Rob
We have total nominal stored energy of 8kWh. This is more than I initially planned because the second set of cells have higher capacity than the first. They were slightly cheaper in terms on $/Wh so were better value. Both systems are completely isolated electrically. On the one occasion we ran one bank down to allowable minimum voltage we got about 5% more charge into it than the nominal capacity. So I suspect we can safely pull out the 8kWh although you do need to be conscious of the battery state similar to any fuel tank. The difference is the energy source is ubiquitous whenever there is light in the sky. The panels drop output when clouds are overhead but still significant output.
With clean hull and low wind we got 4.5kts with 4kWh - I was aiming for 5kts. We were doing 3kts with total of 1.5kW this week. I did not measure the power drain at full speed of 6.5kts but it would have been over 10kW total from the two batteries. So range depends on the speed you are prepared to move along at. We can steer with the rudders using only 500W on both motors - about 2kts. We can spin the boat in its own length using motors alone.
So far only the small battery is being charged with solar power. It is connected to 4 x 50W panels that were at hand. The intention is to get 2 x 200W panels for the larger battery. There is room on the cabin top for more panels but at this stage there will be ample capacity with total of 600W for day sailing getting in and out of the marina and any anchorages. Our little trek across the top of the bay this week used about 20% of the battery capacity but we sailed more than half the 6nm round trip.
In good sunshine the batteries will be recharged in a few hours after motoring out from the mooring.
The 200W panels cost $1/W so they are tremendous value these days. I have some 100W semi-rigid panels for my solar boat that cost $2/W. They were attractive due to their low weight of 3.85kg and ability to fit neatly on a curved surface. These can be fitted on a low trafficked deck or cabin top and walked over with feet or soft shoes.
The durability of what we have built can only be tested with time and use but it has already made the proa more user friendly. The total weight of thrusters, batteries and controls is roughly the same as the 60HP outboard, its mounting, controls and fuel tank. The solar panels are extra weight but worth it when you consider the convenience over liquid fuel.
There is a 2.5kW petrol genset on board at present that is used for power tools but also provides emergency charging capability.
As you know this boat has a lot of windage and it is something that concerns me with regard to open water operation. It is not too hard to build a light boat with materials available these days but windage becomes an issue for performance and ultimately survival.
Rick
On 24/01/2013, at 3:01 PM, Rob Denney wrote:
Also keen to know how long the batteries last on a charge at various boat speeds and how long they take to charge with the solar panels.
Rick Willoughby
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