Why are production boats not 24v

Friends of ours have a new build catamaran which has 12v and 48v DC, and 110v and 220v AC systems.
There are reasons for having all of these voltages aboard but it definitely adds complication.
Another friend (who is an aircraft mechanic!) managed to get confused and cross wire between two different system voltages and cause a fair bit of damage.

But this is just the price we pay to have boats with modern systems onboard. I don't think anybody wants to go back to a single 12v battery powering a handful of dim lightbulbs and nothing else.
 
The NMEA 2000 standard that requires 12V is an unusual one. Virtually all (if not all) the equipment powered by my NMEA backbone, GPS etc will run happily on either 12 or 24V, but the standard requires 12V, so that is what I have done.

Of course, items such as the chartplotter, autopilot, radar etc that require a separate power supply are all powered directly from 24V.
 
NMEA 2000 networks require a voltage range of 9-16 VDC, with a nominal voltage of 12 VDC, and must operate with a total current less than 3 Amps (or 60 Load Equivalency Numbers - LENs - a LEN is 50mA). E.g. a Raymarine MFD is 3 LEN, a Yacht Devices Temp Sensor, 1 LEN.

While some devices and cables may support higher voltages, the 9-16 VDC standard ensures compatibility and proper operation across all certified NMEA 2000 devices and components. (As well as the power supply from NMEA2000 needing to be 12V nominal, there are also signal levels which rely on set voltage levels to distinguish between "1"s and "0"s. - the NMEA transceivers will do this regardless of the input voltage of externally powered NMEA devices.)
 
Like everything else with boats it's all about money. Why do major manufacturers not even fuse batteries unless exported to a country that requires it by law ( NB - I came across this with new Lagoon's in 2016 - it may have improved ) ? Why do I see bits of ply wood on edge with sika holding it in, to support a cockpit floor in the middle (like a 6 inch off cut just stuck in at the factory when the deck presumably was a bit saggy. Why did it take YouTube revelations to get the largest French manufacturer of boats to glass tab their decks down rather than just sika them on to the hull . Every penny, cent, or baht is counted and if it can get away with something it will.

24 or 48 would be better in many ways and safer and lighter in wiring etc but clearly the accountant says "non" when looking at the figures. What makes a boat better or safer or faster or anything else simply doesn't come in to it with production boats
 
Trident said:
Like everything else with boats it's all about money. Why do major manufacturers not even fuse batteries unless exported to a country that requires it by law ( NB - I came across this with new Lagoon's in 2016 - it may have improved ) ? Why do I see bits of ply wood on edge with sika holding it in, to support a cockpit floor in the middle (like a 6 inch off cut just stuck in at the factory when the deck presumably was a bit saggy. Why did it take YouTube revelations to get the largest French manufacturer of boats to glass tab their decks down rather than just sika them on to the hull . Every penny, cent, or baht is counted and if it can get away with something it will.

24 or 48 would be better in many ways and safer and lighter in wiring etc but clearly the accountant says "non" when looking at the figures. What makes a boat better or safer or faster or anything else simply doesn't come in to it with production boats
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I'd add to that and say that any volume manufacturer that deviates from this is putting their business at risk - the "up market" space is already occupied by more expensive boats with a longer history and better pedigrees - you could build a VW from the Porsche parts bin, but no-one would buy it.

Joe public and the charter companies want good enough at the cheapest price point possible.
 
Trident said:
Like everything else with boats it's all about money.
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Boatbuilders are certainly very conscious of reducing costs, as your examples show, but I don’t think this is the reason for avoiding 24V. In most cases, 24V is similar or less expensive because the wire sizes are smaller, and the equipment is mostly the same. Wire costs are significant as anyone who has refitted a boat will attest.

I suspect the reason is that the boatbuying public is not familiar with the readily availability of 24V devices because they have grown up with 12V boats and cars. If potential customers balk if the salesman mentions 24V (which I think has been the case up until recently), boatbuilders will be reluctant to switch even if they know it would make their systems run better.
 
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noelex said:
Boatbuilders are certainly very conscious of reducing costs, as your examples show, but I don’t think this is the reason for avoiding 24V. In most cases, 24V is similar or less expensive because the wire sizes are smaller, and the equipment is mostly the same. Wire costs are significant as anyone who has refitted a boat will attest.

I suspect the reason is that the boatbuying public is not familiar with the readily availability of 24V devices because they have grown up with 12V boats and cars. If potential customers balk if the salesman mentions 24V (which I think has been the case up until recently), boatbuilders will be reluctant to switch even if they know it would make their systems run better.
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I think the new boat buying public is a lot less conscious of voltage than you think. Ask the average car buyer what the battery voltage is, and I bet you get >50% blank stares. I'm sure most don't know that E-cars run on different voltages or what they are. Used boats, yes, but new boats, they see it like buying a car. Turn the key and it works. That is why they bought new.

