12v Boat with 24v bow thruster

[BillKny]

Originally Posted by jordanbigel

But the one thing about this which concerns me - you have to manually flip this switch and then you're in 24v mode, and that means no way to operate both the windlass and the thruster at the same time. Is that right?

Why on earth would you EVER want to do that?

There is never a need to run a bow thruster while pulling the anchor (or dropping it for that matter!) and the potential for a disastrous wrap around the thruster props is much too high to justify even thinking about it.

I think the whole idea of the 12/24 system that is being described here is way too complex, and there are lots of reasons not to do it (especially as described), but this is NOT one of them...

[Joli]

Originally Posted by BillKny

Why on earth would you EVER want to do that?

There is never a need to run a bow thruster while pulling the anchor (or dropping it for that matter!) and the potential for a disastrous wrap around the thruster props is much too high to justify even thinking about it.

I think the whole idea of the 12/24 system that is being described here is way too complex, and there are lots of reasons not to do it (especially as described), but this is NOT one of them...

We always use the bow thruster when paying out chain, it allows us to keep the bow into the wind as we back down. We always use the bow thruster when taking up chain, it allows us to follow the chain although we don't have way on.

[boatpoker]

My two group 31's at the bow are charged from my 12v alternator and 12v charger. The series parallel switch engages when 24VDC power is demanded from either my anchor windlass or bow thruster and you don't need 0000 cable to run to the bow, 10AWG will suffice

A series/parallel switch from a farm supply company will cost a fraction of what you pay for a "marine" unit. It's by far the most simple and least expensive way to charge at 12v and get 24v out.

$202.00 Canadian
https://www.canadiantractorpartsdire...-switch-863227

[jordanbigel]

Originally Posted by BillKny

There is never a need to run a bow thruster while pulling the anchor (or dropping it for that matter!) and the potential for a disastrous wrap around the thruster props is much too high to justify even thinking about it.

I think the whole idea of the 12/24 system that is being described here is way too complex, and there are lots of reasons not to do it (especially as described), but this is NOT one of them...

In my experience, on my boat, I have sometimes found it advantageous to use the thruster to hold the bow into the wind while the admiral lowers the chain. The idea being to not let the bow fall off too soon, before enough chain is out - I have used the thruster in this way a handful of times and have found it helpful. As for the supposition that the chain could somehow catch on the thruster props, well, I cant speak for how other boats are built, but on my boat this is impossible. For one thing, the prop is inset in a tunnel about 2ft from the opening of the tunnel. Anyway, not an issue.

WRT your second comment, "... the whole idea of the 12/24 system that is being described here is way too complex..." - assuming you are referring to the approach which relies on a serial/parallel relay switch, I don't like the idea much so far. However, the only 2 people so far who have commented that they actually have a 24v thruster and 12v windlass both claim to use this method, so I figure it deserves consideration.

I said earlier, I'm leaning towards the idea of replacing my single 4D with a pair of G31s and then putting in 2 DC/DC 30amp chargers connected to the house bank, and just running the 12v windlass off 1 of the 2 batteries. I know it will temporarily create an imbalance between the 2 batteries. How big a deal this is, I am still not certain.

What would you do?

[boatpoker]

Originally Posted by jordanbigel

assuming you are referring to the approach which relies on a serial/parallel relay switch, I don't like the idea much so far.

What don't you like about series/parallel switches ?

[jordanbigel]

Originally Posted by boatpoker

What don't you like about series/parallel switches ?

I'm still not clear on how this switch works - I had the impression it requires manual operation to engage, in which case, I would be concerned (knowing me) that I would either forget to flip it when I needed it flipped, or forget to un-flip it when done. But from what you wrote earlier, it sounded like you were saying it automatically engages when a load is applied? But another contributor said he used one of these (https://www.texasindustrialelectric....lel_switch.asp) and he was clear that he has a switch he throws (and something about a buzzer which I am not really sure about either) - but maybe these are completely different switches? I'm not really knowledgable about high power relays and switches. Any additional detail or pointers would be appreciated.

