The invention concerns a method (200) and system (100) for charging a battery (110). The method includes the steps of receiving (212) an input power supply signal (300), monitoring (216) the input power supply signal to determine when the input power supply signal reaches first and second predetermined thresholds (314, 316) and in response to the monitoring step, selectively controlling (217) a charging switch (122) that controls the flow of the input power supply signal to the battery. The controlling step can include activating (220) the charging switch when the input power supply signal reaches the first predetermined threshold and deactivating (226) the switch when the input power supply signal reaches the second predetermined threshold.