serious discussion about electric power in large boats

[GrowleyMonster]

Originally Posted by StuM

Thanks for that, it shows what a lot of people here have been saying.


Regardless of whether you are driving the prop with diesel or electricity, power requirement roughly doubles for every knot increase in boat speed once you get past idle.

There really isn't any "idle" with electric. You can turn the prop at 50 RPM if you want. But yeah, the relationship between speed and power is definitely exponential. When every watt-hour counts, the first thing you do to adjust is to redefine what "slow" means.



Sieve's performance figures are actually pretty good, especially at the high end, though it might not look so hot to someone who knows nothing about EP. I am sure that bank wasn't cheap, though. But the lesson to take home is that when energy is tightly rationed to the propulsion system, you need to forget about "hull speed" because if you are smart, you will never be going fast enough to be even remotely concerned with it except maybe in testing.

[ramblinrod]

Originally Posted by danstanford

Yes, that would be the model. Do you think this would be a problem?

Most everybody in every marina I have been in come back into the slip and plug in and then MOST of the time unplug before they attempt to leave!

It would appear based on the battery capacity that they claim, I could quite easily go 10 trips or about a month before I would need to re-charge if I chose to do that. Knowing me, I would charge her up full every time I returned though.

I can see how this would not work on a mooring unless you had some solar.
Dan

But almost every one of those marina hoppers had dreams of sailing off into the sunset someday, making EP unacceptable, even if they never actually do.

Consider the limited prospects for resale. The average boat is held in one persons name for about 6 years.

[Adelie]

Originally Posted by ramblinrod

But almost every one of those marina hoppers had dreams of sailing off into the sunset someday, making EP unacceptable, even if they never actually do.



Consider the limited prospects for resale. The average boat is held in one persons name for about 6 years.

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

[Dockhead]

Originally Posted by Adelie

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

Indeed.


Speaking of resale, of course what is unusual and not widely understood, tends not to sell as well as what is standard and well known. So that's certainly a strike against electric propulsion in terms of resale value, meaning you may lose even more money than you would with a normal boat . But if it's well suited for the use case, works well, has clear advantages, some buyer is likely to see that.


There are lots of day sailers out there who can charge up from shorepower after every outing. I expect electric propulsion will become pretty mainstream for this use case.

[CatNewBee]

Maybe for dinghis and small runabouts like Sealine power boats or fishing vessel, I doubt it in sailing vessel given they motorsail most of the time and definitely not in charter fleets.

[a64pilot]

I think that once you begin to see acceptance of electric day sailing boats, the the used resale value for one may be greater than its Diesel brother.
I say that as an electric drive system could age better than it’s Diesel brother, the battery bank being the thing that will really age.

I’ve been following this forum for years, it seems the there are more problems with Diesels than anything else on boats, people have to fix that Diesel often, and often they have very little knowledge with one, and often its big bucks too.
If you could remove that maintenance headache, maybe sailing would more fun.

I’m talking the average boat that sits in the Marina for months and is used during the warm months, the rest of the time it’s not even visited.

[a64pilot]

But speaking of resale value, I can’t make what used electric cars sell for make sense to me, a one or two year old electric car is dirt cheap, much, much less than a gas engine car, but when new it cost more.

Why is that? Why does it seem that people who want an electric car, only want a new one, is it a fashion statement and only new cars are fashionable?

Will it be that way for electric sailboats?

[Jdege]

Originally Posted by a64pilot

I’ve been following this forum for years, it seems the there are more problems with Diesels than anything else on boats, people have to fix that Diesel often, and often they have very little knowledge with one, and often its big bucks too.

If you could remove that maintenance headache, maybe sailing would more fun.

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.

[Auspicious]

Originally Posted by a64pilot

I’ve been following this forum for years, it seems the there are more problems with Diesels than anything else on boats, people have to fix that Diesel often, and often they have very little knowledge with one, and often its big bucks too.
If you could remove that maintenance headache, maybe sailing would more fun.

Refrigeration and watermakers are the really big issues. Diesels are pretty robust if cared for. That may be a problem. What the heck parts are people waiting for? Injectors? Water pumps? Alternators? Starters?

[CatNewBee]

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.

Diesel engines live forever if have the oil and the filters changed from time to time, it is not the engine, it is the bad fuel, and sometimes the corrosion of the exhaust ellbow, that causes salt water ingress. Older diesel are even more reliable than the new one with turbo and electric injectors.

Most problems are dead batteries, failed starter and failed alternators, all electric parts. There are 60 year old diesel tractors around sitting for decades neglected in barns or even outside, and fire up almost instantly.

Electric motors can burn too, the brushes get weared, there can be warer damage and corrosion too. And the batteries are always a problem. Besides this, the power regulation electronics can get fried, and it is nothing you can repair under way. You can fix a diesel, but can you recoil an electro-motor?

[GrowleyMonster]

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.

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.

[john61ct]

Originally Posted by a64pilot

But speaking of resale value, I can’t make what used electric cars sell for make sense to me, a one or two year old electric car is dirt cheap, much, much less than a gas engine car, but when new it cost more.

The people buying electric cars are incentivized by subsidies and warranty.

The official battery replacement cost is more than many spend on a whole working used car.

For those willing to go to not too much trouble, yes great bargains to be had.

[a64pilot]

Leaf is probably about the most accept widely sold one, excepting the Tesla which has a “luxury” status thing going.
It’s the Apple of cars.
New leafs are about mid 30’s price wise, but used ones just a couple of years 0ld go for less than half that.
https://www.carvana.com/cars/nissan-...AaAmGtEALw_wcB

Warranty etc is the same for any car, gas cars don’t tank in resales nearly as bad as electrics, electrics are supposed to be maintenance free right?

I think most of it is the lure of getting “free” money, I’m speaking of the subsidies the rest of us pick up to the tune of $7,500.
Used cars don’t have subsidies, used cars are sold at their real value.
Once those go away and when electric cars are finally required to pay the highway taxes etc that they currently don’t pay. We will see how many sell.

[john61ct]

Yes, pretty sure the U.S. will lag far behind the rest of the world, as in all the great potential green transition economics.

Darn shame too, could really be a shot in the arm, chance to take a leadership position in something actually positive.

[Auspicious]

Originally Posted by a64pilot

Once those go away and when electric cars are finally required to pay the highway taxes etc that they currently don’t pay. We will see how many sell.

Which rapidly turns into politics as proposals like the 'Green New Deal' would mandate electric vehicles.

Originally Posted by john61ct

Yes, pretty sure the U.S. will lag far behind the rest of the world, as in all the great potential green transition economics.

*sigh* Too bad solar power is neither green nor renewable.



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. Electric power does make the energy consumption of an inverter and TV when you fall asleep during movie night pale by comparison, doesn't it? *grin*


There is a famous cartoon that is relevant, copyright by Sydney Harris: https://www.researchgate.net/figure/...fig2_302632920 .



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.