Windlass wiring - which option?

[EugeneR]

I am installing a thruster and windlass and I need some advice with selecting the right wiring option. From reading previous advice, it seems that the main options are:

1) Battery in the bow with dedicated 240v charger. Simple, low-risk since 240v is already present; engine will not charge battery so I will need to hook up every now and then. (Thruster 300A for 120 sec per trip + windlass 90A for 600 sec per trip = 25Ah used from 100Ah battery - seems OK?)

2) Install battery in the bow and charge from main 12v batteries using 12v to 12v charger. 15A charging current means smaller wires required.

3) 30mm2 cables to carry the required 280A from the main batteries to the thruster. Round-trip approx. 16metres so may be the cheapest option but then uses shared battery capacity.

Are there any issues with these options?

Which would you go for?

 

[lw395]

Option 2.

I don't like option 1, because the battery will be left partly discharged after every use, I think it would last longer if recharged immediately.

Option 3 seems like an awful lot of fat cable. Also using the house battery for high current after a couple of days harbour use might not be ideal.

I think it depends on whether there is a convenient place for the battery, or whether it would be easy to install really big cables.

 

[vyv_cox]

We don't have a thruster but have a windlass used frequently, often several times per day, six months of the year. I ran 35 mm2 welding cable from domestic batteries aft, which are the ones more commonly connected when the engine is running. This arrangement has been in place for around 10 years now, never a moment's trouble.

Battery capacity is really not a problem as engine is normally running, although we sometimes adjust anchor chain without running it. Recharging seems to take place without trouble when the engine next runs and solar panels do their bit also. I like this system because all the batteries receive optimum treatment, plus on my boat a bow battery would be highly problematic. Your option one doesn't work for me as we rarely have mains voltage.

 

[KellysEye]

Option 1 if you do the following. We have our anchor battery under the forcabin berth in a ventilated box. It is connected both the the alternator and 240v charging systems. We have smart chargers on both systems that are linked to five batteries.

 

[Norman_E]

Option 1 is a very poor idea. Imagine this, you anchor in a quiet bay, but it takes two or three attampts to get the anchor to set. You stay overnight and in the morning you need to recover the anchor and find that the battery is flat.
On most boats the anchor windlass is connected to batteries that are charged whenever the engine runs and it is used with the engine running.
I agree with Vyv Cox, and suggest option 3, even though my boat has a hybrid of options 2 and 3 with the bow battery being part of the house battery bank, all connected with big cables (50mm I think.)

 

[Blueboatman]

Not saying which is best ( this is an aggro forum innit)..

What I have is a 1200w windlass with wiring back to the two engine start batteries, which are in theory designed to take the short bursts of massive cranking.

Also ( and you are a mobo), this set up allows for max volts to reach the windlass/thruster whilst the engine is idling-in fact I can here the alternator load come on when weighing anchor. The higher the voltage available, my understanding is the longer the motors last, whereas a lower voltage from a partilly discharged battery means the thruster tries to draw more current to do the same job, which is exactly what you don't want.

This being a forum of experts, expect the direct opposite argument to come along in a moment and be equally (un)convincing

 

[lw395]

....
This being a forum of experts, expect the direct opposite argument to come along in a moment and be equally (un)convincing

I agree, having the alternator charging will help a lot.

 

[pvb]

I am installing a thruster and windlass and I need some advice with selecting the right wiring option. From reading previous advice, it seems that the main options are:

1) Battery in the bow with dedicated 240v charger. Simple, low-risk since 240v is already present; engine will not charge battery so I will need to hook up every now and then. (Thruster 300A for 120 sec per trip + windlass 90A for 600 sec per trip = 25Ah used from 100Ah battery - seems OK?)

2) Install battery in the bow and charge from main 12v batteries using 12v to 12v charger. 15A charging current means smaller wires required.

3) 30mm2 cables to carry the required 280A from the main batteries to the thruster. Round-trip approx. 16metres so may be the cheapest option but then uses shared battery capacity.

Are there any issues with these options?

