What can be the reason that an iPhone SE 3rd gen. loses battery power significantly over night when it is completely shut down? The flight mode was activated before the shutdown. The device is brand new, battery capacity and health is on 100%, no background tasks are allowed. It is a replacement for the same model, which had the exact problem some weeks ago.
Oops I just realised you meant when it was completely off - no idea what could be causing it. Are you in an extremely hot or cold climate ?