Sail boat engine choice - electric or diesel

[chrisr]

Originally Posted by newhaul

The weight savings wih lfp bank and electric all in would be about 150 pounds to 200 pounds.

thanks

cheers,

[Scaramanga F25]

A diesel if I was planning to go anywhere. Electric is for a daysail in and out of a marina,

[malcolmwmax]

Have you considered keeping the old diesel for back up and using an electric outboard to give short electric power and using an in water generator while sailing to charge the batteries.
Malcolm, La Paz, Baja

[seandepagnier]

Today I made first trial with electric outboard it cost $200 to build. It is about equal to sculling oar at only 13 volts and uses only 5.4 amps!

https://www.youtube.com/watch?v=nUI1tuZydQ8

This is more than twice the efficiency of typical trolling motors which would use about 12 amps to do the same thing.



I can extrapolate that at 40 volts it will push the boat 3.5 knots using 800 watts. This is not a lot of power especially when I can easily fit 1.2kw in solar panels just on the trampolines.

Originally Posted by Scaramanga F25

A diesel if I was planning to go anywhere. Electric is for a daysail in and out of a marina,

I didn't have diesel or electric and sailed everywhere.



sailing uma proved also the opposite of what you said, and many others as well.

[newhaul]

Originally Posted by seandepagnier

Today I made first trial with electric outboard it cost $200 to build. It is about equal to sculling oar at only 13 volts and uses only 5.4 amps!

This is more than twice the efficiency of typical trolling motors which would use about 12 amps to do the same thing.



I can extrapolate that at 40 volts it will push the boat 3.5 knots using 800 watts. This is not a lot of power especially when I can easily fit 1.2kw in solar panels just on the trampolines.





I didn't have diesel or electric and sailed everywhere.



sailing uma proved also the opposite of what you said, and many others as well.

Did you do a build video? How about a list of materials used ?

[Erik de Jong]

First of all: 18kW will give you almost 5 times as much power as what you have now. Do you really want to go that far with over-powering?

2 hours at 5.5 knots (I assume flat calm conditions) gives you an energy consumption of about 16 kWh for your maxi 87. "Fast charging" in a marina is not going to work. I'm from Holland and I assume that Denmark uses the same electrical standards as we do in Holland. That means that you have 230V that is fused 16A, but seldom gives more than 10A and often even less due to over usage on the marina. So you can basically charge with 2300W max. If you have used 16kWh it would take you 7 hours of cahrging at full capacity. The batteries will not be able to accept that much power in the final stages of charging and I think that you will not manage to get 16kWh back into your bank in a 24hr period.

[mcarthur]

Originally Posted by Erik de Jong

...If you have used 16kWh it would take you 7 hours of cahrging at full capacity. The batteries will not be able to accept that much power in the final stages of charging and I think that you will not manage to get 16kWh back into your bank in a 24hr period.

I was under the impression lithium doesn't suffer from the change between bulk-absorption differential, but instead could do the equivalent of bulk to 100% before going into float. Since some lithium can charge at 3C, and 1C is common, I don't see why recharge overnight (8hrs?) back to 100% for lithium isn't a fact (not a conjecture or "possibility")...

[Erik de Jong]

I'm not sure about the thechnical details, but if I look at our electric car (Nissan Leaf) the first half of the charge goes about 3 times as fast as the last half and the last 10 miles takes really long.
Given the fact that most harbors can barely support an electric heater (1500W) of the standard shore power, I highly doubt that you can fill your batteries overnight, let alone "fast charge" as the OP suggested in his first post.

[newhaul]

Originally Posted by Erik de Jong

First of all: 18kW will give you almost 5 times as much power as what you have now. Do you really want to go that far with over-powering?

2 hours at 5.5 knots (I assume flat calm conditions) gives you an energy consumption of about 16 kWh for your maxi 87. "Fast charging" in a marina is not going to work. I'm from Holland and I assume that Denmark uses the same electrical standards as we do in Holland. That means that you have 230V that is fused 16A, but seldom gives more than 10A and often even less due to over usage on the marina. So you can basically charge with 2300W max. If you have used 16kWh it would take you 7 hours of cahrging at full capacity. The batteries will not be able to accept that much power in the final stages of charging and I think that you will not manage to get 16kWh back into your bank in a 24hr period.

