I know that this is like 2 years old, give or take, but I've done the same, except that I put my laptop in hibernation mode, meaning that, whether The Sims 4 is running or not, the amount of battery drained is reduced due to the laptop being put in hibernation mode, much like the Vampires in said Game Pack - Vampires Game Pack - can hibernate in coffins.
My point is, if you ever do leave The Sims 4 running overnight, instead of just closing the lid, put it in hibernation mode, then close the lid, but like @puzzlezaddict said, it might be your laptop not being able to do as such anymore, how old is/were your computer 2 years ago, because that might be why