Marc wrote in
:

Is there any reson for the reefer to be connected in
common to both batteries? What is common practice?

If the reefer is connected to BOTH batteries, and all the grounds are
connected together (negative terminals), then, all the batteries are
perpetually connected together by the wires to the reefer. The reefer
should not be connected to the starting battery....at all! Nothing should
be connected to the starting battery except the engine, which is the heavy
wire from the starting battery to the starter post. The only other
connection from the starting battery is the heavy wire to the master
switch, so the starting battery can be charged from the house circuit or
the engine started from the house batteries..assuming you have one master
switch.

Having just one charger to charge it all, frankly, sucks. Get a dual 10A
charger and connect one output directly thru a 10A inline fuse to the
starting battery. Connect the other 10A output to your house battery
common point, again directly through an inline fuse. Are all 3 of these
house batteries just hooked in parallel as I suspect? I'm not a great fan
of that. I like to keep battery banks separately switched, so if one of
them shorts or something, I can switch it out of the circuit in 15' waves
offshore without a wrench. Screwing around with battery wires is a
dockside exercise, not offshore rolling around. Switches could be as
simple as those direct-to-the-post on-off switches on each one.

Now, you need do nothing. Leave the 3 house batteries in parallel to their
charger and leave the house switched to ONLY the house batteries, the
normal position, say "A". Chance of losing all of them at once is near
zero, but you could run them down. Starting battery is always connected to
ONLY the starter and its separate 10A charger. You never need to switch it
until something fails. If you only have one alternator on the engine, use
a diode battery isolator to keep the batteries separate, charging through
the isolator with the alternator output only hooked to the isolator's
common post. Again, you start the engine and do nothing to charge it all
from one alternator. Simple...always simple. The isolator connects
directly to the battery posts, too, just like the AC charger.

How are the batteries fused? If the starter shorts the starting battery,
does a fusable link blow or do we just let it explode? If you're using #2
cables to hook the battery to the starter and house battery switch, put a
large fuse between battery MINUS terminal and "ground", negative common
engine block. No circuit, including PRIMARY wiring to the batteries,
should go unfused, like all the rest of the boats on your dock....damn
them. Unlike the car, I can't just get out and walk if it catches fire.


Larry