Originally Posted by flamboyant 1
Until now I have always left my battery in my laptop (IBM T40) when using it regardless of whether I charge or have the battery at 100% when on "real power".
If you run for long periods on AC and you have good power you might consider pulling the battery. The heat (which can be high in a laptop case) is not so good for batter life, this contributed a lot to earily battery death in the 600 series thinkpads. I have a couple of T23's and I know they put the battery in the opposite corner from the CPU. I don't know how the t40 is layed out you might check and see if you battery is near the hot portion of the keyboard or not.