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Old 23-03-2022, 03:05   #481
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by toerail View Post
The battery disharge is from a SOK 48volt 100ah server rack bank 1700.00 dollars about now. 20 amps for 5 hrs.
20A x 48V = 960 Watts ÷ 750W/HP ≈ ± 1-1/4 H.P.
Seems a bit optimistic, to me.
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Old 23-03-2022, 03:31   #482
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Re: Replace Diesel with electric engine

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20A x 48V = 960 Watts ÷ 750W/HP ≈ ± 1-1/4 H.P.
Seems a bit optimistic, to me.
With a good tail wind, 2.7kts is quite probable.
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Old 23-03-2022, 07:00   #483
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by GordMay View Post
20A x 48V = 960 Watts ÷ 750W/HP ≈ ± 1-1/4 H.P.
Seems a bit optimistic, to me.


Boats 32-36’ can make 3.0kt on 900-1200W.

Formosa 41 is 20-30% longer and twice as heavy as these.

Propulsive requirements scale exponentially so I wouldn’t be surprised if the Formosa could do 2.5kt using 1,000W.
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Old 23-03-2022, 07:50   #484
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Re: Replace Diesel with electric engine

Attached a handy spec sheet for top quality lfp cells. They state it’s optimal to use 0.5C discharge and 80% DOD.

Cheaper cells need more conservative numbers or will reduce lifespan more.
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Old 23-03-2022, 08:13   #485
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Re: Replace Diesel with electric engine

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Originally Posted by Adelie View Post
Boats 32-36’ can make 3.0kt on 900-1200W.
3 knots takes perhaps 250-350W (assuming overall efficiency from battery to propulsion about 60%) at that size, not 900-1200W which is assuming about 15% efficiency.

You are probably replacing an inboard diesel with an electric motor to get these numbers. Try putting sails on a power boat. I know a guy who did, he flipped the boat over and it sunk, but it did go a few miles first.

We could also assume boats this size can't sail faster than 7-8 knots.. but my 33ft boat sails much faster than this.
Quote:
Propulsive requirements scale exponentially so I wouldn’t be surprised if the Formosa could do 2.5kt using 1,000W.
Consider 1hp = 745 watts. It looks like a horse could pull this boat 3 knots. They can typically pull 20 ton barges at this speed, so 750 watts for 3 knots is about right for this 41' boat.

20 amps at 48v should give at least 3 knots.

This is all assuming no currents, no waves, and wind < 3mph.
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Old 23-03-2022, 08:22   #486
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Re: Replace Diesel with electric engine

70 ft long. Operated with 2 horses. At full speed 9 mph.

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Old 23-03-2022, 23:45   #487
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Re: Replace Diesel with electric engine

First, just saying
If I wanted to motor I would have a trawler
If I wanted to motor with a sailboat I would have a motor sailor

I have a sailboat and want to sail
People have concerns about no wind
Stay out of the notorious doldrums
I dont consider a couple days with no wind doldrums

I will motor, granted slow, off solar alone in peak daylight if no wind if needed

Wind generator doesnt count except for charging because if its turning I have sails up
I can motor most of the night on batteries, then sleep, then hit it when the sun comes up
A portable generator to push the boat only if necessary, like the small 2200Kw
Cant use heat or AC very much, boats dockside use shore power or genset

Those concerns I see most
Electric is not for everyone



Sailing Uma runs 2.8knts at 20 amps and 48 volts, 15 hr capacity max, 14.4Kw bank

runs over 4knts at 50 amps, I hope to achieve near this
They have a 6ft draft fin keel pearson 36
But I hope to make up the displacement difference, if it matters(torque is torque)
with direct drive using less power to drive the prop, will not know till tested
Prop size and pitch is another variable
Thanks everyone
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Old 23-03-2022, 23:55   #488
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Re: Replace Diesel with electric engine

Just to mention
Diesel or electric loses power at every bearing, some connections,all transmissions
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Old 25-03-2022, 15:18   #489
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Re: Replace Diesel with electric engine

