Principally used to start your engine. Filters/stabilises power to provide extra power for the ignition, lighting and other vehicle accessories when they become too much for the charging system to handle i.e. when idling. Provides power to the electrical system when the charging system is not in operation. 25 Month Guarantee subjected to no physical damage to the battery or battery terminals. Includes a refundable deposit, should old battery be sent back to us.