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Old 16-01-2021, 06:04   #1
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Windlass Info,

A question for the electrical Guru's,

I have a 900 Watt chain Windlass, 12 volt, It has a direct 220 Kg Pull,
It geared 4 to 1

I have an AGM 75 Amphr battery with 900 CCA, Start Battery, Its a coiled one,
It currently flicks over my 300 HP V8 Cat Turbo Diesel and starts it in a few seconds,

How long will this battery last pulling up 40 KGs and fifty feet of 8 mm chain,

Or, How many minutes will it run before running out of Grunt,
Flattening the Battery, and no more Grunt,

I wont be using the windlass to break it free, Just pulling up the anchor,

Thanks in advance, Brian,
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Old 16-01-2021, 07:34   #2
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pirate Re: Windlass Info,

Your supposed to run the engine (assuming it charges your batteries) while raising your ground tackle.. or is this question for in case you suffer engine failure.
I can't give you a time line but it will chew up juice pretty quick methinks.
I now hand you over to the Techies..
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Old 16-01-2021, 07:39   #3
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Re: Windlass Info,

I'd expect it to run long enough to retrieve that chain and anchor plus a decent bit of line before it. Power draw shouldn't be more than 70 - 75 amps, so it'll probably run for 30 minutes or so on that size battery. My bigger concern would be poor performance due to battery voltage dropping under load with that much load on a small battery.
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Old 16-01-2021, 13:20   #4
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Re: Windlass Info,

75ah at 12V is 760Wh of which approx 50% usable if battery fully charged giving 380Wh, which should run your windlass for about 20min - but then you may struggle to start your engine!
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Old 16-01-2021, 13:21   #5
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Re: Windlass Info,

The above assumes that your windlass is pulling full 900W which it probably wouldn't be.
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Old 16-01-2021, 13:36   #6
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Re: Windlass Info,

Quote:
Originally Posted by markcouz View Post
The above assumes that your windlass is pulling full 900W which it probably wouldn't be.
Therein lies the calculation problem. The motor may be 900 watts at "lock rotor" or something else. The power required is the weight of the chain to the bottom, so depth is a variable also.
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Old 16-01-2021, 16:12   #7
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Re: Windlass Info,

Quote:
Originally Posted by markcouz View Post
75ah at 12V is 760Wh of which approx 50% usable if battery fully charged giving 380Wh, which should run your windlass for about 20min - but then you may struggle to start your engine!
Thank you, Thats the one I wanted, approx 20 minutes, Run time,

I havent used it yet, But I assume it would be running only a couple of minutes, Maybe 5 minutes at most, I dont know that either till I try it,
This battery is still in my RV as Im still using it,

Its a stand alone system only for the anchor windlass,
Its charged off the wind generator, Rutland 913
But if the wind genny isnt enough to keep it fully charged,

I can run a lead off my battery bank to it,
Total combined batteys, would then be 995 Amphrs,
Which is run off my solar panels, 500 Watts,
Which is also charged by the diesel when its running,

Or, I can just charge it up with the 3.5 KVA generator, Which sits on the Bow beside it, If it needs it,

This 3.5 KVA generator has a dedicated 12 volt charger in it that takes an hour to charge two x 160 amphr AGM start batterys, Total 360 amphr batterys, enough to start the diesel,
Ive since put in 3 x 200 amphr AGM batterys to boost my battery bank,

And the 75 Amphr 900 CCA AGM which still has to go in to it,

Im getting prepared to go offshore, I will be a long way from No where,
So its easy to do it now before I leave,


Thanks Brian,
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Old 16-01-2021, 16:55   #8
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Re: Windlass Info,

I doubt you'll get 20 minutes windlass run-time, from your battery (discharged to 50% SOC).
The c-rating is a measure of the rate at which a battery is being charged or discharged. The common C/20 rate refers to a discharge over a 20-hour period.
Because of the Peukert effect (aka, the faster a battery is drained, the less overall amperage is available), if you discharge a battery over the course of 100 hours, the AH rating looks higher than if you discharge that same battery over the course of 1 hour.
For deep cycle batteries the standard rating is 20 hours.
So, if a deep cycle battery has a rating of 75AH @ 20Hr rate, then that battery was discharged over 20 hours with a 3.75 amp load.
Starting batteries, on the other hand, are typically rated at 10Hr rate.
So, if a starting battery has a rating of 75AH @ 10Hr rate, then that battery was discharged over 10 hours with a 7.5 amp load.
As others have noted, you don't want to discharge a FLA battery any more than 50%, so halve the above currents, to save your battery.
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Old 01-02-2021, 22:20   #9
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Re: Windlass Info,

Well here's the results,
900 CCA 75 amphr AGM, Coil type,

I started with 12,4 on the multimetre,
After I had it up and sitting on the boat, Upside down, 12.3 on the multimetre,
Thats about 10 minutes running time, All up over a couple of days,

First off I just dropped the 24 KG anchor in the drink to get it out of the way,
Then I fed 100 metres of 8mm chain thru the windlass,
Using the windlass motor to feed it thu, It wont go thru with out the motor,
Then I used the windlass to pull the 24 kg anchor up,
It pulled it up with out a problem, Twisted links stopped it, But rewinding a bit cleared that,
Then I went and found a nice sandy beach to sit on and clean my hulls,

While I was there, I will give it a go with the 40 KG anchor,
Yep, It pulls that one up with no effort,

By the time I was leaving the beach, The wind was screaming, 10-00 PM,
North side of Port Philip Island,
Predicted strong wind warning in excess of 40 knots, BOM, And 2 metre seas,

The 40 KG anchor had buried itself deeply in the sand,,
A bit at a time, I dragged the boat towards the anchor,
Im still partially aground, But as the tide lifted me, I crept forwards,
Eventually I was above the anchor and the boat lifted the anchor out of the sand,
I pulled up the anchor to the bow roller, And sailed it back to the Marina,

Going north and the wind from the N NEast, I was doing 8 knots on the Genoa,
4 knots on the motor into the wind to get back into the Marina's channels,
I sheared 3 fenders docking the boat with the wind sideways across the Marina,
Tore the rope out of the fenders as they got jammed against the jetty,
We could not push the boat away from the dock to get more fenders in,
Good thing I got it in first go as my reverse lock has crapped itself, So I had no reverse,

Playing with the windlass two days later, I wonder just how good this thing is,
My anchors travel hanging off the roller,

They just clear the water line, So Its no big deal, Hanging off the front of the boat while travelling,
I can pull the 24 KG anchor over the roller with great difficulty by hand to get it to sit in its slot on the deck,

The 40 KG anchor, No way as its just too heavy,

So I press the foot button and drag the 40 KG anchor up,
Well, Bugga me,

It drags the 40 KG anchor up and over the roller with no effort at all,
I cant believe this,
No way would I have expected any anchor windlass to do that,

Its a 90 Degree pull, on almost a 3 foot long shank,

The 40 KG anchor is in its slot upside down, But I can lock it down in place for bad weather when Im travelling,
I can live with that,,
I will be using my 40 KG anchor all the time now, Its just so easy to use with the windlass,

Yep, Its a Chinese windlass thats more than half the cost of anything similar,

Its very good quality,
And uses no negligible power to work it,
No, It dont run out off Grunt or lose its power during its working effort,

As for not being strong enough to lift a 40 KG anchor and all that 8 mm chain,
As for draining the battery,
Or killing the Battery,
Thats all conjecture and means nothing,

Im absolutely stoked with my new Windlass,

Cheers, And thanks to all who gave me advise,

Brian,
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