36vdc Motor Bank and 12vdc House Bank

[bobola]

Gordo,

Nope. Even if my wife said yes I might not buy it. But the price is attractive enough to pique my interest. A few months back I walked all over the deck looking for soft spots and found none, which was nice to see in a 40 year old fiberglass sailboat.

There is a sister ship on the east coast which has been almost totally redone in the past few years (almost-new engine as well) which would be the smarter way to go.

But the boat (IMHO) is the perfect trailerable boat as it has a centerboard, a deck stepped mast and is sturdy enough to bash around off shore. Another option would be to remove the electric motor and controller and sell them, and use a big outboard to move the boat, or re-install a diesel for the right price.

I don't have the space, trailer or truck to move it so the idea is just an idea, and will probably stay that way.

I started thinking about the electrics and created this thread looking for opinions.

One interesting thing I found today was that a 36 VDC battery bank is perfect for welding. On a sailboat it could be used as a way to make money - "Bob's floating welding shop"....

Another interesting project idea I found is to take a car alternator and spin it with a small gas engine and make the field circuit adjustable with a potentiometer. Might be a cheap way to make a multi stage charger without having the loss of a step down transformer, and the parts are easy to find anywhere. Spin it to 60 cycles and they can put out 110 VAC if the diodes are rated for that.

[mjname]

Have you thought about joining the electricboats@yahoogroups.com yahoo group? There you will be able to talk to people are already doing this.

[bobola]

I joined it earlier today, actually....

Looks like an active group...

[boatclassic]

I joined this group today and thought I would add a few ideas to this thread.
There are battery chargers available that can charge up to 4 banks with each bank isolated.This enables you to group batteries in 12v,24v,36v or 48v banks.I just bought a 3 bank promariner.I will connect 1 bank to my 12v domestic system and the other two for my 24v drive bank.
I am converting from diesel to electric through necessity.Local conditions prohibit IC engines but the deeper I delved into the subject the more I liked it.
First point is efficiency.The best you can hope from a diesel drive with a reduction gear is about 35% against about 80% for electric.diesels develop very little torque at low revs while electric drives delelop full torque immediately, which gives excellent manoeuverabilty at low speed.The biggest problem at the moment is energy storage.Agm's or gel batteries provide the best alternative at present but by the time your first set is worn out,the will be a whole generation of new litheum batteries developed(they are already available at a price)at a fraction of the weight,greater capacity,you can drain them right down,and they are talking about 8min. charging capabilities.
If one goes for a diesel electric system,the motor can be a fraction of the size of what is required for a propulsion system,can be located anywhere,is much quieter and provides power for tools or appliances.
One needs to spend time researching as there are a lot of off the shelf systems available at pretty reasonable prices.I wish I had known about them sooner.
I am not an expert but found a forum where there are many who do know a lot and are willing to share.
For more information go to electricboats@ yahoogroups.

[Alan Wheeler]

Hi Boatclassic. Welcome to the board. There are some very talented people here as well, that know a tremendouse amoutn about Battery technology and engineering. Rick is one of our regular posters that would be one of the top in the world on this subject. He has designed some of the top and most well know electrical products out there and what he doesn't know would fit on a postage stamp. A verrrry small postage stamp.
I have to take issue with your claims. The comment that Electrical is more efficient than mechanical is rather a broad brush stroke. It depends on many parameters that can not briefly be explained. A gearbox efficiency of only 35% is rather harsh. Most complex boxes are 75% efficient and simple boxes like you see on a boat can be much higher than that as well. It also depends on gear ration. There are a lot more Inefficiencies in eletrical systems than just straight loss from an electrical motor does not cover. There are some simple laws you and I see many that push this technology tend to leave out.
Converting one form of energy to another creates a loss.
Genset engine driving generator =loss, generator drivign charger = loss, charger charging batteries =loss, batteries driving engine speed controll =loss speed controll drivign electic motor = loss and electric energy producing rotational effort = loss.
Being able to charge a battery in 8 min firstly means you have to have a generating ability to replace several hundred amphrs in 8mins. That is not going to be feasible, plus can you imagine the size of the cables to handle that current. Lithium may have pluses, but it has been around for sometime now and trust me, it has major disadvantages to.
Torque of a diesel at low RPM has nothing to do with manourverability. That is a compleat misconception. The size of propellor and rudder is the major affect in Manourvering.

Local conditions prohibit IC engines but the deeper I delved into the subject the more I liked it.

Interesting, can you explain the situation??

[boatclassic]

