A Really Cool Small Generator

[transmitterdan]

Originally Posted by deckofficer

How about the inverter taking on all the AC and A/C loads? 48 volt input, 4400 watt (surge to 8800 watts) output. Housebank use the "no voltage sag" LiFePO4 cells, teamed with a diesel DC gen set at a much reduced weight of the same power AC gen set. Size solar to whatever deck real estate your boat offers.

I've thought this might be a good idea but could not answer why a DC generator weigh less than same wattage AC generator. DC generators are just AC generators with rectifiers to make DC. Even at 48V the rectifiers cause an efficiency hit. Is there a commercial example of a continuously rated 4-5kW DC generator? I could not find one.

[The Garbone]

Polar DC Marine

[Tx J]

Originally Posted by Dockhead

It depends, of course, on the diesel. If it's a one-lunger air-cooled Kubota rototiller diesel, called upon to deliver its max power at 3600 RPM all day long, then all bets are off.

But if it's a real continuous-duty rated, primary not standby power, low speed, heavy duty unit -- then you are supposed to get about 20,000 hours out of them -- by design -- without a major overhaul. YMMV, of course, and you will be less likely to get this 20,000 hours if you are stretching them over many years of use.

I only have 1000 hours on mine (160 when I bought it), so I can't tell you anything from experience yet. But AFAIK it's just barely broken in at this stage.

Dockhead is too modest, he really wants one of these for all that ancillary stuff aboard, a little bitty Wartsila 2400kW genset :


and for the propulsion plant, a wee tiny Rolls marine turbine (a few naval ships and Coastie cutters (Hamilton class) use gas turbines as a secondary propulsion plant):


(images lifted from the Buy or Sell your Diesel Engine - DieselEngineMotor.Com site that somebody referred to on another similar thread)

[capngeo]

Originally Posted by Dockhead

Wow, you sure burst my bubble!

It sure is great to get real world experience, which varies so much sometimes from the pretty theory on the website!!!

Yours is the low-speed 2.2kW one, right?

Yes.... Come get it!

[deckofficer]

Originally Posted by transmitterdan

I've thought this might be a good idea but could not answer why a DC generator weigh less than same wattage AC generator. DC generators are just AC generators with rectifiers to make DC. Even at 48V the rectifiers cause an efficiency hit. Is there a commercial example of a continuously rated 4-5kW DC generator? I could not find one.

Garbon Gary answered that. I would think most the weight savings is from the diesel getting to run at (for its small size) an efficient rpm that isn't dictated by frequency. For an AC gen set it will be running at 1800 rpm for 60 hz or screaming at 3600 rpm. At 1800, you need a larger engine to produce the same output that a smaller engine would produce at 2900 rpm.

The above 8 kw DC gen set is less than 300 lbs and could charge a 48 volt bank at 135 amps.

[Dockhead]

Originally Posted by Tx J

Dockhead is too modest, he really wants one of these for all that ancillary stuff aboard, a little bitty Wartsila 2400kW genset :


and for the propulsion plant, a wee tiny Rolls marine turbine (a few naval ships and Coastie cutters (Hamilton class) use gas turbines as a secondary propulsion plant):


(images lifted from the Buy or Sell your Diesel Engine - DieselEngineMotor.Com site that somebody referred to on another similar thread)

OK, OK -- now I've been outed.

[Dockhead]

Originally Posted by goboatingnow

Its its a ea330 engine they output about 3.7 hp at 200rpm. Then add in any engine driven loads. A 2.2 kw alternator is actually close to 3hp + additional friction losses . This leaves nothing to spare really

I built one of these units years ago. The EA330 engine needs to be run very hard , its very loud too. Other wise it SIGs down and struggles to prove the rated power. Its too tight a design.

The kubota mini series engines are much better. I've used Lombardi in other work and there nice engines too. I believe they make all of Koehlers small engines.

Dave

Actually, I think it's an EL300AR:

http://www.seatechmarineproducts.com...oad/LP1-22.pdf

4.5 horsepower? There are many different versions of the 300cc and 330cc Kubota water-cooled diesel, with different power ratings, different speed, some have balance shafts, others don't.

As far as I can tell, the EL300AR was really rated for continuous use -- was sold for temporary lighted road signs. Sounds great in theory, but now we hear that practice may deviate Naturally, more cylinders and displacement, more derating, is better. The smallest Super Mini is 500cc and two cylinders . . .

Maybe it's hopeless to make a really bulletproof fixed-mount 1-cylinder diesel marine generator.

[FlyingCloud1937]

You guys, and girls,

Continue to miss the target.

AC/DC it matters by design

Lloyd

[goboatingnow]

Maybe it's hopeless to make a really bulletproof fixed-mount 1-cylinder diesel marine generator.

After my attempts some years ago, I would concur. 2 cylinder or better, direct shaft drive, low reving alternators , thats the way to go ( possible water cooled alts too)

dave

[goboatingnow]

Actually, I think it's an EL300AR:

teh EA300 is a discontinued engine, teh EA330 is the Tier 4 compatible replacement.

[Mistress Sirena]

Great thread i love hearing of all the good ideas and thoughts on these subjects
my bud just bought a Dewalt invert gen a little more power and less exhaust noise than the EU 2000 will be watching the reliability issue.
My first EU 2000 9 years and the cord broke ran off 3 gallon OB tank I just went out and bought another they are tireless!

PS I will tackle the cord replacement someday big job !
"another thread"

[ColdEH]

Originally Posted by Dockhead

Wow, you sure burst my bubble!

It sure is great to get real world experience, which varies so much sometimes from the pretty theory on the website!!!

Yours is the low-speed 2.2kW one, right?

Yeah these things suck , seen them heard them , ran away from them , keep your Kohler . There is no replacement for displacement.

Regards

[ColdEH]

Originally Posted by goboatingnow

After my attempts some years ago, I would concur. 2 cylinder or better, direct shaft drive, low reving alternators , thats the way to go ( possible water cooled alts too)

dave

Yep my way of thinking as well , built one and it runs like a champ , makes very little noise , pumps out the amps and uses no belts .

Regards