Conversion to Electric Motor

[CharlieJ]

foggysail-
Yes, REALLY!
I have done it...have you?

[Freedom45]

Electric Boats | Electric Launch | Elco Boats

[Stumble]

From the Elco motors website...

The EP-4000
1,158lbs flooded lead acid
4-6 hours cruising range at 4kn
3-4 hours cruising range at 5kn
1-3 hours cruising range at full power

Assuming their numbers are 100% correct that works out to the energy storage capacity of about 3 gallons (21.5lbs) of diesel on my boat. Which can at 5kn burns right at .75 gallons/hr. 11000lbs / 21.5lbs = 51.2 pounds of batteries per pound of diesel. Certainly within the range of what I indicated above.


There are some other issues on their website that seem to indicate that either they don't know much about batteries (I certainly don't) or they are deliberately trying to deceive potential customers. For instance they claim that lead acid batteries can be recharged in 5 hours. Regardless of the amount of amperage pushed into a FLA they simply can't be recharged that quickly. 18 hours is considered pretty standard to recharge a FLA from 50%, though I guess if you are ok with just the bulk charge at 80% it might be possible in 5 hours.


As I keep saying electric power is absolutely sutable for a small subset of boats that live primarily at the dock, but doesn't seem sutable to me for long range cruisers.

[jeanathon]

Originally Posted by foggysail

More to think about-- 1 gallon of fuel oil contains about 140,000 BTUs
1 BTU = about 0.3 watt hour

Therefore 140,000 BTUs = about 42 KWatt hour (42,000)hour now divide that by 12vdc and you have 3500 amperes for 1 hour. Tesla---right on at least until the subsidies end!

Simple math only works when the problem is simple. What are you doing with those 140,000 btus of heat? If it is burning down your boat than you are pretty efficient. If on the other hand you are using heat to move your boat you can start by dividing that by 2.
Diesel is energy dense, but I wouldn't want to power my radio with it.

[CharlieJ]

Stumble

As I keep saying electric power is absolutely sutable for a small subset of boats that live primarily at the dock, but doesn't seem sutable to me for long range cruisers.

I disagree with the "...live primarily at the dock..." statement. Electric propulsion that is carefully designed is also suitable for:
...boats that use their auxiliary power plant to motor out of the slip or off the mooring, sail, and return to the slip using their auxiliary power plant. This cruising profile would take a minimal battery bank that would be recharged dockside from shore power or from solar panels if on a mooring.

...boats that operate as above but wish to overnight/weekend. With this profile, a larger battery bank can be designed and be perfectly adequate.

...boats that remove their auxiliary ICE, and use the diesel genset to power both the electric propulsion plant and the house loads.

Take a look at the 30' Nonsuch s/v Bianka's conversion to electric propulsion. A real boat, with a real sailor, sharing real data, not opinions. THE BIANKA LOG BLOG

[foggysail]

Originally Posted by jeanathon

Simple math only works when the problem is simple. What are you doing with those 140,000 btus of heat? If it is burning down your boat than you are pretty efficient. If on the other hand you are using heat to move your boat you can start by dividing that by 2.
Diesel is energy dense, but I wouldn't want to power my radio with it.

OK, my posts stuck with basics, it was not intended to provide an energy analysis. Of course a diesel has less efficiency running about 40% compared to an electric motor running anywhere from 90-95%. But YOU can do an energy analysis and share it with the forum starting with the batteries & chargers, power conversions, distributions. But of course, you know all this.

It also called attention to how many assume incorrectly that torque alone is what counts. Yes torque does but only in relationship to both horsepower and RPMs.

[misfits]

If you did the electric conversion & were handy, you could build a small diesel DC generator that would keep the battery bank topped off. You can do this for what it would cost for a straight diesel re-power. You'd use a lot less diesel compared to a typical re-power & unlike a gas generator, there's no need to run it wide open. There's also data out there that suggests that when sailing if you're in neutral with the prop spinning, you're recharging the battery bank.

Anything is possible. You just need to be a willing to conduct your own science experiment!

[Rhapsody-NS27]

As mentioned, look up the Yahoo group for electric boats. Also do a search for the Bianka Blog of a guy who's been using electric for about 5 years now. I don't know of other blogs off hand. I've been looking into it for some time. I have read people will use a small gas generator to supplement the power requirements. Solar and wind could be used too while at anchor to keep noise levels down to not disturb others.

