DC Generator - The Smart Way to Go

[ColdEH]

Originally Posted by Dockhead

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.

Hey Dockhead , isn't your Kohler 6.5KW a yanmar diesel. My diesel engine was once a Kohler, an 8Kw , but don't they use Yanmars in all of them ??

Regards

[Cheechako]

Originally Posted by 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!

Yeah.. those old Yanmar 1 cyl horizontals were wobbling like they wanted out of the boat! I didnt find that with the Kubota horizontal. (as a generator) One nice thing about a DC gen (if it fits your needs) is you can run it fast for the first 15-20 minutes of high amp output and then back off to a low rpm sweet spot while in the lower ampoutput mode. AT that point you can hear the water gurgling out the transom more then the engine!

[Zach]

Originally Posted by Cheechako

Yeah.. those old Yanmar 1 cyl horizontals were wobbling like they wanted out of the boat! I didnt find that with the Kubota horizontal. (as a generator) One nice thing about a DC gen (if it fits your needs) is you can run it fast for the first 15-20 minutes of high amp output and then back off to a low rpm sweet spot while in the lower ampoutput mode. AT that point you can hear the water gurgling out the transom more then the engine!

What series Kubota were you using? I'd be curious to hear more.

Zach

[Dan316]

Originally Posted by typhoon

Started with a three cylinder Yanmar with a hundred hrs on it, that came off a Kohler genset . The electrical component was wired incorrectly and blew the windings , so I bought the engine from the Kohler installer. The engine idles at 1500 rpm no load and 1800 under load. Has a built in governor that controls this. So it is essential to use an engine from a generator

I am attaching a Eco-tech alternator to the crank via a lovejoy connection, above that will be a Hydracell D10 pump for my watermaker . This will be driven by an electric twin Vbelt clutch off of the same output shaft that the the alternator is connected to . Mantenance will be nearly nothing, the pump is only running at 30% of its capacity and the Hydra cell pumps last forever. The double belt is overkill as the pump will only draw around 2.5 HP. The alternator will draw around 8 hp but there are no belts so no side loads to worry about . This will load up the Yanmar to around 80% just were they like it for maximum life and fuel economy.

So the height will be a little higher then your stock 8 kw genset , but not by much . Looks like I will have the room. I am building a sound proof box around it and using Glacier Bays Ultra Db sound deadener in the box . Also using a gensep muffler that seperates the water from the exhaust so you don't get that splashing outside the boat when your generator is running . All this will give me 255 amps of charging power and 40 gallons of water with one hour of running.

I can't really understand why you would have an AC generator on a small sailboat. As small, I mean anything under 75 feet , bigger then that and you just leave the ac generator on all the time. But us, without deep pockets, have to conserve our energy and our diesel. So that means storing your energy in batteries .

So I ask, why use an AC generator to make power then change it to dc to charge your batteries, its nuts! And to just fire up a big genset to make toast? Thats nuts too. So that means you should have a very good inverter on board something like a Victron or a Mastervolt . Leave that on all the time for your AC power , good ones use nothing at idle, and draw all your power from your batteries. You should have at least 1000 ah of batteries so they can handle the high current charging. Get that power back in there as fast as you can so you don't have to run the engine for very long.

So again it turns out the smart thing to do with a genset is to optimize it to make as much dc power as you can, with every hp the engine has, and full use of the power per dollar of diesel fuel you use.

But try to find a powerful DC generator. No such thing.

So this was my solution

Update..... Glacier Bay does not sell Ultra db any more, I have to find a new source, any ideas?

Regards

1. There are massive DC generators, one is sold by a hybrid boat company.
http://electroprop.com/products/generators/
2. DC only makes sense if you never use a large AC unit like we use on our 50'
3. having solar for light loads and battery top off, is the best solution for small loads.
4. a super small (200 watt) wind power unit is great secondary for cloudy days.

So combining a AC small >5KW generator, 500+ watts of solar, 200 watt wind, and 1000AH bank. This is the best way to go. forget the DC generator.

