How can this be labeled as useless? Of course it saves battery life. It shuts down the application instead of having it running in the background.
Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Does killing apps in multitask menu save battery?
- Thread starter Italianblend
- Start date
- Sort by reaction score
As already stated, most apps don't run in the background, they're simply held in RAM until it's reopened or the RAM is needed for another app.
I understand it's stored in the RAM, which makes the iPhone run slower, but does using more RAM not mean using more battery as well? I figured RAM use would co-incide with that of battery use.
No, it doesn't make it run any slower because if any RAM is needed from an app, it would be taken.
RAM being empty or full has no bearing on battery life.
If thephone needs the ram, it dumps the app.
Only a small number of apps truely run in the background. Any app that uploads, for example, may be set to use the "Finish Task" form of background running - but that would only go on as long as it's uploading, etc - once it's done it no longer takes juice.
Another example is Runkeeper - you can have it map your run/ride/etc - and when you minimize it, it keeps going.
Reminders set to alert you on arival or departure of a specific place also use the location run in background setup.
Phone apps can use it as well (such as Phone or Skype) and run in the background.
But the app has to be built to take advantage of this (released in iOS 4) and most apps don't need it. THe only other thing apps can do that would eat power is frequent PUSH alerts/updates.
The only apps that run in the background are ones that play music constantly, ones that play video (if you press the play button in the multitasking tray), and Safari. None of them will severely make your battery drain, except Safari. SafarI keeps tabs running on a flowing stretch.
There is no need to do this, iOS manages memory extremely well. There are not many apps that can constantly run in the background, ones that can for example are the Music app, and navigation apps, but navigation apps will quit once you have reached your destination for example. If you want to quit it before, then you would need to do the double press of the home button and X.
Like what it mention in this link:
http://whenwillapple.com/blog/2010/04/19/iphone-os-4-multitasking-explained-again/
When Steve Jobs and Scott Forstall answer when asked about:
"Q: How do you close applications when multitasking?
A: (Scott Forstall) You don’t have to. The user just uses things and doesn’t ever have to worry about it.
A: (Steve Jobs) It’s like we said on the iPad, if you see a stylus, they blew it. In multitasking, if you see a task manager… they blew it. Users shouldn’t ever have to think about it.
As far as i'venoticed, Safari just uses the "Works until finished" bit. So, it will finish loading a page, etc/.
Flushing an inactive app out of ram is more likely to consume battery than save it. It's forcing the app to rebuild itself and it's data next time you go back to it, either by pulling it all out of flash memory, reading via wifi/3G, recomputing it, or most likely all three. Without killing it, it has a modest chance of resuming exactly where it left off.
Of course it saves battery life - certainly with some apps more than others, though.
Actually the Podcasts app is a massive battery drain, it's bizarre. Others like Safari/Chrome don't.
But generally the ones that use GPS/Location Services a lot definitely drain the battery.
Actually the Podcasts app is a massive battery drain, it's bizarre. Others like Safari/Chrome don't.
But generally the ones that use GPS/Location Services a lot definitely drain the battery.
Those are "push" updates and will come in even if the app had not been launched. You can reboot your phone and never launch the eBay app, for example, and you will still get the push updates because they are sent to your phone from a server. The eBay app is not running and polling for updates as it may appear.
Unfortunately all of the above is half true.
Some apps are frozen in background some are not, if you are jailbroken you can buy an app like Batterydetective which lets you see total battery discharge but also individual app discharge, you'll find a lot of apps which are not frozen in background and thus use battery.
Mail and Phone use power in background for obvious reasons
Pages does not
Goodreader does as well as GoodPlayer
So yes it does help killing background apps.
Some apps are frozen in background some are not, if you are jailbroken you can buy an app like Batterydetective which lets you see total battery discharge but also individual app discharge, you'll find a lot of apps which are not frozen in background and thus use battery.
Mail and Phone use power in background for obvious reasons
Pages does not
Goodreader does as well as GoodPlayer
So yes it does help killing background apps.
Interesting post as I'm one that closes out of apps right after use... I have a most likely stupid question:
Why have this feature if it really doesn't do anything? I can understand closing the apps that run in the background but why do they even put the apps that don't on this menu if they aren't running in the background? I've heard some say it's a "shortcut to apps recently used" but it actually takes me longer to find the apps in this menu than it would be to just go in the folder the app is in (if applicable).
Thanks in advance!
Why have this feature if it really doesn't do anything? I can understand closing the apps that run in the background but why do they even put the apps that don't on this menu if they aren't running in the background? I've heard some say it's a "shortcut to apps recently used" but it actually takes me longer to find the apps in this menu than it would be to just go in the folder the app is in (if applicable).
Thanks in advance!
If you leave them in the background, but open them on springboard they open faster because they are preloaded in the RAM.
using RAM also uses battery though not that much
using RAM also uses battery though not that much
You answered your own question. It serves two purposes, one is a shortcut and the other is a way to force quit apps that are not working as they should.
If you have a lot of apps it is quicker than navigating past pages of apps and going into a folder to get back to an app.
Just writing this to try and clear up some still existing confusion:
In iOS, there are three ways that Apps can get some real background time when you tap the home button to go away from them:
1) They get 10 seconds and then they're frozen: Most apps are like this. These apps don't explicitly request any extra background time from the OS. This is the default mode for all iOS apps.
2) They get 10 minutes and then they're frozen: Any app can do this, but most don't. An App can request additional background time the moment you "home away" from them. Apps usually do this when they're finishing an upload or a download. If, by the time it reaches 10 minutes of background time, the App isn't done, it's forcibly frozen.
3) They get unlimited background time: There are three types of Apps that can get unlimited background time:
3.1) VoIP Apps (Skype, Fring): These apps have to be approved by Apple to get this backgrounding permission. They are allowed to remain running in the background as long as they're connected to their services. Once disconnected, "homing away" from them freezes them.
