A method for starting an internal combustion engine coupled with a cranking motor, which is coupled with an electrical battery, includes connecting a capacitor with an electrical system of another engine or battery, wherein the capacitor is disconnected from the cranking motor coupled with the first engine, and charging the capacitor with the electrical system of the other engine or battery. The method further includes connecting the capacitor with the cranking motor coupled with the first engine, at a time when the first battery has insufficient charge to start the first engine, and starting the first engine with the cranking motor and the capacitor. A portable rapid-delivery power supply apparatus for providing a supplementary source of power to an electrical system includes a capacitor having connectors adapted to be connected to the electrical system and a charging device coupled to the capacitor, wherein the charger is powered by alternating current.