I want to keep my starting battery for starting only and my lights,sonar,stereo on another battery is this what I need? http://www.amarket.com/imdc270.htm
http://www.pkys.com/FAQ/Charging_multiple_batteries.htm <br /><br /><br />That is why Isolators have heat sinks - the inefficiency is dissipated as heat and the voltage drop can prevent full charging. That's why they are cheap. Combiners are simply switches that turn on and odd automatically as needed.The old fashioned way was to use a battery isolator, which is a set of diodes which allow the charge to go to each battery but doesn't allow the batteries to connect to each other. One problem is that there is a voltage drop across the isolator means you need to have an externally regulated alternator with a voltage sense wire downstream of the isolator. Another problem is the high failure rate of isolators. Another is that the voltage drop means wasted energy.