[blacksmith_tb]

The 'range extender' of the BMW i3[1] is basically just that, and the Chevy Volt's engine was also not connected mechanically to its powertrain[2].

1: https://en.wikipedia.org/wiki/BMW_i3#Range_extender_option

2: https://en.wikipedia.org/wiki/Chevrolet_Volt#Drivetrain