I guess I held back a few details to keep it simple.
I am thinking of using an 80ah Expanded Calcium Grid (EXG) battery for the start battery.
This will have a dual role to start the engine and to run the freedom anchor
whinch with the deck hose pump
. (both these units will only being running while the engine is going).
Therefore the auto relay has been connected to the start battery to allow re charging immediately after anchoring.
I agree the battery combination is a trap and would only be useful if the battery state of charge is marginally different.
The existing controller is an 8 amp shunt type and I would like to upgrade to achieve charge efficiency.
The solar panels are in storage at the back of the shed so not sure of the capacity.
Good to hear an MPP controller will look after itself, I was wondering if the auto relay would see the solar controller voltage on the house battery rather than the true battery state of charge and get confused.
I suppose it does not really matter (the engine will be delivering a stronger charge anyway)
as long as the controller takes over after the engine is shut down.