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Re: Electric Conversion log for Kahleesea

Update, 1/3/19.

I've spent the last couple of days pulling parts in preparation for the motor removal tomorrow morning.

Removed: Batteries, inverter, inverter control panel, transmission and throttle linkage, exhaust system, motor cockpit panel, including all gauges, alternator, all motor hoses and fuel lines.

Going tomorrow - motor, diesel tank, any remaining parts pertaining to the motor that I may have missed.

Staying - water heater, engine raw water intake and filter. The water heater will still work, but will run either with the inverter or when on shore power. I don't think I've ever used it before.

Changes to design - since all electrical systems converge in the starboard aft rear compartment, I'm going to place the bulk of the new systems in the two aft compartments. The starter cables are thicker than I expected, rated 00, so they can carry all the current I need to the motor controller, which will still be in the engine compartment. This will greatly simplify the wiring changes for the new system.
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Re: Electric Conversion log for Kahleesea

Just to offer some encouragement - I converted a 32' TomCat catamaran from twin Yamaha 9.9's to Torqeedo Cruise 4.0s over four years ago. I used just the stock Torqeedo components so I can't claim to have accomplished much of an engineering feat but I can tell you it's been great to have an electric system. Quieter (not silent), reliable, and maintenance free.
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Re: Electric Conversion log for Kahleesea

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The motor I'm going with, the Motenergy 1115, weighs 35 lbs. I could run it as a direct drive, but since it's only going to turn at about 1000rpm, it won't turn fast enough to cool itself and I could easily burn it out. So I'll put a gear reducer on it so it runs about 4000 at hull speed, keeping itself cool while giving me what I need. I could go with a water cooled model, but that adds more complexity that I would like for this project. Once the system's finished I can always retrofit if I find that cooling is an issue. The motor comes with a built in temperature sensor so I can monitor it via the motor controller.
Howdy Captain. Being in the middle of an Ericson 29 refit (rebuild?) that includes going to an electric prime mover (same one you are looking at!) I'm on your side. However --

I caution you to test your new motor/controller at your intended voltage before you buy/lock yourself into a gear ratio. Brushless motor speed is based on its KV rating (rpm per volt). You're expecting/designing for 96+v rpm from a 48v power bank, from what I gathered reading the thread. You will not see the rpm you are expecting.

So fire up your no load motor at 48v, measure the RPM (i believe the clearview will tell you the RPM..) knock about 5-10% off of that for load, then figure out your gear ratio.

Thunderstruck recommends a 2-1 gear reduction for a reason with controllers defaulted to 48v.



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I agree with Sean in regards to RPM of the electric drive. I bought a 1115 drive & clearview display from Thunderstruck. At 48 volts the drive will spin approximately 2400 RPM. At a 2:1 ratio that puts 1200 RPM's at the prop which in all likelyhood is close to what she spun when the ICE was at full throttle.

Far as running the electric drive at full throttle for hull speed, you may get 10 minutes if you're lucky before your battery bank hits 50% DOD. In addition to the clearview I also have a victron battery monitor on my bank. At 3.5 knots I'm pulling 20-25 amps out of the bank. At 4-4.5 knots, 35-40 amps. The faster you go, the faster the bank goes.
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Re: Electric Conversion log for Kahleesea

Sean and misfits,

Thanks for the info. The voltage to RPM ratio is a wrinkle I hadn't considered. Good to know before I purchase anything. Can you run the me 1115 at 30kW at 48V, or are you limited to 15kW?

I'm not keeping the ICE prop. I'm going to swap it out for a bigger prop that I can turn much more slowly and efficiently to generate the same thrust. This, coupled with the voltage, will dictate my reduction ratio.

I'm still considering if I should run 96v or 48v. There are a lot more options for accessories (like DC/DC converters and DC/AC inverters) in the 48v space.

I won't be concerned with 50% DOD. I'll be running Lithium batteries, so 80% DOD will be by cutoff. I always thought Peukert was a wanker.
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Re: Electric Conversion log for Kahleesea

Status update, 1/4/19.

Removed: Throttle, shifter, and linkage, primary fuel filter, motor.

Still to go: Fuel tank, which was probably installed before the boat's deck was installed. I have no way to reach in and unscrew the brackets on one side without cutting through something. Ugh. Plus, I have to drain the tank - I have a lot more diesel left in it than I thought. I'm going to have to rig up battery to the fuel pump and full up my 5 gal can a couple of times to empty it.

I also discovered today that the shore power connection has been replaced... and whoever did it used home-grade romex instead of tinned stranded wire. Not a big deal, since I'm rewiring some of the AC side anyway, but still a pain in the ass, as removing the shore power face plate is damn near impossible single-handed.

On the plus side, the motor went to a good home, to repower a 70's era boat that is obviously loved by it's owner.

