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groingo
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# Posted: 4 Nov 2015 12:50
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Ok, I have a 12 volt 400 watt system, but the charge controller is rated at 30 amps at 360 watts....where is the extra 40 watts going if am producing 400 yet the cc can only handle 360....is it throttling back input power to keep from cooking the controller?
All charge controllers seem to be this way, high amperages but low wattage so you have to buy three times the amperage you need to cover you wattage.
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MtnDon
Member
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# Posted: 4 Nov 2015 14:32
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If your system actually produces 400 watts in bright sun then the extra is wasted. The PV in most systems never put out the max rated STC power. Clouds cause losses, dirty panels, sun angle being off reduces production, if the panel is hotter than 75 F (normal test temperature) output is reduced.
About the only environmental factor that increases output is higher altitudes and cold weather. Less air and pollution to block the sun increases the amperage output above the rated Imp. Panels colder than STC (75 F) produce higher voltages. That is often countered a bit by reduced daylight hours.
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MtnDon
Member
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# Posted: 4 Nov 2015 14:35
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IF the CC can handle higher battery voltages, 24, 48, then the rated wattage capacity goes up by a factor of two for 24 volts and 4 for 48 volt systems. The rated maximum amperage output remains the same.
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groingo
Member
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# Posted: 4 Nov 2015 16:41
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So, if the panels do actually produce 400 watts and the charge controller can only handle 360, watts....what happens to that extra 40 watts?
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MtnDon
Member
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# Posted: 4 Nov 2015 16:57 - Edited by: MtnDon
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Perhaps dissipated as heat? Or maybe it just doesn't get used at all, much like a PV panel can sit there unconnected to anything and not cause any problems. I don't know for sure. Does it matter? What I do know for sure is that if a setup is overpaneled a little it is no big deal to the equipment, if it is good equipment. Folks trying to maximize their charge overpanel routinely by 10 to 15%. Manufacturers like Midnite will tell you it is okay, in moderation.
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