I can’t state categorically that the recently released iOS 6.0.2 for the iPhone 5 and iPad mini will hurt battery life, since evidence is still anecdotal and battery life testing requires time. And yet, while there are not so many reports to indicate that the problem is universal, or even necessarily widespread, at least three people on the TidBITS staff noticed unusual battery drains over the 24 hours after updating, and a quick sanity check on Twitter revealed a number of others who have also seen surprisingly low battery levels since updating to iOS 6.0.2.
In my case, when Michael Cohen raised the issue on our staff list at 12:30 PM, my iPhone 5 was at 73 percent. That’s a bit low, given that I’d barely used the iPhone, but I don’t know that I started the day with a full charge. However, 90 minutes later, at 2 PM, I was down to 55 percent — an 18 percent drop — without having used the iPhone at all. Another 90 minutes later, at 3:30 PM, I lost another 12 points to drop to 43 percent, and as I write this at 5:30 PM, I’m down to 28 percent, a 15-percent drop in two hours. And again, apart from the occasional push notification from Twitter turning the screen on, I haven’t used the iPhone at all during this time.
I am not seeing the problem that bit me when I first upgraded to iOS 6, when Safari bookmark syncing to iCloud was failing repeatedly (see “Solving iOS 6 Battery Drain Problems,” 28 September 2012). None of the logs in Settings > General > About > Diagnostics & Usage > Diagnostics & Usage Data show anything that looks unusual at this point.
Our speculation, based on some quick testing that Michael did, is that the problem is related to a change in Wi-Fi behavior, which maps with Apple’s sole release note for iOS 6.0.2: “Fixes a bug that could impact Wi-Fi” (see “iOS 6.0.2 Squashes Unspecified Wi-Fi Bug in iPhone 5 and iPad mini,” 18 December 2012). 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. Subsequently, I manually toggled Wi-Fi off and back on, and that seems to have resolved the problem for my iPhone 5.
For the moment, my advice to anyone who has not noticed any Wi-Fi-related problems with iOS 6.0.1 on an iPhone 5 or iPad mini is to hold off on upgrading to 6.0.2 until more is known. If you are experiencing Wi-Fi weirdness, it may be worth the as-yet-unquantified risk to battery life to improve your wireless connectivity. And if you have already upgraded, be a little more aware of your battery life in case you need to charge more often to get through a long day.