Chassis? Earth? Or ground?

Electricity will travel through your fridge (for example), then back via the earth, or chassis, or ground,.

If there is poor earthing of your battery, your fridge’s motor will run slow or intermittently, and the auxiliary batteries won’t charge.

Y’see, all of the electrons must travel the full circle, from battery positive, to load, to earth, to battery negative. When dual or multiple battery systems are connected, then the chassis or some sort of common grounding must be used between all batteries.

The common ground could be a bus bar, the vehicle chassis or even a battery terminal itself. If this is not done, there won’t be a complete loop and the additional batteries will not be charged.

Here are five points worth knowing

~Testing with a multimeter can prove deceiving if there is one critical point that is missed during diagnostics. You must be sure to test the earth circuit for the device.

~Sometimes a painted surface can prevent contact to the chassis, so paint should be cleaned from the joint prior to connection and then repainted over the connection once it has been tightened to reseal the metalwork.

~Ensuring that the connection point has a good earth return to the battery requires the same measurements of resistance to be taken as before, between the point where the joint will be made and the battery negative terminal.

~Due to paint or rubber blocks, the dashboard and ute trays are another classic example of this. To achieve a good earth in this situation, a heavy lead can be connected to the underside of the tub from the chassis and then devices in the tub can be successfully earthed to the tub itself.

~If the connection is old, corrosion can cause a breakdown of contact over time. Removing the connection and cleaning it might be all that it takes to overcome the fault.

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