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  #1  
Old 04-25-2008
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Electric Propulsion - solidnav.com

I have a friend who is involved in a company called Solidnav. They are selling electric sailboat re-power gear. I thought that it would be neat to hear from anyone who had actually done an electric conversion and see how their conversion went? Who did you go with, and how did it work out?

I've looked a bit and I see a lot of DIY type stuff and then the really expensive saildrives, but little in-between. Would any of you who have done an electric conversion try a product like the Solidnav Explorer in a re-power?

The first one off engine that they made worked well, and it seams that they have solved a lot of issues in the first run that remain on other systems production units. The motors are not brushed motors, the controller is sealed, it is belt driven with a reduction gear, etc.

I guess I am sold on the product, but then I am close to it as well. The Engineers seem to have done a lot right. What do you think?

solidnav.com
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Old 04-26-2008
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Rockter will become famous soon enough
Not for me.

Not enough sun here boys, and none at night.

"Remove your portion from our oil burden while silently cruising into distant harbors".... what????

Beware you don't get swept along with the great global warming cabal.

In blazing heat, through the doldrums, with solar cells everywhere, an 8 kW electric motor will move your ship ok, but from where would you get the energy needed... 8 kW+ ?

And how fast would solar cells really move a 10 ton ship? It's not the power of the motor that bothers me. they could list 100 hP in there. The vital questions is the energy source, not the power of the motor.

Be sceptical.
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Old 04-26-2008
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That is a very NEW company. For the last three years I have pretty much been to every "e-power" website - this was not one of them. Re-e-power has been in the business the longest and even they have problems with keeping up, and the changes they have to make.

The one crucial thing to consider in any endeavor of this type is that they require huge battery capacity. No way any amount of solar unless your hull and deck is made of solar panels - do you get "free energy". The regen capabilities are only a small fraction of the total battery capacity to begin with.

Hence why Soloman, Volvo, and other hybrid sail drive manufactures bundle in generators otherwise you would be limited to 4-6 hours of engine time before needing to spend 12 or more hours recharging. Lets face it - rarely if you are cruising is it always under sail. Here in the PNW I spend more time motoring to get somewhere - unless its a daysail and I don't mind drifting around a bit.

If all you do is casual day sailing - maybe its all worth it as you are not doing anything extended in lines of point to point traveling. Otherwise - you have to look at the actual nature of what you can accomplish with one of these units. But I would say beware - there are no reviews and the company in question maybe just a fledgling company trying to make a start - but in the end you might want to know that for warranty issues etc they will be around awhile...
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  #4  
Old 04-26-2008
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I think that the electric motor will become popular once the price of fuel cells becomes bit more reasonable. The solar option is not really viable in much of the world.

FWIW I intend to install an ASMO set up when my diesel dies (if that is not after I have died )
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Old 04-26-2008
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It looks like they have a good product, nothing new, which is good.
They are using 48volts which is also good. Almost every boat has room for 4- 12volt batteries.

I will consider this system closely as I would like an elect drive for various reasons.

As already mentioned to get any range at all you will need a generator. There are applications where you wouldn't need a diesel gen. These include: Day sailing where motoring out of the harbour only takes a few minutes, offshore sailing where harbours are days away, and for sailors who can adapt to not always having an engine or having to conserve the use of motoring.

The reason electric drives have not taken off is not technical. They always have been a very viable alternative, even superior in many cases but they have a major problem.

All the patents needed for electric propulsion have run out. Electric drive systems are so much cheaper that no major company is going to make billions. Even if they "caught on" and started to sell some company in India or China could undercut the market, heck people can just build them in their garage.

And many do. thousands of people have used electric drive systems. General Motors says they cannot make an electric drive car for less than hundreds of thousands of dollars each but thousands of people have converted cars for less than $20G.

Most of the negative views and opinions about electric drives are a result of the established industries advertising against a competitor. Objectively electric drive systems are better in most applications and this is true for sailboats which already have a need for large battery installations.

It is even better for motorsailors because the generator, battery, motor system gives much better fuel economy and the ability to use power other than that derived from diesel.

The only down side is the high up front cost. People wont insulate their homes to save money later so it is with removing a perfectly good diesel engine and replacing it with a more expensive motor-gen-battery system.

EDIT: They do have these systems available on about 3 weeks notice, which isn't long to wait considering it is a complete engineered package (sans batteries of course).

Last edited by Architeuthis; 04-26-2008 at 05:13 PM.
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Old 04-26-2008
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Rockter will become famous soon enough
There is no way on this earth, with earthly laws of physics, that a fuel-driven electric generator, feeding mechanical energy to a generator, then electrical energy to a motor, and from there mechanical energy to a prop will EVER out-perform the direct drive-to-prop diesel in the first place. There is just no way that can happen.

What am I missing here?

If you want something quiet to get you in and out of harbour, then perhaps, but this stuff must not be advertised as being capable of prolonged motoring into a tide, or headwind, or chop, or all three.

