I just got a new ipad 2 weeks ago,2 or 3 times when i've used it for only about 30min at a time,starting out with a 100% charge,after i've used it with the battery only down to about 95% i'll set it aside in sleep mode,and after a few hrs i'll come back to use it and it's totally dead! it has done this the last several days,last night it did it so i charged overnight fully,used it for about 30 min this afternoon around 4 pm,just went to use it again a few min ago,now 11:41pm and it's totally dead again.What could be causing this?