All Electric Jet Drive Discussion

I just about sprayed my coffee all over the screen when i read the above post...

Frank, are you for real or just totally naive about this?

1000KWH battery.... do you have any idea what this means?- it is an enormous amount of power!!!

Assuming you made up a pack @ 960V nominal to keep current at a reasonably low enough level, this means you would need 300cells in series to get the required voltage, and you still deliver 260 amps. (its actually more as there is no motor and VSD drive losses accounted for) All this requires massive cabling and hugely expensive speed control gear.

To run for 4hours, it works out quite neatly at a bit over 1000amp hours per cell. They happen to sell large prismatic cells rated at 1000ah, 3.2V nominal. Each goes for about $1300USD and your going to need 300 of them. Youll probably get a discount if you buy that many, so maybe you could get them for half price - your still up for ~$200,000 in battery alone.

Each 1000ah cell weighs 40kg - you need 300 of them, so your carrying 12 tonnes of battery with you, not even accounting for the interconnecting cabling.

All this in a trailerable 30' boat.... still think this is a good idea?????

 

groper, his 25' to 30' boat will sink with i/2 of that load and I doubt the pump would move the boat with 24,000 pounds of lead on board. Maybe a very large
steam engine might....................................................

 

Nope- the quoted battery was a lithium iron phosphate battery. If it were a lead acid battery it would weigh over 36 tonnes

And without any electrical trade background, an amateur attempting implementing a system like this - even if it were feasible, would likely result in death from electrocution or explosion... Even with my electrical trade qualifications , I would still be a little scared of building something like this... It would certainly require some careful thought and planning...

 

Having raced a jet boat in offshore races, it takes a 455 ci gas big block tweaked to about 400 hp to push a 25' foot deepvee to 74mph at 5500 rpm on Berkley Jet.
Groper is correct, his spec's are not even in the ballpark.

 

Oops, I typed one too many zeroes after the one. So, what's an order of magnitude bust among friends. I promise I'm not trying to power an air conditioned house for a month.
Thanks for the catch.
100 KWH is closer to the true need. You're right about the current, which I definitely will limit to something below 260 amps, which puts my target voltage at about 440 to 480 for my current power goal. To get more power I would entertain 575 or 640 volts. However, that size motor might be a bit heavy for a 30' boat.
As indicated earlier, this is a project of trial and error to determine the right combination of boat displacement, motor size, battery capacity, battery weight, speed and handling. I may well be biting off more than I can chew. That is why I joined this forum -- to see where it takes me. I may have to give up some speed or go to surface props, but I really do want to keep the EB (Electric Boat) concept.

 

Well if you only have 100kwh battery, then you only have 25kw electric motor for 4hours...

In a 30ft boat, this will limit you to displacement speeds of around 8-10mph.

You will still have a $40,000 cost for a lithium iron phosphate battery weighing 1.2 tonnes, plus your motor and variable speed drive, and circut protection equipment, all of which is rather expensive in a setup like this.

Make no mistake, playing with 480v DC is still extremely dangerous. It's pretty easy to get stuck to the juice when your working down inside confined spaces inside boats.

 

Yep. That's what it's looking like -- a smaller boat, reduced speed and much less time at full power. The voltage is not a problem. And I do know what it's like to get a finger stuck (welded) to a high voltage terminal.
Starting with an 85 KWH battery (semi typical high power EV battery) in a 22' boat, I'm thinking we could run a 125 KW motor at max power for 12 minutes to absorb 25 KWH, leaving 60 KWH in the battery. Then, intermixed with that, we could run at 40 KW for 45 minutes and 30 KW for 60 minutes. This, or some other reasonable schedule, would be totally acceptable if the speeds corresponding to those powers are reasonably close to desired values.

 

Have you priced and specced out a 125kw electric motor? All the ones I've seen are very large, very heavy, and very expensive. And your going to drop all this in a 22ft boat? Your plan still sounds unrealistic. ..

A quick browse of a motor spec sheet gives me 1500 pounds for a 110kw 3 phase induction motor....

 

The electric motors used in cars are not that heavy and expensive. Here is one 112-135 kW continous power motor at 150 lbs and $20 000 including a controller: http://www.evdrive.com/products/evd-motor-controller/

 

Good find. Ok so the weight of the motor and controller is sorted. Still, $20k is not cheap for a 135kw motor. The battery could be sourced from a wrecked car like they do in Norway for cheap, I've heard of second hand Nissan Leaf packs being bought for a few hundred euro.

If your crafty then this could be doable. However the main problem is sourcing that battery pack at a reasonable price and designing the boat to cope with a heavy propulsion package, In excess of 1tonne , when for comparison a gasoline outboard motor and full fuel tank can be done for less than 1/2 the weight and even less again on cost...

 

diesel/electric is old tried and true technology. Diesel fuel still stores more energy per kilogram than the most modern battery. The best thing about diesel/electric is one generator can power more than one electric motor simultaneously.
With a single diesel generator as electricity source, you could have 2, 3, 5, even 10 electric driven jets, or traditionally, props.

 

Whats goin on with the albin rebuild yob. Haven't seen any posts for a while.

 

a jet offshore, what happens when there are waves or was the class all jets?

 

Good finds, indeed. Thanks, guys.
Okay, so we have a motor with controller, battery and water jet pump. Based on a test drive of Leaf a couple of years ago, I don't think the leaf battery stores enough energy. Earlier in this thread I found a 30 KWH battery @ 720 pounds. Cutting the project power down to 60 KWH, we could get by with 2 of these weighing in at 1450 pounds. Based on a post by Joakim, the motor and controller weight is on the order of 1500 pounds.
This puts us at 3000 pounds total for the entire drive train. I am liking this more and more.
Through Joakim's post, I found some good stuff at EVDrive that describes a high performance EV conversion of a BMW 325i that uses a more efficient and lighter battery by A123. I'm digging into these sources, which look very promising, to see if I can obtain good weight and price info.
I'm confident that, through these sources and Intellijet, we have the beginning of our total system.

 

Yobarnacle,
Quite true. I have seriously considered your concept, which would consist of a small ICE (diesel, gasoline, propane, or whatever), generator, batteries and a number of motors, as needed. The motors could total, for example, 200 KW to supply the power required for serious acceleration and intermittent high speed runs, while the generator might be only 50 KW to support a constant cruising speed of, say, 35 MPH, while also maintaining the charge in the battery.
This arrangement, termed Series Hybrid, is similar to how all modern cruise ships operate.
In later posts, I will discuss how I plan to implement this concept into my current project.