How do you all have your dual batterys wired. Do i need an isolater, or can i just run them together?

 

Depends on what you want two batteries for. You use an isolater when you have an aux battery running accessories, so the accessories do not drain the battery that starts the engine. And it's best to have a deep cycle for the aux battery, because a automotive type battery will not last if it's deeply discharged on a regular basis. But the isolater stills lets the alt charge the aux battery.