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Old 21-01-2015, 02:13   #1
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Using electric motors instead of Diesel on your cat

Are there any sailors out there who have electric motors on the boat instead of diesels?

Have been looking in to this and it seems to be interesting option. I have no idea of the price point especially if you have used boat and want to do the switch but if buying a new boat, this might be a good option.

The more blogs I read, the more I see problems with engines (specially with 5+ year old boats).

Advantages that I see with electric motors:
- Save weight
- Save diesel
- No more noise
- Much less maintenance

Disadvantages:
- If something breaks, you won't be able to fix it yourself (just my guess)

And I don't even see batteries running low as a disadvantage because you can charge the batteries with solar panels, wind turbines, sailing or with generator.

Any comments?

One company that I found that supply these for mono and multihulls is:
Oceanvolt »
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Old 21-01-2015, 04:23   #2
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Re: Using electric motors instead of Diesel on your cat

See here Diesel Electric Propulsion for related discussion.


FWIW, I'd speculate problems you read about with 5+ year old diesels are more likely from mis-use or neglect.

-Chris
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Old 21-01-2015, 04:57   #3
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Re: Using electric motors instead of Diesel on your cat

There have been numerous discussions in the past about electric power on boats. At least one production catamaran was built with the option for electric power. There's a reason there are very few electric boats on the water today. Just like there is very small percentage of purely electric cars on the road.

Google is your friend... just search "marine electric propulsion". Do the research and cost analysis and you will see why everyone has a diesel.
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Old 21-01-2015, 07:26   #4
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Re: Using electric motors instead of Diesel on your cat

A quick and simple energy calculation.
Engine power 2 * 10 hp = 2 * 10 * 735 = 14700 W
Run time 0.5 hours.
Energy = 14700 W * 0.5 h = 7350 Wh
Voltage 12 V
The energy from the batteries 7350 / 12 = 612 Ah
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Old 21-01-2015, 08:02   #5
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Re: Using electric motors instead of Diesel on your cat

The main problem with using electric motors to power a boat is that you need a really long extension cord if you want to go anywhere.

Perhaps in five or ten years, solar collectors and batteries will improve enough and become affordable enough to make an electrical powered cruising boat practical. Not today though.
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Old 21-01-2015, 08:56   #6
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Re: Using electric motors instead of Diesel on your cat

I had the pleasure of sailing on a cat a friend of mine just installed electric motors on, in place of his diesel engines, one had failed.

Regardless of how his engine died, he sold the other and both saildrives and installed electric Golf Cart motors, batteries and controls.

No extension cord needed with all the solar panels, batteries and a standby generator.

As he told me, "The motors are auxiliary. After all, it is a sailboat."

Here is the blog for Dan and family:

Bond Voyage: Search results for electric
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Old 21-01-2015, 13:16   #7
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Re: Using electric motors instead of Diesel on your cat

Go to this site. Ive spoken to the owner. Very articulate and gaining recognition.

The Electric Propeller Company Videos - The Electric Propeller Company
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Old 21-01-2015, 13:33   #8
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Re: Using electric motors instead of Diesel on your cat

Quote:
Originally Posted by gixxxer View Post
And I don't even see batteries running low as a disadvantage because you can charge the batteries with solar panels, wind turbines, sailing or with generator.
Take a look at how many kiloWatts a reasonable propulsion engine needs to consume, and how many Watts wind generators and solar panels produce, and then you'll see the disadvantage.
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Old 21-01-2015, 14:08   #9
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Re: Using electric motors instead of Diesel on your cat

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Originally Posted by gixxxer View Post
And I don't even see batteries running low as a disadvantage because you can charge the batteries with solar panels, wind turbines, sailing or with generator.
The problem is at the "with a generator" - you're taking mechanical power from a diesel engine, turning it into electricity, then turning it into chemical energy in a battery, then turning it back into electricity, then back into mechanical energy. You lose a LOT in the process - and can get most of the efficiency benefits of electrical power from a decent reduction gearbox.

Now, I'd say that there are some ways in which electrical power can be practicable, but they aren't (yet) commonplace:
  1. If you're cruising around a lot, and only occasionally use a bit of power to enter or leave harbour/pick up a mooring. Provided you're willing to accept that you can't go very far or very fast, electric motors work just fine.
  2. Parallel hybrids - a small electric motor packaged onto the diesel engine that can be used for (1) above, plus also used as a generator when the engine is running. That cuts down on engine run hours - and maintenence is often as or more expensive than fuel for pottering about entering and leaving harbour.
  3. If you're looking at it as a whole boat system, are willing to spend a lot of money and stretch the technology a bit. In a few years diesel fuel cell APUs for commercial trucks are likely to be a reality, as are far higher capacity batteries. A large, high capacity battery bank that can be recharged silently and cheaply is quite attractive for more than just propulsion - air conditioning, induction hobs and the like are all big power users and have their take-up limited by the current cost of running a generator. A system capable of regeneration, solar power and running a fuel cell generator could potentially be quite attractive.

