Electric inboard motor, my journey to find proper motor

Oh! A kind of pod drive in the rudder.
Not exactly what is on the video you shared.

So, it's can be a good idea, but considering I don't have proper motor for this application and the fact that rudders and boat are not design or ready to receive this kind of system, I look quite complex to design and build this.
It seem like a lot of job compare to simply mount the motor on the actual strait shaft.
And seriously I would not be fully confident to design a reliable ''rudder motor'' who imply perfect sealing of the motor underwater.
Considering all the video of sail drive full of sea water, I will not be temp to put a motor underwater.

 

↑ yabert

If the planetary gearbox is running in an oil bath, there will be additional viscosity losses and it might be necessary to periodically change out the oil, as it's lubricating properties decline with age and use. It might be faster, easier and less costly to replace worn belts periodically. In some applications, metal belts might be used. Usually it's Very easy to change out toothed pulleys to fine-tune the gear ratio and tweak for better efficiency, once real life performance is experienced. There might also be a consideration for magnetic gearboxes, which have essentially no frictional losses with presumably no maintenance, close to if not at 100% efficiency.


PC: It might be a good idea to have the motor efficiency for torque, rpm, PMW, prop, V, etc. curves Peak at the cruising speed or the speed where it will be used the most, or at least where the various factors line up for best efficiency.


"Yes, I will try to find the best efficiency to cruise at 6-7 knot.
Can you explain me what do you mean by: PMW, prop, V,"

PWM =pulse with modulation = ESC= electronic speed control- efficiency can vary depending on what voltage range it was designed for and what the actual voltage is due to temperature, state of charge, and voltage drop of the batteries because of their internal resistance and how much current is being drawn.

Prop= propeller, efficiency can vary depending on number of blades, pitch and how well it matches to load and hull shape, whether it is surface piercing or not, etc.

V= voltage of the battery and motor matching each other; generally higher voltages are more efficient but there's a trade-off if the RPMs are too high, prop cavitation losses can be significantly High without the use of a proper gearbox.

 

Yeap! Anyway, it's why I'm so interested by the direct drive solution with high torque EV motor.
Thanks for all details portacruise.
I'm happy to see that I don't forget anything about the system I plan to put in place.
I use Vicprop calculator to find proper propeller. Of course at the moment I have to first confirm EV motor RPM under load when running at low voltage.
It should be around 1000-1300rpm and I should need 3 blades propellers of 17'' to 19''.
I think I'm lucky because there is 17'' Variprofile prop on the boat at the moment. So I should be able to test and tweak with those prop and change for higher diameter prop in case the RPM is lower than plan.

 

At 48v Leaf motor spin 800rpm without load . Maximum current available and non destructive for motor and high coolant flow and it probably will work .Direct drive . If not you need larger diameter motor .

 

Interesting. Where do you find this?
Personally I've found 886 rpm at 48V on web.
And I've test 1100 rpm at 52V with a Smart EV motor.

 

Some guys video test .Not really big difference . Problem still remain : very weak performance for quite powerfull motor.At 250amps x 48V 12kW per motor. Torque will be probably great . Maybe it will be push that heavy cat somehow.

 

I admit that it's a bit sad to use a motor probably able to output over 250 kW for few seconds at only 10-12 kW.
But hey, they are destroy or sale for nothing at scrapyard. So why not

 

@yabert

It seems to me that you suppose the leaf motor fed by a 48 V battery will run at a current of 250 A only if you change the nissan inverter to a 48 V motor controller. Did you consider Ohm's law? There are windings in the motor with a certain resistance, so the actual current at 48 V will decrease dramatically if the motor windings stay unaltered.

There is a very good book from Charles A. Mathys: My electric boats. Mathys (a retired engineer) started 1994 to build some DIY electric boat drives and he had to rewind AC motors destined for 230 V to use them at 24 V to 48 V. The book is strongly recommended for your project (although it dates from 2010 so very few is said about BLDC motors and batteries with Lithium chemistry).

 

Cool! I will look at that.
Thanks for the advices.

 

250A DC needs wire AWG 4/0. It weighs approximately .9 lbs/foot. That means 1.8 lbs/foot for pos and neg pair.

 

Yeap. I will try to design the battery to inverter as short as possible and I plan 2/0.
It's why I plan the battery to be just in front of the motor room.
Still, aluminum busbars are not exclude at the moment, but if it just to save few pounds (kg) and few $$ I will stick with copper.

 

2/0 is not adequate for the current you plan. Also, is that peak or continuous running?

 

I think you should have wrote: Is that peak or continuous running? Because 2/0 can not be adequate for the current you plan.
The thing is I will only know the continuous power I need when the boat will be converted and in the water.
The thing I know is I have limited energy, so I plan to cruise with 100-150A from each battery and up to 300A for short period of time when I face some current/wind or other situations.
Let see how many knot that will result.

Here good thread about current capability of cables: 4/0 cable: Pushing Over the Current Limit https://diysolarforum.com/threads/4-0-cable-pushing-over-the-current-limit.95466/

 

There is good advice on that thread about not going over the rated ampacity on the cable. Not all cables are the same. The installation has to be taken into account too. The highest rating is for free air. If the cable is in a chase or sleeve, touching another wire, or any other thing that thermally insulates it, the ampacity should be reduced. Also, since the system is DC, voltage drop is very important to calculate. Undersizing a cable and waiting to see if it goes up in flames seems like a bad plan.

 

Use care with aluminum electrical conductors, mechanical connections in particular are subject to oxidation and corrosion especially around Salt Air atmospheres. The oxidation tends to form a thin layer of semiconducting aluminum oxide dust which introduces an electrical resistance that heats up when Electric current flows and that causes an expansion at the contact point. When current is not flowing the connection cools and causes a contraction at the contact point. As this process continues more oxidation occurs and the resistance increases causing ever higher temperatures. Eventually the connection contact point get enough of an insulating Gap that current stops flowing or overheats to the point of being a fire hazard. But there may be stop Gap special alloy connectors that can be used to slow this process down, as I recall. The use of lower cost aluminum electrical wiring instead of Copper for homes had to be discontinued because of these and other issues, around our particular city, and at other places.