[Cheechako]

Originally Posted by Zach

What series Kubota were you using? I'd be curious to hear more.

Zach

I built two with the little 5 hp EL-300AR "Arrow" engine. (Designed to power those road signs with all the light bulbs on them and the flashing/sweeping arrow.)
My buddy built one out of the fancier 7?hp version of the same engine. Bigger flywheel and built in fuel tank etc.
There used to be no problem finding a bolt on heat exchanger that took the place of the built on radiator and heat exchanger module. (Stock engine is air cooled heat exchanger.) Cant remember but I think the 6hp engine weighed about 80 lbs.
I used an aircraft vernier speed control that made it easy to adjust the rpm just right.
Here s alink to the long workshop manual: http://www.paclite-equip.com/pdf/SAV...p%20Manual.pdf

[SV THIRD DAY]

Why in the world would you want all that claptrap when you can buy a Honda 2000 generator for $950 with free shipping and then run a 75A battery charger with it...or AC power devices directly? The KISS principal Wins out!

I've been down this loser road folks.
Back in 2007, I set-up the 6Hp Kubota single cylnder diesel with a water maker pump and a 140A alternator attached. There is a REASON I left that POS on the old boat and didn't bring it to the new boat!

As good as it sounds...it's a PITA and I have now helped about 6 people abandon their Aquamarine water maker/generator that uses this 6Hp Kubota approach in favor of a Honda 2000, battery charger, and 1.0Hp water maker pump.

[Cheechako]

I strongly disagree with you, but with the reliability and etc of the Hondas and similar gens now it is a good point. Problem is... you cant leave it in your lazzarette permanently and run it like a Kubota... and you have the gas fume issue. But yeah.. it's an option. I think many people try to for too much... a 100 amp alternator is great and a lot less trouble than 150 amps on a little 5 hp diesel.
If you've helped 6 people abandon their Aquamarines... well... I've never even seen 6 people with one! You must have hit the motherlode of Aquamarines!

[SV THIRD DAY]

Originally Posted by Cheechako

I think many people try to for too much... a 100 amp alternator is great and a lot less trouble than 150 amps on a little 5 hp diesel.

The 5Hp Kubota can't run a 100A alternator AND a 4.2GPM water maker pump at the same time, the banger will over heat. You first have to run the alternator until the load output trails off then you can turn on the water maker pump.

Originally Posted by Cheechako

If you've helped 6 people abandon their Aquamarines... well... I've never even seen 6 people with one! You must have hit the mother lode of Aquamarines!

Aquamarine, Inc -
Aquamarine being in Seattle, WA and me being on the west coast also in the water maker business, I'm the guy they call when they have had enough of the teeth rattling Kubota. It was once a pretty popular all in one idea. Heck, I was sucked into it after all because having gas aboard was going to kill me I was told and thought, somehow I forgot about my outboard engine and gas can strapped to the rail for it. But then I got out cruising and looked around the anchorages and Sha-zam more people had a Honda 2000 on deck than had Diesel Generators in Mexico!


Run the price difference of the Honda/Battery Charger approach and the decision becomes even easier I think. No problem with disagreeing with me...heck I disagree with myself all the time.

[Zach]

For me the appeal is the generator head on the diesel can be a welding generator head, dive compressor, or crash pump with an RC Plath style power take off. I suppose I've been working around work boats longer than I ought, given that setup makes sense...


Zach

[SV THIRD DAY]

I think you nailed it Zach....
In a situation like this the Kubota approach (at least to me) makes total sense.
It's the idea of strapping a 100A alternator and perhaps water maker pump on it where the complexity I think outweights the positives.

[Dan316]

Honda engines, the blight of many a nice quiet anchorage.
I want to knock them all into the drink.
Nothing more annoying then a honda revving its nuts and bolts off to run an AC or water heater. Further, I carry only a tiny can of gasoline, pre-mix, for my outboard. not enough for a few weeks. I want to see you out starting your honda in a storm cell.

