12 VOLT CABLE SIZING CHART

When sizing up cables for 12v and 24v circuits you must first determine what maximum volt drop % your circuit can handle. If the circuit is a DC circuit the cable length of route is measured from the source of current to the device then back to the source. For an AC application the length of route is from the source of current to the device.

i.e. In the diagram the length from the source of current to device is 5metres and the length from the device back to current is 5metres, therefore the total length of route is 10metres (DC Circuit).

A maximum of 3% volt drop is recommended for electronic equipment such as depth sounders, single side band radios, VHF radios and other installations such as navigation lights and bilge blowers. A maximum of 10% volt drop is satisfactory for most lighting and motor installations.

EXAMPLE 1: The above winch draws 50amps 12VDC and the total route length is 10metres. So to determine the size of cable refer to chart B (12volts 10% volt drop) go to 50amps on the left hand side of the chart align with 10metre mark and the recommended cable will be 10mm2 (copper flex with 90° insulation).

NOTE: In warm areas such as engine rooms and inside switchboards you must consider the de-rating table below when sizing up cables.

These ratings are based on 30°C ambient air temperature and 15°C ambient soil temperature. Maximum conductor temperature 90°C – For other conditions refer to AS/NZS 3008.1.2:1998.

APPROX. DE-RATING FOR DIFFERENT AMBIENT TEMP. °C 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Factor 1.15 1.12 1.08 1.04 1.00 0.96 0.91 0.87 0.82 0.76 0.65 0.58 0.50 0.41 0.29
CONDUCTOR SIZES (mm²) FOR 3% VOLT DROP
Amps 2m 4m 6m 8m 10m 12m 14m 16m 18m 20m 22m 24m 26m 28m 30m 35m 40m 45m 50m
5 0.75 1.5 1.5 2.5 4.0 4.0 4.0 6.0 6.0 6.0 10.0 10.0 10.0 10.0 10.0 10.0 16.0 16.0 16.0
10 1.5 4.0 4.0 6.0 6.0 10.0 10.0 10.0 10.0 16.0 16.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 35.0
15 2.5 4.0 6.0 10.0 10.0 10.0 16.0 16.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 35.0 35.0 35.0 50.0
20 2.5 6.0 10.0 10.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 25.0 35.0 35.0 35.0 50.0 50.0 50.0 70.0
25 4.0 6.0 10.0 10.0 16.0 16.0 25.0 25.0 25.0 35.0 35.0 35.0 35.0 50.0 50.0 50.0 70.0 70.0 70.0
30 4.0 6.0 10.0 16.0 16.0 25.0 25.0 35.0 35.0 35.0 35.0 50.0 50.0 50.0 70.0 70.0 70.0 95.0 95.0
40 6.0 10.0 16.0 25.0 25.0 35.0 35.0 35.0 50.0 50.0 50.0 70.0 70.0 70.0 70.0 95.0 95.0 120 120
50 6.0 16.0 25.0 25.0 35.0 35.0 50.0 50.0 50.0 70.0 70.0 70.0 95.0 95.0 95.0 120 120 150 150
60 10.0 16.0 25.0 35.0 35.0 50.0 50.0 70.0 70.0 70.0 70.0 95.0 95.0 95.0 120 120 150 150 185
70 10.0 16.0 25.0 35.0 50.0 50.0 70.0 70.0 70.0 95.0 95.0 120 120 120 150 150 185 185 240
80 10.0 16.0 35.0 35.0 50.0 70.0 70.0 70.0 95.0 95.0 95.0 120 120 150 150 185 185 240 240
90 10.0 25.0 50.0 50.0 50.0 70.0 70.0 95.0 95.0 120 120 120 150 185 185 240 240 300 300
100 16.0 25.0 50.0 50.0 70.0 95.0 95.0 120 120 150 150 150 185 185 240 240 300 300 400
CONDUCTOR SIZES (mm²) FOR 10% VOLT DROP
Amps 2m 4m 6m 8m 10m 12m 14m 16m 18m 20m 22m 24m 26m 28m 30m 35m 40m 45m 50m
5 0.75 0.75 0.75 0.75 1.0 1.0 1.5 1.5 1.5 2.5 2.5 2.5 2.5 2.5 4.0 4.0 4.0 4.0 6.0
10 0.75 0.75 1.0 1.5 2.5 2.5 2.5 4.0 4.0 4.0 4.0 6.0 6.0 6.0 6.0 6.0 10.0 10.0 10.0
15 0.75 1.0 1.5 2.5 2.5 4.0 4.0 4.0 6.0 6.0 6.0 6.0 10.0 10.0 10.0 10.0 10.0 16.0 16.0
20 0.75 2.5 2.5 4.0 4.0 6.0 6.0 6.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 16.0 16.0 25.0 25.0
25 1.0 2.5 4.0 4.0 6.0 6.0 6.0 10.0 10.0 10.0 10.0 10.0 16.0 16.0 16.0 16.0 25.0 25.0 25.0
30 1.0 2.5 4.0 6.0 6.0 6.0 10.0 10.0 10.0 10.0 16.0 16.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0
40 1.5 4.0 4.0 6.0 10.0 10.0 10.0 16.0 16.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 35.0 35.0 35.0
50 2.5 4.0 6.0 10.0 10.0 10.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 25.0 25.0 35.0 35.0 50.0 50.0
60 2.5 6.0 6.0 10.0 10.0 16.0 16.0 16.0 25.0 25.0 25.0 25.0 35.0 35.0 35.0 35.0 50.0 50.0 50.0
70 2.5 6.0 10.0 10.0 16.0 16.0 16.0 25.0 25.0 25.0 35.0 35.0 35.0 35.0 35.0 50.0 50.0 50.0 50.0
80 4.0 6.0 10.0 16.0 16.0 16.0 25.0 25.0 25.0 35.0 35.0 35.0 35.0 50.0 50.0 50.0 70.0 70.0 70.0
90 4.0 10.0 10.0 16.0 16.0 25.0 25.0 25.0 35.0 35.0 35.0 50.0 50.0 50.0 50.0 70.0 70.0 70.0 95.0
100 4.0 10.0 10.0 16.0 25.0 25.0 25.0 35.0 35.0 35.0 50.0 50.0 50.0 50.0 50.0 70.0 70.0 95.0 95.0

NOTE: For DC applications the distance of cable run measured is from the source to device and back to source

Firstflex has taken every precaution to ensure accurate information in this catalogue but accept no liability for any errors or omissions. Firstflex reserves the right to modify specifications at any time.