Abstract: A voltage maintenance system is provided for an engine-driven vehicle having a primary battery, a starter that is energized by the primary battery, an ignition switch for selectively and momentarily activating the starter to start the engine and one or more electrical accessories that are electrically connected to and energized by the primary battery during normal operation of the vehicle. The voltage maintenance system includes a secondary battery. The system senses activation and subsequent de-activation of the starter each time the engine is started. A switching circuit is provided for electrically connecting the secondary battery to the electrical accessories and electrically isolating the primary battery from the electrical accessories such that the secondary battery energizes the electrical accessories each time activation of the starter is sensed.