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Cable Selection
Cable Tables and Colour Codes for Table 3..
Table 1 - Twin Sheath Two Core Flat 12v Cable
| Code | Description | mm2 |
Amp |
|
|---|---|---|---|---|
| ATS-21603 | 3mm Auto with OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 1.13 |
16 |
|
| MTS-216030 | 3mm Tinned Marine OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 1.13 |
16 |
|
| ATS-22603 | 4mm Auto OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 1.84 |
22 |
|
| MTS-226030 | 4mm Tinned Marine OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 1.84 |
22 |
|
| ATS-24103 | 5mm Auto OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 2.9 |
29 |
|
| ATS-26503 | 6mm Auto OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 4.59 |
38 |
|
| MTS-265030 | 6mm Tinned Marine OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 4.59 |
38 |
|
| ATS-211203 | 8B&S Auto OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 7.71 |
70 |
|
| ATS-218903 | 6B&S OFC Plain Wire 5V90 PVC Sheath V90 PVC Insulation | 13.5 |
100 |
Table 2 - Figure 8 Battery Cable 12v
| Code | Description | mm2 | Amp | |
|---|---|---|---|---|
What Size Cable to use and voltage drop on 12v cables.
To work out what thickness of cable you need for a particular job, you need to know the maximum current it will need to carry, in amps. Usually, this will be written on the device somewhere.
If you can only find a power rating in watts, divide the wattage by 12 to get the amperage.
Next, you need to measure the length of the cable. Longer cables need to be thicker to transmit same power because longer cables tend to suffer voltage drop - where the cable itself uses up some of the power.
You can measure the length of either the positive or negative cable, you don't add them together.
Now just check the chart below to select the appropriate cable thickness.
This will tell you the lightest cable you can get away with, while losing no more than 5% of the voltage in the cable. There is very rarely any harm in using a heavier cable.
Table 3 - Amps and Cable lengths Colour Guide
The colours in the table below reference the colours on the cable size tables above.
Minimum cable size in mm2 (for max 5% volt drop on 12V DC wiring) |
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Total Amps |
Cable length (in metres) |
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|
1 |
2 |
5 |
10 |
15 |
20 |
25 |
30 |
1 |
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2 |
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3 |
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4 |
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5 |
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8 |
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10 |
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15 |
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20 |
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25 |
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30 |
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40 |
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50 |
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60 |
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70 |
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80 |
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90 |
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100 |
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You can calculate the minimum cable size yourself.
To ensure a voltage drop of no more than 5% (0.6V), the formula is:
Minimum cable area (in mm2) = 0.0546 x current (in A) x length (in m)
Again, the length here is the distance from the battery to the device only, and not all the way back again.