Electric transmission or electric powerchain is a transmission system for propelling motor vehicles. It is used for in road, rail, and marine transport. The defining characteristic of electric transmission is that it avoids the need for a gearbox, by converting the mechanical force of the engine into electrical energy (through a dynamo or alternator), and using the electrical energy to drive traction motors, which propel the vehicle mechanically. The traction motors may be driven directly, or in some cases, via a rechargeable battery; if rechargeable batteries are used, the vehicle is considered to be a hybrid vehicle.