Ideal electrical system for 45' boat?

[pmagowan]

What would you think is the ideal electrical system in a 45' sailing boat? 12V vs 24V vs 240V, lithium ion vs AGM vs lead acid etc? Assume standard good equipment such as electric windlass, winches, fridge, eberspacher, bow thruster etc.

Is it easier to stick with 12v everywhere and simply size wires appropriately? Would you avoid long wire runs by having a battery bank forward as well as aft (obviously with charging complications)? Why do so many modern boats have loads of halogen spots instead of LEDs?

If you were starting from scratch and 'doing it right' what would you do?

 

[savageseadog]

24V is better because currents are halved and voltage drops are halved. Given that you have twice the voltage to begin with there is a x4 benefit. The advantages of 12V are obvious. It's a difficult choice. You could make the decision easier by having a separate 12V system possibly using a dropper from the 24V and use 24V for higher power stuff. I would go LED lighting for everything.

 

[superheat6k]

For 45' most of the heavy electrics will concentrated around the engine Bay Area. Only a Bowthruster and Windlass will require any substantial wiring away from the main battery stowage. The vast majority of common kit will be 12volts, and converting from 24 to 12 is not that straightforward.

My boat works very well on 12 v at 40', and the extra bit is always in the middle so in reality at most another 5' from the power pack to the less used windlass / thruster, and these two will never likely be used together, so a common heavy supply run will work for both. Or the option of a forward battery to reduce copper sizes.

Preference for me definitely 12 volts.

The base design Fairline came up with for my boat about 30 years ago I believe is excellent, sharing the twin engine power resources sensibly to give a balanced load distribution. PM me if you would like to see the distribution diagrams I have drawn up from the original rather difficult to read wiring diagram.

 

[pmagowan]

24V is better because currents are halved and voltage drops are halved. Given that you have twice the voltage to begin with there is a x4 benefit. The advantages of 12V are obvious. It's a difficult choice. You could make the decision easier by having a separate 12V system possibly using a dropper from the 24V and use 24V for higher power stuff. I would go LED lighting for everything.

But if you put in chunky wires is there really any benefit to 24v other than for powering things that are very hungry (which can be minimised to ?nothing). I agree LEDs are a given I would have thought, I don't know why they seem so rare. Do you think there is a potential risk with multiple voltage systems running in parallel? Then there is 240V, is it only really required for the fairer sex and their grooming products??

 

[prv]

Our battery bank on Ariam is in the middle. This is good for at least two reasons - 1) the wiring runs can be shorter, and 2) the weight is directly over the middle of the keel.

I would keep things simple by sticking to 12v for the DC system, though I can see the appeal of 24v for windlasses etc.

Lights should all be LED, obviously - ones which produce nice light are available, they don't have to be cold and clinical.

I would go for AGM batteries for simplicity and safety, though again I can see the good points of flooded lead-acid. I don't think lithium is there yet.

A lot of what makes a quality electrical system rather than a mess-that-works is the techniques and small parts used to install it. Things like shrink-on labels, ring terminals onto barrier strips, the anchors and ties used to hold cables in place, etc. Routing cables neatly and cutting them exactly to length makes a big difference aesthetically.

Use tinned cable throughout. You're building the boat from scratch, so you might as well do it right.

Decide whether you're going to run everything through a traditional panel where every circuit first goes through a visible breaker/fuse and switch, or use a more distributed approach. I have two fuseboxes, both inside closed (but accessible) spaces, and one panel which has switches for only a subset of the circuits.

Consider whether some switches would be better in the cockpit. It's not the 1950s any more and reliable waterproof fittings are available. I have the nav light control (a rotary dial to select the various legal light combinations), the deck lights, the deck sockets, and the safety isolator for the windlass all controlled from a panel under the sprayhood.

Speaking of deck lights, you can get some great high-brightness LED strips intended for aftermarket daytime running lights on cars. These are way better than the old living-room lampshades dangled under the spreaders - they're millimetres thick and unnoticeable most of the time, but they light up the whole deck brightly from stem to stern.

Pete

 

[NickTrevethan]

What would you think is the ideal electrical system in a 45' sailing boat? 12V vs 24V vs 240V, lithium ion vs AGM vs lead acid etc? Assume standard good equipment such as electric windlass, winches, fridge, eberspacher, bow thruster etc.

Is it easier to stick with 12v everywhere and simply size wires appropriately? Would you avoid long wire runs by having a battery bank forward as well as aft (obviously with charging complications)? Why do so many modern boats have loads of halogen spots instead of LEDs?

If you were starting from scratch and 'doing it right' what would you do?

What do you want to do with the boat? Long term cruising?

The problem with a 12v you need bigger cabling, but you can get bits anywhere. With a 12/24 system you need battery banks, two alternators, two chargers etc, and your spares list doubles. If you only potter not such a big deal. You sail round the world and want to find a 24volt component for a lithium ion system in Tonga and you.ll struggle.

Save power with led lighting.

