After using my FP2 for 2,5 years, both my batteries (i have a spare one) drains quickly.
With one battery my phone reboots without touching it?
The other battery doesn’t charge very quickly and my phone becomes hot? I tried to deinstall all the apps i don’t need. But i’m afraid i have to buy a new battery.
Check if all contacts are clean and nothing damaged there. Also please read the #batteryguide
This could be due to an app running wild (Facebook app, Netflix etc.), but there could be other reasons for this too.
Try if the phone charges quicker and at a lower temperature when shut down.
Maybe reading here can give you hints on this issue.