Globe technologies is a company that sells products in the gardening market for both commercial and professional use. This study focuses on developing a battery powered accessory for autonomous mowers. The study investigates the possibility to use autonomous mowers in green spaces that do not have access to power by the grid. To provide the autonomous mower with power the study introduces a portable power supply that provides power to the mower.  The development of the portable power supply starts with a market analysis and that lays the foundation for the project. The report continues with the development of the actual product and finishes off with testing of a prototype. To get the product that is wanted relevant theories and methods is investigated and applied. During the thesis a number of iterations of the product are designed to meet the demands of the requirement specification.