This is scientific American's 60 second science. I'm Christopher Intalyata. Got a minute?

Smart phone battery down to 10%? Time to turn down the brightness on the screen, right?

It's a classic strategy to squeeze more juice

from the battery, and it works.

But that trick might be less effective than you think.

Because it turns out nearly half the battery drain

on a phone happens when the screen's not even on.

So says a study presented at a meeting of the Association for Computing Machinery in Portland, Oregon.

Researchers eavesdropped on the activity of more than 1,500 Android phones,

specifically the Samsung Galaxy S3 and S4,

and they used an app they developed called E-Star Energy Saver.

The app logs the energy drain of the phone's apps and activities as they happen.

And you can try out E-Star Energy Saver yourself, if you have an Android.

They found that some 45% of the battery

drain happened while the screen was off and a lot of that energy suck was

apps updating in the background, downloading headlines and weather while you're not actively using them.

And different versions of the same app require different energy supplies.

For instance, some versions of the Facebook app were twice as energy thirsty as other versions, so

app version choice could slow your battery drain.

But one of the most hidden energy draws, zapping 12% of the battery, was just cellular paging.

The pings from a cell tower every 1.28 seconds to tell your phone if a call or text is on the

way, which is ultimately the price of being connected.

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