2 Battery 120 Amp Isolator - This 120 Amp isolator is for use with 2 batteries (please call if you have any questions about whether it will work with your application / alternator). Sure Power battery isolators help prevent accessories powered by a vehicles auxiliary batteries from robbing power from the main starting battery. A battery isolator helps assure that your vehicle will start, even if auxiliary batteries are dead and they also allow your alternator to charge the auxiliary battery as needed to maintain a proper charge level, separate from your vehicle battery. Rugged solid-state construction. 1 year Warranty. (Connector kits and installation kits not included.)