Formula variables
- K is conductor material resistivity in ohm mm2/m.
- I is DC current in amperes.
- L is one-way cable length in metres.
- A is conductor area in mm2.
Assumptions
- Distance is one-way cable length; the formula uses the DC round-trip path.
- The result uses conductor area and material resistivity for a preliminary voltage-drop estimate.
- Low-voltage battery systems are sensitive to small voltage losses because the same volt drop is a larger percentage of nominal voltage.
- This calculator does not choose fuse size, ampacity, short-circuit protection, battery disconnects, cable insulation, or battery safety approvals.
Examples
48 V battery cable. A 100 A, 1 m one-way copper 10 AWG cable on 48 V estimates about 0.656 V drop, or about 1.37 percent.
12 V sensitivity. The same 0.656 V drop is about 5.46 percent on a 12 V system, so low-voltage battery runs need shorter cable or larger conductors.