electrical motor experiment?

[albertjizhang]

Hey guys.

here is the deal. We online, looking for an electric motor, and turns out you can have a custom-made 48v 30kw electric motor for about $2000 in China(including the controller). However the motor is fan cooled instead of a water cooling system, and it is not made for boat use in the first place. I've seen people fitting forklift motors on boats before, and thought I give it a go. Will the fan cooling system be a big deal?

(The original diesel is a volvo penta 25 hp, which is bit small, and leaking into the bilge 24/7, and broken gearbox, and real expensive to fix. A new diesel or a professional boat electric motor is bit(way too) pricey for us.)

[goboatingnow]

Originally Posted by albertjizhang

Hey guys.

here is the deal. We online, looking for an electric motor, and turns out you can have a custom-made 48v 30kw electric motor for about $2000 in China(including the controller). However the motor is fan cooled instead of a water cooling system, and it is not made for boat use in the first place. I've seen people fitting forklift motors on boats before, and thought I give it a go. Will the fan cooling system be a big deal?

(The original diesel is a volvo penta 25 hp, which is bit small, and leaking into the bilge 24/7, and broken gearbox, and real expensive to fix. A new diesel or a professional boat electric motor is bit(way too) pricey for us.)

Going down this road requires professional design work , experienced domain knowledge and hands on results.

Asking your question here is rather bizarre , given we have no idea of the parameters involved

[seandepagnier]

Originally Posted by albertjizhang

Hey guys.

here is the deal. We online, looking for an electric motor, and turns out you can have a custom-made 48v 30kw electric motor for about $2000 in China(including the controller). However the motor is fan cooled instead of a water cooling system, and it is not made for boat use in the first place. I've seen people fitting forklift motors on boats before, and thought I give it a go. Will the fan cooling system be a big deal?

(The original diesel is a volvo penta 25 hp, which is bit small, and leaking into the bilge 24/7, and broken gearbox, and real expensive to fix. A new diesel or a professional boat electric motor is bit(way too) pricey for us.)

Thanks for the post.

This motor you found is maybe not even a very good deal. Keep looking. Consider the mars etek motors or at least use them for comparison.

You dont need water cooling. What that will allow you to do is get higher power density for more duration at the expense of efficiency. In other words, a smaller motor producing more torque before it overheats. If the motor is running efficiently it wont need water cooling because it will not be dissipating much heat for its size.

As for thinking 25hp is a "bit small" I think this is the opposite. Did you mean a "bit ridiculous" ? Imagine having 25 horses tied to ropes pulling your boat. That is an insane amount of power.

Finally.. You cant just take a diesel out and put an electric motor in place and get reasonable efficiency. People do do this, but they consume more than twice as much electrical power to get the same amount of propulsion. This is really crappy and difficult to generate from solar panels.

Would you put sails on a powerboat? You could. It woudl not work very well or go upwind, and the one guy I know who did this actually sunk the boat because it had no righting moment. Why would you take out a diesel and just stick an electric in the same place and expect to get a good result? You have to start from scratch and engineer the propulsion system to achieve the desired level of efficiency (85%-90%) which is completely impossible with a saildrive or inboard shaft. If you using an inboard your propeller efficiency is about 25% at the most efficient speed, this is true no matter what is powering the shaft. The best solar boats have 90% efficient propulsion. Your propeller diameter needs to be at least 5x the average inboard propeller diameter (swept area is 25x) and propeller rpm about 200.