I understand it.
I guess the difficulty is finding the existing cables and working out where to fit a switch which is easily accessible, no mean feat in a 321.
I will go and look tomorrow when I have the boat lifted out.
I started on this because I have an 8 year old starter battery which as far as I can see has a very easy life. The number of engine starts per year is very low (relative to say a car) and then it spends all its time being charged either by the alternator, or when berthed, by a Mastervolt charger.