Does a genset still make sense?

[Chotu]

Originally Posted by team karst

Our H2.2 kW experience is fuel out at 3am, running a 9k BTU. U know who had to refill the hot motor. It holds exactly one gallon.


Very glad to have a diesel fixed unit. Honda sits at home. True on your purchase cost analysis though.

This is funny.

Reminds me of my propane refrigerators I’ve had in the past on the boat and also RVs.

The ONLY time the tank empties and sets off the “out of propane” alarm is between the hours of 2am and 4am. Ha ha ha

It also has a special preference for doing so in storms between those hours.

[sv_isara]

So where are these 400 or even 200 amp alternators people are referencing? At least for small case alternators I don't see much more than 100a *continuous* - as in for well over an hour or two. Maybe for 10 or 15 minutes, maybe slightly more if highly ventilated.

I'm currently working on a 250 -300a *continuous* alternator - that can run for hours at a time.

I'm getting close to leaving for Mexico but since my current alternator is only 100a continuous (rated 140), despite engine charging working I think I'll bring a 2.5kw gas suitcase generator just in case.

[Shaneesprit]

Hi
I have not checked your numbers - only the idea .
The are right 75% of the engine power via the alternator would be near perfect loading for the engine.
However the issues would be around you are assuming that you are to use the Alternator at 100% power ? Do you have a constant load? More likely you would be using a lot less for the majority of the time.
Or if you doing a from scratch installation, big alternator and Electric drive.

[GrowleyMonster]

Separate genset size can be tailored to the user. Separate genset gives redundancy. You could even mount a pulley and additional pillow bearings on the prop shaft, for coupling an electric drive, and have backup propulsion for not a whole lot of money. Especially for a small boat, a PMAC motor and controller, cables, user interface, and mount could be put together for under $1k and use the existing prop. A propulsion battery bank consisting of 8 golf cart batteries in series is a proven EP "gas tank" that is cheap and durable if well maintained, or just run without batteries, only when the genset is running. Then if diesel conks out, you have a way to get home that is far superior to an outboard. A genset also saves wear and tear on the diesel.

The diesel genset is still not very efficient at topping up a bank. It is good for the bulk stage. For the reduced load of the absorption and float stages, solar really shines, as does alternator charging when you have to run the diesel anyway. One can operate for days without actually topping up the battery but eventually it needs to be done for good battery health. I would prefer not to use the genset for that, nor use the main engine unless it is also needed for propulsion or other uses.

A genset is often quieter than the main engine. Being smaller, it is cheaper and easier to rebuild or replace than the main engine.

Driving a refrigeration plant from the generator's engine makes good mechanical sense. If you want central air you wouldn't want to run the compressor from the main engine if it is not being used for propulsion, nor with an electric motor running off the house bank unless it is a large one, and even then it is running indirectly off the genset, but with reduced efficiency. Or off the main engine alternator, with even more reduced efficiency.

Of course a genset is not a necessity. But there are a lot of reasons to have one if it fits the budget. For a user quite dependent on electrical devices such as galley equipment, etc, it can even on larger boats be a good idea to have two gensets.Extra points for being able to run in parallel. Generators can be downsized, and ran in parallel during periods of peak usage. I have personally not seen a yacht running two AC gensets in parallel but there is no reason why it can't be done.

[Lee Jerry]

I'm surprised no one has brought this up yet, but I think the OP has it backwards. The real question is "do propulsion engines still make sense?"

If I were starting from scratch (i.e. new build / purchase, or perhaps re-power of old boat), it would be a hybrid with:
- Two (or more) generators, probably of different sizes
- Electric motor(s) driving sail drive(s), capable of re-generation
- "Large" Li battery bank
- Large solar array
- (Perhaps a wind gen if in higher latitudes)

Solar handles daily loads with ease; use one generator (of appropriate size) when needed to top up batteries or run occasional high loads (washing machine, water maker, etc.).
Solar/batts handle short, silent maneuvering on/off dock or mooring.
Re-gen during sailing (to replace energy used during maneuvers and "top up" as needed, or turn off for less drag).
Generators running for extended motoring - one for calm water "efficient cruising," more for rough conditions or higher speed.

This works better with a cat but can also apply to a mono. Also works better as size increases.




