Methods and apparatus to use a switched-mode power supply as a source of power in a service pack are disclosed. An example power system includes: an engine; a generator configured to generate electrical power from mechanical power delivered by the engine; a switched-mode power supply configured to convert the electrical power from the generator to output power; and control circuitry configured to: when an output load of the switched-mode power supply is a power system load, control the switched-mode power supply to provide the output power for output to the power system load; and when the output load of the switched-mode power supply is a vehicle load, control the switched-mode power supply to provide the output power for output to a vehicle electrical system connected to a vehicle energy storage device.