serious discussion about electric power in large boats

[danstanford]

Originally Posted by Auspicious

That has nothing to do with whether electric power makes sense in large boats. The comparisons in my mind are size, weight, and cost of the entire system, the service life of batteries, and the recharge time. The actual use cases are context: full-time cruising is much different than day sailing with a week or more between at a marina. Propulsion as a limited resource does not appeal to me. Having to charge for days between uses, not being able to motor through calms, and importantly the prospects of single points of failure.

For electric power on large cruising boats to really be productive several things need to happen: yet higher energy density for storage (batteries), higher output photovoltaic solar panels (limited by the physics of how much energy impinges but flexible panels as sails to really get the area up), enough of a market to drive prices down, and some good engineering to get it to all hang together.

Your points made above are all exactly on point. The use cases are really relevant to how sensible electric power is for your sail boat and the makeup of the package. Two things you raised are central to my thinking and pursuit of the topic.

Things are happening and will continue to improve in this area. Battery densities are climbing as costs are dropping and one can imagine this will continue for some time. Other storage mediums like hydrogen fuel cells are evolving and though not prime time yet hold immense promise.

"Propulsion as a limited resource" resonated with me. Is this not just a matter of perspective when you consider the alternatives? The ultimate definition of limited would be an ocean crossing where you cannot refill your fuel tank. If you have a way to utilize the power of wind and sun you are no longer limited. UK sailmakers has a model of sail with a few panels embedded in it that seems to work, now we just need to whole sail to generate!

Sorry if I sound like I am a defender of the model, I am not. I am interested in the concept because I am trying to decide about buying an electric powered boat and I want solutions that work for me so my questions and assertions are genuine.
Dan

[Adelie]

Originally Posted by GrowleyMonster

That initial failure for the brushed motor is of course the brushes. An easy DIY replacement. After about 6 or 8 brush changes, the bearings will be ready to change. Still kinda DIY doable. However, I would advise against brushed motors, anyway. You can't have propane or gasoline equipment on a boat with a brushed EP motor.



Induction motors are usually used for larger boats. For boats under 35' usual choice is a BLDC/PMAC motor. Same/same, basically. BrushLess DC motor or Permanent Magnet AC motor. But like induction motors, the only thing that should ever need changing is the bearings. Well, and hall effect sensors which usually last forever but COULD fail. Anyway, yeah maintenance of the motor and controller is mostly a non issue. You just need to know how to take care of your batteries. Lots of folks think they do, but do not. Absolute worst case, you change the motor or controller. One man job except for really really big induction motors. But should never need to be done.



With EP everything is simple and cheap. EXCEPT THE BATTERIES. That's the 600lb elephant in the room. And if you go with Lithium, you need a BMS. Lots of folks don't use one, but IYAM it is absolutely mandatory for safety. Stuff happens.

IYAM?

[GrowleyMonster]

IYAM WHAT IYAM.

Actually, If You Ask Me.

[GrowleyMonster]

Originally Posted by danstanford

Your points made above are all exactly on point. The use cases are really relevant to how sensible electric power is for your sail boat and the makeup of the package. Two things you raised are central to my thinking and pursuit of the topic.

Things are happening and will continue to improve in this area. Battery densities are climbing as costs are dropping and one can imagine this will continue for some time. Other storage mediums like hydrogen fuel cells are evolving and though not prime time yet hold immense promise.

"Propulsion as a limited resource" resonated with me. Is this not just a matter of perspective when you consider the alternatives? The ultimate definition of limited would be an ocean crossing where you cannot refill your fuel tank. If you have a way to utilize the power of wind and sun you are no longer limited. UK sailmakers has a model of sail with a few panels embedded in it that seems to work, now we just need to whole sail to generate!

Sorry if I sound like I am a defender of the model, I am not. I am interested in the concept because I am trying to decide about buying an electric powered boat and I want solutions that work for me so my questions and assertions are genuine.
Dan

Storage systems will not improve quickly enough, will not improve energy densities or cost enough, to make future prospects enough to tip the scales toward electric. Google for EV-1 and read all about it. In fact, download the movie "Who Killed the Electric Car?". We have had pretty good battery technology even back when the EV-1 was in use. Have we doubled energy density, or battery lifespan, or halved the cost, in all those years? Nah. Yes, the situation is improving and will continue to do so. But don't take it to the bank because it will be a long time before we see critical mass in storage technology.



I gather that you are considering to buy a boat that already has EP. The real dealmaker is your usage pattern. If you fit the profile of a successful eboater, then go for it. If EP is a good fit for you, then you will absolutely love it for its advantages. If you simply cannot stand having a diesel aboard, then go for it and live with the limitations of EP. Otherwise I would not buy an EP boat. For most cruisers, hands down, diesel or at least diesel/electric parallel hybrid, will be the go-to.



