Electric PWC

Now that the battery problem is solved (A123 Lithium batteries), is it now possible to build an electric PWC? I'm not familiar with how much power is needed for this application, but if you want to see an interesting video on what is now possible with these batteries:

www.killacycle.com

Just curious, since I personally abhor PWC in their current form...

Roger

 

I think I will change my name to dreamkiller. Or realityCheck

For a PWC like that : http://www.jmcamper.com/seadoo_pwc_2007/

Let's take the less powered: 130 hp. Assume we run a bit less that half power : 60 hp = 60 * .736 = 44 kW. (rounded to the lowest).

Then the batteries are there : http://www.a123systems.com/html/products/cells.html

They are 3.3 v nominal.

Assume we put by pack of 100 in series. We will be 330 Volts. Then the amperage we need ft the engine, assuming everything is 100% efficiency is 44000/330 = 133 A.

Now, we want to run half an hour between charging. We will need 133/2 = 66.5 Ah. the unit is 2.3 Ah. So we need 66.5/2.3 banks of 330 V = 29 banks.

Allow me 30 banks. of 100 in series : that's 3000 cells. At 70 gr per cell, the battery bank for half an hour will weigth 3000 * 70grs = 210 kg. (460 lbs).
I do not speak of electric engine weigth or electronic controler, Just batteries, without even cables.

And for the price: The absolute best price for theses batteries (seeked by electric RC models) is there : http://cgi.ebay.com/DEWALT-DC9360-3...3068607QQihZ015QQcategoryZ20794QQcmdZViewItem
129$ the pack of 10 cells. You need 3000, so the battery price will be 38700$.

Finally with a 38700$ battery pack weigthing 210 kg, you want to compete with a PWC worth 8500$ (all included), twice the power, and 5 minutes charging/refueling time.

 

Well, in a few more years then..

Thanks for the analysis!

It's getting closer though. The Tesla gets 248hp (185kw)(peak) and a range of 250miles on their pack using regenerative braking (not applicable in a marine situation!).

Maybe in the meantime they could make quieter gas ones that don't smell so bad?

BTW, I have nothing to do with the Killacycle - I just saw their video. Note that Nitro powered 1/4 mile drag bikes get like 250-300mph top speed in less than 5 seconds or so, but 140 in 9 seconds isn't bad (Zero to 60 MPH in 1.4 second, 60 feet)

That's acceleration.

Question - do gas powered PWCs run peak power constantly?
Question - are there PWC drag racing events? Maybe we could start there...

Besides, there are some definite advantages to electric - quiet, no emissions, no petroleum use, very low maintenance and simplicity. I would think an electric PWC would just need a direct drive impeller motor, the battery pack, and the controller. No cooling system, internal combustion engine, etc etc.

Well, these batteries are still very cool (70amps peak from a single cell, no explosions, fast charging, long lasting, environmentally friendly.) As they go into mass automotive production, the cost will likely drop sharply.

Roger

 

Thats a lot of money. There isn't pwc drag racing per say, but there is jet sprint drag boats. pwc's as with all jet driven boats run most efficient at a specific high speed. Low speeds are not efficient. The current draw would be constant in the sense, that most people have the throttle pinned all the time, however with electric, the current is going to fluctuate quite a bit, due to the nature of a pwc, jumping waves, spinning around, cavitation of the impeller. You would need water cooling due to the high performance application here, the electric motor could overheat, same with your speed control. Luckily with jets, water cooling is easy, you have an enormous water pump already in the boat.

Personally I love the smell of pwc's but I guess it could get annoying. Problem with trying to replicate a pwc with electric, is trying to replicate the sheer power of a normal pwc. I would think realistically, you wouldn't use a jet drive, due to the power loss. However, than no one would buy one, since theyd get their legs chopped off from the propeller. I think this idea has some potential but technology has to catch up first. Maybe you could make a hybrid power plant, that would certainly save some batteries but maybe not enough.

