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Date © Simon P Barlow BSc MBCS CITP

Tech Sheet 002 - Wire Size

Simon Barlow

20/11/2018

The cable length is the TOTAL cable length not the distance from the battery to accessory. ● The cable size shown for any given current may not be the rated maximum current capacity for the cable size, it is based on reducing the voltage drop to within acceptable limits. ● Remember of you have a large voltage drop on a cable this is translated directly as heat in the cable. ● For current above 20 Amps do not rely on vehicle bodywork to provide a suitable earth (neutral) return path. Always install a proper neutral conductor. - Remember copper is a better conductor than a steel or aluminium body-shell. ● For current above 50 Amps careful consideration must be given to the routing of cable runs. ● For current above 100 Amps it is alway preferable to locate the accessory as close to the power source as possible to minimise cable length. For automotive, trailer, caravan, motorhome or marine use NEVER use solid conductor cable. For connectors above 6mm2, they should be crimped AND soldered using lead free solder.

Simon P Barlow - CaravanChronicles.com 1 2 3 4 5 6 7 8 9 10

0-5 Amps 1.5 1.5 1.5 1.5 2.5 2.5 4.0 4.0 6.0 6.0

10 Amps 2.5 2.5 4.0 4.0 4.0 4.0 6.0 6.0 10 10

15 Amps 2.5 2.5 4.0 6.0 6.0 6.0 10 10 10 16

20 Amps 4.0 4.0 4.0 6.0 6.0 10 10 16 16 25

25 Amps 4.0 4.0 6.0 6.0 10 10 16 25 25 25

30 Amps 6.0 6.0 6.0 10 16 16 25 25 25 25

35 Amps 6.0 10 10 10 16 16 16 25 25 35

40 Amps 10 10 10 16 16 16 25 25 25 35

45 Amps 10 16 16 16 16 25 25 25 35 35

50 Amps 16 16 16 16 25 25 25 35 35 35

55 Amps 16 16 16 25 25 25 35 35 35 50

60 Amps 16 16 25 25 25 35 35 35 50 50

65 Amps 16 16 25 25 35 35 35 50 50 60

70 Amps 16 16 25 25 25 35 50 50 60 60

75 Amps 16 16 25 25 35 35 50 50 50 60

80 Amps 25 25 25 25 35 35 50 50 50 60

85 Amps 25 25 25 35 35 35 50 50 60 60

90 Amps 25 25 25 35 35 50 50 50 60 60

95 Amps 25 25 25 35 35 50 50 60 60 60

100 Amps 25 25 35 35 50 50 50 60 60 70

110 Amps 25 25 35 50 50 60

120 Amps 35 35 35 50 50 60

130 Amps 35 35 50 50 60 60

140 Amps 35 50 50 60 60 70

150 Amps 50 50 60 60 70 70

160 Amps 50 50 60 70 70 70

170 Amps 60 60 70 95

180 Amps 60 70 95

190 Amps 60 70 95

200 Amps 70 95 95

Wire Selection - Voltage Drop (This is NOT the max current rating of cable)

Total Cable Length (Metres)

Plan

ned

MAX

Cur

rent

(Am

ps)

MM2 Diameter AWG

1.5 1.29 16

2.5 1.63 14

4.0 2.05 12

6.0 2.59 10

10 3.25 8

16 4.11 6

25 5.19 4

35 6.54 2

50 7.35 1

60 8.25 0

70 9.27 00

95 10.40 000

120 11.68 0000Simon P Barlow - CaravanChronicles.com

Standard Cable Size & Conversion

Wire Terminals

MM2 AWG

RED 0.5 - 1.5 22 - 16

BLUE 1.5 - 2.5 16 - 14

YELLOW 4.0 - 6.0 12 - 10

All cable has a resistance and it’s given as ohms per metre – “W/m”. Some manufacturers give this figure, however others give the voltage drop expressed as “mV/A/m” - milli-Volts per Amp per metre . To use the ‘W/m’ figure use the following formula:

Vdrop = I (A) x (L (m) x [W/m}) To use the mV/A/m figure use:

Vdrop = [mV/A/m] x I(A) x L(m)/1000 Don forget to calculate the Vdrop for the neutral cable as well. If the neutral cable is the return path for other circuits, these need to be taken into account as the Vdrop for the neutral cable could be greater than the supply cable. (for more info go to: https://caravanchronicles.com/guides/understanding-cable-and-cable-sizes/

Wire Terminal FerrulesMM2 AWG

ORANGE 0.3 24

YELLOW 0.5 22

WHITE 0.75 20

RED 1.0 18

BLACK 1.5 16

BLUE 2.5 14

GRAY 4.0 12

GREEN 6.0 10