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Old 01-17-2014, 02:45 PM   #1
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How many 12v amps from your solar?

Wondering if y'all can weigh in with what your real world output is from your solar along with a short description of the size watts and number of your panels...

I have 4 narrow panels that I picked up used and am wondering what I might get if I replace with new. I suspect these panels are 10 to 15 years old and I don't know the specs. I end up getting around 8 to 12 amps charging at 12 volts with them.

How about your installs?
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Old 01-17-2014, 04:29 PM   #2
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My 250 watt system will actually peak at around 14 amps if everything is ideal.
I suspect yours are working fine as panels have a long life.
When the wattage is calculated it is at the panel output voltage , usually around 18 volts so if you are calculating wattage at the battery voltage your number will be about 1/3 less. Typical advertising I guess.
The panels are a much better judge of haze in the atmosphere so a lot of times you will think the output is lower than you would expect on what appears to be a clear day.
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Old 01-17-2014, 04:54 PM   #3
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Since you didn't state what the panels are rated at. I am going to guess that each of the 4 panels you have are rated at 40-50watts. 4x40= 160 watts. When you consider the losses thru the controller, the angle of the sun, the atmospheric conditions.
If you are charging at 13.3 volts and 12 amps. That works out to 160 watts. So the panels could be rated closer to 50 watts each.
If you are somewhat conservative with the power usage, these panels should serve you well.
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Old 01-20-2014, 10:28 PM   #4
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TG, I think you are on the money with your estimates. I don't really have the specs so that is why I am asking for others experience so I can try to benchmark to mine.

Rick, how many panels do you have and where mounted?
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Old 01-20-2014, 11:28 PM   #5
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With modern MPPT controllers, the panel amps and battery amps can be two different things. We get 12 amps or so (varies with weather a lot) from our two 100W panels if the batteries are pretty far discharged (rarely happens). It will go higher if there's a lot of sun (Burning Man).

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