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Old 02-09-2015, 08:24   #31
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Re: DC genset to power boat.

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Originally Posted by Sailor Doug View Post
Why not use a Honda inverter generator? It will run my smart charger and run hotter heater at the same time, cheap simple unless you require large AC amperage.


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Because you will die. Its a prime darwin award nomination.
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Old 09-09-2015, 05:48   #32
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Re: DC genset to power boat.

what about a cheap 2-3 kw ac 110/230 v gen with a powerfull 12v battery charger?
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Old 09-09-2015, 06:07   #33
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Re: DC genset to power boat.

This is what I did .

DC Generator - The Smart Way to Go

I have had it all up and running for a year now, and it has worked flawlessly.
I get 200 amps in my batteries with one hour of run time , the water maker is not set up yet as I am still in fresh water .

The Victron inverter crapped out and I replaced it with a Vanner Brutus inverter which has been working great! I have not turned it off since I installed it .

Regards
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Old 09-09-2015, 09:20   #34
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Re: DC genset to power boat.

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Because you will die. Its a prime darwin award nomination.
Is this one of those slow deaths that take 6-8 decades?

We see them frequently and have used on for the last 7-8yrs. No you don't want to run it inside the cabin but with reasonable care, it's no more dangerous than a built in unit.

Maybe the difference is it's a yamaha not a honda...
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Old 09-09-2015, 10:34   #35
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Re: DC genset to power boat.

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Originally Posted by typhoon View Post
This is what I did .

DC Generator - The Smart Way to Go

I have had it all up and running for a year now, and it has worked flawlessly.
I get 200 amps in my batteries with one hour of run time , the water maker is not set up yet as I am still in fresh water .

The Victron inverter crapped out and I replaced it with a Vanner Brutus inverter which has been working great! I have not turned it off since I installed it .

Regards
very interesting

also the polar power product...someone have a price for the 20kw marine genset? maybe the only cons would be the price (shipping and custom tax in italy)
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Old 09-09-2015, 11:01   #36
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Re: DC genset to power boat.

Maybe it's just me but I wan't to hear engines running. Hate things you got to look at the panel to see if there's something on or not. Of course too much noise is a PITA but hearing sound humming gives me a peace of mind, and if there's anything wrong I hear it at once..
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Old 09-09-2015, 11:57   #37
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Re: DC genset to power boat.

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Most marine ac generators run at 3600 rpm. That's screaming.

Most marine generators run at 30 times the desired frequency. The ones that run at 60X are not really that popular. They mainly appear in low end low power units. The typical quality marine generator runs at 1800/1500 RPM for 60/50Hz output.

The idea that a DC genset is "self optimizing" is a bit of a myth in my opinion. Fixed speed 3 cylinder diesels last a long time. If you are worried about light loading then put a load on it. It does not change fuel consumption much to load a genset to 30% of kW output which is enough to keep the engine hot. It's pretty simple to build up a 200-300A mains powered charging system that runs from a genset or shore power.

It's pretty hard to beat the reliability of a shaft connected AC generator. Some DC units have belt drives and somewhat complex engine speed control circuits. And a lot of DC units have one or two cylinder shake-a-lot engines.

You will find people with bad AC genset experiences. But that has more to do with the vast market share they enjoy. There are hundreds of thousands in service. If they were terrible there would be a lot less of them.
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Old 09-09-2015, 12:06   #38
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Re: DC genset to power boat.

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Originally Posted by transmitterdan View Post
Most marine generators run at 30 times the desired frequency. The ones that run at 60X are not really that popular. They mainly appear in low end low power units. The typical quality marine generator runs at 1800/1500 RPM for 60/50Hz output.

The idea that a DC genset is "self optimizing" is a bit of a myth in my opinion. Fixed speed 3 cylinder diesels last a long time. If you are worried about light loading then put a load on it. It does not change fuel consumption much to load a genset to 30% of kW output which is enough to keep the engine hot. It's pretty simple to build up a 200-300A mains powered charging system that runs from a genset or shore power.

It's pretty hard to beat the reliability of a shaft connected AC generator. Some DC units have belt drives and somewhat complex engine speed control circuits. And a lot of DC units have one or two cylinder shake-a-lot engines.

You will find people with bad AC genset experiences. But that has more to do with the vast market share they enjoy. There are hundreds of thousands in service. If they were terrible there would be a lot less of them.
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Old 09-09-2015, 12:27   #39
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Re: DC genset to power boat.

My DC generator design address all the pitfalls you describe. I kept it as simple as possible . Of course you do have to have the space . Been working great so far . I am surprised how little fuel it consumes . Then again I don't need to run it long to charge the lithiums . [
Figured as much , active captain has no information . Thought that was odd . To bad , looks like a very nice little spot . The alternator settles in to 200 amps once it warms up , I wish it would stay at 303 but I would have to belt it to get that much power out of it . It is rated at 205 amps at 1800 rpm / hot so I'm happy with that . With no belts , no belt trouble and no side loading on the crank , I expect this setup to last many many years . Once I am in salt water I will commission the water maker .


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Old 09-09-2015, 13:14   #40
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Re: DC genset to power boat.

Dan--good post.

ty--nice setup. More photos?
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Old 09-09-2015, 13:19   #41
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Re: DC genset to power boat.

Thanks , sorry for the little extra dialog in there, I was posting from my phone and got that in there from another post LOL dunno how .
I have more pics in my profile , I will add a few more with the unit installed in the boat as it is now .

Or you could check out the build process here.

DC Generator - The Smart Way to Go

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Old 09-09-2015, 13:26   #42
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Re: DC genset to power boat.

someone know the price for only a 48v dc generators in the usa? i saw polar and another brand but was very expensive...
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Old 15-09-2015, 21:25   #43
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Re: DC genset to power boat.

I am considering putting a DC generator together also.

Putting aside the arguments for or against it, I have two 3 cylinder diesel engine's available to me for this. One is a Kubota D850 rated at 15 HP @ 2500 rpm and the other is a Yanmar 3TN66CEJUV rated at 14-17 HP @ 3350 rpm.

I want to be able to power a large alternator (200 amp +), a water maker pump and a refrigeration compressor.
The Yanmar is considerably smaller, at least 3 inches in all directions. I believe I could make either one fit but I like the smaller footprint of the Yanmar.

Which of these engines would be the best choice and why?

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Old 15-09-2015, 21:32   #44
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Re: DC genset to power boat.

You really don't want to hear any machine running at thousands of rpm.
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Old 15-09-2015, 22:24   #45
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Re: DC genset to power boat.

I don't think either of these would have to run at their rated HP rpm to provide enough power for what I need them to do. Probably only the minimum rpm needed to get the alternator up to its required rpm. Water maker and A/C compressor should not need high rpm.

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