Charge Cycle Generator

[FlyingCloud1937]

Hi All,

Just joined, I'm a stink pot as some of you may call me.

But we all have the same needs Sail or Power...especially if you spend anytime on anchor.

My house bank is 720 amhr at 12 volts, we use on average about 110 amphrs per 24 hr when on anchorage.

I needed a good charge source on anchor, and charging through a AC gen to shore charger is a very inefficient way, both in fuel costs, and time listening to a generator.

I searched high and low for a good dc generator, and wasn't happy with anything the market had to offer..either price point, or quality, or to small.

So I went about studying the issues and decided I could build a better mouse trap.

Here it is, specs as follows 13 hp Perkins 400.05, Leece Neville 275 amp alternator, heat-exchanger cooled, Balmar MC614 controller, total weight 165 lbs. Fuel burn 1 liter per hr.

Output 3.6kw 12 volt dc, 7k btu domestic HW

Lloyd

below are some pics

[FlyingCloud1937]

The generator Mount In progress.



On vacation,

[FlyingCloud1937]

woops

[sigmasailor]

Hi Lloyd,

Looks really nice. Just one question: if the output is 3.5 kW (14x275) or around 5 Hp why use a 13 Hp engine? You could have selected a smaller (and lighter) engine withe the added advantage that you properly load the diesel. I suspect the efficiency of the package will be more than 40% (5/13).

In the real world the output will probably be below the rated 275 A so even lower engine loads.

Eric

[GordMay]

Greetings and welcome aboard the CF, Lloyd.

[Blue Stocking]

Originally Posted by sigmasailor

Hi Lloyd,

Looks really nice. Just one question: if the output is 3.5 kW (14x275) or around 5 Hp why use a 13 Hp engine? You could have selected a smaller (and lighter) engine withe the added advantage that you properly load the diesel. I suspect the efficiency of the package will be more than 40% (5/13).

In the real world the output will probably be below the rated 275 A so even lower engine loads.

Eric

OTOH, those big mounts just beg for some other goodies, eh LLoyd?

Nice package. Boat's a classic beaut!!

[djmarchand]

Sigmasailor: Small alternators are typically no more than 50% efficient at turning horsepower into KW, thus the need for an engine more than two times the theoretical power.

Flyingcloud: Not to be too picky, but given the above, I suspect that you will burn more than 1 liter per hour, but no more than two.

I like the idea of DC generators, but a well designed AC generator, ie small, with a large charger and/or inverter can do the same thing. Some big inverter/chargers have a 150 amp charging spec and can recharge batteries quickly although they will take almost all of the output from a small genset. The AC charger does suffer from lower efficiency and poor power factor which will hurt it some in comparison to a pure DC generator, but AC generators are more efficient than DC alternators so it probably all washes out.

If you have any significant AC load like airconditioning then it makes sense to install an AC generator with a decent DC charging capability to quickly recharge your batteries.

David

[FlyingCloud1937]

Originally Posted by djmarchand

Sigmasailor: Small alternators are typically no more than 50% efficient at turning horsepower into KW, thus the need for an engine more than two times the theoretical power.

Flyingcloud: Not to be too picky, but given the above, I suspect that you will burn more than 1 liter per hour, but no more than two.

I like the idea of DC generators, but a well designed AC generator, ie small, with a large charger and/or inverter can do the same thing. Some big inverter/chargers have a 150 amp charging spec and can recharge batteries quickly although they will take almost all of the output from a small genset. The AC charger does suffer from lower efficiency and poor power factor which will hurt it some in comparison to a pure DC generator, but AC generators are more efficient than DC alternators so it probably all washes out.

If you have any significant AC load like airconditioning then it makes sense to install an AC generator with a decent DC charging capability to quickly recharge your batteries.

David

Hi David,

This alternator runs about 65% efficiency, some run up to about 75%, and as you said most run about 50%.

I have version 2 in testing right now, it uses the same alternator, but with custom wound stator, that put's out 240v 3 phase, which goes to a torrid buck transformer, and then into a rectifier. In this configuration it runs close 90% at the alt, with the associated transformer losses, and rectifier it should be north of 80% end to end. It does about 5kw cold.

