Vehicle engine starting system and method

The starting system drives a starter motor (20) engaged to start an engine by using a (lithium) secondary battery (1) as a power source. A voltage sensor (9) detects a voltage at the secondary battery (1). A control device (10) allows power to be discharged from the secondary battery (1) to the starter motor (20) if the voltage detected by the voltage sensor (9) is equal to or higher than a predetermined value and disallows a discharge from the secondary battery to the starter motor if the voltage is lower than the predetermined value.