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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #21  
Old 10-18-2011
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Quote:
Originally Posted by tabrar View Post
Hello.

I want to develop a system on solar that the load is 250 watt continous. the battery bank should support it to 2 day. can anyone guide me in it like the solar panel should i have it's ratting and about battery bank.

regards;
taqi abrar
If I understand correctly you want to supply 250W 24 hours a day.
The correct sized solar array will depend on the location and times of year, but its going to a very large solar system something around 1000w. Only large catamarans have room for this amount of solar.
Is there a way the power consumption can be reduced?
Let us now some more information and we can refine the size of panels needed, and work out a battery bank size.
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  #22  
Old 10-18-2011
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Quote:
Originally Posted by tabrar View Post
I want to develop a system on solar that the load is 250 watt continous. the battery bank should support it to 2 day. can anyone guide me in it like the solar panel should i have it's ratting and about battery bank.
The math is pretty simple. Let's start with your total daily load. 250 watts * 24 hours = 6,000 watt/hours per day.

Now battery capacity. 6,000 w/h/day * 2 days = 12,000 w/h capacity. Actual capacity needs to be twice that, since you drastically shorten battery life if you draw them down more than 50%. Hence, 24k w/h capacity battery bank. Converted to amp/hrs = 2,000 a/h. In case you don't know, that is a HUGE battery bank. Most sailboats in the 35' or so range will have maybe a 500 a/h battery bank. On a 40' boat a 1,000 a/h battery bank would be considered fairly big.

How about solar panels? You need to replace 6,000 watt/hrs per day. Depends on where you are, but in the tropics you can typically take the wattage rating of your solar panels, multiply that by about 5, and get a good estimate of how much energy you will generate each day. So we have 6,000 / 5 = 1,200 watts worth of solar panels. On average, solar panels generate about 9 watts per square foot. Therefore you need 1,200 / 9 = 133 square feet worth of solar panels. That's assuming no shading at all on the panels. Any shading will drastically reduce the panel output.

Like noelex said, you need a VERY large catamaran (like, in the hundreds of feet range) to have that much unshaded space for solar panels. Methinks you might want to find a way to reduce the electrical requirements.

Last edited by denverd0n; 10-18-2011 at 11:49 AM.
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  #23  
Old 10-18-2011
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tabrar

Can you be more specific about what you want to run, and what boat and battery bank, as well as location?
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  #24  
Old 10-19-2011
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To All

Since i have camras that have to work for 2 day continously. the watt rating of the cameras are 250 watt. for whole two day i have to run the load on battery.
so please tell me about the solar panel. it's rating, configuration and type. also the charger circuit and all other things in detail...

Thanks.
tabrar
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Old 10-19-2011
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The watt rating printed on the side of equipment (which I presume is what you are quoting) often indicates the maximum current draw. The average power used may be significantly lower. You need to measure this. A clamp on ammeter is the easiest way

The time you are using the camera and the rest time between uses is also important to work out your requirements.
.
Solar production is very dependent on location and time of year.

Without these sort of details we can only guess at a system to meet your needs
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Old 10-19-2011
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I've just gone through as similar exercise to increase my charging capacity. I jumped back and forth from generator to bigger alternator to second alternator. I'm not sure how your boat is set up but it is usually possible to add a second alternator to the PTO pulley on the engine if there's room. You'll need a dual pulley for anything over 120 amps. You might also consider AGM batteries which have a much higher acceptance rate then flooded.

In the end I went with a 160 amp replacement for my standard alternator using a serpentine belt kit. There may be one available for your engine which should allow up to a 180 amp alt. I also have 660 amp hours of AGM house and 370 watts of solar. We have DC refrigeration and a watermaker but still only use maybe 100-150 amps per day. No washing machine.
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  #27  
Old 10-20-2011
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Solar energy

Quote:
Originally Posted by noelex77 View Post
The watt rating printed on the side of equipment (which I presume is what you are quoting) often indicates the maximum current draw. The average power used may be significantly lower. You need to measure this. A clamp on ammeter is the easiest way

The time you are using the camera and the rest time between uses is also important to work out your requirements.
.
Solar production is very dependent on location and time of year.

Without these sort of details we can only guess at a system to meet your needs


I have camera that carries a load of 250Watts as i checked.
now my boat might go on a remote location for 2 day.
i want that my camera that is connected to the battery only will work for 2 day only.
the remote location can be any where.
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  #28  
Old 10-20-2011
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To have a solar system that will replace a continous load of 250w in most location in any season will be very large someting like 3 to 4 KW would be a good starting point. There is not enough room on even a large cataman for this much solar power.

A small generator is your your only practical solution if you want to provide this sort of power in the less sunny parts of the world.

If you are using the camera for 2 days. Then not using it over a longer period. The power for the cameras can be supplied by a large battery bank, with a smaller solar array gradually replacing the power.
The duty cycle is important, 2 days use and how many days rest? You also need to account for other loads such as lights etc.
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  #29  
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Since after 2 day i can have a rest of 4 days so kindly guide me about the solar panel and other details that are necessary for that.
i can charger the battery on a shore so tell me about the batteries also
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  #30  
Old 10-20-2011
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Quote:
Originally Posted by tabrar View Post
Since after 2 day i can have a rest of 4 days so kindly guide me about the solar panel and other details that are necessary for that.
i can charger the battery on a shore so tell me about the batteries also
Without shore power
You need to generate on average about 170 AHrs a day. To do this in a sunny climate would only require about 500w of solar, but to be able to do this year round in most locations 1500-2000w will be needed.
The battery bank will need to be about 1500Ahrs

With shore power every night you do need any solar power and the battery bank alone would be enough.
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