High power alternators vs Genny on a Cat

[44'cruisingcat]

Originally Posted by Thalas

So is the consensus that HP alternators don’t put enough load on a main engine at full 100amp+ output for longevity? I thought these alternators would vary load based on needs (e.g. pull more generation when charging is needed, but would lighted up greatly when prop shaft power was needed).

100 amps at 13 volts is only 1.3 kw. A couple of horsepower. Not enough to load up a propulsion engine.

But that doesn't need to be a problem. With reasonably efficient systems and good solar and batteries, you would only need to run a diesel for battery charging infrequently. As long as you give the diesel a good workout when you use it for propulsion, you'll get good life from it.

In many charter fleets charterers are required to run engines for a couple of hours a day for battery charging, but this doesn't seem to result in excessively shortened engine life.

[tuskie]

Originally Posted by catsketcher

As 44C says, AC is not a must have. In Australia very few boats have it, except for those who live aboard in a marina. If I wanted to be shut up with the doors closed and have the AC on I would stay at work or commute in the car. There, just saved you about 20 grand on your next boat.

I realise I am like a mono guy in a multi thread but I shake my head at the endless upping of comsumerism on cats. I go sailing to get away from incessant consumption and to realise how little we need to be happy.

I agree with your sentiments; we don't have air conditioning either, but don't preach until you've spent a wet season ("summer") on board in Darwin or North Queensland. Playing in the water is often a very dangerous option because of crocodiles and deadly jellyfish. Some people need to spend time in hot windless marinas for a variety of legitimate reasons, such as accessing healty care. If you've cruised happily without AC then great, aren't we lucky, but save us the minimalist sermon.

It's a curious thing about CF; not matter what topic is discussed ( electronics, entertainment systems, lighting, anchor winches, bottle openers) there are always some whose only contribution is "you don't need that!"

Running air con is the main reason people give for installing a genset, but the purpose of my first thread was to give some alternative reasons for such an installation. I've learned heaps from his thread about the possibilities from high output alternators, clearly there is more available technology than I realised. Thanks john61ct !

[44'cruisingcat]

Originally Posted by CatNewBee

the question is, can a high amp alternator replace a generator on a cat. most cats having a gen installed, have it on purpose (e.g. for the AC units, diving compressor etc.) a DC alternator cannot deliver enough juice for those. To replace a 9kW Onan you will need an alternator with 12v / 800A.

Yes, I think everyone agrees that the MAIN reason you'd need a genset is to run air conditioning.

Because aircon uses lots of power for long periods.

High power short duration, like dive compressors or power tools, or low power long duration, like fridges and freezers, can be handled by a good solar array and batteries, supplemented by high output alternators or portable generators.

[smj]

Originally Posted by tuskie

I agree with your sentiments; we don't have air conditioning either, but don't preach until you've spent a wet season ("summer") on board in Darwin or North Queensland. Playing in the water is often a very dangerous option because of crocodiles and deadly jellyfish. Some people need to spend time in hot windless marinas for a variety of legitimate reasons, such as accessing healty care. If you've cruised happily without AC then great, aren't we lucky, but save us the minimalist sermon.

It's a curious thing about CF; not matter what topic is discussed ( electronics, entertainment systems, lighting, anchor winches, bottle openers) there are always some whose only contribution is "you don't need that!"

Running air con is the main reason people give for installing a genset, but the purpose of my first thread was to give some alternative reasons for such an installation. I've learned heaps from his thread about the possibilities from high output alternators, clearly there is more available technology than I realised. Thanks john61ct !

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?

[Thalas]

Originally Posted by 44'cruisingcat

Yes, I think everyone agrees that the MAIN reason you'd need a genset is to run air conditioning.

Because aircon uses lots of power for long periods.

High power short duration, like dive compressors or power tools, or low power long duration, like fridges and freezers, can be handled by a good solar array and batteries, supplemented by high output alternators or portable generators.

