|Subject: Re: [harryproa] Re: Electric drive for Harryproa|
|From: George Kuck |
|Date: 4/3/2008, 8:31 PM|
If you're looking for affordable lithium-ion batteries, check out this link to Everspring Global Limited in China:
ng.net/txt/ product-battery- pricing.htm
Their prices are impressively low, actually in line with gel-cell batteries, but their energy density is obviously way better. 1600 AH for 110 pounds? That's incredible. They also claim 1500 cycles at 70%.
I haven't purchased from them, but am considering doing so in the future for boat power. They claim to be providing batteries for a Citroen model:
ng.net/product- battery-customer reference. htm
You might be able to power a 12m Harry quite well with 6 KW of electric power. That should give you the power of a 9 hp outboard and the thrust of perhaps a 15 hp. With 1600 AH storage, that's about 2.5 hours of full-out thrust before hitting 80% depletion. Of course, you'd want a genset to go along with those batteries.
My favorite at the moment is the OSSA Powerlite series from Glacier Bay:
rlite.com/ products/ generators/ generators. htm
They offer "propulsion duty rated" generators designed to move boats in diesel/electric systems, and can be less than half the weight of the competition. I can't find the specs right now, but I believe their 6 KW generator is under 150 pounds.
If you don't mind leaving your motors in the water, you can also use them to recharge the generator (provided they are the right motors, of course).
A rule of thumb I read on a Solomon system was four hours sailing to every hour of motoring. As long as you're not looking to race, losing a few knots to the generators can be a nice way of keeping the batteries topped off. For me, it's about 1/2 hour out to open water, so the most I'd motor in a given day is perhaps an hour and a half. Most day sailing trips would generate enough power to skip using the generator altogether.
My original plans were to use a retracting thruster near the center of the leeward hull, mainly because: a) I didn't want the motor in the water at times when I cared about performance, b) retracting thrusters are a proven and efficient technology that I wouldn't have to reinvent, c) I have worries about putting electric outboards outside the boat to get hit by waves in a storm, and d) I'm tired of watching the stern-mounted outboard on my current catamaran pop out of the water once the seas go above three feet.
However, Rob's planned design has a lot of advantages. I'm sure it will be tested and proven long before I start a new boat.
I am planing on building a 12 m Harryproa and am thinking of using
electric pods. Pods would be mounted on swing arms similar to what
has been used on African cats. Take a look at the June 14,2007 press
release on Africancats.
com website. Also check out RE-E-Power.com .
In the Re-E-Power Forum link in the photo section is a example of a
pod mounted to a long swing arm.
Has anything been done with electric power on Harryproa's ? I think
there was a recent reference to electric motors on rudders, does
anyone have more information or pictures on this.
I think a Harryproa would be unequally suited to a solar/battery
electric drive system since the sail is offset on lw hull. A solar
canopy over the seats a center area of boat would be less obstructed
by sail than a cattermaran.
The proa does have the problem of how to deal with going in both
directions with the electric drive. You could point one in each
direction and only use one in open water and lower both for
maneuvering in harbor or for extra power when needed. You could use a
prop designed for both directions but I do not know it it would be as
efficient as one designed for one direction.
I would like to hear any sugjestions and comments one this ?
One other concern would be the added weight of a battery pack which
could be as much as 1000lbs or more. I am hoping that newer battery
types will bring down the weight in the next few years to less than
Valence Technology Lithium batteries would be great but the current
price is prohibitive. Firerfly batteries (a new lighter type of lead
acit battery) sound like a good bet but are not yet available. It
may be necessary to start with current lead acid and switch to
lighter batteries in the future. After Lithium batteries get
established in electric cars that will start coming out in the next
few years I expect availability and price to improve. I spoke with
Bob Lutz vic chairman of General motors at a special event a the New
York Auto show a week or two ago and he claims that they will have
the Chevy Volt in production by the end of 2010 ! It will run on
Thanks for any imput on this topic,