# EMRAX motor for boat - direct drive?



## RIPPERTON (Jan 26, 2010)

Emrax = Overkill
heres your 120v motor...
http://www.thunderstruck-ev.com/motenergy-1302-water-cooled-brushless.html
and controller
http://kellycontroller.com/khb1215124-120v150aopto-bldc-controllerwith-regen-p-1298.html
=16kW
Use a Nissan Leaf pack and go with the solar panels


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## yodani (Mar 11, 2015)

Hi Riperton,

Thank you for your reply. I agree with you that EMRAX might be a bit overkill but the thing that attracted me to that motor was the huge torque it produces even at lower speed. This will enable me to use it as a direct drive and still spin a large propeller. If weeds get entangled in the propeller I will need the power to free it by reversing. 

A boat in order to be efficient needs a large propeller - in my case a 40-50 mm diameter propeller that spins slowly, I don't see that 16kW motor spinning such prop without a 1:2 or 1:3 gear ratio. By going with gears I increase the complexity of the build and also the price will come in the same range as EMRAX. 

About controllers - can you limit the RPM in the controller? and do I need an encoder on the motor in order to make it work at low speed with high torque?

I was thinking about two Leaf battery packs but can not see a possibility to buy them from Europe. Any ideas about a supplier of such batteries in the EU?

Obviously the charging is another problem and emergency charging is an issue. I was thinking of making a DC generator using a brushless motor and a Kholer engine - http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=Command PRO EFI ECV980 

Would this be possible? Variable speed generator?

Could it also drive the electric motor or there are problems with fluctuating current? 

Cheers,

Daniel


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## Ai! (May 9, 2014)

http://www.diyelectriccar.com/forums/showthread.php/leaf-battery-sale-147186.html


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## Tomdb (Jan 28, 2013)

Where are you located? 

And the Emrax is great, however its met for bursts but not for continuous without serious cooling and limitations.


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## Yabert (Feb 7, 2010)

yodani said:


> What capacity battery pack would I need for a 8 hour cruise at 9kW with a 120V system? l


Regardless your voltage, you will need 72 kwh of battery to output 9 Kw for 8 hours. That 3 complete Nissan Leaf battery... that's a lot!
About motor, I understand your need of direct drive motor, but for this low power requirement I think it will be way easier to use an industrial gearbox and a small and cheap liquid cool 48v systems like those sold by electric motorsport or golden motor.
48v is safe, imply only 12 to 16 lithium cells in series and is easily compatible with 48v solar system.

Good luck


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## Sunking (Aug 10, 2009)

yodani said:


> 3. What capacity battery pack would I need for a 8 hour cruise at 9kW with a 120V system?


This question might let the wind out of your sails. Voltage is not really a concern at this point. It is weight, volume, and cost that will bite you. Consuming 9Kw of power over an hour is 9000 watts x 1 hour = 9 Kwh. For a lithium battery would require roughly a 11 Kwh battery.

A 11 Kwh battery weighs in around 110 to 120 Kilograms and occupies a space of roughly 55 liters. Want to run 8 hours? Multiply by 8. Now you have a 1000 Kg battery occupying 440 liters of space. Now you have significantly increased the weight of the boat which means it needs more power and capacity to achieve the same speed over the same time period. 

Diesel fuel on the other hand for 9 Kw only requires about 3 Liters per hour weighing 2.4 Kg. Or for 8 hours 24 Liters weighing 20 Kg. You are giving up a ratio of 50:1 in weight and 18:1 in volume. 


Do you have room and can afford the weight to do what you want?

Can you afford the battery at roughly 420 Euros per Kwh? Roughly 40,000 Euros for a 90 Kwh battery

As for solar, forget about it. Someone is smoking too much ganja. You are talking 300,000 to 400,000 Euros to charge that monster size battery on solar and that is limited to bright sunny days in summer only.

Now we can talk about voltage, capacity and answer your question. At 90 Kwh capacity your are talking about 500 volts @ 180 AH, 250 volts @ 360 AH, or *125 volts @ 720 AH*. Take your pick. Best option is 500 volts using 180 AH cells (156 batteries)


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## Sunking (Aug 10, 2009)

Yabert said:


> 48v is safe, imply only 12 to 16 lithium cells in series and is easily compatible with 48v solar system.


In theory I agree with you. Now where is he going to find those 12 to 16 1500 AH cells at? 

Any voltage is going to require roughly 120 to 160 cells.


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## RIPPERTON (Jan 26, 2010)

Actually now Im thinking big DC fork lift motor on a contactor ie no controller.
Low voltage like 24v - 48v.
That's about the only place a DC motor would have any use


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## yodani (Mar 11, 2015)

Thank you for your answers and for the suggestions.

At this moment the boat has the capacity to transport all that weight if I get read of the:

- Diesel engine and gear box - 350-400 kg
- Fuel tank - 300 liters
- Balast - 300-400kg

I was thinking of the Nissan leaf battery pack- 3 of those at 300 kg each would just bring the boat on the same level. The cost of those is about 25000 EUR. 

Motor plus controller - 5000 EUR 
Charger and BMS - ? ? ? 

9 kW is necessary for hull speed - but for a cruising speed (8km/h) the boat would need 3.7-4 kW so with a usable 16 kWh /battery pack that is 48-50kWh giving a 13 hour range. Sure with power bursts and weeds in some lakes this would come down quickly to 6-7 hours. 

