Cable sizing guide

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Is there a standard?

Here are some examples to show how you can size your cable for different situations. It is important to consider both the current and voltage drop when choosing the appropriate cable size. If you want a more precise sizing, or if you are unsure how to do it, you can use our customised calculator.

What should I consider when sizing cables?

Cable calculator

Deepening

Type of wire

The charging circuit

Generator 50 A to the battery bank. A thinner cable can be used between the batteries.

Calculated on max 0.1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
1.5	3	35
2.5	5	50
3.5	7	70
4.5	9	95
5.5	11	120

Bow thruster or anchor winch

Between propeller/winch and battery. This also applies to larger starter motors. 3.5hp = 2500 w ≈ 250 .

Calculated on max 1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
2.5	5	25
3.5	7	35
4.5	9	50
5.5	11	70
6.5	13	95
7.5	15	120

Bow thruster 7 hp

Between propeller and battery. 7 hp ≈ 5000 W ≈ 500 A

Calculated on max 1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
2.5	5	50
3.5	7	70
4.5	9	95
5.5	11	120
7	14	2 x 70
9	18	2 x 95
11	22	2 x 120

Lantern in mast

25 W = 2 A

Calculated on max 0.5V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
18	36	2,5
20	40	4
25	50	4

Supply to the electricity centre

Between battery and switchboard.

500 W = 50 A

Calculated on max 1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
2.5	5	10
3.5	7	16
4.5	9	25
5.5	11	25
6.5	13	25
7.5	15	35
8.5	17	35

Solar panel or charger

50 W = 4 A

Calculated on max 0.1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
2.5	5	4
3.5	7	6
4.5	9	10
5.5	11	10
6.5	13	10
7.5	15	10
8.5	17	16

Fridge or heater

60 W = 5 A

Calculated on max 0.1V voltage drop

Distance (m)	Total cable length (m)	Cable area (mm²)
2.5	5	6
3.5	7	6
4.5	9	10
5.5	11	10
6.5	13	10
7.5	15	10