Thursday, January 28, 2016

Re: [Electric Boats] Re: 12V DC -> 2.3 knots

 

Greetings,
 
Agreed, I get about 3.6 mph (3.1 knots) from a 900 Watt solar array:
 
Details:
^^^^^^^
My system includes a 900 watt solar PV array mounted like a 10' X 6' hard top bimini across the cockpit on a Macgregor 25 Sailboat.
(six 150 Watt Moncrystaline Renogy panels)
 
That's split into two 450 watt 12 V circuits connected to two 30 Amp PWM Charge Controllers that each charge a bank of 12 V wet cell lead acid batteries (488 Amp Hours total)
 
These circuits power two "stock" ($139.00) 50 pound thrust trolling motors that draw about 600 watts each at wide open throttle.
 
With one trolling motor running, my iPhone GPS tells me I can push the 3000 pound boat about 2.8 mph through calm water, no wind. 
 
With two motors running I can push the boat about 3.6 mph calm water no wind.
 
If I run the system with no sun, battery only, I have about a 3 hour range before sustained battery voltages drop below 12.1v. 
 
With the solar collectors on a sunny day, I can run an extra two hours for a total five hour range.
 
The boat's home is on the Kentucky River, so river current is a factor.  Going downstream, I can meander along at 4 – 5 mph speed over ground with full helm control. 
 
Going upstream is a different story...  (you can do the math) 
 
I have powered the trolling motors directly from the solar panels, bypassing the battery array.  It does work but the shade of a cloud,  tree or bridge will stop you dead in the water.
 
The theoretical top speed with this "off the shelf" system is set by the 4" prop pitch and 1500 top RPM's of the stock trolling motors, which is about 4mph. 
 
I have tried mounting larger props with higher pitch on the trolling motors, but it just drops the RPM's.  I can over volt the trolling motors and get a bit extra push, (up to 17 volts) but the manufacturer says I will burn the motors out in short order.
 
Physics is funny like that, only so much work per watt.
 
Silent, peaceful running is a real treat.
 
Thanks for all the great info from this group.  I am learning a great deal from the discussion.
 
Ken
 
 
 
Sent: Sunday, January 24, 2016 12:01 AM
Subject: Re: [Electric Boats] Re: 12V DC -> 120V AC vs. 48V DC -> 120V AC
 
 

Interesting! Am I reading this correctly, a largish solar array of 600W would be able to move a boat at 2-3 knots as long as the sun shines, or at least add a knot or two while under sail?

On Jan 23, 2016, at 15:23, tkgc9 tkgc9@yahoo.com [electricboats] <electricboats@yahoogroups.com> wrote:

 

Here is the profomance data for my Pearson P 30 with Electric Yacht 10 kw. System and a 3 blade prop

 
 
Speed. Knots           RPM.          Amps.     L mrtTemp
2.5.                              774.            7.                 78
3.                                  1079.        17.               80
3.8.                               1305.        28.              80
4..3.                               1505.       42.              84
4.9.                                1754.       64.              86
5.4.                               1926.        90.             93
5.8.                              2115.         122.          100
5.9.                              2193.           141.         107
-------- Original message --------
From: king_of_neworleans <no_reply@yahoogroups.com>
Date: 1/23/2016 5:03 PM (GMT-06:00)
Subject: [Electric Boats] Re: 12V DC -> 120V AC vs. 48V DC -> 120V AC
 
 

I know where stuff ends up when the door flies open. I drill and screw a SS hook and eye to keep it closed.

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Posted by: "Ken Cooke" <ken.cooke@canewoods.com>
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