Switching from 12V to 24V

[john61ct]

Panels are just a centralizing convenience.

CP and/or a switch can of course be added without a panel.

They also often add unnecessary wiring length.

[john61ct]

If Starter is already 12V, I reckon leave it alone. Not really a "heavy load" because so short.

[Cadence]

Originally Posted by john61ct

If Starter is already 12V, I reckon leave it alone. Not really a "heavy load" because so short.

That and the speed may double but what about the torque?

[coopec43]

Originally Posted by john61ct

12V is just a nominal label, means higher IRL.

Most devices will tolerate a wide variation.

Charging can go to ~15V

Of course you are correct re 12V being a nominal label but google wouldn't know that when you are searching.

Regarding 24V availability for other yacht electronics:

Installing an SSB Radio — - Noonsite.com
http://www.noonsite.com/General/Comm...g-an-ssb-radio
Feb 22, 2013 - Most if not all SSB units operate at a nominal 12V. For a boat with a 24V or 32V system, you will need a DC-to-DC power converter.

Raymarine HD Color and Super HD Color Open Array Radar
Raymarine Marine Electronics › ... › Marine Radar › HD & Super HD Color Open Array Radar
Choose a Raymarine HD Color or Super HD Color open array scanner for enhanced ... Find out more about the new Magnum Open Array Radar here .... Voltage, 10.8 to 32 volts DC (using supplied VCM100) for 12V, 24V DC Systems.

Marine Radar | MarineCommander WEBsite | Icom Inc.
https://www.icom.co.jp/world/mc/prod...ine_radar.html
Marine Radar. System Features ... Radar Main Units, MXR-5000T, MXR-5000R. Power supply, 12/24V DC (10.8 to 31.2V DC), 12/24V DC (10.8 to 31.2V DC).

Raymarine Smartpilot - Drive Unit Selection
Raymarine Marine Electronics › Marine Electronics › Raymarine Autopilots
... trained to evaluate your boat and assist you in selecting the right autopilot. ... Drive Type, Type 0.5 (12V), Type 1 (12V or 24V), Type 2 (12V or 24V), Type 3 .

[TonyDove]

Further to my last post (#146):

Re the separate and dedicated battery for VHF & SSB: The battery, and the SSB and VHF units themselves, should be mounted as high as possible - therefore the battery should be small and light (Lithium). Should you be unfortunate enough to take on water, your main batteries, invariably mounted low for weight distribution, will flood and short out. So if your comms gear and their battery are mounted high … they will survive unless the water reaches a level where abandoning ship is a higher priority.

Re NMEA2000: Yes, Maretron rate for 24V … but the point is that the NMEA2000 standard specifies 12V so most (if not all) NMEA2000 certified gear will be rated for 12V.

Happy Sailing

[Pelagic]

Originally Posted by TonyDove

Further to my last post (#146):

Re the separate and dedicated battery for VHF & SSB: The battery, and the SSB and VHF units themselves, should be mounted as high as possible - therefore the battery should be small and light (Lithium). Should you be unfortunate enough to take on water, your main batteries, invariably mounted low for weight distribution, will flood and short out. So if your comms gear and their battery are mounted high … they will survive unless the water reaches a level where abandoning ship is a higher priority.

Re NMEA2000: Yes, Maretron rate for 24V … but the point is that the NMEA2000 standard specifies 12V so most (if not all) NMEA2000 certified gear will be rated for 12V.

Happy Sailing

I agree about location.
My 12v “Radio Battery” is located high in the pilothouse for that emergency reason and can be isolated from the 24v House Bank that feeds it via a DC-DC converter.

Unlike the OP who is building new, if you have an older boat then it is not unusual to see installation compromises in added electrical devices that were put in over the years.

Then you need to decide on priorities and try to improve.

A case in point, when I bought SG in 2004, my DC Board had 36 x 24v Breakers, 12 x 12v Breakers and 10 AC consumer breakers.

The AC panel was installed in an impossible location to inspect and maintain, pressed into a tiny closet at the side with no wiring excess to pull out and the wiring runs pushed into the salty air intake of the engine room first before going aft or forward to the consumer. Thus adding a lot of unnecessary length to the runs

My priority was to move that AC panel to a dry internal location in the electrical locker, away from the engine room heat and have access from above and behind to quickly troubleshoot. Also run cables directly to the consumers rather than via the engine room.

I realized that because of improved Invertor and Solar technology, added AC consumers like induction stove and smart TV’s would require additional breakers, so I put in a new AC sub panel for all the extras that can run off of AC and/or DC (like OzzieFridge).

It meant a lot of rework but now finally completed and cleaned up I feel a lot more confident that I will not be in danger of a fire on board, because of a compromised electrical installation as the boat gets even older.

Something for all to consider when planning electrical changes is the ability to maintain,

[ka4wja]

Clive,
I've tried to read every post you wrote here in this thread....so...

I understand that you're building a boat, and you've decided on using a 24vdc electrical system...
No worries from me at all...
(even if I'm still confused as to what you could actually need on-board a 43' boat that requires that....the choice is of course yours..)


If you desire some hard facts and learned / experienced advice from sailors / voyagers / cruisers, please read here on Cruiser's Forum, etc. (and at Maine Sail's site), and please place a higher amount of seriousness to this info/advice, and a lower emphasis on the advice/recommendations of those selling/using "off-grid home electrical systems", and/or "off-road vehicle" systems....
Yes, there are some similarities, but there are actual large differences (and I'm not even talking about salt-air / sea water corrosion issues, nor constant vibration / g-force issues, etc..)

Originally Posted by coopec43

Tony I have been trying to prove you wrong re the scarcity of 24V SSB, VHF UHF radios.

I searched for 24V and didn't find any.
I searched for 12V and didn't find any (but there were plenty of 13.8V....)
(Most advertisements don't even mention power requirements)

Then I found "ICOM IC-450 80 CH UHF CB TWO WAY RADIO 80 CHANNELS IN VEHICLE LCD SCREEN 12/24V

• 5 Watts (High) and 1 Watt (Low) Selectable Output Power
• 80 CB Channels plus up to 35 receive only Channels
• Noise Cancelling Microphone Icom
• Voice Recorder allowing up to 10 messages recorded with a total recording time of 5 minutes (30 seconds per message)
• Built-in Speaker
• 12 or 24 Volt automatically detected
• Voice Guidance which announces channel type and number
• Small and compact for installation
• Main unit can be mounted out of sight
• New design, compact control speaker microphone with newly designed user interface and menu structure

I'll keep looking.

Thanks

Clive

Clive, "24vdc" marine radios are not scarce at all....they are plentiful, but pricey!!
See below for many details...

