BERLIN: If you have many apps open at the same time, you shouldn't be surprised if your phone battery runs out quickly.

After all, every open app uses energy. So why not just close the running apps to prolong your battery life? At first glance, it does seem to make sense to do that. However, in reality it's not that simple.

That's because a smartphone actually needs more time and processing power to restart an app than if it had remained open in the background all along.

If you close an app completely and then reopen it, you have to go through the entire start-up process again, explains tech journalist Steffen Herget. This means that the processor has to work harder, which in turn uses more energy.

On the other hand, if an app remains open in the background, it's in a sleep state that requires less processing power to wake it up again.

 - dpa