Background Drain

In my Off Grid post about New Zealand tramping I mentioned being quite happy (if not really surprised) with the performance of the iPhone battery. If not touched it was draining less than 5% a day, and up to 20% under normal off grid use - mostly taking photos, using offline topographic maps with GPS and writing up a small journal entry at the end of the day.

These statistics clearly show the phone does nothing in the background. Which is of course possible when the airplane mode is active and it does not even attempt to find a network.

But the airplane mode cannot be used during normal busy days, can it?

Surprisingly yes, it can. Like in an airplane you can still have WiFi active and connected. And iPhone (depending on your SIM card / cellular provider) can support "WiFi calling" which technically is tunneling the cellular connection over WiFi. While it may sound weird to many, it actually is a super useful feature. And actually one of the reasons i decided to switch to iOS from Android. My cell operator - 1Global (formerly Truphone) supports WiFi calling on iOS (and does not on Android, even though Android phones have this capability too). WiFi calling is a really useful feature when you live on the very edge of cell coverage. This is exactly my case and before I had to lean out of a window to be able to talk or send/receive SMSes. Now with WiFi calling I can walk around the house or sit at my desk. It even works during flights when the Airplane mode is activate and you have a WiFi connection active. Flying to New Zealand I was surprised by received SMSes when we were in the middle of Pacific Ocean.

The phone switches to WiFi calling automatically when it logs on to a WiFi network. But it continues to scan for cellular signals if the Airplane mode is not activated. And that background cell scan drains a lot of battery, when the signal is spotty or weak. Up to 50% overnight. 

To reduce this unnecessary battery stress I started activating the Airplane mode while at home. It helped with battery a lot but the downside was I was often forgetting to switch the mode off when leaving. There has been a nice solution though - using the iOS Automation feature I tied the automatic Airplane mode activation to my home location. Now it enters the mode when I arrive at home and leaves it when I leave. Very nice. And the battery lasts 3 days easy, as the background drain is limited.

Last week though I noticed the battery drain being high, despite the active Airplane mode at home. Looking at the Battery / Applications statistics it was the iCloud backup service. Apple says backup runs in the background only when the phone is powered. This clearly is not true. Maybe it starts when the phone is powered, but then it clearly continues in the background when on battery. In my case this backup activity lasted a couple of days slashing the battery uptime by a factor of 3. I did not mind as I could easily recharge the phone at home, but definitely this is something to remember when charging options are limited. 

Lesson learned: check the Battery status in Settings and make sure you do not have any background battery draining activities. I remember Android had some automatic system notifications about that. iOS does not, so it is a good habit to do the check manually once in a while.