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Old 08-01-2004, 14:57   #1
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Aux charger ?????

I am upgrading my current inverter from 1500 watts to 3000 watts. This will power anything on board. What I would like to do is find some sort of a set up that would allow me to run a very, very small diesel engine combined with a high output alternator to put the juice back in the batteries that the inverter uses without running the main engine. Any sugestions on how to do this or anyone with experience with this kind of set would be appreciated. Thanks in advance.
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Old 08-01-2004, 17:49   #2
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A 3000 watt inverter will in all probability drain all your batteries in short order. When going DC -> AC you lose about 20% just in the conversion. If you multiply the AMPs in AC power by 10 you'll get an idea of how long your batteries will last. A good size Microwave does serious amp hours in short order.

What you need is a genset. You run the genset and you don't drain the batteries at all. I know of nothing that can recharge batteries as fast as you drain them. Batteries don't work that fast. A high output alternator won't make 3000 watts.

The trick is to make all the power you need directly. For the best you want a low RPM diesel genset. Something in the 4KW range would probably do the trick. The expensive ones are quiet.
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Old 08-01-2004, 19:57   #3
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Pblais, Thanks for the reply. Your assumption is correct if the inverter is running at 3000 watts for long periods of time. But in fact the microwave only runs for a few minutes. The TV or power tools running for short periods of time will not draw down major amps from the system. We have cruised with 1500 watts for ten years now and recharge with only solar panels and wind generator. The boat is set up to operate well with the inverter and I don't want to reinvent the wheel to add a generator. A small engine running a high out put alternator instead of the main engine will easily keep up with the demands we will place on the inverter. My question was posed in the event that someone might know of a pre-packaged system or someone that has built one. We ran across a fellow several years ago that had built his own in just this way and loved it. Unfortunately we lost track of him. Chuck
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Old 09-01-2004, 03:25   #4
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Small Generators

CHUCK:

A small diesel engine, driving a high output alternator; is a generator by definition.
Although much more common with gasoline engines, there are some smaller diesel generators. I don't think you'll find a diesel under 3Kw.
750 Watts = 1 H.P. - So 3Kw = 4 H.P. - BUT nothing is 100% efficient, so expect it will take a 6 H.P. engine to drive a 240A (3000W) Alternator.
Sorry, cannot think of the references (small diesels) right now. Try a "Google" search.

A 3000 Watt (3 Kw) inverter will draw approximately 240 Amps @ 12.5 VDC Battery input. Balmar makes H.O alternators in that size range, but as Paul indicates - why duplicate equipment? If your auxilliary diesel/alternator (Gen’) will be rated 3Kw (better yet 4Kw), why bother spending the money for an inverter?

It was a "good try", so keep thinking!

Regards,
Gord
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Old 09-01-2004, 12:52   #5
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Small Diesels

In our facilities we have a couple trailer mounted small diesels that run generators and compressors for the equipment. The thing I see being a problem is that they make so much noise and viberate a lot. Unless you have a large heavy vessel your going to hear and feel that thing running.

Myself, I have a carry-on gas genset that I keep in a locker. The new ones today are very compact and quiet. I just put mine up in the cockpit when I'm below and it charges while I'm asleep or whatever. Under sail I tie it down on the deck above the transom so I don't get any of the fumes and it just humms away. It's only a 1000w / 6 amp @ 12V but wieghs 60 lb. with fuel. The gas I have to carry for the dinghy anyway and will run 6 hrs. per gal.

