A plug-in electric vehicle (PEV) is any road vehicle that can utilize an external source of electricity (such as a wall socket that connects to the power grid) to store electrical power within its onboard rechargeable battery packs, which then powers the electric motor and contributes to propelling the wheels. PEV is a subset of electric vehicles, and includes all-electric/battery electric vehicles (BEVs) and plug-in hybrid vehicles (PHEVs). Sales of the first series production plug-in cars began in December 2008 with the introduction of the plug-in hybrid BYD F3DM, and then with the all-electric Mitsubishi i-MiEV in July 2009, but global retail sales only gained traction after the introduction of the mass production all-electric Nissan Leaf and the plug-in hybrid Chevrolet Volt in Decembe