Electric Drive: Who uses it?

[Lost Horizons]

Originally Posted by valhalla360

In calm conditions only used to get in and out of harbor, 10kw is probably adequate. In any kind of adverse conditions, it would be woefully inadequate.

If it's a sailboat, the cockpit area is typically shaded partially or fully by the sails, mast, boom. If you are familiar with solar systems, even a small amount of shading can cut power output by half or more. Typical monohull in that size range peaks out with around 400-500w of solar, which is typically all used up by the house electrical system.

Even if we assume the 2kw is viable, solar only generates for around 4hr per day, so that's around 8kwh per day or around 48min of run time per day if your house loads are ZERO (which they won't be). So if you have a 5hr run on the ICW, that means you need to anchor out for a week using no electricity before heading on.

For a monohull, cargo capacity isn't much of an issue but fitting batteries into the keel would be expensive and complicated, so it doesn't really replace the keel. If it's an existing boat converted, you already have the ballast in the keel, so yes, it's eating into cargo capacity and more importantly taking up limited space.

1) For the AVERAGE power consumption estimate, 10 kW is adequate for boats dispacing up to 10 tonnes. Getting out of harbor, you need less than 5 kW, powering into a gale 30 kW, motoring in calm conditions at 1.1-1.2 speed factor, 10 would suffice.

2) I am surprised you did not mention losing solar efficiency while sailing eastwards or westwards with a southerly breeze.
Note that even if you lose 50% charging efficiency while sailing, it is only 5% loss a year if you sail 10% of the time, which is a lot. You can do even better if you sail at night.

3) Oh, yes, you are right about the ICW crowd who is motoring hundreds of miles day after day. However, this discussion is about sailboats with auxiliary power propulsion, not the other way around. For ICW travellers, full electric sailboat is evidently not a viable choice unless you have a large battery (double-Tesla, which would be too expensive for most) and is pulling into marinas nightly to recharge it. And I agree that on the US East coast ICW travellers dominate cruising community. Another local cruising area where solar sailboats would not be practical is PNW.

4) One can get creative and modify a keel by removing some of the metal at the bottom to compensate for added weight. Make it more Bahamas friendly at the same time.

[john61ct]

Sorry but those last few posts are extremely off-base, pie in the sky too optimistic.

But all the counterpoints have already been made by those who know better, no point in repeating like a ping pong match.

[Lost Horizons]

Originally Posted by valhalla360

The only use cases I've found viable:
- Weekender sailboat or purist sailor who refuses to motor more than absolutely necessary and is willing to risk trying to sail out of any bad situation.
- Canal boat where the entire topside is covered in solar panels.

- someone who wants to spend several months away from civilazation where the next fuel dock is a thousand miles away, but still enjoy refrigiration and other modern conveniences.

- someone who wants to do a non-stop circumnavigation in a boat that cannot carry 200-300 gallons of diesel fuel.

Small market, definitely. Which is why it is not addressed by manufecturers.

Technology is there, but no market with current abandant supply of diesel fuel and no demand for electric aux propulsion.

[Kalinowski]

Originally Posted by Wayfarer1008

LOL the guy just turned his boat into a 41 foot Duffy.
Great for cruising the harbor but forget about going anywhere. I've seen people put electric power plants into boats like Santana 30/30's and other old racing boats thinking like they are upgrading the power systems without understanding that weight is the big overlying concern and if its for getting back and fourth into a slip you can do it better with an outboard.
I can understand if the boat is designed from the ground up to be electric but if you want to take all the value and usefulness out of your boat put in an electrical drive.

We have no problem with our electric system and use it when necessary to get in and out of our slip. The total weight of our motor, batteries , and chargers (we have no generator) is about the same as the diesel system we replaced. We cruise interisland here in HI with the rags up. That's the job for the sails isn't it?

[john61ct]

Originally Posted by Lost Horizons

- someone who wants to spend several months away from civilazation where the next fuel dock is a thousand miles away, but still enjoy refrigiration and other modern conveniences.

- someone who wants to do a non-stop circumnavigation in a boat that cannot carry 200-300 gallons of diesel fuel.

Small market, definitely. Which is why it is not addressed by manufecturers.

