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Old 06-05-2017, 00:05   #16
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Originally Posted by Brann- View Post
It seems I have something like this (not this exact model though)

switching to 24v would definitely be more straightforward, but those 12v to 24v converters are quite expensive, aren't they ?
I would price the step up convertor (12 to 24v) first before deciding

Simplest way to bring your default 12v house and charging system into play.

Then all you need is a 24v solenoid to control the new windlass
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Originally Posted by smac999 View Post
I can't tell from that picture. But I'm guessing you have a relay that puts the 2 batteries in parallel for charging. And in series when you hit the thruster button. Allowing you to charge them from 12v

I would rip the crap out. Make it a 24v bank. Power both devices from the bank. And buy a 12v to 24v dc to dc charger.


Or you have to make it so engaging the windlass also engages the relay to put the batteries in series
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Old 06-05-2017, 06:24   #17
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Actually, in the end, that's what I'll end up doing. I thought the series/parallel switch was wired to a complicated "just-in-time" switching mechanism, but it's not. I have a power switch to change between parallel and series, so I'll just use that and plug the windlass the same way the thruster is plugged in


I don't understand what you're saying. I want to switch to 24v because of the slightly better performance of a 24v windlass vs is 12v equivalent, and also to reduce the voltage drop through the wires. 12v sized wires will be more than adequate for 24v as I would in theory only need a cross section four times smaller, wouldn't I ?
Your existing wires are fine either way. I was was questioning if a 24v windlass would give you better performance.
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Old 08-05-2017, 01:38   #18
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

in reply to Brann- <<to 12v sized wires will be more than adequate for 24v as I would in theory only need a cross section four times smaller, wouldn't I ?>>
No, you need a cross section half as small, it is a linear function. Different if you are talking about wire diameter !
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Old 10-05-2017, 14:05   #19
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Originally Posted by guyrj33 View Post
"This is not an issue for the bowthruster as its use is quite sporadic, but for a windlass, having the battery not being supported by the engine at all for the 5 minutes it takes to retrieve 100m of chain might be an issue, don't you think ?"

let's say your windlass draws 200 amps for 5 minutes,
200A x 5min x 1 hour/50 minutes = 16.66 AmpHours.

17 AH isn't a really big draw on a battery.
Are you neglecting the discharge capacity of the battery bank? A 400ah 12v golf cart battery setup, like I have for a house bank, would be decimated by 200a for 5 minutes, and there'd be a lot of hydrogen offgassing.

Lithium ion house bank of the same size could handle it no problem.
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Old 12-05-2017, 01:11   #20
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Originally Posted by Delafontaine View Post
in reply to Brann- <<to 12v sized wires will be more than adequate for 24v as I would in theory only need a cross section four times smaller, wouldn't I ?>>
No, you need a cross section half as small, it is a linear function. Different if you are talking about wire diameter !
You're absolutely right, thanks for pointing that out!
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Old 12-05-2017, 10:18   #21
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Are you neglecting the discharge capacity of the battery bank? A 400ah 12v golf cart battery setup, like I have for a house bank, would be decimated by 200a for 5 minutes, and there'd be a lot of hydrogen offgassing.

Lithium ion house bank of the same size could handle it no problem.
I'm confused by your comments, yes 200 amps is a significant draw that's why I showed the calculation of amp hours used.
Batteries don't out gas when being discharged, they out gas when being charged so there wouldn't be any hydrogen outgassing.
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Old 18-05-2017, 01:19   #22
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

Wow, upon rereading my post I understand your confusion. Ignore the hydrogen sulfide brain fart portion. I'm talking about discharge rate as a function of xC, and it's effect on the remaining capacity.

To clarify, do you still think 5 min@200a is a reasonable load for a cruiser's house bank, if the 200a is 0.5C or 1C of the house bank?

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Old 18-05-2017, 05:06   #23
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

I think the point you're trying to make is that amp hour capacity goes down as current draw goes up.
From the NP a battery supplying 1X capacity would be fully discharged in about 20 minutes and about 20% discharged after 5 minutes.
Therefore for a 200 amp hour battery supplying 200 amp for 5 minutes the capacity used would be about 40 amp hours, not the 17 AH I originally suggested.
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Old 18-05-2017, 06:33   #24
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

200A @ 12v for 5 mins is a little unrealistic for an anchor winch. Even the largest anchor winch may be drawing 60-80 A while retrieving the chain with a peak of around 90-150 A while breaking out the anchor.
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Old 18-05-2017, 07:34   #25
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

I was just using 200 amps as a SWAG, reasoning that a windlass motor would be similar to a DC starter motor. With a current draw somewhere around 100 amps instead of 200 amps the % capacity of the battery used will be of course be less and pushes the analysis back toward the original assumptions.
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Old 18-05-2017, 08:16   #26
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Originally Posted by guyrj33 View Post
I was just using 200 amps as a SWAG, reasoning that a windlass motor would be similar to a DC starter motor.
Understood Guyrj. I did not mean to nit pick, but I think this is a case where more realistic numbers may lead to different conclusions.
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Old 18-05-2017, 09:38   #27
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Understood Guyrj. I did not mean to nit pick, but I think this is a case where more realistic numbers may lead to different conclusions.
no problems, it's always better to have real world numbers to work with.
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Old 18-05-2017, 16:30   #28
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Re: replacing a 12v windlass by a 24v when there's already a 24v bowthuster

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Originally Posted by guyrj33 View Post
I think the point you're trying to make is that amp hour capacity goes down as current draw goes up.
From the NP a battery supplying 1X capacity would be fully discharged in about 20 minutes and about 20% discharged after 5 minutes.
Therefore for a 200 amp hour battery supplying 200 amp for 5 minutes the capacity used would be about 40 amp hours, not the 17 AH I originally suggested.
Yes, thank you.
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