This paper aims at presenting the experience of the Power Conversion project in teaching students to design a proof-of-principle contactless energy transfer system for the charging of electrical vehicles. The Power Conversion is a second-year electrical engineering (EE) project in which students are to gather and apply EE knowledge to design and test a system. This system is to work with power level and operates independent from an electricity grid. The instructional method used in this project is design-based learning (DBL). As an educational approach, DBL is to support students to gather and apply knowledge in "open-ended" assignments. The set-up of the project has gone through different modifications and iterations in three consecutive years regarding the organisation and supervision of the students. We have analysed the students' design products in the past three academic years in order to evaluate whether the project set-up and supervision have influenced students' designs. Results indicate that the "open-ended" character of the project has a positive influence on the designs especially regarding the criteria on efficiency, Maximum Power Point Tracking algorithm and power tracking.