Extraordinarily fast battery consumption I have been using Xiaomi Mi Max (4/128) (now running on MIUI 10.2.1.0) for over two and a half years and as the time passed, my battery started to die pretty quick - I used AccuBattery to check the battery's health and it was about 40% after 30 charging sessions. On average it could last about 3-4 hours on screen and about 12 hours standby.  

My decision was to change the battery and I did it, but the phone still does not work for 8+ hours on screen (as it did before the battery started dying that quick). I took a look at the power usage graph and the thing that suprised me the most was the distribution of power. I know it should be rather exponential than linear, but it was different - first 30% (from 100 to ~70 percent) has been drained in less than an hour, next 45% was used linearly (approximately 10% per hour), and the rest lasted for 20 minutes, going rapidly down to 0%.

Up to now I deleted apps which I was not using, turned on the auto-brightness and the battery saver. I was thinking about doing a factory reset, but at the moment I am unable to save all my photos and data, so I would like to get any ideas what else could I do instead, in order to lenghten the time the battery can last.
Looks like a software issue for me. I had the same issue on my max 2. I flashed the firmware again using Mi flash tool and there's no battery drainage now.