Windlass cable diameter.

[nickfabbri]

Can anyone advise the diameter of the cable i need to install from my batteries to my anchor windlass. I know i need to have less than a 3% drop and i have 7m there an 7m back ( 14m) to cover.

A figure of 13mm2 or size 6 has been thrown around.

Is this correct.

Many thanks.

 

[neale]

More info needed

Need to know the power of the windlass and whether it is 12 or 24 volt.

 

[neale]

Assuming 500 watt and 12 volt you will need at least 25mm2. This will give you around 3.5% voltage drop.

 

[nickfabbri]

its a lewmar pro 1000 which i believe is a 700w motor on a 12v system.

 

[neale]

its a lewmar pro 1000 which i believe is a 700w motor on a 12v system.

In that case you are really looking at wire around 35mm2, or 1AWG, for an approx 3% voltage drop

 

[neale]

For the record your original wire size of 13mm2 would provide a voltage drop of around 9% at that power over that distance.

You can get away with a bigger drop than 3% on a windlass, so 25mm2 would still be acceptable in my opinion providing a drop of around 4.5%.

 

[oldsaltoz]

Arc welding cable will big enough and cheap.

 

[VicS]

Arc welding cable will big enough and cheap

and arc welding cable comes in a range of sizes. A quick Google and I found on one site alone 16mm, 25mm, 35mm, 50mm, 70mm and 95 mm

 

[pvb]

and arc welding cable comes in a range of sizes. A quick Google and I found on one site alone 16mm, 25mm, 35mm, 50mm, 70mm and 95 mm

But that doesn't exactly help the original poster in his query.

For voltage drop in windlass cables, it's generally accepted that 10% is OK. This is on the basis that the engine will often be running during windlass use.

Lewmar use a 10% voltage drop in their installation instructions. For a Pro 1000 windlass with a 14m cable run (there & back), they specify 25 sq mm cable. I'd have thought that would be fine.

 

[KREW2]

I know it's not Lewmar, but here are the Loframs guides to cable size.
http://www.safety-marine.co.uk/Anch...Battery-Cable-(sold-per-meter).htm?P1354-S38-

 

[VicS]

But that doesn't exactly help the original poster in his query.

It was ntended as an additional comment to oldsaltoz's statement to indicate that even welding cable comes in a range of sizes

However :-

taking the windlass as stated to be 700watts at 12 volts therefore call the current consumption 60 amps.

16mm² has a resistance of 1.06Ω/1000m, The volts drop in 14m will be 0.89V, or 7.4%

for the other sizes mentioned the corresponding figures are:-

25mm², 0.68Ω/1000m, 0.57 V or 4.75%

35mm², 0.49Ω/1000m, 0.41V or 3.4%

50mm², 0.34Ω/1000m, 0.29V or 2.4%

70mm², 0.24Ω/1000m, 0.20V or 1.7%

95mm², 0.18Ω/1000m, 0.15V or 1.25%

Clearly then if 10% volts drop is acceptable 16mm² is more than adequate.
25mm² will keep it below 5%
and it will be only a little above 3% if 35mm² is used

 

[pvb]

As I said, Lewmar recommend 25 sq mm. Why wouldn't anyone go along with the manufacturer's recommendation?

 

[VicS]

Why wouldn't anyone go along with the manufacturer's recommendation?

You only siad you "thought" it would be fine.

I have done the calculations from scratch ... I know excalty what will be fine