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Old 12-08-2018, 01:30 PM
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Atomic 4 -- generator conversion

Ahoy!

Like most sailboats, the engine in my Tartan 27 is designed to provide a lot of propulsion and a little bit of electricity.

But a vast majority of the time, I only use the engine to motor in and out of the harbor. But I do want to have a lot of electricity for things like radar, an induction stove, refrigeration, computers, maybe even HVAC or a dive compressor, etc.

There ain't room for an engine *and* a generator on this boat. So, it is tempting to go diesel electric. Install an electric motor for propulsion, and a diesel generator (plus some solar/wind) for generating electricity. For long distance motoring that is clearly less efficient. However I do not usually motor long distances, but I always want a lot of electricity. And, unlike pure solar electric boats, I still have the option to motor long distances by running the generator.

But that is a pretty major overhaul to commit to in terms of time and money -- especially since it is unproven. That has got me wondering if I can do a quick and dirty trial run.

Here is my thought.

Disconnect the drive shaft from the A4 and install a 5-10KW motor to drive the propeller. I believe I have enough room to do this with out moving anything -- I just need a shorter propeller shaft. I would, of course, need to add mounts for the electric motor.

Install a big 100-200A 48V alternator using the hanley method,

http://www.moyermarineforum.com/foru...2&postcount=12

Make sure the transmission is 'locked' in neutral. (I am assuming the flywheel spins whether or not the transmission is in gear). Disconnect the existing transmission gear shifter and convert it to control the electric motor.

Install a 48V LiFePO4 battery bank and charge controller. One advantage of LiFePO4 batteries is that you can go from fully discharged to fully charged in an hour. (Lead Acid batteries prefer a much longer charge time). So, the engine only needs a short run time to top off the batteries.

The advantage of this hack job is that it is trivial to undo. If it turns out I it is a terrible idea, I can reverse the changes and sell off the alternator and electric motor. I'd probably keep the 48V battery bank, since I'll still be power hungry. And I'd probably just install a smaller 48V alternator.

If it mostly works great but the A4 isn't really up to the job, I can fully commit by replacing the A4 with a proper diesel generator. This also allows me to break up the costs of two time periods. A high output alternator is a lot cheaper than a whole generator. And quicker to install despite the custom mods required to the A4.

Another Tartan 27 owner did do an electric motor conversion and used a 5KW electric motor. They claimed it was strong enough, but that seems underpowered to me. Later models of the Tartan 27 used a 12HP diesel instead of the 30HP atomic 4. So I think 10KW is probably the upper limit of what is required.

In a perfect world, a 200A 48V alternator would require (200A * 48V) / (750 W/HP) = 12.8 HP to drive it. So that A4 should be plenty. But I am wondering what a real world limit would be. Keeping in mind that the A4 is not *also* (directly) driving the propeller anymore.

What else am I overlooking? It is a bad idea to run the A4 for hours on end with out engaging the transmission?

Does this seem like a viable experiment? Or am I overlooking a huge glaring flaw? Has someone already tried this?

(The battery system will be hella expensive, but let's assume I am going to end up buying that either way).

Also, I just want to reiterate that I am fully aware that when motoring this will absolutely be less efficient than a direct drive system. I am willing to make that sacrifice because I want to have a generator on board but don't want to install a second internal combustion engine. And, a majority of the time, motoring will just use the batteries and be topped off using solar or shore power. I am also aware that this will be less efficient than a true generator -- but this is just a stepping stone to that.

Another shortcoming is that a true generator will have a feedback loop that adjusts the throttle to match the current load. In this hack job, I'd have to control the throttle manually. While annoying, I don't think it is a deal breaker. The batteries will make up for any temporary shortcoming. After all, in theory, everything can be powered off the battery bank alone. Though, running the HVAC while motoring is probably a bit excessive.

