Second Battery Option for Fujitsu Lifebook N6410

The Fujitsu Lifebook N6410 has an option of having a second battery in place of the optical drive to give users longer battery life. This is of course optional for all.

And Acer seems to have this function in some of their computers as well and they call it the Acer MediaBay second battery which is optional as well.

but well, having a second battery surely brings a huge improvement as it doubles the usage time!