Technology is there, but no market with current abandant supply of diesel fuel and no demand for electric aux propulsion.

Again, No.

The technology is just NOT there without spending millions on a freakishly impractical boat.

[a64pilot]

Originally Posted by Lost Horizons

My first trailerable sailboat, which I sailed extensively on Lake Ontario, Fingerlakes, New England coast, and Florida including two trips to Dry Tortugas, had a 2-stroke Nissan outboard with a 3.5 gallon tank that I fueled once per season. So I probably motored about 30 miles or so out of, say, 1000 miles sailed annually. A 7-8 tonn mid-thirties cruiser with a Tesla-like capacity battery can go twice as far at near hull speed on a single charge. Without any solar supplement. And it will be practical for some.

Compare the cost of a small outboard and 3.5 gls of fuel with a Tesla like battery and the corresponding electric motor.
Now maybe you see what there aren’t any

[skipmac]

Originally Posted by Lost Horizons

- someone who wants to spend several months away from civilazation where the next fuel dock is a thousand miles away, but still enjoy refrigiration and other modern conveniences.

Guess what? Hundreds of cruisers have diesel engines yet still manage to spend months away from fuel docks and marinas AND have refrigeration and all the other conveniences. Just because there is a diesel engine in a boat does not mean that you have to run all the time.

I have a diesel and solar and can run my 9 cu ft refrigerator/freezer, LED lights, stereo and other modern conveniences solely off solar and never have to crank the engine. Running the nav gear; AP, GPS, radar, etc does require some charging from engine or generator until I can add another panel or so.

The big difference between most well set up cruising boats with a diesel vs a boat with electric, the one with the diesel can motor 200-400 nm while the one with electric can motor 20-40 nm.

Originally Posted by Lost Horizons

- someone who wants to do a non-stop circumnavigation in a boat that cannot carry 200-300 gallons of diesel fuel.

Same thing applies. Just because a boat has an engine why can't it make a non-stop circumnavigation? Oh wait, they have. In fact I would guess quite a few have done so.

Originally Posted by Lost Horizons

Technology is there, but no market with current abandant supply of diesel fuel and no demand for electric aux propulsion.

Actually, based on what I see on this and other forums, there's lots of demand for electric propulsion. I for one would buy one in a minute IF it didn't add cost, complexity and/or limit my range under power.

Electric power on a boat is like the sign I've seen posted in some boatyards and mechanics shops. You can have your work done here good, fast and cheap. But you only get to choose two of the three.

Electric to get cruising range and equivalent power to the original diesel installation will add complexity and cost double or triple the cost to completely replace the engine and transmission. I've looked at every system on the market (though I'm sure a few new ones have popped up in the last year so since I last went through the exercise) and when you add the cost of the motor, controllers and batteries AND a generator the cost is far exceeds the cost of a diesel.

As an aside, one thing that I cannot understand. I looked at a number of "marine" electric motors and found most larger ones, 15-25 kW priced in the $8,000 - $15,000 range. You can buy an industrial, continuous duty rated electric motor of the same power for 10-25% of that. I called the Toyota dealer and a new electric motor for a Prius was under $1000 (plus labor) and if I recall, rated 50 kW or so. Sure wish I knew what was so special about these marine electric motors.

[skipmac]

Originally Posted by john61ct

Again, No.

The technology is just NOT there without spending millions on a freakishly impractical boat.

Not millions but certainly tens of thousands.

[Corvidae]

Fun little thread going on here. Since I'm about to convert my boat to electric tomorrow, it should be fun to see how it pans out in reality. It's not the usual use case though, seeing as I'll be running dual 10kw motors to replace the twin diesels. So in my case I'll be going from 3 down to the 1 diesel in the 13kw generator. So a lot of moving parts are going away, and being replaced by almost their weight in batteries. 200ah per motor, with room to double that on each side, plus the range extension of the generator. Given the latest quotes on replacement engines in Ft. Lauderdale, it's also costing me about $3k less than diesel replacements, including upsizing the generator.

It should be interesting in that the original diesels were way more power than the boat really needed. One motor at less than half throttle was easily able to maintain 6.5 knots with twice that in head winds. The electrics will have to work considerably harder to match that, but should be up to the task. The real questions are going to come down to longevity and range. I'll check back in after I've had a chance to compare.