It won't cut it, unless you have a very big battery bank indeed, and a lot of time to charge it.

For example, 25 hp (shaft power at the prop shaft) for 6 hours is about 112 kWh delivered, and probably about 1/4 more than that is needing storing to deliver on it. They will not try to deliver that at 12V, but, if they did I calculate the energy storage to be (corect me if I am wrong)...

112 kWh * 1.25 = 140 kWh = 140,000 Wh = 140,000*3600 = 504 MJ

.... call it E.

If you are to find E from your battery bank, then...

E = current*voltage*time

E = I*V*t

Make the product of I*t the subject...

I*t = E/V

Say, for argument, your power is delivered at 12 volt...

I*t = 504,000,000/12 = 42,000,000 amp.second

= 11,666 Ah

My current house battery is 275 Ah.... that is about 1/42 of what would be needed for 6 hours motoring.

That was 6 hours motoring, and I'd need 11,666 Ah to do it, discharging the batteries to nil to do it.

My current tank capacity will keep the motor running for about 30 hour.

Pls correct me on this one there guys. Did I get it wrong?

Last edited by Rockter; 04-26-2008 at 01:22 PM.
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Old 04-26-2008
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Nope Rocket -you summed it up well
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Old 04-26-2008
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Quote:
Originally Posted by Rockter View Post
What am I missing here??

A: The efficiency increase in the diesel engine being used to drive the generator.

Many drive systems do not have the diesel engine directly connected to the drive wheels or propeller and most do not use the battery bank. A sailboat would because it has many other uses for a battery bank, including silent drive mode.

And your are missing the fact that it is not a straight conversion of HP to KW when looking at replacing a diesel with an electric drive. The drive in question is using a 4KW system (7.2KW peak, 48v@150a) to replace a 24HP system. Again efficiencies of the electric system and the inefficiencies of the diesel system are not being taking into account.
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Old 04-26-2008
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Quote:
Originally Posted by Rockter View Post
There is no way on this earth, with earthly laws of physics, that a fuel-driven electric generator, feeding mechanical energy to a generator, then electrical energy to a motor, and from there mechanical energy to a prop will EVER out-perform the direct drive-to-prop diesel in the first place. There is just no way that can happen.

What am I missing here?

If you want something quiet to get you in and out of harbour, then perhaps, but this stuff must not be advertised as being capable of prolonged motoring into a tide, or headwind, or chop, or all three.

It won't cut it, unless you have a very big battery bank indeed, and a lot of time to charge it.

For example, 25 hp (shaft power at the prop shaft) for 6 hours is about 112 kWh delivered, and probably about 1/4 more than that is needing storing to deliver on it. They will not try to deliver that at 12V, but, if they did I calculate the energy storage to be (corect me if I am wrong)...

112 kWh * 1.25 = 140 kWh = 140,000 Wh = 140,000*3600 = 504 MJ

.... call it E.

If you are to find E from your battery bank, then...

E = current*voltage*time

E = I*V*t

Make the product of I*t the subject...

I*t = E/V

Say, for argument, your power is delivered at 12 volt...

I*t = 504,000,000/12 = 42,000,000 amp.second

= 11,666 Ah

My current house battery is 275 Ah.... that is about 1/42 of what would be needed for 6 hours motoring.

That was 6 hours motoring, and I'd need 11,666 Ah to do it, discharging the batteries to nil to do it.

My current tank capacity will keep the motor running for about 30 hour.

Pls correct me on this one there guys. Did I get it wrong?
If this is true than why are almost all cargo ships and ALL locomotives diesel/electric and have been for 50 years?

MedSailor
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trolling motors

Another short term option for using electric propulsion is a removable trolling motor. It will not push your boat very fast, but is possible to dock, anchor, tour close to shore and motor sail effectively with no noise and not having to warm up the diesel. It is not possible as the only propulsion source, but can be a great add-on. The new Torqeedo 2.0 looks sufficient for our 33' boats for that purpose.

We used a pair of EM54 Minn Kota trolling motors one season on our Pearson 33 day sail charter boat. These trolling motors on brackets wore out because they are not meant to be towed or left in the water. We did use it for 1-4 hours per day for about 70 days. With both of them on, we could go about 2.5-3 kts. It was a 24v system and would run at about 30 amps, if I remember right. On two 3 hours sails with almost no wind, we used about 200 amp hours on the heaviest days. There were weeks doing twice-per day trips that the diesel was not used at all. Our docking situation is simple, so that helped. The best part was that you can just flip a switch for instant power. We were able to sail into situations that most people would use the motor and have the instant boost of power if the wind failed us. A little boost on light wind days to get to another puff of wind, or just to get some air moving over the sails really cut down on diesel motoring.

Experimenting with electric drives is fun and will drive technology. What we need is an electric motor that works on the current drivetrain when needed. Briggs & Stratton made a brushless motor (Etec?) that was about 8 hp, worked in both directions, charging and driving, and was for golf carts.
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