A hybrid electric vehicle (HEV) equipped with an electric drive operates with two different drive systems: an electric motor and an internal combustion engine. There are different concepts of how and when which drive is used or whether both are combined.
The serial concept is different. In terms of drive technology, this concept works exclusively with the electric drive. The combustion engine drives a generator that charges the batteries. This electric car variant is called a hybrid electric vehicle (HEV), whereas the former, in which the batteries must be charged at a charging station, is called a plug-in hybrid electric vehicle( PHEV).
The electrical system for both concepts is generally a 48 V electrical system.