Best Way to Power a Windlass

[waterman46]

2 output FET battery isolator, input wired to alternator and all other charge sources. One output to engine start battery, one output to windlass battery, charging a Group 27 battery in the bow. Some will say use echocharger. But they limit charge current to a rarher low value and you want to direct a lot of alternator charge into windlass if that battery should become discharged, and you already have large cables installed, so leave them in place.

[FuzzyFeat]

Ditch the electrics. Nothing but trouble. Doubt that? Just search this forum.
Find a Sea Tiger 555A manual windless and use the small effort required to pull the hook part of your fitness program.

[sailingharry]

Originally Posted by FuzzyFeat

Ditch the electrics. Nothing but trouble. Doubt that? Just search this forum.
Find a Sea Tiger 555A manual windless and use the small effort required to pull the hook part of your fitness program.

There is a huge difference between the ground tackle of a lightweight 37' catamaran and a 24,000 pound 43' foot monohull. On my 34' Sabre, the "manual windlass" (my back) was fine -- I could pull the 33lb anchor and 10' of chain by hand with no worries, and I suspect your manual windlass is overkill.


The OP, on the other hand, probably has ground tackle closer to our current boat, a Saga 43, with 5/16 chain and a 55 pound Rocna, where deeper anchorages can easily have suspended weights exceed 100 pounds. That's a fair bit more work to pull!





Harry

[stormalong]

Originally Posted by sailingharry

Oh, and there is another myth repeated here. DC is different from AC. In AC with rotating machinery (only rotating machinery -- not resistive loads like light bulbs, stoves, etc), the speed (and therefore the power demand) is set by the frequency (all synchronous motors run at a multiple of frequency, normally 1/2, or 1800 RPM, but some rotate at 1 revolution per cycle or 3600 RPM) . As voltage drops, current increases to maintain the same power. In DC the speed is not fixed (compare the cranking speed of an engine with a nearly dead battery vs one with a freshly charged battery). As voltage drops, speed drops, power drops -- and current DROPS! Lightbulbs and motors do NOT draw more current as voltage goes down. Motors might run longer (if the windlass speed drops, it takes longer to pull the anchor).

Harry

Sorry Harry, not quite right. The difference between AC ad LOW VOLTAGE DC is very significant. Powerline losses are related to current. Known as I squared R losses. The resistance of the wire causes more voltage drop as the current increases. That is why long distance power lines are high voltage. AC has the advantage of easily changing voltage - doubling the voltage halves the current and vice versa. Thank you Nicola Tesla and George Westinghouse.

Also, stalled motors draw much more current than spinning motors and motor load also increases current draw.

[SVTatia]

Originally Posted by Q Xopa

...Also they are only aiming for a max 10% voltage drop which they think is acceptable.......

Originally Posted by Q Xopa

... No need to design engineer this stuff as the manufacturer has already done it. ...

I am looking at getting a Lofrans Cayman, @1000 watts, 100 amps, 50 feet both ways, the cable run recommended by the manufacturer is #2, whereas for 3% drop the chart points to 3/O which has substantial price difference not counting the difficulty to run such a thick cable like a stiff garden hose.

I have no experience with electric windlasses, so is a 10% drop acceptable?

[FuzzyFeat]

Originally Posted by sailingharry

There is a huge difference between the ground tackle of a lightweight 37' catamaran and a 24,000 pound 43' foot monohull. On my 34' Sabre, the "manual windlass" (my back) was fine -- I could pull the 33lb anchor and 10' of chain by hand with no worries, and I suspect your manual windlass is overkill.

The OP, on the other hand, probably has ground tackle closer to our current boat, a Saga 43, with 5/16 chain and a 55 pound Rocna, where deeper anchorages can easily have suspended weights exceed 100 pounds. That's a fair bit more work to pull!
Harry

My primary ground tackle is an all chain, 5/16" HT, rode with a 20kg Rocna. A bit over kill, but i sleep well. Breaking it out with the two speed SeaTiger and getting it up is a piece of cake. I have anchored in 40 feet and had no problems. On one occasion i hauled up an old engine block along with the anchor.


I am 78 years old.

I once had a marine hardware store. Constant sellers were repair parts for electric windlass; stitches, relays and motors.

[Q Xopa]

Originally Posted by SVTatia

I am looking at getting a Lofrans Cayman, @1000 watts, 100 amps, 50 feet both ways, the cable run recommended by the manufacturer is #2, whereas for 3% drop the chart points to 3/O which has substantial price difference not counting the difficulty to run such a thick cable like a stiff garden hose.

I have no experience with electric windlasses, so is a 10% drop acceptable?

10% drop is what the Manufacturers Manual for my Windlass says. I cant speak for others. Id check yours, or ask your manufacturer. You can often download a manual if you dont have one. The first thing I do when I get or even am looking at any equipment is find out about, get the manuals etc.

Of course if you can do less than a 10% drop that is obviously better.

[sailingharry]

Originally Posted by stormalong

Sorry Harry, not quite right. The difference between AC ad LOW VOLTAGE DC is very significant. Powerline losses are related to current. Known as I squared R losses. The resistance of the wire causes more voltage drop as the current increases. That is why long distance power lines are high voltage. AC has the advantage of easily changing voltage - doubling the voltage halves the current and vice versa. Thank you Nicola Tesla and George Westinghouse.