Last edited by LordGothington; 12-08-2018 at 01:34 PM.
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Old 12-08-2018, 03:32 PM
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Interesting idea and I haven't digested it all to respond intelligently but my first thought is this sounds like a Tartan 27 with the heart of a Hinkley 48.
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Old 12-08-2018, 05:09 PM
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Interesting idea - convert to electric drive.
I don't think hanley's drive is going to hack it. That Balmar is 1.5 Kw, while you're talking about an alternator that almost 10 Kw! More belts, more belt tension, etc. I can see you breaking off the front end of the crankshaft.
I think you need a direct drive to the alternator - more like the vehicle mounted welding generators.
Besides, electric drive is not trouble free. Cleaning carbon dust out of the motor and dodging fireballs from the electrical controls will be in your future.
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Old 12-08-2018, 05:49 PM
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Perhaps a cog belt to drive it, no slip and far less tension. Set the A-4's max output RPM at around 22~2400 RPM for the alt' output rating. I think that at that RPM transferring 13+Hp via the front should not be a big deal. And at lower RPM's the alt won't load the drive. I've seen huge "blower loads" on the end of many cranks with "cog drives". Belts and drive pulleys are also readily available.

Also check to see that the RPM's you drive at are within the thermal ratings IE so the alt won't overheat.

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Old 12-08-2018, 08:04 PM
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You say that there is no room for a gen and an engine, but yet there would be room for a dive compressor and HVAC, and a large battery bank , (and additional tankage)?

I have a 100 amp alternator driven off the crank (like Hanley) and I worry about the load on the main bearing.

What size battery bank and how would you charge it? It would need to be quite large if you were heating, cooking, running radar, running computers, and running air conditioning all off electric.

My question is why...
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Old 12-10-2018, 11:32 AM
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OK Lord, it's clear you have given this a lot of thought although I'm a little confused on whether or not you plan to run a 48V 200A generator/alternator off of the A-4 or install a diesel genset instead. I read intentions for both. My thoughts anyway are:
  1. The electric drive alone does not save much, if any, space. If space saving is the goal I think you'll be disappointed.
  2. Space again, Romantic Comedy's comments about dive compressor, air conditioning, etc. are noted.
  3. If intending to use the A4 to power a generator/alternator, the Hanley drive requires an early model head and cooling system.
  4. Converting to electric drive will cost somewhere around $6K. If fitting a diesel genset, figure another $10K by the time you're done. Big money in my opinion for an electric range and air conditioning.
  5. If driving a gen/alt with the A4 or a diesel, a 200A 48V genny is about the same size as an A4, maybe slightly smaller so I'm not seeing the space savings.
  6. I think driving a big gen/alt off of the output end of an engine, any engine, is preferred to a belt drive off of the flywheel if for no other reason than avoiding side loads on the crank.
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Old 12-10-2018, 11:51 AM
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Basically you are trying to create a miniature version of a diesel electric tug, cruise ship, submarine, or locomotive.
You certainly can do this and thousands, if not tens of thousands, vessels with electric motors exist and work well all over the world. The modern way to design a cruise ship is with 2 or 4 electric motors driving the props and 4 or more generators to run them and supply the ship. Losing an engine hardly impacts the ship, just a little less top speed. You still have both/4 props turning and in low speed low load conditions no need to run all the gensets.
That said, there are reasons this is not common on small boats:
1. Engine to prop is more efficient than engine to generator to motor to prop, every transition loses power.
2. You don't have engineering staff onboard and this is a lot more complicated than a driveshaft.
3. It takes up more space.
4. Specific to A4s, the Atomic 4 is about the worst engine I can imagine for this job. The A4 was NEVER intended to do anything but move boats. Gensets on boats use engines with standard bell housings that make adding a generator quite easy. Diesel engines are better suited to be generators for the most part, although there certainly are gasoline marine generators. In either case these will be WAY more reliable and efficient than kluging a generator onto an Atomic 4.
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Old 12-10-2018, 12:15 PM
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Quote:
Originally Posted by joe_db View Post
Basically you are trying to create a miniature version of a diesel electric tug, cruise ship, submarine, or locomotive.
. . . and the primary reason for a locomotive to have electric drive is to eliminate a transmission the size of a house. Imagine getting a few million pounds of train moving from a standing start with a geared transmission connected to an internal combustion engine.
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Last edited by ndutton; 12-10-2018 at 03:17 PM.
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Old 12-10-2018, 01:27 PM
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{to eliminate a transmission the size of a house.}
On SSN 671, they eliminated the reduction gear and ended up with a steam turbine the size of a house!
I'm quite familiar with one electric drive submarine, the Glenard P Lipscomb, SSN685. On this boat, the generator and motor were the size of a house. The motor had lights and deck grating inside to facilitate going into the motor to clean the carbon dust. Forces adrift used to say that the 'P' in the name stood for 'pierside' - she didn't get to sea much!
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Old 12-10-2018, 03:05 PM
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My wife and I looked at a diesel-electric tug for sale. The reason for this setup was fingertip control of engine power and direction. The boat was huge on the outside, but the engine-genset-motor combo took up a large percentage of the interior.
Thread creep - to eliminate a gigantic transmission, diesel cargo ships just don't have one at all. They stop the engine and restart it going the other way.
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Old 12-12-2018, 12:57 PM
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There are a lot of questions about 'why', which I will answer. But what I care about is the 'how' So, I am hoping we can focus on the 'how' instead talking about what a terrible idea this is. Buying a boat is already a stupid idea -- why stop there!

