DC Generator - The Smart Way to Go

[Cheechako]

Originally Posted by goboatingnow

That horizontal kubota has a reputation for being very loud.

Dave

That info is not true. I've built two myself and my buddy built one. Just like any diesel, pick the sweet spot. If you use a waterlift muffler, you can hardly hear it run once you've backed off rpm after the initial 15-20 minutes of high amperage output. The whole unit weighs a littel over 100 lbs and will fit in a lazzarette. I also built a unit with a 2 cyl in line Kubota (13hp)and it was the noisiest of the bunch....

[Windseeker]

Interesting conversation. I've been reading Nigel Calder's book. That doesn't make me an expert – just dangerous. Very Dangerous. His argument is the the same as yours. Put on a generator if you want Air Conditioning. If you are on a larger yacht where Air or other AC loads will be running all the time, then AC generators make a lot of sense. Apparently, they do not like to run unloaded. I guess it tears them up. From my readings, if you have inductive AC loads, you have to oversize the generator to account for the high inrush current. The drawback is excess size, weight, fuel, etc. The benefit is pure sine waveform and no conversion losses or excessive cabling.


He talks about the inverter-based boat where a properly sized inverter and battery bank absorbs those peak spikes and you can size a DC generator for the nominal load. The DC generator can then be smaller and more efficient with variable speed technology. Fed into a Pure Sine Wave inverter and I think we have the best of both worlds.


That is my understanding of this after staying at a Holiday Inn Express last night. At least that is the direction I am headed. Comments?

[ColdEH]

Thanks for the thumbs up .

I actually never read Nigel Calder 's book. I have read many of his articals over the years.

Just seemed like the best way to manage power on board a small boat.

Im not giving up air conditioning complete . I plan on having two units on board, a 16000 BTU unit in the main cabin for those really crazy hot days at the dock when shore power is available to run it . A 12 volt 4000 BTU unit in the aft cabin for sweaty nights at anchor, when it is just unbearable.

Cruise N Comfort USA Marine Air Conditioning - Welcome

They make a 4000 BTU unit that takes 18 amps on low and 35 amps on hi. Close the head door and the door leading to the main cabin and it should cool down the small aft cabin area of a Hunter Passage 42 through the night , at least enough to get a non sweaty sleep . If I leave it on for 10 hours I will need to put back 180 amps into my batteries in the morning. And I won't have to listen to a generator pounding away all night . Not to mention the cost of the fuel and the hours put on the Yanmar .

Makes sense ?

Regards

[Cowboy Sailer]

I sometimes let my Honda 2000i run thru the night. If the only load it is running is the 40 amp battery charger it is so quiet that I can not hear it from the v-berth. The next morning the batteries are fully charged and I can turn it off. If I only use the built in fuel tank it will run out of fuel after midnight and I don't have to turn it off in the morning but the batteries are well charged.
That might be a good way to run the small air conditioner.

[foggysail]

My old Hunter 30 had a horizontal 12HP Yanmar, IT WAS HORRIBLE!!! Forget the power limitations, it was the vibrations. Everything seemed to resonant at low frequencies including interior doors, life lines (they vibrated at least 6" from peak to peak) and NOISE! Most of the noise was from vibration sources.

What a pig! I would never recommend a horizontal single cylinder engine for any boating purpose. There were enough of those things around that others might share their experience with them.

I later replaced that engine with a 2 cylinder Kubota (Universal) that was just great!

[Dockhead]

Originally Posted by typhoon

Thanks for the thumbs up .

I actually never read Nigel Calder 's book. I have read many of his articals over the years.

Just seemed like the best way to manage power on board a small boat.

Im not giving up air conditioning complete . I plan on having two units on board, a 16000 BTU unit in the main cabin for those really crazy hot days at the dock when shore power is available to run it . A 12 volt 4000 BTU unit in the aft cabin for sweaty nights at anchor, when it is just unbearable.

Cruise N Comfort USA Marine Air Conditioning - Welcome

They make a 4000 BTU unit that takes 18 amps on low and 35 amps on hi. Close the head door and the door leading to the main cabin and it should cool down the small aft cabin area of a Hunter Passage 42 through the night , at least enough to get a non sweaty sleep . If I leave it on for 10 hours I will need to put back 180 amps into my batteries in the morning. And I won't have to listen to a generator pounding away all night . Not to mention the cost of the fuel and the hours put on the Yanmar .