Which would you go for?

I'd go for option 3 (indeed I have gone for option 3 on my boat). It's the most cost-effective and easy solution.

Your Ah assumption in option 1 is flawed - taking 300A from a typical 100Ah battery will reduce its effective capacity massively (the result of the Peukert effect). Your suggested usage would effectively almost flatten the battery, and wouldn't allow either the thruster or windlass to operate at peak efficiency.

Option 2 would be better, but note that you need to fuse the cable at both ends. You still have the problem of the weight of the additional battery in the bows. And at only 15A charge rate, it will take a while between uses of the thruster/windlass to recharge the battery.

Option 3 is cost-effective and has minimal downsides. It also means that you can draw on the greater Ah capacity of your engine and domestic batteries, as well as having the additional boost of the alternator's output.

 

[EugeneR]

As usual, lots of opinons but it's made things clear for me - thanks all.

I will go with option 3, saves cost, weight and having to install another battery tray etc. We have a genny so battery capacity is not overly critical and more.

pvb - I realised Peukert affected this but lazily assumed that my 2x capacity would be sufficient... although I suspected it might not be

 

[pvb]

pvb - I realised Peukert affected this but lazily assumed that my 2x capacity would be sufficient... although I suspected it might not be

I think 300A would flatten a 100Ah battery in about 10 mins!

 

[Conachair]

I am installing a thruster and windlass and I need some advice with selecting the right wiring option. From reading previous advice, it seems that the main options are:

1) Battery in the bow with dedicated 240v charger. Simple, low-risk since 240v is already present; engine will not charge battery so I will need to hook up every now and then. (Thruster 300A for 120 sec per trip + windlass 90A for 600 sec per trip = 25Ah used from 100Ah battery - seems OK?)

2) Install battery in the bow and charge from main 12v batteries using 12v to 12v charger. 15A charging current means smaller wires required.

3) 30mm2 cables to carry the required 280A from the main batteries to the thruster. Round-trip approx. 16metres so may be the cheapest option but then uses shared battery capacity.

Are there any issues with these options?

Which would you go for?

I went for option 3, luckily wasn´t too hard to run the cables in. Wasn´t aware of the existance of 12v-12v chargers at the time, which might have swayed it. Using the alternator to charge a batt up front would have meant fat cables anyway to be safe. If I was doing it again, then toss up between 2 and 3. That fat cable ain´t cheap.
Option 1 is almost option 2 but just waiting to go wrong

 

[sailinglegend420]

I went for option 3, luckily wasn´t too hard to run the cables in.

As described by the OP option three is a BAD IDEA. The cables you need for 300 amps over an 8 metre run - 16 in total - are 300 mm2 for a 3% voltage drop, not 30 mm2. They don't make cables that big!!! Option three is OK if just running a windlass, but not a bowthruster. Option 2 is best, but make sure the batteries are deep cycle not starter batteries. A 105Ah AGM would probably be fine. Use a Balmar DC to DC multi-stage charger that can be set for AGM batteries.

 

[pvb]

As described by the OP option three is a BAD IDEA. The cables you need for 300 amps over an 8 metre run - 16 in total - are 300 mm2 for a 3% voltage drop, not 30 mm2. They don't make cables that big!!!

I think 100mm2 cable (say 2 x 50mm2 for ease of installation) would be fine, with just under 1v drop. Especially as engine will be running when using thruster.

 

[EugeneR]

The thruster manual gives the following cable length (return) vs cross-section:

6m - 25mm2, 10m - 35mm2, 15m - 50mm2, 21m - 70mm2

From a safety perspective, am I correct in thinking that 50mm2 and up would be OK? In other words, the resulting W/foot won't cause anything to go up in flames?

The issue then becomes one of the voltage drop to the thruster. The manual states that it requires 10V or more to operate. Also, the manual clarifies the current to be 200A and not 280A as previously used. (It is a 2.2kW motor so it should use around 183A at 12V?).

