In conventional EV powertrains the main energy storage system is based on battery banks. Potential higher current stress on battery during transient operation can considerably reduce its expected lifetime, while battery size is overrated to respond under heavy transient demands. The regenerative braking capability is also getting limited due to its charging dynamic constraints. Hybrid Energy Storage Systems (HESS) based on batteries and supercapacitors (SC) have the potential to solve this issue. However, SCs size and weight can deteriorate the power density of the solution. In this paper, a Partial Power Configuration (PPC) based on Dual-Active-Bridge (DAB) is proposed as a power interface to increase the power density of an HESS-based EV powertrain. A comprehensive efficiency analysis is provided, while transient dynamic results are provided to validate the proposed power configuration.