Quote:
Originally Posted by romantic comedy View Post
You say that there is no room for a gen and an engine, but yet there would be room for a dive compressor and HVAC, and a large battery bank , (and additional tankage)?
Well, the dive compressor is a stretch -- especially when I consider also needing enough dive gear for 2 people. It was just the first example of something that would require a high load for more than a minute but less than an hour. It is not a good example. Let's just say that sometimes I need to spend an hour blow drying my hair, but it makes the boat too hot, so I have to run the AC as well. The point is that I expect to sometimes want to drive a load that goes beyond what a reasonable battery bank could provide. But I don't need to run that load all the time.

If we assume that I am definitely going to install a new battery bank plus some other stuff -- and that I need a generator to top off the batteries -- then it seems like something has to go. So, one idea is to replace the current drive system with an electric motor. That gets rid of an engine and exhaust system, and means I can use the existing tankage to instead supply the generator. An electric motor is definitely much smaller than the Atomic 4 + exhaust system + fuel tank. Also, I can get rid of the two starter batteries -- so that frees up more space for the added LiFePO4 batteries.


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Originally Posted by romantic comedy View Post
What size battery bank and how would you charge it? It would need to be quite large if you were heating, cooking, running radar, running computers, and running air conditioning all off electric.
I have not done the math yet, I am still exploring what is even feasible. My gut instinct is 4x 100A LiFePO4 batteries. I think that should provide a balance where if I am being conservative I can run a generator for an hour a day or less to top off the batteries. Additionally, if I am doing something short term with a high load (like running the magically small dive compressor), I can run the generator during the period of high loads.

The AC might be too much for the batteries alone. That would be something that I might only run on shore power -- or maybe that is when I fire up the generator.

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Originally Posted by romantic comedy View Post
My question is why...[
I decided that instead of spending $1500-2000 a month on rent, I'd rather spend it on stupid boat projects. So now I cruise full time.

Right now it is basically like camping full-time -- there is no fridge, the condensation drips from the ceiling when it gets cold at night, I use an oil lamp to light the boat, and I have to pay $30-60/night if I want electricity and WiFi, etc. And that assumes I am even near a marina.

I'm also not wild about gasoline on a boat, and eventually this A4 is going to need to be replaced or need an expensive rebuild. So I want to have my options mapped out clearly in advance. While replacing a dead A4 with a diesel engine is a common and non-controversial option, I am not sure it is the best option for me. A vast majority of the time I motor for less than 10 minutes -- which is not stellar for a diesel engine. Also, I like electricity. If I can only be good at generator propulsion or generating power, but not both, I choose power.

