1954 Kettenburg K-38 conversion from 12hp diesel

[Greasecakes]

I am trying to best decide what size/type of electric motor and battery bank before investing.

The vessel is 38' overall however only 25' are touching the water. It's built of the finest Honduran mahogany and weighs in at 12,000 lbs.

The yanmar 12hp currently makes 6 knots before the lack of propeller surface makes throttling up anitproductive.

I was planning on using a large bank of 6volt blue top gel batteries. There is an exceptional amount of space and need for more weight so we will be overkilling what is normally required.

I am not sure what is better 72/48 voltage motor? I hear of guys using forklift motors and such that are 115v 20 amp 2hp reversible motors as well. How much do the Tesla drive motors in the cars cost and would I be better off installing something used like this?

Does Tesla make battery controllers?! It sure would be cool to have a Tesla digital battery controller on my 65 year old sailboat!

Thanks for taking the time to answer any of these questions. Much appreciated!

 

[Krash]

Beautiful boat. This would be an interesting conversion. You'd want salvage battery modules and motor with a third party battery management system like Jason Hughes (wk057) built for his home.

How much weight can you handle? You could just pay the extra expense to put Tesla PowerWalls in. Some of the older models had DC in. Not sure about DC out.

When you sail, is it ever practical to slow the boat by regenerating power and running the prop backwards? Would solar panels mess up the aesthetics? Can you fit standard sized panels in the hold? Maybe consider a portable wind generator to charge?

 

[Greasecakes]

The boat sits 8" out of the water so I still have over 1,000lb weight I can bolt in. Can the wall battery be mounted and run at all angles of incline as the boat heels?

Regeneration with the prop while sailing is going to be utilized. I already have solar mounted that tucks away while I am sailing.

Is there an advantage to using DC or AC motors? The existing diesel tank will be used for a stove/heater and small backup generator.

From other people's conversions I would say a 15kw motor would be sufficient to replace my 10hp diesel that rotates at 3000 rpm and is reduced out the transmission to 1500 rpm.
How long could I run a motor of this size off a Tesla PowerWall at a reasonable rpm that meets the efficiency of power/drain ratio?

 

[Krash]

Officially the wall battery can't be run in a boat, obviously, but I doubt that it has components which can't operate at an incline. The individual battery modules weigh 55 pounds each. Much of the Tesla value add was in thermal battery management. Not sure how developed the modding of the thermal system is.

Tesla motors are three phase AC and very efficient. You'll want an S/X induction motor. It will be slightly less efficient than the Model 3 rear (Permanent Magnet Switched Reluctance Motor) but the induction motor can freewheel and there are many more third party tools for retrofitting it. If you want to be adventurous use the Model 3 AWD front induction motor. It will be lighter and maybe slightly more efficient.

The Tesla drivetrain are unfortunately 40x the power you need, and the smaller S/X induction unit weighs 200 pounds ish. It includes a 9:1 ish reduction and can spin up to 18000 rpm so 2000 rpm at the shaft, so you can probably ditch your current reduction. DC to AC inverters are in that unit so you would go DC from the batteries directly into the motor. Battery modules are 25v each. The cheaper S/X use 14 modules for 350v so if you can handle that much weight the tesla your project will require less custom work. If you use 12v on the boat for lights and electronics the Tesla has a 12v subsystem.

If you run the motor at 15kW with 75kWh of batteries (until recently the 14 module setup) you get five hours (15x5=75) without any losses.

I assume the batteries will eventually end up in the keel on new builds. Keels would be an ambitious project to one off retrofit though, especially without a drop keel.

You'll want to talk to @Jallum.pa.us about his Swan 57 if you are serious.

 

[wycolo]

The SmartED motor has all the power you really need. Many of these, lease returns, were allowed to die in storage so Merc should have a few drive trains remaining. Remove the differential and optimize the reduction gear for your prop and you are set to go high tech. A salvage Leaf battery would be an easy Li-Ion solution. A Rheinhart controller could possibly run this.
--