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Does killing apps in multitask menu save battery?

Italianblend

Italianblend

macrumors 68000
Original poster
Mar 21, 2011
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Fatima
I have a friend. Yes just 1.

She claims that killing apps from the multitask menu helps to save battery because the apps aren't running anymore. She repeatedly kills all of the apps that are running. It's not a memory issue but a battery issue. I've never heard this but it sort of makes sense. But I don't know the truth. Do we know the answer? Thanks.
 
It does, because many Apps are not really optimized. Especially apps that access the GPS on your iPhone tend to be a battery waster even when not in active use as I have found out.

Personally I always quit my apps after I used them. But this might also just be an old habit from my DOS/Windows times ;)
 
No, it doesn't matter at all in any way, with one exception: apps that are active in the background.

Only those apps make an impact on battery life or memory consumption. This can be an app that has requested to finish a task in the background (like upload a photo or something), a music player app, a gps app, or a VoIP app like skype. These apps are active in the background (the first option only for a maximum of 10 minutes, the second only while playing, the third only while using gps and the last is harder to define). Oh and apps specifically need to support this-- it's not like an app that uses gps will always run in the background if you exit it while it's doing something. It needs to be specifically made to do this.

Other apps, when in the background, are frozen. They are not scheduled for execution on the CPU at any time, until you open them up again. They are retained in memory for as long as possible. That is, if the foreground app doesn't need the memory, the frozen app can stay in it so it can resume more easily when you want it to. However, if the foreground app needs more memory than is free, the largest frozen app is killed and its memory freed for the foreground app.

So basically: removing apps from the multitasking bar is useless for this purpose. It has other purposes though.
 
i always kill those apps cuz they take up lots of ram even in the background as i can clearly see on sbsettings. its kind of OCD, as soon as i close an app i have to kill it too ^^
 
I'm a little confused: you say that some apps which are running might drain battery, then you say killing apps is useless for this purpose.
 
Apps doing background tasks may use battery. GPS apps may be the biggest drain. This isn't too common.

Other than that, background apps will be using a bit of RAM (not battery).
 
Italianblend said:
I'm a little confused: you say that some apps which are running might drain battery, then you say killing apps is useless for this purpose.
Click to expand...

Apps that are running in the background will. But most apps are frozen in the background and they don't. Can't, even. An app that is listed in the multitask bar is not necessarily running. Basically, that bar is a list of recently-used apps, a shortcut to the iPod control and for some reason it has a volume slider in there. Nothing more.

For this you need to very clearly understand what running means: it means the OS kernel schedules the process for execution on the CPU. There is no way an app that is not scheduled on the CPU can use battery because at that point, all it is is a few entries in some lists and a bunch of pages in RAM (which does not impact battery life in any way.)

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bushido said:
i always kill those apps cuz they take up lots of ram even in the background as i can clearly see on sbsettings. its kind of OCD, as soon as i close an app i have to kill it too ^^
Click to expand...

SBSettings lists the ram used but you're not taking into account that that ram is freed the instant the foreground app needs it. There is no reason to kill an app unless you want to accomplish roughly the same as force-quitting an application on the Mac: get it to stop misbehaving.

The foreground app is given the top priority in iOS; any background process that isn't a system process will be killed if it's using resources the foreground app needs. (System processes are exempt of course because they make sure the phone does stuff like communicate with the telco's network and make it so it is, you know, able to actually take calls.)
 
No it does NOT matter at all.
I have Apps that have been in Multi task(open) since day I bought phone almost year ago.
It hasnt effected my battery life or phone performance at all.
Its the beauty of iOS. The way Apple operates, once you hit the Home button, all Apps are paused in current state. This way Apps open but NOT being used are paused and are not using memory or battery.
I confirmed this with Genius at Apple Store.
Also, you can confirm it yourself.
Two ways:
1). An App open that uses location like Yelp.....hit Home button and watch the GPS symbol go away on top of phone.
2). You can go to, Settings, Location Services and see a list of Apps. The ones that have used your GPS location within last 24hrs will have a Grey GPS icon next to it. I haven't used Yelp in 3 weeks, no icon at all.

You can close Apps if you like, but Ive done both and this is why I currently have 29 Apps open.....3 of which have been open for almost a year.
It just doesn't matter. Enjoy Apple design. No need for Task Killers etc.

