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Old 25-10-2008, 11:05   #1
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Ultimate DC Genset - Your Thoughts?

Hi every one. This is my first post, hopefully I will find more time to write more . Refitting boats takes a lot of time , LOL.

I am in the process of putting together the final steps on my charging system. I got a 13.5 Hp Yanmar 3 Cyl diesel from a Kohler AC genset that fried itself. The motor side has only 100 Hrs on it . Perfect candidate for a DC genset , it will always run at 1800 rpm under load with it's mechanical governor.

On the side the genset sate I am installing two 160 amp large case alternators mounted opposite each other so there is no load on the crank. They will be ran at 60% of full load to minimize heat, using the pulley size to control there RPM. I hope to have them put out around 120 amps each. I am driving them with a dual track custom made multi groove pulley attached right to the flywheel. Tension on the belts will be from a stainless turnbuckle pushing the alternators apart from each other , thereby tightening the belts. I will be putting an Ample Power Smart Alternator Regulator v3 SARV3-12P that will drive both alternator fields.

The batteries are Fullriver AGMs mounted in the keel with a total of 1040 amp hours.

The system is completely separate from the start battery and that will only be charged from the alternator on the propulsion engine .

Just wondering if any one had any thoughts or comments on such a setup .

Great to be part of this forum , see you out there.
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Old 25-10-2008, 11:26   #2
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Three things come to mind: Exhaust, cooling, fuel. And, I'll presume starting is electric?

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Old 25-10-2008, 11:53   #3
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Hi Thomas

Cooling via a heat exchanger and a wet exhaust and water lock muffler, fuel, diesel from main tanks, and yes the Yanmar is an electric start, with all the controls and sensors found on a comparable Ac genset. The motor mounts and pan had to be changed a little because the unit is much shorter without it's AC components. I will be building it into an enclosure under my compainion way with "Db quiet" insulation from Glacier Bay, the stuff is expensive but I think it may be the best sound deadener around. I will put a good blower in the encloser with ducts running right into the alternators to keep tempertatures under control.

Regards John
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Old 25-10-2008, 13:44   #4
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WE want pictures ...you dont need advice...
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Old 25-10-2008, 14:00   #5
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sounds like a decent plan. I don't think you will get the full 240A output with that engine. Try it and see.
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Old 25-10-2008, 14:15   #6
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You might be right, I may stick to 220 amps if it loads down the Yanmar to much. All I really want to do is get 200 amps back in the batteries with about one hour of running.

I will post pictures soon.

Regards John.
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Old 25-10-2008, 14:21   #7
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Git the pic of the Yanmar, the red paint was just to freshen it up before it went in.

Regards John.
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Old 25-10-2008, 15:10   #8
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Sounds like a great plan to me, I hope you post your results when they are in. How about a pic of the alternators and their mounts and tensioner?

Is it really unrealistic to expect 3400 watts DC from an engine that is used to get 4000 (or even 5000?) watts from an AC generator? I'm just trying to educate myself here.
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Old 25-10-2008, 15:13   #9
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The rule I was taught was 10A per hp
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Old 25-10-2008, 15:36   #10
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Could that rule be intended to limit crankshaft side loads from a single alternator? It seems low when 1 hp is equivalent to 746 watts - or 53 amps at 14 volts. 10 amps per hp would translate to awfully low efficiency on the part of the alternators.
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Old 25-10-2008, 20:30   #11
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HP at the crank is not the same as advertised HP.
Just sayin'

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Old 26-10-2008, 00:38   #12
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Will controlling two alternators with one regulator result in the load balancing between the two alternators?
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Old 26-10-2008, 01:05   #13
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Hi Typhoon,


Welcome to the Forum. I recently installed 8 of the 260DC Fullriver AGMís to give me 1040 @ 24V and have been testing discharge-recharge profiles to find the optimum charging scenario.

Playing the Devilís Advocate here:

The only question I would have with your double large case idea is Ö..why choose a complicated and risky solution that is dependant on maintaining the balance between opposing 2 belt driven units instead of solidly bolting on to the back end a DC generator sized to your needs? What happens if one side fails and you need to run just one side?

I have a 12KW Northern Lights AC gen and I asked the same question to Dick Gee, their Technical Director, about putting a large case DC alternator off the front end.

His response:
1] The problem is the tremendous side load imposed onto the nose of the engine crankshaft by the "V" belts when driving the alternator. We know from experience this can cause catastrophic failure.

2] Based on this experience our 24 alternator limit is 40 Amps.

3] Again based on experience we do not offer this service.

4] Because of the potential damage we do not even offer an optional crankshaft pulley.


Typhoon, Keep in mind that belt driven alternators are purposely kept light weight because of their side bolting and need to adjust for belt tension. They run hotter (less efficient) because of that

Bolting inline off the back end will allow a much better torsional balance, cut down on vibration and with a unit sized for better heat dissipation. Zero maintenance!

Donít know the cost differential but that would be my choice if even close.

Be interested to hear back if you had researched that route.
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Old 26-10-2008, 08:18   #14
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Quote:
Originally Posted by Cowboy Sailer View Post
Will controlling two alternators with one regulator result in the load balancing between the two alternators?
Yes the Ample Power regulator will control both field windings of the alternators, and balance them. Thats one reason I picked it . You can do the same thing with a balmar setup but with 2 regulators and a centerfielder unit.

I was thinking of a dc generator, but I couldn't figure out how to control it to charge the batteries properly. I you can think of a way I would be interested in it. I even looked at 1800 rpm alternators that would put out enough current and direct conect them . I did find a few (echotech) but again they would not except an external regulator. So I was back to the tried and proven.

Also I will rig up a idler pulley if I loose one of the alternators so I could run one alone if I have to have one repaired . I want to make sure not to side load the crank bearing with a single alternator.

Also all the research tells me that it should take around 1hp for every 25 amps, at least so Balmar says. So if i put out 220 amps that should take roughly 9 hp . That should load up the engine just fine , not good to run a diesel without enough load.

Thanks

Regards John
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Old 01-11-2008, 08:26   #15
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Had problems with the 160 amp alternators. My alternator guy built them both from the ground up based on large case ford alternators . All heavy duty windings and stators, avalanche diodes , etc . Got them on the test bench , wound them up to speed and only got 120 amps out of them. I really wanted to use a local builder for my alternators , someone that was reputable and been in business for a long time. As I read through all the forums on "Balmar" and other marine alternator manufactures I realized that there are good ones and bad ones and I should source them locally so I can get them matched up for my application. Plus if I have one melt down on me during this process the guy that built the thing is just down the road and gives me all the hands on help and warranty I need without shipping them halfway across the country.

Ok time to rethink. At least that's what he told me, and , " this is not rocket science" We had to build an alternator that could be easily run at 110 amps without struggling. So an alternator of around 160 should do , and of course externally regulated. Chrysler! he said , they make a new alternator as an up grade on all there 2005 and up vehicles , it puts out 160 amps, and they are externally regulated. He grabbed one that he had built off the shelf , put it on the machine, and viola, 180 amps under full load!! OK lets slow it down to 110 amps (1500 rpm) and let it run under that load. Fifteen minutes later it was still running and I could keep my hand on it , it was hot but it didn't come close to burning me . Some alternators get so hot you could use them for cabin heaters. They are also spark arrested and have sealed brushes. Grabbed two of them and had him build me two more for spares to keep on board. At 225 bucks each I couldn't go wrong. Once I get them in the boat and on the battery load he said we could work out the best pulley diameter to give the best results. Now that is sevice

Regards
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