Brand new ipad owner. I am at 16% of battery of the new ipad and have yet to charge it. I am leaving for a flight in a few hours and will be unable to drain the battery and charge it back up. I know that 16% will probably not get me thorough a few movies. Can I charge it up now or am I supposed to let it charge all the way down until it shuts off on the first use before the first charge? Thanks!