03-24-2010, 12:16 AM #1
All electric jet ski.... anyone seen it.
Ran across this and thought this was interesting..... check it out.
EDIT - this one is even better
( inflatable jet ski )
LOL @ that!!
03-24-2010, 10:17 AM #2
03-24-2010, 10:56 AM #3
- Join Date
- Jul 2007
- near Toronto, Canada
Energy requirements for an electric PWC
It really comes down to energy density and weight of the battery system, and the power required to make the watercraft perform.
To make a PWC move, you need power. Lots of power.
The jet pump throws away about 1/2 the total input power, the other half actually appears as forward thrust. (If you want more efficiency, install a propeller behind the hull.)
A basic two cylinder watercraft engine puts out about 100HP, and moves along nicely, so lets make that the power target for discussion.
100HP is about 70 Kilowatts (roughly). If you want to ride for an hour at full throttle (which you can easily do with a two cylinder gasoline engine with a full gas tank), you need around 70 Kilowatt-Hours of battery output.
The problem with electric watercraft is not the motor, or the control system. Both can be adapted from other applications, like electric/hybrid cars and other vehicles.
The problem is the batteries.
Batteries don't like to be fully discharged, so you need battery capacity in the range of 80 Kwh to 100 Kwh.
For comparison, the standard PWC 19AH battery is rated at 19AH. Taken at face value, that means it puts out 1 Amp for 19 hours, or 19 Amps for one hour (the actual numbers aren't quite that simple).
12 volts times 1 Amp for 19 hours = 228 Watt hours
Four of those batteries would give you 912 Watt hours, or a little less than 1 Kilowatt hour.
Three hundred and fifty of those batteries would give you about 80Kwh, and would run your 100HP electric motor wide open for an hour. Each battery weighs over 15 lbs, so the total battery pack would weigh over 5,000lbs
If you use larger capacity lead-acid batteries, the total weight would shrink a little, but not all that much. Clearly, lead is heavy, and lead-acid batteries are not the answer.
Right now, Lithium-ion battery technology is the contender for light weight combined with energy storage capacity. Panasonic is one of the top names in battery development, and recently announced a 1.5Kwh battery module that weighs about 17 pounds.
This Panasonic module delivers about 85 Watt-hours for each pound of battery weight (or about 190 W-h per Kg). To deliver 80 Kilowatt-hours of power, the combined 53 battery modules would weigh about 940lbs. Not very light for a PWC, but only 1/5 the weight of the lead-acid batteries!
If you cut the battery pack in half, size and weight wise, then you would have half the energy capacity available, so you could go fast for half the time, or cruise for half the distance.
If you cut the motor power in half (to 50HP), then you double the cruise distance at full throttle.
A 50HP electric motor powered by a Lithium battery pack weighing 500 lbs would run for an hour at WOT.
A 100HP motor powered by a 250lb Lithium-ion battery pack would run for about 15 minutes at full power.
These high power electric motors and battery packs are not 100% efficient, and both would require cooling systems and have some energy loss as waste heat. The waste heat consumes power from the batteries, so that power is not available to actually push the machine forward. At least a PWC has an ample supply of cooling water
Imagine you could use an extension cord from your lakeside house, and run around the lake with the cord trailing behind. The 200 Amp electric service into your house, with 240 volt power, can deliver a maximum of only 48 Kilo-watts. The entire electrical feed into your house would not be enough to run your battery-less 70Kw electric PWC motor at full throttle!
You can see how much energy is contained, not in your engine, but inside that plastic fuel tank. A gallon of gasoline contains a lot of energy.
Putting electric power into a standup watercraft seems inspired. These machines rarely use full power for more than a few seconds. What they need is bursts of power, which an electric motor can provide.
Battery life is then determined mostly by the average power consumption, rather than the maximum electric motor power.
I suspect weight and energy capacity of the battery pack is still going to be the biggest factor in the performance of this electric standup.
All eyes are on advances in battery technology. From cell phones to laptop computers to Hybrid and electric vehicles - as the energy density and weight of the battery improves, more range, and more interesting uses will become possible.
Waterside recharging of a PWC battery pack could also be be issue. Large quantities of electric power need to be transferred from the power source into the battery pack. Electricity in wet environments is always a concern.
Fast charging creates heat, which means either re-charging the batteries slowly, or somehow running cooling water or air through the battery pack while charging it.
It would also require a rather large electric generator, or a smaller one running for hours.
03-24-2010, 11:19 PM #4
K4- very interesting info. Ive fiddled around with mobile electronics myself for a few yrs. certainly not to the degree of knowledge you have
I, myself, wouldn't think these would be worth much, but you never know what the future holds.....
Thanks for the info!
03-29-2010, 05:02 AM #5
- Join Date
- Nov 2007
- Odessa, TX
04-08-2010, 10:17 PM #6
- Join Date
- Oct 2007
I think that the technology will have to get better with batteries before it could happen in a consumer production environment
04-11-2010, 11:35 PM #7
Big deverlopments in battery packs comming soon
Nanowire lithium ion battery technology is just a few years away. It is possible to increase the energy density by about a factor of 2. This will have big implications for electric automobiles. We are talking about ranges of 300 or so miles on a full charge and I could see an electric jet ski with this type of battery system running for at least an hour and 1/2 at full throttle. Electric motors are quite efficient with 100 percent torque at 0 rpm to near 10,000 rpm red lines so they will work well in a pwc. I feel that its quite possible to build a practical electric pwc that would satisfy all but the most demanding of consumers. Also since electric motors are inherently much less complicated than gasoline engines they should be very reliable too. Battery packs will have to come down in price in order to make them affordable to the average consumer. Look at the Tesla Roadster at $109,000. About $20,000 to $25,000 is in the battery pack alone
Last edited by GustoGuy; 04-13-2010 at 11:19 PM.
04-15-2010, 11:09 AM #8
What about the noise and smell of burning gasoline!!!
Electric is cool but I wanna feel the rumble and noise as I go WOT.
Im kinda big into RC racing and its mostly going electric but I love the smell of that burning nitro, not the whine of some electric motor. Another 10 years and batterys will really shine.. were kinda on the verge on some great stuff.
Inflatable Boat .... i love the amatuer marketing.. they need billy maze! also great how he mentions the aerodynamic design.. when your going a whoppin 8.5kmh not kph.
04-22-2010, 09:38 PM #9
- Join Date
- Aug 2006
07-01-2010, 10:32 PM #10
- Join Date
- May 2010
boring... I cant be without the sound of a throaty powerful engine!
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