Just another note:
I just changed to a 96 volt controller thereby doubling the power of the motor
For instance before it was 48V x 250 amps continuous to give 12Kw power
I changed the controller to 96v x 250 amps continuous for which makes the motor 24Kw motor
Thats max continuous on that motor I believe
Its ad says it will go to 55Kw but thats not continuous
I thought I would start at 48v but seeing how some other big boats are

running two motors back to back I decided to skip that experiment
The power numbers to push the boat will be the same no matter
the voltage used, I dont have deep pockets so changed it
Controllers are 1200 to 1700 range

Ive worked with 130v battery banks a lot
Compare that to electric cars at 600v
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Old 25-03-2022, 19:20   #490
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by toerail View Post
Just another note:
I just changed to a 96 volt controller thereby doubling the power of the motor
For instance before it was 48V x 250 amps continuous to give 12Kw power
I changed the controller to 96v x 250 amps continuous for which makes the motor 24Kw motor
Thats max continuous on that motor I believe
Its ad says it will go to 55Kw but thats not continuous
I thought I would start at 48v but seeing how some other big boats are

running two motors back to back I decided to skip that experiment
The power numbers to push the boat will be the same no matter
the voltage used, I dont have deep pockets so changed it
Controllers are 1200 to 1700 range

Ive worked with 130v battery banks a lot
Compare that to electric cars at 600v
I have a 120V solar array… could feed that straight into the motor controller for free propulsion
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Old 25-03-2022, 21:33   #491
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Re: Replace Diesel with electric engine

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Originally Posted by toerail View Post
A portable generator to push the boat only if necessary
When people say they "use the engine only when necessary" it means they never use it.
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Old 02-04-2022, 22:02   #492
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Re: Replace Diesel with electric engine

Hey Sean
What I mean by a portable generator to push the boat only if necessary is
Say I am trying to tow in someone stranded at sea
A medical emergency onboard and running past the battery limits to get to a hospital if no wind
Something like that
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Old 02-04-2022, 22:09   #493
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Re: Replace Diesel with electric engine

s/v Jedi
Yes and with a victron charge controller I could watch it do that
But I have dropped back to a 48v design
Got a little worried over my displacement
Spoondrifter ran on one motor and with pretty much the same amps and speed as the others
Spoondrifter is a morgan 462 at 33,000 lbs
Outweighs me by 5000 lbs
Although it is a semi full keel with shorter draft
I think the single motor at 48v will be ok for me
We will see
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Old 02-04-2022, 23:00   #494
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Re: Replace Diesel with electric engine

Buy, buy for natures sake!
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Old 20-04-2022, 06:09   #495
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Re: Replace Diesel with electric engine

Interesting thread. I read about five pages and then fast forwarded to the end. I'm contemplating finishing a part finished Bruce Roberts Voyager 495 steel hull. I like the look of this 'houseboat':



Jorma Ponkala seems to be a bit of a genius, but trying to find out anymore about his boat seems to hit a a blank.

Anyhow, I primarily want somewhere to live, that will be fairly comfortable but which can motor down the coast for up to fifty miles or so, and then anchor up. I could follow the coastline and after seeing what the range was like contemplate maybe longer journeys.

After watching and studying most electric motors online, I've come to the conclusion the best fit for a 15ton steel boat will be the motor out of a Nissan Leaf (I'd actually buy two motors and two battery packs). This is equivalent to around 110Hp engine and given that most diesel engines are only around 40% efficiency at best, the 90% efficiency of an electric motor may be an advantage. The other thing about the Leaf is that the car has been sold all around the world, so unlike a motor such as an Elco (which looks fabulous) spare parts should be easily obtainable.

The solar deck will be around 8kW. The controllers / inverter I'm looking at is a paralleled system of three, Iconic IC-ZTR5000. These will give an inverter power of 15kW max, where 6kW of this could be utilised for the 'spare battery' of the Leaf (while the other one is powering the boat) and the rest powering the house electrics. I'm thinking of supporting this with three Pylontech US3000C lithium batteries (giving around 200Ah @ 48V).

I'm not interested in 'sailing' as such, but I am interested in cruising to new places etc.

If anyone has any thoughts on this mad capped idea, I'd love to hear them.
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