Ok. I installed a new Promariner 2000 PS inverter charger last year. Well, I did some of the work, and the “main electrical guy” on our lake did the rest. In order for the alternators to charge the battery while underway, I replaced the two alternator three battery bank diode charger with ProIso 2 alt 4 battery version. The alternators put out 100 amps a piece. Promariner said the circuit must be able to handle 200 amps, the total of the two alternators.

I was having trouble keeping the inverter bank (4 6 volt batteries in a 2 battery 12 volt configuration charged while underway. When I checked the voltage at the four outputs, I was getting 13.8 to 14.1 at the engine outputs on the isolator and 15.1 volts at the inverter isolator output. The other bank was not charging at the time I was checking which may or may not be ok. When I checked the voltage at the inverter battery bank, it was receiving only 12.8. When I spoke with Promariner, they told me the wire from the isolator to the inverter battery bank should be no longer than 12 feet and if that long should be 2/0. It is 13.66 feet with no way to shorten it. The wire is the same size as the wires that go to the two engine batteries (close to 10 feet), and the house battery (close to 5 feet) from the original isolator which were original installation by Carver. I think it is probably 2 gauge, but I haven’t attempted to figure that out.

Anyway, here are my questions. I am stuck with the distance. Would you advise using 2/0 on the Isolator to inverter bank, or would you go with 3/0? When I look at ABYC guidelines, it looks like 2/0 would work. If I change out the cable to the inverter bank, should I also consider changing out the cables to the two engines?

If you scroll down the link below, you will see the recommended wire sizes.

https://baymarinesupply.com/bosns_corner_wire_sizes

Thanks for any advice that could be thrown my way.