Electric Windlass - what battery/electrical setup?

[Sans Bateau]

I have an Advec controller, and even if the engine battery takes seconds to charge, then the domestic bank may still take a little while to become charged enough. I grant you with only a demand for 25 amps that wouldnt take long at all.

 

[prv]

It doesn't. The Sterling Alternator to Battery Charger has a straight connection (via a diode) to the start battery, so the start battery has immediate charging.

Right, but does it delay charging to the service bank until the engine battery is full?

(Genuine question, I have no idea.)

Pete

 

[pvb]

I have an Advec controller, and even if the engine battery takes seconds to charge, then the domestic bank may still take a little while to become charged enough. I grant you with only a demand for 25 amps that wouldnt take long at all.

The Adverc isn't a split charge device though, so presumably your domestic batteries are getting charge immediately?

 

[prv]

I have an Advec controller, and even if the engine battery takes seconds to charge, then the domestic bank may still take a little while to become charged enough.

So it depends whether your windlass can outpace your alternator. If not, then there's no problem - regardless of battery state, the alternator will supply the windlass. If it can, then you have the potential to flatten your engine battery if you connect the windlass there.

Pete

 

[Sans Bateau]

Given the typical sizes, two or three times more than I could with an engine battery!

Pete

I was basing my question on me drawing 90amps from a domestic battery. I am of the understanding that to draw a heavy current (rather than a slow trickle) from a domestic battery would harm it.

 

[pvb]

Right, but does it delay charging to the service bank until the engine battery is full?

(Genuine question, I have no idea.)

No, it doesn't. It has two outputs. One, for the starter battery, is simply the connected to the alternator (via a diode to prevent accidentally discharging the starter battery). The second output is electronically boosted in voltage to provide more efficient charging of the domestic batteries. The unit has a "start up" phase during which, for several minutes, it just acts as a passive splitter, in order to ensure that the starter battery is recharged - however there is still unboosted output to the domestic batteries during this phase. It's a clever device, and one which I'd be interested in fitting if I didn't already have 2 alternators.

 

[maby]

I was basing my question on me drawing 90amps from a domestic battery. I am of the understanding that to draw a heavy current (rather than a slow trickle) from a domestic battery would harm it.

Indeed - but that is the point about not running the windlass without the engine running. I think you'll find that most modern boats built with an electric windlass installed include interlocks that disconnect the power to it until the engine is running - certainly the case on our Jeanneau.

 

[prv]

I am of the understanding that to draw a heavy current (rather than a slow trickle) from a domestic battery would harm it.

I'm not at all sure that's true.

I'm no expert in battery technology, but when I was reading up for a possible replacement of KS's batteries I'm sure I read that deep cycle batteries can be used for engine starting if you wish, just not the other way round. The deep cycle one will have a lower limit to how many amps it can supply, but if you try to draw more than that it doesn't cause any damage, just won't get your big engine running. But most yacht engines are small enough that all reasonable deep cycle batteries can cope with their demands - so windlasses should definitely be ok.

This is all very vague half-remembered stuff though, so don't take it as gospel. I'm hoping one of the forum's battery experts will comment.

Pete

 

[Sans Bateau]

I knew I'd find it after a search!

When I installed my windlass back in 2006 I asked on the forum where and how to connect it, heres the thread:

http://www.ybw.com/forums/showthrea...-battery-and-where&highlight=windlass+battery

Although there are some posters in that thread who suggested connecting to the domestic bank, some suggest an extra battery in the bow, there were a good many who suggested connecting to the starter battery, including the eminent Tome (RIP). Anyone who remembers him will know his knowledge of all things electrical and electronic went without question (it was his job working with off shore survey vessels after all!). It was after discussing the installation with him (when he loaned me all the crimping gear I needed) that I installed as I did. I'm sure all the installations which run off the domestic batteries are fine, but just read this, post 43 in that thread:

"On a note of caution - I used to run both the windlass & bow thruster from the domestic battery - After destroying 3 auto pilot computers Raymarine suggested that the bow thruster or windlass was creating voltage spikes which caused the auto pilot to fail (it is aslo powered from the domestic battery)
I have now powered both the windlass & the bowthruster from the engine battery both fed with large csa welding cables - i couldn't afford tinned marine cable that long and taht size."