[StuM]

200Ah per motor at what voltage? It's the Wattage that matters. And what chemistry?

Gallart 13.50 MS. Doesn't MS stand for "motor sailor' i.e. a vessel which relies to a certain extent on its motoring capabilities? If I'm not mistaken, it comes with about 135 HP of diesel propulsion.

And you are replacing that power source with a 13kW generator that is likely to be putting out about 15 HP at best? One motor at less than half throttle would still be considerably more than that.

I'd say the real question is going to come down to maximum speed pushing into a head wind and a bit of chop.

[Dockhead]

Originally Posted by skipmac

. . . Actually, based on what I see on this and other forums, there's lots of demand for electric propulsion. I for one would buy one in a minute IF it didn't add cost, complexity and/or limit my range under power.

Electric power on a boat is like the sign I've seen posted in some boatyards and mechanics shops. You can have your work done here good, fast and cheap. But you only get to choose two of the three.

Electric to get cruising range and equivalent power to the original diesel installation will add complexity and cost double or triple the cost to completely replace the engine and transmission. I've looked at every system on the market (though I'm sure a few new ones have popped up in the last year so since I last went through the exercise) and when you add the cost of the motor, controllers and batteries AND a generator the cost is far exceeds the cost of a diesel.

As an aside, one thing that I cannot understand. I looked at a number of "marine" electric motors and found most larger ones, 15-25 kW priced in the $8,000 - $15,000 range. You can buy an industrial, continuous duty rated electric motor of the same power for 10-25% of that. I called the Toyota dealer and a new electric motor for a Prius was under $1000 (plus labor) and if I recall, rated 50 kW or so. Sure wish I knew what was so special about these marine electric motors.

Well, I think there are two issues with electric propulsion.

One is how do you store the energy.

The other is how do you produce it.

There's nothing magical about electric propulsion -- it's simply a way to use previously produced and stored energy.

Battery technology is probably the main bottleneck. Power density of lithium batteries, even Tesla LiIon types (as opposed to the much safer LiFePo4 ones) is two orders of magnitude less than diesel fuel. Electric vehicles can get some of that disadvantage back because electric motors are simpler and lighter, so the whole powertrain together with storage is not as much heavier then just the storage would be. But that doesn't apply to electric boats if you have a diesel engine besides the electric one.

This very great disadvantage in storage of energy makes it not very practical to store enough to use for anything other than getting in and out of harbors, as has been discussed. So we get to the issue of producing power. The only realistic way to produce enough power for motoring any kind of distance is with -- an internal combustion engine. So once you add that back into the system, what have you gained with all the electrickery?

Well, you could take and store some shore power, provided it's free or included in a fixed price of a berth and you have enough battery storage. That can be a plus in some cases.

You might reduce the size of the diesel engine because you can "peak shave" using battery power. That's another plus because a smaller diesel working harder will be slightly more efficient and might be more healthy.

You might eliminate a whole separate diesel generator since you're already producing electrical power on a largish scale -- to my mind, that is the single biggest advantage of hybrid propulsion on a cruising boat, although rarely discussed on here.

Most electric propulsion schemes lower the bar by reducing the amount of power and range available. Well, that's fine, and appropriate to a system where power and range are relatively harder to achieve. But it's a fantasy to think that it's all the same and you're not giving up anything. Some electric enthusiasts even imagine that a horsepower from an electric motor is somehow magically worth several horsepower from a diesel, which is pure fantasy.

Hybrid cars benefit enormously from regenerative braking. We don't have that on boats, unless you consider driving the motor in reverse with a spinning prop under sail, but experience shows that this is not all that useful. Hybrid cars benefit enormously from the effect of "peak shaving" -- because of the huge difference between peak and average power required in a car. We don't have that, as normal cruising speed on most boats will be a significant percentage of maximum power -- a very good, very efficient regime for using a diesel engine. Hybrid cars, or at least electric cars, benefit from simplification of the drive train, especially, the elimination gearboxes and lessening of gear reduction because of the large starting torque of electric motors. But boats, unlike cars, don't need gears anyway, so there's nothing much to simplify.

