Used multiple types of batteries all of them after few days, with no use, are drained!!!!
Is this normal?
No, it is not normal for the battery to drain without using the 521.
I have the same battery installed since I received the device and the level meter is still nearly on full - I make several coils per week on average, the rest of the time the 521 is turned off and doing nothing.
What kind of battery are you using?