Switch to 24V or 12/24V Hybrid Electrical System

[Wil]

As an aside, the best change I made on my boat was switcihing my 120v fridge and freezer for 12v and adding four 110w solar panels to my pilot house roof. Yes, within the week, I will post the details)

Hooobaby, I reeeally hope you do. That sounds interesting as hell.

 

[Wil]

Oh, I thought we were explaining why that person doesn't exist, so don't hold your breath waiting.

So don't wonder if it has happened, and don't ask if anyone has done it then you dummy....

 

[Wil]

Ok, the thread is petering out, time to fall back and punt. Enjoyed the heck out of this spirited conversation and am happy that it has not deteriorated into name-calling, as happens in lots of chat rooms on lots of subjects.

Learned that 24v might not have enough efficiency, power, and cooler-running advantages to make a conversion worthwhile; that bigger boats use it for its smaller size, power, voltage loss and perhaps other unnamed advantages. Learned that there is a dearth of 24v components on the market and that the dearth of 24v components is for those living on another planet. Learned that perhaps the main reason that the switch to 24v in smaller boats hasn't happened is because the manufacturers have been making 12v for a long time, and it would be a risk to make more and thus cheaper 24v stuff because there wouldn't be a demand for it. That only slightly larger boats use it (e.g., N47). That the efficiency (or cooler running or none) gains aren't worth it. That it would be a good idea in a new build but not as a retrofit. We're all happy for the most part with our 12v stuff, why rock the boat. Fair enough.

The theme about lack of economic sense for the conversion started early on, and I got it. Should I accept that answer on its own and pipe down? No. I think I advocated 24v too passionately. It got everyone involved in the discussion of 12v vs. 24v. I wanted to know if anyone had done it, and was surprised at the 'No, and don't dream about it either because you're a newbie, and that's what newbies do' theme that cropped up. That probably is what spurred me to over-defend 24v. I am a newbie--who likes to learn through the thought experiment process as I said a ton of times. Looked around on TF and didn't come across such a discussion (maybe missed it), so started one. The final answer appears to be 'no one has done it, and for good reason'. Got it.

Ok, the reason for the punt. Asked other questions, didn't get answers, sure would like to hear back.

I asked eyeschulman(#18),
asked twistedtree (#27),
asked peterb(#36),
asked FF(#37, #49),
asked Cathy and David(#51) Ski says the starters
asked(#47) Maybe nobody on this list has done it. Maybe nobody on the planet has done it.

Maybe I missed answers to these questions in all the hoo-rah somewhere. Have lots to think about, really like that mucho.

Regards,
Wil

 

[twistedtree]

twistedtree,
Had a look at your blog and really enjoyed the Watermakers and Shore Power Conversion sections. I want to put a watermaker on 'my' boat and the Spectra is now on my short list.

Glad you found the blog helpful/enjoyable.

Is your charging system set up so that both engine alternators can dump into your house bank?

Yes and No. The big alternator (190A) goes to the house bank, and the smaller on (85A) goes to the Starter bank, so on first blush they are separate. However there are parallel switches that allow the banks to be combined which would also combine the charge current. I'm contemplating rewiring so both alternators charge the house bank, and using an electronic charger to top up the start bank, but it's only a thought at this point. I just expect the start bank to recharge quickly leaving me with an underutilized 85A alternator.

What other house bank recharge system(s) do you have?

The house bank can also be charged via shore power or generator power using dual Outback inverters in charge mode, plus a 100A Victron charger. The total is 260A. Also, in a pinch, the house bank could be charged via the wing or generator alternators, again by paralleling battery banks.

Do you carry alot of 24v spares?

I'm sorting through spares now and have list that's many pages long. I'm doing it in two waves. This first will be for roughly our first year of cruising where we won't be anywhere more remote than Alaska. Then the second wave will be before we cross the Pacific and will add a bunch more parts.

