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Old 05-31-2014, 03:34 PM   #1
Wil
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Switch to 24V or 12/24V Hybrid Electrical System

We don't own a trawler right now, but that hasn't stopped some pretty extensive day-dreaming about what is the best energy independent (of land), quiet, and efficient power system possible.

The most interesting idea (not new) I've had so far is to switch from a purely 12v system to a 12/24v hybrid or even pure 24v system. Here's a really good synopsis I found of the advantages & drawbacks of the various electrical systems available: http://www.polardcmarine.com/downloa...r_Systems3.pdf.

I would get rid of the AC generator and go to a DC high output (say 300-400A) alternator driven by a small water-cooled diesel engine like this: Marine Micro-Cogen for recreational and commercial vessels (I'm using these links not to advertise this company, but because they have really helped me learn about this stuff). The small engine in place of the large AC generator allows more room for batteries and it's low hp means it will be working in its happy load range, as opposed to the AC generator loafing, wasting fuel, glazing its cylinders, and charging the house bank too slowly. Same for using the propulsion engine to charge the house bank (even with a big alternator on the propulsion engine)--much more efficient use of diesel fuel to charge the house bank, no underloading the engine.

A large 24v housebank (say, 1500 amps), solar panels (on the pilothouse roof of a KK42 for instance) and wind generator would extend the time intervals where the very quiet little DC generator would be needed. Paralleled 3000watt true sine-wave inverters would handle the 110v duties where necessary (e.g., you bought a cheaper 110v RV type fridge due to budget constraints). 24V reduces your wire size alot and really increases the efficiency of whatever appliances you might get (fridge, freezer, anchor winch, thruster, starter motor, etc.). You can always get local down-converters for say your 12v nav & communication equipment. Complicated?--perhaps, but I think a reliable system can be created where the various charging systems work harmoniously together. I'm sure it has been done before--there must be a lot of off-grid houses with this kind of setup.

A long intro to the question, but here it finally is: has anyone switched from a 12v to a 24v or 12/24v hybrid boat electrical system? I realize the capital outlay for this system is large (especially a 1500A, 24v AGM or TPPL housebank!), but even if it doesn't pay itself back in hard financial terms, the increased reliability, comfort, and quietness due to minimal generator runtime means alot imo. The goal is lots of power with maximized quiet times.....

Feasible? Not even?

Rgds,
Wil
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Old 05-31-2014, 04:18 PM   #2
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No, haven't switched out, it get very expensive, but have given it a bunch of thought, since as you will see I became master of many voltages (or should I say, they of me!) The Hatt is a 32 volt boat; I left all the baseline stuff that way (starters, alternators, DC freshwater pump, bilge pumps, DC lights, to name some majors), used 12 volt converters for stuff like electronics. The came to me also with a 24v thruster powered by two 8ds, a 12v started generator. When I added the inverter and its bank, went with 24v for a variety of reasons. But the basic thing is, I never felt it made sense to change anything for the sake of change. I promised myself the next boat would ideally all be 24 volt, but changing stuff out for the sake of doing it makes no economic or use-of-time-sense.

Some people advocate an approach similar to what you are proposing, I like the idea of a DC generator. Since you are in the study and theoretical mode. Let me give you a couple more sources: first, despite an awfully formatted web site, very dense with information and quite knowledgeable:

ZRD Electric Designer OEM - Your Source for DC Generator, Alt, ...

But first, get yourself a copy of Nigel Calder's "Boatowner's Mechanical and Electrical Manual". You'll need it when you get a boat and in the meantime it will educate you about all this stuff and more in easy to read and very thorough fashion.

Good reading!
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Old 05-31-2014, 05:17 PM   #3
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Unless you are trying to drive your boat with electricity, then there isn't anything you can't do in 120 VAC and 12VDC with a small AC genset, a reasonable size battery bank- say 400 AH and a 2,000 watt inverter/100 amp charger.

Your DC wiring will be bigger than a 24V system, but there are really only two big amp consumers: the starter and the inverter. All else is 6 gauge or smaller.

And this system is the cheapest and easiest to make work. No DC/DC converters or changing out DC motors to work with 24V. Even solar panels can easily be used with 12V. Yes it takes a bigger amp controller and a size or two bigger wire, but the cost is small compared to all of the things you have to do to work with a 24/12V DC system.

And you have AC to drive your A/C.

