I have a problem with the battery draining too quickly on my iPhone 8 Plus (current iOS is 11.3). If I recharge it to 100% and then leave it overnight while I sleep, the battery is already down to 85% or less. Even on Airplane Mode overnight it does this. It didn't use to do this before until within the last week or so (no new apps or behavior either). I have Background App Refresh off, have drained the battery down to 0% and recharged to 100% to recalibrate, and have even factory restored my phone but it still drains fast despite all this. Battery Health says the battery is at 97% so I'm not sure what else I can do or check to resolve this problem?
That's how my phone normally behaves i.e. losing 15% at night if I leave data on especially. Over time battery becomes less and less efficient which is kind of how companies like Apple get you to buy new models. One of the things anyway. I use an android but I bring a powerbank with me for a midday charge and that works for me. They are not too costly and can be a lifesaver.
I am not a Three employee. I'm just a little helper