Adding Bow Thruster and Windlass . . . What to Do with Batteries

[geoffr]

Hi,

I am in the process of figuring out what I need in order to add an anchor windlass and perhaps a bow thruster to our boat.

I am wondering should I be adding a new battery bank for both (or one of them)? Or should I simply hook it up to our current house bank.

I don't like the idea of the extra weight of the batteries at the bow...

This is on a 37' catamaran (with a single engine, hence the thruster)
Current house bank is 6 T105s (675 Ahr)
One starting battery which charges off the house bank
Balmer Alternator (100Amp I think).

What are people thoughts/advice here?

Geoff.

[AnchorageGuy]

Geoff, it depends. Understanding that weight is an important factor for a catamaran, I understand your reluctance. The question becomes, with the combined potential of bow thrusters and windlass, how big are the cables going to need to be to the house bank? You will probably never operate both at the same time but there is the potential so you should size the cables accordingly and keep in mind that sizing for DC wiring is factored round trip and not just the distance to the batteries. With that information you can move forward. Chuck

[rwidman]

Originally Posted by geoffr

Hi,

I am in the process of figuring out what I need in order to add an anchor windlass and perhaps a bow thruster to our boat.

I am wondering should I be adding a new battery bank for both (or one of them)? Or should I simply hook it up to our current house bank.

I don't like the idea of the extra weight of the batteries at the bow...

This is on a 37' catamaran (with a single engine, hence the thruster)
Current house bank is 6 T105s (675 Ahr)
One starting battery which charges off the house bank
Balmer Alternator (100Amp I think).

What are people thoughts/advice here?

Geoff.

My boat has the thruster and windlass powered from the house bank and this has caused no problems for me. You will need to run some heavy cables to each and install appropriate circuit protection.

Each of these will put heavy draw on the batteries but the load will be for a very short period.

Your engine will normally be running while using either so the alternator will be supplying part of the current.

[motion30]

My thruster uses the house bank with no issues the actual use time is very small

[djmarchand]

Geoff:

A catamaran has two problems in dealing with a bowthruster: a lot of windage and a pivot point further forward than most boats. So looking at the Sidepower lineup I would choose one a bit larger, say their 4.4 KW model. This much wattage is going to draw a lot of current, about 400 amps with a 12 V supply. You are going to need to install it with big cables, at least 2/0 and probably bigger. To stay within the ampacity spec you need to go with 4/0.

Even buying from best boat wire at $7.74/ft for 4/0 it will cost a bunch. But you can put a big battery forward, say a Grp 31 and wire it with much smaller wire. See www.yandina.com and click on the project button at the bottom for info on how to wire and protect this circuit. Since you are using the house battery, you don't need the combiner to protect it from discharge.

But wire the remote battery to the house bank with 10 guage and put a 60 amp fuse on both ends as shown on the Yandina drawing.

David

[matauwhi]

I have both the bow thruster and windlass wired to the starting battery. I normally have the engine running when I use either of these. Having the engine running will give you the advantage of having the alternator working raising the voltage of the system above 14+ (if your battery is fairly charged) delivering more power to do the job desired. As mentioned above, use the largest cable size (despite the cost) your space will allow to minimize the voltage drop between the battery and the BT & windlass. You won't regret it if you ever have to anchor in 75+ of water or docking with a 10 to 15 knot crosswind. Cheers

[CharlieJ]

Have you considered using 24 volt equipment for these heavy, remote loads? Reduces the cable size significantly.

SidePower makes a 24 volt bow thruster with a very slick contactor box that places one battery in series with the rest of the bank when 24 volts is required. The remainder of the time that battery is in parallel with the rest of the house bank.

Just a thought.

Charlie

[FlyWright]

I wholeheartedly agree with matauwhi. Your engine will be running when operating either of these accessories, neither will be operated at the same time and you gain the advantage of having the alternator online during operation for increased voltage and battery recovery. If you run your house bank low after an extended anchorage, you want to have full use of the windlass when departing.

[foggysail]

Originally Posted by CharlieJ

Have you considered using 24 volt equipment for these heavy, remote loads? Reduces the cable size significantly.

SidePower makes a 24 volt bow thruster with a very slick contactor box that places one battery in series with the rest of the bank when 24 volts is required. The remainder of the time that battery is in parallel with the rest of the house bank.

