12v Boat with 24v bow thruster

[jordanbigel]

The only thing I remain unhappy about with the 24v conversion plan is that I lose the ability to combine my house bank (12v) with the thruster bank (24v), thus allowing my secondary alternator to charge the house bank in case the primary alternator fails. I will have to literally remove the combiner switch (to avoid blowing up my batteries by mistake).

Which leaves me wondering, is there a way to compensate for this loss and still be able to charge the house bank from the secondary alternator in an emergency?

I believe there are a bunch of options for this out there, like this Victron (https://www.solar-electric.com/victr...c-charger.html) - I could wire this between the thruster bank and the house bank, and even though it is only 30amps, it should be enough to keep the house bank alive. Maybe I can find a slightly bigger one, that would be great, but 30a would do in a pinch.

I would wire this with a switch at the nav station to enable/disable this charger only when needed (I am assuming this is possible with a device like this - I was thinking like a field wire on a voltage regulator, but maybe the only way is to break the circuit, in which case I may be able to re-use my battery combiner switch as a charger cutoff switch).

Is this feasible? Is there a better device made for doing this?

Thanks again to everyone who has been so helpful on this thread - I knew I would get some good feedback from the forum but I have been pleasantly surprised at how helpful this has been for me (usually I just muddle through and figure **** out on my own - it's worked for 20 years, but this is faster!).

[sailingharry]

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?

That's an easy problem. Wire the windlass to one battery. It does run a long time, but the current isn't all that high, a single battery can support.


When the switch is in 24-mode, you only have one battery for the windlass. When the switch is in 12-mode, you have both batteries for the windlass, and since they are paralled the "other" battery will equalize with the windlass mode, and the charger will bring both to 100% together. Set-and-forget!

[Cadence]

Originally Posted by sailormed

If you have 2 12V batteries in parallel for your house bank you can obtain temporary 24V for use with the bow thruster when needed.
I installed this myself a couple of years ago.
Before using the thruster I flip a switch to get 24V, then use the thruster normally, after use switch back to 12V. I have buzzer to remind me of this.
Yo need a 12/24V series/parallel relay commonly used for starting with 24V by heavy trucks.
PM me if you need more details.

Edit: the post of jt11791 just shows up, he covers the details already.

Out of curiosity, what did the DPDT contactor cost and what was the amperage rating. That may help the OP.

[Dockhead]

Originally Posted by jordanbigel

All good points!



For me (WRT the series/paralell switch) another issue is I try to avoid things I don't understand well and it seems like there are a lot of different switches out there, some of which may allow 12v and 24v simultaneous operation, but I am not qualified to judge and not confident that I can learn enough to make this a sure thing, and I don't like taking risks with electricity, or money. (see below for discussion about finding a local electrical expert).



However, the cost of the motor is a bit higher than what your lewmar windlass motor cost - the 12v windlass motor I bought last year (which I've never installed) cost me US$468 - I just checked, they have a 24v version for the same price (https://www.hodgesmarine.com/maxp120...le-flange.html). I doubt they would take the 12v in exchange since I bought it over a year ago (maybe 18 months) - my plan was to keep using the old one until right before we leave for S. Pac next year. But if they won't take it back, I can surely sell it online (at a loss of course).



I guess if I do this, and it comes down to either pulling 12v from one of the batteries in the bank vs installing a 24v->12v converter for the windlass vs replacing the motor I think the new 24v motor is the obvious choice., though not the cheapest. Pulling 12v from one of the two batteries sounds simplest, but I am still not clear on the ramifications of uneven discharge, so I would prefer to just avoid that issue (either with the 24v motor or the DC-DC converter).



I did find a 24v to 12v converter which can handle up to 150amps (the windlass motor is 1200watts) - but the cost of the converter is appx. $568, so replacing the motor is a no brainer at this point. Of course, then I will want to buy a second motor to keep as a spare (who doesn't love spares when cruising remote areas?).



WRT batteries, my original idea was to replace the single 4D with a pair of 110ah batteries (group 27 or 31) - but I have been convinced that this will not be enough juice, the suggestion was made to use 4 G27 (or G31s) - but if that is the case, it will be far easier for me to just add a second 4D under the forepeak bunk) which would then give me 200ah @ 24v. I definitely have the room for it, I checked last night.