Good luck on your search.........................._/)
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Old 13-01-2004, 12:07   #6
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3.8 kW Diesel Gen'

Westerbeke has some small Diesel Generators:
WESTERBEKE www.westerbeke.com

Specifications for 3.8 BCDT:
3.8 kW @ 60Hz (3600 RPM)
Cylinders: 1
Bore: 3.2 in.
Stroke: 2.2 in.
Displacement: 18.0 cu. in.
Aspiration: Natural
Length: 24 in.
Width: 13.6 in.
Height: 21.4 in.
Weight: 183.0 Lbs. c/w Soundguard

Specifications for 4.0 BCD:
4.0 kW @ 60 Hz (1800RPM)
Cylinders: 3
Bore: 2.8 in.
Stroke: 2.8 in.
Displacement: 49.0 cu. in.
Aspiration: Natural
Length: 28.8 in.
Width: 15.4 in.
Height: 20.7 in.
Weight: 358.0 lbs.
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Old 13-01-2004, 20:38   #7
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Thanks for the replies. I have done some research and found a few systems that are exactly what I am looking for. Unfortunately they are all expensive. But then what isn't on a boat
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Old 14-01-2004, 03:16   #8
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Chuck:
Please share some of your newfound expertise - what have you found?
Regards,

Quote:
Chuck Baier once whispered in the wind:
Thanks for the replies. I have done some research and found a few systems that are exactly what I am looking for. Unfortunately they are all expensive. But then what isn't on a boat
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Old 15-01-2004, 20:44   #9
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Gord, Here is the system I am seriously looking at.

http://www.amplepower.com/products/genie/index.html
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Old 15-01-2004, 20:45   #10
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And here is another

http://www.watermakerstore.com/Gener...nerators2.html
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Old 12-03-2009, 03:25   #11
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We have an early model of Marine DC Diesel Generators - Onsite Power Systems It is a 3.5HP single cylander Kubota driving a 140A Prestolite large case alternator. Max amps at startup is 80A but this drops as the regulator cuts it back. Sits at around 65 - 70A for quite a while. Also gives us hot water through the heat echanger. 8years ago it cost AUD6000.

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Old 12-03-2009, 12:19   #12
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Chuck,
No personal experience, but way back in 1986 friends with a Val-40 built a neat little system that fit under the berth in their aft cabin. Consisted of a 6 hp single cyl Kubota diesel which could be coupled to any of three items: a 200 amp large-case alternator, a fridge compressor or a watermaker pump. Worked for a few years, then the little Kubota wore out and they replaced it with a two cyl Kubota of a bit more power (don't remember just hdow much). This set up lasted through their circumnavigation and as far as I know is still going.

It was awkward to service there under the berth, but it was doable, and certainly did what they required.

Cheers

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Old 12-03-2009, 18:10   #13
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Guys...Chuck is no longer here...and the question was asked in 2004. Just a heads up.
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Old 12-03-2009, 19:14   #14
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Also, you guys seem to miss the point that the batteries are not in the loop when a DC generator is running. The inverter draws all (or most if alternator not big enough) input power from the alternator, not from the batteries. You still have the loss of the inverter but not the loss of the batteries.

Same for solar power or windpower: when it is used while generated, the batteries are out of the loop and efficiency improved.

We can generate 450 Amps alternator power using the two Lestec 225A Brute alternators on the main engine.

This doesn't change the fact that I prefer a direct AC generator for AC needs bigger than what my solar/battery system can supply.

cheers,
Nick.
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Old 14-03-2009, 20:49   #15
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Quote:
Originally Posted by Chuck Baier View Post
I am upgrading my current inverter from 1500 watts to 3000 watts. This will power anything on board. What I would like to do is find some sort of a set up that would allow me to run a very, very small diesel engine combined with a high output alternator to put the juice back in the batteries that the inverter uses without running the main engine. Any sugestions on how to do this or anyone with experience with this kind of set would be appreciated. Thanks in advance.
Why "diesel"? Burning fossil fuel stinks. There ought to be better ways to produce DC to charge batteries. You already mentioned solar, but to produce, say, 2 to 4 kWh (in battery language that's 200 - 400 Ah @ 12 V and 80%) - guessing that's what you might typically use daily - will take too many square feet of panel for most ships.
What else? Windmills? Stationary bikes and hamsterwheels? Ocean salt potentials? Hot air? Sigh... Yeah, maybe that stinky old 19th century diesel technology is still all we have.......
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