The battery filling plug is the centre of a single point watering system for industrial batteries e.g. in electric vehicles, for energy storage (battery back-up, renewable energy). Task: Quick and secure filling of battery cells, considering both ecology and economy. The solution has been a patented injection system where rotating water is creating suction. Technical precision within smallest space. The aim of the design has been to define the single filling plug in a minimalist way, however clear in its function and exemplary in the integration of the filling system on the battery top.