Case Study:Diesel AC Gen to DC Gen- Larger boat

[Typhoon]

You all know I have such a system you are all talking about . All I can tell you a DC generator is a great option , then couple that to a Lifepo4 bank , works excelent . Almost 4 years full time service , no trouble . With your big generator I would build a gearbox with helical gears and run two Eco tech alternators at 6000 rpm this would give you over 500 amps hot . Only measure hot amps ! Put that into two lifepo4 banks . You have your own power station .

Regards John

[Q Xopa]

No offense intended or taken. Just my 'not so funny' attempt at a bit of humor. I know there is far greater interest generated in more controversial or emotionally charged threads.

I agree that, the Ecotechs are good but as you say a little 'exotic' certainly not inexpensive. Again I would find it hard to justify the expense.

I do and have sunk a ton of cash into my hole in the water. However I also do try and maximize my value where possible. Doesn't always pan out that way.

I agree that the 'School bus' style large case alternators are certainly hard to pass up for value and ease of replacement and maintenance. Which specific models are you running or recommending?

Cheers.

[Pauls]

Pelagic:

2….The whole engine room is now very well soundproofed so no sound shield is needed with a new DC Gen.
It has been proven to me that on most diesel engines, the best operating RPM is between 1200 -1500 RPM for both noise and mean time between failures.
So I would prefer to gear DC Gen to operate at their optimum output in that speed range. I dislike belts because of the dust and dirt they slew off and contaminate the ER.

Your solution to this is to use a toothed belt. They are quiet, efficient, and will greatly reduce the dust. In effect they are like a gear drive without the complications that gears require. Sprockets and belts are a standard commercial item, easily available. These will allow you to keep a low engine RPM and still spin an alternator at efficient higher RPMs.

[Q Xopa]

Yes your system is one of my major inspirations. Always glad to hear yours is working well for you.
24V x 500A is 12kW. To Generate this sort of power at least 16 HP id needed. Assuming we don’t want to run this thing the motor to it’s absolute limit which is obviously not ideal. Most engineering designs allow some reserve so it has some life and efficiency etc. Practically speaking this is going to be a close to 30 HP motor set up to utilize 2 of your Echotechs. We can have a smaller motor and don’t try to suck all of these Alternators output out of them. This is what I am doing.
Speaking of trying to keep this operating quietly, this sort of Gear box you are suggesting will make some noise. I’m sure a Gear box like this is doable, but I would not think common. Do you know of any like this?
This is also starting to sound like a pretty complicated, exotic and again reasonably costly. As if I can talk. 2 x Echotechs are going to be $3k +? Although 2 for redundancy sounds nice.
You know I have gone for my ex Military Gens, which less than a third (1/6th for 2 Echotechs) of the cost with 400A. You can get 570A as well if you want. I’m sure I will report on how it goes when I get it all up and running.

[Typhoon]

Originally Posted by Q Xopa

Yes your system is one of my major inspirations. Always glad to hear yours is working well for you.
24V x 500A is 12kW. To Generate this sort of power at least 16 HP id needed. Assuming we don’t want to run this thing the motor to it’s absolute limit which is obviously not ideal. Most engineering designs allow some reserve so it has some life and efficiency etc. Practically speaking this is going to be a close to 30 HP motor set up to utilize 2 of your Echotechs. We can have a smaller motor and don’t try to suck all of these Alternators output out of them. This is what I am doing.
Speaking of trying to keep this operating quietly, this sort of Gear box you are suggesting will make some noise. I’m sure a Gear box like this is doable, but I would not think common. Do you know of any like this?
This is also starting to sound like a pretty complicated, exotic and again reasonably costly. As if I can talk. 2 x Echotechs are going to be $3k +? Although 2 for redundancy sounds nice.
You know I have gone for my ex Military Gens, which less than a third (1/6th for 2 Echotechs) of the cost with 400A. You can get 570A as well if you want. I’m sure I will report on how it goes when I get it all up and running.

