Development of a universal adaptive battery charger as an educational project

The number of small portable electronic devices (such as notebooks, mobile phones, etc.) has risen continuously over the last years. For charging the batteries of these devices a mains charger is required. Unfortunately each portable device requires an own special battery charger which shows a low efficiency and a poor power factor in many cases. In order to solve this problem the IEEE has organised the international student competition "future energy challenge 2007" aiming at the development of a highly efficient universal battery charger. This charger should be operated at all AC voltages between 90 V and 270 V and it should be able to optimal charge four different battery types (lead acid, NiCd, NiMH, Li-Ion) with an unknown number of cells. As a very challenging task the type and number of cells of the battery has to be determined by the terminal behaviour of the battery only. Within the paper the competition contribution of a combined student team from the RWTH Aachen University and the Cologne University of Applied Sciences is presented. This includes organisation, support and experiences of the student team, design and development of the universal battery charger as well as measurements at the prototype.