But, first, please let me repeat that you do seem like a smart guy and the fact that you're asking lots of questions is of course great!

And, the fact that you are starting from scratch and building a boat (and its electrical system), allows you to have an excellent system....assuming you do actually design a system, of course...

Whether, you choose 24vdc, or 12vdc...or a 24vdc & 12vdc systems, or a 24vdc system with some 24vdc-to-12vdc DC-DC converters (which will cause you some on-board RFI)....whatever your choice, you'll be in good shape if you actually design a system and not take a piece-meal approach...

You're obviously motivated and seeking advice / recommendations....but I am concerned about 2 things...one, not actually designing a "system"....and the other being your odd sources of info for your electrical needs??

Earlier, I gave you my decades of experience in both electronics and marine electrics, attempting to guide you to take a systems approach....but you decided against this, so I decided to not bother you anymore with anything further....(figured you'd heard enough from me, huh?? ) As I read more of your thread here, seeing your odd sources of info, seemed off to me....but again figured you'd rather not hear more from me...so, again I kept mute...

But, then I read your words about looking for "24 volt radios", and since I'm a "radio guy", I thought maybe I could just politely point you to where you will find this info...although these might be moot or ignored as I'd need to add some context to all of this...so...


1) So, please have a look at what I wrote earlier regarding designing your electrical system, not just trying to throw things together that should work... And, then look at the details about 24vdc radios....

Originally Posted by ka4wja

....<snip>....

1) And, you've already determined that you can run your existing "12vdc" frig and windlass on 24vdc??
2) Or, have you already converted your refrig/freezer and windlass to 24vdc??

3) Also, it isn't clear what you actually need on-board...I realize that your question was rather narrow and you didn't ask us to design your electrical system, but just your asking of this question and the limited info you provided, makes me wonder if you have thoroughly looked at your entire electrical / electronics system? As a whole system? And designed it as such, as a "system"? Or are you just "trying to get stuff to work"??


Notwithstanding your desire to just ask your question about tapping into your "24vdc house bank" for 12vdc systems (a bad idea), that you've already got answered... (it's best to use only one voltage battery bank...)
The answer to these questions above matter here, in regards to the best approach for you to follow...

Also, the answer to these following few questions are even more important..

4) Are you not including a large solar array in your energy system for some reason??
And, you're going to rely on burning diesel fuel to charge batteries??
That just seems so very "1970's"??


5) Are the "two 150A/H AGM batteries" in your house bank, in fact two 12v, 150A/H batteries in series, giving you 150A/H, 24vdc house bank??
This is a very small house bank, and you'd do well to triple that, or even quadruple this!

This is very important to clarify!!
{and fyi, even if you do have a 24vdc, 300A/H house bank, this is considered on the small end of the scale, of what is "typical" / "average"...usually 450A/H, or more, at 24vdc is typical (that would be about 900A/H at 12vdc)..} And, many with 24vdc systems will have even larger battery banks, due to their larger on-board systems...
'Cuz if you're writing about "heavy loads" (whatever those may be), remember two things:

a) higher current draws (above the 20-hr discharge rate of 15 amps for a 300A/H bank, or above 7.5amps for a 150A/H bank) will reduce the actual "A/H" capacity of the bank....
b) to survive any significant length of time (even normal current draws from normal cruising boat devices, refrig/freezer, autopilot, radar, etc., etc.) you will need a larger battery bank than you mention, unless you do have a large solar array??


6) How are you planning on getting your AGM batteries up to 100% charge??
You do realize that, while AGM's are an established battery design, they have one drawback for most cruising boats, their requirement to get back to 100% charge, or they lose capacity (10% to 20%) rather quickly...and this is almost never able to be brought back...
Now, if you do have a large solar array, that is great!!
And, a large solar array is almost an absolute for any cruising boat with AGM's...



7) Although this question might seem less important, it is actually an important question that I assume you have already answered for yourself, so for us here it's just curiosity...
Curious as to what you have on your 43' sailboat that draws so much current that 12vdc system will not work??
What are you trying to accomplish??
[I acknowledge your further details of what you have / will have on-board....and be clear that except for a 3000watt inverter, these are fairy common and rather normal / small loads, even for 12vdc boats...]

'Cuz...
--- Best overall refrig/freezer systems, for most small boats, are Danfoss-based....not the large 1/4-hp or 1/2-hp compressors freezing cold plates...but, even if you've chosen that less efficient route, there are many 12vdc high-current/high capacity compressors keeping food cold on many older cruising boats, without the need for 24vdc systems..
{now, of course, if this was a commercial vessel, fishing vessel, etc., where constant, very cold, deep freezing was necessary, then I see the desire for 24vdc system...but on a 43' cruising boat??}

--- How big anchor and chain to do have??
'Cuz, I've seen 55' - 60' boats, with Maxwell 3500 windlasses hoisting 110lb - 120lb anchors and 300' of 3/8" chain, all on 12vdc, just fine...
And, most 40' - 50' cruising boats, with 60 - 90lb anchors and 250' - 300' of 5/16" chain, running big enough windlasses, all on 12vdc just fine as well..

--- Of course in regard to "inverters", for high-power inverters, yes 24vdc to 110vac-250vac, is much better than trying to do this from 12vdc!!
But, what in the world could you be attempting to power thru an inverter that you'd have hooked up to a rather small 300A/H battery bank??
With that small of battery bank (yes, even at 24vdc, that is on the low end of the scale), you couldn't run a big inverter for very long...perhaps to run a microwave to make popcorn??
Just saying if you have large inverter loads, that require a 24vdc inverter, that is a great reason for a 24vdc battery bank....but a 300A/H battery bank is rather small to power large inverter loads...


Again, thinking you may not have really designed this all as a "system"??


8) And, while commercial 24vdc electronics are available (and of course almost all commercial vessels are 24vdc / 110-230vac), I've never seen them at reasonable prices or on the shelves / immediately available in remote areas....so the initial cost is usually more as are the costs of cruising with spares...
Which is why most will use either modern 12vdc electronics that will operate over a wide voltage range (typ 10-32vdc), or some are forced to use 24vdc to 12vdc converters, and then deal with RFI mitigation / elimination...

This doesn't apply to many "radios", as many are not usually designed for multi-voltage use...so, you will need to spend more on commercial 24vdc radios...or spend more on high-current 24vdc to 12vdc converters, and deal with RFI issues...
This may also apply to autopilots...depends on brand and model...

FYI, as for radios....
--- 24vdc commercial VHF-DSC-FM radios are 3 - 4 times the cost of 12vdc consumer / yacht versions
--- 24vdc commercial MF/HF-DSC-SSB radios are 2 - 3 times the cost of 12vdc consumer / yacht versions

Using "12vdc electronics" (some will of course work from 10vdc to 32vdc) might seem inelegant, but is actually a good approach, rather than using "voltage converters" (especially those budget-priced models that produce a great deal of RFI!)

