Add second large alternator to charge house batteries

[69Datsun510]

Originally Posted by roland stockham

The issues with very large alternators is always cost v output, allowable load on front pulley, overheating and how to reduce load when motoring. Generally belt driven alternators are not that good as generators. If instead you added a clutch driven A/C generator sized to the motors rated output you would have all the power needed, not have to worry about light engine loads and could easily disconnect it while motoring. Don't know if it has been do e this way but may be worth some research if the is space at the front of the engine. If you literally just want battery charging the are very good DC units designed for direct drive from people like Polar power in the 5-10Kw range which have the advantage of not need a fixed speed governor. DC generators are significantly more efficient than alternators.

Interesting proposal, the weight, brush wear, life span, and cost have obsoleted the DC generators. Being replaced with lighter, more power at the lower rpm range, alternator.
Where one would need to mount a heavy generator, top of the motor, would require heavy custom metal brackets. Then the belt pulleys and arrangement could be a challenge too. All solvable task, once again, like the large frame alternator conversion, is it worth the cost per gained output.
Thank you for proposing an interesting solution. Nice to have a constructive comment.

[Augi]

Originally Posted by 69Datsun510

Interesting proposal, the weight, brush wear, life span, and cost have obsoleted the DC generators. Being replaced with lighter, more power at the lower rpm range, alternator.
Where one would need to mount a heavy generator, top of the motor, would require heavy custom metal brackets. Then the belt pulleys and arrangement could be a challenge too. All solvable task, once again, like the large frame alternator conversion, is it worth the cost per gained output.
Thank you for proposing an interesting solution. Nice to have a constructive comment.

I have space for a potential generator. I would only go with a bigger alternators to replace the existing made by and recommended by the manufacturer of the existing engines. If I can get enough solar on to the boat, I have space for the lithium batteries to match the solar. I am analyzing now. Slightly larger alternator on both engines may work well enough for my use. When I increase solar and add lithium batteries I will make sure I can add to the system larger alternators or generators if necessary for my use, and not have change out want I installed to facilitate the new added solar and new lithium batteries.

[Cheechako]

The problem with an engine drive AC gen is they are rpm specific. 3600 rpm gets you 120 volts or 1800 rpm on some. You must maintain that rpm. There are a couple that are not linked to rpm but they are complicated and not widely used.

[Augi]

Originally Posted by Cheechako

The problem with an engine drive AC gen is they are rpm specific. 3600 rpm gets you 120 volts or 1800 rpm on some. You must maintain that rpm. There are a couple that are not linked to rpm but they are complicated and not widely used.

Thanks for the input. I am researching that aspect. It is possible with enough solar I can get by without a generator. Just a Yanmar recommended larger alternators for my Yanmar engines might work with increased solar and lithium batteries for my use. Then I can avoid the expense, added complexity and maintenance of adding a generator.

If I get a generator it will be in to the 5-7 KW range with two cylinders. I will not go with a smaller one cylinder.

Fisher Panda, and Whisper Power makes variable rpm ac generators that so far seem ok in the 5-7KW range. Although I am afraid to buy a Fisher Panda generator because part of the model numbers include the letters "PMS". The last thing I want is a generator that is having "PMS" continually.

Next Gen has a 5.5 ac generator that is not variable speed but runs at constant 2800 rpm rather than in the mid 3000 rpm range that all the other generators I can afford will run at including the variable speed ones with any kind of load on them. The Next Gen 5.5 KW can be bought for about $8K with everything you need including sound enclosure not including installation.

I am looking at dc generators but I don't think dc makes sense because the two biggest users of energy are ac: air cond. and water maker.

[mvweebles]

If you can afford the space, weight, and cost premium, Northern Lights cannot be beat. All marine engines need 250 hour maintenance and the exhaust elbow replaced from time to time, but the NL generators routinely go 5000 to 6000 hours before any non-routine service (leaking main seal, for example), and often go over 10,000 hours before a rebuild. Fisher Panda, Nextfen, etc just don't come close.

