Electric Propulsion on Catamarans

[BigBeakie]

Yes, thanks, and you suggested to bring the discussion over to this thread, which is more appropriate.

I will open the issue of support for electric propulsion because it is something that concerns me. Not being an electrical engineer, it seems to me that a solution for cruisers in far flung places would need really good reliability AND warranty/support from any vendors that supply any of the bits in the electric propulsion system ie the motors, the controller, the batteries, the BMS, the generator, the invertor(s) etc etc.

What attracts me to Torqeedo is that they seem to be taking a whole system, or integrated approach, so they supply and support most of the components. They also seem to have on-board diagnostics to identify any faults or failed components.

Are there any other electric motor vendors that take a similar stance re warranty support and taking ownership of the whole system?

[nimblemotors]

Originally Posted by BigBeakie

I am seeking feedback on any aspects of planning an electric 46 foot bluewater cruising cat that others have had a think about. I am at the stage of feasibility analysis, looking for the main factors in a cost-benefit review.
..
Are there any show stoppers that I should be aware of?

The price of a ticket to the show. Turnkey integrated supported warrantied installed is going to be hundreds of thousands.

[Stumble]

DeckOfficer,

Let's assume that the two Torquedo 4's will get you to 8.5kn at full throttle, which I doubt but let's go with it. If you want a range of 100nm, then the numbers are pretty easy to run...

The motors use 4,000watts at 48V at top speed. Assuming you are using a 48v battery bank, each hour of run time requires a usable 83.33amp hours. For 100 miles distance then 100/8.5=11.75hrs using 83.33ah/hr then you need a usable 980ah at 48v.

For you 120nm range you need 1,176 usable ah at 48v. So you need to go to a larger battery no matter what. Lifepo4 are typically recommended to no cycle below 80%, so you really need a bare minimum of 1500ah, or about double what you initially suggested.

Oh and this is per engine. So the boat needs a total installed battery bank of 3,000ah at 48V. Instead of the (16) 700ah batteries you asked about, you really need (32) 1000ah batteries.

On the charging side...

The rate of charge is luckily not a real issue with lifepo4 batteries so let's just ignore that. But to produce enough power to recharge a 3000ah 48V bank from 80% discharge we need 3750ah @ 48v or 180,000watt hours. So assuming you had a power plug at the end of the trip you would take just about 30 hours to recharge the batteries.

You didn't specify a solar array, but let's assume you are willing to completely cover the boat in solar panels. The boat is 30'x9.5' or 360" long by 114" wide. The panels are 62" long by 30" wide. So you could set up a maximum size array 6 panels long by 3 wide. So a total of 18 panels.

The panels I am working from are 190watts each. So to replace the 180,000watts used you would need 606 hours for two panels, or 67.33 hours for the entire array. Of course in the best case solar only produces for 6 hours a day on average, so you would need about 12 days of recharge time. The panels also run right at $400, so you need to figure another $6,500. Plus the frame and installation costs. Which will be substantial for the weight (528lbs)

So 12days to recharge from a 120nm cruise... The boat will average about 10nm/day or .42 knots. Even in dead light wind I could make better than .4kn on any sailing catamaran.

[BigBeakie]

Well, we shall see what the costing comes out like. From my discussions so far it will not be as dramatic as that, otherwise it will cruel the market. We are discussing a solution that will be appropriate for "ordinary" cruisers, not luxury superyachts.

Who have you had costings from?

The prices indicated by the Moonwave folks, for example, are over the top IMHO, and may be an ambit claim to gauge market feedback. I have given them my feedback

[deckofficer]

Greg,

You crunched some interesting numbers but with the assumption I would be cruising at 8.5 kt. With no headwinds or steep waves, that hull can run at 4.5 kt and only consume 300 whr per nm. So on a cat, one motor up, the other driving on 1350 watts, about 2 hp.

Battery bank (16) 700 ahr, so 700 X 3.25 X 16 X 0.8 (DOD) = 29120 usable whr / 300 = 97 nm plus 6 hours of solar harvesting 12000 / 300 = 40 nm. My claim of 120 nm day runs if speed is bumped from 4.5 to 5.0 kt is quite possible in calm conditions.

[deckofficer]

Greg,

On the weight issue, a bit off there too. With my training I'm anal about CG and would never place that weight that high. The 180 watt panels I would use weigh 6 lbs, 72 lbs for all 2160 watts worth.

[deckofficer]

Greg,

I'm curious as to how you got your numbers? Just to show how easy a solar boat is, here is a link to a solar boater that is doing the Great Loop right now. His boat is heavier, hull not as efficient, and the batteries are LEAD. Because of low energy density of his lead batteries, he only cruises when the sun is out, running on his 3200 watt solar panels and manages 40 mile daily runs. Needless to say, he isn't high tech.