Okay, enough of my ramblings for now...

Fair winds.

John

Originally Posted by ka4wja

Now, Clive...I'm sorry I did not understand that you were constructing a new boat....and I suspect others here were confused as well, with a title of "Switching from 12v to 24v" and writing this: I assumed you already had the boat and all equipment installed and were in fact switching from 12vdc to 24vdc....but, it appears that I was incorrect...opps..

However, this makes it all the more important to answer the questions I posed earlier, as you are starting from scratch here!
Again, I may be wrong, but it appears to me that you are trying to make things work and getting a good deal of well-meaning advice/info from off-grid alternative energy sites?? Instead of taking a systems approach and designing your on-board energy system yourself, for your needs and your application??

I realize that your initial question was about starting batteries and whether you could "tap into" your 24vdc battery bank, from 12vdc....but, please have a look at what I wrote, 'cuz whether you believe me or not, it will help you...



Also, except for a 3000 watt inverter (mine is smaller) and the bread maker (I knead by hand), I have all equipment that you listed as "currently installed" and "intend to install", on my present 47' sloop, as well as a great deal more...but, as you'll see, you should design your energy system as just that, a "system", and all should work out well for you (whether someone goes 24vdc, or 12vdc & 24vdc, or even 12vdc only...they need a proper design, or they'll be chasing their tails and "solving problems", instead of enjoying life, sailing/cruising...)



To be clear, there are 3 major parts of your on-board energy system design, and they should be fully understood and analyzed, so that you can design your energy system that meets your specific needs...these parts are:

1) Energy Storage (i.e. batteries....not just the A/H rating, but also their charge and discharge profiles, which are gotten from the manufacturer)

If, as you wrote, you have two 150 A/H batteries in your house bank, assuming they are 12vdc batteries (as you talked about tapping into this bank to access 12vdc), then you have a 150 A/H house bank (at 24vdc....which is like a 300A/H house bank at 12vdc)....and this is not only quite small, but will be unable to support a 3000 watt inverter for very long, before running the batteries very low (a very deep discharge) and even at 24vdc, a 75 amp current draw from a 150 A/H house bank is going to pull the battery voltage down while this is being drawn (this is not the voltage drop in the wiring, but in the battery due to the high current versus the battery capacity...

{BTW, "150 A/H's" is a quite small capacity for a Group 4D (which would typically be 180 - 210 A/H), and quite large capacity for a Group 31 (which would typically be 100 - 130 A/H's)....I don't know what batteries you're spec'ing out....but assume you've gotten the info from the battery manufacturer....just want you to be sure of the capacity of your house bank...}

And as I and others have mentioned, the higher current draw from the bank above the "20-hour rate" (7.5amps) the lower the actual capacity....a 50% increase in current above the battery's "20-hour rate", the capacity is typically 90% of "rated", and doubling of the 20-hour rate (15 amps) current draw capacity is typically 80% of rated....

But FYI, even more important for those looking to drive large appliances, if you draw a significant current, say 75 amps (@24dvc) to run your microwave....just 20 minutes will use approx. 30% of your entire battery bank's capacity....and that's assuming you started with batteries at 100% charge (which might not be possible, unless you have sufficient solar array, to handle your on-board needs and charge the batteries up to 100%, as well), so typically figure you're starting from 90% capacity....

Sorry to ramble on, there is just so much here to write, and I don't have the time now to write more....



2) Energy Sources / Charge Sources (for most mid-seized sailboats, solar is of course primary, these days...but some in very windy environs still get some effective use from wind power, too...and some that do long passages get a great deal of energy from towed-water-gens....of course there is also diesel gensets....and lastly, main engine alternators...)



3) Energy Consumption / Energy Budget (this is simply the power used by all of the devices on-board, times the amount of hours per 24hr day each is used....although we've become accustomed to using "A/H's per day", this does introduce a problem if you're using two different voltages on-board, as well as confuse many who are used to doing this only with 12vdc...so using "watt-hours per day" would allow you to easily compile a detailed energy budget...)


And, don't forget that many of us are able to live energy self-sufficiently, as long as the sun shines every few days....
We design our systems to not just "get thru the day" / "get thru the night" / "until we charge up", no....rather we design the system to actually run seamlessly, so we aren't just looking to charge, but the system is always operating as a system, where we use energy and it is replaced...we typically don't think along the lines of "charging", but along the lines of just providing power as needed, when needed, and the system handles it just fine...

{fyi, with ~900 A/H of battery capacity, 500+ watts of solar, and lots of extra frig/freezer insulation, and attention to detail in energy system design, as long as the sun shines every few days (every 3 - 4 days when at sea, and every 4 - 5 days when at anchor) everything is just seamless, and no "charging" is thought about....if there are many days of cloudy weather at sea, I use a towed-water-gen to supplement...or even my genset, or even the main engine....and at anchor, more than 4 - 5 cloudy/overcast days means I will probably crank-up the genset, but that's only happened once in many years... }


While I've listed these 3 criteria (used for designing your on-board electrical / electronics systems), in the generally accepted order of importance for most cruising boats....this assumes that the owner/designer has already done a complete energy budget...so, if you have, that's good (and it would be cool if you'd post it), but in case you haven't please stop and take the time to do this now....it will save you a LOT of time/effort and probably save much frustration along the way!!


If you look at your energy system on-board, as a system....and design it as such, you'll be a very happy sailor, whether 12vdc, 24vdc, 32vdc, etc.....but most that take a hap-hazard / piece-meal approach tend to run into trouble, and have a good deal of frustration...

Just as examples, there are quite pricey (> $500,000 USD) new sailboats that the factory made little effort to design an efficient / effective energy system on-board....also, I've anchored near slick, new, fancy sailing yachts that have to run a genset or main engine to keep their frig/freezer cold, and/or just to make water, etc....and even seen brand-new boats with piss-poor 2awg wire used for battery wire, and windlass wiring, at 12vdc!!! As well as the ubiquitous unfortunate issue suffered by almost all modern cruising boats = lack of adequate frig/freezer insulation!!

(remember, except for those sailing in cold weather, your frig/freezer will be the largest energy consumer on-board, followed by autopilot in 2nd place.....then generally followed by chartplotter/radar/computers/navigation system, in 3rd place...)

Fyi, most find domestic hot water to be their Achilles....if they run their engine, which almost always has a cooling loop thru the hot water heater, they get LOTS of hot water, but then they're burning diesel, same for running a genset and 110vac/230vac heating elements....and the power drain of 800 watt to 1200 watt heating elements is just too much for many on-board energy systems...so some sort of solar assist (water heated by the sun, not by electricity) is a great approach, as is a DC heating element to be used when you have sufficient sun shine...