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Originally Posted by ndutton View Post
OK Lord, it's clear you have given this a lot of thought although I'm a little confused on whether or not you plan to run a 48V 200A generator/alternator off of the A-4 or install a diesel genset instead.
The dream is to eventually replace the A-4 with a diesel genset. But given the high cost of doing that -- and the possibly disappointing results, I am trying to find ways to test the idea before committing 100%.


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Originally Posted by ndutton View Post
[*]The electric drive alone does not save much, if any, space. If space saving is the goal I think you'll be disappointed.
I would agree that simply replacing an Atomic 4 with a diesel electric setup is not going to save space. However, if I am already planning to add a large battery bank, and also want an efficient generator to charge it, and that generator runs on diesel -- now we see space savings. It seems clear that:

electric motor+motor controller+batteries+diesel genset+diesel tank

takes up less space than:

atomic 4 + atomic 4 exhaust system + gas tank + batteries + diesel genset + diesel tank


Quote:
Originally Posted by ndutton View Post
[*]If intending to use the A4 to power a generator/alternator, the Hanley drive requires an early model head and cooling system.
I probably meet those requirements. I have an very early model engine -- though the cylinder block (?) has been replaced -- so I do have the front oil fill tube. Everything else is early early model. I don't even have a thermostat and recirculation loop, it just runs at maximum cooling all the time. (This is a separate issue that should perhaps be dealt with).

Quote:
Originally Posted by ndutton View Post
[*]Converting to electric drive will cost somewhere around $6K. If fitting a diesel genset, figure another $10K by the time you're done. Big money in my opinion for an electric range and air conditioning.
Hence the desire to break up the conversion into smaller steps -- and perhaps realize along the way that I don't need to go whole hog. I assume the $6K includes the cost of the batteries? I think the motor is around $1K and I think another $1K for the motor controller,etc? And $4K for the batteries? I am probably spending $4K on the batteries anyway.

Quote:
Originally Posted by ndutton View Post
[*]If driving a gen/alt with the A4 or a diesel, a 200A 48V genny is about the same size as an A4, maybe slightly smaller so I'm not seeing the space savings.
The space savings is in having an electric motor+genset instead of A4+genset. The primary purpose of the genset is for keeping the house batteries topped off and power high load electronics. The secondary use is long distance motoring.

Quote:
Originally Posted by ndutton View Post
[*]I think driving a big gen/alt off of the output end of an engine, any engine, is preferred to a belt drive off of the flywheel if for no other reason than avoiding side loads on the crank.
By output side, I am guessing you mean the output of the transmission where it hooks up to the propeller shaft? I considered that as well. It seems to have two potential drawbacks

1. it requires the transmission to be engaged -- which is more moving parts to break. Since the engine and transmission share an oil system, I do not think it is viable to remove the transmission?

2. I believe the transmission is reducing the RPM, and for the alternator we want to be increasing the RPM?

I do not have a good solution though -- and that is really what this question is about. People are distracted by the 'why' but what I actually want to know is the 'how'.

Quote:
Originally Posted by joe_db View Post
Basically you are trying to create a miniature version of a diesel electric tug, cruise ship, submarine, or locomotive.
Yes. This is a stepping stone to eventually building a turbine-electric boat someday.

Quote:
Originally Posted by joe_db View Post
1. Engine to prop is more efficient than engine to generator to motor to prop, every transition loses power.
Yes. Going electric would definitely decrease fuel efficiency. But for a sailboat that is mostly sailed, that isn't really a concern. There are sailboats out there with electric motors that are charged purely via solar. But, they don't have a good plan B for when they do actually need range. The genset provides that plan B for when you absolutely must motor a long distance.

If all you are focused on is propulsion, then converting an existing boat to diesel electric will never pay for itself. In my use case, powering the electric motor is a secondary use of the genset, not the primary.

