Hybridization of the lithium energy storage for an urban electric vehicle

This paper discusses benefits of introducing an ultracapacitor (UC) bank into a battery electric vehicle (BEV) powertrain. The case of 12kWh LiFePO4 battery pack is studied quantitatively. Simulation results refer, inter alia, to three main scenarios: fresh cells, half-used battery cells, and half-used ultracapacitors and batteries. Thermal modeling is incorporated into the simulation. Data from real world are considered: various driving cycles recorded using GPS receiver (incl. elevation), discharge curves from battery manufacturer, and UC equivalent series resistance (ESR) variations due to cycling according to real data reported in papers. Cost, as well as gravimetric and volumetric issues are presented. The key decisions referring to an energy storage for BEV being currently designed within the frame of ECO-Mobility Project are highlighted.