Multitasking Probably Isn’t Killing Your iPhone’s Battery

Recently one of our iPhone 3GS units began needing to be recharged before the end of the day. Quite unusual given that we were only sending a handful of text messages a day from that phone and hadn’t taken any phone calls on the day we noticed the problem. My wife mentioned that this had been a bit of a problem for a few days but it had suddenly gotten much worse that day.

For a moment the thought of new iPhones put a gleam in my eye. My wife quickly squashed that notion by assuring me that this was not a good excuse to get new iPhones. It might, in fact, be a reason to get rid of the ones we already owned if they couldn’t survive two years of light use. I better solve this one quickly. Why was a two-year-old phone with light use losing power so quickly?

A quick double tap of the Home button brought up the multitasking bar which showed several apps in the list. A quick recharge and closing all apps except phone and messaging brought battery life back to normal. Oh well, problem solved, time for a congratulatory pat on the back then on to other things. I assumed that having all those apps open was the source of the problem. Later, I started wondering why that phone was losing power so much faster than mine. While searching for the answer to that question I learned something about iOS devices, multitasking, and its effect on battery life.

I Thought I Understood Multitasking

Until I started writing this tip I assumed that an app in the multitasking bar was draining the battery. Leaving apps open drained the battery. Leaving many apps open drained the battery much faster than leaving just a few open. If leaving apps open drained the battery, closing those apps should stop that drain.

But when I thought about it, that didn’t explain my iPad experience. I routinely have several apps open simultaneously and have never had to recharge before the end of a day unless I’ve forgotten to charge it the day before. Clearly what I thought I knew about battery life in IOS devices was wrong. If leaving several apps open doesn’t always drain the battery what does?

What Actually Happens

If you’ve opened several apps recently and you double tap the Home button on your iOS device, those apps appear in the multitasking bar. Like many users, I assumed that all of these apps were running simultaneously. Well they’re not. This is actually a list of recently run apps. Some of these apps may still be running but others aren’t. Which apps are running depends somewhat upon what each app is doing.

The hard reality is that when pushed into the background by another app, most apps stop actively running within a few seconds. The memory and resources that were being used become available as needed without user intervention. These apps have little or no effect on battery life. The beauty of the iOS is that you don’t need to micromanage this process. Just as OS X manages resources on the Mac for most efficient use, the iPhone operating system manages this process on those devices without user intervention.

Some types of iOS apps can remain actively running in the background for extended periods of time. Audio players, location-deponent apps, iTunes syncing, and some apps that depend upon active network connections for some of their functions may remain active. In some cases, it can remain active for extended periods of time. If an app is going to drain battery life it will likely fall into one of these groups. In my case the culprit appears to have been a weather-related application repeatedly checking for severe weather updates coupled with the repeated search for a strong network connection.

The bottom line is that most users don’t need to micromanage which apps are open or closed on their iOS devices. Let the OS handle things. Until you experience problems, don’t worry about it. If you experience problems, try shutting down some of the apps that depend heavily upon network access or location services. The more time your device spends searching for wi-fi, bluetooth, or cellular networks to push your data around the more battery life you will use. You can find more information here.

Apple’s suggestions for network-related apps to check are here along with links to specific suggestions for preserving iPod, iPhone, and iPad battery life.

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