First at 24 volt the Eco-techs are putting out around 160 amps each when hot . That works out to be 11 hp each alternator. I don't know what your generators hp is but you do want to load it up to 80% of it capacity. As for noise I wouldn't worry about that to much you won't run it for long, maybe an hour every two days like me . As for a gear box . Any good machine shop can build one and you can order the gears on line . I did quite a bit of machining done to mate the drive to the alternator it was painless and not expensive. The gear box would be closed and sealed , half full of gear oil. You could mount the alternators any way room would allow . Remember it is best to use a generator motor , they have a speed control/load controller that adjusts for load and holds the rpm to what you set it . 1500 or 1800 rpm.

Regards John

[Q Xopa]

All sounds good. I agree with your numbers, which were a bit more accurate than mine. But I think we are singing the same tune.

My generator motor is a Yanmar 2YM15, paid $5,800 for a new one (Brochure attached for those that are interested), which is rated at 15 HP, around 11 kW. Realistically I am hoping to get maybe 7 or 8kW of electric output at best. That’s still what I would consider a pretty good number for a setup of this cost and size.

The generator I am working on hanging off the back of my 2YM15 is rated at 28V 400A at any RPM above 3,500, so this is over 11kWs. The gen is meant to be good for 28V 200A which is 5.6kW, at 1500 RPM. At this RPM this seems like plenty of power and wont be too loud. Lower RPMs may also be sufficient for my needs. Let's see? It is also brushless. There is a 22C output graph in the brochure. Schmoozing around in the warmer tropical climes let's see what real world number it can do.

IMNSHO at $450 it seems like pretty good value to me. Hopefully it is reasonably bullet proof. (Brochure also attached for those that are interested).

The 2YM best TQ RPM (best fuel efficiency for our diesel dollar and electric output) is 2,400. Its max power (HP) RPM is at 3,400. We could get our max elec output at this RPM, but we will spend proportionally more to get it. So unless we really need that much power, to me it is not desirable to run at this level. I guess it’s good to have that capacity if we do need it.

The max RPM for the 2YM is 3,600 and the max for the Generator is 8,000 RPM. So I’ve gone for a direct drive which I think should work ok. Let’s see how all this works out in practice.

Your obviously a ‘can do’ industry trail blazer. Sounds like a bit more of a project than I would be comfortable taking on. I’m usually sillier than most and try what others dare not. I haven’t learnt my lesson yet and often still usually manage to get in over my head.

I applaud your capability and confidence and I always love to hear of what you and others have created. Its this sort of attitude that got us outta the caves.

Keep up the good work.

[Q Xopa]

Oops, I obviously haven't got this attaching docs thing happening.

[Typhoon]

Ok so your engine is a twin with max 15 HP? Thats just about waht I have with my 3 cyl yanmar at 1800 RPM

My setup takes around 7hp to turn my alternator at 1800 putting out just over 200 amps at 12v . You are trying to get 200Amps at 28 volts out of your alternator at 1500 rpm. Thats 400 amps or slightly more at 12v . Thats not going to work. Best case , if you are using an Echo-Tech which take the least power to amp of any alternator at 400 amps hot you will need around 14 hp at 1500 , I don't think your motor will put out that much HP at that rpm . Also I am giving you hot numbers , cold you can add a third more power to turn because alternators put out more power when cold therefore require more power to turn them .

With that engine I recommend you do what I did . I could have belted the alternator on and spun it up to 6000 rpm for the extra power but I went with lower power and less chance of crank damage and belt failures/maintenance and dust. You could use the alternator mount on the other side to charge a second smaller bank , I do not use that alternator for anything other then belt tension right now . Remember , one alternator per bank or you will need some sort of centerfielder , more things to break.

Try to attach those DOCs on the alternator , maybe my numbers are wrong .

Regards John.

[Q Xopa]

Sorry, I’m not smart enough to work out how to attach docs on here yet. Any clues?

However there is a link to the manufacturer’s brochure at the bottom of this page-

CE Niehoff, P/N N1602-3, 28 Volt DC, 400 amp Generator Alternator, 30 available, (Shipping included in price to most locations in the continental U.S)

Yes you are correct, your 3 cyl engine sounds like it has pretty much the same as my max rated HP at 3,400 as yours has at 1,800.

No I don’t think I ever said I was hoping to get 200A at 28V at 1,800 RPM. Certainly not what I was trying to say, my apologies if that’s what it looked like. I was only quoting the Generators quoted max output at that RPM.