The other problem I see with this plan, as a boat modeler, is the dangers of lithium ion batteries. You say no explosions, but when a lithium cell is breached by water it flares up violently. Which is why a lot of modelers including myself, wont put them in dangerous applications, such as a jet boat. The constant banging around and proximity of water scares me. A pwc is the perfect example of a bad application for lithium cells. You'd need some protective case for them, so you can tack on another 5 grand or so for that and it still might not be safe. Not only are you dealing with sealing this pack of packs, but you'll have 3000 times the chance of flaring one up(3000 individual packs) and they are known to fail for no apparent reason. All you need is one to go and it'll start a chain reaction. I could be wrong here, but I wouldn't want to be sitting on top of that.

Another problem I see is marketability, lets say you get this to work and you got the cost down to maybe $15,000. It probably isnt going to 60mph, because you had to compromise on battery cost, so now you have a $15000 slow electric pwc. From what I know of pwc owners this wont fly. They like that awful smell, they like the noise. You know, theyre not prius drivers were talking about.

I'll give you an alternative, how about a skiff, like 14ft or larger. Then you have the ability to use the same power plant probably the same batteries, but in a safer more reasonable application. A boat would be easier to get on plane, easier to seal the batteries, besides putting lithium cells in a boat will be inherently safer, easier to market(as a tender), and would cater to the wealthy....I'm saving the environment crowd. This would also be a great application for a hybrid. Small diesel/electric maybe. Another thing, no jet drive, so now you have more power to play with.

I dont know, just trying to give you some things to think about, not trying to rip the idea apart, but some things do not seem feasible.

 

Are your batteries charged by God spirit ? Mine are charged by nuclear or coal power plants. They are not exactly no emissions.

Now, if you want to speak of the simplicity of a 100+ Amperes electronic controller, feel free. I know a bunch of people interested.

99.9999% of powerboats, cars and planes under 500hp are powered by IC engines, although they are designed by hundreds of thousands engineers in a bunch of countries, all commercially competing against each others.

So there are probably some very very very very very hard facts to break.


Just back to the original PWC. a 100 hp Rotax gasoline engine will burn slightly over 18l/h at 60 hp power. That 9 l for 30 min = 6.6 kg. (gasoline density 0.74) To compare with the 210 kg of batteries needed to store the same power, same time.

And you win NOTHING on the engine weigth. The rotax 914 is less than 70 Kg. http://www.kodiakbs.com/engines/datasheets/914.pdf ( although it is 100 hp continuous, 115 hp for 5 mins).
An electric engine than is 100 hp peak, 50 hp for 5 mins, but only 28 hp continuous will weigth 150 lbs : 67 kg. http://www.evparts.com/shopping/product_details.php?id=1013&product_id=1128

 

Jet sprint drag boats...

"There is jet sprint drag boats." - How can I find these? Do you have a url I could start with?

"dangers of lithium ion batteries" see:
http://www.a123systems.com/html/tech/safety.html#

However, they don't show being plunged into water at the same time. This would be an interesting experiment. But MUCH better than earlier lithium batteries. A123 did a smart thing by putting their cells in power tools. A more abusive environment would be hard to find.

Gasoline is also rather volatile I've noticed...

"They like that awful smell, they like the noise. You know, theyre not prius drivers were talking about. "

True, true, I am a prius driver, but still enjoy fast, and could do without all the noise and pollution.

Enough politics - I just wanted to see if it were possible. What I'd like to make would be the Tesla of PWCs - really expensive, but also faster, cleaner, quieter, and more fun. Or, maybe an electric surf board...

 

yeah, then run that 28hp through a jet drive, what are you left with 20hp or so. So it'll go for like 8mph, until you get tired of the silly thing, hit the throttle and go 20mph till all of a sudden the seat gets really hot and melts. Lighting yourself on fire and swearing off electric power forever.

