[ltp] Battery charging control ?

[Paul RIVIER]

Hi,

As I am on holliday for 2 months, my laptop stay pluged on AC all along 
the day.
As recommended I should let battery discharges until 40%.
I dont want to remove my battery, I just want to stop charging it even 
if my laptop is plugged.
Someone told me that windows can do this, but I don't have windows to 
check by myself.
Do you know if it is possible and how please ? should I inspect ecdumps ?
My laptop is a T42.
Thank you

paul RIVIER