As for 24V spares, there actually aren't that many now that you mention it. On my boat a lot of things are AC powered where on a smaller boat (like our Grand Banks) then are DC powered. Galley, head, engine room, laz, etc. fans are all AC and I am stocking one of each type used (3 types in total). Refrigeration is all AC as well as all the water pumping. I think the big 24DC items, other than the various engine controls, are lights and electronics. I'm carrying spare bulbs and the electronics are set up to be either redundant or I carry a spare, but it's mostly redundant. But now I'll need to go through the boat with this in mind and check, so I'm glad you asked.

If your refrigeration is 24v, is it hard to come by?

Are other 24v appliances you might have hard to come by?

No, refrigeration is all AC.

The water maker is a significant DC appliance, and one that's important to keep running. I'll carry a set of spares, but haven't made that list yet.

Interestingly, one of the boats biggest vulnerability is the 12V DC system that is derived from the 24V system. It's just as you contemplate for yourself. The 12V system powers all the radios, the navigation computer, the horn, the propane control, and the NMEA 2000 bus. If I lose 12V, I'm screwed. Needless to say, I'm carrying a spare power converter.

 

[psneeld]

#47 ..... and how many are on 'pure' 24v or higher (just the DC side) boats? Is there such a thing? Are they all 12/24v+ combos with a very substantial amount (half or more?) of the electrical items being 12v?

It's hard for someone to say they did it if there aren't any...so far you DO have your answer to that or the people out there that have done it aren't here or going to answer.

Every boat I have ever been on and that's probably more than most people can say (probably not everyone) due to my employment in the marine business for 15 years and living aboard for a good chunk too...in 3 active boating areas...

In my experience, every boat that had 24 or 36 volt systems also had a 12 volt system. The bigger the boat, yes more 24 volt appliances/systems but only in a small range...say from mid 40's (though there are smaller) to the upper 50's. After that much of the equipment is 120V because one of the 2 generators on boars are always running when underway. There are still 12v and 24 or 36 volt systems aboard...usually electronics 12v and engines 24 /36 volt.

 

[BruceK]

... the only car I remember with a 6v system was early VW beetles, and they had huge issues getting bright enough lights, so gave in to 12v in the end...

The only safe 6v VW Beetle at night was one preceded by a man with a candle. Maybe some early GM Holden 215 series cars were 6v.
I enjoy this thread having owned both 12v and 24v boats, it seems to be developing a touch of the Monty Python "Argument" sketch.

 

[Wil]

I enjoy this thread having owned both 12v and 24v boats, it seems to be developing a touch of the Monty Python "Argument" sketch.

Heh, got that right:

 

[Wil]

Thanks twisted & ps , hope to hear more from the other guys too.

 

[Ski in NC]

Just another tidbit: When working around 24, 32 and 36Vdc and saltwater, you can get one heck of a shock (ask me how I know). 12V, not so much, just a tingle. I wonder if that factors in to this. Saltwater on skin really increases conductivity.

 

[FF]

What make/model of fridge and freezer do you have?

Dometic Propane , mounted in a custom cabinet (well OK a plywood box) standing outside on a self draining cockpit.

The unit is 40 or more years old operates flawlessly and is a delight when we row out after a weeks absence to have cold beer and stiff ice cream ready.

For folks changing over I recommend the Serville , built for the Amish with far thicker insulation than my old RV unit.

Installed in a well inside above the WL with a 2 in overboard drain could be a reasonable modification to most boats over 30 ft or so.

The Amish version has an inside light with D cell power.

Ice is made with std ice trays as in a dirt house.

Motion helps the propane fridge operate , what it doesnt like is a high angle of heel for hours on end , as on a sailboat .

Have a new boat on the drawing board (just need to win the lottery) that would have the Servelle mounted below , although the current cockpit location is great in the PM at snack & Brew time.

ON bus conversions a 12/24v system is not uncommon.

The 24V is used for engine start ,ans with usually a 250A or 300A alt the 4000W sine wave inverter is used for air cond on the road.

