Solar panel, controller, isolator, and 4 batteries...need a genius

[jc55]

Hey guys, I'm rewiring and I have...

1) 2 batteries in the rear of the boat. One starting, one accessory on a 1, 2, Both, Off switch. Normal everyday configuration.
2) 2 additional batteries in the pilot house in parallel. I have a 500watt inverter, and my anchor windlass connects here, that is all.
3) All 4 batteries share a common ground, there is a positive cable between the pilot house batteries and the rear batteries but it is not connected. I ran it just in case.

I'm adding a 100 watt Renogy solar kit to charge the pilot house batteries when I am away. No problem, the charge controller will charge 2 batteries in parallel and not overcharge.

Now...
I could add an isolator to charge both banks(all 4) batteries BUT! there will be no overcharge protection because feedback to the solar controller is prevented by the isolator...common knowledge.

Can I...
Solar panel-->charge controller--->2 pilot house batteries in parallel--->Positive battery cable out from pilot house batteries--->90 amp Isolator in series with two batteries at rear of boat which are in parallel. (Battery switch at rear of boat will change from one to two batteries depending on it's position)

Will the 2 pilot house batteries act as a buffer, provide feedback to the charge controller while charging or NOT charging the 2 batteries in the rear of the boat at the same rate, since they will have no feedback due to the isolator?

Does that make sense? Will the solar charger control via feedback not overcharge the pilot house batteries and do the same for the rear batteries with no feedback?

 

[UncleWillie]

Re: Solar panel, controller, isolator, and 4 batteries...need a genius

You will have feedback to the charger through the isolator. It will always see ~0.7 volts less than the actual voltage. If you use an Isolator, the voltage drop to the stern batteries will guarantee that they always receives less of a charge.

Using an ACR, instead of an old school isolator, will let the solar controller see the actual voltage.
Plus the alternator will charge the Batteries in the pilot house while underway.

 

[jc55]

Re: Solar panel, controller, isolator, and 4 batteries...need a genius

Perfect. So the pilot house batteries will be on an accurate feedback mode with the solar charger, and the voltage drop of .7 across the isolator diodes and extra run will ensure that the rear batteries are not overcharged. Thank you UncleWillie, for reading and replying to my post. I owe ya one. I may run a 9.9 quite a bit so I'd like to try this configuration for a while with room for expansion.