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Sailboat Controller/Motor/Generator

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Thu, 2020-05-28 21:55
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Joe Lorkovic
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Joined: 2019-11-30 23:02
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Sailboat Controller/Motor/Generator

I was not able to find an acceptable solution for electric sailboat. The use case is unique and I found most sellers provide preexisting off the shelf motor solutions adapted poorly to the use case or engineered solutions not properly addressing the real world need. The solution if it existed would be 95% power generator and only 5% motor usage. I am not an electronics engineer but a software engineer, I do have some knowledge about BLDC inner workings from experience. I thought a controller regeneration feature could work nicely for powering and generation but I was wrong about that. I assumed a low rpm motor could be driven from propeller dragging through the water. Motors are typically 5,000 rpm or so requiring gearing of 2:1 wasting power and even so 4 knots of speed is required to even start any generation. I have learned a little about generation technics of coil sets cutting in at different speeds, this led to the idea of motor design where individual coil circuits are also managed in the controller to enable optimal charging.

I have thought of in drive line generator as well as the BLDC electric motor to overcome the limitation with charging at low speed that is critically important, not a very elegant solution though, I wanted to see if anyone here has ideas or knowledge applicable to the issue.  

 

 

               

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Thu, 2020-05-28 23:10
david
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Joined: 2017-09-12 01:01
Posts: 15
  • VESC 75/300 is probably ok for a small sailboat application.
  • if you want regen from the propellor you need a motor with very low cogging unless you "jump start" the motor/generator so inertia can carry it through the cogging torque ripple.  I.e. boat speed ->XX -> jump start motor -> regen.  You'd need to write some arduino code to do this properly, and have it hooked up to both your vesc and BMS/charge controller.  This def isn't impossible but i imagine is a bit of work.
  • You may want a motor with hall sensors so starting is more reliable.
  • A belt reduction is pretty easy to design and is robust...and solves any prop/motor mismatch although adds drag.
  • Since weight isn't a big deal, you could get a low kv motor and just drive the prop directly from the motor/gen.
  • prob have motors here that would work fine https://www.thunderstruck-ev.com/motors-dc-and-pmac/ or do some searching on Alibaba for some low cost chinese EV motors.  Otherwise ebay for extracted EV motors.  Maybe a nissan leaf motor?
  • Corrosion is going to be your number one enemy.  Seal everything up as much as possible.  Potting is prob a good idea.
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Sat, 2020-06-06 19:11
Eric Crouch
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Joined: 2020-06-06 18:12
Posts: 3

Hi Joe,

I am a Mechanical Engineer that works for an electric propulsion marine company. My specific position is a field engineer. I am currently looking for a similar solution as my company doesn't offer the 5kw-15kw inboard motor designed around regen that i am interested in. I have a very good understanding of the fluid dynamics needed to get the most kw form regen.

My current understanding of the equation is basically sped will make it or break it in terms if regen is actually worth it or not.  

I am currently looking into how to optimize motors, controls, props, and rpm ranges to get the most juice out a regen with a small sailboat in the 30 ft range, but my current conclusion is that hull speed of around 8 knots is keeping boats just below the exponential part of the power output curve. 

Regen/Speed Curve

 

ec

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