The rest of the coach uses a 75A Vannir for 12v house loads , lights et all.

75 A of 12V is usually enough for reasonable house loads,fans , FW pump, furnace ,,,,

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[Peter B]

Great answer with excellent detail and reasoning. Thank you. I got it, understand what you propose, and agree that's what I should do. I don't have the skills--yet--to do the analysis you speak of, that's what I was hoping someone on TF might have already done. It's along the lines of why I asked if anyone had already done a 24v conversion and what was the result.

Ah, Wil, one final point of refrigeration, coming back to a comment FF made. Yes, I agree the refrigeration is the power hog - or rather, was. Now however, these Danfoss compressor driven 12v (yeah, 12v) fridges and freezers are so damn efficient now it is no longer necessary to go propane or kero for refrigeration. When my eutectic system finally died, (not cheap to repair or replace, and not as good anyway unless on the move a lot even when working), I converted the well-insulated frig to 12v with a conversion pack by Waeco, and it runs beautifully. We can easily keep up with its demands on the pick, via solar, wind power, and the engine running on the move. however, for cooking I would still advocate propane for power frugality unless you also planned for heavy AC use, which I gather you want to avoid.

By the way. I totally agree with you re sometimes it being worthwhile to put up a theory or concept, just for the sake of examining it fully, even if it is ultimately only to prove why things took a different direction.
Another could well be why we drive on the left, as does the UK, NZ, Japan, and a few others, while the bulk of the world drives on the right, so why don't we change..? But that's a whole different and non-boating related issue.

 

[Peter B]

Heh, got that right:

Ahhhhh, that was a good laugh…
What happened to the good comedians like that. No-one these days seems to be able to get a laugh without resorting to swearing, smut, and sexual innuendo. There was not one swear word or smutty joke in all of that, and it had me really splitting my sides…we'll…figuratively speaking, of course. It would be really messy if everyone split their sides when they laughed, would it not..?

 

[twistedtree]

Back to the whole "efficiency" question, I don't think it's nearly as large a factor as one might think. Conceptually it's based on the fact that given a resistance (every wire has some level of resistance), the power loss varies as the square of the current. So twice the current, as in a 12V system vs a 24V system, means 4x the power loss.

But that's not really how it works out since wires are sized to limit the % voltage drop. You end up with fatter wires, which have less resistance, which counteracts the power loss. Fatter wires means more cost, and bigger motors like has been discussed relative to starter motors, but the power losses will be largely the same.

I think Wxx3 nailed the dominant reason for 12V, namely the massive 12V infrastructure that industry has built up, largely thanks to cars. 6V went away because it was too little for engine starters and headlights. 12V is just fine for cars and reasonably balances performance with wiring costs. That reasonable balance extends to most boats, and leverages the industrial 12V infrastructure. But as boats get bigger and the 12V loads grow, the cost of 12V starts to become a problem and 24V makes sense.

 

[psneeld]

For those with 12 v and another setup...be careful about wheelhouse electronics and only a converter setup.

I read this sage advice and have worked on commercial fishing boat electronics and have seen the "required by USCG 12 V separate battery"...

"Rather than using a converter, on a boat of reasonable size with real cruising ambitions, one should install a set of dedicated electronics batteries in the wheelhouse so that no matter what happens in the engine room or in 24V switchboards or subpanels, the wheelhouse will have a dependable supply of critical power in an emergency. That is how commercial vessels are fitted out and for good reason. All the converters in the world won't provide 12V from a flooded or burning engine room."

 

[Insequent]

I have a number of voltages on board. For DC I have 36V, 12V and 5V. For AC it is 230V and 110V.