Well this clearly answers my question. I appreciate the dialogue.

If I'm reading correctly, with a large LiPo bank and a 4000W inverter, the HO alternators working with 1.5kw Solar COULD handle short run items like washing machine runs, dive compressor, water maker, (these activities tend to be 1-2 hour runs) but not as efficiently as a generator. Long run AC use would be better served by a generator.

So if I want a dive compressor, clean clothes and hot showers, but don't really care about AC, I might save some weight and maintenance by skipping the genny, yes?

[MV Alchemy]

Originally Posted by Thalas

Well this clearly answers my question. I appreciate the dialogue.



If I'm reading correctly, with a large LiPo bank and a 4000W inverter, the HO alternators working with 1.5kw Solar COULD handle short run items like washing machine runs, dive compressor, water maker, (these activities tend to be 1-2 hour runs) but not as efficiently as a generator. Long run AC use would be better served by a generator.



So if I want a dive compressor, clean clothes and hot showers, but don't really care about AC, I might save some weight and maintenance by skipping the genny, yes?

Correct. You can even run limited air con from the batteries (say 1 cabin overnight on a particularly windless night) with a decent sized LiPo bank. We have been doing just that for the last 2 years.

[tuskie]

Originally Posted by Thalas

Well this clearly answers my question. I appreciate the dialogue.

If I'm reading correctly, with a large LiPo bank and a 4000W inverter, the HO alternators working with 1.5kw Solar COULD handle short run items like washing machine runs, dive compressor, water maker, (these activities tend to be 1-2 hour runs) but not as efficiently as a generator. Long run AC use would be better served by a generator.

So if I want a dive compressor, clean clothes and hot showers, but don't really care about AC, I might save some weight and maintenance by skipping the genny, yes?

I have a friend cruising on a FP Lipari with almost exactly the setup you describe. His system works very efficiently and is further supplimented by a D400 wind gen. His alternators are Balmars fitted as belt driven replacements to the original Volvo fitment. He has 800 AH LiFePO4 so can take quite a few days of rainy days before recharge is required. If he then intends to motor, then all is good. If he wishes to stay, then the choice is running one of the mains under low load or perhaps, invest in a genset?

As far as weight is concerned, our Paguro 2000 water cooled diesel genset, weighs 51kg. Not a large extra penalty over a portable petrol genset or a jack shaft driven HO alternator to one or both main engines?

[Barra]

Originally Posted by Thalas

Well this clearly answers my question. I appreciate the dialogue.

If I'm reading correctly, with a large LiPo bank and a 4000W inverter, the HO alternators working with 1.5kw Solar COULD handle short run items like washing machine runs, dive compressor, water maker, (these activities tend to be 1-2 hour runs) but not as efficiently as a generator. Long run AC use would be better served by a generator.

So if I want a dive compressor, clean clothes and hot showers, but don't really care about AC, I might save some weight and maintenance by skipping the genny, yes?

Yep as per the very first post to this thread but we do all like to natter don't we.

And get in the odd sermon or 2.[emoji3]

[blubaju]

missing one point, or maybe I have overlooked it. The miserable charge rate when a battery is more than half full. On our Schionning 2 Yanmar with their original 80Ah generators, each w small starter battery, larger house bank and 100Ah dedicated navi-bat w combiner. No genset, but 6x64W solar panel, the one for roofings, walk on. I use a digital mobile charger between generator and batteries, in some electronic miracle (not really) this unit basically pretends to the Hitachi-regulator a lower voltage of the batteries, hence more output. They claim 5 times faster charging, well I never measured that, but it works for me.
Washing machines do not use much power, just be sure the heater is off! 2000W Inverter, No aircon, engines for charging when sailing overnight maybe an hour before dawn. High power alternators do not help you when the batteries do not accept it. Of course if you want to run appliances directly, this is a different topic

[valhalla360]

If I was starting from scratch on a new boat and was ready to think outside the box:

Let's say the standard power is a pair of 25hp engines with a 10kw generator.

