T-Pain Is On A Boat: Re: [Electric Boats] Why gear reduction?

I can definitely back up James' claim for his systems. As a satisfied Electroprop customer with 2 years of use, I have yet to push my coils past 90 degrees C. And the 90 was only obtained during my "let's see what she can do" tests. Most of the time the coils heat to 60degC and current is kept under 50A.

The only direct-drive inboard vendor I know if on this list was AMeP (Advanced Marine Electric Propulsion). Their motors looked great and made for very nice, clean installs and used Kelly controllers. They ceased selling motors a few years ago.

I also wholeheartedly agree with James regarding conditions in which the boat will operate affecting the sizing. Earlier, you were talking about operating on calm water but you never mentioned what would happen when things turn ugly, which they can very quickly. When your system is operating at capacity under light conditions, you have no headroom for fighting a headwind which can make you late reaching an inlet before the tide turns against you, forcing you to stay out until it next turns in your favour and you have to wait out a nasty squall and keep off the rocky lee shore. Your light motor will quickly overheat after prolonged operation at high current.

What about your hull and prop fouling over the course of the season, robbing you of performance and costing you extra amps to reach your target speed and reducing your range.

Your 24V pack will really not like running at higher current. So you parallel up. But now, you have just as much battery weight as the geared drive, so you lose that advantage. Since your system

Will be running at higher currents, you may need to upsize you cabling. That increases cost a fair bit. My system uses 2awg cabling and the cable runs are within the 1% loss range at 110A, the max my controller can put out continuously. Had I gone 24V, I would have required 2/0 cable, a significant cost increase, just in cable and terminals.

Once I'm geared, I can swap out my motor without having to realign the drive. That saves me a good half day of my time or the money for somebody else's.

I did look for direct drive options when I was shopping around for vendors. I even designed a few on paper. But price/performance and value proposition wise, it's going to be hard to beat my setup. In the end result, the customer is pleased and that's the most important factor.

/Jason

Jason Taylor

v:514-815-8204

e:j@jtaylor.ca

On Feb 25, 2016, at 4:10 PM, 'james@electroprop.com' james@electroprop.com [electricboats] <electricboats@yahoogroups.com> wrote:

There are a lot of vendors on the marketplace many with unrealistic ratings and few with continuous ratings. Sailboats typically use very little power and are limited by the battery capacity so vendors with unrealistic ratings seldom get caught because the batteries will be empty before the motor comes up to temperature. In the industry many consider the continuous rating to be after 1 hour without exceeding the motors maximum temp. Even this number is up for interpretation with vendors going up to the temp
Rating of the winding varnish of 150C. More conservative max temp is below 100C.

All the motors are capable of running at 3 times or more of their continuous rating. So you might think your motor has power but you probably only used it at a top
Power rating for minutes not hours so you need to understand what the vendors rating really means. What con ditions was it running in. What was the ambient temp. What was around the motor. What cooling and most important what rpm was the motor running at

When a motor develops power from rpm instead of torque it is running on voltage not current and the motor will run cooler. The fan will turn faster too. All motor losses are proportional to current not voltage so decreasing current makes the motor more efficient.

While it is true that a direct drive motor will be more efficient than a geared system you have to realize the motor will have to be larger to develop the higher amount of torque. If you are replacing a geared system with 2,5:1 ratio, the motor would need to be at least 2.5 times heavier to make the same power. Larger output direct drive motors are expensive. Almost always they are operating at diesel prop
Rpm of 1200 rpm to make that power. Contrast this with the 750 prop rpm of an Electroprop

The direct drive motor cannot be optimized for different propeller sizes and will almost certainly require a smaller prop so any gains in efficiency will be lost at the prop,

It used to be that sailboats were best with larger diameter propellers. While this may be true with a diesel it is not true with an electric motor where pitch and propeller shape rules the day.

There are a lot of false and misleading claims out there with motors because there is no standards so all the manufacturers are essentially making up their own ratings.

My advice to you is to look at actual
Performance of knots watts, controller temp and most importantly motor temp after 1 hour or whatever time you need that power for. If you go hybrid it matters even more cause the limiting fa ctor is no longer the energy in the batteries and the system can run indefinitely backed by the generator. Thats why many systems must be derated if used in a hybrid application.

When we designed the Electroprop we had all these things in mind so we can run all of our systems continuously in hybrid applications Our ratings are so conservative that we could double our ratings and still be less than some competitors lofty ratings made to make you feel good at the time of purchase. Indeed the first motor i bought was rated at 8.5 kw but over heated at 2kw.

Do your homework and make sure what you are buying is what you are getting!

James Lambden
Electroprop
6 Harbor Way #226
Santa Barbara, CA
93109

www.electroprop.com

On Feb 25, 2016, at 9:44 AM, 6 6b6dcd5b59507e7d751ea81382ea1f6 <no_reply@yahoogroups.com> wrote:

Mike,

My question to you and James is how can a professional geared system from ElectroProp, Electric Yacht, or Thoosa as you suggest, either with 36V or 48V system battery voltages be lighter than a direct drive 24V or 36 V system such as professional systems from those below whose motors all weigh around 12Kg? Indeed don't Thoosa use these type of motors? To compare weight all systems should use the same type and Ah of batteries? In fact isn't it reasonable to compare all up system weight too? Direct drive from other professional vendors:

http://greenstarmarine.se/en/

or

http://www.bellmarine.nl/ (Mastervolt partner)

English pricelist and system here: http://www.bellmarine.nl/files/Price%20List%20september2015%20Bellmarine%20export%20.pdf

or

http://lynchmotors.co.uk/

Thrust management is built into these systems above within the motor subject to ones requirements for that. Heat management is not an issue in the systems subject to the power required. I think what you and James need to say is at what power you require gearing, improved thrust management and improved heat management for higher powered systems?

I note you also refer to Elco. They make this statement "Why is our electric motor the most efficient?"

on this page:

http://www.elcomotoryachts.com/electric-101.shtml

They say "The efficiency on even a good D/C motor is seldom above 80-85 percent efficient which sounds pretty good. Now take an A/C motor, especially a 3 phase A/C induction motor there are no brushes, no commutator, there is no rotating, winding and the efficiency of a good motor starts at the high 80 percentile and goes up into the low 90 percentile."

on this page:

http://www.elcomotoryachts.com/?testimonial=ac-electric-motor-compared-to-a-dc-motor

But my motor is a Lynch, DC and brushed and at my power requirements is around 88% efficient. It can be 93% subject to system design it seems.

Personally all these statements from professional vendors makes me (the public) confused. I don't know who to believe anymore! I'm a DIY'er and would like to know why there seems to be such differing claims made amongst professional vendors?

John R.

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