The Classic offers some unique opportunities if you are faced with longer than normal wire runs
between the DC source and the Classic. The Classic comes in 3 input voltage ranges letting you design
a DC source at a higher voltage if it is beneficial. For example let‘s say you have a 300 ft run from a
PV array to the Classic you could wire for an open circuit voltage close to 250vdc accounting for the
coldest temperature you will encounter
. This will allow you to run a smaller gauge wire than with a
lower voltage charge controller. The efficiency of a high voltage Classic is less than the lower voltage
versions, so you need to weigh the benefit. If this sounds too complicated use this rule of thumb in
selecting the proper Classic. PV runs up to 100 feet, use the Classic 150. Runs up to 180 feet, use the
Classic 200. Above 180 feet use the Classic 250.
Yeah that's kind of what I was wondering, but I figure it should be safe to give 60+ volts to the 48v charge controller right? Open circuit voltage of those panels for example is 38v, so the charge controller would see 76v max. Found this in the documentation of the Midnite controller. (not dead set on any equipment just using that one as example)
So whether my panels are in series or parallel, my system wattage is equivalent to how many panels I have and not how many strings I have.
Basically, 1000w of solar, no matter what the nominal voltage of the system is, should power 1000w of AC 120v right?
Another solar related question, figured I'd use the same thread. When you have multiple strings of panels spread out over different areas, they will get different sun exposure, angle etc and thus, probably also each have a different maximum power point. With that said, is it best to have one small charge controller for each string so they can each achieve maximum power per string, or do you just stick them in parallel and the MPPT controller will just kind of find the average maximum power point for the whole system? Or do lot of charge controllers actually have capability to add separate strings that are handled independently? Been pondering on where I could put panels other than the south facing roof, and I could stick some strings in places that are less optimal, but still get some sun, but I would not want those strings to basically affect the main ones. I imagine each string would also have it's own diode to prevent the higher output strings from feeding the lower output ones as well?
When you have multiple strings of panels spread out over different areas, they will get different sun exposure, angle etc and thus, probably also each have a different maximum power point. With that said, is it best to have one small charge controller for each string so they can each achieve maximum power per string, or do you just stick them in parallel and the MPPT controller will just kind of find the average maximum power point for the whole system?
, though MPPTs generally aren't available in big current ratings for parallel strings.
The MPPT point for a panel will change with the irradiance
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
That's what I was thinking too, so each array should be on it's own mppt then? How would this work for battery charging, would I need to just set them to float, and maybe only have one that charges at a higher/variable rate? Otherwise they'd all fight each other. Or would it just work?
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
That's what I was thinking too, so each array should be on it's own mppt then? How would this work for battery charging, would I need to just set them to float, and maybe only have one that charges at a higher/variable rate? Otherwise they'd all fight each other. Or would it just work?
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
That's what I was thinking too, so each array should be on it's own mppt then? How would this work for battery charging, would I need to just set them to float, and maybe only have one that charges at a higher/variable rate? Otherwise they'd all fight each other. Or would it just work?Look at how much the peak power point will vary with temperature/insolation, going from a single voltage on all strings to individual MPPT on all strings will only gain a few % in increased generation. Then you can compare the costs of adding additional MPPT and cabling compared to the additional energy produced, or adding more panels to the strings.
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
That's what I was thinking too, so each array should be on it's own mppt then? How would this work for battery charging, would I need to just set them to float, and maybe only have one that charges at a higher/variable rate? Otherwise they'd all fight each other. Or would it just work?Look at how much the peak power point will vary with temperature/insolation, going from a single voltage on all strings to individual MPPT on all strings will only gain a few % in increased generation. Then you can compare the costs of adding additional MPPT and cabling compared to the additional energy produced, or adding more panels to the strings.
Yeah true guess if it's not that much of a difference it may not be worth going through the trouble. I could probably also put arrays on relays, have the relay of the less optimal one turn on when there is enough sun.
This is more of a what if scenario anyway, chances are good I'd start with just the roof top array. What I've been thinking about as well is I need to build a shed, I might make it use solar power for lights etc and it will make a decent solar project as a start to get an idea of what is involved.
The MPPT point for a panel will change with the irradiance, so if you have panels at different orientations paralleled into one controller then the mppt point selected by the controller will less than optimal for any of them.
As far as I have seen with solar installations you would always use separate mppt tracking regulators for each array of panels if they are significantly different from each other in either orientation or design.
That's what I was thinking too, so each array should be on it's own mppt then? How would this work for battery charging, would I need to just set them to float, and maybe only have one that charges at a higher/variable rate? Otherwise they'd all fight each other. Or would it just work?Look at how much the peak power point will vary with temperature/insolation, going from a single voltage on all strings to individual MPPT on all strings will only gain a few % in increased generation. Then you can compare the costs of adding additional MPPT and cabling compared to the additional energy produced, or adding more panels to the strings.
Yeah true guess if it's not that much of a difference it may not be worth going through the trouble. I could probably also put arrays on relays, have the relay of the less optimal one turn on when there is enough sun.
This is more of a what if scenario anyway, chances are good I'd start with just the roof top array. What I've been thinking about as well is I need to build a shed, I might make it use solar power for lights etc and it will make a decent solar project as a start to get an idea of what is involved.Disconnecting panel strings when they are only illuminated even from diffuse light would just reduce production capacity, the MPPT would find the peak of all the strings together and none would be "taking" power away unless they were in complete darkness (measure the output under moonlight if you don't believe it!). It's very hard to come up with situations where reverse leakage will be a problem especially if the string voltages are well above the battery voltage and using a buck regulator.
Disconnecting panel strings when they are only illuminated even from diffuse light would just reduce production capacity, the MPPT would find the peak of all the strings together and none would be "taking" power away unless they were in complete darkness (measure the output under moonlight if you don't believe it!). It's very hard to come up with situations where reverse leakage will be a problem especially if the string voltages are well above the battery voltage and using a buck regulator.I was thinking it might drive the MPPT curve down for the rest of the panels but guess I'm probably just overthinking this.