Sure Power Multi-Battery Isolators are the original Battery Isolator, and still the best on the market. Multi-Battery Isolators are used to eliminate multi-battery drain when two or more battery banks are in a charging system. They perform as well or battery then existing factory installed components. Specifically designed to exceed OEM Specifications, they are equipped with Solid-State Electronics, which isolate each battery circuit and allows each battery to discharge and charge according to its own needs. They are more efficient and reliable then mechanical or solenoid systems, and have the reputation as the most comprehensive line of Battery Isolators on the market.