If you have or are strongly considering, a boat with no running engine at all, and the budget is tight and the boat is old and tired and not worth the cost of a diesel, then an electric repowering is a natural option, but remember you will have to live with the limitations of EP. And keep in mind that components and batteries for a larger boat are going to be seriously more significant than for the more typical EP boat of 30' or less.

[seandepagnier]

Originally Posted by LongRange

I very much like the concept of electric power, and my next car will probably be electric, but I cannot envisage getting rid of the diesel anytime soon on my sailboat.

Like most sailing monohulls, we struggle to meet our "house" electrical needs, let alone powered propulsion. Our solar panels generate maybe 250 watts in bright sunlight. Without wholesale conversion to electrical, around 250 W is the most we could possibly invest in propulsion. Many jurisdictions impose a 250 watt limit on motor power in e-bicycles. That is equivalent to a strong adult rider bicycle pedaling hard.

On our sailboat which is 13.75 m LOA and ~12 t loaded, pedaling an exercise bike contraption that drives the prop would probably fail to make a dent unless it is flat calm, when I could achieve maybe a knot if I give it everything I've got. Therefore, my thinking goes, adding a ~250 W electric propulsion unit is a waste of money and time.

This is a wrong way of thinking. Already sailing alone is enough to get you everywhere, and with oars and human power you can basically do it most of the time as well.

Adding electric of 250 watts is going to give you the same versatility and ability to navigate anywhere most of the time without having to do any physical effort.

... of 30 kW propulsion! Afterwards, I could fire up the exercise bike contraption in the

This is again the wrong way of thinking. 30kw of propulsion is too much for one or two people to consume anyway.

You can get brushless electric motors rated to 4kw that cost $50, I am putting this system into a 28ft boat, will be interesting to see how fast it goes at 200-400 watts.

y "serious discussion" about electrical power can only arrive at a "NO" answer, at least in the context of a cruising sailing monohull. The limits are imposed by physics.

Since the limits by physics were there before engines existed then I can only conclude you are confused about something.

[ramblinrod]

Originally Posted by Adelie

If people were worried about resale they wouldn’t buy a boat in the first place.

Resale can be a very important consideration.

Some boat models tend to hold their value far better than other comparators.

There are some boat models, that well cared for, will sell 30 or 40 years later for what they sold when new.

Other boat models will never hold their value like that.

Of course the dollar value is far less at selling vs purchasing time, but that is a different issue, that applies equally to all.

And for short term ownership of a new or newer vessel, resale value is a huge consideration.

[GrowleyMonster]

Originally Posted by boat_alexandra

This is a wrong way of thinking. Already sailing alone is enough to get you everywhere, and with oars and human power you can basically do it most of the time as well.

Adding electric of 250 watts is going to give you the same versatility and ability to navigate anywhere most of the time without having to do any physical effort.

This is again the wrong way of thinking. 30kw of propulsion is too much for one or two people to consume anyway.

You can get brushless electric motors rated to 4kw that cost $50, I am putting this system into a 28ft boat, will be interesting to see how fast it goes at 200-400 watts.




Since the limits by physics were there before engines existed then I can only conclude you are confused about something.

Be careful. You are falling in love with a concept.


Yes a 4kw motor is in theory big enough for your 28' boat. But I would still go with a 10kw to 12kw motor. Why? Because first of all you will get better heat dissapation from the bigger motor. The motor will be operating at a smaller fraction of its rated power. Should you decide to upgrade from the usual 48v bank to 96v or 144v or whatever, the motor will be good at the higher voltage. You have all that peak power available for when you need high power for brief periods or just want to show off. The cost difference is not a dealbreaker. The 10kw motor has very little parasitic losses over the 4kw or 5kw motor. A diesel consumes power just turning itself over at zero load. A bigger diesel consumes even more power just to turn itself over. A lot more, in fact. The difference in power consumed within the electric motor varies only by an insignificant amount between small motors and motors twice the size. The weight will double, yes, but still less than 30lbs for the motor, and a pound or two more for the bigger controller and heat sink. So go bigger than you think, on the motor. On your cables, too. I strongly recommend at least 2/0 wire for feed to controller, and phase cables to motor.