I have no doubts my poor little engine couldn’t produce that much power.

The same as I know that my engine wont produce enough power at max power RPM, around 3,400 to get the max power from the gen that it’s capable of. But I’m fine with that. In fact I am happy that I will be running my gen at significantly below it’s max capability. That way hopefully heat, life and reliability should be less likely to be problems.

Speaking of output numbers being heat effected. Yes I know you are right. I’m not sure of the scale of the difference, but if you are saying 1/3rd more HP reqd at lower temps. I am certainly not arguing. It sounds reasonable to me. I’ll let you know what I see when I get it going.

As far as your recommendation of how I should drive it, like you have done. I think you are recommending I do a direct drive instead of belts. I’m not sure whether you saw my previous posts when I was saying direct drive is what I am working on. I have a guy from Hayse doing a direct Lovejoy style coupling set up.

I am definitely a fan of Belt drives, if the situation is appropriate. However in this case, no need to complicate things. I'm all for keeping things as simple as practically possible.

Have I got this right that is what you are recommending?

Always open to suggestion from you guys. There is a lot of good info to be had from forum contributors.

As for charging of banks. This is a refit in progress. It will take some time, in between working away etc. However I have most of the parts for my upgrade to a 24V house system. I intend all alternators and chargers to be 24V. Except for a 24-12V B2B charger for the 12V start and windlass batts.

Cheers.

[Typhoon]

Are you using LiFeP04 batteries?

I had a look at the specs , to get 400 amps @ 28v out of this thing you are going to need 34HP . Thats a bunch of power no doubt.

Its good you are going to direct drive it .

How are you going to regulate it for battery charging. It may just bog down your engine when connected to a hungry battery bank.

At 1500 rpm under full load this alternator will need 10hp and 32 ft-lbs of torque .

You may need a bigger Yanmar

Regards John.

[Q Xopa]

LiFePO4 batts, yes it is on the list.

However not immediately as I am busily working my way through other projects right at the moment, eg this Generator for one. I am gearing up for them, getting things in place first. I have a bunch of the hardware like Low and charge relays etc. Anyway that’s more for another thread.

Yes agreed to get the max out of this gen would require that sort of HP, 34 yeh probably. That seller was suggesting 24 HP. Whatever, it’s all more than mine so it’s academic to me. The one on his video is meant to be a 10 HP, which is less than mine still.

Not sure exactly what HP your 3 cyl is but it sounds like it might be closer to being able drive this Gen to it’s capacity. Around the same money these units are also available in 28V 570A, which is even more outrageous. It’s certainly a lot of out put Amps for your Generator dollar.

But it sounds like your more going for Echomechs, which I agree sound like very good units. I await your next development. As I mentioned previously I like them, but they are not cheap.

There is always some limiting component in a system. Either you could have a big motor that could drive a generator until you loaded it up and melted it. Or you can have a Generator that will stall our motor, like in this case.

Of course in either scenario you can regulate both your current output and your motor.

Yes I will have a Generator Controller and output regulator. Already have the Regulator, a DC. The Controller is coming.

Direct drive looks fine for these Generators as they don’t need to be spun too quickly to make reasonable power. The RPM ranges of both the Gen and Motor seem to match reasonably closely. Close enough for my purpose anyway. As you say the output power don’t match so well though but that’s ok.

The OP is looking for a gen for his 65 foot, but he specified for a 50 foot + boat. Mine is 49 feet so not quite as specified. It is not small, but still doesn’t have a huge volume to stash things like generators.


So I’m trying to keep a bit of a lid on (never works, though) generator size and costs etc. having said that I think this should be good for 7 or 8 kW, which is still quite a lot. Many people happily get by with no Generator or Honda 2000s.

[Pelagic]

Originally Posted by a64pilot

DC or AC, a Watt, is a Watt.
Why do you think you can go so much smaller with a DC generator?

My opinion is once you get into even decently sized generators that AC or DC is irrelevant, they are so easily converted to each other with decent efficiency now that it’s not really an issue. Now what would be slick is if someone builds a larger inverter / generator that could automatically vary engine RPM to load like a Honda. For some reason I assume that just isn’t scalable?
And to be even more argumentative it’s not RPM that determines engine life so much as piston speed, just as it’s piston speed that determines upper RPM limit of an engine too, short strokes mean higher RPM and longer, lower. It is that simple.