I could be wrong. Obviously, some who have boats built for them are very involved.

I really think it is as simple as $$$. When lithium becomes common, which will take a while, it will change. The wire and component cost is interesting. With the exceptions of starters, battery cables, windlass, and inverter, most of the wire sizes on my boat are the ABYC minimum for robustness, and going to 24V won't change that. Nothing on the 120V side will change.

Also momentum. I saw an interesting episode of "Connections" (BBC I think) some years ago that explained why the Space Shuttle Booster size was determined by the width of a horses arse.
  • Roman chariot wheel track was set by the width of 2 horses.
  • Chariots made grooves in the stone road. If your carriage had a different width track you broke wheels.
  • The Romans invaded England.
  • The English made the first steam locomotives, and the cars were made by English carriage makers.
  • US rail adopted the English track gauge.
  • The Space Shuttle boosters were moved by rail, and unlike trucking, you can't drive around low bridges; rail max dimensions are fixed.
Someone decided 6 lead acid cells made a nice battery, so we'll use 12V long after lead is gone.;)
 
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I suppose we could be asking the same question for cars... electric windows, air con, infotainment systems, etc are generally all still on 12v. With the notable exception of the Cyberskip which uses 48v.
 
Most large trucks in the US are 12V, but some can be ordered 24V. I've had both at work. Some diesel pick-ups are 24V for the starter only. No idea the reasons. A lot of dual voltage accessories and lights are common, but generally not so much though marine outlets. So 24V would be a minor nuisance. Not enough to dissuade me.
 
thinwater said:
The wire and component cost is interesting. With the exceptions of starters, battery cables, windlass, and inverter, most of the wire sizes on my boat are the ABYC minimum for robustness, and going to 24V won't change that.
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We have very different yachts, but the minimum permitted ABYC wire size for most single-conductor runs is only 16 AWG (a little smaller than 1.5 square millimetres) , with some exceptions for even smaller 18 AWG ( a little smaller than 1 square millimetre). It is hard to satisfy the voltage drop requirements with this sized cable.

My yacht is 24V but has a frightening amount of wire much thicker than 1.5 mm. Of course, if it were 12V, the vast majority of the wires would need to be over double the thickness.
 
noelex said:
We have very different yachts, but the minimum permitted ABYC wire size for most single-conductor runs is only 16 AWG (a little smaller than 1.5 square millimetres) , with some exceptions for even smaller 18 AWG ( a little smaller than 1 square millimetre). It is hard to satisfy the voltage drop requirements with this sized cable.

My yacht is 24V but has a frightening amount of wire much thicker than 1.5 mm. Of course, if it were 12V, the vast majority of the wires would need to be over double the thickness.
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Because of the square law, most of the cables can be 1/4 of the cross section when you double the voltage. It's crazy when you start looking at the potential drop in cable size🙂
 
noelex said:
We have very different yachts, but the minimum permitted ABYC wire size for most single-conductor runs is only 16 AWG (a little smaller than 1.5 square millimetres) , with some exceptions for even smaller 18 AWG ( a little smaller than 1 square millimetre). It is hard to satisfy the voltage drop requirements with this sized cable.

My yacht is 24V but has a frightening amount of wire much thicker than 1.5 mm. Of course, if it were 12V, the vast majority of the wires would need to be over double the thickness.
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Correct. The larger the yacht, the greater the benefit of higher voltage, because of greater distances and loads. There are many corollaries in power distribution.

So I would expect to see a migration to higher voltages happen first in larger yachts (the time is now), and later (maybe never) in smaller yachts. The other thing I keep expecting on larger boats is distributed panels and digital switching, but that is also slow coming. Heck, I have sub-panels and a few wireless switches on my 24-foot tri, just because it's easier.
 
thinwater said:
Correct. The larger the yacht, the greater the benefit of higher voltage, because of greater distances and loads. There are many corollaries in power distribution.

So I would expect to see a migration to higher voltages happen first in larger yachts (the time is now), and later (maybe never) in smaller yachts. The other thing I keep expecting on larger boats is distributed panels and digital switching, but that is also slow coming. Heck, I have sub-panels and a few wireless switches on my 24-foot tri, just because it's easier.
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My friends 40ft cat has digital switching. He hates it and has built a bypass panel for essential switched items.
The Dutch superyacht construction industry loves everything canbus. My friend was build Captain for a Dutch built 72ft custom motorboat. He had to fight to have the boat designed such that canbus was not running the whole boat. He went on to be the Captain of the vessel for 18 years. Is said that boat was far less trouble free running more conventional systems. By comparison, another friend is Captain on a 72ft motorsailor. That is French built and canbus runs the boat. It's a never ending process of engineers visiting the boat resolving problems. These are custom boats, so one offs. It's
Possible that on production boats the canbus systems are more reliable, but the motor industry tests, test and test again and they still get reliability issues with canbus based systems. They have massive budgets compared to production boat manufacturers that have by comparison, relatively small production runs. Not all progress is beneficial to the owner who has to live with these system further down the line.
 