First the AC. I bought the boat in Seattle, but have since brought it back to Australia. I retained some legacy 110 VAC equipment which will get largely be replaced over time, but mostly changed to become a 230 VAC boat during the refit. I can take either 110 VAC or 230 VAC shore power, and charge batteries via a Victron Phoenix charger that can accept an amazing range of voltage and frequency as input. I have a 230 VAC inverter, and can get still get 110 VAC when away from NA marina's via a large transformer, albeit this is at 50 Hz. The washer and dryer seem to run OK on 110VAC at just 50Hz, but they will soon be replaced now i have the boat home. The Uline icemaker runs with the 50Hz supply, but not particularly well. It is old, and the power supply spec may not be the main problem. I would prefer to replace it, but so far have not located a local replacement of the right dimensions. I am contemplating trying to fit a 230VAC/50Hz kit to it, but I could still end up with a poorly performing unit so that problem is deferred for now.

For refrigeration, the Norcold's in the galley and pilothouse are dual voltage, 12 VDC or 110 VAC, but the frequency spec is too tight to run on my transformer supplied AC. Norcold want 60 HZ +/- 1 Hz only. So they run on 12 VDC. Interestingly, the motor current draw is stated to be less when on 12 V, so overall power consumption is less when in 12 V mode. A plus, so this favours DC ahead of AC equipment, where it makes sense. Part of the reason I chose the Nick Jackson crane and Spectra watermaker is that they use 12 VDC and do not need any AC. Obviously washer, dryer and microwave are going to be AC.

My charging system has two other options as well as the 230VAC or 110VAC shore power. There is 1820W of solar capacity, which is delivered at 36V to the 2x Outback controllers, which are limited to 80 A each at 12 VDC. Voltage drop is typically the Achilles heel of solar installations as cable runs are difficult to keep short, and higher voltage panels help keep wire sizes down. The third charging system is the engine alternators - twin engines, and there is a single 200 A alternator on each engine. That's good, but it is a little scary having a 400 A fuse in the line as a result. To keep cable and fuse sizes down it is tempting to have 24 V engines, alternators and battery banks to avoid high amperage in the charger circuit as well as supplying the inverter. My house bank is largish at 1284 AH, and inverter is a 3000VA Quattro. With hindsight I would have gone for a larger house bank and next size up inverter.

But there are a lot of 12V loads, such as the refrigeration, which I would not be comfortable running via converters and I did not want to replace perfectly serviceable 12V items with 24V ones. It cost more than enough just for the materials that were necessary! This aspect is the 'con' for 24V temptation. Invariably there is a long list of 12V stuff.

Finally I have some 5V reticulation for WiFi Camera's and convenience for charging a bunch of handheld devices. They dont draw a lot of current, and having USB ports around the boat is the way of the future.

For an existing boat, even with an extensive refit I agree with folks above - stick with whatever it is already. In the hypothetical new-build scenario I might well go down the path of domestic AC appliances, like Twisted has elected. The range to choose from, lower cost and ease of replacement are big plusses. One downside to this is the inverter capacity then needs a substantial boost, and the overall system losses end up higher. There is a catch in inverter sizing too. They are invariably quoted as nnnn VA, not watts which is a lower number on a continuous basis, and have significantly lower performance with even modestly raised temperature. So you have to go really large, or have power management protocols that the crew can remember to keep on top of. With high output alternators, high charge-acceptance batteries (eg AGM) and a huge house bank this would be still Ok. If you have to have ballast then it might as well be LA batteries.

I would then run 24 V engines, alternators, inverter, house and start battery bank. Bow thruster and windlass would probably be hydraulic. Also, as noted above, have a small 12V bank for electronics, with a dedicated AC charger to it. Overall its quite inefficient to run a charger from inverter supplied AC, but loads would be low and it is a simple way to do it.

Apologies for such a long post......

 

[Wil]

Wow, wow, wow ! Absolutely awesome stuff gentlemen. This is the kinda stuff that I trust not just newbies would like to read about to get a stronger background in what the various power vs. efficiency (not just 12v vs. 24v with regard to efficiency) vs. comfort trade-offs are.

