battery in AlBook17

[silvo conticello]

I've got the AlBook17, as somebody might have understood from the 
numbers of requests to the list...

Here there is something I don't understand:
Yesterday I've calibrated the battery (wow, it lasted so long...) and 
I've recharged it to 100%, but now it has dropped to 99% (although the 
computer has been  always plugged) and the battery status indicates 
that the battery is charged.
I've tried to use the battery to let it down to 94% and then recharge 
to 100% few times today, but after few minutes at 100% it always drops 
to 99%.

Why?

Thanks,
Silvo