So to my mind, it's really hard to see a case for them at the current stage of battery technology. A lot of cost and complexity is added with very little benefit. Of course you can just do without motoring ability except rudimentary ability to get in and out of harbor -- but that's not a case for electric power, that's a case for doing without something. As someone said, if you're OK with that, then why not take it a step further and just have a small outboard and a small can of gasoline? Much lighter, cheaper (order of magnitude), simpler, than an electric setup.

It would be different if batteries would be five times cheaper per kW/h and with ten times more power density. That would be a game-changer. And it will happen someday. If we could store energy with that kind of efficiency, then that would open up all kinds of possibility for storing say wind power or tide power, or nuclear, in quantities great enough to be of some actual use for a cruising sailboat. Or from solar after long periods in the sun. But as it is, we can't practically store that much power -- we have to produce it onboard. And once we're doing that, with a diesel engine, then it's impossible to justify the cost and complexity of the system on the basis of having a slightly smaller diesel engine which will operate marginally more efficiently, plus the ability to operate for a few hours at a time silently. Except for real hardcore enthusiasts who just like the idea of it -- and more power to them (so to speak ). For practical users it just doesn't make any sense. No amount of fantasizing or wishful thinking changes the hard numbers.

[Dockhead]

Originally Posted by Corvidae

Fun little thread going on here. Since I'm about to convert my boat to electric tomorrow, it should be fun to see how it pans out in reality. It's not the usual use case though, seeing as I'll be running dual 10kw motors to replace the twin diesels. So in my case I'll be going from 3 down to the 1 diesel in the 13kw generator. So a lot of moving parts are going away, and being replaced by almost their weight in batteries. 200ah per motor, with room to double that on each side, plus the range extension of the generator. Given the latest quotes on replacement engines in Ft. Lauderdale, it's also costing me about $3k less than diesel replacements, including upsizing the generator.

It should be interesting in that the original diesels were way more power than the boat really needed. One motor at less than half throttle was easily able to maintain 6.5 knots with twice that in head winds. The electrics will have to work considerably harder to match that, but should be up to the task. The real questions are going to come down to longevity and range. I'll check back in after I've had a chance to compare.

We'll look forward very much to hearing about how this all works. It's one thing to theorize about something, and it's something entirely different to actually do it. More power to you!

I'm sure everyone here would be interested in the details of your setup -- kW of the motors, amount of battery storage, etc. etc.

The Gallart 13.50 is a nice boat! 2x 65 horsepower, 13.5 long tonnes light ship (about fifteen tons). Those diesels are making about 48kW each, so half of the power of one engine is 24kW. You say you need full power of one engine to go upwind -- that would be 24kW per electric motor -- are they that big? If so, you will need a lot of batteries, because a 13kW generator won't produce even half the power you need for normal cruising speed.

To have the ability to go one hour into the wind (at half the previous full power), you will need 48kW/h of storage, equivalent to 96kW/h of the nominal capacity of a lead-acid battery bank. If you're using golf cart batteries, like the popular Trojan T-105, you get nominally 1.35kW/h (practically 0.67 kW/h) out of 28 kg, so using these you would need 143 of those batteries, weighing 4 tonnes. It would take quite a charging system too! But I guess you might reduce the spec to half an hour at full power, and then it would be only 2 tonnes of batteries.

[skipmac]

Originally Posted by Corvidae

Fun little thread going on here. Since I'm about to convert my boat to electric tomorrow, it should be fun to see how it pans out in reality. It's not the usual use case though, seeing as I'll be running dual 10kw motors to replace the twin diesels. So in my case I'll be going from 3 down to the 1 diesel in the 13kw generator. So a lot of moving parts are going away, and being replaced by almost their weight in batteries. 200ah per motor, with room to double that on each side, plus the range extension of the generator. Given the latest quotes on replacement engines in Ft. Lauderdale, it's also costing me about $3k less than diesel replacements, including upsizing the generator.

It should be interesting in that the original diesels were way more power than the boat really needed. One motor at less than half throttle was easily able to maintain 6.5 knots with twice that in head winds. The electrics will have to work considerably harder to match that, but should be up to the task. The real questions are going to come down to longevity and range. I'll check back in after I've had a chance to compare.