Dreaming is fun, but practically and cost effectively it doesn't make sense to have a DC only system with 24/12 V.

David
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Old 05-31-2014, 05:20 PM   #4
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George, I don't believe in change for its own sake either. It does seem to me that the advantages to be gained by 24v are substantial, though really expensive. Probably the only thing I would actually do early with my boat is convert to a DC generator, inverters, and more batteries--just don't like the sound of an AC generator running every time I need to cook (that will probably be propane anyhow, though diesel stoves are getting better Wallas Heater | Boat | Stoves | Cooking Equipment | ScanMarineUSA.com | Wallas Heater | Boat | Stoves | Cooking Equipment | ScanMarineUSA.com), play the stereo, or microwave something.

I do indeed have a copy of Calder's book, it has been the starting point several times on questions that came up. And thanks for the ZRD website, good stuff that, it will be great reading fun.

Cheers,
Wil
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Old 05-31-2014, 05:34 PM   #5
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Hi Will,

My N47 is a 24 Volt Boat with a large house bank ( 8 8d AGM's ). The only real disadvantage is that it is sometimes more difficult to find 24volt parts when something breaks. That just means it's prudent to carry spare 24volt pumps and other parts that might be hard to find.

I do have to maintain a small 12V bus for some of the navigation gear and the Wallas Furnaces, but most modern navigation equipment is happy running on 24 volts.
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Old 05-31-2014, 05:58 PM   #6
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We are also a 24 volt boat and do carry a spare 24 volt water pump but I'd carry a spare freshwater pump anyway even if it was 12 volts. My pilothouse and flying bridge are hybrids just because of the electronics. I have a small breaker panel just for the 12 volt stuff.

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Old 05-31-2014, 06:08 PM   #7
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Well David, I guess that's a vote for "Not Even?". I should have been clearer in the premise: I don't like AC and would rather not have it on my boat (except of course in sine wave inverter form where AC is needed) if DC will fulfill the power requirement. We'll agree to disagree on that one.

Battery, inverter, and DC charging (incl. wind, solar) & regulating technology is getting to the point (and closer to the price point) where it is feasible. 12v is inherently less efficient and reliable than 24v in every way. For example, the same difference 6v starter motors were to 12v starter motors.

An advantage to the 12/24v hybrid system is you can run your electronics off the 12v bank and so keep all noise out of their power, as the charging happens in the 24v bank. No DC converters needed.

Naysayers give valuable input, but I would really like to hear from anyone who has actually done it partially (thanks George) or fully and their thoughts on the process. Interesting ideas on how it could be done, rather than 'no, don't' do it, and stop dreaming about it too'. Perhaps it's still just too new-fangled an idea....but I don't think so. The systems on Steve Dashew's boats come to mind, though that is a whole different category of bucks. Think Dashew on a small scale .

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Old 05-31-2014, 06:17 PM   #8
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Scott and Dave, yeh, 24v spares make perfect sense due to their (I'd guess) relative scarcity. Have you guys looked into the cost of things like 24v fridges or freezers? Is there such a thing as a 24v say RV fridge that would get you by budget-wise until you could buy proper, super-stud, marine 24v cooling units?

Rgds,
Wil
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Old 05-31-2014, 06:27 PM   #9
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Scott, you have Wallas furnaces--niiice. I went to I think it was Scan Marine on Lake Union and looked at their Wallas furnaces and stoves. Nice quiet stuff, though the diesel stoves need more development. And the N47 is the boat I'd really like to have, though the KK42 I eventually find will do nicely.

Anyhow, how do you charge your large 24v house bank? 8x8D AGMs, you're pushing towards 2000A for a house bank and can just pour flat out amps into those suckers! How do you care and feed them?
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Old 05-31-2014, 06:33 PM   #10
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I have run 12/24/36 volt boats and for boats under 65 feet or and see no real advantage to going to any one or the other system.

If the boat comes that way...great...but retrofitting one to a different voltage...you would have to know something I don't and having been a pro captain for a good number of years.

Worked in marine electronics as an installer for 5 years and currently work on many different size and voltage boats up to 65 feet...just don't see the advantage of switching....new build is one thing... but not retro.
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Old 05-31-2014, 07:00 PM   #11
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psneeld, Ok, that's experience talking. And I am a newbie at this.

I want to increase my 12v house bank anyhow so that would be a sunk cost. If I plan them correctly, could I convert the same bank from 12v parallel to 24v series-parallel configuration? I can use the same wiring already present in the boat, it will unload it alot, maybe not such an advantage.

