WHAT IS A GOOD GENERATOR ??

[geoleo]

One that has a heat exchanger and 12volt output as well as 120 volt AC ??? Approximately 4-6 KW---- Don't say MASE!

[Jman]

I am by no means an expert, but pretty sure you are not going to find a marine generator that has both 120ac and 12v. Normally 120 (or 220). Battery charger used to get 12v. There are a few 12v models, then you use inverter to get to 120.

[geoleo]

Yes I know-- but a friends trawler Northern Lights 8KW does have a 120+ a 12 volt output-besides if a gen with a alternator that can charge its own battery why cant it also charge a house bank? or is it rocket science

[Lepke]

Most generators have a 12v charging circuit intended for the generator's separate battery. The 12 volt circuit isn't intended to quickly charge large banks of semi discharged batteries, except on generators large enough have an alternator.
If you're running the generator, you have ac for your normal charger if the generator is sized correctly.
Don't buy a generator with an air cooled engine.

[Dockhead]

If it's an AC generator, use AC power via charger or charger/inverter to charge the house bank.

As far as choice of generators goes - first decision is intermittent duty rated high speed vs continuous duty rated low speed. The latter is more expensive, heavier, and bulkier, but quieter and more reliable and longer lasting.

Then, if heavy duty, choose from leading makers - Northern Lights, Onan, Kohler. I think most people consider NL to be the best, but I can't see a lot of difference between these.

If light duty, then different choices.

[contrail]

Originally Posted by geoleo

One that has a heat exchanger and 12volt output as well as 120 volt AC ??? Approximately 4-6 KW---- Don't say MASE!

I am curious by not MASE?

[savoir]

The best generator that I ever owned was one of these.

NEXT-GEN - Marine Power Units

[Dockhead]

Originally Posted by savoir

The best generator that I ever owned was one of these.

NEXT-GEN - Marine Power Units

Those look good to me, too. Can you give details about your experience?

[john61ct]

I wish there were more commercially made units dedicated to just spinning large-frame high-output alternators, I have very little use for shore power.

300+ amps continuous output, even x2 for redundancy.

Pulley sizes to optimize output at lowest rpm producing enough torque when loaded.

Balmar adjustable VRs

Powerful cooling over the diodes.

Perfect into a big LFP bank, no more than 30min runtime per day.

I suppose not too hard to DIY with a good engine guy, maybe 20-25HP?

But purpose built OTS would be better.

Q: stock truck alts or speciali$ed marine ones?

[Dockhead]

Originally Posted by john61ct

I wish there were more commercially made units dedicated to just spinning large-frame high-output alternators, I have very little use for shore power.

300+ amps continuous output, even x2 for redundancy.

Pulley sizes to optimize output at lowest rpm producing enough torque when loaded.

Balmar adjustable VRs

Powerful cooling over the diodes.

Perfect into a big LFP bank, no more than 30min runtime per day.

I suppose not too hard to DIY with a good engine guy, maybe 20-25HP?

But purpose built OTS would be better.

Q: stock truck alts or speciali$ed marine ones?

Noelex had something like this on his old boat, using a small propulsion engine (IIRC) to drive a jumbo school bus alternator.

I consider something like this for my own next boat.

I use a lot of AC power on board (comforts of home ), but I don't care whether power is generated by AC or DC, because the conversion is very efficient, first of all, and second even I don't use more AC power, than I do DC power, so I'm converting in any case.

I like this idea because a bog standard school bus alternator (there isn't any such thing as a "specialized marine alternator" AFAIK) is cheap and can be repaired by any third world auto electric shop with a screwdriver and a hammer, or by me. Or swapped out with a spare.

So easier to keep running than a regular AC generator.

The challenge, which I don't understand, is how to operate it. Maybe you just increase the revs if you think you will need more power -- you can work out max available power at different revs. Being careful not to leave it running at higher speeds with no load on. Or maybe it would be possible to invent some control system which would drop the revs automatically.

[a64pilot]

An issue with having a pure DC generator is how good a battery charger will it be?
There are many, very good, very sophisticated AC battery chargers.
However the biggest problem with a pure DC genset in my opinion is their relative non availability. In truth I have never seen one.
As much as I like Science projects I have decided to as much as possible to buy off the shelf as opposed to trying to roll my own, watermaker for example. They are not Rocket Science.
Same for a generator.
It’s so easy now to convert back and forth between AC and DC with decent efficiency that even if you only want DC power, an AC generator still makes sense based on cost and availability.

[a64pilot]

Originally Posted by Dockhead

Those look good to me, too. Can you give details about your experience?

