Abstract: A method and apparatus provides supplemental power to an engine. The method and apparatus includes a pair of conductive leads for connecting the supplemental power to an engine electrical system, a battery, a relay connected to the conductive leads, a shunt cable connecting the battery to the relay and a processor for controlling the relay to selectively apply electrical power to the engine electrical system. The method and apparatus includes safety features to reduce the risk of injury to the operator and damage to the apparatus and/or engine electrical system.