The current setup max charge amps has been 260 into the bank, it has both alt and bat temp. & sensors. We just spent 28 days out, and fuel burn is in fact 1 liter per hr. Currently I have the engine running at 2400 rpm =7.7 hp, the max continious is 2800 rpm = 9 hp, and at it's top rated 3600 rpm = 13hp. Over the 28 days, I would run it for an hour and a half every other day, it would bring the bats well into absorption, at which time my HW tank element which has current sense turns on to keep it loaded, until shut down.

I have found running an AC gen and shore charger to be very poor. First most small AC gens put out a peak sign wave somewhere below 150 loaded, and I have seen em all the way down to 140. The shore charge makes most of its current between the land base peek of 170, so when you clip that much off the peek you lose up to 50% of charge source, so that 150 amp charger can only put out 80-90 amps. The end to end losses are disgusting. Been my experience that it takes a 12kw AC gen to maitain the peek voltage close to 170, so if that's the only load on the gen then it is being lightly loaded.

Onboard air can be dc now with the newer style units which run more efficiently.

Blue Stocking...certainly capable of adding a cold plate compressor, or an air compressor, even a water maker, which all could be used with the right timing to keep the engine running at peek output.

GordMay & sigmasailor...thanks

Lloyd

[Dockhead]

Welcome to CF, Lloyd! Stinkpot or not, that is one fanastically gorgeous boat! In fact I'm just running for a towel to soak up the drool I just got all over my shirt front! Wow! I think we would all love to read more and see more photos of this fantastic vessel and your adventures with her.

Your project sounds fun, and we will all be interested to hear how it shapes up.

I would not have taken this approach at all, myself, which makes me even more interested to know how it turns out.

The reason is NVH - noise, vibration and harshness. A one-lunger diesel running at 2400 RPM will be the very devil to isolate. It will shake your boat and set up all kinds of resonation in that wooden structure. What kind of sound enclosure will you have? What kind of exhaust will you have? Even with a top-notch sound enclosure and a water lift muffler with water separator (so that the cooling water is discharged under the waterline, to eliminate the splashing), I bet it will be very unpleasantly noisy. If you don't have top notch sound enclosure and exhaust, it will be unbearable, I will guess.

I have nothing against DC gensets, but as others have commented, modern high quality electronically regulated AC gensets are quite capable of putting out their rated power, and continuously. They do just fine driving good quality charger/inverters.

That is why the top builders of boats your size will invariably use a 1500 RPM heavy-duty AC genset. My boat has a Kohler 6.5kW genset which is driven by a 3-cylinder Yanmar diesel, 1000cc, running at 1500 RPM. The difference between a three cylinder engine running at 1500 RPM and a one-lunger running at 2400 is dramatic. The three-cylinder is just loping along, producing no vibration which can be felt through the hull. It is installed in a sound enclosure supplied by Kohler which was designed for it - that means that resonation frequencies and so forth were considered -- home-made sound enclosures will never work as well. This is intalled inside a sound-proof engine room, so the genset is almost inaudible. I use a Victron charger/inverter that puts out 70 amps at 24 volts, and it will put out its full output, even when other AC loads are in use.

That is a conventional solution, so boring. Yours is much more interesting! Hope you are successful and prove us skeptics wrong. Don't forget to post more photos of your boat.

[FlyingCloud1937]

Originally Posted by Dockhead

Welcome to CF, Lloyd! Stinkpot or not, that is one fanastically gorgeous boat! In fact I'm just running for a towel to soak up the drool I just got all over my shirt front! Wow! I think we would all love to read more and see more photos of this fantastic vessel and your adventures with her.

Thanks Dockhead

Your project sounds fun, and we will all be interested to hear how it shapes up.

I would not have taken this approach at all, myself, which makes me even more interested to know how it turns out.

Well I have version one installed, and have about 20 hrs run time so far. It's worked as planned. And because I also get the waste heat for domestic it helps increase end to end eff...

The reason is NVH - noise, vibration and harshness. A one-lunger diesel running at 2400 RPM will be the very devil to isolate. It will shake your boat and set up all kinds of resonation in that wooden structure. What kind of sound enclosure will you have? What kind of exhaust will you have? Even with a top-notch sound enclosure and a water lift muffler with water separator (so that the cooling water is discharged under the waterline, to eliminate the splashing), I bet it will be very unpleasantly noisy. If you don't have top notch sound enclosure and exhaust, it will be unbearable, I will guess.

