iOS11 Battery and Other Survival Tips
I may be really lucky, because I have four devices running iOS11 and on all of them I get exactly the same battery life as pre-updating. Whether you believe excessive battery-drain is real or imagined can be discussed elsewhere... here I just want to share 10 favorite tips that may help bring your batterylife back to how it was before you hit the "update" button.
1: Don't panic right away
There's lots of stuff going on in the background even after the installation has completed. The local system is resyncing a load of data with iCloud. Some file databases need to be re-indexed, etc. Let it settle down for a bit before whipping out the timer to clock your new batterylife.
2: Kill them zombies
First thing I tend to do after installing a new system is try out a bunch of music apps. Invariably, some of those will turn into IAA zombies and suck your battery dry. After your first run through the system, don't forget to do a soft/hard reset to kill 'em all.
3: Set your screen brightness back to the level you had it on before the update
Next up - Settings! New iOS releases tend to introduce new features that need to be switched off. They also re-enable settings you thought you had disabled.
4: Hey Siri - Stop listening!
Settings -> Siri & Search -> Listen for "Hey Siri". Switch this one off. It keeps the microphone on at all times, so Siri can hear your commands. Which you most likely don't care for.
5: Enable Wifi Assist for Mobile Data
Data connections are the second most energy consuming feature in your iDevice (after the screen). And poor connections are even worse than good connections. In Settings->Mobile Data is a switch called "Wifi Assist" which will let the device switch to 4G whenever Wifi is really bad. This will help a bit.
6: Disable Automatic Downloads
This one is really crucial: go to Settings -> iTunes & App Stores and disable all "Automatic Downloads". These cause battery drain and slow down your device while pumping 100s of megabytes through the network and installing in the background.
7: Wifi / Bluetooth (and Airdrop)
You need to disable these from the settings menu, as the Command Centre just disconnects them instead of fully switching them off. Every iOS update also re-enables Bluetooth, even if you had it switched off before.
8: Disable location services
If you don't need these, switch them off.
9: Check for worst offenders
If you go into Settings -> Battery you can see which apps have been consuming the most energy. Try avoiding that app for a while (or be conscious of how much you're using it) and see if that has an influence on battery drain. Around iOS update time lots of apps release updates and it could be one of these updates for a particular app that is causing grief.
10: Auto off
Go through all other settings (also app-settings) and investigate anything that has the words "Auto", "Sync", "iCloud" or "Smart" in it. Those are immediately suspect. Be extra critical of anything that involves network access.
Also: how old is your device? Could it be that the battery was already degrading prior to updating? Are you comparing to a measurement you did over a year ago or does it just 'feel' like battery is draining faster because you're looking at that battery icon more than before. It's easy to get paranoid about batterylife because it seems so many other people are also complaining...
Hope this helps some people!