Q: iPhone 5S getting incredibly hot and high battery usage after iOS 8 update

Hey Guys.. Me too is having the same issue.. did all the stuff to resolve the issue but that didn't helped. Talked to apple care like almost 20 times, even visited Apple Store twice but none of them worked. Got a call from Apple Representative today that i will be exclusively getting the update to fix the bug within 72 hours. Fingers crossed! That means update or patch will be rolled out by the end of this month... CHEERS!

Please be careful of updating to 8.0.1!!!!
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Apple has released an update for its devices to add HealthKit app support and to fix a number of lingering bugs from iOS 8, which was released September 17th.

iOS 8.0.1 has the following updates:

• Fixes a bug so HealthKit apps can now be made available on the App Store
• Addresses an issue where 3rd party keyboards could become deselected when a user enters their passcode
• Fixes an issue that prevented some apps from accessing photos from the Photo Library
• Improves the reliability of the Reachability feature on iPhone 6 and iPhone 6 Plus
• Fixes an issue that could cause unexpected cellular data usage when receiving SMS/MMS messages
• Better support of Ask To Buy for Family Sharing for In-App Purchases
• Fixes an issue where ringtones were sometimes not restored from iCloud backups
• Fixes a bug that prevented uploading photos and videos from Safari

We’re hearing, though, that the update has created problems for many iPhone users, affecting their ability to connect to a cellular network. iPhone 6 users are also reporting issues with Touch ID.

We’ve reached out to Apple and are waiting to hear back, but in the meantime hold off on pressing that “Update” button."

I am holding off on the update as I don't know if it will affect my phone, for those who want to update go ahead, but I thought this would be useful info for those who are paranoid of being one of the "1%" that got affected with certain disabilities when updating (like the battery drain when upgrading to 8.0)

SOURCE: http://mobilesyrup.com/2014/09/24/apple-releases-ios-8-0-1-with-healthkit-suppor t-but-hold-off-on-download/?utm_content=bufferd3e52&utm_medium=social&utm_source =facebook.com&utm_campaign=buffer

EDIT: PS, I'd like to hear experiences of those who did update to 8.0.1! Did your problems go away? Did more problems come like the ones from my source appear? Did the pre-8.0.1 problems persist and become worse?

Calibrated The iphone 5s battery two times.

Deleted facebook.

And phone seems to work fine.

Usage: 30 mins

Stand by: 4 Hours 32 mins.

Apps installed: Instagram, whatsapp

• Add tracking: off
• Background app refresh: off
• Reduce Motion: On
  Track Me(Safari): Off
• Location: off

P.S. Try Calibrating your phones battery for twice or thrice. And I hope you guys will be good to go..!

Thanks for the suggestion! I just upgraded to 8.0.2 (I skipped the 8.0.1 in case of any side affects and bugs), I will see how my battery is, and if there is anything bad, I will follow your suggestions! I have thought many times to delete Facebook but I kind of need it to effectively manage my page on there. There are certain share options that are on FB app but not on mobile FB Such as sharing to my page through my account looking at my personal account's feed. If there was, I'd do away with my stupid FB app. It's such a huge battery drainer even when background is off and loc-ser is off >_<...

Guys pls would love to heat from those who have updated from 8.0,don't wanna get into more problems that's why I have not done my update yet.is d problem still there or its gone away cause I just can't wait to get my phone back(normal battery life and it been as hot as it is now  )

I never suffered from the heat issue, but I did the battery issue, and I say update it! I haven't hit any problems yet!

I unplugged my phone at 100% at around 12/1 and I woke up at 7AM EST with 100% Now, it is 9:04AM, and I returned a few texts and made a call, and now I am at school with 89%. I wouldn't say it is too accurate since my phone HAS been on standby since 12AM, and so it's at 9HRS, 14 MIN of standby with 50minutes of usage. I'd say this is an improvement if I were comparing to iOS 8.0.0, but probably not the same (still) as 7.1.2, that's my take on it though... Anyone else?

