My iPhone 7 normally lasts about a week, but sometimes it suddenly starts draining very quickly. I have Background App Refresh completely turned off, and I wasn't using the phone at all when the activity shows 100% screen turned off. Why does it do this, and how do I stop it?

I wasn't able to find anything online, since searches only result in "turn off your apps" or similar.

  • Was your iPhone connected to wifi in that time period? If am at work I experience the same thing, my iPhone is just switching around wifi access points (bad spot). Because of this my iPhone is draining like hell. Maybe this is the same case by your iPhone location? – Davy de Vries Feb 19 '19 at 11:07
  • @DavydeVries Yes, but the reception is good (router 2 meters away), so there should be no reason for it to switch networks. I could try disabling wifi to see if it stops draining next time it happens, but that's around once every two months, and I usually find out about it when the phone's dead and speed-draining is over. – usernumber Feb 19 '19 at 11:17
  • Try power cycling it. I had a similar issue with my 7+ a few weeks ago where the battery drained quite rapidly for no apparent reason. The power cycle seemed to have fixed the issue. – Allan Feb 19 '19 at 19:10
  • @Allan Experimented a bit today, since there was another large drain (see comment on answer by modlin). Half the time I was home, and half the time I was driving in the middle of nowhere, without any effect on drain speed (it's very constant). Manually telling iCloud to sync didn't affect it. However, draining stopped after turning it on and off. Now the only problem is I usually don't find out about the draining until after the phone is dead... – usernumber Feb 20 '19 at 21:48

You should be able to scroll down farther on that screen with battery level and activity and see specifically which applications are using energy. Never seen the "not available message" however...

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  • I can't scroll down farther, there's nothing there. If you don't use your phone at all (and no background things happen) in the selected hour (or the latest 24 hours), the Usage by app thing doesn't show up and you only get the message. Try it on an hour in the middle of the night or something. – usernumber Feb 25 '19 at 21:26
  • Check before midnight and/or see if the 10 day gives any hints? It looks like on my phone the activity is a running 24 hours, not midnight to midnight. – Daryl Monge Feb 25 '19 at 21:47
  • What I meant is, you can select an hour where you didn't use your phone (or just don't use it for 24 hours) to see the "Usage by app is not available" thing. Also, when there is data there, it doesn't indicate anything that would drain the battery so much. Usually it's just something like "weather app: 1 minute. 0%" and similar. – usernumber Feb 26 '19 at 9:04

Did you setup automatic iCloud backups? They occur at night, if the iPhone is locked and plugged in the charger, and connected to WiFi. Also is iTunes WiFi sync turned on?

iCloud Backups(iOS 12.1.4): Settings->AppleID->Phone->iCloud Backup.

You could check for iTunes WiFi sync on your Mac or PC.

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  • If the phone is plugged in as you say is needed then the battery would not be discharging then so I do not see how this answers the question. – user151019 Feb 19 '19 at 19:59
  • True. My bad. It need to be connected to WiFi and locked for iCloud Backups to occur. No need to be plugged in charger – modlin Feb 19 '19 at 20:04
  • I do have iCloud backups on, but I'm not sure that it's causing the battery drains. Forcing a backup just now took 1 minute (as opposed to the 7+ hours you see in the screenshot). Also, I think the backups happen every few days, whereas the battery draining happens around once a month. I'll check back in a few days and see if a backup has been made without being plugged in, and without the battery draining, in which case this would be false. – usernumber Feb 19 '19 at 22:33
  • Aaand proven wrong. Major battery drain happened again today, but during half that time (several hours) I was driving, which means no wifi networks. I tried backing up manually just now, and it still takes about 1 minute. – usernumber Feb 20 '19 at 17:58

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