The high-capacity battery on the ibm last almost 7 hours reading documents and organizing my emails and addressbook with radio turned off. Not bad. It is a little larger than the stadard battery which comes with t41, except it sticks out an extra 2cm which is hardly visible espacially for myself because the battery is behind the sreen. Actually I would like to have a even larger one if it can go beyond 10 hours. The t41 with the big battery is still *much* smaller and lighter than my friend's new compaq.