You bring up a good point though, a nuclear powered pwc, now that would be green, efficient and low maintenance......oh wait never mind

edit: I think there already is electric surf boards, but this is less efficient, since usually they use a human.
also gas is explosive, but it doesnt cost $38000 either.

jet sprint racing info is kind of scattered about, but just search google for it, heres something to give you the idea http://www.ussbaracing.com/Classified/index.html
I do see electric drag racing as a future sport, heck we've got electric rc boats, going over 150mph now.
here a video of a previous record, I cant find the 150mph boat. http://www.youtube.com/watch?v=nzk3fH1ItzY

 

No. It is very easy. Power tools are intended to be hold by hands. You do not take in your hands a drill at -20°c or + 60°C. Any car engine (or boat or plane) that starts in Norway in winter and in Morocco in summer will experience much greater thermal stress.

 

not too mention as far as I know, electric drills aren't meant for using underwater. I forgot also how dangerous they are to charge. Water + litium ion = boom. I cannot stress this enough.

 

Cool Videos

Thanks for the link.

>>You do not take in your hands a drill at -20°c or + 60°C

Hmm, -20 to 40c I have. - and they weren't too careful with their tools either.

Sprint boating - a very crazy "sport" Quite a video on that site. I'm not sure I'm up for that kind of thrills!

A couple of questions:

1) Are electric RC boats faster than nitro?

2) Are there any fundamental physical reasons where the higher RPM of an electric might be used to advantage over an ICE? (over short distances, like a sprint - 49 seconds is all that is needed).

3) Do you think a high powered electric sprint boat might beat a gas one?

 

Yes and yes, the nitro boats as of yet cannot beat the electric in speed. Gas powered rc boats are even farther behind. However, they are pretty close, but I guess when your getting up into the likes of 150mph, then 50mph faster is a lot faster. Electric motors spin at ridiculous rpm's. I'm not into nitro so, I'm not sure what they run, but most of these motor in the FE boats(fast electric), can run up to 50,000rpm's, these arent cheap motors, but when combined with a good surface drive, are allowed to completely wind up to there max. load rpm. The fastest use direct drive.

I actually just ordered a new motor a few days ago for my new jet boat, it's rated at about 2hp, 35,000rpm and weighs about 280g. In my jet boat it'll be maxing out at about 25,000rpm, which should give me 25+ mph. See here, perfect example, my boat will do 25mph, where a similar boat using a surface drive will run well over 30-40mph. I'm using thew jet for running rapids, only reason, plain and simple. I use NiMH batteries, right now the boat will be set up with 3.8amp hr packs. Which should give a run time of 6-8minutes. Yes, that is a lot of amps. I dont know, how that works with real electric boats, but our electronic speed controllers (ESC), can run upwards of 125amps.

I just found something funny, isnt it wierd that electric works great only for very small boats and very large boats... I understand why, but it's just funny.

Not knowing much really about these huge DC motors that you'd use to run a sprint boat, I'm not sure I guess someone needs to crunch the numbers.

edit: thinking about it, since were talking drag boats, this idea might work, you'd basically be making a scaled up rc boat, instead of an rc boat, which is scaled down. I would think all the same things apply. I would like to see you scale this up

first pic, is my first jet boat, second and third pic, is the new one I'm building, note it will have a different motor. second pic motor is brushed, the new one is brushless. Also in the second pic, you can see my experimental variable nozzle....I dont know what it's going to do, but I'm hoping I go faster .

 

http://edisonboats.com/

These boats are no alternative for a jetski but the perform well and are electric.
Watch the last video from the gallery...they are pulling a wakeboarder.
Thats actually the application I am looking for...some electriv watercraft that will pull wakeboarder and surfer (for surfing you only need a max of 10mph or even slower.)

 

i would like to just join in and say
i have the boat and the motor ready for testing
real time test are the answer of all answers
i need the batteries and the controler from the motorcycle
and lets start testing real time
ps i have a few props as well and the wire
my uneducated first test was a flop but its there
send me what you have and ill figure it out
my only hold back is missing parts
sponsor me and see is all i ask just one more shot at it