Another battery charger question

[Omatako]

Let me first try to describe my layout.

I have a house bank that is 4 off 220Ah 6v batteries. These are split into two units, one connected to position 1 on the 1-ALL-2 switch and the other to position 2. They are charged by a 160A alternator.

I also have another bank of 2 12v batteries, one for the starter and the other for the anchor winch. These are independant of the above and have their own alternator (85A).

I have 110v mains system that is driven either by shore power or by the house bank via an inverter. When shore power is connected (assuming it's 110v) then the inverter supplies the system with 110v through a bypass relay and it also charges the batteries.

This is all cool but here's the problem. The boat is based in New Zealand where we have 220v mains. But the problem is also complicated by the fact that the frequency is different. The US system is (I think) 50 cycles and NZ is 60 cycles (it could be the other way round). So it doesn't help me to just step the 220v down to 110v because there is no way of correcting the frequency and a lot of the appliances required don't like different frequencies and I don't really want to replace all the appliances. So. . . . .

My total draw on the mains system would probably never exceed 30 amps at any one time. What would the forum say to me installing a 60 amp battery charger that runs on 220v and feeding the 12v output into the system somewhere between the house bank and the inverter? I've also thought about putting an isolator between the battery bank and the charger so that when the charger is on, only the inverter is powered. I'm not sure whether the inverter would then continue to charge the batteries, I think not because I think this is a function of the 110v circuit.

This way I could power all my 110v mains requirements without having to worry about frequencies or "warrants of fitness" for my mains system.

I have had one electrical contractor tell me it will be fine and another who said it won't work . So I guess I want confirmation one way or another.

[Idiens]

Sounds to me like it should work - if the NZ battery charger is one that is designed to recognise and take domestic loads as well as the battery charging task. Of course, it has to be rated higher than the load that you intend to take off the DC and inverter circuits together. You would want to make sure that the inverter is protected from the shore power, that is the NZ charger is to only item to receive shore power and preferably the inverter has an automatic self isolation switch too. Definitely leave all the batteries in the DC circuit, to get charged and to act as a buffer to the inverter.