Many of us have them.
Biggest draw is cost, size, weight and fuel consumption. It’s small and with the sound enclosure included only weighs 200 lbs, 160 without the sound enclosure. Two people can easily carry it and lower it into a Lazarette.
I don’t have enough Boat to warrant a full size gen, and I didn’t want to lose the storage space, and gain all that much weight. I have a 30amp electrical system so anything over 3.5 KW I couldn’t use anyway without rewiring the Boat.
I have always been amazed when I see a Cat with a huge, heavy generator. I would have thought that the weight wouldn’t be wanted.
According to the guy at Nex Gen they have many on shrimp boats etc that have over 5000 hours, he says very few if any actually wear out, it’s usually disuse and corrosion that gets them.
It is louder and not as smooth as a NL or other 1800 RPM gen, it’s actually a mid RPM as it runs at I believe 2850 RPM and drive the gen head through a serpentine belt at 3600 RPM.
The motor is a Kubota single cylinder horizontal Diesel used primarily on garden equipment, construction dirt tampers and the like.
It oddly enough has a ball bearing crankshaft, and I believe a wet cylinder, so it ought to be child’s play to overhaul. However as the cost isn’t all that bad and since it’s compact and only weighs 160 lbs, likely if or when mine wears out I’ll likely just replace it with a couple of hours work to R&R.

They are capacitor regulated, not an AVR so simple but not as sophisticated. I learned you can change the voltage by slightly changing the Uf of the capacitor.

If your the type that cranks the generator before you unplug from shorepower and it runs until you return to the dock, then this may not be your generator, but if you want to run it a couple of times a week to make water, charge batteries or when it’s hot and the mosquitos come out, it’s great for that. Think of it as a big, built in Diesel Honda.

[Dockhead]

Originally Posted by a64pilot

An issue with having a pure DC generator is how good a battery charger will it be?
There are many, very good, very sophisticated AC battery chargers.
However the biggest problem with a pure DC genset in my opinion is their relative non availability. In truth I have never seen one.
As much as I like Science projects I have decided to as much as possible to buy off the shelf as opposed to trying to roll my own, watermaker for example. They are not Rocket Science.
Same for a generator.
It’s so easy now to convert back and forth between AC and DC with decent efficiency that even if you only want DC power, an AC generator still makes sense based on cost and availability.

Yes, I agree about conversion efficiency, and I don't care that much whether I generate AC or DC power.

But a DC generator like this has some profound advantages. Note that I do NOT list "getting DC power directly" as an advantage

* Can run at different RPMs so that engine runs with a more healthy load for a given RPM.

* Cutting back the revs when small power is needed, will be quieter and less wear on the engine, not to mention more healthy.

* Using a standard school bus alternator (or a pair of them) is cheap, easy to repair, easy to carry a spare for -- in other words, easier to keep running in remote locations.

* Separating engine from generator makes both easier to get at and service.


Making it into a good battery charger is trivial -- a good external controller will do that -- Balmar or Sterling.

[Dockhead]

Originally Posted by a64pilot

Many of us have them.
Biggest draw is cost, size, weight and fuel consumption. It’s small and with the sound enclosure included only weighs 200 lbs, 160 without the sound enclosure. Two people can easily carry it and lower it into a Lazarette.
I don’t have enough Boat to warrant a full size gen, and I didn’t want to lose the storage space, and gain all that much weight. I have a 30amp electrical system so anything over 3.5 KW I couldn’t use anyway without rewiring the Boat.
I have always been amazed when I see a Cat with a huge, heavy generator. I would have thought that the weight wouldn’t be wanted.
According to the guy at Nex Gen they have many on shrimp boats etc that have over 5000 hours, he says very few if any actually wear out, it’s usually disuse and corrosion that gets them.
It is louder and not as smooth as a NL or other 1800 RPM gen, it’s actually a mid RPM as it runs at I believe 2850 RPM and drive the gen head through a serpentine belt at 3600 RPM.
The motor is a Kubota single cylinder horizontal Diesel used primarily on garden equipment, construction dirt tampers and the like.
It oddly enough has a ball bearing crankshaft, and I believe a wet cylinder, so it ought to be child’s play to overhaul. However as the cost isn’t all that bad and since it’s compact and only weighs 160 lbs, likely if or when mine wears out I’ll likely just replace it with a couple of hours work to R&R.

They are capacitor regulated, not an AVR so simple but not as sophisticated. I learned you can change the voltage by slightly changing the Uf of the capacitor.

If your the type that cranks the generator before you unplug from shorepower and it runs until you return to the dock, then this may not be your generator, but if you want to run it a couple of times a week to make water, charge batteries or when it’s hot and the mosquitos come out, it’s great for that. Think of it as a big, built in Diesel Honda.

Sounds very good!

Is it reliable? Have you had any trouble with yours?

[skipmac]

Originally Posted by Dockhead

Sounds very good!

Is it reliable? Have you had any trouble with yours?

Bill Trayfors (btrayfors) has had one of these for years and has been happy with his. The only problem he reports, unloaded the AC wave form is kind of dirty and his inverter wouldn't kick in and sync with it unless he first added some kind of pure resistive load, then no problem.

I think later generations have fixed this but maybe A64 has some experience in this area.

You might also PM Bill to see if he has any new comments.