Hi Sweetas and MarkTheBike,
The system fitted was apparently to comply with the surveyors request to have such system fitted in order for the boat to be certified for charter. I say apparently as I did not see anything written down regarding it, neither was there a specific point raised in the survey document. Anyway it seemed like a good idea, and having seen the results of some of the antics that charterers got up to, I can also see the point of having something, forgive me for saying this, that was idiot proof. As boat owners you will take care of your investment, and responsible charterers may do so but experience indicated that responsibility was rarely present and if they mess up and get hurt it becomes the boat owners problem. So jumper leads were out for the reasons raised by Marchi, and as batteries give off hydrogen gas during charging, it is a wise decision to minimise the risks from sparks. Fortunately hydrogen is lighter than air and so if you are lucky it should not normally accumulate within the bilge and battery storage areas provided they are satisfactorily ventilated. On my B36 2002 the battery locker has large cut outs in the tops of the locker side that supports the settee above, so some ventilation is possible.
As for a wiring diagram, I need to take another look later this week at the system that was fitted and will then draw it out and take some photos.