Again, sorry I misunderstood....I thought you were "switching from 12vdc to 24vdc", but I now see that you are building a new boat....so, please know that it is even more important to design your own energy system / electrical system, according to your needs/desires, not mine...
(just remember that burning diesel, and running an engine and/or genset, gets old...real fast!!)

And, except for large amount of domestic hot water, most mid-sized cruising boats are (or can easily be) set-up to be energy self-sufficient, even on 12vdc....but, even if you choose a 24vdc system, the key to success is to design a system...

The key is to design a system based on your specific energy storage capacity, your energy generation/charging, and your own energy budget...on your boat (not a house).....typically using large solar arrays and fairly sizable battery banks....'cuz silence is golden!...nobody wants to listen to an engine run, nor smell diesel exhaust...


Perhaps reading over the above, and the questions I asked earlier, and having a look at Maine Sail's site, etc., will show you how important taking a system approach is....learn about your batteries, charging sources, and make a complete energy budget...and you can easily design your energy system to best suit your on-board needs / application....not doing so is, in my opinion, a mistake...


Fair winds....and wishing you good luck..


John

2) If you don't mind me reiterating my observation here, you seem to be getting/taking a good deal of info/advice from those selling/using "off-grid home electrical systems", and other non-maritime / non-offshore sailing sources....rather than those for offshore sailboats....there are of course many differences between these...

Not-the-least-of-which are:

--- the need to eliminate any RFI sources on-board (which is usually a moot point for land-based systems);

--- the need to have adequate solar without any shading (usually difficult on-board, but quite easy on land);


--- the need to have enough battery capacity to sustain your energy needs during a few days of cloudy skies / storms, as well as handle some high-current loads with partially-charged batteries (which can be a problem in some areas on land, but usually not in the Australian outback...and of course many off-grid homes have other energy sources and can usually have adequate access to fossil-fuel supplies, that are non-existent at sea);

--- the relatively short wiring runs on-board are usually not detrimental for use of 12vdc systems, except for large items such as large (3000+ watt inverters, large motors run for long periods of time, etc.) where higher-voltage devices can be of importance...but both the typical short wiring runs and the fairly short periods of time these devices are usually used, can make the 23vdc advantage smaller than many realize (not that this is a mistake, but rather that you should understand the smaller advantage up front, when designing your energy system)





3) And, as for "24vdc radios"....the "12vdc" or "24vdc" nomenclature is "nominal battery voltage", meaning a "12vdc" radio is usually spec'd at 13.6vdc (or 13.8vdc) +/- 15%....and a "24vdc" radio is of course usually spec'd at 24vdc to 30vdc (some spec'd for 22vdc to 32vdc)...

BTW, even though it appears to still be a thing in Australia, and I think is still used by some Australian pleasure boaters (for fun!), I was sort of taking by surprise by your reference to CB radio....and, this is another example of where your information sources seem very odd to me....Maritime communications (both in Australia and worldwide) is well-established and afar cry from "CB Radio"...

Again, I'm looking at your boat and electrical system, from a "maritime" view rather than a "land" view, so I do see where/how we seem to be talking past each other, rather than to/with each other...
So...

So Clive, here are just some of the popular 24vdc marine radios (there are others)....enjoy!

BTW, for a 24vdc boat, here are my two favs...

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-vhf-radios/sailor-6222-vhf-dsc-class-a/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6320-mfhf-dsc-class-a-250w/



Icom
https://www.icom.co.jp/world/products/marine/mobile/gm600/index.html (note the GM600 is 24vdc and/or 12vdc when using the associated Icom PS-310 power supply / DC-DC converter)


https://www.icom.co.jp/world/products/marine/hf/gm800/



Furuno
https://www.furuno.com/en/products/radiotelephone/FM-8900S
https://www.furuno.com/files/Brochure/199/upload/FM-8900S.pdf


https://www.furuno.com/en/products/radiotelephone/FS-1575
https://www.furuno.com/en/products/radiotelephone/FS-2575
https://www.furuno.com/en/products/radiotelephone/FS-5075


https://www.furuno.com/files/Brochure/200/upload/fs-xx75.pdf



Sailor / Cobham
https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-vhf-radios/sailor-6222-vhf-dsc-class-a/ (like the Icom GM600, the Sailor 6222 is a 12vdc and/or 24vdc radio, as it includes their #6090 power supply / DC-DC converter)


https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6310-mfhf-dsc-class-a-150-w/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6320-mfhf-dsc-class-a-250w/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6350-mfhf-dsc-class-a-500w/

https://www.indumarver.com/archivos/SAILOR/SAILOR_6300MFHF.pdf




JRC
https://jrc.am/products/jhs-770s-jhs-780d/features
https://jrc.am/products/jhs-770s-jhs-780d/specs

https://jrc.am/products/jss-2150-2250-2500/features
https://jrc.am/products/jss-2150-2250-2500/specs



SEA
http://www.seacomcorp.com/pdfs/SEA%207157_%200711.pdf (24vdc OR 12vdc model, you must specify which)


http://www.seacomcorp.com/pdfs/SEA_330.pdf (old design, non-DSC, non-GMDSS)



BTW, there are other / older design, non-DSC, "24vdc" radios, but none are actually recommended for maritime comms in the past 15 - 20 years....as well as some old/used radios, salvaged from old decommissioned ships, etc., but would certainly never recommend any of these either....


Hope this actually helps...

Fair winds.

John


P.S. I still have not found any Adler Barbour info recommending 24vdc vs. 12vdc....could you please provide a link to this??

[ka4wja]

kapnd, sailingjack, Clive, et al,
I didn't want to drift this thread too far afield, so didn't delve into this...but, guess I should have...

Yes, "cheap" DC-DC converters are to be avoided!!

Originally Posted by sailing_jack

One point of concern regarding cheap dc to dc converters.
They all have a high frequency oscillator to do the conversion, either by pulse width modulation or a high frequency transformer.

Cheap Chinese (and maybe other low cost suppliers) often take shortcuts with shielding. If you are wondering why your HF or VHF radio is noisy, try turning off the converters.

It is as always, Buyer Beware !

Originally Posted by kapnd

This may be true, but on my vessel would be hard to prove, as my VHF is one of the few items onboard that requires 12 the volts!
The radio works fine on a Mastervolt 24/12 v converter, not noticeably noisy.
This thread has been a pertinent read for me, thank you all for your contributions.

