[Xiaomi Mi A1 Questions & Answers] SirEldo:
[TL;DR]

Phone battery suddenly drains faster than usual, drains to 0% overnight. Problem still persist even after April update and after battery change. Can't find any solutions. Help me.

Hey, so about a week ago something very strange happened to my Mi A1 and got worse overtime. So what happened was my battery went from 80+% to 0% overnight. I woke up confused and just recharged it and didn't think too much. After a full charge, I noticed the battery drains abit more than usual and had to plug it in constantly. Before going to bed I charged my phone to 100% to see if it would drain to 0% again. It did. As time passes the problem gets worst. The phone started getting warm when charging (around 40+°C up to 50°C) then after a while the phone runs warm even when not charging (never goes below 40°C). My phone always used to run at about 30-35°C even when charging. I changed the battery myself because there was no warranty on it but it didn't fix the problem. However it did help abit. The battery drains ever so slightly slower now but still drains to 0% overnight. It still runs warm but now it does go below 40°C (rarely). Before and after the battery change, the discharging rate is about 700mA and sometimes reaches 1000+mA (used an app called Ampere, not too sure how accurate it is). The phone was also warmer than usual when charging even when the phone was off (before and after the battery change). I tried factory resetting to see if that does anything but had no luck. I also tried using a Wakelock detector app to see if there was an app excessively triggering a wakelock but all seemed normal. I even tried downloading a "battery calibration app" which obviously didn't work. So I feel like it's a hardware problem.

Now here's what I did and did not do to the phone before the problem happened. What I did was I do charge the phone quite alot most of the time. What I mean by that is when it hits about 30% I'll plug it in but I never leave it plugged in after a full charge or charge it overnight and I seldom let the battery drain to below 10%. Even so, the phone never got warm like how it is now. That's about all I did to it. Now what I didn't do was, I never tried to install custom ROMs or root/modify my phone in anyway except for the post about how to enable 4G+ which didn't work for me.. My phone is completely stock. I also didn't install any new apps from the playstore or from any 3rd party sites nor were there any updates for any apps installed in my phone. I've had the same apps installed for a couple of months before this happened. I also haven't dropped my phone for a couple of months. I only dropped it less than 5 times from short heights and I have a very rugged case on. I also didn't use any 3rd party chargers. I'm still using the charging brick and cable that came with the phone. I have tried using other chargers that are 2A but no luck. So basically I didn't do anything out of the ordinary prior to this problem.

Just some extra information

1. The hottest part of the phone is at the top right corner of the back. I assume the CPU is there (?).

2. It happened before the April update. It was the same before and after the April update.

3. Phone is running on Android Pie if that wasn't clear

4. The phone is only 10 months old

5. My phone is the Global ROM version

6. Performance wise, its still responsive and snappy. Doesn't lag or freeze or anything.

6. I always have mobile data on and use it as hotspot for my laptop at uni. I have been using it like that for the past 9 months. However the problem happened when I was at home during sem break so I was mostly connected to Wi-Fi.

Sorry for such a long post. I hope somewhere out there, there is someone who can help me or other people that have a similar problem so we can fix it.

Thanks.