Install dual batteries in Boat Talk Posted April 8, 2013 http://www.yandina.com/I went with Perko 2-ALL-1-OFF switch and west marine combiner. Batt number 2 DOES have the AMP directly wired to the Batt (had problems with alt whine through the stereo when going through the switch). If I do kill Batt 2 on the hook playing the stereo for hours, I simply switch to Batt 1, start and go home (have done this a number of times). I DID leave the original ON OFF switch with the "key" handle as a "little bit"(very little bit) of extra security when I leave the boat overnight at unfamiliar marina ( I pull the key out in the OFF position and take with boat key)To me, the above set up for the most part is right. The combiner from ( http://www.yandina.com/ ) works very well. It come in 3 types 50, 100 & 150 amps. Note the green wire, that is a control wire. From the helm you can set it to Auto, close the combiner or open it. Giving you full control over it. So if your battery is having a hard time starting your engine. From the helm you can combine 2 batteries with out moving.