First it is a 2 cylinder, and runs without vibration. No sound enclosure yet but one in the works. It's mounted to the main engine stringer on soft mounts. The base was constructed as follows 1/2 inch marine ply in bedding compound, then a layer of 1/8 sheet lead in bedding compound, with another layer of 1/2 marine ply bedded on top, the gen is mounted to that base with soft mount isolation. Outside the boat it is very quiet, and at 50 feet from my kayak you can't even hear it. Don't have enough height to in stall a water separator, but is does have the Vetus water-lock muffler.

I have nothing against DC gensets, but as others have commented, modern high quality electronically regulated AC gensets are quite capable of putting out their rated power, and continuously. They do just fine driving good quality charger/inverters.

That is why the top builders of boats your size will invariably use a 1500 RPM heavy-duty AC genset. My boat has a Kohler 6.5kW genset which is driven by a 3-cylinder Yanmar diesel, 1000cc, running at 1500 RPM. The difference between a three cylinder engine running at 1500 RPM and a one-lunger running at 2400 is dramatic. The three-cylinder is just loping along, producing no vibration which can be felt through the hull. It is installed in a sound enclosure supplied by Kohler which was designed for it - that means that resonation frequencies and so forth were considered -- home-made sound enclosures will never work as well. This is intalled inside a sound-proof engine room, so the genset is almost inaudible. I use a Victron charger/inverter that puts out 70 amps at 24 volts, and it will put out its full output, even when other AC loads are in use.

That is a conventional solution, so boring. Yours is much more interesting! Hope you are successful and prove us skeptics wrong. Don't forget to post more photos of your boat.

I have put a scope on dozens of AC gens under 12kw, and found all of them were well below the peak SW. Here in the states 120v peak SW is 170, and that is where small on-board AC with Switch mode charger design takes a big hit, when the peak SW falls below 60.

I don't know what the peak SW is in your country, but I'll bet if you scope the land grid, and compare it to your on-board AC it will be much the same clipping.

Here's a link to some pics of the boat under going the ground up restoration we have been doing over the past 9 years In The Yard 09

Thanks

Lloyd

[FlyingCloud1937]

Originally Posted by FlyingCloud1937

I have put a scope on dozens of AC gens under 12kw, and found all of them were well below the peak SW. Here in the states 120v peak SW is 170, and that is where small on-board AC with Switch mode charger design takes a big hit, when the peak SW falls below 60.

Sorry meant 160 SW...not 60

Also if anyone is interested in how this system developed, I am a member at a micro-co-generation forum microcogen.info


Thanks

Lloyd

[Dockhead]

Originally Posted by FlyingCloud1937

Thanks Dockhead



Well I have version one installed, and have about 20 hrs run time so far. It's worked as planned. And because I also get the waste heat for domestic it helps increase end to end eff...



First it is a 2 cylinder, and runs without vibration. No sound enclosure yet but one in the works. It's mounted to the main engine stringer on soft mounts. The base was constructed as follows 1/2 inch marine ply in bedding compound, then a layer of 1/8 sheet lead in bedding compound, with another layer of 1/2 marine ply bedded on top, the gen is mounted to that base with soft mount isolation. Outside the boat it is very quiet, and at 50 feet from my kayak you can't even hear it. Don't have enough height to in stall a water separator, but is does have the Vetus water-lock muffler.



I have put a scope on dozens of AC gens under 12kw, and found all of them were well below the peak SW. Here in the states 120v peak SW is 170, and that is where small on-board AC with Switch mode charger design takes a big hit, when the peak SW falls below 60.

I don't know what the peak SW is in your country, but I'll bet if you scope the land grid, and compare it to your on-board AC it will be much the same clipping.

Here's a link to some pics of the boat under going the ground up restoration we have been doing over the past 9 years In The Yard 09

Thanks

Lloyd

Great photos. Let us have more boat porn! How about some shots of the interior?

Victron did a very in-depth test of a number of marine gensets a few years ago, including analysis with oscilloscopes under different load condiios. It can be downloaded here: Marine Generator Test - Victron Energy

They did note some problems with waveform with some of the cheaper gensets, but in general all of the better gensets performed well from an electrical point of view, and worked well with the Victron charger/inverters. They really put them to the test, hooking them up to a massive bank of three parallel inverter/chargers with a capacity greater than most of the gensets' rated output.

Another reason I like charging batteries with an AC genset is that AC chargers have better controls. I can force a longer absorption charge if I want, I can precisely set up the parameters of each charging stage, and I an do an equalization charge, too. I have not seen an alternator regulator which does any of this nearly as well.

