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

I was having the same exact issue! I let my battery drain multiple times. This last time I watched it go from 43% to 8% in about 15 minutes. At 8% everything froze up and wouldn't even let me shut it down. I did a soft reboot, and now it's not turning back on at all. This is absolutely ridiculous!

I have the same issues as described by many users in this post.

I made me a question: What parts of an iPhone uses most of battery available in any normal use? (I mean when the operation of the device is normal, which is not the case after the upgrade to iOS 8)

my first answer would be: CPU, Wi-Fi, GPS, 3G data transmission, not necessarily in this order from higher to slower usage of battery)

I then run the app "Lirum Info Lite", which can show the CPU usage for both cores of the iPhone 5S, as well as a lot of data about your iDevice. So far, after monitoring the % of CPU usage sinde yesterday, I have seen a strange behavior of both cores. Having the iPhone with no app running (only Lirum) for some time I found it runs at about 55-60%, then slows down to 5-15%. On one observation a saw a strange pattern: one core going 100% and the other showed "nan" (zero data), meanwhile the battery suffered a noticeable decline after some minutes. I then turned off iphone, then on again. After this the CPU run almost normal for a time, then I found moments where while one core went runing higher the other core went the opposite way slowing down, when normally both run at similar paces. For a period of a couple of hours it seemed to slowed down to 3-5%. Today the pattern of two levels of core usage stays similar, adding another behavior where one core goes at 0%, while the other goes at 8-16%, then the usage shifts from one to the other for some seconds then goes back.

My tests were made with location services off and wi-if only for data connection.

After the upgrade the iPhone got hot and battery drained fast. But today the CPU usage seems to get more normal, it doesn't get hot and the cycles of 50-60% of CPU usage are shorter. The statistic of battery use shows for the last 4 days 21% for Mail and Home/Lock screen with 15%.

I am a bit of confused about how iOS 8 manages those cores in iPhone 5S. My wife's 5C isn't showing the above behavior or battery drain after I updated it to iOS 8, nor do my iPad 2 Retina (from which I typed this post) and iPad Mini. So the problem seem to be iPhone 5S specific.

Anyway one normal user shouldn't be making these kind of tests to find a possible clue to solve the unsolvable. Because this is Apple iOS's team responsibility to deliver an upgrade free of this obvious problems as has been seen since customers downloaded the upgrade and saw their iPhones 5S get hot and eat battery totally abnormal.

I don't believe any trick brained in this community will solve the bug. So better expect for and iOS update soon.

Meanwhile, have a power adapter handy in case your battery goes too low tocharge your iPhone 5S.

One last question, Are the new iPhone 6 and 6 Plus with iOS 8 experiencing the same problem?

I have the same excessive battery usage in IOS 8. I have tried all known fixes for the issue. Apple will have to fix this soon.

I have the same problem with my 5s.

Apple do sth.

Same problem here on my 5s,after a full charge phone can't even go 2hours and gets so hot I can't hold it for long

BTW I found another problem. "Phone noise cancelation " doesn't work. It doesn't turn on or off.

I accidently went into "setting" and I saw "phone noise cancelling" doesn't work. I soft reset it, but nothing. Still not turning on or off. Its color faded. It means it doesn't active.

I fixed it. I don't know how "hearing aids" turned on. It deactivated the "phone noise cancellation". I turned "hearing aid mode" off and it fixed the problem.

Basically it's just Facebook app taking up to 25%..home and lock screen,bbm,Safari,IG all take 7%,apps like whatsapp take just 2%,just wishing I had atleast waited before rushing to upgrade ,now I basically walk around with my charger,always charging even at work..

Aparte de reinicio y dejarlo como nuevo no hay otra opcion porque mi 5s calienta exageradamente y la bateria se descarga super rapido alguna otra opcion

While I believe it has been mentioned in this thread, I've found that doing a soft reset (holding down the power button + home button until the iphone shuts down, then releasing the home button but keeping the power button held down until the Apple logo appears, then letting go of the power button) has helped me the most. I used Lirum Info Lite, thanks to a previous poster on that, and was running at 90% combined CPU for hours prior to the soft reset. After that I was down 5-8%.

I've also turned off Handoff and Suggested Apps (without Yosemite, there's no need to have Handoff turned on).

I'm still monitoring how long this will last until the CPU goes back up.