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arecuk · 06-04-2020, 09:49

hey guys,

so I'm contemplating swapping 30yo volvo penta MD11C with saildrive for an electric drive, but can't spend too much money for the professional solution, and so DIY approach has to work for me somehow

I got 35ft, 12000lb sailboat, performance oriented for IRC racing

and so, I've found decent 10kW 48V bare electric engine, see attached pic and the link here:
https://www.thunderstruck-ev.com/sev...it-10.5kw.html

my biggest concern is the transmission ... I got saildrive, and now trying to figure out how to couple it with the electric unit

see the pic attached

I think either Option A or B would do best, but I'm not sure what would it take to do in DYI approach, any ideas?

and so, Option C seems to be more straightforward, but I guess I would lose some output due to multiple gears involved in various positions ... is that right?

in your opinion, what are the pros and cons between Option A and C, in terms of work needed and efectivnes of power transmission?

thanks a lot!

tp12 · 06-04-2020, 09:54

Run. Run now and don't look back. This is not the forum to be discussing anything regarding electric propulsion. The people that are out there now using hybrids are being told that their solution doesn't work even though they're using them.

Continue at your peril!

AndyEss · 06-04-2020, 12:06

The discussions are not about whether or not electric motors work or not - it is about energy storage.
An EV on land has a certain limited range based on its battery capacity. At worst, if your batteries flatline, you can coast to a road shoulder.
The ocean is a far, far more dangerous place not to have adequate propulsion and control over what is your survival capsule.

arecuk · 06-04-2020, 14:39

hi tp12, well Im not sure I understand your point ...

arecuk · 06-04-2020, 14:40

well my question is about figuring out the right way how couple the electric unit with saildrive ... while being aware of all pros and cons of electric units

**Pete7** · 06-04-2020, 14:55

Quote:

Originally Posted by arecuk

hey guys,

so I'm contemplating swapping 30yo volvo penta MD11C with saildrive for an electric drive, but can't spend too much money for the professional solution, and so DIY approach has to work for me somehow

I got 35ft, 12000lb sailboat, performance oriented for IRC racing

So before you go ahead with this project, can you share the financials with us to see how they stack up? The reason I ask is I did a back of the envelop exercise a month ago for fun and couldn't get the numbers to work.

The cost of a replacement Beta 25hp is likely £5000 in Europe. The cost of a 14.4kw LFP bank and electric drive was £18000. The electric range was 50-70miles on a full charge, the new diesel 300 miles.

Given you have said you are on a limited budget, how are you going to bring this electric conversion in for the price of a new diesel engine?

Pete

Montanan · 06-04-2020, 15:02

It appears that the MD11C which was produced from 1975 to 1981 came in three power ratings. You likely should keep to a comparable power rating if you are happy with the performance of your existing engine propulsion system when and if you shift to an electric drive.

I see one reference where in the maximum rating was 16 Kw. It appears that you had reference to a 10 kW motor which would seem to be very under powering your boat.

The batteries and BMS will be the largest component expense, if one is going for an all electric drive scheme [short motoring range due to limit of kWh capacity of energy storage] and if you go hybrid there will be the added expense of a generator.

seandepagnier · 06-04-2020, 15:06

As warned there are a lot on this forum who will dissuade you from an electric drive. This is usually because these people are used to motoring very far at fast speeds and can't understand why other people do not want to listen to a loud engine for many hours while it makes entire boat stink.

Good luck and thank you for making the transition.

Quote:

Originally Posted by AndyEss

The discussions are not about whether or not electric motors work or not - it is about energy storage.
An EV on land has a certain limited range based on its battery capacity. At worst, if your batteries flatline, you can coast to a road shoulder.
The ocean is a far, far more dangerous place not to have adequate propulsion and control over what is your survival capsule.

If it's dangerous to loose your motor, it's better to choose electric by far more reliable.

The ocean not only is statistically safer than a road, you also have adequate propulsion from sails to continue which is already sufficient without any motor anyway. It is also sufficient to enter and leave harbors, and most cruising boats actually can tack into (for me 50ft) wide channels. With electric you can be confident tacking in narrow channel the same as my sculling oar prevents missing tacks from wind shift or collisions to other boats using the motor to hold place when other boats pass in channel then continuing tacking.

In this way the battery capacity actually needed is very small, about 100wh per ton already enough to motor a few miles which is more than enough.

arecuk · 06-04-2020, 15:06

hi pete7,

well, I've inquired for a new yanmar 28hp with transmission, and that's about 9000E ... yes, there are probably cheaper marine diesel engines

regarding the electric drive, a complete sets comes around 12000E+, depending on the battery bank

DYI electric:
- 10kW, 2000US, https://www.thunderstruck-ev.com/sev...it-10.5kw.html ... +200US shipping to europe
- single 100A LFP battery around 250US+ (lots of options)
- 12x 100A battery bank > 3000US

so, DYI electric unit + battery bank 5000US, plus work and other related electronic devices, not assessed yet

**Pete7** · 06-04-2020, 15:18

Whose batteries are you getting for $250? a Battleborn is $950 and that doesn't include shipping, import duty or VAT.

Scroll down the page and you will find some examples of yachts that have been converted:

https://lynchmotors.co.uk/marine-motors.html

**Pete7** · 06-04-2020, 15:30

Quote:

Originally Posted by boat_alexandra

As warned there are a lot on this forum who will dissuade you from an electric drive.

Not at all and more than happy to see yachts converted if it fits the users requirements. However, I do question the costs.

Option one, would be a used 48v forklift truck motor and some AGMs, with a set up like Sailing Uma. They managed for 5 years with this set up which is pretty good.

Option two, would be a new electric motor and an nice LFP bank.

Clearly there are options in between, just curious to see the numbers up front.

Pete

**Pete7** · 06-04-2020, 15:37

I have never used these people but they seem pretty cheap for Europe.

https://shop.gwl.eu/LiFeYPO4-batteries-12V-1-1/

Good luck.

Dsanduril · 06-04-2020, 16:27

So, staying with the question as asked, are you going to use the existing saildrive?

If so, it already has a right-angle gearbox built in, with the engine shaft horizontal. Any reason you can't attach your motor to the same location? I could see gear ratios being an issue, is that why you want to go with a different connection?

If the motor speeds are right the option A seems easiest. Would have to remove the right-angle gearbox from the saildrive, but then very straightforward. My only question would be about the vertical shaft in the saildrive, is the top bearing part of the gearbox, or would it still be in place with the gearbox removed? That would go a long way to defining difficulty. If the bearing would still be in place then a simple Lovejoy coupling and a way to mount the motor above the shaft. Done. But if you need to place a new bearing then the process becomes a bit more complex.