Electric energy storage units in Electrically Propelled Vehicles (xEV) are one of the main contributors to the total mass and volume in the vehicle because a large number of storage cells is required to supply the motor’s voltage. This large number of cells brings problems of rapid degradation, system failures, power losses, and high costs. Consequently, reconfiguration, sizing and downsizing of the storage unit are techniques that have been reported as effective to improve the shelf life and the performance of the storage cells. However, these solutions might decrease the rated voltage of the storage unit and therefore DC-DC converters with high voltage-gain are a suitable solution to connect these low voltage storage units to the motor drive, keeping a good performance of the vehicle. Moreover, parasitic resistances presented in the components of these converters have proved to influence the efficiency and the voltage-gain of the converter. In this paper, the ideal voltage-gain of four remarkable high step-up converters is analysed, derived, and compared. These converters were selected because of their potential to be applied in electric mobility and their similarity in the techniques that use to achieve high voltage-gain: interleaving phases and magnetic integration. One of the analysed topologies is proposed by the authors. Afterwards, the parasitic resistance effect is analysed to obtain the non-ideal voltage-gain and the efficiency of these four topologies. Finally, the topology that presents the best trade-off between the nonideal voltage-gain and the efficiency is experimentally tested with a 100W prototype.