I'm not surprised about the ECO watercraft disappearing, many things that sound reasonable end up not working out in real life. Let's try another approach to evaluate the feasability of your project.
Gasoline represents about 33kWh/gallon. Internal combustion engines convert somewhere between 25-30% of that potential energy into crankshaft power, the rest is given up as heat through the cooling system and exhaust. Electric motors can operate above 80% efficiency, which means that for the same shaft power, an electric motor will consume about 1/3 the energy as a fueled engine.
So 11kWh of batteries and an electric motor has the same effective power as an IC engine with a gallon of gas.
Now let's talk batteries. Lithium batteries have the best energy to weight ratios of commercially available batteries today. Lithium batteries also allow deeper discharges while retaining many hundreds of charging cycles. 80% discharge is considered normal (others will promote 100% DoD, but that is a personal choice), so a 14kWh battery pack will be close to one gallon of gas in regular use.
My 8kWh pack of LiFePO4 cells cost $3500US, weighs 200 pounds and has a usable capacity equivalent of 0.6 gallons of gas. More money will buy cells that have 10% more capacity for the weight, like the Tesla batteries. You can see that the Tesla has the equivalent of a 3-3.5 gallon tank, which fits it's range numbers fairly well.
So the last question about converting existing Jet skis to electric motors, would you swap out your gas tank for a 200 pound one that holds less than 3 quarts of gas? If that still sounds OK, then you can start trying to conquer many of the other challenges beyond mere storage density.
If I was tackling this project, my first step would be to see if I could optimize a jet ski to be worth riding with only 1/2 gallon of fuel, keeping in mind that it takes about 4 or 5 hours to fill it back up again. Some where in that process, I might end up with something more like the Samba than a regular jet ski.
I'm not trying to discourage you, just trying to explain the current (no pun intended) limits to our technology.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Rob McAfee <rob_mcafee@...> wrote:
>
> Eric,
>
> Thanks for the pointer to the message... the Samba is an interesting-looking
> concept machine and I hope they are successful, but as a long-time jet ski
> owner, the posture they chose to put the rider in looks uncomfortable and
> unsafe. The low-weight approach makes sense until you realize how much you
> *want* the extra weight when moving at high speed. I certainly wouldn't be
> willing to go 65 mph on that little boat, especially in that stance. Looks like
> a good way to break your jaw!
>
> I do think converting existing jet skis to electric makes at least as much sense
> as building a brand-new platform. Lots of people have old jet skis sitting
> around, and would be thrilled to convert to electric if there was a reasonable
> path to doing so. I was hopeful when I saw this article last year on ECO
> Watercraft:
> http://www.engadget.com/2009/05/26/eco-watercraft-electric-waverunner-makes-no-sound-burns-no-fuel/
>
>
> But since then, I haven't heard anything from them. Their website is dead and
> the proof-of-concept video wasn't that impressive. The boat seemed to be
> traveling at 1/4 the speed that it would move with a gas engine.
>
> The Tesla, with its 1000 lb battery pack and 70 lb motor, gives me hope... I'd
> only need a quarter the power, half the RPMs, and could live with half the
> run-time if necessary, so a 200 lb system that runs for an hour or so doesn't
> seem completely pie-in-the-sky. Of course, if I needed to spend $20K or more to
> get there, it's probably a non-starter, for me anyway.
>
> Anyway, I'll keep looking. Thanks again for the help. So far I'm gathering that
> powering the motor is a bigger issue than the motor itself.
>
> Rob
>
>
>
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