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Old 13-12-2011, 21:36   #271
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Re: Electric Propulsion

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Old 13-12-2011, 21:43   #272
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Re: Electric Propulsion

Before there were engines and motors, sailors were capable to waiting out a day or two with little wind. If you have places to go, have a big heavy boat, are in a hurry to get there, and don't care about $5+ gallon for fuel. Electric motors and current batteries aren't there, but they would work with a lot of sailboats.

And if the designs for catamarans factored in multiple solar panels as a bimini shade, you could generate a fair amount of power to move a little during the day and not effect the amp hours remaining in the batteries.
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Old 13-12-2011, 23:01   #273
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Re: Electric Propulsion

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Originally Posted by SunDevil View Post
Before there were engines and motors, sailors were capable to waiting out a day or two with little wind. If you have places to go, have a big heavy boat, are in a hurry to get there, and don't care about $5+ gallon for fuel. Electric motors and current batteries aren't there, but they would work with a lot of sailboats.

And if the designs for catamarans factored in multiple solar panels as a bimini shade, you could generate a fair amount of power to move a little during the day and not effect the amp hours remaining in the batteries.

It seems they do work for small sailboats under appropriate conditions, and certainly having a broad base for panels helps but the engine is only one part of the demand, there's the navigation, autopilot and fridge running so you have to get above those levels. As a sailor these are the things I'm running when I'm under canvas; when I get to my destination, and it's been a windy day, I fire up the engine, pull into harbour, drop the anchor and settle in and likely my alternator has made up any deficiency in battery charge. This won't be the case if my motor is electric.

I'm a monohull but still, if memory serves (good luck with that), I've about 4800 watts of solar, with sails furled at when the sun is high I'll produce 20 amps. When the sails are out there's a lot of shade and the batteries will draw down.

For most of us, I think more efficient panels are needed before electric engines will be very practical. I would need about 300 sq feet of panels to replace my diesel on a sunny day (guessing).
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Old 14-12-2011, 02:44   #274
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Re: Electric Propulsion

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Originally Posted by Adamante View Post
Is that enough? I guess that would depend on the circumstances, but I would probably plan to put two 10KW generators on a boat this size. They need not be run together, but two sets would provide redundancy. And even with a dead battery bank, with both generators running, the boat should be able to move at 7-8 knots, which would be enough to make the passage of the PanamaCanal within the required time limit.
Thanks for the reply ... in case of a catamaran that would basically mean to replace each engine with a genset. I like that idea since the first diesel engine driven boat was a diesel-electric system ...
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Old 14-12-2011, 08:37   #275
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Re: Electric Propulsion

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Silly debate, a 10-20kw electric system with its controllers etc is no more demountable then a diesel.

Dave
Now your straw man arguments are really getting ridiculous. FYI I am talking about a 10 kw system and YES it is a lot easier to remove than a diesel engine if you wanted too. I might add it is a lot cleaner to do it too! Yeah, can remove a diesel engine. I've done it and am glad I will never have to do it again. But, you are not going to be taking a 27 HP diesel ashore in an 8 foot dingy!
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Old 14-12-2011, 12:27   #276
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Re: Electric Propulsion

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Originally Posted by mbianka View Post
Now your straw man arguments are really getting ridiculous. FYI I am talking about a 10 kw system and YES it is a lot easier to remove than a diesel engine if you wanted too. I might add it is a lot cleaner to do it too! Yeah, can remove a diesel engine. I've done it and am glad I will never have to do it again. But, you are not going to be taking a 27 HP diesel ashore in an 8 foot dingy!
My guess is that if an install is done with one eye on future ease of removal (whether to another boat or partial upgrades as technology develops) that would be easier than removing a fully plumbed in diesel......if buying another boat (and like your current Electric install) can swap engines - and time the removal process .
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Old 14-12-2011, 13:20   #277
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Re: Electric Propulsion

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Originally Posted by hummingway View Post
A 200w engine doesn't seem very powerful. Kind of like trying to run your boat off a battery powered drill isn't it? About .3 HP?

(I realize you said "Staggeringly incorrect" just clarifying).

I have a 200watt electric motor running an 8 ft dinghy, for a full sized boat about 2000watts is the minimum, 10kW is more realistic.

Sun energy reaching the earth is about 1000watts per square meter at 100% efficiency, at best current technology is 10-18% so to get 2000watts you need 10 of the high efficiency panels for total area of 30 sq feet. or 50-60 sq ft of the cheaper panels. Doable barely.

On the other hand 20 Trojan T-106's will give you about 8 hrs of run time, if fully top'ed off before you leave the dock.

