How is single-point grounding implemented?
In single-point grounding all negative returns meet at a single collection busbar and go from there to the battery negative on one heavy conductor. That way the power current does not pass through the signal reference. The drop measured under load on the cable joining the busbar to the battery negative should be around 0.05 V, and at worst below 0.2 V.
The aim is simple: the copper carrying the high current and the copper the sensitive electronics take as reference should not be the same piece. Implementation steps:
- Place a conductive collection busbar somewhere dry and accessible near the battery negative.
- Connect the busbar to the battery negative with a single short conductor sized to carry the system's total current. Verify the cross-section from the voltage drop formula: dU = 2 x L x I x rho / A, with rho = 0.0175 ohm x mm2/m for copper.
- Bring the negatives of high-current consumers such as motors, cranes and heaters to the busbar individually; do not chain them to each other.
- Bring the negatives of control, sensor and measurement circuits to the busbar on separate conductors too. These conductors should not run over the power returns.
- Connect the shields of screened cables not to this busbar but to the single chassis point you have designated, with 360-degree contact.
Verify the result by measurement: if you see a difference exceeding 0.2 V between the busbar and the battery negative while the system draws full load, the cross-section is inadequate or a lug is bad. On a good chassis path the expected value is of the order of 0.05 V.
Full coverage of the topic: Installation, redundancy and field continuity