I have a really strange issue with my iPhone. I had an iPhone 6 and suddenly I would notice the rear case was very warm and the battery was being discharged at an excessive rate. I have an app called System Status Pro which shows CPU usage. When the issue occurred, the CPU usage was fluctuating around 20-30%. I left it thinking iOS was busy doing stuff, but the battery continued to discharge quickly (i.e. 100% to empty in an hour or so). I force restarted the phone and everything returned to normal. CPU usage averaging 3-5% with no apps running.

This issue continued to return randomly. I could last a week with no issue, then it would happen 3 times in one day.

My investigations so far:

  1. The issue is not related to my phone’s hardware. I upgraded to an iPhone 8 (restoring my phone’s from a backup) and the issue continued
  2. The battery app in Settings, which shows each app’s CPU usage does not show a particular app causing the usage
  3. Background app refresh is turned off
  4. No obvious Apple services (i.e. iCloud backup) are running at the time of high CPU usage
  5. When the issue occurs CPU usage is always 20-30%. Never more, never less
  6. It is not iOS version specific
  7. The phone is not hacked/jailbroken
  8. The phone does not have Enterprise certificates installed (which would allow non-App Store approved apps)
  9. High CPU usage continues with no apps running (double clicking home button shows no apps running)
  10. The only resolution is to restart the phone and usually a single restart fixes it, although occasionally it returns and another restart is needed, sometimes even a third restart. But restarting always fixes it eventually
  11. I have 15GB free of the phone’s 64GB storage
  12. I realise I could wipe the phone. This is my last resort and I want to avoid this

Has anyone experienced something similar?

Does anyone know how I can view CPU usage at a more granular level, ideally identifying each individual processes CPU usage?

Many thanks in advance for any advice!

  • Was mobile data on in a low network coverage area? Does low power mode help in increasing the 100 to 0 in an hour battery health? – anki Aug 21 '19 at 14:45
  • Network coverage does not affect it. The issue occurs even with full network coverage (4 bars). Not sure about low power mode. Will investigate when the issue happens again. Thx! – Chris Driver Aug 21 '19 at 14:54
  • 2
    Update: low power mode drops cpu usage down to a consistent 17.5-20% with no apps running. So low power mode does reduce some CPU’s age, but whatever it is causing the primary CPU usage, it is still present. – Chris Driver Aug 23 '19 at 15:01

I finally found the issue!

It was an iPhone game called Minesweeper which runs as a widget in the Notification Center/Today View. I guess to be in the Notification Center/Today View as a widget, it has to be running, yet it was not listed as a running app when I double tapped the home button.

I have no idea why Minseweeper was causing the high CPU or why it occurred randomly, but as soon as I deleted Minesweeper, the problem went away.

The only reason I discovered the cause of the problem was because I was in the Battery app in Settings and I happened to tap a section of the Battery Level graph and it showed app activity for that specific moment in time. Minesweeper was there at 30% usage and I hadn't run that game for months.

I hope this solution helps someone somewhere!

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