[Augi]

Originally Posted by mvweebles

If you can afford the space, weight, and cost premium, Northern Lights cannot be beat. All marine engines need 250 hour maintenance and the exhaust elbow replaced from time to time, but the NL generators routinely go 5000 to 6000 hours before any non-routine service (leaking main seal, for example), and often go over 10,000 hours before a rebuild. Fisher Panda, Nextfen, etc just don't come close.

Thanks for the input. I am aware that northern lights generators are excellent. I don't have the space, don't want to carry the weight, and would rather not spend that much.

I am hoping to get by without a generator. If I get a generator I am not going to use it very much. But as already discussed I don't want to use a portable generator unless it an emergency.

[a64pilot]

I find it interesting that after a link was given to show what the max limit of the PTO output of this engine is allowable, everyone chooses to ignore it, and continue to talk about large alternators.
I guess it’s information you don’t like so just ignore it? By the way if you choose to look it up, if you have a pulley on your harmonic balancer and it happens to be 30 mm in front of the balancer that means you use mount A, and I believe we all do.

[a64pilot]

Originally Posted by Dsanduril

Yanmar is pretty good about providing details for this. The summary is this picture.

Attachment 215866

The details for the 3YM30 are in the installation manual.

You can mostly unload the engine when the alternator is not needed by using an external regulator and interrupting the field current. This is pretty straightforward and just leaves the spinning friction load. You might be able to unload slightly more by using a clutch on the alternator pulley, but you won't gain much (an unquantified value) other than complexity compared with just turning off the field.

Note: remember that your alternator is probably only ~50% efficient, the values in the graph are the load on the engine, not the power output at the alternator. Figure maximum power output at alternator = about one-half the value on the graph. At 2000 engine RPM that leaves about 85A output. So, maybe a 100A alternator, but it might need a load manager in the regulator (starting to get into specifics that would depend on pulley ratio, mounting conditions as compared to other overhung equipment, ...)

In order to make it easier for people, here is the post with the link. Page 18. I believe the conversion puts max draw about 3 HP at 1800 and we know that it takes about 1 HP to make 25 amps, then you can put a 75 amp draw on that motor at 1800 RPM.
Here is a link to a KW to HP conversion https://www.rapidtables.com/convert/power/kw-to-hp.html

This link tells how many hp per amps are required and there are many sources of this, Balmar is one.
https://alternatorparts.com/how-much...ator-make.html

[Jammer]

Originally Posted by roland stockham

Generally belt driven alternators are not that good as generators. If instead you added a clutch driven A/C generator sized to the motors rated output you would have all the power needed, not have to worry about light engine loads and could easily disconnect it while motoring. Don't know if it has been do e this way but may be worth some research if the is space at the front of the engine.

Belt drives lose 5-10%. Other drives also have losses.


The efficiency problems with what you call "belt driven alternators" are because the frame sizes are so small compared the output power and output current. Switching to 24v helps a little because the currents are halved but switching to a larger frame, with a larger rotor and a larger stator, is what is needed to significantly improve output and efficiency. The problem is that there usually isn't room.

If you literally just want battery charging the are very good DC units designed for direct drive from people like Polar power in the 5-10Kw range which have the advantage of not need a fixed speed governor. DC generators are significantly more efficient than alternators.

The last time I looked into Polar Power they were no longer shipping a standard marine product and were only interested in OEM and military contracts. They never have sold generator heads without the associated engine primarily because their rotor design does not have its own bearings instead being bolted to the crankshaft output flange in place of a flywheel. There is nothing magic about their design other than an extremely large frame, rotor, and stator. Electrodyne and others have brought permanent magnet armature products to the market also.

[Jammer]

Originally Posted by Augi

Fisher Panda, and Whisper Power makes variable rpm ac generators that so far seem ok in the 5-7KW range.