I love the idea of the serial/parellel switch, but as much as I see the appeal, as described by the guy with the Hylas54 said (sorry, cant recall the name) his has worked for 10+ years - but it was wired by Hylas, who presumably know what they are doing! If I knew exactly which switch he was using, and had a diagram of exactly how it was wired, I could copy it easily - I'm good at wiring stuff, just not an expert at designing electrical systems - so I am tending to shy away from that idea due to the complexity, risk involved, etc. If I knew a reliable boat electrician I might try to get some help, but the odds of finding one who knows what he is doing AND has installed one of these switches before (to handle a scenario like this) seems unlikely. San Diego is a great boating town, but unless you own a superyacht, tradesmen like this either won't even talk to boaters like me, or never show up when they say they will (repeatedly).



I like the plan currently in the lead (in my brain its in the lead) because I can understand it and am confident I can do it myself. So, basically, 1) 2nd 4D battery to make 200ah @ 24v bank, 2) 24v alternator to replace my current 12v alternator, 3) 24v windlass motor. Simple. And I believe no new wiring will be required with this plan. Definitely not cheap though.



Plus, if I am not mistaken, the 24v windlass motor will also have the advantage over the 12v windlass motor in terms of longevity (my understanding is that in general 24v motors last longer and run cooler).

Well, a couple of ideas for you:

1. Look for OEM for your windlass motor. Google whatever part number you see stamped on the motor - that's how I found mine, which turned out to be a Mahle part.

2. Look into having the motor rewound for 24v. This is a pretty simple process, could be cheap.

3. Worse than 1 and 2, but better than tapping just one batt - use a 24-12 convertor. This is better than you might think because a dropper will lift the voltage - it can use the higher input voltage to get rid of most voltage sag. I think this is much preferable to tapping one batt or using a series parallel switch, and shouldn't be expensive.

4. Or just bite the bullet and buy the motor you found. Even at $500 it's not going to be much if any more expensive than extensive rewiring.

I like your plan with two 4D's

[Wotname]

Originally Posted by jordanbigel

..........

Which leaves me wondering, is there a way to compensate for this loss and still be able to charge the house bank from the secondary alternator in an emergency?

I believe there are a bunch of options for this out there, like this Victron (https://www.solar-electric.com/victr...c-charger.html) - I could wire this between the thruster bank and the house bank, and even though it is only 30amps, it should be enough to keep the house bank alive. Maybe I can find a slightly bigger one, that would be great, but 30a would do in a pinch.

I would wire this with a switch at the nav station to enable/disable this charger only when needed (I am assuming this is possible with a device like this - I was thinking like a field wire on a voltage regulator, but maybe the only way is to break the circuit, in which case I may be able to re-use my battery combiner switch as a charger cutoff switch).

Is this feasible? .........

Yes, the Victron DC/DC charger does have hard wired remote on/off features built in, several of them in fact.

It also has software controlled shutdown options so that it can be user programmed to operate only when (say) the second alternator is running or (say) when the thruster bank is fully charged. Thus the shutdown becomes automatic and does not need any external wiring/switches.

[jt11791]

Originally Posted by Dockhead

That depends on the cost of the switch plus wiring vs. the cost of a 24v windlass motor. The motor for my 24v Lewmar Ocean 3 cost less than €200.


How much does a series-parallel switch rated for say 500 amps continuous cost? A cheap one for starter motors won't do.



The Vetus series-parallel switch costs £886, nearly a thousand euros. https://www.vetus-shop.com/vetus-ser...-vo-p-941.html And this won't do -- it's only 100 amps continuous and the parallel is only for charging the thruster bank.

You think nothing of finding the OEM for a motor, do you think Vetus made that switch? (no, they did not) Do you think they marked it up less than 300%? I can find all kinds of other expensive switches that won't work, but what does that mean?


Even if you find a suitable switch, then you've still got a bunch of extra wiring to do, including extra battery cabling. That alone can cost €200.



A few wires are not a big deal to most of us. OP is already adding a new battery and will need a few cables for that. I won't pull a cost out of my butt like you did, but I don't see it being that high.


All that expense, trouble, and extra complexity just to avoid buying a €200 windlass motor? Really?


And the cost of a 24V alternator, let's not forget. I don't see adding one switch as the massive extra complexity that you do and I can charge all of the batteries on my boat with either of my 12V alternators, an advantage in my humble opinion.


And it's another point of failure; probably you'd want a spare on hand.


I do have a spare switch on board. It's been here, unneeded, for 20 years. What happens when the 24V alternator fails? Better carry a spare!

