If cell phone batteries on a smartphone have been draining a little bit faster than usual, the suspect may be ads in free applications, according to researchers from Microsoft and the University of Purdue. People who use many free apps may want to invest in battery packs or other useful accessories to help the phone last longer.

"Most smartphones can show a basic breakdown of which resources are consuming the battery life … but the way in which individual apps use that power is more opaque," Ars Technica said. "To unpack the details at this level of power consumption, three researchers developed a tool called 'eprof', a 'fine-grained energy profiler.' Eprof can track power used at the level of individual threads as well as routines running in an app, and can also track what the authors call 'asynchronous power behavior.'"

As an example, researchers found that the free version of Angry Birds has 45 percent of its energy tracking the user's location and serving ads to the app. Over a 3G connection, this can take up a lot of the phone's energy and make it die much sooner than it normally would.

Violeta-Loredana Pascal writes on Everything PR that with cell phone batteries and accessories that help charge them, it may be worth it to use these free apps if people find them to be fun or useful.