Like Stu, I also have to question some of the numbers here.

If the boat for the conversion is indeed the Gallart MS then you will have a 13.5 meter motorsailor with 20 kW or approximately 27 HP. I have a similar sized boat with 58 HP diesel and occasionally need every bit of that, mainly for maneuvering around docks in wind or current. Motoring in any kind of winds and seas I estimate I'm using about half of that which would be more than your total electric power.

Another question, you mention the cost of two electric motors about $3K less than new diesels and bigger generator. Were you comparing the cost of a pair of 13-15 HP diesels which is what your electrics will be or larger engines comparable to the original equipment? Need to compare like to like for a valid comparison.

[valhalla360]

Originally Posted by Lost Horizons

1) For the AVERAGE power consumption estimate, 10 kW is adequate for boats dispacing up to 10 tonnes. Getting out of harbor, you need less than 5 kW, powering into a gale 30 kW, motoring in calm conditions at 1.1-1.2 speed factor, 10 would suffice. The problem is needing the high output happens from time to time. Unless the battery bank or generator can supply that 30kw for a significant period of time, 2% of the times you go out you get run up onto the rocks due to lack of power, that's still not acceptable.

2) I am surprised you did not mention losing solar efficiency while sailing eastwards or westwards with a southerly breeze.
Note that even if you lose 50% charging efficiency while sailing, it is only 5% loss a year if you sail 10% of the time, which is a lot. You can do even better if you sail at night. You missed the point. I wasn't talking strictly about sailing. The shadow of the boom can cut your output by 50% and most booms are over the cockpit so, those panels will rarely if ever put out 100% of their rated power. If the sails are blocking, you are likely to lose close to 100%. There's a reason you typically see solar panels mounted way back on the davits. Even there we sometimes see shadows impacting the output (just less often).

3) Oh, yes, you are right about the ICW crowd who is motoring hundreds of miles day after day. However, this discussion is about sailboats with auxiliary power propulsion, not the other way around. For ICW travellers, full electric sailboat is evidently not a viable choice unless you have a large battery (double-Tesla, which would be too expensive for most) and is pulling into marinas nightly to recharge it. And I agree that on the US East coast ICW travellers dominate cruising community. Another local cruising area where solar sailboats would not be practical is PNW. No, the thread is about electric drivetrains. In fact the starting post talked about a trawler converted to electric drivesI readily agree that if you are a purist who rarely if ever motors any significant distance, it's possible. Of course the fuel savings then are probably pretty negligible. I know a few guys like that who brag about using less than 5 gal of diesel per year. I disagree about the PNW. If you rarely motor for more than a 1/4 mile and only go out once a week, solar can work...but again, there is really no gain to be had for what is likely a more expensive system.

4) One can get creative and modify a keel by removing some of the metal at the bottom to compensate for added weight. Make it more Bahamas friendly at the same time.It's fairly straightforward physics. If you put 1000lb in 1ft from the center of rotation, it only removes 200lb from 5ft down. 200lb off the bottom of the keel might be 1/2", so no noticable impact. But again a custom battery designed to fit into the keel is an issue on small space limited boats.

I stand by my point that there are only a few rare situations where it can work but usually is still impractical.

[valhalla360]

Originally Posted by Lost Horizons

- someone who wants to spend several months away from civilazation where the next fuel dock is a thousand miles away, but still enjoy refrigiration and other modern conveniences. Not many places where the net fuel dock is a thousand miles away but... house loads and propulsion are two different things. House loads are very much practical (short of high demand items like air/con. That's a totally different discussion.

- someone who wants to do a non-stop circumnavigation in a boat that cannot carry 200-300 gallons of diesel fuel. What percentage of cruisers do a non-stop circumnavigation. That sounds more like a race situation or some other stunt. Even if you found the incredibly rare cruiser who wants to do it, if the boat doesn't have room for a 200gal tank, it probably doesn't have room for the battery bank.

Small market, definitely. Which is why it is not addressed by manufecturers.

Technology is there, but no market with current abandant supply of diesel fuel and no demand for electric aux propulsion.

The technology is far from there. Battery power density and solar output needs to improve by a factor of 4-6 before it becomes marginally comparable to the motoring capability of a simple diesel.