Installing iOS 5.0.1 over-the-air

Today I've installed the new version of ios over the air with no problem on my iPhone 4. From the preferences I selected software update and after asking if I wanted to install the software it started downloading. In a couple of minutes it finished and then forced me to plug in the battery cable because it requires at least 50% of battery. In 5-10 minutes my iPhone was online again :)