Several discussion boards and Apple-centric sites report a potential battery issue with the recently-released iOS 6.0.2 update. Users report reduced battery life, even when not using their iOS device.
In addition, Apple appears to be working on it, and has removed the online Support Note for the update, a frequent sign that an update to an update will be forthcoming. Not that iOS 6.0.2 update page had said much, other than it targeted a “bug that could impact Wi-Fi” on the iPhone 5 and iPad mini.
According to a detailed post on TidBITS, the problem with the WiFi fix update appears to be with WiFi.
Michael started a car trip that takes him past numerous Wi-Fi access points in Santa Monica with the battery at 97 percent. When he arrived at LAX, his iPhone 5 was warm and had dropped to 85 percent. He then put it in Airplane Mode for the return trip, and arrived home with a cool iPhone and no change in battery percentage. Of course, Airplane Mode turns off all other radios too, so it's far from conclusive, but indicates that the problem may be related to wireless communication in some fashion.
Reading the TidBITS report and others — along with the missing page at support.apple.com — I can only suggest holding off on installing the update until more information is available. And if you have already installed the update, then be aware of this behavior and carry a recharger with you.