Want to drain your smartphone's battery really quickly? Run a lot of apps. Want to drain it so fast that you'll be sprinting for the nearest outlet? Run a lot of free, ad-supported apps. This is the conclusion reached by a team of researcher from Purdue University. They found that third-party ads running in free apps downloaded from the Android Market (now the Google Play Store) could account for a whopping 65-75% of the battery drain coming from an app. That isn't to say that ads themselves are draining three-quarters of a smartphone's battery, just that the vast majority of processing power, memory and data consumption for most free apps goes towards serving ads.