Thanks a64Pilot and others for their suggestions and ideas, specific to my case study of

1. Boat Size
2. Location
3. What I have to Generate/Store 24V DC
4. What are my largest Consumers

I have been looking at the discussions on AC vs DC Generators as well as the LifePo Batteries for future planning over the next few years. This in concert with replacing a Dive Compressor, which will be a purchase next year.

I tend to look at things from a “form following function” perspective and here are mine:

• I live in SE Asia, where support for new technology is slow, or just doesn’t exist, so KISS is important!
  
• My NLights 12kw AC Gen has been reliable, but I prefer redundancy of using another driver in case my Generator went down, while we were in those remote dive spots. (Murphy's Law! )
  
• While Scuba Diving is a luxury, that mindset made me switch to a DC ¾ HP motor for the new water-maker, so that the large case 24v-140Amp alternator off the main engine, feeds the water maker thru the House Bank when I am motor sailing in clean water.
  
• So with my large 24v House Bank, I have 2 Diesel primary movers to recharge the batteries and feed the heavy consumers.
  
• For diving, a Junior Bauer 3.9 CFM which uses 2.2Kw for a 3HP 240V electric drive is the largest consumer.
  
• Original was AC but would ideally love it to be 24v DC motor if practical.

Quote Dockhead:
“Pelagic, why do you want to change the generator at all? Your generator will be fantastic with LiFePo batteries. It's large and powerful and will pump power into the batteries in short, efficient generator runs. If it's in good condition, I would leave it, and save a lot of money!

My suggestion would be to use a GANG of charger/inverters. The Victron Multiplus ones can be put together two or three at a time. It will be cheaper to rectify those 12kW (or whatever part of the whole capacity you want to use for charging), than changing out the generator, by far. And then you have failure-proof redundancy in this critical item of gear and you will have tons of inverting capacity to match the qualities of the LiFePo bank.”


Dockhead’s sage advice rings true for my situation including cable sizes and using what I have.

But that AC 3hp motor means the Gen is critical unless I can get a DC to AC invertor sized for 2.2kw loads continuously, including original surge.

Presently I have only one Victron Multiplus 24v-3000w-70amp Multi-Charger-Invertor.

I keep the Multi simple by not allowing it to “manage” shore power/Invertor….
I just have the standard Lock out Switch Over Breaker for the AC Board and a standby Victron Skyla 50a 24V Charger that I could plug into a weak shore power feed if needed or as a back up charger if the Multi went down.

Don’t know enough to say if it is wise to Gang a 2nd Multi with the first for the Dive Compressor load or is there another conservative solution?

[Dockhead]

Originally Posted by Pelagic

Thanks a64Pilot and others for their suggestions and ideas, specific to my case study of

1. Boat Size
2. Location
3. What I have to Generate/Store 24V DC
4. What are my largest Consumers

I have been looking at the discussions on AC vs DC Generators as well as the LifePo Batteries for future planning over the next few years. This in concert with replacing a Dive Compressor, which will be a purchase next year.

I tend to look at things from a “form following function” perspective and here are mine:

• I live in SE Asia, where support for new technology is slow, or just doesn’t exist, so KISS is important!
• My NLights 12kw AC Gen has been reliable, but I prefer redundancy of using another driver in case my Generator went down, while we were in those remote dive spots. (Murphy's Law! )
• While Scuba Diving is a luxury, that mindset made me switch to a DC ¾ HP motor for the new water-maker, so that the large case 24v-140Amp alternator off the main engine, feeds the water maker thru the House Bank when I am motor sailing in clean water.
• So with my large 24v House Bank, I have 2 Diesel primary movers to recharge the batteries and feed the heavy consumers.
• For diving, a Junior Bauer 3.9 CFM which uses 2.2Kw for a 3HP 240V electric drive is the largest consumer.
• Original was AC but would ideally love it to be 24v DC motor if practical.

Quote Dockhead:
“Pelagic, why do you want to change the generator at all? Your generator will be fantastic with LiFePo batteries. It's large and powerful and will pump power into the batteries in short, efficient generator runs. If it's in good condition, I would leave it, and save a lot of money!

