The battery capability gives 2 unit watch winders the ability to work without the use of an AC electrical plugin that requires an attached cord. This feature is important because most homes do not have electrical plugins in master bedroom closets. The battery feature option allows the watch winder to become wireless for use inside closets, safes, or high shelf in an office. The battery option requires (2) AA batteries.(not included). The add-on battery feature which comes with the standard removable AC adaptor eletrical cord is an available option at checkout.
The AC only standard feature is a separate unit that does not allow the use of batteries on the bottom. The downside to AC only adaptor is that if later the battery option is desired, the unit will have to be returned for this upgrade as the battery option is a separate product entirely.
We highly recommend the battery and ac adaptor option at checkout.