Which battery for windlass/ bow thruster.

[captmikem]

i have 2 group 31 batteries fwd for my thruster and windlass.(small boat, 46' does not need a thruster but the PO put a vetus thruster in her). i also have 4 ought cable coming back to the 2ed alternator with a 100 amp breaker/switch. also have a small 110 V dual battery charger on the two fwd batteries.

This system works very well as there is just a short run from the batteries to the windlass/thruster, I can close the breaker and charge them from the 2ed alternator, or start the main engine or gen set from them, or charge them when the gen set is running or shore power.

I have been very happy with this setup.

M

[Pelagic]

Originally Posted by john61ct

I agree **if** it is practical to run the required heavy wiring to beef up the existing House bank for these consumers rather than using a separate forward bank.

Fewer points of failure, overall simpler design.

But that will be a very fat heavy expensive hunk of copper!

I agree as being able to draw from House/Start/ Emerg. Parallel..... in a grounding emergency is well worth the wiring run if possible.
Not to mention the centralized charging and monitoring simplicity.

Luckily my house system is 24v so cable size was not an issue.

[stormalong]

Originally Posted by john61ct

I agree **if** it is practical to run the required heavy wiring to beef up the existing House bank for these consumers rather than using a separate forward bank.

Fewer points of failure, overall simpler design.

But that will be a very fat heavy expensive hunk of copper!

That fat heavy expensive hunk of copper is:

A one time expense as opposed to replacing that forward battery every few years.

Is lighter than a battery forward.

Is more reliable than a battery charged via an ACR.

Will always have power from the house bank and alternator unlike a forward battery that will become discharged more quickly and take more time to recharge due to the lighter wiring going forward.

And, it is far less complex than the forward battery.

[john61ct]

Yes exactly.

Just wanted those going that better route to be aware.

Sometimes the shock translates to "no way" when in fact it's entirely do-able.

[stormalong]

Originally Posted by john61ct

Yes exactly.

Just wanted those going that better route to be aware.

Sometimes the shock translates to "no way" when in fact it's entirely do-able.

Of course it is do-able. The real question is: What is the best way to do it?

[john61ct]

No, sometimes the boat design and distance involved means the "best" single-bank option is **not** do-able.

In which case the more complex/fragile and (usually) costly multi-bank + DCDC charger solution becomes necessary.

[JOHNMARDALL]

Originally Posted by stormalong

I am sure to open a can of worms with this post but here goes.

Don't do a bow mounted battery bank. Use appropriate heavy wiring back to your house bank. When using your bow thruster or windlass you want as much power coming from your alternator as possible, not the least which is what you are proposing.

The disadvantages of batteries up forward far outweigh the supposed advantage.

Your boat is about the same length as mine. With the anchor, chain, windlass and bow thruster forward you already have a lot of weight concentrated there.

The bow is the place with the most motion in your boat. Any batteries forward will need to be very solidly secured.

The moment you engage the windlass or thruster the heavy load will cause a voltage drop. With an ACR you will be disconnected from the best power source you have - your alternator.

Best solution to your power needs is heavy wiring back to your house bank which is fed from a large alternator. You can use large wire from an electrical supplier rather than paying the marine premium. The cable is stiff and hard to bend but you only have to do it once. The conductors are heavy gauge and with good crimped terminals and heat shrink sealed ends water intrusion is not an issue. I did this on my boat in 1991 and it is still good.

I understand what you're getting at Storm, but even a large alternator can't come close to meeting the power needs of a thruster. Our 12 volt models range from 200 amps to 800 amps. In addition, properly sized power cables running from the engine room to the bow will cost more than a battery for the smallest thruster and more than the thruster for the largest thruster. A thruster pulls so much current that we recommend a dedicated battery, close to the thruster and not pulling down the house bank.



No offense intended
John Mardall
Vetus Maxwell Boat Equipment

[stormalong]

Originally Posted by JOHNMARDALL

I understand what you're getting at Storm, but even a large alternator can't come close to meeting the power needs of a thruster. Our 12 volt models range from 200 amps to 800 amps. In addition, properly sized power cables running from the engine room to the bow will cost more than a battery for the smallest thruster and more than the thruster for the largest thruster. A thruster pulls so much current that we recommend a dedicated battery, close to the thruster and not pulling down the house bank.



No offense intended
John Mardall
Vetus Maxwell Boat Equipment

No offense taken. That is my opinion and I am sticking to it.

The op did not state the size of the thruster load. It is a 43 ft sailboat so I would expect it to be small. The OP did say a 105 A.H. battery so it can't be that big of a load.

[Oceansailor]

Originally Posted by stormalong

No offense taken. That is my opinion and I am sticking to it.

The op did not state the size of the thruster load. It is a 43 ft sailboat so I would expect it to be small. The OP did say a 105 A.H. battery so it can't be that big of a load.

Well I do agree 100% with Stormalong. I did a test on my own boat. 44 feet.
Originally the boat was wired to run the bow thruster from the house batteries in the aft.

I installed a bow thruster battery 5 feet from the bowthruster. It did improve bowthruster perfomance marginally as the there was less voltage drop which means it spinns faster. But it was only marginally. I will not replace the bowthruster battery when it is time for replacement.

[Pelagic]

For larger boats with large bow thrusters and longer runs odds are they already have a generator.
So maybe they should consider an AC powered Thruster

[bobmcd625]

I am jumping into this discussion since I am about to install a Lewmar H3 windlass (1000w) in my DownEaster 38 and am debating the question of "dedicated battery" vs. long run of heavy cables. My round trip will be about 100 ft and Lewmar recommend 1 AWG wire for that length. Sure the cable is expensive, but the installation is simpler. If I were to choose a dedicated battery how big should it be and how big should the charging wires be? I once did a rough cost comparison and it seemed like a push, but I'd like more expert advice. Thanks in advance.

[john61ct]

Wire is one time and simpler.

Adding a remote batt becomes an ongoing consumable and more complex, fragile.