Hi Roger, on my boat the negative wire to the battery is approx 20mm dia, not sure how to connect such a large cable to the shunt, good idea to use 2 cables in parrallel from the shunt to the battery. I also have 6 other wires from various pieces of equipment connected directly to the negative terminal of the battery, and have been thinking for a while that these would be better on a seperate buzz bar, but not sure how to wire it up…Ed