Suggest we all would like to hear from other owners what kinds of power they have onboard their boats and what advantages & disadvantages that power entails. Including speculation about what future power layouts you would like to have and why. Oh yeaah (wish TF had the Glass of Beer-Cheers smiley, put it here twice) I know I would.

Outstanding stuff, thanks.

 

[Wil]

Ahhhhh, that was a good laugh…
What happened to the good comedians like that. No-one these days seems to be able to get a laugh without resorting to swearing, smut, and sexual innuendo.

Holy smokes did you nail that one. I listen to most of the comedians out there for a few minutes and switch elsewhere--no imagination or intelligence. I still miss the heck out of Johnny Carson.

 

[Wil]

Ah, Wil, one final point of refrigeration, coming back to a comment FF made. Yes, I agree the refrigeration is the power hog - or rather, was. Now however, these Danfoss compressor driven 12v (yeah, 12v) fridges and freezers are so damn efficient now it is no longer necessary to go propane or kero for refrigeration. When my eutectic system finally died, (not cheap to repair or replace, and not as good anyway unless on the move a lot even when working), I converted the well-insulated frig to 12v with a conversion pack by Waeco, and it runs beautifully. We can easily keep up with its demands on the pick, via solar, wind power, and the engine running on the move. however, for cooking I would still advocate propane for power frugality unless you also planned for heavy AC use, which I gather you want to avoid.

Yes, I definitely want to go for propane cooking. That is some good news indeed there about the efficiency of Danfoss compressors . Was your eutectic system top-loading (so perhaps still is with the Danfoss)?

By the way. I totally agree with you re sometimes it being worthwhile to put up a theory or concept, just for the sake of examining it fully, even if it is ultimately only to prove why things took a different direction.

Pete, thanks for that, much appreciated.

 

[FF]

For folks that want electric refrigeration the newer smart 12V units are fine BUT its the size and insulation of the box that is the other half of the equation.
IF x number of BTU need to be removed , a 10% better compressor is fine , but a 75% lower BTU daily removal requirement is far better.

The Sun Frost have excellent insulation but do not fit the std RV or dirt house sized cutout in many boats. Pulling the windshield is a PIA way to get it aboard.

If efficiency is to be increased , folks may have to go back to building their own refrigeration chests.

6 inch freon blown urithane cuts the electric demand down , but the cost in lost volume ,,exterior size vs interior size.

Might be worth the effort for a world cruiser , where 90% of the cruise is at anchor.

Certainly its still the std for sailors.

For most power boat folks installing a factory made reefer will be the easy way out , and the propane is the only system that will go FOREVER with zero electric.

 

[refugio]

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.

Have you priced a hydraulic windlass? And I'm a bit boggled at a KK42 with a hydraulic thruster.

I have a dual 12v/24v configuration because my Volvo TMD100A is 24v. I don't have a thruster but do have a Kolestrand hydraulic windlass. Frankly, I don't have a single piece of 12v equipment that I would prefer in 24v.

 

[kulas44]

I dont understand the aversion to 120v ac power. Or a properly sized and used ac generator. Given the right sized house batt bank and right sized charger/inverter system it is every bit as efficient as a more expensive dc setup. All power generated by rotating magnets is a.c. Why convert it to d.c. (which is not free by the way) when it is more efficient to use an inverter to convert it to d.c. Another plus is that 120v wiring is MUCH smaller than 12 or 24 volt d.c. wiring. My trawler has a 2 hp Ideal windlass on the bow. Its 120v motor can run continuosly with no fear of overheating and has 10 gauge wire to it. It can be ran off of either inverter or the generator. It is more reliable than a dc powered windlass and WAY more powerfull. My water heater is 120v or main engine heated. My fridges/freezers are 120 volt dirt units. Washer/dryer are 120v. Lighting is all 12v. I can charge the house bank at 300 amps, make hot water and do laundry while loading the 15 kw gen reasonably well (read efficiently). In the summer the air conditioning load down here makes efficiency a moot point. We just run the gen and try to stay cool. I can run the 5000 btu air unit in the master with the inverters, so we dont have to run the gen all night. That seriously increases the charge time. If I boated up north the dc approach might make sense, but not down here. And, I dont really want to "camp" in a boat, just not my thing. My wife and I did spend 2 weeks camping in a tent and cooking over a camp fire on Kodiak Island a few years ago. It was great fun, but she didnt get eaten by a bear so I dont want to do it again.

