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southernwind 02-13-2009 11:41 PM

Electric drive owners need some advice
i am intrested in a electric sail drive from Thunderstruck Motors - Electric Sailboat motor Kit. Mars Brusless motor with Sevcon PMAC millipak regen controller. and have worked out the regen range weight battries and all that fun stuff.

I can come in at just about the same range and weight. but what I want is the regen ability when i am out sailing the extra energy could run a fridge and was wanting to hear from owners that have them and was whanting to know what they think as far as pros vs. cons and all that. I am thinking about 144v for the charging i was thinking about 3 48v wind for harbor charging.

happy sails

tommays 02-14-2009 09:09 AM

I don't think electric is ready :D

But looking at the "KIT" it is really NOT ready you have to come up with your own gear box , The control looks very small to handle 100 to 200 amps

I work with all types of AC and DC electric motors forklifts to machines and the motor looks way to small to replace a 10 HP diesel

Dick Pluta 02-14-2009 11:00 AM

Take a look at some of the recent back issues of SAIL magazine. Nigel Calder is outfitting a boat with electric drive. His main premise is that we don't know anything about the practicality of electric drive and he is gathering data. Like the electric car issue, batteries are the big problem. He has already given up on Lithium Ion batteries in favor of the Optima TPPL (thin plate pure lead) batteries.

merc2dogs 02-14-2009 12:43 PM

I think electric is a good idea, but don't think the technology for anything other than cruising near your home port is here yet.

Think currently the most viable system is a diesel electric, with a large enough battery bank to do some manuevering, get you out of the harbor with maybe enough reserve to get you another mile or two on battery alone.
Think that system would allow for cruising, especially if you used a regen type motor.

Now if you're talking about my fantasy system, I looked into placing the electric motor/generator between the diesel engine and shaft with a clutch between them. Figure that way I could run the electric, then when I wanted, engage the clutch and use the diesel for propulsion while running the motor as a generator.
Would have the best of both worlds, instant power and convenience of the electric drive, with the range of a diesel.


eMKay 02-14-2009 03:55 PM


Originally Posted by tommays (Post 448049)
I don't think electric is ready :D

But looking at the "KIT" it is really NOT ready you have to come up with your own gear box , The control looks very small to handle 100 to 200 amps

I work with all types of AC and DC electric motors forklifts to machines and the motor looks way to small to replace a 10 HP diesel

That site an many other sites have a wide range of motors and controllers, you can customize them at your will, and as LiFePO4 batteries (same type that's going in the Volt and other electric and hybrids in the pipeline) come down in price, this becomes a viable alternative. I've been researching this quite a bit for another project of mine (electric locost, google it) and have figured out that for a 10,000lb boat something like 15kw is needed, you can get by with the 8.5kw kit, plus it has regen and has been able to put up to 4ah back into the battery bank just using the spinning prop. But watch the lithium iron battery prices carefully, once they begin to drop, not only is it cheaper than a new diesel engine, you can make a relatively light bank that can store a great deal of power. With a 600ah battery bank on say this system here Thunderstruck Motors - D&D Motor Systems. Seperately Excited Motor/Controller packages for 24-48V or 60-84V ranges. at 72v you are looking at well under 200 amp draw to push a 27-30 foot boat to 5kts, a Catalina 27 was converted to a 48v system and they were getting a draw of 125amps at 5 kts. They were getting 10 hours of run time at 3-4kts, and 2 hours at full throttle. That is not bad at all.

southernwind 02-14-2009 05:45 PM

the person that has a knee jerk reaction that says it cant replace 10 horse diesel is the person that don't know what he is talking about that's why I was wanting to hear from other actual owners. Its simple as a horsepower consumes 750 watts regardless of the power source here is the difference. your diesel can ONLY create the 10 horsepower at full power and max torque close to the same. A 8hp electric motor creates the same torque that your diesel does but from the time it starts turning regardless of RPM. All alternators are motors and all motors are alternators. Just spin them backwards that's it. When your sailing the prop spins and charges the batteries and you have endless power when you are sailing.

