Hey Electrical experts, got a question for you. A buddy of mine runs a guide service and has a bunch of motorized decoys (ducks). Currently they all run on an individual SLA battery and each has a remote to turn them on/off. He would like to run wires and eliminate the small batterys in favor of one big one that will run all of them. So the question is, what gauge wire, what connectors, etc. will he need?

The decoys are 6 volt and currently run a 4.5Ah battery each.
Span between each decoy would be about 15 feet, with maximum height of 4' above ground (wires must run down the poles and along the ground/under water)
He would like a system to be expandable from a base of 5 decoys up to a maximum of 8.
The main battery would be about 10 yards from the middle decoy typically, with a wing off each side for additional decoys.
He is looking at a 6 volt 50ah or so battery to run the system (golf cart or similar type battery)

Anybody done something like this or have recommendations for specs? Thanks in advance.