Good summary of how that's done John R.
Edge of cloud effect can add up to 30% more insolation(incoming solar radiation). I've witnessed some big spikes on partly cloudy days but they are not sustained. Design peaks occur on clear, cold days when the high current lasts for hours straight. That's when your hardware and connections get tested.
Hi Cal,
An example coming up below.
Firstly though, not sure who you are replying to here so easier if you address the person, so that saves me jumping in if your post intended for another. For example Capt Qullian has more actual experience with solar. All I can tell you is what I've learned from my 2 x 30W panels in series for my 24V system which runs my internet router, but still even that has given me insight over time.
My solar panel data online goes back 6 months but shows only yield, but the actual controller gives a 30 day history and as it is Summer here I can't give you max voltages in winter. Like I said before try this sheet and it is obvious how voltage changes. Every panel data sheet has a V temp and I temp coefficient given as percent per degree C. Enter your choice/combination of panels in the sheet in the modules tab. See other tabs for calcs.
https://www.victronenergy.com/upload/software/VE-MPPT-Calc-2_2.xlsx
Bear in mind that a panel not covered in snow and ambient temperature of zero C will have a lower actual temp if well cooled on a boat, say minus 5 C. Maybe worse with wind chill factor which further raises panel voltage.
An example of 7 x 140W x 12v panels in series giving 980 Wp, using a 150V rated MPPT, with panel temps between minus 5 C and plus 70 C, then max PV voltage at min temp would be 167.1V string Voc max and min PV voltage at max temp would be 101.7V, so you can see the range we are talking about and how temperature changes things - so whatever panels you use and controller needs to be matched so you don't exceed the MPPT voltage rating and damage the controller. Not an issue with current on Victron MPPTs as power limiting kicks in when adding more panels in parallel.
Often I will note with my setup that I will exceed the STC power rating of my panels therefore harvesting more instantaneously than the 60W installed power, one of the beneficial outcomes maybe from using a good MPPT. It could also be that and a combination of edge of cloud effect I understand.
John R.
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Posted by: Carter Quillen <twowheelinguy@yahoo.com>
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