My suggestion would be to use a GANG of charger/inverters. The Victron Multiplus ones can be put together two or three at a time. It will be cheaper to rectify those 12kW (or whatever part of the whole capacity you want to use for charging), than changing out the generator, by far. And then you have failure-proof redundancy in this critical item of gear and you will have tons of inverting capacity to match the qualities of the LiFePo bank.”


Dockhead’s sage advice rings true for my situation including cable sizes and using what I have.

But that AC 3hp motor means the Gen is critical unless I can get a DC to AC invertor sized for 2.2kw loads continuously, including original surge.

Presently I have only one Victron Multiplus 24v-3000w-70amp Multi-Charger-Invertor.

I keep the Multi simple by not allowing it to “manage” shore power/Invertor….
I just have the standard Lock out Switch Over Breaker for the AC Board and a standby Victron Skyla 50a 24V Charger that I could plug into a weak shore power feed if needed or as a back up charger if the Multi went down.

Don’t know enough to say if it is wise to Gang a 2nd Multi with the first for the Dive Compressor load or is there another conservative solution?

Well, you can just install the next larger (5kW?) Victron charger/inverter, and that should run your 2.2kW dive compressor with ease. But I would add a second one just like the first, and then besides plenty of capacity, you also have some built-in redundancy in case one of them goes down (which they do from time to time -- happened to me). Even one of them MIGHT run your dive compressor. These units will support a brief startup load. But ganging them is good practice -- they are made for that.

And why aren't you letting the charger/inverter manage shore power? It's a great function -- limiting the current taken by dialing down charging, and then boosting the current with inverted power to shave peaks. These are great functions.

For redundancy of generation, as we've discussed -- big second alternator on the main engine should power the boat pretty well if the generator goes down.

[ShaktisBoy]

Man this discussion is right up my alley. I have just spent the last couple of years prototyping reworking and testing my CanDoItAll DC genset. The ease of maintenance ability to easily source parts and the desire to combine as many functions as possible into one unit drove me here. The unit I designed has a large frame Leece Neville alternator “200 amps”, a high pressure pump for our water maker, a 134A compressor for air conditioning “30,000 BTU” and a removable Bauer JRII compressor head to fill the scuba tanks. Our original Northern Lights generator took a long hot bath in salt water when the heat exchanger rubber elbow split covering the entire rotor stator assembly, the electronics box and just about ever other component susceptible to salt water damage. The quote to remove, repair/rebuild and reinstall was not to far off from a brand new generator. The expected turn around time was equally breathtaking at 6 to 8 weeks! This in south Florida one of the worlds highest density of yachts and marine services. For your entertainment here are a few pictures of the latest rework of the unit installed in our Leopard 40.

[Pelagic]

Originally Posted by Dockhead

Well, you can just install the next larger (5kW?) Victron charger/inverter, and that should run your 2.2kW dive compressor with ease. But I would add a second one just like the first, and then besides plenty of capacity, you also have some built-in redundancy in case one of them goes down (which they do from time to time -- happened to me). Even one of them MIGHT run your dive compressor. These units will support a brief startup load. But ganging them is good practice -- they are made for that.

And why aren't you letting the charger/inverter manage shore power? It's a great function -- limiting the current taken by dialing down charging, and then boosting the current with inverted power to shave peaks. These are great functions.

For redundancy of generation, as we've discussed -- big second alternator on the main engine should power the boat pretty well if the generator goes down.

I remember you had problems with the Victron Multi, but also most of the Diesel Ducks that end up on my Subic dock over the years after commissioning in Hong Kong have all had problems with the twin Muti's doing Shore Management.

The way it was originally wired in China, when the Multi failed, they lost all AC power.........(much more colorful language than I remember from you )

So that influenced me going with Kiss and my 9 year old Multi has performed flawlessly.

I will get a 2nd Multi, (more for the new induction hob back up) and the same size fits nicely......

But what is wrong with making the 3hp compressor motor DC as I did with the water maker, so I am not dependent on any invertor for such an occasional heavy load?..... Cable run from DC Buss Bars is only about 8ft.

I did put this new 24v 110a on the big perkins main engine, (75a at idle) but wont know till I am in cruising mode if it is big enough