U Will Need To Install A Auxillary Battery Solinoid Which Will Only Open When Engine Is Running Or U Can Install A Battery Isolator. The Solinoid Will Cost Far Less And Should Be Rather Easy To Install U Just Need To Wire The Excitor Lead To The Cold Side Of The Ignition And Route Your Battery To Battery Cables Thru The Solinoid. This Is How The House Batteries On A Motorhome Get A Charge From The Engine Same Concept. Hope This Helps You Can Get 3 Or 4 Post Solinoid From Almost Any Rv Dealer. If You Are Really Industrius You Could Also Wire In A Switch If You Get A 4 Post Solinoid And Then Could Use The Secondary Battery To Start The Engine If The Engine Battery Were To Die.