Electric propulsion

[Bob Bois]

This has been discussed on several other forums. We are interested in electric propulsion for our Tiki 46 and have been in touch with several builders who have installed e-pods, etc. However, does anyone currently using electric motors for propulsion have a report on the practicality of the current products?
There's been alot of discussion regarding the weight of the batteries as a limiting factor, the best (and worst) power regeneration methods, the best (and worst) products currently available.
I don't want to summarize it all here, but I would like to open the discussion and see if there is any further interest within this really knowledgeable community in brainstorming how this might (or might not) be worthwhile (and cost-efficient). I'd be interested in any aspect of electric propulsion anyone might want to discuss, from recharging batteries to the best placement of electric motors and the pros and cons of the overall concept. I received an email from some builders who are using e-pods with their Pahi 63 and say they are really pleased with it. Ther

[Bertrand FERCOT]

Present time I prefer to pass more time to build my Tiki46 than going to the forums but I can't keep the silence concerning the abusive adverts of Re-Epower. From its website I copied the technical specifications of the E-pod 3000 system :

In reading that I can't know what is the max continuous power at the shaft. I have to estimate it : absorbed power 48Vx100A=4800W - a minimum of 15% of losses in the engines and its controller = 4080W or 5,5Hp.
So by which miracle a 5,5Hp can do the job of 25 hp inboard!!!!!!

I know the advantages of an electric engine are to deliver a good torque at low rpm and to have a quick reply when you request the full power and can even during a very short time deliver a peak power as example to stop the boat (if the controller accept that). So it's easier to handle the boat with precision when docking. To have a good reply with a such little engine on heavy boats you need a large propeller with a little pitch.
All that seems marvelous only if you have good conditions with no wind and or no current.
As soon as you have to motor against the waves and the wind, the torque at low rpm and the quick reply don't change anything and you'll never get the push of a 25 hp inboard engine with a 5.5hp electric engine.
If you try to reach a shelter in a gale against the wind and waves in a long rocky entrance, you'll push the throttle at the maximum to get the maximum continuous power of 5,5hp at the shaft (in fact the propeller has an efficiency of 50% and the useful power to push the boat is only of 2,25hp). As you draw a high amperage, the real capacity of your battery bank will be lower than if you draw a little amperage. Your speed is very low, so you have no hull speed inertia and each gust or wave will stop the boat. As the speed is very low, the angle of attack of the propeller blades increases, so the propeller stalls reducing its efficiency. The engine and controller warm more and more and so the useful power is going down.........
The boat don't progress and in less of a half hour (if you have a good battery bank) you loose the control of the boat due to lack of electric energy ( if the controller or engine don't shut down before). The boat wrecks on the rocks in hoping you don't loose your life!!!!!

So I can say it's criminal to affirm to his customers that an electric engine of 5.5hp can does the job of a 25hp inboard engine!!!!!!!


Now have a look at the technical data & measures of the Torqueedo Cruise4.0 which seems more honest :

It's always the same, you can't easily compare because you have the input power in kw and the comparable petrol outboard in hp. A good point, they give the propulsive power of 2kw (that means with the power loss of the propeller).
2kw=2,7hp. I suppose the power loss of the electric engine and its controller is about 9% and the power loss of the propeller is about 40% (good efficiency).
They compare it at the power of a 8hp petrol outboard (at the shaft), so if we suppose a 50% efficiency propeller, the propulsive power is 4hp. And it is 9,9/2=4.95hp for the thrust comparison (due to the high efficiency of the propeller I suppose).
So after to be obliged to calculate all that, I understand the Torqueedo company says its 2,7hp useful power do the job of a 4hp outboard petrol useful power.It's more realistic than with the Re-Epower company.

But an hp is an hp, there is no difference if the power is produced by electricity, or by humans, or by animals or by petrol or by nuclear, so and so. Behind the power delivers on the shaft the difference depends of the efficiency of the propeller and if the propeller is well adapted with the hull. This kind of comparison is only available about facilities to handle a boat in an harbour but it's not possible at full throttle. With the same propeller efficiency, with the same boats, the bigger power engine will produce the bigger propulsion power.