Finally, be wary of a $50 motor with a vendor determined rating of 4kw. I can tell you from experience that good 5kw motor costs a minimum of $350, new. This being a Motenergy or equivelant motor. You might ask yourself if this is maybe peak (60 seconds max) power rather than sustained (forever or until you decide to shut it down) power. Or if that is with water cooling, which IN GENERAL is a foolish concept. Anyway take the vendor's rating with a hyoooooge grain of salt. Yes I know you have visions of always running at only 400w anyway and that is admirable. That is actually a very good electrocruising power level for a boat of 28' LOA and average displacement. But there will be times when you simply need a kw or two, for the task at hand. Or the whole enchilada, for freeing a stuck anchor or pulling someone off a mud bank or something like that. For an extra ten pounds of weight and a few hundred bucks, go ahead and get a big boy motor.


BTW, the 10-12kw motor face will usually be the same as that of most 5kw motors so you can upgrade or downgrade or whatever just by bolting in the different motor. If you ignore my advice and install a 4kw motor you can in the future buy a proper motor and controller and swap them out without admitting your mistake and nobody will be the wiser. And you can quietly sell your old underpowered motor and controller on fleabay for half what you paid for them. You are welcome.

[a64pilot]

One issue with electric propulsion is that in order to increase efficiency as your very limited in power output requires a rather large diameter prop turning at slow RPM.
Large diameter props present problems for sailing.
With a Diesel you can accept the decreased efficiency of a smaller prop and just burn more Diesel.

[ramblinrod]

Originally Posted by Jdege

Sailing Uma posted a video of a group of cruisers who'd converted to electric discussed their experiences.

One of them remarked that the anchorages throughout the Caribbean are full of boats sitting waiting for diesel parts to be shipped in.

I seem to remember reading that MTBF for a brushed DC motor is 6,000 hours, for a three-phase AC induction motor, 50,000.

There is some attraction, there.

Be careful of the source.

In that episode, only UMA had any actual experience using EP. The other testimony was based solely on conjecture. One hadn’t even started to install the EP system. Of the 3 UMA actually had experience cruising with EP.

The first DIY system had a serious drive train issue that required complete rework. Noisier than a diesel. Then they melted the terminal right off a battery. Could have set the boat on fire. They ended up stuck in a hurricane path, as they didn’t have the speed/range to get out of the way. Neither was happy with speed/range so they installed a new electric motor, drive system, and large bank of drop in LFP. I suspect most was gifted or deeply discounted for marketing ops.

Now they have ditched the electric outboard for a gas powered one, on the inflatable, spent an episode wasting Dino juice pulling countless donuts in an abandoned marina, and often tie the dinghy with the gas outboard to propel the boat when they really need to get somewhere.

I think its a great channel, and I’m impressed with many of their boat mods and travels, but even they declare their EP a substitute for a sculling oar but not a substitute for a diesel.

[zloitapok]

Strange, why people think only about replacing a diesel engine? I know that nobody who use an electric motor never tell that it fully replace diesel engine. Electric motor have it sphere of application with own advantages and disadvantages compared to diesel. So many times this was written at multiple forums and same questions asked again

[ramblinrod]

Originally Posted by zloitapok

Strange, why people think only about replacing a diesel engine? I know that nobody who use an electric motor never tell that it fully replace diesel engine. Electric motor have it sphere of application with own advantages and disadvantages compared to diesel. So many times this was written at multiple forums and same questions asked again

Not that strange in my opinion. 99% of cruising sailboats have a diesel. I suspect the majority of EP considerations are made when it is time to repower. Pulling a perfectly working diesel to go EP is the least green thing one can do.

[zloitapok]

Originally Posted by ramblinrod

Not that strange in my opinion. 99% of cruising sailboats have a diesel. I suspect the majority of EP considerations are made when it is time to repower. Pulling a perfectly working diesel to go EP is the least green thing one can do.

You don't like EP - it is good.
I'm very happy with my EP - this is good as well

[john61ct]

I think EP would be great, but no replacement for ICE.

Definitely perfect for those owners who consider a sculling oar or yuloh practical.

[ramblinrod]

Originally Posted by zloitapok

You don't like EP - it is good.
I'm very happy with my EP - this is good as well

I think you misunderstand.

It isn’t that I don’t like EP. I think it is awesome for the right application. I don’t think it appropriate for a cruising boat needing to bug out, during the calm before the storm, or needing / wanting to motorsail any distance (without running an ICE generator.)

[zloitapok]

Originally Posted by ramblinrod

I think you misunderstand.

It isn’t that I don’t like EP. I think it is awesome for the right application. I don’t think it appropriate for a cruising boat needing to bug out, during the calm before the storm, or needing / wanting to motorsail any distance (without running an ICE generator.)

Ok, I got you. I have a stationary ICE generator onboard, but I use it very rare - only at long passages (330-340 km). Solar panels and shore power do the most of job to charge batteries.