Q: ios 9.2 battery drain (iPhone 6)

I agree with this post.

Like him I foundthat it's an iCloud backup related problem. Confirmed with ipad mini and iphone 6.

Re-wiped the phone and restored from backup = same problem. Re-wiped and setup as new device = battery as before.

(Luckily nowadays everything is stored in the cloud so wasn't really a problem - except for logging back in to all my apps)

TY for your comment!  I've not upgraded my software yet and I'm glad I didn't, due to horrible experience with my 5s in the past when I upgraded from iOS 7 to iOS 8 which was a nightmare.

Apple really have become unreliable recently, I stopped bragging about early updates to my friends who own Android devices....

I spoke too soon.

Battery levels aren't dropping like crazy any more - but I'm still down at least 30% or more per day on my iphone. I'm now dropping to 40% on a phone that's not being used over an 18 hour period.

My iPad mini battery also drops more than I'm used to. 10% or more every 12 hours OF NOT BEING USED and with no background apps/email pull/etc.

I did a "Reset All Settings" and for the last couple of days- things seem to have returned to normal. I couldn't find any music downloads (as reported by others) or anything else that pointed to the cause of the problem. I'm not going to get excited yet- as I know this has only worked temporarily for some others. I'm just glad I can get through a day without plugging in again.

My iPad Air 2 is still rapidly draining. The other two seem to have stabilized (without a reset, which is very strange). I'm going to reset it today to see if it makes a difference. I checked app updates on the phone to see if there was anything there. Nothing that updated was anywhere near the top of the battery meter.

The same here, from Brazil, iOS 9.2, iPhone 6 and draining battery.

Here's my experience:

• Link to this post

After already trying everything above I have cracked it! Turn Wifi assist off. My phone is now cold all day and has excellent battery life As opposed to very hot and lasting 15 mins Since the 9.2 update.

Unfortunately that was one of the first things I did, so no that's not the fix we (at least I) am looking for.

I tried again - completely wiped phone - no restore from backup. Background takss turned off. iCloud stuff all turned off. Not using battery save mode...

Phone sat unused = brilliant battery life. Almost no drain.

Added Gmail account for email and contacts and calendars = great battery life. Dropped 10% (down to 90%) over 11-ish hours.

So not being caused by Google.

I'm currently messing with the icloud settings/services like Lawrence has advised. Will advise when I have any conclusions.

Seems that I did not manage to fix the whole issue with this backup, only part of it

I was looking at device statistics with dev tools and saw that my device managed to get into sleep mode and then almost immediately after this woke up again.

Once I disabled wlan, I noticed that Calendar is using quite a lot of network bandwidth (saw this under mobile data statistics) even I had disabled and deleted all calendars except the one on phone which cannot be disabled. So it should not really have any reason to consume any network bandwidth at all.

After I disabled mobile data from Calendar, phone was able to get into sleep for 3/4 of the time so much better than before, but still not where it was with earlier version.

So with current 9.2 version I can get more usage time from my phone when wlan is disabled, this used to be opposite...

I've stopped my investigations now, can get two days of usage now with this setup so I can wait for Apple to fix this issue in next version

There seems to be - at least Calendar - forcing phone to stay awake, and also other system services consume quite a lot of network bandwidth without any good reason so something is trying to do something with network pretty much all the time and consuming battery at the same time.

Update:

Lawrence is correct (as far as I'm concerned)

It's an iCloud issue. I now have my phone EXACTLY the same as before the update EXCEPT for Mail, Contacts, Calendars and iMessages/Facetime under iCloud being turned off. All other iCloud features turned on and battery life is now perfect.

Going to be testing iMessages/Facetime today.

Same issue here. iOS 9.2 on iPhone 6. Battery just started getting very warm and then dropping at roughly a percent a minute even when not in use.... Looks like 25% of battery usage was mail and 24% was calendar when I haven't even used those 2 applications. I tried turning off icloud sync for calendar and mail to see if that fixes the issue... Very frustrating to have to go through such headaches to figure out Apple's problem.

Great find whoever discovered it was the calendar. I tried what seems like everything but it was indeed turning off the calendar on iCloud that did the trick.

If your data was drained and went over like mine, make sure you get on your provider. I'm on AT&T and got them to issue me a credit for the extra data costs.

Found even more issues:

1. iCloud Backup, disabled this and got more juice
2. Calendar sync, not just iCloud but also Office365 was giving issues
3. Safari history. Even when I cleared Safari history, it did not sync anything to/from iCloud history. This *fixed* somehow during the past few days, not sure if it had anything to do with this issue.
4. Google e-mail account. Deleting this gave a lot more battery life and after I had it off for a while I recreated account and this is now also working just fine
5. Bluetooth. This is still an issue. I have one device that keeps connected to my iPhone (that was not the case before 9.2 update). Now that I keep this device in airplane mode and switch bluetooth on only when needed phone gets into standby.
6. Noticed also lots of push notifications using network bandwidth and that dropped dramatically when I uninstalled Skype and Google Hangouts. Skype I have not yet reinstalled to see what happens, Hangouts is back.

Now I have Standby time 24 hrs and Usage 2 hrs. Battery left still 79%. I would say that it is now even better than before 9.2 update.

And I have since enabled iCloud backup, both iCloud and Office365 calendar, Google e-mail account and Hangouts. Skype I will try one day.

Thank you for this!  I suddenly encountered severe battery drain problems, and I didn't know what was happening!  Found out that I was downloading 4 songs that never finished and kept downloading.  I was losing just about 1% of battery PER MINUTE.  After I cancelled those downloads, the phone resumed normal battery behavior!