High power alternators vs Genny on a Cat

[contrail]

With regard to A/C, I attribute that fact that we have NO " boat smell' nor mildew, to the fact that we run the air conditioners for an hour or so, every day, even when it's not really hot. The decrease in maintenance on a "dry" boat rather than a humid one, is considerable.

[SeaSon]

Originally Posted by Bean Counter

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.

Yup. Try as I might to play with the numbers, but running my existing generator is virtually free and so no solar panels will be bought for many years.

[Thalas]

Originally Posted by SeaSon

Yup. Try as I might to play with the numbers, but running my existing generator is virtually free and so no solar panels will be bought for many years.

I think his point was that you didn't factor in maintenance, repairs, and the eventual replacement cost. That might make the comparison closer and he has silent power whereas you have a noisy run everyday. Granted, if you bought a used boat with a genny already installed, you didn't pay for that the first time around.

My initial question was more for new boat owners on what their logic was for the generator instead of the HO alternator upgrades since they ARE paying upfront. There must be advantages, but thus far, the only argument I've read in 2 full pages of the thread is high draw appliances which I thought HO alternators could power just as well as a generator.

[smj]

Originally Posted by contrail

With regard to A/C, I attribute that fact that we have NO " boat smell' nor mildew, to the fact that we run the air conditioners for an hour or so, every day, even when it's not really hot. The decrease in maintenance on a "dry" boat rather than a humid one, is considerable.

Sorry but we live in a really humid area and running the Ac for an hour will do very little to dry the boat out and once the Ac is shut of the moisture returns.

[tuskie]

We have installed a small diesel genset to allow us to sail.

Sounds stupid, but I'll explain. We have a good solar/lithium set up that usually adequately supplies our house load at anchor. We have lots of fridge/freezer space of the inefficient kind, as well as entertainment systems, lights, computers. We're "power pigs". It was cheaper to increase the power supply side of the equation than to replace the inefficient refridgeration. At anchor, were fine and self sufficient. Day sailing is also fine, even if the sails shading in panels means that we run the bank into further deficit.

The real issue comes when we do overnighters or longer passages. We'll start out with a bank that's a bit depleted from running the house load overnight, and then sail all day perhaps further depleting the bank if the panels are shaded. At night the power loads increase with additional draw from lights, electric winches and increased use of radar. Sooner or later, the battery bank will need a recharge.

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.

[contrail]

Originally Posted by smj

Sorry but we live in a really humid area and running the Ac for an hour will do very little to dry the boat out and once the Ac is shut of the moisture returns.

Hmmm. More humid that the East Coast and the Caribbean?

I didn't say that it can heat up or be humid after the Aircon is turned off. But drying things out really helps keep the odor and mildew down. Insulation is also a big help in retaining the effects of the AC for longer. Or, at least that is how it has worked for for me over the past thirteen years in the areas I mentioned. Including the summers!

[smj]

Originally Posted by contrail

Hmmm. More humid that the East Coast and the Caribbean?

I didn't say that it can heat up or be humid after the Aircon is turned off. But drying things out really helps keep the odor and mildew down. Insulation is also a big help in retaining the effects of the AC for longer. Or, at least that is how it has worked for for me over the past thirteen years in the areas I mentioned. Including the summers!

Galveston Tx and the Florida Keys, both extremely humid areas. I stand by what I say from over 18 years of liveaboard in high humidity areas, running the Ac for an hour a day will do nothing to keep mildew and odors down.

[JSLExplores]

Originally Posted by valhalla360

Another vote for it's about running the air/con (or other high power demand items).

Another complication is maintenance. Drawing 5-10hp off a belt driven alternator and you better have the belts perfectly aligned or it can start eating them.

On a cat, if you don't run the air/con, it's very much viable to handle almost all your power needs with solar.

This is what happened to me. Worse, I only had one engine and the belts always seemed to blow everytime I entered a cut under power.
I never could get the alignment perfect and finally decided to pull the Balmar and replace it with the original alternators.
John

[john61ct]

Originally Posted by Colin A

Always liked this for over the top Alternator charging.
https://www.setsail.com/fpb-78-batte...rging-details/

That's actually what I'll be shooting for, 450+A @28V

[Bean Counter]

Originally Posted by Thalas

I think his point was that you didn't factor in maintenance, repairs, and the eventual replacement cost. That might make the comparison closer and he has silent power whereas you have a noisy run everyday. Granted, if you bought a used boat with a genny already installed, you didn't pay for that the first time around.

My initial question was more for new boat owners on what their logic was for the generator instead of the HO alternator upgrades since they ARE paying upfront. There must be advantages, but thus far, the only argument I've read in 2 full pages of the thread is high draw appliances which I thought HO alternators could power just as well as a generator.

OK forgetting solar for a moment. Cruising is 80% plus on the hook.

Generator

Designed to run at constant and fuel efficient rpms, quite often in a sound absorbent cabinet.

in about 2 hours produces sufficient AC current to make 50 gallons of water, heat 20 gallons of water, charge the batteries at 100 amps or more, run the clothes washer (which may use half the water made on max load settings) and other AC devices. Aircon is another matter but a 6KVA genny can run this too if so desired for say 48,0000btu.

Uses same fuel as propulsion engines and often same engine oil.

If operated correctly can achieve 10,000 hrs plus of run time before any serious overhaul needed.


Hi Amp alternators

Need to run a considerably more powerful propulsion engine in neutral (which is not good for it - doubt you will get 10,000 hrs out of it) to achieve same amps as the genny for battery charging. Those amps are AC regulated to 12V DC to charge the batteries. You can also get hot water from heat exchanger.

So if you want to run AC equipment noted above you will need a big inverter say 6 kVA which are not cheap either. There will be an inverter efficiency loss converting back to AC. You will need a significant battery bank, lithium or gel to power this stuff or else you will be needing to recharge again.

You could run DC on some stuff like watermaker, but it will produce less water per hour than an AC unit.

It is all a trade off. If it were me starting with a new boat today, I would be tempted to go the solar lithium path and have a small diesel genny for backup ideally, or may be run the propulsion engine with a high amp alternator as a cheaper alternative. My last choice would be a noisy gas powered portable generator. A wind turbine may add a little bit of buffer too.

[john61ct]

Originally Posted by Thalas

as LiPo prices fall, isn't it possible to build a bank large enough to run AC at night with no incoming power

That would deep-cycle a **huge** bank.

And take more than an hour to recharge even with huge amps avilable.

[john61ct]

Originally Posted by tuskie

incorrectly labeled 80 A alternator.

With LFP, if the alts are true high output and set up properly, they can make an A/C genset redundant.

[tuskie]

Originally Posted by john61ct

With LFP, if the alts are true high output and set up properly, they can make an A/C genset redundant.

Yes, I'm sure you are correct.

Ours are the standard "80 amp" Hitachi alternators fitted to Yanmar diesels. They are a poor choice for battery recharge. I decided not to fit the type you are suggesting, as I'd still have to run a main propulsion engine under low load to generate power. I consider that a correctly sized genset is a better alternative in our situation.

[john61ct]

Not arguing, but note that a big enough single alt will make continuous use of 30HP charging a thirsty LFP bank.

Load enough for many, too much in some cases.

[44'cruisingcat]

Originally Posted by Cheechako

You have weather helm on a cat? My Lagoon 42 TPI seemed to have no helm feel at all, it was a bit distracting for an old mono sailor. (Also, I wonder if your AP is effected by the engine alternator magnetic field?)

For cats with big roachy mains and smaller jibs, it's pretty normal to have a little weather helm.