POWER SYSTEM FOR A TRANSPORT REFRIGERATION UNIT

A vehicle for transporting goods and a method of operating a power system of the vehicle are described. The vehicle comprises an axle; transport refrigeration unit; and power system. The power system comprises an energy storage device; a generator to generate electrical power and to supply electrical power to the energy storage device; a multi-speed gearbox mechanically coupling the axle to the generator; and a controller to receive data indicative of a speed of the vehicle and a state-of-charge of the energy storage device, and to control the multi-speed gearbox. The controller is configured to set a gear ratio of the multi-speed gearbox to a speed-based gear ratio when the vehicle is in a first state, wherein the speed-based gear ratio is selected based on the speed of the vehicle, and wherein the state-of-charge of the energy storage device is below a first charge threshold in the first state.