User's Guide

A.2.2 Proper Grounding on Mobile Machinery
It is common for light and heavy duty mobile equipment that use DC voltage to be designed
such that the DC Negative (DC-) of the battery bank is tied to the chassis, frame and other
structural sub-components of the machine. This is known as a “grounded” system. Each of
these structural sub-components that are bolted together, such as the machine frame, machine
chassis, cab chassis, etc. are often not particularly good electrical conductors due to paint and
corrosion.
In an attempt to ensure that the chassis of the machine is the same electrical potential across
all of these sub-components, grounding straps are typically installed across each interface. The
diagram below illustrates the resistances between each of the sub-components.
The main objective of proper grounding is to ensure all chassis or grounding points on the
machine are at the same potential as the battery negative. To accomplish this, 3D-P generally
advises that each resistance between the sub-components be less than 1.5 ohms.
At the start of any installation it the grounding and chassis straps on each sub-component
should be checked. This step is imperative. It must be verified that there is proper electrical
bonding across the complete machine. Please refer to the document: IEP Ground
Troubleshooting Guide, 3D-P, Revision 1.1, 130906-01-BM for further instructions on how to
complete this task.
Figure 13: Machine grounding