Powering a windlass - Thoughts

[evm1024]

I blocked this out about a year ago and never got around to posting it. Sitting at home and I dusted it off after reading in another thread.

I've divided ways of powering a windlass into 4 basic types and list a few pro's and con's.

I am using type 3 on my boat currently. I have most of the parts to try out type 4 using some Headway LiFePO4 cells (16 cells for 32 AH@13.2 volts).

--------------------------Here we go -------------------------

1) Heavy Cable

Advantages to running heavy cable (2/0, 4/0) include “unlimited
runtime, no extra technology and pretty much zero maintenance. Tried and true.

Disadvantages include the cost and weight of the cable, 10% or more voltage drop.

2)Remote Battery small cable

Advantages include essentially no voltage drop due to the short cable run to the windlass. The small gauge charging cable is easy to run from the charge source to the battery. The “echo charge” or combiner can be located at the windlass battery. In a pinch the windlass battery can be disconnected and used as a start battery.

Disadvantages include runtime limited to that of the windlass battery. Given the small gauge of the charge cable there is a potential for long recharge times. The charging system and the windlass battery must be of compatible technology, typically the same technology. A largish remote battery implies weight, the potential for fumes if FLA and such.

3) Remote Battery Remote Mains Charger

Advantages include essentially no voltage drop to the thruster due to the short cable length. With a remote charger running off the mains voltage you can have the battery technology and voltage of your choice for the windlass. That is to say you can put a 24 volt windlass in an otherwise 12 volt boat.

Disadvantages are an increase in complexity – you need to be running the inverter to run the charger that charges the windless battery. Runtime is limited to the remote batteries capacity and charge time is determined by the charger rating and of course the inverter capabilities. Overall efficiency is around 80%.

4) Remote Battery DC to DC Charger

Advantages include essentially no voltage drop to the windlass as well as a small gauge charge cable. Using a DC to DC charger you can have a different windlass battery voltage and chemistry from your house bank. You could run a 24 volt LiFePO4 windlass battery in a 12 volt lead acid boat.

Disadvantages include runtime limited by the battery capacity, more complexity and log charge times. Interestingly the overall efficiency is around 87% which is comparable to running heavy cable.

[SVHarmonie]

I would though out some things for you to think about (or not!)

Forget about "efficiency." In no real world scenario does a windlass consume a significant percentage of the power onboard the boat. A few percentage loss is totally irrelevant.

Forget about "optimum." Perfect is the enemy of the good. If what you have works, and has no significant operational or reliability problems, save your money and thoughts for a real issue, or (better yet) just go sailing.

Successful boats have been sailed around the world with EACH of the designs you describe. Sometimes good enough really is good enough.

My only technical thought is that 32 A-hrs at 13 volts seems (to me) inadequate. I assume you are looking at windlasses for you 50 foot boat. They will be 1500W to 2000W motors. 32A-hr at 13.2 volts (420 W-hrs) will run such a windlass for only about 10 or 15 minutes.

Since most of these run about 15 m/min no-load speed, that would give you the opportunity to pull in no more than 200 m of chain before you are dead. That might seem enough, but if you have to anchor more than once or strain and load up a bit you might find you're hand cranking...


On the other hand, if you are doing this whole exercise for fun, then option four is the way to go. Just use a battery with at least 600W-hours of usable capacity.

There is an advantage to a direct cabled system that people never think about. At typical windlass power loads (100+ Amps), you get a fair amount of voltage sag from the battery, aside from the cables. Cabling directly to the house batteries allows a large engine alternator or genset powered charger to keep full voltage at the battery terminals. You might end up with HIGHER voltage at the windlass than with a remote battery because the voltage drop through the cables is LESS than the voltage sag from internal battery resistance...

[evm1024]

Originally Posted by SVHarmonie

I would though out some things for you to think about (or not!)

Forget about "efficiency." In no real world scenario does a windlass consume a significant percentage of the power onboard the boat. A few percentage loss is totally irrelevant.

Efficiency has been brought up in the past. I don't worry much about it but others have so I addressed it. Plus for the most part I only raise anchor with the engine running. Solar of course charges when the sun shines.

Forget about "optimum." Perfect is the enemy of the good. If what you have works, and has no significant operational or reliability problems, save your money and thoughts for a real issue, or (better yet) just go sailing.

Successful boats have been sailed around the world with EACH of the designs you describe. Sometimes good enough really is good enough.

Agreed.

My only technical thought is that 32 A-hrs at 13 volts seems (to me) inadequate. I assume you are looking at windlasses for you 50 foot boat. They will be 1500W to 2000W motors. 32A-hr at 13.2 volts (420 W-hrs) will run such a windlass for only about 10 or 15 minutes.

Since most of these run about 15 m/min no-load speed, that would give you the opportunity to pull in no more than 200 m of chain before you are dead. That might seem enough, but if you have to anchor more than once or strain and load up a bit you might find you're hand cranking...