[SkiprJohn]

Originally Posted by jeanathon

You mean diesel range is finite where as electric is not?

Sorry I wasn't clear.

I'm not really certain what your question is.

[jeanathon]

Originally Posted by foggysail

OK, my posts stuck with basics, it was not intended to provide an energy analysis. Of course a diesel has less efficiency running about 40% compared to an electric motor running anywhere from 90-95%. But YOU can do an energy analysis and share it with the forum starting with the batteries & chargers, power conversions, distributions. But of course, you know all this.

It also called attention to how many assume incorrectly that torque alone is what counts. Yes torque does but only in relationship to both horsepower and RPMs.

Foggy,
I should put forth an energy analysis. I too often read this forum on my phone which does not allow much of a reply except a very basic one.
I am currently going to electric with lots of solar and hopefully regenerative. I will post when I have some actual real world data.
Here is an interesting site though with some useful links. Above the Waterline | Electrical, Electronics and Propulsion Products
Jon

[jeanathon]

Originally Posted by SkiprJohn

Still doesn't have the range of a diesel. __________________
John
Sorry I wasn't clear.

I'm not really certain what your question is.

Don't mind me. Just your comment conjured an image in my head of a diesel boat having more range but trying to pull up to a gas dock mid ocean to refuel whereas the electric not being able to go as far at once, but recharging mid ocean via solar and not worried about finding a gas dock or tanker to give them some diesel.

[SkiprJohn]

Originally Posted by jeanathon

Don't mind me. Just your comment conjured an image in my head of a diesel boat having more range but trying to pull up to a gas dock mid ocean to refuel whereas the electric not being able to go as far at once, but recharging mid ocean via solar and not worried about finding a gas dock or tanker to give them some diesel.

Ok, I get it. I sailed across the Pacific using 40 gallons of diesel and averaging 5 knots. I'm certain if I had motored more then I'd have used quite a bit more. I still had another 40 left. The point I was trying to make is that the last 24 hours I was in non-existent winds and contrary currents and needed the diesel after 4 days of no sun (PNW). I doubt that I would have been able to do that with electric and therefore the range when I needed it was there with the diesel and would not have been with the electric. I could be wrong here but I just returned from a trip where motoring was more than sailing because of contrary or non-existent winds. The sun was strong but electric would not have done up to 3 day periods of constant motoring. Maybe a hybrid would do it but then I would have had to have two power plants and it seems cost prohibitive. For me, I'm staying diesel.

kind regards,

[foggysail]

Originally Posted by jeanathon

Foggy,
I should put forth an energy analysis. I too often read this forum on my phone which does not allow much of a reply except a very basic one.
I am currently going to electric with lots of solar and hopefully regenerative. I will post when I have some actual real world data.
Here is an interesting site though with some useful links. Above the Waterline | Electrical, Electronics and Propulsion Products
Jon

Jon-- Below is quoted from one of my earlier posts in this thread:

"If you are happy with auxiliary electric propulsion that is all that matters!"

Everyone has goals but not usually the same as others. Although I have zero desire to power my boat with electricity, I surely enjoy the benefits that solar provides. I have almost 600 watts (4 panels) on board.

If you believe your approach is workable then go for it! And I do wish you good luck. Before you get too involved, check every detail of your analysis to save from costly errors.

Foggy

[nimblemotors]

Electric motors are generally rated at CONTINUOUS power output.
Engines are generally rated at PEAK power output.
The Torque curves are very different.
Efficiency along the curve is very different.
The waste heat output is also very different.

Kinda like saying 1 horse is the same as a 1hp engine.

[jeanathon]

Originally Posted by foggysail

Jon-- Below is quoted from one of my earlier posts in this thread:

"If you are happy with auxiliary electric propulsion that is all that matters!"

Everyone has goals but not usually the same as others. Although I have zero desire to power my boat with electricity, I surely enjoy the benefits that solar provides. I have almost 600 watts (4 panels) on board.

If you believe your approach is workable then go for it! And I do wish you good luck. Before you get too involved, check every detail of your analysis to save from costly errors.

Foggy

Thank you for the well wishes. I have to say though I'm Polish, costly errors is how I learn!