Abstract: A portable computer docking unit comprises a computer docking bay for receiving a portable computer on the docking unit. The docking unit also has a charging cradle that charges a battery of the portable computer. As a result, even if the battery installed in the portable computer can be charged while the computer is connected to the docking unit, an additional battery can be simultaneously brought to a full state of charge in the charging cradle, thereby providing the user with a backup battery to effectively double the time over which the portable computer can be operated without access to an alternating current power source. Preferably, the charging cradle is located under the computer docking bay. Installation of the portable computer, thus, prevents physical access to the battery in the charging cradle. A latching system is provided for securing the portable computer to the docking bay. This combination of features has the effect of providing security for any battery in the charging cradle.