Abstract: A portable, electric propulsion unit for attachment to a cart or the like including a longitudinal frame member, a battery storage container connected at one end to said frame member, a pair of side frame members connected to said battery storage container and said longitudinal frame member, a wheel mounted between said frame members, an electric motor mounted on one side frame member, a gearing means connecting said motor to said wheel, a connecting bracket rigidly coupled to one wall of said battery storage container and a battery charger connected on a side opposite said motor. The device is readily attachable to a cart, such as a golf bag cart, to provide propulsion of the cart upon command from an electric switch. The device has improved structural rigidity and dynamic balance for increased mobility and reliability.