Bowthruster Battery Charger

Dino

Dino

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My 12v bowthruster is fed off one of the batteries in my 24v engine battery bank. This is not a good set up. The cable feeding it is very long and it is not good to take a high load 12v feed off a 24v bank. Well that's what I've been told.
I'm thinking of putting a sealed battery charger up front and the only charging mechanism will be through a dedicated 220v ac Victron battery 12v charger. The boat is usually plugged into shore power and the only issue might arise is when I go cruising for a week or two and end up away from shore power for 4 or 5 days. This is fairly rare.
Will this work okay or am I likely to deplete the dedicated 100ah battery too much?
 
I am just about to install a bow battery for my thruster. Mine will be charged via a MOSFET split charge controller that has outputs for start, domestic and thruster banks which is easier for me as everything is 12v. I don't think a dedicated 240v charger is really the right solution. I would look at a battery to battery charger such as those offered by Sterling. I haven't looked into them but I'm sure someone must do a 24v to 12v charger.
 
But your engines are running are they not ?,mine are when the BT is operated .

What perceived problem are you trying to mitigate .
Presume there's a pair of correctly specced alternators attached to the engine packages .
 
Portofino said:
What perceived problem are you trying to mitigate .
Presume there's a pair of correctly specced alternators attached to the engine packages .
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I suspect the concern is that he is depleting one 12v battery in a 24v bank and as such there will be an unequal charge resulting.
 
dherraghty said:
The cable feeding it is very long and it is not good to take a high load 12v feed off a 24v bank.
Well that's what I've been told.
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What you've been told is somewhat wrong.
I mean, yes, it's never a good idea to feed high load 12V equipment with long cables, regardless of whether the 12V are taken from a 12V bank or from a 24V bank - though the latter is worse, but only for the batteries, not for the thruster or cables as such.
But assuming to have properly sized cables (and up to a certain boat size, say 60' or so) that's the most common solution, mostly because it's simpler than anything else.
What is AWFULLY wrong is using a 12V thruster in a 24V boat - was it possibly installed/replaced after the boat was built?
I don't think that any builder with a pinch of salt would cut such a huge corner, also because during build the cost difference between a 12V and a 24v thruster is negligible (if any).

That said, the solution you envisage could work, but replacing the thruster with a 24V motor would be my preferred choice, in principle.
Btw, if the cables were sized correctly for 12V, using them for 24V would make their life much easier, reducing the risk of overheating and the power loss at the thruster end.
 
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Yes, that's the issue. I have read a lot about this online. Apparently it is a very bad practice to take a 12v feed off a 24v bank. It can damage one or both of the batteries in the bank. On my boat, the 12v battery feeding the bowthruster does not match the other batteries in the two engine banks. So I'm guessing it has killed a battery already.
I've looked into a battery to battery charger but they are big money when you also need to step down.
I'm also considering adding an inverter so I could use it to top up the bowthruster battery in emergencies.
 
I agree Mapism, but the bowthruster was fitted years ago by someone else. I only bought the boat earlier this year. I'm guessing a new motor would be big money. The thruster is made by Cramm and they no longer make this model. AR Peachment have taken over the parts and rights to sell it but they only seem to offer a hydraulic unit.
 
Mmm... Too bad, I'm afraid that in this case you should replace the whole thing... :ambivalence:
Still, your solution (even if surely much less expensive) implies some parts and labour anyway.
Before going that way, I'd rather look around also for 24V thrusters, anyhow.
It might be worth biting the bullet...
All the best for your project anyway, whatever route you'll choose! :encouragement:

PS: on 2nd thought, I believe that most if not all thruster builders actually use electric motors sourced by some other suppliers.
Maybe you can try to find out who built yours, and get in touch with them.
If they are still producing the thing, chances are that they are making both a 12 and a 24V version...
 
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In your shoes I would do the same, use the current cables from your 24 volt bank to supply dedicated 12v charge up to a battery next to the thruster.

Re needing to top up the thruster battery in an emergency.... It's only the bow thruster. Yes nice to have but hardly the end of the world. Also unlikely you'll manage to use it so much as to run it down over a week?
 
Keith-i said:
I suspect the concern is that he is depleting one 12v battery in a 24v bank and as such there will be an unequal charge resulting.
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Yup that what I thought ,just wanted to here it from the OP

" Perception " well perceived was a well choosen word by me --cos one can,t be absolutely sure of any of this .
It all depends how the batts are connected ---if robbing 12 from a 24 v bank is gonna do any harm ,it may not ? It all depends how they are connected .We don,t know !
Remember the bank is not just giving power to the truster on its own ,it's giving 24 v to the engine electrics (assume running -why would you operate the truster sans engines ?) AND recieving 26 -28 V from the alternator(s) .
What I,am saying here its not just a static dead bank with one the designated "12" only seeing action giving Volts out .

So I don,y buy into the theory that this "12 " with 12 v being taken out --with engines running is necessarily being damaged prematurely .

How old are they ?

Agree with MapishM and others ideally source a 24 v motor --- and bolt on .
Might be worth checking the windlass motor too ---again 24 v ideally ? .Cos if that's 12v sourced similarly you are chasing shadows .

It the thuster any good ,cos if it's crap the next lift out up specc it rarther than fork out for a sep bat ( big one too ) new wires ,new charger ,dedicated etc ,
If its not crap it's a £ 200-300 motor that need s changing .------ If poss ??
 
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KevB said:
In your shoes I would do the same, use the current cables from your 24 volt bank to supply dedicated 12v charge up to a battery next to the thruster.

Re needing to top up the thruster battery in an emergency.... It's only the bow thruster. Yes nice to have but hardly the end of the world. Also unlikely you'll manage to use it so much as to run it down over a week?
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+100%
 
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