If you are happy with your installation, I'm happy for you.

 

[pvb]

There's no problem running a windlass off the domestic bank, countless thousands of boatowners do it.

 

[NormanS]

Indeed - but that is the point about not running the windlass without the engine running. I think you'll find that most modern boats built with an electric windlass installed include interlocks that disconnect the power to it until the engine is running - certainly the case on our Jeanneau.

Seems a shame to make it impossible to sail away from your anchor, which I quite often do.
My engine start battery is for starting the engine.

 

[William_H]

Right, but does it delay charging to the service bank until the engine battery is full?

(Genuine question, I have no idea.)

Pete

A voltage sensing relay senses the voltage of the charging system and at some preset point operates to connect the service battery to the engine battery and alternator. It is this preset voltage that determines the answer to your question.
The engine battery voltage may well drop to 12.0v after the start but almost immediately the alternator begins charging this voltage will rise. As said the VSR should operate at about 13.5 volts. At this voltage the starter battery will be pretty well recharged but certainly not fully charged. The addition of the service battery as a charge load will not make much difference again after just a minute or 2. You see the voltage at a battery when being charged is not linear to its charge state but very non linear as voltage rises quite quickly compared to charge degree. (voltage of a battery after standing off charge for some time is a better indicator of charge state.) So I think a VSR would operate to connect service batteries with 30 seconds or so of engine start under normal conditions.
For all that I would connect a windlass to my engine start battery and always start engine for departure. This means that windlass current comes from the alternator without concern about current carrying ability of 1,2,both switches diodes or VSR. olewill
(who has neither windlass alternator or even engine)

 

[prv]

A voltage sensing relay senses the voltage of the charging system
[...]
So I think a VSR would operate to connect service batteries with 30 seconds or so of engine start under normal conditions.

...and what does that have to do with the Sterling Alternator to Battery Charger that I was asking about, then?

Pete

 

[ukmctc]

Run it from the engine battery, use a foot switch easy to fit and install, no hassle. You don't need to run the engine, but it does help and saves on power loss, keeps domestic battery free for other requirements.

 

[maby]

Seems a shame to make it impossible to sail away from your anchor, which I quite often do.
My engine start battery is for starting the engine.

Even greater shame to subsequently find that you've flattened your batteries - either engine start or domestic! As you say, the engine battery should be reserved for starting the engine. I really don't know how great the risk of damage to domestic grade batteries is from drawing a hundred amps or more for several minutes is. Personally, I put up with the inconvenience (?) of having to start the engine before raising the anchor - even if I expect to sail away from the mooring. Again, it possibly depends on the nature of your sailing grounds - when we anchor up, it is normally in a fairly narrow tidal creek. Usually not suitable for sailing away from the mooring and, even when we can, I feel safer having the engine running just in case...

 

[vyv_cox]

Run it from the engine battery, use a foot switch easy to fit and install, no hassle. You don't need to run the engine, but it does help and saves on power loss, keeps domestic battery free for other requirements.

Surely depends entirely on the relative sizes of each bank? My admittedly small starter battery has a capacity of 13Ah. My domestic bank is 330Ah. As has been said, it doesn't matter much if the engine is running anyway, but for those other occasions it makes far more sense to connect to the domestics.

 

[KREW2]

Just use your engine as a generator, don't engage gear and, you can still sail off.
I keep my boat on a swing mooring, and often sail onto it, even though I keep the engine running, so as to have a good charge in them for my next sail

 

[Sans Bateau]

Surely depends entirely on the relative sizes of each bank? My admittedly small starter battery has a capacity of 13Ah. My domestic bank is 330Ah. As has been said, it doesn't matter much if the engine is running anyway, but for those other occasions it makes far more sense to connect to the domestics.

Indeed, and when I came to the conclusion which I did, and I knew I had to upgrade the batteries anyway, so I utilised the space I had with a much larger starting battery. In choosing the battery I learned that the CCA (cold cranking amps) was an important factor in specifying a battery for this type of work, hence I installed a battery with a 900CCA and around 150ah. This should allow me to retrieve the anchor without the engine running and then later still have enough power to start it.