[jt11791]

Originally Posted by jordanbigel

This is very interesting - I'm definitely going to research this idea more.

But the one thing about this which concerns me - you have to manually flip this switch and then you're in 24v mode, and that means no way to operate both the windlass and the thruster at the same time. Is that right?

No, the switch is automatic, completely transparent to the user. I can run my windlass and thruster simultaneously, but I'm not clear on exactly how that works. Probably, the windlass only pulls from one battery when the thruster is also on. That is a rare situation on my boat anyhow.

[boatpoker]

Originally Posted by jordanbigel

I'm still not clear on how this switch works - I had the impression it requires manual operation to engage, in which case, I would be concerned (knowing me) that I would either forget to flip it when I needed it flipped, or forget to un-flip it when done. But from what you wrote earlier, it sounded like you were saying it automatically engages when a load is applied? But another contributor said he used one of these (https://www.texasindustrialelectric....lel_switch.asp) and he was clear that he has a switch he throws (and something about a buzzer which I am not really sure about either) - but maybe these are completely different switches? I'm not really knowledgable about high power relays and switches. Any additional detail or pointers would be appreciated.

The switch is automatic and it draws from both 12v batteries (thats how it puts out 24V). They've been used on farm equipment since the 60's and is a far simpler and less expensive way of doing it than adding two more battery chargers.
You can buy an inexpensive one from a farm supply outfit or a very expensive one from any of the thruster manufacturers.

I suggest you don't try to do this yourself as you do not have the electrical knowledge and the potential for serious damage is high. Talk to an ABYC Certified Marine Electrician, not some guy on the dock that says he's an electrician.

[Dockhead]

Originally Posted by BillKny

Why on earth would you EVER want to do that?

There is never a need to run a bow thruster while pulling the anchor (or dropping it for that matter!) and the potential for a disastrous wrap around the thruster props is much too high to justify even thinking about it.

I think the whole idea of the 12/24 system that is being described here is way too complex, and there are lots of reasons not to do it (especially as described), but this is NOT one of them...

I use thruster and windlass together all the time. To hold the bow of the boat into the wind as I'm paying out chain. Very useful. With heavy chain there is zero risk of a wrap around a thruster prop.


But I agree with you about the complexity fo the 12/24 system.


TO THE OP: Note that the new thruster uses THREE TIMES the power of the old one. It's desirable to support the system voltage with a large alternator whilst using it. And I'm afraid that two G27 batteries are not enough.


I don't actually think there is a cheap way to do this. I would be more inclined to do something like this:


1. Replace thruster alternator with large case 24v school bus alternator, 100 or maybe 150 amps. This will be expensive (biggest headache is the drive system), but you'll get a significant bonus from this -- you can charge house bank from it using a B2B charger, and get a massive increase in alternator charging ability for your house bank.



2. Replace your windlass motor with 24v. This is NOT expensive if you chase down the OEM part. I replaced the motor in my Lewmar Ocean 3 windlass for about €200 when I found the Hungarian maker of the OEM part.


3. Install adequate batteries for the thruster. You don't want too much weight in the bow but if the batteries are inadequate, voltage will sag too much, and you can burn out the thruster motor.

[Loredo]

Maybe my experience installing a more powerful BT motor can be of some help to the OP.


First of all, I'd question the need for a 15 KW motor.
Reason I say this is...
New to me Jeanneau 57 had a 24V, 8KW BT motor. Abused motor, most of all, under-powered with the shallow draft keel the boat has. Anything more than 10 KT wind on the beam and it became impossible keep the bow from being blown away while docking in reverse.
The BT is a Quick "BTQ 250". After much research and a couple phone calls with Quick, the same thruster can be had with 6 - 8 - 10 KW motors, everything else remaining the same. Now, as per Quick technical documentation the 8KW one has 140 KGF while the 10KW one has 220 KGF. No typo, that's what Quick says.)



