Passive hybrid energy storage system based on lithium-ion capacitor for an electric motorcycle

This paper presents the multiple energy storage system usability for an electric motorcycle focused on passive hybrid topology. The studied hybridization is based on a passive parallel topology connecting lithium manganese nickel 18650-type cells and lithium-ion-capacitor to supply the motorcycle powertrain. The passive hybrid energy storage system design is fully addressed based on an extension of Ns/Np battery pack sizing maps to passive hybrid topology using lithium-ion-batteries and lithium-ion-capacitors. The improved sizing method is able to size simultaneously an integrated energy storage system made from two different cells chemistries. The proposed design optimizes the common voltage range and distribute the current according to the intrinsic cells characteristics. Relationship between dimensions are established to plot as a traditional two-dimensional map a four-dimension sizing problem. The benefits and performance improvements obtained by the Ns/Np hybrid design for a case study involving an electric motorcycle are presented and discussed based on root-mean-square and mean value of the current cell, standard deviation of the C-rate and instantaneous current peaks variation coefficient. The proposed configuration could reduce the stress on the battery cells by 42% on standard deviation and 36% on variation coefficient with a decrease of 9% in average current while reducing the root-mean square value by 15% on a specific motorbike race simulation.