The isolator is generally used in the presence of a generator; but that’s not my area of expertise!
What I will recommend is getting rid of the ‘1/both/2/off’ switch. That thing has been the source of more confusion and loss of good batteries than anything else. Given a house and an engine-starting bank, LEAVE THEM SEPARATE. Any combining, on the ‘both’ circuit, of different-type, different-size, different-age, differently-charged batteries will effectively kill the weaker of the two.
There is no sensible reason on a well-designed cruising boat to combine the engine bank and the house bank except in some emergency, for which a separate circuit can be rigged and manually/mechanically connected such as to run bilge pumps off the engine battery (with the engine already running) or to start - for only one foreshortened leg of the cruise - the engine from the house. For ALL charging and discharging they should always be separated.
Modern ‘smart’ chargers can facilitate charging of two separate banks without electrically combining them. So, in answer to your question, maybe you don’t need the isolator at all.
My system is just like what I recommend to others. I was told by my cousin Rick, the family ABYC electrical tech, that I don’t need the isolator and so I don’t have one.
Thanks to Tim Allen of Home Improvement for reminding us that in many cases, more power is the best solution! Diana has, in fact, three s...
dianaofburlington.blogspot.com