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[Larry S.]

so i don't have the possibility of the deep cell not charging enough if everything is powered off of it, shouldn't i just put the isolator on the starting batteries instead of the deep cycle?

I will back off a bit. Diode isolators isolate both batteries. With an internal regulator on the alternator, like our Fords have, the isolators will drop the charging voltage as much as 0.4 to 0.5 volts on the batteries when high current is being drawn through the isolator. If there is no load on the battery and no load current being drawn from it the voltage drop will go down to somewhere between 0.2 and 0.3 volts. This means the batteries will reach full charge but it will take a longer time. Rvers live with this reduced charging rate all the time but in my opinion it is not the correct way. A relay isolator isolates only the deep cycle/trailer battery when the engine is not running so that the load on the deep cycle does not discharge the starting battery. Give some info on exactly what you are wanting and why. Maybe there is a different and or a better way to achieve what you need. In most cases if the alternator is operating there is no need to isolate batteries. Its only when the alternator is not working/engine not running that isolation is needed.