High power alternators vs Genny on a Cat

[BigBeakie]

Thalas,

No soft start on the trial. If it doesnt start with the Victron MP5000, the soft start is our last hope.


Sent from my iPad using Cruisers Sailing Forum

[contrail]

Originally Posted by smj

Yes, and let’s please cut out the sermon from the people who believe if you don’t have AC, generator and Washer dryer then you must be a lower form of life out there camping. Goes both ways doesn’t it?

Of course, there are those of us who are minimalists set up to live on solar, when by ourselves, but who have gensets and aircon for charter guests, when they are aboard

And, I would guess we are grateful for the ability to "cheat", and use it, when we "need" it, without overdoing it. After all, the charter guests have "paid" for it.

[44'cruisingcat]

Originally Posted by BigBeakie

Thalas,

No soft start on the trial. If it doesnt start with the Victron MP5000, the soft start is our last hope.


Sent from my iPad using Cruisers Sailing Forum

Isn't there a way to unload the compressor, so it's not actually compressing air at first, then when it's running you can load it?

[Simi 60]

Originally Posted by BigBeakie

Anyone on Oz east coast with aVictron Multiplus 5000 they would be willing to try and start an electric dive compressor???

I run one of these for hookah effortlessly on a 5000 while running several 240v fridges at the same time.
Does that count?
Always in + amps when the sun is shinning.


https://www.bunnings.com.au/ozito-24...essor_p6290553

[smj]

Originally Posted by contrail

Of course, there are those of us who are minimalists set up to live on solar, when by ourselves, but who have gensets and aircon for charter guests, when they are aboard

And, I would guess we are grateful for the ability to "cheat", and use it, when we "need" it, without overdoing it. After all, the charter guests have "paid" for it.

Yep your money and your boat, no doubt use it as you wish[emoji1303]

[c-reel]

Originally Posted by Simi 60

I run one of these for hookah effortlessly on a 5000 while running several 240v fridges at the same time.
Does that count?
https://www.bunnings.com.au/ozito-24...essor_p6290553

It's good to know but won't be able to conclude as the in-rush current for this compressor is not going to be the same as for a higher power dive compressor.

Part of the problem is to find out the exact value of the required starting current of motors in general.

The Bauer Oceanus has a fuse spec of 20A at 230V (single phase), but it's mentioned slow-blow fuse. They dont tell what's the inrush current.
The Victron quatro 5k is spec at 10kW peak, so there is hope if it includes also some type of slow-start mechanisms.

If anyone has an opportunity to try a Victron 5k (12V to 230) to start a dive-compressor (Bauer Oceanus, Junior II or any other type), it would be awesome to know !

[Want2cruz]

Originally Posted by Bean Counter

To try to answer the question, to define " most modern cats from the big 3" - the majority of modern catamaran production is for charter fleets. A lot of charter fleets operate in tropical climes or mid summer. A lot of charter patrons who put up to 10 people aboard for a week like to run air conditioning. So in order to make your charter cat attractive to a larger market audience and so maximize your charter income - you put in air conditioning - and hence a generator. If you search yacht world you will see a lot of >42ft 4 cabin cats with Aircon.

For "owner version" cats you will see a mixture of both, some now days purely solar/lithium but no Aircon, and those that want as comfortable existence as possible with aircon, washer dryer, AC water heater, and other AC loads, who will put in a genny, and then hybrids of these two.

For those who buy a 5 year old charter cat, or a fully loaded private cat, it comes with the genny which probably has years of life left in it.

At diesel consumption rate of .5gph for 2 hrs per day = $3 per day.
Compared to a solar lithium replacement installation that delivers the same energy requirement would cost say $10,000 / 3 = 3,333 days or 9 years of diesel.

So that is probably why you see many cats with generators.

If you are starting from scratch - sure the solar lithium solution may be able to deliver most things (except Aircon unless a really big system) and will need topping up when there are weeks of low sunlight. Some people buy a cheap noisy gasoline genny to do this, (and I dislike being anchored next to them in a quiet harbor), and they will need to carry gasoline aboard to keep it fed. An alternative is to run a main propulsion engine, which when at anchor is an inefficient way to charge batteries even with high amp alternators. The main engines are not designed to run at 1500 rpm for hours in neutral - it wastes diesel and will probably prematurely wear out the engine, detracting from its prime purpose. The hi amp alternator comes in to its own when under way using motor(s) which in a cruising scenario is quite a low time percentage to warrant the upgrade cost.

I would opine as follows:

Rest is important, and AirCon contributes greatly to that in hot climes. Dehumindification is beneficial as well.

Running a main propulsion engine just to spin an alternator may or may not be hard on it, but it sure would run up the engine hours

A GenSet seems to me to be the sensible option if you ever anticipate hot climes, unless you enjoy waking up wet from sweat.

[Na Mara]

Originally Posted by tuskie

Do we start an engine and get a small charge from the incorrectly labeled 80 A alternator. Or do we pull out a portable genset in the dark, sit it on deck in salt spray and plug it into the mains socket? Or do we push the start button of a properly installed diesel generator and engage the real 80 A lithium battery charger for a couple of hours and keep sailing? We chose the latter option.

My thinking is very much along these lines.

Option 1 of using the main engine for charging has multiple disadvantages. The biggest of those is that you are drastically increasing wear on what is probably your single most important piece of equipment after your mast. Even if running your diesel without load didn’t glaze the bores, just the extra run time and the extra start ups and stops is all eating into the life of a crucial piece of equipment. Furthermore, using a 90hp 4 cylinder (in my case) diesel to produce say 2kW of DC is just woefully inefficient on fuel. Idling at 1500rpm my engine uses 2l of diesel an hour. Assuming its fitted with a 2kW alternator, I would then be getting a fuel economy of 1l/kWh. Modern diesel generators have economies of 0.35l/kWh generated and so have 3 times the fuel economy.