I proceeded and ordered the 10 KW motor. A couple months later it finally showed up (Supply chain problems, they said.). I installed the new motor and HOLLY COW the difference is night and day!


Now let's do a few considerations. 15 KW @ 24V = 625 A!!!
Sure, normally one needs only a few seconds of that power. But what IF one is in a bind and needs more than a few seconds? NO, charger / alternator will be capable of supplying that much power or even only help to keep up the voltage. Let's not even mention the cable size needed to support 625A. I've tested a few things on my boat. Fully charged batteries sitting @ 27.6 V (BTW 4 Optima Red top, 100AH @ 24V) after a couple seconds i run the BT the voltage sags down to 22.1V. After 30 seconds the batteries are roughly @ 20 Volt.
Keeping the engine revs up (90A 24V alternator) does not help the voltage staying higher. Engine revs up AND running the generator to power the two 60A chargers might gain a "." (dot) something. Nothing worth to even mention. Keep in mind, mine is "only" 10KW @ 24V = 416A.

My boat is taller than yours and probably has a lot more surface exposed to the wind that yours. 10KW is really plenty for it.

This is why I ask if you really need 15KW?


Bac to the "Quick electric motor". Upon delivery, on the fan cover I did see a "Best Motor". Long story short, Best Motor is the company who does all the motors for Quick.

Here: https://www.bestmotor.it/
Any chance they have / do a 12 V motor powerful enough for your needs?
Besides the possible savings buying direct form the MFR...


IMHO, I'd either stay all 12V or eventually convert the whole boat to a 24V system IF that's feasible. 24 Volt has several advantages over 12V but of course only you can say if it is reasonable to do the conversion.

[jordanbigel]

Originally Posted by Loredo

Maybe my experience installing a more powerful BT motor can be of some help to the OP.

First of all, I'd question the need for a 15 KW motor.

My boat is taller than yours and probably has a lot more surface exposed to the wind that yours. 10KW is really plenty for it.

This is why I ask if you really need 15KW?

Here: https://www.bestmotor.it/
Any chance they have / do a 12 V motor powerful enough for your needs?
Besides the possible savings buying direct form the MFR...

IMHO, I'd either stay all 12V or eventually convert the whole boat to a 24V system IF that's feasible. 24 Volt has several advantages over 12V but of course only you can say if it is reasonable to do the conversion.

Thanks for your detailed response Loredo!

I will definitely check out quick/best - the manufacturer of my thruster (Wesmar) tells me there is no more powerful 12v motor which can mate with this thruster, which is 21 years old by the way. They may be wrong, so I will definitely investigate this.

However, two things - first, my current bow thruster is 5hp, not 5kw and the other option - offered by the same manufacturer and fits the same tunnel and has the same prop size - is 15hp, not 15kw. A 5hp motor is equivalent to appx. 3.7kw, and a 15hp motor is equivalent appx. to 11.1kw - ie. 1kw more than the 10kw you have had success with. I guess in the US things are done in HP not KW, I had to google the HP to KW calculator to get the HP equivalents. Also, an 8kw (the one you replaced) is appx. 11hp, so your old 8kw was already twice as powerful as my 5hp/3.7kw unit!

Second, I am not sure the comparisons between our two boats is as simple as you say. To start with, from what I found in sailboat data, your boat (ODYSSEY 49) has a displacement of appx. 14 tons whereas my boat (Shannon50) hs a displacement of appx. 19.5 tons (I suspect both boats are 2 tons heavier than the builder weight when gear and supplies are taken into account) - plus the Odyssey has a fin keel/spade rudder while the underwater profile of my boat is much more substantial in terms of water resistance (semi-full keel w/skeg hung barn door). Thus, I think we are in complete agreement as to the question of how big a thruster is needed - and in complete agreement that the 5hp thruster was almost useless it was so underpowered.