PS - don't you love it when the OP never participates in the thread they started?

[wingssail]

Originally Posted by Dockhead

Sure, as long as you don't have to make miles upwind.

Windage of all kinds has a big effect on upwind performance. Solar arrays aren't as bad in this on cats because they heel less (presenting less area to the wind), but a big array on a mono is, aerodynamically speaking, really ugly, when the mono is heeled.

Making miles upwind is disproportionately laborious so most cruisers just don't really do it -- they wait for better wind or use the motor or choose a different destination. In those cases solar is not really a problem....

I agree with dockhead on this. A large solar array on an arch is bad for performance. It is weight (in a bad place) and windage. Even more so with a dingy hanging back there. Can't prove it with numbers, but it's like all the other things people put on their boats: "That little difference doesn't do a thing." But they all add up.

I've gone a completely different direction: I keep my boat light, simple, and efficient. Great sailing performance is why I bought my boat and I want to keep it that way. I have no arch and minimal windage. My dingy is below deck when underway. I have no genset and use the main engine to supplement my minimal, railing mounted, panels. I keep my electrical loads down and have few gadgets and appliances. My boat is light, fast and simple. I avoid complexity, knowing that all electronics fail eventually and diagnosis is hard enough with a simple system, plus back-up and redundancy is easier with simple systems.

By the way, I have 6700 hours on my main engine and it is still very good. 90% or more of those hours has been battery charging since I rarely motor. I have only a 130amp small frame alternator but that usage does not seem to have harmed the engine. I see no need for a second diesel engine with the weight, complexity and cost.

This is not to say that I live a spartan life onboard. I have a comfortable boat with all the toys I find fun and useful, plenty of power to do what I want, good ventilation (although I have AC for at the dock) Hot and cold 24/7 running water, and I enjoy great sailing performance and few maintenance issues and my boat is capable and easy to manage (and an easy, clear, deck to work on) in heavy weather.

I only mention all this to note that there is more than one way to go cruising, and some of us don't buy boats just to have a platform to add things to.

[Takitimu]

I can honestly say a generator right now sounds beautiful. Currently in the pacific more than 1,000 miles from land. The starter went out on the main engine and it shorted, took out the alternator and 1/3 of the solar on the boat, and half the lithium batteries. Took us an entire day to get the starter situation fixed and an entire day to bypass the regulator on the alternator, so we can get some power but we can only run in short periods so the alternator does not overheat.. I'll never leave shore without a backup generator.. hand stearing by the stars sucks big-time. The boat I'm on is a charter not mine and he had talked the generator out long ago.. can't wait to get back on my boat. The boat I'm on is beautiful but we picked up 3 stranded people a couple days ago that had been dismasted and drifting for a week. It's miserable with 8 people onboard and all their stuff, but we are managing and everyone is in good spirits. Anytime you have a packed boat on an ocean crossing it's not ideal, the new stowaways are doing everything they can to help but they are French and speak little English.

[Adelie]

Originally Posted by pwillems

I have always read that the purpose behind installing a standalone genset rather than just using the main engine to charge batteries is due to the inefficiencies of running a diesel engine with only the light load from the alternator. This makes sense, and I would agree. But, these days, it is quite easy to get hold of some very large alternators and very large inverters, so I am not sure it always makes all that much sense anymore.



Let's say a small catamaran owner has 2 * 20hp and a decent lithium bank that will happily accept high charge rates. A 400amp/12v alternator uses ~16hp (1 hp per 25 amps). At the full 400 amps output, that engine is at over 75% working load. Taking into account heat derating and other inefficiencies, the engine is still getting a pretty good workout for the entire duration of the charge.



Of course, you wouldn't want that alternator putting out its full charge when you actually need that engine to push the boat into some challenging seas, but that is easily managed with a clever regulator, or even a potentiometer if required.

Getting a 400A/12v alternator seems like a stretch.
You could probably get a 250-300A bus alternator for about about $500-800. In operation it’ll heat up and output will drop to 200-250A. To make that work you are going to need to spend another $500-1000 for a serpentine belt system which is almost certainly not stock on a 20hp inboard. And you need a regulator which is more money.

Question arrises about how much side load the prime mover can take on the output shaft, even with a serpentine belt. That you will need to talk to the engine maker about.