Please understand it does not matter at all if you're using one of these cheaper voltage converters to power the radio or not....as just their presence on-board and being "plugged-in" (even if "turned off", in standby mode, not powering anything), is enough for them to produce significant RFI (Radio Frequency Interference)....whether wide-band noise, narrower bands of noise, hash, etc., or blurps/chirps/birdies/etc., these can produce significant RFI that can drown-out all but the strongest HF signals (shortwave, SSB, ham, etc.)...and the worst of them can also disrupt VHF comms as well...
Of course, if powering something, and supplying current, their RFI is usually worse than in "standby mode", some produce significant RFI even in stand-by mode, even when drawing only 50ma - 150ma...

These typically radiate RFI from their own cases and their own wiring (and your boat's wiring) that is picked up by your radio's antenna, just like it picks-up / receives all its radio signals...

Proper design, proper shielding, and proper isolation can make these voltage converters (which are really DC-to-AC-to-DC inverters), almost silent to radios, and have few, to no, ill effects on-board....but..
But, these "properly designed and built units" are not cheap (think hundreds of dollars, each), and will also usually require use of external ferrites and a specific wiring runs, to eliminate RFI altogether...

The cheap units, will almost certainly reduce (possibly almost eliminate) your effective use of HF radio on-board (this means "marine SSB", HF-DSC, ham radio, CB Radio, etc...)
And, some of them can also have bad enough RFI to reduce your VHF radio reception...
{note these will typically have no effect on your transmission, only your reception....but, as we say, if you can't hear 'em, you can't talk to them...}


BTW, the $300 to $400 (for 300 watt model) Isolated versions of the MasterVolt MAC, aren't too bad...but from what I've heard anecdotally, they do have significant HF RFI, but I haven't used them myself...


Fair winds....

John

[noelex 77]

Originally Posted by rgleason

24vdc is tantalizing:

As you can see by my posts, I think 24v would be a better choice for many boats. However, I think it would be a mistake in your case. I would stay with 12v for your boat.

There has been a lot of confusing information in this thread with posts suggesting chartplotters, radar, lights, fans, etc, etc, have to be powered by 12v. This is not the case. These days all these devices will run fine from 24v.

If you have many older devices that are restricted to 12v only, and are not planning on replacing these soon, staying with 12v is much better idea. In your case you have few large power devices such as inverter, bow thruster, anchor winch, under-deck autopilot, which is where the significant efficiency and power advantages of 24v become apparent.

A modern boat with a 24v house bank should be running almost everything from 24v, not trying to set up both a 24v and 12v system.

[rom]

Originally Posted by ka4wja

Proper design, proper shielding, and proper isolation can make these voltage converters (which are really DC-to-AC-to-DC inverters), almost silent to radios, and have few, to no, ill effects on-board....but..
But, these "properly designed and built units" are not cheap (think hundreds of dollars, each), and will also usually require use of external ferrites and a specific wiring runs, to eliminate RFI altogether...

Any brand/model you have in mind ? What kind of certification should we be looking for ?


The Victron Orion 24/12VDC 25A costs about 80 EUR, and is CE EMC approved. They may also have the equivalent US FCC certification, but I couldn't find it on their website.

[CatNewBee]

Not necessary to do DC-AC-DC conversion for step down from 24V DC to 12V DC. Just a regulator circuit needed - for small loads e.g. 7812 plus some capacitors.

There are ready to use waterproof units for cars and boats :

24V - 12V Step down converter 20A / 240W

You can use any solar controller too to do a step-down conversion (PWM or MPPT) but there may be HF issues.

[svlamorocha]

Originally Posted by NPCampbell

I haven't figured out how some of the larger boats even manage with 12V while using a windlass that requires 1500+ watts. At 125+ amps you need to be using HUGE cables. A 15 ft run requires 1/4 inch thick #2 wires to limit the voltage drop to 5% and the steady state wire temp to 195F.

There is no mistery. Windlasses need much fatter wires than AWG2. If you see thinner wires going to a windlass you are probably looking at the wires that control a relay that switches the "real" supply wiring.

[coopec43]

Originally Posted by rom

It would be interesting (for Clive at least) to know how Amel does that. Which components they use and if there is a 12V subsystem, how is it connected to the 24V system. Does the engine start on 24V ?

Electrical:

Circuits 12, 24 and 220 VOLTS

• 8 Lifeline AGM Batteries 105 Amp Hours (new 2018)
• 2x100 Watt Energie-Mobie solar panels on rear Davits
• 6 walk-on Solara SM solar panels glued flat in front of cockpit - 172 watts)
• D-400 wind generator on Davits (new 2010) 40 watts @ 10 kts and 400 watts @32 kts
• Battery charger VICTRON 80 amps
• Sinergex inverter 2000W ( New 2012 )
• Victron Inverter 400W for nav table (New 2018)
• 12 Volt Alternator for start battery
• 24 Volt Bosch Alternator for House Bank (New 2016)
• LED Nav & Anchor Lights

[john61ct]

Originally Posted by CatNewBee

Not necessary to do DC-AC-DC conversion for step down from 24V DC to 12V DC. Just a regulator circuit needed - for small loads e.g. 7812 plus some capacitors.

There are ready to use waterproof units for cars and boats :

24V - 12V Step down converter 20A / 240W

Are you recommending those specifically?

Upthread we asked OzePete and he responded with a reco here http://www.cruisersforum.com/forums/....php?p=2754333. I have also just asked him about RFI.

[ka4wja]

Uh...I'm busy with a client, so can't get into detailss..
I have no knowledge/experience with this particular devcie...
But...

Originally Posted by CatNewBee

Not necessary to do DC-AC-DC conversion for step down from 24V DC to 12V DC. Just a regulator circuit needed - for small loads e.g. 7812 plus some capacitors.

There are ready to use waterproof units for cars and boats :

24V - 12V Step down converter 20A / 240W

You can use any solar controller too to do a step-down conversion (PWM or MPPT) but there may be HF issues.

But, since the argument for using 24vdc is for better [sic] energy efficiency, why in the world would you want to use a voltage regulator, to get from 24vdc to 12vdc, and get 50% eff at best??? (I mean if you needed 12vdc at 5amps, etc., you'd take 24vdc at 5 amps just to get that 12vdc at 5 amps...)

35 years ago, when doing solar, we'd use the old Ford truck voltage regulators to take the 18-19vdc from the panels and have it supply 13.8vdc to the batteries (for "float" and "trickle charging")...
But, this is the 21st century....

Not sure what the issue is here...

Bottom line, if you want a 24vdc boat....then you design and build a 24vdc boat....you do not need to use 12vdc for much of anything...but, it isn't cheap....
Have a look at what I wrote...

Originally Posted by ka4wja

Clive,
I've tried to read every post you wrote here in this thread....so...

