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Old 10-19-2019, 09:08 PM   #1
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Solar Panel Output

How many amps should two 120 watt solar panels put out on a sunny day in mid-October in the mid-Atlantic area?
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Old 10-19-2019, 09:21 PM   #2
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Average sunlight/day 7 hours in Asheville NC in October. So, 120x2x7= 1680W/12= 140Ah for the day.... Or, 120x2/12= 20A/hr * 7 hours is 140Ah

HOWEVER.... what quality panels, how old, what efficiency, how clean, how well oriented? In other words how many of those 120W it says on the box do you actually get?

So the real answer is: "No way to tell from here". Anywhere from 10-20/hr so 70-140Ah/day is my guess.....
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Old 10-19-2019, 09:41 PM   #3
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Well you asked about amps not amp hours so 120 watts of solar panels should put out 10 amps if they have good exposure. P=IxE so I= P/E or amps = watts/volts.
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Old 10-20-2019, 09:57 AM   #4
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We had two 140 watt panels on our last boat. I think I calculated maximum theoretical amps at around 26. The most we ever saw was one day with the sun directly overhead and that was 22.5 amps. Usually we were happy to get 14 to 16 amps. But, they would be putting out 2 amps when the sun was barely up.

This was in Florida and the Bahamas.
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Old 10-20-2019, 10:21 AM   #5
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Presuming that the panels are mounted horizontal on the roof or similar:

In mid October in Virginia Beach the sun never gets perpendicular to the surface of the panel, maybe 30 degrees at best. And then before and after that peak output it is less than 30 degrees, probably 60 degrees at 9:00 in the morning or 3:00 in the afternoon.

One rule of thumb is that a horizontal panel will put out 40% of its rated wattage in amp hours on a sunny day in the summer months in a moderate latitudes. Your panel doesn't meet those latter two criteria of course.

So maybe use 25% or 60 amp hours as a SWAG.

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