I like your plan to recover waste heat from your genset. I am working on something to do the same from mine -- adding a circulation pump and heat exchanger to transfer waste heat into my calorifier and central hydronic heating system. When you sail in a cold climate it's a crying shame to dump 10kW or more of heat into the ocean.

[FlyingCloud1937]

Originally Posted by Dockhead

Great photos. Let us have more boat porn! How about some shots of the interior?

Victron did a very in-depth test of a number of marine gensets a few years ago, including analysis with oscilloscopes under different load condiios. It can be downloaded here: Marine Generator Test - Victron Energy

Dock....d,

I am familiar with that study, it's really not on point, as it was more in re boost applications. If you read the last sections you will see that there are charge issues that they address in the study.

Here are a couple of links to studies on point, for cycle charge systems.

http://www.mechron.com/pdf/Final%20S...e%20Charge.pdf

http://www.mechron.com/pdf/Cycle%20Charge.PDF

About 99% of remote Tele-Micro sites have all moved from Prime AC to DC Cycle Charge systems, and are saving thousands per year.

I have a lot of photos of the boat in various stages of restoration, I just need to organize em.

Below are couple of interiors

Lloyd

[IMG]file:///C:/DOCUME%7E1/OWNER%7E2.STU/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]

[FlyingCloud1937]

Here's a couple of snapshots from the Xantrex manual, showing rated output versus actual output base on peak to peak voltages.

As you can see from the 1st snapshot peak to peak voltage has a real effect, so if you're running a 6.5kw AC gen and shore charger and the only load is the charger then not only will it take longer to charge, the price per kw hr increases rapidly have a look at the fuel usage in the Victron study on lite loading.

Lloyd

[Dockhead]

A fascinating discussion which is expanding my meagre knowledge about electrickery.

I don't see -- maybe I don't understand something -- how DC generation solves the problem of underloading the diesel, which seems to me to be inherent to lead-acid batteries and their charge acceptance rates. On the contrary, it looks to me that this problem will be somewhat easier to deal with using a conventional AC generator.

In my particular setup -- Kohler 6.5kW 1500RPM 230v genset plus Victron 70 amp * 24v charger cum 3kW inverter -- I have never observed any falloff in charging rates due to waveform clipping. Which is not to say that it is not a common problem; just one data point. I try not to run the genset at maximum output just on the theory that nothing electrical likes to be pushed to its limits, although this genset is rated to produce 6.5kW continuously. So I set the current-limiting function on my Victron to 25 amps (3 amps less than the rated 28 amps). Like most cruisers, I save up AC power tasks to peform all at once during genset runs, so I do often have a load of 20+ amps on the genset (washer/dryer running, vacuum cleaner, microwave, etc., not to mention water heating or oil-filled radiators).

I have never seen the battery charger putting out less current than it is supposed to. Although it is rated at 70 amps * 24v, it will actually put out 80 amps during the bulk stage of charging. That's about 2.1kW at 27 volts, so with a loss of 10% it will be using about 10 amps at 230v, or 40% of the genset's 25 amp capacity. I always get these 80 amps if the batteries can accept them, even if I have the genset well loaded up with other loads. The pictures of the waveforms in the Victron test of the better gensets seem to show no clipping. Certainly, I have never experienced such a problem.

The genset uses about 1.2 liters/hour of diesel at a 40% load, so it is reasonably efficient even if only the charger is running -- provided the charger is in bulk charge mode.

Ah but there's the rub -- bulk charge mode only gets me up to a 70% or 75% charge or so -- then the current falls off. So whether you are using a DC genset or an AC genset you will still not be able to load the genset optimally for very long. And I would think that with the much more primitive regulation of DC charging systems, this high loading will end sooner, than with a sophisticated AC charger like the Victron.

Of course one will add other loads. But with a DC genset, you will be doing that through an inverter, which introduces other losses.

So I'm having difficulty seeing any profound advantage of DC generation. All power generated on board starts as AC power, as I understand it. This is rectified to DC in a DC genset. Then it is turned back into AC power by the inverter to run AC loads. An AC genset produces AC power which can be used directly by AC consumers on board. DC power is produced in the charger -- one conversion step. It looks to me that less conversion is going on with an AC genset, than with a DC one.

The quality of the equipment will be key, in any case, not so? A crappy AC genset will produce crappy power which will cause problems. Probably the same with a crappy DC genset. But a good AC genset will produce good clean power, at least, that has been my experience.