Makes sense ?

Regards

If I'm not mistaken, those units have small inverters built in. If someone has different information, I would be glad to be corrected.

If that is true, then there is unlikely to be any benefit compared to running a regular AC current air conditioning unit off your main inverter.

I don't like the idea of running a genset all night for air conditioning. I would be very happy to find some realistic battery-powered solution. But AFAIK it would take a lot of battery power, and would be hard on the batts Maybe a case some day for a huge LiIon battery bank -- if the prices ever come down.

[ColdEH]

Nope , the Cruise in comfort air conditioners are 12 volt .

Take a look.

Cruise N Comfort USA Marine Air Conditioning - Brochure

Regards

[swisscraft]

Originally Posted by typhoon

Thanks. Yep heading south , in about three years , will live aboard for as long as my body and wallet lets me . I want a freezer and cold drinks so solar won't cut it . plus if im in a little place that I want to stay for awhile it would be nice to have hot water. So I would have to run the engine or generator for that any way. The fuel will go . Hey the Yanmar burns a gallon an hour. If I run it for an hour every day, thats 4 bucks . Cheaper then being home thats for sure. More likely run it every second day, what will I do with all that water , hey maybe I could sell it to people on solar .

Can't make to many sacrifices, or the woman won't come .

Regards

Hi, not sure what you say with heading South. But as soon you enter the Caribbean you will not get a gallon diesel for 4 bucks, neither in the Bahamas. It will be much closer to 6 bucks. Still not to much per day, but 50% above planning....

PS: Like your project. But just to be clear: I run a freezer, have ice and make water - all from my 440 Watt of Solar over here....

[Dockhead]

Originally Posted by typhoon

Nope , the Cruise in comfort air conditioners are 12 volt .

Take a look.

Cruise N Comfort USA Marine Air Conditioning - Brochure

Regards

It nowhere says there that the compressor motors are native 12v. If they are -- then that's a very cool device. But all the ones I've ever seen (CruiseAir, Dometic, etc.) which run on 12v do have inside the unit a small inverter to supply AC power to the compressor motors. They typically use AC synchronous motors because, first of all, they are much cheaper, and secondly, small AC compressors with AC synchronous motors are mass produced.

If that unit has a DC brushless motor, that would be super cool -- because besides saving the inefficiency of inverting the power from 12v to 230v (or 110v), DC brushless motors are themselves more efficient.

But nowhere in the literature in the site you linked says that the compressor motors are native 12v. I would check before buying, if I were you. If they are like the Dometic 12v air conditioning units, I wouldn't bother -- I would just buy a regular AC aircon and wire it to your main inverter. Will be cheaper and more efficient, and plus better to run off shore power (a Dometic-type 12v aircon will have two inversion stages -- AC shorepower to DC via your battery charger, then DC back to AC inside the unit).

[downunder]

Originally Posted by Windseeker

Interesting conversation. I've been reading Nigel Calder's book. That doesn't make me an expert – just dangerous. Very Dangerous. His argument is the the same as yours. Put on a generator if you want Air Conditioning. If you are on a larger yacht where Air or other AC loads will be running all the time, then AC generators make a lot of sense. Apparently, they do not like to run unloaded. I guess it tears them up. From my readings, if you have inductive AC loads, you have to oversize the generator to account for the high inrush current. The drawback is excess size, weight, fuel, etc. The benefit is pure sine waveform and no conversion losses or excessive cabling.


He talks about the inverter-based boat where a properly sized inverter and battery bank absorbs those peak spikes and you can size a DC generator for the nominal load. The DC generator can then be smaller and more efficient with variable speed technology. Fed into a Pure Sine Wave inverter and I think we have the best of both worlds.


That is my understanding of this after staying at a Holiday Inn Express last night. At least that is the direction I am headed. Comments?

Check out the Vitron website. With the quattro inverter chargers you can get away with a smaller AC genset.