Sending 200A over 48ft of AWG2 i.e. 35mm2 copper, the drop is 1.54v. The question is, what will the battery voltage be when supplying 200A? If less than 11.5v then the thruster voltage will be too low.

Sailinglegend240 - 300mm2 sounds high even for 300A current - I assume it's calculated to achieve a specified 3% drop?

prv - 2 times 50mm2 is getting expensive... already £200 for 20m of 35mm2 tinned / 40mm2 non-tinned, so we would be looking at more than £500 which is not worth it.

I am being swayed towards option 2. It means I cannot rely on the engine to provide current, which is a pity. I could put the charger on a switch so that it does not start charging from my main bank after I have anchored but only when I am under way again.

 

[Boathook]

I am installing a thruster and windlass and I need some advice with selecting the right wiring option. From reading previous advice, it seems that the main options are:

1) Battery in the bow with dedicated 240v charger. Simple, low-risk since 240v is already present; engine will not charge battery so I will need to hook up every now and then. (Thruster 300A for 120 sec per trip + windlass 90A for 600 sec per trip = 25Ah used from 100Ah battery - seems OK?)

2) Install battery in the bow and charge from main 12v batteries using 12v to 12v charger. 15A charging current means smaller wires required.

3) 30mm2 cables to carry the required 280A from the main batteries to the thruster. Round-trip approx. 16metres so may be the cheapest option but then uses shared battery capacity.

Are there any issues with these options?

Which would you go for?

Option 2. I have this fitted and don't worry about the charging. It is also possibly the cheaper option when looking at the price of cables.

 

[pvb]

3) 30mm2 cables to carry the required 280A from the main batteries to the thruster.

Also, the manual clarifies the current to be 200A and not 280A as previously used. (It is a 2.2kW motor so it should use around 183A at 12V?).

People generally get more sensible answers when they give accurate information in their original posts.

 

[EugeneR]

People generally get more sensible answers when they give accurate information in their original posts.

In so far as that information is required to help answer the post, yes. I honestly don't recall the source - I had it written down - but I might have made a mistake and if so, apologies.

That said, I note that the windlass data from the same manufacturer shows a similar level of variance: motor power 320W (implies 26.6A at 12V?), normal current draw 45A, circuit breaker 35A.

Either value (280A or 200A), the voltage drop in addition to the dropping battery voltage at high current does appear to be a risk for anything but overly expensive cables...

 

[Boathook]

.....
I am being swayed towards option 2. It means I cannot rely on the engine to provide current, which is a pity. I could put the charger on a switch so that it does not start charging from my main bank after I have anchored but only when I am under way again.

My 12 /12 volt charger only starts charging the b/t battery once the main batteries are charged so no switch is required. I seem to remember that it is an Adverc unit, possibly http://www.adverc.co.uk/product/679 but quite a few years (7) older. I'm hazy about the details as the unit is in a locker that I rarely look in.

 

[Blueboatman]

Complete thread drift and apologies to the OP but, with the recent price of tinned copper and the 10 year requirement to ditch seemingly perfectly good stainless steel semi flexible standingrigging,( you knwo whats next)...who will be the first DIYer to fit sleeved ex-rigging round their boat, a 12v ring main wrapped in pvc, conduit or what have you?

Btw, to the Op, ( as possibly a point of interest only) don't forget that with an engine running and the alternator offering up a charging voltage, the available volts at the bow with Option 3 ( EDITED, DUH!) may well be usefully higher than the nominal 12-13v of a battery at rest.

What does the manufacturer advise in your specific instance, by the way? Do they do phone help? I ask because it is they that will be warranting the installed product..

 

[Dockhead]

As others have suggested, Option 3 is by far the best. Because:

1. The bigger house bank will suffer less from Peukert disproportionate draining, than a single battery.

2. You for sure want to have the windlass connected to a battery which is being directly fed by an alternator connected to a running engine -- it shaves the peak off the current draw, which will make it much easier on the batteries -- Mr. Peukert again -- 100 amps is much less than half as difficult for the batts as 200 amps.


Good luck!