I would look at installing a 40hp engine in one hull and a 10hp electric motor with an 8-9kw generator in the other hull along with a moderate sized battery bank (maybe 5kw-hr of usable power) and a decent size solar array.
- In and out of the dock, both engines (yeah, you need to adjust for the different power outputs but very doable).
- Just tooling along on a sunset cruise, battery power...if you run low, the generator kicks on and keeps you going.
- Long distance runs, Mostly on the 40hp engine but you could supplement a little with battery power. Say you are doing a 2hr run, you could put out 2kw to the electric motor with 1kw-h in reserve for docking.
- Emergency: 40hp with 10hp and generator keeping the batteries up.
- Hanging out on the hook without the air/con: Battery/solar
- Hanging out on the hook with air/con but only at night: Assuming a 50% duty cycle, the 5kw battery bank could handle around 8hrs and then it's usually fairly cool in the morning, allowing a quick generator bulk charge in the morning and solar finishing the job.
- Hanging out on the hook with air/con 24/7: Crank up the generator as needed to keep the batteries up.

[CatNewBee]

It's all doable, however the more complicated it gets the more trouble it could cause especially in remote places.


I am for redundancy, weight is second to this.

Another thing to consider if you want to replace the existing alternators on a recent production boat. They usually add diode / MOSFET battery separators nowadays that have some 40...80 Amp throughput to distribute charging current to the start battery and the house bank. You would fry them with your brand new alternator in no time.

You will have to change the set up to a battery combiner relay or you work with 2 alternators per engine, dedicating the high-amp alternator to the house bank only. Maybe you will also add a custom charge regulator to fit your battery setup and protect the alternator from overload / overheating when using high-capacity LFP batteries.

[john61ct]

Originally Posted by blubaju

missing one point, or maybe I have overlooked it. The miserable charge rate when a battery is more than half full.
…
High power alternators do not help you when the batteries do not accept it.

NP if motoring many hours per day anyway.

If not, the key to care-free reliance on HO alts is an LFP bank, which gets fully recharged in well under an hour, so 3-4 hours a week is usually plenty.

But also note LFP has no need to get to full anyway as lead does.

Otherwise with lead any dino juice source only makes sense for the time it takes to get SoC up to 80-85%, and you need solar and a lot of time to finish the long tail.

[c-reel]

Do you think it is feasible to start a dive compressor (like the most commun Bauer Jr II) just through the investor, even a powerful 3kw or 5kw Victron quatro?
The issue being the inrush current that the motor will need to start (>25A, while still looking at exact spec). Maybe workable with a soft-start, but i havent seen anyone doing this yet.
Many people using dive compressor and not having generator would have the gasoline variant.

Originally Posted by 44'cruisingcat

Yes, I think everyone agrees that the MAIN reason you'd need a genset is to run air conditioning.

Because aircon uses lots of power for long periods.

High power short duration, like dive compressors or power tools, or low power long duration, like fridges and freezers, can be handled by a good solar array and batteries, supplemented by high output alternators or portable generators.

[BigBeakie]

C-reel,

I know the Victron Multiplus 3k will not start a Poisidon PE100. Because I tried it. But I'm getting the 5k multiplus and sincerely hope that will work. It should work.

But equipping a boat based on hope and "should be Ok" , is not good enough so I'll be trying it when I can find a multiplus 5k to try it out.

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


Sent from my iPad using Cruisers Sailing Forum

[Thalas]

Originally Posted by BigBeakie

C-reel,

I know the Victron Multiplus 3k will not start a Poisidon PE100. Because I tried it.

Did you connect a soft-start to it? Can you use them with compressors?

Originally Posted by CatNewBee

I am for redundancy, weight is second to this.

Doesn't the redundancy come from having two engines with HO alternators?