Hi, thanks for all comments so far.
I prb should have made 3 points clearer in my original post:
1) the two bow thruster batteries are currently at the front of the boat (rest at the back-ish). The previous owner didn't have them wired to the domestic bank (though it was clearly intended. not sure why. there is evidence of something going quite wrong and it being dismantled, and hence no charging currently). There is substantial cabling that goes between the front and the back of the boat already to make this join, so reconnecting it is easy. Bizarrely the switch gear
for the windlass is mid-ship with the intended battery at the back. Moving the switch gear
forward and sharing the 2 bow thruster batteries for the windlass is doable relatively easily - I have no idea why they put the windlass battery at the back. It only makes sense to me if they needed the capacity of a 3rd battery on the bow thruster /windlass. Which in the UK seems less likely than the med, say.
2) I currently have a 115A alternator so it can charge reasonably hard.
3) I was proposing 3 banks (not 4) - ie starter x 1, domestic x 3, and then a combined windlass/bow thruster set x2
Maybe I can ask a few more questions to help clarify what I am learning
from this and maybe my questions expose my understanding which may need 'adjusting'
People have criticised AGM batteries because they don't like a 'hard charge' from the alternator (ie when Alex uses on bow thruster and only engine charges). So this would be the case when out at sea for a few days and after some hard domestic use and we fire the engine up.... So should I discern from this that AGM is only good if you back in port super regularly and hooked up to the shore-power so the fancy charger used?
People seem to worry about using sealed marine
batteries for starter use.... Not enough CCA vs a basic flooded lead acid I guess. Yet I hear a Diesel
engine is a light start load and hence doesn't need much charging ? So why is sealed marine
battery with lower CCA bad here? Surely if the load isn't bad, marine battery is better as the CCA will be lower but adequate and the overall capacity (RC?) is higher which will give you a longer ability to start?
Re golf car batteries - what are they inside? I don't need war and peace - short explanation is fine.
Really appreciate everyone's comments.
I'll look into SWR meter - I've just fitted AIS
with an antenna
sharer and have a ham radio
background too, so this is familiar turf. I have my SWR meter ready to test my own system this week
Merry Xmas everyone. Blowing a gale here in south UK today!