 

[refugio]

It was great fun, but she didnt get eaten by a bear so I dont want to do it again.

To be clear, if the goal was to get her eaten by a bear, and that was accomplished, um why would you want to repeat? Or are you hypothesizing a subsequent wife who needed a similar fate?

 

[kulas44]

Just joking, bears are afraid of her, even Kodiac Brown bears I like camping, just not in my boat. Full air conditioning, microwave, etc. but still kinda power concerned. I dont like to run the gen unless neccessary, and then I like it loaded properly if possible.

 

[FF]

>I can charge the house bank at 300 amps.<

WOW , most batts are charged for long life at C/10 , so with a 300A charge you are charging a 3000AH bank that weighs about 3000lbs?

Way back when there were more universal motors (AC or DC) it was not uncommon to string 10 12V batts together and simply go all house for bulbs and electric toys.

A 60 cps vibrator would change the DC into AC with little loss, tho they had points so were amps sensitive.

Where air cond is required 24/7 noisemaker is the norm , but 1 gal an hour for fuel is $100 per day in money burn.

We live in FL ,( Winters only) and find if we can reduce the boat temperature to about water temperature , with a fan on , nothing else is required.

The coolest air is in the bilge on hot days , with a bit of work the bilge need not stink of diesel or engine.

 

[Insequent]

Putting 300 A into a battery bank is no big deal these days.

An advantage of AGM batteries is their charge acceptance rate. There are other advantages as well. Typically C/3 is the limit, but Odyssey batteries can take a higher charge rate.

I have a 1284 AH Odyssey house bank, made up of 6 x PC 1800-FT and total weight is 790#. I have seen my alternators feed in up to 360 A when the bank has been discharged a bit. The batteries could take higher inrush current if I had it available.

 

[Wil]

Came across this long, interesting article on DC Charging System Design: Duckworks - DC Charging System Design. It's DIY cruiser oriented, ABYC--what's that, small type with paragraphs repeated, but good food for thought imo. I made a cleaned up copy in Word, PM me if you want a copy. Hope you find it enjoyable.

 

[Wil]

Have you priced a hydraulic windlass?

No, I don't even own the boat yet, it's all speculation. Maybe instead I'll go with a 24v windlass, or a 110v windlass, or keep the 12v windlass, who the hell knows. Just want to get on the bloody thing and start living on it, seatrial & survey aren't until early July.

 

[Wil]

Putting 300 A into a battery bank is no big deal these days.

An advantage of AGM batteries is their charge acceptance rate. There are other advantages as well. Typically C/3 is the limit, but Odyssey batteries can take a higher charge rate.

I have a 1284 AH Odyssey house bank, made up of 6 x PC 1800-FT and total weight is 790#. I have seen my alternators feed in up to 360 A when the bank has been discharged a bit. The batteries could take higher inrush current if I had it available.

+1 . The article I posted goes into this pretty well.

 

[Billylll]

I have always felt Lifeline AGM's were by far the best. They can also be equalized if done carefully if they start to go into replacement mode.
Bill

 

[MYTraveler]

when I spec'ed my boat, I gave much thought to a 24v system. But since ease of maintenence/parts availability in remote foreign ports is critical to this boat's mission, I opted for a 12v system (thruster is 24). Carrying lots of extra spares is an alternative (the list is really extensive, if you get down to it), but I concluded that cost and on-going effort wasn't justified by really rather marginal benefits of a 24v system.