Quote:
Originally Posted by joe_db View Post
Specific to A4s, the Atomic 4 is about the worst engine I can imagine for this job. The A4 was NEVER intended to do anything but move boats. Gensets on boats use engines with standard bell housings that make adding a generator quite easy. Diesel engines are better suited to be generators for the most part, although there certainly are gasoline marine generators. In either case these will be WAY more reliable and efficient than kluging a generator onto an Atomic 4.
Exactly! My A4 is great at moving my boat and not very good at generating electricity. What I think I want is a system that is great at generating electricity, and (because you can't have everything), not as great at moving the boat. That is because I value electricity for creature comforts more than motoring efficiently.

Given enough space I could install all the creature comforts, plus a diesel genset, and keep the A4. But, given the space constraints something has to go.

Given the high upfront costs and potentially disappointing end result, I am looking for ways to break the conversion process up into smaller steps. One way to test the waters is to convert the existing A4 into an inefficient generator. If everything is peachy except for the noise and fuel consumption of the hacked up A4 genset, then it could make sense to yank the A4 and put in a diesel genset, because at that point I will have proven that the idea works. And, if it turns out I don't want to go that route after all -- I still have a functioning A4.

So I think I can break this up into 3 steps instead of my original 2 steps. It seems to me that while a big alternator has the *potential* to require a lot of HP -- if the alternator is lightly loaded, it should only be marginally more taxing than my current alternator? So I just shouldn't try to motor *and* blowdry my hair at the same time?

This is my new plan:

step 1: install a new house battery system powered by 4 100Ah LiFePO4 batteries. (I need to put together a spreadsheet to calculate my real expected usage, but 4 seems like a good number based on what I have seen installed on other boats).

I don't see how that step is avoidable if I want to be able to do things like leave my AIS/anchor lights on, run my laptop, have sufficient interior lighting, using radar, etc. Especially if I am primarily sailing.

I will do what I can to install solar and/or wind generation - but being on a Yawl makes placing solar panels effectively pretty tricky. If I run it as a 48VDC instead of 12VDC system then I will need a 48VDC alternator -- but it doesn't have to be huge.

In this setup the A4 still drives the propeller. It can also top off the battery bank, but I'd potentially have to run it for several hours per day or charge it up at a marina (which costs $30+/night).

Maybe it turns out that I can generate enough power via solar+wind. Also, I do already own an Honda EU2000i (it is currently used to power my PA system, and not on my boat). Maybe I'll decide that solar+wind+honda is sufficient. Since the A4 and Honda are both gas, I don't have to carry two types of fuel. If this is the case, then I am done!

With out the generator, I am not going to be running any heavy loads for extended time periods. The generator gives me the ability to run a 1500W load indefinitely.

step 2: install an electric motor and a much beefier alternator.

This step allows me to test the electric drive idea. The fuel efficiency will be terrible compared to the direct drive system -- but it should also provide a lot of useful data on how big of a genset I would really need, etc.

With this setup, I expect my cruising speed would probably be reduced. For short bursts, the batteries + hacked up genset could provide enough current, but I'd probably have to reduce my cruising speed for long distance runs. On calm water, my boat does almost 3 knots with the A4 at minimum throttle. It takes quite a bit of throttle to get it above 5 knots. So, maybe for this part of the experiment, I cruise at 3 knots and only go 5 when I really need it.

A majority of my motoring is in the harbor, so 3 knots is plenty. It could definitely be a problem when running against strong currents though.

In general, I don't have to be anywhere, and I'd rather be sailing than motoring. If I have sufficient power and Internet I can stay put until conditions are favorable for sailing most of the time. (But not always, hence the need for a motor than can do long runs when needed).

With this setup I can also run higher loads for longer time periods -- if I am willing to run the engine while I am doing it.

