iOS 11.3 has a new power management feature that unfortunately only works on iPads: Charge Management. This is Apple's dummied down explanation as to what it's doing. https://support.apple.com/en-us/HT208710 Basically it's keeping the device at a lower charge level to save the battery if it's plugged in all the time. This is Apple's first acknowledgement that keeping a device (iPad, iPhone, MacBook) plugged in continuously degrades the battery. Yet---- they are only implementing this power management feature for the iPad. I sure wish they included this new feature for iPhone as well.