Abstract: An auxiliary power device for attachment to an existing refrigeration unit of a refrigerated trailer to serve as a power source to a truck cab, thereby allow operation of electrical devices in said cab without idling of the truck's engine. The auxiliary power device comprises a housing attached beneath the existing refrigeration unit, an electric generator enclosed within the housing, and a pulley assembly mounted in the housing and connected by drive shaft to the generator. The pulley assembly is connected via drive belt to the diesel motor in the existing refrigeration unit. When the generator is activated a first relay governs the speed of the diesel motor in the refrigeration unit, which turns the generator to generate power, and a second relay prevents drainage of the refrigeration unit battery. The power from the generator is routed through a breaker panel mounted in the cab of the truck for distributing and regulating power from the battery and/or generator into the truck cab.