Google just announced the launch of a new metric for app developers that tracks battery usage. If a developer consistently violates Google’s battery usage guidelines, a warning will appear in the Play Store to alert end-users.This metric will keep a particular eye on so-called “wake locks,” which are when smartphones are deterred from entering sleep mode by battery-hungry apps that want to run background processes when the screen is off. Google states that “wake locks” are a “heavy contributor to battery drain” and has developed a threshold for what is considered acceptable for apps running in the background.A user session is considered excessive if it lasts more than two hours of non-exempt “wake locks” within a 24-hour period. There are exceptions for background processes that provide clear benefits to the user. Examples of these exemptions include audio playback and user-initiated data transfers.If a developer doesn’t fix the underlying “wake lock” issue, they get slapped with a visible warning. The Play Store label says that “this app may use more battery than expected due to high background activity.” That will likely turn off potential downloaders. No user would want to pop one of those apps on their phone.Google will take a more aggressive stance, making certain non-compliant apps ineligible for discovery in specific sections of the Play Store. These new rules take effect on March 1st, leaving us with only a few months to see just how rapidly an Android phone’s battery can drain from full to empty.