Concerning my boat, when I begun her building, I read the book "Home is where the boat is" and I decided to have so one classic propeller on each hull just in front of the skegs to have a reliable boat under engines easy to handle. Initially I thought to put one diesel engine outside + hydraulic transmission toward the hulls.
Year after year I study the evolution of the electric engines on the boats and since 3 years I'm in contact with hybrid marine who has developed a parallel hybrid system for canal boats last year in partnership with Beta Marine and for the next Southampton boat show they prepare the sail version .
In a first time I just bought 2 Beta marine engines of 25hp which are ready to receive the electric engines. In the next months I'll install them in the hulls with just after the gearbox a big pulley and an additional clutch to allow to use the electric engine as a generator at anchor. I'll installed the electric engines before or after the launch day when I'll have the money.
So I'll have one independent parallel hybrid system in each hull. According the circumstances I'll can run 1 or 2 diesel engines or 1 or 2 electric engines. Under sail it'll be possible to regenerate the battery banks or to stop the propeller with the gear box (I hope one day to put some efficiency feathering propellers). When motoring on flat sea,the best will be to run only one diesel engine at half throttle which will turn its own propeller and will produce electricity to run the electric engine of the other hull. A propeller absorb all the diesel engine power only at full throttle and so at half throttle all the power which is not absorbed by the propeller will be used by the other electric engine and if there is an exceed of electricity it will recharge its battery bank.
In the next months I'll make a blog page to describe all the building from the beginning until the launch day with all the main steps.

Bertrand

[Jeff Kittle]

Bertrand

Can you persuade Cinthia and John Paul to tell us about their electric motor performance?

Jeff

[Bertrand FERCOT]

Hi Jeff, I have already invited Cynthia and Jean-Paul to join us but they are tired with the building, they said they are now sailors and not builders.
I'l try again. Present time they seems satisfied with their two 10kw electric engines mounted at the same position than your pods. They made tests to dock with strong winds without problem. They can motor at around 4kts with there diesel generator on flat sea without drawing their battery bank. Initially they planed to sail to Turkey but they had at first a problem of bad electric connections and at second their generator don't deliver all the power expected, so they are waiting for a reparation in the islands near Toulon.
When sailing with them the engines made a light whistle according the rpm when motoring, but no whistle when sailing.
To avoid the transmission of the noises from one hull to the other, do you put pieces of rubber at the points of contact with the hull? Present time I'm gluing thick 7mm rubber strips around the 3 bottom faces where are the contacts with the hulls to avoid noises transmission and to allow a little flexibility with high tension of the lashings because I don't' want to have vertical or lateral movements.

Hi Chuck thank you for the link. I know the company and I don't regret as our Belgium friends to haven't bought their engines. Perhaps it's OK for local use but not enough reliable and powerful for offshore cruises.

Hi Bob take your time to stop your decision. You'll need several years to build your Tiki46 and a lot of new products can appears, especially for the batteries which are the weakness of the electric propulsion system (I hope to see soon on the market the new batterie with carbon foam instead lead).
For the best handle the distance between the 2 engines will have to be at the maximum : along the hulls and not under the seas cockpit. Personnally as you know I prefer a propeller in front of each skeg, but for that you have to put the tube shafts at the first step of the building when making the keels on the ground.

Bertrand

[Ann and Neville Clement]

Nev and I have two Honda generators about the size of a bread box because they are needed to recharge the battery for the electric windlass. If one is broken, we can still lift the anchors by using the other Honda generator to charge the windlass battery and one is 110 and the other is British 240 to operate the European tools we still have. We have a smart charger which will take either one and those are clever devices and worth every penny because charging goes quick and safe. We also have a battery monitor called a Link 10 which was a gift from a kind old cruiser friend. Whatever else you do with the limited cash you have, I suggest a Honda, a Link 10, and a smart charger.

We make all our electrics by solar and wind with a tiny bit of generator if there is no wind but lots of cloud. We would not need that gen time if we had all LED lights. Spend on LEDs. Note that we do have an electric freezer now too.

We do not have our outboards charging the house batteries but they recharge their own starting batteries and all that is kept separated from the house batteries. I think Budget Boater is singing our song re electrics here.

Ann and Nev

Bob Bois said:

Hi Ann and Nev,
If I don't take the opinions of the rest of the crew into account, I will hear about quickly - have no doubt.
Here's a question for everyone (especially Ann and Nev as they have the most extensive Tiki 46-specific live aboard experience (in the world, I would figure):
Can 15hp outboards be set up to recharge the batteries to run all electrics on board (with solar and wind assistance)?
The reason I ask is this: I would not want to sail into a nice quiet anchorage and have to fire up a deck-mounted diesel generator.
The thought of an electric drive that can be hoisted clear of the water that can be recharged with a small diesel gen to minimize the number of batteries required is appealing until I envision that gen running when all should be quiet. That said, I would rather carry diesel than gas and it's not like the outboards are quiet. So many considerations...it will end up as a compromise of course and I'm glad we have a few more years to think about it.

