Battery for Bow Thuruster and Windlass

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AndrewPalmer

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Very grateful for any advice regarding the power supply for these items. I have asked the yard to fit a bow thruster and electric windlass in my newly aquired Moody 35. I have proposed that they run heavy cables from the domestic batteries located in the aft cabin to the forepeak. The yard's recommendation though is to fit an additional battery in the forepeak which they suggest will be cheaper to install and safer. Personally I would very much like to avoid having 4 batteries on board with the associated requirement to maintain them, I also think this would mean installing another isolator since the current setul only allows for 2 battery banks.

Any suggestions as the the best aproach?

Regards
Andrew Palmer
 
As far as I am aware the bow thruster and windlass are no different from any other electrical appliance but simply have a higher draw. You should be able to size cables appropriately for the volt drop but they will be large. There are tables online, google helps, to tell you what size cable you need for specific volt drops and current.
 
Andrew, are you really sure you need a bow thruster on a Moody 35?

It's a lot of expensive work to retrofit one and will add little value to your boat. Electric windlass I'd 100% agree with
 
I have a similar set-up in a longer (43-foot) boat: inherited system is batteries in aft cabin with very long runs to the windless/thruster.
Whilst there is no 'right' answer, if the installation were for a windlass only, my preference would be for cables run the length of the boat, since we're only talking of around 100A max. The thruster, however, will have a substantially higher rating than the windlass and may well require cables of 95 square mm. If I were installing from scratch in that situation, and if there were room for batteries forward, that's the option I'd favour.
Note that fairly hefty charging cables would still be needed from the alternator to the forward battery (unless you went for an 240V/dedicated charger set-uo).
 
I am just battling with this issue from the viewpoint of having both thruster and electric windlass plus a battery in the forward lazerette, and wanting to move that battery back to join the others. Because the thruster has a 3000 watt motor, therefore drawing 250 amps the cable size needed is beyond anything sensible. The batteries are linked by big thick cables, but it is clear that without the forward battery they would be quite inadequate. The Vetus 35Kgf thruster, which would be smaller than recommended for a 35 foot boat has a 1500 watt motor, and the next size up is 55Kgf which has a 3000 watt one. Even the former would need very thick cables if you are using 12 volts. Required cable cross sections are halved if you are using 24 volts, so you could consider buying a 24 volt thruster and windlass and putting your two domestic batteries in series, with a tapping between the two to supply any existing kit that cannot be converted to 24 volts. All lighting can easily be changed to use 24 volt bulbs, and much other boat equipment is made to accept a wide range of voltage input.

My original post on the issue is here. http://www.ybw.com/forums/showthread.php?403604-Battery-cables
 
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Just to make sure OP is aware he only needs 2 cables +ve and -ve to be shared by thruster and anchor winch. Assuming he will only use one at a time.
I think I would persevere with cables option. If cables are too thick/stiff then go for multiple cables. Another battery will wear out in time and meanwhile take maintenance to look after it. olewill
 
Just fit cables.

If you fit a battery up front you'll need to run cables to charge it anyway.

I'd say get the largest cable you can get for + and - run and wire to that.

And at least if your just running cables- you can isolate it all from the same point as everything else keeping it safe

I'd also agree with the logic of using the same cables for both items on the logic of you could only use 1 at a time. Just bear in mind the current draw from each to fuse the circuit correctly otherwise - 1 item would either fuse instantly or be unprotected.
 
I don't like the idea of remote batteries. 1500w isn't much of a problem for cabling but 3000w cables would cost a fortune. Our windlass (on a Moody 376) is fed from the battery isolator switch on the panel, via a circuit breaker, so I can feed it from any battery(ies). Never seen the need for a thruster.
 
Vonasi said:
Good electrical practice says that if there is the possibility that both motors could be operated at the same time then cable should be sized to take this into account.
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I'm finding it difficult to envisage a scenario in which both the windlass and the thruster might be used simultaneously.
 
pvb said:
I'm finding it difficult to envisage a scenario in which both the windlass and the thruster might be used simultaneously.
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I often seen them used like this when going stern too in the med. However the winch is using so little power when lowering the chain, that it probably doesn't matter.

However the length of time some people run them, using them even just to turn a corner, one hopes they have an adequate thickness of wire.