I understand that you're building a boat, and you've decided on using a 24vdc electrical system...
No worries from me at all...
(even if I'm still confused as to what you could actually need on-board a 43' boat that requires that....the choice is of course yours..)


If you desire some hard facts and learned / experienced advice from sailors / voyagers / cruisers, please read here on Cruiser's Forum, etc. (and at Maine Sail's site), and please place a higher amount of seriousness to this info/advice, and a lower emphasis on the advice/recommendations of those selling/using "off-grid home electrical systems", and/or "off-road vehicle" systems....
Yes, there are some similarities, but there are actual large differences (and I'm not even talking about salt-air / sea water corrosion issues, nor constant vibration / g-force issues, etc..)



Clive, "24vdc" marine radios are not scarce at all....they are plentiful, but pricey!!
See below for many details...

But, first, please let me repeat that you do seem like a smart guy and the fact that you're asking lots of questions is of course great!

And, the fact that you are starting from scratch and building a boat (and its electrical system), allows you to have an excellent system....assuming you do actually design a system, of course...

Whether, you choose 24vdc, or 12vdc...or a 24vdc & 12vdc systems, or a 24vdc system with some 24vdc-to-12vdc DC-DC converters (which will cause you some on-board RFI)....whatever your choice, you'll be in good shape if you actually design a system and not take a piece-meal approach...

You're obviously motivated and seeking advice / recommendations....but I am concerned about 2 things...one, not actually designing a "system"....and the other being your odd sources of info for your electrical needs??

Earlier, I gave you my decades of experience in both electronics and marine electrics, attempting to guide you to take a systems approach....but you decided against this, so I decided to not bother you anymore with anything further....(figured you'd heard enough from me, huh?? ) As I read more of your thread here, seeing your odd sources of info, seemed off to me....but again figured you'd rather not hear more from me...so, again I kept mute...

But, then I read your words about looking for "24 volt radios", and since I'm a "radio guy", I thought maybe I could just politely point you to where you will find this info...although these might be moot or ignored as I'd need to add some context to all of this...so...


1) So, please have a look at what I wrote earlier regarding designing your electrical system, not just trying to throw things together that should work... And, then look at the details about 24vdc radios....

Quote:
Originally Posted by ka4wja
....<snip>....

1) And, you've already determined that you can run your existing "12vdc" frig and windlass on 24vdc??
2) Or, have you already converted your refrig/freezer and windlass to 24vdc??

3) Also, it isn't clear what you actually need on-board...I realize that your question was rather narrow and you didn't ask us to design your electrical system, but just your asking of this question and the limited info you provided, makes me wonder if you have thoroughly looked at your entire electrical / electronics system? As a whole system? And designed it as such, as a "system"? Or are you just "trying to get stuff to work"??


Notwithstanding your desire to just ask your question about tapping into your "24vdc house bank" for 12vdc systems (a bad idea), that you've already got answered... (it's best to use only one voltage battery bank...)
The answer to these questions above matter here, in regards to the best approach for you to follow...

Also, the answer to these following few questions are even more important..

4) Are you not including a large solar array in your energy system for some reason??
And, you're going to rely on burning diesel fuel to charge batteries??
That just seems so very "1970's"??


5) Are the "two 150A/H AGM batteries" in your house bank, in fact two 12v, 150A/H batteries in series, giving you 150A/H, 24vdc house bank??
This is a very small house bank, and you'd do well to triple that, or even quadruple this!

This is very important to clarify!!
{and fyi, even if you do have a 24vdc, 300A/H house bank, this is considered on the small end of the scale, of what is "typical" / "average"...usually 450A/H, or more, at 24vdc is typical (that would be about 900A/H at 12vdc)..} And, many with 24vdc systems will have even larger battery banks, due to their larger on-board systems...
'Cuz if you're writing about "heavy loads" (whatever those may be), remember two things:

a) higher current draws (above the 20-hr discharge rate of 15 amps for a 300A/H bank, or above 7.5amps for a 150A/H bank) will reduce the actual "A/H" capacity of the bank....
b) to survive any significant length of time (even normal current draws from normal cruising boat devices, refrig/freezer, autopilot, radar, etc., etc.) you will need a larger battery bank than you mention, unless you do have a large solar array??


6) How are you planning on getting your AGM batteries up to 100% charge??
You do realize that, while AGM's are an established battery design, they have one drawback for most cruising boats, their requirement to get back to 100% charge, or they lose capacity (10% to 20%) rather quickly...and this is almost never able to be brought back...
Now, if you do have a large solar array, that is great!!
And, a large solar array is almost an absolute for any cruising boat with AGM's...



7) Although this question might seem less important, it is actually an important question that I assume you have already answered for yourself, so for us here it's just curiosity...
Curious as to what you have on your 43' sailboat that draws so much current that 12vdc system will not work??
What are you trying to accomplish??
[I acknowledge your further details of what you have / will have on-board....and be clear that except for a 3000watt inverter, these are fairy common and rather normal / small loads, even for 12vdc boats...]

'Cuz...
--- Best overall refrig/freezer systems, for most small boats, are Danfoss-based....not the large 1/4-hp or 1/2-hp compressors freezing cold plates...but, even if you've chosen that less efficient route, there are many 12vdc high-current/high capacity compressors keeping food cold on many older cruising boats, without the need for 24vdc systems..
{now, of course, if this was a commercial vessel, fishing vessel, etc., where constant, very cold, deep freezing was necessary, then I see the desire for 24vdc system...but on a 43' cruising boat??}

--- How big anchor and chain to do have??
'Cuz, I've seen 55' - 60' boats, with Maxwell 3500 windlasses hoisting 110lb - 120lb anchors and 300' of 3/8" chain, all on 12vdc, just fine...
And, most 40' - 50' cruising boats, with 60 - 90lb anchors and 250' - 300' of 5/16" chain, running big enough windlasses, all on 12vdc just fine as well..

--- Of course in regard to "inverters", for high-power inverters, yes 24vdc to 110vac-250vac, is much better than trying to do this from 12vdc!!
But, what in the world could you be attempting to power thru an inverter that you'd have hooked up to a rather small 300A/H battery bank??
With that small of battery bank (yes, even at 24vdc, that is on the low end of the scale), you couldn't run a big inverter for very long...perhaps to run a microwave to make popcorn??
Just saying if you have large inverter loads, that require a 24vdc inverter, that is a great reason for a 24vdc battery bank....but a 300A/H battery bank is rather small to power large inverter loads...


Again, thinking you may not have really designed this all as a "system"??


