Abhinav Rakesh
Beginner
i am not here to say who is wrong or who is right. However one thing that I can confirm is the issue is not software. I had experienced this exact issue in real world with one of my GPS tracker connected to raspberry I do make some hobby projects and have DIY skills so 2 things which can cause this quick battery drain issue is listed below.
1. BMS on motherboard has shorted resistance which is giving faulty reading to phone which in turn the software in phone is misinterpreting the actual charge level.
2. All phone batteries specially phone batteries have separate BMS circuit. a Shorted BMS can also cause this problem.
Buyer can try to use a different test battery however for that you need to open the phone and it will make things even worse.
1. BMS on motherboard has shorted resistance which is giving faulty reading to phone which in turn the software in phone is misinterpreting the actual charge level.
2. All phone batteries specially phone batteries have separate BMS circuit. a Shorted BMS can also cause this problem.
Buyer can try to use a different test battery however for that you need to open the phone and it will make things even worse.