A polarity protection circuit for a battery booster device is provided. According to an exemplary embodiment, the polarity protection circuit is comprised of solid-state devices. Preferably no mechanical or electro-mechanical devices, such as solenoids are included in the polarity protection circuit. The polarity protection circuit is electrically connected to the battery to be charged and to the boosting battery. The polarity protection circuit prevents current flow between the batteries unless proper polarity is achieved.