Quattro / 3kVA - 5kVA - 8kVA - 10kVA - Victron Energy

Cneck out the marine generator Test.
Marine Generator Test - Victron Energy

[Dockhead]

Originally Posted by downunder

Check out the Vitron website. With the quattro inverter chargers you can get away with a smaller AC genset.

Quattro / 3kVA - 5kVA - 8kVA - 10kVA - Victron Energy

Cneck out the marine generator Test.
Marine Generator Test - Victron Energy

Not just the Quattro, but also the Multiplus inverter/chargers. The MasterVolt inverter/chargers also have this function.

I have a Victron Multiplus and can confirm that this function works brilliantly. You can definitely get by with a smaller genset, which will be more efficient to run, cheaper, smaller, and you will keep it loaded better.

[OceanPlanet]

Indeed. We run the Victron Quattros and/or Multiplus (since both have load support) off the Genasun LiFePo4 banks and can run the A/C, water heaters, washer/dryers, cookers, whatever...without the genset on. Also allows running all those loads when on a small shore power source that could never support all those loads. The shore power is usually just dedicated to charging via a Victron Skylla charger.

[goboatingnow]

Having built a DC generator and ran it for a while, I now really think its a "outlier" solution. Buy a good quality AC genny and use it , The DC route is quirky, hard to maintain and ultimately does not allow the occasional use of high powered AC devices,

Dave

[FlyingCloud1937]

Well, I have been running my 160 lb 250 amp dc diesel charger for 2 years now. It is the perfect solution to my needs. My only AC loads are HW and battery charging. Since I have a DC diesel Charger I don't need AC for battery charging, that leaves me with HW, but since my DC diesel charger is also a co-gen that makes hot water as a by-product of charging my bank, than I don't need AS for HW either.

I run my gen for 2 hrs every other day while on the hook, it variable speed, I start it up when the bank is down 250 amp hrs, it burns 1.75 liters of diesel during the 2 run.

I can also use it as an inverter-gen with my Magnum inverter, up to 2800 watts out-put.

My Diesel DC gen

Lloyd

My generator mount.

[Dockhead]

Originally Posted by FlyingCloud1937

Well, I have been running my 160 lb 250 amp dc diesel charger for 2 years now. It is the perfect solution to my needs. My only AC loads are HW and battery charging. Since I have a DC diesel Charger I don't need AC for battery charging, that leaves me with HW, but since my DC diesel charger is also a co-gen that makes hot water as a by-product of charging my bank, than I don't need AS for HW either.

I run my gen for 2 hrs every other day while on the hook, it variable speed, I start it up when the bank is down 250 amp hrs, it burns 1.75 liters of diesel during the 2 run.

I can also use it as an inverter-gen with my Magnum inverter, up to 2800 watts out-put.

My Diesel DC gen

Lloyd

My generator mount.

That sounds good. I especially like the idea of the variable speed.

What I don't like is when these DC generators are based on one-cylinder Kubotas - wake the dead, and shake your boat apart.

I don't really see that there is so much to choose between DC and AC generators. DC generators are fine -- just invert whatever AC power you need. But AC generators are also fine -- just use a charger/inverter to produce DC power and charge your batts. I don't see what the big deal is.

For me, the most important thing about a genset is that the damned thing will be reliable, will be smooth, will be quiet. I will deal with whatever type of current it produces. I don't want to be futzing around with it. So the "gold standard" for me would be the little 4.5kW low speed three cylinder Northern Lights -- drool! I can't imagine what could be better than that. I would buy it whether it were DC, or AC, IF I were in the market.

I have a 6.5kW Kohler low speed, three cylinder, AC genset. It's -- well, ok. It's not so beautifully made as the Northern Lights, and Yanmar is, well, not Lugger. I've had some trouble with it. But it gets the job done -- it's very quiet, running at 1500 RPM, and having three cylinders, and living in a sound enclosure. A three cylinder engine running at 1500 rpm also has a sound which is not only quiet, it has a pleasant tone -- a relaxed hum, not like the hysterical scream of, say, a one-cylinder Fischer-Panda. I wouldn't trade it for something with a noisy, shaky one-lunger Kubota, to be honest.