geem said:
My friends 40ft cat has digital switching. He hates it and has built a bypass panel for essential switched items.
The Dutch superyacht construction industry loves everything canbus. My friend was build Captain for a Dutch built 72ft custom motorboat. He had to fight to have the boat designed such that canbus was not running the whole boat. He went on to be the Captain of the vessel for 18 years. Is said that boat was far less trouble free running more conventional systems. By comparison, another friend is Captain on a 72ft motorsailor. That is French built and canbus runs the boat. It's a never ending process of engineers visiting the boat resolving problems. These are custom boats, so one offs. It's
Possible that on production boats the canbus systems are more reliable, but the motor industry tests, test and test again and they still get reliability issues with canbus based systems. They have massive budgets compared to production boat manufacturers that have by comparison, relatively small production runs. Not all progress is beneficial to the owner who has to live with these system further down the line.
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The motor industry does use CAN extensively, but the problems are not with the reliability of the bus - it's been in production for over 35 years and is electrically bombproof. The problems come with the software on components receiving and sending the CAN messages - the transcievers which receive and transmit CAN messages had their problems ironed out decades ago. Absolutely no reason why a working, stable, CAN system should be any less reliable than a rats-nest of individual wiring - pretty much every button and actuator on modern cars relies on bus communication over LIN, CAN, FlexRay or Ethernet.

The problem is that diagnosing problems with CAN based systems requires a bit more than a bulb and a couple of probes - so they are not as DIY friendly as individual wiring, but I would say the majority of problems are not HW, but SW incompatibilities when components are exchanged or running with incompatible versions.
 
There is here in this question a similarity with cars if 1930 on with 6v battery and systems. Probably due to cost of battery itself. The move to 12v was a huge improvement in volt drop concerns. VWs with dim head lights and old cars with very slow starter motors. So eventually the motoring world got the idea 12v is better.
Of course 24v is better again. As dictated by big diesel engines requiring real cranking power.
Now in aircraft for a very long time 12v is only used on smallest single piston engined planes and 24v is the norm. Even the biggest jets use 24v battery as emergency power.
So in answer to OP question who knows? Probably in time they will move to 24v being more common. ol'will
 
Baggywrinkle said:
The motor industry does use CAN extensively, but the problems are not with the reliability of the bus - it's been in production for over 35 years and is electrically bombproof. The problems come with the software on components receiving and sending the CAN messages - the transcievers which receive and transmit CAN messages had their problems ironed out decades ago. Absolutely no reason why a working, stable, CAN system should be any less reliable than a rats-nest of individual wiring - pretty much every button and actuator on modern cars relies on bus communication over LIN, CAN, FlexRay or Ethernet.

The problem is that diagnosing problems with CAN based systems requires a bit more than a bulb and a couple of probes - so they are not as DIY friendly as individual wiring, but I would say the majority of problems are not HW, but SW incompatibilities when components are exchanged or running with incompatible versions.
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But that is the problem. My crappy Peugeot car is all canbus. There is a known fault in the bus where it runs alon the rear suspension to the wheel brake sensor. The wire corrodes. The canbus system tells you there is a faulty handbrake. It's obviously not the handbrake. Imagine this is a boat after a few years. It only takes a burst house on the engine to spray a mist of salt water everywhere. You canbus connectors corrode and you are then plagued with faults and the engine goes into limp mode. This is what happens. It happened to a guy I know. Now imagine everything in the boat is canbus. Faults everywhere. This is what happens on the custom 72ft boat my pal is Captain on. The boat is now 12 years old and it's a constant source of pain and irritation. The boat is professionally maintained by a Captain with a degree in mechanical engineering. All maintenance and fault finding is done by flying out the engineers from you build yard in France at great expense, on a regular basis. This is the reality of canbus 'flying' the boat.
On another racer cruiser that I did some deliveries on, the boat is all canbus. Fly by wire engine controls to both helm stations. It uses tiny joysticks for throttle and gear control. It is supposed to be impossible to start the engines with the throttle position in anything but tick over. Canbus controlled.
The Captsin started the engine whilst the boat was at anchor. The throttles were wide open but the inhibitor didn't function and the boat shot forward at high speed! Csn you imagine the damage if it had happened in a marina berth. The Dutch engineers flew out to Antigua to interrogate the system. It couldn't be reproduced and it hasn't yet, happened again.
Who really want these systems on their boat? Certainly not me
 
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