It seems to me that the major expense would be converting the various appliances (fridge, anchor winch, etc.) and charger (DC generator, large frame engine-mounted alternator). Some of these could be done piecemeal, if a hybrid 12/24v system is used during the conversion process.

The boat I'm looking at has a hydraulic thruster and I would want to convert the anchor winch to hydraulic since most of the plumbing already exists. The fridge they have now wastes too much space so I would want to change that anyhow.

It sounds like you think 24v vs. 12v is a good idea ("....new build is one thing... but not retro."). What in particular makes the retrofit not feasible in your opinion?
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Old 05-31-2014, 07:09 PM   #12
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Ok, breaker panels just came to mind.....is that the big one, or is there other too.
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Old 05-31-2014, 07:10 PM   #13
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Buying or replacing things that can run on the existing system that cost more or just don't need replacing unless the switch have kept me from switching.

Look...at some point arguing over a couple hundred, even thousand dollars to get things the way you want is peanuts in boat ownership...maybe I missed it...but what makes you think the "overall" system has to be switched. Many run a 24V thruster yet have a 12V boat...not a big deal...just not sure why you see this bg need to switch from the norm as has been said before...plenty of boaters have lived with 12V for a ong time with the same needs you have described....

If you want it...go for it...but I haven't ever seen the need to switch...but I would probably go 24V if a total rebuild. Why...why do I like bourbon over scotch???? Probably the same scientific reason for switching voltage...none....
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Old 05-31-2014, 07:41 PM   #14
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I had my boat built with 24 V but not a simple task. We found several things that just don't come 24v and had to put in multiple 24-12 converters a PITA. Some advantages of 24v are in wire size and ability to send power further from source with less lost. Good for thrusters and starting motors. A mixed bag.
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Old 05-31-2014, 07:45 PM   #15
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psneeld,
Fair enough. I advocate the same reasons that car manufacturers went to 12v from 6v systems, why some boat manufacturers build 24v systems in smaller boats. More efficiency, reliability, and power, less heat and voltage drops. I suggest that the 12v 'norm' will eventually go the same route 6v systems did, and for the same reasons.

What I trying to do is explore the possibilities. And advocating the 24v position. That doesn't mean I'll do it. I want to find out the specific pros and cons to each system. It sounds as if you like 24v, just don't want to make any redundant expenditures. Perhaps a 12v/24v system would alleviate those legitimate redundant expenditure issues, perhaps it's just too much bother to undertake. That might be where I come out on this too.

Appreciate the opinion and input, have a good day.
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Old 05-31-2014, 07:46 PM   #16
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The fridge they have now wastes too much space so I would want to change that anyhow.
How do you reach that conclusion?
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Old 05-31-2014, 07:59 PM   #17
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How do you reach that conclusion?
The owner installed a separate icemaker (a good thing) but that left a large unused space right next to the fridge. I will look into finding a fridge that fills the space more and have an icemaker onboard as well. Don't know if there is such a thing. It's all theoretical anyhow, I don't own the boat yet.
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Old 05-31-2014, 08:04 PM   #18
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We found several things that just don't come 24v and had to put in multiple 24-12 converters a PITA......A mixed bag.
I can see how that would be a pita. Lack of 24v appliances and hardware will surely put a damper on 24v system evolution.

What were the things that didn't come in 24v form?
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Old 05-31-2014, 08:11 PM   #19
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Not sure about the PNW, but out east here no issues sourcing 32 volt stuff, let alone 24.
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Old 05-31-2014, 08:45 PM   #20
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psneeld,
Fair enough. I advocate the same reasons that car manufacturers went to 12v from 6v systems, why some boat manufacturers build 24v systems in smaller boats. More efficiency, reliability, and power, less heat and voltage drops. I suggest that the 12v 'norm' will eventually go the same route 6v systems did, and for the same reasons.

What I trying to do is explore the possibilities. And advocating the 24v position. That doesn't mean I'll do it. I want to find out the specific pros and cons to each system. It sounds as if you like 24v, just don't want to make any redundant expenditures. Perhaps a 12v/24v system would alleviate those legitimate redundant expenditure issues, perhaps it's just too much bother to undertake. That might be where I come out on this too.

Appreciate the opinion and input, have a good day.
Please explain to me where a properly designed 12V system lacks any of these except needing heavier wiring????
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