You said you are going to split the load between two relays and plan to use starter relays, won't you need four relays total? Two to power forward and two more to power backward?
One battery directly wired to the winch contactor set.
The winch I ordered has an industrial contactor set instead of 'Starter Relays', one reason I ordered it.
If Warn didn't lie to me, it's a 500 Amp industrial contactor set, reversible polarity, so 'Forward' & 'Backward' will be handled at the Winch.
The idea with Winch (Starter) Relays is to isolate the SECOND battery when it's not in use,
But still add plenty of current when the winch relays are tripped.
Since they are hard wired into the system, when tripped, they also effect self rescue by self jump starting, extra current to the starter, ect.
There will be 4 high amperage relays total.
'Winch' (2) and 'Starter' (2).
Doesn't make sense to have a second battery and put the heavy relay between battieres when you can use a second starter relay and DOUBLE the power to the starter.
Primary battery has a 'Pass Through' connector, seen on the bottom buss,
And the 'Secondary' will terminate at the top buss,
Connectors shown on image above, but without the cables yet...
I use BIG HONKIN CONNECTORS with a large contact patch so they conduct current like they are supposed to, and I'm not above soldering them into place on the buss either!
Since the relay is the restriction point, why not put it in line to the starter doubling your current to the starter,
Instead of putting the power to the FIRST battery, then all that current trying to pass the factory starter relay...
Parallel instead of series.
I really like the quick connects.
They have been MONSTROUSLY HANDY!
I was hoping for SOME
help when I first installed them, but they have just found more uses down through the years.
Hooking up the snow plow is a SNAP now where it used to be a pain in the butt!
No one ever needs a snow plow on a bright, sunny, warm day!
Plugging in my inverter (hung on the front brush guard) makes 110 volt tools a SNAP!
We all know how frustrating it is to start a hard hole with a battery powered drill and the battery goes dead in the middle of things!
Pull a battery and stick it in the lawn more, tractor, generator, what ever!
About everything I have is on quick disconnects now, and my batteries have stopped walking off in unattended farm equipment, and I always have a charged battery in things I don't use very often,
Not to mention the expense savings of having a dozen batteries in a dozen different pieces of equipment!
Take a battery to camp, to work on electrical stuff in camp, to power fans and radios, charge up cell phones, ect.
With the quick connects, you are only limited where you can jump start someone by where you can carry the battery!