If your engine room is spacious enough you could mount 2 alternators on opposite sides of the engine so side loading the output shaft is minimized.

What’s the alternative?

A. Honda 2200
B. Larger diesel genset.

Honda 2200 ($1100) is rated for 1800W continuous. That’s 150A at 12v. Problem is it’s hard to find a 12v charger larger than 40-50A. You could double up a couple 50A chargers. Using 3 or 4 chargers means needing to MickyMouse the sockets on the 110vAC side.

If you get a large diesel genset most/all output AC and you need to source 1 or many charger(s) to convert that to 12v.

If you change the battery bank from 12v to 48v then you can fairly easily source a golfcart charger that will use 900-1800W so one or two will use the full output of the Honda.

The big reason to have a 48v system is if you are going to use electric propulsion or an electric galley. If you aren’t going to do either of those I don’t see going to 48v.

Really you want to look at the whole system. How much solar do you have? How much is you normal consumption? How often do you need a secondary charging source (engine-alternator or genset)?

[s/v Jedi]

Originally Posted by wingssail

I agree with dockhead on this. A large solar array on an arch is bad for performance. It is weight (in a bad place) and windage. Even more so with a dingy hanging back there. Can't prove it with numbers, but it's like all the other things people put on their boats: "That little difference doesn't do a thing." But they all add up.

I've gone a completely different direction: I keep my boat light, simple, and efficient. Great sailing performance is why I bought my boat and I want to keep it that way. I have no arch and minimal windage. My dingy is below deck when underway. I have no genset and use the main engine to supplement my minimal, railing mounted, panels. I keep my electrical loads down and have few gadgets and appliances. My boat is light, fast and simple. I avoid complexity, knowing that all electronics fail eventually and diagnosis is hard enough with a simple system, plus back-up and redundancy is easier with simple systems.

By the way, I have 6700 hours on my main engine and it is still very good. 90% or more of those hours has been battery charging since I rarely motor. I have only a 130amp small frame alternator but that usage does not seem to have harmed the engine. I see no need for a second diesel engine with the weight, complexity and cost.

This is not to say that I live a spartan life onboard. I have a comfortable boat with all the toys I find fun and useful, plenty of power to do what I want, good ventilation (although I have AC for at the dock) Hot and cold 24/7 running water, and I enjoy great sailing performance and few maintenance issues and my boat is capable and easy to manage (and an easy, clear, deck to work on) in heavy weather.

I only mention all this to note that there is more than one way to go cruising, and some of us don't buy boats just to have a platform to add things to.

That’s what I wrote: you do not have a large solar array, yet you conveniently know that it is bad to have one anyway

Availability of fossil fuels may last longer than our lifetime but I don’t think so: they will refuse to sell it to you or they will make it unaffordable. Opinions on large solar arrays will quickly change at that time but of course there will be no solar panels to be had at that time because of extreme shortages.

I’m not sure how many people have lived through natural disasters but we have had a range of them and have personally been confronted with armed men blocking access to fuel service stations, refusing to let you buy fuel. It all quickly stops when that happens.

[rslifkin]

The relative performance impact of adding a given item to a boat isn't an absolute thing. Depending on what else is already present (or going to be added), the effect varies. A huge solar arch off the stern will definitely be a penalty compared to nothing back there. But solar over the cockpit may be a smaller penalty. And if there's already a bimini over the cockpit, then making that hold solar panels has almost no additional effect on windage, etc. But going from nothing over the cockpit to solar or a bimini will have some effect on upwind performance.

A fast, low drag boat may actually be effected less than a high windage boat that already can't make hull speed upwind before being overpowered. For the slow boat, any additional windage will make the boat even slower. For the fast boat, it might be slightly harder to reach hull speed, but if the hull form is one that can't easily exceed hull speed upwind, then the bit of extra drag won't be much of a penalty (provided the boat can still reach hull speed upwind with the extra drag). Hull forms that are fastest at lower angles of heel will also see less drag from items like biminis and solar panels compared to hulls that are heeled further and exposing more of the underside of these items.

So what's reasonable to install really depends on the total package of your needs (and therefore what else you'll also have on the boat) as well as the boat in question.

