Charging battery treshold bug?

[puco]

Hi

I have set my battery charging treshold to 80% (because I'm working mostly on the AC and I don't want the battery to be charged whenever I move my NB). The point is that when I plug in the AC the battery starts chaging even if it is around 95%. When I then restart the computer the battery stops charging.

So my question is: Is this the designed behavior? And how should I use the AC? Should I shut it down before plugging in?