Just a thought.

Charlie

YEAH!!! YEAH!!! RIGHT ON!!!

Charlie has it correct!!! When one starts/attempts to pull 4-500 amperes from a battery bank things happen that will make your mind wonder. Consider for example the simple act of getting good connections, internal battery resistances and they are a function of temperature, fuses AND YOU SHOULD USE FUSES, voltage drops just from DC resistance.

I could go on but a smart person will consider voltages higher than 12. Heck, good battery chargers and inverters are now priced reasonable. ONe could share the thruster bank with things such as a windlass and an inverter for TV or whatever.----Just my thoughts

[geoffr]

Thanks for the comments.
I think I'll be using the house bank to run the thruster and windlass.

Now the question is 24V or 12V. I like the idea of 24V for both as it reduces the cable size from the house back to the truster (30' or so). I don't like the idea of adding a battery to the house bank to get 24V (as shown by yandina). Is anyone aware of a step-up converter that is marine certified that can supply the required current?

Geoff.

[Mule]

Considering the advantages of 110 over 12/24 DC how come there are not any 110volt ac bow thrusters out there? My 2.5kw inverter would handle this with ease with no batteries up front or a conducting wire(s) the size of my big toe.

?????

[foggysail]

Originally Posted by Mule

Considering the advantages of 110 over 12/24 DC how come there are not any 110volt ac bow thrusters out there? My 2.5kw inverter would handle this with ease with no batteries up front or a conducting wire(s) the size of my big toe.

?????

Mule--

I have a davit crane operating on 110vac, huge Maxwell windlass on 24vdc and an inverter operating on 24vdc.

No thruster......was going to install one until I learned how versatile twin 454's are when docking time comes.

Windlass-- I looked and looked! At the time I installed mine, there was nothing operating on 110vac which I could easily provide from my Kohler 7.5KW generator.

The 24 volts auxillary system I use is just great. I use it for the windlass and the house inverter for 110vac.

Getting back to your using a 2.5KW inverter for a thruster, forget about it! It would be inadequate! Another thing, even if you could get an inverter with a high enough rating, you would suffer from the efficiencies of operating on 12vdc, 24 vdc would be better but still a power loss pig. Thruster need at least 4- 500 amperes at 12 vdc so your up around 6KW without accounting for the efficiency losses.

[rwidman]

Originally Posted by Mule

Considering the advantages of 110 over 12/24 DC how come there are not any 110volt ac bow thrusters out there? My 2.5kw inverter would handle this with ease with no batteries up front or a conducting wire(s) the size of my big toe.

?????

One could make the argument that boats should come with a native 24 volt electrical system, not 12 volts. Batteries, alternator, everything. Or even 36 or 48 volts. This would reduce wire and cable sizes and voltage drop. Remember when cars had six volt systems?

But as for a 120 volt AC bow thruster, not all boats have inverters and of those that do, not all would handle the load of a bow thruster. I keep mine off when not in uses so I would have to go down to the electrical panel to turn it on, then back to the flybridge to use it. Not convenient.

Also, a problem with the inverter would mean no bow thruster. It's far simpler just to run it directly from the boat's electrical system.

The larger thrusters are hydraulic. I'm assuming that draws less electrical power for a given performance level.

[foggysail]

Sure-- I agree with you, the way to get 120vac at high power is not via the inverter route even if the inverter used SCRs instead for transistors of various materials. ONe still needs to provide the huge currents from a battery source.

When I was doing my search for a 120vac windlass, I hoped to use my Kohler 4 cylinder, 7.5killowatt generator to power it.

Remember the old 6 volt stuff??? Some auto manufacturers actually used higher voltage systems way back in time. But back then, wiring insulation was a form of rubber which degraded over time. Hence, the lower 6 volt systems became popular. I have heard rumors that higher voltage systems are being considered by the auto industry but again, only rumors. They could go as high as 48vdc and be considered safe; the telephone industry uses 48vdc for much of their equipment.

[meridian@]

Regarding batteries forward for windlass and or thruster ... I remember reading on a forum years ago about someone who did that. The details are hazy, but somehow the batteries flattened and were connected to the house or charging system with light weight cables. The huge current burnt out the cables and then the boat to the waterline.

meridian@
Borneo