Hallo Allen,Thanks for the welcome It feels good to have a place to exchange ideas.I will try to answer some of your points although as I said,I am definitely NOT an expert.
I did not say a reduction gear alone, but rather a diesel motor driving through a reduction gear has an efficiency of about 35%.An electrical motor,directly coupled to a shaft,which is not a problem with the available motors,can easily achieve an 80% efficiency.These are not figures that I have invented.
As to torque,in an electric motor this is no neutral,just forward,stop and reverse.The moment the motor is started in either direction one has full torque.With a diesel there is a curve directly related to rpm.Again these are not facts that I have invented.
Of course there are inefficiencies in every system.Up to this point I have been talking about the drive itself,supposing that all things are equal and both systems have the correct diameter and pitch wheel etc.
The fuel,or energy supply of an electric motor is clearly the biggest problem but not insurmountable and I am aware that lithium technology has been around for a long time but not in a usable form for us.There are systems on the market but at a cost of between $5000 and $10000,its out of reach of most of us.The 8 min.claim came from the auto industry and I use it only as a pointer to future trends.
Sure a gen set is innefficient but if,most of the time,it is only used to recharge batteries,does it matter? the main point is that it can be a fraction the size of a diesel propultion unit and as I said can be positioned anywhere,with isolation mounts so that it is not intrusive.
Paguro,in Italy make a beautiful 3.5 Kw water cooled genset that is light,quiet and would suit my requirments.
I am living in Austria.The boat that I am presently fitting out is a 40 year old "Atalanta 26" by Fairley Marine in the UK.It's a trailer sailer that has many ocean passages under its belt.Local conditions prohibit IC motors.

[Alan Wheeler]

These are not figures that I have invented.

No don't get me wrong, I was not taking you task on that. I think the "electrical propulsion industry" is stacking figures in their favour. 35% efficiency is just plane wrong. 35% loss is closer to the truth.

With a diesel there is a curve directly related to rpm

Well yes. That' because the Diesel in this situation is speed controlled. But you have to understand some important physical points here, that are being compleatly missed. Speed control of the RPM gives you speed controll of the boat. Plus low RPM equals less fule used.
If you are saying the motor is full RPM fwd/stop/Full RPM rev. Then you have no controll of the boat. You are always consuming maximum energy with the electric motor. There are electric speed controlls available and I think the industry is making the electrical system complex and short on ability by using DC motors. AC allows greater controll of torgue by controlling waveform not voltage with DC. But thats another story.

With a diesel there is a curve directly related to rpm

Yes, but I don't think you understand what these curves actually mean. And I think that is what the Electrical drive industry play on as well.
Just becasue the Diesel has low HP at low RPM, does not mean it does not have sufficient power at low RPM. Low RPM means high torque. High RPM means High HP. The two curves meet ruffly in the middle. It's two very different power outputs of rotational energy. Not one is missing so you have an inefficiency. The ability of coupling that energy to the water is where the variable reving motor falls down. But it is not a fault of the motor. It is a fault of the propellor. A mechanical varying pitch propellor goes along way to solving that problem, but the best solution would be having the ability to vary the diameter of the blade swing(which we know is impossible) or the surface area of the blade(which we also know as impossible). So we have to take a compromise and say the propellor has to be the best choice of dimension at the max RPM of the diesel. Max RPM is where the greatest efficiency comes into play of coupling the prop to the water. The non variable speed electric drive is doing exactly that. It has the ability to have a prob mathed perfectly for water coupling, engine power and RPM. But you have ground inbetween. It is full or nothing.

Sure a gen set is innefficient but if,most of the time,it is only used to recharge batteries,does it matter?

Weellllll, it depends. Isn't the whole point of the exercise saving fuel??? Energy is energy. If you use 1kw of energy in one minute or 4 hrs, you have to replace that 1kw of energy. If your charger can put that 1kw back in in 8min or 8hrs, it doesn't matter, it was still 1kw of energy. Lets say for figures your genset is 100% efficient. You would still use 1KW worth of Diesel, whether it was that 8min or 8hrs.
Then their is the fact that you have to have a genset as well as the electric drive. so how have you saved on weight and space. At least with a diesel engine, you can infact mount a geny to the engine and not have a seperate genset.
As for size of the motor, yep OK, that is one major advantage. However, I am still to see an apples for apples comparison in most scenarios. I have seen 30 and 40HP diesels replaced with 10HP electric. Not a fair comparison. Yes the 10HP will drive the boat, but only for one reason. The electric motor is doing full noise. And even then, even though it will move the boat, it still has no where near the power through the water the 30hp diesel does. No one anywhere to my knowledge has done a bollard test. That is coupling the boat to a set of scales tied to the dock and done a comparison apples for apples pull test. Electric motor at say 10HP and Diesel at 10HP output.

Local conditions prohibit IC motors.

Is this a local authority prohibiting?? I don't quite understand. You mean no one is allowed a combustion engine in their boat??

[GordMay]

Electric motors have infinate speed control.
An electric motor doesn't "idle" in neutral (using less fuel), it's stopped (using none); but immediately available.

[boat-energy]

Hi Everyone,

I had to comment that this is the classic dino-petrol-head argument...

Alan - please do more research because people have now done the tests you claim haven't been done.

And I'm not going to enter into any argument - just a plea for Alan to do some further research into the inefficiencies of the ICE.

Thanks,

A boat owner of 25 years, and energy consultant.

[Woodsy]

Originally Posted by bobola

Another interesting project idea I found is to take a car alternator and spin it with a small gas engine and make the field circuit adjustable with a potentiometer. Might be a cheap way to make a multi stage charger without having the loss of a step down transformer, and the parts are easy to find anywhere. Spin it to 60 cycles and they can put out 110 VAC if the diodes are rated for that.

I am going to atempt to quote this:
I have done this, ran my house for years! 2X 1100 lb batteries (think lead keel) with great results. Delco alternator. Lifetime warrantee. Smooooke them mothers! 5 HP Honda, never failed. Still on line and capable.