Also, stalled motors draw much more current than spinning motors and motor load also increases current draw.

Not sure which item in my post you disagreed with. Everything you said was correct -- but had nothing to do with my post. Perhaps we don't disagree!


My point had to do with earlier posts that indicated that lower voltages (due to battery drop, IR drop, bad connections, etc) lead to increasing current and higher motor temperatures -- until the voltage drops to the point that the motor stalls, lower voltages provide lower currents and lower temperatures.


I will say that your point about higher voltages and AC current is something that has often intrigued me. Given that most larger boats have robust inverters, and given that inverters have a strong track record of reliability (I know a full time cruiser with a 20 year old Xantrax -- Freedom maybe? -- inverter still going strong), it would seem to me that a 110V windlass would be a huge improvement. For starters, current would be cut by 90%, making wiring almost trivial (instead of 2/0, it would be #8 or even #10).

[sdj]

If the house battery is in good condition then its just the chart plotter being sensitive, as suggested.

In answer to your other question, I made a spreadsheet to evaluate battery AH ratings for windlasses for LiFePo4 batteries, and it seems that 30AH at 24V gave me about 7 full retrieves on a single charge. This was for a Lewmar CPX4 windlass. I'd double that for an AGM battery, and of course it goes without saying that liquid filled batteries are out of the question.

You can easily charge any battery using a mains charger plugged into your inverter, but make sure that the target system was isolated.

[SVTatia]

Originally Posted by Q Xopa

10% drop is what the Manufacturers Manual for my Windlass says. I cant speak for others. Id check yours, or ask your manufacturer. You can often download a manual if you dont have one. The first thing I do when I get or even am looking at any equipment is find out about, get the manuals etc.

Of course if you can do less than a 10% drop that is obviously better.

Originally Posted by SVTatia:
I am looking at getting a Lofrans Cayman, @1000 watts, 100 amps, 50 feet both ways, the cable run recommended by the manufacturer is #2, whereas for 3% drop the chart points to 3/O which has substantial price difference not counting the difficulty to run such a thick cable like a stiff garden hose....

See above - I took it from the manual.... I can't see why anyone installing such a piece of equipment would not look at the manual.

The question of whether or not 10% is acceptable was a general one to the real world, what do they use, did they over spec, etc. not to tell me to go ask the makers.

[CarinaPDX]

I think this discussion is missing the point: the "problem" is the voltage drop at the chartplotter - there is no indication that there is a problem with the windlass or its wiring (the problem most posters are trying to solve). Windlass (and starter) motors have a low impedance, which draw high current and thus can pull down the voltage if the supply is not very substantial. That is normal. If the cables were undersized or had corrosion causing resistance the total impedance in the loop would increase, and hence draw less current - not more - and pull the voltage down less - not more. So the low voltage at the chartplotter, and at least to some extent at the batteries, is not caused by windlass wiring problems. The cause is at least in part that the new windlass has a larger motor, with lower impedance that pulls the voltage down at the battery. This is normal.

To lessen the voltage sag during use of the windlass and starter motor the battery bank should have a larger cranking ability (ability to deliver higher currents). This can be done by enlarging the bank, or by buying batteries with higher cranking capability (lower internal resistance).

It may also be that there is some voltage loss between the battery and the chartplotter. This is probably not that significant, but worth checking.

The usual answer is to put electronics loads on a different battery than the windlass and starter motor. In other words use the engine battery for the windlass. Start batteries are designed for high currents for short periods of time; deep cycle house batteries are not. And of course run the engine while operating the windlass.

Greg

[davenrino]

Originally Posted by Simi 60

I was always of the belief that you use start batts with engine running so alt provides input.
Our engine and starts are at the front half of vessel, house bank at back half so this works for us

+1

[stormalong]

Sailingharry, You started your post with: Oh, and there is another myth repeated here. DC is different from AC.

That is what prompted my reply.

You also wrote: As voltage drops, speed drops, power drops -- and current DROPS! That is not really accurate with motor loads. The current actually increases as the motor load increases.

I'm not sure we disagree either, other than terminology.

The idea of an AC windlass has merit except that the starting loads for AC motors is so much higher than running loads that the ability of an inverter to supply that load is questionable. This is also an issue for generators.

[stimpsonjcat]

Originally Posted by Dark Horse

DC power is different from AC AC small wires, no problem. DC small wires big problem.
.

Electrical engineer here just trying to be helpful and not critical.

The only reason this might be considered true is that the AC voltages we encounter commonly are also higher than than the DC voltages we commonly encounter.

Power is voltage times current.

Solving for current we get I=P/V so for the same power (devices use power) a higher voltage will mean lower amps.

It's the lower amps that result in smaller wires.

Lower amps is a good thing for two reasons:
-can use smaller wires
-voltage drop is reduced

Hope that helps.

[stimpsonjcat]

Originally Posted by stormalong

The idea of an AC windlass has merit except that the starting loads for AC motors is so much higher than running loads that the ability of an inverter to supply that load is questionable. This is also an issue for generators.

This is correct. Locked rotor current can be 6 to 7 times the FLA on the nameplate.