Once all the removal is done, I'm going to have a *lot* of cleaning to do.
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
Sean and misfits,

Thanks for the info. The voltage to RPM ratio is a wrinkle I hadn't considered. Good to know before I purchase anything. Can you run the me 1115 at 30kW at 48V, or are you limited to 15kW?
The limit on a motor is the amperage that the windings can handle. The specs I see from Thunderstruck EV https://www.thunderstruck-ev.com/mot...in-cosine.html (I trust them) are 125a AC (180amps into the controller to achieve 125 continuous through the motor)

It's a brain-twister to explain RMS and back EMF and motor phases and etc so i'll skip that -- let's just assume you can put 180 amps into the controller continuously. That means: 180x48v = 8640 -- 8.6KW continuous, or 11.58hp. And -- because of the Kv constant, you'll only be able to reach that if you are propped optimally. You might think of a max prop or kiwi prop so you can adjust pitch such that at max throttle you are also at max amperage. 96v is double that, but the higher voltage presents more every-day risks and a whole different class of ABYC wiring/grounding/etc requirements. Best to avoid that in my opinion.

You may want to rethink your "biggest most efficient two-blade prop" plan too. Not to pooh pooh on the efficiency parade (I'm a big fan of efficiency, it's a fun mental exercise. I've done it before on a 1-man solar powered fishing pontoon boat..) Unfortunately, efficiency matters little when you're fighting a 22kt wind on the nose gusting to 30 and you're making .7kts headway in the gusts with your really efficient propeller. Better to back off of max efficiency a touch and design a little extra slip/torque into your prop in order to make reasonable headway against sh!t assed conditions before your power runs out. Just a suggestion, of course. I'm just a dumb redneck and I don't know much, so you should take this with a grain of salt.

Quote:
I won't be concerned with 50% DOD. I'll be running Lithium batteries, so 80% DOD will be by cutoff. I always thought Peukert was a wanker.
He was! you're absolutely correct! I prefer LiFePO4 to other chem's because of the safety factor, but you pays your money and you takes your chances, as they say. My practical experience comes from my 24v 100ah (so 2.4kwh) LiFepO4 system on my Macgregor 26s in a slip at the local lake for the past few years -- it's 2hp electric outboard treats me well, and the 480 watts of solar keeps it charged. The lack of peukert's interference REALLY helps the solar keep up with the refrigerator keeping the beer cold.

The Ericson 29 I'm refitting will have a somewhere between 5 and 10kwh bank, and a 5kw diesel genset for range. Not interested in hull speed here. It's a waste of power. Shoot, most diesel aux boats can't make hull speed unless they're under sail.


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Re: Electric Conversion log for Kahleesea

Hi Sean,

Thanks for all the great info. I really appreciate it. I have some questions, though.

If I'm going to run at 48V, there might be a better choice of motor out there. I'll have to do some digging. I hadn't considered the ABYC requirements, but I guess I'll have to sell the boat eventually. One of the reasons I'm doing this is to gain experience for the next boat. I fully anticipate screwing things up at least once. I find turning a wrench is worth a thousand technical manuals.

Hull speed is more of a personal design challenge. I'm not looking to skip along the water on my wing keel, or maintain it for any period of time, I just want to be able to touch it and say "yeah, the boat can do that". I realize that I would suck the battery dry in no time. I'm going to start with 8kWh and see how far I can get with that. If I need more, I can always keep adding until I run out of space.

I have a basic knowledge of electricity, but I'm not a professional, and my knowledge of hydrodynamics is about as complete as someone who's two weeks into their first college course. What I don't understand is why the speed of the prop is an issue. If I get X thrust from a prop spinning at 1200 RPM, and the same thrust from a prop spinning at 800 RPM, what's the difference, regardless of weather conditions, other than the gearing necessary? Won't both props push the boat equally well? You can even argue that fewer RPMs means less wear on all moving components.

What more risks are there at 96v vs 48v? I don't know much about DC, but surely the risks can't be as high as the risks for the 120VAC that the boat also runs? Are you talking about undersizing your cables, or is it something else?

Thanks for your help. I appreciate it.
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Re: Electric Conversion log for Kahleesea

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Originally Posted by Captain Canuck View Post
Hi Sean,

Thanks for all the great info. I really appreciate it. I have some questions, though.

If I'm going to run at 48V, there might be a better choice of motor out there. I'll have to do some digging. I hadn't considered the ABYC requirements, but I guess I'll have to sell the boat eventually. One of the reasons I'm doing this is to gain experience for the next boat. I fully anticipate screwing things up at least once. I find turning a wrench is worth a thousand technical manuals.

