Short battery life after iOS 14.2

My “old” SE battery runs out so very fast, even when not in use. I have done all those little things to extend it (no auto refresh and such), and restarted it several times, power down and hard restart. For example, battery at 100% just before bedtime and anywhere between 50-70% at start of next day. It is not being used at all so how does this happen? Even when using to check a contact info or calendar entry, the battery drains rapidly. Any suggestions or information?