This steps proves that the idea is viable, and gives additional data about what size genset would be appropriate. One reason to move onto step 2 is if step 1 is proving unsatisfactory. But, I also need to consider what happens if my A4 dies.

step 3: after abusing my A4 as a genset, it kicks the bucket and I convert to a real diesel genset

At some point the A4 is going to suffer an expensive catastrophe. For most people that means either rebuilding the A4, or installing a modern diesel engine.

But if steps 1 & 2 have gone well, I could feel confident in the 3rd option, which is installing a diesel genset and going diesel electric. If I *already* have to replace my engine, then the cost of installing a diesel genset is less scary.

In summary, step 1 needs to happen regardless because while I can get by with out creature comforts, I do still enjoy them.

step 2 is a moderate investment, but fully or partially reversible. If the electric drive is a failure, maybe I sell the electric motor, but keep the larger alternator.

step 3 is deferred until I have to replace the A4 anyway -- in which case I would have to pay big $$ for a new engine anyway, so a diesel genset is a less extravagant expense. Or, I decide for other reasons, that I am willing to pay for that extravagance. In the long run, the monetary payoff is not paying for transient slips all the time. It would have to avoid transient slip fees several hundred times for that to be profitable, but as a fulltime cruiser, I have 365 chances a year to do that. (And some times 366).

So, back to my original question which is:

What is the best way to hook a big alternator up to an A4, assuming I am willing to disconnect propeller shaft from the engine.

It sounds like side loading is a big concern with mounting an alternator+pulley system on the front of the engine. But if I mount it at the rear, how do I get the required RPM?
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Old 12-12-2018, 03:26 PM
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I hate to be a downer, but this just is not going to work. The Atomic 4 is from a pre-electrical age almost. Not only is it incapable of being made into a genset, it has a really marginal system to drive the alternator too. Back when the basic layout was conceived getting 20 amps out of a generator was really something.
You can, given some time and fabricating skill, make a crank driven alternator setup. You will be then be at the same level as almost any modern engine in a boat. You might get 100+ amps charge instead of the 50 or so we are all lucky to max out at. That will make charging your batteries easier. You are still very very far away from anything resembling electric propulsion. Trying to make an A4 into an actual genset is not actually impossible if you have an unlimited budget for fabrication and experiments, but it is kind of like trying to convert a microwave oven into a tractor - cheaper and vastly easier to buy a tractor
* I used to do this stuff for a living and there is no escaping the laws of thermodynamics. Things that require a lot of power to run need a lot of power supplied to them and batteries - even the newest ones - are vastly inferior to hydrocarbons as a way to store energy. Trying to make an air conditioned boat that runs off batteries is a losing proposition and a request we got ALL the time.

Last edited by joe_db; 12-12-2018 at 03:29 PM.
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Old 12-12-2018, 04:23 PM
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Quote:
Originally Posted by joe_db View Post
You might get 100+ amps charge instead of the 50 or so we are all lucky to max out at. That will make charging your batteries easier.
Hmm. 100+ amps @ 12VDC would be meager 1200W. If that is a reasonable upper limit, then I might as well just use my Honda EU2000i as the 'stop gap' measure for experimenting with electric.

Quote:
Originally Posted by joe_db View Post
You are still very very far away from anything resembling electric propulsion.
For long range motoring -- yes. I'd still be able to experiment and figure out what size motor would really be needed.

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Originally Posted by joe_db View Post
Trying to make an air conditioned boat that runs off batteries is a losing proposition and a request we got ALL the time.
Which is why I need a generator. The end game here is to have a beefy generator on my boat, even if it means I am less efficient at motoring.
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Old 12-12-2018, 07:46 PM
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Hate to keep being a downer, but even if you did have a nice big genset, your air conditioner will be working VERY hard to remove the heat from the engine running inside a small boat. The only way I have ever seen a 27 foot boat have decent air-conditioning is either shore power or a Honda generator on the stern or in a dinghy.
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Old 12-12-2018, 09:08 PM
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Originally Posted by LordGothington View Post
I assume the $6K includes the cost of the batteries? I think the motor is around $1K and I think another $1K for the motor controller,etc? And $4K for the batteries? I am probably spending $4K on the batteries anyway.
The figure I tossed out was based on the actual cost of a slip neighbor's electric conversion of his Islander 28.
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prior boats 1987 Westsail 32, 1970 Catalina 22
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Old 12-13-2018, 11:13 AM
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Quote:
Originally Posted by LordGothington View Post
...
By output side, I am guessing you mean the output of the transmission where it hooks up to the propeller shaft? I considered that as well. It seems to have two potential drawbacks