[Bob Bois]

Bertrand,
Thanks so much for your comments. We hope to be gluing up our backbones this fall and I'm not sure we're prepared to put the tube for the shaft in at this point. We are still committed to a propulsion system that lifts entirely free of the water. We realize we are sacrificing some manouverability with this decision. I"ve read with interest the developments in the carbon foam 3-D architecture that allows for quicker recharging etc. It will be interesting to see what comes onto the market in the next 3-5 years. In the meantime, we'll be cutting wood, mixing epoxy, and sewing our sails. I hope Cynthia and Jean-Paul are enjoying themselves. Perhaps once they have fully transitioned to cruiser mode, they can be persuaded to make a report on their electric drive set up. Their building blog was one we followed from very early on and its nice to see them out and sailing now (Dave Vinni and Beat and the Kittles and so many others also). It's so encouraging to see the piles of plywood and dimensional lumber and then, one day, a vessel floating on her lines.

Ann and Nev,
Budget Boater makes an excellent case for a quiet Honda generator, listing all the systems it powered on their Tiki 30. I'm looking very carefully at that. Tess wants 'some' refrigeration if we are to be liveaboards and we are going to be homeschooling the boys, which means computers etc. When I was in engineering school, I had a professor who claimed his children were allowed to watch television only if they 'pedaled' the generator. Something to think about

[Ann and Neville Clement]

Bob and Tess,
The most likely thing will be that computers for young students will come cheaper and with their own solar power and able to be used outside in the cock;it with good wireless. Even I have this good set up with my cheapo laptop here on Peace and it is powered from our big solar array outside. They will be better and better and geared for third world situations which is pretty much what you have on a boat.

Tess will want some refrig. The boys will eat and eat and eat. I have had many teen agers and it is unbelievable! But if you place the solar panels with care and if you have a Bimini with even more solar panels, it will work out. The wind generators are quieter each year. You can put very hard rubber in the mounts.

Yes, you will be unpopular if you run your generator in quiet harbors. the time to run the generator is right after you raise the anchor and when the outboards are on to give you that manouvering ability in the anchorage so you do not bump the other boats as you leave.. Just switch from charging the anchor windlass's battery to charging the house batteries as you leave harbor. Then you can reverse the process when you are approaching the next anchorage because the other boats will be glad that you are under good control with outboards running as you enter harbor..After the anchor is set, you turn everything off and it is grand and quiet and wonderful. All day while sailing, it is quiet. All evening and night at anchor it is quiet because everything is charged.At least that is the usual situation on Peace. Very Peaceful!

Ann and Nev

Bob Bois said:

Bertrand,
Thanks so much for your comments. We hope to be gluing up our backbones this fall and I'm not sure we're prepared to put the tube for the shaft in at this point. We are still committed to a propulsion system that lifts entirely free of the water. We realize we are sacrificing some manouverability with this decision. I"ve read with interest the developments in the carbon foam 3-D architecture that allows for quicker recharging etc. It will be interesting to see what comes onto the market in the next 3-5 years. In the meantime, we'll be cutting wood, mixing epoxy, and sewing our sails. I hope Cynthia and Jean-Paul are enjoying themselves. Perhaps once they have fully transitioned to cruiser mode, they can be persuaded to make a report on their electric drive set up. Their building blog was one we followed from very early on and its nice to see them out and sailing now (Dave Vinni and Beat and the Kittles and so many others also). It's so encouraging to see the piles of plywood and dimensional lumber and then, one day, a vessel floating on her lines.

Ann and Nev,
Budget Boater makes an excellent case for a quiet Honda generator, listing all the systems it powered on their Tiki 30. I'm looking very carefully at that. Tess wants 'some' refrigeration if we are to be liveaboards and we are going to be homeschooling the boys, which means computers etc. When I was in engineering school, I had a professor who claimed his children were allowed to watch television only if they 'pedaled' the generator. Something to think about

[Jeff Kittle]

Bertrand
Thanks for the update on Cynthia and JeanPaul. We have Teflon blocks on hardwood in our beamtroughs. Rubber might silence it better as you say.

Thanks
Jeff

[Ann and Neville Clement]

It would be interesting to compare the weight of your complete engine and electric system on APATIKI, Cynthia and Jean-Paul, against the weight of the complete engine and electric system on PEACE which has outboards. We have the two 9.9 Yamahas, two 12 gallon fuel tanks near the engines, and 6 jerry jugs of 6 gallons each for back up. A seventh 6 gallon jerry jug is carried for the dinghy outboard but sometimes we use that fuel for the big boat too. Our wind generator is an Air X Marine, and we have two large solar panels feeding the 4 100 amp batteries. The engines also have their own smaller batteries. We use a small Honda generator about the size of a bread box providing 120 volt and keep a second one for back up which is 240 volt because we have lots of European tools still. Those Honda generators are not used very often in actual full time cruising mode. We use a smart charger for our house batteries but the engines charge their own batteries which are all on separate systems. I will ask Nev to add up all that weight and also the expense so folks can compare. Might be a few days before that can happen unless one of you can add it up before hand. Likely a lot of you on this web have the info ready to hand and our expense info will be 7 years old so not very usefull. Probably a better engine choice for the Tiki 46 would be the 15 horse outboards which were not available when we launched back in 2002. We would likely select Yamaha again though.

