After upgrading BIOS from v6 to v12, laptop battery gets drained very fast

Dear forum users,

I have a big problem as my Dell Inspiron15 3000 series laptp started to behave strangely since I updated the bios from the version on the dell drivers and support website. 

I upgraded to the V12 version Dell Inspiron 3442,3542,5748 System BIOS Version: A12 ,A12, when originally the laptop came with version A06. 

However, since the upgrade, my laptop battery drains after I have switched the laptop off. Therefore I'm having all kinds of issues starting the laptop in the morning and I am afraind this behaviour will lead to a disfunctioning laptop rather soon.

Downgrading the bios version to version A06 is not possible as the utility exists with the message that Dell doesn't recommend downgrading the BIOS version.

What can I do?