Personally on a Moody 35, I wouldn't bother to get a bow thruster.
 
symondo said:
Just fit cables.

If you fit a battery up front you'll need to run cables to charge it anyway.

I'd say get the largest cable you can get for + and - run and wire to that.

And at least if your just running cables- you can isolate it all from the same point as everything else keeping it safe

I'd also agree with the logic of using the same cables for both items on the logic of you could only use 1 at a time. Just bear in mind the current draw from each to fuse the circuit correctly otherwise - 1 item would either fuse instantly or be unprotected.
Click to expand...

You would be well advised, especially if fitting a bow thruster, to make sure the cable sizes are correct. Its just not good enough to say , "get the largest you can". If your batteries are under the stern bunk, then its going to be a hell of a long way the the bows and back corners and all. You must check it out thoroughly before you do it. You may find that the cable is just too thick to pull through the length of the boat. Don't under estimate how hard it is to pull a cable like that through - hence, this is why people end up with a bow battery set up. Even then you will end up with cables to the bows which are pretty thick (but manageable), just to carry the much reduced current without loss of voltage.
 
Thanks everyone for your comments. I want to install the thruster for marina berthing as I often sail with novice crew which I have found in difficult berthing situations is more problematic than single handed! It's for crew safety as much as anything. Still keen to avoid the additional battery so I am going to do my own research on cable size and ask the yard to go through their calculations. Might even abandon the thruster idea if it means another battery. Engine would be running when thruster used so voltage should be high, also I would be happy with a low power thruster, not planning to use it much, but yard advise against that. Will also look at ensuring thruster and windlass cannot be used together as I can't imagine needing both together..
 
I have both a thruster and windless on my Halberdier, the dedicated battery is in the forepeak, just renewed it with a 134 amp sealed unit therefore no top ups needed the thruster and windless is selected with the normal 1,2, both switch. As Demoiselle has a long keel the thruster is a godsend! I would however agree with others re the close quarter handling of a fin keel yacht and the requirement for a thruster, but the electric windless is another matter.
 
halb said:
.....
..... but the electric windless is another matter.
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Yes, totally - cannot believe that we spent our first 5 years of sailing without an electric windlass - probably had something to do with being in my twenties !

Having had our first SL electric one fail due to corrosion, it is one of the most pampered bits of kit on the boat.
 
Vonasi said:
+1 I can't think of any situation where a bow thruster would be of any use on a Moody 35. Cost/benefit analysis takes about 3 seconds to say don't bother.

Having swapped from a manual to electric windlass experience says - do it!

I ran cables from amidships on a 10 metre boat and by the time I'd gone around a few corners and up through the heads the amount of cable needed was two lots of 10 metre lengths. That's a lot of voltage drop. I used 60mm squared cable and would not of wanted the job of running anything much bigger. You are proposing to go from the aft cabin so I think you'll need an even longer run of cable, unless that is your running it straight through the middle of the saloon!

I'd go for a battery up forward and then something like the Sterling battery to battery charger so as to keep cable sizes smaller. http://www.sterling-power.com/products-battbatt-install.htm
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Depends if you are in the MED...
 
halb said:
I have both a thruster and windless on my Halberdier, the dedicated battery is in the forepeak, just renewed it with a 134 amp sealed unit therefore no top ups needed the thruster and windless is selected with the normal 1,2, both switch. As Demoiselle has a long keel the thruster is a godsend! I would however agree with others re the close quarter handling of a fin keel yacht and the requirement for a thruster, but the electric windless is another matter.
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Can I ask whether your forepeak battery is linked to the house batteries (like mine) with big thick cables, or just has charging cables from the alternator and/or a dedicated battery charger output?
 
Norman_E said:
Can I ask whether your forepeak battery is linked to the house batteries (like mine) with big thick cables, or just has charging cables from the alternator and/or a dedicated battery charger output?
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When I did this I sized the battery to give me 5mins unassisted running and sized the charging cables to account for a hearty inrush from the house bank when the vsr kicked in if the windlass battery was low, about 70 amps if I remember correctly. I learnt about allowing for such an inrush after seeing my campervan vsr start to smoke when it clicked in. Uprated to 70 amps after that and never had any problems.
 
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