I will have to repower the boats, so a new 55hp engine would be 12-15K EUR that is why I was thinking about the full electric. Also 70% of the investment would be payed with EU funds. If I buy a full electric with 30.000 EUR I will pay 9000 for the system and the fuel is payed for the next 5-10 years by the EU  . 

My first option was a hybrid electric but I was thinking a bit further as I foresee some access restrictions in a few years for boats with classic engines.

By the way, I operate in the Danube Delta, Romania and the boats are used for day tours. 

The big impediment with such large battery packs is the charging... I think it will need a lifetime to charge if you only have a 10kW 220V power source...

Cheers,

Daniel


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## Yabert (Feb 7, 2010)

Sunking said:


> ... where is he going to find those 12 to 16 1500 AH cells at?


It's why I wrote: cells in series...
150 Nissan Leaf cells 60Ah correctly connect will give a 45v 1500Ah battery.



> The big impediment with such large battery packs is the charging... I think it will need a lifetime to charge if you only have a 10kW 220V power source


Right. In best case, you will charge just under 2 Kwh each hour.
So, 12 hours of charge will only provide less than 24 kwh of energy.


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## DIY eddy (Apr 19, 2015)

The only weak factor in the equation is battery power,So I would spend most of my money and thought there.You have to calculate the best size and pitch prop to propel the boat at a given speed and torque,So if the prop is most efficient at say 1200 [email protected] 30lbs of torque you need a motor that has the same specs,90+% [email protected]@30lbs torque....this will be nowhere near the peak power of the motor so you will have plenty of extra power.A large slow prop is the way to go especially with a DC motor which I recommend,With a lower voltage...volts=speed and amps=torque,so I would go with a 48v system since you need torque.And you really don't need a expensive controller for a boat,you could just have multiple packs of battery's to use in series of 12-24-36-48v to control the speed.I guess just a bunch of contacter's and a few switches I'm sure someone more qualified could tell you the best way to do this without a controller.Even though 48v controllers are cheaper than other's I would save the money for more of those batterys you will need.


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## yodani (Mar 11, 2015)

So do you have any suggestion for such a motor? Torque is what I need indeed to spin a larger prop without gearing down and keeping it simple.

I don't think the cost of the controller is a big problem. The weight of the battery is an issue too but nothing is as complicated as charging...


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## yodani (Mar 11, 2015)

It seems like there is no easy solution for going electric on a boat so I am comming back to the idear of a hybrid drive. 

I have seen some of the range extenders in the automobile industrie that weigh 70kg and produce 30kW of power to recharge bateries anddrive the car. 

So I am thinking at the following setup:
- one 30 kW motor direct drive to the propeller 
- one 24kW Leaf baterie 
- one range extender - 30kW 

I have the following questions:

1. What dc generator should I use for such power? - would an Emrax motor work?
2. Will a small diesel work as a generator drive? I was thinking of one Hatz common rail. 
3. What would be required to make this generator work in tandem with the battery? Can it be a variable speed generator or it should be set as a fixed speed? 
4. For quick charging would it need a special BMS? 
5. Is it possible to keep this simple or it will get complicated and highly expensive? 
6. How fast can a Leaf battery charge with such a generator? 
7. Can anyone list some off the shelf parts for this project?

The advantage of this setup would be that I can get by with the 24kW battery just fine for my usual use and also have a possibility to drive further when the battery is depleated. I can also use the generator to charge bateries when shore power is not available and do it fast. 

The weight of the system will be around 600kg or so if using the above mentioned components - reasonable for what I plan. 

There will be no gears, pulleys and shaft alignments to be dealt with just electronics


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## yodani (Mar 11, 2015)

Hi again, 

Say I have the Kohler KDI diesel engine plus a EMRAX 228 coupled direcly to the flywheel. This combo will generate about 20 to 25 kW @ 1500-2000RPM. The EMRAX is a three phase AC motor and will be used as a variable speed generator so I'm asking for your help regarding:

1. What type of rectifyer should I use in order to use these 24kW and charge a Nissan Leaf battery bank reconfigured at 120V 24kW?

2. What is the most economical and robust charger and bms combo that can handle such power and the voltage fluctuations given the fact this is a variable speed generator?

I found these:

http://www.emotorwerks.com/products...lv-a-25kw-charger-for-lower-voltage-batteries

And for rectifyer- maybe a Vienna model but have not found a off the shelf solution. 
http://www.microsemi.com/document-portal/doc_view/14743-35-kw-active-rectifier-with-integrated-pm

Thank you for your support.

Cheers,

Daniel


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## bigmotherwhale (Apr 15, 2011)

If its a boat its on the sea and is reasonably large, go with wind power as well as the solar, 
you can charge your batteries tacking into the wind, just like a sail does. some boats use vertical axis turbines to this very neat, google it.. 

i would worry about using a high voltage system on a boat, you will need some serious insulation. if its in the sea even more so, ive heard if you have been submerged in seawater you become so conductive that even 24 volts can give you a nasty shock.

I also think a dc forklift motor might be your best bet, high starting torque and relatively low voltage.


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## yodani (Mar 11, 2015)

It is a river boat in a reserve so wind and solar are out of the question. This is a tour boat that has to work in electric mode for about 4 hours and in hybrid mode for 5-6 hours a day. 

I know the low voltage up to 48v is used for marine applications but the latest tek is going high voltage - Ex. Torqueedo Inboard. What is the common practice in automobile industry today for electrical isolation? If a boat can electrocute you so can a car running in the rain for a few hours. 

But back to the questions above.... Any help appreciated.

Cheers Daniel


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