Lithium ion batteries? No, too expensive and need a very specific charging regime

AGm or ordinary lead acid still offer most bang for buck, and weight on a sailboat not an issue if you locate them properly. For a cruising boat keep it simple.

 

[jac]

Simplicity (at least for the core of the system) would be key for me.

So 12v, lead acid, centrally mounted.

Led would be a definite. Not sure about the idea of switch panel on deck but can see the benefits.
Lots of charging and via different sources, so big alternator, solar panels, wind gens to cover all eventualities.

 

[RobWheatley]

This could be interesting for the future maybe, would not have to run the engine for hours to charge the domestic pack up either.
https://www.youtube.com/watch?v=GPJao1xLe7w

 

[Tranona]

What would you think is the ideal electrical system in a 45' sailing boat? 12V vs 24V vs 240V, lithium ion vs AGM vs lead acid etc? Assume standard good equipment such as electric windlass, winches, fridge, eberspacher, bow thruster etc.

Is it easier to stick with 12v everywhere and simply size wires appropriately? Would you avoid long wire runs by having a battery bank forward as well as aft (obviously with charging complications)? Why do so many modern boats have loads of halogen spots instead of LEDs?

If you were starting from scratch and 'doing it right' what would you do?

12v as the range of equipment available is bigger. Your choice of power storage and charging will depend on how you are going to use the boat and what your typical consumption will be. There is more than enough material around arguing the pros and cons of different arrangements for you to make up your own mind which is the most suitable for your particular application. The fact that there is so much choice is just a reflection of differing requirements.

Halogen lights have been the norm because they are cheap and simple, and for most weekend sailors are perfectly adequate. LEDs become sensible if you are speccing the boat with high consumption and limited capacity when part of your objective will be reducing consumption, so LEDs, super insulated fridges, low consumption electronics assume a greater importance.

 

[ip485]

Mine is 54 feet and all 12V. Absolutely fine and happy not to have the additional cost of 24v with few apparent advantages.

I agree with the comments regarding batteries.

If you are going to be "off grid" for any length of time having a back up is vital and the place to spend your pennies. I have given this much thought. I have a 8KW Genset which is great but was surprised to find Gensets are quite noisy (at least running for a length of time), can prove unreliable and are hopeless at charging batteries. If you think about it any battery bank depleted to say 50% requires a long charge period to restore at relatively low power draw, a disastrous way to use a Genset.

For me by far and away the best answer was a really good solar array. Panels have come a huge way and it is really worth the investment in an arch (really the only practical and neat way of providing the space needed) with 600 to 800 watts of panels with a good MCCP controller. I have been really pleasantly surprised that I can produce all the power I need to run totally off grid without resorting to the Genset in an English summer and with some power hungry equipment including a fridge and freezer.

 

[pmagowan]

Wow, some interesting comments. Thanks for the offer Superheat but I wouldn't want to cause you hassle when I am at such an early stage in the thought process.

I like the KISS approach you all seem to be going for. 12V seems to be the ideal all round. This is what I was hoping anyway as this is what I am used to. I did a total rewire on my current boat with the help of this forum but it is only 28' and very basic. I used only top quality tinned wire from Merlin and I used proper glue/crimp terminals with glue heat shrink and all the good connectors etc. It has worked very well in that my boat leaks like a sieve and yet the wiring has no problems. I have all led lighting which makes my power consumption for lighting next to nothing (i could leave it on for a week). My concept boat will be significantly larger at ~45' and will have various mod cons that I am not used to but which certainly will draw more power.

I like the idea of alternative power generation to the main engine but I have to admit I was thinking of a genet and had not foreseen the obvious flaw with this in the way that it generates power. I don't like either solar or wind power for aesthetic reasons and I also don't like the whooshing noise of the wind turbines. I can contemplate some small tastefully hidden solar panels for trickle charging but I don't think I would want a significant array although compromises may need to be made

The type of cruising I mostly do at present is about a month at a time up the west coast of Scotland. I would like this 'fantasy' boat to be my last and thus able to cope with extending the cruise much wider with potential to trans-atlantic, med, Norway and various adventures. I want the boat to be rugged and very well put together.

Does anyone else have any ideas regarding auxiliary generators. I have quite good battery monitoring on my current boat and this is essential for peace of mind. It may be possible to combine automatic generation with monitoring but this may be overcomplicated. Also, what about 240V, is it required at all? Can you get 12V hairdryers and all the other stuff women 'need'?

 

[ip485]

Think carefully about solar. I agree on aesthics but an arch can look very attractive and has loads of other uses.

It is all very well using the alternator to produce power but its those days at anchor that provide the challenge. As i said earlier you will find its a lot of very inefficient engine or genset time to bring the house batteries up each day. I agree with your wind generator comments - noisy and really unattractive, and while good for scotland not much good in the med on all those windless days. Solar has very little to go wrong is silent and provides exactly the trickle big batteries banks need.

I ran the air con in the rear cabin at the weekend on 240 v from the inverter and was amazed the solar array almost kept up with the fridge, freezer, and chart plotter running.

