dual battery battery

[HEM49]

Iv been given two optima blue tops 800cca 110rc 50ah, they have only been in a boat for a few years and they are in good condition. Question is can i run them in my d22 as dual batteries, ill be running one in the engine bay with winch, spotlights, cb off it and the other in the tray for the fridge and as an extra 12v socket.
How do i run 3 batteries ie set up?

 

[Old.Tony]

You could run a pair of isolators. Neither aux battery needs to know the other is there. Sort of like this:

Starter -----> isolator ----> engine bay aux battery
l
l----> isolator ----------------------------------------------------------> tub aux battery

Don't forget to fuse both ends of the cables.

What works to isolate one battery will also work to isolate a hundred, as long as there's enough power to do charge them all up.