8) And, while commercial 24vdc electronics are available (and of course almost all commercial vessels are 24vdc / 110-230vac), I've never seen them at reasonable prices or on the shelves / immediately available in remote areas....so the initial cost is usually more as are the costs of cruising with spares...
Which is why most will use either modern 12vdc electronics that will operate over a wide voltage range (typ 10-32vdc), or some are forced to use 24vdc to 12vdc converters, and then deal with RFI mitigation / elimination...

This doesn't apply to many "radios", as many are not usually designed for multi-voltage use...so, you will need to spend more on commercial 24vdc radios...or spend more on high-current 24vdc to 12vdc converters, and deal with RFI issues...
This may also apply to autopilots...depends on brand and model...

FYI, as for radios....
--- 24vdc commercial VHF-DSC-FM radios are 3 - 4 times the cost of 12vdc consumer / yacht versions
--- 24vdc commercial MF/HF-DSC-SSB radios are 2 - 3 times the cost of 12vdc consumer / yacht versions

Using "12vdc electronics" (some will of course work from 10vdc to 32vdc) might seem inelegant, but is actually a good approach, rather than using "voltage converters" (especially those budget-priced models that produce a great deal of RFI!)

Okay, enough of my ramblings for now...

Fair winds.

John
Quote:
Originally Posted by ka4wja
Now, Clive...I'm sorry I did not understand that you were constructing a new boat....and I suspect others here were confused as well, with a title of "Switching from 12v to 24v" and writing this: I assumed you already had the boat and all equipment installed and were in fact switching from 12vdc to 24vdc....but, it appears that I was incorrect...opps..

However, this makes it all the more important to answer the questions I posed earlier, as you are starting from scratch here!
Again, I may be wrong, but it appears to me that you are trying to make things work and getting a good deal of well-meaning advice/info from off-grid alternative energy sites?? Instead of taking a systems approach and designing your on-board energy system yourself, for your needs and your application??

I realize that your initial question was about starting batteries and whether you could "tap into" your 24vdc battery bank, from 12vdc....but, please have a look at what I wrote, 'cuz whether you believe me or not, it will help you...



Also, except for a 3000 watt inverter (mine is smaller) and the bread maker (I knead by hand), I have all equipment that you listed as "currently installed" and "intend to install", on my present 47' sloop, as well as a great deal more...but, as you'll see, you should design your energy system as just that, a "system", and all should work out well for you (whether someone goes 24vdc, or 12vdc & 24vdc, or even 12vdc only...they need a proper design, or they'll be chasing their tails and "solving problems", instead of enjoying life, sailing/cruising...)



To be clear, there are 3 major parts of your on-board energy system design, and they should be fully understood and analyzed, so that you can design your energy system that meets your specific needs...these parts are:

1) Energy Storage (i.e. batteries....not just the A/H rating, but also their charge and discharge profiles, which are gotten from the manufacturer)

If, as you wrote, you have two 150 A/H batteries in your house bank, assuming they are 12vdc batteries (as you talked about tapping into this bank to access 12vdc), then you have a 150 A/H house bank (at 24vdc....which is like a 300A/H house bank at 12vdc)....and this is not only quite small, but will be unable to support a 3000 watt inverter for very long, before running the batteries very low (a very deep discharge) and even at 24vdc, a 75 amp current draw from a 150 A/H house bank is going to pull the battery voltage down while this is being drawn (this is not the voltage drop in the wiring, but in the battery due to the high current versus the battery capacity...

{BTW, "150 A/H's" is a quite small capacity for a Group 4D (which would typically be 180 - 210 A/H), and quite large capacity for a Group 31 (which would typically be 100 - 130 A/H's)....I don't know what batteries you're spec'ing out....but assume you've gotten the info from the battery manufacturer....just want you to be sure of the capacity of your house bank...}

And as I and others have mentioned, the higher current draw from the bank above the "20-hour rate" (7.5amps) the lower the actual capacity....a 50% increase in current above the battery's "20-hour rate", the capacity is typically 90% of "rated", and doubling of the 20-hour rate (15 amps) current draw capacity is typically 80% of rated....

But FYI, even more important for those looking to drive large appliances, if you draw a significant current, say 75 amps (@24dvc) to run your microwave....just 20 minutes will use approx. 30% of your entire battery bank's capacity....and that's assuming you started with batteries at 100% charge (which might not be possible, unless you have sufficient solar array, to handle your on-board needs and charge the batteries up to 100%, as well), so typically figure you're starting from 90% capacity....

Sorry to ramble on, there is just so much here to write, and I don't have the time now to write more....



2) Energy Sources / Charge Sources (for most mid-seized sailboats, solar is of course primary, these days...but some in very windy environs still get some effective use from wind power, too...and some that do long passages get a great deal of energy from towed-water-gens....of course there is also diesel gensets....and lastly, main engine alternators...)



3) Energy Consumption / Energy Budget (this is simply the power used by all of the devices on-board, times the amount of hours per 24hr day each is used....although we've become accustomed to using "A/H's per day", this does introduce a problem if you're using two different voltages on-board, as well as confuse many who are used to doing this only with 12vdc...so using "watt-hours per day" would allow you to easily compile a detailed energy budget...)


And, don't forget that many of us are able to live energy self-sufficiently, as long as the sun shines every few days....
We design our systems to not just "get thru the day" / "get thru the night" / "until we charge up", no....rather we design the system to actually run seamlessly, so we aren't just looking to charge, but the system is always operating as a system, where we use energy and it is replaced...we typically don't think along the lines of "charging", but along the lines of just providing power as needed, when needed, and the system handles it just fine...

{fyi, with ~900 A/H of battery capacity, 500+ watts of solar, and lots of extra frig/freezer insulation, and attention to detail in energy system design, as long as the sun shines every few days (every 3 - 4 days when at sea, and every 4 - 5 days when at anchor) everything is just seamless, and no "charging" is thought about....if there are many days of cloudy weather at sea, I use a towed-water-gen to supplement...or even my genset, or even the main engine....and at anchor, more than 4 - 5 cloudy/overcast days means I will probably crank-up the genset, but that's only happened once in many years... }


While I've listed these 3 criteria (used for designing your on-board electrical / electronics systems), in the generally accepted order of importance for most cruising boats....this assumes that the owner/designer has already done a complete energy budget...so, if you have, that's good (and it would be cool if you'd post it), but in case you haven't please stop and take the time to do this now....it will save you a LOT of time/effort and probably save much frustration along the way!!


If you look at your energy system on-board, as a system....and design it as such, you'll be a very happy sailor, whether 12vdc, 24vdc, 32vdc, etc.....but most that take a hap-hazard / piece-meal approach tend to run into trouble, and have a good deal of frustration...