The 32 Ah pack is just a test bed and does not represent what I would use in the real world. But in reality a 32 Ah LiFePO4 battery is much like a 74 Ah AGM battery like I am currently using.

Also, my Ideal BHW windlass uses quite a bit lower current than under full load (of course!). A good test would be to dump the chain out and see how long it needs to pull it all up and the AH used. But still 32 AH is undersized and has no safety margin.

On the other hand, if you are doing this whole exercise for fun, then option four is the way to go. Just use a battery with at least 600W-hours of usable capacity.

For fun and as a prototype for what we will eventually install in the boat. If I ever have to replace the windlass motor (or the windlass) I'll likely go for a 24 v model.

600 WH also is a bit shy for me. Given the near constant voltage for discharge of LiFePO4 and 13.2 volts we get only 45 Ah for the battery. With a safety margin tossed in we could say 100Ah for the battery.

There is an advantage to a direct cabled system that people never think about. At typical windlass power loads (100+ Amps), you get a fair amount of voltage sag from the battery, aside from the cables. Cabling directly to the house batteries allows a large engine alternator or genset powered charger to keep full voltage at the battery terminals. You might end up with HIGHER voltage at the windlass than with a remote battery because the voltage drop through the cables is LESS than the voltage sag from internal battery resistance... (depending on batteries, and a lot of other things...)

That is also another test that is worth trying. With a LiFePO4 house battery I would expect the banks voltage to be around 13 volts after a night of powering the house loads. The LiFePO4 house bank would take all the current your genset or alternator could produce (or nearly so) and thus you would not get "full voltage" e.g. 13.9 volts, out of the alternator. Plus the current would need to be shared between the house bank charging and the windlass draw.

With a lead acid house bank the situation could be better due to a lower acceptance rate of the LA bank and the higher charge voltage target voltage of 14.4 volts. Still something to model out or to test.

Thanks for your thoughtful comments.

Oh, as a side note - The bank I'm playing with uses the Headway 8 AH cells. These cells are are the high discharge current models rated at 20C cont. That 's 160 amps and the pack has 4 strings for a theoretical 640 Amp discharge rate not that I have any need for that.

In the end this pack will likely become the start battery.

[Dsanduril]

5) Windlass not installed at bow

Advantages are this moves the weight of chain/chain locker out of the ends of boat (and that doesn't matter whether mono or multi, it's a benefit), and can then provide short cable runs to the main house bank (dependent on location of both items, but generally much less than going all the way to the bow).

Disadvantage, that chain running across the foredeck to the windlass location. There are various ways of dealing with this, some requiring thought at construction time, others that can be retrofitted.

This is another option that has been successfully used by boats for a long time.

[a64pilot]

You say a small remote battery won’t have voltage drop due to it being close to the load, that’s not true, it may not have voltage drop due to the wiring loss, but it will due to it being a single battery as opposed to a whole bank of batteries.
Which drop is larger? Depends on size of remote battery and size of wiring of house bank installation.

But there are other considerations, like having another battery you have to buy every so often and another battery you have to service, and it’s weight and size etc.
It’s not a simple answer.

In my opinion it’s a pay me now or pay me later. I’m not even convinced that the savings from smaller cable will pay for the extra battery, battery box, mounting hardware, and echo charger or whatever means you choose. But I do know that it’s a battery you get to buy every five years or so, and you only buy the cable once

[EmeraldCoastSailor]

Running windlass off of house batts with engine running is best in terms of simplicity and amount of juice to the windlass. Unless cable runs are prohibitive, that’s the option I’d go with.

[Mike OReilly]

You forgot one:

5) Handle (as in manual windlass)

[evm1024]

Originally Posted by Mike OReilly

You forgot one:

5) Handle (as in manual windlass)

Quite! (forgot that is)

[moseriw]

1) NEVER DO IT!!!

By now I have to repair my bowthruster and windlass motor as the Voltage dropped, regardless if engine running or not! from 12,6/14,4V down to 8 (EIGHT!) Volts.

The bowtruster motor was close to catching FIRE!

Cable length 12m 95 mm²

What I will do is: 225Ah AGM closest possible to thruster and windlass
And I keep the 95 mm² wires for charging and supply of engine with a new 160A alternator.

[Pizzazz]

The best solution is to install the batteries midship. Even on a 50 ft boat, the windlass is 3-4 ft from the bow, the engine is 15 ft from the stern, if the batteries are halfway between the engine (starter) and the windlass), the distance is 15-20 ft. For each. Not so bad.

SVHarmonie summed it up nicely. Most of the time, the battery voltage drop will be much bigger than the cable drop. Just measure it and address the offending issue. For boats > 45 ft you should consider going to a 24V system for windlass, bow thruster and starter/alternator.