I did the 8.0.2 update last night.  I closed all app except for Lirum so I can monitor the CPU's.  I still have the heat and high CPU issues.  My CPU's are hovering around 80% (combined).

I'm still under AppleCare (iPhone 5) so I need to determine my next step: take it back to Apple and swap for a different (refurb) unit or do a clean iOS 8 install.  Each of those has its own ups and downs so I'll figure out what to do tonight.  I made an Apple Genius Bar appointment for Saturday morning, just in case.

I did a compete reinstall of iOS 8, my apps, and then the 8.0.2 upgrade.  It's been several hours now and my CPU is still hovering between 80-100% on a consistent basis.  I posted a picture of my CPUs. 

Apple stopped signing iOS 7.1.1 so you can't install it even if you have a copy of it.  It looks like I'll be forced to have this iPhone replaced.

well I decided to do the upgrade but it's still the same thing,same battery issue and phone is still hot too

I Upgraded to 8.0.2 too. Still with heating and battery issues. I noticed that the CPU clock was running at 1.888 MHz for a while, this is well above the CPU maximum clock informed by Lirum Info. Most of the time it runs at around 400 MHz, even when the CPUs are 60% bussy.

So the cpu's not only adjust the amount of work they can handle, but also the speed of the clock can be incremented when the load of tasks go up and needs extra  processing power to crunch more bits per second.

Why I have seen the cpu clock running at 1.88 GHz, when the maximum cpu clock should be 1.4 GHz?

would be this overclocking of the cpu abnormal and started with the iOS 8 upgrade?

Yes, I wish I could say 8.0.2 has solved the problems but my phone still runs hot at times, with no clear reason why...

Messages seems unstable too - often, it will seem to 'freeze' on starting, then either 'crash' and return to the Home screen, or, proceed to work.

Strange... and disappointing.

at this point i must say am really not feeling great anymore,my phone hangs all the time,restarts applications and closes them when ever it wishes,still hot and battery hasnt improved either,having serious propblems connecting to wifi,now i wished i didnt even upgrade to 8.0.2 cause its more of a mess than 8.0 to me.just had to drop the phone at home and go to work cause its annoying hanging all the time

Yes,  i have the exactly same problem! Processor getting around 80% then goes down to around 10%, then goes up again... =/, Tried Everything already... That really sad =/. I Did the update over OTA directly from iOS 7.0.4! Already did the update to 8.0.2, tried several times to restore it, but nothing seems to fix!

It seems I did a mislecture when I said cpu clock was running at 1.88 GHz (it was 1.88 MHz instead), It was a miscalculation of Lirum info when having too few data to calculate it accurately. After some seconds It was actually running at just below 400 MHz.

In my case I haven't experienced app crashes, or system hang. My problem still remains associated to high cpu usage (around 60%) while doing nothing. Sometimes it slows down to 8-10% and after some minutes of not using the phone you can feel it has cooled down to normal.

As it is known that de location services (GPS activity) eats lots of energy from the battery, I looked then which services were accessing Always location and I turned them to Never all but the necessary apps like Maps, Google Maps, Waze, etc.

I'll see what happens with battery usage now and get back to this thread soon.

I understand that iOS testing had its limitations in field but only in relation to the new iPhone 6 and 6 Plus, due to the restricted testing by few in Apple organization to keep the secrecy of the details of the new hardware until launched to market. In the case of testing on the iPhone 5S there is no limitation on testing because there is no secrecy on the hardware after a year on the market. So it seems to me that the problem is may be related to the better management of energy on the A8 chip compared to the 5S's A7 and also may be because iOS 8 was planned with iPhone 6 in mind. Or iOS 8 should be aware of the harware it is intalled on and adjust itself to it to run the cpu's at proper levels to avoid overheating and overdraining the battery?