A retro-fit battery system for attachment to a mobile workstation having a generally upright post. The battery system includes a main body shaped so as to locate around at least part of the perimeter of a generally upright post and having a removable attachment to the post, wherein the main body further includes at least one battery docking mount to which a battery can be detachably connected, an electrical outlet and a control system for providing electrical energy from the battery to the electrical outlet.