Will lfp it is entirely possible . My bank while just for house loads ( I have an md2b) . I can charge at up to 3C but for longevity .5C is recommended ,. Right up to 98%.
Diy bank 250AH lfp . I have never seen a marina in the USA that can put out 85 amps at 120Vac. The best I have ever seen is 50amps . Or about 2C .

[seandepagnier]

Originally Posted by newhaul

Did you do a build video? How about a list of materials used ?

This outboard is made using 2x4 and wood screws, and is easy to modify to different belts and ratios. I changed the belt tension, put a longer belt and shaft alignment in under an hour.


https://hackaday.io/project/174537-solar-powered-boat

Originally Posted by Erik de Jong

I'm not sure about the thechnical details, but if I look at our electric car (Nissan Leaf) the first half of the charge goes about 3 times as fast as the last half and the last 10 miles takes really long.
Given the fact that most harbors can barely support an electric heater (1500W) of the standard shore power, I highly doubt that you can fill your batteries overnight, let alone "fast charge" as the OP suggested in his first post.

around here, the marinas all have dual 30A or 50A at 240v. You can run several space heaters off that. I have never plugged into a marina. I suggest the batteries for propulsion should be entirely powered by the solar, wind and hydro generators.


With lithium iron phosphate (I think nissan leaf is lithium ion), you can charge fast the whole way, but it will degrade the batteries faster if you do as the voltage will be higher. It's better to keep the voltage less, than 3.5 per cell even though they claim 3.65 is fine.


So there is always a trade-off here, if you will really will need the power or not to how fast to charge. Sitting fully charged for prolonged periods also degrades the battery so I keep mine 3.45 per cell . These will still outlast lead acid regardless, but I hope to get 10 years (3650 cycles) with 80% capacity. My lead acid batteries had 25% capacity after 10 years and much lower efficiency as well.



The easiest solution is to have a 20% larger battery and then you only charge fast in rare cases.


Most electric conversions use the same size prop: It is too small. You need something with minimum 1 meter, preferred at least 1.5 meter diameter for a typical cruising boat of 16,000lbs. This likely needs to be an outboard. The inboard may be useful for maneuvering in harbors, but for actual efficient propulsion in open water and very light conditions, this much larger slow turning propeller will give twice the efficiency of typical setups such as oceanvolt or torqeedo. This means you can cut batteries, and solar in half and get the same performance, so I think it's a really important factor rarely considered.

[Erik de Jong]

Originally Posted by seandepagnier

Most electric conversions use the same size prop: It is too small. You need something with minimum 1 meter, preferred at least 1.5 meter diameter for a typical cruising boat of 16,000lbs. This likely needs to be an outboard.

I think your 1 to 1.5m diameter must be a typo. That is 3 to 5 feet in diameter.
I disagree with your assessment for inboard electric propulsion. That is used so often and functions as well and often better compared to normal ICE engines.

[newhaul]

Originally Posted by Erik de Jong

I think your 1 to 1.5m diameter must be a typo. That is 3 to 5 feet in diameter.
I disagree with your assessment for inboard electric propulsion. That is used so often and functions as well and often better compared to normal ICE engines.

This should help your point .

https://www.vicprop.com/displacement_size.php

[Erik de Jong]

Vicprop is not more than a tool to make a rough estimate. It does not differentiate for power source nor does it take some other very important factors in place.

Prop diameter is mostly based on available torque. Torque is generally higher for electrical motors and you can make a more efficient propeller if you go larger diameter, it does not mean that you have to. 16.000 lbs boat is about 37-38 ft for the average cruiser. I'd like to see an example of a 38ft sailboat with a 5 ft diameter propeller.

[NPCampbell]

Originally Posted by Erik de Jong

I think your 1 to 1.5m diameter must be a typo. That is 3 to 5 feet in diameter.
I disagree with your assessment for inboard electric propulsion. That is used so often and functions as well and often better compared to normal ICE engines.

Large, slow turning propellers are more efficient than small fast turning propellers in air and water. However, a 5 foot propeller is going to weigh 700-800 pounds. It'll cost probably $20k and the drag when sailing will be ginormous even if freewheeling.

[carstendenmark]

seandepagnier, I read your page. Interesting !
Did you went to a hydrodynamic facility or institute to test your theory to be pracital for use ? Sailboats can have a GRP or CarbonRP prop (light and strong) and could be made foldable.You might be in a million $ business then :-)