Bowthruster Battery & fuse

[Dino]

Hi,
I'm installing a dedicated bowthruster battery in the bow to power the 3kW unit in my boat. I am hearing conflicting opinions about what type of battery to use. I was planning on using a 100-115ah starter battery with high CCA but a few people have mentioned that I should use a leisure battery. Apparently the leisure battery will be happier to be depleted more.
Initially, I will have a dedicated smart charger to charge the battery when it is on shore power but I will add a DC to DC battery charger or a dedicated alternator once I get it set up. My boat is 24V but the thruster is 12V.
Also, is a 250A fuse suitable for a 3kW motor? Vetus use a 250A fuse in their 3kW unit.
Do I need a slow-blow fuse?

 

[jrudge]

Will leave others to reply re the battery.

You need alternator connection from the off - drain is hi and alternators replenish the battery.

Mixing 12 v /24 c has complicated things. Can you not fit a 24v one and then you dont need dedicated alternators and chargers .

Indeed - just run a decent set of cables from front to back. You can probably just connect to the Anchor Winch supply ( others will disagree!)

 

[Dino]

Thanks rjudge,
The bowthruster is currently fed from one of the 12v batteries making up the port engine bank. It causes an imbalance and seems to affect the charging. As a result I have had to regularly jump start the port engine off the starboard bank. One of the port batteries has also been replaced so I am guessing it is not a good solution.
There is a long, but very heavy, cable from the port battery bank to the bowthruster.
I bought a Victron DC to DC battery charger but from talking to the guys in Energy Solutions, it turns out it is not a smart charger so needs to be remotely switched on.
Another option that one supplier suggested was to use the existing system but use a Victron Battery Balancer on the Port battery bank to keep everything in good shape.

 

[[165042]]

24v thruster would make much more sense.

 

[jrudge]

24v thruster would make much more sense.

is it not cheaper to replace the motor with a 24v one and then feed 24v down the line.

Trying to mix high current 12 and 24v is going to cause you endless grief ( as you are finding out!)

If you do that no battery, no additional charger, no dc dc charger .... and it will work better anyways as the current will be half as the volts are double.

Money wise there can be much in it.

You could ( out of my pay grade) get the motor rewound as 24v.

All to me are preferable to the 12v model .

 

[kashurst]

+1 go with a 24V motor, keep it simple. By the time you have spent money on various devices it will be cheaper to just change the motor. If you already have the thruster see if the manufacturers will swap the motor for a 24v.
The nice fat wire you already have should be happy with 24v as the current will be half, so less power loss in the cable = more power at the actual thruster making it nice and responsive.
Yes it is a bad idea to take 12V from the the middle of two 12v batteries in series as you have discovered.
Which type of battery leisure or starter? - I tend to use starter batteries as they are happy with very high currents, and I don't use the thrusters much or for long. (unless I've made a b@lls of backing in and the winds got me).
*Edit not sure a leisure battery would like the very high current surges.

A 250A fuse for a 3Kw 12v motor is right on the limit and will probably blow quite a lot

A 250A fuse for a 3Kw 24v motor would arguably be a bit big but I would be happy with it.

 

[Momac]

I have 3kW bow thruster . It works off a starter battery which is appropriate to deliver high current in short bursts. Since the battery is charged by the engine it doesn't become drained. I think its a 75Ah battery and is coming up to 4 years since fitted.
My thruster is 12Volt but as said if your boat is 24V stick with that.

 

[Dino]

Thanks for all the info. The bowthruster was fitted to the boat when I bought it. Unfortunately, the manufacturers, Cramm in Holland, no longer make or support this model. They sold the rights to AR Peachment but they only used the Hydraulic version and never seen the 12v version. The motor has no plate or makers badge and I doubt it would be easy to replace with a 24v version. I replaced the old solenoid because it was badly corroded.
I have twin engines so I don’t really rely on it. I just felt that it would be a good idea to have it working seeing as it’s there.
Another option is to just have a dedicated battery in the bow that I charge on shore power with a dedicated smart charger. It would be very simple and the boat is usually plugged in when not underway.

 

[[165042]]

It would be simple to remove and fit a second-hand 24v thruster - the hard part is fitting the tunnel which you already have. If you go down this route just make sure the tube diameter is compatible.

 

[Momac]

Is it not possible to have a 12V battery for the existing bow thruster charged from the 24V system via a voltage converter?

 

[Dino]

I already bought one of these https://www.es-store.co.uk/product_...=Victron-Non-Isolated-&cat_id=93&show_menu=26
It can work as a charger but not a smart charger so it will need a remote switch to turn it on when the engine is running.

I'm not in a position to replace the 12V bowthruster with a 24V one at the moment and I'm hoping to launch next week.

 

[Eren]

The most suitable type of batteries for bow thrusters are spiral-cell type batteries like "Optima". They have the highest CCA values, charge back quickly and they are very tolarable in working in line with rather complex setups like yours.