Excessive Android phone battery drain

 I had my battery on a Pixel phone go from 100% to 30% overnight with the phone turned off so I think that either the battery sucks and has an internal resistance or there is something running on the phone even if it is turned off, which is even scarier.  So I get similar results several times and I try to leave the phone in airplane mode, no big overnight drain, very strange.  So next I try to drain the battery all the way, I get a 24 hour usage on battery saver with airplane mode at 2% for 24 hours, well now we are getting somewhere, it is a miscalibrated indicator.  I will next try to calibrate it by running the phone up to 100% twice then running it down to shutdown twice and try again to measure the result.