I don't think an all 24V system is a bad way to go, it's just not the only way to go.

12345

[boatpoker]

Originally Posted by jt11791

12345

Yup, nice to see a little sanity.

My system is ...
two G31 wet cells ($120ea)
one relay (9.00)
20' of red 10AWG (had it lyin around)
20' of black 10AWG (had it lyin around)
10' of red 6AWG battery cable ($20)
10' of black 6AWG battery cable ($20)
some terminals (had them lyin' around)
one series/parallel switch from local farm supply dealer ($200).

Entire system installed in one day and working perfectly for years.
(not including the 2 days to install the tube.)

All connected to the existing 12v charger and alternator.

Why did I buy a 24v thruster ?
I met a dealer who was going out of business and he sold me his boat show display unit (I had to take the entire display stand including the clear acrylic tube it was mounted in) for half of what I could buy a new 12v unit.

[sailormed]

JT11791 I admire your stamina for continuing this conversation. We both have found a simple solution to the installation of a powerfull bow thruster that is reliable.

As for one of the posters that had a remark on the buzzer I installed:
The series// switch needs a high current to latch.
This current is not necessary to maintain the latch position of the relay.

If the relay is energized to long the windings become to hot and isolation will start to burn or melt.
These S// relays are designed for use in lorries for starting big engines, so the relay is only used for a short time. For a bowthruster time is longer and it is always possible to forget a simple switch position.

There is an electronic solution for diminishing the latch current once the relay is activated, but it is horribly expensive and an unnecessarily complication.
I installed a simple buzzer that sounds when I activate the 24V circuit.
The noise reminds me that I need to deactivate the 24V circuit after 1 or 2 minutes.

Once installed I found out that the buzzer has the frequency and sound of a lorry backing up. On occasion I get question from slips next to me as I have to do med mooring 100% of the time and reverse into my berth with a lorry blaring buzzer. Just a bit of fun

EDIT: yes I carry a spare 12/24V relay as well. Never needed so far :-)

[Carlisle Spirit]

I would suggest rethinking the 24 V thruster

I have a Vetus 12 v thruster on a 58’ sailboat which has plenty of grunt

[Bill_Giles]

For simplicity I would stick to 12V. We have a new Sidepower thruster which seems very well made and has low maintenance.

[drcot3]

Just a thought why not buy a 24 DC volt mains charger run it off an inverter at 110/240 60/50 Hz Then using either house/starter battery banks which are charged via 12 DC volt alternator as you motor or via mains dockside. Simple is best I think.

[nofacey]

Struggling to see why batteries can’t be tied together to allow 24v alternator to back up 12v in a pinch.
- feed two 12v batteries in series off a 24v bus alternator. This one is 24v 125amp, 12v excited, so existing ignition wiring will still work
https://www.amazon.com/ALTERNATOR-TH..._t2_B00A2VITDC

- pull off batteries in series to feed 24v to thruster
- tap off one battery to feed windlass, or via battery switch to house bank as emergency back up. Yes, the battery draw is unbalanced, but it’s very intermittent.

Seems like a reasonably simple way to give you the higher output side thruster.

[aqfishing]

Not sure what the power usage of your thruster is, but could you not just add a 12-24v converter between your battery and your thruster?

https://dcpoweronboard.com/12-to-24v...up-converters/

I am guessing the don’t make them strong enough??

Just asking!

[Thebaysailor]

I once had a 1955 Ford F100 truck that was 6 volts. I installed a 1966 Ford 289 V-8 engine that was 12 volts. To fix my voltage problem I installed a 6 to 12 starter solenoid and all was fine.
You could install a second 12 volt battery in parallel with the present battery and use this ........ https://www.amazon.ca/Current-Starte.../dp/B071Y4JVKC ..........
Series/Parallel solenoid to manage 24 volts to the thruster.
No changes to alternator or windlass.

Cheers.

[piloto]

Originally Posted by aqfishing

Not sure what the power usage of your thruster is, but could you not just add a 12-24v converter between your battery and your thruster?

https://dcpoweronboard.com/12-to-24v...up-converters/

I am guessing the don’t make them strong enough??

Just asking!

For awhile I thought I wasn’t going to see this suggestion. I have a step up transformer (or step down) from a company named Vanner that has a current capability of 20A on the 12V side. I’m thinking there must be a variety of capacities of these devices around.