[akopac]

I have always been a proponent of less is more…
Using less power gives you more to work with. Before I’d be looking at any genset I would be looking at why you need so much power?reducing power consumption is much cheaper and requires less maintenance than adding power generation.
I’ll use myself as an example.
Fridge box Reinsulation is labor intensive but is the most rewarding solution to power consumption. If done right it requires no maintenance.
Replacing ALL lights with LEDs is cheap and easy
Going to low power computer for navigation at night
New low power radar isn’t cheap, but when you replace a broken unit a Black Friday special pays off big. Watermaker type can be a solution too. I use a spectra and it sips power.
My consumption cruising in the tropics is :
At anchor 34 overnight charged by 10am
Underway 52 overnight charged by noon
Underway using radar overnight 60 charged by 1:30pm

460 amphr firefly batteries
400 watts solar
Engine or Honda 1000 backup, but very very rarely ever use them for charging purposes.

[s/v Jedi]

Originally Posted by akopac

I have always been a proponent of less is more…
Using less power gives you more to work with. Before I’d be looking at any genset I would be looking at why you need so much power?reducing power consumption is much cheaper and requires less maintenance than adding power generation.
I’ll use myself as an example.
Fridge box Reinsulation is labor intensive but is the most rewarding solution to power consumption. If done right it requires no maintenance.
Replacing ALL lights with LEDs is cheap and easy
Going to low power computer for navigation at night
New low power radar isn’t cheap, but when you replace a broken unit a Black Friday special pays off big. Watermaker type can be a solution too. I use a spectra and it sips power.
My consumption cruising in the tropics is :
At anchor 34 overnight charged by 10am
Underway 52 overnight charged by noon
Underway using radar overnight 60 charged by 1:30pm

460 amphr firefly batteries
400 watts solar
Engine or Honda 1000 backup, but very very rarely ever use them for charging purposes.

I bet you are cheating with propane or other additional fuels

[Simi 60]

Originally Posted by akopac

I have always been a proponent of less is more…
Using less power gives you more to work with

Nope
Less is simply, less

Originally Posted by akopac

. Before I’d be looking at any genset I would be looking at why you need so much power?

Because we like nice things

It's nice to be able to stay out for months at a time and pull a fillet steak out of the freezer
Cook it in the Air Fryer
Have large ice cubes in my adult beverage
And ice cream when I want it

reducing power consumption is much cheaper and requires less maintenance than adding power generation.
I’ll use myself as an example.
Fridge box Reinsulation is labor intensive but is the most rewarding solution to power consumption

.
I found it far cheaper and easier to buy a new 500 litre 240v fridge freezer.
Did it online, a few clicks of a keyboard.
The guys who delivered it took the old one away and installed the new one.

I'd hate to think what it would cost to build a 500 litre DC fridge/freezer

If done right it requires no maintenance

.
In the decades I have been cruising and in the boatbuilding game, DC refrigeration seems to be high up on the list of things being repaired

Replacing ALL lights with LEDs is cheap and easy

Generally, yes

Going to low power computer for navigation at night

And we have these X 2 running 24/7 for a lot more than night navigation.

New low power radar isn’t cheap, but when you replace a broken unit a Black Friday special pays off big.

Or you could have no radar at all.
Cruised for 30 years without one, didn't die once

Watermaker type can be a solution too. I use a spectra and it sips power

.
You'd need to prove how for me to believe it.
I believe they use the same pumps and membranes as other watermakers
Therefore the same power and pressure requirements to work.

We have 2500 watts of solar
We can and do run everything off of solar, battery and inverter - have done for 7 years full time cruising
No marinas or shore power.
Genset only gets used after 3 days of no sun.

[team karst]

Originally Posted by akopac

I have always been a proponent of less is more…
.

Amen brother. I had to do some electrical work on a 76’ motor sailor. It had 3 gensets, one was 220V/50Hz. The others 60Hz 240/120.

[skipperpete]

Dockhead’s observations regarding upwind performance and and solar arrays makes perfect sense to me, my own boat is affected by exactly this, but the OP has a Roberts 57 and this is a vessel that really can carry a genset and fuel comfortably. On the other hand it could just as easily be self sufficient electrically with that much deck and cabintop space for a really large solar array.