# electric jetski conversion. need help and info



## k_muff (Sep 24, 2015)

Hi there everyone. I am wanting to do a conversion to my jetski to electric. I am capable of the installation and manufacturing side just require some help on the direction of what motor, controller, batteries and reduction drive if required.

The build.
I have a full carbon fibre standup jetski for flips and rolls and such. So i am looking for low end power and id be happy with 10 to 15 minute runs out of the batteries as it will only be short but large squirts of the throttle, and id be buggered after 15 mins of flips and tricks anyway lol.
the only dyno information i can find is on a stock superjet with a pipe which i will attach the picture of but i will require atleast that power plus another half. So roughly 6500rpm and 150+hp in petrol numbers.
I have 2 inlet water feeds that i can use to keep everything cool. And can completely seal the hull from leakage. 

All your input and information on what brands/parts that i will require is really appreciated.


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## RIPPERTON (Jan 26, 2010)

Good news is that there exists the type of power that you want but I hope you have a big budget and strong nerves.
At minimum you could use a 228 Emrax ($6k) on a 700v Rinehart for about 100kW / 5-6krpm but you will need to supply a very high flow water cooling system.
For about $10k you could get the big 268 Emrax on the same controller for 136kW and longer run times.

http://www.enstroj.si/

http://www.rinehartmotion.com/standard.html

LiPo cells are a must and the short run times are the reason for the 700v system ie low current draw matches the small capacity pack.
In 15 minutes of heavy throttle action you might use 9kWh.
In our 6 minute bike races we use 4kWh so that would be 168 cells in series and about 12Ah so 3 x 4Ah cells in parallel (50kg/8.5kWh) or 2x 5Ah in parallel for 7kWh.


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## jk1981 (Nov 12, 2010)

The 2stroke ICE couldn't be any more perfectly suited to something like a lightweight jetski. Swapping to electric is daft unless you absolutely have to for noise compliance or some other reason. There's almost certainly no real environmental or cost benefit and with the battery weight you'll probably not get any performance benefit. Plus there's very serious safety risk hundreds of volts of batteries pose when combined with (salty?) water.

jk


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## samwichse (Jan 28, 2012)

Ah electric jetski sounds awesome! 

Nothing worse than ruining fun water time with a smelly, loud 2-stroke.


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## major (Apr 4, 2008)

k_muff said:


> I am wanting to do a conversion to my jetski to electric.
> The build.
> 15 minute runs out of the batteries.
> 150+hp in petrol numbers.


Some rough calculation. 150+hp -> ~150kW from the battery. For 15 minutes ---> 37kWh stored energy. For Lithium (available) cells, capable of 4C, maybe 130 Wh/kg energy density. So that would be about 625 pounds of cells. And likely cost about $19,000.


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## Hollie Maea (Dec 9, 2009)

jk1981 said:


> The 2stroke ICE couldn't be any more perfectly suited to something like a lightweight jetski. Swapping to electric is daft unless you absolutely have to for noise compliance or some other reason. There's almost certainly no real environmental or cost benefit and with the battery weight you'll probably not get any performance benefit. Plus there's very serious safety risk hundreds of volts of batteries pose when combined with (salty?) water.
> 
> jk


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## Hollie Maea (Dec 9, 2009)

major said:


> Some rough calculation. 150+hp -> ~150kW from the battery. For 15 minutes ---> 37kWh stored energy. For Lithium (available) cells, capable of 4C, maybe 130 Wh/kg energy density. So that would be about 625 pounds of cells. And likely cost about $19,000.


There are a lot better cells for power than that available these days. The LG INR18650HG2 has a continuous rating of 6C. That's really pushing it, but it can easily do 4C (12A). It has a cell energy density of 230Wh/kg. With housings and interconnects, 200Wh/kg is achievable. So that could get your battery weight down to 407 lbs. Still heavy, but a lot better. Still probably cost you $19,000 though.

Do jetskis really pull 150hp continuous (I don't really know anything about them but that sounds like a lot)?


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## RIPPERTON (Jan 26, 2010)

They had 1000cc 4 strokes in them 15 years ago


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## jk1981 (Nov 12, 2010)

It may be just my opinion and don't get me wrong, I'm all for electric vehicles in the right context but a sensible person picks their battle.

If you consider the stated energy, power and cooling requirements, look at cost and weight, consider what could happen should there be a hull or cooling system leak and the logistics of charging something (at home?) when you have to trailer it to and from the water for 15min of fun... It's doable but I don't think it's worth doing.


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## nimblemotors (Oct 1, 2010)

Standups only had 50hp engines. I build one of the first electric jetskis in the world.

I would limit it to 48volts to be safe. The good news is you don't need reverse.
A 12v series motor from a winch might work well, hit it with an on/off switch on 24volts for a motor controller. and perhaps a 6 volt slow mode pack. Simple and cheap. You want a battery pack that can take the abuse, dish out big amps and drain to zero without damage. A pack you can swap out easily and recharge quickly.


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