[Nicholson58]

Originally Posted by typhoon

Started with a three cylinder Yanmar with a hundred hrs on it, that came off a Kohler genset . The electrical component was wired incorrectly and blew the windings , so I bought the engine from the Kohler installer. The engine idles at 1500 rpm no load and 1800 under load. Has a built in governor that controls this. So it is essential to use an engine from a generator

I am attaching a Eco-tech alternator to the crank via a lovejoy connection, above that will be a Hydracell D10 pump for my watermaker . This will be driven by an electric twin Vbelt clutch off of the same output shaft that the the alternator is connected to . Mantenance will be nearly nothing, the pump is only running at 30% of its capacity and the Hydra cell pumps last forever. The double belt is overkill as the pump will only draw around 2.5 HP. The alternator will draw around 8 hp but there are no belts so no side loads to worry about . This will load up the Yanmar to around 80% just were they like it for maximum life and fuel economy.

So the height will be a little higher then your stock 8 kw genset , but not by much . Looks like I will have the room. I am building a sound proof box around it and using Glacier Bays Ultra Db sound deadener in the box . Also using a gensep muffler that seperates the water from the exhaust so you don't get that splashing outside the boat when your generator is running . All this will give me 255 amps of charging power and 40 gallons of water with one hour of running.

I can't really understand why you would have an AC generator on a small sailboat. As small, I mean anything under 75 feet , bigger then that and you just leave the ac generator on all the time. But us, without deep pockets, have to conserve our energy and our diesel. So that means storing your energy in batteries .

So I ask, why use an AC generator to make power then change it to dc to charge your batteries, its nuts! And to just fire up a big genset to make toast? Thats nuts too. So that means you should have a very good inverter on board something like a Victron or a Mastervolt . Leave that on all the time for your AC power , good ones use nothing at idle, and draw all your power from your batteries. You should have at least 1000 ah of batteries so they can handle the high current charging. Get that power back in there as fast as you can so you don't have to run the engine for very long.

So again it turns out the smart thing to do with a genset is to optimize it to make as much dc power as you can, with every hp the engine has, and full use of the power per dollar of diesel fuel you use.

But try to find a powerful DC generator. No such thing.

So this was my solution

Update..... Glacier Bay does not sell Ultra db any more, I have to find a new source, any ideas?

Regards

New to the thread so there is a lot of discussion following, but I am a PE. I read that you are focused on efficiency. I see a lost of good things in your plan. Suggest you consider that V-belts are only about 85 % efficient in power transmission. Timing belts are 97%. Cost is a bit higher but the reliability is great. I use Panther belts in my business.

[Dan316]

Originally Posted by Nicholson58

Suggest you consider that V-belts are only about 85 % efficient in power transmission. Timing belts are 97%. Cost is a bit higher but the reliability is great. I use Panther belts in my business.

If that is a fact, that may be why phasor uses a timing belt on my generator.
Phasor Marine Generators LP1-3.5KW

[Andrew Troup]

Originally Posted by Dan316

Honda engines, the blight of many a nice quiet anchorage.
I want to knock them all into the drink.
Nothing more annoying then a honda revving its nuts and bolts off to run an AC or water heater. Further, I carry only a tiny can of gasoline, pre-mix, for my outboard. not enough for a few weeks. I want to see you out starting your honda in a storm cell.

Amen on all counts. People put em aft and sleep up forrard. "Can't hear a thing"

Yeah, right ...

Trouble is the sound travels downwind, over water, for what seems like miles.

[SV THIRD DAY]

Originally Posted by Dan316

I want to see you out starting your honda in a storm cell.

Oh sure, HondaHaters are out there, but how long are the storm cells you have been in? There is this technology called an Engine and Alternator to make power in conditions you can't use the trusty Honda. If you are anchored close enought to be annyed by a Honda 2000...then it's time for you to move...you anchored too close...