I am not prepared to upgrade the entire boat to 24v, my list is too long already.

[caffel]

Amen to:
jt11791 and sailormed

[Loredo]

Sorry, my bad! I should have read with a bit more attention!
HP of course is not exactly the same as KW!



Yet, I've sold the SO 49 and today sit on a Jeanneau 57 ( as I said in my rambling above.) Reading with attention must not be the thing we both are best in!


Note to myself, update my profile with the new boat details!


BTW, speaking about the SO 49, it had a 4KW 12V motor which was more than enough for THAT boat.


I think that the thrust-power needed to contrast the wind force has more to do with what's above the waterline than what's below. Well, kinda, almost... Yes / No?


If it was me, I'd hate to have a mixed 12-24V system on board. Too many headaches, too much stuff that could go wrong. IMHO.

[jordanbigel]

Originally Posted by Dockhead

TO THE OP: Note that the new thruster uses THREE TIMES the power of the old one. It's desirable to support the system voltage with a large alternator whilst using it. And I'm afraid that two G27 batteries are not enough.

I don't actually think there is a cheap way to do this. I would be more inclined to do something like this:

1. Replace thruster alternator with large case 24v school bus alternator, 100 or maybe 150 amps. This will be expensive (biggest headache is the drive system), but you'll get a significant bonus from this -- you can charge house bank from it using a B2B charger, and get a massive increase in alternator charging ability for your house bank.

2. Replace your windlass motor with 24v. This is NOT expensive if you chase down the OEM part. I replaced the motor in my Lewmar Ocean 3 windlass for about €200 when I found the Hungarian maker of the OEM part.

3. Install adequate batteries for the thruster. You don't want too much weight in the bow but if the batteries are inadequate, voltage will sag too much, and you can burn out the thruster motor.

First, thanks very much for your thoughtful reply Dockhead.

WRT the question of the dedicated alternator, I was always of the opinion that supporting the fwd battery with the dedicated alternator was key to keeping the thruster battery powered up during usage. However, other contributors have stated that at the rate the battery can accept amps, the difference between a 30amp charger and a 150amp charger is negligible, and the battery will be depleted almost as fast and probably before the thermal cutout on the thruster kicks in.

I don't know about this - I believe the AGM batteries can accept (in bulk phase) close to the full 150amps the alternator is capable of putting out - wouldn't this at least keep the voltage high which would provide better thruster performance overall? I have to believe there is a difference between a dedicated high output alternator compared to a pair of 30amp chargers...

Second, I agree completely, there is no cheap way to do this. There are certainly cheaper and more expensive ways of doing this... no doubt. I am not looking for the cheapest way, I am looking for the best compromise. Sounds trite I guess. Sorry.

I am leaning in the direction of #1 - replacing my 12v 150amp Balmar small-case alternator with the same deal in 24v - same belt (serpentine), same form factor, should just bolt on (I hope).

WRT to your comment about sufficient bank size - "voltage will sag too much" - you don't think the 150amp alternator will be enough to keep the voltage up during use? This is definitely an important concern. And, you may be right, I may need more than 200ah in the bank - obviously the question is can I fit 3 of them (300ah) and at this point I am not sure.

Replacing the windlass motor with a 24v model might be possible, but I suspect the ancillary wiring (relays, switches) may make this more complicate, PLUS, I just bought a new 12v motor which I have not installed yet (the idea was to install the new motor and keep the old one as a spare) - the current windlass motor works fine, but it is 21 years old and I feel it will die in the next few years if I don't replace it (a hunch).

[Loredo]

I still have the Quick papers laying around.
It seems to me that the most powerful 12V motor Quick has in production for a BT is a 6.5Kw one. Roughly 8.5 Hp 120Kgf where 140 kgf were not enough for the J57.



Model: MOTOR BT 6500W 12V BTQ250+T

Part #: FVEMFEL65122500


Maybe this helps researching options?