Now, right now (1) is cheap and practical but a minority interest because it doesn't fit with how most want to use their boats. (2) is possible but expensive - in the vast majority of cases the fuel savings won't pay for all the extra installation costs. (3) is horrendously expensive but coming down in price because it's all being developed for the automotive and consumer electronics markets, which have enormously greater buying power than sailors. If the price comes down far enough, something like (3) starts to become of interest to those beyond the super-rich.
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Old 21-01-2015, 14:09   #10
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Re: Using electric motors instead of Diesel on your cat

What do you mean by the term “price point”? Does that mean the price? If so it could be all over the box. If you are talking about sufficient power to just get you out of the slip so you can set sail and sail around the bay my guest is this could be done relatively inexpensively but so is diesel if that is all you use it for. If you are talking about electric power that would give you 6-8 knots of cruise speed under power and plenty or reserve power when you need it I’m thinking big bucks for the right motors, high-tech batteries plus a solar and/or wind generating system. In this case I doubt the all-in price of electric would have a payback compared to an internal combustion engine even considering fuel and maintenance costs. Otherwise all the charter operators would already be doing it.
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Old 21-01-2015, 14:10   #11
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Re: Using electric motors instead of Diesel on your cat

Nigel Calder has been doing some testing of electric and hybrid propulsion. There was a great 2-part writeup last year in Practical Boat Owner (UK) that was both rigorous and comprehensible.

If I understand correctly, Calder focussed in on the efficiency of both systems at varying speeds and for different usage patterns. My takeaway was that for short jaunts in and out of harbour, docking, and other intermittent use, electric propulsion was most efficient and more responsive, whereas for long runs at near full speed, straight diesels were most efficient and practical. Assuming that most cruisers are in the latter camp and will need the ability to motor long distances, diesel is still the best overall choice for them.

I believe hybrids (diesel on propshaft, with electric co-drive) will become more practical as automotive electrical tech and hardware, and cheaper batteries, find their way into the marine market.

Some more discussion: The Science of Hybrid Propulsion: The Great Debate | | PassageMaker
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Old 21-01-2015, 14:15   #12
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Re: Using electric motors instead of Diesel on your cat

I'm sure Steve of Electra Glide will chime in here with real world experience. He has the only Lagoon 410 on the planet with electric drives. Steve?
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Old 22-01-2015, 08:04   #13
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Re: Using electric motors instead of Diesel on your cat

It's totally a reality to power your boat with electricity. Shoot, many people don't even have an engine on board - sheedang! It's all in what the individual wants to do with their boat. Most sailboats these days seem to be 'Motor-Sailers' more than pure sailing vessels. I would think a catamaran would be a good option for an electric conversion, lots of places to put solar panels. But, if all you want to do is putt around with the engine on and pretend you are sailing then this may not be the way to go. This also goes for electric cars, I drive an electric car and I love it. No more standing out in the cold pumping gas, no expensive maintenance (haven't been to the dealership in two years for anything!) and I can 'fuel' up at home on hydro-generated electricity. When I move up to my 'big boat' - it's going to be electric or maybe no engine at all like they used to be. Sorry if I sound insulting but I'm a huge proponent of electric propulsion. Nothing is more efficient than generating electricity and putting it directly to work without any 'middle' processing like fuel cells or diesel.
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Old 22-01-2015, 08:13   #14
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Re: Using electric motors instead of Diesel on your cat

Diesel electric systems or diesel-electric motor-battery systems do not save weight over a purely diesel drive system. The propulsive thrust generated per pound of drive system mass is greater for a strictly diesel drive system.

Weight is critical for a catamaran because the increase in wetted surface per pound of increase in displacement is greater for a cat than a monohull.

Increased weight at the bow or stern also means an increase in pitching moment which increases "hobby horsing" with a cat.

As far as overall performance goes, a purely diesel drive system is better....although not necessarily better for the environment...but that's debatable.
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Old 22-01-2015, 11:10   #15
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Re: Using electric motors instead of Diesel on your cat

Pure Electric: Consider the Tesla, the ultimate electric vehicle (by some accounts). Ignoring the energy conversion efficencies and simply look at range an equivilent diesel powered car would have maybe a 5 gal gas tank. Tesla uses a huge very expensive battery bank and it takes hours to refill the tank. Drop back to something more modest like a nissan leaf and the tank (ie: batteries) hold an equivilent of maybe 2 gallons. This is the ultimate problem with running a pure electric boat. Now if you don't cruise and just need to get in and out of the harbor, it can work. But since you asked this on a cruising forum and 99% of cruisers will want/need to motor for hours at a time, a pure electric powered boat is not ready for prime time without major sacrafices in motoring capability. A very small percentage of people may be willing to live with those sacrafices but count on a significant drop in resale value as most buyers won't.

Diesel/Electric options: This can work fine but now you have the diesel you were trying to avoid and the cost is more than a traditional drivetrain (definetly more if you scrap an operatonal diesel to retrofit)

Reality is a 10yr old diesel that has had reasonable maintenance (nothing exotic or paticularly difficult) and hasn't been abused (or run an exhorbidant number of hours) will be good for another 20yrs of reliable use. You are solving a non-existent problem.
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