Recently, some users have been noticing some strange things regarding their Nexus 5 battery life (along with other devices) running Android 4.4.2. It seems that a bug in the latest version of Android is causing the camera to ramp up the CPU and thus cause massive battery drain throughout a day's use. It was first thought that this was a bug related just to the Nexus 5, but it looks like this one goes a little further than that, and users of other devices have reported the same issue. In a big tracker, a Google employee has come out and said that they have some fixes ready and that an update could be on its way soon.
Speaking in a bug tracker a Google employee has said that "we believe we have fixes for the current high CPU reports on N5 due to mm-qcamera-daemon, and they will be included in the next maintenance update." It's well worth noting that this bug fix release won't apply to other devices, such as Samsung devices. This maintenance release, which could end up being Android 4.4.3, is destined for the Nexus 5 only at this point. Besides, as this particular Googler notes, if you have the same problem with a Samsung, HTC or Motorola device then you should get in contact with them.
The root of the problem appears to be some apps that use the camera, and thus call upon the "mm-qcamera-daemon" process some of you can see eating up your battery (which you can check from your system settings under the battery menu). This is because your device has camera processing from Qualcomm, which more than likely means you're running a Snapdragon-powered device. Skype has been called out a number of times as the main culprit for causing this sort of battery drain but other apps are just as likely to cause the same issue. It's unclear just when this update will be hitting the Nexus 5 (and possibly the AOSP as well), but we'd imagine that Google would want to get this one out pretty quickly. Nobody likes to charge their phone two or more times a day, am I right?