I was given a used iPad for Chrisrmas. The battery gauge read 100%. It was accompanied by a cable (USB) and an adapter for the power outlet both wrapped up as if completely new. When I plugged the cable into my iPad and the USB port of a computer the battery gauge continued to fall, as described in the (online) manual. I then connected it to a socket of my UPS for six hours and the charge went from 49 to 50%, lastly I connected it to a normal socket for 48 hours and now it reads 97%. How do I identify an original power cable and adapter? How does the iPad indicate charging status? The battery symbol does not change on my iPad when plugged in.