1. it requires the transmission to be engaged -- which is more moving parts to break. Since the engine and transmission share an oil system, I do not think it is viable to remove the transmission?

2. I believe the transmission is reducing the RPM, and for the alternator we want to be increasing the RPM?
...
You'll be happy to know that both of these suppositions are incorrect. The A4 does not have a full-flegded transmission. It is more properly called a reversing gear. In reverse, a planetary gear system is engaged, and does provide a small reduction (somewhere around 1.28:1). But in forward, it is a simple friction clutch system that locks the output shaft to the crankshaft. 1:1 transfer and no moving parts.
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Old 12-13-2018, 12:16 PM
Dave Neptune Dave Neptune is offline
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Rethinking

Lord, after some consideration and conversations I don't think you will achieve your charging specs with the A-4 and an "off axis" drive. The reliability due to the strength of the set up is just to suspect.

The A-4 has the power but it needs to be transferred axially and then you seriously lack RPM's to achieve an efficient alt speed. About the only reliable way I can see harnessing the power from an A-4 is mounting a planetary drive between the engine and alt. That way the loads can be absorbed by the mounting pads and not all of the stuff hooked together.

Another possibility that may just help with space considerations is a hydraulic drive. They are quite sturdy and operate quite efficiently.

Both of these types of drives could readily be mounted to either end of the engine.

Dave Neptune
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  #18   IP: 65.79.132.37
Old 12-31-2018, 11:42 AM
LordGothington LordGothington is offline
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Quote:
Originally Posted by Dave Neptune View Post
Lord, after some consideration and conversations I don't think you will achieve your charging specs with the A-4 and an "off axis" drive. The reliability due to the strength of the set up is just to suspect.
Agreed.

Quote:
Originally Posted by Dave Neptune View Post
The A-4 has the power but it needs to be transferred axially and then you seriously lack RPM's to achieve an efficient alt speed.
So, perhaps the problem is trying to use an alternator that is designed for use with an engine. What is needed is an alternator that has peak performance in the 700-2000RPM range.

I'm thinking I need to look at alternators designed to be used with lower RPM applications such as wind power. Something like this,

http://www.windbluepower.com/Permane...d_p/dc-512.htm

A direct drive system would be nice to minimize parasitic losses. But if I need to be able to disconnect the load, then maybe a lockup torque converter could be used?
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Old 12-31-2018, 04:10 PM
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Quote:
Originally Posted by LordGothington View Post
Agreed.



So, perhaps the problem is trying to use an alternator that is designed for use with an engine. What is needed is an alternator that has peak performance in the 700-2000RPM range.

I'm thinking I need to look at alternators designed to be used with lower RPM applications such as wind power. Something like this,

http://www.windbluepower.com/Permane...d_p/dc-512.htm

A direct drive system would be nice to minimize parasitic losses. But if I need to be able to disconnect the load, then maybe a lockup torque converter could be used?
You are going to end up spending 2 times the money for something half as good as a generator designed for the purpose.
That said, the best high output DC system I know of was someone using an alternator from this company - http://www.electrodynealternators.com/e-series - directly driven off their crankshaft with an extension shaft. No way would most marine engines - and especially the A4 - take the side loads these beasts would have if they were belt driven. IIRC, the boat was getting either 200 or 400 amps at 24 volts. This company has 12, 24, 32, and 48 volt versions.
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