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Discussion Starter #1
Greetings,

Looking for advice on a 15kW 48V electric motor to fit to a Yanmar SD25 sail drive (new model of the SD20).

Application is an under construction 52' sailing catamaran.

Some broad boat parameters:

Ocean going world cruising catamaran – composite epoxy structure.
L 52’, Draft 2’ Weight approx. 8500kg / 19,000lb
Full electric propulsion, galley and other services including hot water.
Motors retractable: 2 x 15kw 48v + regen
Battery bank: circa 16kw 48v
House loads: 24V DC – Estimated peak approx. 3kw
Solar: circa 3kW.
16kW 48v DC gen set.

The plan is to fit motor to a Yanmar sail drive SD25 and complete unit be retractable. This involves a wet lower tube and a watertight inner tube with hull closure plate below the prop – motor and sail drive leg fitted to this at their join. We should be able to couple motor shaft to SD25 upper gear box shaft with a coupler and bolt units together without too many modifications. Be great to hear of others experience with this.

We are trying to limit motor voltage to 48V – makes batteries & solar easier plus ability to share bank via DC:DC converters & battery for house loads at 24V.

The boat will be light and shallow draft = easily driven. A similar 62’ catamaran was fitted with 2 x OV SD15s and achieved over 9 knots in flat water so we believe 12 to 15kW motors will be adequate.


According to Vic Prop boat specs, twin 12kW (16hp) motors with RPM max of 2200 (2:1 gear reduction on SD25 so prop speed 1100 max.) & 3 blade 15" x 13" prop will yield a top speed of 8.92 kts which is fine.

We have looked at turn-key offerings from Bell marine, Oceanvolt & Electric yachts but none tick all our boxes so would like to have a crack at customizing our own solution.

Some motor options Ive stumbled across include:
1. Motenergy ME1302 or ME1616 Liquid cooled
2. Parker GVM210-100-DPW
3. Go cart or Elec motorcycle motors: Revolt, Zero, ???

Bearing in mind 48V supply and max RPM of around 2400, be grateful to get your thoughts on best motor and associated controller and any tips or constructive suggestions for our project.

Thanks RC
 

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How much do you want to spend?

Are you a thrifty person who likes making stuff work, or are you more of a "I want to spend the money and get it done" kind of person?
 

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Discussion Starter #3
Hi Matt

This application is for an ocean going catamaran so needs to be bullet proof. Budget is not unlimited but generous. Regarding build I am an electrician by trade so comfortable with the wiring side of things, just no experience with DC supplied motors & their associated controllers.

I think coupling the motor to the sail drive leg should be a straight forward engineering exercise that Im comfortable with.

The boat will be offgrid for 95% of the time and needs to be self-sustaining so we are limited to a DC bank of 48V. At this voltage we can get solar and a DC Gen Set to work effectively. Over this becomes problematic. Regeneration function is an important part of the energy mix.

There appears to be many motor options although less so at 48V. Max RPM needs to be 4000 or less to enable an appropriate propeller fitting so motor has to be efficient around the 2-3000 RPM mark. It also has be able to run continuously at say 70% capacity (say 10kW) without overheating. Liquid cooling is easy to arrange on a boat.

I saw a Parker motor that seems to fit our requirement. Im guessing there expensive but have no experience to judge whether they represent value or are the best option. Motenergy also a possibility ?

Hopefully this information gives you a clue. Appreciate your comments and suggestions.
 

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Usually the cheap option is to grab a used forklift motor. You can usually get them for $200. They're bulletproof and functionally last forever.

In your case, since you're dead set on a low voltage battery solution, it might still be the best option since forklift motors are low voltage and slow.

For low power requirements, you might be able to get away with just reusing the forklift speed controller too.

You'll need to fabricate a coupler, but, this is no big deal.

Alternatively, you could buy something like a Gen2 or Gen3 Prius inverter, which has an onboard boost converter, and then use it to crank your 48v to 400v or whatever you want to use to drive the motor. Then you could use an AC motor which has nearly zero consumables (DC motors have brushes that will have to be replaced once every other decade or so, depending on use). I imagine that AC motors are better in marine environments, what with there being physical contact and corrosion potential for a DC commutator.
 

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A motor is not the problem, lot's of options available.

Any capable machine shop can couple it to a sail-drive leg (if I can do it..;)

I've done some testing with a Siemens motor on 48 volt, works fine, but the aluminium housing I would not use in a salt water setup (on fresh water it already deteriorates fast)

If you want to keep it simple: DC motor, air cooled.

