Hi guys I probably found a problem related with the battery drain, just after having unplugged it from the charger ( so 100% battery level ) I've changed the language and restarted the phone, the battery level is now to 48% after ~10 minutes after having unplugged it, with everything turned off and low luminosity.
Probably is a problem with the charging method itself, in fact ( especially in my phone, a Lumia 820* ) after having rebooted the phone the battery level is more accurate as is recalculated after alot of time.
Probably there's a bug in the battery estimation method so it stops charging not at the real 100% but alot lower, virtually discharging faster.
It can be also a problem related only to my device.
Tell me what do you think.
* if you don't know it the L820 way to calculate the battery level is to me alot so stupid, as it doesn't check directly the battery level, it does calculations based on how you are using your phone, and after a fixed period it checks the real battery level, so after the reboot is displayed the real battery level, as I don't think I used 53% of the battery in less than one minute.
--update--
Here's a screen that shows the notification from the 'battery' app
"Battery is draining quickly, 62% in 36 minutes"
( I can't actually show you the screen as I don't find the way to upload it from the phone I'll post it as fast i can )