Option 2 of using a portable gasoline generator is just totally impractical offshore as Tusky rightly points out. It is precisely on passages that the typical cruiser’s energy needs are greatest. My energy needs basically triple underway due to all the instrumentation and, predominantly, the autopilot. Unfortunately most generation modes are at their weakest (with the exception of hydro) when under typical cruising conditions. Typical trade wind sailing reduces the output of most wind generators and solar output also often drops due to shading from sails or heeling. Thus the greatest need of petrochemical generation will be under precisely those conditions that least suit running a portable generator.

This, and the fact that there is nowhere suitable to put a significant amount of solar on my boat, led me to the conclusion that I needed either a fuel cell, or a small diesel generator, to meet my power requirements. For multiple reasons, fuel availability, life expectancy, water heating, and the ability to run high load electrical equipment like electrical trash pumps, water makers, etc has all led me to ask my yard to quote for installing a diesel generator. It will cost about 2-3 times what upgrading my engine to a high powered alternator would cost, but the peace of mind of abundant energy at need no matter the conditions (generators can even be set up to automatically startup and stop in response to the battery charge levels.) is priceless.

[malbert73]

I can see for a catamaran with 2 smaller engines that running a high output DC generator into lithium could meet your needs. For example could run the engine opposite your sleeping cabin. Also I have heard cats sometimes cruise under 1 engine alone so that could balance things out.
But for my mono, with a beefy 50 Beta main engine which easily drives me at 7-7.5 kts, no way to do that so a nextgen 5.5 supplies AC, hot water, and 100 amp charging. Also eventually a water maker. Best of all, very quiet - particularly in the cabin - partly because it’s only a 10hp Diesel engine which most main engines can’t boast.

[wingssail]

Originally Posted by oleman

If you want to have a good life on the high seas most boaters will want good heating and air conditioning as a minimum. Most will want full size refers and freezers with an array of kitchen appliances, and washers and dryers. AND the ability to take a hot water shower daily using fresh water.
These needs will never be supported by a few hundred watts of solar panels and automotive generators on a 40 HP diesel.
When you have sailed many days near the equator, you can really appreciate amenities.
I guess the real question is which end of the boating use do you want to be on?

Your definition of "a good life on the high seas" sounds an awful lot like a condo in Miami. Your subsequent reference to life being hell if you don't provide those things for your wife confirms my suspicions.

So your idea of a good life at sea is a Miami condo on the water and a high maintenance wife who is only happy with all the comforts of home?

THAT sounds like hell to me.

I prefer a simple, but comfortable, well sailing, sailboat with as little of those household gadgets as possible and a beautiful wife who is happy with the simple life and who is my partner running the boat, loves to sail and not a pampered passenger.

THAT, is a good life.

[wingssail]

Originally Posted by Na Mara

...The biggest of those is that you are drastically increasing wear on what is probably your single most important piece of equipment after your mast. Even if running your diesel without load didn’t glaze the bores, just the extra run time and the extra start ups and stops is all eating into the life of a crucial piece of equipment...

Can you substantiate that?

Furthermore, using a 90hp 4 cylinder (in my case) diesel to produce say 2kW of DC is just woefully inefficient on fuel. Idling at 1500rpm my engine uses 2l of diesel an hour. Assuming its fitted with a 2kW alternator, I would then be getting a fuel economy of 1l/kWh. Modern diesel generators have economies of 0.35l/kWh generated and so have 3 times the fuel economy...

My 34 hp Yanmar, at 2000rpm, producing 1.2kw with a Balmar 110amp alternator, uses .88 Liters/hour. So that is .73 l/kWh

Option 2 of using a portable gasoline generator is just totally impractical offshore as Tusky rightly points out...Yes

The solution which has worked for us is a light, simple, approach which goes 80% of the way towards perfect. No Genset=no weight, no cost, no complexity, no extra maintenance, and no loss of usable space in the hull.

35 years, our air con works at the dock, the engine is not worn out, and we have everything we need at sea or anchor. Right now, mid summer in the hot part of Mexico, sitting in the shade at anchor with a bit of light breeze is cool, and at 5:00 iced drinks are on the way. We'll start the engine in a minute and run for 1.5 hours, generating about 110amp. Solar provides the rest.

Why do we need all that stuff?

[CatNewBee]

Our Onan can yeld 7kW, 3.5kW goes straight into the battery (250A charge current), the other 3.5kW are at disposal to make water, hot water, A/C or cooking during this time.

We can recharge 50% of the battery capacity in 2 hours, costs about 2l Diesel for recharging 500Ah.

[BillKny]

People reading this thread might be interested in what we chose and why. Our monohull just does not allow solar panels sized large enough to meet all our electrical needs.

We have minimal AC needs away from the dock.

We cruise long distances and prefer more remote locations, and we like our comforts, so freezers are our big electrical consumers.

Here is what we looked at and how we decided on what to do.

Power to the People!

After using this setup for a year, we are 150% happy with it and would change nothing.

[malbert73]

Originally Posted by BillKny

People reading this thread might be interested in what we chose and why. Our monohull just does not allow solar panels sized large enough to meet all our electrical needs.

We have minimal AC needs away from the dock.

We cruise long distances and prefer more remote locations, and we like our comforts, so freezers are our big electrical consumers.

Here is what we looked at and how we decided on what to do.

Power to the People!

After using this setup for a year, we are 150% happy with it and would change nothing.

Did you use the Kubota Z482 block? Looks same as my 2800 RPM NextGen 5.5KW