Hi,
Same problem here, with my 1st gen SE 128G!
Talked to support yesterday, diagnostic, etc., nothing wrong.
I should take it to service for further investigation.
Warranty is over so it is coming out of my pocket!
Before IOS 14 the phone was working just fine.
I charged in the morning and it was OK until next morning. Or longer.
Now I charge in the morning and start using (unplugging) at around 9AM.
If I am not using the phone just sitting on the table, it is down to 1% by 2-3PM.
If I am using it (only ligth use, calls and bit of messenger), it is down to 1% by noon.
But, the interesting part comes after this! The phone works fine at 1%, until next morning.
I can take pictures, send messages, go to the internet etc., it is working fine. But, I have no idea what is the real battery life.
The other thing is that my "battery health" is 100%! I remember before it was down to 98% or even less!
Ibelieve it doesn't matter how power hungry is IOS 14!
Something is wrong with the battery management, or else.
The other strange thing is, that my wife's SE works just fine!
My SE is about a year and a half year old, her phone is much older.
And her "battery helath" is only 94%.
I love my phone, it is a very powerfull and handy phone, and this is crazy how IOS 14 killed it!
Guess, all I can do wait for the miracle update on IOS 14.1!
However, if anyone comes to a solution, please let me know. Thanks!