eMKay I totally agree with your Car project and thanks for the site I have been looking for that forum and couldn't remember the name of it. any way in a car yes your right, however we are talking about a boat that has a wave pushing it that's why it takes so little power to push a boat at hull speed. in a boat system i think for my own personal reasons i think 96v should be the smallest amount of power that should be used. i actually prefer 144v the amp draw at cruising speed should be in the 6000 watts range for a 30 to 32 footer and around 45-50 amps figuring in line losses.

another difference is the batteries in a boat you don't need the super fast discharge capabilities of the LiFePO4 batteries. They actually work against you and Trojan T105's would be a great choice. 220AH @ 20 hours with 144v in the system its 24 batteries a little heavy yea but factor this in at 50% discharge there is 2640 usable amps (of course you arent going to use them all at once) and thats a 50 hour or so burn rate and a (no wind no wave ideal condition) range of around 260 miles. when you get back under sail the system charges its self.

ok this is the plan I am puttin together

Oh and the "Gearing" is no more (on 90% of the systems) than a 2:1 pully system to slow down the electric motor to about 600 to 800 rpm

Architeuthis 02-14-2009 05:52 PM

Too bad there are not more owners out there to answer your post. There are a couple in this marina and their experience would support the position that Elect drive is not for everybody.

Here is my 2 cents:

There is no extra power. If you do not have a diesel gen to recharge your batteries will slowly die unless:

You have only short sails and the boat is returned to the dock for charging from the grid.

You have only long sails, days in length, and good wind.

You have a very short power use to get out of your slip and only sail on days with good wind.

I would suggest getting a larger motor, smaller bank and diesel gen large enough to drive your boat at cruising speed.

Better yet wait for a turn key system. They are coming they just are not here yet for less than big money.

eMKay 02-15-2009 01:12 PM


Originally Posted by southernwind (Post 448138)
tAll alternators are motors and all motors are alternators. Just spin them backwards that's it.

This is not exactly true. All motors are GENERATORS would be the correct term. An alternator is a totally different animal, it is a large electromagnet, so requires a current that creates a powerful magnetic field. A generator can be spun by hand and generates a small amount of power compared to an alternator. When an alternator is generating a full field it can take up to 20hp just to turn it, but the benefit of that is they can generate well over 100 amps while a similar sized generator can only generate a few amps. (for short periods, then they overheat and fry)

timangiel 02-15-2009 01:39 PM

I have often wondered how well they work and how good of a replacement they would make for a saildrive. I have a 26ft boat with a 15hp saildrive and primarily day sail with an occasional weekend cruise. I am not having trouble with my saildrive right now, but the day will come when I need to repower. I like the idea of an electric drive, quiet & clean power, but would be hesistant to go that route right now. I would be interested in hearing about the experiences of anyone who did go that route.

tommays 02-15-2009 01:54 PM


I can only comment on what YOU point me to which is a tiny motor and control

Vs the motor

That eMKay shows that is big enough to have chance of putting out the power necessary to move the boat

"Our Sailboat Kit will convert your 3-12 HP diesel engine to clean, silent electric!

We've supplied these systems for sailboats up to 30 ft. long, and 12,000lb displacement, that are achieving hull speed. All systems have reverse on-the-fly and contactor disable.

Brushless means no brushes to wear out, and no ignition source for on-board gas appliances."

I always like it when they cant show you a single working install ;)

The gas or diesel motor that was there had a powerband that had to followed to allow the boat to move efficiently and the electric motor has a powerband that will also have to followed to allow the motor to work efficiently

Then your not even thinking about the air flow necessary to keep the electric motor and control from having a meltdown when its closed up inside a boat a drawing 100 + amps

And most of what we do at work is change out OLD school mechanical Variable Speed Drives to Modern Electronic Variable Speed Drives and if you don't do your homework on the it does not work out well.

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