Under current technology covering the entire surface of a catamaran 30ft * 18 ft will give you just enough power under full sunlight to operate at reduced speed, or as mentioned above 10 hours of charging for 1 hour of electric motoring.
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Old 14-12-2011, 13:46   #278
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Re: Electric Propulsion

7.5 kilo watts is equal to 10 horse power. Because dc electric motors produce almost constant torque regardless of rpm you can often use a smaller motor when using electric. But nothing that is as cheap and available as diesel has the energy storage capaciyy as diesel. So unless you only need power for a few hours you should consider a hybrid system where you have a diesel dc genset that can charge battery bank and also supply enough watts to run dc motor directly even if only at say 50%.
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Old 14-12-2011, 20:42   #279
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Re: Electric Propulsion

Off topic - is it possible to convert an existing diesel engine into a "generator" ? Any kits out there ? Thanks.
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Old 14-12-2011, 21:07   #280
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Re: Electric Propulsion

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Off topic - is it possible to convert an existing diesel engine into a "generator" ? Any kits out there ? Thanks.
The two electric drive systems I have looked into both indicated they could generate from water flow, so I surmised that piggy backing the system onto the prop shaft between the tranny and packing gland would let you operate the electrical system as a generator.
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Old 14-12-2011, 23:40   #281
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Re: Electric Propulsion

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... Because dc electric motors produce almost constant torque regardless of rpm you can often use a smaller motor when using electric ...
Fact check. Myth busting. No less than MIT says this. Plus the efficiency at both zero RPM and maximum RPM is zero. Peak efficiency is somewhere just above the maximum power point. So both DC motors and diesels have interesting torque, speed and power curves. With both diesel and DC motor the designer must be careful to select the motor, power supply, gearing and propeller so as to end up with an effective solution. It's never simple.
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Old 15-12-2011, 00:18   #282
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Re: Electric Propulsion

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Originally Posted by daddle View Post
Fact check. Myth busting. No less than MIT says this. Plus the efficiency at both zero RPM and maximum RPM is zero. Peak efficiency is somewhere just above the maximum power point. So both DC motors and diesels have interesting torque, speed and power curves. With both diesel and DC motor the designer must be careful to select the motor, power supply, gearing and propeller so as to end up with an effective solution. It's never simple.
This same info should be used in mating a good gen setup to an ICE as below. Yes, it can be done, but you want the gen setup to be getting it's best charging output somewheres around the best efficiency RPM of the engine.

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Off topic - is it possible to convert an existing diesel engine into a "generator" ? Any kits out there ? Thanks.
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Originally Posted by Adelie View Post
The two electric drive systems I have looked into both indicated they could generate from water flow, so I surmised that piggy backing the system onto the prop shaft between the tranny and packing gland would let you operate the electrical system as a generator.
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Old 15-12-2011, 05:31   #283
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Re: Electric Propulsion

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Originally Posted by David_Old_Jersey View Post
My guess is that if an install is done with one eye on future ease of removal (whether to another boat or partial upgrades as technology develops) that would be easier than removing a fully plumbed in diesel......if buying another boat (and lhike your current Electric install) can swap engines - and time the removal process .
David:

Indeed. When I was installing my system I did take into account how easy it would be to access and service the components. Not that I've had to do any servicing or repairs in the past four years. The nice thing about EP is it allows for a lot of flexibility in the install. I can access all the battery and motor connections from inside the cabin and the controller box is also mounted in a comfortable location to get to and remove if I want to.
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Old 15-12-2011, 06:25   #284
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Re: Electric Propulsion

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Originally Posted by Adelie View Post
The two electric drive systems I have looked into both indicated they could generate from water flow, so I surmised that piggy backing the system onto the prop shaft between the tranny and packing gland would let you operate the electrical system as a generator.
Adelie:

How well this works depends on lot of factors. Such as prop size, pitch location, water flow and boat speed. I'm able to get regen with my system once the boat speed hits about six knots.
THE BIANKA LOG BLOG: ANOTHER ADVANTAGE OF ELECTRIC PROPULSION: REGEN
Of course I'm using the same prop I had when I had my diesel. I might be able to improve on it with a more optomized prop but, if it ain't broke. Though you don't really want too much regen either because you can overcharge your battery bank if you are not careful. Other boats with a little more speed can have pump a few more amps into the bank:
THE BIANKA LOG BLOG: MORE REGEN!
I know of an electric powered catamaran on an ocean crossing that had to run the air conditioning to make sure there was sufficent load to prevent over charging the bank. As they say "results may vary" I don't count on regen for my charging but, when it happens it's a good thing.
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Old 15-12-2011, 07:24   #285
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Re: Electric Propulsion

The Cat Mike is referring to was a 410 SE, one of 3, sister boat to mine, and fitted with the Solomons Tech System. To read about the crossing First Electric Lagoon Crosses Atlantic to Annapolis...Then Heads to Tortola
This was 7 years ago. By the way the solution to over charging was to put the motors in a slight reverse position on the throttles. We should all have such problems. My system is still running strong and other than a controller (15 mins. to replace) and an upgrade and reconfig. to AGM batteries I have absolutely no complaints.


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