Does killing apps in multitask menu save battery?

Italianblend

macrumors 68000
Original poster
Mar 21, 2011
1,785
237
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.
 

Galatian

macrumors 6502
Dec 20, 2010
326
62
Berlin
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 ;)
 

CyBeRino

macrumors 6502a
Jun 18, 2011
732
26
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.
 

bushido

Suspended
Mar 26, 2008
8,070
2,754
Germany
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 ^^
 

Italianblend

macrumors 68000
Original poster
Mar 21, 2011
1,785
237
Fatima
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.
 

Xenomorph

macrumors 65816
Aug 6, 2008
1,307
552
St. Louis
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).
 

CyBeRino

macrumors 6502a
Jun 18, 2011
732
26
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 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.)

----------

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 ^^
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.)
 

Photogdave

macrumors regular
Dec 20, 2011
155
11
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.
 

Italianblend

macrumors 68000
Original poster
Mar 21, 2011
1,785
237
Fatima
So if an app is scheduled to check for updates and its not in the multitask menu, does it still check for updates?
 

Mumford

macrumors regular
Oct 8, 2006
181
2
Altadena, CA
Other than that, background apps will be using a bit of RAM (not battery).
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.
 

Mal

macrumors 603
Jan 6, 2002
6,249
17
Orlando
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.
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
 

Mumford

macrumors regular
Oct 8, 2006
181
2
Altadena, CA
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.
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.
 

Fatboy71

macrumors 65816
Dec 21, 2010
1,221
151
UK
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.
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/
 

Italianblend

macrumors 68000
Original poster
Mar 21, 2011
1,785
237
Fatima
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?
 

mrapplegate

macrumors 68030
Feb 26, 2011
2,818
8
Cincinnati, OH
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?
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.
 

CyBeRino

macrumors 6502a
Jun 18, 2011
732
26
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.
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.
 

jdaniel

macrumors 65816
Mar 21, 2009
1,150
14
Lviv, Ukraine
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.
 

Schtibbie

macrumors 6502
Jan 13, 2007
304
3
get sysstatslite... and see the avail memory start increasing...avail and not being used = not using as much power.
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.
 

faroZ06

macrumors 68040
Apr 3, 2009
3,387
1
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.

----------

any other easier way to kill apps besides double pressing home button and 'X' the app?
There are tools to do this and tweaks that disable multitasking altogether, and you can get them on Cydia. I don't recommend that.
 

Troneas

macrumors 65816
Oct 26, 2011
1,378
58
At the alternatives section.
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:

Similar threads

  • Retromac2008
1
Replies
1
Views
520
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.