One thing that we often do is allow Peace to take the ground if it is not rocky. I do not know if this would be safe with your system or not. We always lift our engines when sailing because it does make a difference in the speed especially when we are in light air. I have heard that some folks with electric propulsion have lifting props so they can sail at normal speeds when required.

Do you know how easy it would be for you to obtain spares or repair services if needed in remote locations with your system?

What is good, is to have choices. This is especially good if you are building your dream boat. One wants the dreams to come true after all that work. The detailed info you have provided here will be extremely helpful for people still building their boat or considering a change in propulsion. Information - especially experienced information - will be invaluable.

Peace has noisy engines and there is no kidding about that. We do not have much conversation in the cockpit when the engines are running. We can talk, but it requires close listening and raised voices. Not relaxed conversation at all, and we do not listen to music at all when engines are on. Admittedly we have done nothing about insullating the cockpit seats over the engines. That might help. Someday we may try it.

It is good of you to provide such detailed and illustrated information on your system and I am sure many on the site appreciate it. It does look like a good installation so congratulations on that. What I especially like is your ability to motor for long distances in calms. Life's like that some times and you may want or need to move the boat regardless. By the way, Peace motors in calms at 4 knots with one engine not at full throttle and at 6 or 7 knots with 2 engines not at full throttle.

I will get Nev to add some more details soon.

Ann and Nev

[boatsmith]

Many thanks to Apatiki, Cynthia and Jean-Paul for some very high quality information on your electric motor set-up. This kind of hard data is really helpful to many of us , I am sure David www.boatsmithfl.com

[Bob Bois]

Many thanks to Cynthia and Jean-Paul for providing what is, to the best of my knowledge, the most comprehensive treatise on electric propulsion for Wharrams anywhere on the web. This information is not only well-presented, but is based in real-world application, and not theory or marketing misinformation.

Again, to Jean Paul and Cynthia, thank you so much. We hope you have a nice end of summer cruise and we'll hear back from you at some point.

Kind regards,

Bob

[Axel]

Thank you for all the effort you put into reporting your experience. It has helped to clarify it for me, unfortunately confirming what I found when I looked at electric propulsion 5 years or so ago. That is that there is still a BIG penalty in weight and cost. Certainly prohibitive for me no matter how badly I would like to have silent electric motors.

I really appreciate your efforts,

Alex

[Bertrand FERCOT]

Cynthia and Jean-Paul welcome in this Wharrambuilders site and thank you to share here your own experiences.

Present time the batteries are the only way to store electric energy on board and unhappily the ratio weight/volume/energy stored is very poor compared with the hydrocarbon energy. It's why I think necessary for long cruising to install an hybrid system : diesel + electric engine in serie or parallel according your personal options and preferences.
It's not possible to produce your diesel when sailing but it's possible to produce and store your own electric energy and for me it's the main reason to have electric engines on board able to produce electricity when sailing. So it'll be possible to stay a lot of months in isolated islands without the need to sail in a main harbor to buy some diesel.

It's necessary to well understand the limitations of the lead acid batteries. Here is a graph of one 100Ah battery where you can show the variation of the real capacity according the intensity drew.

In fact you can get almost 100Ah from this battery only if you draw 5Amp during 20h. As soon you increase the intensity, the real capacity decreases. When drawing 64Amp, the real capacity is only of 64Ah and I suppose when drawing 100Amp the real capacity will be about a maximum of 50Ah with a complete discharge after about only 30 minutes.
The energy wasted in the battery is approximately proportional to the square of the intensity and to don't reduce too quickly the battery life it's necessary to don't draw more than 80% of its capacity. So in fact if at full throttle the intensity is 100A, after 20 minutes you have to stop your electric engine if you don't have a diesel generator.

In fact the batteries alone can drive the electric engine only when manoeuvring the boat or at low speed on a flat sea without wind, waves and current. As soon you request power for a long time you need an hybrid system.

With the hybrid serie configuration it should be better if you have a 48V engine to have a 48V generator to avoid to loose power in the 220V/48V or 110V/48V conversion and to be able to use the total capacity of the generator to drive one or two electric engines; you are not limited by the low power of the chargers if using this inverter system.

I'm not so affirmative than Jean-Paul to say the direct drive pods are more efficient than the inboard drive engines with a belt reduction because slower is the propeller RPM with a bigger propeller, better is its efficiency.
We'll compare that when we'll have the opportunity to sail together in order to compare a Tiki46 equipped with 2 x 10kw electric pod with one another Tiki46 equipped with 2 x 10kw electric inboard engines with a belt reduction and with the 2 x 25hp diesel engines......

Bertrand