Just as examples, there are quite pricey (> $500,000 USD) new sailboats that the factory made little effort to design an efficient / effective energy system on-board....also, I've anchored near slick, new, fancy sailing yachts that have to run a genset or main engine to keep their frig/freezer cold, and/or just to make water, etc....and even seen brand-new boats with piss-poor 2awg wire used for battery wire, and windlass wiring, at 12vdc!!! As well as the ubiquitous unfortunate issue suffered by almost all modern cruising boats = lack of adequate frig/freezer insulation!!

(remember, except for those sailing in cold weather, your frig/freezer will be the largest energy consumer on-board, followed by autopilot in 2nd place.....then generally followed by chartplotter/radar/computers/navigation system, in 3rd place...)

Fyi, most find domestic hot water to be their Achilles....if they run their engine, which almost always has a cooling loop thru the hot water heater, they get LOTS of hot water, but then they're burning diesel, same for running a genset and 110vac/230vac heating elements....and the power drain of 800 watt to 1200 watt heating elements is just too much for many on-board energy systems...so some sort of solar assist (water heated by the sun, not by electricity) is a great approach, as is a DC heating element to be used when you have sufficient sun shine...



Again, sorry I misunderstood....I thought you were "switching from 12vdc to 24vdc", but I now see that you are building a new boat....so, please know that it is even more important to design your own energy system / electrical system, according to your needs/desires, not mine...
(just remember that burning diesel, and running an engine and/or genset, gets old...real fast!!)

And, except for large amount of domestic hot water, most mid-sized cruising boats are (or can easily be) set-up to be energy self-sufficient, even on 12vdc....but, even if you choose a 24vdc system, the key to success is to design a system...

The key is to design a system based on your specific energy storage capacity, your energy generation/charging, and your own energy budget...on your boat (not a house).....typically using large solar arrays and fairly sizable battery banks....'cuz silence is golden!...nobody wants to listen to an engine run, nor smell diesel exhaust...


Perhaps reading over the above, and the questions I asked earlier, and having a look at Maine Sail's site, etc., will show you how important taking a system approach is....learn about your batteries, charging sources, and make a complete energy budget...and you can easily design your energy system to best suit your on-board needs / application....not doing so is, in my opinion, a mistake...


Fair winds....and wishing you good luck..


John






2) If you don't mind me reiterating my observation here, you seem to be getting/taking a good deal of info/advice from those selling/using "off-grid home electrical systems", and other non-maritime / non-offshore sailing sources....rather than those for offshore sailboats....there are of course many differences between these...

Not-the-least-of-which are:

--- the need to eliminate any RFI sources on-board (which is usually a moot point for land-based systems);

--- the need to have adequate solar without any shading (usually difficult on-board, but quite easy on land);


--- the need to have enough battery capacity to sustain your energy needs during a few days of cloudy skies / storms, as well as handle some high-current loads with partially-charged batteries (which can be a problem in some areas on land, but usually not in the Australian outback...and of course many off-grid homes have other energy sources and can usually have adequate access to fossil-fuel supplies, that are non-existent at sea);

--- the relatively short wiring runs on-board are usually not detrimental for use of 12vdc systems, except for large items such as large (3000+ watt inverters, large motors run for long periods of time, etc.) where higher-voltage devices can be of importance...but both the typical short wiring runs and the fairly short periods of time these devices are usually used, can make the 23vdc advantage smaller than many realize (not that this is a mistake, but rather that you should understand the smaller advantage up front, when designing your energy system)





3) And, as for "24vdc radios"....the "12vdc" or "24vdc" nomenclature is "nominal battery voltage", meaning a "12vdc" radio is usually spec'd at 13.6vdc (or 13.8vdc) +/- 15%....and a "24vdc" radio is of course usually spec'd at 24vdc to 30vdc (some spec'd for 22vdc to 32vdc)...

BTW, even though it appears to still be a thing in Australia, and I think is still used by some Australian pleasure boaters (for fun!), I was sort of taking by surprise by your reference to CB radio....and, this is another example of where your information sources seem very odd to me....Maritime communications (both in Australia and worldwide) is well-established and afar cry from "CB Radio"..

Again, I'm looking at your boat and electrical system, from a "maritime" view rather than a "land" view, so I do see where/how we seem to be talking past each other, rather than to/with each other...
So...

So Clive, here are just some of the popular 24vdc marine radios (there are others)....enjoy!

BTW, for a 24vdc boat, here are my two favs...

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-vhf-radios/sailor-6222-vhf-dsc-class-a/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6320-mfhf-dsc-class-a-250w/



Icom
https://www.icom.co.jp/world/products/marine/mobile/gm600/index.html (note the GM600 is 24vdc and/or 12vdc when using the associated Icom PS-310 power supply / DC-DC converter)


https://www.icom.co.jp/world/products/marine/hf/gm800/



Furuno
https://www.furuno.com/en/products/radiotelephone/FM-8900S
https://www.furuno.com/files/Brochure/199/upload/FM-8900S.pdf


https://www.furuno.com/en/products/radiotelephone/FS-1575
https://www.furuno.com/en/products/radiotelephone/FS-2575
https://www.furuno.com/en/products/radiotelephone/FS-5075


https://www.furuno.com/files/Brochure/200/upload/fs-xx75.pdf



Sailor / Cobham
https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-vhf-radios/sailor-6222-vhf-dsc-class-a/ (like the Icom GM600, the Sailor 6222 is a 12vdc and/or 24vdc radio, as it includes their #6090 power supply / DC-DC converter)


https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6310-mfhf-dsc-class-a-150-w/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6320-mfhf-dsc-class-a-250w/

https://www.cobham.com/communications-and-connectivity/satcom/radio-communication-at-sea/maritime-mfhf-radios/sailor-6350-mfhf-dsc-class-a-500w/

https://www.indumarver.com/archivos/SAILOR/SAILOR_6300MFHF.pdf




JRC
https://jrc.am/products/jhs-770s-jhs-780d/features
https://jrc.am/products/jhs-770s-jhs-780d/specs

https://jrc.am/products/jss-2150-2250-2500/features
https://jrc.am/products/jss-2150-2250-2500/specs



SEA
http://www.seacomcorp.com/pdfs/SEA%207157_%200711.pdf (24vdc OR 12vdc model, you must specify which)


http://www.seacomcorp.com/pdfs/SEA_330.pdf (old design, non-DSC, non-GMDSS)



BTW, there are other / older design, non-DSC, "24vdc" radios, but none are actually recommended for maritime comms in the past 15 - 20 years....as well as some old/used radios, salvaged from old decommissioned ships, etc., but would certainly never recommend any of these either....


Hope this actually helps...

Fair winds.

John


P.S. I still have not found any Adler Barbour info recommending 24vdc vs. 12vdc....could you please provide a link to this??

Gotta go..

John