit:
Kind of like this -> http://www.engadget.com/2004/11/02/i...-battery-pack/