[evm1024]

Originally Posted by Pizzazz

The best solution is to install the batteries midship. Even on a 50 ft boat, the windlass is 3-4 ft from the bow, the engine is 15 ft from the stern, if the batteries are halfway between the engine (starter) and the windlass), the distance is 15-20 ft. For each. Not so bad.

SVHarmonie summed it up nicely. Most of the time, the battery voltage drop will be much bigger than the cable drop. Just measure it and address the offending issue. For boats > 45 ft you should consider going to a 24V system for windlass, bow thruster and starter/alternator.

That is the reality especially with FLA house bank of any (reasonable) size. The bank just cannot supply the currents needed without significant voltage drop due to the batteries internal resistance. This is somewhat reduced in any battery chemistry that has a low internal resistance. AGM, carbon foam, LiFePO4 to name a few.

Not looking for the best or even the recommended system. Each has advantages and dis-advantages. Each has those who swear by them and each has those who swear at them.

As noted with type 3 and 4 (remote battery with a charger at the battery) you can install a 24 volt windlass in an otherwise 12 volt boat.

The same holds true for the engine starter.

[moseriw]

1) NEVER DO IT!!!

By now I have to repair my bowthruster and windlass motor as the Voltage dropped, regardless if engine running or not! from 12,6/14,4V down to 8 (EIGHT!) Volts.

The bowtruster motor was close to catching FIRE!

Cable length 12m 95 mm²

What I will do is: 225Ah AGM closest possible to thruster and windlass
And I keep the 95 mm² wires for charging and supply of engine with a new 160A alternator.

[evm1024]

Originally Posted by moseriw

1) NEVER DO IT!!!

By now I have to repair my bowthruster and windlass motor as the Voltage dropped, regardless if engine running or not! from 12,6/14,4V down to 8 (EIGHT!) Volts.

The bowtruster motor was close to catching FIRE!

Cable length 12m 95 mm²

What I will do is: 225Ah AGM closest possible to thruster and windlass
And I keep the 95 mm² wires for charging and supply of engine with a new 160A alternator.

Sorry to hear about your near fire.

95 mm^2 is 3/0 AWG and one would think that it was plenty big. There are a few questions...

What type and size of house bank?

What size/type windlass and thruster?

It sounds like you have a real life case where type 1 does not cut it.

You experience will add to the body of knowledge.

[triibutu]

Originally Posted by moseriw

By now I have to repair my bowthruster and windlass motor as the Voltage dropped, regardless if engine running or not! from 12,6/14,4V down to 8 (EIGHT!) Volts.

The bowtruster motor was close to catching FIRE!

I am interested to learn, how reduced voltage causes a dc motor to overheat?

[Adelie]

Originally Posted by evm1024

I blocked this out about a year ago and never got around to posting it. Sitting at home and I dusted it off after reading in another thread.



I've divided ways of powering a windlass into 4 basic types and list a few pro's and con's.



I am using type 3 on my boat currently. I have most of the parts to try out type 4 using some Headway LiFePO4 cells (16 cells for 32 AH@13.2 volts).



--------------------------Here we go -------------------------



1) Heavy Cable



Advantages to running heavy cable (2/0, 4/0) include “unlimited

runtime, no extra technology and pretty much zero maintenance. Tried and true.



Disadvantages include the cost and weight of the cable, 10% or more voltage drop.



2)Remote Battery small cable



Advantages include essentially no voltage drop due to the short cable run to the windlass. The small gauge charging cable is easy to run from the charge source to the battery. The “echo charge” or combiner can be located at the windlass battery. In a pinch the windlass battery can be disconnected and used as a start battery.



Disadvantages include runtime limited to that of the windlass battery. Given the small gauge of the charge cable there is a potential for long recharge times. The charging system and the windlass battery must be of compatible technology, typically the same technology. A largish remote battery implies weight, the potential for fumes if FLA and such.



3) Remote Battery Remote Mains Charger



Advantages include essentially no voltage drop to the thruster due to the short cable length. With a remote charger running off the mains voltage you can have the battery technology and voltage of your choice for the windlass. That is to say you can put a 24 volt windlass in an otherwise 12 volt boat.



Disadvantages are an increase in complexity – you need to be running the inverter to run the charger that charges the windless battery. Runtime is limited to the remote batteries capacity and charge time is determined by the charger rating and of course the inverter capabilities. Overall efficiency is around 80%.



4) Remote Battery DC to DC Charger



Advantages include essentially no voltage drop to the windlass as well as a small gauge charge cable. Using a DC to DC charger you can have a different windlass battery voltage and chemistry from your house bank. You could run a 24 volt LiFePO4 windlass battery in a 12 volt lead acid boat.



Disadvantages include runtime limited by the battery capacity, more complexity and log charge times. Interestingly the overall efficiency is around 87% which is comparable to running heavy cable.

You forgot the 5th way:
Hands, arms and back.