Dual Battery Earthing

In this short write up we will be answering a few commonly asked questions we receive on a daily basis.

“What is an Earth?”

In an automotive electrical situation, the earth is the Negative terminal of the start battery. Using the chassis as an earthing point puts further strain on the factory cabling and runs the risk of earthing issues in the future. Earth is signified in circuit diagrams as this symbo


Fig.1: Shunt on 2017 Navara

Fig.2: First Earth Point on 2017 Navara

“How important is the Earth in a circuit?”

Earthing is just as important as the Positive cabling in completing a DC circuit. If you have inadequate earthing the circuit will suffer a larger voltage drop, in turn increasing strain on charging system components.

“My vehicle has a smart alternator and I have been told not to earth to the start battery”

Yes that is correct.. (Sort of). Some vehicles that have a Variable voltage alternator are fitted with a shunt on the negative terminal to monitor charging and consumption. Often found on EU designed vehicles for emission control/ Fuel economy guidelines.

If your vehicle is fitted with this shunt (See picture Fig.1) the best place to Earth your Dual Battery System will be the first point of contact with the body of the vehicle (see picture Fig.2) otherwise you can cause issues with the vehicles computer and start battery.

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