I believe these are inverter generators, similar in design to the Honda suitcase generators.

Next Gen has a 5.5 ac generator that is not variable speed but runs at constant 2800 rpm rather than in the mid 3000 rpm range that all the other generators I can afford will run at including the variable speed ones with any kind of load on them. The Next Gen 5.5 KW can be bought for about $8K with everything you need including sound enclosure not including installation.

For what it's worth, the Next Gen is a belt drive machine with the engine running at 2800 RPM and the generator head running at 3600 RPM. Forum participant a64pilot has one, as I recall. I think they are fine for occasional use to supplement solar. They do not last as long as 1800 rpm machines and require more frequent service.


Large cats have so much room for solar panels that I am at something of a loss to understand the rationale for a genset. Particularly so given that weight is always a concern on a cat. But then I am not a cat person so perhaps I don't understand.

[69Datsun510]

Originally Posted by a64pilot

I find it interesting that after a link was given to show what the max limit of the PTO output of this engine is allowable, everyone chooses to ignore it, and continue to talk about large alternators.
I guess it’s information you don’t like so just ignore it? By the way if you choose to look it up, if you have a pulley on your harmonic balancer and it happens to be 30 mm in front of the balancer that means you use mount A, and I believe we all do.

Your point wasn’t missed by me, caught my eye immediately, but was distracted by having to go get some groceries for my wife and I.

When I got back on the forums, Dsanduril posted the graph of the Yanmar used by the OP and close to my 3JH5E. So, I used his post to comment should be taking in to consideration.

I have gotten new folding props for my catamaran, and have concerns with a heavy payload for cruising, proper rpms will be reached. So, loading up an alternator only leaves so much power available if underway. At anchor, not as much of an issue, but with my setup, I would only use at anchor as a last resort.

So, I just need to put on a decent small frame bolt on an serpentine belt, externally regulated, MC 614, and draw what I can while I’m motoring for lack of wind.
The alternator by Howard Ferris, mentioned, looks decent, even built for low rpms for best output.

[mvweebles]

Originally Posted by a64pilot

I find it interesting that after a link was given to show what the max limit of the PTO output of this engine is allowable, everyone chooses to ignore it, and continue to talk about large alternators.
I guess it’s information you don’t like so just ignore it? By the way if you choose to look it up, if you have a pulley on your harmonic balancer and it happens to be 30 mm in front of the balancer that means you use mount A, and I believe we all do.

What I find interesting is that post #21 was largely ignored. Captstu more or less did exactly what the OP was asking about (including being on a cat) with a similar use case - to run A/C. Was a good post about his experience over several thousand hours and included lessons learned about overloading the engines and expensive cable runs included.

In the end, OP has a 1200w solar array (!) and 800ah LFP battery bank (! ) and wants to run AC through the night in The Rio. There is no free lunch in replacing that much power day-in/day-out - his solar/battery system will probably replenish about 8-hours of AC usage, maybe more on sunny days, less on rainy days.

But if ever there was a use case for a robust, low rpm generator, this is it.

[Captn_Black]

Originally Posted by Jammer

I think it is important to mention the drawbacks of this approach even though it is increasingly common.

1. There is a carbon monoxide risk. People have died as a result of running generators on deck. In Minnesota we now have a burdensome law requiring three separate placards on carbon monoxide risk from generators because of a particularly unfortunate accident where three people died below decks on a cold rainy day.
2. There is a fire risk from the gasoline used to fuel the generator. Where will you keep the fuel? Where will you store the generator? What if there is a fuel leak while it is being stored?
3. There is an electric shock risk particularly if the portable generator is used in adverse weather or sea state.
4. Portable generators are prime targets for theft.
5. You will use more fuel. Honda generators will give you 4-6 kwh per gallon of gasoline while a typical diesel genset will give you 9-11 kwh per gallon.
6. They won't last as long. While reports vary widely, I put the useful life of the better suitcase generators at around 2000 hours. The low-speed diesel sets (Northern Lights etc) are good for 20,000 hours, and the economy diesel sets (Farymann/Entec, Next-gen) about half that.

