My iPhone sometimes gets very hot and drains battery extremely quickly. When I use the app iStat to check processor load, it shows high numbers (above 2, where it is normally 0.5, not sure about the format of those numbers but that is what is reported). It seem to be the equivalent of a computer stuck at 100% CPU load.

Restarting the iPhone and closing all apps does not help. Previously, it went away after a number of restarts, but this time, so far not. Do you know a way, except re-installing, that can fix the iPhone? Any app that can kill all processes?

  • Did you jailbreak your phone? Commented Mar 30, 2011 at 12:09
  • 2
    I did not jailbreak, but considering doing it just to get some shell access to check the processes running.
    – RipperDoc
    Commented Mar 30, 2011 at 15:05

7 Answers 7


As others already let clear, Apple doesn't offer any good solution for those issues. They shouldn't exist, Apple would say. But they do.

That said, your best bet is jailbreaking and getting SBSettings to "Free Memory" or some specific app that does it, such as MemTool. I've just installed it on mine through hackyouriphone repo, but you can also find it on http://ispaziorepo.com/cydia/apt/

  • 3
    Memory managers are snake oil; they do nothing. Also, memory leaks (or at best, poor management of memory) don't have much to do with errant CPU load. If anything, killing the processing (which you can do once jailbroken) would likely solve the issue but that's assuming the issue isn't systemic (just one errant process).
    – user10355
    Commented Oct 7, 2012 at 18:19
  • @cksum agreed, the issue can't be systemic for this to make sense. Keep killing a process that keeps coming will keep on working, but it's not exactly solving the issue source - just its symptoms.
    – cregox
    Commented Oct 8, 2012 at 10:40

I had exactly this problem on my a little over one year old iPhone 4. The battery was draining in like 4 hours and the CPU was working overtime all the time.

All i did was a backup and then a restore in iTunes. It worked perfectly. The battery drained less than a percent in the following four hours!

I'm trying to figure out if it was any particular app that was causing the problem by uninstalling some of the later ones.


Do you use Exchange on your iPhone? At our company we have some trouble with contact sync every once in a while. Various iPhones will run at 80% CPU and their batteries empty in about 2 hours.

One temporary fix is to turn off contacts in Exchange Settings and turn it on again. Then contacts will be sync again and after this CPU runs at a normal 5-15%.

  • Thanks, will try next time. The problem is less regular now but seem to often happen when roaming!
    – RipperDoc
    Commented Nov 21, 2011 at 1:10

iPhone 3GS, iPad(3G 3rd generation), & iPod Touch(4G 4th generation) were all getting terrible battery life after iOS 6 update.

Solution for me was to turn off Push for email and other network features. This brought battery life back to where it was before the iOS6 upgrade:

  • Go to Settings > Mail, Contacts, and Calendars > Fetch New Data
  • Disable push e-mail and set "Fetch" to manual."

Taken from this article with other good tips as well but for me the key was turning off Push as this essentially seems to keep the phone active and connected constantly.


A great app (free) from the engineering department at UC Berkeley has been released specifically for debugging problems such as this. It's available through the app store so does not require jailbreaking. The method involves running the app for several days to a week. During that time it logs the energy usage of the various apps that you are running. You can then see which are the energy hogs that are causing the problem.


  • Wow this is incredible!! Thanks so much for bringing this to my attention. Commented Mar 12, 2013 at 23:28

It is usually an app that goes haywire and reinstalling the app will usually do the trick.

  • Yeah, makes sense, but how can I find which app is the faulty one? iStat only shows total processor load and active processes, not how much they drain. I guess I need something like Activity Monitor in OS X.
    – RipperDoc
    Commented Mar 30, 2011 at 15:06
  • I start with the most recent (and most likely) to have gone bad. Commented Mar 30, 2011 at 15:34

There's no official way to close apps other than invoke que "task switcher" (by double clicking on the home button) and press+hold one of the apps, then closing them individually. After doing that, a cold reset (press and hold the power button until the slider says: "power off". That's the only way to do it.

If -after all that- you still have a process that's bothering your iPhone's then you'll have to re-install it, because it will have to be an application that was installed by Apple and therefore there isn't much you can do about it.

Reinstalling ought to normalize the situation and you can always restore a backup (but make sure things work ok first).

Now if there's a method in the Jailbreak world I don't know, but I'm sure there is a "task manager" in Cydia.

  • Makes sense, but actually, even when a (non-Apple) app have not been started, it may exist as a process. Through iStat, I have seen app processes running that are not in the task switcher (requires you to start the app and then close it to get rid of).
    – RipperDoc
    Commented Mar 30, 2011 at 15:09
  • @Ripper that'd be weird. Perhaps if the app has some sort of Push activated, but if the app is not running, any process that it has or had while it was, should be frozen. You might see some activity, but nothing that should compromise your battery life like that. If that's the case, try removing the app from the device. (You will be later able to add it again when you sync) Commented Mar 30, 2011 at 16:24

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