Passive Coupling of Batteries and Supercapacitors Based on Module-Scaled Models

The use of hybrid energy sources in electric vehicles is an interesting prospect towards extending batteries lifetime and vehicles autonomy. Supercapacitors are used in this study to absorb the high current variations during the real use of a light electric vehicle. This paper aims to determine the number or battery and supercapacitors modules to associate in parallel, following a passive topology, to respond to the requirements of a driving cycle for a three-wheel recreational vehicle. The vehicle has been modelled following the energetic macroscopical representation formalism. Module-scaled models of batteries and supercapacitors have been made describing their behavior in relation to their state-of-charge using the galvanostatic intermittent titration technique. This approach allows significant gains in calculation time compared to a cell-scaled model for full-scale vehicle simulations. Standard FTP and WLTC driving cycles are used for the comparisons. They firstly highlight the need of a sufficient number of battery modules to limit the current through them and preserve battery cells. Also, they show the need for supercapacitors to reduce both the amplitude and the magnitude of current peaks in the batteries. Results are of very different nature considering the driving cycle. Several supercapacitors modules are needed to best preserve batteries in urban context. However, for a driving cycle involving higher speeds, they show to be barely useful.