Wire gauge

By current and allowed voltage drop: minimum cross-section + losses over length

Parameters

Recommended cross-section

Power loss: 44,8 Вт

4 мм²

By current (6 A/mm²)
2,67 мм²
By voltage drop
1,62 мм²
Actual drop
2.80 В (1.2%)

Copper: 6 A/mm² is a conservative density for continuous load in conduit. S ≥ 2·ρ·L·I/ΔV. For 12 V lines drop matters more than heating: 0.5 V on 12 V is 4% and watts lost in the cable.