Cole Hersee 48530 Smart Battery Isolator 200A Prevents loads on auxiliary battery from draining the starting battery. It works with all types of alternator. Smaller and lighter than traditional isolators. There are no efficiency losses due to diodes. It allows bi-directional charging from the alternator or from shore power. It reduces the load on the charging system by not connecting the auxiliary battery until the primary battery is charged to 13.2V.