Windlass Cable size?

[neil1967]

The Lofrans cayman 1000W windlass on our 40’ yacht has always been rather slow to retrieve the 10mm chain rode, at least in my ownership. The PO had substituted the Cayman for a Sea Wolf, which I think might only have been 800W. On checking, I have found the cable from the batteries to the relay (9m each way) is only 16 or 20 mm2, which I believe is grossly undersized and might be a cause of the slow retrieve. I think 50mm2 would be more appropriate, but the cable trunking into the fore peak where the windlass relay is is rather narrow, and I will need to do some surgery to enlarge the holes. So, what size cable would you recommend and what difference might I expect to see between the existing 16/20mm2 cable and either 35mm2 or 50mm2?

many thanks

 

[sailaboutvic]

We have the same windlass on 42 foot .
Mine is 50mm sq , we did have some problems with it tripping the breaker some time but since I replace batteries and gome to lithium the problem gone ,
So maybe the cable could been losing some voltage drop and as lithium stay around 13.2v or it could had been something else

 

[Boathook]

I would go for 50mm cable. Total wire run is 18m and at around 66 amps (assuming 12 volts) even 50mm might struggle. Blue Sea recommend cable nearer 90mm which makes life even more difficult.

 

[PaulRainbow]

The Lofrans cayman 1000W windlass on our 40’ yacht has always been rather slow to retrieve the 10mm chain rode, at least in my ownership. The PO had substituted the Cayman for a Sea Wolf, which I think might only have been 800W. On checking, I have found the cable from the batteries to the relay (9m each way) is only 16 or 20 mm2, which I believe is grossly undersized and might be a cause of the slow retrieve. I think 50mm2 would be more appropriate, but the cable trunking into the fore peak where the windlass relay is is rather narrow, and I will need to do some surgery to enlarge the holes. So, what size cable would you recommend and what difference might I expect to see between the existing 16/20mm2 cable and either 35mm2 or 50mm2?

many thanks

The correct size cables are 95mm if taking into account the voltage drop, but Lofrans fitting instructions say 35mm up to 25m round trip. Mine was fitted before i bought the boat and is indeed 35mm, it works OK, but if i'd have fitted it i ight have been tempted to use 50mm cable.

 

[sailaboutvic]

You could just add a battery in the bow just for the windlass with B2B to charge it .
It probably be cheaper and less hussle then putting in a bigger cable

 

[coopec]

I would go for 50mm cable. Total wire run is 18m and at around 66 amps (assuming 12 volts) even 50mm might struggle. Blue Sea recommend cable nearer 90mm which makes life even more difficult.

Hoping you don't mind me chipping in.

If the cable is 9m each way then the circuit would be around 50ft. Looking at the table for a 1000W motor it wood require 3/0 cable.


Looking at the AWG to mm² conversion table that would indicate you would need 85 mm². (That would seem to be in line with what you say Blue Sea recommend)

 

[Gary Fox]

You could just add a battery in the bow just for the windlass with B2B to charge it .
It probably be cheaper and less hussle then putting in a bigger cable

That's what I plan to do. You still need reasonably thick cables anyway, so you can start the engine with the winch battery if neccessary.

 

[PaulRainbow]

I would go for 50mm cable. Total wire run is 18m and at around 66 amps (assuming 12 volts) even 50mm might struggle. Blue Sea recommend cable nearer 90mm which makes life even more difficult.

1000w at 12V is 83A, not 66A

 

[coopec]

Thank heavens I've gone for a 24V system! ?

 

[Boathook]

1000w at 12V is 83A, not 66A

Seems I misread the post as I was working on 800 watts.

 

[PaulRainbow]

Hoping you don't mind me chipping in.

If the cable is 9m each way then the circuit would be around 50ft. Looking at the table for a 1000W motor it wood require 3/0 cable.


Looking at the AWG to mm² conversion table that would indicate you would need 85 mm². (That would seem to be in line with what you say Blue Sea recommend)

A perfect case of a little knowledge being dangerous and Goggling answers doesn't always help, most certainly not without some understanding of the subject matter.

If it needs 85mm cables, why do you suppose the manufacturers state that it only needs 35mm cables?

 

[Bru]

35sq.mm is a compromise

It's adequate but there will be significant voltage drop (on our previous boat with an 800w windlass and about a 6m run of 35sq.mm sufficient to drop the chart plotter out with a low voltage warning even with the engine running unless I cranked the revs up a fair way)

When I fit an electric windlass to Pagan, which will be a 1000w one, I'll be doubling up on the recommended cable size on the grounds that this is one situation where, cost aside, bigger is always better!

(Space being limited otherwise I'd go with my preferred option of a dedicated battery forward)

 

[neil1967]

Thanks for all the advice. If I'm going to have to start chopping holes to put in bigger cables, I might as well go for the 50mm2, as it should be much more difficult than for 35mm2. Hopefully I'll see an appreciable improvement over using the existing cables.

 

[xeitosaphil]

That's what I plan to do. You still need reasonably thick cables anyway, so you can start the engine with the winch battery if neccessary.

If you intend to use the winch battery to start the engine, surely your problem still exists but going the other way?

Better to make provision of an additional battery at the engine end I would have thought. Maybe an additional Redflash battery as backup start battery.

 

[PaulRainbow]

It's worth noting that voltage drop tables do not apply in all applications, other than in theory. Yes, the volts will drop, no getting around that, but some DC motors are rated to actually work at those lower voltages. This is why some manufacturers of bow thrusters and windlasses will quote what seems to be undersized cables. Some bow thrusters, for instance, are actually rated at about 10.5V, on a typical 12V boat that gives an acceptable voltage drop of 2V

Rather than Googling answers, or reading posts on internet forums from those Google specialists, it can often be useful to read the installation manuals.

 

[sailaboutvic]

If you intend to use the winch battery to start the engine, surely your problem still exists but going the other way?

Better to make provision of an additional battery at the engine end I would have thought. Maybe an additional Redflash battery as backup start battery.

You don't need a big cable going back to the engine
A separate in bow just for the windless and then a b2b charger from the house batteries to keep it charged ,
He could do away with the old cable, he just need to move the breaker closer to the bow .

 

[Bru]

Rather than Googling answers, or reading posts on internet forums from those Google specialists, it can often be useful to read the installation manuals.

Read the manual? Dear Gods above man! We're roughty tufty sailing blokes, we NEVER read the manual!