3.2) Audio Apps (Pandora, Instacast): These apps are closely watched by Apple when being approved so they don't abuse their stay in the background. They are allowed to remain running in the background as long as they're playing audio. Once paused, "homing away" from them freezes them.
3.3) GPS Apps (Waze, Garmin): These apps are also closely watched. They get to be in the background all the time in order to provide proper directions to the user. As far as my tests go with Waze, it must be explicitly closed (removed from the recent apps tray) in order to stop running in the background. I don't have Garming or Tom Tom's apps to test if they get frozen when not offering directions.
Note that when I say "frozen", the App is really frozen. It takes up RAM, but gets no CPU time and consequently no battery consumption.
There are also ways that apps can appear to be running in the background, but really are frozen:
1) Local notifications (Alarms, Timers): Apps can tell the OS to notify the user at X time in the future. They don't have to be running for these notifications to appear. They appear with the App's icon and everything, but come from the OS itself, even if the App is frozen. If you slide or tap the notification, the App gets brought back from the dead.
2) Push notifications (IM+, Twitter clients): Apps can subscribe with their own servers in order to receive push notifications. These notifications can pop up even when the App is frozen. It works like this:
2.1) The App subscribes with its own service server for push notifications.
2.2) When the user "homes away" from the App, the App gets its 10 seconds and freezes.
2.3) All the hard work is done in the service's server for you.
2.4) When something new arrives, the service's server pushes a notification to your device for you to deal with.
2.5) If you slide or tap the notification, the App gets brought dead from the dead.
Push notifications work well because every iOS device keeps a single connection with Apple's push notification servers. If you have one App that wants push notifications, that's one connection. If you have 10 apps that want push notifications, that's still one connection as opposed to every app being kept running in the background and each managing its own connection with its service server.
I wanted to write about memory consumption of background apps, but this post is already too long, right?
Sorry for the long post and hope it helps!
In iOS, there are three ways that Apps can get some real background time when you tap the home button to go away from them:
1) They get 10 seconds and then they're frozen: Most apps are like this. These apps don't explicitly request any extra background time from the OS. This is the default mode for all iOS apps.
2) They get 10 minutes and then they're frozen: Any app can do this, but most don't. An App can request additional background time the moment you "home away" from them. Apps usually do this when they're finishing an upload or a download. If, by the time it reaches 10 minutes of background time, the App isn't done, it's forcibly frozen.
3) They get unlimited background time: There are three types of Apps that can get unlimited background time:
3.1) VoIP Apps (Skype, Fring): These apps have to be approved by Apple to get this backgrounding permission. They are allowed to remain running in the background as long as they're connected to their services. Once disconnected, "homing away" from them freezes them.
3.2) Audio Apps (Pandora, Instacast): These apps are closely watched by Apple when being approved so they don't abuse their stay in the background. They are allowed to remain running in the background as long as they're playing audio. Once paused, "homing away" from them freezes them.
3.3) GPS Apps (Waze, Garmin): These apps are also closely watched. They get to be in the background all the time in order to provide proper directions to the user. As far as my tests go with Waze, it must be explicitly closed (removed from the recent apps tray) in order to stop running in the background. I don't have Garming or Tom Tom's apps to test if they get frozen when not offering directions.
Note that when I say "frozen", the App is really frozen. It takes up RAM, but gets no CPU time and consequently no battery consumption.
There are also ways that apps can appear to be running in the background, but really are frozen:
1) Local notifications (Alarms, Timers): Apps can tell the OS to notify the user at X time in the future. They don't have to be running for these notifications to appear. They appear with the App's icon and everything, but come from the OS itself, even if the App is frozen. If you slide or tap the notification, the App gets brought back from the dead.
2) Push notifications (IM+, Twitter clients): Apps can subscribe with their own servers in order to receive push notifications. These notifications can pop up even when the App is frozen. It works like this:
2.1) The App subscribes with its own service server for push notifications.
2.2) When the user "homes away" from the App, the App gets its 10 seconds and freezes.
2.3) All the hard work is done in the service's server for you.
2.4) When something new arrives, the service's server pushes a notification to your device for you to deal with.
2.5) If you slide or tap the notification, the App gets brought dead from the dead.
Push notifications work well because every iOS device keeps a single connection with Apple's push notification servers. If you have one App that wants push notifications, that's one connection. If you have 10 apps that want push notifications, that's still one connection as opposed to every app being kept running in the background and each managing its own connection with its service server.
I wanted to write about memory consumption of background apps, but this post is already too long, right?
Sorry for the long post and hope it helps!
Oh, right. I didn't realize that even though I knew about it before.
----------
Unused RAM uses the same amount of power as used RAM.
No need, I already did.
Unfortunately, even though I have both the technical info and a highly technical background, no one seems to want to believe me. Or us more accurately because I don't think anyone believes you either, even though what you say is accurate.
Anyone else here use the Caret app?
It is a crowdsourced effort from UC Berkeley to identify apps that use a lot of power. It is pretty darn cool and it updates the list of high-draw apps it has identified that you own and recommends some to shut down that are known to draw a lot of power.
Worth checking out on the app store.
It is a crowdsourced effort from UC Berkeley to identify apps that use a lot of power. It is pretty darn cool and it updates the list of high-draw apps it has identified that you own and recommends some to shut down that are known to draw a lot of power.
Worth checking out on the app store.
Just downloaded it. Going to see if it can help me out. I hope it tells me more then just closing apps because I already do that.
EDIT: looks like that's exactly what it does. Guess its still nice to know what's using up my battery.
Last edited:
+1 for recommending this; I just downloaded it and it seems to be solving all the problems listed on this thread.