Hull speed is more of a personal design challenge. I'm not looking to skip along the water on my wing keel, or maintain it for any period of time, I just want to be able to touch it and say "yeah, the boat can do that". I realize that I would suck the battery dry in no time. I'm going to start with 8kWh and see how far I can get with that. If I need more, I can always keep adding until I run out of space.

I have a basic knowledge of electricity, but I'm not a professional, and my knowledge of hydrodynamics is about as complete as someone who's two weeks into their first college course. What I don't understand is why the speed of the prop is an issue. If I get X thrust from a prop spinning at 1200 RPM, and the same thrust from a prop spinning at 800 RPM, what's the difference, regardless of weather conditions, other than the gearing necessary? Won't both props push the boat equally well? You can even argue that fewer RPMs means less wear on all moving components.

What more risks are there at 96v vs 48v? I don't know much about DC, but surely the risks can't be as high as the risks for the 120VAC that the boat also runs? Are you talking about undersizing your cables, or is it something else?

Thanks for your help. I appreciate it.
My recommendation is to not only consider ABYC for resale value.

Quite frankly, who knows what impact an electric vs diesel propulsion system will have on it. If you can find someone who wants electric, maybe it will be OK. For someone like me, who wants a diesel (for the range and rapid refuel capability) I would completely pass on the boat, else devalue by the cost to install a diesel (and all supporting equipment) and an amount to cover my time, trouble, and risk to convert it back.

ABYC standards are designed to help prevent people from setting their boats on fire.

These are the minimum.

There is skill and craftsmanship required to make a boat safe and reliable that no standard, books reading, or YouTube watching can impart.
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Re: Electric Conversion log for Kahleesea

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Sailing Uma did a 3-way chat comparing electric setups with them, Sailing Saoirse and Learning the Lines. It was all over my head when they started talking about which motor and battery set up they went with

Electric Motors, An Honest Discussion €” Sailing Uma [Step 140] - YouTube
Yes they did.

I'm a subscriber to their channel.

IMHO, some of the things they do is OK, and some is ill-conceived.

It appeared that the intent of the episode was to help validate their decision to covert to electric.

I believe the real motivator was the 40 year old diesel was baffed and they believed an electric motor would be lower cost.

They ran into all kinds of trouble with the drive system, and it was quite noisy. Perhaps not as noisy as the diesel, but certainly no where near "silent".

They had a severe problem with speed and range.

Once, they had to hunker down and sit through a hurricane at anchor, risking his life (she left him their) because they did not have speed and range to escape the forecast path, in the calm before the storm.

Often they are forced to sit at anchor longer than desired to wait for favourable wind, where most cruisers with diesels would just motor to get where they want when they want.

Then they had an electrical problem due to a high current, high impedance connection.

This left them propelling the electric boat with the gasoline outboard on the dinghy strapped to the mother ship.

They explained that the electric was NOT to replace the diesel, but to replace a sculling oar, that they would otherwise have if they did not replace the diesel.

The other two couples who were in that episode touting the benefits of electric propulsion were either about to, or in the process of a build, and had no actual life experience with an electric cruising boat.

Then a couple episodes later the crew of UMA burned who knows how much gasoline turning countless donuts in an abandoned marina.

Kinda blows the primary factor to reduce carbon footprint outa the water.

Then, they changed out the electric motor, drive, and batteries after a couple years (obviously it was not living up to their expectations) for a much more expensive system including a bunch of LFP batteries (likely donated or sponsored) that would cost much more than putting in a used diesel, or about the same as a new.

The last episode I watched, their dinghy gas outboard failed (from admitted lack of proper maintenance) and they put on a Torquedo they had aboard that was donated by a Patreon.

(Wait a minute, they have a Torquedo aboard that one could claim was reducing their carbon footprint but they are using a 5 HP gas outboard? Why?

Then they advised that the Torquedo was unsatisfactory due to limited speed and range, and they are going to replace it with an even bigger gasoline outboard.

Long story short, I give that episode and their reasoning for electric propulsion an "F" grade on the sincerity scale.

I'm not suggesting electric propulsion is bad, in fact I recommend it to clients where it is a viable technology for their use case.

But there are a lot of factors to consider.

On my cruising boat, after motoring 30 hours at 5 knots, I start looking for a marina with diesel as I have about 4 hours left.

If I converted to a turnkey commercially available electric system (with only 8 hours at 5 knot range) ) I would have as much money and weight into it as I would a diesel system with 34 hours at 5 knot range.

What's more, the diesel system can be refueled very inexpensively in about 10 minutes, whereas the electric system will take at least 24 hours, and cost at least one night of marina fees.

If one will be doing a lot of motoring, like down the ICW, or just getting from one anchorage to another between norther's, an electric propulsion system is not a viable option, without an ICE generator onboard, and then what is the point?

Last edited by boatsurgeon; 01-05-2019 at 11:47 AM.
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