What are the different types of hybrid electric vehicle (HEV) configurations, and how do parallel hybrids, series hybrids, and plug-in hybrids differ in terms of their powertrain architecture, operating modes, and energy storage systems?

Hybrid electric vehicles (HEVs) come in various configurations, including parallel hybrids, series hybrids, and plug-in hybrids. Parallel hybrids have both an internal combustion engine and an electric motor connected to the transmission, allowing the vehicle to operate on either power source alone or a combination of both. Series hybrids use the internal combustion engine solely to generate electricity, which powers the electric motor that drives the vehicle’s wheels. Plug-in hybrids have larger battery packs that can be recharged from an external power source, allowing for longer electric-only driving ranges compared to traditional hybrids.