As to 240v it is surpringly redundant. An inverter solves the problem for most 240v tools and bits and bobs you have and may find useful. The one thing it just cant solve without a huge an almost impracticable set up is water heating or boat heating. In that respect the genset comes into its own. An hour on the genset with the immersion on will give you all the hot water you need and run up the fan heaters. Of course an ebby is a bet bet for cabin heater, but while they can be set up to heat water thats a level of sophistication i havent explored.

 

[prv]

Also, what about 240V, is it required at all?

The only use I find for shore power is for keeping the calorifier hot when staying put for more than one night. Also battery charging, in theory, except that I still haven't got round to wiring up the new charger and so far haven't missed it. 420Ahr goes a long way when you have relatively little drain, and a 115amp alternator with a smart booster means it doesn't take too much engine time to refill.

I did consider fitting an inverter when I rewired Ariam, but realised I couldn't think of a single thing that I might plug into it. But we are a "weekends and holidays" boat, not a voyager, so I daresay you'll find a use for 240v at sea.

Pete

 

[pmagowan]

I think you can use some of the eberspachers to heat a calorifier so that would be more dc efficient. I would definitely need some kind of shore power hookup for when at my pontoon but I don't have any 240v appliances on board my current boat. I suppose that brings about all the galvanic isolator concerns also. I should maybe have one on my current system as I leave a smart charger attached to the batteries when I am away.

 

[Tranona]

Having basic 240v shorepower is simple and useful. I have just 3 points plus a 350w inverter from the house battery. Main use for shorepower is battery charger and immersion heater for the calorifier. However if you want to go down the route of 240v appliances for regular use then you need to look at generators. If you do that you are into serious money and particularly space.

Of course by the time you get to build this boat, hybrid power just might have developed to the point where you can have a diesel electric propulsion and power generation system. Several engine builders have tried it but none seem to have caught on yet in the power range that is suitable for your proposed boat.

 

[TQA]

44 ft boat year round liveaboard on the hook. 12 volt system. 6 lead acid golf carts giving 675 ah for the battery bank plus an engine start battery. I have an electric windlass and went the heavy cable route.

400 watts of tiltable solar with a MPPT controller. Balmar 100 am alternator with a 4 stage smart regulator. I very rarely need to run the engine to charge batteries maybe 3 times a year.

Adler Barbour Supercold machine which makes ICE at 90f ambient and keeps a big top loading fridge really cold. I could reduce my daily consumption by switching to LED lights and trading in my power hungary Toshiba lappie for a tablet. But I am fully charged by early afternoon on a typical day.

I do have a Spectra watermaker but very rarely use it.

I have two inverters to 110v 600w and 2400w.

A 40 am battery charger used it once in 5 years.

I would not switch to AGM because they seem a little fragile and Lithiums are not cost effective and are not yet proven safe.

I can not think of anything I would change except that I would like a big digital ammeter on the main line.

 

[William_H]

There is no doubt that 24v system is far better for a bigger boat however it does dpend on what voltage system you get with the engine. If you have the engine with 12v electrics then probably best to stick with that. Winches even fridges often work on 24v and are far better for it. There is not much that won't work on 24v thse days but if there is just fit a converter 24 to 12v for the device. You need to make a list of every thing you will need to run on battery on the boat.
You will of course need duplicate 24v (or12v) batteries with VSR for charging quarantining one battery system for engine start.
An alternative which may appeal to you (cheaper simpler) is to run a single 24v battery system for engine and anchor winch. Then have a 24v to 12v converter fed by a VSR from the main 24v to charge a 12v battery. This 12v battery becomes your domestic supply. It may have to be big to feed a fridge 24/7.
I think a 240v supply for dockside should be simple and stand alone. However I did look at a lovely boat on Sun 47ft mobo with big twin diesels and an Onan gnerator so cooking etc was all electric. Just 6 years old. Very nice but huge price tag. (no I was not thinking of buying)
Anyway the complexity of electrics will reflect the convenience you demand. I think simple is best. good luck olewill

 

[prv]

You will of course need duplicate 24v (or12v) batteries with VSR for charging quarantining one battery system for engine start.

Separate banks, yes, but certainly not duplicate!

I have 120kg of AGM service bank, which seems a little excessive to start an engine, no?

My engine battery (as supplied by Merlin) is a small AGM actually marketed as a snowmobile battery!

Pete

 

[pmagowan]

I wonder about setting the battery banks low for stability. In my current scheme the engine would be quite well forward towards the midline rather than directly under the cockpit. This brings the weight to a better position. It would be good to have the batteries close to it. One problem I have been thinking of is the risk with very minor flooding of overwhelming these important systems. I was thinking about the posibility of a waterproof engine 'box' (obviously with piped in air and piped out electrics etc). Perhapsa similar thing would be needed with the battery. I am used to a boat where the bilge always has water in it but my intention is that this boat would have dry bilges!

 

[KellysEye]

We have sailed a variety of different size and make of boats boats up to 52 feet and all had a 12v system and 240 volt shore power. They also had the anchor battery in the bows and lead acid batteries, gel hadn't come in. I wouldn't touch Lithium batteries or LED's.