As a result of 4, 5, & 6 over the course of years it's hard to save much money.

The dangers of having gasoline onboard should not be underestimated either. Additionally, I have read of CO poisoning in cases where the ship was on a 2 point anchor/mooring or at the marina, and the exhaust fumes were able to blow into the cabin with a light breeze and settle there.

[Maine Sail]

Originally Posted by a64pilot

I find it interesting that after a link was given to show what the max limit of the PTO output of this engine is allowable, everyone chooses to ignore it, and continue to talk about large alternators.

Nigel Calder and Integrel Solutions also go beyond this as do many boat owners. Neither Volvo nor Yanmar can really give solid engineering data to back up these limits (had this discussion at the training). Nigel has done more testing of large DC alternators on both Yanmar and Volvo engines than anyone I know of, thousands of hours.. (we are Integrel trained installers) Integrel carries an insurance policy "just in case" and has never once used it.

I know Nigel himself is pulling about 8kW off his crank pulley and Bruce Schwab has numerous systems out there on Yanmar's well in excess of 200A. We have a customer with a massive E-300 Electrodyne that has over 7K hours on his Yanmar and the alt is being driven off the crank.

[a64pilot]

Originally Posted by Maine Sail

Nigel Calder and Integrel Solutions also go beyond this as do many boat owners. Neither Volvo nor Yanmar can really give solid engineering data to back up these limits (had this discussion at the training). Nigel has done more testing of large DC alternators on both Yanmar and Volvo engines than anyone I know of, thousands of hours.. (we are Integrel trained installers) Integrel carries an insurance policy "just in case" and has never once used it.

I know Nigel himself is pulling about 8kW off his crank pulley and Bruce Schwab has numerous systems out there on Yanmar's well in excess of 200A. We have a customer with a massive E-300 Electrodyne that has over 7K hours on his Yanmar and the alt is being driven off the crank.

It pretty much boils down one of a couple of things.

1. Yanmar intentionally, and with little to no engineering studies publishes an incorrect limit for their engines, one that if anything hurts their marketability.

2. People who sell products that exceed Yanmar’s published limits and do so by a large margin are simply smarter and more knowledgeable than Yanmar.

My belief is that those that do so, have a financial reason for saying that Yanmar is ignorant and doesn’t know what they are doing, and that the majority of people with the big loads don’t often operate the engine overloaded for enough time for the damage to become apparent.
Showing me people who have done so and had nothing happen is akin to me showing you people who have smoked for decades as proof that smoking doesn’t cause cancer and isn’t bad for your health.

Most engine manufacturers are pretty liberal with their limits, and will publish what amounts to engine oil change intervals that don’t lend themselves to max life etc., but will make one last long enough.
On edit, it’s hard to believe they publish a fake low limit, and apparently have done so for a long time, what’s to gain?

So you have to ask yourself, why would Yanmar go to all the trouble to develop a chart, publish it and even develop a formula to account for crankshaft offset, and do so for each of their engine models different charts etc if it was bogus

All I would ask for is for sellers of these products, especially when kits are sold for specific engines, if these kits knowing and intentionally exceed an engine manufacturers published limitations, that they buyer should be made aware of that fact. And let them decide if they want to do that or not.
I wasn’t made aware of it when I purchased my equipment, and believe that I should have been.
Now I would like to believe that the person who sold me the materials didn’t know that use of it would exceed the engines limit, I didn’t know of the limit myself until recently.

To not inform the consumer is wrong, and I’d bet it may even be illegal.

I had wondered why Yanmar didn’t offer a 200 amp or so stock alternator, the market is plainly there.
For instance my 2001 Duramax pickup truck had as an option dual I believe 220 AMP alternators, I know dual alts were an option, just not sure if the were 200 amp alts or not, and that was 19 years ago.