If you want a little more sophisticated: AC motor, air cooled or water cooled. you might even be able to use it as a generator while sailing.

look for a commonly used 'standard' setup like the AC35 or AC50 HPEV motors:
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-35.htm
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-50.htm
 

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A motor is not the problem, lot's of options available.

Any capable machine shop can couple it to a sail-drive leg (if I can do it..;)

I've done some testing with a Siemens motor on 48 volt, works fine, but the aluminium housing I would not use in a salt water setup (on fresh water it already deteriorates fast)

If you want to keep it simple: DC motor, air cooled.

If you want a little more sophisticated: AC motor, air cooled or water cooled. you might even be able to use it as a generator while sailing.

look for a commonly used 'standard' setup like the AC35 or AC50 HPEV motors:
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-35.htm
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-50.htm
The costs are in the saildrives + custom machining, and the whole battery / charging / etc, the motors are not the expensive part, so best to get the most suitable available (and something that replacement can be found if needed)

'used forklift motors' is not what you want here, often difficult to find a replacement of the same size, and 15 kW continuous will need a big amount of old air provided to them.
 

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Discussion Starter #8
Gents thanks for comments.

Boekel your spot on regarding motor costs compared to the sail drive, engineering & batteries. Definitely worth researching and investing in the best motor for our application which needs to be a continuous rating at around 15kW @ 48v with max motor RPM 3000

The HPEVS motors look interesting. I think the AC 34 or 35 would be more than adequate, perhaps even the AC20. Have had a quick looks at specs and output graphs and need to get my head around them. Assume continuous means just that and peak will be at max power for short periods. The peak amp ratings look extreme. Are these meant to be theoretical?

In practice are these sorts of loads for short periods or are max peaks are programmed out of the controller to avoid system and battery melt down?

Presumably need to look closely at C-rating on batteries need to ensure they can deal with these sorts of current draws?

In a boat application we are more interested in continuous rating and the safety requirement to be able to run for long periods. As mentioned in my first post we have a 16kW 48V DC gen set + 3kw of solar to provide continuous power.

As the boat needs to be self-sufficient and generate its our power, have assumed that we would be limited to a max of 48V. The possibility of using a buck-boost inverter to increase voltage is intriguing but beyond my simple electrician's brain.

Regarding motor enclosure material, our motors will be located inside an engine room and so not exposed to salt water or even rain. The motor /sail drive unit be lowered via cutout in the hull when propulsion required and then raised out of the water into the engine room when under sail and not in regen mode.

Im surprised the HPEVS motors are not offered with liquid cooling since at low RPM, air cooling is reduced and heat build up may be an issue ? Boekel Im sure your familiar with the Bell marine motors which are from Holland and offered with air cooling for light duty and liquid cooling for commercial/ heavy duty applications.

Appreciate your comments - please keep them coming.
 

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The peak current specs on the motors are just for indication of capability--they could operate at this extreme current for a short time (5-10 seconds) without damage.

The motor controller (aka drive inverter, buck-boost converter, etc) would be configured to limit the current (torque) for your application.

Electric golf carts come to mind with low voltage motors in the 48V range. a quick search found some, but they are series DC motors with brushes;

i would want a brushless 3-phase motor if possible, such as PM or AC. Have you seen these: https://www.electricmotorsport.com/ev-parts/motors/brushless-motors?limit=all

Looks like an interesting and fun project, post up some pictures of your boat.
 

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Discussion Starter #10
Some photos of our boat + a simple sketch of proposed engine retraction system.

Any further suggestions on motor types to research ?

Is it correct to assume that once a motor is selected, a suitable controller is matched and programmed by motor supplier to suit application OR do we need to get our heads around programming controller parameters as well?
 

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A motor is not the problem, lot's of options available.

Any capable machine shop can couple it to a sail-drive leg (if I can do it..;)

I've done some testing with a Siemens motor on 48 volt, works fine, but the aluminium housing I would not use in a salt water setup (on fresh water it already deteriorates fast)

If you want to keep it simple: DC motor, air cooled.

If you want a little more sophisticated: AC motor, air cooled or water cooled. you might even be able to use it as a generator while sailing.

look for a commonly used 'standard' setup like the AC35 or AC50 HPEV motors:
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-35.htm
https://www.hpevs.com/hpevs-ac-electric-motors-power-graphs-ac-50.htm
Hi, I wane converted my sailboat 33feet to electric drive with driveshaft too. Can you please tell me what kind of siemens motor did you use? Thanks, and by the way nice work eith your outboard motor!!!
 
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