battery not holding charge

Since I upgrade to iOS11.1.2 my battery wont hold charge.

I charge it to 100% and even when not using it much to rapidly goes below 20%. I charged it before bed and was at above 80% and the phone was dead when I woke ie.with no use.

I check Settings - Battery and there is no unusual app usage and I turned off app brackground refresh. I restored the phone from iTunes. Any ideas?