This said......it DOES depend on how you have your phone configured.
Example: Apps are paused, but if App is set to check for updates every 10minutes, then yes that App will use battery
But its not the fact its open, its the fact you have configured to stay notified.
Some DON'T do this for battery conservation. I have friends that have a saying about it, "My phone came with a charger, so when it gets low and I know I'm gonna need it, I charge, Id rather use features of a smart phone as opposed to running a crippled iPhone just to go another hour or two without charge"
I agree somewhat. If I know I'm gonna be away from AC power for a while, I may disable some of these things.
But if Im around power, who cares, just plug it up.
 
So if an app is scheduled to check for updates and its not in the multitask menu, does it still check for updates?
 
Xenomorph said:
Other than that, background apps will be using a bit of RAM (not battery).
Click to expand...

Using RAM means using battery. Power must be cycled through to keep the RAM alive. Although at the scales we're talking about for iPhone memory, the power usage would be extremely negligible.
 
Mumford said:
Using RAM means using battery. Power must be cycled through to keep the RAM alive. Although at the scales we're talking about for iPhone memory, the power usage would be extremely negligible.
Click to expand...

RAM is powered regardless of how much is being used. Inactive or free RAM is not powered down. It uses more power when you pull information from RAM or place it in there than if you're not accessing the information, but that's because you start using the CPU more, but how much info is in RAM doesn't affect battery life directly.

jW
 
Mal said:
RAM is powered regardless of how much is being used. Inactive or free RAM is not powered down. It uses more power when you pull information from RAM or place it in there than if you're not accessing the information, but that's because you start using the CPU more, but how much info is in RAM doesn't affect battery life directly.
Click to expand...

Of course you're right. Not sure why I would say that except I imagined that as part of the power savings mechanisms, I assumed Apple would put in some heuristics to not power unused memory, considering how they're trying to squeeze every milliwatt they can out of the batteries.
 
Italianblend said:
I have a friend. Yes just 1.

She claims that killing apps from the multitask menu helps to save battery because the apps aren't running anymore. She repeatedly kills all of the apps that are running. It's not a memory issue but a battery issue. I've never heard this but it sort of makes sense. But I don't know the truth. Do we know the answer? Thanks.
Click to expand...

There is no need, its a waste of time apart from the exception of apps that are running in the background. For example, a navigation app, that perhaps you wanted to quit running before you had reached your destination (which is when the app would quit normally)

This article explains very well why there is no need to kill apps to save battery etc. The article is a couple of years old but the information is still valid today.

http://whenwillapple.com/blog/2010/04/19/iphone-os-4-multitasking-explained-again/
 
Thanks but that link didn't open for me

The apps in play here are:

Facebook, Pinterest, Evernote, Calendar, Alarm, Messages, E-mail

I can't imagine those are a huge battery drain?
 
Italianblend said:
Thanks but that link didn't open for me

The apps in play here are:

Facebook, Pinterest, Evernote, Calendar, Alarm, Messages, E-mail

I can't imagine those are a huge battery drain?
Click to expand...

Depending on your mail settings that program could be a drain. Again see this article for example apps that can run background processes that might drain your battery. All others should suspend if written correctly.
 
Mumford said:
Of course you're right. Not sure why I would say that except I imagined that as part of the power savings mechanisms, I assumed Apple would put in some heuristics to not power unused memory, considering how they're trying to squeeze every milliwatt they can out of the batteries.
Click to expand...

It'd be cool if they did, but that would require some incredibly serious memory-management mojo. But this type of memory is, as I understand it, actually pretty power-efficient so I don't think you'd save very much if you did this.
 
get sysstatslite... run it... then double click home button and start closing apps and see the avail memory start increasing...avail and not being used = not using as much power.
 
jdaniel said:
get sysstatslite... and see the avail memory start increasing...avail and not being used = not using as much power.
Click to expand...

Wow. So wrong. Ram with ones and zeros that's allocated to a process does not use more power than ram with ones and zeros that's left over from a closed process and hasn't been initialized for a new one yet.
 
The main concern is the automatic updates. For example, eBay will tell me if someone has made a bid even when the app is in the background. But I doubt it uses that much more power, and I don't think it's worth the extra trouble.

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armoredsaint said:
any other easier way to kill apps besides double pressing home button and 'X' the app?
Click to expand...

There are tools to do this and tweaks that disable multitasking altogether, and you can get them on Cydia. I don't recommend that.
 
c'mon people be reasonable.


do you think apple would expect you to double click on the home button, and manually shut down apps after using them so that the system runs as intended in a phone that costs hundreds of dollars?

next iOS you might find a command prompt in notification center that requires you to type:

iOS7:\>cd Angry Birds
iOS7:\Angry Birds>exit
iOS7:\>freemem *.*
 
Last edited:
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