RA’s Power System | Solar Boat Chronicles

[mbianka]

I'm about to start my 7th season with electric propulsion on my 30 foot 16,000lb monohull. I takes around 900 watts of power to move it around 3 knots. My Thoosa 9000 system uses a LEMCO motor and has been so much more reliable than the previous diesel and the bilge is always clean! My advice is keep it simple. On a sailboat you can use EP in ways you would never consider with a diesel. With the proper solar panels and wind turbine you can even make your own fuel(energy). Something you can't do with a diesel.

[Mr B]

There is a big solar powered cat Ferry operating in Sydney Harbour,

They do have super magnet, electric motors these days, The motor itself is very small, but the power it puts out is tremendous,

Sorry, I dont have a link to it, Its been a few years since I was reading up on it,
I was considering it for my steel Boat,

[deckofficer]

Originally Posted by mbianka

I'm about to start my 7th season with electric propulsion on my 30 foot 16,000lb monohull. I takes around 900 watts of power to move it around 3 knots. My Thoosa 9000 system uses a LEMCO motor and has been so much more reliable than the previous diesel and the bilge is always clean! My advice is keep it simple. On a sailboat you can use EP in ways you would never consider with a diesel. With the proper solar panels and wind turbine you can even make your own fuel(energy). Something you can't do with a diesel.

That also works out to 300 whr per mile. 16,000 lbs at 3 kt for that consumption scales to a 6500 lb cat at 4.5 kt for the same consumption per mile.

I wonder if Greg gets his numbers from tank tests and early adopter's experience or just playing the role of a litigator, to dismiss through argument.

[nimblemotors]

A very large battery bank is needed to go any distance on electric power.
Unless you have an ultra-light and ultra-efficient boat.
A 46ft cruising cat is neither.

4 miles/hour needs 25 hours to go 100 miles, that is more than 1 day.

My boat has ~5Kw of solar, so ~5hp when the sun shines, and should
go 4mph until the sun goes down, 32 miles a day, no batteries.
But I have two gasoline engines, they can add 2 to 100hp, so 64 miles a day using 2hp of gasoline for 8 hours. If I had a 40,000 watt-hour pack,
I could not use any gasoline, but would have to sit and charge one day.

Consider a $100k Tesla Model S has 85,000 watt-hours battery pack, that is about the best deal you can get.
A $30k Nissan Leaf has 24,000 watt-hours battery.
These cars have more volatile Lithium batteries.

Now take a high volume car and price it as a 1/1000th volume marine warranty turn-key solution, and raise the price 10x, and you have $300,000 to $1,000,000.
As a DIY..

[Stumble]

Deck officer,

I used your numbers, and the numbers from manufacturers websites for the The Torquedo numbers were from them, the solar panel was from SouthCoast solar (I believe) but were for their Keyocera panels, the battery info was from a google search for Lifepo4 batteries. Other than that I did all the math in the post.

I have had an electric sailboat. But I don't really believe that battery or solar technology is capable of making a pure electric boat realistic. By the time you add a large enough generator for propulsion needs you might as well just use the generator motors to drive the prop.

For very limited uses it works great. But if the goal is a distance cruiser it just isn't realistic.

[deckofficer]

Originally Posted by Stumble

Deck officer,

I used your numbers, and the numbers from manufacturers websites for the The Torquedo numbers were from them, the solar panel was from SouthCoast solar (I believe) but were for their Keyocera panels, the battery info was from a google search for Lifepo4 batteries. Other than that I did all the math in the post.

I have had an electric sailboat. But I don't really believe that battery or solar technology is capable of making a pure electric boat realistic. By the time you add a large enough generator for propulsion needs you might as well just use the generator motors to drive the prop.

For very limited uses it works great. But if the goal is a distance cruiser it just isn't realistic.

My calculations were based on known efficiency of the hull in a water medium. I don't need anymore than a 120 mile range but for distance, a 45' cat crossed the Atlantic with lead acid batteries and 10 kw of solar, no fuel or generator.
transatlantic21: The world's first crossing of the Atlantic on a solar boat

I use 62 lbs of LiFePO4 cells in my electric kayak and have an 80 mile range.

[cwjohm]

This has been very interesting. I enjoyed the link. It appears that a solar boat is feasible if you:-

(a) Make the boat light
(b) Use the full area of the boat for solar panels
(c) Are prepared to tootle along at low speeds - 5knots or so
(d) Do not wish to make long passages on any given day

This is definitely a technology which will see the light of day sometime in the future, but unless you are a very slow cruiser and want your boat to look like a Chinese junk, this will not be applicable to cruising for a few years. Better motors, batteries and solar panels will see this as standard fitout in cruising boats some day, but I doubt I will be alive to see it unfortunately.

[Stumble]

The transatlantic21 is using twin 8kw motors and has a top speed of 7kn. The Torquedo 4 is a 4kw motor. So right off the bat you are down to 1/2 the available hp of the Transatlantic21.

The TS21 has an installed 10kw of solar panels taking up 65sq meters. I couldn't find exactly which ones, but that is a pretty large array.


Like I said, an electric only boat is perfectly possible if you accept short range hops between harbors. Or use hyper-specialized boats with tens of thousands of dollars in batteries and solar arrays.